Work vehicles

Abstract

Provided is a work vehicle (1) that can effectively assist, by virtue of the rotational power of a flywheel, the rotational power of an engine (4) when a workload is large.　This work vehicle (1) comprises: an engine (4); a first flywheel (13) that rotates by receiving the rotational power of the engine (4); a transmission (16) that selectively receives, shifts, and outputs the rotational power of the engine (4) or the rotational power of either the engine (4) or the first flywheel (13); a first power transmission path (31) that transmits the rotational power of the engine (4) to the first flywheel (13); and a second power transmission path (32) that transmits the rotational power of the first flywheel (13) to the transmission (16), wherein the first power transmission path (31) and the second power transmission path (32) are mutually independent paths, the first power transmission path (31) is provided with a first clutch (26) that continues or discontinues the transmission of rotational power from the engine (4) to the first flywheel (13), and the second power transmission path (32) is provided with a second clutch (27) that continues or discontinues the transmission of rotational power from the first flywheel (13) to the transmission (16).

Description

[Technical Field]

[0001] The present invention relates to a work vehicle such as a tractor. [Background technology]

[0002] Conventionally, the technology disclosed in Patent Document 1 below is known.

[0003] The technology disclosed in Patent Document 1 is an energy recovery system for a vehicle driveline that includes an engine, a flywheel, and a transmission. This system receives rotational energy from the driveline of the wheels, stores it in the flywheel, and returns the stored rotational energy to the driveline. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication "Patent No. 5554323" Summary of the Invention [Problem to be solved by the invention]

[0005] In the above-disclosed technology, power transmission paths are configured between the engine and the flywheel, and between the flywheel and the transmission. However, these paths are not independent of each other. Specifically, both of the above-disclosed two paths pass through a planetary gear mechanism.

[0006] Therefore, the rotational speed of the rotational power input to the flywheel when the rotational power is transmitted from the engine to the flywheel and the rotational speed of the rotational power output to the transmission when the rotational power is transmitted from the flywheel to the transmission are determined based on the gear ratio of the planetary gear mechanism. As a result, even if the rotational power of the engine is increased in speed by the planetary gear mechanism and input to the flywheel, the rotational power output from the flywheel is reduced in speed by the planetary gear mechanism and output to the transmission, so the rotational energy stored in the flywheel cannot be output to the transmission efficiently. For this reason, when the rotational power of the engine is insufficient, it is difficult to effectively compensate for the insufficient rotational power with the rotational power of the flywheel.

[0007] Therefore, when the above-disclosed technology is applied to a work vehicle that drives a work implement using the rotational power of an engine, the rotational power of the engine cannot be effectively assisted by the rotational power of the flywheel when the work load is heavy.

[0008] The present invention has been made in consideration of the above problems, and has an object to provide a work vehicle that can effectively assist the rotational power of the engine with the rotational power of the flywheel when the work load is heavy. [Means for solving the problem]

[0009] The technical means adopted by the present invention to solve the above problems are characterized as follows.

[0010] A work vehicle according to one aspect of the present invention includes an engine, a first flywheel that receives rotational power from the engine and rotates, a transmission that selectively receives rotational power from either the engine or the engine and the first flywheel, changes the speed of the rotational power, and outputs the rotational power, a first power transmission path that transmits the rotational power of the engine to the first flywheel, and a second power transmission path that transmits the rotational power of the first flywheel to the transmission, the first power transmission path and the second power transmission path are paths independent of each other, the first power transmission path is provided with a first clutch that interrupts the transmission of rotational power from the engine to the first flywheel, and the second power transmission path is provided with a second clutch that interrupts the transmission of rotational power from the first flywheel to the transmission device. and a third power transmission path that transmits the rotational power of the engine to the transmission device without passing through the first flywheel, and the third power transmission path always connects the output shaft of the engine and the input shaft of the transmission device. .

[0011] A work vehicle according to one aspect of the present invention includes an engine, a first flywheel that receives rotational power from the engine and rotates, a transmission that selectively receives rotational power from either the engine or the engine and the first flywheel, changes the speed, and outputs the rotational power, a first power transmission path that transmits the rotational power of the engine to the first flywheel, and a second power transmission path that transmits the rotational power of the first flywheel to the transmission, the first power transmission path and the second power transmission path being paths independent of each other, the first power transmission path being provided with a first clutch that interrupts the transmission of rotational power from the engine to the first flywheel, and the second power transmission path being provided with a front clutch that interrupts the transmission of rotational power from the engine to the first flywheel. A second clutch is provided to interrupt the transmission of rotational power from the first flywheel to the transmission device, and the first power transmission path is provided with a speed-increasing mechanism that increases the speed of the rotational power of the engine and transmits it to the first flywheel. The second power transmission path transmits the rotational power of the first flywheel to the transmission device without passing through a reduction mechanism. The speed-increasing mechanism is composed of a planetary gear mechanism including a sun gear, planetary gears, and a ring gear, and the ring gear is fixed so that it cannot rotate. The rotational power of the engine is input to the planetary gears and transmitted to the first flywheel via the sun gear, and the rotational power of the first flywheel is transmitted to the transmission device without passing through the planetary gear mechanism.

[0014] The work vehicle may include a second flywheel connected to an output shaft of the engine, and the first flywheel may be rotatable independently of the second flywheel.

[0015] In the work vehicle, the first flywheel may be arranged between the second flywheel and the transmission in the axial length direction of the output shaft.

[0016] The work vehicle may include an intermediate shaft that is interposed between the output shaft and the transmission and forms the third power transmission path, and the intermediate shaft may be arranged to pass through the first flywheel.

[0017] The first clutch and the second clutch may be arranged side by side in a radial direction of the intermediate shaft.

[0018] The first clutch and the second clutch may be arranged side by side in the axial direction of the intermediate shaft.

[0019] The work vehicle may include a housing that accommodates the first flywheel, the first clutch, and the second clutch, and a partition wall is provided inside the housing to separate the interior into a space that accommodates the first flywheel and a space that accommodates the first clutch and the second clutch, and the first clutch and the second clutch may be arranged in a position facing the partition wall.

[0020] The first clutch and the second clutch may be multi-plate clutches including a plurality of friction plates, and may be arranged on the inner circumferential side of the first flywheel. [Effects of the Invention]

[0021] According to the work vehicle of the present invention, when the work load is heavy, the rotational power of the engine can be effectively assisted by the rotational power of the flywheel. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a schematic side view showing a work vehicle according to the present invention. [Figure 2] FIG. 2 is a diagram showing the configuration of a power transmission mechanism of the work vehicle. [Figure 3] 3A and 3B are diagrams illustrating a configuration of a first power transmission portion according to a first embodiment. [Figure 4] 5A and 5B are diagrams illustrating a configuration of a second embodiment of the first power transmission portion. [Figure 5] 10A and 10B are diagrams illustrating a configuration of a third embodiment of a first power transmission portion. [Figure 6] FIG. 10 is a diagram showing the configuration of a fourth embodiment of a first power transmission portion. [Figure 7] FIG. 10 is a diagram showing the configuration of a fifth embodiment of a first power transmission portion. [Figure 8] FIG. 10 is a diagram showing the configuration of a sixth embodiment of a first power transmission portion. [Figure 9] FIG. 2 is a collinear diagram of a planetary gear mechanism that constitutes a speed increasing mechanism. [Figure 10] 10 is a cross-sectional view showing a power transmission mechanism including a first power transmission part according to a fifth embodiment and a part of a transmission case that houses the power transmission mechanism. FIG. [Figure 11] FIG. 11 is an enlarged view of a part of FIG. [Figure 12] FIG. 2 is a perspective view showing a first flywheel, a partition wall, a support body, a first friction plate, and a second friction plate. [Figure 13] 1 is a block diagram showing a schematic configuration of a control system provided in a work vehicle. [Figure 14] 3 is a diagram showing the states of the engine, the first flywheel, the first clutch, and the second clutch in each operating mode executed by the control system. FIG. [Figure 15] FIG. 2 is a state transition diagram of the operating modes executed by the control system. [Figure 16] FIG. 10 is a diagram showing conditions (thresholds) for transitioning between operation modes. [Figure 17] 10 is a flowchart showing the flow of operations when shifting from a free mode to a sleep preparation mode. [Figure 18] 10 is a flowchart showing the flow of operations when transitioning from a stickiness preparation mode to a stickiness mode or a free mode. [Figure 19] 10 is a flowchart showing the flow of operations when transitioning from a tenacity mode to a charge preparation mode or a free mode. [Figure 20] 10 is a flowchart showing the flow of operations when shifting from a charge preparation mode to a charge mode or a free mode. [Figure 21] 10 is a flowchart showing the flow of operations when transitioning from a charge mode to a boost preparation mode or a free mode. [Figure 22] 10 is a flowchart showing the flow of operations when transitioning from a boost preparation mode to a boost mode. [Figure 23] 10 is a flowchart showing the flow of operations when shifting from the boost mode to the sting mode or the free mode. [Figure 24A] This is an example of a screen display when a display on the screen of a display input device notifies the user that switching from charge mode to boost preparation mode is possible, and shows the screen of the display input device in a state where switching to boost preparation mode is not possible. [Figure 24B] This is an example of a screen display when a notification is given that switching from charge mode to boost preparation mode is possible by displaying it on the screen of a display input device, and shows the screen of the display input device in a state where switching to boost preparation mode is possible. [Figure 25] 1 is an example of a timing chart of a control system. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, an embodiment of the present invention will be described with reference to the drawings as appropriate.

[0024] In the following description, the direction of arrow A1 in FIG. 1 is the forward direction, and the direction of arrow A2 is the rearward direction.

[0025] <Work vehicle> 1 is a schematic side view showing a work vehicle 1 according to the present invention. In this embodiment, a tractor is shown as an example of the work vehicle 1. However, the work vehicle 1 is not limited to a tractor, and may be other work vehicles such as a wheel loader, compact track loader, backhoe, rice transplanter, etc.

[0026] The work vehicle 1 comprises a vehicle body 2 and a traveling device 3 .

[0027] The vehicle body 2 has an engine 4 and a transmission case 5 connected to the rear of the engine 4. The traveling device 3 supports the vehicle body 2 so that it can travel. The traveling device 3 has front wheels 3F and rear wheels 3R.

[0028] A lifting device 7 is provided at the rear of the vehicle body 2. A work implement can be attached to the lifting device 7. The work implement attached to the lifting device 7 is an implement that performs work on a field, such as a tilling implement or a spraying implement. The lifting device 7 is configured, for example, with a three-point link mechanism. The lifting device 7 can raise and lower the attached work implement.

[0029] A PTO shaft 8 is provided protruding from the rear of the transmission case 5. A working device attached to the lifting device 7 can be driven by the driving force transmitted from the PTO shaft 8.

[0030] The transmission case 5 has a flywheel housing 9 and a transmission case 10. The flywheel housing 9 houses flywheels (a first flywheel 13, a second flywheel 14) and other components described below. The flywheel housing 9 is provided in the front of the transmission case 5. Hereinafter, the flywheel housing 9 may be simply referred to as the housing 9. The transmission case 10 houses a transmission 16 and other components described below. The transmission case 10 is provided in the rear of the transmission case 5.

[0031] <Power transmission mechanism> As shown in Fig. 2, a power transmission mechanism 6 is disposed inside the transmission case 5. The power transmission mechanism 6 is a mechanism that transmits the rotational power of the engine 4 to the traveling device 3 and the PTO shaft 8 shown in Fig. 1.

[0032] The power transmission mechanism 6 has a first power transmission unit 11 and a second power transmission unit 12. The first power transmission unit 11 is disposed inside the flywheel housing 9. The second power transmission unit 12 is disposed inside the transmission case 10. The first power transmission unit 11 receives rotational power from the engine 4 and transmits it to the second power transmission unit 12. The second power transmission unit 12 transmits the rotational power transmitted from the first power transmission unit 11 to the traveling device 3 and the PTO shaft 8.

[0033] Figures 3 to 8 show different embodiments of the first power transmission section 11. Figure 3 shows a first embodiment of the first power transmission section 11, Figure 4 shows a second embodiment of the first power transmission section 11, Figure 5 shows a third embodiment of the first power transmission section 11, Figure 6 shows a fourth embodiment of the first power transmission section 11, Figure 7 shows a fifth embodiment of the first power transmission section 11, and Figure 8 shows a sixth embodiment of the first power transmission section 11.

[0034] <First power transmission section (basic configuration)> The configuration of the first power transmission portion 11 will be described below.

[0035] First, the configuration of the first power transmission section 11 that is common to all the embodiments (first to sixth embodiments) (basic configuration of the first power transmission section 11) will be described.

[0036] 2 to 8, the first power transmission section 11 has a first flywheel 13 and a second flywheel 14. The first flywheel 13 and the second flywheel 14 receive rotational power from the engine 4 and rotate.

[0037] The second flywheel 14 is formed in a disk shape. The second flywheel 14 is connected to the output shaft (crankshaft) 4a of the engine 4. Therefore, the second flywheel 14 rotates at the same rotation speed as the rotation speed of the engine 4. In this specification, the term "rotation speed" refers to the number of rotations per unit time (for example, rpm).

[0038] The first flywheel 13 is configured in a cylindrical shape having a through-hole 13d penetrating the first flywheel 13 in the front-rear direction. Specifically, the first flywheel 13 has an outer cylindrical portion 13a, an inner cylindrical portion 13b, and a connecting portion 13c. The outer cylindrical portion 13a is a cylindrical portion that includes the outer peripheral surface of the first flywheel 13. The inner cylindrical portion 13b is a cylindrical portion that includes the inner peripheral surface of the first flywheel 13, and is disposed inside (on the inner circumferential side of) the outer cylindrical portion 13a. The inner circumferential side of the inner cylindrical portion 13b forms the through-hole 13d. The connecting portion 13c is formed in a disk shape that connects the outer cylindrical portion 13a and the inner cylindrical portion 13b.

[0039] The first flywheel 13 may be configured with only the outer cylindrical portion 13a among the outer cylindrical portion 13a, the inner cylindrical portion 13b, and the connecting portion 13c. In this case, the portions corresponding to the inner cylindrical portion 13b and the connecting portion 13c are configured with a member separate from the first flywheel 13, and the separate member and the outer cylindrical portion 13a are connected to rotate integrally.

[0040] An intermediate shaft 17 is inserted through the through-hole 13d of the first flywheel 13. The intermediate shaft 17 passes through the center of the first flywheel 13 and extends in the front-to-rear direction. The intermediate shaft 17 acts as an intermediate between the second flywheel 14 and the transmission 16. The inner cylindrical portion 13b is supported by a bearing provided on the intermediate shaft 17. This allows the inner cylindrical portion 13b to be rotatable relative to the intermediate shaft 17. This allows the first flywheel 13 to rotate about the axis of the intermediate shaft 17 independently of the intermediate shaft 17.

[0041] The inner cylindrical portion 13b may be directly supported by a bearing provided on the intermediate shaft 17, or may be indirectly supported by a bearing provided on the intermediate shaft 17 via another member. In the latter case, the first flywheel 13 is connected to another member (such as a support member 65 (see FIG. 11) described below), and the other member is supported on the intermediate shaft 17 via the bearing.

[0042] The first flywheel 13 is disposed between the second flywheel 14 and the transmission 16 in the axial direction (front-rear direction) of the output shaft 4a. The first flywheel 13 receives rotational power from the engine 4 via the first flywheel 13 and a speed increasing mechanism 20, which will be described later, and rotates.

[0043] A first rotation speed sensor 18 is provided near the first flywheel 13 to measure the rotation speed of the first flywheel 13. A second rotation speed sensor 15 is provided near the second flywheel 14 to measure the rotation speed of the second flywheel 14 (= the rotation speed of the engine 4).

[0044] The first power transmission unit 11 has a first power transmission path 31 and a second power transmission path 32 .

[0045] The first power transmission path 31 is a path that transmits the rotational power of the engine 4 to the first flywheel 13. The second power transmission path 32 is a path that transmits the rotational power of the first flywheel 13 to the transmission 16.

[0046] The first power transmission path 31 and the second power transmission path 32 are paths independent of each other. Therefore, when the rotational power of the engine 4 is transmitted to the first flywheel 13, the rotational power of the engine 4 is transmitted to the first flywheel 13 via the first power transmission path 31 without passing through the second power transmission path 32. Furthermore, when the rotational power of the first flywheel 13 is transmitted to the transmission 16, the rotational power of the first flywheel 13 is transmitted to the transmission 16 via the second power transmission path 32 without passing through the first power transmission path 31.

[0047] The first power transmission section 11 includes a clutch device 25 consisting of a first clutch 26 and a second clutch 27. The first power transmission path 31 is provided with the first clutch 26. The second power transmission path 32 is provided with the second clutch 27.

[0048] The first power transmission path 31 is a path that passes through the first clutch 26 but does not pass through the second clutch 27. The second power transmission path 32 is a path that passes through the second clutch 27 but does not pass through the first clutch 26.

[0049] The first clutch 26 connects or disconnects (connects or disconnects) the transmission of rotational power from the engine 4 to the first flywheel 13. The second clutch 27 connects or disconnects (connects or disconnects) the transmission of rotational power from the first flywheel 13 to the transmission 16.

[0050] The first clutch 26 and the second clutch 27 are hydraulic clutches that operate by the supply of hydraulic oil. The first clutch 26 includes first friction plates 26A, second friction plates 26B, and a hydraulic piston. The second clutch 27 includes first friction plates 27A, second friction plates 27B, and a hydraulic piston. By driving the hydraulic piston, the first friction plates 26A, 27A can be moved, and the first friction plates 26A, 27A and the second friction plates 26B, 27B can be switched between a pressed-contact state and a separated state.

[0051] In the first to sixth embodiments, the first friction plates 26A are configured to be pressed against or separated from the second friction plates 26B, and the first friction plates 27A are configured to be pressed against or separated from the second friction plates 27B. However, in each embodiment, the second friction plates 26B may be configured to be pressed against or separated from the first friction plates 26A, and the second friction plates 27B may be configured to be pressed against or separated from the first friction plates 27A.

[0052] The first clutch 26 is connected when the first friction plates 26A and the second friction plates 26B are in a pressed contact state, and is disconnected when the first friction plates 26A and the second friction plates 26B are in a separated state. The second clutch 27 is connected when the first friction plates 27A and the second friction plates 27B are in a pressed contact state, and is disconnected when the first friction plates 27A and the second friction plates 27B are in a separated state.

[0053] The first clutch 26 and the second clutch 27 each include a hydraulic control valve (not shown) that controls the supply of hydraulic oil to the oil chambers of the hydraulic pistons. The hydraulic control valve is configured as a solenoid valve controlled by the supply of electric current. The hydraulic control valve is configured as, for example, a proportional valve whose opening degree changes according to the current value. By supplying electric current to the hydraulic control valve, the opening and closing of the hydraulic control valve is controlled, and the supply of hydraulic oil to the oil chambers of the hydraulic pistons is controlled. This controls the operation of the hydraulic pistons, and the engagement and disengagement of the first clutch 26 and the second clutch 27 are controlled.

[0054] The first friction plates 26A, 27A are biased in the return direction (away from the second friction plates 26B, 27B) by a spring, and when hydraulic oil is supplied to the oil chamber of the hydraulic piston, they move against the biasing force of the spring and approach the second friction plates 26B, 27B.

[0055] When the first clutch 26 and the second clutch 27 are to be connected, first, a set amount of hydraulic oil that balances the biasing force of the spring is supplied in a single burst to increase the pressure of the hydraulic oil in the oil chamber of the piston (hereinafter referred to as a "connection preparation state"). Then, when the conditions for connecting the first clutch 26 and the second clutch 27 are met in the connection preparation state, hydraulic oil is continuously supplied at a pressure that allows the first friction plates 26A, 27A to be pressed against the second friction plates 26B, 27B. This connects the first clutch 26 and the second clutch 27. In other words, the connection preparation state transitions to the connected state. In this way, when connecting the clutches (first clutch 26, second clutch 27), the response of the clutch connection can be improved by passing through the connection preparation state before transitioning to the connected state.

[0056] In order to supply a set amount of hydraulic oil that balances the biasing force of the spring in a single burst, a single current (one-shot pulse current) is supplied to the hydraulic control valve (solenoid valve). In other words, when a one-shot pulse current is supplied to the hydraulic control valve, a set amount of hydraulic oil that balances the biasing force of the spring is supplied in a single burst, and the hydraulic control valve becomes ready for connection.

[0057] Hereinafter, supplying a one-shot pulse current will be referred to as "one-shot execution." Furthermore, the number of times a one-shot pulse current is supplied will be referred to as "the number of one-shot executions" or "the number of attempts to engage the clutch (first clutch 26 or second clutch 27)."

[0058] 3, the first clutch 26 is provided with a first pressure sensor 28. The second clutch 27 is provided with a second pressure sensor 29.

[0059] 4 to 8 (second to sixth embodiments), the first pressure sensor 28 and the second pressure sensor 29 are not shown, but the second to sixth embodiments also include the first pressure sensor 28 and the second pressure sensor 29, as in the first embodiment. Also, the first rotation speed sensor 18 and the second rotation speed sensor 15 are not shown in FIGS. 4 to 8 (second to sixth embodiments), but the second to sixth embodiments also include the first rotation speed sensor 18 and the second rotation speed sensor 15, as in the first embodiment.

[0060] First pressure sensor 28 detects the pressure of hydraulic oil in an oil passage (operating pressure of the oil passage piston) for supplying hydraulic oil to the hydraulic piston of first clutch 26. Second pressure sensor 29 detects the pressure of hydraulic oil in an oil passage (operating pressure of the oil passage piston) for supplying hydraulic oil to the hydraulic piston of second clutch 27. The states (engaged state, disengaged state) of first clutch 26 and second clutch 27 can be determined from the pressure of hydraulic oil detected by first pressure sensor 28 and second pressure sensor 29.

[0061] 3 to 8, the first power transmission path 31 is provided with the speed-increasing mechanism 20. In other words, the first power transmission path 31 is a path that passes through the speed-increasing mechanism 20. On the other hand, the second power transmission path 32 is a path that does not pass through the speed-increasing mechanism 20. However, the speed-increasing mechanism 20 does not necessarily have to be provided in the first power transmission path 31.

[0062] The speed-increasing mechanism 20 is a mechanism that increases the rotational power of the engine 4 and transmits it to the first flywheel 13. The speed-increasing mechanism 20 is composed of a planetary gear mechanism including a sun gear 21, planetary gears 22, and a ring gear 23. The ring gear 23 is fixed to the flywheel housing 9. Therefore, the ring gear 23 is unable to rotate. The planetary gears 22 mesh with the internal teeth of the ring gear 23. The sun gear 21 meshes with the planetary gears 22. The sun gear 21 can rotate around the axis of the intermediate shaft 17. The planetary gears 22 can rotate (revolve) around the periphery of the sun gear 21.

[0063] FIG. 9 is a collinear diagram of the planetary gear mechanism constituting the speed-increasing mechanism 20. The vertical axis in FIG. 9 represents the number of rotations (rotational speed). As indicated by arrow B in FIG. 9, the planetary gear mechanism constituting the speed-increasing mechanism 20 can increase the rotational power input from the planetary gear 22 and output it from the sun gear 21. The speed-increasing ratio of the speed-increasing mechanism 20 is set to a value exceeding 1 (i.e., speed-increasing ratio > 1), preferably 2 or more, and more preferably 3 or more. As an example, the speed-increasing ratio can be set in the range of 3 to 5.

[0064] The rotational power of the engine 4 is input to the planetary gear 22 of the speed-increasing mechanism 20, transmitted from the planetary gear 22 to the sun gear 21, and transmitted from the sun gear 21 to the first flywheel 13. As a result, the rotational power of the engine 4 is accelerated and transmitted to the first flywheel 13. As a result, the rotational speed of the first flywheel 13 becomes higher than the rotational speed (actual rotational speed) of the engine 4. (Hereinafter, unless otherwise specified, the rotational speed of the engine 4 refers to the actual rotational speed of the engine 4.) This allows a large amount of rotational energy to be stored in the first flywheel 13.

[0065] As described above, by providing the speed increasing mechanism 20 in the first power transmission path 31, the first power transmission path 31 can increase the rotational power of the engine 4 via the speed increasing mechanism 20 and transmit it to the first flywheel 13.

[0066] On the other hand, the second power transmission path 32 is not provided with a speed-increasing mechanism 20. If the second power transmission path 32 were a path that passed through the speed-increasing mechanism 20 provided in the first power transmission path 31, the speed-increasing mechanism 20 would function as a speed-reduction mechanism. Specifically, the rotational power of the first flywheel 13 is input to the sun gear 21 and transmitted to the first flywheel 13 via the planetary gears 22. Therefore, the rotational power of the first flywheel 13 is decelerated and transmitted to the transmission 16. In contrast, in the embodiment according to the present invention, the second power transmission path 32 is not provided with a speed-increasing mechanism 20, and therefore the rotational power of the first flywheel 13 is transmitted to the transmission 16 without being decelerated. Therefore, it can be said that the second power transmission path 32 is not provided with a speed-reduction mechanism.

[0067] In this way, since the second power transmission path 32 is not provided with a speed reduction mechanism, the second power transmission path 32 transmits the rotational power of the first flywheel 13 to the transmission 16 without going through a speed reduction mechanism. Therefore, the second power transmission path 32 can transmit the rotational power of the first flywheel 13 to the transmission 16 without reducing the speed.

[0068] In the first to sixth embodiments, the second power transmission path 32 is not provided with a mechanism for increasing the speed of the rotational power of the first flywheel 13 and transmitting it to the transmission 16. Therefore, the rotation speed of the first flywheel 13 and the rotation speed input to the input shaft 16a of the transmission 16 are equal to each other.

[0069] From the above, "the first power transmission path 31 and the second power transmission path 32 are paths independent of each other" can also be specifically stated as "the first power transmission path 31 is a path that passes through the speed-up mechanism 20, while the second power transmission path 32 is a path that does not pass through the speed-up mechanism 20 provided in the first power transmission path 31."

[0070] However, the second power transmission path 32 may be provided with a speed-increasing mechanism different from the speed-increasing mechanism 20 (a speed-increasing mechanism independent of the speed-increasing mechanism 20) provided in the first power transmission path 31. In this case, the second power transmission path 32 can increase the speed of the rotational power of the first flywheel 13 and transmit it to the transmission 16. Therefore, the rotation speed input to the input shaft 16a of the transmission 16 becomes higher than the rotation speed of the first flywheel 13.

[0071] As shown in FIGS. 3 to 8, the first power transmission unit 11 has a third power transmission path 33.

[0072] The third power transmission path 33 is a path that transmits the rotational power of the engine 4 to the transmission 16 without passing through the first flywheel 13. The third power transmission path 33 is also a path that transmits the rotational power of the engine 4 to the transmission 16 without passing through either the first clutch 26 or the second clutch 27. In other words, the third power transmission path 33 is not provided with a clutch that connects and disconnects the path. Therefore, the third power transmission path 33 constantly connects the output shaft 4a of the engine 4 and the input shaft 16a of the transmission 16.

[0073] The third power transmission path 33 includes an intermediate shaft 17 interposed between the output shaft 4a of the engine 4 and the transmission 16. The intermediate shaft 17 passes through the through hole 13d of the first flywheel 13. Therefore, the third power transmission path 33 is formed by passing through the through hole 13d of the first flywheel 13. The third power transmission path 33 linearly connects the output shaft 4a of the engine 4 and the input shaft 16a of the transmission 16 via the second flywheel 14 and the intermediate shaft 17.

[0074] One end (front end) of the intermediate shaft 17 is connected to the second flywheel 14. The other end (rear end) of the intermediate shaft 17 is connected to the input shaft 16a of the transmission 16. In this way, the intermediate shaft 17 connects the second flywheel 14 and the transmission 16.

[0075] As shown in FIG. 2, the first flywheel 13, the second flywheel 14, the first clutch 26, and the second clutch 27 are accommodated inside a flywheel housing 9. The flywheel housing 9 has a first wall 9a, a second wall 9b, and a peripheral wall 9c. The first wall 9a and the second wall 9b are arranged opposite each other. The first wall 9a is arranged on the engine 4 side (front side). The second flywheel 14 is arranged near the inner surface (rear surface) of the first wall 9a. The second wall 9b is arranged on the transmission 16 side (rear side). The transmission 16 is arranged near the outer surface (rear surface) of the second wall 9b. The peripheral wall 9c connects the first wall 9a and the second wall 9b. The peripheral wall 9c is provided to surround the peripheries (outer periphery side) of the first flywheel 13, the second flywheel 14, the first clutch 26, and the second clutch 27.

[0076] The first flywheel 13 can rotate independently of the second flywheel 14. Specifically, when the first clutch 26 and the second clutch 27 are disengaged, the first flywheel 13 can rotate independently of the second flywheel 14. When the first clutch 26 and the second clutch 27 are disengaged, once the first flywheel 13 starts to rotate, it can continue to rotate even when the second flywheel 14 stops.

[0077] The above is the basic configuration of the first power transmission portion 11 (common to all the embodiments).

[0078] Next, before describing the configuration other than the basic configuration of the first power transmission unit 11, the configuration of the second power transmission unit 12 will be described in order to understand the overall configuration of the power transmission mechanism 6.

[0079] <Second power transmission section> The configuration of the second power transmission portion 12 will be described below with reference to FIG.

[0080] The second power transmission section 12 has a transmission 16 .

[0081] The transmission 16 is a hydrostatic continuously variable transmission (HST: Hydro Static Transmission). The transmission 16 has a hydraulic pump P1 and a hydraulic motor M1. The hydraulic pump P1 and the hydraulic motor M1 are connected by an oil passage (oil circulation passage) through which hydraulic oil flows. The hydraulic pump P1 is a variable displacement pump that can change the amount of hydraulic oil discharged. The hydraulic pump P1 is driven by power input from an input shaft 16a of the transmission 16 to discharge hydraulic oil. The hydraulic motor M1 is driven by the hydraulic oil discharged from the hydraulic pump P1. The driving speed of the hydraulic motor M1 can be continuously adjusted by increasing or decreasing the amount of hydraulic oil supplied from the hydraulic pump P1.

[0082] The rotational power is transmitted to the transmission 16 from the first power transmission unit 11. The transmission 16 selectively receives the rotational power of either the engine 4 or the engine 4 and the first flywheel 13, changes the speed, and outputs the rotational power. In other words, the transmission 16 may receive the rotational power of the engine 4, change the speed, and output the rotational power, or may receive the rotational power of the engine 4 and the first flywheel 13, change the speed, and output the rotational power.

[0083] Specifically, when the second clutch 27 is disengaged, the transmission 16 receives only the rotational power of the engine 4, changes the speed, and outputs the power. At this time, the rotational power of the engine 4 is transmitted via the third power transmission path 33. When the second clutch 27 is engaged, the transmission 16 receives the rotational power of the engine 4 and the first flywheel 13, changes the speed, and outputs the power. At this time, the rotational power of the engine 4 is transmitted via the third power transmission path 33, and the rotational power of the first flywheel 13 is transmitted via the second power transmission path 32.

[0084] The transmission 16 has a first output shaft 16b and a second output shaft 16c. The first output shaft 16b is a shaft that outputs power to the PTO shaft 8. The second output shaft 16c is a shaft that outputs power to the traveling device 3.

[0085] The second power transmission unit 12 has a clutch unit 41 and a speed change unit .

[0086] The clutch unit 41 has a PTO clutch 43 .

[0087] The PTO clutch 43 can connect and disconnect the rotational power output from the first output shaft 16b. When the PTO clutch 43 is connected, the rotational power output from the first output shaft 16b is taken out from the first transmission shaft 44, and the PTO shaft 8 can be rotated by the taken out rotational power. When the PTO clutch 43 is disconnected, the rotational power output from the first output shaft 16b is not taken out from the first transmission shaft 44, so that the rotation of the PTO shaft 8 stops.

[0088] The transmission unit 42 has a PTO transmission unit 45 and a travel transmission unit 46 .

[0089] The PTO transmission unit 45 is capable of changing the speed of the rotational power extracted from the first transmission shaft 44 and outputting it to the PTO shaft 8. A first torque sensor 35 is provided between the PTO transmission unit 45 and the PTO shaft 8. The first torque sensor 35 is capable of detecting the torque acting on the PTO shaft 8.

[0090] A power relay unit 40 is provided between the traveling transmission unit 46 and the second output shaft 16c. The power relay unit 40 transmits the power output from the second output shaft 16c to the traveling transmission unit 46. A second torque sensor 36 is provided on a second transmission shaft 50 that extracts power from the power relay unit 40. The second torque sensor 36 can detect the torque acting on the second transmission shaft 50.

[0091] The traveling transmission unit 46 changes the speed of the rotational power transmitted from the second output shaft 16c of the transmission 16 via the second transmission shaft 50 and transmits the changed speed to the traveling device 3. The traveling transmission unit 46 is provided with a third rotation speed sensor 37. The third rotation speed sensor 37 can detect the rotation speed of the rotational power transmitted to the traveling device 3.

[0092] The traveling transmission unit 46 has a gear transmission mechanism 48 and a differential gear 49. The gear transmission mechanism 48 can change the speed of the rotational power extracted from the second transmission shaft 50 and transmit it to the differential gear 49. The differential gear 49 transmits the rotational power transmitted from the gear transmission mechanism 48 to the rear wheel 3R of the traveling device 3.

[0093] <First power transmission section (specific configuration)> Next, a specific configuration of the first power transmission portion 11 will be described.

[0094] The specific configuration of the first power transmission portion 11 differs among the first to sixth embodiments shown in FIGS. 3 to 8, and will therefore be described for each embodiment.

[0095] <<First Embodiment>> First, a specific configuration of the first power transmission section 11 according to the first embodiment will be described with reference to Fig. 3. Hereinafter, the first power transmission section 11 according to the first embodiment will be referred to as "first power transmission section 11A."

[0096] In the first power transmission section 11A, the first clutch 26 and the second clutch 27 are arranged side by side in the axial direction (front-rear direction) of the intermediate shaft 17. The first clutch 26 is arranged on the second flywheel 14 side (front side). The second clutch 27 is arranged on the transmission 16 side (rear side). The first clutch 26 is arranged near the first wall 9a of the flywheel housing 9. The second clutch 27 is arranged near the second wall 9b of the flywheel housing 9. The second clutch 27 is also arranged on the inner peripheral side of the first flywheel 13.

[0097] The first clutch 26 is a single-plate clutch and includes one first friction plate 26A and one second friction plate 26B. The first friction plate 26A is formed in a disk or annular shape. The second friction plate 26B is formed in annular shape.

[0098] The first friction plate 26A of the first clutch 26 is attached to one end side (second flywheel 14 side) of the intermediate shaft 17 and is movable in the axial direction of the intermediate shaft 17. The second friction plate 26B of the first clutch 26 is attached to the planetary gear 22 of the speed increasing mechanism 20.

[0099] The second clutch 27 is also a single-plate clutch and has one first friction plate 27A and one second friction plate 27B. The first friction plate 27A is formed in a disk or annular shape. The second friction plate 27B is formed in annular shape.

[0100] The first friction plate 27A of the second clutch 27 is attached to the other end side (transmission device 16 side) of the intermediate shaft 17 and is movable in the axial direction of the intermediate shaft 17. The second friction plate 27B of the second clutch 27 is attached to the first flywheel 13.

[0101] The first power transmission path 31 of the first power transmission unit 11A is a path that transmits the rotational power of the engine 4 in the following order: the second flywheel 14, the intermediate shaft 17, the first clutch 26, the planetary gear 22, and the sun gear 21, and then to the first flywheel 13.

[0102] The second power transmission path 32 of the first power transmission unit 11A is a path that transmits the rotational power of the first flywheel 13 to the second clutch 27 and the intermediate shaft 17 in this order, and then to the transmission 16.

[0103] The third power transmission path 33 of the first power transmission unit 11A is a path that transmits the rotational power of the engine 4 to the transmission 16 via the intermediate shaft 17.

[0104] The operation of the first power transmission section 11A will now be described.

[0105] The rotational power output from the output shaft 4a of the engine 4 is transmitted to the second flywheel 14. This causes the second flywheel 14 to rotate, and the intermediate shaft 17 connected to the second flywheel 14 also rotates. At this time, the rotational speed of the engine 4, the rotational speed of the second flywheel 14, and the rotational speed of the intermediate shaft 17 become the same. The rotational power transmitted from the output shaft 4a to the intermediate shaft 17 is then transmitted from the intermediate shaft 17 to the input shaft 16a of the transmission 16.

[0106] In this way, the rotational power output from the output shaft 4a of the engine 4 is transmitted to the transmission 16 via the intermediate shaft 17 that constitutes the third power transmission path 33. The transmission of the rotational power via this third power transmission path 33 is always performed regardless of whether the first clutch 26 and the second clutch 27 are engaged or disengaged.

[0107] When the first clutch 26 is in an engaged state and the second clutch 27 is in a disengaged state, the rotational power output from the output shaft 4a of the engine 4 is transmitted to the first flywheel 13 via the first power transmission path 31. Specifically, the rotational power transmitted from the output shaft 4a of the engine 4 to the second flywheel 14 and the intermediate shaft 17 is transmitted from the first friction plate 26A to the second friction plate 26B of the first clutch 26. This causes the planetary gear 22 to rotate, and the sun gear 21 rotates in conjunction with the rotation of the planetary gear 22. Then, because the sun gear 21 is connected to the first flywheel 13, the first flywheel 13 rotates together with the sun gear 21. In this way, the rotational power of the engine 4 is transmitted to the first flywheel 13 via the first clutch 26 and the speed increasing mechanism 20.

[0108] Here, the rotational power of the engine 4 is accelerated when it is transmitted from the planetary gear 22 to the sun gear 21. Therefore, the rotational power of the engine 4 is accelerated and transmitted to the first flywheel 13. As a result, the first flywheel 13 rotates at a rotational speed higher than the rotational speed of the engine 4. As a result, a high rotational energy can be stored in the first flywheel 13.

[0109] When the first clutch 26 is in a disengaged state and the second clutch 27 is in an engaged state, the rotational power of the first flywheel 13 is transmitted to the transmission 16 via the second power transmission path 32. Specifically, the rotational power of the first flywheel 13 is transmitted from the second friction plate 27B of the second clutch 27 to the first friction plate 27A. As a result, the rotational power of the first flywheel 13 is transmitted from the first friction plate 27A to the intermediate shaft 17, and from the intermediate shaft 17 to the input shaft 16a of the transmission 16. At this time, the rotational power of the first flywheel 13 is transmitted to the input shaft 16a of the transmission 16 without being reduced in speed (without passing through a reduction mechanism).

[0110] According to the power transmission mechanism 6 including the above-described first power transmission part 11A, the following operational effects can be achieved.

[0111] By connecting the first clutch 26 and disconnecting the second clutch 27, the rotational power of the engine 4 can be accelerated and transmitted to the first flywheel 13. This allows a large amount of rotational energy to be stored in the first flywheel 13.

[0112] Furthermore, by disengaging the first clutch 26 and engaging the second clutch 27, the rotational power of the first flywheel 13 can be transmitted to the transmission 16 without decelerating. This allows the high rotational energy stored in the first flywheel 13 to be transmitted to the transmission 16. At this time, the rotational power output from the output shaft 4a of the engine 4 can also be transmitted to the transmission 16 via the third power transmission path 33. This allows both the rotational power of the engine 4 and the rotational power of the first flywheel 13 to be transmitted to the transmission 16. Therefore, when the rotational power of the engine 4 is insufficient due to an increase in the load of the working device connected to the PTO shaft 8, for example, the rotational power of the first flywheel 13 can effectively assist the rotational power of the engine 4. This prevents or suppresses a decrease in the rotational speed of the engine 4 when the load of the working device connected to the PTO shaft 8 increases.

[0113] The first power transmission sections 11 according to the first to sixth embodiments each have their own unique features, but the features of the first power transmission section 11A according to the first embodiment are as follows.

[0114] In the case of the first power transmission section 11A according to the first embodiment, the first clutch 26 is disposed near the first wall 9a of the flywheel housing 9, and the second clutch 27 is disposed near the second wall 9b of the flywheel housing 9. Therefore, an oil passage for supplying hydraulic oil to the first clutch 26 can be provided along the first wall 9a, and an oil passage for supplying hydraulic oil to the second clutch 27 can be provided along the second wall 9b. This makes it easy to provide oil passages for supplying hydraulic oil to the first clutch 26 and the second clutch 27. In other words, the oil passage structure is excellent in terms of oil passage establishment.

[0115] Furthermore, by providing a bearing on the first wall 9a of the flywheel housing 9, one end of the intermediate shaft 17 can be rotatably supported. Furthermore, by providing a bearing on the second wall 9b of the flywheel housing 9, the other end of the intermediate shaft 17 or the input shaft 16a of the transmission 16 connected to the other end can be rotatably supported. This makes it possible to reliably and easily support both ends of the intermediate shaft 17 for rotation. In other words, the shaft support is excellent.

[0116] Furthermore, because the first clutch 26 and the second clutch 27 are made up of single-plate clutches, the clutches and the structures associated with them can be simplified, and the number of parts can be reduced. In other words, this is advantageous in that the number of parts can be reduced.

[0117] <<Second embodiment>> Next, a specific configuration of the first power transmission section 11 according to the second embodiment will be described with reference to Fig. 4. Hereinafter, the first power transmission section 11 according to the second embodiment will be referred to as "first power transmission section 11B."

[0118] In the first power transmission section 11B, the first clutch 26 and the second clutch 27 are disposed on the transmission 16 side (rear side) in the axial length direction (front-rear direction) of the intermediate shaft 17. The first clutch 26 and the second clutch 27 are disposed with a shift in position in the front-rear direction. Specifically, the first clutch 26 is disposed forward of the second clutch 27. The rear part of the first clutch 26 and the front part of the second clutch 27 are positioned to overlap in the front-rear direction.

[0119] The first clutch 26 is disposed on the outer circumferential side (the side farther from the intermediate shaft 17). The second clutch 27 is disposed on the inner circumferential side (the side closer to the intermediate shaft 17). In other words, the second clutch 27 is disposed on the inner circumferential side of the first clutch 26.

[0120] The first clutch 26 is disposed on the inner peripheral side of the first flywheel 13. The first clutch 26 is positioned so as to overlap with the first flywheel 13 in the front-rear direction. The second clutch 27 is positioned so that only the front portion thereof overlaps with the first flywheel 13 in the front-rear direction.

[0121] The first clutch 26 is disposed on the inner peripheral side of the speed increasing mechanism 20 (the inner peripheral side of the sun gear 21). The second clutch 27 is disposed in front of the speed increasing mechanism 20.

[0122] The first clutch 26 is a multi-plate clutch and includes a plurality of first friction plates 26A and a plurality of second friction plates 26B. The first friction plates 26A and the second friction plates 26B are arranged alternately in the front-rear direction. The first friction plates 26A and the second friction plates 26B are formed in an annular shape. An intermediate shaft 17 passes through the centers of the first friction plates 26A and the second friction plates 26B.

[0123] The first friction plate 26A is attached to the first flywheel 13. The first friction plate 26A is movable in the axial direction of the intermediate shaft 17. The second friction plate 26B is attached to the sun gear 21 of the speed increasing mechanism 20.

[0124] The second clutch 27 is also a multi-plate clutch and has a plurality of first friction plates 27A and a plurality of second friction plates 27B. The first friction plates 27A and the second friction plates 27B are arranged alternately in the front-rear direction. The first friction plates 27A and the second friction plates 27B are formed in an annular shape. An intermediate shaft 17 passes through the centers of the first friction plates 27A and the second friction plates 27B.

[0125] The first friction plate 27A is attached to the first flywheel 13. The first friction plate 27A is movable in the axial direction of the intermediate shaft 17. The second friction plate 27B is connected to the planetary gear 22 of the speed increasing mechanism 20.

[0126] The first power transmission path 31 of the first power transmission unit 11B is a path that transmits the rotational power of the engine 4 in the following order: the second flywheel 14, the intermediate shaft 17, the planetary gear 22, the sun gear 21, and the first clutch 26, and then transmits it to the first flywheel 13.

[0127] The second power transmission path 32 of the first power transmission unit 11B is a path that transmits the rotational power of the first flywheel 13 to the transmission 16 via the second clutch 27.

[0128] The third power transmission path 33 of the first power transmission unit 11B is a path that transmits the rotational power of the engine 4 to the transmission 16 via the intermediate shaft 17. The third power transmission path 33 transmits the rotational power of the engine 4 to the transmission 16 without passing through either the first clutch 26 or the second clutch 27.

[0129] The operation of the first power transmission section 11B will now be described.

[0130] The rotational power output from the output shaft 4a of the engine 4 is transmitted to the second flywheel 14. This causes the second flywheel 14 to rotate, and the intermediate shaft 17 connected to the second flywheel 14 to also rotate. At this time, the rotational speed of the engine 4, the rotational speed of the second flywheel 14, and the rotational speed of the intermediate shaft 17 become the same. The rotational power transmitted to the intermediate shaft 17 is transmitted to the input shaft 16a of the transmission 16.

[0131] In this way, the rotational power output from the output shaft 4a of the engine 4 is transmitted to the transmission 16 via the third power transmission path 33. The transmission of the rotational power via this third power transmission path 33 is always performed regardless of whether the first clutch 26 and the second clutch 27 are engaged or disengaged.

[0132] When the first clutch 26 is in an engaged state and the second clutch 27 is in a disengaged state, the rotational power output from the output shaft 4a of the engine 4 is transmitted to the first flywheel 13 via the first power transmission path 31. Specifically, the rotational power transmitted from the engine 4 to the second flywheel 14 is transmitted from the second flywheel 14 to the planetary gear 22 via the intermediate shaft 17. This causes the planetary gear 22 to rotate, and the sun gear 21 rotates in conjunction with the rotation of the planetary gear 22. The sun gear 21 is connected to the second friction plate 26B of the first clutch 26. Therefore, the rotational power of the sun gear 21 is transmitted to the second friction plate 26B, and then from the second friction plate 26B to the first flywheel 13 via the first friction plate 26A.

[0133] Here, the rotational power of the engine 4 is accelerated when it is transmitted from the planetary gear 22 to the sun gear 21. That is, the rotational power of the engine 4 is accelerated and transmitted to the first flywheel 13. Therefore, the first flywheel 13 rotates at a rotational speed higher than the rotational speed of the engine 4. This allows high rotational energy to be stored in the first flywheel 13.

[0134] Furthermore, when the first clutch 26 is disengaged and the second clutch 27 is engaged, the second power transmission path 32 is connected, and therefore the rotational power of the first flywheel 13 is transmitted to the transmission 16. Specifically, the rotational power of the first flywheel 13 is transmitted from the first friction plate 27A to the second friction plate 27B of the second clutch 27. As a result, the rotational power of the first flywheel 13 is transmitted from the second friction plate 27B to the input shaft 16a of the transmission 16 via the intermediate shaft 17. At this time, the rotational power of the first flywheel 13 is transmitted to the input shaft 16a of the transmission 16 without being reduced in speed (without passing through a reduction mechanism). Therefore, the high rotational energy of the first flywheel 13 can be input directly to the transmission 16.

[0135] When the first clutch 26 and the second clutch 27 are both in a disengaged state, the first power transmission path 31 and the second power transmission path 32 are disconnected, so that the rotational power of the engine 4 is not transmitted to the first flywheel 13, and the rotational power of the first flywheel 13 is not transmitted to the transmission 16.

[0136] The first power transmission part 11B can achieve the same effects as those of the first power transmission part 11A described above.

[0137] The first power transmission section 11B according to the second embodiment has the following features.

[0138] In the first power transmission section 11B according to the second embodiment, the first clutch 26 and the second clutch 27 are configured as multi-plate clutches, and therefore high power transmission performance can be obtained between the first friction plates 26A, 27A and the second friction plates 26B, 27B. Therefore, the power transmission performance of the clutch device 25 is superior to that of the first power transmission section 1A.

[0139] Furthermore, because the clutch device 25 has excellent power transmission performance, power can be reliably transmitted to the first flywheel 13, and high rotational energy can be stored in the first flywheel 13. Therefore, the first power transmission unit 1A is superior to the first power transmission unit 1A in the storage performance of rotational energy by the first flywheel 13.

[0140] <<Third Embodiment>> Next, a specific configuration of the first power transmission section 11 according to the third embodiment will be described with reference to Fig. 5. Hereinafter, the first power transmission section 11 according to the third embodiment will be referred to as "first power transmission section 11C."

[0141] In the first power transmission section 11C, the first clutch 26 and the second clutch 27 are arranged side by side in the radial direction of the intermediate shaft 17 (direction away from the axis of the intermediate shaft 17). The first clutch 26 is arranged on the outer circumferential side (side farther from the intermediate shaft 17). The second clutch 27 is arranged on the inner circumferential side (side closer to the intermediate shaft 17). In other words, the second clutch 27 is arranged on the inner circumferential side of the first clutch 26. The first clutch 26 and the second clutch 27 are arranged near the second wall 9b of the flywheel housing 9. Specifically, the first clutch 26 and the second clutch 27 are arranged in a position facing the second wall 9b.

[0142] The first clutch 26 and the second clutch 27 are disposed between the first flywheel 13 and the transmission 16 in the front-rear direction. The first clutch 26 and the second clutch 27 are offset from the first flywheel 13 in the front-rear direction. In other words, the first clutch 26 and the second clutch 27 do not overlap with the first flywheel 13 in the front-rear direction. The outer diameter of the clutch device 25 consisting of the first clutch 26 and the second clutch 27 is smaller than the outer diameter of the first flywheel 13.

[0143] The first clutch 26 is a multi-plate clutch and has a plurality of first friction plates 26A and a plurality of second friction plates 26B. The plurality of first friction plates 26A and the plurality of second friction plates 26B of the first clutch 26 are arranged alternately in the front-rear direction. The first friction plates 26A and the second friction plates 26B are formed in an annular shape. An intermediate shaft 17 passes through the centers of the first friction plates 26A and the second friction plates 26B.

[0144] The first friction plate 26A is attached to the intermediate shaft 17 and is movable in the axial direction of the intermediate shaft 17. The second friction plate 26B is attached to the planetary gear 22 of the speed increasing mechanism 20.

[0145] The second clutch 27 is also a multi-plate clutch and has a plurality of first friction plates 27A and a plurality of second friction plates 27B. The first friction plates 27A and the second friction plates 27B are arranged alternately in the front-rear direction. The first friction plates 27A and the second friction plates 27B are formed in an annular shape. An intermediate shaft 17 passes through the centers of the first friction plates 27A and the second friction plates 27B.

[0146] The first friction plate 27A is attached to the intermediate shaft 17 and is movable in the axial direction of the intermediate shaft 17. The second friction plate 27B is attached to the sun gear 21 of the speed increasing mechanism 20.

[0147] The first power transmission path 31 of the first power transmission unit 11C is a path that transmits the rotational power of the engine 4 in the order of the second flywheel 14, the intermediate shaft 17, the first clutch 26, the planetary gear 22, and the sun gear 21, and then transmits it to the first flywheel 13.

[0148] The second power transmission path 32 of the first power transmission unit 11C is a path that transmits the rotational power of the first flywheel 13 to the second clutch 27 and the intermediate shaft 17 in this order, and then to the transmission 16.

[0149] The third power transmission path 33 of the first power transmission unit 11C is a path that transmits the rotational power of the engine 4 to the transmission 16 via the intermediate shaft 17. The third power transmission path 33 transmits the rotational power of the engine 4 to the transmission 16 without passing through either the first clutch 26 or the second clutch 27.

[0150] The operation of the first power transmission section 11C will be described below.

[0151] The rotational power output from the output shaft 4a of the engine 4 is transmitted to the second flywheel 14. This causes the second flywheel 14 to rotate, and the intermediate shaft 17 connected to the second flywheel 14 also rotates. At this time, the rotational speed of the engine 4, the rotational speed of the second flywheel 14, and the rotational speed of the intermediate shaft 17 become the same. The rotational power transmitted from the output shaft 4a to the intermediate shaft 17 is then transmitted from the intermediate shaft 17 to the input shaft 16a of the transmission 16.

[0152] In this way, the rotational power output from the output shaft 4a of the engine 4 is transmitted to the transmission 16 via the intermediate shaft 17 that constitutes the third power transmission path 33. The transmission of the rotational power via this third power transmission path 33 is always performed regardless of whether the first clutch 26 and the second clutch 27 are engaged or disengaged.

[0153] When the first clutch 26 is in an engaged state and the second clutch 27 is in a disengaged state, the rotational power output from the output shaft 4a of the engine 4 is transmitted to the first flywheel 13 via the first power transmission path 31. Specifically, the rotational power transmitted from the output shaft 4a of the engine 4 to the second flywheel 14 and the intermediate shaft 17 is transmitted from the first friction plate 26A to the second friction plate 26B of the first clutch 26. This causes the planetary gear 22 to rotate, and the sun gear 21 rotates in conjunction with the rotation of the planetary gear 22. Then, because the sun gear 21 is connected to the first flywheel 13, the first flywheel 13 rotates together with the sun gear 21. In this way, the rotational power of the engine 4 is transmitted to the first flywheel 13 via the first clutch 26 and the speed increasing mechanism 20.

[0154] Here, the rotational power of the engine 4 is accelerated when it is transmitted from the planetary gear 22 to the sun gear 21. That is, the rotational power of the engine 4 is accelerated and transmitted to the first flywheel 13. Therefore, the first flywheel 13 rotates at a rotational speed higher than the rotational speed of the engine 4. This allows high rotational energy to be stored in the first flywheel 13.

[0155] When the first clutch 26 is in a disengaged state and the second clutch 27 is in an engaged state, the rotational power of the first flywheel 13 is transmitted to the transmission 16 via the second power transmission path 32. Specifically, the rotational power of the first flywheel 13 is transmitted from the second friction plate 27B of the second clutch 27 to the first friction plate 27A. As a result, the rotational power of the first flywheel 13 is transmitted from the first friction plate 27A to the intermediate shaft 17, and from the intermediate shaft 17 to the input shaft 16a of the transmission 16. At this time, the rotational power of the first flywheel 13 is transmitted to the input shaft 16a of the transmission 16 without being reduced in speed (without passing through a reduction mechanism).

[0156] The first power transmission part 11C can achieve the same effects as those of the first power transmission part 11A described above.

[0157] The first power transmission section 11C according to the third embodiment has the following features.

[0158] In the first power transmission section 11C according to the third embodiment, the first clutch 26 and the second clutch 27 are configured as multi-plate clutches, and therefore high power transmission performance can be obtained between the first friction plates 26A, 27A and the second friction plates 26B, 27B. In other words, the power transmission performance of the clutch device 25 is excellent.

[0159] Furthermore, because the first clutch 26 and the second clutch 27 are arranged side by side in the radial direction of the intermediate shaft 17, both the first clutch 26 and the second clutch 27 can be arranged near the second wall 9b of the flywheel housing 9. This allows an oil passage for supplying hydraulic oil to the first clutch 26 and an oil passage for supplying hydraulic oil to the second clutch 27 to be provided along the second wall 9b. This makes it easy to provide oil passages for supplying hydraulic oil to the first clutch 26 and the second clutch 27. In other words, the oil passage establishment is excellent.

[0160] Furthermore, by providing a bearing on the first wall 9a of the flywheel housing 9, one end of the intermediate shaft 17 can be rotatably supported. And by providing a bearing on the second wall 9b of the flywheel housing 9, the other end of the intermediate shaft 17 or the input shaft 16a of the transmission 16 connected to the other end can be rotatably supported. This makes it possible to reliably and easily support both ends of the intermediate shaft 17 for rotation. In other words, the shaft support is excellent.

[0161] Furthermore, since the first clutch 26 and the second clutch 27 are arranged side by side in the radial direction of the intermediate shaft 17 near the second wall 9b, it is possible to use the same members for supporting the first clutch 26 and the second clutch 27, thereby reducing the number of parts. In other words, this is advantageous in that the number of parts can be reduced.

[0162] <<Fourth Embodiment>> Next, a specific configuration of the first power transmission section 11 according to the fourth embodiment will be described with reference to Fig. 6. Hereinafter, the first power transmission section 11 according to the fourth embodiment will be referred to as "first power transmission section 11D."

[0163] In the first power transmission section 11D, the first clutch 26 and the second clutch 27 are arranged side by side in the axial direction (front-rear direction) of the intermediate shaft 17. The first clutch 26 is arranged at the rear (transmission 16 side) of the intermediate shaft 17 in the axial direction. The second clutch 27 is arranged at the front (second flywheel 14 side) of the intermediate shaft 17 in the axial direction. The first clutch 26 is arranged near the second wall 9b of the flywheel housing 9. The second clutch 27 is arranged near the first wall 9a of the flywheel housing 9.

[0164] The outer diameter of the first clutch 26 and the outer diameter of the second clutch 27 are smaller than the outer diameter of the first flywheel 13. The first clutch 26 and the second clutch 27 are disposed on the inner circumferential side of the first flywheel 13. More specifically, the first clutch 26 and the second clutch 27 are disposed on the inner circumferential side of the outer cylindrical portion 13a of the first flywheel 13.

[0165] The first clutch 26 is disposed between the speed increasing mechanism 20 and the transmission 16 in the front-rear direction. The speed increasing mechanism 20 is disposed between the first clutch 26 and the second clutch 27 in the front-rear direction.

[0166] The first clutch 26 and the second clutch 27 are positioned so that at least a portion of them overlaps with the first flywheel 13 in the front-rear direction. Specifically, the first clutch 26 is positioned so that its entirety overlaps with the first flywheel 13 in the front-rear direction. The second clutch 27 is positioned so that its front portion overlaps with the first flywheel 13 in the front-rear direction.

[0167] The first clutch 26 is a multi-plate clutch and includes a plurality of first friction plates 26A and a plurality of second friction plates 26B. The first friction plates 26A and the second friction plates 26B are arranged alternately in the front-rear direction. The first friction plates 26A and the second friction plates 26B are formed in an annular shape. An intermediate shaft 17 passes through the centers of the first friction plates 26A and the second friction plates 26B.

[0168] The first friction plate 26A is attached to the intermediate shaft 17 and is movable in the axial direction of the intermediate shaft 17. The second friction plate 26B is attached to the planetary gear 22 of the speed increasing mechanism 20.

[0169] The second clutch 27 is also a multi-plate clutch and has a plurality of first friction plates 27A and a plurality of second friction plates 27B. The first friction plates 27A and the second friction plates 27B are arranged alternately in the front-rear direction. The first friction plates 27A and the second friction plates 27B are formed in an annular shape. An intermediate shaft 17 passes through the centers of the first friction plates 27A and the second friction plates 27B.

[0170] The first friction plate 27A is attached to the intermediate shaft 17 and is movable in the axial direction of the intermediate shaft 17. The second friction plate 27B is attached to the first flywheel .

[0171] The first power transmission path 31 of the first power transmission unit 11D is a path that transmits the rotational power of the engine 4 in the order of the second flywheel 14, the intermediate shaft 17, the first clutch 26, the planetary gear 22, and the sun gear 21, and then transmits it to the first flywheel 13.

[0172] The second power transmission path 32 of the first power transmission unit 11D is a path that transmits the rotational power of the first flywheel 13 to the second clutch 27 and the intermediate shaft 17 in this order, and then to the transmission 16.

[0173] The third power transmission path 33 of the first power transmission unit 11D is a path that transmits the rotational power of the engine 4 to the transmission 16 via the intermediate shaft 17. The third power transmission path 33 transmits the rotational power of the engine 4 to the transmission 16 without passing through either the first clutch 26 or the second clutch 27.

[0174] The operation of the first power transmission part 11D will now be described.

[0175] The rotational power output from the output shaft 4a of the engine 4 is transmitted to the second flywheel 14. This causes the second flywheel 14 to rotate, and the intermediate shaft 17 connected to the second flywheel 14 also rotates. At this time, the rotational speed of the engine 4, the rotational speed of the second flywheel 14, and the rotational speed of the intermediate shaft 17 become the same. The rotational power transmitted from the output shaft 4a to the intermediate shaft 17 is then transmitted from the intermediate shaft 17 to the input shaft 16a of the transmission 16.

[0176] In this way, the rotational power output from the output shaft 4a of the engine 4 is transmitted to the transmission 16 via the intermediate shaft 17 that constitutes the third power transmission path 33. The transmission of the rotational power via this third power transmission path 33 is always performed regardless of whether the first clutch 26 and the second clutch 27 are engaged or disengaged.

[0177] When the first clutch 26 is in an engaged state and the second clutch 27 is in a disengaged state, the rotational power output from the output shaft 4a of the engine 4 is transmitted to the first flywheel 13 via the first power transmission path 31. Specifically, the rotational power transmitted from the output shaft 4a of the engine 4 to the second flywheel 14 and the intermediate shaft 17 is transmitted from the first friction plate 26A to the second friction plate 26B of the first clutch 26. This causes the planetary gear 22 to rotate, and the sun gear 21 rotates in conjunction with the rotation of the planetary gear 22. Then, because the sun gear 21 is connected to the first flywheel 13, the first flywheel 13 rotates together with the sun gear 21. In this way, the rotational power of the engine 4 is transmitted to the first flywheel 13 via the first clutch 26 and the speed increasing mechanism 20.

[0178] Here, the rotational power of the engine 4 is accelerated when it is transmitted from the planetary gear 22 to the sun gear 21. That is, the rotational power of the engine 4 is accelerated and transmitted to the first flywheel 13. Therefore, the first flywheel 13 rotates at a rotational speed higher than the rotational speed of the engine 4. This allows high rotational energy to be stored in the first flywheel 13.

[0179] When the first clutch 26 is in a disengaged state and the second clutch 27 is in an engaged state, the rotational power of the first flywheel 13 is transmitted to the transmission 16 via the second power transmission path 32. Specifically, the rotational power of the first flywheel 13 is transmitted from the second friction plate 27B of the second clutch 27 to the first friction plate 27A. As a result, the rotational power of the first flywheel 13 is transmitted from the first friction plate 27A to the intermediate shaft 17, and from the intermediate shaft 17 to the input shaft 16a of the transmission 16. At this time, the rotational power of the first flywheel 13 is transmitted to the input shaft 16a of the transmission 16 without being reduced in speed (without passing through a reduction mechanism).

[0180] The first power transmission part 11D can achieve the same effects as those of the first power transmission part 11A described above.

[0181] The first power transmission part 11D according to the fourth embodiment has the following features.

[0182] In the first power transmission section 11D according to the fourth embodiment, the first clutch 26 and the second clutch 27 are configured as multi-plate clutches, and therefore high power transmission performance can be obtained between the first friction plates 26A, 27A and the second friction plates 26B, 27B. In other words, the power transmission performance of the clutch device 25 is excellent.

[0183] Furthermore, because the first clutch 26 and the second clutch 27 are configured as multi-plate clutches and are arranged side by side in the axial direction of the intermediate shaft 17, the outer diameter of the clutch device 25 can be reduced and arranged on the inner peripheral side of the first flywheel 13 while maintaining high power transmission performance. This allows the axial length (length in the front-to-rear direction) of the first flywheel 13 to be increased, thereby increasing the moment of inertia of the first flywheel 13 and increasing the rotational energy that can be stored in the first flywheel 13. In other words, the first flywheel 13 has excellent rotational energy storage performance.

[0184] Furthermore, because the first clutch 26 and the second clutch 27 are arranged side by side in the axial direction of the intermediate shaft 17, the outer diameter of the clutch device 25 made up of the first clutch 26 and the second clutch 27 can be made smaller than that of the first power transmission parts 11B and 11C. This makes it possible to reduce the drag torque (friction torque that causes co-rotation) of the clutch device 25.

[0185] Furthermore, because first clutch 26 is disposed near second wall 9b and second clutch 27 is disposed near first wall 9a, an oil passage for supplying hydraulic oil to first clutch 26 can be provided along second wall 9b, and an oil passage for supplying hydraulic oil to second clutch 27 can be provided along first wall 9a. This makes it easy to provide oil passages for supplying hydraulic oil to first clutch 26 and second clutch 27. In other words, the oil passage structure is excellent in terms of oil passage establishment.

[0186] <<Fifth Embodiment>> Next, a specific configuration of the first power transmission section 11 according to the fifth embodiment will be described with reference to Fig. 7. Hereinafter, the first power transmission section 11 according to the fifth embodiment will be referred to as "first power transmission section 11E."

[0187] A partition wall 9d is provided inside the flywheel housing 9 that accommodates the first power transmission unit 11E according to the fifth embodiment. The partition wall 9d is provided between the first wall 9a and the second wall 9b. One surface of the partition wall 9d faces the first wall 9a. The other surface of the partition wall 9d faces the second wall 9b.

[0188] The partition wall 9d divides the interior of the flywheel housing 9 into a space 51 that houses the first flywheel 13 and a space 52 that houses the first clutch 26 and the second clutch 27. Hereinafter, the space 51 that houses the first flywheel 13 will be referred to as the "first space 51," and the space 52 that houses the first clutch 26 and the second clutch 27 will be referred to as the "second space 52."

[0189] The first space 51 is provided in the front part (engine 4 side) of the flywheel housing 9. In addition to the first flywheel 13, the second flywheel 14 is also accommodated in the first space 51. The second space 52 is provided in the rear part (transmission 16 side) of the flywheel housing 9. In addition to the first clutch 26 and the second clutch 27, the speed increasing mechanism 20 is also accommodated in the second space 52.

[0190] In the first power transmission section 11E, the first clutch 26 and the second clutch 27 are arranged side by side in the radial direction of the intermediate shaft 17 (direction away from the axis of the intermediate shaft 17). The first clutch 26 is arranged on the outer circumferential side (side farther from the intermediate shaft 17). The second clutch 27 is arranged on the inner circumferential side (side closer to the intermediate shaft 17). In other words, the second clutch 27 is arranged on the inner circumferential side of the first clutch 26.

[0191] The first clutch 26 and the second clutch 27 are disposed near the partition wall 9d of the flywheel housing 9. Specifically, the first clutch 26 and the second clutch 27 are disposed at positions facing the partition wall 9d.

[0192] The first clutch 26 and the second clutch 27 are disposed between the first flywheel 13 and the transmission 16 in the front-rear direction. The first clutch 26 and the second clutch 27 are shifted from the first flywheel 13 in the front-rear direction. In other words, the first clutch 26 and the second clutch 27 do not overlap with the first flywheel 13 in the front-rear direction. Furthermore, the first clutch 26 and the second clutch 27 are disposed between the first flywheel 13 and the speed increasing mechanism 20 in the front-rear direction.

[0193] The first clutch 26 is a multi-plate clutch and includes a plurality of first friction plates 26A and a plurality of second friction plates 26B. The first friction plates 26A and the second friction plates 26B are arranged alternately in the front-rear direction. The first friction plates 26A and the second friction plates 26B are formed in an annular shape. An intermediate shaft 17 passes through the centers of the first friction plates 26A and the second friction plates 26B.

[0194] The first friction plate 26A is attached to the first flywheel 13. Specifically, the first friction plate 26A is attached to the first flywheel 13 via a support member 65 (see FIG. 11) described later. The first friction plate 26A is movable in the axial direction of the intermediate shaft 17. The second friction plate 26B is attached to the sun gear 21 of the speed increasing mechanism 20. Specifically, the second friction plate 26B is attached to the sun gear 21 via an attachment member 69 (see FIG. 11) described later.

[0195] The second clutch 27 is also a multi-plate clutch and has a plurality of first friction plates 27A and a plurality of second friction plates 27B. The first friction plates 27A and the second friction plates 27B are arranged alternately in the front-rear direction. The first friction plates 27A and the second friction plates 27B are formed in an annular shape. An intermediate shaft 17 passes through the centers of the first friction plates 27A and the second friction plates 27B.

[0196] The first friction plate 27A is attached to the first flywheel 13. Specifically, the first friction plate 27A is attached to the first flywheel 13 via a support 65 (see FIG. 11 ), which will be described later. The first friction plate 27A is movable in the axial direction of the intermediate shaft 17. The second friction plate 27B is connected to the planetary gear 22 of the speed increasing mechanism 20. Specifically, the second friction plate 27B is connected to the planetary gear 22 via a connecting body 60 and a planetary carrier 24. The connecting body 60 connects the intermediate shaft 17 and the input shaft 16 a of the transmission 16. The planetary carrier 24 supports the planetary gear 22.

[0197] The first power transmission path 31 of the first power transmission unit 11E is a path that transmits the rotational power of the engine 4 in the following order: second flywheel 14, intermediate shaft 17, connecting body 60, planet carrier 24, planet gear 22, sun gear 21, first clutch 26, and then to the first flywheel 13.

[0198] The second power transmission path 32 of the first power transmission unit 11E is a path that transmits the rotational power of the first flywheel 13 to the second clutch 27 and the connecting body 60 in this order, and then to the transmission 16.

[0199] The third power transmission path 33 of the first power transmission unit 11E is a path that transmits the rotational power of the engine 4 to the transmission 16 via the intermediate shaft 17 and the connector 60. The third power transmission path 33 transmits the rotational power of the engine 4 to the transmission 16 without passing through either the first clutch 26 or the second clutch 27.

[0200] The operation of the first power transmission section 11E will be described below.

[0201] The rotational power output from the output shaft 4a of the engine 4 is transmitted to the second flywheel 14. This causes the second flywheel 14 to rotate, and the intermediate shaft 17 connected to the second flywheel 14 also rotates. At this time, the rotational speed of the engine 4, the rotational speed of the second flywheel 14, and the rotational speed of the intermediate shaft 17 become the same. The rotational power transmitted to the intermediate shaft 17 is transmitted to the input shaft 16a of the transmission 16 via the connector 60.

[0202] In this way, the rotational power output from the output shaft 4a of the engine 4 is transmitted to the transmission 16 via the third power transmission path 33. The transmission of the rotational power via this third power transmission path 33 is always performed regardless of whether the first clutch 26 and the second clutch 27 are engaged or disengaged.

[0203] When the first clutch 26 is in an engaged state and the second clutch 27 is in a disengaged state, the rotational power output from the output shaft 4a of the engine 4 is transmitted to the first flywheel 13 via the first power transmission path 31. Specifically, the rotational power transmitted from the engine 4 to the second flywheel 14 is transmitted from the second flywheel 14 to the planetary gear 22 via the intermediate shaft 17, the connecting body 60, and the planet carrier 24. This causes the planetary gear 22 to rotate, and the rotation of the planetary gear 22 causes the sun gear 21 to rotate. The sun gear 21 is connected to the second friction plate 26B of the first clutch 26. Therefore, the rotational power of the sun gear 21 is transmitted to the second friction plate 26B, and from the second friction plate 26B to the first flywheel 13 via the first friction plate 26A.

[0204] Here, the rotational power of the engine 4 is accelerated when it is transmitted from the planetary gear 22 to the sun gear 21. That is, the rotational power of the engine 4 is accelerated and transmitted to the first flywheel 13. Therefore, the first flywheel 13 rotates at a rotational speed higher than the rotational speed of the engine 4. This allows high rotational energy to be stored in the first flywheel 13.

[0205] Furthermore, when the first clutch 26 is disengaged and the second clutch 27 is engaged, the second power transmission path 32 is connected, and therefore the rotational power of the first flywheel 13 is transmitted to the transmission 16. Specifically, the rotational power of the first flywheel 13 is transmitted from the first friction plate 27A to the second friction plate 27B of the second clutch 27. As a result, the rotational power of the first flywheel 13 is transmitted from the second friction plate 27B to the input shaft 16a of the transmission 16 via the connector 60. At this time, the rotational power of the first flywheel 13 is transmitted to the input shaft 16a of the transmission 16 without being reduced in speed (without passing through a reduction mechanism). Therefore, the high rotational energy of the first flywheel 13 can be input directly to the transmission 16.

[0206] When the first clutch 26 and the second clutch 27 are both in a disengaged state, the first power transmission path 31 and the second power transmission path 32 are disconnected, so that the rotational power of the engine 4 is not transmitted to the first flywheel 13, and the rotational power of the first flywheel 13 is not transmitted to the transmission 16.

[0207] The first power transmission part 11E can achieve the same effects as those of the first power transmission part 11A described above.

[0208] The first power transmission section 11E according to the fifth embodiment has the following features.

[0209] In the first power transmission section 11E according to the fifth embodiment, the first clutch 26 and the second clutch 27 are configured as multi-plate clutches, and therefore high power transmission performance can be obtained between the first friction plates 26A, 27A and the second friction plates 26B, 27B. In other words, the power transmission performance of the clutch device 25 is excellent.

[0210] Furthermore, because the first clutch 26 and the second clutch 27 are arranged side by side in the radial direction of the intermediate shaft 17, the length in the front-rear direction can be shortened. This allows the axial length (length in the front-rear direction) of the first flywheel 13 to be lengthened. This increases the moment of inertia of the first flywheel 13, and increases the amount of rotational energy that can be stored in the first flywheel 13. In other words, the first flywheel 13 has excellent rotational energy storage performance.

[0211] Furthermore, because the first clutch 26 and the second clutch 27 are disposed in a position facing the partition wall 9d of the flywheel housing 9, oil passages for supplying hydraulic oil to the first clutch 26 and the second clutch 27 can be provided along the partition wall 9d. This makes it easy to provide oil passages for supplying hydraulic oil to the first clutch 26 and the second clutch 27. In other words, the oil passages are excellent in terms of their efficiency.

[0212] Furthermore, by providing a bearing on the first wall 9a of the flywheel housing 9, one end of the intermediate shaft 17 can be rotatably supported. And by providing a bearing on the second wall 9b of the flywheel housing 9, the other end of the intermediate shaft 17 or the input shaft 16a of the transmission 16 connected to that other end can be rotatably supported. Furthermore, by providing a bearing on the partition wall 9d, the intermediate shaft 17 can be rotatably supported at its intermediate portion. This makes it possible to reliably and easily support both ends and the intermediate portion of the intermediate shaft 17 for rotation. In other words, the shaft support is excellent.

[0213] Furthermore, since the first clutch 26 and the second clutch 27 are arranged side by side in the radial direction of the intermediate shaft 17 near the partition wall 9d, it is possible to use the same members for supporting the first clutch 26 and the second clutch 27, thereby reducing the number of parts. In other words, this is advantageous in that the number of parts can be reduced.

[0214] As described above, the first power transmission section 11E according to the fifth embodiment is excellent in power transmission performance, rotational energy storage performance, oil passage feasibility, shaft support feasibility, and reduced number of parts. Therefore, it is possible to achieve a high level of balance between performance-related features (power transmission performance, rotational energy storage performance) and structural features (oil passage feasibility, shaft support feasibility, reduced number of parts).

[0215] <<Sixth Embodiment>> Next, a specific configuration of the first power transmission section 11 according to the sixth embodiment will be described with reference to Fig. 8. Hereinafter, the first power transmission section 11 according to the sixth embodiment will be referred to as "first power transmission section 11F."

[0216] A partition wall 9d is provided inside the flywheel housing 9 that accommodates the first power transmission unit 11F according to the sixth embodiment. The partition wall 9d is provided between the first wall 9a and the second wall 9b. One surface of the partition wall 9d faces the first wall 9a. The other surface of the partition wall 9d faces the second wall 9b.

[0217] The partition wall 9d divides the interior of the flywheel housing 9 into a first space 51 in which the first flywheel 13 is housed and a second space 52 in which the first clutch 26 and the second clutch 27 are housed.

[0218] The first space 51 is provided in the front part (engine 4 side) of the flywheel housing 9. In addition to the first flywheel 13, the second flywheel 14 is also accommodated in the first space 51. The second space 52 is provided in the rear part (transmission 16 side) of the flywheel housing 9. In addition to the first clutch 26 and the second clutch 27, the speed increasing mechanism 20 is also accommodated in the second space 52.

[0219] In the first power transmission section 11F, the first clutch 26 and the second clutch 27 are arranged side by side in the radial direction of the intermediate shaft 17 (direction away from the axis of the intermediate shaft 17). The first clutch 26 is arranged on the outer circumferential side (side farther from the intermediate shaft 17). The second clutch 27 is arranged on the inner circumferential side (side closer to the intermediate shaft 17). In other words, the second clutch 27 is arranged on the inner circumferential side of the first clutch 26. The first clutch 26 and the second clutch 27 are arranged near the partition wall 9d of the flywheel housing 9. Specifically, the first clutch 26 and the second clutch 27 are arranged in a position facing the partition wall 9d.

[0220] The first clutch 26 and the second clutch 27 are disposed between the first flywheel 13 and the transmission 16 in the front-rear direction. The first clutch 26 and the second clutch 27 are shifted from the first flywheel 13 in the front-rear direction. In other words, the first clutch 26 and the second clutch 27 do not overlap with the first flywheel 13 in the front-rear direction. Furthermore, the first clutch 26 and the second clutch 27 are disposed between the first flywheel 13 and the speed increasing mechanism 20 in the front-rear direction.

[0221] The first clutch 26 is a multi-plate clutch and includes a plurality of first friction plates 26A and a plurality of second friction plates 26B. The first friction plates 26A and the second friction plates 26B are arranged alternately in the front-rear direction. The first friction plates 26A and the second friction plates 26B are formed in an annular shape. An intermediate shaft 17 passes through the centers of the first friction plates 26A and the second friction plates 26B.

[0222] The first friction plate 26A is attached to the first flywheel 13 and is movable in the axial direction of the intermediate shaft 17. The second friction plate 26B is attached to the sun gear 21 of the speed increasing mechanism 20.

[0223] The second clutch 27 is also a multi-plate clutch and has a plurality of first friction plates 27A and a plurality of second friction plates 27B. The first friction plates 27A and the second friction plates 27B are arranged alternately in the front-rear direction. The first friction plates 27A and the second friction plates 27B are formed in an annular shape. An intermediate shaft 17 passes through the centers of the first friction plates 27A and the second friction plates 27B.

[0224] The first friction plate 27A is attached to the first flywheel 13 and is movable in the axial direction of the intermediate shaft 17. The second friction plate 27B is attached to the planetary gear 22 of the speed increasing mechanism 20. The second friction plate 27B is connected to the planetary gear 22 of the speed increasing mechanism 20 via a connecting body 60 and a planetary carrier 24. The connecting body 60 connects the intermediate shaft 17 and the input shaft 16a of the transmission 16. The planetary carrier 24 supports the planetary gear 22. The second friction plate 27B is arranged on the outer circumferential side of the first friction plate 27A.

[0225] The first power transmission path 31 of the first power transmission unit 11F is a path that transmits the rotational power of the engine 4 in the following order: the second flywheel 14, the intermediate shaft 17, the connecting body 60, the planet carrier 24, the planet gear 22, the sun gear 21, and the first clutch 26, and then transmits it to the first flywheel 13.

[0226] The second power transmission path 32 of the first power transmission unit 11F is a path that transmits the rotational power of the first flywheel 13 to the second clutch 27 and the connecting body 60 in this order, and then to the transmission 16.

[0227] The third power transmission path 33 of the first power transmission unit 11F is a path that transmits the rotational power of the engine 4 to the transmission 16 via the connector 60 and the intermediate shaft 17. The third power transmission path 33 transmits the rotational power of the engine 4 to the transmission 16 without passing through either the first clutch 26 or the second clutch 27.

[0228] The operation of the first power transmission section 11F will be described below.

[0229] The rotational power output from the output shaft 4a of the engine 4 is transmitted to the second flywheel 14. This causes the second flywheel 14 to rotate, and the intermediate shaft 17 connected to the second flywheel 14 also rotates. At this time, the rotational speed of the engine 4, the rotational speed of the second flywheel 14, and the rotational speed of the intermediate shaft 17 become the same. The rotational power transmitted to the intermediate shaft 17 is transmitted to the input shaft 16a of the transmission 16 via the connector 60.

[0230] In this way, the rotational power output from the output shaft 4a of the engine 4 is transmitted to the transmission 16 via the third power transmission path 33. The transmission of the rotational power via this third power transmission path 33 is always performed regardless of whether the first clutch 26 and the second clutch 27 are engaged or disengaged.

[0231] When the first clutch 26 is in an engaged state and the second clutch 27 is in a disengaged state, the rotational power output from the output shaft 4a of the engine 4 is transmitted to the first flywheel 13 via the first power transmission path 31. Specifically, the rotational power of the engine 4 is transmitted from the second flywheel 14 to the planetary gear 22 via the intermediate shaft 17, the connecting body 60, and the planet carrier 24. This causes the planetary gear 22 to rotate, and the sun gear 21 rotates in conjunction with the rotation of the planetary gear 22. The sun gear 21 is connected to the second friction plate 26B of the first clutch 26. Therefore, the rotational power transmitted to the sun gear 21 is transmitted from the second friction plate 26B to the first friction plate 26A, and then from the first friction plate 26A to the first flywheel 13.

[0232] Here, the rotational power of the engine 4 is accelerated when it is transmitted from the planetary gear 22 to the sun gear 21. That is, the rotational power of the engine 4 is accelerated and transmitted to the first flywheel 13. Therefore, the first flywheel 13 rotates at a rotational speed higher than the rotational speed of the engine 4. This allows high rotational energy to be stored in the first flywheel 13.

[0233] Furthermore, when the first clutch 26 is disengaged and the second clutch 27 is engaged, the second power transmission path 32 is connected, and therefore the rotational power of the first flywheel 13 is transmitted to the transmission 16. Specifically, the rotational power of the first flywheel 13 is transmitted from the first friction plate 27A to the second friction plate 27B of the second clutch 27. As a result, the rotational power of the first flywheel 13 is transmitted from the second friction plate 27B to the input shaft 16a of the transmission 16 via the connector 60. At this time, the rotational power of the first flywheel 13 is transmitted to the input shaft 16a of the transmission 16 without being reduced in speed (without passing through a reduction mechanism). Therefore, the high rotational energy of the first flywheel 13 can be input directly to the transmission 16.

[0234] When the first clutch 26 and the second clutch 27 are both in a disengaged state, the first power transmission path 31 and the second power transmission path 32 are disconnected, so that the rotational power of the engine 4 is not transmitted to the first flywheel 13, and the rotational power of the first flywheel 13 is not transmitted to the transmission 16.

[0235] The first power transmission part 11F can achieve the same effects as those of the first power transmission part 11A described above.

[0236] The first power transmission section 11F according to the sixth embodiment has the following features.

[0237] In the first power transmission section 11F according to the sixth embodiment, the first clutch 26 and the second clutch 27 are configured as multi-plate clutches, and therefore high power transmission performance can be obtained between the first friction plates 26A, 27A and the second friction plates 27B. In other words, the power transmission performance of the clutch device 25 is excellent.

[0238] Furthermore, because the first clutch 26 and the second clutch 27 are arranged side by side in the radial direction of the intermediate shaft 17, the length in the front-rear direction can be shortened. This allows the axial length (length in the front-rear direction) of the first flywheel 13 to be lengthened. This increases the moment of inertia of the first flywheel 13, and increases the amount of rotational energy that can be stored in the first flywheel 13. In other words, the first flywheel 13 has excellent rotational energy storage performance.

[0239] Furthermore, because the first clutch 26 and the second clutch 27 are disposed in a position facing the partition wall 9d of the flywheel housing 9, oil passages for supplying hydraulic oil to the first clutch 26 and the second clutch 27 can be provided along the partition wall 9d. This makes it easy to provide oil passages for supplying hydraulic oil to the first clutch 26 and the second clutch 27. In other words, the oil passages are excellent in terms of their efficiency.

[0240] Furthermore, by providing a bearing on the first wall 9a of the flywheel housing 9, one end of the intermediate shaft 17 can be rotatably supported. And by providing a bearing on the second wall 9b of the flywheel housing 9, the other end of the intermediate shaft 17 or the input shaft 16a of the transmission 16 connected to that other end can be rotatably supported. Furthermore, by providing a bearing on the partition wall 9d, the intermediate shaft 17 can be rotatably supported at its intermediate portion. This makes it possible to reliably and easily support both ends and the intermediate portion of the intermediate shaft 17 for rotation. In other words, the shaft support is excellent.

[0241] Furthermore, since the first clutch 26 and the second clutch 27 are arranged side by side in the radial direction of the intermediate shaft 17 near the partition wall 9d, it is possible to use the same members for supporting the first clutch 26 and the second clutch 27, thereby reducing the number of parts. In other words, this is advantageous in that the number of parts can be reduced.

[0242] As described above, the first power transmission section 11F according to the sixth embodiment is excellent in power transmission performance, rotational energy storage performance, oil passage feasibility, shaft support feasibility, and reduced number of parts, and therefore can achieve a good balance between performance-related features (power transmission performance, rotational energy storage performance) and structural features (oil passage feasibility, shaft support feasibility, and reduced number of parts).

[0243] However, the fifth embodiment is superior in terms of oil passage establishment, shaft support establishment, and reduction in the number of parts, which is due to the difference in the specific configuration of the clutch device 25 between the fifth embodiment and the sixth embodiment.

[0244] In the case of the sixth embodiment (see FIG. 8), the portions supporting the first friction plates 26A, the portion supporting the second friction plates 26B, the portion supporting the second friction plates 27B, and the portion supporting the first friction plates 27A are arranged in this order from the outer circumferential side (the side farther from the axis of the intermediate shaft 17) to the inner circumferential side (the side closer to the axis of the intermediate shaft 17). In contrast to this, in the case of the fifth embodiment (see FIG. 7), the portions supporting the first friction plates 26A, the portion supporting the second friction plates 26B, the portion supporting the first friction plates 27A, and the portion supporting the second friction plates 27B are arranged in this order from the outer circumferential side to the inner circumferential side.

[0245] Due to this difference in configuration, the fifth embodiment can simplify the support structure of the clutch device 25 and reduce the number of parts compared to the sixth embodiment. Also, the fifth embodiment makes it easier to form oil passages for supplying hydraulic oil to the first clutch 26 and the second clutch 27 compared to the sixth embodiment.

[0246] In the fifth embodiment, a portion 80 (see FIG. 7) extending rearward from the inner cylindrical portion 13b of the first flywheel 13 along the intermediate shaft 17 is provided on the inner circumferential side of the portion supporting the second friction plate 26B, and a bearing (a fifth bearing 66 (see FIG. 11) described later) can be disposed in this portion 80. This makes it possible to reliably and easily support the intermediate shaft 17 so that it can rotate. The portion 80 corresponds to the rear portion of a support body 65 (see FIG. 11) described later.

[0247] <Detailed configuration of the fifth embodiment> Next, based on Figures 10 and 11, the detailed configuration of the first power transmission section 11E according to the fifth embodiment, which is a particularly preferred embodiment of the first power transmission section 11 according to the first to sixth embodiments described above, will be described.

[0248] Fig. 10 is a cross-sectional view showing a power transmission mechanism 6 including a first power transmission part 11E according to a fifth embodiment and a part of a transmission case 5 that houses the power transmission mechanism 6. Fig. 11 is an enlarged view of a part of Fig. 10.

[0249] As shown in Figure 10, the transmission case 5 has a front section 5A, a middle section 5B, and a rear section 5C. The front section 5A is located at the front of the transmission case 5. The middle section 5B is connected to the rear section of the front section 5A. The rear section 5C is connected to the rear section of the middle section 5B.

[0250] A front wheel drive shaft 63 for transmitting rotational power to the front wheels 3F is disposed below the transmission case 5 and passes through the transmission case 5. The front wheel drive shaft 63 extends in the front-to-rear direction, passing through the front region 5A, the middle region 5B, and the rear region 5C.

[0251] The front portion of the front portion 5A, the middle portion 5B, and the front portion of the rear portion 5C form a flywheel housing 9. The rear portion of the rear portion 5C forms the front portion of the transmission case 10. The rear portion 5C has a structure that combines the rear portion of the flywheel housing 9 and the front portion of the transmission case 10.

[0252] The front section 5A has a first cylindrical portion 91 and a first wall 9a. The first cylindrical portion 91 covers the periphery of the second flywheel 14. The first wall 9a is the first wall 9a of the flywheel housing 9 described above, and is disposed in front of the second flywheel 14.

[0253] The intermediate section 5B has a second cylindrical section 92 and an intermediate wall 95. The second cylindrical section 92 is connected to the rear of the first cylindrical section 91 of the front section 5A. Specifically, the second cylindrical section 92 is connected to the rear of the first cylindrical section 91 by a bolt B1. The second cylindrical section 92 covers the periphery of the first flywheel 13 and the periphery of the front section of the clutch device 25 (the first clutch 26 and the second clutch 27). The intermediate wall 95 is provided between the first flywheel 13 and the second flywheel 14. The intermediate wall 95 divides the first space 51 into a space in which the first flywheel 13 is disposed and a space in which the second flywheel 14 is disposed.

[0254] The rear section 5C has a third cylindrical section 93, a second wall 9b, and a fourth cylindrical section 94. The third cylindrical section 93 is connected to the rear section of the second cylindrical section 92 of the intermediate section 5B. Specifically, the third cylindrical section 93 is connected to the rear section of the second cylindrical section 92 by a bolt B2. The third cylindrical section 93 covers the periphery of the speed-increasing mechanism 20. The second wall 9b is the second wall 9b of the flywheel housing 9 described above, and is disposed rearward of the speed-increasing mechanism 20.

[0255] The first cylindrical portion 91, the second cylindrical portion 92, and the third cylindrical portion 93 form a peripheral wall 9c of the flywheel housing 9. The interior of the flywheel housing 9 is divided into a first space 51 and a second space 52 by a partition wall 9d.

[0256] As shown in Fig. 10, the partition wall 9d is fixed to the intermediate wall 95. Specifically, the intermediate wall 95 is fixed to the partition wall 9d by a bolt B3 inserted into a mounting hole 9e (see Fig. 12) formed in the partition wall 9d.

[0257] 11, a first bearing 61 and a second bearing 62 are attached to the intermediate wall 95. The first bearing 61 rotatably supports the front portion of the intermediate shaft 17. The second bearing 62 rotatably supports the front portion of the first flywheel 13.

[0258] 11 and 12, the first flywheel 13 has an outer cylindrical portion 13a, an inner cylindrical portion 13b, and a connecting portion 13c. The length of the connecting portion 13c in the front-to-rear direction is smaller than the lengths of the outer cylindrical portion 13a and the inner cylindrical portion 13b in the front-to-rear direction. In other words, the thickness of the connecting portion 13c is smaller than the thicknesses of the outer cylindrical portion 13a and the inner cylindrical portion 13b.

[0259] The first flywheel 13 has a first recess 13e and a second recess 13f. The first recess 13e is recessed in front of the connecting portion 13c and between the outer cylindrical portion 13a and the inner cylindrical portion 13b. The second recess 13f is recessed in rear of the connecting portion 13c and between the outer cylindrical portion 13a and the inner cylindrical portion 13b.

[0260] A second bearing 62 is disposed in the first recess 13e. A third bearing 64 is disposed in the second recess 13f. The first flywheel 13 is rotatably supported by the second bearing 62 and the third bearing 64.

[0261] As shown in Fig. 11, a support body 65 is disposed on the outer circumferential side of the intermediate shaft 17. The support body 65 supports the first flywheel 13 rotatably relative to the intermediate shaft 17. As shown in Figs. 11 and 12, the support body 65 has a first portion 65a, a second portion 65b, a third portion 65c, a fourth portion 65d, a fifth portion 65e, and a sixth portion 65f.

[0262] The first portion 65a is cylindrical, and the intermediate shaft 17 passes through it. A rear portion of the first portion 65a is supported by a fifth bearing 66 attached to the outer peripheral surface of the intermediate shaft 17. This allows the support body 65 to rotate relative to the intermediate shaft 17. A middle portion of the first portion 65a in the front-to-rear direction is supported by a sixth bearing 67 attached to the inner peripheral surface of the partition wall 9d. This allows the support body 65 to rotate relative to the partition wall 9d. A first flywheel 13 is attached to a front portion of the first portion 65a. The first flywheel 13 and a front portion of the support body 65 are spline-coupled. This allows the first flywheel 13 to rotate integrally with the support body 65 relative to the intermediate shaft 17 and the partition wall 9d.

[0263] The second portion 65b extends outward (in a direction away from the intermediate shaft 17) from the rear portion of the first portion 65a. The second portion 65b is formed in a disk shape. The third portion 65c extends rearward from the outer circumferential end of the second portion 65b. The third portion 65c is formed in a cylindrical shape. The fourth portion 65d extends rearward from between the outer circumferential end and inner circumferential end of the second portion 65b. The fourth portion 65d is formed in a cylindrical shape with a smaller diameter than the third portion 65c. The fourth portion 65d is located on the inner circumferential side of the third portion 65c.

[0264] The fifth portion 65e extends forward from the outer circumferential end of the second portion 65b. The fifth portion 65e is formed in a cylindrical shape. The diameter of the fifth portion 65e is approximately equal to the diameter of the third portion 65c. The sixth portion 65f extends forward from between the outer circumferential end and the inner circumferential end of the second portion 65b. The sixth portion 65f is formed in a cylindrical shape with a smaller diameter than the fifth portion 65e. The diameter of the sixth portion 65f is approximately equal to the diameter of the fourth portion 65d.

[0265] 11 and 12, the partition wall 9d has a wall portion 96, a cylindrical portion 97, a first protruding portion 98, and a second protruding portion 99. The wall portion 96 is formed in a disk shape and separates the first flywheel 13 from the clutch device 25. As shown in FIG. 11, an oil passage 70 for supplying hydraulic oil to the clutch device 25 is formed in the wall portion 96. A supply pipe 71 is connected to the oil passage 70. Hydraulic oil can be supplied to the oil passage 70 from outside the flywheel housing 9 through the supply pipe 71.

[0266] The oil passage 70 is composed of a main oil passage 70a, a first branch oil passage 70b, and a second branch oil passage 70c. The main oil passage 70a extends from the outer periphery side to the inner periphery side of the partition wall 9d. A supply pipe 71 is connected to the outer periphery side end of the main oil passage 70a. The first branch oil passage 70b and the second branch oil passage 70c branch off from the main oil passage 70a and extend rearward.

[0267] The main oil passage 70a is a passage that receives hydraulic oil from the outside of the flywheel housing 9 through a supply pipe 71. The first branch oil passage 70b is an oil passage that supplies the hydraulic oil supplied to the main oil passage 70a to the first clutch 26. The second branch oil passage 70c is an oil passage that supplies the hydraulic oil supplied to the main oil passage 70a to the second clutch 27.

[0268] The tubular portion 97 is formed in a cylindrical shape. A sixth bearing 67 is interposed between the inner peripheral surface of the tubular portion 97 and the outer peripheral surface of the first portion 65a of the support body 65. The tubular portion 97 has a front tubular portion 97a extending forward from the inner peripheral end of the wall portion 96, and a rear tubular portion 97b extending rearward from the inner peripheral end of the wall portion 96. A third bearing 64 is interposed between the outer peripheral surface of the front tubular portion 97a and the first flywheel 13.

[0269] The first protrusion 98 extends rearward from the wall 96. The first protrusion 98 is formed in a cylindrical shape. The second protrusion 99 extends rearward from between the outer circumferential end and the inner circumferential end of the wall 96. The second protrusion 99 is formed in a cylindrical shape with a smaller diameter than the first protrusion 98. The second protrusion 99 is disposed on the inner circumferential side of the first protrusion 98.

[0270] As shown in Figure 11, the intermediate shaft 17 and the input shaft 16a of the transmission 16 are connected by a connecting body 60. External splines are formed on the outer peripheral surface of the rear portion of the intermediate shaft 17 and on the outer peripheral surface of the front portion of the input shaft 16a. Internal splines are formed on the inner peripheral surface of the connecting body 60. The external splines and the internal splines mesh with each other, connecting the intermediate shaft 17 and the input shaft 16a via the connecting body 60. This allows the connecting body 60, intermediate shaft 17, and input shaft 16a to rotate integrally.

[0271] The connecting body 60 is disposed behind the support body 65. The connecting body 60 has a cylindrical connecting portion 60a and an extending portion 60b that extends outward (away from the intermediate shaft 17) from the front portion of the connecting portion 60a and then extends forward. The inner circumferential surface of the connecting portion 60a is formed with the internal splines described above. The outer end of the extending portion 60b is formed in a cylindrical shape with a larger diameter than the connecting portion 60a. The outer circumferential surface of the extending portion 60b faces the inner circumferential surface of the fourth section 65d.

[0272] The sun gear 21 of the speed increasing mechanism 20 is supported on the outer circumferential surface of the connecting part 60a via a seventh bearing 68. This allows the sun gear 21 to rotate relatively to the connecting body 60. A mounting member 69 is fixed to the sun gear 21. The mounting member 69 has a fixed part 69a fixed to the sun gear 21 and a front extension part 69b extending forward from the fixed part 69a. The fixed part 69a is formed in a disk shape. The front extension part 69b is formed in a cylindrical shape.

[0273] The planetary gears 22 of the speed increasing mechanism 20 are supported by a planetary carrier 24. An internal spline is formed on the inner peripheral surface of the planetary carrier 24. The internal spline of the planetary carrier 24 meshes with an external spline formed on the outer peripheral surface of the connecting portion 60a. This allows the planetary carrier 24 to rotate together with the connecting body 60 and the intermediate shaft 17.

[0274] The ring gear 23 of the speed increasing mechanism 20 is attached to a ring support 72. The ring support 72 is fixed to the intermediate portion 5B of the flywheel housing 9. Specifically, the ring support 72 is fixed to the intermediate portion 5B with bolts B4. This prevents the ring gear 23 from rotating relative to the flywheel housing 9.

[0275] The first friction plates 26A and the second friction plates 26B of the first clutch 26 are disposed rearward of the second portion 65b of the support body 65. The first friction plates 26A and the second friction plates 26B are disposed between the third portion 65c of the support body 65 and the forward extending portion 69b of the mounting member 69.

[0276] The first friction plate 26A of the first clutch 26 has an annular shape, and its outer periphery is supported by the third portion 65c of the support body 65. More specifically, a plurality of protrusions 26A1 (see FIG. 12) formed on the outer periphery of the first friction plate 26A are fitted into a plurality of notches 65g (see FIG. 12) formed in the third portion 65c. This prevents the first friction plate 26A from rotating relative to the support body 65, but allows it to move in the front-rear direction along the notches 65g.

[0277] The second friction plate 26B of the first clutch 26 has an annular shape, and its inner circumferential portion is supported by the forward extending portion 69b of the mounting member 69. The second friction plate 26B is fixed to the forward extending portion 69b so as not to move.

[0278] The hydraulic piston 73 of the first clutch 26 (hereinafter referred to as the "first hydraulic piston 73") is disposed between the partition wall 9d and the second portion 65b of the support body 65. More specifically, the first hydraulic piston 73 is disposed in a space surrounded by the wall portion 96 of the partition wall 9d, the first protruding portion 98, the second protruding portion 99, and the second portion 65b, fifth portion 65e, and sixth portion 65f of the support body 65. An opening 65h (see FIGS. 11 and 12) is formed in the second portion 65b of the support body 65, and the tip end of the first hydraulic piston 73 protrudes from the opening 65h. The tip end of the first hydraulic piston 73 is adjacent to the first friction plate 26A, which is located most forward.

[0279] Hydraulic oil is supplied from the first branched oil passage 70b to the base end side of the first hydraulic piston 73. When hydraulic oil is supplied from the first branched oil passage 70b, the first hydraulic piston 73 moves rearward and pushes the first friction plate 26A, causing the first friction plate 26A to press against the second friction plate 26B.

[0280] The first hydraulic piston 73 is biased forward by the first spring 74. Therefore, when hydraulic oil is not supplied from the first branch oil passage 70b, the first hydraulic piston 73 moves forward by the biasing force of the first spring 74. When the first hydraulic piston 73 moves forward, the first friction plates 26A move away from the second friction plates 26B.

[0281] The first friction plate 27A and the second friction plate 27B of the second clutch 27 are disposed behind the second portion 65b of the support body 65. The first friction plate 27A and the second friction plate 27B are disposed between the fourth portion 65d of the support body 65 and the outer peripheral surface of the extension portion 60b of the connecting body 60.

[0282] The first friction plate 27A of the second clutch 27 has an annular shape, and its outer periphery is supported by a fourth portion 65d of the support body 65. More specifically, a plurality of protrusions 27A1 (see FIG. 12) formed on the outer periphery of the first friction plate 27A are fitted into a plurality of notches 65i (see FIG. 12) formed in the fourth portion 65d. This prevents the first friction plate 27A from rotating relative to the support body 65, but allows it to move in the front-rear direction along the notches 65i.

[0283] The second friction plate 27B of the second clutch 27 is annular, and its inner circumferential portion is supported by the extension portion 60b of the connecting body 60. The second friction plate 27B is fixed to the extension portion 60b so as not to move.

[0284] A hydraulic piston 75 of the second clutch 27 (hereinafter referred to as the "second hydraulic piston 75") is disposed between the partition wall 9d and the second portion 65b of the support body 65. More specifically, the second hydraulic piston 75 is disposed in a space surrounded by a wall portion 96 of the partition wall 9d, a cylindrical portion 97, a second protruding portion 99, and the first portion 65a, second portion 65b, and sixth portion 65f of the support body 65. An opening 65j (see FIGS. 11 and 12) is formed in the second portion 65b of the support body 65, and the tip end of the second hydraulic piston 75 protrudes from the opening 65j. The tip end of the second hydraulic piston 75 is adjacent to the first friction plate 27A, which is located most forward.

[0285] Hydraulic oil is supplied from the second branched oil passage 70c to the base end side of the second hydraulic piston 75. When hydraulic oil is supplied from the second branched oil passage 70c, the second hydraulic piston 75 moves rearward and pushes the first friction plates 27A, causing the first friction plates 27A to press against the second friction plates 27B.

[0286] The second hydraulic piston 75 is biased forward by the second spring 76. Therefore, when hydraulic oil is not supplied from the second branch oil passage 70c, the second hydraulic piston 75 moves forward by the biasing force of the second spring 76. When the second hydraulic piston 75 moves forward, the first friction plates 27A move away from the second friction plates 27B.

[0287] <Control System> 13 is a block diagram showing a schematic configuration of a control system 100 provided in a work vehicle 1 according to the present invention. This control system 100 is a control system that can be provided in the work vehicle 1 described above. In other words, the control system 100 can be applied to a work vehicle 1 equipped with the first power transmission unit 11 of all of the above-described embodiments (first to sixth embodiments).

[0288] The control system 100 includes a control device 110 , an information acquisition unit 120 , a display / input device 130 , and an operation unit 140 .

[0289] The control device 110 includes an ECU (Electronic Control Unit). The control device 110 receives various information and signals transmitted (input) from the information acquisition unit 120, performs calculations, and transmits a control signal to the operation unit 140 to control the operation of the operation unit 140 based on the calculation results, etc.

[0290] The control device 110 has a calculation unit 111, a storage unit 112, and a communication unit 113. The calculation unit 111 is composed of a CPU or the like, and reads out various programs stored in the storage unit 112 to execute various calculations and processes. The storage unit 112 stores the programs executed by the calculation unit 111 and various data. The storage unit 112 is composed of a ROM (Read Only Memory), a RAM (Random Access Memory), or the like. The storage unit 112 may be an external storage device connected to the control device 110. The communication unit 113 communicates between the control device 110 and the information acquisition unit 120, the display input device 130, and the operation unit 140 via an electric communication line or wirelessly, and transmits and receives various information and various signals.

[0291] The information acquisition unit 120 acquires information relating to the operation of the work vehicle 1 and transmits it to the control device 110. The information acquisition unit 120 includes a first pressure sensor 28, a second pressure sensor 29, a first rotation speed sensor 18, a second rotation speed sensor 15, and an accelerator opening sensor 19.

[0292] As described above, first pressure sensor 28 detects the pressure of hydraulic oil in the oil passage for supplying hydraulic oil to the hydraulic piston of first clutch 26 (operating pressure of the oil passage piston). Second pressure sensor 29 detects the pressure of hydraulic oil in the oil passage for supplying hydraulic oil to the hydraulic piston of second clutch 27 (operating pressure of the oil passage piston).

[0293] The first rotation speed sensor 18 measures the rotation speed of the first flywheel 13. The second rotation speed sensor 15 measures the rotation speed of the second flywheel 14 to calculate the rotation speed (actual rotation speed) of the engine 4. The accelerator opening sensor 19 detects the command injection amount (command value of the injection amount for the fuel injection valve (injector)) according to the amount of depression of the accelerator pedal.

[0294] Although not shown in FIG. 13, the information acquisition unit 120 may include the first torque sensor 35, the second torque sensor 36, and the third rotation speed sensor 37 described above.

[0295] The display input device 130 is configured to be capable of displaying various information and accepting manual operations. The display input device 130 is, for example, a touch panel display device. The display input device 130 is disposed, for example, near the driver's seat of the work vehicle 1.

[0296] The calculation unit 111 includes a load factor calculation unit 111a, a torque factor calculation unit 111b, a drop factor calculation unit 111c, and an operation mode determination unit 111d.

[0297] The load factor calculation unit 111a calculates the load factor of the engine 4 (hereinafter, may be simply referred to as "load factor"). More specifically, the load factor calculation unit 111a calculates the load factor based on the command injection amount detected by the accelerator opening sensor 19 and the limited injection amount corresponding to the boost pressure stored in the storage unit 112. Specifically, the load factor calculation unit 111a calculates the load factor using the calculation formula "command injection amount / limited injection amount corresponding to the boost pressure x 100".

[0298] The "boost pressure" is the pressure of compressed air forcibly sent to the engine 4 by the supercharger. The "limited injection amount" is a value that is determined so that the amount of fuel injected by the fuel injection valve (injector) cannot exceed this value. The "limited injection amount corresponding to the boost pressure" is a limited injection amount determined so as to correspond to the boost pressure. The limited injection amount is determined so as to increase in response to an increase in the boost pressure. The "limited injection amount corresponding to the boost pressure" is stored in the memory unit 112.

[0299] The torque rate calculation unit 111b calculates the torque rate of the engine 4 (hereinafter, may be simply referred to as "torque rate"). More specifically, the torque rate calculation unit 111b calculates the torque rate based on the command injection amount detected by the accelerator opening sensor 19 and the limited injection amount of the full load curve stored in the storage unit 112. Specifically, the load rate calculation unit 111a calculates the torque rate using the calculation formula "command injection amount / limited injection amount of the full load curve×100".

[0300] The "limited injection amount of the full load curve" is a limited injection amount determined in accordance with the full load curve of the engine 4 (a full load curve with the engine speed on the horizontal axis and the fuel injection amount on the vertical axis). The "limited injection amount of the full load curve" is stored in the storage unit 112.

[0301] The drop rate calculation unit 111c calculates the drop rate of the engine 4 (hereinafter, may be simply referred to as the "drop rate"). In detail, the drop rate calculation unit 111c calculates the drop rate based on the actual rotation speed of the engine 4 (hereinafter, may be simply referred to as the "actual rotation speed") detected by the second rotation speed sensor 15 and the target rotation speed of the engine 4 (hereinafter, may be simply referred to as the "target rotation speed") stored in the storage unit 112. Specifically, the drop rate calculation unit 111c calculates the drop rate using the calculation formula "actual rotation speed / target rotation speed x 100". Note that the target rotation speed of the engine 4 is the rotation speed of the engine 4 that is predetermined in accordance with the opening degree of the accelerator, etc.

[0302] The operation mode determination unit 111d determines an operation mode (described later) of the control system 100 based on information (detection values, etc.) acquired by the information acquisition unit 120, values ​​calculated by the load rate calculation unit 111a, torque rate calculation unit 111b, and drop rate calculation unit 111c, etc. The control device 110 transmits a control signal to the operation unit 140 based on the operation mode determined by the operation mode determination unit 111d.

[0303] The operating unit 140 operates in response to a control signal transmitted from the control device 110. The operating unit 140 includes a first clutch 26 and a second clutch 27.

[0304] First clutch 26 operates based on a first control signal transmitted from control device 110. The first control signal is a control signal for driving a hydraulic piston (first hydraulic piston 73) of first clutch 26, and includes a command pressure of hydraulic oil for driving the hydraulic piston of first clutch 26 (hereinafter referred to as "first command pressure"). The operating pressure of the hydraulic piston of first clutch 26 is determined by the first command pressure included in the control signal transmitted from control device 110. First clutch 26 is engaged or disengaged by driving the hydraulic piston based on the first command pressure.

[0305] Second clutch 27 operates based on a second control signal transmitted from control device 110. The second control signal is a control signal for driving a hydraulic piston (second hydraulic piston 75) of second clutch 27, and includes a command pressure of hydraulic oil for driving the hydraulic piston of second clutch 27 (hereinafter referred to as "second command pressure"). The operating pressure of the hydraulic piston of second clutch 27 is determined by the second command pressure included in the control signal transmitted from control device 110. Second clutch 27 is engaged or disengaged by driving the hydraulic piston based on the second command pressure.

[0306] In order to switch between a plurality of operation modes, the control device 110 executes control relating to the engagement and disengagement of the first clutch 26 and the second clutch 27. In particular, the control device 110 switches the operation mode by controlling the engagement and disengagement of the first clutch 26 and the second clutch 27, or notifies the operator of the work vehicle 1 that the operation mode can be switched.

[0307] 14, the plurality of operation modes include a free mode, a charge preparation mode, a charge mode, a boost preparation mode, a boost mode, a tenacity preparation mode, a tenacity mode, and an engine-off mode. Each of the operation modes will be described below.

[0308] <Free Mode> The free mode is the operating state mode immediately after the engine 4 is started. In the free mode, the engine 4 is started but has not yet reached idling speed. The first clutch 26 and the second clutch 27 are disengaged. Because the first clutch 26 and the second clutch 27 are disengaged, the first flywheel 13 is stopped. However, when transitioning to the free mode from another operating mode, the first flywheel 13 may still be rotating due to inertial force.

[0309] <Charge mode> The charge mode is a mode in which rotational energy is stored in the first flywheel 13.

[0310] In the charge mode, the engine 4 rotates at a target rotation speed that exceeds the idling rotation speed. However, when the load on the engine 4 increases due to a work load or the like, the rotation speed may fall below the target rotation speed. In the charge mode, the rotation speed of the first flywheel 13 is higher than the rotation speed (actual rotation speed) of the engine 4 but lower than the target rotation speed of the first flywheel 13. The target rotation speed of the first flywheel 13 is higher than the rotation speed of the engine 4. Specifically, the target rotation speed of the first flywheel 13 is the rotation speed obtained by multiplying the actual rotation speed of the engine 4 by the speed-up ratio of the speed-up mechanism 20. For example, if the speed-up ratio of the speed-up mechanism 20 is 3, then "the target rotation speed of the first flywheel 13 = the actual rotation speed of the engine 4 × 3" is obtained. In the following description, the target rotation speed of the first flywheel 13 may be referred to as the "first target rotation speed" to distinguish it from the target rotation speed of the engine 4.

[0311] In the charge mode, the first clutch 26 is engaged and the second clutch 27 is disengaged. When the first clutch 26 is engaged, the first flywheel 13 and the engine 4 are connected via a first path in which the speed increasing mechanism 20 is provided.

[0312] The first path is a path (power transmission path) connecting the engine 4 and the first flywheel 13, on which the speed increasing mechanism 20 and the first clutch 26 are provided. For example, in the case of the embodiment (first embodiment of the first power transmission unit 11) shown in FIG. 2 , the first path is a path that runs from the output shaft 4 a of the engine 4 to the first flywheel 13 via the second flywheel 14, the intermediate shaft 17, the first clutch 26, and the speed increasing mechanism 20.

[0313] When the first flywheel 13 and the engine 4 are connected via the first path provided with the speed-increasing mechanism 20, the rotational power of the engine 4 is accelerated by the speed-increasing mechanism 20 and transmitted to the first flywheel 13. As a result, the rotational speed of the first flywheel 13 becomes higher than the rotational speed of the engine 4, and the rotational power of the engine 4 can be effectively accumulated in the first flywheel 13.

[0314] <Charge preparation mode> The charge preparation mode is a preparatory mode before transitioning to the charge mode, and is a mode switched to before transitioning to the charge mode.

[0315] In the charge preparation mode, the engine 4 rotates at a target rotation speed. However, when the load on the engine 4 increases due to the workload or the like, the rotation speed may fall below the target rotation speed. In the charge preparation mode, the rotation speed of the first flywheel 13 is less than the target rotation speed (first target rotation speed) of the first flywheel 13. The rotation speed of the first flywheel 13 is greater than or equal to the rotation speed (actual rotation speed) of the engine 4. In the charge preparation mode, the first clutch 26 is in the process of switching from a disengaged state to an engaged state, and the second clutch 27 is disengaged. When the first clutch 26 switches from a disengaged state to an engaged state, the mode transitions to the charge mode.

[0316] The state in which the first clutch 26 is in the process of switching from the disengaged state to the engaged state is a state in which the first friction plates 26A of the first clutch 26 are pushed by the hydraulic piston (first hydraulic piston 73) and approach the second friction plates 26B, but are not yet in a state in which power can be transmitted. In other words, this is a state in which a one-shot operation is being performed to prepare the first clutch 26 for engagement. Hereinafter, this state will be referred to as a "void stroke eliminated" state of the first clutch 26. Also, in FIG. 14, this state is represented as "void stroke eliminated."

[0317] <Boost mode> The boost mode is a mode in which the rotational power of the engine 4 is assisted by the rotational power of the first flywheel 13 when the rotational speed of the first flywheel 13 is higher than the rotational speed of the engine 4 (actual rotational speed).

[0318] In boost mode, the engine 4 rotates at a target rotation speed. However, when the load on the engine 4 increases due to a work load or the like, the rotation speed may fall below the target rotation speed. In boost mode, the rotation speed of the first flywheel 13 is higher than the rotation speed (actual rotation speed) of the engine 4. This is because the rotation speed of the first flywheel 13 is higher than the rotation speed (actual rotation speed) of the engine 4 in the charge mode, which is executed before switching to boost mode. Also, in boost mode, a load is placed on the engine 4 due to a work load or the like, causing the actual rotation speed of the engine 4 to decrease. A work load occurs, for example, when a working device is connected to the PTO shaft 8 of the work vehicle 1 and power is transmitted from the PTO shaft 8 to the working device to drive it.

[0319] In the boost mode, the first clutch 26 is disengaged and the second clutch 27 is engaged. In the boost mode, the second clutch 27 transitions from a half-clutch state to an engaged state. By engaging the second clutch 27, the first flywheel 13 and the engine 4 are connected via a second path.

[0320] The second path is a path (power transmission path) connecting the engine 4 and the first flywheel 13 that is not provided with the speed increasing mechanism 20 and is provided with the second clutch 27. For example, in the case of the embodiment shown in FIG. 2 (first embodiment of the first power transmission unit 11), the second path is a path that runs from the output shaft 4a of the engine 4 to the first flywheel 13 via the second flywheel 14, the intermediate shaft 17, and the second clutch 27.

[0321] When the first flywheel 13 and the engine 4 are connected via the second path, the rotational speed of the first flywheel 13 is higher than the rotational speed of the engine 4, and therefore the rotational power of the first flywheel 13 can assist the rotational power of the engine 4. In other words, the boost mode is an operation mode in which the rotational power of the first flywheel 13 assists the rotational power of the engine 4 when the rotational speed of the first flywheel 13 is higher than the rotational speed (actual rotational speed) of the engine 4.

[0322] <Boost preparation mode> The boost preparation mode is a preparatory mode before transitioning to the boost mode. The boost preparation mode is a mode that is switched to before transitioning to the boost mode. The boost preparation mode is a mode that is transitioned to when the load on the engine 4 increases due to an increase in work load, etc. By transitioning to the boost preparation mode, preparations are made to transition to the boost mode, in which the rotational energy stored in the first flywheel 13 in the charge mode is used to assist the engine 4.

[0323] In the boost preparation mode, the engine 4 rotates at a target rotation speed. However, when the load on the engine 4 increases due to the workload or the like, the rotation speed may fall below the target rotation speed. In the boost preparation mode, the rotation speed of the first flywheel 13 is the first target rotation speed and is higher than the rotation speed (actual rotation speed) of the engine 4. In addition, the first clutch 26 is engaged, and the second clutch 27 is in the process of switching from a disengaged state to an engaged state (a state where the idle stroke is full). When the second clutch 27 switches to the engaged state, the mode transitions to the boost mode.

[0324] The state in which second clutch 27 is in the process of switching from the disengaged state to the engaged state is a state in which first friction plates 27A of second clutch 27 are pushed by the hydraulic piston (second hydraulic piston 75) and approach second friction plates 27B, but are not yet in a state in which power can be transmitted. In other words, this is a state in which one shot is being performed to prepare second clutch 27 for engagement. Hereinafter, this state will be referred to as a "void stroke eliminated" state of second clutch 27. Also, in FIG. 14, this state is represented as "void stroke eliminated."

[0325] <Staple mode> The tenacity mode is a mode in which, when the rotation speed of the first flywheel 13 is equal to or lower than the rotation speed of the engine 4 (actual rotation speed), the inertial force of the first flywheel 13 prevents a sudden drop in the rotation speed of the engine 4.

[0326] In the tenacity mode, the engine 4 rotates at a target rotation speed. However, when the load on the engine 4 increases due to the workload or the like, the rotation speed may fall below the target rotation speed. In the tenacity mode, the rotation speed of the first flywheel 13 is equal to or lower than the rotation speed (actual rotation speed) of the engine 4. In more detail, when the mode is shifted from the boost mode to the tenacity mode, the rotation speed of the first flywheel 13 at the time of shifting to the tenacity mode is the same as the rotation speed (actual rotation speed) of the engine 4. When the mode is shifted to the tenacity mode from another operating mode, the rotation speed of the first flywheel 13 at the time of shifting to the tenacity mode is smaller than the rotation speed (actual rotation speed) of the engine 4.

[0327] In the tenacity mode, the first clutch 26 is disengaged and the second clutch 27 is engaged. In the tenacity mode, the second clutch 27 transitions from a half-clutch state to an engaged state. By engaging the second clutch 27, the first flywheel 13 and the engine 4 are connected via the second path.

[0328] When the first flywheel 13 and the engine 4 are connected via the second path, the first flywheel 13 and the engine 4 rotate together. Therefore, when a high load is applied to the engine 4, the inertial force of the first flywheel 13 can prevent a sudden drop in the rotation speed of the engine 4.

[0329] In the stickiness mode, the rotational speed of the first flywheel 13 is equal to or lower than the rotational speed of the engine 4, so the rotational power of the first flywheel 13 cannot assist the rotational power of the engine 4, but it can prevent a sudden drop in the rotational speed of the engine 4. Therefore, in the stickiness mode, when the first flywheel 13 does not have enough rotational energy to assist the rotational power of the engine 4, the rotational power can be used to prevent a sudden drop in the rotational speed of the engine 4 (to make the engine 4 stick).

[0330] <Sticky preparation mode> The stickiness preparation mode is a preparation mode before transitioning to the stickiness mode. The stickiness preparation mode is a mode that is switched to before transitioning to the stickiness mode.

[0331] In the persistence preparation mode, the engine 4 rotates at a target rotation speed. However, when the load on the engine 4 increases due to the work load or the like, the rotation speed may fall below the target rotation speed. In the persistence preparation mode, the rotation speed of the first flywheel 13 is lower than the rotation speed (actual rotation speed) of the engine 4. Also, the first clutch 26 is disengaged, and the second clutch 27 is in the process of switching from the disengaged state to the engaged state (a state where the idle stroke is reduced). When the second clutch 27 switches to the engaged state, the mode transitions to the persistence mode.

[0332] <Engine off mode> The engine-off mode is a mode in which the engine 4 is off (the spark plug is not igniting), but the first flywheel 13 is rotating while decelerating.

[0333] In the engine-off mode, the spark plug of the engine 4 is not ignited, but the engine 4 rotates by inertia while decelerating. The first flywheel 13 also rotates by inertia while decelerating.

[0334] In the engine-off mode, the first clutch 26 and the second clutch 27 are connected. Therefore, the first flywheel 13 is connected to the engine 4 via the first clutch 26 and the second clutch 27. Because the first flywheel 13 has a large inertia force, it tends to continue rotating for a while even after the engine 4 is turned off. However, by being connected to the engine 4 via the first clutch 26 and the second clutch 27, the rotation is braked, and the rotation can be stopped early.

[0335] However, in the engine-off mode, if the rotation speed of the first flywheel 13 is sufficiently low (for example, if the engine 4 is started and then stopped immediately), it is not necessary to engage both or either one of the first clutch 26 and the second clutch 27. This is because, if the rotation speed of the first flywheel 13 is sufficiently low, the first flywheel 13 will stop in a short time without braking the rotation. An example of a sufficiently low rotation speed of the first flywheel 13 is when the rotation speed of the first flywheel 13 is equal to or lower than the idling rotation speed of the engine 4.

[0336] <About transitioning (switching) operation modes> Next, the transition of the operation mode will be described.

[0337] FIG. 15 is a state transition diagram relating to the operation modes.

[0338] Free mode can be entered from all other operating modes except boost preparation mode. Charge mode can be entered from charge preparation mode. Charge preparation mode can be entered from stickiness mode. Stickiness mode can be entered from stickiness preparation mode and boost mode. Stickiness preparation mode can be entered from free mode. Boost mode can be entered from boost preparation mode. Boost preparation mode can be entered from charge mode. Engine off mode can be entered from all operating modes.

[0339] The conditions for transitioning between operation modes will be explained below.

[0340] Fig. 16 shows conditions (thresholds) for transitioning between operation modes. Fig. 17 to Fig. 23 are flowcharts showing an example of the flow (steps) of transitioning between operation modes.

[0341] <Transition from free mode to preparation mode> The transition from the free mode to the nebari preparation mode will be described with reference to FIG.

[0342] First, the transition to the free mode is automatically executed by starting the engine 4, or is executed when predetermined conditions (described later) are satisfied in another operation mode (see Figures 18 to 21 and 23). The transition from another operation mode to the free mode will be explained later.

[0343] In the free mode, the engine 4 is running, and the first clutch 26 and the second clutch 27 are in a disengaged state. Because the first clutch 26 and the second clutch 27 are in a disengaged state, the rotational power of the engine 4 is not transmitted to the first flywheel 13, and the first flywheel 13 is stopped. However, as described above, when transitioning to the free mode from another operating mode, the first flywheel 13 may be rotating due to inertial force.

[0344] The transition from the free mode to the negation preparation mode is executed when the rotation speed of the first flywheel 13 is smaller than the rotation speed (actual rotation speed) of the engine 4 and the load factor of the engine 4 is less than a predetermined value X1 (%). In other words, the transition from the free mode to the negation preparation mode is executed when the rotation speed of the first flywheel 13 is smaller than the rotation speed (actual rotation speed) of the engine 4 (first condition AA1) and the load factor of the engine 4 is less than a predetermined value X1 (second condition AA2) are satisfied. The predetermined value X1 is stored in the memory unit 112.

[0345] Here, if the transition to the free mode is automatically executed by starting the engine 4, the first flywheel 13 is not yet rotating. On the other hand, if the transition to the free mode is executed from another operation mode (see FIGS. 18 to 21 and 23), the first flywheel 13 is rotating at a rotation speed lower than the rotation speed (actual rotation speed) of the engine 4. For example, if the transition is made from the tenacity mode to the tenacity preparation mode via the free mode, the first flywheel 13 is rotating at a rotation speed lower than the rotation speed (actual rotation speed) of the engine 4.

[0346] After transitioning to the free mode, the calculation unit 111 of the control device 110 determines whether or not the first condition AA1 is satisfied (S3). Specifically, the calculation unit 111 compares the rotation speed of the first flywheel 13 measured by the first rotation speed sensor 18 with the rotation speed (actual rotation speed) of the engine 4 calculated by the second rotation speed sensor 15 to determine whether or not the first condition AA1 is satisfied.

[0347] If the first condition is satisfied, the calculation unit 111 determines whether or not a second condition AA2 is satisfied (S4). Specifically, the calculation unit 111 (load factor calculation unit 111a) calculates a load factor based on the command injection amount detected by the accelerator opening sensor 19 and the limited injection amount corresponding to the boost pressure stored in the memory unit 112, and compares the load factor with a predetermined value X1 to determine whether or not the second condition AA2 is satisfied (S4).

[0348] If both the first condition AA1 and the second condition AA2 are satisfied, the calculation unit 111 (operation mode determination unit 111d) determines to transition to the tenacity preparation mode. As a result, the control device 110 transmits a control signal for transitioning to the tenacity preparation mode to the operation unit 140, and the control system 100 transitions from free mode to the tenacity preparation mode (S5). At this time, the second hydraulic piston 75 of the second clutch 27 is driven based on the control signal (one-shot pulse current) transmitted from the control device 110, causing the first friction plate 27A to move, and the second clutch 27 transitions to a state in the middle of switching from a disengaged state to an engaged state (a state with the idle stroke reduced). If at least one of the first condition AA1 and the second condition AA2 is not satisfied (No in S3 or No in S4), the transition to the tenacity preparation mode is not made.

[0349] The reason why the condition for the transition from the free mode to the stickiness preparation mode is that the rotation speed of the first flywheel 13 is smaller than the rotation speed (actual rotation speed) of the engine 4 (first condition AA1) is required is that if the transition from the stickiness preparation mode to the stickiness mode is made while the rotation speed of the first flywheel 13 is larger than the rotation speed (actual rotation speed) of the engine 4, the load on the engine 4 will increase. Also, the reason why the condition for the load factor of the engine 4 is less than a predetermined value X1 (second condition AA2) is required is that if the transition from the stickiness preparation mode to the stickiness mode is made while the load factor of the engine 4 is high, the load on the engine 4 will increase.

[0350] <Transition from perseverance preparation mode to perseverance mode> The transition from the stickiness preparation mode to the stickiness mode will be described with reference to FIG.

[0351] The transition from the stickiness preparation mode to the stickiness mode is executed when the rotation speed of the first flywheel 13 is smaller than the rotation speed (actual rotation speed) of the engine 4, the torque rate of the engine 4 is less than a predetermined value Y1 (%), and the actual rotation speed of the engine 4 is equal to the target rotation speed. In other words, the transition from the stickiness preparation mode to the stickiness mode is executed when all of the following conditions are satisfied: the rotation speed of the first flywheel 13 is smaller than the rotation speed (actual rotation speed) of the engine 4 (first condition BB1), the torque rate of the engine 4 is less than the predetermined value Y1 (second condition BB2), and the actual rotation speed of the engine 4 is equal to the target rotation speed (third condition BB3). The predetermined value Y1 is stored in the memory unit 112.

[0352] After transitioning to the stickiness preparation mode, the calculation unit 111 of the control device 110 determines whether or not the first condition BB1 is satisfied (S6). Specifically, the calculation unit 111 compares the rotation speed of the first flywheel 13 measured by the first rotation speed sensor 18 with the rotation speed (actual rotation speed) of the engine 4 calculated by the second rotation speed sensor 15 to determine whether or not the first condition BB1 is satisfied.

[0353] If the first condition BB1 is satisfied, the calculation unit 111 determines whether or not the second condition BB2 is satisfied (S7). Specifically, the calculation unit 111 (torque rate calculation unit 111b) calculates a torque rate based on the command injection amount detected by the accelerator opening sensor 19 and the limited injection amount of the full load curve stored in the storage unit 112, and compares the torque rate with a predetermined value Y1 to determine whether or not the second condition BB2 is satisfied (S7).

[0354] If the second condition BB2 is satisfied, the calculation unit 111 compares the target rotation speed of the engine 4 stored in the memory unit 112 with the rotation speed (actual rotation speed) of the engine 4 calculated by the second rotation speed sensor 15 to determine whether the third condition BB3 is satisfied (S8).

[0355] If the first condition BB1, the second condition BB2, and the third condition BB3 are all satisfied, the calculation unit 111 (operation mode determination unit 111d) determines to transition to the tenacity mode. As a result, a control signal for transitioning to the tenacity mode is sent from the control device 110 to the operation unit 140, and the control system 100 transitions from the tenacity preparation mode to the tenacity mode (S10). At this time, the second clutch 27 switches from the ineffective stroke filled state to the half-clutch state and then to the engaged state based on the control signal (second control signal) from the control device 110. If at least one of the first condition BB1, the second condition BB2, and the third condition BB3 is not satisfied (No in S6, No in S7, or No in S8), the transition to the tenacity mode is not made.

[0356] The reason why the condition for the transition from the stickiness preparation mode to the stickiness mode is that the rotation speed of the first flywheel 13 is smaller than the rotation speed (actual rotation speed) of the engine 4 (first condition BB1) is required is because, in the stickiness preparation mode, the rotation speed of the first flywheel 13 is smaller than the rotation speed (actual rotation speed) of the engine 4. The reason why the condition for the torque rate of the engine 4 is less than a predetermined value Y1 (second condition BB2) is required is because, if the engine 4 transitions to the stickiness mode while the torque rate of the engine 4 is high, the load on the engine 4 will increase. The reason why the condition for the actual rotation speed of the engine 4 is the target rotation speed (third condition BB3) is required is because the transition to the stickiness mode is made after confirming that the actual rotation speed of the engine 4 has settled at the target rotation speed. The third condition BB3 makes it possible to prevent a transition to the stickiness mode when a load is applied to the engine 4 due to a work load or the like (when the actual rotation speed of the engine 4 is smaller than the target rotation speed).

[0357] <Transition from Perseverance Preparation Mode to Free Mode> The transition from the tenacity preparation mode to the free mode will be described with reference to FIG.

[0358] The transition from the tenacity preparation mode to the free mode is executed when the rotation speed of the first flywheel 13 is smaller than the rotation speed (actual rotation speed) of the engine 4 and the number of attempts to engage the second clutch 27 (the number of one-shot attempts) within a predetermined time T1 reaches a predetermined number N1. In other words, the transition from the tenacity preparation mode to the free mode is executed when the rotation speed of the first flywheel 13 is smaller than the rotation speed (actual rotation speed) of the engine 4 (first condition CC1) and the number of attempts to engage the second clutch 27 (the number of one-shot attempts) within the predetermined time T1 reaches a predetermined number N1 (second condition CC2). The predetermined time T1 and the predetermined number N1 are stored in the memory unit 112. The predetermined time T1 is measured by a timer (not shown), and the measured value is transmitted to the control device 110.

[0359] In other words, the second condition CC2 is satisfied when the number of one-shot pulses for connecting second clutch 27 within a predetermined time T1 reaches a predetermined number N1. The number of one-shot pulses for connecting second clutch 27 refers to the number of times a one-shot pulse current is supplied to a hydraulic control valve (solenoid valve) that drives second hydraulic piston 75 that presses first friction plate 27A of second clutch 27.

[0360] After transitioning to the stickiness preparation mode, the calculation unit 111 of the control device 110 determines whether or not a first condition CC1 is satisfied (S6). Specifically, the calculation unit 111 compares the rotation speed of the first flywheel 13 measured by the first rotation speed sensor 18 with the rotation speed (actual rotation speed) of the engine 4 calculated by the second rotation speed sensor 15 to determine whether or not the first condition CC1 is satisfied.

[0361] If the first condition CC1 is satisfied, and if at least one of the second condition BB2 and the third condition BB3 is not satisfied (if the conditions for transitioning to the tenacity mode are not satisfied), the calculation unit 111 determines whether the second condition CC2 is satisfied (S9). Specifically, the calculation unit 111 counts the number of one-shots performed within a predetermined time T1 (number of one-shots), and determines whether the number of one-shots within the predetermined time T1 has reached N1 (S9).

[0362] If the first condition CC1 and the second condition CC2 are satisfied, the calculation unit 111 (operation mode determination unit 111d) determines to transition to the free mode. As a result, a control signal for transitioning to the free mode is sent from the control device 110 to the operation unit 140, and the control system 100 transitions from the resilience preparation mode to the free mode (S11). At this time, the second clutch 27 switches from the ineffective stroke reduced state to the disengaged state based on the control signal (second control signal) from the control device 110. If at least one of the first condition CC1 and the second condition CC2 is not satisfied (No in S6 or No in S10), the transition to the free mode is not performed.

[0363] In the tenacity preparation mode, one-shots (supply of one-shot pulse current) for connecting second clutch 27 are performed at predetermined time intervals, but if the conditions for switching to the tenacity mode are not met even after a predetermined number N1 of one-shots have been performed within a predetermined time T1, the execution of the one-shots is stopped and the connection preparation state of second clutch 27 is canceled. As a result, the mode switches to the free mode without switching to the tenacity mode.

[0364] For example, if the workload increases in the tenacity preparation mode and the torque rate increases, transitioning from the tenacity preparation mode to the tenacity mode may result in a sudden drop in the rotation speed of the engine 4 because the engine 4 and the first flywheel 13 are connected via the second clutch 27. In this case, even when one-shots have been performed a predetermined number N1 times within a predetermined time T1 in the tenacity preparation mode, if the condition for transitioning to the tenacity mode (torque rate less than Y1%) is not met, control is performed so that transition to the tenacity mode is not made (transition to the free mode), thereby preventing a sudden drop in the engine rotation speed.

[0365] The reason why the condition for the transition from the stickiness preparation mode to the free mode is that the rotation speed of the first flywheel 13 is smaller than the rotation speed (actual rotation speed) of the engine 4 (first condition CC1) is satisfied is because, in the stickiness preparation mode, the rotation speed of the first flywheel 13 is smaller than the rotation speed (actual rotation speed) of the engine 4. The reason why the condition for the transition from the stickiness preparation mode to the free mode is that the number of attempts to engage the second clutch 27 (number of one-shot attempts) within the predetermined time T1 reaches a predetermined number N1 (second condition CC2) is satisfied is because, if the condition for transitioning to the stickiness mode is not satisfied even when the one-shot attempt has been performed the predetermined number N1 within the predetermined time T1, it is determined that the transition to the stickiness mode should be abandoned in order to prevent a sudden drop in the engine rotation speed, as described above.

[0366] <Transition from Tenacity Mode to Charge Preparation Mode> The transition from the tenacity mode to the charge preparation mode will be described with reference to FIG.

[0367] The transition from the tenacity mode to the charge preparation mode is executed when the rotation speed of the first flywheel 13 is the same as the rotation speed (actual rotation speed) of the engine 4 and the load factor of the engine 4 is less than a predetermined value X2 (%). In other words, the transition from the tenacity mode to the charge preparation mode is executed when the rotation speed of the first flywheel 13 is the same as the rotation speed (actual rotation speed) of the engine 4 (first condition DD1) and the load factor of the engine 4 is less than a predetermined value X2 (second condition DD2) are satisfied. The predetermined value X2 is stored in the memory unit 112.

[0368] After the transition to the tenacity mode, the calculation unit 111 of the control device 110 determines whether or not a first condition CC1 is satisfied (S12). Specifically, the calculation unit 111 compares the rotation speed of the first flywheel 13 measured by the first rotation speed sensor 18 with the rotation speed (actual rotation speed) of the engine 4 calculated by the second rotation speed sensor 15 to determine whether or not the first condition DD1 is satisfied.

[0369] If the first condition DD1 is satisfied, the calculation unit 111 determines whether or not the second condition DD2 is satisfied (S13). Specifically, the calculation unit 111 (load factor calculation unit 111a) calculates the load factor based on the command injection amount detected by the accelerator opening sensor 19 and the limited injection amount corresponding to the boost pressure stored in the memory unit 112, and compares the load factor with a predetermined value X2 to determine whether or not the second condition DD2 is satisfied (S13).

[0370] If the first condition DD1 and the second condition DD2 are satisfied, the calculation unit 111 (operation mode determination unit 111d) determines to transition to the charge preparation mode. As a result, a control signal for transitioning to the charge preparation mode is sent from the control device 110 to the operation unit 140, and the control system 100 transitions from the tenacity mode to the charge preparation mode (S14). At this time, the first hydraulic piston 73 of the first clutch 26 is driven based on the control signal (first control signal) sent from the control device 110, causing the first friction plate 26A to move, and the first clutch 26 enters a state in the middle of switching from a disengaged state to an engaged state (a state with the void stroke reduced). Furthermore, the second clutch 27 switches from an engaged state to a disengaged state based on the control signal (second control signal) sent from the control device 110. If at least one of the first condition DD1 and the second condition DD2 is not satisfied (No in S12 or No in S13), the system does not transition to the charge preparation mode.

[0371] The reason why the condition for the transition from the persistence mode to the charge preparation mode described above is that the rotation speed of the first flywheel 13 must be the same as the rotation speed (actual rotation speed) of the engine 4 (first condition DD1) is that, because the rotation speed of the first flywheel 13 is the same as the actual rotation speed of the engine 4, it can be determined that preparations are in place to increase the rotation speed of the first flywheel 13 to a value greater than the actual rotation speed of the engine 4. In addition, the reason why the condition for the load factor of the engine 4 to be less than a predetermined value X2 (second condition DD2) is that when the load factor of the engine 4 is low, there is no need to assist the rotation power of the engine 4 with the rotation power of the first flywheel 13, and therefore it is determined that preparations for transition to the charge mode should be executed to accumulate rotation power in the first flywheel 13 in preparation for future assistance.

[0372] <Transition from Persistent Mode to Free Mode> The transition from the persistent mode to the free mode will be described with reference to FIG.

[0373] The transition from the tenacity mode to the free mode is executed when the rotation speed of the first flywheel 13 is smaller than the rotation speed (actual rotation speed) of the engine 4 and the torque rate of the engine 4 is equal to or greater than a predetermined value Y2 (%). In other words, the transition from the tenacity mode to the free mode is executed when the rotation speed of the first flywheel 13 is smaller than the rotation speed (actual rotation speed) of the engine 4 (first condition EE1) and the torque rate of the engine 4 is equal to or greater than a predetermined value Y2 (second condition EE2). The predetermined value Y2 is stored in the storage unit 112.

[0374] After transitioning to the persistence mode, the calculation unit 111 of the control device 110 determines whether or not the first condition EE1 is satisfied (S12). Specifically, the calculation unit 111 compares the rotation speed of the first flywheel 13 measured by the first rotation speed sensor 18 with the rotation speed (actual rotation speed) of the engine 4 calculated by the second rotation speed sensor 15 to determine whether or not the first condition EE1 is satisfied. Note that in the persistence mode, the rotation speed of the first flywheel 13 does not exceed the rotation speed (actual rotation speed) of the engine 4. Therefore, if "engine rotation speed = first flywheel rotation speed" is not satisfied in step 12 executed after transitioning to the persistence mode, "engine rotation speed > first flywheel rotation speed" will be satisfied.

[0375] If the first condition EE1 is satisfied, the calculation unit 111 determines whether or not the second condition EE2 is satisfied (S15). Specifically, the calculation unit 111 (torque rate calculation unit 111b) calculates a torque rate based on the command injection amount detected by the accelerator opening sensor 19 and the limited injection amount of the full load curve stored in the storage unit 112, and compares the torque rate with a predetermined value Y2 to determine whether or not the second condition EE2 is satisfied (S15).

[0376] If the first condition EE1 and the second condition EE2 are satisfied, the calculation unit 111 (operation mode determination unit 111d) determines to transition to the free mode. As a result, a control signal for transitioning to the free mode is sent from the control device 110 to the operation unit 140, and the control system 100 transitions from the tenacity mode to the free mode (S16). At this time, the second clutch 27 switches from the connected state to the disconnected state based on the control signal (second control signal) from the control device 110. If at least one of the first condition EE1 and the second condition EE2 is not satisfied (No in S12 or No in S15), the transition to the free mode is not performed.

[0377] The reason why the condition for the transition from the persistence mode to the free mode described above is that the rotation speed of the first flywheel 13 is smaller than the rotation speed (actual rotation speed) of the engine 4 (first condition EE1) is required is because in the persistence mode, the rotation speed of the first flywheel 13 is smaller than the rotation speed (actual rotation speed) of the engine 4. In addition, the reason why the condition for the torque rate of the engine 4 to be equal to or greater than a predetermined value Y2 (second condition EE2) is required is because, in the persistence mode, if the load (torque rate) of the engine 4 suddenly increases due to the addition of a work load, for example, the mode transitions to the free mode and the load on the engine 4 is reduced.

[0378] <Transition from charge preparation mode to charge mode> The transition from the charge preparation mode to the charge mode will be described with reference to FIG.

[0379] The transition from the charge preparation mode to the charge mode is executed when the rotation speed of the first flywheel 13 is the same as the rotation speed (actual rotation speed) of the engine 4 and the torque rate of the engine 4 is less than a predetermined value Y3 (%). In other words, the transition from the charge preparation mode to the charge mode is executed when the rotation speed of the first flywheel 13 is the same as the rotation speed (actual rotation speed) of the engine 4 (first condition FF1) and the torque rate of the engine 4 is less than a predetermined value Y3 (second condition FF2) are satisfied. The predetermined value Y3 is stored in the storage unit 112.

[0380] After transitioning to the charge preparation mode, the calculation unit 111 of the control device 110 determines whether or not the first condition FF1 is satisfied (S17). Specifically, the calculation unit 111 compares the rotation speed of the first flywheel 13 measured by the first rotation speed sensor 18 with the rotation speed (actual rotation speed) of the engine 4 calculated by the second rotation speed sensor 15 to determine whether or not the first condition FF1 is satisfied.

[0381] If the first condition FF1 is satisfied, the calculation unit 111 determines whether or not the second condition FF2 is satisfied (S13). Specifically, the calculation unit 111 (torque rate calculation unit 111b) calculates a torque rate based on the command injection amount detected by the accelerator opening sensor 19 and the limited injection amount of the full load curve stored in the storage unit 112, and compares the torque rate with a predetermined value Y3 to determine whether or not the second condition FF2 is satisfied (S18).

[0382] If the first condition FF1 and the second condition FF2 are satisfied, the calculation unit 111 (operation mode determination unit 111d) determines to transition to charge mode. As a result, a control signal for transitioning to charge mode is sent from the control device 110 to the operation unit 140, and the control system 100 transitions from charge preparation mode to charge mode (S19). At this time, based on the control signal (first control signal) sent from the control device 110, the first clutch 26 switches from a state where the idle stroke is reduced to a connected state. If at least one of the first condition FF1 and the second condition FF2 is not satisfied (No in S17 or No in S18), the transition to charge mode is not made.

[0383] The reason why the condition for the transition from the charge preparation mode to the charge mode described above is that the rotation speed of the first flywheel 13 is the same as the rotation speed (actual rotation speed) of the engine 4 (first condition FF1) is that, when the rotation speed of the first flywheel 13 has reached the same as the rotation speed (actual rotation speed) of the engine 4, it can be determined that preparations are complete to increase the rotation speed of the first flywheel 13 to a value greater than the actual rotation speed of the engine 4. The reason why the condition for the torque rate of the engine 4 is less than a predetermined value Y3 (second condition FF2) is that transitioning to the charge mode when the load (torque rate) of the engine 4 is high is undesirable because it increases the load on the engine 4, and it is preferable to transition to the charge mode when the load (torque rate) of the engine 4 is low and store rotational energy in the first flywheel 13.

[0384] <Transition from Charge Preparation Mode to Free Mode> The transition from the charge preparation mode to the free mode will be described with reference to FIG.

[0385] The transition from the charge preparation mode to the free mode is executed when the rotation speed of the first flywheel 13 is the same as the rotation speed (actual rotation speed) of the engine 4 and the number of attempts to engage the first clutch 26 (the number of one-shot attempts) within a predetermined time T2 reaches a predetermined number N2. In other words, the transition from the charge preparation mode to the free mode is executed when the rotation speed of the first flywheel 13 is the same as the rotation speed (actual rotation speed) of the engine 4 (first condition GG1) and the number of attempts to engage the second clutch 27 (the number of one-shot attempts) within the predetermined time T2 reaches a predetermined number N2 (second condition GG2). The predetermined time T2 and the predetermined number N2 are stored in the memory unit 112. The predetermined time T2 is measured by a timer (not shown), and the measured value is transmitted to the control device 110.

[0386] In other words, the second condition GG2 is satisfied when the number of one-shot pulses for connecting the first clutch 26 within a predetermined time T2 reaches a predetermined number N2. The number of one-shot pulses for connecting the first clutch 26 is the number of times a one-shot pulse current is supplied to the hydraulic control valve (solenoid valve) that drives the first hydraulic piston 73 that presses the first friction plate 26A of the first clutch 26.

[0387] After transitioning to the charge preparation mode, the calculation unit 111 of the control device 110 determines whether or not a first condition GG1 is satisfied (S17). Specifically, the calculation unit 111 compares the rotation speed of the first flywheel 13 measured by the first rotation speed sensor 18 with the rotation speed (actual rotation speed) of the engine 4 calculated by the second rotation speed sensor 15 to determine whether or not the first condition GG1 is satisfied.

[0388] When the first condition GG1 is satisfied, if the second condition FF2 is not satisfied (when the condition for transitioning to charge mode is not satisfied), the calculation unit 111 determines whether the second condition GG2 is satisfied (S20). Specifically, the calculation unit 111 counts the number of one-shots performed within a predetermined time T2, and determines whether the number of one-shots performed within the predetermined time T2 has reached N2 (S20).

[0389] If the first condition GG1 and the second condition GG2 are satisfied, the calculation unit 111 (operation mode determination unit 111d) determines to transition to the free mode. As a result, a control signal for transitioning to the free mode is sent from the control device 110 to the operation unit 140, and the control system 100 transitions from the charge preparation mode to the free mode (S21). At this time, the first clutch 26 switches from the ineffective stroke narrowed state to the disengaged state based on the control signal (first control signal) from the control device 110. If at least one of the first condition GG1 and the second condition GG2 is not satisfied (No in S17 or No in S20), the transition to the free mode is not performed.

[0390] In the charge preparation mode, one-shots (supply of one-shot pulse current) for connecting first clutch 26 are performed at predetermined time intervals, but if the conditions for switching to charge mode are not met even after a predetermined number N2 of one-shots have been performed within a predetermined time T2, the execution of the one-shots is stopped and the connection preparation state of first clutch 26 is canceled. As a result, the mode switches to free mode without switching to charge mode.

[0391] The reason why the condition for the transition from the charge preparation mode to the free mode described above is that the rotation speed of the first flywheel 13 must be the same as the rotation speed (actual rotation speed) of the engine 4 (first condition GG1) is because, in the charge preparation mode, the rotation speed of the first flywheel 13 is the same as the rotation speed (actual rotation speed) of the engine 4. The reason why the condition for the transition from the charge preparation mode to the free mode is that the number of attempts to engage the second clutch 27 (number of one-shot attempts) within the predetermined time T2 has reached a predetermined number N2 (second condition GG2) is because, if the condition for transitioning to the charge mode is not met even after the predetermined number N2 of one-shot attempts have been performed within the predetermined time T2, the transition to the charge mode should be abandoned.

[0392] <Transition from Charge Mode to Boost Preparation Mode> The transition from the charge mode to the boost preparation mode will be described with reference to FIG.

[0393] The transition from the charge mode to the boost preparation mode is executed when the rotation speed of the first flywheel 13 is a target rotation speed (first target rotation speed NA) that is greater than the rotation speed (actual rotation speed) of the engine 4, and the load factor of the engine 4 is less than a predetermined value X3 (%). In other words, the transition from the charge mode to the boost preparation mode is executed when the rotation speed of the first flywheel 13 is the first target rotation speed NA that is greater than the rotation speed (actual rotation speed) of the engine 4 (first condition HH1) and the load factor of the engine 4 is less than a predetermined value X3 (second condition HH2). The predetermined value X3 is stored in the storage unit 112.

[0394] The target rotation speed (first target rotation speed) NA of the first flywheel 13 is "the actual rotation speed of the engine 4 × the speed-increasing ratio a (a>1) of the speed-increasing mechanism 20." For example, when the speed-increasing ratio a=3, the target rotation speed of the first flywheel 13=the actual rotation speed of the engine 4 × 3. That is, in this case, the target rotation speed of the first flywheel 13 is three times the actual rotation speed of the engine 4. The speed-increasing ratio a is stored in the memory unit 112.

[0395] After transitioning to the charge mode, the calculation unit 111 of the control device 110 determines whether or not the first condition HH1 is satisfied (S22). Specifically, the calculation unit 111 determines whether or not the first condition HH1 is satisfied based on the rotation speed of the first flywheel 13 measured by the first rotation speed sensor 18, the rotation speed (actual rotation speed) of the engine 4 calculated by the second rotation speed sensor 15, and the first target rotation speed NA and the speed increase ratio a stored in the storage unit 112.

[0396] If the first condition HH1 is satisfied, the calculation unit 111 determines whether or not the second condition HH2 is satisfied (S23). Specifically, the calculation unit 111 (load factor calculation unit 111a) calculates the load factor based on the command injection amount detected by the accelerator opening sensor 19 and the limited injection amount corresponding to the boost pressure stored in the memory unit 112, and compares the load factor with a predetermined value X3 to determine whether or not the second condition HH2 is satisfied (S23).

[0397] If the first condition HH1 and the second condition HH2 are satisfied, the calculation unit 111 (operation mode determination unit 111d) determines to transition to the boost preparation mode. As a result, a control signal for transitioning to the boost preparation mode is sent from the control device 110 to the operation unit 140, and the control system 100 transitions from the charge mode to the boost preparation mode (S24). At this time, the second hydraulic piston 75 of the second clutch 27 is driven based on the control signal (one-shot pulse current) sent from the control device 110, and the first friction plate 27A moves, and the second clutch 27 enters a state in the middle of switching from a disengaged state to an engaged state (a state where the void stroke is full). If at least one of the first condition HH1 and the second condition HH2 is not satisfied (No in S22 or No in S23), the mode does not transition to the boost preparation mode.

[0398] The reason why the condition for the transition from the charge mode to the boost preparation mode described above is that the rotation speed of the first flywheel 13 is the first target rotation speed NA, which is higher than the rotation speed (actual rotation speed) of the engine 4 (first condition HH1), is that when the rotation speed of the first flywheel 13 reaches the first target rotation speed NA, it can be determined that an amount of rotational energy capable of assisting the engine 4 has been accumulated in the first flywheel 13. Also, the reason why the condition for the load factor of the engine 4 being less than a predetermined value X3 (second condition HH2) is that when the load factor of the engine 4 is small, it can be determined that there is no need to assist the engine 4 (it is sufficient to prepare for transition to the boost mode without transitioning to the boost mode).

[0399] <Transition from Charge Mode to Free Mode> The transition from the charge mode to the free mode will be described with reference to FIG.

[0400] The transition from charge mode to free mode is executed when the rotation speed of the first flywheel 13 is greater than the rotation speed (actual rotation speed) of the engine 4 and less than the first target rotation speed NA, and the torque rate of the engine 4 is equal to or greater than a predetermined value Y4. In other words, the transition from charge mode to free mode is executed when the following conditions are met: the rotation speed of the first flywheel 13 is greater than the rotation speed (actual rotation speed) of the engine 4 and less than the first target rotation speed NA (first condition JJ1), and the torque rate of the engine 4 is equal to or greater than the predetermined value Y4 (second condition JJ2). The first target rotation speed NA and the predetermined value Y4 are stored in the storage unit 112. As described above, the target rotation speed NA of the first flywheel 13 is "the actual rotation speed of the engine 4 × the speed-up ratio a (a>1) of the speed-up mechanism 20."

[0401] After transitioning to the charge mode, the calculation unit 111 of the control device 110 determines whether or not a first condition JJ1 is satisfied (S22). Specifically, the calculation unit 111 determines whether or not the first condition JJ1 is satisfied based on the rotational speed of the first flywheel 13 measured by the first rotational speed sensor 18, the rotational speed (actual rotational speed) of the engine 4 calculated by the second rotational speed sensor 15, and the first target rotational speed NA and speed increase ratio a stored in the storage unit 112. Note that in the charge mode, the rotational speed of the first flywheel 13 is greater than the actual rotational speed of the engine 4 and does not exceed the first target rotational speed NA. Therefore, if "engine rotational speed × a (a > 1) = first flywheel rotational speed" is not satisfied in step 22 performed after transitioning to the charge mode, the condition "the rotational speed of the first flywheel 13 is greater than the actual rotational speed of the engine 4 and less than the first target rotational speed NA" is satisfied.

[0402] If the first condition JJ1 is satisfied, the calculation unit 111 determines whether the second condition JJ2 is satisfied (S25). Specifically, the calculation unit 111 (torque ratio calculation unit 111b) calculates a torque ratio based on the command injection amount detected by the accelerator opening sensor 19 and the limited injection amount of the full load curve stored in the storage unit 112, and compares the torque ratio with a predetermined value Y4 to determine whether the second condition JJ2 is satisfied (S25).

[0403] If the first condition JJ1 and the second condition JJ2 are satisfied, the calculation unit 111 (operation mode determination unit 111d) determines to transition to the free mode. As a result, a control signal for transitioning to the free mode is sent from the control device 110 to the operation unit 140, and the control system 100 transitions from the charge mode to the free mode (S26). At this time, the first clutch 26 switches from the connected state to the disconnected state based on the control signal (first control signal) from the control device 110. If at least one of the first condition JJ1 and the second condition JJ2 is not satisfied (No in S22 or No in S25), the transition to the free mode is not performed.

[0404] The reason why the conditions for the transition from charge mode to free mode described above are that the rotation speed of the first flywheel 13 is greater than the rotation speed (actual rotation speed) of the engine 4 and less than the first target rotation speed NA (first condition JJ1) and that the torque rate of the engine 4 is greater than or equal to a predetermined value Y4 (second condition JJ2) is that if a large load is placed on the engine 4 while the first flywheel 13 is storing an amount of rotational energy capable of assisting the engine 4, the mode will transition to free mode and the load on the engine 4 will be reduced.

[0405] <Transition from boost preparation mode to boost mode> The transition from the boost preparation mode to the boost mode will be described with reference to FIG.

[0406] The transition from the boost preparation mode to the boost mode is executed when the rotation speed of the first flywheel 13 is the first target rotation speed NA that is greater than the rotation speed (actual rotation speed) of the engine 4, the load factor of the engine 4 is equal to or greater than a predetermined value X4 (%), and the drop rate of the engine 4 is equal to or greater than a predetermined value Z. In other words, the transition from the boost preparation mode to the boost mode is executed when all of the following conditions are satisfied: the rotation speed of the first flywheel 13 is the first target rotation speed NA that is greater than the rotation speed (actual rotation speed) of the engine 4 (first condition KK1), the load factor of the engine 4 is equal to or greater than a predetermined value X4 (second condition KK2), and the drop rate of the engine 4 is equal to or greater than a predetermined value Z (third condition KK3). The first target rotation speed NA, the predetermined value X3, and the predetermined value Z are stored in the storage unit 112. As described above, the target rotation speed NA of the first flywheel 13 is "the actual rotation speed of the engine 4 × the speed-up ratio a (a>1) of the speed-up mechanism 20."

[0407] After transitioning to the boost preparation mode, the calculation unit 111 of the control device 110 determines whether or not a first condition KK1 is satisfied (S27). Specifically, the calculation unit 111 determines whether or not the first condition KK1 is satisfied based on the rotation speed of the first flywheel 13 measured by the first rotation speed sensor 18, the rotation speed (actual rotation speed) of the engine 4 calculated by the second rotation speed sensor 15, and the first target rotation speed NA and the speed increase ratio a stored in the storage unit 112.

[0408] If the first condition KK1 is satisfied, the calculation unit 111 determines whether or not the second condition KK2 is satisfied (S28). Specifically, the calculation unit 111 (load factor calculation unit 111a) calculates the load factor based on the command injection amount detected by the accelerator opening sensor 19 and the limited injection amount corresponding to the boost pressure stored in the memory unit 112, and compares the load factor with a predetermined value X4 to determine whether or not the second condition KK2 is satisfied (S28).

[0409] If the second condition KK2 is satisfied, the calculation unit 111 determines whether or not the third condition KK3 is satisfied (S29). Specifically, the calculation unit 111 (drop rate calculation unit 111c) calculates a drop rate based on the actual rotation speed of the engine 4 detected by the second rotation speed sensor 15 and the target rotation speed of the engine 4 stored in the memory unit 112, and compares the drop rate with a predetermined value Z to determine whether or not the third condition KK3 is satisfied (S29).

[0410] If the first condition KK1, the second condition KK2, and the third condition KK3 are all satisfied, the calculation unit 111 (operation mode determination unit 111d) determines to transition to the boost mode. As a result, a control signal for transitioning to the boost mode is sent from the control device 110 to the operation unit 140, and the control system 100 transitions from the boost preparation mode to the boost mode (S30). At this time, the second clutch 27 switches from a state where the idle stroke is full to a half-clutch state and then to an engaged state based on the control signal (second control signal) from the control device 110. In other words, the second clutch 27 switches from a state where the clutch is ready to be engaged to an engaged state. If at least one of the first condition KK1, the second condition KK2, and the third condition KK3 is not satisfied (No in S27, No in S28, or No in S29), the transition to the boost mode is not performed.

[0411] In the transition from the boost preparation mode to the boost mode described above, the condition that the rotational speed of the first flywheel 13 is a first target rotational speed NA that is higher than the rotational speed (actual rotational speed) of the engine 4 (first condition KK1) is set is because, when the rotational speed of the first flywheel 13 reaches the first target rotational speed NA, it can be determined that an amount of rotational energy that can assist the engine 4 has been accumulated in the first flywheel 13. In addition, the conditions that the load factor of the engine 4 is equal to or greater than a predetermined value X4 (second condition KK2) and the drop rate of the engine 4 is equal to or greater than a predetermined value Z (third condition KK3) are set are because, in a situation where these conditions are met, there is a risk that the engine will stop unless the load on the engine 4 is reduced, and therefore it can be determined that it is necessary to assist the rotational power of the engine 4 with the rotational power of the first flywheel 13.

[0412] <Transition from Boost Mode to Nebari Mode> The transition from the boost mode to the slack mode will be described with reference to FIG.

[0413] The transition from the boost mode to the negligence mode is performed when the rotation speed of the first flywheel 13 becomes the same as the rotation speed (actual rotation speed) of the engine 4. In other words, the transition from the boost mode to the negligence mode is performed when the rotation speed of the first flywheel 13 is the same as the rotation speed (actual rotation speed) of the engine 4 (condition LL1) is satisfied.

[0414] After transitioning to the boost mode, the calculation unit 111 of the control device 110 determines whether or not a condition LL1 is satisfied (S31). Specifically, the calculation unit 111 determines whether or not the condition LL1 is satisfied by comparing the rotation speed of the first flywheel 13 measured by the first rotation speed sensor 18 with the rotation speed (actual rotation speed) of the engine 4 calculated by the second rotation speed sensor 15.

[0415] If the condition LL1 is satisfied, the mode is switched to the tenacity mode (S32). At this time, the states of the first clutch 26 and the second clutch 27 remain unchanged from the boost mode, but the rotation speed of the first flywheel 13 changes from being higher than the actual rotation speed of the engine 4 to being lower than it. If the condition LL1 is not satisfied (No in S31), the mode is not switched to the tenacity mode.

[0416] The reason why the condition LL1 (the rotational speed of the first flywheel 13 being the same as the rotational speed (actual rotational speed) of the engine 4 is a condition for transitioning from the boost mode to the slack mode is that when the rotational speed of the first flywheel 13 becomes the same as the rotational speed (actual rotational speed) of the engine 4, it can be determined that the rotational power accumulated in the first flywheel 13 can no longer assist the rotational power of the engine 4 (the rotational energy that can be supplied to the engine assist has been used up). In other words, since it can be determined that the engine can no longer be assisted in the boost mode, the system transitions from the boost mode to the slack mode. As a result, although the rotational power of the engine 4 cannot be assisted, it is possible to slacken the engine 4 and prevent a sudden drop in the rotational speed of the engine 4.

[0417] <Transition from Boost Mode to Free Mode> The transition from the boost mode to the free mode will be described with reference to FIG.

[0418] The transition from boost mode to free mode is executed when the rotation speed of the first flywheel 13 is smaller than the rotation speed (actual rotation speed) of the engine 4, the load factor of the engine 4 is less than a predetermined value X5 (%), and the actual rotation speed of the engine 4 is less than the target rotation speed. In other words, the transition from boost mode to free mode is executed when all of the following conditions are satisfied: the rotation speed of the first flywheel 13 is smaller than the rotation speed (actual rotation speed) of the engine 4 (first condition MMM1), the load factor of the engine 4 is less than a predetermined value X5 (second condition MM2), and the actual rotation speed of the engine 4 is less than the target rotation speed (third condition MM3). The predetermined value X5 and the target rotation speed of the engine 4 are stored in the memory unit 112.

[0419] After transitioning to the boost mode, the calculation unit 111 of the control device 110 determines whether or not the first condition MM1 is satisfied (S33). Specifically, the calculation unit 111 determines whether or not the first condition MM1 is satisfied by comparing the rotation speed of the first flywheel 13 measured by the first rotation speed sensor 18 with the rotation speed (actual rotation speed) of the engine 4 calculated by the second rotation speed sensor 15.

[0420] If the first condition MM1 is satisfied, the calculation unit 111 determines whether or not the second condition MM2 is satisfied (S34). Specifically, the calculation unit 111 (load factor calculation unit 111a) calculates the load factor based on the command injection amount detected by the accelerator opening sensor 19 and the limited injection amount corresponding to the boost pressure stored in the memory unit 112, and compares the load factor with a predetermined value X5 to determine whether or not the second condition MM2 is satisfied (S34).

[0421] If the second condition MM2 is satisfied, the calculation unit 111 determines whether or not the third condition MM3 is satisfied (S34). Specifically, the calculation unit 111 determines whether or not the third condition MM3 is satisfied by comparing the actual rotation speed of the engine 4 detected by the second rotation speed sensor 15 with the target rotation speed of the engine 4 stored in the memory unit 112 (S35).

[0422] If the first condition MM1, the second condition MM2, and the third condition MM3 are all satisfied, the calculation unit 111 (operation mode determination unit 111d) determines to transition to the free mode. As a result, a control signal for transitioning to the free mode is sent from the control device 110 to the operation unit 140, and the control system 100 transitions from the boost mode to the free mode (S36). At this time, the second clutch 27 is switched from the connected state to the disconnected state based on the control signal (second control signal) from the control device 110. If at least one of the first condition MM1, the second condition MM2, and the third condition MM3 is not satisfied (No in S33, No in S34, or No in S35), the transition to the free mode is not performed.

[0423] The reason why the condition for the transition from the boost mode to the free mode described above is that the rotational speed of the first flywheel 13 is smaller than the rotational speed (actual rotational speed) of the engine 4 (first condition MM1) is set is because it can be determined that the rotational power of the first flywheel 13 can no longer assist the rotational power of the engine 4 (the boost mode cannot be maintained) when the rotational speed of the first flywheel 13 becomes smaller than the rotational speed (actual rotational speed) of the engine 4. In addition, the reason why the condition for the load factor of the engine 4 is less than a predetermined value X5 (second condition MM2) is set is because, in the boost mode, if the load on the engine 4 decreases while the rotational power of the first flywheel 13 is assisting the rotational power of the engine 4 and the assist is no longer necessary, it is necessary to prevent the rotational power of the first flywheel 13 from assisting the engine 4 even though the load on the engine 4 is light. In addition, the reason why the condition that the actual rotation speed of engine 4 is less than the target rotation speed (third condition MM3) is required is that in boost mode, the actual rotation speed of engine 4 is recovering (increasing) from a decreased state, and therefore the actual rotation speed of engine 4 is less than the target rotation speed.

[0424] <Transition to engine off mode> The transition to the engine-off mode is performed by an operator in the work vehicle 1 turning the key off or the like. When the work vehicle is in an operating mode other than the engine-off mode, performing a key-off operation or the like turns the engine 4 off (a state in which the spark plug is not ignited), and the work vehicle 1 transitions to the engine-off mode. When transitioning to the engine-off mode, if any of the first clutch 26 and the second clutch 27 is not engaged, that clutch is engaged based on a control signal (first control signal or second control signal) from the control device 110. As a result, the first clutch 26 and the second clutch 27 are engaged. However, as described above, in the engine-off mode, if the rotation speed of the first flywheel 13 is sufficiently low (for example, if it is equal to or lower than the idling rotation speed of the engine 4), one or both of the first clutch 26 and the second clutch 27 do not need to be engaged.

[0425] <Additional explanation regarding operation mode transition> The following provides additional explanation regarding the transition of the above-mentioned operation modes.

[0426] As is clear from FIG. 15 and the above description, in the control system 100, it is possible to transition from free mode to tenacity preparation mode and then to tenacity mode, but it is not possible to transition from free mode to charge preparation mode and then to charge mode. To transition to charge mode, it is necessary to transition from tenacity mode via charge preparation mode. In other words, to transition from free mode to charge mode, it is necessary to transition via tenacity mode. The reason for this will be explained below.

[0427] In charge mode, first clutch 26 is engaged, causing the rotational speed of first flywheel 13 to be greater than the rotational speed (actual rotational speed) of engine 4 (for example, when the acceleration rate is 3, the rotational speed is three times the engine rotational speed), which places a heavy load on engine 4. Therefore, if the mode is shifted from free mode to charge mode without passing through tenacity mode, a heavy load is suddenly placed on engine 4. On the other hand, in tenacity mode, second clutch 27 is engaged, causing the rotational speed of first flywheel 13 to be equal to or less than the rotational speed (actual rotational speed) of engine 4, so the load on engine 4 is small. Therefore, by shifting from free mode to charge mode via tenacity mode, it is possible to prevent a sudden load from being placed on engine 4.

[0428] In the work vehicle 1, it is desirable for the first flywheel 13 to rotate at a higher rotational speed than the rotational speed of the engine 4 so that it can assist the engine 4 when the load on the engine 4 increases due to an increase in the workload or the like. To achieve this, it is necessary to switch to charge mode, thereby accelerating the rotational power of the engine 4 and transmitting it to the first flywheel 13. However, switching to charge mode when the workload is heavy increases the load on the engine 4, which interferes with work. Therefore, the control system 100 is configured to gradually increase the rotational speed of the first flywheel 13 by switching from free mode to tenacity mode and then to charge mode, while checking whether the load on the engine 4 is at a level that does not interfere with work.

[0429] As described above, the condition for transitioning between operating modes may be the load rate of the engine 4 or the torque rate. This will be explained below. The reason why the torque rate is sometimes used instead of the load rate is that even when the load on the engine 4 is light, the load rate becomes 100% when the rotation speed of the engine 4 is increasing. For example, when transitioning from the charge preparation mode to the charge mode, the first clutch 26 is engaged, increasing the rotation speed of the first flywheel 13, thereby increasing the rotation speed of the engine 4. In this case, if the condition (threshold) for transitioning from the charge preparation mode to the charge mode is set to "the load rate being less than a predetermined value," transition to the charge mode is not possible. On the other hand, when the load on the engine 4 is light, the torque rate does not become 100% even when the rotation speed of the engine 4 increases. Therefore, if the condition (threshold) for transitioning from the charge preparation mode to the charge mode is set to "the torque rate being less than a predetermined value," transition to the charge mode is possible.

[0430] In this way, when the rotation speed of the engine 4 is increasing under a light workload (when the rotation speed of the first flywheel 13 is increasing), a discrepancy occurs between the load rate and the torque rate. When the rotation speed of the engine 4 is increasing, the torque rate is used instead of the load rate as a condition for switching the operating mode, so that the operating mode can be switched reliably even under a light workload and when the rotation speed of the engine 4 is increasing.

[0431] For this reason, it is preferable to use the load rate as a condition for switching the operation mode when the rotation speed of the engine 4 is increasing (when the rotation speed of the first flywheel 13 is increasing), and to use the torque rate as a condition for switching the operation mode when the rotation speed of the engine 4 is not increasing (when the rotation speed of the first flywheel 13 is not increasing).

[0432] The load factors X1, X2, X3, X4, and X5, which are the conditions (threshold values) for transitioning to the above-mentioned operating modes, may all be the same value, or some or all of them may be different values. Furthermore, the torque factors Y1, Y2, Y3, and Y4 may all be the same value, or some or all of them may be different values. Furthermore, the predetermined times T1 and T2 may be the same time or may be different times. Furthermore, the one-shot counts N1 and N2 may be the same number of times or may be different numbers of times.

[0433] As described above, transition to each operation mode (switching between a plurality of operation modes), except for transition to the engine-off mode, is executed when a predetermined condition is satisfied.

[0434] The control device 110 executes control regarding the engagement and disengagement of the first clutch 26 and the second clutch 27 in order to switch between a plurality of operating modes. Here, "executing control regarding the engagement and disengagement of the first clutch 26 and the second clutch 27" includes a method (first method) in which the control device 110 transmits control signals (first control signal, second control signal) for engaging and disengaging the first clutch 26 and / or the second clutch 27 and switches the engagement and disengagement of the first clutch 26 and / or the second clutch 27 using the control signals, and a method (second method) in which the control device 110 notifies an operator that switching of the first clutch 26 and / or the second clutch 27 is possible, and the operator performs a predetermined operation based on the notification, thereby switching the engagement and disengagement of the first clutch 26 and / or the second clutch 27. Either the first method or the second method may be employed in the control system 100.

[0435] The first and second methods are applicable to all of the transitions between the operating modes described above (except for the transition to the engine-off mode), but the second method is particularly suitable for the transition from the charge mode to the boost preparation mode.

[0436] The following describes the case where the second method is applied to the transition from the charge mode to the boost preparation mode. In this case, when the rotation speed of the first flywheel 13 reaches the first target rotation speed in the charge mode (first condition HH1) and the load factor of the engine 4 is less than a predetermined value X3 (second condition HH2), the control device 110 notifies the operator that it is possible to switch (transition) from the charge mode to the boost preparation mode.

[0437] In this case, the operation mode determination unit 111d of the control device 110 determines to transition from the charge mode to the boost preparation mode, and then notifies the operator that switching (transition) to the boost preparation mode is possible. The control device 110 does not transmit a control signal to the operation unit 140 for automatically transitioning to the boost preparation mode based on the determination of the operation mode determination unit 111d, but transmits a control signal to the operation unit 140 for transitioning to the boost preparation mode based on an operation by the operator. In other words, the control device 110 first notifies the operator that switching to the boost preparation mode is possible, and when the operator performs an operation to switch to the boost preparation mode in response to this notification, transmits a control signal to the operation unit 140 for transitioning to the boost preparation mode.

[0438] The notification that switching from the charge mode to the boost preparation mode is possible is made, for example, by display on the screen of the display input device 130. Figures 24A and 24B show examples of screen displays when notifying that switching from the charge mode to the boost preparation mode is possible by display on the screen of the display input device 130. Figures 24A and 24B show the case where the display input device 130 is a touch panel display device.

[0439] FIG. 24A shows a screen 131A of the display / input device 130 in a state in which switching from the charge mode to the boost preparation mode is not possible in the charge mode (a state in which either the first condition HH1 or the second condition HH2 is not satisfied). In this state, the screen 131A only displays that the charge mode is being executed (charging is in progress). In this state, the operator cannot perform an operation to switch from the charge mode to the boost preparation mode. An indicator 132 showing the progress of charging (the accumulation of rotational energy in the first flywheel 13) is displayed on the screen 131A. In the illustrated example, the indicator 132 indicates the progress of charging by the length of a bar graph 132b within a display frame 132a. The progress of charging is calculated by (actual rotational speed of the first flywheel 13 / target rotational speed of the first flywheel 13). The operator can easily grasp the progress of charging by visually checking the indicator 132.

[0440] FIG. 24B shows a screen 131B of the display / input device 130 in a state in which switching from the charge mode to the boost preparation mode is possible (a state in which both the first condition HH1 and the second condition HH2 are satisfied). In this state, the indicator 132 on the screen 131B indicates that the charge has reached 100% (the actual rotation speed of the first flywheel 13 has reached the target rotation speed). Also, a message 133 reading "TRANSITION TO BOOST PREPARATION MODE" is displayed. This message 133 notifies the operator that switching from the charge mode to the boost preparation mode is possible. In this state, the operator can switch from the charge mode to the boost preparation mode by touching the message 133 reading "TRANSITION TO BOOST PREPARATION MODE." In other words, the control device 100 transmits a control signal to the second clutch 27 based on the operator's touch operation on the message 133.

[0441] The method of informing the operator that it is possible to switch from the charge mode to the boost preparation mode is not limited to a method of displaying the information on the screen of the display / input device 130. For example, a method of informing by lighting or flashing a lamp such as an LED, or a method of informing by voice may be adopted. Furthermore, the method by which the operator switches from the charge mode to the boost preparation mode in response to the notification is not limited to a method of touching the screen of the display / input device 130, and may be, for example, by operating an operation switch (operation button or the like) provided separately from the display / input device 130.

[0442] FIG. 25 is an example of a timing chart of the control system 100.

[0443] An example of the transition of the operation mode by the control system 100 will be described below with reference to Fig. 25. Fig. 25 shows a case where the load rates X1 to X5, which are the conditions for transitioning the operation mode, are all the same value, and the torque rates Y1 to Y4 are all the same value.

[0444] When the engine 4 starts, it transitions to the free mode, and the rotation speed (actual rotation speed) of the engine 4 increases over time. At this time, the command pressure (first command pressure) of the first clutch 26 and the command pressure (second command pressure) of the second clutch 27 are 0, and the first clutch 26 and the second clutch 27 are in a disengaged state. Therefore, the rotation speed (actual rotation speed) of the first flywheel 13 is 0. In addition, the load factor and torque factor of the engine 4 increase as the engine 4 starts, and decrease when the engine 4 reaches the target rotation speed.

[0445] When the load factor of the engine 4 decreases to less than a predetermined value X1 while the rotation speed of the first flywheel 13 is smaller (zero) than the rotation speed (actual rotation speed) of the engine 4, the mode shifts from free mode to tenacity preparation mode. In tenacity preparation mode, the first clutch 26 remains disengaged, but the second clutch 27 is brought into a state where the idle stroke is reduced by executing a one-shot (adding a one-shot pulse current).

[0446] When the actual rotation speed of the engine 4 reaches the target rotation speed, the rotation speed of the first flywheel 13 is smaller (zero) than the rotation speed (actual rotation speed) of the engine 4, and the torque rate of the engine 4 is less than a predetermined value Y1, the system transitions from the tenacity preparation mode to the tenacity mode. In the tenacity mode, the first clutch 26 remains disengaged, but the second clutch 27 is engaged. Engaging the second clutch 27 causes the first flywheel 13 to rotate and accelerate.

[0447] In the tenacity preparation mode, when the torque rate of the engine 4 is low (less than a predetermined value Y1), a control signal is sent to switch the second clutch 27 from a connection preparation state to a connection state, whereby the second clutch 27 switches to the connection state and transitions to the tenacity mode.

[0448] When the second clutch 27 is engaged, the first flywheel 13 is connected to the engine 4, causing the rotation speed (actual rotation speed) of the engine 4 to temporarily decrease, but then recover to the target rotation speed. Furthermore, when the second clutch 27 is engaged, the first flywheel 13 starts to rotate and increases until it becomes the same as the actual rotation speed of the engine 4. At this time, the load rate and torque rate of the engine 4 increase. The drop rate of the engine 4 temporarily increases when the second clutch 27 is engaged, but then decreases.

[0449] In the tenacity mode, when the rotation speed of the first flywheel 13 reaches the same rotation speed as the rotation speed (actual rotation speed) of the engine 4, the load factor and torque factor of the engine 4 decrease. When the load factor falls below a predetermined value X2, a sudden decrease in the rotation speed of the engine 4 becomes less likely, and the mode shifts from the tenacity mode to the charge preparation mode. In the charge preparation mode, the first clutch 26 is brought into a state where the idle stroke is reduced by performing a one-shot (adding a one-shot pulse current), and the second clutch 27 is switched from the connected state to the disconnected state.

[0450] When the rotation speed of the first flywheel 13 is the same as the rotation speed (actual rotation speed) of the engine 4, and the torque rate of the engine 4 falls below a predetermined value Y3, the mode transitions from the charge preparation mode to the charge mode. In the charge mode, the first clutch 26 is engaged, and the second clutch 27 remains disengaged. Engaging the first clutch 26 temporarily reduces the rotation speed (actual rotation speed) of the engine 4, but then recovers to the target rotation speed. Engaging the first clutch 26 also increases the rotation speed of the first flywheel 13 beyond the actual rotation speed of the engine 4.

[0451] When the rotation speed of the first flywheel 13 reaches a first target rotation speed NA, which is higher than the rotation speed (actual rotation speed) of the engine 4, and the load factor of the engine 4 is less than a predetermined value X3, the mode shifts from charge mode to boost preparation mode. In boost preparation mode, the first clutch 26 remains connected, and the second clutch 27 is brought into a state where the idle stroke is reduced by executing a one-shot (adding a one-shot pulse current).

[0452] 25 shows a state in which, after transitioning to boost preparation mode, the workload of the work vehicle 1 increases suddenly, causing the load rate, torque rate, and drop rate of the engine 4 to increase suddenly, and the rotational speed (actual rotational speed) of the engine 4 to decrease. In this state, the rotational power of the engine 4 needs to be assisted by the rotational power of the first flywheel 13. Therefore, it is necessary to transition from boost preparation mode to boost mode.

[0453] The transition from the boost preparation mode to the boost mode is executed when the rotation speed of the first flywheel 13 is a first target rotation speed NA that is higher than the rotation speed (actual rotation speed) of the engine 4 (in FIG. 25, the first target rotation speed is reached at the initial stage of the boost preparation mode), the load factor of the engine 4 is equal to or greater than a predetermined value X4 (%), and the drop rate of the engine 4 is equal to or greater than a predetermined value Z.

[0454] In the boost mode, the first clutch 26 is switched to a disengaged state, and the second clutch 27 is switched to an engaged state. As a result, the rotational power of the first flywheel 13 is transmitted to the engine 4, and the rotational power of the engine 4 is assisted by the rotational power of the first flywheel 13. As a result, the rotational speed (actual rotational speed) of the engine 4 increases, and the load factor, torque factor, and drop factor of the engine 4 decrease. Furthermore, the rotational speed of the first flywheel 13 decreases as the assist time becomes longer.

[0455] FIG. 25 shows a state in which the mode has been switched from boost mode to engine-off mode. When the engine is turned off in boost mode, the engine 4 and the first flywheel 13 gradually decelerate while rotating by inertia. In engine-off mode, the first clutch 26 and / or the second clutch 27 are engaged, and the first flywheel 13 is connected to the engine 4 via the first clutch 26 and / or the second clutch 27. This allows the first flywheel 13, which has a large inertial force, to be stopped in a short time. Note that FIG. 25 shows a case in which only the second clutch 27 is engaged, but both the first clutch 26 and the second clutch 27 may be engaged.

[0456] <Effects> The characteristic configuration of the work vehicle 1 according to the above embodiment and the effects based on this configuration are as follows.

[0457] The work vehicle 1 is equipped with an engine 4, a first flywheel 13 that rotates upon receiving the rotational power of the engine 4, a transmission 16 that selectively receives the rotational power of either the engine 4 or the rotational power of the engine 4 and the first flywheel 13, changes the speed, and outputs it, a first power transmission path 31 that transmits the rotational power of the engine 4 to the first flywheel 13, and a second power transmission path 32 that transmits the rotational power of the first flywheel 13 to the transmission 16, the first power transmission path 31 and the second power transmission path 32 being paths independent of each other, and the first power transmission path 31 is provided with a first clutch 26 that interrupts the transmission of rotational power from the engine 4 to the first flywheel 13, and the second power transmission path 32 is provided with a second clutch 27 that interrupts the transmission of rotational power from the first flywheel 13 to the transmission 16.

[0458] According to this configuration, the first power transmission path 31, which transmits the rotational power of the engine 4 to the first flywheel 13, and the second power transmission path 32, which transmits the rotational power of the first flywheel 13 to the transmission 16, are configured as paths independent of each other. Therefore, if a speed change mechanism is provided in one path, the speed change mechanism does not affect the other path. Therefore, the rotational power output from the engine 4 can be accelerated by the first power transmission path 31 and transmitted to the first flywheel 13, and the transmitted rotational power can be output to the transmission 16 without being decelerated by the second power transmission path 32. Furthermore, each path is provided with a clutch (first clutch 26, second clutch 27) that interrupts the transmission of the rotational power. Therefore, it is possible to switch between a state in which the rotational power of the engine 4 is transmitted to the first flywheel 13 and a state in which the rotational power of the first flywheel 13 is output to the transmission 16. As a result, when the workload is light, the rotational power of the engine 4 is stored in the first flywheel 13 as rotational energy, and when the workload on the engine 4 is heavy, the rotational power of the engine 4 can be assisted by the rotational power of the first flywheel 13.

[0459] In addition, the first power transmission path 31 is provided with a speed increasing mechanism 20 that increases the rotational power of the engine 4 and transmits it to the first flywheel 13, and the second power transmission path 32 transmits the rotational power of the first flywheel 13 to the transmission 16 without going through a reduction mechanism.

[0460] According to this configuration, the rotational power of the engine 4 is accelerated by the speed-increasing mechanism 20 and transmitted to the first flywheel 13, and the rotational power of the first flywheel 13 can be output to the transmission 16 without being decelerated, so that high rotational energy can be accumulated in the first flywheel 13 and transmitted directly to the transmission 16. Therefore, when the work load is heavy, the rotational power of the engine 4 can be effectively assisted by the rotational power of the first flywheel 13.

[0461] The work vehicle 1 also has a third power transmission path 33 that transmits the rotational power of the engine 4 to the transmission 16 without passing through the first flywheel 13, and the third power transmission path 33 always connects the output shaft 4a of the engine 4 and the input shaft 16a of the transmission 16.

[0462] According to this configuration, the rotational power of the engine 4 can be transmitted to the transmission 16 via the third power transmission path 33 without going through the first flywheel 13, making it possible to input the rotational power of the engine 4 to the transmission 16 independently of the rotation of the first flywheel 13.

[0463] The speed increasing mechanism 20 is composed of a planetary gear mechanism including a sun gear 21, planetary gears 22, and a ring gear 23. The ring gear 23 is fixed so that it cannot rotate. The rotational power of the engine 4 is input to the planetary gear 22 and transmitted to the first flywheel 13 via the sun gear 21. The rotational power of the first flywheel 13 is transmitted to the transmission 16 without passing through the planetary gear mechanism.

[0464] According to this configuration, the rotational power of the engine 4 can be accelerated by transmitting it from the planetary gear 22 to the sun gear 21 and then input to the first flywheel 13. Furthermore, by transmitting the rotational power of the first flywheel 13 to the transmission 16 without passing through a planetary gear mechanism, the rotational power of the first flywheel 13 can be output to the transmission 16 without being decelerated.

[0465] The work vehicle 1 also includes a second flywheel 14 connected to the output shaft 4a of the engine 4, and the first flywheel 13 is rotatable independently of the second flywheel 14.

[0466] According to this configuration, when the first clutch 26 and the second clutch 27 are disengaged, the first flywheel 13 can be rotated independently of the rotation of the second flywheel 14. As a result, even if the second flywheel 14 stops or decelerates, the rotation of the first flywheel 13 can be maintained without being affected by the second flywheel 14.

[0467] The first flywheel 13 is disposed between the second flywheel 14 and the transmission 16 in the axial direction of the output shaft 4a of the engine 4.

[0468] This configuration allows the radial size (outer diameter dimension) of the power transmission mechanism 6 to be reduced, and also allows for smooth power transmission from the second flywheel 14 to the first flywheel 13 and from the second flywheel 14 to the transmission 16.

[0469] The work vehicle 1 also has an intermediate shaft 17 that is interposed between the output shaft 4a of the engine 4 and the transmission 16 to form a third power transmission path 33, and the intermediate shaft 17 is arranged to pass through the first flywheel 13.

[0470] According to this configuration, the third power transmission path 33 is formed by the intermediate shaft 17 that passes through the first flywheel 13, so that the third power transmission path 33 can be formed linearly over a short distance without using a complex mechanism.

[0471] Furthermore, with the configuration in which the first clutch 26 and the second clutch 27 are arranged side by side in the radial direction of the intermediate shaft 17, it is possible to arrange both the first clutch 26 and the second clutch 27 side by side along the wall of the housing 9. This makes it possible to provide an oil passage for supplying hydraulic oil to the first clutch 26 and an oil passage for supplying hydraulic oil to the second clutch 27 along the wall. Therefore, it is easy to provide oil passages for supplying hydraulic oil to the first clutch 26 and the second clutch 27.

[0472] Furthermore, with the configuration in which the first clutch 26 and the second clutch 27 are arranged side by side in the axial direction of the intermediate shaft 17, it is possible to reduce the outer diameter of the clutch device 25 made up of the first clutch 26 and the second clutch 27. As a result, it is possible to reduce the inner diameter while maintaining the outer diameter of the first flywheel 13, thereby increasing the moment of inertia.

[0473] The work vehicle 1 also has a housing 9 that houses the first flywheel 13, the first clutch 26, and the second clutch 27. Inside the housing 9, a partition wall 9d is provided that separates the interior into a space that houses the first flywheel 13 and a space that houses the first clutch 26 and the second clutch 27, and the first clutch 26 and the second clutch 27 are positioned facing the partition wall 9d.

[0474] According to this configuration, an oil passage for supplying hydraulic oil to the first clutch 26 and the second clutch 27 can be provided along the partition wall 9d. Therefore, it is easy to provide an oil passage for supplying hydraulic oil to the first clutch 26 and the second clutch 27.

[0475] The first clutch 26 and the second clutch 27 are multi-plate clutches having a plurality of friction plates, and are disposed on the inner circumferential side of the first flywheel 13.

[0476] According to this configuration, the first clutch 26 and the second clutch 27 are made up of multiple disc clutches, so that the outer diameter can be reduced while maintaining high power transmission performance. Also, by arranging the first clutch 26 and the second clutch 27 on the inner peripheral side of the first flywheel 13, it is possible to increase the axial length (length in the front-to-rear direction) of the first flywheel 13. Therefore, the moment of inertia of the first flywheel 13 is increased, and the rotational energy that can be stored in the first flywheel 13 can be increased.

[0477] The work vehicle 1 also includes an engine 4, a flywheel 13 (meaning a first flywheel 13: the same applies hereinafter) that rotates upon receiving rotational power from the engine 4, a first clutch 26 that is provided on a first path connecting the engine 4 and the flywheel 13 and that interrupts the transmission of rotational power via the first path, a second clutch 27 that is provided on a second path connecting the engine 4 and the flywheel and that interrupts the transmission of rotational power via the second path, and a clutch 28 that is provided on the first path and that accelerates the rotational power of the engine when the first clutch 26 is in an engaged state. and a control device 110 that controls the engagement and disengagement of the first clutch 26 and the second clutch 27 to switch between a plurality of operation modes. The plurality of operation modes include a boost mode in which the rotation speed of the flywheel 13 is higher than the rotation speed of the engine 4, the first clutch 26 is disengaged, and the second clutch 27 is engaged, and a tenacity mode in which the rotation speed of the flywheel 13 is equal to or lower than the rotation speed of the engine 4, the first clutch 26 is disengaged, and the second clutch 27 is engaged.

[0478] According to this configuration, the rotational power of the flywheel 13 can be efficiently utilized not only when the rotational speed of the flywheel 13 is sufficiently high to assist the rotational power of the engine 4, but also when the rotational speed of the flywheel 13 is not sufficient to assist the rotational power of the engine 4. More specifically, in the boost mode, the rotational speed of the flywheel 13 is sufficiently high to assist the rotational power of the engine 4, so that the rotational power of the engine 4 can be assisted by the rotational power of the flywheel 13. In the stickiness mode, although the rotational speed of the flywheel 13 is not sufficient to assist the rotational power of the engine 4, the inertial force of the flywheel 13 can prevent a sudden drop in the rotational speed of the engine 4.

[0479] The plurality of operation modes also includes a charge mode in which the rotation speed of the flywheel 13 is less than the target rotation speed and greater than the rotation speed of the engine 4, the first clutch 26 is engaged, and the second clutch 27 is disengaged.

[0480] According to this configuration, in the charge mode, the rotational power of the engine 4 is accelerated and transmitted to the flywheel 13, thereby allowing high rotational energy to be stored in the flywheel 13.

[0481] The multiple operating modes also include a tenacity preparation mode, which is a mode that is switched to before transitioning to the tenacity mode.In the tenacity preparation mode, the rotation speed of the flywheel 13 is smaller than the rotation speed of the engine 4, the first clutch 26 is disengaged, and the second clutch 27 is in the process of switching from the disengaged state to the engaged state.

[0482] According to this configuration, in the tenacity preparation mode, the second clutch 27 is in the process of switching to the connected state, so that preparations for transition to the tenacity mode are completed, and the transition to the tenacity mode can be carried out smoothly.

[0483] The multiple operating modes also include a boost preparation mode, which is a mode switched to before transitioning to the boost mode.In the boost preparation mode, the rotation speed of the flywheel 13 is the target rotation speed and is higher than the rotation speed of the engine 4, the first clutch 26 is connected, and the second clutch 27 is in the process of switching from a disconnected state to a connected state.

[0484] According to this configuration, in the boost preparation mode, the second clutch 27 is in the process of switching to the connected state, so that preparations for the transition to the boost mode are completed, and the transition to the boost mode can be carried out smoothly.

[0485] The multiple operating modes also include a charge preparation mode, which is a mode that is switched to before transitioning to the charge mode.In the charge preparation mode, the rotation speed of the flywheel 13 is less than the target rotation speed, the first clutch 26 is in the process of switching from a disconnected state to a connected state, and the second clutch 27 is disconnected.

[0486] According to this configuration, in the charge preparation mode, the first clutch 26 is in the process of switching to the connected state, so that preparations for the transition to the charge mode are completed, and the transition to the charge mode can be carried out smoothly.

[0487] The plurality of operation modes also includes a free mode in which the engine 4 is started, the first clutch 26 and the second clutch 27 are disengaged, and the flywheel 13 is stopped.

[0488] According to this configuration, in the free mode, the first clutch 26 and the second clutch 27 are disengaged, thereby separating the flywheel 13 from the engine 4, and therefore the load on the engine 4 can be reduced.

[0489] The plurality of operating modes also includes an engine-off mode in which the spark plug of the engine 4 is not firing, the first clutch 26 and the second clutch 27 are engaged, and the flywheel 13 is decelerated.

[0490] According to this configuration, in the engine-off mode, the first clutch 26 and the second clutch 27 are connected to the engine 4, thereby quickly decelerating the flywheel 13. Therefore, it is possible to prevent the flywheel 13 from continuing to rotate for a long time due to inertial force even after the engine 4 is turned off.

[0491] Furthermore, when the rotation speed of the flywheel 13 is lower than the rotation speed of the engine 4 and the load factor of the engine 4 is less than a predetermined value, the control device 110 switches from the free mode to the standby mode.

[0492] According to this configuration, when the rotation speed of the flywheel 13 is low and the load on the engine 4 is small, preparations for transitioning to the tenacity mode can be made, so that the transition to the tenacity mode can be made smoothly.

[0493] In addition, the control device 110 switches from the stickiness preparation mode to the stickiness mode when the rotation speed of the flywheel 13 is smaller than the rotation speed of the engine 4, the torque rate of the engine 4 is less than a predetermined value, and the actual rotation speed of the engine 4 is at the target rotation speed.

[0494] According to this configuration, the rotation speed of the flywheel 13 can be increased by transitioning to the tenacity mode when the rotation speed of the flywheel 13 is lower than the rotation speed of the engine 4, the load on the engine 4 is small, and the actual rotation speed of the engine 4 is not decreasing. As a result, in a state where there is no need to assist the engine 4, the rotation speed of the flywheel 13 can be increased to the rotation speed of the engine 4, and preparations can be made for transitioning to the charge mode, in which the rotation speed of the flywheel 13 is further increased.

[0495] Furthermore, when the rotation speed of the flywheel 13 is lower than the rotation speed of the engine 4 and the number of attempts to connect the second clutch 27 within a predetermined time period reaches a predetermined number, the control device 110 switches from the tenacity preparation mode to the free mode.

[0496] According to this configuration, if the load on engine 4 increases due to an increase in work load or the like in the tenacity preparation mode and it becomes impossible to transition to tenacity mode, it is possible to transition to free mode and reduce the load on engine 4.

[0497] Furthermore, when the rotation speed of the flywheel 13 becomes the same as the rotation speed of the engine 4 and the load factor of the engine 4 is less than a predetermined value, the control device 110 switches from the tenacity mode to the charge preparation mode.

[0498] According to this configuration, when the load on the engine 4 is low, preparations can be made to switch to charge mode in order to store rotational energy in the flywheel 13, thereby enabling a smooth transition to charge mode.

[0499] Furthermore, when the rotation speed of the flywheel 13 is lower than the rotation speed of the engine 4 and the torque rate of the engine 4 is equal to or higher than a predetermined value, the control device 110 switches from the tenacity mode to the free mode.

[0500] According to this configuration, when the load on engine 4 increases due to an increase in work load, etc., the load on engine 4 can be reduced by switching from tenacity mode to free mode, thereby preventing interference with work.

[0501] Furthermore, when the rotation speed of the flywheel 13 becomes the same as the rotation speed of the engine 4 and the torque rate of the engine 4 is less than a predetermined value, the control device 110 switches from the charge preparation mode to the charge mode.

[0502] According to this configuration, when the load on the engine 4 is small and the rotational speed of the flywheel 13 is relatively high, the mode can be switched to the charge mode in order to store rotational energy in the flywheel 13.

[0503] Furthermore, when the rotation speed of the flywheel 13 becomes the same as the rotation speed of the engine 4 and the number of attempts to engage the first clutch 26 within a predetermined time period has been reached, the control device 110 switches from the charge preparation mode to the free mode.

[0504] According to this configuration, if the load on engine 4 increases in charge preparation mode due to an increase in work load or the like and it is not possible to transition to charge mode, the load on engine 4 can be reduced by transitioning to free mode.

[0505] In addition, when the rotation speed of the flywheel 13 is a target rotation speed that is higher than the rotation speed of the engine 4 and the load factor of the engine 4 is less than a predetermined value, the control device 110 switches from the charge mode to the boost preparation mode or notifies that switching to the boost preparation mode is possible.

[0506] According to this configuration, the rotation speed of the flywheel 13 is increased sufficiently to assist the engine 4, but when the load on the engine 4 is small, preparations can be made to switch to the boost mode in preparation for an increase in the load on the engine 4. This allows for a smooth transition to the boost mode when the load on the engine 4 increases.

[0507] Furthermore, when the rotation speed of the flywheel 13 is greater than the rotation speed of the engine 4 but less than the target rotation speed, and the torque rate of the engine 4 is equal to or greater than a predetermined value, the control device 110 switches from the charge mode to the free mode.

[0508] According to this configuration, when the rotation speed of the flywheel 13 is increased and the load on the engine 4 increases due to an increase in the work load or the like, the engine 4 can be switched to the free mode to reduce the load on the engine 4.

[0509] In addition, the control device 110 switches from the boost preparation mode to the boost mode when the rotation speed of the flywheel 13 is a target rotation speed that is higher than the rotation speed of the engine 4, the load factor of the engine 4 is equal to or greater than a predetermined value, and the drop factor of the engine 4 is equal to or greater than a predetermined value.

[0510] According to this configuration, when the load on the engine 4 increases while the rotational speed of the flywheel 13 is sufficiently increased to assist the engine 4 (when high rotational energy is accumulated in the flywheel 13), the mode can be switched to boost mode, and the rotational power of the flywheel 13 can assist the rotational power of the engine 4.

[0511] Furthermore, when the rotation speed of the flywheel 13 becomes the same as the rotation speed of the engine 4, the control device 110 switches from the boost mode to the lean mode.

[0512] According to this configuration, in the boost mode, when the rotational power of the flywheel 13 is assisted to the rotational power of the engine 4, and as a result the rotational power of the flywheel 13 decreases and is no longer able to assist, a sudden drop in the rotational speed of the engine 4 can be prevented by switching to the tenacity mode.

[0513] In addition, the control device 110 switches from boost mode to free mode when the rotation speed of the flywheel 13 is lower than the rotation speed of the engine, the load factor of the engine 4 is less than a predetermined value, and the actual rotation speed of the engine 4 is lower than the target rotation speed.

[0514] According to this configuration, when the load on the engine 4 decreases in the boost mode due to a decrease in the workload or the like and the assistance of the engine 4 becomes unnecessary, the mode is switched to the free mode, thereby preventing the flywheel 13 from assisting the engine 4 when the load on the engine 4 is low.

[0515] Although the embodiments of the present invention have been described above, the embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0516] 1 Work vehicle 4 Engine 4a Engine output shaft 9 Housing (flywheel housing) 9d Partition wall 13 First flywheel 14 Second flywheel 16 Transmission 16a Transmission input shaft 17 Intermediate shaft 20 Speed ​​increasing mechanism 21 Sun Gear 22 Planetary gear 23 Ring Gear 26 First clutch 27 Second clutch 31 First power transmission path 32 Second power transmission path 33 Third power transmission path

Claims

1. The engine and a first flywheel that rotates by receiving rotational power from the engine; a transmission that selectively receives rotational power from the engine or rotational power from the engine and the first flywheel, changes the speed of the rotational power, and outputs the rotational power; a first power transmission path that transmits rotational power of the engine to the first flywheel; a second power transmission path that transmits rotational power of the first flywheel to the transmission; Equipped with The first power transmission path and the second power transmission path are paths independent of each other, a first clutch that interrupts transmission of rotational power from the engine to the first flywheel is provided in the first power transmission path; a second clutch that interrupts transmission of rotational power from the first flywheel to the transmission device is provided in the second power transmission path, a third power transmission path that transmits the rotational power of the engine to the transmission device without passing through the first flywheel; The third power transmission path constantly connects the output shaft of the engine and the input shaft of the transmission device to each other in the work vehicle.

2. An engine; a first flywheel that rotates by receiving rotational power from the engine; a transmission that selectively receives rotational power from the engine or rotational power from the engine and the first flywheel, changes the speed of the rotational power, and outputs the rotational power; a first power transmission path that transmits rotational power of the engine to the first flywheel; a second power transmission path that transmits rotational power of the first flywheel to the transmission; Equipped with The first power transmission path and the second power transmission path are paths independent of each other, a first clutch that interrupts transmission of rotational power from the engine to the first flywheel is provided in the first power transmission path; a second clutch that interrupts transmission of rotational power from the first flywheel to the transmission device is provided in the second power transmission path, a speed increasing mechanism that increases the rotational power of the engine and transmits the increased rotational power to the first flywheel is provided in the first power transmission path; the second power transmission path transmits the rotational power of the first flywheel to the transmission device without passing through a reduction mechanism; the speed increasing mechanism is composed of a planetary gear mechanism including a sun gear, planetary gears, and a ring gear, The ring gear is fixed so as not to rotate, The rotational power of the engine is input to the planetary gear and transmitted to the first flywheel via the sun gear, A work vehicle in which the rotational power of the first flywheel is transmitted to the transmission without passing through the planetary gear mechanism.

3. A second flywheel connected to the output shaft of the engine, 3. The work vehicle according to claim 1, wherein the first flywheel is rotatable independently of the second flywheel.

4. A work vehicle as described in Claim 3, wherein the first flywheel is arranged between the second flywheel and the transmission in the axial length direction of the output shaft.

5. A relay shaft is provided between the output shaft and the transmission device to form the third power transmission path, The work vehicle according to claim 1 , wherein the intermediate shaft is provided so as to pass through the first flywheel.

6. A work vehicle as described in Claim 5, wherein the first clutch and the second clutch are arranged side by side in the radial direction of the intermediate shaft.

7. A work vehicle as described in Claim 5, wherein the first clutch and the second clutch are arranged side by side in the axial length direction of the intermediate shaft.

8. A housing that accommodates the first flywheel, the first clutch, and the second clutch, a partition wall is provided inside the housing to separate the interior into a space in which the first flywheel is accommodated and a space in which the first clutch and the second clutch are accommodated; The work vehicle according to claim 6, wherein the first clutch and the second clutch are disposed in positions facing the partition wall.

9. A work vehicle as described in Claim 7, wherein the first clutch and the second clutch are multi-plate clutches having multiple friction plates and are arranged on the inner side of the first flywheel.

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