Continuously variable speed power transmission device for work vehicle and work vehicle

Abstract

To detect rotation numbers properly and perform efficient variable speed control in a continuously variable power transmission device including combination of a continuously variable transmission and a planetary transmission.SOLUTION: A continuously variable power transmission device includes: a continuously variable transmission 28 where engine power is input and variable speed power is output; a planetary transmission 31 where the engine power and the variable speed power are input and planetary power is output; a planetary clutch mechanism 32 which selects a shift level of the planetary transmission; a shift control unit 50 which generates control signals for controlling the continuously variable transmission 28 and the planetary clutch mechanism 32. In the shift control unit 50, at least one of an engine rotation number obtaining unit 62, a variable speed rotation number obtaining unit 63, a planetary rotation number obtaining unit 64, and a travel rotation number obtaining unit 65 obtains a corresponding rotation number based on rotation number signals from multiple rotation detectors which detect the same rotation number.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a continuously variable speed power transmission device for a work vehicle that includes a continuously variable speed device and a planetary speed device, and to a work vehicle that includes the continuously variable speed power transmission device for a work vehicle. [Background technology]

[0002] Continuously variable transmissions (also called HMTs), which combine a continuously variable transmission and a planetary transmission, are used in the power transmission structure of work vehicles such as wheel loaders and tractors. For example, Patent Document 1 discloses a continuously variable transmission in which power from an engine is branched to a hydraulic pump of the continuously variable transmission and to a planetary transmission, and further, continuously variable output from a hydraulic motor shaft of the continuously variable transmission is input to the planetary transmission. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-96208 Summary of the Invention [Problem to be solved by the invention]

[0004] In a continuously variable transmission such as that disclosed in Patent Document 1, the desired speed-changing power is obtained by combining the speed-change output of the continuously variable transmission, which is input to the sun gear of the planetary transmission, with the output from the planetary transmission selected from an internal gear, a planetary gear, and a carrier. In this continuously variable transmission, the engine output and the continuously variable output are input to the planetary transmission, and the output from selected members of the planetary transmission (internal gear, planetary gear, carrier) is transmitted to the subsequent stage. Therefore, for proper speed change control, it is important to detect the rotational speed of each transmission element in real time.

[0005] The present invention aims to provide a continuously variable transmission system and a work vehicle equipped with a continuously variable transmission system that combines a continuously variable transmission and a planetary transmission, in which the rotation speed of each transmission element is detected appropriately and efficient continuously variable transmission control is performed. Another object of the present invention is to provide a fail-safe by obtaining rotation speeds from multiple rotation speed detectors. [Means for solving the problem]

[0006] The continuously variable speed power transmission device for a work vehicle according to the present invention is a device that transmits engine power from an engine to a traveling device, and comprises: a continuously variable speed transmission that inputs the engine power and outputs continuously variable speed power; a planetary speed change device that inputs the engine power and the continuously variable speed power and outputs planetary power; a planetary clutch mechanism that selects a gear stage of the planetary speed change device; a forward / reverse switching device that inputs the planetary power and outputs forward power or reverse power to the traveling device; and a speed change control unit that generates control signals to control the continuously variable speed transmission device, the planetary clutch mechanism, and the forward / reverse switching device, the transmission control unit includes an engine rotation speed acquisition unit that acquires an engine rotation speed of the engine, a continuously variable transmission rotation speed acquisition unit that acquires a continuously variable transmission rotation speed that is the rotation speed of the continuously variable transmission power, a planetary rotation speed acquisition unit that acquires a planetary rotation speed that is the rotation speed of the planetary power, and a traveling rotation speed acquisition unit that acquires a traveling rotation speed that is the rotation speed of the forward power or the reverse power, The engine rotation speed acquisition unit acquires the engine rotation speed based on an engine rotation speed signal sent from an engine control unit of the engine, and when the engine rotation speed cannot be acquired from the engine control unit, the engine rotation speed acquisition unit acquires the engine rotation speed based on a redundant engine rotation speed signal from a redundant engine rotation detector that detects the rotation speed of a continuously variable transmission input shaft that inputs power to the continuously variable transmission device. .

[0007] According to this configuration, at least one of the engine rotation speed (engine output rotation speed) acquired by the engine rotation speed acquisition unit, the continuously variable transmission rotation speed (continuously variable transmission output rotation speed) acquired by the continuously variable transmission rotation speed acquisition unit, the planet rotation speed (planet output rotation speed) acquired by the planet rotation speed acquisition unit, and the traveling rotation speed (vehicle speed) acquired by the traveling rotation speed acquisition unit is obtained by inputting rotation speed signals from multiple rotation detectors, i.e., there is redundancy or a dual system (fail-safe) for detecting at least one rotation speed, thereby improving the safety of rotation speed detection and allowing the transmission control unit to achieve safe and efficient continuously variable transmission control.

[0008] In the present invention, the engine rotation speed acquisition unit acquires the engine rotation speed based on an engine rotation speed signal sent from an engine control unit of the engine, the continuously variable transmission rotation speed acquisition unit acquires the continuously variable transmission rotation speed based on a continuously variable transmission rotation speed signal sent from a continuously variable transmission rotation detector that detects rotation of a continuously variable transmission output shaft of the continuously variable transmission device, the planetary rotation speed acquisition unit acquires the planetary rotation speed based on a planetary rotation speed signal sent from a planetary rotation detector that detects rotation of a planetary output shaft of the planetary transmission device, and the traveling rotation speed acquisition unit acquires the traveling rotation speed based on a traveling rotation speed signal sent from a traveling rotation detector that detects rotation of a forward / reverse output shaft of the forward / reverse switching device. With this configuration, the rotation speeds of the engine output and the continuously variable transmission output input to the planetary transmission device, the output rotation speed of the planetary transmission device, and the traveling rotation speed as the final gear change result (vehicle speed) are accurately detected, and the transmission control unit can accurately achieve efficient continuously variable transmission control based on the detection results.

[0009] Since the engine output, the continuously variable transmission output RPM, the planetary transmission output RPM, and the running RPM are important factors in speed change control, if the sensors that detect them fail, accurate continuously variable transmission control will become impossible. For this reason, a fail-safe for speed detection, such as using duplicate sensors, is required.

[0010] In one preferred embodiment of the present invention, the engine speed acquisition unit can acquire the engine speed based on a redundant engine speed signal from a redundant engine speed detector that detects the rotation speed of a continuously variable transmission input shaft that inputs power to the continuously variable transmission. Since the engine speed is an essential factor for engine control, it is detected by an engine control unit. However, if a situation arises in which the engine speed cannot be acquired from the engine control unit, the engine speed acquisition unit must acquire the engine speed from a separate detection system. In this configuration, a separate rotation speed detector that detects the rotation speed of the continuously variable transmission input shaft is provided as a redundant engine speed detector for the engine speed acquisition unit, thereby achieving a fail-safe for acquiring the engine speed.

[0011] In one preferred embodiment of the present invention, the planetary rotation detector includes a main planetary rotation detector and a redundant planetary rotation detector, wherein the main planetary rotation detector detects the rotation of a first rotating body that rotates in accordance with the rotation of a planetary output shaft of the planetary transmission, and the redundant planetary rotation detector detects the rotation of a second rotating body that rotates in accordance with the rotation of the planetary output shaft of the planetary transmission. In this configuration, the output rotation speed of the planetary transmission can be detected by the main planetary rotation detector and the redundant planetary rotation detector. In other words, detection of the output rotation speed of the planetary transmission is redundant, thereby achieving a fail-safe for the output rotation speed of the planetary transmission. In a further preferred embodiment, the main planetary rotation detector can detect rotation direction, and the redundant planetary rotation detector cannot detect rotation direction. In this configuration, while the main planetary rotation detector can detect rotation direction, the redundant planetary rotation detector is an inexpensive detector that cannot detect rotation direction, thereby reducing the cost required for the fail-safe.

[0012] In one preferred embodiment of the present invention, the running rotation detector includes a main running rotation detector and a redundant running rotation detector, where the main running rotation detector detects the rotation of a first rotating member that determines vehicle speed, and the redundant running rotation detector detects the rotation of a second rotating member that determines vehicle speed. In this configuration, the running rotation count (vehicle speed) can be detected by the main running rotation detector and the redundant running rotation detector. In other words, running rotation detection, which is vehicle speed detection, is made redundant, and a fail-safe for the running rotation count is realized. In a further preferred embodiment, the main running rotation detector can detect rotation direction, and the redundant running rotation detector cannot detect rotation direction. In this configuration, while the main running rotation detector can detect rotation direction, the redundant running rotation detector is an inexpensive detector that cannot detect rotation direction, thereby reducing the cost required for the fail-safe.

[0013] The present application also covers a work vehicle equipped with the above-described continuously variable speed power transmission device for a work vehicle. Such a work vehicle has the functions and effects of the above-described continuously variable speed power transmission device for a work vehicle. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. [Figure 2] FIG. 1 is a schematic diagram of a continuously variable speed power transmission device. [Figure 3] FIG. [Figure 4] FIG. 2 is a block diagram showing input / output devices in the transmission control unit. [Figure 5] FIG. 2 is a control function block diagram of the continuously variable speed power transmission device. [Figure 6] FIG. 4 is an explanatory diagram of a vehicle speed change in the speed change control unit. DETAILED DESCRIPTION OF THE INVENTION

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described with reference to the accompanying drawings. In the following explanation, with respect to the running body of a tractor (an example of a "work vehicle"), the direction of arrow F shown in Figure 1 will be referred to as the "front side of the body," the direction of arrow B shown in Figure 1 will be referred to as the "rear side of the body," the direction of arrow U shown in Figure 1 will be referred to as the "upper side of the body," the direction of arrow D shown in Figure 1 will be referred to as the "lower side of the body," the direction toward the front of the page in Figure 1 will be referred to as the "left side of the body," and the direction toward the back of the page in Figure 1 will be referred to as the "right side of the body."

[0016] [Overall tractor] FIG. 1 shows a tractor. This tractor has a traveling body 3 supported by a pair of steerable and drivable front wheels 1 (traveling gear) on the left and right, and a pair of drivable rear wheels 2 (traveling gear). A prime mover 5 equipped with an engine 4 is provided at the front of the traveling body 3. A driver's section 6, where a driver sits and operates the vehicle, and a link mechanism 7, which connects a work implement such as a rotary tiller so that the implement can be raised and lowered, are provided at the rear of the traveling body 3. The driver's section 6 is equipped with a driver's seat 8, a steering wheel 9 for steer- ing the front wheels 1, and a cabin 10 that covers the riding space. A body frame 11 of the traveling body 3 is composed of the engine 4, a transmission case 12 whose front portion is connected to the rear of the engine 4, a front wheel support frame 13 connected to the bottom of the engine 4, and the like. A power takeoff shaft 14 is provided at the rear of the transmission case 12, which extracts and transmits power from the engine 4 to the work implement connected by the link mechanism 7.

[0017] [Power transmission device for driving] 2, a power transmission device 15 for driving, which transmits power (engine power) from the engine 4 to the front wheels 1 and the rear wheels 2, includes a transmission 18 that changes the speed of the power from the engine 4 and transmits it to a rear wheel differential mechanism 16 and a front wheel differential mechanism 17. The transmission 18 is housed in a transmission case 12.

[0018] As shown in FIG. 2, the transmission 18 is provided with: an input shaft 20 that is provided in the front part of the transmission case 12 and to which the power of the output shaft 4 a of the engine 4 is transmitted; a main transmission unit 21 that receives the power of the input shaft 20, changes the speed of the input power, and outputs it; a forward / reverse switching device 23 that receives the output of the main transmission unit 21; a gear mechanism 24 that transmits the output of the forward / reverse switching device 23 to the input shaft 16 a of the rear wheel differential mechanism 16; and a front wheel transmission unit 25 that receives the output of the forward / reverse switching device 23, changes the speed of the input power, and outputs it to the front wheel differential mechanism 17.

[0019] [Main transmission section] As shown in Figure 2, the main transmission unit 21 includes a continuously variable transmission 28 to which the power of the input shaft 20 is input, a planetary transmission 31 to which the power of the input shaft 20 and the output of the continuously variable transmission 28 are input, and a planetary clutch mechanism 37 that selects the gear stage of the planetary transmission 31.

[0020] 2, the continuously variable transmission 28 includes a variable displacement hydraulic pump P connected to a pump shaft 28a serving as a continuously variable transmission input shaft which is connected to the input shaft 20 via a first gear mechanism 27 connected to the rear end of a rotating shaft 26 which is connected to the rear end of the input shaft 20, and a hydraulic motor M driven by pressure oil from the hydraulic pump P. By changing the swash plate angle of the hydraulic pump P, the power from the input shaft 20 is changed into forward rotation power and reverse rotation power, and the rotational speeds of the forward rotation power and reverse rotation power are changed continuously, and output from a motor shaft 28b serving as a continuously variable transmission output shaft. The continuously variable transmission 28 is a hydrostatic continuously variable transmission known as an HST (hydraulic static transmission).

[0021] Planetary transmission 31 has a planetary transmission section 31A to which the power of input shaft 20 and the output of continuously variable transmission 28 are input. Planetary clutch mechanism 37 functions as output section 31B of planetary transmission 31, and outputs the output of planetary transmission section 31A by dividing it into four speed ranges.

[0022] 2 and 3, the planetary transmission unit 31A is provided with a first planetary transmission unit 32 having a first sun gear 32a, a first planetary gear 32b meshing with the first sun gear 32a, and a first ring gear 32c with internal teeth meshing with the first planetary gear 32b. The planetary transmission unit 31A is provided with a second planetary transmission unit 33 located rearward of the first planetary transmission unit 32 and having a second sun gear 33a, a second planetary gear 33b meshing with the second sun gear 33a, a second ring gear 33c with internal teeth meshing with the second planetary gear 33b, and a second carrier 33d supporting the second planetary gear 33b.

[0023] As shown in Fig. 2, a second gear mechanism 30 is provided between the first sun gear 32a and the motor shaft 28b of the continuously variable transmission 28, and the output of the continuously variable transmission 28 is input to the first sun gear 31a via the second gear mechanism 30. A third gear mechanism 29 is provided between the first ring gear 32c and the input shaft 20, and the power of the input shaft 20 is input to the first ring gear 32c via the third gear mechanism 29. As shown in Figs. 2 and 3, the first planetary transmission unit 32 is provided with an interlocking gear 32d that meshes with the first planetary gear 32b, and the interlocking gear 32d and the second planetary gear 33b are interlocked and connected by a connecting member 33e. The first planetary transmission unit 32 and the second planetary transmission unit 33 constitute a so-called compound planetary transmission unit.

[0024] As shown in Figures 2 and 3, the planetary clutch mechanism 37 includes a triple-shaft structure of a first input shaft 34a, a second input shaft 34b, and a third input shaft 34c, and an output shaft 35 positioned parallel to the first input shaft 34a. The first input shaft 34a is connected to the second ring gear 33c, the second input shaft 34b is connected to the second carrier 33d, and the third input shaft 34c is connected to the second sun gear 33a. A first range gear mechanism 36a is connected to the first input shaft 34a, and a first clutch CL1 is provided between the first range gear mechanism 36a and the output shaft 35. A second range gear mechanism 36b is connected to the third input shaft 34c, and a second clutch CL2 is provided between the second range gear mechanism 36b and the output shaft 35. A third range gear mechanism 36c is connected to the second input shaft 34b, and a third clutch CL3 is provided between the third range gear mechanism 36c and the output shaft 35. A fourth range gear mechanism 36d is connected to the third input shaft 34c, and a fourth clutch CL4 is provided between the fourth range gear mechanism 36d and the output shaft 35.

[0025] In the main transmission unit 21, power from the engine 4 is input to the hydraulic pump P via the input shaft 20, the rotating shaft 26, and the first gear mechanism 27, and the power is changed in speed by the continuously variable transmission 28 to forward rotation power and reverse rotation power and output from the motor shaft 28b, and the rotation speed of the output forward rotation power and reverse rotation power is changed continuously. The output of the continuously variable transmission 28 is input to the first sun gear 32a of the first planetary transmission unit 32 via the second gear mechanism 30, and the power from the engine 4 is input to the first ring gear 32c of the first planetary transmission unit 32 via the input shaft 20 and the third gear mechanism 29. The input power from the continuously variable transmission 28 and the power from the engine 4 are combined by the first planetary transmission unit 32 and the second planetary transmission unit 33 of the planetary transmission unit 31A, and the combined power is transmitted from the second planetary transmission unit 33 to the output unit 31B and output from the output shaft 35.

[0026] In the main transmission section 21, when the continuously variable transmission 28 is operated to change speeds with the first clutch CL1 engaged, the combined power generated by the planetary transmission section 31A is transmitted from the second ring gear 33c to the first input shaft 34a of the output section 31B, and in the output section 31B, the combined power is converted into power that changes speed continuously in the first gear range by the first range gear mechanism 36a and the first clutch CL1, and is output from the output shaft 35.

[0027] When the continuously variable transmission 28 is operated to change speeds with the second clutch CL2 engaged, the combined power generated by the planetary transmission unit 31A is transmitted from the second sun gear 33a to the third input shaft 34c of the output unit 31B, and is converted into power that changes speed continuously in the second gear range by the second range gear mechanism 36b and the second clutch CL2 in the output unit 31B and is output from the output shaft 35.

[0028] When the continuously variable transmission 28 is operated to change speeds with the third clutch CL3 engaged, the combined power generated by the planetary transmission unit 31A is transmitted from the second carrier 33d to the second input shaft 34b of the output unit 31B, and in the output unit 31B, the combined power is converted into power that changes speed continuously in the third gear range by the third range gear mechanism 36c and the third clutch CL3, and is output from the output shaft 35.

[0029] When the continuously variable transmission 28 is operated to change speeds with the fourth clutch CL4 engaged, the combined power generated by the planetary transmission unit 31A is transmitted from the second sun gear 33a to the third input shaft 34c of the output unit 31B, and in the output unit 31B, the combined power is converted into power that changes speed continuously in the fourth gear range by the fourth range gear mechanism 36d and the fourth clutch CL4, and is output from the output shaft 35.

[0030] [Forward / forward switching device] 2, the forward / reverse switching device 23 includes an input shaft 23a connected to the output shaft 35 of the planetary transmission 31, and an output shaft 23b provided in parallel to the input shaft 23a. A forward clutch CLF and a reverse clutch CLR are provided on the input shaft 23a. A forward gear interlock mechanism 23c is provided between the forward clutch CLF and the output shaft 23b, and a reverse gear interlock mechanism 23d is provided between the reverse clutch CLR and the output shaft 23b.

[0031] When the forward clutch CLF is engaged, it connects the input shaft 23a to the forward gear interlock mechanism 23c, creating a forward transmission state in which the power of the input shaft 23a is transmitted to the output shaft 23b via the forward gear interlock mechanism 23c. When the reverse clutch CLR is engaged, it connects the input shaft 23a to the reverse gear interlock mechanism 23d, creating a reverse transmission state in which the power of the input shaft 23a is transmitted to the output shaft 23b via the reverse gear interlock mechanism 23d.

[0032] In the forward / reverse switching device 23, the output of the planetary transmission 31 is input to the input shaft 23a, and when the forward clutch CLF is engaged, the power of the input shaft 23a is converted into forward power by the forward clutch CLF and the forward gear interlock mechanism 23c and transmitted to the output shaft 23b. When the reverse clutch CLR is engaged, the power of the input shaft 23a is converted into reverse power by the reverse clutch CLR and the reverse gear interlock mechanism 23d and transmitted to the output shaft 23b. The forward power and reverse power of the output shaft 23b are transmitted to the rear wheel differential mechanism 16 and the front wheel transmission part 25 by the gear mechanism 24.

[0033] In the rear wheel differential mechanism 16, the forward or reverse power transmitted from the forward / reverse switching device 23 is transmitted from the left and right output shafts 16b to the left and right rear wheels 2. The power of the left output shaft 16b is transmitted to the left rear wheel 2 via a planetary reduction mechanism 38B. A steering brake 38A is provided on the left output shaft 16b. Although not shown, the transmission system from the right output shaft 16b to the right rear wheel 2 is provided with a planetary reduction mechanism 38B and a steering brake 38A, similar to the transmission system to the left rear wheel 2.

[0034] [Front wheel transmission section] As shown in Fig. 2, the front wheel transmission unit 25 includes an input shaft 25a connected to the output shaft 24a of the gear mechanism 24, and an output shaft 25b positioned parallel to the input shaft 25a. A constant speed clutch CLT and an accelerating clutch CLH positioned rearward of the constant speed clutch CLT are provided on the input shaft 25a. A constant speed gear mechanism 40 is provided between the constant speed clutch CLT and the output shaft 25b. A accelerating gear mechanism 41 is provided between the accelerating clutch CLH and the output shaft 25b. A parking brake 39 is provided on the output shaft 24a of the gear mechanism 24.

[0035] In the front wheel transmission unit 25, when the constant speed clutch CLT is engaged, the power of the input shaft 25a is transmitted to the output shaft 25b by the constant speed clutch CLT and the constant speed gear mechanism 40, a constant speed transmission state is created by the constant speed gear mechanism 40, and power for driving the front wheels 1 is output from the output shaft 25b in a state in which the peripheral speed of the front wheels 1 is the same as the peripheral speed of the rear wheels 2. When the speed-up clutch CLH is engaged, the power of the input shaft 25a is transmitted to the output shaft 25b by the speed-up clutch CLH and the speed-up gear mechanism 41, and a front wheel speed-up transmission state is created by the speed-up gear mechanism 41, and power for driving the front wheels 1 is output from the output shaft 25b in a state in which the peripheral speed of the front wheels 1 is faster than the peripheral speed of the rear wheels 2. The output from the output shaft 25b is input to the front wheel differential mechanism 17 via a rotary shaft 42 that connects the output shaft 25b to the input shaft 17a of the front wheel differential mechanism 17.

[0036] When the constant velocity clutch CLT is engaged, the traveling vehicle body 3 enters a four-wheel drive state in which the front wheels 1 and rear wheels 2 are driven in a state in which the average peripheral speed of the left and right front wheels 1 is the same as the average peripheral speed of the left and right rear wheels 2, and when the speed-up clutch CLH is engaged, the traveling vehicle body 3 enters a four-wheel drive state in which the front wheels 1 and rear wheels 2 are driven in a state in which the average peripheral speed of the left and right front wheels 1 is faster than the average peripheral speed of the left and right rear wheels 2. As a result, when the speed-up clutch CLH is engaged, the traveling vehicle body 3 can turn with a turning radius that is smaller than the turning radius when the constant velocity clutch CLT is engaged.

[0037] [Regarding the rotation detector group] The power transmission device 15 is provided with a group of rotation detectors 70 that detects the engine speed, which is the rotation speed of the engine power; the continuously variable transmission speed, which is the rotation speed of the continuously variable transmission power (output of the continuously variable transmission 28); the planetary speed, which is the rotation speed of the planetary power (output of the planetary transmission 31); and the travel speed, which is the rotation speed of the forward power (output of the forward / reverse travel switching device 23). The group of rotation detectors 70 is made up of multiple rotation detectors, and in particular, includes a main engine rotation detector 71 and a redundant engine rotation detector 72 that detect the engine speed; a main continuously variable transmission rotation detector 73 that detects the continuously variable transmission rotation speed; a main planetary rotation detector 74 and a redundant planetary rotation detector 75 that detect the planetary rotation speed; and a main travel rotation detector 76 and a redundant travel rotation detector 77 that detect the travel rotation speed. The rotation detectors labeled "redundant" are backup rotation detectors for the rotation detectors labeled "main." In this embodiment, the only rotation detector that detects the continuously variable transmission rotation speed is the main continuously variable transmission rotation detector 73, and no backup rotation detector is provided. Since the redundant rotation detector is a backup for the main rotation detector, an inexpensive rotation detector that cannot identify the direction of rotation (cannot detect the direction of rotation) is used to reduce costs.

[0038] The main engine rotation detector 71 is a rotation detector managed by the engine control unit EU that controls the engine 4. The engine control unit EU strictly manages the engine rotation speed, so the engine rotation speed measured by the main engine rotation detector 71 is highly reliable and can also identify the rotation direction (forward or reverse). This engine rotation speed is acquired from the engine control unit EU via an on-board LAN. The redundant engine rotation detector 72 is provided to detect the gear rotation speed (corresponding to the engine rotation speed) of the first gear mechanism 27 that is interlocked with the input shaft 20, but does not identify the rotation direction. If the engine rotation speed information from the engine control unit EU is cut off, the engine rotation speed is calculated from the detection signal from the redundant engine rotation detector 72.

[0039] The main variable speed rotation detector 73 is provided to detect the gear rotation speed of the second gear mechanism 30 (corresponding to the output rotation speed of the continuously variable transmission 28), and is also capable of identifying the rotation direction. When the continuously variable transmission 28 is in neutral, the rotation speed detected by the main variable speed rotation detector 73 is zero.

[0040] The main planetary rotation detector 74 and the redundant planetary rotation detector 75 are rotation detectors that detect the input rotation speed of the forward / reverse switching device 23, which is the output rotation speed of the planetary transmission 31. The main planetary rotation detector 74 is provided to detect the rotation speed of a clutch housing (a type of first rotating body) that rotates integrally with the input shaft 23a of the forward / reverse switching device 23. The redundant planetary rotation detector 75 is provided to detect the rotation speed of a clutch housing (a type of second rotating body) of the planetary clutch mechanism 37 that rotates integrally with the output shaft 35 of the planetary transmission 31. The main planetary rotation detector 74 is also capable of identifying the direction of rotation, but the redundant planetary rotation detector 75 does not identify the direction of rotation.

[0041] The rotation speed of the input side (engine side) of forward / reverse switching device 23 varies depending on the gear position of planetary transmission 31. Furthermore, the input rotation speed of forward / reverse switching device 23 can be calculated from the engine rotation speed, the output rotation speed of continuously variable transmission 28, and the gear position of planetary transmission 31. However, it is taken into consideration that co-rotation may occur even when all clutches of planetary clutch mechanism 37 are OFF.

[0042] The main running rotation detector 76 and the redundant running rotation detector 77 are rotation detectors that detect the running rotation speed, which is the rotation speed of a member that determines the vehicle speed. The main running rotation detector 76 is provided to detect the rotation speed of a clutch housing (a type of first rotating member) of a constant velocity clutch CLT that interlocks with the input shaft 25a of the front wheel transmission unit 25. The redundant running rotation detector 77 is provided to detect the rotation speed of a clutch housing (a type of second rotating member) of a speed increasing clutch CLH that interlocks with the input shaft 25a of the front wheel transmission unit 25. The main running rotation detector 76 is also capable of identifying the direction of rotation, but the redundant running rotation detector 77 does not identify the direction of rotation.

[0043] The rotation speed on the output side of the forward / reverse switching device 23 can be calculated from the detection signal of the main running rotation detector 76 or the redundant running rotation detector 77. However, the relationship between the rotation speed on the input side of the forward / reverse switching device 23 and the rotation speed on the output side of the forward / reverse switching device 23 changes based on the engagement state of the clutch of the forward / reverse switching device 23.

[0044] [About the gear change control unit] Shift control in this continuously variable transmission device is performed by a shift control unit 50 shown in Figures 4 and 5. Shift operations by the driver are performed using a shift pedal 46 and a forward / reverse lever 47, which are provided in the driving section 6 as a shift operation device 45 that issues shift operation commands. The amount of operation of the shift pedal 46 and the forward / reverse lever 47 is input to the shift control unit 50. A detection signal (number of rotations) from the rotation detector group 70 is also input to the shift control unit 50. The shift control unit 50 generates control signals for hydraulically controlling the operation of the continuously variable transmission 28, planetary clutch mechanism 37, forward / reverse switching device 23, etc.

[0045] As shown in FIG. 5, the transmission control unit 50 includes a transmission control unit 51, a rotation detector determination unit 60, and a rotation speed acquisition unit 61. The transmission control unit 51 includes a continuously variable transmission control unit 52, a planetary clutch control unit 53, and a forward / reverse clutch control unit 54. The continuously variable transmission control unit 52 generates a control signal that controls the operation (swash plate angle adjustment) of the continuously variable transmission 28. The planetary clutch control unit 53 generates a control signal that controls the ON (engagement) / OFF (disengagement) of the four hydraulic clutches of the planetary clutch mechanism 37, namely, the first clutch CL1, the second clutch CL2, the third clutch CL3, and the fourth clutch CL4. The forward / reverse clutch control unit 54 generates a control signal that controls the ON (engagement) / OFF (disengagement) of the two hydraulic clutches of the forward / reverse switching device 23, namely, the forward clutch CLF and the reverse clutch CLR.

[0046] The rotation speed acquisition unit 61 includes an engine rotation speed acquisition unit 62, a continuously variable transmission rotation speed acquisition unit 63, a planetary rotation speed acquisition unit 64, and a traveling rotation speed acquisition unit 65. The engine rotation speed acquisition unit 62 acquires detection signals (a type of detected value) that are engine rotation speed signals from the main engine rotation detector 71 and the redundant engine rotation detector 72, and determines the engine rotation speed (a type of detected value) of the engine 4. The continuously variable transmission rotation speed acquisition unit 63 acquires detection signals (a type of continuously variable transmission rotation speed signal, which is a type of detected value) from the main continuously variable transmission rotation detector 73, and determines the continuously variable transmission rotation speed (a type of detected value). The planetary rotation speed acquisition unit 64 acquires detection signals (a type of planetary rotation speed signal, which is a type of detected value) from the main planetary rotation detector 74 and the redundant planetary rotation detector 75, and determines, for example, the planetary rotation speed (a type of detected value), which is the rotation speed of a planetary output shaft. The running rotation speed acquisition unit 65 acquires detection signals from the main running rotation detector 76 and the redundant running rotation detector 77 (a type of detected value as a running rotation speed signal, for example a detected value indicating the rotation of the forward / reverse output shaft) and determines the running rotation speed (a type of detected value). Note that in this embodiment, with regard to detection of the continuously variable transmission rotation speed, only the main continuously variable transmission rotation detector 73 is provided, and no redundant continuously variable transmission rotation detector is provided, but in another embodiment, a redundant continuously variable transmission rotation detector may be provided.

[0047] FIG. 6 is an explanatory diagram of vehicle speed changes performed by the transmission control unit 51. The vertical axis of FIG. 6 represents the gear ratio G, which is the ratio (traveling rotation speed / engine rotation speed) between the engine rotation speed and the traveling rotation speed (vehicle speed), which is the rotation speed of the input shaft 16a to the traveling device corresponding to the vehicle speed. The vertical axis also represents the traveling rotation speed (vehicle speed): V of the input shaft 16a. The horizontal axis of FIG. 6 represents the speed change state of the continuously variable transmission 28, with [N] representing the neutral state and [-MAX] representing the speed change state in which reverse power is output at the highest speed. [+MAX] representing the speed change state in which forward rotation power is output at the highest speed. [-K] represents the speed change state for clutch switching on the reverse side (the speed change state just before [-MAX]), and [+K] represents the speed change state for clutch switching on the forward side (the speed change state just before [+MAX]). [G1], [G2], [G3], and [G4] represent preset gear ratios G. The transmission control unit 51 controls the transmission speed (vehicle speed): V of the input shaft 16a by switching between the first clutch CL1, the second clutch CL2, the third clutch CL3 and the fourth clutch CL4 based on the gear ratio: G and the transmission state of the continuously variable transmission 28.

[0048] That is, with the first clutch CL1 engaged, as the continuously variable transmission 28 is shifted from [-MAX] toward [+MAX], the traveling speed (vehicle speed): V increases continuously from zero speed [0] in the first gear range. When the continuously variable transmission 28 reaches [+K] and the gear ratio: G reaches [G1], the gear change control means 48 switches the first clutch CL1 off and the second clutch CL2 on. With the second clutch CL2 engaged, as the continuously variable transmission 28 is shifted toward [-MAX], the traveling speed (vehicle speed): V increases continuously in the second gear range. When the continuously variable transmission 28 reaches [-K] and the gear ratio: G reaches [G2], the gear change control means 48 switches the second clutch CL2 off and the third clutch CL3 on. When continuously variable transmission 28 is operated to change gears toward [+MAX] with third clutch CL3 engaged, traveling speed (vehicle speed): V increases steplessly in the third-speed range. When continuously variable transmission 28 reaches [+K] and the gear ratio: G reaches [G3], transmission control means 48 switches third clutch CL3 off and fourth clutch CL4 on. As continuously variable transmission 28 changes gears toward [-MAX] with fourth clutch CL4 engaged, traveling speed (vehicle speed): V increases steplessly in the fourth-speed range.

[0049] [Regarding abnormality detection of the rotation detector] The rotation detector determination unit 60 selects at least one selection determination rule from a plurality of abnormality determination rules based on the clutch operation state (ON / OFF state) of the planetary clutch mechanism 37 and the forward / reverse switching device 23, and determines abnormalities in each rotation detector using this selection determination rule.

[0050] Abnormalities in the rotation detectors constituting the rotation detector group 70 determined by the rotation detector determination unit 60 are classified into a low-level abnormality state in which only a warning is issued, a moderate-level abnormality state in which temporary driving is permitted, and a severe-level abnormality state in which an emergency stop is made to driving.

[0051] [Abnormality Judgment Rule @1] If communication between the engine control unit EU and the on-board LAN is interrupted and the engine speed data periodically transmitted by the main engine speed detector 71 is no longer received, the engine speed is calculated using the detection signal from the redundant engine speed detector 72, and gear shift control continues. If the redundant engine speed detector 72 has previously been determined to be abnormal, all clutches of the planetary clutch mechanism 37 and the forward / reverse switching device 23 are turned OFF, power transmission from the engine 4 is cut off, and the vehicle stops. The engine control unit EU not only determines whether the main engine speed detector 71 is abnormal, but also has a backup function. If the backup function of the engine control unit EU is active, gear shift control using the redundant engine speed detector 72 is not performed. The engine control unit EU's determination of an abnormality in the main engine speed detector 71 is sent to the speed detector determination unit 60. In other words, in this case, the engine control unit EU functions as the speed detector determination unit 60 for the main engine speed detector 71.

[0052] [Abnormality Judgment Rule @2] When engine speed data is being received normally from the engine control unit EU, if a difference (mismatch in detected values) that exceeds the threshold condition occurs between the engine speed from the engine control unit EU and the engine speed detected by the redundant engine speed detector 72, it is determined that the redundant engine speed detector 72 is abnormal. While engine speed data is not available from the engine control unit EU, the redundant engine speed detector 72 is not determined to be abnormal, and gear shift control is performed using the redundant engine speed detector 72. If only the redundant engine speed detector 72 is abnormal, vehicle travel continues without restriction. A warning is issued that the redundant engine speed detector 72 is abnormal.

[0053] [Abnormality Judgment Rule @3] When the planetary clutch mechanism 37 is in the ON state, the absolute value of the planetary rotation speed calculated from the engine rotation speed and the continuously variable transmission rotation speed is compared with the absolute value of the main planetary rotation detector 74 and the three values ​​of the redundant planetary rotation detector 75, two of each, and if a difference that exceeds a predetermined threshold condition (mismatch in detected values) occurs, an abnormality in the specific rotation detector is determined as follows: The rotation speed from the main continuously variable transmission rotation detector 73 is "Nm", the rotation speed from the main planetary rotation detector 74 is "Ns_m", and the rotation speed from the redundant planetary rotation detector 75 is "Ns_r". (1) When Ns_m and Ns_r are normal and Nm and Ns_m and Nm and Ns_r are abnormal, it is determined that the main continuously variable transmission rotation detector 73 is abnormal. (2) If Nm and Ns_r are normal, and Ns_m and Nm and Ns_m and Ns_r are abnormal, it is determined that the main planet rotation detector 74 is abnormal. (3) If Nm and Ns_m are normal, and Ns_r and Nm, and Ns_r and Ns_m are abnormal, it is determined that the redundant planetary rotation detector 75 is abnormal. If only the main continuously variable transmission rotation detector 73 is abnormal, or if only the main planetary rotation detector 74 is abnormal, the forward / reverse switching device 23 is put into neutral (even if the forward / reverse switching device 23 is not operated when the vehicle speed drops, once the vehicle speed drops below a certain level, all clutches of the planetary clutch mechanism 37 and all clutches of the forward / reverse switching device 23 are turned off, causing the vehicle to stop. If only the redundant planetary rotation detector 75 is abnormal, the vehicle continues to travel without restriction. If all of the main continuously variable transmission rotation detector 73, main planetary rotation detector 74, and redundant planetary rotation detector 75 are abnormal, all clutches of the planetary clutch mechanism 37 and all clutches of the forward / reverse switching device 23 are turned off (completely disconnected), and the vehicle stops.

[0054] [Abnormality Judgment Rule #4] When the planetary clutch mechanism 37 is in the OFF state (incompletely coupled state), the absolute values ​​of the rotation speeds of the main planetary rotation detector 74 and the redundant planetary rotation detector 75 are compared, and if there is a difference that exceeds the threshold condition (mismatch in detected values), it is determined that both the main planetary rotation detector 74 and the redundant planetary rotation detector 75 are abnormal. If only the main continuously variable transmission rotation detector 73 becomes abnormal, or if both the main planetary rotation detector 74 and the redundant planetary rotation detector 75 become abnormal, all clutches of the planetary clutch mechanism 37 and all clutches of the forward / reverse switching device 23 are turned OFF (completely disconnected), and the vehicle stops.

[0055] [Abnormality Judgment Rule @5] When the clutch of the forward / reverse switching device 23 is fully engaged, three values ​​(absolute values) of the rotation speed measured by the main running rotation detector 76, the rotation speed measured by the redundant running rotation detector 77, and the rotation speed measured by the main planetary rotation detector 74 are compared, two for each pair, and if a difference that exceeds a predetermined threshold condition (mismatch in detected values) occurs, an abnormality in the specific rotation detector is determined as follows: The rotation speed measured by the main running rotation detector 76 is defined as "Nv_m," and the rotation speed measured by the redundant running rotation detector 77 is defined as "Nv_r." (1) When Nv_r and Ns_m are normal, and Nv_m and Nv_r and Nv_m and Ns_m are abnormal, it is determined that the main running rotation detector 76 is abnormal. (2) If Nv_m and Ns_m are normal, and Nv_r and Nv_m and Nv_r and Ns_m are abnormal, it is determined that the redundant running rotation detector 77 is abnormal. (3) If Nv_m and Nv_r are normal and Ns_m and Nv_m and Ns_m and Nv_r are abnormal, it is determined that the main planet rotation detector 74 is abnormal. (4) If there is a discrepancy between Nv_m and Nv_m and Ns_m that exceeds the threshold condition, the main running rotation detector 76, the redundant running rotation detector 77, and the main planetary rotation detector 74 are all determined to be abnormal. If only the main planetary rotation detector 74 becomes abnormal, the forward / reverse switching device 23 is set to neutral (even if the forward / reverse switching device 23 is not operated when the vehicle speed drops, if the vehicle speed drops below a certain level, all clutches of the planetary clutch mechanism 37 and all clutches of the forward / reverse switching device 23 are turned off, and the vehicle stops. If only the main running rotation detector 76 becomes abnormal, the forward / reverse switching device 23 is set to neutral, and then all clutches of the planetary clutch mechanism 37 are turned off. If only the redundant running rotation detector 77 becomes abnormal, the vehicle continues to run without restriction. If the main running rotation detector 76, redundant running rotation detector 77, and main continuously variable transmission rotation detector 73 all become abnormal, all clutches of the planetary clutch mechanism 37 and all clutches of the forward / reverse switching device 23 are turned off (completely disconnected), and the vehicle stops.

[0056] [Abnormality Judgment Rule @6] When the clutch of the forward / reverse switching device 23 is in a disengaged state (incompletely engaged state), the absolute values ​​of the rotation speed detected by the main running rotation detector 76 and the rotation speed detected by the redundant running rotation detector 77 are compared, and if there is a difference exceeding the threshold condition, it is determined that both the main running rotation detector 76 and the redundant running rotation detector 77 are abnormal. When only the main planetary rotation detector 74 becomes abnormal, all clutches of the planetary clutch mechanism 37 and all clutches of the forward / reverse switching device 23 are turned OFF (completely disconnected), and the vehicle comes to a stop.

[0057] When each rotation detector indicates that the detected rotation speed is zero under conditions in which the object to be detected is considered to be rotating, it is assumed that a wire break has occurred. In particular, the main running rotation detector 76 and the redundant running rotation detector 77 cannot normally detect rotation unless either the planetary clutch mechanism 37 or the forward / reverse switching device 23 clutch is engaged, so a wire break check is performed after it is confirmed that the planetary clutch mechanism 37 and the forward / reverse switching device 23 are in a power transmission state.

[0058] The abnormality determination of the rotation detector group 70 is skipped under the following predetermined circumstances. (1) At low vehicle speeds, where rotational speed accuracy decreases. (2) When the engine speed drops to a level close to engine stall due to the load, abnormality determination is skipped to prioritize control calculations for engine stall. (3) When the rotation speed detected by a specific rotation detector deviates from a predetermined threshold condition, the abnormality determination in which the specific rotation detector is incorporated is skipped.

[0059] [Another embodiment] (1) In the above-described embodiment, a hydrostatic continuously variable transmission is used as the continuously variable transmission 28, but a belt-type continuously variable transmission or a friction-type continuously variable transmission may also be used. (2) The arrangement of the rotation detectors constituting the rotation detector group 70 is not limited to the arrangement in the above-described embodiment. The rotation detector group 70 may be arranged in any position where it can detect substantially the same number of rotations. (3) The control function section included in the transmission control unit 50 may be integrated with other control function sections or may be divided into multiple sections. In addition, a specific control function section may be implemented in a control unit (ECU) other than the transmission control unit 50. (4) In the above-described embodiment, the planetary transmission 31 is configured to have four gear stages, but it may also be configured to have three or fewer or five or more gear stages.

[0060] (5) In the above-described embodiment, an example was shown in which the vehicle was equipped with front wheels 1 and rear wheels 2, but the running device may also be a crawler running device or a combination of a mini crawler and wheels.

[0061] (6) In the above embodiment, an example was shown in which the speed change pedal 46 was provided, but this is not limiting, and a speed change lever may be used as the speed change operating device 45.

[0062] (7) In the above embodiment, an example was shown in which the forward / reverse lever 47 was provided, but this is not limiting, and a forward / reverse pedal may be used as the speed change operating device 45.

[0063] The configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, as long as no contradiction arises. Furthermore, the embodiments disclosed in this specification are examples, and the embodiments of the present invention are not limited to these, and can be modified as appropriate within the scope that does not deviate from the purpose of the present invention. [Industrial Applicability]

[0064] The present invention can be applied to a continuously variable speed power transmission device for a work vehicle that includes a continuously variable speed device and a planetary speed device, and to various work vehicles that include this continuously variable speed power transmission device for a work vehicle. [Explanation of symbols]

[0065] 4: Engine 15: Power transmission device 16: Rear wheel differential mechanism 18: Transmission 20: Input shaft 21: Main transmission section 23: Forward / forward switching device 23a: Input shaft 23b: Output shaft 28: Continuously variable transmission 31: Planetary transmission 31A: Planetary transmission 31B: Output section 32: First planetary transmission section 33: Second planetary transmission section 35: Output shaft 37: Planetary clutch mechanism 48: Speed ​​change control means 50: Transmission control unit 51: Transmission control section 52: Continuously variable transmission control unit 53: Planetary clutch control unit 54: Forward / reverse clutch control unit 60: Rotation detector determination unit 61: Rotation speed acquisition section 62: Engine RPM acquisition section 63: Variable speed rotation speed acquisition unit 64: Planetary rotation speed acquisition section 65: Running speed acquisition unit 70: Rotation detector group 71: Main engine rotation detector 72: Redundant engine rotation detector 73: Main variable speed rotation detector 74: Main planet rotation detector 75: Redundant planetary rotation detector 76: Main running rotation detector 77: Redundant running rotation detector EU: Engine control unit M: Hydraulic motor P: Hydraulic pump

Claims

1. A continuously variable speed power transmission device for a work vehicle that transmits engine power from an engine to a traveling device, a continuously variable transmission that receives the engine power and outputs continuously variable power; a planetary transmission that receives the engine power and the continuously variable transmission power and outputs planetary power; and a planetary clutch mechanism that selects a gear position of the planetary transmission. a forward / reverse switching device that receives the planetary power and outputs forward power or reverse power to the traveling device; a transmission control unit that generates control signals for controlling the continuously variable transmission, the planetary clutch mechanism, and the forward / reverse switching device, the transmission control unit includes an engine rotation speed acquisition unit that acquires an engine rotation speed of the engine, a continuously variable transmission rotation speed acquisition unit that acquires a continuously variable transmission rotation speed that is the rotation speed of the continuously variable transmission power, a planetary rotation speed acquisition unit that acquires a planetary rotation speed that is the rotation speed of the planetary power, and a traveling rotation speed acquisition unit that acquires a traveling rotation speed that is the rotation speed of the forward power or the reverse power, The engine speed acquisition unit acquires the engine speed based on an engine speed signal sent from an engine control unit of the engine, and if the engine speed cannot be acquired from the engine control unit, the engine speed acquisition unit acquires the engine speed based on a redundant engine speed signal from a redundant engine speed detector that detects the rotation speed of a continuously variable transmission input shaft that inputs power to the continuously variable transmission.

2. The continuously variable transmission rotation speed acquisition unit acquires the continuously variable transmission rotation speed based on a continuously variable transmission rotation speed signal sent from a continuously variable transmission rotation detector that detects rotation of the continuously variable transmission output shaft of the continuously variable transmission device, the planetary rotation speed acquisition unit acquires the planetary rotation speed based on a planetary rotation speed signal sent from a planetary rotation detector that detects rotation of a planetary output shaft of the planetary transmission device, 2. The continuously variable transmission power transmission device for a work vehicle according to claim 1, wherein the travel rotation speed acquisition unit acquires the travel rotation speed based on a travel rotation speed signal sent from a travel rotation detector that detects rotation of a forward / reverse output shaft of the forward / reverse switching device.

3. 3. The continuously variable speed power transmission device for a work vehicle according to claim 2, wherein the planetary rotation detector includes a main planetary rotation detector and a redundant planetary rotation detector, the main planetary rotation detector detects rotation of a first rotating body that rotates in accordance with rotation of a planetary output shaft of the planetary transmission, and the redundant planetary rotation detector detects rotation of a second rotating body that rotates in accordance with rotation of a planetary output shaft of the planetary transmission.

4. 4. The continuously variable speed power transmission device for a work vehicle according to claim 3, wherein the main planetary rotation detector is capable of detecting a rotation direction, and the redundant planetary rotation detector is incapable of detecting a rotation direction.

5. 3. The continuously variable speed power transmission device for a work vehicle according to claim 2, wherein the travel rotation detector includes a main travel rotation detector and a redundant travel rotation detector, the main travel rotation detector detects rotation of a first rotating member that determines vehicle speed, and the redundant travel rotation detector detects rotation of a second rotating member that determines vehicle speed.

6. 6. The continuously variable speed power transmission device for a work vehicle according to claim 5, wherein the main running rotation detector is capable of detecting a rotation direction, and the redundant running rotation detector is not capable of detecting a rotation direction.

7. A work vehicle comprising the continuously variable speed power transmission device for a work vehicle according to any one of claims 1 to 6.

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