Transmission control device

Abstract

To provide a control device which can execute a mode switching process when a shock from a switching of the mode can be suppressed without limiting to a state where an accelerator opening position is at high level.SOLUTION: An ECU includes a belt transmission mechanism 33. In switching modes from a split mode to a belt mode, when performing a non-split point mode switching process in a state where a total transmission ratio does not match the split transmission ratio, a transmission torque capacity in a clutch C2 is adjusted according to a differential torque capacity in which a transmission torque capacity of the clutch C1 is deducted from the input torque, while adjusting a transmission torque capacity on the clutch C1 to set an input shaft rotation speed to a target rotation speed according to the target input shaft rotation speed set based on the accelerator opening position.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control device for a transmission. [Background technology]

[0002] As a transmission to be installed in vehicles such as automobiles, a power split type continuously variable transmission has been proposed, which is equipped with a belt transmission mechanism that changes the power speed continuously and can transmit the power by dividing it into two paths between the input shaft and the output shaft.

[0003] The transmission control device disclosed in Patent Document 1 listed below is provided to suppress the occurrence of gear shift shock when downshifting from the second mode (split mode) to the first mode (belt mode) in the power split continuously variable transmission described above. The control device of Patent Document 1 switches from split mode to belt mode, i.e., switches the engagement of the first clutch and the second clutch, when the target total gear ratio in split mode is set to a value greater than a certain value. In this case, if the time rate of change of the pulley ratio in the upshift direction when a kickdown request is generated is equal to or greater than a predetermined shift threshold, the control device of Patent Document 1 prohibits clutch-to-clutch control when the pulley ratio does not match the split point. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-118278 Summary of the Invention [Problem to be solved by the invention]

[0005] Here, the present inventors have studied control of the first engagement element and the second engagement element when switching modes from split mode to belt mode in a power split continuously variable transmission such as that disclosed in Patent Document 1. As a result, they have found that when switching modes from split mode to belt mode in a power split continuously variable transmission with the accelerator pedal position at a low to medium opening, the shock that occurs when switching from split mode to belt mode can be minimized by changing the pulley ratio to a state where no differential rotation occurs between the first engagement element and the second engagement element, as shown in Figure 6(a).

[0006] On the other hand, when mode switching is performed with the accelerator pedal position at a large position, as shown in Fig. 6(b), without reducing the total gear ratio to the split point (split gear ratio), and when mode switching is performed when the total gear ratio does not match the split point, a conceivable method is to vary the transfer torque capacities (clutch torque) of the first engagement element (clutch C1) and the second engagement element (clutch C2) as shown in Fig. 10. Specifically, when mode switching is performed when the total gear ratio does not match the split point, a conceivable method is to adjust the magnitude of the transfer torque capacity (clutch torque) of the first engagement element (clutch C1) in accordance with a target input shaft rotation speed set based on the accelerator pedal position so that the input shaft rotation speed becomes the target rotation speed, while adjusting the transfer torque capacity (clutch torque) of the second engagement element (clutch C2) so that it matches the input torque (= turbine torque) to the transmission. However, when the mode is switched with the accelerator pedal fully open, if the first and second engagement elements are controlled using the method described above, the sum of the transmission torque capacity (clutch torque) of the first engagement element and the transmission torque capacity (clutch torque) of the second engagement element becomes larger than the input torque to the transmission. This results in the input rotation being strongly pulled in the negative direction, which could cause a large engagement shock.

[0007] Therefore, the present invention aims to provide a control device that enables mode switching without causing a large engagement shock, even when mode switching is performed when the total gear ratio does not match the split point. [Means for solving the problem]

[0008] (1) The control device of the present invention, which is provided to solve the above-mentioned problems, controls a transmission including a first engagement element interposed on a first power transmission path between an input shaft and an output shaft, and a second engagement element interposed on a second power transmission path between the input shaft and the output shaft, and a belt transmission mechanism on the second power transmission path, and a first mode in which the total speed ratio between the input shaft and the output shaft increases as the pulley ratio by the belt transmission mechanism increases by disengaging the first engagement element and engaging the second engagement element, and a second mode in which the total speed ratio decreases as the pulley ratio increases by engaging the first engagement element and disengaging the second engagement element, and a transmission configured so that differential rotation does not occur between the first engagement element and the second engagement element when the pulley ratio is a predetermined split speed ratio, and the control device includes a target total speed ratio setting unit that sets a target of the total speed ratio as a target total speed ratio, and a target total speed ratio setting unit that sets a target of the total speed ratio as a target total speed ratio. and a switching control unit that performs non-split point mode switching processing to switch from the second mode to the first mode by disengaging the first engagement element and engaging the second engagement element in a state in which the total speed ratio does not match the split speed ratio, on condition that the target total speed ratio set by the target total speed ratio setting unit in the second mode is greater than the split speed ratio, wherein during the non-split point mode switching processing, the switching control unit adjusts the magnitude of the transfer torque capacity of the first engagement element in accordance with a target rate of change of input shaft speed so that the input shaft speed becomes the target speed, and adjusts the magnitude of the transfer torque capacity of the second engagement element in accordance with a differential torque capacity derived by subtracting the transfer torque capacity of the first engagement element from the input torque to the transmission.

[0009] As described above in (1), the control device of the present invention adjusts the magnitude of the transfer torque capacity of the first engagement element in the non-split point mode switching process to achieve a target rate of change of the input shaft rotation speed in accordance with a target input shaft rotation speed set based on the accelerator pedal position, while adjusting the magnitude of the transfer torque capacity of the second engagement element in accordance with a differential torque capacity derived by subtracting the transfer torque capacity of the first engagement element from the input torque to the transmission. Therefore, performing the non-split point mode switching process with the control device of the present invention prevents the input rotation speed from being strongly pulled in the negative direction, minimizing the occurrence of engagement shock. Therefore, the control device of the present invention can perform mode switching without causing a large engagement shock, even when mode switching is performed when the total gear ratio does not match the split point.

[0010] (2) The control device of the present invention preferably performs a non-split point mode switching process on the condition that the accelerator opening is higher than a predetermined threshold opening, and performs a split point mode switching process to switch from the second mode to the first mode by disengaging the first engagement element and engaging the second engagement element when the total gear ratio matches the split gear ratio on the condition that the accelerator opening is lower than the threshold opening.

[0011] The control device of the present invention can perform mode switching without causing a large engagement shock by performing the non-split point mode switching process as described above in (1) when the accelerator opening is greater than a predetermined threshold opening. Furthermore, the control device of the present invention can perform mode switching without causing a large engagement shock by performing the split point mode switching process as described above in (2) when the accelerator opening is small, equal to or less than the threshold opening, in which the first engagement element is disengaged and the second engagement element is engaged to switch from the second mode to the first mode when the total speed ratio matches the split speed ratio. Therefore, the control device of the present invention can prevent a large engagement shock from occurring when switching from the second mode to the first mode, regardless of the magnitude of the accelerator opening. [Effects of the Invention]

[0012] According to the present invention, the above-mentioned problems of the present invention can be solved. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a skeleton diagram showing the configuration of a drive system of a vehicle that employs a transmission system according to an embodiment of the present invention. [Figure 2] 2 is a diagram showing the states of each engagement element provided in a transmission that constitutes the gear change system of FIG. 1. FIG. [Figure 3] 2 is a collinear diagram showing the relationship between the rotational speeds (rotational speeds) of a sun gear, a carrier, and a ring gear of a planetary gear mechanism provided in a transmission that constitutes the transmission system of FIG. 1. [Figure 4] 2 is a diagram showing the relationship between the pulley ratio of a belt transmission mechanism provided in a transmission that constitutes the transmission system of FIG. 1 and the reduction ratio (unit speed ratio) of the entire power split continuously variable transmission. [Figure 5] 2 is a diagram showing the configuration of a control system provided in the transmission system of FIG. 1. FIG. [Figure 6] 10A and 10B are explanatory diagrams relating to a split point mode switching process and a non-split point mode switching process. [Figure 7]1. FIG. 1 is a timing chart showing changes in the accelerator opening, target input shaft rotation speed, belt rotation speed, split mode rotation speed, input shaft rotation speed, turbine torque, and transmission torque capacity of clutches C1 and C2 when non-split point mode switching processing is executed in the transmission system of FIG. [Figure 8] 10 is a flowchart showing the flow of a mode switching process. [Figure 9] 9 is a flowchart showing a subroutine related to split point mode switching processing executed in the mode switching processing shown in FIG. 8. [Figure 10] 10 is a timing chart showing the changes in the accelerator opening, target input shaft rotation speed, belt rotation speed, split mode rotation speed, input shaft rotation speed, turbine torque, and transmission torque capacity of clutches C1 and C2 when non-split point mode switching processing is executed in the non-split point mode switching processing of the reference example. DETAILED DESCRIPTION OF THE INVENTION

[0014] A transmission system S according to one embodiment of the present invention will be described in detail below with reference to the drawings, taking a vehicle 1 equipped with the transmission system as an example.

[0015] <Vehicle drive system> 1 is a skeleton diagram showing the configuration of a drive train of a vehicle 1. The vehicle 1 is an automobile that uses an engine 2 as a drive source.

[0016] The engine 2 is equipped with an electronic throttle valve for adjusting the amount of air intake into the combustion chamber of the engine 2, an injector (fuel injection device) for injecting fuel into the intake air, and a spark plug for generating an electrical discharge in the combustion chamber. The engine 2 is also equipped with a starter for starting the engine 2. The power of the engine 2 is transmitted to a differential gear 5 via a torque converter 3 and a transmission 4, and from the differential gear 5 to left and right drive wheels 7L, 7R via left and right drive shafts 6L, 6R, respectively.

[0017] The engine 2 is provided with an E / G output shaft 11. The E / G output shaft 11 is rotated by the power generated by the engine 2.

[0018] The torque converter 3 includes a front cover 21, a pump impeller 22, a turbine runner 23, and a lock-up mechanism 24. The E / G output shaft 11 is connected to the front cover 21, and the front cover 21 rotates integrally with the E / G output shaft 11. The pump impeller 22 is disposed on the opposite side of the front cover 21 from the engine 2 side. The pump impeller 22 is provided so as to be rotatable integrally with the front cover 21. The turbine runner 23 is disposed between the front cover 21 and the pump impeller 22, and is provided so as to be rotatable about a common rotation axis with the front cover 21.

[0019] The lockup mechanism 24 includes a lockup piston 25. The lockup piston 25 is provided between the front cover 21 and the turbine runner 23. The lockup mechanism 24 is locked on (engaged) and off (released) by the differential pressure between the hydraulic pressure in a release oil chamber 26 between the lockup piston 25 and the front cover 21 and the hydraulic pressure in an engagement oil chamber 27 between the lockup piston 25 and the pump impeller 22. That is, when the hydraulic pressure in the release oil chamber 26 is higher than the hydraulic pressure in the engagement oil chamber 27, the differential pressure causes the lockup piston 25 to move away from the front cover 21, resulting in lockup off. When the hydraulic pressure in the engagement oil chamber 27 is higher than the hydraulic pressure in the release oil chamber 26, the differential pressure causes the lockup piston 25 to be pressed against the front cover 21, resulting in lockup on.

[0020] In the lockup off state, when the engine output shaft 11 rotates, the pump impeller 22 rotates. When the pump impeller 22 rotates, oil flows from the pump impeller 22 toward the turbine runner 23. This oil flow is received by the turbine runner 23, causing it to rotate. At this time, the torque converter 3 acts as an amplifier, and a torque greater than the torque of the engine output shaft 11 is generated in the turbine runner 23.

[0021] In the lock-up on state, when the E / G output shaft 11 rotates, the E / G output shaft 11, the pump impeller 22, and the turbine runner 23 rotate together.

[0022] The transmission 4 is a so-called power split (torque split) transmission that includes an input shaft 31 and an output shaft 32 and is configured so that power input to the input shaft 31 can be branched into two paths and transmitted to the output shaft 32. To configure the two power transmission paths, the transmission 4 includes a belt transmission mechanism 33, a front reduction mechanism 34, a planetary gear mechanism 35, and a split transmission mechanism 36.

[0023] The input shaft 31 is connected to the turbine runner 23 of the torque converter 3 and is provided so as to be rotatable integrally with the turbine runner 23 about the same rotation axis.

[0024] The output shaft 32 is provided in parallel to the input shaft 31. An output gear 37 is supported on the output shaft 32 so as to be non-rotatable relative to the input shaft 31. The output gear 37 is in mesh with the differential gear 5 (a ring gear of the differential gear 5).

[0025] The belt transmission mechanism 33 is configured by a belt-type continuously variable transmission (CVT). Specifically, the belt transmission mechanism 33 includes a primary shaft 41, a secondary shaft 42, a primary pulley 43, a secondary pulley 44, and a belt 45. The primary shaft 41 and the secondary shaft 42 are disposed parallel to each other. The primary pulley 43 is supported on the primary shaft 41 so as not to rotate relative to the primary pulley 43. The secondary pulley 44 is supported on the secondary shaft 42 so as not to rotate relative to the secondary pulley 44. The belt 45 is wound around the primary pulley 43 and the secondary pulley 44.

[0026] The primary pulley 43 includes a fixed sheave 51 and a movable sheave 52. The fixed sheave 51 is a sheave fixed to the primary shaft 41. The movable sheave 52 is disposed opposite the fixed sheave 51 with the belt 45 sandwiched therebetween, and is a sheave supported on the primary shaft 41 so as to be movable in the axial direction of the primary shaft 41 but not rotatable relative to the fixed sheave 51. A cylinder 53 is provided on the opposite side of the movable sheave 52 from the fixed sheave 51. The cylinder 53 is fixed to the primary shaft 41. A hydraulic chamber 54 is formed between the movable sheave 52 and the cylinder 53.

[0027] The secondary pulley 44 includes a fixed sheave 55 and a movable sheave 56. The fixed sheave 55 is a sheave fixed to the secondary shaft 42. The movable sheave 56 is disposed opposite the fixed sheave 55 with the belt 45 sandwiched therebetween, and is a sheave supported on the secondary shaft 42 so as to be movable in the axial direction but non-rotatable relative to the fixed sheave 55. A cylinder 57 is provided on the opposite side of the movable sheave 56 from the fixed sheave 55. The cylinder 57 is fixed to the secondary shaft 42. A hydraulic chamber 58 is formed between the movable sheave 56 and the cylinder 57. In the rotational axis direction, the positional relationship between the fixed sheave 55 and the movable sheave 56 is reversed to the positional relationship between the fixed sheave 51 and the movable sheave 52 of the primary pulley 43.

[0028] In the belt transmission mechanism 33, the oil pressure supplied to the hydraulic chamber 54 of the primary pulley 43 and the hydraulic chamber 58 of the secondary pulley 44 is controlled, thereby changing the groove widths of the primary pulley 43 and the secondary pulley 44. This allows the belt transmission mechanism 33 to continuously and steplessly change the pulley ratio (the pulley ratio between the primary pulley 43 and the secondary pulley 44).

[0029] Specifically, when the pulley ratio is reduced, the hydraulic pressure supplied to the hydraulic chamber 54 of the primary pulley 43 is increased. As a result, the movable sheave 52 of the primary pulley 43 moves toward the fixed sheave 51, and the gap (groove width) between the fixed sheave 51 and the movable sheave 52 becomes smaller. Accordingly, the winding diameter of the belt 45 around the primary pulley 43 increases, and the gap (groove width) between the fixed sheave 55 and the movable sheave 56 of the secondary pulley 44 increases. As a result, the pulley ratio between the primary pulley 43 and the secondary pulley 44 becomes smaller.

[0030] When the pulley ratio is increased, the hydraulic pressure supplied to the hydraulic chamber 54 of the primary pulley 43 is reduced. This reduces the thrust ratio, which is the ratio of the thrust of the primary pulley 43 (primary thrust) to the thrust of the secondary pulley 44 (secondary thrust), and reduces the gap between the fixed sheave 55 and the movable sheave 56 of the secondary pulley 44, while increasing the gap between the fixed sheave 51 and the movable sheave 52. As a result, the pulley ratio between the primary pulley 43 and the secondary pulley 44 increases.

[0031] On the other hand, the thrust of the primary pulley 43 and the secondary pulley 44 must be large enough to prevent slippage (belt slippage) between the primary pulley 43 and the secondary pulley 44 and the belt 45. Therefore, the hydraulic pressure supplied to the hydraulic chamber 54 of the primary pulley 43 and the hydraulic chamber 58 of the secondary pulley 44 is controlled so as to obtain a clamping pressure sufficient to prevent belt slippage.

[0032] The front reduction mechanism 34 is configured to reverse and reduce the speed of the power input to the input shaft 31 and transmit it to the primary shaft 41. Specifically, the front reduction mechanism 34 includes an input shaft gear 61 and a primary shaft gear 62. The input shaft gear 61 is a gear supported on the input shaft 31 so as not to be rotatable relative to the input shaft 31. The primary shaft gear 62 has a larger diameter and a greater number of teeth than the input shaft gear 61 and is meshed with the input shaft gear 61. The primary shaft gear 62 is supported on the primary shaft 41 by spline fitting so as not to be rotatable relative to the input shaft 31.

[0033] The planetary gear mechanism 35 includes a sun gear 71, a carrier 72, and a ring gear 73. The sun gear 71 is supported on the secondary shaft 42 by spline engagement so as to be non-rotatable relative to the secondary shaft 42. The carrier 72 is externally fitted onto the output shaft 32 so as to be rotatable relative to the output shaft 32. The carrier 72 rotatably supports a plurality of pinion gears 74. A plurality of pinion gears 74 are arranged circumferentially, and each pinion gear 74 meshes with the sun gear 71. The ring gear 73 has an annular shape that collectively surrounds the plurality of pinion gears 74, and meshes with each pinion gear 74 from the outer side in the rotational radial direction of the secondary shaft 42. The output shaft 32 is connected to the ring gear 73, and the ring gear 73 is provided so as to be rotatable integrally with the output shaft 32 about the same rotational axis.

[0034] The split transmission mechanism 36 is a parallel shaft gear mechanism including a split drive gear 81 and a split driven gear 82 that meshes with the split drive gear 81.

[0035] The split drive gear 81 is fitted onto the input shaft 31 so as to be rotatable relative to the input shaft 31 .

[0036] The split driven gear 82 is provided so as to be rotatable integrally with the carrier 72 of the planetary gear mechanism 35 about the same rotation axis as the carrier 72. The split driven gear 82 is formed to have a smaller diameter than the split drive gear 81 and has fewer teeth than the split drive gear 81.

[0037] The transmission 4 also includes clutches C1 and C2 and a brake B1.

[0038] The clutch C1 (first engagement element) is hydraulically switched between an engaged state in which the input shaft 31 and the split drive gear 81 are directly connected (coupled so as to be rotatable together), and a released state in which the direct connection is released.

[0039] The clutch C2 (second engagement element) is hydraulically switched between an engaged state in which the sun gear 71 and ring gear 73 of the planetary gear mechanism 35 are directly connected (coupled so as to rotate integrally), and a released state in which the direct connection is released.

[0040] The brake B1 is hydraulically switched between an engaged state in which the carrier 72 of the planetary gear mechanism 35 is braked and a released state in which the carrier 72 is allowed to rotate.

[0041] <Power transmission mode> Fig. 2 is a diagram showing the states of the clutches C1, C2 and the brake B1 when the vehicle 1 is moving forward and backward. Fig. 3 is a collinear diagram showing the relationship between the rotational speeds (rotational speeds) of the sun gear 71, carrier 72 and ring gear 73 of the planetary gear mechanism 35. Fig. 4 is a diagram showing the relationship between the pulley ratio of the belt transmission mechanism 33 and the total speed ratio (unit speed ratio) of the entire transmission 4.

[0042] 2, "◯" indicates that the clutches C1, C2 and the brake B1 are engaged, and "X" indicates that the clutches C1, C2 and the brake B1 are released.

[0043] A displacement member that can be displaced among a plurality of positions is provided in a position operable by the driver within the cabin of the vehicle 1. In this embodiment, a shift lever (select lever) is provided as the displacement member. Within the movable range of the shift lever, for example, a P (parking) position, an R (reverse) position, an N (neutral) position, a D (drive) position, an S (sports) position, and a B (brake) position are provided, arranged in a line in this order.

[0044] When the shift lever is in the P position, the clutches C1, C2 and brake B1 are all released and a parking lock gear (not shown) is locked, thereby establishing the P range, which is one of the shift ranges of the transmission 4. When the shift lever is in the N position, the clutches C1, C2 and brake B1 are all released and the parking lock gear is not locked, thereby establishing the N range, which is one of the shift ranges of the transmission 4. When both the clutch C1 and brake B1 are released, the power of the engine 2 is transmitted to the secondary shaft 42 and the secondary shaft 42 rotates, but the sun gear 71 and pinion gear 74 of the planetary gear mechanism 35 rotate freely, and the power of the engine 2 is not transmitted to the drive wheels 7L, 7R.

[0045] When the shift lever is in the D position, S position, or B position, a forward range, which is one of the shift ranges of the transmission 4, is established. The power transmission modes in this forward range include a belt mode and a split mode. The belt mode and the split mode are switched by switching between a state in which the clutch C1 is engaged and a state in which the clutch C2 is engaged (switching between the clutches C1 and C2).

[0046] In the belt mode, as shown in Fig. 2, the clutch C1 and the brake B1 are released, and the clutch C2 is engaged, which disconnects the split drive gear 81 from the input shaft 31, frees the carrier 72 of the planetary gear mechanism 35 (freely rotates), and directly connects the sun gear 71 and the ring gear 73 of the planetary gear mechanism 35.

[0047] The power input to the input shaft 31 is reversed and reduced in speed by the front reduction gear mechanism 34 and transmitted to the primary shaft 41 of the belt transmission mechanism 33, causing the primary shaft 41 and the primary pulley 43 to rotate. The rotation of the primary pulley 43 is transmitted to the secondary pulley 44 via the belt 45, causing the secondary pulley 44 and the secondary shaft 42 to rotate. Because the sun gear 71 and the ring gear 73 of the planetary gear mechanism 35 are directly connected, the sun gear 71, the ring gear 73, and the output shaft 32 rotate integrally with the secondary shaft 42. Therefore, in the belt mode, as shown in FIGS. 3 and 4, the total speed ratio (unit speed ratio) of the transmission 4 matches the value obtained by multiplying the pulley ratio of the belt transmission mechanism 33 (the pulley ratio between the primary pulley 43 and the secondary pulley 44) by the front reduction gear ratio α (the rotation speed of the input shaft 31 / the rotation speed of the primary shaft 41).

[0048] 2, in the split mode, the clutch C1 is engaged, and the clutch C2 and the brake B1 are released. This connects the input shaft 31 and the split drive gear 81, allowing the rotation of the input shaft 31 to be transmitted to the carrier 72 of the planetary gear mechanism 35 via the split drive gear 81 and the split driven gear 82, and disconnects the sun gear 71 and ring gear 73 of the planetary gear mechanism 35.

[0049] The power input to the input shaft 31 is accelerated and transmitted from the split drive gear 81 to the split driven gear 82 and then to the carrier 72 of the planetary gear mechanism 35. The power transmitted to the carrier 72 is divided and transmitted from the carrier 72 to the sun gear 71 and the ring gear 73. The power of the sun gear 71 is transmitted to the primary shaft gear 62 via the secondary shaft 42, secondary pulley 44, belt 45, primary pulley 43, and primary shaft 41, and then from the primary shaft gear 62 to the input shaft gear 61. Therefore, in the belt mode, the input shaft gear 61 serves as the drive gear and the primary shaft gear 62 serves as the driven gear, whereas in the split mode, the primary shaft gear 62 serves as the drive gear and the input shaft gear 61 serves as the driven gear.

[0050] Because the gear ratio between the split drive gear 81 and the split driven gear 82 is constant and unchanging (fixed), in split mode, if the power input to the input shaft 31 is constant, the rotation speed of the carrier 72 of the planetary gear mechanism 35 is maintained at a constant speed. Therefore, when the pulley ratio is increased, the rotation speed of the sun gear 71 of the planetary gear mechanism 35 decreases, and the rotation speed of the ring gear 73 (output shaft 32) of the planetary gear mechanism 35 increases, as shown by the dashed line in Fig. 3. As a result, in split mode, as shown in Fig. 4, the greater the pulley ratio of the belt transmission mechanism 33, the smaller the reduction ratio of the transmission 4, and the sensitivity of the reduction ratio to the pulley ratio (the ratio of the change in the reduction ratio to the change in the pulley ratio) is lower than in belt mode.

[0051] In the belt mode and the split mode, the rotation of the output shaft 32 is transmitted to the differential gear 5 via the output gear 37. This causes the drive shafts 6L, 6R and the drive wheels 7L, 7R of the vehicle 1 to rotate in the forward direction.

[0052] Regardless of whether the shift lever is in the D, S, or B position, in the forward ranges, the transmission control automatically and continuously changes the gear ratio without any step. However, when the shift lever is in the S position (S range), the transmission ratio is changed so that the engine speed is maintained higher than when the shift lever is in the D position (D range). This allows the driver to enjoy sportier driving in the S range compared to the D range, and also provides stronger engine braking during deceleration. When the shift lever is in the B position (B range), the transmission ratio is changed so that the engine speed is maintained even higher than in the S range, providing stronger engine braking during deceleration than in the S range.

[0053] When the shift lever is in the R position, the transmission 4 is in a reverse range, which is one of the gear ranges. In the reverse range, as shown in Fig. 2, the clutches C1 and C2 are disengaged and the brake B1 is engaged. As a result, the split drive gear 81 is disconnected from the input shaft 31, the sun gear 71 and ring gear 73 of the planetary gear mechanism 35 are disconnected, and the carrier 72 of the planetary gear mechanism 35 is braked.

[0054] The power input to the input shaft 31 is reversed and reduced in speed by the front reduction mechanism 34 and transmitted to the primary shaft 41 of the belt transmission mechanism 33. From the primary shaft 41, it is transmitted to the secondary shaft 42 via the primary pulley 43, the belt 45, and the secondary pulley 44, causing the sun gear 71 of the planetary gear mechanism 35 to rotate integrally with the secondary shaft 42. Because the carrier 72 of the planetary gear mechanism 35 is braked, when the sun gear 71 rotates, the ring gear 73 of the planetary gear mechanism 35 rotates in the opposite direction to the sun gear 71. The rotation direction of this ring gear 73 is opposite to the rotation direction of the ring gear 73 during forward travel (belt mode and split mode). The output shaft 32 then rotates integrally with the ring gear 73. The rotation of the output shaft 32 is transmitted to the differential gear 5 via the output gear 37. As a result, the drive shafts 6L, 6R and the drive wheels 7L, 7R of the vehicle 1 rotate in the reverse direction.

[0055] <Vehicle control system> FIG. 5 is a block diagram showing the configuration of the control system of the vehicle 1.

[0056] The vehicle 1 is equipped with an ECU 91 (Electronic Control Unit) configured to include a microcomputer (microcontroller unit) as a control device. The microcomputer includes, for example, a CPU, a non-volatile memory such as a flash memory, and a volatile memory such as a DRAM (Dynamic Random Access Memory). Although only one ECU 91 is shown in FIG. 5, the vehicle 1 is equipped with multiple ECUs having the same configuration as the ECU 91 to control various parts. The multiple ECUs including the ECU 91 are connected to enable two-way communication using a CAN (Controller Area Network) communication protocol.

[0057] The ECU 91 controls an electronic throttle valve, injectors, spark plugs, and the like provided in the engine 2 to start, stop, and adjust the output of the engine 2. The ECU 91 also controls various valves included in a hydraulic circuit 92 that supplies hydraulic pressure to each part of the unit including the torque converter 3 and the transmission 4 to control lockup of the torque converter 3 and shifting of the transmission 4.

[0058] Various sensors required for the control are connected to the ECU 91. As an example, the ECU 91 is connected to a turbine rotation sensor 93 that outputs a pulse signal as a detection signal synchronized with the rotation of the turbine runner 23 of the torque converter 3, a primary rotation sensor 94 that outputs a pulse signal as a detection signal synchronized with the rotation of the primary shaft 41, a secondary rotation sensor 95 that outputs a pulse signal as a detection signal synchronized with the rotation of the secondary shaft 42, an output rotation sensor 96 that outputs a pulse signal as a detection signal synchronized with the rotation of the output shaft 32, and an accelerator sensor 97 that outputs a detection signal corresponding to the amount of operation of an accelerator pedal (not shown) operated by the driver.

[0059] The ECU 91 obtains the turbine rotation speed, which is the rotation speed of the turbine runner 23, the primary rotation speed, which is the rotation speed of the primary shaft 41 (primary pulley 43), the secondary rotation speed, which is the rotation speed of the secondary shaft 42 (secondary pulley 44), and the output rotation speed, which is the rotation speed of the output shaft 32, from the detection signals of the turbine rotation sensor 93, the primary rotation sensor 94, the secondary rotation speed, which is the rotation speed of the secondary shaft 42 (secondary pulley 44), and the output rotation speed, which is the rotation speed of the output shaft 32. The ECU 91 also obtains the accelerator opening, which is the ratio of the operation amount to the maximum operation amount of the accelerator pedal, from the detection signal of the accelerator sensor 97, that is, the accelerator opening, which is a percentage where 0% is when the accelerator pedal is not depressed and 100% is when the accelerator pedal is fully depressed.

[0060] In addition, some of the turbine rotation sensor 93, primary rotation sensor 94, secondary rotation sensor 95, output rotation sensor 96 and accelerator sensor 97 may be connected to another ECU, and information obtained from some of these sensors may be received from the other ECU.

[0061] <Gear shift control> The total gear ratio of the transmission 4 is controlled by the ECU 91 by changing the pulley ratio and engaging / disengaging the clutches C1, C2 and brake B1. In this gear change control, a target rotation speed corresponding to the accelerator opening and vehicle speed is first set based on a shift map. The shift map is a map that defines the relationship between the accelerator opening and vehicle speed and the target rotation speed, and is stored in the ROM of the ECU 91. Information on the vehicle speed is transmitted to the ECU 91, for example, from the engine ECU that controls the engine 2. Once the target rotation speed is set, a target total gear ratio is determined that matches the rotation speed input to the input shaft 31, i.e., the turbine rotation speed, with the target rotation speed, and a target pulley ratio is set according to that target.

[0062] Thereafter, command values ​​for the primary pressure, which is the hydraulic pressure supplied to the movable sheave 52 of the primary pulley 43, and the secondary pressure, which is the hydraulic pressure supplied to the movable sheave 56 of the secondary pulley 44, are set based on the target pulley ratio, and the primary pressure and secondary pressure are controlled based on each command value so that the deviation between the target pulley ratio and the actual pulley ratio approaches zero. The actual pulley ratio is calculated by dividing the primary rotation speed by the secondary rotation speed.

[0063] When the total speed ratio is changed across a split point (split speed ratio) equal to the gear ratio between split drive gear 81 and split driven gear 82, the change in the total speed ratio is accompanied by switching between belt mode and split mode (hereinafter simply referred to as "mode switching"). Mode switching is achieved by control that switches the engagement of clutches C1 and C2 (clutch-to-clutch control). That is, by controlling the hydraulic pressure supplied to clutches C1 and C2, the released clutch C1 (engagement side) is engaged and the engaged clutch C2 (release side) is released, thereby switching from belt mode to split mode. Conversely, the engaged clutch C1 (release side) is released and the released clutch C2 (engagement side) is engaged, thereby switching from split mode to belt mode.

[0064] Here, when the total gear ratio deviates from the split point (split gear ratio), a differential rotation occurs between the output shaft 32 and the secondary shaft 42, resulting in a difference between the turbine rotation speed (= rotation speed of the input shaft 31) and the synchronous rotation speed calculated by multiplying the output rotation speed by the pulley ratio.

[0065] In this state, if a downshift request (kick-down request) is made, for example by the driver quickly and strongly depressing the accelerator pedal, the hydraulic pressure supplied to the engaged clutch C1 is reduced accordingly. This reduction in hydraulic pressure reduces the transmission torque capacity of the clutch C1, and when the transmission torque capacity falls below the input torque, the clutch C1 enters a half-clutch state, causing slippage in the clutch C1, and the turbine rotation speed begins to increase at the target rate of change corresponding to the driver's kick-down request.

[0066] When the turbine speed exceeds the synchronous speed, the target pulley ratio starts to be changed in the downshift direction. When the actual pulley ratio changes in the downshift direction accordingly, the synchronous speed increases.

[0067] Here, in the shift control of the shifting system S of this embodiment, a process for switching from split mode to belt mode can be performed by a split point mode switching process or a non-split point mode switching process. The split point mode switching process (single point switching process) is a process for switching from split mode to belt mode by clutch-to-clutch control in a state where the total speed ratio is reduced to the split point (split speed ratio), as shown in FIG. 6(a). In contrast, the non-split point mode switching process is a process for switching from split mode to belt mode by clutch-to-clutch control in a state where the total speed ratio does not match the split point, without reducing the total speed ratio to the split point (split speed ratio), as shown in FIG. 6(b). The difference between the two is that the split point mode switching process is a process in which the mode is switched by changing the total gear ratio so as to pass through the split point (split gear ratio), whereas the non-split point mode switching process is a process in which the mode is switched at a gear ratio higher than the split point (split gear ratio) without passing through the split point (split gear ratio).

[0068] In the transmission system S of this embodiment, the ECU 91 determines whether to use the non-split point mode switching process or the split point mode switching process when switching from the split mode to the belt mode, depending on the accelerator pedal position. Specifically, when the accelerator pedal position is greater than a predetermined threshold position, the ECU 91 switches the mode using the non-split point mode switching process. When the accelerator pedal position is equal to or smaller than the predetermined threshold position, the ECU 91 switches the mode using the split point mode switching process.

[0069] As can be seen from FIG. 7, when the ECU 91 performs mode switching by the non-split point mode switching process, the ECU 91 performs control to adjust the magnitude of the transfer torque capacity (clutch torque) of the clutch C1 in accordance with the target input shaft rotation speed set based on the accelerator pedal position so that the input shaft rotation speed becomes the target rotation speed. Specifically, when the driver depresses the accelerator pedal heavily to generate a downshift request (kick-down request), the hydraulic pressure supplied to the engaged clutch C1 is reduced in response, and the transfer torque capacity of the clutch C1 decreases. Thereafter, the magnitude of the transfer torque capacity of the clutch C1 is adjusted so that the input shaft rotation speed becomes the target rotation speed, as shown in FIG. 7.

[0070] While adjusting the transmission torque capacity of the clutch C1 as described above, the ECU 91 also controls the magnitude of the clutch torque of the clutch C2 to be adjusted in accordance with a differential torque capacity derived by subtracting the transmission torque capacity (clutch torque) of the clutch C1 from the input torque (turbine torque) to the transmission 4. This brings the input torque (turbine torque) to the transmission 4 into balance with the sum of the transmission torque capacities of the clutches C1 and C2, and the input torque (turbine torque) to the transmission 4 can be maintained approximately level without being drawn in, thereby minimizing the occurrence of engagement shock.

[0071] The above-described mode switching from the split mode to the belt mode by the ECU 91 is executed in accordance with the flow shown in Figures 8 and 9. This will be specifically described below with reference to Figures 8 and 9.

[0072] (Step 1-1) In step 1-1, the ECU 91 checks whether a request to switch the mode from the split mode to the belt mode has been issued. If it is determined that a request to switch the mode has been issued while the total speed ratio is deviated from the split point, the control flow proceeds to step 1-2.

[0073] (Step 1-2) In step 1-2, the ECU 91 checks whether the accelerator opening is greater than a predetermined threshold value. If the accelerator opening is greater than the predetermined threshold value, the control flow proceeds to step 1-3. If the accelerator opening is equal to or less than the threshold value, the control flow proceeds to step 1-4.

[0074] (Steps 1-3) When the control flow proceeds from step 1-2 to step 1-3, mode switching is performed by non-split point mode switching processing. That is, in step 1-3, processing is performed to switch mode from split mode to belt mode by clutch-to-clutch control in a state where the total speed ratio does not match the split point (split speed ratio) without lowering the total speed ratio to the split point (split speed ratio) as shown in FIG. 6(b). Specifically, mode switching is performed by non-split point mode switching processing by performing clutch-to-clutch control by adjusting the transmission torque capacities of clutches C1 and C2 in accordance with the control flow of the subroutine shown in FIG.

[0075] (Steps 1-4) On the other hand, when the control flow proceeds from step 1-2 to step 1-4, mode switching is performed by split point mode switching processing. That is, in step 1-4, with the total speed ratio reduced to the split point (split speed ratio) as shown in Figure 6(a), processing is performed to switch mode from split mode to belt mode by clutch-to-clutch control.

[0076] The subroutine relating to mode switching by the non-split point mode switching process executed in step 1-3 above will be described below with reference to FIG.

[0077] (Step 2-1) When mode switching is performed using the non-split point mode switching process, first, in step 2-1, the ECU 91 derives and adjusts the magnitude of the transfer torque capacity (clutch torque) of the clutch C1 in accordance with the target input shaft rotation speed set based on the accelerator pedal position so that the input shaft rotation speed becomes the target rotation speed. The ECU 91 controls the hydraulic circuit 92 to adjust the hydraulic pressure acting on the clutch C1 so that the transfer torque capacity of the clutch C1 becomes the magnitude of the transfer torque capacity derived in this manner. In this way, the magnitude of the transfer torque capacity of the clutch C1 is adjusted so that the input shaft rotation speed becomes the target rotation speed. Thereafter, the control flow proceeds to step 2-2.

[0078] (Step 2-2) In step 2-2, the ECU 91 derives a set value for the transmission torque capacity of the clutch C2. Specifically, the ECU 91 derives a differential torque capacity as the set value for the transmission torque capacity of the clutch C2 by subtracting the transmission torque capacity (clutch torque) of the clutch C1 set in step 2-1 from the input torque (turbine torque) to the transmission 4. Thereafter, the control flow proceeds to step 2-3.

[0079] (Step 2-3) In step 2-3, the ECU 91 adjusts the transmission torque capacity (clutch torque) of the clutch C2 by controlling the hydraulic circuit 92 so that the transmission torque capacity of the clutch C2 becomes the set value derived in step 2-2. Thereafter, the control flow proceeds to step 2-4.

[0080] (Steps 2-4) In step 2-4, the ECU 91 checks whether the mode change from the split mode to the belt mode has been completed. If the mode change is not completed, the control flow returns to step 2-1. On the other hand, if the mode change is completed, the subroutine according to FIG. 8 ends.

[0081] <Action and effect> The ECU 91 (control device) of the transmission 4 of the present embodiment described above has the following characteristic configurations (a) and (b), which enable the ECU 91 of the transmission 4 to achieve the following unique effects.

[0082] (a) The ECU 91 (control device) of this embodiment controls a transmission 4 that includes a clutch C1 (first engagement element) interposed on a first power transmission path between the input shaft 31 and the output shaft 32, and a clutch C2 (second engagement element) interposed on a second power transmission path between the input shaft 31 and the output shaft 32, and has a belt transmission mechanism 33 on the second power transmission path, and by releasing the clutch C1 and engaging the clutch C2, a belt mode (first mode) is entered in which the total speed ratio between the input shaft 31 and the output shaft 32 increases as the pulley ratio by the belt transmission mechanism 33 increases, and by engaging the clutch C1 and releasing the clutch C2, a split mode (second mode) is entered in which the total speed ratio decreases as the pulley ratio increases, and when the total speed ratio is a predetermined split speed ratio, no differential rotation occurs between the clutch C1 and the clutch C2. The ECU 91 controls a transmission 4 that includes a target total speed ratio setting unit that sets a target of the total speed ratio as a target total speed ratio, and a target total speed ratio setting unit that sets a target of the total speed ratio as a target total speed ratio. and a switching control unit that performs non-split point mode switching processing to switch from split mode to belt mode by releasing clutch C1 and engaging clutch C2 in a state where the total speed ratio does not match the split speed ratio, on the condition that the target total speed ratio set by the target total speed ratio setting unit in split mode is greater than the split speed ratio. In the non-split point mode switching processing, the switching control unit adjusts the magnitude of the transfer torque capacity of clutch C1 in accordance with the target input shaft speed set based on the accelerator opening so that the input shaft speed becomes the target speed, and adjusts the magnitude of the transfer torque capacity of clutch C2 in accordance with a differential torque capacity derived by subtracting the transfer torque capacity of clutch C1 from the input torque to transmission 4.

[0083] As described above in (a), during the non-split point mode switching process, the ECU 91 of this embodiment adjusts the magnitude of the transfer torque capacity of the clutch C1 in accordance with the target input shaft rotation speed set based on the accelerator pedal position so that the input shaft rotation speed becomes the target rotation speed, while adjusting the magnitude of the transfer torque capacity of the clutch C2 in accordance with the differential torque capacity calculated by subtracting the transfer torque capacity of the clutch C1 from the input torque to the transmission 4. Therefore, when the non-split point mode switching process is performed by the ECU 91 of this embodiment, it is possible to prevent the input rotation speed from being strongly pulled in the negative direction and minimize the occurrence of engagement shock. Therefore, the ECU 91 of this embodiment can perform mode switching without causing a large engagement shock even when mode switching is performed when the pulley ratio does not match the split point.

[0084] (b) The ECU 91 of this embodiment preferably performs non-split point mode switching processing when the accelerator opening is greater than a predetermined threshold opening, and performs split point mode switching processing to switch from split mode to belt mode by releasing clutch C1 and engaging clutch C2 when the accelerator opening is less than the threshold opening and the pulley ratio matches the split gear ratio.

[0085] The ECU 91 of this embodiment can perform mode switching without causing a large engagement shock by performing the non-split point mode switching process as described above in (a) when the accelerator pedal position is greater than a predetermined threshold position. Furthermore, the ECU 91 of this embodiment can perform mode switching without causing a large engagement shock by performing the split point mode switching process as described above in (b) when the accelerator pedal position is small, equal to or less than the threshold position, in which the pulley ratio matches the split gear ratio and the clutch C1 is released and the clutch C2 is engaged. Therefore, the ECU 91 of this embodiment can prevent a large engagement shock from occurring when switching from split mode to belt mode, regardless of the accelerator pedal position.

[0086] <<Variations>> The ECU 91 of the transmission 4 illustrated in the above embodiment is merely one example of the present invention, and, for example, the configurations according to (a) and (b) above may be different from those illustrated in the above embodiment without departing from the spirit of the present invention. Furthermore, the ECU 91 of the transmission 4 may be provided with other configurations in addition to or instead of the configurations included in (a) and (b) above, or may be configured with some of the configurations omitted. Specifically, the following modifications are possible.

[0087] In this embodiment, an example is shown in which the engine 2 is used as a driving source and driving force is input to the transmission 4, but the present invention is not limited to this, and the transmission may operate by receiving power from a driving source such as a motor in addition to or instead of the engine 2.

[0088] In this embodiment, an example has been given in which ECU91 is equipped with all of the functions of the target total speed ratio setting unit, pulley ratio changing unit, and switching control unit that constitute the present invention, but the present invention is not limited to this, and at least one of the target total speed ratio setting unit, pulley ratio changing unit, and switching control unit may be configured by an ECU other than ECU91.

[0089] In the present embodiment, as described in (b) above, the non-split point mode switching process is performed when the accelerator opening is greater than a predetermined threshold opening, and the split point mode switching process is performed when the accelerator opening is equal to or less than the threshold opening. However, the present invention is not limited to this. For example, the ECU 91 may perform mode switching by a process other than the split point mode switching process when the accelerator opening is equal to or less than the threshold opening. Furthermore, other conditions may be set as the start condition for performing the non-split point mode switching process in addition to the accelerator opening being greater than the predetermined threshold opening. Similarly, other conditions may be set as the start condition for performing the split point mode switching process in addition to the accelerator opening being equal to or less than the predetermined threshold opening.

[0090] In addition, in this embodiment, an example is shown in which the engine 2, torque converter 3, and hydraulic circuit 92 of the CVT 4 are controlled by the ECU 91, but the engine 2, torque converter 3, and hydraulic circuit 92 of the transmission 4 may also be controlled by separate ECUs.

[0091] The present invention is not limited to the above-described embodiments and modifications, and other embodiments may be possible within the scope of the claims, based on the teachings and spirit of the invention. The components of the above-described embodiments may be arbitrarily selected and combined. Furthermore, any component of the embodiment may be arbitrarily combined with any component described in the Summary of the Invention or any component embodying any component described in the Summary of the Invention. The present invention intends to obtain rights to these as well through amendments to this application or divisional applications, etc. [Industrial Applicability]

[0092] The present invention can be suitably used in all types of transmission systems equipped with a so-called power split transmission mechanism. [Explanation of symbols]

[0093] 4: Transmission 31: Input shaft 32: Output shaft 33: Belt transmission mechanism 91: ECU C1: Clutch C2: Clutch

Claims

1. a control device for controlling a transmission including a first engagement element interposed on a first power transmission path between an input shaft and an output shaft, and a second engagement element interposed on a second power transmission path between the input shaft and the output shaft, and a belt transmission mechanism on the second power transmission path, wherein a first mode is entered in which the total speed ratio between the input shaft and the output shaft increases as the pulley ratio of the belt transmission mechanism increases by disengaging the first engagement element and engaging the second engagement element, and a second mode is entered in which the total speed ratio decreases as the pulley ratio increases by engaging the first engagement element and disengaging the second engagement element, and wherein when the total speed ratio is a predetermined split speed ratio, no differential rotation occurs between the first engagement element and the second engagement element, a target total speed ratio setting unit that sets the target total speed ratio as a target total speed ratio; a pulley ratio changing unit that changes the pulley ratio based on the target total speed ratio set by the target total speed ratio setting unit; a switching control unit that performs a non-split point mode switching process to switch from the second mode to the first mode by disengaging the first engagement element and engaging the second engagement element in a state in which the total speed ratio does not match the split speed ratio, on the condition that the target total speed ratio set by the target total speed ratio setting unit in the second mode is greater than the split speed ratio; and a control device characterized in that, during the non-split point mode switching process, the switching control unit adjusts the magnitude of the transmission torque capacity of the first engagement element in accordance with a target rate of change of the input shaft rotation speed so that the input shaft rotation speed becomes a target rotation speed, while adjusting the magnitude of the transmission torque capacity of the second engagement element so that the sum of the transmission torque capacity of the first engagement element and the transmission torque capacity of the second engagement element is balanced with the input torque to the transmission.

2. The non-split point mode switching process is performed on the condition that the accelerator opening is greater than a predetermined threshold opening, 2. The control device according to claim 1, wherein, on the condition that the accelerator opening is a small opening equal to or less than the threshold opening, when the total speed ratio matches the split speed ratio, a split point mode switching process is performed to switch from the second mode to the first mode by disengaging the first engagement element and engaging the second engagement element.

Images