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. When switching modes from a split mode to a belt mode, it is derived: an increase prediction rotation speed derived based on a target change rate of an input share rotation speed and a switching time required for a release of a clutch C1 and an engagement of the clutch C2 in a non-split point mode switching process; and a differential rotation speed drive based on a difference between a target input shaft rotation speed after switching to a belt 45 mode and a switching input shaft rotation speed which is an input shaft rotation speed at the time of switching to the belt mode. On condition that the increase prediction rotation speed is smaller than the differential rotation speed, a determination is made to permit an execution of the non-split point mode switching process.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] The present inventors conducted extensive research into control of a power split type continuously variable transmission such as that disclosed in Patent Document 1 when switching from split mode to belt mode when the accelerator pedal is at a low to medium rotational angle. As a result, they found that, as shown in FIG. 6(a), if the pulley ratio is adjusted to a state where there is no differential rotation between the first and second engagement elements before switching from split mode to belt mode, the shock generated during the mode change is reduced, but the mode change takes time, making the user more likely to feel a time lag. On the other hand, they found that if the clutch-to-clutch control described above is performed when the differential rotation between before and after switching from split mode to belt mode is small, such as when the accelerator pedal is at a low to medium rotational angle, the second engagement element will be engaged after the target input shaft rotation speed is exceeded, resulting in a greater shock during the mode change. Therefore, if clutch-to-clutch control is to be performed based on the accelerator opening, there is a problem that the shock associated with switching modes cannot be suppressed unless clutch-to-clutch control is performed under the limited condition that the accelerator opening is high.

[0006] Therefore, the present invention aims to provide a control device that can perform mode switching from split mode to belt mode using clutch-to-clutch control in situations where the shock associated with mode switching can be suppressed, without being limited to situations where the accelerator opening is high. [Means for solving the problem]

[0007] (1) A control device of the present invention controls a continuously variable 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 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. 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, 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, and a pulley ratio changing unit that changes the target total speed ratio in the second mode. The non-split point mode switching control unit has 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 when the total gear ratio does not match the split gear ratio, on the condition that the target total gear ratio set by a target total gear ratio setting unit is greater than the split gear ratio, and a judgment unit that judges whether the non-split point mode switching process can be executed, wherein the judgment unit derives a predicted increased rotation speed derived based on a target rate of change of input shaft rotation speed and the time required for the first engagement element to be disengaged and the second engagement element to be engaged in the non-split point mode switching process, and a differential rotation speed derived based on the difference between the target input shaft rotation speed after switching to the first mode and a switching time input shaft rotation speed, which is the input shaft rotation speed at the time of switching to the first mode, and makes a judgment to allow the non-split point mode switching process to be executed on the condition that the predicted increased rotation speed is smaller than the differential rotation speed.

[0008] The control device of the present invention determines whether to permit a non-split point mode switching process for switching from the second mode to the first mode when the total speed ratio does not match the split speed ratio. The control device derives a predicted increase in rotation speed based on the rate of change of the input shaft rotation speed and the time required for the first engagement element to disengage and the second engagement element to engage. The control device of the present invention also derives a differential rotation speed based on the difference between the target input shaft rotation speed after switching to the first mode and the input shaft rotation speed at the time of switching to the first mode (switching input shaft rotation speed). If the predicted increase in rotation speed thus derived is smaller than the differential rotation speed, executing the non-split point mode switching process will not cause engine surges, minimizing shock associated with switching from the second mode to the first mode. Based on this finding, the control device of the present invention permits execution of the non-split point mode switching process when the predicted increase in rotation speed is smaller than the differential rotation speed. Therefore, the control device of the present invention can switch from split mode to belt mode by non-split point mode switching processing in situations where shock can be suppressed, without being limited to situations where the accelerator opening is at a high opening.

[0009] (2) In the control device of the present invention, the input shaft rotation speed at switching may be derived based on the rotation speed of the output shaft and the pulley ratio.

[0010] The control device of the present invention, configured as described above in (2), can appropriately derive the input shaft rotation speed at switching based on the output shaft rotation speed and the pulley ratio, thereby enabling the control device of the present invention to accurately determine whether or not to permit execution of the non-split point mode switching process.

[0011] (3) The control device of the present invention is provided with a front reduction mechanism that reduces the power input to the input shaft and outputs it to the belt transmission mechanism, and the input shaft rotation speed at the time of switching is preferably derived based on the reduction ratio in the front reduction mechanism, the rotation speed of the output shaft, and the pulley ratio.

[0012] By configuring the control device of the present invention as described above in (3), the control device of the present invention can appropriately derive the input shaft rotation speed at switching by taking into account the reduction ratio of the front reduction mechanism in addition to the rotation speed of the output shaft and the pulley ratio. As a result, the control device of the present invention can accurately determine whether to permit execution of the non-split point mode switching process when configured with a front reduction mechanism.

[0013] (4) In the control device of the present invention, the determining unit may determine to prohibit the non-split point mode switching process on the condition that the predicted increased rotation speed is equal to or less than the differential rotation speed.

[0014] The control device of the present invention, configured as described above in (4), can suppress the occurrence of a surge caused by the non-split point mode switching process, thereby suppressing the occurrence of a large shock that occurs when switching from the second mode to the first mode.

[0015] (5) The control device of the present invention may preferably perform 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, provided that the increased predicted rotational speed is equal to or less than the differential rotational speed.

[0016] By configuring the control device of the present invention as described above in (5), when performing the non-split point mode switching process is likely to cause engine revving or a large shock, the control device of the present invention can perform mode switching by the split point mode switching process rather than the non-split point mode switching process. As a result, even under conditions where the predicted increase in engine speed is equal to or less than the differential engine speed, the control device of the present invention can perform mode switching from the second mode to the first mode while suppressing engine revving or a large shock. [Effects of the Invention]

[0017] According to the present invention, the above-mentioned problems of the present invention can be solved. [Brief explanation of the drawings]

[0018] [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] 10 is an explanatory diagram relating to a determination for determining whether or not a non-split point mode switching process can be executed. FIG. [Figure 8] 10 is a flowchart showing the flow of mode switching processing that is performed after a determination is made as to whether or not non-split point mode switching processing can be performed. DETAILED DESCRIPTION OF THE INVENTION

[0019] 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.

[0020] <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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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).

[0030] 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.

[0031] 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.

[0032] 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.

[0033] In the belt transmission mechanism 33, the oil pressure supplied to the oil pressure chamber 54 of the primary pulley 43 and the oil pressure chamber 58 of the secondary pulley 44 are 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 ratio between the primary pulley 43 and the secondary pulley 44).

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] The split drive gear 81 is fitted onto the input shaft 31 so as to be rotatable relative to the input shaft 31 .

[0041] 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.

[0042] The transmission 4 also includes clutches C1 and C2 and a brake B1.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] <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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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).

[0051] 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.

[0052] 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 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).

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] <Vehicle control system> FIG. 5 is a block diagram showing the configuration of the control system of the vehicle 1.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] <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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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, the synchronous speed increases.

[0072] 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).

[0073] In the transmission system S of this embodiment, a determination (non-split point mode switching determination) for determining whether or not the above-described non-split point mode switching process can be performed is executed by the ECU 91. The ECU 91 executes mode switching by the non-split point mode switching process on the condition that a determination is made to permit non-split point mode switching (permission determination). On the other hand, the ECU 91 executes mode switching by the split point mode switching process rather than the non-split point mode switching process on the condition that a determination is made to not permit non-split point mode switching (prohibition determination).

[0074] Specifically, when determining whether to switch to the non-split point mode, the ECU 91 derives a predicted value of the increase in the rotation speed (predicted increase in rotation speed Rs) based on a target rate of change of the turbine rotation speed (=input shaft rotation speed to the input shaft 31) that is set according to the accelerator pedal position and the time (switching time) required to execute the non-split point mode switching process by releasing the clutch C1 and engaging the clutch C2 through clutch-to-clutch control. That is, when the target rate of change of the turbine rotation speed (input shaft rotation speed) is C and the switching time is t, the ECU 91 derives the predicted increase in rotation speed Rs as Rs = C × t (see FIG. 7).

[0075] Furthermore, as shown in FIG. 7, the ECU 91 derives the difference (Ng-Ns) between the target turbine rotation speed (target input shaft rotation speed Ng) after switching to the first mode and the input shaft rotation speed at switching Ns, which is the turbine rotation speed (input shaft rotation speed) at the time of switching to the first mode, as the differential rotation speed Rd.

[0076] The input shaft rotation speed Ns at the time of switching is calculated by the ECU 91 based on the output rotation speed Nout, which is the rotation speed of the output shaft 32 acquired based on the detection signal of the output rotation sensor 96, and the pulley ratio γ at the time of mode switching. In this embodiment, since the front reduction mechanism 34 is provided, the ECU 91 derives the input shaft rotation speed at the time of switching taking into account the front reduction ratio α of the front reduction mechanism 34. Specifically, the ECU 91 derives the input shaft rotation speed Ns at the time of switching as Ns = Nout × α × γ.

[0077] The ECU 91 derives the differential rotational speed Rd based on the rotational speed Ns of the input shaft at the time of switching derived as described above, and compares the predicted increase rotational speed Rs derived based on the above-described mathematical formula with the differential rotational speed Rd. When the predicted increase rotational speed Rs is smaller than the differential rotational speed Rd (Rs < Rd), even if clutch-to-clutch control is executed by switching the clutches C1 and C2, there is a low possibility of blow-up occurring, and there is also a low possibility of a shock occurring due to mode switching. Therefore, when the predicted increase rotational speed Rs is smaller than the differential rotational speed Rd, the ECU 91 makes a determination (permission determination) to permit clutch-to-clutch control. On the other hand, when the predicted increase rotational speed Rs is larger than the differential rotational speed Rd (Rs > Rd), if clutch-to-clutch control is executed by switching the clutches C1 and C2, there is a possibility that blow-up will occur and a shock will occur. Therefore, in the non-split point mode switching determination, when the predicted increase rotational speed Rs is larger than the differential rotational speed Rd, the ECU 91 makes a determination (prohibition determination) not to permit the execution of clutch-to-clutch control.

[0078] The non-split point mode switching determination by the above-described ECU 91 is executed according to the flow shown in FIG. 8. Hereinafter, a specific description will be given while referring to FIG. 8.

[0079] (Step 1) In Step 1, the ECU 91 checks whether a request to execute mode switching from the split mode to the belt mode has occurred in a state where the total gear ratio is deviated from the split point. Here, when it is confirmed that a request to execute mode switching has occurred in a state where the total gear ratio is deviated from the split point, the control flow proceeds to Step 2.

[0080] (Step 2) In step 2, the ECU 91 derives the predicted increased rotation speed Rs. Specifically, as described above, the ECU 91 multiplies the target rate of change C of the turbine rotation speed, which is set according to the accelerator opening, by the switching time t to derive the predicted increased rotation speed Rs (Rs=C×t). Thereafter, the control flow proceeds to step 3.

[0081] (Step 3) In step 3, the ECU 91 derives the input shaft rotation speed Ns at the time of switching. Specifically, as described above, the ECU 91 derives the input shaft rotation speed Ns at the time of switching (Ns = Nout × α × γ) by multiplying the output rotation speed Nout by the pulley ratio γ and the front reduction ratio α of the front reduction mechanism 34. Thereafter, the control flow proceeds to step 4.

[0082] (Step 4) In step 4, the ECU 91 derives a differential rotation speed Rd from the difference (Ng−Ns) between the target input shaft rotation speed Ng and the input shaft rotation speed at switching Ns derived in step 3. Thereafter, the control flow proceeds to step 5.

[0083] (Step 5) In step 5, the ECU 91 compares the magnitude of the predicted increased rotation speed Rs derived in step 2 with the magnitude of the differential rotation speed Rd derived in step 4. As a result, if the predicted increased rotation speed Rs is smaller than the differential rotation speed Rd (YES in step 5), the control flow proceeds to step 6. On the other hand, if the predicted increased rotation speed Rs is larger than the differential rotation speed Rd (NO in step 5), the control flow proceeds to step 8.

[0084] (Step 6) When the control flow proceeds from step 5 to step 6, the predicted increased rotation speed Rs is smaller than the differential rotation speed Rd. Therefore, even if the clutches C1 and C2 are switched by clutch-to-clutch control and the non-split point mode switching process is executed while the total speed ratio does not match the split point (split speed ratio), there is little possibility of the engine revving up or shock occurring due to the mode switching. Therefore, the ECU 91 makes a determination to permit the non-split point mode switching process (permission determination). Thereafter, the control flow proceeds to step 7.

[0085] (Step 7) When the control flow proceeds to step 7, the ECU 91 executes a process for switching the mode from the split mode to the belt mode by a non-split point mode switching process. That is, the ECU 91 performs a mode switch from the split mode to the belt mode by clutch-to-clutch control without lowering the total speed ratio to the split point (split speed ratio) and while the total speed ratio does not match the split point.

[0086] (Step 8) On the other hand, if the control flow proceeds from step 5 to step 8, the predicted increased rotation speed Rs is greater than the differential rotation speed Rd. Therefore, if the clutches C1 and C2 are switched by the clutch-to-clutch control and the non-split point mode switching process is executed, there is a high possibility that the engine will jump up and a shock will occur due to the mode switching. Therefore, the ECU 91 makes a determination to prohibit the non-split point mode switching process (prohibition determination). Thereafter, the control flow proceeds to step 9.

[0087] (Step 9) When the control flow proceeds to step 9, the ECU 91 executes a process for switching the mode from the split mode to the belt mode by a split point mode switching process. That is, the ECU 91 reduces the total speed ratio to the split point (split speed ratio) and, in a state where the pulley ratio is matched with the split point (split speed ratio), switches the mode from the split mode to the belt mode by clutch-to-clutch control.

[0088] <Action and effect> The ECU 91 (control device) of the transmission 4 of the present embodiment described above has the following characteristic configurations (a) to (e), which enable the ECU 91 of the transmission 4 to achieve the following unique effects.

[0089] (a) The ECU 91 (control device) of this embodiment 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. The second power transmission path is provided with a belt transmission mechanism 33. When the clutch C1 is released and the clutch C2 is engaged, the belt mode (first mode) is entered in which the total speed change ratio between the input shaft 31 and the output shaft 32 increases as the pulley ratio γ of the belt transmission mechanism 33 increases. The ECU 91 controls the transmission 4, which is configured such that a split mode (second mode) is entered in which the total speed ratio decreases as the pulley ratio γ increases by engaging the clutch C1 and releasing the clutch C2, and when the total speed ratio is a predetermined split speed ratio, no differential rotation occurs between the clutches C1 and C2. The ECU 91 includes a target total speed ratio setting unit that sets a target for the total speed ratio as a target total speed ratio, and a pulley ratio changing unit that changes the pulley ratio γ based on the target total speed ratio set by the target total speed ratio setting unit. 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 larger than the split speed ratio; and a determination unit that determines whether or not the non-split point mode switching processing can be performed, wherein the determination unit determines a target rate of change C of the input shaft rotation speed that is set in accordance with an accelerator opening degree, The non-split point mode switching process is characterized by deriving an increased predicted rotation speed Rs, which is derived based on the switching time t required for releasing the clutch C1 and engaging the clutch C2 in the non-split point mode switching process, and a differential rotation speed Rd, which is derived based on the difference between the target input shaft rotation speed Ng after switching to the belt mode and the input shaft rotation speed at switching Ns, which is the input shaft rotation speed at the time of switching to the belt mode, and making a determination to allow execution of the non-split point mode switching process on the condition that the increased predicted rotation speed Rs is smaller than the differential rotation speed Rd.

[0090] In this embodiment, the ECU 91 determines whether to permit a non-split point mode switching process for switching from split mode to belt mode when the total speed ratio does not match the split speed ratio. The ECU 91 derives a predicted increase in rotation speed Rs based on a target rate of change C of the input shaft rotation speed and a switching time t required for disengaging clutch C1 and engaging clutch C2. The ECU 91 also derives a differential rotation speed Rd based on the difference between the target input shaft rotation speed Ng after switching to belt mode and the input shaft rotation speed at the time of switching to belt mode (switching input shaft rotation speed Ns). If the predicted increase in rotation speed Rs is smaller than the differential rotation speed Rd, executing the non-split point mode switching process will not cause engine surges, minimizing shock associated with the mode switch from split mode to belt mode. Based on this knowledge, the ECU 91 of this embodiment is configured to permit execution of the non-split point mode switching process when the predicted increased rotation speed Rs is smaller than the differential rotation speed Rd. Therefore, the ECU 91 of this embodiment can execute the non-split point mode switching process to switch from the split mode to the belt mode in any situation where shock can be suppressed, not just when the accelerator opening is large.

[0091] (b) The ECU 91 of this embodiment may derive the input shaft rotation speed Ns at the time of switching based on the output rotation speed Nout of the output shaft 32 and the pulley ratio γ.

[0092] By being configured as described above in (b), the ECU 91 of this embodiment can appropriately derive the input shaft rotation speed Ns at the time of switching based on the output rotation speed Nout and the pulley ratio γ of the output shaft 32. This allows the ECU 91 of this embodiment to accurately determine whether or not to permit execution of the non-split point mode switching process.

[0093] (c) The ECU 91 of this embodiment is equipped with a front reduction mechanism 34 that reduces the power input to the input shaft 31 and outputs it to the belt transmission mechanism 33, and it is preferable that the input shaft rotation speed Ns at the time of switching is derived based on the front reduction ratio α of the front reduction mechanism 34, the output rotation speed Nout of the output shaft 32, and the pulley ratio γ.

[0094] By being configured as described above in (c), the ECU 91 of this embodiment can appropriately derive the input shaft rotation speed Ns at the time of switching by taking into account the front reduction gear ratio α of the front reduction gear mechanism 34 in addition to the output rotation speed Nout and pulley ratio γ of the output shaft 32. As a result, the ECU 91 of this embodiment can accurately determine permission for execution of the non-split point mode switching process when the ECU 91 is configured to include the front reduction gear mechanism 34.

[0095] (d) In the ECU 91 of this embodiment, the determining unit may determine to prohibit the non-split point mode switching process on the condition that the predicted increased rotation speed Rs is greater than the differential rotation speed Rd.

[0096] The ECU 91 of this embodiment, by being configured as described in (d) above, can suppress the occurrence of a sudden rise in the engine speed due to the non-split point mode switching process, thereby suppressing the occurrence of a large shock that occurs when switching from the split mode to the belt mode.

[0097] (e) The ECU 91 of this embodiment preferably performs split point mode switching processing to switch from split mode to belt mode by releasing clutch C1 and engaging clutch C2 when the total gear ratio matches the split gear ratio, provided that the predicted increased rotation speed Rs is greater than the differential rotation speed Rd.

[0098] By configuring as described above in (e), the ECU 91 of this embodiment can perform mode switching by the split point mode switching process rather than the non-split point mode switching process when performing the non-split point mode switching process would cause engine revving or a large shock. As a result, even under conditions where the predicted increased rotation speed Rs is greater than the differential rotation speed Rd, the ECU 91 of this embodiment can switch the mode from the split mode to the belt mode while suppressing engine revving or a large shock.

[0099] <<Variations>> The ECU 91 of the transmission 4 illustrated in the above embodiment is merely one example of the present invention, and, as long as it does not deviate from the spirit of the present invention, for example, the configurations (a) to (e) described above may be different from those illustrated in the above embodiment. 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) to (e) described above, or may be configured with some configurations omitted. Specifically, the following modifications are possible.

[0100] 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.

[0101] In the present embodiment, as described in (b) above, the input shaft rotation speed Ns at the time of switching is calculated by multiplying the output rotation speed Nout of the output shaft 32 by the pulley ratio γ, but the present invention is not limited to this. For example, the input shaft rotation speed Ns at the time of switching may be calculated by taking into account other factors in addition to or instead of the output rotation speed Nout and the pulley ratio γ.

[0102] In this embodiment, as described above in (c), the transmission 4 is provided with the front reduction gear mechanism 34, and therefore the input shaft rotation speed Ns at the time of switching is derived by taking into account the front reduction gear ratio α of the front reduction gear mechanism 34 in addition to the output rotation speed Nout of the output shaft 32 and the pulley ratio γ, but the present invention is not limited to this. For example, if the transmission 4 does not include the front reduction gear mechanism 34, it is not necessary to take into account the front reduction gear ratio α when deriving the input shaft rotation speed Ns at the time of switching.

[0103] In the present embodiment, as in (d) above, the determination unit makes a determination to prohibit the non-split point mode switching process (prohibition determination) when the predicted increase speed Rs is greater than the differential speed Rd, but the present invention is not limited to this. For example, the ECU 91 may determine to prohibit the non-split point mode switching process when another condition is satisfied in addition to the condition that the predicted increase speed Rs is greater than the differential speed Rd, rather than immediately making the prohibition determination when the predicted increase speed Rs is greater than the differential speed Rd.

[0104] In the present embodiment, as in (e) above, the split point mode switching process is performed on the condition that the predicted increase in rotation speed Rs is greater than the differential rotation speed Rd, but the present invention is not limited to this. For example, the ECU 91 may perform the mode switching process by a processing method other than the split point mode switching process on the condition that the predicted increase in rotation speed Rs is greater than the differential rotation speed Rd, or may not perform the mode switching on the condition that the predicted increase in rotation speed Rs is greater than the differential rotation speed Rd.

[0105] 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.

[0106] 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]

[0107] 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]

[0108] 4: Transmission 31: Input shaft 32: Output shaft 33: Belt transmission mechanism 34: Front reduction mechanism 91: ECU C: Target rate of change C1: Clutch C2: Clutch Ng: Target input shaft rotation speed Nout: Output RPM Ns: Input shaft rotation speed at switching Rd: Differential rotation speed Rs: predicted increase in rotation speed t: switching time α: Front reduction ratio γ: Pulley ratio

Claims

1. a control device for controlling a continuously variable transmission comprising: 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; a belt transmission mechanism on the second power transmission path; 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 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; a determination unit that determines whether the non-split point mode switching process can be executed; and The determination unit: an increased predicted rotation speed derived based on a target rate of change of the input shaft rotation speed and a time required for the first engagement element to be released and the second engagement element to be engaged in the non-split point mode switching process; deriving a differential rotation speed derived based on a difference between a target input shaft rotation speed after switching to the first mode and a switching input shaft rotation speed which is the input shaft rotation speed at a start point when switching from the second mode to the first mode begins; The control device is characterized in that it determines whether to permit execution of the non-split point mode switching process on the condition that the predicted increased rotation speed is smaller than the differential rotation speed.

2. 2. The control device according to claim 1, wherein the input shaft rotation speed at the time of switching is derived based on the rotation speed of the output shaft and the pulley ratio.

3. a front reduction mechanism that reduces the speed of the power input to the input shaft and outputs the reduced speed power to the belt transmission mechanism; 2. The control device according to claim 1, wherein the input shaft rotation speed at the time of switching is derived based on a reduction ratio in the front reduction mechanism, the rotation speed of the output shaft, and the pulley ratio.

4. 3. The control device according to claim 1, wherein the determining unit determines to prohibit the non-split point mode switching process on the condition that the predicted increased rotation speed is greater than the differential rotation speed.

5. 3. The control device according to claim 1, wherein, on the condition that the predicted increased rotation speed is greater than the differential rotation speed, when the total speed ratio matches the split speed ratio, the control device 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.

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