JP7102076B2 - Control device for continuously variable transmission - Google Patents

Description

The present invention relates to a control device for a continuously variable transmission.

As a transmission mounted on a vehicle such as an automobile, it is equipped with a continuously variable transmission mechanism that shifts power steplessly, and power division that can divide and transmit power between an input shaft and an output shaft in two paths. A continuously variable transmission has been proposed.

In an example of a continuously variable transmission, the continuously variable transmission has a structure similar to that of a known belt-type continuously variable transmission (CVT), that is, a continuously variable transmission has an endless belt on a primary pulley and a secondary pulley. It has a wound configuration. The engine power input to the input shaft is transmitted to the primary shaft of the continuously variable transmission mechanism. The secondary shaft of the continuously variable transmission mechanism is connected to the sun gear of the planetary gear mechanism.

Further, the power split type continuously variable transmission is provided with a parallel shaft type gear mechanism. The parallel shaft gear mechanism includes a split drive gear in which the power of the input shaft is transmitted / cut off, and a split driven gear that constitutes a gear train with the split drive gear and rotates integrally with the carrier of the planetary gear mechanism. An output shaft is connected to the ring gear of the planetary gear mechanism. The rotation of the output shaft is transmitted to the differential gear, and is transmitted from the differential gear to the left and right drive wheels.

In this power split type continuously variable transmission, a belt mode and a split mode are provided as power transmission modes during forward traveling.

In the belt mode, the first clutch that switches the transmission / disconnection of power between the input shaft and the split drive gear is released, the split drive gear is put into a free rotation state (free), and the carrier of the planetary gear mechanism is free. It is put into a rotating state. Further, the second clutch that engages / separates the sun gear and the ring gear of the planetary gear mechanism is engaged, and the sun gear and the ring gear are coupled. Therefore, the power output from the continuously variable transmission mechanism causes the sun gear and the ring gear to rotate integrally, and the output shaft to rotate integrally with the ring gear. Therefore, in the belt mode, the larger the belt gear ratio (pulley ratio), which is the gear ratio of the stepless speed change mechanism, the total shift, which is the gear ratio of the entire power split type stepless transmission, in proportion to the gear ratio. The ratio (the number of rotations of the input shaft / the number of rotations of the output shaft) increases.

In the split mode, the second clutch is released and the coupling between the sun gear and the ring gear of the planetary gear mechanism is released. Further, the first clutch is engaged and power is transmitted from the input shaft to the split drive gear. That is, switching between the belt mode and the split mode is achieved by switching the engagement between the first clutch and the second clutch. The power transmitted from the input shaft to the split drive gear is changed at a constant gear ratio (split point) from the split drive gear via the split driven gear, and is input to the carrier of the planetary gear mechanism. The sun gear rotates at a rotation speed according to the belt gear ratio. Therefore, in the split mode, the larger the belt gear ratio, the smaller the total gear ratio, and the total gear ratio below the split point can be realized.

Japanese Unexamined Patent Publication No. 2016-142302

There are various modes of downshifting from the split mode to the belt mode.

For example, as shown in FIG. 4, in the downshift in which the transition from the state A in which the total gear ratio is smaller than the split point to the state B in which the belt gear ratio is the same and the total gear ratio is larger than the split point, the belt gear ratio is changed. Since it can be left fixed, the clutch-to-clutch control that releases the first clutch and engages the second clutch enables shifting with a shift shock similar to that of a stepped automatic transmission (AT). It is possible.

In the downshift from the state C where the belt gear ratio is almost the same as the split point, there is almost no differential rotation between the sun gear and the carrier, so even if clutch-to-clutch control is performed, a large shift shock due to the differential rotation. Does not occur.

Further, in the downshift in which the belt gear ratio is changed from the state D closer to the split point than the state A to the state E where the total gear ratio is smaller than the state B, the clutch-to-clutch control is performed while changing the belt gear ratio to the low side. By performing the above, smooth shifting with a small shift shock is possible.

However, in other downshift modes, shift shock may occur.

An object of the present invention is to provide a continuously variable transmission control device capable of suppressing the occurrence of shift shock in a downshift transitioning from a second mode (split mode) to a first mode (belt mode).

In order to achieve the above object, the control device for the stepless transmission according to the present invention includes a first engaging element interposed on a first power transmission path between an input shaft and an output shaft, and an input shaft. It has a second engaging element interposed in a second power transmission path between the and the output shaft, has a belt transmission mechanism on the second power transmission path, releases the first engaging element and a second. Due to the engagement of the engaging elements, the larger the belt gear ratio by the belt transmission mechanism, the larger the total gear ratio between the input shaft and the output shaft becomes the first mode. 2 By releasing the engaging elements, the second mode is set in which the total gear ratio decreases as the belt gear ratio increases, and when the belt gear ratio is a constant value, the first engaging element and the second engaging element rotate differently. It is a control device that controls a stepless transmission configured so that When the target of the belt gear ratio changing means to be changed and the total gear ratio set by the target setting means in the second mode are larger than a constant value, the first engagement is performed in a state where the belt gear ratio does not match the constant value. When the switching control means that controls the element to be released and the second engaging element is engaged and the switching control means controls, the belt gear ratio is reduced by the belt gear ratio changing means at a time change rate equal to or higher than a predetermined threshold. If so, it includes a prohibition means for prohibiting control by the switching control means.

According to this configuration, in the stepless transmission, the first engaging element is interposed on the first power transmission path between the input shaft and the output shaft, and the second is between the input shaft and the output shaft. A second engaging element is interposed on the power transmission path. By releasing the first engaging element and engaging the second engaging element, the continuously variable transmission becomes the first mode. In this first mode, the larger the belt gear ratio by the belt transmission mechanism, the more the input shaft and the output. The total gear ratio with the shaft increases. On the other hand, the engagement of the first engaging element and the release of the second engaging element put the continuously variable transmission into the second mode. In this second mode, the larger the belt gear ratio, the smaller the total gear ratio. When the belt gear ratio is a constant value, the differential rotation does not occur in the first engaging element and the second engaging element.

In the second mode, for example, when a downshift request (kickdown request) is generated by the driver depressing the accelerator pedal quickly and greatly, and the target of the total gear ratio is set to a value larger than a certain value. It is necessary to switch from the second mode to the first mode, that is, to switch the engagement between the first engaging element and the second engaging element. In this case, the downshift request by the driver can be met by controlling the engagement between the first engaging element and the second engaging element in a state where the belt gear ratio does not match the constant value.

However, when the belt gear ratio is changed in the upshift direction with a large time change rate and the control is performed, the rotation number of the input shaft is increased by controlling the first engaging element to the release side. Even if the belt gear ratio is increased by switching from the upshift direction to the downshift direction after increasing, it takes time to increase the rotation speed of the output shaft and the synchronous rotation speed obtained from the belt gear ratio, and the synchronous rotation speed is input. A situation may occur in which the rotation speed of the shaft cannot be kept up. If the second engaging element is engaged in a state where the rotation speed of the input shaft and the synchronous rotation speed are not synchronized, a large shift shock occurs due to the differential rotation.

Therefore, when the belt gear ratio is changed in the upshift direction with a large time change rate, the first engaging element and the second engaging element are engaged with each other in a state where the belt gear ratio does not match a certain value. Switching control is prohibited. As a result, the occurrence of shift shock can be suppressed.

According to the present invention, it is possible to suppress the occurrence of shift shock in the downshift that transitions from the second mode to the first mode.

It is a skeleton diagram which shows the structure of the drive system of a vehicle. It is a figure which shows the state of each engaging element provided in a transmission. It is a collinear diagram which shows the relationship of the rotation speeds of a sun gear, a carrier and a ring gear of a planetary gear mechanism provided in a transmission. It is a figure which shows the relationship between the belt gear ratio of the belt transmission mechanism provided in a transmission, and the total gear ratio of the whole transmission. It is a figure which shows the structure of the control system which concerns on one Embodiment of this invention. It is a figure which shows the time change of the turbine rotation speed and the synchronous rotation speed at the time of mode switching from a split mode to a belt mode. It is a flowchart which shows the flow of the process which determines the permission or disapproval of a clutch-to-clutch control.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<Vehicle drive system>
FIG. 1 is a skeleton diagram showing the configuration of the drive system of the vehicle 1.

The vehicle 1 is an automobile whose drive source is the engine 2.

The engine 2 is provided with an electronic throttle valve for adjusting the amount of intake air into the combustion chamber of the engine 2, an injector (fuel injection device) for injecting fuel into the intake air, an ignition plug for generating an electric discharge in the combustion chamber, and the like. Has been done. Further, the engine 2 is provided with a starter for starting the engine 2. The power of the engine 2 is transmitted to the differential gear 5 via the torque converter 3 and the transmission 4, and is transmitted from the differential gear 5 to the left and right drive wheels 7L and 7R via the left and right drive shafts 6L and 6R, respectively. ..

The engine 2 includes an E / G output shaft 11. The E / G output shaft 11 is rotated by the power generated by the engine 2.

The torque converter 3 includes a front cover 21, a pump impeller 22, a turbine runner 23, and a lockup 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 arranged on the side opposite to the engine 2 side with respect to the front cover 21. The pump impeller 22 is provided so as to be rotatable integrally with the front cover 21. The turbine runner 23 is arranged between the front cover 21 and the pump impeller 22 and is rotatably provided about a rotation axis common to the front cover 21.

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 based on the difference pressure between the hydraulic pressure of the release oil chamber 26 between the lockup piston 25 and the front cover 21 and the hydraulic pressure of the engagement oil chamber 27 between the lockup piston 25 and the pump impeller 22. Lockup on (engaged) / off (released). That is, when the hydraulic pressure of the release oil chamber 26 is higher than the hydraulic pressure of the engaging oil chamber 27, the lockup piston 25 is separated from the front cover 21 due to the differential pressure, and the lockup is turned off. When the hydraulic pressure of the engaging oil chamber 27 is higher than the hydraulic pressure of the releasing oil chamber 26, the lockup piston 25 is pressed against the front cover 21 by the differential pressure to lock up on.

In the lock-up-off state, when the E / G output shaft 11 is rotated, the pump impeller 22 rotates. When the pump impeller 22 rotates, an oil flow from the pump impeller 22 to the turbine runner 23 is generated. This flow of oil is received by the turbine runner 23, and the turbine runner 23 rotates. At this time, the amplification action of the torque converter 3 occurs, and a torque larger than the torque of the E / G output shaft 11 is generated in the turbine runner 23.

In the lockup-on state, when the E / G output shaft 11 is rotated, the E / G output shaft 11, the pump impeller 22 and the turbine runner 23 rotate together.

The transmission 4 includes an input shaft 31 and an output shaft 32, and is configured to be able to branch the power input to the input shaft 31 into two paths and transmit the power to the output shaft 32, that is, a so-called power split type (torque). Split type) transmission. In order to form two power transmission paths, the transmission 4 includes a belt transmission mechanism 33, a front reduction gear mechanism 34, a planetary gear mechanism 35, and a split transmission mechanism 36.

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

The output shaft 32 is provided parallel to the input shaft 31. An output gear 37 is supported on the output shaft 32 so as to be relatively non-rotatable. The output gear 37 meshes with the differential gear 5 (the ring gear of the differential gear 5).

The belt transmission mechanism 33 has the same configuration as a known belt-type continuously variable transmission (CVT). Specifically, the belt transmission mechanism 33 includes a primary shaft 41, a secondary shaft 42 provided in parallel with the primary shaft 41, a primary pulley 43 non-rotatably supported by the primary shaft 41, and a secondary shaft 42. It includes a secondary pulley 44 that is supported so as not to rotate relative to each other, and a belt 45 that is wound around the primary pulley 43 and the secondary pulley 44.

The primary pulley 43 is arranged to face the fixed sheave 51 fixed to the primary shaft 41 with the belt 45 sandwiched between the fixed sheave 51, and is supported by the primary shaft 41 so as to be movable in the axial direction and non-relatively rotatable. It is equipped with 52. A cylinder 53 fixed to the primary shaft 41 is provided on the opposite side of the movable sheave 52 from the fixed sheave 51, and a hydraulic chamber 54 is formed between the movable sheave 52 and the cylinder 53.

The secondary pulley 44 is arranged so as to face the fixed sheave 55 fixed to the secondary shaft 42 with the belt 45 sandwiched between the fixed sheave 55, and is supported by the secondary shaft 42 so as to be movable in the axial direction and non-relatively rotatable. It has 56. A cylinder 57 fixed to the secondary shaft 42 is provided on the opposite side of the movable sheave 56 from the fixed sheave 55, and a hydraulic chamber 58 is formed between the movable sheave 56 and the cylinder 57. In the direction of the rotation axis, the positional relationship between the fixed sheave 55 and the movable sheave 56 is reversed from the positional relationship between the fixed sheave 51 and the movable sheave 52 of the primary pulley 43.

In the belt transmission mechanism 33, 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, and the groove widths of the primary pulley 43 and the secondary pulley 44 are changed. The belt gear ratio (pulley ratio) is continuously and steplessly changed.

Specifically, when the belt gear 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 distance (groove width) between the fixed sheave 51 and the movable sheave 52 becomes smaller. Along with this, the winding diameter of the belt 45 with respect to the primary pulley 43 becomes large, and the distance (groove width) between the fixed sheave 55 and the movable sheave 56 of the secondary pulley 44 becomes large. As a result, the pulley ratio between the primary pulley 43 and the secondary pulley 44 becomes small.

When the belt gear ratio is increased, the hydraulic pressure supplied to the hydraulic chamber 54 of the primary pulley 43 is lowered. As a result, the thrust ratio, which is the ratio of the thrust (primary thrust) of the primary pulley 43 to the thrust of the secondary pulley 44 (secondary thrust), becomes smaller, and the distance between the fixed sheave 55 and the movable sheave 56 of the secondary pulley 44 becomes smaller. , The distance between the fixed sheave 51 and the movable sheave 52 becomes large. As a result, the pulley ratio between the primary pulley 43 and the secondary pulley 44 becomes large.

On the other hand, the thrust of the primary pulley 43 and the secondary pulley 44 needs to have a magnitude such that slip (belt slip) does not occur 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 that the necessary and sufficient pinching pressure that does not cause belt slippage can be obtained.

The front reduction gear mechanism 34 has a configuration in which the power input to the input shaft 31 is reversed and decelerated and transmitted to the primary shaft 41. Specifically, the front reduction gear mechanism 34 has a larger diameter and a larger number of teeth than the input shaft gear 61, which is supported by the input shaft 31 so as not to rotate relative to the input shaft 31, and is spline-fitted to the primary shaft 41. Includes a primary shaft gear 62 that is supported by the relative non-rotatable gear and meshes with the input shaft gear 61.

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 so as not to rotate relative to each other by spline fitting. The carrier 72 is externally fitted to the output shaft 32 so as to be relatively rotatable. The carrier 72 rotatably supports a plurality of pinion gears 74. A plurality of pinion gears 74 are arranged on the circumference and mesh with the sun gear 71. The ring gear 73 has an annular shape that collectively surrounds a plurality of pinion gears 74, and meshes with each pinion gear 74 from the outside in the radial direction of rotation of the secondary shaft 42. Further, an output shaft 32 is connected to the ring gear 73, and the ring gear 73 is provided so as to be integrally rotatable around the same rotation axis as the output shaft 32.

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.

The split drive gear 81 is externally fitted to the input shaft 31 so as to be relatively rotatable.

The split driven gear 82 is provided so as to be integrally rotatable around the same rotation axis as the carrier 72 of the planetary gear mechanism 35. The split driven gear 82 is formed to have a smaller diameter than the split drive gear 81, and has a smaller number of teeth than the split drive gear 81.

Further, the transmission 4 includes clutches C1 and C2 and a brake B1.

The clutch C1 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 integrally rotatable) and an released state in which the direct connection is released.

The clutch C2 is hydraulically switched between an engaged state in which the sun gear 71 of the planetary gear mechanism 35 and the ring gear 73 are directly connected (coupled so as to be integrally rotatable) and an released state in which the direct connection is released.

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

<Power transmission mode>
FIG. 2 is a diagram showing the states of the clutches C1 and 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 rotation speeds (rotational speeds) of the sun gear 71, the carrier 72, and the ring gear 73 of the planetary gear mechanism 35. FIG. 4 is a diagram showing the relationship between the belt gear ratio by the belt transmission mechanism 33 and the total gear ratio of the transmission 4 as a whole.

In FIG. 2, “◯” indicates that the clutches C1 and C2 and the brake B1 are in the engaged state. “X” indicates that the clutches C1 and C2 and the brake B1 are in the released state.

A shift lever (select lever) is arranged in the vehicle interior of the vehicle 1 at a position where the driver can operate the vehicle. In the movable range of the shift lever, for example, a P (parking) position, an R (reverse) position, an N (neutral) position, and a D (drive) position are provided in this order in a row.

When the shift lever is in the P position, all of the clutches C1 and C2 and the brake B1 are released, and the parking lock gear (not shown) is fixed, which is one of the shift ranges of the transmission 4. The P range is configured. Further, when the shift lever is in the N position, all of the clutches C1 and C2 and the brake B1 are released, and the parking lock gear is not fixed, so that the N range, which is one of the shift ranges of the transmission 4, is set. It is composed. When both the clutch C1 and the 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 the pinion gear 74 of the planetary gear mechanism 35 slip and the engine The power of 2 is not transmitted to the drive wheels 7L and 7R.

When the shift lever is in the D position, a forward range, which is one of the shift ranges of the transmission 4, is configured. Power transmission modes in this forward range include belt mode and split mode. The belt mode and the split mode are switched by switching between the state in which the clutch C1 is engaged and the state in which the clutch C2 is engaged (replacement of the clutches C1 and C2).

In the belt mode, as shown in FIG. 2, the clutch C1 and the brake B1 are released and the clutch C2 is engaged. As a result, the split drive gear 81 is separated from the input shaft 31, the carrier 72 of the planetary gear mechanism 35 becomes free (free rotation state), and the sun gear 71 of the planetary gear mechanism 35 and the ring gear 73 are directly connected.

The power input to the input shaft 31 is reversed and decelerated by the front reduction gear mechanism 34 and transmitted to the primary shaft 41 of the belt transmission mechanism 33 to rotate the primary shaft 41 and the primary pulley 43. The rotation of the primary pulley 43 is transmitted to the secondary pulley 44 via the belt 45 to rotate the secondary pulley 44 and the secondary shaft 42. Since the sun gear 71 of the planetary gear mechanism 35 and the ring gear 73 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 gear ratio of the entire transmission 4 is the front reduction ratio (the rotation speed of the input shaft 31 / the primary shaft 41) to the belt gear ratio of the belt transmission mechanism 33. It matches the value multiplied by (the number of rotations of).

In the split mode, as shown in FIG. 2, the clutch C1 is engaged and the clutch C2 and the brake B1 are released. As a result, the input shaft 31 and the split drive gear 81 are coupled, and the rotation of the input shaft 31 can be transmitted to the carrier 72 of the planetary gear mechanism 35 via the split drive gear 81 and the split driven gear 82. The sun gear 71 of 35 and the ring gear 73 are separated.

The power input to the input shaft 31 is accelerated and transmitted from the split drive gear 81 to the carrier 72 of the planetary gear mechanism 35 via the split driven gear 82. 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, the secondary pulley 44, the belt 45, the primary pulley 43, and the primary shaft 41, and is transmitted from the primary shaft gear 62 to the input shaft gear 61. Therefore, in the belt mode, the input shaft gear 61 becomes the drive gear and the primary shaft gear 62 becomes the driven gear, whereas in the split mode, the primary shaft gear 62 becomes the drive gear and the input shaft gear 61 becomes the driven gear. ..

Since the gear ratio between the split drive gear 81 and the split driven gear 82 is constant and invariant (fixed), in the split mode, if the power input to the input shaft 31 is constant, the carrier 72 of the planetary gear mechanism 35 rotates. Is held at a constant speed. Therefore, when the belt gear ratio is increased, the rotation speed of the sun gear 71 of the planetary gear mechanism 35 decreases. Therefore, as shown by the broken line in FIG. 3, the rotation speed of the ring gear 73 (output shaft 32) of the planetary gear mechanism 35 is decreased. Goes up. As a result, in the split mode, as shown in FIG. 4, the larger the belt gear ratio of the belt transmission mechanism 33, the smaller the total gear ratio of the transmission 4, and the sensitivity of the total gear ratio to the belt gear ratio (belt shift). The ratio of the total gear ratio change to the ratio change) is lower than in the belt mode.

The rotation of the output shaft 32 in the belt mode and the split mode is transmitted to the differential gear 5 via the output gear 37. As a result, the drive shafts 6L and 6R and the drive wheels 7L and 7R of the vehicle 1 rotate in the forward direction.

When the shift lever is in the R position, the reverse range, which is one of the shift ranges of the transmission 4, is configured. In the reverse range, as shown in FIG. 2, the clutches C1 and C2 are released 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 of the planetary gear mechanism 35 and the ring gear 73 are disconnected, and the carrier 72 of the planetary gear mechanism 35 is braked.

The power input to the input shaft 31 is reversed and decelerated by the front reduction gear mechanism 34, transmitted to the primary shaft 41 of the belt transmission mechanism 33, and transmitted from the primary shaft 41 via the primary pulley 43, the belt 45, and the secondary pulley 44. The sun gear 71 of the planetary gear mechanism 35 is rotated integrally with the secondary shaft 42. Since 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 the ring gear 73 is opposite to the rotation direction of the ring gear 73 during forward movement (belt mode and split mode). Then, the output shaft 32 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 and 6R and the drive wheels 7L and 7R of the vehicle 1 rotate in the reverse direction.

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

The vehicle 1 is provided with an ECU (Electronic Control Unit) having a configuration including a microcomputer (microcontroller unit). The microcomputer has, for example, a built-in non-volatile memory such as a CPU and 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, a plurality of ECUs having the same configuration as the ECU 91 are mounted on the vehicle 1 in order to control each part. A plurality of ECUs including the ECU 91 are connected so as to be capable of bidirectional communication by a CAN (Controller Area Network) communication protocol.

The unit including the torque converter 3 and the transmission 4 is provided with a hydraulic circuit 92 for supplying hydraulic pressure to each part. The ECU 91 controls various valves and the like included in the hydraulic circuit 92 for shifting control of the transmission 4 and the like.

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

In the ECU 91, the turbine rotation speed, which is the rotation speed of the turbine runner 23, and the primary shaft 41 (primary pulley 43) are obtained from the detection signals of the turbine rotation sensor 93, the primary rotation sensor 94, the secondary rotation sensor 95, and the output rotation sensor 96. The primary rotation speed, which is the rotation speed, 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, are acquired. Further, in the ECU 91, from the detection signal of the accelerator sensor 97, the ratio of the operation amount to the maximum operation amount of the accelerator pedal, that is, 0% when the accelerator pedal is not depressed, and 100 when the accelerator pedal is depressed to the maximum. The accelerator opening, which is a percentage of%, is obtained.

A part of the turbine rotation sensor 93, the primary rotation sensor 94, the secondary rotation sensor 95, the output rotation sensor 96 and the accelerator sensor 97 is connected to another ECU, and the information acquired from the part of the sensors is , May be received from another ECU.

<Shift control>
The total gear ratio of the transmission 4 is controlled by changing the belt gear ratio by the ECU 91 and engaging / disengaging the clutches C1 and C2 and the brake B1. In this shift control, first, the target rotation speed according to the accelerator opening and the vehicle speed is set based on the shift diagram. The shift line diagram is a map that defines the relationship between the accelerator opening and the vehicle speed and the target rotation speed, and is stored in the ROM of the ECU 91. The vehicle speed information is transmitted from the engine ECU that controls the engine 2 to the ECU 91, for example. When the target rotation speed is set, the rotation speed input to the input shaft 31, that is, the target of the total gear ratio that matches the turbine rotation speed with the target rotation speed is obtained, and the target of the belt gear ratio according to the target is obtained. Set.

After that, the command values of 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 of the belt gear ratio. , The primary pressure and the secondary pressure are controlled so that the deviation between the target of the belt gear ratio and the actual belt gear ratio approaches zero based on each command value. The actual belt gear ratio is obtained by dividing the primary rotation speed by the secondary rotation speed.

When the total gear ratio is changed across a split point equal to the gear ratio of the split drive gear 81 and the split driven gear 82, the total gear ratio can be changed by switching between the belt mode and the split mode (hereinafter, simply "" It is called "mode switching"). Mode switching is achieved by switching the engagement of the clutches C1 and C2. That is, by controlling the hydraulic pressure supplied to the clutches C1 and C2, the clutch C1 (engaged side) in the disengaged state is engaged, and the clutch C2 (disengaged side) in the engaged state is released, so that the belt mode is released. Switch to split mode. On the contrary, the clutch C1 (disengaged side) in the engaged state is released, and the clutch C2 (engaged side) in the disengaged state is engaged, so that the split mode is switched to the belt mode.

FIG. 6 is a diagram showing an example of time changes in the turbine rotation speed and the synchronous rotation speed when the mode is switched from the split mode to the belt mode.

When the total gear ratio deviates from the split point, a difference rotation occurs between the output shaft 32 and the secondary shaft 42, and the turbine rotation speed (= the rotation speed of the input shaft 31) and the output rotation speed are changed to the belt. There is a difference from the synchronous rotation speed calculated by multiplying the ratio.

In this state, the hydraulic pressure supplied to the engaged clutch C1 is reduced in response to a downshift request (kickdown request) caused by the driver depressing the accelerator pedal quickly and greatly (time T1). : Release pressure release start). Due to this reduction in hydraulic pressure, the transmission torque capacity of the clutch C1 decreases, and when the transmission torque capacity falls below the input torque, the clutch C1 becomes a half-clutch state, the clutch C1 slips, and the driver kicks down. The turbine speed starts to increase at the target rate of change according to the request (time T2).

After that, when the turbine rotation speed exceeds the synchronous rotation speed, the change of the belt gear ratio target in the downshift direction is started (time T3, T4: belt shift start determination). In response to this, when the actual belt gear ratio shifts in the downshift direction, the synchronous rotation speed increases with the shift.

If the accelerator pedal was not depressed and the belt speed was constant before the kickdown request was made, the belt speed target change was initiated, as shown by the alternate long and short dash line in FIG. Within a certain period of time, the synchronous rotation speed synchronizes with the turbine rotation speed (time T5). By raising the hydraulic pressure supplied to the clutch C2 to the maximum pressure and completely engaging the clutch C2 at the timing when the synchronized rotation speed is synchronized with the turbine rotation speed, mode switching with a small irregular shock is achieved.

However, if the accelerator pedal is slightly depressed and the belt gear ratio is shifted in the upshift direction before the kickdown request is generated, the belt gear ratio target is increased as shown by the solid line in FIG. Even when switching from the shift direction to the downshift direction, it takes time to reverse the increase and decrease of the hydraulic pressure with respect to the primary pulley 43 and the secondary pulley 44, and the belt gear ratio increases as compared with the case indicated by the two-point chain line. Is delayed, and the increase in the synchronous rotation speed is delayed. Therefore, depending on the time change rate of the belt gear ratio in the upshift direction when a kickdown request is generated (hereinafter, this time change rate is referred to as "belt shift change rate"), the change of the belt gear ratio target is started. Within a certain period of time, the synchronous rotation speed may not be synchronized with the turbine rotation speed. In this case, if clutch-to-clutch control is performed by releasing the clutch C1 and engaging the clutch C2, the control times out and the clutch C2 is released in a state where the synchronous rotation speed is not synchronized with the turbine rotation speed. When fully engaged, a large shift shock is generated.

Therefore, in the shift control, the ECU 91 executes a process of determining whether or not the clutch-to-clutch control is permitted in a state where the belt gear ratio does not match the split point when the mode is switched from the split mode to the belt mode.

FIG. 7 is a flowchart showing a flow of processing for determining whether or not clutch-to-clutch control is permitted.

In this permission / rejection determination process, first, it is determined whether or not it is necessary to switch the mode from the split mode to the belt mode in response to the kickdown request (S1: kickdown determination). When the mode switching is not necessary (NO in step S1), the permission / rejection determination process is once completed and then newly started.

When it is determined that the mode switching from the split mode to the belt mode in response to the kickdown request is necessary (YES in step S1), the differential rotation between the turbine rotation speed and the synchronous rotation speed is less than the predetermined rotation speed. Whether or not it is determined (step S2).

When the difference rotation between the turbine rotation speed and the synchronous rotation speed is larger than the rotation threshold value (NO in step step S2), it is further determined whether or not the belt shift change rate is equal to or higher than the predetermined shift threshold value (step S3). ..

When the belt shift change rate is less than the shift threshold value (NO in step S3), the execution of the clutch-to-clutch control is permitted (step S4), and the permission / rejection determination process is terminated.

On the other hand, when the belt shift change rate is equal to or higher than the shift threshold value (YES in step S3), the execution of clutch-to-clutch control in a state where the belt shift ratio does not match the split point is prohibited (step S5), and the permission / rejection is determined. The process is finished.

Further, even when the difference rotation between the turbine rotation speed and the synchronous rotation speed is less than the rotation threshold (YES in step S2), the execution of the clutch-to-clutch control is prohibited (step S5), and the permission / rejection determination process is completed. Will be done. When the difference rotation between the turbine rotation speed and the synchronous rotation speed is less than the rotation threshold, the belt gear ratio is changed to the split point, the clutch C1 is released, the clutch C2 is engaged, and then the belt gear ratio is changed. Even if you change to the downshift direction, it does not take time to change the total gear ratio. Therefore, even if the execution of clutch-to-clutch control is prohibited in this case, it is possible to respond to the kickdown request due to the accelerator pedal being depressed quickly and greatly in the split mode, and smooth shifting with a small shift shock is possible. Is.

<Effect>
As described above, when the belt shift change rate is equal to or higher than the shift threshold, the execution of clutch-to-clutch control is prohibited, so that the belt can be switched from the split mode to the belt mode in response to the kickdown request. It is possible to eliminate the possibility that the synchronous rotation speed may not be synchronized with the turbine rotation speed within a certain period of time after the change of the gear ratio target is started. As a result, it is possible to prevent the clutch-to-clutch control from timing out because the synchronous rotation speed is not synchronized with the turbine rotation speed, and the clutch C2 is completely engaged in a state where the synchronous rotation speed is not synchronized with the turbine rotation speed. As a result, the occurrence of a large shift shock can be suppressed.

<Modification example>
Although one embodiment of the present invention has been described above, the present invention can also be implemented in other embodiments.

For example, in the above-described embodiment, the configuration in which the power is transmitted by branching into the first power transmission path via the split transmission mechanism 36 and the second power transmission path via the belt transmission mechanism 33 has been taken up, but the split transmission has been taken up. The mechanism 36 is not limited to the parallel shaft type gear mechanism including the split drive gear 81 and the split driven gear 82, and may be a mechanism other than the gear mechanism such as the belt mechanism. When a belt mechanism is adopted, the belt mechanism may have a fixed gear ratio or a variable gear ratio.

In addition, various design changes can be made to the above-mentioned configuration within the scope of the matters described in the claims.

4: Transmission (continuously variable transmission)
31: Input shaft 32: Output shaft 33: Belt transmission mechanism 91: ECU (control device, target setting means, belt gear ratio changing means, switching control means, prohibition means)
C1: Clutch (first engaging element)
C2: Clutch (second engaging element)

Claims (1)

A first engaging element interposed on the first power transmission path between the input shaft and the output shaft and a second intervening in the second power transmission path between the input shaft and the output shaft. It is provided with an engaging element, has a belt shifting mechanism on the second power transmission path, and by releasing the first engaging element and engaging the second engaging element, the belt shifting ratio by the belt shifting mechanism. The larger the value, the larger the total gear ratio between the input shaft and the output shaft. In the first mode, the belt shift is performed by engaging the first engaging element and releasing the second engaging element. The second mode is set in which the larger the ratio, the smaller the total gear ratio. When the belt gear ratio is a constant value, the first engaging element and the second engaging element are configured so that differential rotation does not occur. It is a control device that controls the stepless transmission
Goal-setting means for setting the target of the total gear ratio and
A belt gear ratio changing means for changing the belt gear ratio based on a target set by the goal setting means, and a belt gear ratio changing means.
When the target of the total gear ratio set by the target setting means in the second mode is larger than the constant value, the first engaging element is set in a state where the belt gear ratio does not match the constant value. A switching control means that controls the release and engagement of the second engaging element,
In the control by the switching control means, when the belt gear ratio is reduced by the belt gear ratio changing means at a time change rate equal to or higher than a predetermined threshold value, the control by the switching control means is prohibited. Control device.

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