JP2020118278A - Control device of continuously variable transmission - Google Patents

Abstract

To provide a control device of a continuously variable transmission capable of suppressing generation of shift shock in down shift for transition from a second mode (split mode) to a first mode (belt mode).SOLUTION: For example, a kick-down is requested when an accelerator pedal is quickly and largely depressed by a driver, and a target of a total change gear ratio is set to a value more than a fixed value in a split mode, the split mode is switched to a belt mode, that is, engagement of a first clutch and a second clutch is switched. Here, when a time change rate to an up-shift direction of the belt change gear ratio in the kick-down request, is a prescribed gear change threshold value or more (S2:YES), execution of control of clutch-to-clutch in a state that the belt change gear ratio is not agreed with a split point, is prohibited (step S5).SELECTED DRAWING: Figure 7

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, a continuously variable transmission mechanism that continuously changes power is provided, and power can be split between an input shaft and an output shaft by two paths for transmission. A continuously variable transmission has been proposed.

In an example of the power split type continuously variable transmission, the continuously variable transmission has a configuration similar to that of a known belt type continuously variable transmission (CVT), that is, an endless belt is provided on a primary pulley and a secondary pulley. It has a wound structure. The power of the engine 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 type gear mechanism includes a split drive gear that transmits/blocks the power of the input shaft, and a split driven gear that forms a gear train with the split drive gear and that 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 belt mode, the first clutch that switches transmission/interruption of power between the input shaft and split drive gear is released, the split drive gear is set to the free rotation state (free), and the carrier of the planetary gear mechanism is set to free. It is rotated. Further, the second clutch that connects/disconnects the sun gear and the ring gear of the planetary gear mechanism is engaged, and the sun gear and the ring gear are connected. Therefore, the sun gear and the ring gear rotate integrally with the power output from the continuously variable transmission mechanism, and the output shaft rotates integrally with the ring gear. Therefore, in the belt mode, as the belt gear ratio (pulley ratio), which is the gear ratio of the continuously variable transmission mechanism, increases, the total gear ratio that is the gear ratio of the entire power split type continuously variable transmission increases 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 connection between the sun gear and the ring gear of the planetary gear mechanism is released. Also, the first clutch is engaged, and power is transmitted from the input shaft to the split drive gear. That is, the 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 shifted from the split drive gear through the split driven gear at a constant gear ratio (split point) and 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 it is possible to realize the total gear ratio below the split point.

JP, 2016-142302, A

There are various modes for the downshift that shifts from the split mode to the belt mode.

For example, as shown in FIG. 4, in a downshift in which a state A in which the total gear ratio is smaller than the split point is changed to a 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 may be fixed, the clutch-to-clutch control in which the first clutch is disengaged and the second clutch is engaged allows gear shifting with a gear shift shock similar to that of a stepped automatic transmission (AT: Automatic Transmission). It is possible.

In the downshift from the state C in which the belt gear ratio substantially matches 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 will occur due to the differential rotation. Does not occur.

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, it is possible to perform a smooth shift with little shift shock.

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

An object of the present invention is to provide a control device for a continuously variable transmission that can suppress the occurrence of a shift shock in a downshift in which the second mode (split mode) transits to the first mode (belt mode).

To achieve the above object, a control device for a continuously variable transmission according to the present invention includes a first engagement element interposed on a first power transmission path between an input shaft and an output shaft, and an input shaft. And a second engagement element interposed in a second power transmission path between the output shaft and the output shaft, and has a belt transmission mechanism on the second power transmission path. Due to the engagement of the engaging elements, the first mode in which the total speed ratio between the input shaft and the output shaft increases as the belt speed ratio of the belt speed change mechanism increases becomes the first mode. By releasing the two engagement elements, a second mode is set in which the total gear ratio decreases as the belt gear ratio increases, and when the belt gear ratio has a constant value, differential rotation occurs between the first engagement element and the second engagement element. A control device for controlling a continuously variable transmission configured so as to prevent the occurrence of a belt gear ratio change based on a target setting means for setting a target of the total speed ratio and a target set by the target setting means. When the belt gear ratio changing means to be changed and the target of 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. In the control by the switching control means for releasing the element and engaging the second engagement element, and the control by the switching control means, the belt speed ratio is reduced by the belt speed ratio changing means at a time change rate of a predetermined threshold value or more. In this case, the prohibition means for prohibiting the control by the switching control means is included.

With this configuration, in the continuously variable transmission, the first engagement element is interposed on the first power transmission path between the input shaft and the output shaft, and the second engagement member is provided between the input shaft and the output shaft. The second engagement element is interposed on the power transmission path. The disengagement of the first engagement element and the engagement of the second engagement element cause the continuously variable transmission to be in 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 is increased. On the other hand, the continuously variable transmission enters the second mode by the engagement of the first engagement element and the release of the second engagement element. 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, differential rotation does not occur between the first engagement element and the second engagement element.

In the second mode, for example, when a downshift request (kickdown request) is generated by the driver's rapid and large depression of the accelerator pedal, 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 engagement element and the second engagement element. In this case, it is possible to meet the driver's downshift request by performing control to switch the engagement between the first engagement element and the second engagement element in a state where the belt gear ratio does not match a constant value.

However, when the belt gear ratio is changed in the upshift direction at a large time rate of change, if the control is performed, the first engagement element is controlled to the disengagement side, so that the rotational speed of the input shaft fluctuates. Even if the belt gear ratio is switched from the upshift direction to the downshift direction and then increased after rising, it takes time to increase the synchronous rotation speed obtained from the output shaft rotation speed and the belt gear ratio, and the synchronous rotation speed is input. A situation may occur in which the number of rotations of the shaft cannot be kept up. If the second engagement element is engaged in a state where the rotational speed of the input shaft and the synchronous rotational speed are not synchronized, a large shift shock will occur due to the differential rotation.

Therefore, when the belt gear ratio is shifted in the upshift direction with a large time change rate, the engagement between the first engagement element and the second engagement element is performed in a state where the belt gear ratio does not match a constant 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 a shift shock in a downshift in which the second mode transits to the first mode.

It is a skeleton diagram showing a configuration of a drive system of a vehicle. It is a figure which shows the state of each engagement element with which a transmission is equipped. FIG. 6 is a collinear chart showing the relationship between the rotational speeds of a sun gear, a carrier, and a ring gear of a planetary gear mechanism included in the transmission. FIG. 3 is a diagram showing a relationship between a belt speed ratio of a belt speed change mechanism provided in the transmission and a total speed ratio of the entire 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 turbine rotation speed and synchronous rotation speed at the time of mode switching from split mode to belt mode. 7 is a flowchart showing a flow of processing for determining whether to permit 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 that uses the engine 2 as a drive source.

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 intake air, and an ignition plug for producing electric discharge in the combustion chamber. Has been. 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 rotate integrally with the front cover 21. The turbine runner 23 is disposed between the front cover 21 and the pump impeller 22 and is rotatably provided about a common rotation axis with 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 uses a differential 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. The lockup is turned on (engaged)/off (released). That is, when the oil pressure in the release oil chamber 26 is higher than the oil pressure in the engagement oil chamber 27, the lockup piston 25 separates from the front cover 21 due to the pressure difference, and the lockup is turned off. When the oil pressure in the engagement oil chamber 27 is higher than the oil pressure in the release oil chamber 26, the lockup piston 25 is pressed against the front cover 21 by the pressure difference, and the lockup is turned on.

In the lock-up off state, when the E/G output shaft 11 is rotated, the pump impeller 22 is rotated. When the pump impeller 22 rotates, a flow of oil from the pump impeller 22 toward the turbine runner 23 occurs. This oil flow is received by the turbine runner 23, and the turbine runner 23 rotates. At this time, the amplifying 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 lock-up 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 are integrally rotated.

The transmission 4 includes an input shaft 31 and an output shaft 32, and is configured to branch the power input to the input shaft 31 into two paths and transmit the power to the output shaft 32. It is a split type transmission. 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 about the same rotation axis as the turbine runner 23.

The output shaft 32 is provided in parallel with the input shaft 31. An output gear 37 is supported on the output shaft 32 so as not to rotate relative to it. The output gear 37 meshes with the differential gear 5 (the ring gear of the differential gear 5).

The belt transmission mechanism 33 has a configuration similar to that of 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 supported by the primary shaft 41 so as not to rotate relative to each other, and a secondary shaft 42. A secondary pulley 44 supported so as to be relatively non-rotatable, and a belt 45 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 and the fixed sheave 51 with the belt 45 sandwiched therebetween, and the movable sheave supported by the primary shaft 41 so as to be movable in the axial direction thereof and non-rotatable. And 52. A cylinder 53 fixed to the primary shaft 41 is provided on the side opposite to the fixed sheave 51 with respect to the movable sheave 52, and a hydraulic chamber 54 is formed between the movable sheave 52 and the cylinder 53.

The secondary pulley 44 is arranged to face a fixed sheave 55 fixed to the secondary shaft 42, and a movable sheave that is arranged to face the fixed sheave 55 with the belt 45 sandwiched therebetween, and is supported by the secondary shaft 42 so as to be movable in the axial direction of the secondary shaft 42 and non-rotatably. And 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 rotational axis direction, the positional relationship between the fixed sheave 55 and the movable sheave 56 is opposite to 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 pressures supplied to the hydraulic chamber 54 of the primary pulley 43 and the hydraulic chamber 58 of the secondary pulley 44 are respectively controlled to change the groove widths of the primary pulley 43 and the secondary pulley 44, The belt gear ratio (pulley ratio) is continuously and continuously 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 to the fixed sheave 51 side, and the interval (groove width) between the fixed sheave 51 and the movable sheave 52 decreases. Along with this, 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.

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 of the primary pulley 43 (primary thrust) to the thrust of the secondary pulley 44 (secondary thrust), becomes smaller, and the gap between the fixed sheave 55 and the movable sheave 56 of the secondary pulley 44 becomes smaller. The gap 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 increases.

On the other hand, the thrust of the primary pulley 43 and the secondary pulley 44 needs to be large enough so that slippage (belt slip) does not occur between the belt 45 and the primary pulley 43 and secondary pulley 44. 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 necessary and sufficient clamping pressure that does not cause belt slip.

The front reduction gear mechanism 34 is configured to reverse and reduce the power input to the input shaft 31 and transmit the power to the primary shaft 41. Specifically, the front reduction gear mechanism 34 has an input shaft gear 61 supported by the input shaft 31 so as to be relatively non-rotatable, and has a larger diameter and a larger number of teeth than the input shaft gear 61, and is spline-fitted to the primary shaft 41. Includes a primary shaft gear 62 that is supported so as to be relatively non-rotatable by 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 by the secondary shaft 42 by spline fitting so as not to rotate relative to each other. The carrier 72 is fitted onto the output shaft 32 so as to be relatively rotatable. The carrier 72 rotatably supports a plurality of pinion gears 74. The 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 the plurality of pinion gears 74, and meshes with each pinion gear 74 from the outer side in the radial direction of rotation of the secondary shaft 42. Further, the output shaft 32 is connected to the ring gear 73, and the ring gear 73 is integrally rotatably provided about the same rotation axis as the output shaft 32.

The split transmission mechanism 36 is a parallel shaft type 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 fitted onto the input shaft 31 so as to be relatively rotatable.

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

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

The clutch C1 is switched by an oil pressure between an engaged state in which the input shaft 31 and the split drive gear 81 are directly connected (integrally rotatably connected) and a released state in which the direct connection is released.

The clutch C2 is switched by the hydraulic pressure between an engaged state in which the sun gear 71 and the ring gear 73 of the planetary gear mechanism 35 are directly connected (integrally rotatably connected) and a released state in which the direct connection is released.

The brake B1 is switched by the hydraulic pressure between an engaged state in which the carrier 72 of the planetary gear mechanism 35 is braked and a released state in which the rotation of the carrier 72 is allowed.

<Power transmission mode>
FIG. 2 is a diagram showing 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 chart showing the relationship among the rotational 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 speed ratio by the belt speed change mechanism 33 and the total speed 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 a vehicle compartment of the vehicle 1 at a position where a driver can operate it. 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 arranged in this order in a line.

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. A P range is constructed. Further, when the shift lever is in the N position, all of the clutches C1, 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 changed. Composed. In a state in which 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 idle and the engine rotates. The power of 2 is not transmitted to the drive wheels 7L and 7R.

When the shift lever is in the D position, the forward range, which is one of the shift ranges of the transmission 4, is formed. The power transmission mode in the forward range includes 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 (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 and the ring gear 73 of the planetary gear mechanism 35 are directly connected.

The power input to the input shaft 31 is reversely rotated and decelerated by the front reduction gear mechanism 34, is transmitted to the primary shaft 41 of the belt transmission mechanism 33, and rotates 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 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 FIG. 3 and FIG. 4, the total speed ratio of the entire transmission 4 becomes equal to the belt speed ratio of the belt speed change mechanism 33, ie, the front speed reduction ratio (the rotation speed of the input shaft 31/the primary shaft 41). The number of rotations of is equal to the value multiplied by.

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 to each other, 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 serves as a driving gear and the primary shaft gear 62 serves as a driven gear, whereas in the split mode, the primary shaft gear 62 serves as a driving gear and the input shaft gear 61 serves as a driven gear. ..

Since the gear ratio between the split drive gear 81 and the split driven gear 82 is constant and invariable (fixed), in the split mode, if the power input to the input shaft 31 is constant, the rotation of the carrier 72 of the planetary gear mechanism 35 will rotate. Is maintained 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, so that the rotation speed of the ring gear 73 (output shaft 32) of the planetary gear mechanism 35 is reduced as shown by the broken line in FIG. Goes up. As a result, in the split mode, as shown in FIG. 4, the total gear ratio of the transmission 4 decreases as the belt gear ratio of the belt gear mechanism 33 increases, and the sensitivity of the total gear ratio to the belt gear ratio (belt gear ratio The ratio of the change amount of the total speed ratio to the change amount of the ratio) is lower than that 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, 6R and the drive wheels 7L, 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 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 separated from the input shaft 31, the sun gear 71 and the ring gear 73 of the planetary gear mechanism 35 are separated, and the carrier 72 of the planetary gear mechanism 35 is braked.

The power input to the input shaft 31 is reverse-rotated 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. Is transmitted to the secondary shaft 42 and rotates the sun gear 71 of the planetary gear mechanism 35 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 the configuration of the control system of the vehicle 1.

The vehicle 1 is provided with an ECU (Electronic Control Unit) having a configuration including a microcomputer (micro controller unit). The microcomputer includes, for example, a 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, the vehicle 1 is equipped with a plurality of ECUs having the same configuration as the ECU 91 in order to control each unit. A plurality of ECUs including the ECU 91 are connected so as to be capable of bidirectional communication according to 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 gear shift control of the transmission 4.

Various sensors required for the control are connected to the ECU 91. As an example, to the ECU 91, a turbine rotation sensor 93 that outputs a pulse signal that is 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 that is 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 corresponding to the operation amount of an accelerator pedal (not shown) operated by the driver is connected.

In the ECU 91, 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 turbine rotation speed that is the rotation speed of the turbine runner 23 and the primary shaft 41 (primary pulley 43) are detected. The primary rotation speed that is the rotation speed, the secondary rotation speed that is the rotation speed of the secondary shaft 42 (secondary pulley 44), and the output rotation speed that is the rotation speed of the output shaft 32 are acquired. Further, the ECU 91 determines from the detection signal of the accelerator sensor 97 that 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, is 100% when the accelerator pedal is fully depressed. The accelerator opening, which is a percentage in %, is obtained.

In addition, 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 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, C2 and the brake B1. In this shift control, first, a target rotational speed according to the accelerator opening and the vehicle speed is set based on the shift diagram. The shift map 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 to the ECU 91 from the engine ECU that controls the engine 2, 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 speed ratio that matches the turbine speed with the target speed is obtained, and the target of the belt speed ratio corresponding to the target is obtained. Is set.

Then, based on the target of the belt gear ratio, 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 each command value, the primary pressure and the secondary pressure are controlled so that the deviation between the target belt gear ratio and the actual belt gear ratio approaches zero. 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 over a split point equal to the gear ratio of the split drive gear 81 and the split driven gear 82, the total gear ratio is changed by switching between the belt mode and the split mode (hereinafter, simply " It is called "mode switching". The 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 disengaged clutch C1 (engagement side) is engaged, and the engaged clutch C2 (disengagement side) is disengaged, so that the belt mode is released. Switch to split mode. Conversely, the split mode is switched to the belt mode by disengaging the engaged clutch C1 (disengagement side) and engaging the disengaged clutch C2 (engagement side).

FIG. 6 is a diagram showing an example of temporal 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 is deviated from the split point, a differential rotation occurs between the output shaft 32 and the secondary shaft 42, and the turbine gear speed (=rotation speed of the input shaft 31) and the output gear speed are belt-shifted. There is a difference in 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's rapid and large depression of the accelerator pedal (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 enters a half-clutch state, slipping occurs in the clutch C1, and the driver kicks down. The turbine speed starts increasing at the target change rate according to the request (time T2).

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

If the accelerator pedal is not depressed and the belt gear ratio is constant before the kickdown request is issued, the target change of the belt gear ratio is started as shown by the chain double-dashed line in FIG. The synchronous rotation speed is synchronized with the turbine rotation speed within a fixed time after the start (time T5). At the timing when the synchronous rotation speed is synchronized with the turbine rotation speed, the hydraulic pressure supplied to the clutch C2 is increased to the maximum pressure and the clutch C2 is completely engaged, whereby mode switching with a small irregular shock is achieved.

However, when the accelerator pedal is stepped on a little before the kick down request is generated and the belt gear ratio is shifted in the upshift direction, the target of the belt gear ratio is increased as shown by the solid line in FIG. Even if the shift direction is switched 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 chain double-dashed line. Is delayed, and the increase in synchronous speed is delayed. Therefore, depending on the time rate of change of the belt gear ratio in the upshift direction when a kickdown request is generated (hereinafter, this time rate of change is referred to as “belt gear change rate”), the target change of the belt gear ratio is started. There is a case where the synchronous rotation speed is not synchronized with the turbine rotation speed within a fixed time after the start. In this case, if clutch-to-clutch control for releasing the clutch C1 and engaging the clutch C2 is performed, the control times out, and the clutch C2 is operated in a state where the synchronous rotation speed is not synchronized with the turbine rotation speed. By being completely engaged, a large shift shock occurs.

Therefore, in the shift control, the ECU 91 executes a process of determining whether to permit the clutch-to-clutch control when 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 the flow of processing for determining whether to permit clutch-to-clutch control.

In this permission/prohibition determination processing, first, it is determined whether or not it is necessary to switch the mode from the split mode to the belt mode according to the kickdown request (S1: kickdown determination). When the mode switching is unnecessary (NO in step S1), the permission/prohibition determination process is once ended 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 threshold value. It is determined whether or not (step S2).

When the differential rotation speed between the turbine rotation speed and the synchronous rotation speed is larger than the rotation threshold value (NO in step S2), it is further determined whether the belt shift change rate is equal to or higher than a predetermined shift threshold value (step S3). ..

When the belt shift change rate is less than the shift threshold value (NO in step S3), the clutch-to-clutch control is permitted to be performed (step S4), and the permission/prohibition determination process is ended.

On the other hand, if the belt gear change rate is equal to or greater than the gear shift threshold (YES in step S3), the clutch-to-clutch control is prohibited from being performed in the state where the belt gear ratio does not match the split point (step S5), and the approval/denial is determined. The process ends.

Even when the differential rotation speed between the turbine rotation speed and the synchronous rotation speed is less than the rotation threshold value (YES in step S2), the clutch-to-clutch control is prohibited from being executed (step S5), and the approval/denial determination process ends. To be done. When the differential rotation speed between the turbine rotation speed and the synchronous rotation speed is less than the rotation threshold value, the belt gear ratio is changed to the split point, the clutch C1 is released and 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 long to change the total gear ratio. Therefore, even if the clutch-to-clutch control is prohibited in this case, it is possible to respond to the kickdown request due to the accelerator pedal being quickly and greatly depressed in the split mode, and it is possible to perform a smooth shift with a small shift shock. Is.

<Effect>
As described above, when the belt shift change rate is equal to or higher than the shift threshold value, the clutch-to-clutch control is prohibited from being performed, so that when the mode is 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 fixed time after the change of the target of the gear ratio is started. As a result, it is possible to prevent the clutch-to-clutch control from timing out because the synchronous speed is not synchronized with the turbine speed, and the clutch C2 is completely engaged in a state where the synchronous speed is not synchronized with the turbine speed. By doing so, it is possible to suppress the occurrence of a large shift shock.

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

For example, in the above-described embodiment, the configuration in which the power is branched and transmitted to the first power transmission path passing through the split speed change mechanism 36 and the second power transmission path passing through the belt speed change mechanism 33 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 a 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-described configuration within the scope of the matters described in the claims.

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

Claims (1)

A first engagement element interposed on a first power transmission path between the input shaft and the output shaft, and a second engagement element interposed on a second power transmission path between the input shaft and the output shaft. An engaging element, and a belt speed change mechanism on the second power transmission path, and by releasing the first engaging element and engaging the second engaging element, a belt speed change ratio by the belt speed changing mechanism. Becomes larger, the total speed ratio between the input shaft and the output shaft becomes larger, and the first mode is set. The engagement of the first engaging element and the release of the second engaging element cause the belt speed change. A second mode in which the total speed ratio decreases as the ratio increases, is configured so that differential rotation does not occur between the first engagement element and the second engagement element when the belt speed ratio is a constant value. A control device for controlling the continuously variable transmission,
Target setting means for setting a target of the total speed ratio,
Belt gear ratio changing means for changing the belt gear ratio based on the target set by the target setting means;
When the target of the total speed ratio set by the target setting means in the second mode is larger than the constant value, the first engagement element is operated in a state where the belt speed ratio does not match the constant value. Switching control means for releasing and controlling the engagement of the second engagement element,
In the control by the switching control means, a prohibiting means for prohibiting the control by the switching control means when the belt speed ratio is reduced by the belt speed ratio changing means at a time change rate of a predetermined threshold value or more, Control device.

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