JP2020026840A - Controller of continuously variable transmission - Google Patents

Abstract

To provide a controller of a continuously variable transmission capable of transmitting power more efficiently and improving travel fuel consumption of a vehicle.SOLUTION: A first threshold value used to determine the switching from a low mode to a high mode is set to a gear ratio A at an intersection of a low mode efficiency line representing the relationship between the transmission ratio and transmission efficiency of a CVT in the low mode and a high mode efficiency line representing the relationship between the transmission ratio and transmission efficiency of the CVT in the high mode, and a second threshold value used to determine the switching from the high mode to the low mode is set to a gear ratio Mat the time when the transmission efficiency is the highest in the low mode.SELECTED DRAWING: Figure 4

Description

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

  As a transmission mounted on a vehicle, a belt-type CVT (hereinafter, simply referred to as “CVT”) is widely known.

  In the CVT, an endless belt is wound around a pair of pulleys. By changing the groove width of each pulley, the winding diameter of the belt around each pulley is changed to continuously change the speed ratio continuously. Can be changed. Therefore, in a vehicle equipped with a CVT, the engine can be operated in a highly efficient rotation range, and the fuel efficiency of the vehicle can be improved (fuel efficiency can be reduced).

  Some CVTs include an auxiliary speed change mechanism that can switch the shift speed between a low speed stage and a high speed stage. In the CVT including the subtransmission mechanism, the low speed having the first speed ratio width is set by setting the speed to the low speed, and when the speed is switched from the low speed to the high speed, the first speed ratio is set. The high mode having the second speed ratio width in which the maximum speed ratio and the minimum speed ratio are each smaller (higher side) than the width is set. The maximum gear ratio in the second gear ratio width is larger than the minimum gear ratio in the first gear ratio width. Therefore, by switching the gear stage between the low gear stage and the high gear stage in accordance with the traveling condition of the vehicle, the maximum gear ratio in the first gear ratio width and the minimum gear ratio in the second gear ratio width are respectively set to the maximum gear ratio and the minimum gear ratio. A wide speed ratio width can be realized as a ratio.

  By expanding the speed ratio width (ratio coverage), the speed ratio that can be used at the time of starting or accelerating increases to the low side, so that the power performance of the vehicle can be improved. In addition, the speed ratio that can be used during high-speed running increases to the high side, so that the fuel efficiency of the vehicle can be improved.

JP 2010-78028 A

  In the CVT including the subtransmission mechanism, there is a problem of a timing of switching between the low mode and the high mode, that is, a timing of switching the shift speed of the subtransmission mechanism. For example, in response to the change of the speed ratio in the low mode to the minimum speed ratio in the first speed ratio width, the mode is switched from the low mode to the high mode, and in the high mode, the speed ratio changes to the maximum speed ratio in the second speed ratio width. In response to this, a configuration for switching from the high mode to the low mode is conceivable. In this case, frequent switching between the low mode and the high mode can be suppressed.

  However, in such a configuration, in each of the low mode and the high mode, a transmission ratio with a low CVT transmission efficiency (unit efficiency) may be used, and there is a possibility that the fuel efficiency of the vehicle may not be improved.

  An object of the present invention is to provide a control device for a continuously variable transmission capable of performing more efficient power transmission and improving running fuel efficiency of a vehicle.

  In order to achieve the above object, a continuously variable transmission control device according to the present invention includes an endless belt wound around a primary pulley and a secondary pulley on a power transmission path between an input shaft and an output shaft. A low mode set to a first speed ratio width, and a high mode set to a second speed ratio width each having a maximum speed ratio and a minimum speed ratio smaller than the first speed ratio width. And a control device for controlling the continuously variable transmission, which is used in a vehicle equipped with a continuously variable transmission having a mode and a target speed ratio that is a target of the speed ratio of the continuously variable transmission. The ratio setting means and the target speed ratio set by the target speed ratio setting means in the low mode are set to a low mode efficiency line indicating a relationship between the speed ratio in the low mode and the transmission efficiency of the continuously variable transmission, and a high mode. From a low mode when the value is smaller than a first threshold value set within a predetermined range including a speed ratio at an intersection of a high mode efficiency line representing a relationship between a speed ratio and a transmission efficiency of the continuously variable transmission. Mode switching for switching from the high mode to the low mode when the target speed ratio set by the target speed ratio setting means in the high mode is larger than a second threshold value set within a predetermined range. Means.

  According to this configuration, the low mode efficiency line representing the relationship between the transmission ratio and the transmission efficiency of the continuously variable transmission in the low mode and the high mode representing the relationship between the transmission efficiency and the transmission ratio of the continuously variable transmission in the high mode Within a predetermined range including the gear ratio at the intersection with the efficiency line, a first threshold used to determine switching from the low mode to the high mode and a second threshold used to determine switching from the high mode to the low mode. A threshold is set.

  In the belt speed change mechanism, the transmission efficiency is the best when the difference between the winding diameter of the belt on the primary pulley and the winding diameter of the belt on the secondary pulley is small, that is, when the belt speed ratio is close to 1, and the belt speed ratio is high. The further away from 1, the lower the transmission efficiency. Therefore, in the entire continuously variable transmission, in each of the low mode and the high mode, the transmission efficiency is highest at the speed ratio when the belt speed ratio is around 1, and the speed ratio is determined from the speed ratio at the highest transmission efficiency. It has the characteristic that the transmission efficiency decreases as the distance increases. Therefore, the low mode efficiency line and the high mode efficiency line change so that the transmission efficiency is the highest at the speed ratio when the belt speed ratio is around 1, and the transmission efficiency decreases as the belt speed ratio increases from the speed ratio. The portion of the efficiency line where the transmission efficiency decreases toward the high side intersects with the portion of the high mode efficiency line where the transmission efficiency decreases toward the low side.

  Therefore, by switching between the high mode and the low mode near the speed ratio at the intersection of the low mode efficiency line and the high mode efficiency line, the transmission efficiency of the continuously variable transmission is suppressed from being excessively reduced, so that more efficient transmission is achieved. Power transmission can be performed, and the driving fuel efficiency of the vehicle can be improved.

  The first threshold value may be set to a speed ratio at an intersection of the low mode efficiency line and the high mode efficiency line. In this case, the second threshold value may be set to the speed ratio at the intersection of the low mode efficiency line and the high mode efficiency line, but may be set to be larger than the speed ratio at the intersection of the low mode efficiency line and the high mode efficiency line. It is preferable to set the ratio.

  When both the first threshold value and the second threshold value are set to the speed ratio at the intersection of the low mode efficiency line and the high mode efficiency line, when the target speed ratio vibrates near the speed ratio, the low mode and the high mode are switched. The switching is frequently performed, and there is a possibility that the control may fall into a busy state. When the first threshold value is set to the speed ratio at the intersection of the low mode efficiency line and the high mode efficiency line, the speed ratio is larger than the speed ratio at the intersection of the low mode efficiency line and the high mode efficiency line , The frequent switching between the low mode and the high mode can be suppressed even if the target gear ratio vibrates near the gear ratio at the intersection of the low mode efficiency line and the high mode efficiency line. . Also, when the mode is switched from the high mode to the low mode with the deceleration of the vehicle, the fuel consumption is small, so even if the transmission efficiency of the continuously variable transmission decreases due to the continuation of the high mode, the fuel consumption of the vehicle is reduced. The effect is small.

  The mode switching means sets the vehicle speed at the speed ratio at the intersection of the low mode efficiency line and the high mode efficiency line even when the target speed ratio smaller than the first threshold is set by the target speed ratio setting means in the low mode. When the running resistance is not balanced with the vehicle, the switching from the low mode to the high mode may be delayed until the vehicle speed is balanced with the running resistance. If there is no delay, the vehicle is decelerated due to the torque reduction accompanying the switch from the low mode to the high mode, and when the target gear ratio is set to a value larger than the second threshold, the mode is switched from the high mode to the low mode, There is a concern that switching between the low mode and the high mode is frequently performed. The switching from the low mode to the high mode is delayed until the vehicle speed is balanced with the running resistance, so that the frequent switching between the low mode and the high mode can be suppressed, and the control busy state can be suppressed. .

  ADVANTAGE OF THE INVENTION According to this invention, more efficient power transmission can be performed and the driving | running fuel efficiency of a vehicle can be improved.

FIG. 2 is a skeleton diagram illustrating a configuration of a drive system of the vehicle. It is a figure showing the state of the low clutch and the high clutch in each mode of the low mode and the high mode. FIG. 2 is a block diagram illustrating a configuration of a control system of the vehicle. FIG. 5 is a diagram illustrating a relationship between a speed ratio (pulley ratio × sub speed ratio) of the CVT and transmission efficiency, and a switching timing between a low mode and a high mode.

  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 a configuration of a drive system of the vehicle 1.

  The vehicle 1 is an automobile driven by 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 intake air, a spark plug for generating electric discharge in the combustion chamber, and the like. Have been. In addition, the engine 2 is provided with a starter for starting the engine. The power of the engine 2 is transmitted to the differential gear 5 via the torque converter 3 and the CVT 4, and transmitted from the differential gear 5 to the left and right drive wheels 7L, 7R via the left and right drive shafts 6L, 6R, respectively.

  The engine 2 has an E / G output shaft 11. The E / G output shaft 11 is rotated by 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 lock-up mechanism 24. The E / G output shaft 11 is connected to the front cover 21, and the front cover 21 rotates integrally with the E / G output shaft 11. The pump impeller 22 is arranged on the side opposite to the engine 2 with respect to the front cover 21. The pump impeller 22 is provided so as to be able 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 provided so as to be rotatable around a common rotation axis with the front cover 21.

  The lockup mechanism 24 includes a lockup piston 25. The lock-up piston 25 is provided between the front cover 21 and the turbine runner 23. The lock-up mechanism 24 uses a differential pressure between the oil pressure in the release oil chamber 26 between the lock-up piston 25 and the front cover 21 and the oil pressure in the engagement oil chamber 27 between the lock-up piston 25 and the pump impeller 22. Lock-up 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 is separated from the front cover 21 due to the pressure difference, and the lockup is turned off. When the oil pressure of the engagement oil chamber 27 is higher than the oil pressure of the release oil chamber 26, the lock-up piston 25 is pressed against the front cover 21 by the pressure difference, and the lock-up is turned on.

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

  CVT 4 transmits power input from torque converter 3 to differential gear 5. The CVT 4 includes an input shaft 31, an output shaft 32, a belt transmission mechanism 33, and an auxiliary transmission mechanism.

  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 arranged in parallel with the input shaft 31. An output gear 35 is supported by the output shaft 32 so as not to rotate relatively. The output gear 35 meshes with a ring gear 36 of the differential gear 5.

  The belt transmission mechanism 33 includes a primary shaft 41 and a secondary shaft 42. The primary shaft 41 is arranged on the same axis as the input shaft 31, is connected to the input shaft 31, and is provided so as to be able to rotate integrally with the input shaft 31. The primary shaft 41 may be formed integrally with the input shaft 31. The secondary shaft 42 extends parallel to the primary shaft 41 at a distance from the primary shaft 41 in the radial direction of rotation, and is provided to be rotatable about a central axis.

  The belt transmission mechanism 33 has a configuration in which an endless belt 45 is wound around a primary pulley 43 supported on a primary shaft 41 and a secondary pulley 44 supported on a secondary shaft 42.

  The primary pulley 43 is opposed to a fixed sheave 51 fixed to the primary shaft 41 with a belt 45 interposed between the fixed sheave 51 and a movable sheave supported on the primary shaft 41 so as to be movable in its axial direction and relatively non-rotatable. 52. A piston 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 piston chamber 54 is formed between the movable sheave 52 and the piston 53.

  The secondary pulley 44 is opposed to a fixed sheave 55 fixed to the secondary shaft 42 with the belt 45 interposed therebetween, and is supported by the secondary shaft 42 so as to be movable in the axial direction thereof and relatively non-rotatable. And a movable sheave 56. A piston 57 fixed to the secondary shaft 42 is provided on a side opposite to the fixed sheave 55 with respect to the movable sheave 56, and a piston chamber 58 is formed between the movable sheave 56 and the piston 57.

  As the movable sheave 52 of the primary pulley 43 moves, the groove width, which is the distance between the fixed sheave 51 and the movable sheave 52, changes continuously. As the movable sheave 56 of the secondary pulley 44 moves, the groove width, which is the distance between the fixed sheave 55 and the movable sheave 56, changes continuously. By continuously changing the groove widths of the primary pulley 43 and the secondary pulley 44, it is possible to change the winding diameter of the belt 45 around the primary pulley 43 and the secondary pulley 44, and to reduce the pulley ratio (belt speed ratio). It can be changed continuously in stages.

  Although not shown, a bias spring for applying an initial clamping pressure (initial thrust) to the belt 45 is interposed between the movable sheave 56 and the piston 57. The movable sheave 56 and the piston 57 are urged away from each other by the elastic force of the bias spring.

  The rotation of the input shaft 31 causes the primary shaft 41 and the primary pulley 43 of the belt transmission mechanism 33 to rotate. The rotation of the primary pulley 43 is transmitted to the secondary pulley 44 via the belt 45. Thereby, the secondary pulley 44 rotates, and the secondary shaft 42 rotates integrally with the secondary pulley 44.

  The auxiliary transmission mechanism 34 is interposed between the secondary shaft 42 and the output shaft 32. The sub-transmission mechanism 34 has two speed stages, a low speed stage and a high speed stage. In the CVT 4, a low mode (Lo mode) is set by setting the shift speed of the sub-transmission mechanism 34 to a low speed step, and a high mode (Lo mode) is set by setting the shift speed of the sub-transmission mechanism 34 to a high speed step. Hi mode) is set.

  The auxiliary transmission mechanism 34 includes a low drive gear shaft 61, a load driven gear shaft 62, a high drive gear shaft 63, a driven gear shaft 64, a low clutch C1, and a high clutch C2.

  The low drive gear shaft 61 is arranged on the same axis as the secondary shaft 42, is connected to the secondary shaft 42, and is provided so as to be able to rotate integrally with the secondary shaft 42. The low drive gear shaft 61 may be formed integrally with the secondary shaft 42.

  The load-driven gear shaft 62 is arranged at intervals on the same axis as the output shaft 32, and is provided rotatable about the same axis.

  On the low drive gear shaft 61, a low drive gear 65 is supported so as not to rotate relatively. On the other hand, a load driven gear 66 is supported by the load driven gear shaft 62 so as not to rotate relatively. The low drive gear 65 and the load driven gear 66 are meshed. The load driven gear 66 has a larger diameter than the low drive gear 65, and the rotation of the low drive gear 65 is transmitted to the load driven gear 66 at a reduced speed.

  The high drive gear shaft 63 is disposed on the same axis as the low drive gear shaft 61 with a space therebetween, and is provided so as to be rotatable about the same axis.

  The driven gear shaft 64 is disposed on the same axis between the output shaft 32 and the load driven gear shaft 62. The driven gear shaft 64 is connected to the output shaft 32 and is provided so as to be able to rotate integrally with the output shaft 32.

  A high drive gear 67 is supported by the high drive gear shaft 63 so as not to rotate relatively. On the other hand, a driven gear 68 is supported by the driven gear shaft 64 so as to be relatively non-rotatable. The high drive gear 67 and the high driven gear 68 mesh with each other. The high driven gear 68 has a smaller diameter than the high drive gear 67, and the rotation of the high drive gear 67 is transmitted to the high driven gear 68 at an increased speed.

  The low clutch C1 is interposed between the load-driven gear shaft 62 and the driven gear shaft 64. The high clutch C2 is switched by an oil pressure to an engaged state in which the load driven gear shaft 62 and the driven gear shaft 64 are directly connected (coupled so as to be integrally rotatable) and a released state in which the direct connection is released.

  The high clutch C2 is interposed between the low drive gear shaft 61 and the high drive gear shaft 63. The low clutch C1 is switched by hydraulic pressure between an engaged state in which the low drive gear shaft 61 and the high drive gear shaft 63 are directly connected (integrally rotatable) and a released state in which the direct connection is released.

<Low mode / High mode>
FIG. 2 is a diagram showing states of the low clutch C1 and the high clutch C2 in each of the low mode and the high mode.

  Switching between the low mode and the high mode is achieved by switching between a state in which the low clutch C1 is engaged and a state in which the high clutch C2 is engaged (switching between the low clutch C1 and the high clutch C2).

  In the low mode, the low clutch C1 is engaged, and the high clutch C2 is released. Thus, the low drive gear shaft 61 and the high drive gear shaft 63 are separated from each other, and the load driven gear shaft 62 and the high driven gear shaft 64 are directly connected. The rotation is transmitted to the load driven gear 66 at a reduced speed, and the load driven gear shaft 62, the driven gear shaft 64, and the output shaft 32 are rotated integrally with the load driven gear 66. Since the output gear 35 meshes with the ring gear 36 of the differential gear 5, rotation of the output shaft 32 is transmitted from the output gear 35 to the differential gear 5. In the low mode, the speed ratio (reduction ratio) of the CVT 4 matches the product of the pulley ratio (belt speed ratio) of the belt transmission mechanism 33 and the sub speed ratio (gear ratio) of the low drive gear 65 and the load driven gear 66.

  In the high mode, the high clutch C2 is engaged and the low clutch C1 is released. As a result, the low drive gear shaft 61 and the high drive gear shaft 63 are directly connected, and the load driven gear shaft 62 and the high driven gear shaft 64 are separated. Therefore, the rotation of the secondary shaft 42 is performed via the low drive gear shaft 61. And transmitted to the high drive gear shaft 63 from the high drive gear 67 to the high driven gear 68 at an increased speed. The high drive gear shaft 63 and the output shaft 32 are rotated together with the high drive gear 68. In the high mode, the speed ratio (reduction ratio) of the CVT 4 matches the product of the pulley ratio (belt speed ratio) of the belt transmission mechanism 33 and the sub speed ratio (gear ratio) of the high drive gear 67 and the high driven gear 68.

<Vehicle control system>
FIG. 3 is a block diagram illustrating a configuration of a control system of the vehicle 1.

  The vehicle 1 is provided with an ECU (Electronic Control Unit) 71 including a microcomputer (microcontroller unit). Although only one ECU 71 is shown in FIG. 3, a plurality of ECUs having the same configuration as the ECU 71 are mounted on the vehicle 1 to control each unit. The plurality of ECUs including the ECU 71 are connected so as to be capable of two-way communication according to a CAN (Controller Area Network) communication protocol.

  The ECU 71 controls various valves included in a hydraulic circuit 72 for supplying hydraulic pressure to each unit of the unit including the torque converter 3, the CVT 4, and the differential gear 5 for controlling the speed of the CVT 4 and the like.

  The ECU 71 is connected to various sensors necessary for the control, such as a vehicle speed sensor 73 and a G sensor 74. The vehicle speed sensor 73 outputs a pulse signal synchronized with the rotation of the rotating body that rotates as the vehicle 1 travels as a detection signal. The G sensor 74 outputs a signal corresponding to the displacement of the weight as a detection signal corresponding to the acceleration of the vehicle 1. The ECU 71 calculates the vehicle speed of the vehicle 1 from the detection signal of the vehicle speed sensor 73. Further, the ECU 71 calculates the acceleration of the vehicle 1 from the detection signal of the G sensor 74.

  The acceleration calculated from the detection signal of the G sensor 74 includes an acceleration component due to a change in the vehicle speed and an acceleration component due to the gradient of the road surface on which the vehicle 1 is traveling. On the other hand, the acceleration obtained by differentiating the vehicle speed obtained from the output signal of the vehicle speed sensor 73 is only an acceleration component due to a change in the vehicle speed. Therefore, by obtaining the difference between the acceleration obtained from the detection signal of the G sensor 74 and the differential value of the vehicle speed, the acceleration component due to the road surface gradient is obtained. Therefore, it is possible to estimate the road surface gradient based on the acceleration component. it can.

<Mode switching>
FIG. 4 is a diagram showing the relationship between the speed ratio (pulley ratio × sub speed ratio) of the CVT 4 and the transmission efficiency, and the switching timing between the low mode and the high mode.

In the belt speed change mechanism 33, the transmission efficiency is highest when the difference between the winding diameter of the belt 45 around the primary pulley 43 and the winding diameter of the belt 45 around the secondary pulley 44 is small, that is, when the pulley ratio is close to 1, As the pulley ratio departs from 1, the transmission efficiency decreases. Therefore, the CVT 4, in the low mode, the highest transmission efficiency in the gear ratio M _L when the pulley ratio is near 1, a higher transmission efficiency decreases characteristic transmission ratio away from the gear ratio M _L I have. In the high mode, the transmission efficiency is the highest at the gear ratio _MH when the pulley ratio is near 1, and the transmission efficiency decreases as the gear ratio is further away from the gear ratio _MH .

Therefore, the low mode efficiency curve showing the relationship between the speed ratio of the CVT4 in low mode and transmission efficiency is highest transmission efficiency in the gear ratio M _L when the pulley ratio is near 1, transmitted farther from the gear ratio It changes to reduce efficiency. The high mode efficiency line representing the relationship between the transmission ratio of the CVT 4 and the transmission efficiency in the high mode has the highest transmission efficiency at the transmission ratio _MH when the pulley ratio is near 1, and the transmission increases as the distance from the transmission ratio increases. It changes to reduce efficiency. Then, the low mode efficiency line and the high mode efficiency line intersect at a portion where the transmission efficiency decreases toward the high side of the low mode efficiency line and a portion where the transmission efficiency decreases toward the low side of the high mode efficiency line.

  In the CVT 4, a first threshold value used for determining whether to switch from the low mode to the high mode is set within a predetermined range including the gear ratio A at the intersection of the low mode efficiency line and the high mode efficiency line, And a second threshold value used for the determination of the switching to.

Predetermined range, for example, the gear ratio M _H when the highest transmission efficiency in high mode the lower limit may range up to a maximum of speed ratio M _L when in low mode the highest transmission efficiency. The predetermined range may be a narrower range than to the lower limit speed ratio A in the intersection of the low mode efficiency line and the high mode efficiency line, the speed ratio when in the low mode with the highest transmission efficiency M _L May be the upper limit. In this case, the first threshold is set to the gear ratio A in the intersection of the low mode efficiency line and the high mode efficiency line, the second threshold, the transmission efficiency in low mode is a speed change ratio M _L when the highest Is also good.

  In the low mode, the ECU 71 sets, for example, a target engine torque which is a target of the torque of the engine 2 based on an accelerator operation amount which is an operation amount of an accelerator pedal provided on the vehicle 1 and a vehicle speed of the vehicle 1. Subsequently, the target engine speed, which is the target of the engine speed corresponding to the target engine torque, is set by the ECU 71 based on the optimum fuel consumption line for the low mode, and further, based on the vehicle speed, according to the target engine speed. The target gear ratio which is the target of the gear ratio of the CVT 4 is set. Thereafter, a thrust ratio corresponding to the target speed ratio is obtained by the ECU 71, and a belt necessary for preventing the belt 45 of the belt speed change mechanism 33 from slipping from the thrust ratio and the torque input to the primary shaft 41. 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 so that the clamping pressure is obtained. Then, the valve for controlling the primary pressure and the secondary pressure included in the hydraulic circuit 72 is controlled by the ECU 71 based on each command value.

  When the target gear ratio is set to a value smaller than the gear ratio A, which is an example of the first threshold, the valve included in the hydraulic circuit 72 is controlled by the ECU 71 so that the engaged low clutch C1 is activated. The released high clutch C2 is disengaged and engaged. Thereby, switching from the low mode to the high mode is achieved.

  However, even if a target speed ratio equal to or less than the first threshold value is set in the low mode, the vehicle speed at the speed ratio A at the intersection of the low mode efficiency line and the high mode efficiency line does not match the running resistance of the vehicle 1. The switching from the low mode to the high mode is delayed until the vehicle speed balances the running resistance. The running resistance of the vehicle 1 is the sum of the air resistance, the rolling resistance, the gradient resistance, and the acceleration resistance, and these resistances can be calculated by a known method using the vehicle weight, the vehicle speed, the road surface gradient, and the like. The relationship between the running resistance and the vehicle speed at the gear ratio A corresponding thereto is stored in the memory of the ECU 71 in the form of a calculation formula or a map.

  In the high mode, the ECU 71 sets a target engine torque based on, for example, the accelerator opening and the vehicle speed. Subsequently, a target engine speed corresponding to the target engine torque is set by the ECU 71 based on the optimal fuel consumption line for the high mode, and a target gear ratio corresponding to the target engine speed is set based on the vehicle speed. You. Thereafter, a thrust ratio corresponding to the target speed ratio is obtained by the ECU 71, and a belt necessary for preventing the belt 45 of the belt speed change mechanism 33 from slipping from the thrust ratio and the torque input to the primary shaft 41. Each command value of the primary pressure and the secondary pressure is set so that the clamping pressure is obtained. Then, the valve for controlling the primary pressure and the secondary pressure included in the hydraulic circuit 72 is controlled by the ECU 71 based on each command value.

When the target gear ratio is set to a value greater than the gear ratio M _L, which is an example of the second threshold value, the ECU 71, it is controlled valve included in the hydraulic circuit 72, the high clutch C2 engaged Is released, and the released low clutch C1 is engaged. Thereby, switching from the high mode to the low mode is achieved.

<Effects>
As described above, the shift at the intersection of the low mode efficiency line representing the relationship between the transmission ratio of the CVT 4 in the low mode and the transmission efficiency and the high mode efficiency line representing the relationship between the transmission efficiency and the transmission ratio of the CVT 4 in the high mode. A first threshold used to determine switching from the low mode to the high mode and a second threshold used to determine switching from the high mode to the low mode are set within a predetermined range including the ratio A. . As a result, the high mode and the low mode are switched near the speed ratio A at the intersection of the low mode efficiency line and the high mode efficiency line, so that the transmission efficiency of the CVT 4 is prevented from being excessively reduced. As a result, more efficient power transmission can be performed, and the driving fuel efficiency of the vehicle 1 can be improved.

When both the first threshold and the second threshold are set to the speed ratio A at the intersection of the low mode efficiency line and the high mode efficiency line, when the target speed ratio vibrates near the speed ratio, the low mode and the high mode are switched. Is frequently switched, and there is a possibility that the control may become busy. The first threshold value is set to the speed ratio A at the intersection of the low mode efficiency line and the high mode efficiency line, and the second threshold value is greater than the speed ratio at the intersection of the low mode efficiency line and the high mode efficiency line, for example, by transmission efficiency in low mode is set to the gear ratio M _L when the highest, even if the target gear ratio is vibrated in the vicinity of gear ratios a at the intersection of the low mode efficiency line and the high mode efficiency line, low Frequent switching between the mode and the high mode can be suppressed. Further, when the mode is switched from the high mode to the low mode with the deceleration of the vehicle 1, the fuel consumption is small. Therefore, even if the transmission efficiency of the CVT 4 decreases due to the continuation of the high mode, the fuel consumption of the vehicle 1 is reduced. The effect is small.

The mode switching unit is configured to control the speed ratio A at the intersection of the low mode efficiency line and the high mode efficiency line even when the target speed ratio smaller than the first threshold value A is set by the target speed ratio setting unit in the low mode. If the vehicle speed does not match the running resistance of the vehicle 1, the switching from the low mode to the high mode is delayed until the vehicle speed matches the running resistance. If this delay is not, the torque down with the low mode to switch to the high mode to decelerate the vehicle 1, the target gear ratio is set to a value greater than the second threshold value M _L, the low mode from the high mode And there is a concern that switching between the low mode and the high mode is frequently performed. The switching from the low mode to the high mode is delayed until the vehicle speed is balanced with the running resistance, so that the frequent switching between the low mode and the high mode can be suppressed, and the control busy state can be suppressed. .

<Modification>
As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented in another form.

  For example, in the above-described embodiment, the vehicle 1 equipped with the CVT 4 with the auxiliary transmission mechanism 34 has been described. However, the control device according to the present invention is not limited to such a vehicle 1, and a power split type continuously variable transmission may be used. It can also be used for vehicles equipped with it. The power split type continuously variable transmission includes, for example, a belt transmission mechanism that continuously changes the power by changing the speed ratio, and can transmit the power by dividing the power between the input shaft and the output shaft by two paths. Transmission.

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

1: vehicle 2: engine 4: CVT (continuously variable transmission)
31: input shaft 32: output shaft 33: belt transmission mechanism 34: auxiliary transmission mechanism 43: primary pulley 44: secondary pulley 45: belt 71: ECU (control device, target gear ratio setting means, mode switching means)

Claims (1)

A low speed mode set to a first speed ratio width on a power transmission path between an input shaft and an output shaft, including a belt speed change mechanism having an endless belt wound around a primary pulley and a secondary pulley. And a high mode in which a maximum speed ratio and a minimum speed ratio are respectively set to a second speed ratio width smaller than the first speed ratio width. A control device for controlling a step transmission,
Target speed ratio setting means for setting a target speed ratio that is a target of the speed ratio of the continuously variable transmission,
The target speed ratio set by the target speed ratio setting means in the low mode is a low mode efficiency line indicating a relationship between the speed ratio in the low mode and the transmission efficiency of the continuously variable transmission, and a high speed mode in the high mode. When the value is smaller than a first threshold value set within a predetermined range including the speed ratio at an intersection of a high mode efficiency line representing a relationship between the speed ratio and the transmission efficiency of the continuously variable transmission, When the mode is switched from the low mode to the high mode, and the target speed ratio set by the target speed ratio setting means in the high mode is a value larger than a second threshold set within the predetermined range, A mode switching means for switching from a high mode to the low mode.

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