JP5977271B2 - Continuously variable transmission and control method thereof - Google Patents

Description

  The present invention relates to control of a continuously variable transmission.

  The variator is a continuously variable transmission mechanism including a pair of pulleys whose groove width can be changed by hydraulic pressure and a belt wound around these pulleys.

  In a vehicle equipped with such a variator, when the accelerator pedal is depressed, the hydraulic pressure supplied to the pulley is increased according to the input torque to increase the torque capacity of the variator and prevent the belt from slipping. Furthermore, the variator is downshifted to achieve acceleration intended by the driver (power-on downshift).

  In addition, since the belt may slip if the hydraulic pressure supplied to the pulley cannot be increased for some reason, in Patent Document 1, in such a situation, torque-down control for reducing the torque input from the engine to the variator To do.

JP 2011-208680 A

  However, if the variator cannot be downshifted due to the fact that the hydraulic pressure supplied to the pulley cannot be increased in addition to the torque down control being performed, or if the downshift speed becomes slow, the driver requests The discrepancy between the acceleration and the realized acceleration is increased, which gives the driver a sense of incongruity.

  The present invention has been made in view of such a technical problem, and requires a driver in a situation where the hydraulic pressure supplied to the pulley cannot be increased during power-on downshift and torque down control is executed. The purpose is to reduce the discrepancy between acceleration and realized acceleration and to give the driver a sense of incongruity.

According to an aspect of the present invention, there is provided a continuously variable transmission that shifts rotation input from a power source, and includes a primary pulley and a secondary pulley whose groove width is changed by hydraulic pressure, and a belt wound around these pulleys. A variator having a plurality of shift speeds disposed on the input side or output side of the variator, and when the accelerator pedal is depressed, the hydraulic pressure supplied to the secondary pulley is increased to increase the variator increasing the torque capacity, the reducing the hydraulic pressure supplied to the primary pulley, or a power-on downshift means for performing a power-on downshift to downshift the variator raises the hydraulic pressure supplied to the secondary pulley If, when the accelerator pedal is depressed the power-on downshift is performed A pressure regulation failure time control means for performing torque down control for reducing the torque of the power source and downshifting the auxiliary transmission mechanism when the hydraulic pressure supplied to the secondary pulley does not increase. A continuously variable transmission is provided.

  According to another aspect of the present invention, a control method corresponding to the above aspect is provided.

  According to these aspects, even if the driving force decreases due to the torque down control, the reduction range of the driving force can be suppressed by downshifting the auxiliary transmission mechanism. The discrepancy between acceleration and realized acceleration can be reduced, and the uncomfortable feeling given to the driver can be reduced.

1 is a schematic configuration diagram of a vehicle equipped with a continuously variable transmission according to an embodiment of the present invention. It is the figure which showed the internal structure of the controller. It is an example of a shift map. It is the flowchart which showed the control content of the controller when the gear stage of a subtransmission mechanism is 2nd speed. It is the time chart which showed the operation | movement when a secondary pressure does not rise at the time of a power-on downshift.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the “transmission ratio” of a transmission mechanism is a value obtained by dividing the input rotational speed of the transmission mechanism by the output rotational speed of the transmission mechanism. The “lowest speed ratio” is the maximum speed ratio of the transmission mechanism, and the “highest speed ratio” is the minimum speed ratio of the transmission mechanism.

  FIG. 1 is a schematic configuration diagram of a vehicle equipped with a continuously variable transmission according to an embodiment of the present invention. This vehicle includes an engine 1 as a power source. The output rotation of the engine 1 is transmitted to the drive wheels 7 via the torque converter 2, the first gear train 3, the transmission 4, the second gear train 5, and the differential device 6. The second gear train 5 is provided with a parking mechanism 8 that mechanically locks the output shaft of the transmission 4 at the time of parking.

  The engine 1 is an internal combustion engine such as a gasoline engine or a diesel engine, and the rotation speed and torque are controlled by the engine controller 50.

  The torque converter 2 includes a lockup clutch 2a. When the lockup clutch 2a is engaged, slippage in the torque converter 2 is eliminated, and the transmission efficiency of the torque converter 2 can be improved.

  Further, the vehicle includes an oil pump 10 that is driven by using a part of the power of the engine 1, a hydraulic control circuit 11 that regulates the hydraulic pressure from the oil pump 10 and supplies the hydraulic pressure to each part of the transmission 4, A transmission controller 12 that controls the hydraulic control circuit 11 is provided.

  The transmission 4 is a continuously variable transmission including a variator 20 and a sub-transmission mechanism 30 provided in series with the variator 20. “Provided in series” means that the variator 20 and the auxiliary transmission mechanism 30 are provided in series in the power transmission path from the engine 1 to the drive wheels 7. In this example, the auxiliary transmission mechanism 30 is provided on the output side of the variator 20, but the auxiliary transmission mechanism 30 may be provided on the input side.

  The variator 20 is a continuously variable transmission mechanism that includes a primary pulley 21, a secondary pulley 22, and a belt 23 that is wound around the pulleys 21 and 22. Each of the pulleys 21 and 22 includes a fixed conical plate, a movable conical plate that is arranged with a sheave surface facing the fixed conical plate, and forms a V-groove between the fixed conical plate, and the movable conical plate. And a hydraulic cylinder that displaces the movable conical plate in the axial direction.

  When the hydraulic pressure (primary pressure and secondary pressure) supplied to the pulleys 21 and 22 is adjusted, the force with which the pulleys 21 and 22 hold the belt 23 changes, and the torque capacity (maximum torque that can be transmitted) of the variator 20 changes. Further, the width of the V-groove changes, the contact radius between the belt 23 and the pulleys 21 and 22 changes, and the transmission ratio of the variator 20 changes steplessly.

  The subtransmission mechanism 30 is a transmission mechanism having two forward speeds and one reverse speed. The sub-transmission mechanism 30 is connected to a Ravigneaux type planetary gear mechanism 31 in which two planetary gear carriers are connected, and a plurality of friction elements connected to a plurality of rotating elements constituting the Ravigneaux type planetary gear mechanism 31 to change their linkage state. Elements (Low brake 32, High clutch 33, Rev brake 34). The gear position of the subtransmission mechanism 30 is changed by adjusting the hydraulic pressure supplied to the friction elements 32 to 34 and changing the engagement state of the friction elements 32 to 34.

  Specifically, if the Low brake 32 is engaged and the High clutch 33 and the Rev brake 34 are released, the gear position of the subtransmission mechanism 30 is the first speed. If the high clutch 33 is engaged and the low brake 32 and the rev brake 34 are released, the speed stage of the subtransmission mechanism 30 becomes the second speed having a smaller speed ratio than the first speed. Further, if the Rev brake 34 is engaged and the Low brake 32 and the High clutch 33 are released, the shift speed of the subtransmission mechanism 30 is reverse. In the following description, it is expressed that “the transmission 4 is in the low speed mode” when the shift speed of the auxiliary transmission mechanism 30 is the first speed, and “the transmission 4 is in the high speed mode” when the speed is the second speed. Express.

  The torque (hereinafter referred to as “capacity”) that can be transmitted by the friction elements that are engaged at the respective speeds is determined by the hydraulic pressure supplied from the hydraulic control circuit 11 to the friction elements 32 to 34.

  As shown in FIG. 2, the transmission controller 12 includes a CPU 121, a storage device 122 including a RAM and a ROM, an input interface 123, an output interface 124, and a bus 125 that interconnects them.

  The input interface 123 includes an output signal of an accelerator opening sensor 41 that detects an accelerator opening APO that represents the amount of operation of the accelerator pedal, an input rotation speed of the transmission 4 (= rotation speed of the primary pulley 21, hereinafter referred to as “primary rotation”). The output signal of the rotational speed sensor 42 for detecting the vehicle speed VSP, the output signal of the vehicle speed sensor 43 for detecting the vehicle speed VSP, the output signal of the hydraulic sensor 44 for detecting the secondary pressure, and the inhibitor switch for detecting the position of the select lever. The output signal of 45, the output signal of the rotation speed sensor 46 for detecting the rotation speed of the secondary pulley 22 (= the input rotation speed of the auxiliary transmission mechanism 30), and the like are input.

  The storage device 122 stores a shift control program (FIG. 4 and the like) for the transmission 4 and a shift map (FIG. 3) used in the shift control program. The CPU 121 reads out and executes the shift control program stored in the storage device 122, performs various arithmetic processes on various signals input via the input interface 123, and supplies the hydraulic pressure to each part of the transmission 4. And the set instruction value is output to the hydraulic control circuit 11 via the output interface 124. Various values used in the arithmetic processing by the CPU 121 and the arithmetic results are appropriately stored in the storage device 122.

  The hydraulic control circuit 11 includes a plurality of flow paths and a plurality of hydraulic control valves. The oil pressure control circuit 11 controls a plurality of oil pressure control valves based on the instruction value from the transmission controller 12 to switch the oil pressure supply path, and uses the oil pressure generated by the oil pump 10 as a base pressure to respond to the instruction value. Is supplied to each part of the transmission 4. As a result, the variator 20 is shifted, the shift stage of the auxiliary transmission mechanism 30 is changed, the capacities of the friction elements 32 to 34 are controlled, and the lockup clutch 2a is engaged and released.

  FIG. 3 shows an example of the shift map stored in the storage device 122. The transmission controller 12 refers to this shift map, and according to the driving state of the vehicle (in this embodiment, the vehicle speed VSP, the primary rotational speed Npri, and the accelerator opening APO), the variator 20, the auxiliary transmission mechanism 30, and The lockup clutch 2a is controlled.

  In this shift map, the operating point of the transmission 4 is defined by the vehicle speed VSP and the primary rotational speed Npri. The slope of the line connecting the operating point of the transmission 4 and the zero point of the lower left corner of the transmission map is the transmission ratio of the transmission 4 (the overall transmission ratio obtained by multiplying the transmission ratio of the variator 20 by the transmission ratio of the subtransmission mechanism 30; Hereinafter, this corresponds to “through transmission ratio”. As in the shift map of the conventional belt continuously variable transmission, a shift line is set for each accelerator opening APO, and the shift of the transmission 4 is selected according to the accelerator opening APO. Done according to the line.

  When the transmission 4 is in the low speed mode, the transmission 4 can be obtained by setting the low speed mode lowest line obtained by setting the speed ratio of the variator 20 to the lowest speed ratio and the speed ratio of the variator 20 being the highest speed ratio. The speed can be changed between the highest lines (A and B regions in the figure). On the other hand, when the transmission 4 is in the high speed mode, the transmission 4 is obtained by setting the maximum speed line of the high speed mode obtained by setting the transmission ratio of the variator 20 as the lowest transmission ratio and the transmission ratio of the variator 20 as the highest transmission ratio. The speed can be changed between the high-speed mode highest lines (B and C regions in the figure).

  In addition, on this shift map, a mode switching line for switching the mode of the transmission 4 is set so as to substantially overlap the low speed mode Highest line.

  The mode switching for upshifting the auxiliary transmission mechanism 30 from the first speed to the second speed is performed when the target operating point of the transmission 4 crosses the mode switching line from the B area side to the C area side. On the other hand, mode switching for downshifting the sub-transmission mechanism 30 from the second speed to the first speed is equivalent to a conventional kick-down because the accelerator pedal is greatly depressed while the gear position of the sub-transmission mechanism 30 is at the second speed. It is executed when an increase in driving force is requested or when the vehicle speed VSP enters a predetermined low vehicle speed region.

  Further, when shifting the subtransmission mechanism 30, the transmission controller 12 performs a coordinated shift that changes the transmission ratio of the variator 20 in a direction opposite to the direction in which the transmission ratio of the subtransmission mechanism 30 changes. Specifically, the transmission controller 12 changes the speed of the variator 20 in accordance with the inertia phase of the subtransmission mechanism 30, and during the inertia phase, the engagement side friction element or the release side friction element (low brake) of the subtransmission mechanism 30 is provided. 32 or the high clutch 33) is controlled, and the input rotational speed of the auxiliary transmission mechanism 30 (corresponding to the actual transmission ratio of the auxiliary transmission mechanism 30) is continuously changed in accordance with the change of the transmission ratio of the variator 20. This prevents a step in the through gear ratio during the coordinated shift, and suppresses a shift shock during the shift of the auxiliary transmission mechanism 30.

  In addition, when the accelerator pedal is depressed, the transmission controller 12 increases the torque capacity of the variator 20 by increasing the primary pressure and the secondary pressure in accordance with the increase in torque input from the engine 1 to the variator 20, and the belt 23. Prevents slipping. Further, by reducing the primary pressure or increasing the secondary pressure, a power-on downshift is performed to downshift the variator 20 so that the acceleration intended by the driver is realized.

  At this time, the primary pressure increases, but if the secondary pressure cannot be increased for some reason, such as when the hydraulic control valve bites into contamination and does not operate normally, the torque capacity of the variator 20 becomes insufficient and the belt 23 There is a possibility of slipping. For this reason, when the secondary pressure cannot be increased, the transmission controller 12 outputs a torque down signal to the engine controller 50 to reduce the torque of the engine 1 and to increase the torque input from the engine 1 to the variator 20. By reducing this, the belt 23 is prevented from slipping (torque down control).

  However, in a situation where the downshift of the variator 20 is executed by increasing the secondary pressure, the variator 20 cannot be downshifted or the downshift speed becomes slow unless the secondary pressure can be increased. In addition, the driving force is greatly insufficient due to the torque reduction of the engine 1 due to the torque-down control, and the difference between the acceleration requested by the driver and the realized acceleration becomes large, and the driver feels uncomfortable. Will be given.

  Therefore, in the present embodiment, even when the secondary pressure cannot be increased, the sub-transmission mechanism 30 is provided when the primary pressure can be increased based on the command pressure (when the hydraulic pressure other than the secondary pressure is normal). If the secondary pressure cannot be increased although the power-on downshift is executed when the shift speed of the subtransmission mechanism 30 is the second speed, the subtransmission mechanism 30 is turned on. By downshifting from the second speed to the first speed, the uncomfortable feeling is alleviated.

  FIG. 4 is a flowchart showing the control contents of the transmission controller 12 when the sub-transmission mechanism 30 is in the second speed.

  Explaining this, the transmission controller 12 determines whether the gear position of the subtransmission mechanism 30 is the second speed in S1, and determines whether the accelerator pedal is depressed in S2. If the gear position of the subtransmission mechanism 30 is the second speed and the accelerator pedal is depressed, the process proceeds to S3, and if not, the process ends.

  After S3, the transmission controller 12 performs a power-on downshift.

  In S3, the transmission controller 12 increases the torque of the engine 1 by depressing the accelerator pedal and increases the torque input to the variator 20, thereby preventing the belt 23 from slipping. The secondary pressure command value (hereinafter referred to as the command secondary pressure) to be output is increased. In response to this, the hydraulic control circuit 11 operates so that the secondary pressure supplied to the secondary pulley 22 increases.

  In S <b> 4, the transmission controller 12 determines whether the actual secondary pressure has increased based on the actual secondary pressure detected by the hydraulic sensor 44. If the state in which the actual secondary does not increase continues for a predetermined time (for example, 1 or 2 seconds) even though the instruction secondary pressure has increased, it is determined that a pressure adjustment failure has occurred for some reason, and the process proceeds to S5. Proceed to Otherwise, the process proceeds to S21.

  In S5, the transmission controller 12 outputs a torque down signal to the engine controller 50, and starts torque down control. The engine controller 50 that has received the torque down signal reduces the torque of the engine 1 by reducing the intake air amount of the engine 1 or delaying the ignition timing. The amount of torque reduction of the engine 1 is set so that the torque input to the variator 20 is reduced to the torque capacity realized by the secondary pressure at that time, thereby preventing the belt 23 from slipping ( Torque down control).

  In S6, the transmission controller 12 starts a downshift of the auxiliary transmission mechanism 30 from the second speed to the first speed. At this time, the transmission controller 12 adjusts the shift speed of the sub-transmission mechanism 30 to be equal to the shift speed when the power-on downshift is executed only by the variator 20, and the sub-transmission mechanism 30 shifts suddenly. The shock caused by doing this is suppressed and the driver feels less uncomfortable.

  In S7, the transmission controller 12 determines whether the auxiliary transmission mechanism 30 is shifting. During the speed change, the process proceeds to S8, and the transmission controller 12 maintains the speed ratio of the variator 20 at the current speed ratio. Thus, the hydraulic pressure is exclusively used for shifting the auxiliary transmission mechanism 30, and the auxiliary transmission mechanism 30 can be sufficiently downshifted even in a situation where the actual secondary pressure does not increase. When the shift of the subtransmission mechanism 30 is completed, the process proceeds to S9.

  In S <b> 9, the transmission controller 12 reduces the primary pressure by lowering the primary pressure, and further downshifts the variator 20, thereby further reducing the difference between the acceleration requested by the driver and the realized acceleration. Like that.

  The torque input to the variator 20 is reduced by the torque-down control, and the torque input to the variator 20 and the torque capacity of the variator 20 are balanced. Thus, the primary pressure is reduced and the variator 20 is downshifted. The belt 23 will not slip even if it is made to.

  In S10, the transmission controller 12 determines whether the actual secondary pressure has returned to the normal state. This determination can be made based on whether the deviation between the instruction secondary pressure and the actual secondary pressure is smaller than a predetermined value. Until the actual secondary pressure returns to the normal state, the process proceeds to S11 and the torque-down control is continued. When the actual secondary pressure returns to the normal state, the process proceeds to S12 and the torque-down control is terminated.

  On the other hand, when the routine proceeds from S4 to S21, in S21, the transmission controller 12 determines whether or not mode switching for downshifting the auxiliary transmission mechanism 30 from the second speed to the first speed is necessary, and it is determined that the mode switching is necessary. If so, the process proceeds to S22. Mode switching is performed when the accelerator pedal is greatly depressed and the accelerator opening APO, its amount of change exceeds a predetermined value, and an increase in driving force corresponding to the conventional kickdown is required, or when the vehicle speed VSP is a predetermined low It is judged necessary when entering the vehicle speed range.

  In S <b> 22, the transmission controller 12 executes a coordinated shift that upshifts the variator 20 while downshifting the auxiliary transmission mechanism 30 from the second speed to the first speed. In S23, the transmission controller 12 downshifts the variator 20, and realizes acceleration according to the driver's intention.

  If mode switching is not required, the process proceeds to S23, where only the variator 20 is downshifted to achieve acceleration in line with the driver's intention.

  In the above control, the sub-transmission mechanism 30 is downshifted regardless of whether or not the primary pressure can be increased based on the command pressure. However, when the accelerator is ON, the primary pressure increases based on the command pressure. If the primary pressure is determined to have increased based on the command pressure, the auxiliary transmission mechanism 30 may be downshifted.

  Then, the effect by performing said control is demonstrated.

  FIG. 5 shows the operation when the secondary pressure does not increase during the power-on downshift.

  According to this, the accelerator pedal is depressed at time t1, and the command primary pressure and the command secondary pressure increase as the engine torque increases, but only the actual primary pressure increases, and the actual secondary pressure does not increase. Has occurred. Since only the actual primary pressure increases, the variator gear ratio changes to the high side.

  If the state where the actual secondary pressure does not increase continues for a predetermined time, it is determined that a pressure regulation failure has occurred, torque reduction control of the engine 1 is executed, and the subtransmission mechanism 30 is downshifted from the second speed to the first speed. It is started (t2).

  When the torque down control is performed, the driving force decreases. In such a case, the subtransmission mechanism 30 is downshifted from the second speed to the first speed, thereby suppressing the reduction range of the driving force. The difference between the acceleration requested by the driver and the realized acceleration can be reduced, and the uncomfortable feeling given to the driver can be reduced (effect corresponding to claims 1 and 3).

  Further, when the downshift from the second speed to the first speed of the auxiliary transmission mechanism 30 is completed at time t3, the downshift of the variator 20 is executed by reducing the primary pressure.

  As a result, the through gear ratio is further increased, so that the reduction in the driving force is further suppressed to further reduce the difference between the acceleration requested by the driver and the realized acceleration, thereby further reducing the uncomfortable feeling given to the driver. (Effect corresponding to claim 2).

  The embodiment of the present invention has been described above, but the above embodiment is merely one example of application of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. is not.

  For example, in the above-described embodiment, the auxiliary transmission mechanism 30 is a transmission mechanism having two speeds of first speed and second speed as the forward shift stage. A transmission mechanism having stages may be used.

  Moreover, although the engine 1 is provided as a power source, the power source is not limited to the engine 1 and may be, for example, a power source combining the engine 1 and a motor, or a power source including only a motor.

1 Engine (Power source)
4 Transmission 12 Transmission controller (Power-on downshift means, control means for poor pressure regulation)
20 variator 21 primary pulley 22 secondary pulley 23 belt 30 auxiliary transmission mechanism

Claims (3)

A continuously variable transmission for shifting rotation input from a power source,
A variator having a primary pulley and a secondary pulley whose groove width is changed by hydraulic pressure, and a belt wound around them;
A sub-transmission mechanism disposed on the input side or output side of the variator and having a plurality of shift stages;
When the accelerator pedal is depressed, the hydraulic pressure supplied to the secondary pulley is increased to increase the torque capacity of the variator, and the hydraulic pressure supplied to the primary pulley is decreased, or supplied to the secondary pulley. A power-on downshift means for performing a power-on downshift for raising the hydraulic pressure to downshift the variator;
When the accelerator pedal is depressed and the power-on downshift is executed , if the hydraulic pressure supplied to the secondary pulley does not increase, torque down control is performed to reduce the torque of the power source, and the auxiliary transmission mechanism is A control means at the time of poor pressure regulation to downshift;
A continuously variable transmission comprising: The continuously variable transmission according to claim 1,
The control means at the time of poor pressure regulation, after downshifting the auxiliary transmission mechanism, lowers the hydraulic pressure supplied to the primary and downshifts the variator,
A continuously variable transmission. A variator having a primary pulley and a secondary pulley whose groove width is changed by hydraulic pressure, and a belt wound around them; and a sub-transmission mechanism having a plurality of shift stages arranged on the input side or output side of the variator. And a control method for a continuously variable transmission that shifts rotation input from a power source,
When the accelerator pedal is depressed, the hydraulic pressure supplied to the secondary pulley is increased to increase the torque capacity of the variator, and the hydraulic pressure supplied to the primary pulley is decreased, or supplied to the secondary pulley. Performing a power-on downshift to increase the hydraulic pressure to downshift the variator;
When the accelerator pedal is depressed and the power-on downshift is executed , if the hydraulic pressure supplied to the secondary pulley does not increase, torque down control is performed to reduce the torque of the power source, and the auxiliary transmission mechanism is and bring down shift,
A control method for a CVT, which comprises a.

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