JP2001173770A - Control device for continuously variable transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problems that, in a lower limit guard to prevent the occurrence of a belt slip and the damage of a continuously variable transmission, since lowering of the press force of a primary pulley is not realized, transient responsiveness becomes a problem and further, when by applying a sufficient press force on two pulleys, the pulleys are prevented from hooking the lower limit guard, fuel consumption is worsened. SOLUTION: To solve the above problems opposite to each other, fuel consumption is reduced by controlling the oil pressure of a primary pulley by a low press force. When a primary oil pressure indication value is lower than a lower limit guard like a transient response time, the oil pressure of a secondary pulley is increased based on a difference between an oil pressure indication value and a lower limit guard value. Such a way always maintains a desired change gear ratio and realize control not to damage gear shift responsiveness. Further, by using a sliding mode PID controller, reduction of the number of suitable processes is practicable and property to follow a target change gear ratio is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission control device for electronically controlling a belt type continuously variable transmission for a vehicle.

[0002]

2. Description of the Related Art In recent years, there has been a trend to adopt a continuously variable transmission as a vehicle transmission from the viewpoint of reducing fuel consumption. One example of the continuously variable transmission is a V-belt type. this is,
There is provided a pair of variable pulleys, a primary side pulley and a secondary side pulley, in which the width of the contact pulley with the V-belt is variably controlled based on the hydraulic pressure. As a driving source of the pressing force of the pulley against the belt, there is a driving source using a hydraulic pressure generated by a hydraulic pump driven by an engine or another driving source. From the viewpoint of reducing fuel consumption, it is necessary to control the pressing force of the pulley against the belt to the minimum necessary.

For this reason, there is a control method in which a minimum pressing force at which a belt slip does not occur in a primary pulley or a secondary pulley is obtained by calculation, and control is performed with the minimum pressure. On the other hand, during transient response such as kick down or shift down, it is necessary to secure a large difference between the pressing force on the primary side and the secondary side. The control is performed to secure the shift response.

On the other hand, in order to follow a target gear ratio, Japanese Patent Laid-Open No. 9-229172 and Japanese Patent No. 29002
As disclosed in Japanese Patent Application Laid-Open No. 82-182, and Japanese Patent Application Laid-Open No. 11-37277, shift feedback control is performed according to a deviation between a target value and an actual value.

When shifting on the downshift side, the pressing force of the secondary pulley is temporarily increased, and the pressing force of the primary pulley is reduced. At this time, feedback control is performed according to the deviation between the target value and the actual value so that the pressing force of the secondary pulley follows the target gear ratio. As a result of this feedback control, the pressing force of the primary pulley temporarily drops until it can follow the target gear ratio. However, since the control on the pressing force lowering side may decrease the durability of the continuously variable transmission due to belt slip or the like, the pressing force of the secondary pulley and the primary pulley may be provided with a lower limit guard.

[0006]

However, although the lower limit guard can prevent the durability of the continuously variable transmission from decreasing, it is impossible to sufficiently reduce the primary pressing force. The pushing force is increased each time a determination is made during a transient response to ensure the fuel economy, resulting in a decrease in fuel efficiency.

Further, in order to determine how much the pressing force should be increased, that is, in order to achieve both a request for reduction of fuel consumption and a shift response, a shift response required by a driver based on a vehicle state or a sensor signal is determined. Complex logic for estimation and many man-hours were required.

Therefore, the present invention improves the fuel efficiency by reducing the pressing force of the secondary and primary pulleys as compared with the prior art, and minimizes the reduction of the shift transient response performance that occurs with this. It is an object to provide a control measure for a step transmission.

It is a further object of the present invention to provide a control device for a continuously variable transmission that can satisfy these contradictory control requirements without requiring many adapting man-hours.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and a control device for a continuously variable transmission according to a first aspect of the present invention provides a hydraulic pressure supply for a primary pulley and a control for a secondary pulley. Among the supply oil pressures, a lower limit guard means for guarding a lower oil pressure command value with a predetermined lower limit value when the supply oil pressure command value is lower than or equal to the predetermined lower limit value. Correction means for correcting the other hydraulic pressure instruction value to a higher value based on the lower hydraulic pressure instruction value and the supplied hydraulic pressure value.

According to this configuration, since the lower limit guard means guards the lower hydraulic pressure instruction value, the supplied hydraulic pressure can be controlled with the minimum required hydraulic pressure. Further, even if the hydraulic pressure command value is lower than the lower limit value during the transient response, the lower limit guard can perform control that does not cause belt slip and damage to the continuously variable transmission. Further, the fuel consumption can be reduced without impairing the responsiveness to the target gear ratio by correcting the oil pressure instruction value to the larger side by the compensation means based on the lower limit guard value and the oil pressure instruction value.

According to a second aspect of the present invention, there is provided a control device for a continuously variable transmission.
When the supply hydraulic pressure of the primary pulley is lower than the supply hydraulic pressure of the secondary pulley, the lower-limit guard means guards the hydraulic pressure instruction value of the primary pulley at a predetermined lower limit value, and the correction means corrects the hydraulic pressure instruction value of the primary pulley to the above-mentioned value. A configuration is provided for correcting the hydraulic pressure instruction value of the secondary pulley based on the lower limit value.

According to this configuration, the primary pulley and the secondary pulley can be controlled with the minimum required hydraulic pressure, so that fuel efficiency is improved. Further, even when the hydraulic pressure command value of the primary pulley is lower than the lower limit guard value, the lower limit guard means does not damage the belt slip or the continuously variable transmission. Further, by providing a correction means based on the lower limit guard value and the hydraulic pressure command value of the primary pulley, the responsiveness to the target speed ratio is also improved.

According to a third aspect of the present invention, there is provided a control device for a continuously variable transmission.
A supply oil pressure ratio setting unit configured to set a supply oil pressure ratio between a supply oil pressure of the primary pulley and a supply oil pressure of the secondary pulley, wherein the correction unit detects a difference between the oil pressure instruction value of the primary pulley and the lower limit value. A configuration is provided in which the correction value is added to the hydraulic pressure command value of the secondary pulley.

According to this configuration, the correction value is calculated based on the hydraulic pressure ratio set by the supply hydraulic pressure ratio setting means and the difference between the hydraulic pressure instruction value of the primary pulley and the lower limit value. Therefore, the minimum required compensation value can be added to the secondary pulley, and excellent followability in shifting during transient response or the like can be realized without changing the target gear ratio.

According to a fourth aspect of the present invention, there is provided a control device for a continuously variable transmission.
Input torque ratio setting means for setting an input torque ratio between the engine torque and the maximum torque that can be transmitted by the continuously variable transmission;
The supply oil pressure setting means includes a map for obtaining the supply oil pressure ratio from a relationship between the target gear ratio and the input torque ratio, and the supply oil pressure ratio obtained from the map, and a hydraulic pressure instruction value for the primary pulley. A configuration for calculating the correction value based on the difference from the lower limit.

According to this configuration, the supply hydraulic pressure ratio obtained from the relationship between the target gear ratio and the input torque ratio by a map and the difference between the hydraulic pressure instruction value of the primary pulley and the lower limit value are determined. Therefore, the minimum compensation value can be calculated with higher accuracy.

According to a fifth aspect of the present invention, there is provided a control device for a continuously variable transmission.
5. The control device for a continuously variable transmission according to claim 4, further comprising a map for obtaining the supply hydraulic pressure from a predetermined relationship between the representative input torque ratio and the target gear ratio.

As a result, the calculation for obtaining the hydraulic pressure ratio can be easily performed, so that the calculation load on the control device can be reduced. In addition, since the map is set for a representative input torque, it is not necessary to obtain values for a plurality of input torques by adaptation, so that the number of adaptation steps can be reduced.

In the control device for a continuously variable transmission according to a sixth aspect, in the control device for a continuously variable transmission according to the fourth aspect, the supply hydraulic pressure ratio is set to an arbitrary coefficient, so that the hydraulic pressure can be easily calculated. Since the ratio can be obtained, a complicated calculation is not required, and the calculation load on the control device can be reduced. In addition, it is possible to reduce the number of adaptation steps and thereby the cost.

In the control device for a continuously variable transmission according to a seventh aspect of the present invention, in the control device for a continuously variable transmission according to the fourth aspect, the supply hydraulic pressure ratio is obtained by using a past supply hydraulic pressure ratio as the supply hydraulic pressure ratio. This eliminates the need for complicated calculations, and can reduce the calculation load on the control device. In addition, it is possible to reduce the number of adaptation steps and thereby the cost.

In the control device for a continuously variable transmission according to the present invention, the lower limit guard value is set to a value for preventing the belt from slipping. , It is possible to suppress a decrease in the durability of the continuously variable transmission due to the slip of the belt.

Meanwhile, the pulley of the continuously variable transmission generates centrifugal oil pressure by its own rotational movement. When this centrifugal oil pressure is generated, the oil pressure supplied to the pulley cannot be reduced below the centrifugal oil pressure. Therefore, even if the supply oil pressure command value to the pulley becomes equal to or less than the centrifugal oil pressure, the supply oil pressure cannot be reduced, and control responsiveness may be impaired.

Therefore, in the control device for a continuously variable transmission according to the ninth aspect, in the control device for a continuously variable transmission according to the first to eighth aspects, the lower limit guard value is set by the rotation of the primary pulley itself. By providing a configuration based on the generated centrifugal oil pressure, it is possible to prevent responsiveness to the target gear ratio from being impaired.

In the control device for a continuously variable transmission according to a tenth aspect, in the control device for a continuously variable transmission according to any one of the first to ninth aspects, the lower limit guard value is set to a hydraulic pressure supplied to the primary pulley or to the primary pulley. The setting is made in consideration of the lower limit value of the mechanical variation of the actuator for adjusting the supply oil pressure to the secondary pulley.

Thus, it is possible to suppress a decrease in the durability of the continuously variable transmission due to the belt slip.

In the control device for a continuously variable transmission according to the eleventh aspect, in the control device for a continuously variable transmission according to any one of the first to tenth aspects, the primary pulley supply hydraulic pressure and the secondary pulley supply hydraulic pressure are fed back. A feedback control unit for controlling the feedback control unit, wherein the feedback gain used for the feedback control is continuously changed according to a deviation between the target speed ratio and the actual speed ratio.

According to this configuration, the optimum feedback gain can be set according to any deviation, so that the response to the target speed ratio can be improved, and the stability can be improved.

According to a twelfth aspect of the present invention, there is provided the continuously variable transmission control device according to the first to tenth aspects, wherein the traveling mode detecting means for detecting a traveling state of the vehicle includes: A feedback control unit that performs feedback control of the secondary pulley supply hydraulic pressure and the secondary pulley supply hydraulic pressure, and the feedback control unit sets a feedback gain used for feedback control based on the traveling mode detected by the traveling mode detection unit. .

As a result, the optimum feedback gain can be set according to the traveling mode, the response to the target speed ratio can be improved, and the stability can be improved.

[0031]

<First Embodiment> Next, a first embodiment of the present invention will be described.

FIG. 1 shows a continuously variable transmission used in this embodiment. Reference numeral 20 denotes an engine.
Is connected to the primary pulley 1 of the continuously variable transmission 23 via the torque converter 21 and the forward / reverse switching mechanism 22. The continuously variable transmission 23 includes a primary pulley 1, a secondary pulley 2, and a belt 3. Continuously variable transmission 23
The secondary pulley 2 is disposed in parallel with the primary pulley 1, and a belt 3 is hung between the primary pulley 1 and the secondary pulley 2. And
By changing the ratio of the winding diameter of the belt 3, the speed ratio can be changed in a stepless manner. The winding diameter is the primary pulley 1 and the secondary pulley 2
And is controlled by adjusting the hydraulic pressure supplied to the power supply. For example, when the supply hydraulic pressure to the primary pulley 1 is reduced and the supply hydraulic pressure to the secondary pulley 2 is increased, the winding diameter of the primary pulley 1 decreases, and the winding diameter of the secondary pulley 2 increases, and as a result, the gear ratio increases. can do. The driving force is further transmitted from the secondary pulley 2 to the wheels 27 via the gear 24, the differential device 25, and the axle 26.

In the hydraulic control system of the continuously variable transmission 23, the secondary pulley-side pressure control valve 5 supplies a hydraulic pressure to the secondary cylinder 2a via an oil passage 29. The secondary pulley control valve 5 supplies a hydraulic pressure according to the transmission torque to the secondary pulley 2 as a secondary hydraulic pressure, and applies a pressing force to the secondary pulley 2 according to the transmission torque.

The primary pulley side pressure control valve 4 is connected to the oil passage 3
The hydraulic pressure is supplied to the primary cylinder 1a via the oil passage 28 using the secondary hydraulic pressure from zero. The primary pulley-side pressure control valve 4 supplies a hydraulic pressure according to the transmission torque to the primary pulley 1 as a primary hydraulic pressure, and applies a pressing force to the primary pulley 1 according to the transmission torque.

At this time, the primary pulley side pressure control valve 4
Uses the secondary hydraulic pressure to supply the primary hydraulic pressure, and cannot supply hydraulic pressure exceeding the secondary hydraulic pressure. However, it is possible to apply a large pressing force to the primary pulley 1 by designing the pressure receiving area of the hydraulic pressure applied to the primary cylinder 1a to be small.

Primary pulley 1 and secondary pulley 2
In order to control the gear ratio to a desired gear ratio, in the related art, the lower limit guard is provided for the hydraulic pressure supplied by the primary pulley side pressure control valve 4 to prevent the belt 3 from slipping. However, if the hydraulic pressure applied to the primary pulley 1 is controlled by the hydraulic pressure just before the belt 3 slips in consideration of fuel efficiency, the primary hydraulic pressure always falls below the lower limit guard during a transient response in which the deviation between the actual value and the target value is large. It was difficult to ensure responsiveness.

Conversely, in order to ensure the response during the transient response, a high oil pressure is applied in advance to the secondary pulley side pressure control valve 5 so that the oil pressure supplied to the primary pulley 1 does not fall below the lower limit guard. must not.
In order to increase the supply hydraulic pressure as a whole, the driving force of the oil pump must be increased. In addition, in order to increase the driving force of the oil pump, it is necessary to increase the load on the engine in some way, which causes a reduction in fuel efficiency.

In this embodiment, the hydraulic pressure of the secondary pulley 2 is set to the minimum required hydraulic pressure value, and thereafter, the hydraulic pressure value of the primary pulley 1 is set based on the target gear ratio, thereby improving fuel efficiency. Let me. Further, a lower limit guard is set for the hydraulic pressure command value to the primary pulley 1, and when the target hydraulic pressure on the primary pulley 1 side falls below the lower limit guard value during a transient response or the like, the hydraulic pressure command value of the primary pulley 1 is set. And the compensation value based on the lower limit guard value is compensated for the secondary pulley 2. As a result, feedback control for a continuously variable transmission that can improve responsiveness to a target gear ratio while suppressing deterioration in fuel efficiency is realized.

Next, feedback control of the continuously variable transmission, which is a feature of this embodiment, will be described.

The feedback control system controls the primary pulley side pressure control valve 4 and the secondary pulley side pressure control valve 5 by the control unit 35 shown in FIG. Thus, the belt 3 on the primary pulley 1 side
Of the belt 3 on the secondary pulley 2 side is controlled, and the speed ratio is controlled to the target speed ratio.

The control unit 35 comprises an engine torque estimating means 7, a target gear ratio setting means 6, and a secondary pulley required oil pressure calculating means 8 as a second control means.
, Secondary pressure measuring means 9 and actual gear ratio detecting means 14
The hydraulic pressure instruction value is set based on the parameters obtained from the above, and the pressure-current conversion processing means 12 and 19 convert the hydraulic pressure instruction value into a current value to which a desired hydraulic pressure can be applied. Give to.

The engine torque estimating means 7 carries out processing for estimating the torque of the engine 20 from the engine speed and the throttle opening. The target gear ratio setting processing means 6 carries out the vehicle speed or the rotational speed of the secondary pulley and the throttle opening. The processing for setting the target gear ratio is performed. The secondary pulley required hydraulic pressure calculation processing means 8 performs processing for setting a hydraulic pressure instruction value required for the secondary pulley 2, and the secondary pressure detection means 9 measures the hydraulic pressure of the secondary pulley 2. The actual speed ratio detecting means 14 detects the actual speed ratio based on the ratio between the rotation speed of the secondary pulley 2 and the rotation speed of the primary pulley 1. The pressure-to-current conversion processing means 12 and 14 are elements for converting a hydraulic pressure instruction value into a current value for driving an actuator (not shown).

The control unit 35 controls the hydraulic pressure of the primary pulley 1 and the secondary pulley 2 based on the parameters set by the above means.

The secondary required oil pressure calculation processing means 8 includes the engine torque estimation processing means 7 and the actual speed ratio detection processing means 1
Then, the required hydraulic pressure command value for the secondary pulley 2 is calculated from the above. The gear ratio → hydraulic conversion processing means 15 as the first control means includes a command oil pressure value of the secondary pulley 2 calculated by the secondary required oil pressure calculation processing means 8 and a target gear ratio calculated by the target gear ratio setting processing means 6. , The required hydraulic pressure value for the primary pulley 1 is set.

Scheduling mode PID control means 1
0 feedback-controls the oil pressure instruction value in order to reduce the deviation between the target gear ratio obtained from the target gear ratio setting processing means 6 and the actual gear ratio obtained from the actual gear ratio detecting means 4. The primary lower-limit guard processing unit 17 as a lower-limit guard unit sets a lower limit of the hydraulic pressure applied to the primary pulley 1 and performs a guard process on the hydraulic pressure instruction value of the primary pulley 1.

The primary hydraulic cutoff processing means 18
When the hydraulic pressure command value of the primary pulley 1 obtained by the gear ratio → hydraulic pressure conversion processing means 15 is compared with the lower limit guard value obtained by the primary lower limit guard processing means 17, and the hydraulic pressure command value of the primary pulley 1 falls below the lower limit guard value. Next, a process of calculating the difference between the hydraulic pressure instruction value and the lower limit guard value is performed. The secondary hydraulic pressure compensation processing means 11 as a compensating means is required for the secondary pulley 2 based on the hydraulic pressure instruction value of the secondary pulley 2 obtained by the secondary required hydraulic pressure calculation processing means 8 and the value calculated by the primary hydraulic pressure cutoff processing means 18. Calculate the appropriate hydraulic pressure compensation value.

The PID processing means 16 obtains a deviation from the secondary pressure sensor value obtained by the secondary pressure measuring means 9 and the hydraulic pressure compensation value of the secondary pulley 2 obtained from the secondary hydraulic pressure compensation processing means 11, and provides feedback on the deviation. Control is performed and input to the pressure → current conversion processing 12. Similarly, the primary lower limit guard processing means 17 inputs the obtained oil pressure command value of the primary pulley 1 to the pressure → current conversion processing means 19.

The control flow will be described with reference to the flowchart of FIG.

In step S1, the estimated engine torque value is estimated by the engine torque estimation processing means 7, and the target gear ratio is set based on the target gear ratio setting processing means 6. The actual gear ratio detection processing means 14 calculates the actual gear ratio from the ratio between the rotational speed of the primary pulley 1 and the rotational speed of the secondary pulley 2.

In step S2, the hydraulic pressure required for preventing the belt slip from occurring and reducing the durability of the continuously variable transmission 23, that is, the hydraulic pressure of the secondary pulley 2, is determined based on the estimated engine torque and the target gear ratio obtained in step S1. The command value is calculated by the secondary required oil pressure calculation processing means 8.

In step S3, the target gear ratio is determined from the gear ratio → hydraulic pressure conversion processing means 15 based on the hydraulic pressure command value of the secondary pulley 2 calculated in step S2 and the target gear ratio and engine torque estimated value obtained in step S1. A hydraulic pressure instruction value of the primary pulley 1 necessary for realizing the same is calculated.

In step S4, a deviation between the target gear ratio and the actual gear ratio is calculated in order to make the actual gear ratio follow the target gear ratio, and feedback control according to the difference is performed by the sliding mode PID processing means 10. Do it. In this embodiment, sliding mode PID control is used as feedback control. FIG. 3 shows the details of this subroutine.

Step S7 in FIG. 3 is the same as step S3 described above.
The hydraulic feedforward value of the primary pulley 1 is calculated from the hydraulic pressure command value of the secondary pulley 2, the target gear ratio, and the engine torque estimated value. Next, step S8
In step 2, a deviation between the target speed ratio and the actual speed ratio is obtained. The correction amount for correcting this deviation is represented by the following relationship.

Correction amount = proportional correction amount + nonlinear proportional correction amount +
Non-linear integral correction amount + differential correction amount Then, the above-mentioned respective correction amounts are obtained so that the deviation between the target speed ratio and the actual speed ratio becomes zero. As the sliding mode PID control means, a proportional correction amount calculation is performed in step S9a, a boundary layer width with respect to the nonlinear proportional correction amount is calculated from the target gear ratio and the throttle opening in step S9b, and the nonlinear proportional correction amount is calculated in step 9c. Calculate.

Here, as shown in FIG. 19, the boundary layer width means the width of the deviation e until the gain Ppp set based on the deviation e is saturated. When the boundary layer width is large (boundary layer width B), the change in gain with respect to the deviation e is small, and when the boundary layer width is small (boundary layer width A).
Changes the gain with respect to the deviation e.

In step S10a, the boundary layer width for the nonlinear integral correction amount is calculated from the target gear ratio and the throttle opening in the same manner as in step S9b. In step S10b, the nonlinear integral correction amount is calculated. In step S11, a differential correction amount calculation is performed. Then, in step S12, a feedback correction value is added to the hydraulic pressure feedforward value of the primary pulley 1 obtained above to calculate a hydraulic pressure instruction value of the primary pulley 1, and this routine ends.

When the deviation between the target speed ratio and the actual speed ratio is small, the gain is set in accordance with the sliding mode control so as to exhibit stable controllability.
Further, when the deviation of the speed ratio becomes large as in the case of a transient response, the gain is set in accordance with the deviation amount, so that the large deviation can be quickly followed to the target speed ratio. Further, the above-mentioned feature makes it possible to reduce the number of adaptation man-hours because the traveling mode determination and the like are not required as compared with the gain scheduling PID control described later.
At the same time, it leads to cost reduction.

By the way, depending on the feedback correction amount such as at the time of transient response, the hydraulic pressure command value of the primary pulley 1 may become a very small value or a negative value.

In such a case, the hydraulic pressure applied to the primary pulley 1 becomes low, and the belt 3 slips, so that a desired gear ratio cannot be realized. Therefore, the oil pressure at which the belt 3 slips is set as the lower limit guard value, and when the oil pressure instruction value of the primary pulley 1 falls below the lower limit guard value, the oil pressure instruction value of the primary pulley 1 is set at the lower limit guard value.

However, if the hydraulic pressure of the primary pulley 1 is set to the lower limit guard value, the hydraulic pressure ratio between the secondary pulley 2 and the primary pulley 1 changes, making it impossible to control to a desired gear ratio. Therefore, in step S5 in FIG. 2, a hydraulic pressure compensation amount necessary for the hydraulic pressure command value of the secondary pulley 2 is calculated in order to obtain a desired gear ratio by the lower limit guard means and the compensation means.

Hereinafter, the details of step S5 will be described with reference to the flowchart of FIG.

In step S14, the primary lower limit guard processing means 17 sets the lower limit to the oil pressure at which the primary pulley 1 does not slip according to the map according to the target gear ratio and the estimated engine torque value or the actual gear ratio and the hydraulic pressure command value of the secondary pulley 2. Set the guard value. Details of the setting of the lower limit guard value will be described later.

In step S15, when the previously determined lower limit guard value is compared with the hydraulic pressure instruction value of the primary pulley 1, if the hydraulic pressure instruction value of the primary pulley 1 falls below the lower limit guard value, the process proceeds to step S16. .

Setting the hydraulic pressure command value of the primary pulley 1 to the lower limit guard value causes a problem that a desired gear ratio cannot be maintained. Therefore, in order to control the actual gear ratio to the target gear ratio, the processing from step S16 to step S19 is performed by the correcting means to correct the hydraulic pressure instruction value of the secondary pulley 2.

In step S16, first, a difference between the lower limit guard value and the hydraulic pressure command value of the primary pulley 1 is determined. Hereinafter, the difference between the lower limit guard value and the hydraulic pressure instruction value of the primary pulley 1 is referred to as a primary guard cutoff hydraulic pressure.

Next, in step S17, an input torque ratio is obtained from the estimated engine torque value and the primary guard cutoff hydraulic pressure used in step S16. The input torque ratio is a value obtained by (estimated engine torque value / maximum transmission torque), and maximum transmission torque is the maximum torque that can be transmitted by the continuously variable transmission according to the estimated engine torque value.

Then, in step S18, the hydraulic pressure ratio is calculated. FIG. 6 shows the hydraulic ratio between the primary pulley 1 and the secondary pulley 2 for each input torque ratio with respect to the target speed ratio when the horizontal axis is the target picture speed ratio and the vertical axis is the hydraulic ratio. In the present embodiment, this is provided in advance as a map, and if the input torque ratio and the target gear ratio are determined, the hydraulic pressure ratio can be uniquely obtained. After determining the hydraulic pressure ratio, the process proceeds to step S19.

In step S19, the secondary hydraulic pressure compensating means 11 divides the primary hydraulic pressure cutoff hydraulic pressure by the hydraulic pressure ratio to calculate a hydraulic pressure compensation value of the secondary pulley 2 required to obtain a desired hydraulic pressure ratio. Less than,
The hydraulic pressure compensation value required for the secondary pulley 2 is called a secondary hydraulic pressure compensation value. As described above, the secondary hydraulic pressure compensation value obtained from step S16 to step S19 is:
It is determined from the proportional relationship of the gear ratio to the primary guard cutoff hydraulic pressure.

However, even at the same oil pressure ratio, the oil pressure of the primary pulley 1 and the oil pressure of the secondary pulley 2 may vary due to a mechanical error. That is, the primary guard value may be different even with the same hydraulic pressure ratio. As a result, there is a possibility that the gearshift may not be performed even at the same hydraulic pressure ratio. In consideration of the above-described reasons, in step S20, a calculation for multiplying a predetermined hydraulic pressure is performed in order to perform the gearshift safely. Hereinafter, the above is referred to as calculation of the safety factor.
Next, the process proceeds to step S21, in which a lower limit guard process is performed on the hydraulic pressure instruction value of the primary pulley 1, and the flow in FIG. 4 ends.

When the lower limit guard value is smaller than the hydraulic pressure command value of the primary pulley 1 in step S15, the hydraulic pressure compensation value of the secondary pulley 2 is set to 0 as shown in step S22. When the calculation of the hydraulic pressure compensation value of the secondary pulley 2 is completed, the process proceeds to step S21 to perform the lower limit guard processing of the hydraulic pressure instruction value of the primary pulley 1 and FIG.
Then, the process goes to step S6 in FIG.

Finally, in step S6 of FIG. 2, the final hydraulic command value of the secondary pulley 2 and the final hydraulic command value of the primary pulley 1 obtained from the above control flow are used to operate the actuator. The current is converted into a necessary current value, the hydraulic pressure applied to each pulley is controlled, and this flow ends.

Referring to FIG. 7, details of the lower limit guard processing means for setting the lower limit guard value to the hydraulic pressure instruction value of the primary pulley 1 in step S14 shown in the flowchart of FIG.

FIG. 7 shows a step S14 based on the target gear ratio and the estimated engine torque obtained in the step S14a.
At 14b, a lower limit guard value is obtained from a pressure lower limit map on the primary pulley 1 side that prevents belt slip or damage to the continuously variable transmission.

This pressure lower limit map is determined by the mechanical characteristics of the continuously variable transmission and has the characteristics as shown in FIG. That is, the primary pressure lower guard value increases as the target gear ratio increases, and increases as the engine torque increases. Further, since the mechanical characteristics of the continuously variable transmission include variations such as individual differences or measurement errors, a safety factor is multiplied in step S14c so that the shift is performed safely in anticipation of the variations.

An example of the actual operation will be described with reference to the time chart of FIG. FIG. 5 shows an operation of the control device when a downshift is performed according to, for example, a driver's will. The target gear ratio changes in the Lo direction simultaneously with the downshift. At this time, a deviation occurs between the actual speed ratio and the target speed ratio, and feedback correction is performed on the hydraulic pressure instruction value of the primary pulley 1 according to the deviation.

However, if the hydraulic pressure command value of the primary pulley 1 to which the feedback correction has been applied has a large deviation from the target gear ratio, the hydraulic pressure command value of the primary pulley 1 falls below the lower limit guard value. Here, the primary cutoff hydraulic pressure is obtained by subtracting the hydraulic pressure instruction value of the primary pulley 1 from the lower limit guard value of the primary pulley 1. After calculating the primary cutoff hydraulic pressure, a lower limit guard process is performed on the hydraulic pressure instruction value of the primary pulley 1 so that the durability of the continuously variable transmission does not decrease.

Next, based on the primary cutoff hydraulic pressure,
Using the target speed ratio and the input torque ratio, a required increase in the hydraulic pressure of the secondary pulley 2, that is, a secondary hydraulic pressure compensation value, is calculated from the hydraulic ratio between the primary pulley 1 and the secondary pulley 2 for achieving the target speed ratio. The secondary hydraulic pressure command value is compensated by the set secondary hydraulic pressure compensation value.

As described above, according to the first embodiment, in the method of performing feedback control based on the difference between the target value and the actual value in the control device of the continuously variable transmission, the control is usually performed on the minimum necessary pulley. Fuel economy is minimized by oil pressure, and the oil pressure instruction value after feedback correction during transient
When the value is lower than the lower limit guard, the shift responsiveness can be temporarily secured by calculating the amount of increase in the oil pressure of the other pulley based on the cutoff by the guard process.
When the shift is completed and the gear does not fall below the lower limit guard, the pressing force returns to the minimum necessary, so that it is possible to achieve both the minimum fuel consumption and the shift responsiveness.

Further, by setting a lower limit value map in the lower limit guard so as to prevent a belt slip and a reduction in durability of the continuously variable transmission, the above control can be performed without impairing controllability. it can.

<Second Embodiment> In the second embodiment, instead of the lower limit guard operation processing of FIG. 7 of the first embodiment, FIG.
The processing shown in is performed.

In the process of FIG. 8, there is a lower limit of the pressure that can be realized by the centrifugal hydraulic pressure in the primary pulley 1 and the secondary pulley 2 of the continuously variable transmission 23, and this is set as the lower limit guard of the hydraulic pressure instruction value. The centrifugal hydraulic pressure is a hydraulic pressure generated by applying a hydraulic pressure according to the rotation speed of the primary pulley 1 without supplying a pressing force to the hydraulic pressure in the pulley by the rotation of the primary pulley 1.

In step S14e, a lower limit guard value is obtained by searching a lower limit hydraulic pressure map of the primary pulley 1 as shown in FIG. In this figure, the centrifugal oil pressure increases as the rotation speed increases. For example, as compared with the lower limit guard process shown in the first embodiment, the lower limit guard value used in the first embodiment increases according to the engine torque value and the target gear ratio. Therefore, by setting the centrifugal oil pressure to the lower limit guard value, it is possible to prevent belt slip and damage to the continuously variable transmission 23 and realize control excellent in shift response. Then, in step S14c, the safety factor is multiplied for the same reason as in FIG. 7 of the first embodiment.

By setting the lower limit based on the centrifugal oil pressure generated in the pulley as described above, it is possible to prevent belt slip and decrease in the durability of the continuously variable transmission 23, and to achieve safe control excellent in shift response. Can be performed.

<Third Embodiment> In the third embodiment, the processing shown in the flowchart of FIG. 15 is executed instead of the lower limit guard processing in step S14 of FIG. 7 of the first embodiment.

The flowchart shown in FIG. 15 performs a lower limit guard process on the oil pressure command value in the pressure adjustment range of the pressure control valves 4 and 5 with the oil pressure applied to the primary pulley 1 and the secondary pulley 2. When a current flows through the solenoids of the pressure control valves 4 and 5, as shown in FIG. 17, the actual pressure on the high pressure side and the low pressure side deviates from the ideal pressure characteristics. Here, a pressure range in which the pressure control valves 4 and 5 can be actually controlled due to this deviation is referred to as a pressure regulation range. In this embodiment, the lower limit is the hydraulic pressure applied in a state where no current flows.

In step S14g, the pressure control valves 4, 5
The lower limit is set in the adjustment range of step S14c.
Therefore, the safety factor is multiplied for the same reason as in FIG. 7 of the first embodiment.

By setting the lower limit as described above, it is possible to prevent a belt slip and a decrease in the durability of the continuously variable transmission 23, and to perform safe control.

<Fourth Embodiment> In the fourth embodiment, instead of the control for calculating the oil pressure compensation required for the oil pressure command value of the secondary pulley 2 in step S5 in FIG. 2 of the first embodiment, FIG. Is executed.

FIG. 11 does not require the processing of step S17 of FIG. 4 in the first embodiment. That is, complicated calculations for obtaining the hydraulic pressure ratio are not required. In order to omit complicated calculations, in the fourth embodiment, the hydraulic pressure compensation required for the secondary pulley 2 is obtained by using the past hydraulic ratio as the hydraulic ratio, and in the present embodiment, the previous hydraulic ratio. Note that by using the previous oil pressure ratio, the memory for storing the previous oil pressure ratio can be minimized.

This embodiment will be described with reference to the time chart of FIG. FIG. 13 shows that the vehicle starts at a start B from a stop state A, shifts to a steady run at a steady run C, and from there,
FIG. 9 is a diagram showing a series of changes in the speed ratio that is kicked down by a kickdown D and reaches a target speed ratio E.

After the steady running C shown in FIG. 13, the speed ratio during normal running except for starting does not change much compared to the speed ratio at the time of starting, so that the hydraulic pressure ratio does not change significantly. For this reason, during normal running other than when starting, the previous hydraulic ratio can be used to determine the hydraulic pressure compensation value required for the secondary pulley 2, similar to the hydraulic pressure compensation for the secondary pulley 2 of the first embodiment. The effect of can be obtained. Further, since complicated logic is not required, the number of adaptation steps and the cost can be reduced.

<Fifth Embodiment> A fifth embodiment is different from the first embodiment in that the processing for calculating the hydraulic pressure compensation required for the hydraulic pressure command value of the secondary pulley 2 in steps S17 to S19 in FIG. The flowchart shown in FIG. 18 is executed.

As compared with the first embodiment, the processing in steps S17 and S18 in FIG. 4 is not required. That is, complicated calculations for obtaining the hydraulic pressure ratio are not required. In order to omit this complicated calculation, in the fifth embodiment, the hydraulic pressure ratio is set to 0.5
A typical coefficient is set in the range of 0.7 to 0.7, and this representative coefficient is used as the hydraulic pressure ratio, thereby obtaining the hydraulic pressure compensation required for the secondary pulley. At the time of shifting, the smaller the coefficient is, the larger the hydraulic pressure compensation value for compensating the secondary pulley 2 is. Therefore, the coefficient set within the range of 0.5 to 0.7 can be safely used in a frequently used gear ratio. This is the value at which the shift is performed.

The present embodiment will be described below with reference to FIG.

After the primary oil pressure cutoff is calculated in step S16, in step S19a,
The secondary pressure compensation value is calculated by dividing the primary hydraulic pressure cutoff value by a predetermined coefficient within the range of 0.5 to 0.7. Thereafter, the process proceeds to step S20, where the safety factor is calculated.

Thus, step S shown in the first embodiment is performed.
A complicated operation such as 17 becomes unnecessary. This achieves a reduction in the number of adaptation steps and cost.

<Sixth Embodiment> A sixth embodiment will be described with reference to FIG.

The sixth embodiment is different from the first embodiment in that a gain scheduling P
ID control is used.

The gain scheduling PID control is realized by changing the sliding mode PID processing means 10 to a gain scheduling PID processing means (not shown). Here, in order to execute the gain scheduling PID control processing, a vehicle traveling mode determining means for determining a control gain is required. In the gain scheduling PID control, an optimal gain can be set according to the vehicle traveling mode. For example, by switching the feedback correction amount at a high gain during steady driving with relatively little change in the gear ratio, and at a high gain during transient driving such as kickdown or downshift that requires a quick gear ratio response, It is possible to achieve both control and responsiveness.

<Seventh Embodiment> A seventh embodiment will be described with reference to FIG.

In the seventh embodiment, PID control processing means (not shown) is used in place of the scheduling mode PID processing 10 of the first embodiment. FIG. 16 shows a flowchart of the PID control processing. In step S7, the feedforward value of the primary pulley 1 is calculated from the hydraulic pressure command value of the secondary pulley 2, the target gear ratio, and the estimated engine torque value. In step S8, a deviation between the target speed ratio and the actual speed ratio is determined. Then, steps S9, S10, and S11 are performed so that the deviation becomes zero.
The PID feedback correction is performed as shown in FIG. In step S12, a feedback correction value is added to the feedforward value obtained above to calculate a hydraulic pressure instruction value for primary pulley 1.

Feedback control can also be performed by the above-described PID control.

<Eighth Embodiment> In the eighth embodiment, the lower limit guard values used in the first, second, and third embodiments are set in combination.

That is, in a certain driving state, the lower limit guard value obtained from the vehicle speed or the primary rotation speed shown in FIG.
The lower limit guard value obtained from the target gear ratio of FIG.
The lower limit value of the pressure regulation range is compared with the lower limit value of the pressure regulation range, and the one showing the largest lower limit guard value is defined as the lower limit guard value of the present embodiment.

As a result, the lower limit guard process suitable for various operating conditions can be executed.
Is more accurately set, it is possible to improve the responsiveness of the feedback control.

In the above embodiment, the hydraulic pressure supplied to the primary pulley is set to be lower than the hydraulic pressure supplied to the secondary pulley.
The present invention can be applied to a case where the hydraulic pressure supplied to the primary pulley is set higher than the hydraulic pressure supplied to the secondary pulley.

Specifically, a lower limit guard is set for the hydraulic pressure command value set when controlling the hydraulic pressure of the secondary pulley, and when the hydraulic pressure command value of the secondary pulley falls below the lower limit guard, the lower limit guard value is set. The hydraulic pressure command value on the primary pulley side may be compensated based on the difference between the hydraulic pressure command value and the hydraulic pressure command value. For example, a value obtained by multiplying the difference between the lower limit guard value and the hydraulic pressure instruction value by the hydraulic pressure ratio may be calculated as a compensation value, and the compensation may be performed by adding the compensation value to the hydraulic pressure instruction value on the primary side.

Thus, even if the hydraulic pressure supplied to the primary pulley is set higher than the hydraulic pressure supplied to the secondary pulley, the same effect as the present invention can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of a continuously variable transmission and a control device according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing a main routine of control of a continuously variable transmission performed in the present embodiment.

FIG. 3 is a flowchart of a subroutine that uses scheduling mode PID control for speed ratio feedback control of the present embodiment.

FIG. 4 is a flowchart illustrating a subroutine of control for obtaining a secondary hydraulic pressure compensation value according to the present embodiment.

FIG. 5 is a diagram showing feedback control during a transient response as an actual operation of the embodiment.

FIG. 6 is a hydraulic ratio map for obtaining a hydraulic pressure compensation value of a secondary pulley according to the present embodiment.

FIG. 7 is a flowchart illustrating a subroutine for calculating a lower limit guard value according to the present embodiment.

FIG. 8 is a flowchart illustrating a subroutine for calculating a lower limit guard value according to the present embodiment.

FIG. 9 is a diagram of the centrifugal oil pressure depending on the rotation speed in the present embodiment.

FIG. 10 is a diagram for calculating a primary pressure lower limit guard value for each engine torque estimated value with respect to a target gear ratio in the embodiment.

FIG. 11 is a flowchart illustrating a subroutine for calculating a secondary hydraulic pressure compensation value according to the present embodiment.

FIG. 12 is a map for obtaining a hydraulic pressure ratio from a target gear ratio according to the present embodiment.

FIG. 13 is a diagram showing a hydraulic pressure ratio during traveling of the vehicle according to the embodiment.

FIG. 14 is a flowchart illustrating a subroutine using gain scheduling PID control for feedback control according to the present embodiment.

FIG. 15 is a flowchart illustrating a subroutine of a lower limit guard operation according to the present embodiment.

FIG. 16 shows a PID for the shift feedback control of the present embodiment.
9 is a flowchart illustrating a subroutine using control.

FIG. 17 is a diagram showing a minimum value as a lower limit guard in the pressure adjustment range of the actuator according to the embodiment.

FIG. 18 is a flowchart illustrating a subroutine for calculating a secondary hydraulic pressure compensation value according to the present embodiment.

FIG. 19 is a diagram for setting a gain by a boundary layer width in the sliding mode PID control of the embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Primary pulley 2 Secondary pulley 3 Belt 4 Primary pulley side pressure control valve 5 Secondary pulley side pressure control valve 6 Means for setting target gear ratio 7 Means for estimating engine torque value 8 Processing means for calculating hydraulic pressure required for secondary pulley 9 Processing means for measuring secondary pressure 10 Scheduling PID processing means 11 Processing means for compensating for secondary hydraulic pressure 12 Processing means for converting pressure to current 14 Processing means for detecting actual gear ratio 15 Primary pulley based on gear ratio and secondary hydraulic pressure Processing means for obtaining the hydraulic pressure instruction value 16 PID processing means 17 Processing means for setting the lower limit guard value 18 Hydraulic cutoff processing means for the primary pulley below the lower limit guard value 20 Engine 21 Torque converter 22 Forward / reverse switching mechanism 23 Continuously variable transmission

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3J552 MA07 MA12 MA26 NA01 NB01 PA12 PA20 PA59 PA63 SA36 SB02 TA01 TA10 TB03 TB11 VA18W VA18Y VA74W VA74Y VC02Z

Claims (13)

[Claims] 1. A continuously variable transmission in which a primary pulley and a secondary pulley are linked by a belt and a driving force of an internal combustion engine is transmitted to wheels at a predetermined gear ratio. Target speed ratio setting means for setting the target speed ratio, and setting a hydraulic pressure instruction value for controlling the primary pulley so as to achieve the target speed ratio, and setting the primary pulley so as to achieve the instruction value. First control means for controlling the supplied hydraulic pressure, and a hydraulic pressure instruction value for controlling the secondary pulley so as to attain the target gear ratio, and the secondary pulley is controlled to attain the instruction value. Second control means for controlling the supplied hydraulic pressure; and a lower limit for guarding a hydraulic pressure instruction value of a lower supplied hydraulic pressure among a supplied hydraulic pressure of the primary pulley and a supplied hydraulic pressure of the secondary pulley with a predetermined lower limit value. A guard means, wherein the supply oil When the lower hydraulic pressure command value is equal to or less than the predetermined lower limit value, the correction for correcting the other hydraulic pressure instruction value to a larger value based on the lower limit value and the lower hydraulic pressure instruction value for the supplied hydraulic pressure. A control device for a continuously variable transmission, characterized by comprising means. 2. The supply hydraulic pressure of the primary pulley is lower than the supply hydraulic pressure of the secondary pulley, the lower limit guard means guards a hydraulic pressure instruction value of the primary pulley at a predetermined lower limit value, and the correction means The control device for a continuously variable transmission according to claim 1, wherein a hydraulic pressure instruction value of the secondary pulley is corrected based on a hydraulic pressure instruction value of the primary pulley and the lower limit value. 3. The control device for a continuously variable transmission according to claim 2, further comprising: a supply hydraulic pressure ratio setting unit configured to set a supply hydraulic pressure ratio between a supply hydraulic pressure of the primary pulley and a supply hydraulic pressure of the secondary pulley. The correction means adds the correction value to the hydraulic pressure instruction value of the secondary pulley based on a difference between the hydraulic pressure instruction value of the primary pulley and the lower limit value, and the correction value is the supply hydraulic pressure. A control device for a continuously variable transmission, which is calculated based on a hydraulic pressure ratio set by a ratio setting means and a difference between a hydraulic pressure instruction value of the primary pulley and the lower limit value. 4. The control device for a continuously variable transmission according to claim 3, wherein input torque ratio setting means for setting an input torque ratio between an engine torque and a maximum torque that can be transmitted by the continuously variable transmission; The oil pressure setting means includes a map for obtaining the supply oil pressure ratio from a relationship between the target gear ratio and the input torque ratio, wherein the correction value is the supply oil pressure ratio obtained from the map, and a hydraulic pressure of the primary pulley. A control device for a continuously variable transmission, which is calculated based on an instruction value and a difference between the lower limit value and the instruction value. 5. The control device for a continuously variable transmission according to claim 4, wherein the map is a map for obtaining the supply hydraulic pressure from a predetermined relationship between the representative input torque ratio and the target gear ratio. A control device for a continuously variable transmission. 6. The control device for a continuously variable transmission according to claim 4, wherein the supply hydraulic pressure ratio is an arbitrary coefficient. 7. The control device for a continuously variable transmission according to claim 4, wherein the supply hydraulic pressure ratio uses a past supply hydraulic pressure ratio. 8. The control device for a continuously variable transmission according to claim 1, wherein the lower limit guard value is set to a value that prevents the belt from slipping. A control device for a continuously variable transmission, characterized by: 9. The control device for a continuously variable transmission according to claim 1, wherein the lower limit guard value is determined by a centrifugal hydraulic pressure generated by a rotational motion of the primary pulley itself. A control device for a continuously variable transmission, wherein the control device is set based on: 10. The control device for a continuously variable transmission according to claim 1, wherein the lower limit guard value is a hydraulic pressure supplied to the primary pulley or a hydraulic pressure supplied to the secondary pulley. A control device for a continuously variable transmission, wherein the control device is set in consideration of a lower limit value of a mechanical variation of an actuator to be adjusted. 11. The control device for a continuously variable transmission according to claim 1, further comprising: feedback control means for performing feedback control of the primary pulley supply hydraulic pressure and the secondary pulley supply hydraulic pressure, wherein the feedback is provided. The control means includes a sliding mode PID control means for continuously changing a feedback gain used for the feedback control according to a deviation between the target gear ratio and an actual gear ratio. Control device. 12. The control device for a continuously variable transmission according to claim 1, wherein a traveling mode detecting means for detecting a traveling state of the vehicle, the primary pulley supply hydraulic pressure and the secondary pulley supply hydraulic pressure. And a feedback control means for performing feedback control on the gain scheduling PID control means for setting a feedback gain used for the feedback control based on the traveling mode detected by the traveling mode detection means. A control device for a continuously variable transmission, comprising: 13. A continuously variable transmission in which a primary pulley and a secondary pulley are linked by a belt to transmit a driving force of an internal combustion engine to wheels at a predetermined gear ratio. Target speed ratio setting means for setting the target speed ratio of the motor; setting a target operation amount for controlling the primary pulley so as to achieve the target speed ratio; and controlling the operation amount so as to achieve the target operation amount. A first control unit that sets a target operation amount for controlling the secondary pulley so as to achieve the target gear ratio, and controls the operation amount so as to achieve the target operation amount. And lower limit guard means for guarding one of the target operation amount of the primary pulley and the target operation amount of the secondary pulley at a predetermined lower limit value. The amount is determined by the lower guard means. When equal to or less than the lower limit value is guarded, the control device for a continuously variable transmission, characterized in that it comprises a correcting means for correcting the other control input variable on the basis of said target operation variables and said lower limit guard value.