JPH0428948B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of controlling a continuously variable transmission for a vehicle, and particularly to speed ratio control during rapid operation of an acceleration operating member of a vehicle.

Prior Art The present applicant previously proposed a continuously variable transmission mounted on a vehicle in Japanese Patent Application No. 57-67362 (Japanese Unexamined Patent Publication No. 58-184347).
The application was filed as In vehicles equipped with such continuously variable transmissions, the actual acceleration, such as the throttle valve opening, is A control target value is determined based on the manipulated variable, and the speed ratio of the continuously variable transmission is adjusted so that the actual engine rotational speed or speed ratio becomes the control target value. In such continuously variable transmissions for vehicles, when the driver suddenly operates the acceleration operation member, the control target value is rapidly changed to increase the driving force of the vehicle, and the control target value is changed rapidly to increase the driving force of the vehicle. The speed ratio of the continuously variable transmission is changed in order to change the engine rotational speed or speed ratio to match the changed control target value.

Problems to be Solved by the Invention By the way, as described above, in the case where the control target value is rapidly changed in connection with a sudden operation of the acceleration operation member, for example, if the operation is a sudden acceleration operation. Sometimes, because the engine rotational speed is rapidly increased, a significant portion of the engine output torque is consumed to increase the rotational speed of the engine with a given rotational inertia weight, during which the engine output torque The torque that contributes to driving the vehicle did not increase as expected, and as a result, sufficient acceleration performance during acceleration operations, ie, acceleration response and acceleration feeling, etc., could not be obtained.

On the other hand, the applicant first proposed that during a transient period when the acceleration operating member is suddenly operated, a transient control target value that changes more slowly than the normal control target value is used. He devised a control method for a continuously variable transmission and filed an application. Special request 1988-
This is number 17550. According to this, during a sudden acceleration operation, the transient control target value does not change stepwise like a normal control target value, but changes smoothly, so the engine rotation speed increases gradually and acceleration is smooth. becomes.

However, in the conventional control method described above, the control target value during transition is changed in the same way when the acceleration operation member is suddenly accelerated and when it is suddenly decelerated. It was difficult to obtain suitable drivability at both times. In other words, for example, if the transient control target value is made gentle to improve drivability during sudden acceleration operations as described above, the engine rotational speed will gradually decrease even during sudden deceleration operations, compared to normal deceleration operations. As a result, deceleration occurs without the feeling of engine braking, resulting in an uncomfortable feeling, which may impair drivability.

The present invention has been made against the background of the above circumstances, and its purpose is to provide a continuously variable transmission for a vehicle that can provide suitable drivability both during acceleration and deceleration operations. The objective is to provide a control method.

Means for Solving the Problems The gist of the present invention to achieve the above object is that in a continuously variable transmission for a vehicle in which the gear ratio is changed steplessly, an actual acceleration operation is performed based on a predetermined relationship. A control method that determines a control target value based on the amount and controls the engine rotation speed or speed ratio to follow the control target value,
During a transient period in which the acceleration operating member of the vehicle is rapidly operated, a transient control target value that changes stepwise by a predetermined width and then gradually changes after a predetermined time after the operation is replaced with the control target value. The purpose is to set the change width of the stepwise change portion of the transient control target value to be smaller during a sudden acceleration operation than during a sudden deceleration operation.

Operation and Effects of the Invention With this arrangement, during a transient period in which the acceleration operating member of a vehicle is rapidly operated, during a transient period in which the acceleration operating member of the vehicle changes stepwise by a predetermined width after the operation, and then changes gradually. The control target value is
The change width of the stepwise change portion of the transient control target value, which is set in place of the control target value, is made smaller during a sudden acceleration operation than during a sudden deceleration operation. Therefore, during a sudden acceleration operation, the stepwise change in the transient control target value has a smaller change range than during a sudden deceleration operation, so the engine rotation speed increases smoothly during a sudden acceleration operation. Acceleration becomes smoother. In addition, during sudden deceleration operations, the range of change in the stepwise change in the transient control target value is larger than during sudden acceleration operations, so the engine rotation speed decreases more quickly than during acceleration, resulting in an appropriate adjustment. The deceleration feels like engine braking. Therefore, suitable drivability can be obtained both during acceleration and deceleration operations.

Example Embodiments of the present invention will be described with reference to the drawings.

In FIG. 1, the CVT 10 includes an input shaft 12 and an output shaft 14 that are parallel to each other. Input shaft 1
2 is provided coaxially with respect to the crankshaft 18 of the engine 16, and is connected to the crankshaft 1 through a clutch 20.
Connected to 8. The input pulleys 22a and 22b are provided facing each other, and one input pulley 2
2a is a movable pulley that can move in the axial direction;
It is fixedly provided on the input shaft 12 in the rotational direction, and the other input side pulley 22b is fixed to the input shaft 12 as a fixed pulley. Similarly, output side pulley 2
4a and 24b are also provided facing each other, and one of the output side pulleys 24a is a fixed pulley that is connected to the output shaft 1.
4, and the other output side pulley 24b is provided on the output shaft 14 as a movable pulley so as to be movable in the axial direction and fixed in the rotational direction. Input side pulleys 22a, 22b and output side pulley 24a,
The opposing surface of the belt 24b is formed into a tapered shape, and the belt 26 having an isosceles trapezoid cross section is connected to the input pulleys 22a and 22b.
and the output pulleys 24a, 24b. The oil pump 28 sends oil from the oil sump 30 to the pressure regulating valve 32. The pressure regulating valve 32 is connected to the drain 34
The line pressure of the oil passage 36 is controlled by changing the amount of oil released to the oil passage 36, and the line pressure of the oil passage 36 is sent to the hydraulic cylinder of the output pulley 24b and the flow rate control valve 38. The flow control valve 38 controls the amount of oil supplied from the oil path 36 to the oil path 40 connected to the hydraulic cylinder of the input pulley 22a, and the amount of oil discharged from the oil path 40 to the drain 34. Input side pulley 2 for belt 26
2a, 22b and output side pulleys 24a, 24b
The pressing force of the belt 26 on the tapered surface of the input side pulleys 22a, 22b and the output side pulleys 24a, 24b is controlled by the hydraulic pressure of the input side hydraulic cylinder and the output side hydraulic cylinder.
As a result, the speed ratio e of the CVT 10 (=Nout/Nin, where Nout is the rotation speed of the output shaft 14, Nin is the rotation speed of the input shaft 12, and in this example, Nin = engine rotation The velocity Ne) changes. In order to suppress drive loss of the oil pump 28, the line pressure of the output side hydraulic cylinder is controlled to the minimum necessary value that can avoid slipping of the belt 26 and ensure power transmission, and is controlled by the oil pressure of the input side hydraulic cylinder. The speed ratio e is controlled.
Note that the hydraulic pressure of the input side hydraulic cylinder ≦ the hydraulic pressure of the output side hydraulic cylinder, but since the pressure receiving area of the input side hydraulic cylinder > the pressure receiving area of the output side hydraulic cylinder, the pressing force of the input side pulleys 22a and 22b is equal to the pressure receiving force of the output side hydraulic cylinder. The pressing force can be made larger than that of 24a and 24b. The input side rotation angle sensor 42 and the output side rotation angle sensor 44 detect the rotation speeds Nin and Nout of the input shaft 12 and the output shaft 14, respectively,
Water temperature sensor 46 detects the temperature of the cooling water of engine 16. An accelerator pedal 50 is provided in the driver's seat 48,
The throttle valve in the intake passage is linked to the accelerator pedal 50, and the throttle opening sensor 52 detects the throttle opening θ. A shift position sensor 54 detects the shift range of a shift lever located near the driver's seat.

FIG. 2 is a block diagram of the electronic control unit. The address data bus 56 includes a CPU 58, a RAM 60,
ROM62, I/F (interface) 64,
An A/D (analog/digital converter) 66 and a D/A (digital/analog converter) 68 are connected to each other. The I/F 64 receives pulse signals from the input side rotation angle sensor 42, the output side rotation angle sensor 44, and the shift position sensor 54,
The A/D 66 receives analog signals from the water temperature sensor 46 and the throttle opening sensor 52, and
68 outputs a pulse to the pressure regulating valve 32 and the flow rate control valve 38.

In the conventional control device as described in Japanese Patent Application No. 57-67362 (Japanese Unexamined Patent Publication No. 58-184347), the throttle opening θ is At the time point to when the operation is performed significantly, the target engine rotation speed No. is changed from the steady target engine rotation speed Nos', which was determined corresponding to the throttle opening θ1 before the operation, to the throttle opening θ2 after the operation. However, in the control system of this embodiment, as shown by the solid line in FIGS. 3 and 4, the steady target engine speed Nos is changed stepwise from Nos' to Nos. In contrast to the steady-state target engine rotation speed that changes over time, the transient target engine rotation speed No. changes stepwise by a predetermined width and then changes gradually. Target engine speed No. during this transition
is determined in steps 88 and 90, which will be described later, which are executed in a state where it is determined that the throttle opening degree θ has changed significantly. Figure 3 above shows the change in target engine speed No. during a transient period during a sudden acceleration operation when the throttle opening degree θ greatly increases, and Figure 4 shows the change in target engine speed No. during a transient period during a sudden deceleration operation when the throttle opening degree θ greatly decreases. It shows the change in target engine rotational speed No. When the throttle opening degree θ greatly increases or decreases from θ1 to θ2 at time to, the target engine rotational speed No.
Until t1, the steady target engine rotation speed Nos' is maintained at the throttle opening θ1, and then at time t1, the engine rotation speed discontinuously increases or decreases by the amount corresponding to the step change rate B, and reaches the value No.
After t1, the engine speed gradually increases or decreases at a slope C toward the steady target engine rotational speed Nos at the throttle opening θ2. Note that the step change rate B is defined as a positive number smaller than 1 by the following equation. Here, the step change rate in Figure 3 during sudden acceleration operation is
B1, step change rate in Figure 4 during sudden deceleration operation.
If B2 is set, B1<B2.

B=Nob-Nos'/Nos-Nos' The delay time A from time t0 to t1 confirms the driver's true intention to request acceleration or deceleration, and if the driver accelerates within delay time A. When the amount of depression of the pedal 50 is returned to the original level, transient control of the CVT 10 is not performed. The step change of the target engine rotational speed No. by the step change rate B is performed in order to ensure a predetermined appropriateness during a transition. slope C
The increase or decrease of the target engine rotation speed No.
To make the change in the target engine rotational speed No gradual, and to smoothly and quickly shift the actual engine rotational speed Ne to Nos.

Figure 5 shows the target engine rotational speed during a transient period, as shown in Figure 3 above, during sudden acceleration operation, for example.
When No is changed, it shows the changes in the actual engine rotation speed Ne, drive wheel torque Tp, and acceleration Gp in the longitudinal direction of the vehicle (with the forward direction being positive) with respect to the change in the target engine rotation speed No. ing.
Torque is significantly increased by changing the throttle opening from θ1 to θ2, but as shown in the figure, the target engine rotational speed during transient
Since No cannot be changed stepwise from time t1, the actual engine speed Ne rises more slowly and gradually than before, so in such a transient state, the vehicle driving force of the above torque is The proportion of torque consumed increases,
This provides a suitable acceleration feeling and acceleration response.

On the other hand, during a sudden deceleration operation, the step change rate B2, which is larger than the step change rate B1 during the acceleration operation, is used, so the target engine rotational speed No. changes more quickly than during the sudden acceleration operation. It will be done. This allows the actual engine speed
Ne decreases more quickly than during sudden acceleration, resulting in deceleration with a proper engine braking feel. Therefore, suitable drivability can be obtained both during acceleration and deceleration operations.

FIG. 6 is a flowchart of a routine for calculating the target engine rotational speed No. During acceleration or deceleration when the throttle opening θ is significantly increased or decreased, the target engine rotational speed is calculated according to the graphs in FIGS. 3 and 4. That is, during acceleration, the step change rate B is set to B1, and during deceleration, the step change rate B is set to B2 (0<B1<B2<1).
is set to In addition, during transient and steady states where the change in throttle opening θ is small, the target engine rotational speed
No is calculated using the following formula.

No=Nos′+D1・(Nos−Nos′)±D2 However, D1 and D2 are constants, and D1・(Nos−Nos′)±D21/100・(Nos−Nos′). That is, fluctuations in the target engine rotational speed are suppressed during transient and steady states when the change in the throttle opening degree θ is small. Steps to explain each step in detail
72, the difference between the steady target engine rotation speed Nos at the throttle opening θ after the opening change and the steady target engine rotation speed Nos′ at the throttle opening θ before the change is determined by the absolute value |Nos−Nos′| and the predetermined value ΔNa If |Nos−Nos′|∆Na, that is, if the throttle opening θ has changed significantly, proceed to step 74, and if |Nos−Nos′|<∆Na,
That is, if the change in throttle opening θ is small, the process advances to step 94. In step 74, the steady target engine rotation speed Nos after the change in throttle opening is compared with the steady target engine rotation speed Nos′ before the change in throttle opening. If Nos>Nos′, that is, when accelerating, step 75 is performed. To, Nos<
If it is Nos', that is, if it is decelerating, the process proceeds to step 76. In step 75, a predetermined value B1 is substituted for the step change rate B, and in step 76, a predetermined value B2 is substituted for the step change rate B. However, 0<B1<B2<1. In step 78, an elapsed time measuring timer is started. At step 80, A, C1, and C2 are read from memory. However, C1, C2
is a constant, and C1·(Nos-Nos')±C2 is equal to the slope C in FIG. In step 82, the value Tm of the elapsed time measurement timer is compared with A. If Tm<A, the process proceeds to step 84, and if TmA, the process proceeds to step 84.
Proceed to 86. In step 84, the target engine rotation speed No.
Assign Nos′ to and return to step 82. step
In step 86, the value Tm of the elapsed time measurement timer is compared with a predetermined value A, and if Tm=A, the process advances to step 88.
If Tm>A, proceed to step 90. step 88
Then, Nos'+B.(Nos-Nos') is substituted for the target engine rotational speed No, and the process returns to step 86. step 90
Then, set the target engine speed No. as C1・(Nos−Nos′)±
Increases by C2. At step 92 | Nos−No |
and a predetermined value ΔNb, |Nos−No|ΔNb
In other words, the throttle opening θ after the opening change
If the current target engine rotational speed No is far from the steady target engine rotational speed Nos at
If is close enough to Nos, exit the routine. In step 94, set No+D1 to the target engine speed No.
Substitute (Nos−Nos′)±D2.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of the entire CVT to which the present invention is applied, Fig. 2 is a block diagram of the electronic control device, and Fig. 3 is a schematic diagram of the entire CVT to which the present invention is applied.
The figure shows the change in target engine rotational speed according to the present invention during acceleration when the throttle opening is greatly increased.
Fig. 4 shows the change in target engine rotation speed according to the present invention during deceleration when the throttle opening is greatly reduced, and Fig. 5 shows the actual engine rotation speed and the change in the drive wheel speed with respect to the change in target engine rotation speed during acceleration. FIG. 6, which is a diagram showing changes in torque and acceleration in the longitudinal direction of the vehicle, is a flowchart of a routine for calculating a target engine rotational speed. 10...CVT, 16...engine, 38...flow control valve, 42...input side rotation angle sensor, 44...
Output side rotation angle sensor, 52...Throttle opening sensor.

Claims (1)

[Claims] 1. In a continuously variable transmission for a vehicle in which the speed ratio is changed steplessly, a control target value is determined based on the actual acceleration operation amount from a predetermined relationship, and the engine rotational speed or A control method for controlling the ratio to follow the control target value, and in a transient state where an acceleration operating member of the vehicle is rapidly operated, the ratio is changed stepwise by a predetermined width after a predetermined time from the operation. A transient control target value that changes gradually after the change is set in place of the control target value, and the change width of the stepwise change part of the transient control target value is set during a sudden acceleration operation compared to a sudden deceleration operation. A control method for a continuously variable transmission for a vehicle, characterized by reducing the size of the transmission.