JPS6060360A - Control method of continuously variable transmission for vehicle - Google Patents

Abstract

PURPOSE:To obtain good driving performance and drive feeling when a vehicle is accelerated and decelerated, by setting a step change rate at deceleration to a value larger than that of the step change rate at acceleration. CONSTITUTION:A step change rate B at deceleration is set to a value larger than that of the step change rate B at acceleration. In this way, an acceleration response characteristic and acceleration feeling of a vehicle, when it is accelerated, are improved by prompt appearance of torque accelerating the vehicle without causing any necessity for largely accelerating the input side member of a CVT and moment of inertia of an engine because an actual engine speed Ne quickly reaches the target engine speed No. While good drive feeling of the vehicle, when it is decelerated, is obtained by the quick follow-up action of the actual engine speed Ne to a large decrese of the target engine speed No because of no necessity for accelerating the moment of inertia in the input side.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a method of controlling a continuously variable transmission (hereinafter referred to as "CvT") used as a power transmission device for a vehicle, and particularly to a method of controlling a CVT during transient periods.

BACKGROUND ART A CVT is capable of continuously controlling a speed ratio e (=output side rotational speed Nout/input side rotational speed Nin) and is used in a vehicle as a power transmission device with excellent fuel consumption efficiency. In a CVT, the required horsepower is set as a function of the throttle opening θ, and the engine rotational speed Ne that achieves each required horsepower with the minimum fuel consumption is determined as the steady target (2) engine rotational speed at the throttle opening 0. In conventional cvT, the transient target engine rotation speed is not set in particular and is set equal to the steady target engine rotation speed.In this case, it takes time for the actual engine rotation speed to reach the steady target engine rotation speed, and the transition There was a problem with poor response times. Therefore, in order to eliminate such problems, the present applicant disclosed a CVT control method in the earlier patent application No. 17550 of 1981. According to this control method, a target engine rotational speed is set as a function of the throttle opening, and the engine rotational speed or the speed ratio of the Hi-speed transmission is controlled so that the actual engine rotational speed becomes the target engine rotational speed. Define the step change rate B as a positive number less than 1, and if the throttle opening changes significantly, the steady target engine rotation speed Nos after the throttle opening change and the steady target engine rotation speed No5' before the throttle opening change Difference No5-No5
' is multiplied by the step change rate B, B・(Nos −N
os'), and then the target engine rotation speed (3) is gradually changed toward the steady target engine rotation speed Nos after the throttle opening change.

That is, since the target engine rotational speed during the transition smoothly increases by -L, the engine rotational speed Ne quickly increases and acceleration becomes smooth. However, since the step change rate B for ensuring a predetermined response is set without distinguishing between acceleration and deceleration in this control method, the driving performance (drive It was difficult to optimize both performance (ability) and driving sensation (drive feeling). In other words, during acceleration, the increased engine torque is consumed by the moment of inertia of the input side members of the engine and CVT and does not contribute to the acceleration of the vehicle until the actual engine rotational speed Ne reaches the target engine rotational speed ffNo. The acceleration of the vehicle becomes noticeable after the engine rotational speed Ne reaches the target engine rotational speed No. Therefore, if the step change rate B is large, the time it takes for the actual engine rotational speed Ne to reach the target engine rotational speed No. As a result,
The time delay between when the driver presses the accelerator pedal (4) and when the driver feels a sense of acceleration becomes longer, and the sense of acceleration worsens. On the other hand, during deceleration, there is no need to accelerate the moment of inertia of the input side members of the engine and CVT, and the actual engine rotation speed Ne quickly follows the target engine rotation speed NO. Setting it to a relatively large value and quickly changing gears to run at a large speed ratio gives a better feeling and improves fuel consumption efficiency.

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a CVT control method that can provide good driving performance and driving feel both during acceleration and deceleration.

In order to achieve this objective, according to the CVT control method of the present invention, the step change rate 8B during deceleration is set to a larger value than the step change rate B during acceleration.

Therefore, during acceleration, the step change rate n is set to a relatively small value, so that the actual engine rotation speed Ne quickly reaches the target engine rotation speed (5). There is no need to greatly accelerate the moment, and the torque that accelerates the vehicle appears quickly, resulting in good acceleration response and a good acceleration feeling.

Also, during deceleration, the step change rate B is set to a relatively large value, but since there is no need to accelerate the moment of inertia on the input side, the actual engine rotation speed Ne quickly changes due to a large decrease in the target engine rotation speed No. As a result, the speed number of the CVT increases rapidly, providing a good sense of deceleration, and also increases the time the engine is operated at a low engine speed, improving fuel consumption efficiency.

According to a preferred embodiment, acceleration and deceleration are detected from a comparison between the target engine rotational speed Nos after the throttle opening changes and the steady target engine rotational speed Nos' before the throttle opening changes.

Example The present invention will be described in detail with reference to the drawings.

(6) In Fig. 1, CVT In has input shafts 12 parallel to each other.
and an output shaft 14. The input shaft 12 is the engine 1
6, and is connected to the crankshaft 18 via a clutch 20. The input pulleys 22a and 22b are provided opposite to each other, and one of the input pulleys 22a is provided on the input shaft 12 as a movable pulley so as to be movable in the axial direction and fixed in the rotational direction.
The other input side pulley 22h is a fixed pulley that connects the input shaft 1.
It is fixed at 2. Similarly, output side pulleys 24a, 24
b are also provided facing each other, and one output side pulley 24
A is fixed to the output shaft 14 as a fixed pulley, and the other output side pulley 24b is provided as a movable pulley to the output shaft 14 so as to be movable in the axial direction and fixed in the rotational direction. Input side pulleys 22a, 22b and output side pulley 24
The opposing surfaces of a and 24b are tapered, and a belt 26 having an isosceles trapezoid cross section is hung between the input pulleys 22a and 22b and the output pulleys 24a and 24b. The oil pump 28 sends oil in the oil sump 30 to the pressure regulating valve 32 (7
) Ru. The pressure regulating valve 32 controls the line pressure of the oil passage 36 by changing the amount of oil released to the drain 34, 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. It will be done. The flow control valve 38 is
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 are controlled. The pressing forces of the input pulleys 22a, 22b and the output pulleys 24a, 24b against the belt 26 are controlled by the oil pressure of the input hydraulic cylinder and the output hydraulic cylinder, and the input pulleys 22a, 22b and the output are controlled in relation to this pressing force. The radius of engagement of the belt 26 on the tapered surfaces of the side pulleys 24a, 24b changes, and as a result, the speed ratio e (=Nout/Nin) of the CVT 10.

However, Nout is the rotational speed of the output shaft 14, and Nin is the rotational speed of the input shaft 12, and in this embodiment, Nin-engine rotational speed Ne. ) changes.

In order to suppress the drive loss of the oil pump 28, the line pressure of the output side hydraulic cylinder is controlled to the minimum value necessary to avoid slipping of the belt 26 (8) and ensure power transmission, and the line pressure of the input side hydraulic cylinder is Since the pressure receiving area of the side hydraulic cylinder>pressure receiving area of the output side hydraulic cylinder, the pressing force of the input side pulleys 22a and 22b is
The pressing force can be made larger than that of a and 24b. The input side rotation angle sensor 42 and the output side rotation angle sensor 44 measure the rotation speed NIn+ of the input shaft 12 and output shaft 14, respectively.
Nout is detected, and the water temperature sensor 46 detects the cooling water temperature of engine +6. An accelerator pedal 50 is provided in the driver's seat 48, a throttle valve in the intake passage is interlocked with the accelerator pedal 50, and a throttle opening sensor 52 detects zero throttle opening. The shift position sensor detects the shift range of the shift lever located near the driver's seat.

FIG. 2 is a block diagram of the electronic control device.

The address data bus 56 is connected to the CPU 58. RAM 6
0. ROM62, T/F (Inter'7 Ace)
64. A/r) (7s (9) log/digital converter) 66 and D/A (digital/analog converter) 68 are interconnected. r/
F 64 receives pulse signals from input side rotation angle sensor 42, output side rotation angle sensor 44, and shift position sensor 54, and A/D 66 receives analog signals from water wetness sensor 46 and throttle opening sensor 52. Receipt, I)/
A 68 outputs pulses to the pressure regulating valve 32 and flow control valve 38.

Figures 3 and 4 show cases where the throttle opening θ increases greatly (during acceleration) and decreases greatly (during acceleration), respectively.
Fig. 3 shows the change in target engine rotational speed NO during deceleration).

When the throttle opening degree θ greatly increases or decreases from 01 to 02 at time to, the target engine rotational speed NO is maintained at the steady target engine rotational speed Nos' at the throttle opening degree of 01 until time tl when the delay time A has elapsed. , then at time tl, the engine rotational speed increases or decreases discontinuously by the amount corresponding to the step change rate B to a value of 9N.
ob, and after time tl, it gradually rises or falls at an inclination C toward the steady target machine opening (10) at the throttle opening degree 02 and the rotation speed Nos. Note that the step change iR is defined as a positive number smaller than 1 by the following equation.

The delay time A from time to to 11 is to confirm the driver's true intention in requesting acceleration or deceleration, and if the driver returns to the original state by depressing the accelerator pedal 50 within the delay time A, No transient control of CvTlo is performed. The step change in the target engine rotational speed NO by the step change rate l( is performed to ensure a predetermined appropriateness during transient times. The increase or decrease in the target engine rotational speed NO at the slope C is the change in the target engine rotational speed NO. To smoothly and quickly shift the actual engine rotational speed Ne to Nos by slowing down the change.

Figure 5 shows the change in target engine rotation speed NO during acceleration, actual engine rotation speed Ne, and 1-luk Tp of the drive wheels.
1 and the longitudinal acceleration Gp of the vehicle (the forward direction is assumed to be positive). Actual engine speed Nc
Until time t3 reaches the target engine rotation (11) speed No., the increased engine torque is consumed to accelerate the input side members of the CVT In and the moment of inertia of the engine, and the torque of the drive wheels is small and the vehicle is not sufficiently accelerated, and full-scale vehicle acceleration occurs after time t3. Therefore, in the present invention, the step change rate B during acceleration is set to a relatively small discount to shorten the time until the actual engine rotation speed Ne reaches the target engine rotation speed No, thereby improving the power performance during acceleration and the operation. Heal your senses. On the other hand, during deceleration, there is no need to accelerate the moment of inertia, and the actual engine rotation speed Ne quickly follows the change in the target engine rotation speed No, so the step change rate B during deceleration is set to a relatively large value B2. By setting the speed ratio e of the CVT 10, the speed ratio e of the CVT 10 is quickly increased to obtain good deceleration, and the period during which the engine is operated at a low rotational speed is lengthened to improve fuel consumption efficiency.

FIG. 6 is a flowchart of a routine for calculating the target engine rotational speed No. During acceleration or deceleration when the throttle opening degree 0 (12) greatly increases or decreases, the target engine rotational speed is calculated according to the graphs in FIGS. 3 and 4. In other words, during acceleration, the step change rate B
is set to old, and during deceleration, the step change rate B is R2 (
However, it is set to 0 (old < 82 < +). In addition, during transient and steady states in which the change in the throttle opening degree θ is small, the target engine rotational speed NO is calculated by the following equation.

No = Nos'10 years old- (Nos -Nos')
8D mawashi r)I, r)2 are constants, old - (No5 - No5') ÷ n2 = dirt - (Nos -
Nos'). That is, fluctuations in the target engine rotational speed are suppressed during transient and steady states in which the change in throttle opening degree 0 is small. To explain each step in detail, in step 72, the absolute value l Nos of the difference between the steady target engine speed Nos at the throttle opening of 0 during the opening change and the steady target engine speed Nos' at the throttle opening of 0 before the change is made.
−Nos' l and a predetermined value ΔNa are compared, and l Nos'
-Nos' 1 ≧ ΔNa (13), that is, when the throttle opening ff8 has changed significantly, the process proceeds to step 74; If so, proceed to step 94. In step 74, the steady target engine rotation speed No. after the throttle opening change is determined.
Compare s with the steady target engine rotational speed Nos' before the throttle opening change, and if Nos >Nos', that is, when accelerating, proceed to step 75, and if Nos <
If No', that is, if deceleration is occurring, the process proceeds to step 76, respectively. In step 75, a predetermined discount 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 old < 112
< +. In step 78, an elapsed time measuring timer is started. In step 80, A, CI, and C2 are read from memory. However, CI and C2 are constants,
C1.(Nos - Nos') +02 is equal to the slope C in FIG. In step 82, the value Tm of the elapsed time measurement timer is compared with A, and if T+n<A, step 84
If Tm≧A(14), proceed to step 86.1. In step 84, Nos' is substituted for the target engine rotational speed No, and the process returns to step 82. In step 86, the value Tm of the elapsed time measurement timer is compared to a predetermined value, and if T+n=A, step 88
If T+n>A, the process advances to step 90. In step 88, Nos'10B・(Nos −Nos')
is substituted into the target engine rotational speed No. and the process returns to step 86. In step 90, the target engine rotational speed NO.
Nos −No,' ) increases by 102. In step 92, l Nos - No 1 is compared with a predetermined value ΔNb, and if l Nos - No l≧ΔNt+, that is, the current target engine rotation is changed from the steady target engine rotation speed Nos at throttle opening 0 after the opening change. If the speed NOs are far apart, return to step 82, l No5 - No l
If <ΔNh, that is, if No is sufficiently close to Nos, the routine ends. In step 94, the target engine rotational speed NO is NO + old (Nos - Nos').
Substitute ±1]2.

[Brief explanation of the drawing]

Fig. 1 is an overall schematic diagram of the CVT to which the present invention is applied, Fig. 2 is a block diagram of the electronic control device, and Fig. 3 is the target engine rotational speed in the present invention during acceleration with a large increase in throttle opening. Figure 4 is a diagram showing the change in target engine rotation speed in the present invention during deceleration when the throttle opening is greatly reduced. Figure 5 is a diagram showing the actual engine rotation with respect to the change in target engine rotation speed during acceleration. FIG. 6, which is a diagram showing changes in speed, drive wheel torque, and acceleration in the longitudinal direction of the vehicle, is a flowchart of a routine for calculating the target engine rotation speed. 10...CVT, +6...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. Setting a target engine rotation speed as a function of the throttle opening, and controlling the engine rotation speed or the speed ratio of the continuously variable transmission so that the actual engine rotation speed becomes the target engine rotation speed, Define the step change rate B as a positive number less than 1, and if the throttle opening changes significantly, the steady target engine rotation speed Nos after the throttle opening change and the steady target engine rotation speed Nos' before the throttle opening change B・ which is the difference Nos −Nos' multiplied by the step change rate B
(Control of a continuously variable transmission for a vehicle that discontinuously changes the target engine rotational speed by Nos −Nos and then gradually changes the target engine rotational speed toward the steady target engine rotational speed Nos after changing the throttle opening. In the method,
The step change rate B during deceleration is the step change rate B during acceleration.
A method for controlling a gear transmission for a vehicle (1), characterized in that the value is set to a larger value. 2. Acceleration and deceleration are detected from a comparison between the steady target engine rotation speed Nos after the throttle opening changes and the steady target engine rotation speed Nos' before the throttle opening changes. 'fIi-described control method.