JPS63125448A - Gear ratio control method for vehicle continuously variable transmission device - Google Patents

Abstract

PURPOSE:To obtain substantially constant braking operation, by correcting a desired value in accordance with the input shaft rotational speed and gear ratio of a continuously variable transmission which are factors for actually determining the degree of engine braking operation. CONSTITUTION:A flow control valve 46 which is a change-over valve controlled by a controller, feeds hydraulic oil from a line hydraulic passage 44 into a primary hydraulic cylinder 36 for applying a thrust force to a primary variable pulley 22, so as to decrease the gear ratio, or discharges hydraulic oil from the hydraulic cylinder 36 into a drain to increase the gear ratio. In order to make a desired engine rotational speed coincident with an actual engine rotational speed, the flow control valve 46 is changed over so that the actual engine rotational speed approaches the desired engine rotational speed.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a method of controlling a gear ratio of a continuously variable transmission for a vehicle, and more particularly to a technique for appropriately applying engine braking of a vehicle.

Conventional technology In general, in vehicles equipped with a continuously variable transmission, a target value is determined based on the amount of accelerator pedal operation, etc. from a predetermined relationship in order to operate the engine on the minimum fuel efficiency curve. The gear ratio is adjusted so that the input shaft rotational speed or gear ratio of the transmission matches the target value.

For this reason, when such a vehicle is dismounting, an effective engine brake is not applied and the vehicle continues to accelerate.

On the other hand, if the accelerator pedal is released, the vehicle speed is above a predetermined value, and the acceleration of the vehicle is above a predetermined value, then the gear ratio of the continuously variable transmission (=human power shaft rotation speed/output It has been considered to modify the target value in the direction of increasing the shaft rotation speed). For example, there is a control method described in Japanese Patent Application No. 125448/1988 filed by the present applicant.

Problems to be Solved by the Invention By the way, when the accelerator pedal operation amount is zero, that is, when the throttle valve is fully closed, the negative torque of the engine increases in accordance with its rotational speed, and the gear ratio of the continuously variable transmission ratio increases. As the torque increases, the negative torque on the output shaft increases and the engine braking effect increases. However, according to the conventional gear ratio control method, the amount of correction of the target value is determined based on the vehicle speed or vehicle acceleration. There was a disadvantage that a constant engine braking effect could not be obtained. This inconvenience becomes particularly noticeable when driving on roads in mountainous areas.

Means for Solving the Problems The present invention has been made against the background of the above circumstances.
The gist is that the vehicle is equipped with a continuously variable transmission that continuously changes the engine rotation and transmits it to the drive wheels, and that the input shaft rotational speed or gear ratio of the continuously variable transmission matches a target value. A gear ratio control method for controlling the gear ratio of the continuously variable transmission as shown in FIG. (C) detecting the acceleration of the vehicle; (d) detecting the input shaft rotational speed and gear ratio of the continuously variable transmission; If the speed of the vehicle exceeds a predetermined value and the acceleration of the vehicle exceeds a predetermined value, the input shaft rotation speed of the continuously variable transmission is determined from the predetermined relationship. and a gear ratio modifying means for modifying the target value based on the gear ratio.

Operation and Effect of the Invention With this arrangement, the amount of depression of the accelerator pedal is zero, the speed of the vehicle exceeds a predetermined value, and the acceleration of the vehicle exceeds a predetermined value. If so, the gear ratio correcting means corrects the target value based on the input shaft rotational speed and gear ratio of the continuously variable transmission from a predetermined relationship. In this way, the target value is corrected based on the input shaft rotation speed and gear ratio of the continuously variable transmission, which are the factors that actually determine the magnitude of the vehicle's engine braking action, so the vehicle speed or vehicle acceleration A substantially constant engine braking effect can be obtained regardless of the engine speed. Therefore, compared to conventional gear ratio control methods,
This provides an effective engine braking effect when driving on roads in mountainous areas.

EXAMPLE Hereinafter, an example of a control device for a continuously variable transmission for a vehicle to which the present invention is applied will be explained in detail.

In FIG. 1, a crankshaft 12 of an engine 10 is connected to an input shaft 18 of a belt type continuously variable transmission 16 via a clutch 14.
The output shaft 2 of the belt type continuously variable transmission 16
0 is connected to the drive wheels of the vehicle via a differential gear device (not shown) or the like. Thereby, the rotational force of the engine 10 is transmitted to the drive wheels.

The input shaft 18 and output shaft 20 of the belt type continuously variable transmission 16 are provided with variable pulleys 22 and 24 whose effective diameters are variable, and a transmission belt 26 is wound between the variable pulleys 22 and 24. There is. The variable pulleys 22 and 24 are fixed rotating bodies 28 and 30 fixed to the input shaft 18 and the output shaft 20, and fixed rotating bodies 28 and 30 fixed to the input shaft 18 and the output shaft 20
The movable rotating bodies 32 and 34 are provided to be movable in the axial direction and non-rotatable about the axis. and,
By changing the thrust applied to the movable rotors 32 and 34 from the hydraulic cylinders 36 and 38, the fixed rotors 28 and 30 and the movable rotors 32 and 34
The width of the V-groove formed between the belt and the belt, that is, the diameter of the belt can be changed.

The hydraulic oil collected in the oil tank 40 is pumped by an oil pump 41, and the pressure is regulated to line oil pressure by a pressure regulating valve 42 controlled by a controller 48, which will be described later. This line oil pressure is supplied to the secondary side hydraulic cylinder 38 through a line oil passage 44 that applies thrust to the secondary side variable boob 124. Normally, the line oil pressure is calculated from a predetermined relational expression by calculating the output torque Tll of the engine 10 and the belt-type continuously variable transmission 16.
The gear ratio Tcvt ("rotational speed N of the human-powered shaft 18, 7
/rotational speed N0uL of the output shaft 20), etc., and the clamping force on the transmission belt 26 is adjusted to a value determined based on the
In other words, the tension that prevents the transmission belt 26 from slipping is maintained at a necessary and sufficient value.

The flow rate control valve 46 is a switching valve controlled by a controller 48, which will be described later, and supplies the hydraulic oil in the line oil passage 44 to the primary side hydraulic cylinder 36 that applies thrust to the primary side variable pulley 22. Then, the gear ratio γ is decreased, or the hydraulic oil in the hydraulic cylinder 36 is discharged to the drain to increase the gear ratio T.

The intake pipe of the engine 10 is provided with a throttle valve 52 that is opened and closed by an accelerator pedal 50, and a throttle sensor 54 that detects the opening degree of the throttle valve 52. The engine 10 is provided with a water temperature sensor 56 for detecting the temperature of the cooling water. Continuously variable transmission 16
Fixed rotating body 28 on the primary side and fixed rotating body 3 on the secondary side
A first rotation sensor 58 and a second rotation sensor 60 for detecting the rotation speeds of the input shaft 18 and the output shaft 20 are provided near the rotation speed. A shift sensor 64 for detecting the operating position of the shift lever 62 is provided in the vicinity of the seat.

As shown in FIG. 2, the controller 48 includes a CPU 66
, ROM68, RAM70, ink face 72, A/
It is a so-called microcomputer equipped with a D converter 74 and a D/A converter 76, and the input shaft rotation signal and the output shaft output from the first rotation sensor 58 and the second rotation sensor 60 according to a program stored in advance in the ROM 68. Processes input signals such as a rotation signal, a shift position signal output from the shift sensor 64, a water temperature signal output from the water temperature sensor 56, and a throttle signal output from the throttle sensor 54, and processes the pressure regulating valve 42 and the flow rate control valve 46.
Outputs drive signals to etc.

The control operation of the controller 48 will be explained below with reference to FIG. The flowchart in FIG. 3 exclusively shows the operation of speed ratio control.

In step S1, the input signal is read, and the input rotational speed N1fi (=engine rotational speed N, ), output shaft rotational speed N (ILIL, vehicle speed ■, gear ratio Tcvt, vehicle acceleration dV/dt, etc.) are calculated. be done.

In the following step S2, it is determined whether the content of the flag F indicating engine brake control is rlJ. During normal driving, it is determined that the content of flag F is not "1", that is, engine brake control has not been started, so steps 83 and subsequent steps are executed. Step S3, S
4. In S5, whether or not the throttle valve opening degree θ is zero, whether the vehicle speed ■ is equal to or greater than a predetermined value α,
It is then determined whether the acceleration dV/dt of the vehicle is greater than or equal to a predetermined value β. The predetermined values α and β are selected to be suitable for starting engine brake control.

If any of the judgments in steps S3, S4, and S5 is negative, step S6 is executed, and the target engine Rotational speed N, (=N, (
θ)] is determined.

This relationship is determined in advance in order to operate the engine 10 on the minimum fuel efficiency curve, and is stored in the form of a data map or the like. Note that the above relationship may be a function of the accelerator pedal operation amount, or a function of the throttle valve opening θ and the vehicle speed ■.

In step S7, in order to match the target engine rotation speed N0 determined in this way with the actual engine rotation speed N, the actual engine rotation speed N is adjusted toward the target engine rotation speed N0.

The flow control valve 46 is switched so that the

If all the determinations in steps S3, S4, and S5 are affirmative, the content of the flag F is set to "1" in step S8, and the correction value ΔN6& of the target engine rotational speed N0 is set to "1" in step S9. 5
It is calculated based on the actual gear ratio γ and the input shaft rotational speed N in from the pre-stored relationship shown in the figure. This relationship is due to the fact that the negative torque of the engine 10 increases as the engine rotational speed N increases, as shown in FIG. 6, and the engine braking effect increases as the gear ratio T of the continuously variable transmission 16 increases. , are determined using the gear ratio γcvt and the input shaft rotational speed Ni as parameters so as to obtain a constant engine braking effect. As a result, the larger the actual gear ratio Tcvt, the
And the higher the input shaft rotational speed N i n is, the higher the correction value ΔN
o a is determined to be a small value. And step S
10, the correction value ΔN c determined as above
, , to the previous target engine rotation speed N0 to obtain the target engine rotation speed N0. Update.

In the next control cycle, since it is determined in step S2 that the content of flag F is "1", steps S11, 512, and 513 are executed. In steps Sll and S12.513, it is determined whether the throttle valve opening degree θ is zero, whether the vehicle speed ■ is equal to or greater than a predetermined value α°, and the acceleration dV/dt of the vehicle is predetermined. It is determined whether or not the value β1 is greater than or equal to the value β1.

The predetermined values α1 and β1 are selected to be suitable for terminating the engine brake control.

Usually, α1 and β1 are set slightly smaller than α and β in order to provide an appropriate hysteresis between the start condition and the end condition of engine brake control.

If all of the determinations in steps Sll, S12, and S13 are affirmative, step S14 and step SIO, which are similar to step S9, are executed to continue engine brake control. However, step 31
If any of the judgments in S1, S12, and S13 is negative, a correction value ΔN6b is calculated in step S15. This correction value ΔN0. is the target engine rotational speed N that is highly corrected for the engine brake control.

is the value N during normal driving. It corresponds to the speed at which the rotational speed is gradually returned to (θ), and is determined to a value that does not cause a sudden change in the drive wheel torque, that is, a sense of discomfort that would occur if the rotational speed is suddenly returned to the normal target rotational speed. Next step S1
6 is the target engine speed N up to that point. The target engine rotational speed N0 is updated by subtracting the correction value ΔNob from the target engine speed N0.

In step S17, the target engine rotational speed N0 is set to the value N during normal driving due to the update as described above.

It is determined whether or not the value has decreased to (θ). If the target engine rotational speed N0 has not decreased, the execution of the above steps is repeated in order to bring the target engine rotational speed N0 closer to the value No(θ) during normal driving. However, in step S17, the target engine rotation speed N.

When it is determined that the value has decreased to the value N, (θ) during normal driving, step 31B is executed and the content of the flag F is set to "0".
will be reset to

As described above, according to this application example, during engine brake control, the correction value ΔNo is determined from the actual gear ratio 7 cvL and the input shaft rotational speed N in from the relationship shown in FIG.
The relationship shown in Figure 5 is determined based on
As shown in FIG. 6, the negative torque of the engine 10 causes the engine rotation speed N. The gear ratio γ is set so that a constant engine braking effect can be obtained because the larger the gear ratio γ of the continuously variable transmission 16, the greater the engine braking effect. V and input shaft rotational speed N in as parameters. Therefore, if the amount of depression of the accelerator pedal is zero, the vehicle speed ■ exceeds the predetermined value α, and the vehicle acceleration dV/dt exceeds the predetermined value β, the vehicle speed (2) Alternatively, a substantially constant engine braking effect can be obtained regardless of the vehicle acceleration dV/dt. Therefore, compared to conventional gear ratio control methods, an effective engine braking effect can be obtained when driving on roads in mountainous areas.

Although one application example of the present invention has been described above, the present invention can also be applied to other aspects.

For example, in the application example described above, the target input shaft rotation speed may be used instead of the target engine rotation speed N0.

Also, if the vehicle speed is the same, the gear ratio γ and the human power shaft rotation speed N
i and n have a certain relationship with each other, so the gear ratio is controlled so that the target engine rotation speed N0 and the actual engine rotation speed N match, and the target engine rotation speed N0 and the actual engine rotation speed This is substantially the same as determining a target gear ratio to match N0 and controlling the gear ratio so that the actual gear ratio matches the target gear ratio.

Further, the accelerator pedal operation amount or the like may be used instead of the throttle valve opening degree θ in the above application example.

Note that the above-described example is only one application example of the present invention, and the present invention is also applicable to other embodiments.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating a continuously variable transmission for a vehicle, which is an application example of the present invention. FIG. 2 is a block diagram illustrating a control device for the continuously variable transmission shown in FIG. 1. FIG. 3 is a flowchart showing the operation of the control device of FIG. 2. 4 and 5 are diagrams showing relationships used in the flowchart of FIG. 3. Figure 6 is the first
FIG. 3 is a diagram showing the relationship between the engine rotation speed and the output torque in a state where the throttle valve opening is zero in the engine shown in the figure. lO: Engine 16: Belt type continuously variable transmission 18: Input shaft Fig. 2, 48 Fig. 3 Fig. 4

Claims (1)

[Scope of Claims] A continuously variable transmission for a vehicle that continuously changes the speed of the engine and transmits the rotation to the driving wheels, the input shaft rotational speed or gear ratio of the continuously variable transmission being adjusted to match a target value. A gear ratio control method for controlling the gear ratio of the continuously variable transmission, comprising: detecting the amount of depression of the accelerator pedal of the vehicle; detecting the speed of the vehicle; and detecting the acceleration of the vehicle. a step of detecting an input shaft rotational speed and a gear ratio of the continuously variable transmission; the amount of depression of the accelerator pedal is zero and the speed of the vehicle exceeds a predetermined value; and when the acceleration of the vehicle exceeds a predetermined value, a gear ratio that corrects the target value based on the input shaft rotational speed and gear ratio of the continuously variable transmission based on a predetermined relationship. 1. A method for controlling a gear ratio of a continuously variable transmission for a vehicle, the method comprising: correcting means.