JPH02234852A - Speed ratio control device for vehicle continuously variable transmission - Google Patents

Abstract

PURPOSE:To enable the regularly sufficient exhibition of anti-lock effect by measuring the time for which the brake liquid pressure is being reduced, at the time of anti-lock brake control, and changing the speed ratio of a continuous ly variable transmission to the accelerating side when the decompression continu ing time exceeds a determined value. CONSTITUTION:The rotation of an engine 10 is transmitted to a belt type contin uously variable transmission (CVT) 16 through a fluid joint 14, and the power continuously varied is transmitted to left and right driving wheels 22, 24 through a frontward and backward switching device 18 and a differential gear device 20. The speed ratio of the CVT 16 is changed by controlling a CVT hydraulic control circuit 26 by means of a CVT ECU 51. At the time of breaking, an anti-lock break (ABS) ECU 64 is operated to keep the slipping state of the wheels within a determined range, and the break liquid pressure is increased or reduced. In this case, the time for which the brake liquid pressure is being reduced is measured, and when the decompression continuing time exceeds a determined value, the CVT 16 is controlled to change the speed ratio to the accelerating side.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a speed ratio control device for a continuously variable transmission for a vehicle. 2. Description of the Related Art Vehicles are known that are equipped with a continuously variable transmission that continuously changes the speed of the rotation of an engine and transmits the same to drive wheels.

In such vehicles, for example, Japanese Patent Application Laid-Open No. 59-1
As described in No. 44850, the speed ratio is set so that the target input shaft rotation speed determined based on the throttle valve opening of the vehicle and the vehicle speed is equal to the input shaft rotation speed of the continuously variable transmission. be controlled. This allows the engine to operate along the optimal curve, resulting in a high fuel efficiency rate. Problems to be Solved by the Invention By the way, in a vehicle equipped with a continuously variable transmission as described above, it is necessary to automatically adjust the brake fluid pressure to maintain the slip state of the wheels within a predetermined range in connection with the braking operation of the vehicle. It may be equipped with an anti-lock brake system that adjusts the

In such cases, it may be difficult to obtain sufficient anti-lock action when braking the vehicle. In other words, in the speed ratio control of a continuously variable transmission, the vehicle speed is detected from the rotational state of a member that rotates together with the drive wheels of the vehicle (hereinafter referred to as the drive wheel vehicle speed), and the speed ratio is adjusted based on at least the drive wheel vehicle speed. However, when the vehicle speed of the driving wheels rapidly decreases due to a braking operation of the vehicle, the speed ratio is rapidly changed to the maximum deceleration side, and engine braking action is applied to the driving wheels. For this reason, even if the brake fluid pressure is reduced by the operation of the anti-lock brake system when the vehicle's brakes are operated, the drive shaft vehicle speed may not return to the vehicle body speed, and a sufficient anti-lock effect may not be obtained. be.

The present invention has been made against the background of the above circumstances,
The purpose of this is to use a continuously variable transmission that continuously changes the speed of the engine and transmits it to the drive wheels, and a system that maintains the slip state of the wheels within a predetermined range in relation to the vehicle's braking operation. In a vehicle equipped with an anti-lock brake device that automatically adjusts the brake fluid pressure, a speed ratio control device that adjusts the speed ratio of the continuously variable transmission so that the anti-lock effect of the anti-lock brake device can be sufficiently obtained is provided. It is about providing.

Means for Solving the Problems The gist of the present invention to achieve the above object is to provide a continuously variable transmission that continuously changes the speed of the engine rotation and transmits it to the driving wheels, and a vehicle braking operation. In a vehicle equipped with an anti-lock brake device that automatically increases or decreases brake fluid pressure so as to maintain wheel slippage within a predetermined range, at least a target value determined based on a driving wheel vehicle speed is provided. A speed ratio control device for a continuously variable transmission for a vehicle, which controls the speed ratio of the continuously variable transmission so that the actual input shaft rotational speed or speed ratio of the continuously variable transmission matches,
(a) a timer for measuring the duration of depressurization during which the brake fluid pressure is reduced by the anti-lock brake device; and (b) when the decompression duration time measured by the timer exceeds a predetermined value, the belt The present invention includes speed ratio control means for changing the speed ratio of the continuously variable transmission to the speed increasing side.

Operation and Effect of the Invention With this structure, the brake fluid pressure is reduced by the anti-lock brake device in connection with the brake operation of the vehicle, and when the pressure reduction duration exceeds a predetermined value, the speed ratio control means reduces the belt pressure. Since the speed ratio of the continuously variable transmission is actively changed to the speed increasing side, no engine braking action is applied to the drive wheels, and in addition, the rotational speed of the drive wheels increases due to the positive torque from the engine. This tends to be the case. Therefore, the driving wheel speed can quickly return to a value corresponding to the vehicle body speed, and a sufficient anti-lock effect can be obtained. Here, the timer preferably measures the duration of pressure reduction during which the brake fluid pressure is reduced by the anti-lock brake device in a state where the driving wheel vehicle speed is lower than the target vehicle speed determined based on the estimated vehicle speed. Measure time. EXAMPLE Hereinafter, an example of the present invention will be explained in detail based on the drawings. In FIG. 1, the rotation of the engine 10 is controlled by a fluid coupling engine 4 equipped with a fluid coupling clutch 12 in parallel.
The transmission is transmitted to a belt type continuously variable transmission (CVT) 16 via the belt type continuously variable transmission (CVT) 16, and after being continuously changed by the belt type continuously variable transmission 16, the left and right transmission is transmitted via the forward/reverse switching device 18 and the differential gear device 20. The power is transmitted to the drive wheels (front wheels) 22 and 24. In the fluid coupling 14, the lock-up clutch 12 is released or engaged by changing the flow direction of the hydraulic oil supplied from the CVT hydraulic control circuit 26. The belt type continuously variable transmission 16 also includes an input shaft 2 connected to the engine 10 via a fluid coupling 14.
and an output shaft 3 connected to left and right drive wheels 22 and 24 via a forward/reverse switching device 18 and a differential gear device 20.
0, a pair of variable pulleys IJ32 and 34 with variable effective diameters provided on the human power shaft 28 and the output shaft 30, respectively, and a transmission belt 36 wound around the pair of variable pulleys 32 and 34. It is equipped with For this reason, the CVT hydraulic control circuit 26 supplies hydraulic oil to one of the pair of hydraulic cylinders that apply the squeezing force (thrust) of the pair of variable booleans 32 and 34, respectively, and discharges the hydraulic oil from the other. , the speed ratio can be changed. In addition, the forward/reverse switching device 18
is equipped with a planetary gear mechanism, a forward clutch, and a reverse brake, and is linked to operation to a forward range such as D range or R range by a manual valve 38 that is mechanically linked to operation of a shift lever 36. By selectively operating the forward clutch or the reverse brake, the vehicle is caused to move forward or backward. Further, when the shift lever 36 is operated to the P range or the N range and neither the forward clutch nor the reverse brake is operated, power transmission is cut off within the forward/reverse switching device 18. ing. A signal representing the engine rotation speed N is output from the engine rotation sensor 40 for detecting the rotation speed of the engine 10.
The throttle sensor 42 for detecting the required output for the engine 10 outputs a signal representing the throttle valve opening degree θ, and the first rotation sensor 44 for detecting the rotation speed of the input shaft 28 outputs a signal representing the input shaft rotation speed N in The signal representing
The second rotation sensor 46 for detecting the rotation speed of the output shaft 30 outputs a signal representing the output shaft rotation speed N e a t, and the brake sensor 50 for detecting the operation of the brake pedal 48 outputs a signal representing the brake operation. The signals are supplied to each CVT ECU (electronic control unit) 51. This CVT ECU 51 includes a CPU, ROM,
It is a so-called microcomputer that includes a RAM, and its CPU processes input signals according to a program stored in the ROM in advance while utilizing the storage function of the RAM.
The VT hydraulic control circuit 26 controls the engagement state of the lock-up clutch l2, the speed ratio of the belt type continuously variable transmission 16, etc.

For example, in the CVT ECU 51, the output shaft rotation speed N for the lock-up clutch l2 is determined based on the pre-stored reduction ratio, drive wheel diameter, etc. While the actual vehicle speed (driving wheel vehicle speed) SPD is calculated based on The lock-up clutch 12 is released when the vehicle speed drops below a reference speed or when a brake operation is performed.

In addition, in the CVT ECU 5 1, the belt type continuously variable transmission 16 determines the actual throttle valve opening based on a pre-stored relationship for operating the engine engine along an optimal curve that takes fuel efficiency and driving performance into consideration. Based on θ and vehicle speed SPD, target engine rotational speed values N, . 1
1 is determined, and the speed ratio of the belt-type continuously variable transmission 16 is adjusted so that this target engine rotational speed value Ni - and the actual input shaft rotational speed N i n match. Alternatively, the input shaft rotation speed Ni6 and the output shaft rotation speed N. From uL to the actual speed ratio e of the belt type continuously variable transmission 16 (=N
oat/N=a) is calculated, the actual throttle valve opening θ and vehicle speed SPD are calculated from the pre-stored relationship for operating the engine 10 along the optimal curve.
The target speed ratio e8 is determined based on the target speed ratio e8.
9 and the actual speed ratio e are adjusted. Speed ratio e, input shaft rotation speed N 1 m, and output shaft rotation speed N corresponding to vehicle speed SPD. . , between e ”” N c+uL
/N! ．． Therefore, the former control and the latter control described above are substantially the same.

On the other hand, the vehicle of this embodiment is provided with an anti-lock brake device that automatically adjusts the brake fluid pressure so as to maintain the slip state of the wheels within a predetermined range in relation to the braking operation. That is, the left and right front wheels 22 and 24 and the left and right rear wheels 52 and 54 are provided with wheel rotation sensors 56, 58, and 6 for detecting their respective rotational speeds.
The wheel rotation sensors 56, 58, 60, 62 output signals from the wheels 22, 24, 62, respectively.
The signal representing the rotational speed of 52 and 54 is sent to the ABS ECU 64.
is being supplied to. Further, the ABSJIECU 64 is supplied with a signal representing a brake operation from the brake sensor 50.

The ABS ECU 64 is also a so-called microcomputer that includes a CPLI, ROM, and RAM, and the CPU uses the storage function of the RAM and processes input signals according to a program stored in the ROM in advance to calculate the estimated vehicle speed. SΦ is calculated, and the slip rate is calculated from the wheel rotation speed corresponding to this estimated vehicle speed vSΦ and the actual rotation speed of each wheel during braking, and the ABS control is performed so that the slip rate is within a predetermined range. Activate the hydraulic control circuit 66. The predetermined range is a predetermined area where the road surface friction coefficient μ is large and cornering force can be ensured. As is well known, the ABS hydraulic control circuit 66 includes a pump, a damper, a reservoir, a control valve, etc., and is connected between a mask cylinder 68 and wheel cylinders 70, 72, 74, and 76 provided on each wheel. placed in
The hydraulic pressure to each wheel cylinder 70, 72, 74, 76 is reduced, increased, or
Alternatively, the braking force of each wheel can be adjusted by holding it. Below, the above CVT ECU 5 1 and ABS ECU
The main part of the operation of 64 will be explained according to the flowcharts of FIGS. 2, 3, and 4.

FIG. 2 shows an interrupt routine that is repeatedly executed at predetermined time intervals in the ABS ECU 64. First, in step SAI, anti-CI7 brake control is performed in an anti-lock brake control routine (not shown). III (ABS!II'4I1) 0) It is determined whether or not it is being executed. If it is determined in step SAI that ABS control is not in progress, this interrupt routine is terminated, but if it is determined that ABS control is in progress, step SA2 determines whether drive wheel vehicle speed W is smaller than target vehicle speed VSL. It is determined whether or not. This drive wheel vehicle speed VW is determined by adopting the lower value of the rotation speed VWFL of the left drive wheel 22 and the rotation speed VWFR of the right drive wheel 24. The target vehicle speed VSL is successively calculated and updated by the interrupt routine shown in FIG.

That is, in step SWI, as is well known, the estimated vehicle speed ■SΦ is calculated based on the rotational speed of the wheel that is least slipping among the rotational speeds of the four wheels 22, 24, 52, and 54. and step SW2
, the target vehicle speed VSL is calculated based on the estimated vehicle speed ■SΦ according to the following equation (1).

VSL-VS(t)-VSΦ×A...(1) Here,
The above A is a constant slip rate, for example, a value of about several percent is adopted. Therefore, the target vehicle speed VSL is
The value is determined to be several percent lower than the estimated vehicle speed ■SΦ.

Returning to FIG. 2, if it is determined in step SA2 that the drive shaft vehicle speed VW is not smaller than the target vehicle speed VSL, the braking fluid pressure supplied to each wheel cylinder 72, 74, 76, 78 by ABSIIIIl is reduced, for example. When the rotational speed of the drive wheels 22, 24 recovers to the wheel rotational speed corresponding to the target vehicle speed VSL or higher by
After the contents of T are reset to "O", this interrupt routine is terminated. However, if it is determined in step SA2 that the driving wheel vehicle speed vW is smaller than the target vehicle speed VSL, then in step SA3 the brake is supplied to each wheel cylinder 72, 74, 76, 78 in an anti-lock brake control routine (not shown). It is determined whether or not the brake fluid pressure is under pressure reduction control. If it is determined in step SA3 that the pressure reduction control is not in progress, this interrupt routine is terminated via step SA6, which will be described later. However, if it is determined in step SA3 that the pressure reduction control is in progress, step SA
In step 4, it is determined whether pressure reduction control was also in progress in the previous control cycle. If it is determined in this step SA4 that the pressure reduction control is not in progress in the previous control cycle, the content of the timer counter COUNT is cleared to "0" in step SA5 because the pressure reduction control is not continuous, and the process proceeds to step SA6. After that, this interrupt routine is ended.

However, if it is determined in step SA4 that the pressure reduction control was in progress in the previous control cycle, the pressure reduction control is continuous, so after "1" is added to the contents of the timer counter COUNT in step SA7, In step SA8, it is determined whether the content of the timer counter COUNT is greater than a predetermined criterion value B.

This judgment reference value B is determined by actively changing the speed ratio C of the belt type continuously variable transmission 16 to the speed increasing side.
, 24, for example, 0.2 to 0.3 s.
It is set to about ec. In this embodiment, the contents of the timer counter COUNT correspond to the depressurization duration of the depressurization control. Initially, the contents of the timer counter COUNT have not reached the determination reference value B, and the determination at step SA8 is negative, so the present interrupt routine is terminated via step SA6. However, while the above routine is repeatedly executed, when the content of the timer counter COUNT reaches the judgment reference value B, the content of the flub FCVT is set to "1" in step SA9. The contents of this flub F cvt are from ABS ECU64 to CV
It is communicated to ECU 5l for T. FIG. 4 shows an interrupt routine that is repeatedly executed at predetermined time intervals in the CVT ECU 51. First, in step SCI, it is determined whether the content of the flag FCVT communicated from the ABS ECU 64 to the CVT ECU 51 is "0". This step S
If the CI determines that the contents of the flag F'cv〒 is "0", this interrupt routine is terminated, but if it is determined that the contents of the flag F'cvy is not "0", then , in step SC2, the speed ratio e of the belt type continuously variable transmission 16 is preferentially changed to the speed increasing side by a predetermined amount Δe. This predetermined amount Δe is determined experimentally.

By repeatedly executing the above interrupt routine, the speed ratio e of the belt type continuously variable transmission 16 is quickly changed to the speed increasing side in response to the slip of the drive wheels 22 and 24 exceeding the judgment reference value B. Therefore, in a state where the duration of brake fluid pressure reduction control in ABS control exceeds the judgment reference value B, the engine braking effect on the drive wheels 22, 24 is eliminated, and furthermore, the engine braking action on the drive wheels 22, 24 is
The rotation speed tends to be increased. As a result, the driving wheel rotational speed can quickly return to the value corresponding to the estimated vehicle speed ■SΦ, in other words, the driving wheel vehicle speed can quickly return to the estimated vehicle speed ■SΦ, and a sufficient anti-lock effect can be obtained. Arrows a, b, c, etc. on the curve indicating the speed ratio e in FIG. 5 indicate changes in the speed ratio toward the speed increasing side due to the above operation.

Incidentally, FIG. 6 shows the operation of a conventional speed ratio control device for a vehicle equipped with an anti-lock brake device and a belt-type continuously variable transmission. In the figure, the rotation of the driving wheels rapidly decreases due to slipping at the same time as the brake operation starts, and the speed ratio controlled based on the driving wheel vehicle speed is suddenly changed toward the maximum deceleration side. Even if the brake fluid pressure is reduced due to operation, the speed ratio e
In connection with the change to the maximum deceleration side, the negative torque of the engine 10 is transmitted to the fluid coupling 14 and the belt-type continuously variable transmission l6.
, is transmitted to the drive wheels 22 and 24 via the forward/reverse switching device 18 and the differential gear system if20, so the drive wheels cannot return to the estimated vehicle speed ■SΦ due to the engine braking action.
Anti-lock effect is not sufficiently obtained. Further, according to the present embodiment, unlike the conventional planetary gear type automatic transmission mechanism, a one-way clutch for preventing engine braking is not provided, so that the structure is simplified.

In addition, since a complicated algorithm is required to calculate the estimated vehicle speed VSΦ, the estimated vehicle speed vSΦ and the target vehicle speed VSL are set by the ABS ECU 6 4 as in this embodiment.
In addition, receiving the flag Fcvy via a 1-bit line has the advantage of simplifying the programming of the CVT ECU 51. Although one embodiment of the present invention has been described above based on the drawings,
The invention also applies to other aspects. For example, in the above-mentioned embodiment, the time measurement requirements for the depressurization duration are during ABS control in step SAI, target vehicle speed VSL>driving wheel vehicle speed vW in step SA2, and depressurization control in step SA3. By measuring the duration of decompression while the depressurization control is in progress, a certain degree of effect can be achieved.

Further, in step SAI of the above-described embodiment, the ABS
Instead of determining whether the control is in progress, it may be determined whether or not a brake operation is detected by the brake sensor 50, and the drive shaft vehicle speed VW used in step SA2 is determined by the left and right front transport 22 and A value based on the rotational speed of one of the 24 rotational speeds or the average rotational speed of both may be used.

Further, the judgment reference value B in the above-mentioned embodiment may be a constant value, but may also be a function of vehicle speed, slip ratio, braking fluid pressure, etc., for example.

Furthermore, although the above-mentioned embodiments have been described in detail for FF vehicles, the present invention can be similarly applied to FR vehicles. The above-mentioned embodiment is merely one embodiment of the present invention, and various modifications may be made to the present invention without departing from the spirit thereof.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a block diagram showing a power transmission control mechanism and a brake control mechanism of a vehicle including an embodiment of the present invention, FIGS. 2, 3, and 4. 2 are flowcharts showing main parts of control operations in the embodiment of FIG. 1. FIG. FIG. 5 is a time chart explaining the operation of the embodiment shown in FIG. FIG. 6 is a diagram corresponding to FIG. 4 in a conventional control device. I6 Belt type continuously variable transmission Front left wheel (drive wheel) Front right wheel (drive wheel) ECU for CVT (speed ratio control means) ECU for ABS (timekeeping means)

Claims (1)

[Scope of Claims] A continuously variable transmission that continuously changes the speed of the engine and transmits it to the drive wheels, and a brake that maintains the slip state of the wheels within a predetermined range in relation to the braking operation of the vehicle. In a vehicle equipped with an anti-lock brake device that automatically increases or decreases hydraulic pressure, the actual input shaft rotational speed or speed ratio of the continuously variable transmission matches a target value determined based on at least the driving wheel vehicle speed. A speed ratio control device for a continuously variable transmission for a vehicle, which controls a speed ratio of the continuously variable transmission, the timer for measuring the duration of pressure reduction during which the brake fluid pressure is reduced by the anti-lock brake device. and speed ratio control means for changing the speed ratio of the belt-type continuously variable transmission to the speed increasing side when the depressurization duration time measured by the timer exceeds a predetermined value. Speed ratio control device for continuously variable transmissions for vehicles.