JPH02234851A - Speed ratio control device for vehicle continuously variable transmission - Google Patents

Abstract

PURPOSE:To enable the regularly sufficient exhibition of anti-lock effect by replacing driving wheel vehicle speed by an estimated vehicle body speed at the time of anti-lock brake control, and determining a target value on the basis of the estimated vehicle body speed to control the speed ratio of a continuously variable transmission. CONSTITUTION:The rotation of an engine 10 is transmitted to a belt type continuously 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. The ECU 51 controls the speed ratio on the basis of a target value determined oh the basis of at least the driving wheel vehicle speed. In this case, an estimated vehicle body speed is detected on the basis of the rotating speed of each wheel detected by wheel rotation sensors 56-62, and at the time of anti-lock brake control, the driving wheel vehicle speed is replaced by the estimated vehicle body speed to determined the target value.

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 controlled so that the target input shaft rotation speed determined based on the vehicle throttle valve opening and vehicle speed matches the input shaft rotation speed of the continuously variable transmission. be done.

This allows the engine to operate along the optimum curve, resulting in a high fuel efficiency.

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 operation 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 brakes are operated, the driving wheel speed does not return to the vehicle body speed, and there are cases where a sufficient anti-lock effect cannot 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 brake fluid pressure, a speed ratio control device that adjusts the speed ratio of a 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 adjusts brake fluid pressure so as to maintain a wheel slip condition within a predetermined range, the vehicle may be provided with an anti-lock brake device that automatically adjusts brake fluid pressure to maintain the slip state of the wheels within a predetermined range. 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) wheel speed detection means that detects the rotational speed of each of a plurality of wheels provided on the vehicle; and (b) estimated vehicle speed detection that detects the estimated vehicle speed of the vehicle based on the rotational speed of each of the wheels. (C) at least when the anti-lock brake device is in operation;
and replacing means for replacing the driving wheel vehicle speed with the estimated vehicle speed detected by the estimated vehicle speed detecting means.

Effects and Effects of the Invention With this arrangement, at least when the anti-lock brake system is in operation, the driving wheel vehicle speed is replaced with the estimated vehicle speed detected by the estimated vehicle speed detection means. Since the target value is determined based on this estimated vehicle speed, compared to the case where the target value is determined based on the vehicle speed of the driving wheels, even if the speed of the driving wheels decreases due to the braking operation of the vehicle, there is no step change. The speed ratio of the transmission is controlled slowly toward the maximum deceleration side based on the estimated vehicle speed, making it difficult to apply engine braking to the drive wheels. For this reason, the vehicle. When the brake fluid pressure is reduced by the operation of the anti-lock brake system in the braking state, the driving wheel speed or the vehicle speed can be quickly returned to the vehicle speed, and a sufficient anti-lock effect can be obtained.

Here, preferably, when the brake pedal is operated and the slip ratio represented by the difference between the estimated vehicle speed and the drive wheel vehicle speed becomes equal to or higher than a predetermined value, the target value determining means calculates the slip ratio based on the estimated vehicle speed. and determining the target value.

EXAMPLE Hereinafter, an example of the present invention will be described in detail based on the drawings.

In FIG. 1, the rotation of an engine 10 is controlled by a fluid coupling 14 having a lock-up 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 transmission is transmitted to the forward/reverse switching device 18 and the differential gear W. 20 to the left and right drive wheels (front wheels) 22 and 24. In the fluid coupling 14, the lock knob 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.
8, 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 boots 1J32 and 34 with variable effective diameters provided on the input shaft 28 and output shaft 30, respectively, and a transmission belt 36 wound around the pair of variable pulleys 32 and 34. ing. For this reason,
A pair of variable booleans 3 are controlled by the CVT hydraulic control circuit 26.
The speed ratio can be changed by supplying hydraulic oil to one of a pair of hydraulic cylinders that apply clamping forces (thrusts) of 2 and 34, respectively, and discharging hydraulic oil from the other.

In addition, the forward/reverse switching device 1 is equipped with a planetary gear mechanism, a forward clutch, and a reverse brake, and a manual valve 38 that is mechanically linked to the operation of the shift lever 36 allows forward ranges such as D range to be adjusted. , or by selectively operating the forward clutch or the reverse brake in conjunction with the operation to the R range, the vehicle is made 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.

An engine rotation speed N is output from an engine rotation sensor 40 for detecting the rotation speed of the engine 10.

A signal representing the throttle valve opening θ is sent from the throttle sensor 42 for detecting the required output to the engine 10, and a signal representing the throttle valve opening θ is sent from the first rotation sensor 44 for detecting the rotational speed of the input shaft 28. Rotational speed N in
A signal representing the output shaft rotation speed N is output from the second rotation sensor 46 for detecting the rotation speed of the output shaft 30. A signal representing uL is output from the brake sensor 50 for detecting the operation of the brake pedal 48, and a signal representing the brake operation is output from the brake sensor 50 for detecting the operation of the brake pedal 48.
Each is supplied to an ECU (electronic control unit) 51 for CVT. This CVT ECU 5 1 includes a CPU,
It is a so-called microcomputer that includes ROM and RAM, and its CPU uses the storage function of RAM and is programmed with RAM in advance.
The input signal is processed according to a program stored in the OM, and the CVT hydraulic control circuit 26 controls the engagement state of the lock-up clutch 12, 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. ．． The actual vehicle speed (driving wheel vehicle speed) SPD is calculated based on the actual vehicle speed SPD, and when the actual vehicle speed SPD exceeds a predetermined judgment reference vehicle speed, the lock-up clutch l2 is engaged and the actual vehicle speed SPD becomes the predetermined judgment reference vehicle speed. The lock-up clutch 12 is released when the brake force is lowered or when a brake operation is performed.

Also, in ECU5 1 for CVT, belt type? Regarding the gear transmission 16, a target engine rotational speed value is determined based on the actual throttle valve opening θ and vehicle speed SPD from a pre-stored relationship for operating the engine 10 along an optimal curve that takes fuel efficiency and driving performance into consideration. N1J is determined, and the speed ratio of the belt type continuously variable transmission 8!16 is adjusted so that the target engine rotation speed value N 1 n and the actual input shaft rotation speed N i n match. Or input shaft rotation speed N. fi and output shaft rotation speed N. U, to the actual speed ratio e of the belt type continuously variable transmission 16 (=N.
■／Ni. ) is calculated, a target speed ratio e1 is determined based on the actual throttle valve opening θ and vehicle speed SPD from a pre-stored relationship for operating the engine 10 along the optimal curve, and this target speed ratio The speed ratio e of the belt type continuously variable transmission 16 is adjusted so that e1 matches the actual speed ratio e. Speed ratio C, input shaft rotation speed N! fi
, and the output shaft rotational speed N ou corresponding to the vehicle speed SPD
Since there is a relationship e=N out /NtA between t, 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 of the vehicle 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 ABS ECU 64 is supplied with a signal representing a brake operation from the brake sensor 50.

The ABS ECU64 is also a so-called microcomputer that includes a CPU, ROM, and RAM, and the CPU is
Using the memory function of AM, the input signal is processed according to a program stored in ROM in advance, and the estimated vehicle speed v is calculated.
SΦ is calculated, and the slip rate is calculated from the wheel rotation speed corresponding to this estimated vehicle speed ■SΦ and the actual rotation speed of each wheel during braking, and the ABS is adjusted so that the slip rate is within a predetermined range. The hydraulic control circuit 66 is activated. 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 bomb, 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. A
The braking force of each wheel is adjusted by reducing, increasing, or maintaining the hydraulic pressure to each wheel cylinder 70, 72, 74, and 76 in accordance with commands from the BS ECU 64. Below, the above CVT ECU 5 1 and ABS ECU
The main parts of the operation of 64 will be explained according to the flowcharts in FIGS. 2 and 3. FIG. 2 shows an interrupt routine that is repeatedly executed at predetermined time intervals in the ABS ECU 64. First, in step SAI, it is determined based on a signal from the brake sensor 50 whether or not the brake pedal 48 has been operated. If it is determined in step SAI that the brake operation is not being performed, this interrupt routine is terminated, but if it is determined that the brake operation is being performed, the drive wheel rotational speed V
WF 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. Also, the following step SA
3, the slip ratio X of the driving wheels is determined according to the following equation (1). ■SΦ1 in equation (1) is the wheel rotation speed corresponding to the estimated vehicle speed ■SΦ obtained in advance in an anti-lock brake control routine (not shown), and as is well known, the four wheels 22, 24,
It is determined based on the rotational speed of the least slipping wheel among 52 and 54.

X- (VSΦ'-VWF)/VSΦ1 ・ ・(1
) In step SA4, it is determined whether the slip ratio X of the driving wheels determined as described above is greater than or equal to a predetermined criterion value a. This judgment reference value a indicates that even if the braking oil pressure to the wheel cylinders 70, 72, 74, and 76 is reduced due to anti-lock operation, the speed ratio e of the belt type continuously variable transmission 16 is the maximum due to the braking operation of the vehicle. At the lower limit of the drive wheel slip range that is required to prevent the drive wheel vehicle speed from being unable to quickly return to the vehicle body speed due to engine braking that occurs in connection with the change to the deceleration side. Compatible.

Therefore, when it is determined in step SA4 that the slip ratio X of the driving wheels is equal to or higher than the predetermined judgment reference value a, the vehicle speed replacement signal SC and the estimated vehicle body speed ■SΦ are output to the CVT ECU 5 1 in step SA5. It will be done. Furthermore, even if it is determined in step SA4 that the slip ratio Step SA5 is executed. However, if it is determined in step SA6 that anti-lock brake control is not in progress, this interrupt routine is ended.

FIG. 3 shows an interrupt routine that is repeatedly executed at predetermined time intervals in the CVT ECU 51. First, in step SCI, it is determined based on a signal from the brake sensor 50 whether or not the brake pedal 48 has been operated. If it is determined in step S01 that the brake operation is not being performed, this interrupt routine is terminated, but if it is determined that the brake operation is being performed, the vehicle speed replacement signal SC is sent to the ABS ECU 6 in step SC2. 4, it is determined whether or not it is being supplied. In step SC2, if it is determined that the vehicle speed replacement signal SC is not supplied from the ABS ECU 64, step SC3 is not executed, but it is determined that the vehicle speed replacement signal SC is supplied from the ABS ECU 64. In this case, in step SC3, the content of the actual vehicle speed (driving wheel vehicle speed) SPD previously determined from the output shaft rotational speed N O LI L for speed ratio control in a speed ratio control routine (not shown) is determined as the estimated vehicle speed. ■
Replaced with SΦ. In the following step SC4, the vehicle speed change rate ΔSPD is determined by subtracting the vehicle speed SP Dz-+ one cycle ago from the current vehicle speed SPDi, and in step SC5,
It is determined whether the rate of change in vehicle speed ΔSPD is less than or equal to a pre-stored determination reference value X. Since the rate of change in vehicle speed ΔSPD is a negative value when the vehicle is decelerating, a negative value is adopted as the judgment reference value X. When the vehicle is in a state where the deceleration is large (sudden braking), it is necessary to quickly change the speed ratio e to the maximum deceleration side in preparation for restarting, so step SC5 is provided for this purpose.

If it is determined in step SC5 that the rate of change in vehicle speed ΔSPD is less than the pre-stored judgment reference value X, that is, if it is a sudden braking operation and the vehicle deceleration is large, then in step Transmission 1
Control is executed to quickly change the speed ratio e of 6 to the maximum deceleration side. However, if it is determined in step SC5 above that the rate of change in vehicle speed ΔSPD is greater than the pre-stored judgment reference value
7, normal speed ratio control is performed as described above. In a state where the above interrupt routine is repeatedly executed, when a braking operation is performed on a vehicle running on a road surface with low frictional resistance μ, the lock-up clutch 12 is released, and at the same time, the slip ratio X of the drive wheels is set as the judgment criterion. It is determined that the value a has been exceeded, and the ABS ECU 6.4 to the CVT ECU
A vehicle speed replacement signal SC is supplied to 51. This results in
The CVT ECU 5 1 receives the estimated vehicle speed vSΦ from the ABS ECU 6 4, and calculates the vehicle speed SP for speed ratio control.
Since the content of D is replaced with the estimated vehicle speed ■SΦ, the determination at step SC5 is denied and speed ratio control is executed according to step SC7. In other words, by replacing the contents of the vehicle speed SPD with the estimated vehicle speed vSΦ from the driving wheel vehicle speed determined from the output shaft rotational speed N out as described above, the deceleration of the vehicle approximates the actual vehicle speed. If it is determined that there is no sudden deceleration, the speed ratio is gradually changed toward the maximum deceleration side by the speed ratio control in step SC7. Therefore, the engine braking action is less likely to be applied to the driving wheels 22 and 24, and in response to the reduction in brake fluid pressure due to the operation of the anti-lock brake system in the braking state of the vehicle, the driving wheel rotational speed changes to the estimated vehicle body speed. In other words, the drive wheel vehicle speed can quickly and repeatedly return to the estimated vehicle speed, and a sufficient anti-lock effect can be obtained. FIG. 4 shows the above operation.

Incidentally, FIG. 5 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 16.
, the forward/reverse switching device 18, and the differential gear device 20 to the driving wheels 22, 24. Therefore, the driving wheel vehicle speed cannot be restored to the estimated vehicle speed due to the engine braking action, and a sufficient anti-lock action cannot be obtained. do not have.

Furthermore, according to the present embodiment, the content of the vehicle speed SPD (driving wheel vehicle speed) is not simply replaced with the estimated vehicle speed VSΦ with the brake operation as a requirement, so that the engine braking action can be easily performed when the road surface friction coefficient is high. There are benefits to be gained.

Furthermore, unlike the conventional planetary gear type automatic transmission mechanism, there is no one-way clutch for preventing engine braking, which simplifies the structure.

Furthermore, the CVT ECU 51 has the advantage that the estimated vehicle speed ■SΦ is used to the minimum necessary extent only during the ABS operation period, thereby increasing the reliability of other controls. The estimated vehicle speed ■SΦ is subject to many disturbances, and it is difficult to obtain an accurate vehicle speed.

In addition, since a complicated algorithm is required to calculate the estimated vehicle speed ■SΦ, by receiving the estimated vehicle speed ■SΦ from the ABS ECU 64 as in this embodiment, the program of the CVT ECU 51 is It has the advantage of being simple.

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 embodiment described above, the brake sensor 5
0, when a brake operation is detected and the drive wheel slip rate
5. The contents of the vehicle speed SPD may be replaced with the estimated vehicle speed ■SΦ, with the requirement that the brake operation is detected by the brake sensor 50 in step 1. Further, a signal indicating that anti-lock brake control has been started is received from the ABSmECU 64, and the CVT ECU 5
1, the contents of the vehicle speed SPD are set to the estimated vehicle speed V, with the requirement that the anti-lock brake control has been started.
It may be replaced with SΦ. In short, it is only necessary to determine the target value for speed ratio control based on the estimated vehicle speed ■SΦ while at least the anti-lock brake system is in operation.

Furthermore, when determining the slip ratio in step SA3 of the above-described embodiment, the average rotational speed of one or both of the left and right front wheels 22 and 24 may be used.

In addition, although the above-mentioned embodiment deals with a front-wheel drive vehicle, the present invention can also be applied to a front-wheel drive vehicle. 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 explanation of 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 and 3 are flowcharts showing the main parts of the control operation in the embodiment of FIG. 1, respectively. Fourth
The figure is a time chart illustrating the operation of the embodiment of FIG. 1. FIG. 5 is a diagram corresponding to FIG. 4 in a conventional control device. 16: Belt type continuously variable transmission 22: Left front wheel (drive wheel) 24: Right front wheel (drive wheel) 51: ECU for CVT (replacement means) 56.58, 60.62

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 adjusts 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 the speed ratio of the continuously variable transmission, comprising wheel speed detection means for detecting the rotational speed of each of a plurality of wheels provided on the vehicle. , an estimated vehicle speed detection means for detecting an estimated vehicle speed of the vehicle based on the rotational speed of each wheel; and at least in a state where the anti-lock brake device is in operation, the estimated vehicle speed detection means detects the vehicle speed of the driving wheels. A speed ratio control device for a continuously variable transmission for a vehicle, comprising: replacement means for replacing the estimated vehicle body speed detected by the means with the estimated vehicle speed detected by the means.