JP2527026B2 - Speed ratio control device for continuously variable transmission for vehicles - Google Patents

Description

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 A vehicle equipped with a continuously variable transmission that continuously changes the rotation of an engine and transmits the rotation to driving wheels is known. In such a vehicle, for example, as described in JP-A-59-144850, the target input shaft rotation speed determined based on the throttle valve opening and the vehicle speed of the vehicle and the continuously variable transmission are used. The speed ratio is controlled so that the input shaft rotation speed matches.
As a result, a high fuel consumption rate is obtained by operating the engine along the optimum curve.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention By the way, in a vehicle equipped with a continuously variable transmission as described above, the brake fluid pressure is automatically adjusted so as to maintain the slip state of the wheels within a predetermined range in association with the braking operation of the vehicle. It may be equipped with an anti-lock brake device that adjusts to. In such a case, it may be difficult to obtain sufficient antilock operation when braking the vehicle. That is, in the speed ratio control of the continuously variable transmission, the vehicle speed (hereinafter referred to as the drive wheel vehicle speed) is detected from the rotation state of the member that rotates with the drive wheels of the vehicle, and the speed ratio is adjusted based on at least the drive wheel vehicle speed. However, when the vehicle speed of the drive wheels is rapidly reduced by the braking operation of the vehicle, the speed ratio is rapidly changed to the most decelerated side, and the engine braking action is applied to the drive wheels. For this reason, even if the brake fluid pressure is reduced by the operation of the anti-lock brake device during the brake operation of the vehicle, the drive wheel vehicle speed may not return to the vehicle body speed, and the anti-lock effect may not be sufficiently obtained. is there.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to relate to a continuously variable transmission that continuously changes the rotation of an engine and transmits it to drive wheels, and a braking operation of a vehicle. In a vehicle equipped 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, the anti-lock action of the anti-lock brake device can be sufficiently obtained. Another object of the present invention is to provide a speed ratio control device for adjusting the speed ratio of a continuously variable transmission.

Means for Solving the Problems The gist of the present invention for achieving such an object is to provide a continuously variable transmission that continuously changes the rotation of an engine and transmits the rotation to a drive wheel, and a braking operation of a vehicle. In a vehicle equipped 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, a target value determined based on at least the drive wheel vehicle speed is set. A speed ratio control device for a continuously variable transmission for a vehicle, which controls a speed ratio of the continuously variable transmission such that an actual input shaft rotation speed of the continuously variable transmission or a speed ratio thereof matches. Wheel speed detecting means for respectively detecting rotational speeds of a plurality of wheels provided on the vehicle; (b) estimated vehicle body speed detecting means for detecting an estimated vehicle body speed of the vehicle based on the rotational speeds of the respective wheels; (C) At least Also, when the anti-lock brake device is in operation, a replacement unit that replaces the drive wheel vehicle speed with the estimated vehicle body speed detected by the estimated vehicle body speed detection unit is included.

In this way, the driving wheel vehicle speed is replaced with the estimated vehicle body speed detected by the estimated vehicle body speed detecting means, at least when the antilock brake device is operating. Since the target value is determined based on this estimated vehicle body speed, as compared with the case where the target value is determined based on the drive wheel vehicle speed, even if the drive wheel vehicle speed decreases due to the braking operation of the vehicle, it is continuously variable. The speed ratio of the transmission is slowly controlled toward the most decelerated side on the basis of the estimated vehicle speed, so that it becomes difficult to apply the engine braking action to the drive wheels. Therefore, when the braking fluid pressure is reduced by the operation of the anti-lock brake device in the braking state of the vehicle, the vehicle speed of the driving wheels can be quickly returned to the vehicle body speed, and the anti-lock effect can be sufficiently obtained.

Here, preferably, when the brake pedal is operated and the slip ratio represented by the difference between the estimated vehicle body speed and the drive wheel vehicle speed becomes equal to or more than a predetermined value, the target value determination means determines the estimated vehicle body speed based on the estimated vehicle body speed. To determine the target value.

Embodiment Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

In FIG. 1, the rotation of the engine 10 is transmitted to a belt-type continuously variable transmission (CVT) 16 via a fluid coupling 14 having a lock-up clutch 12 arranged in parallel. After the speed is changed steplessly, it is transmitted to left and right drive wheels (front wheels) 22 and 24 via a forward / reverse switching device 18 and a differential gear device 20.

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.

Further, the belt type continuously variable transmission 16 has an input shaft 28 connected to the engine 10 via a fluid coupling 14,
An output shaft 30 connected to the left and right drive wheels 22 and 24 via the forward / reverse switching device 18 and the differential gear device 20, and a pair of variable effective diameters provided on the input shaft 28 and the output shaft 30, respectively. The variable pulleys 32 and 34 and the transmission belt 35 wound around the pair of variable pulleys 32 and 34 are provided. Therefore, by supplying the hydraulic oil to one of the pair of hydraulic cylinders that apply the clamping pressure (thrust) of the pair of variable pulleys 32 and 34 by the CVT hydraulic control circuit 26 and discharging the hydraulic oil from the other, The speed ratio can be changed.

The forward / reverse switching device 18 includes a planetary gear mechanism, a forward clutch, and a reverse brake, and is a manual valve mechanically linked to the operation of the shift lever 36.
By 38, the forward clutch or the reverse brake is selectively operated in conjunction with the operation to the forward range such as the D range or the R range, whereby the vehicle is moved forward or backward. Further, when the shift lever 36 is operated to the P range or the N range and the forward clutch and the reverse brake are not operated, power transmission is cut off in the forward / reverse switching device 18. ing.

A signal indicating the engine rotation speed _Ne is output from the engine rotation sensor 40 for detecting the rotation speed of the engine 10, and a signal indicating the throttle valve opening θ is output from the throttle sensor 42 for detecting the required output to the engine 10. , Input shaft
A signal indicating the input shaft rotation speed N _in is output from the first rotation sensor 44 for detecting the rotation speed of the output shaft 28, and the output shaft rotation speed N in output from the second rotation sensor 46 for detecting the rotation speed of the output shaft 30. A signal indicating “ _out” and a signal indicating a brake operation are supplied from a brake sensor 50 for detecting operation of the brake pedal 48 to an ECU (electronic control unit) 51 for CVT. The CVT ECU 51 is a so-called microcomputer including a CPU, a ROM, and a RAM. The CPU uses the storage function of the RAM to process an input signal according to a program stored in the ROM in advance, and the CVT hydraulic control. Engagement of lock-up clutch 12 in circuit 26, belt type continuously variable transmission
16 speed ratio etc. are controlled.

For example, in the CVT ECU 51, with respect to the lockup clutch 12, the actual vehicle speed (driving wheel vehicle speed) SPD is calculated based on the output shaft rotation speed N _out from the prestored reduction ratio, the diameter of the driving wheel, and the like. When the actual vehicle speed SPD exceeds the predetermined determination reference vehicle speed, the lockup clutch 12 is engaged, and when the actual vehicle speed SPD falls below the predetermined determination reference vehicle speed, or when the brake operation is performed, the lockup clutch 12 is engaged. Let go.

Further, in the CVT ECU 51, regarding the belt type continuously variable transmission 16, the actual throttle valve opening θ and from the pre-stored relationship for operating the engine 10 along the optimum curve in consideration of fuel consumption and driving performance. The target engine speed value N _in ^* is determined based on the vehicle speed SPD, and the speed ratio of the belt type continuously variable transmission 16 is adjusted so that the target engine speed value N _in ^* and the actual input shaft speed N _in match. Is adjusted. Alternatively, from the input shaft rotation speed N _in and the output shaft rotation speed N _out , the actual speed ratio e (=
After N _out / N _in ) is calculated, the engine follows the optimum curve
The target speed ratio e ^* is determined based on the actual throttle valve opening θ and the vehicle speed SPD from the relationship stored in advance for operating 10, and the target speed ratio e ^* and the actual speed ratio e match. Thus, the speed ratio e of the belt type continuously variable transmission 16 is adjusted. Speed ratio e, input shaft rotation speed N _in , and vehicle speed S
Between the output shaft rotation speed N _out corresponding to PD, e = N _out / N
_Since there is a relation of in, the former control and the latter control 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
Wheel rotation sensors 56, 58, 60, 62 for detecting respective rotation speeds are provided on the 24 and the left and right rear wheels 52, 54, respectively, and these wheel rotation sensors 56, 58, 6 are provided.
Signals representing the rotation speeds of the wheels 22, 24, 52, 54 are supplied to the ABS ECU 64 from 0, 62. Also, the ECU for ABS
A signal representing the brake operation from the brake sensor 50 is supplied to 64. ECU 64 for ABS also has CPU, ROM, RA
A so-called microcomputer including M, whose CPU is
While processing the input signal according to the program stored in advance in ROM while using the memory function of RAM, the estimated vehicle speed VSΦ is calculated, and the wheel rotation speed corresponding to this estimated vehicle speed VSΦ and each wheel at the time of braking are calculated. The slip ratio is calculated from the actual rotation speed, and the ABS hydraulic control circuit 66 is operated so that the slip ratio falls within a predetermined range. The predetermined range is a predetermined area in which the road surface friction coefficient μ is large and the cornering force can be secured. As is well known, the ABS hydraulic control circuit 66 includes a master cylinder 68 provided with a pump, a damper, a reservoir, a control valve, etc., and wheel cylinders 70, 72 provided for each wheel.
It is arranged between 74 and 76, and reduces the hydraulic pressure to each wheel cylinder 70, 72, 74, 76 according to the command from the ECU 64 for ABS,
The braking force of each wheel is adjusted by increasing or maintaining the pressure.

The main parts of the operation of the CVT ECU 51 and the ABS ECU 64 will be described below with reference to the flowcharts of FIGS. 2 and 3.

FIG. 2 shows an interrupt routine that is repeatedly executed at a predetermined time in the ABS ECU 64. First, in step SA1, it is determined according to a signal from the brake sensor 50 whether the brake pedal 48 has been operated. When it is determined in step SA1 that the brake operation is not performed, this interrupt routine is ended, but when it is determined that the brake operation is performed, the drive wheel rotation speed VWF is set to the left side in step SA2. It is determined by adopting the lower value of the rotation speed VWFL of the drive wheel 22 and the rotation speed VWFR of the right drive wheel 24. Also,
In the following step SA3, the slip ratio X of the drive wheels is calculated according to the following equation (1). VS in equation (1)
Φ ′ is a wheel rotation speed corresponding to the estimated vehicle body speed VSΦ previously obtained in the anti-lock brake control routine (not shown), and as is well known, four wheels are used.
It is determined based on the rotational speed of the wheel that is least slipped among 22, 24, 52 and 54.

X = (VSΦ′−VWF) / VSΦ ′ (1) At step SA4, it is determined whether or not the slip ratio X of the driving wheels obtained as described above is equal to or larger than a predetermined judgment reference value a. To be judged. This judgment reference value a is such that the speed ratio e of the belt-type continuously variable transmission 16 is maximized in accordance with the braking operation of the vehicle even if the braking hydraulic pressure to the wheel cylinders 70, 72, 74, 76 is reduced by the antilock operation. It corresponds to the lower limit value of the slip range of the drive ratio, which is required to prevent the drive wheel vehicle speed from being unable to quickly return to the vehicle body speed due to the engine braking generated in connection with the change to the deceleration side. ing.

Therefore, when it is determined in step SA4 that the slip ratio X of the driving wheels is equal to or greater than the predetermined determination reference value a, the vehicle speed replacement signal SC and the estimated vehicle body speed VSΦ are output to the CVT ECU 51 in step SA5. . Even if it is determined in step SA4 that the slip ratio X of the driving wheels is lower than the predetermined determination reference value a, step SA
When it is determined in 6 that the anti-lock brake control is still in progress, step SA5 is similarly executed.
However, if it is determined in step SA6 that the antilock brake control is not being performed, this interrupt routine is ended.

FIG. 3 shows an interrupt routine that is repeatedly executed in the CVT ECU 51 at predetermined time intervals. First, in step SC1, it is determined according to a signal from the brake sensor 50 whether the brake pedal 48 has been operated. If it is determined in step SC1 that the brake operation is not being performed, this interrupt routine is ended, but if it is determined that the brake operation is being performed, the vehicle speed replacement signal SC is set in the ABS ECU 64 in step SC2. It is determined whether or not it is supplied from. When it is determined in step SC2 that the vehicle speed replacement signal SC is not supplied from the ABS ECU 64, step SC3 is not executed, but when it is determined that the vehicle speed replacement signal SC is supplied from the ABS ECU 64. In step SC3, the actual vehicle speed (driving wheel vehicle speed) SPD previously obtained from the output shaft rotation speed N _out for speed ratio control in a speed ratio control routine (not shown) is replaced with the estimated vehicle body speed VSΦ. To be done.

In the following step SC4, the vehicle speed change rate ΔSP is calculated by subtracting the vehicle speed SPD _i-1 one cycle before from the current vehicle speed SPD _i.
D is determined, and in step SC5, it is determined whether or not the vehicle speed change rate ΔSPD is a previously stored determination reference value x. Since the rate of change ΔSPD of the vehicle speed is a negative value when the vehicle is decelerating, a negative value is adopted as the determination reference value x. In the state where the deceleration of the vehicle is large (rapid braking), the speed ratio e needs to be quickly changed to the maximum deceleration side in preparation for restarting, so the above step SC5 is provided for this purpose.

If it is determined in step SC5 that the rate of change ΔSPD of the vehicle speed is equal to or less than the previously stored determination reference value x, that is, if the vehicle is in a sudden braking operation and the deceleration of the vehicle is large, the belt type stepless operation is performed in step SC6. The control is executed to quickly change the speed ratio e of the transmission 16 to the maximum deceleration side. However, in step SC5 above, the rate of change in vehicle speed ΔS
When it is determined that PD is larger than the previously stored determination reference value x, that is, when the deceleration of the vehicle is not so large and not during the sudden braking operation, the normal speed ratio control is executed as described above in step SC7. .

In the state where the above interrupt routine is repeatedly executed, when the braking operation of the vehicle running on the road surface having the low frictional resistance μ is performed, the lockup clutch 12 is released, and at the same time, the slip ratio X of the driving wheels is the criterion It is judged that the value a has been exceeded, and the vehicle speed replacement signal is sent from the ABS ECU 64 to the CVT ECU 51.
SC is supplied. As a result, the ECU 51 for CVT becomes the ECU 64 for ABS.
Since the estimated vehicle body speed VSΦ is received from the vehicle body and the content of the vehicle speed SPD for speed ratio control is replaced with the estimated vehicle body speed VSΦ, the determination at step SC5 is denied and the speed ratio control is executed according to step SC7. That is, as described above, the vehicle speed SP
By replacing the content of D with the estimated vehicle body speed VSΦ from the drive wheel vehicle speed obtained from the output shaft rotation speed N _{out, the} estimated vehicle body speed VSΦ with which the vehicle deceleration approximates the actual vehicle body speed
If it is determined that it is not a sudden deceleration,
The speed ratio is gently changed toward the most deceleration side by the speed ratio control in step SC7. Therefore, the drive wheels
It becomes difficult to add engine braking action to 22, 24,
In response to a reduction in hydraulic fluid pressure due to the operation of the anti-lock brake device in the braking state of the vehicle, the drive wheel rotation speed reaches a value corresponding to the estimated vehicle body speed, in other words,
The drive wheel vehicle speed can be quickly and repeatedly returned to the estimated vehicle body speed, and a sufficient antilock 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 antilock brake device and a belt type continuously variable transmission. In the figure, at the same time when the brake operation is started, the drive wheels rapidly rotate due to slip,
Since the speed ratio controlled based on the driving wheel vehicle speed is rapidly changed toward the most decelerated side, even if the brake fluid pressure is reduced by the operation of the antilock brake device, the speed ratio e is most decelerated. The negative torque of the engine 10 is related to the change of the drive wheels 22, 24 via the fluid coupling 14, the belt type continuously variable transmission 16, the forward / reverse switching device 18, and the differential gear device 20.
Therefore, the vehicle speed cannot be restored to the estimated vehicle speed due to the engine braking action, and the antilock action is not sufficiently obtained.

Further, according to the present embodiment described above, the content of the vehicle speed SPD (driving wheel vehicle speed) is not simply replaced with the estimated vehicle body speed VSΦ on the basis of the brake operation, so that the engine braking action is facilitated when the road surface friction coefficient is high. There are advantages to be obtained.

Further, unlike the conventional planetary gear type automatic transmission mechanism, a one-way clutch for preventing the engine braking action is not provided, so that the structure is simplified.

Further, the CVT ECU 51 has an advantage that the estimated vehicle body speed VSΦ is utilized to the minimum necessary only during the ABS operation period, and the reliability of other controls is enhanced. The estimated vehicle speed VSΦ is subject to many disturbances and it is difficult to obtain accurate vehicle speed.

Further, since a complicated algorithm is required to calculate the estimated vehicle body speed VSΦ, by receiving the estimated vehicle body speed VSΦ from the ABS ECU 64 as in this embodiment, the CVT
There is an advantage that the program of ECU51 becomes simple.

Although one embodiment of the present invention has been described above with reference to the drawings, the present invention is also applicable to other aspects.

For example, in the embodiment described above, the brake sensor
When the brake operation is detected by 50 and the slip rate X of the driving wheels is equal to or more than the predetermined value a, the content of the vehicle speed SPD is replaced with the estimated vehicle body speed VSΦ. However, in the CVT ECU 51, the brake sensor 50 operates the brake operation. The content of the vehicle speed SPD may be replaced with the estimated vehicle body speed VSΦ on the condition that it is detected. In addition, the signal indicating that the anti-lock brake control has been started is received from the ABS ECU 64, and in the CVT ECU 51, the content of the vehicle speed SPD is set to the estimated vehicle speed VSΦ on the condition that the anti-lock brake control is started. It may be replaced. In short, the target value in the speed ratio control should be determined based on the estimated vehicle speed VSΦ at least while the anti-lock brake device is operating.

Further, when obtaining 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 can be used.

Further, although the FF vehicle is used in the above-described embodiment, the present invention can be applied to the FR vehicle.

The above description is merely one embodiment of the present invention, and the present invention can be variously modified without departing from the spirit thereof.

[Brief description 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. 2 and 3 are flow charts showing the main parts of the control operation in the embodiment of FIG. FIG. 4 is a time chart explaining the operation of the embodiment shown in FIG. FIG. 5 is a diagram corresponding to FIG. 4 in the conventional control device. 16: Belt type continuously variable transmission 22: Left front wheel (driving wheel) 24: Right front wheel (driving wheel) 51: CVT ECU (replacement means) 56,58,60,62: Wheel rotation sensor (wheel speed detection means) 64: ABS ECU (Estimated vehicle speed detection means)

Claims (1)

(57) [Claims] 1. A continuously variable transmission that continuously changes the rotation of an engine and transmits it to driving wheels, and a brake fluid for maintaining a slip state of the wheels within a predetermined range in relation to a braking operation of a vehicle. In a vehicle equipped with an anti-lock brake device that automatically adjusts pressure, an actual input shaft rotation speed or speed ratio of the continuously variable transmission should match a target value determined based on at least the driving wheel vehicle speed. A speed ratio control device for a vehicle continuously variable transmission for controlling a speed ratio of the continuously variable transmission, comprising wheel speed detection means for detecting respective rotational speeds of a plurality of wheels provided in the vehicle, An estimated vehicle body speed detecting means for detecting an estimated vehicle body speed of the vehicle based on the rotation speeds of the respective wheels; and, at least in a state where the antilock brake device is in operation, estimating the drive wheel vehicle speed. Speed ratio control device for a continuously variable transmission for a vehicle characterized in that it comprises a and a replacement means for replacing the estimated vehicle speed detected by the body speed detecting means.