JPH02271160A - Lock-up clutch controller for automatic transmission - Google Patents

Abstract

PURPOSE:To ensure satisfactory running stability by providing a slip detecting means for detecting slips of wheels and a control means for controlling a lock-up clutch the releasing direction when the slips or wheels are detected by said detecting means durably speed reduction. CONSTITUTION:When a shift-down operation is carried out under the condition of a turned-up lock-up clutch in speed reduction, in other words, a engine brake is required, the rotational frequencies N1, N2 of drive and driven wheels are read by signals from rotation sensors 30, 31 to judge whether or not N1<N2. When the drive wheels slip by the operation of the engine brake in the travelling on a low mu path, the rotational frequency of the drive wheel becomes lower than that of driven wheel, so that N1<N2 is obtained. When N1<N2 is judged, a controller 26 outputs a control signal to a solenoid valve 25 to release the lock-up clutch 16. Thus, the mechanical connection between the drive wheel and engine is released so that the slip is released.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an automatic transmission, and particularly to a control device for a lock-up clutch in an automatic transmission that engages a lock-up clutch provided in a torque converter during deceleration. .

(Prior Art) In automatic transmissions installed in vehicles, in order to minimize the reduction in power transmission efficiency caused by the torque converter and improve fuel efficiency, the torque converter is equipped with a
A lock-up clutch is provided that directly connects the output side, and the lock-up clutch is controlled to be engaged in a predetermined operating range that does not require the torque increasing action or shock absorbing action of the torque converter.

In that case, for example, as shown in Japanese Patent Application Laid-Open No. 62-242173, a deceleration region in which the engine throttle opening is below a predetermined value is set as the above-mentioned predetermined operating region, and the lock-up clutch is activated during deceleration. There are cases where the engine brake operation is improved by fastening the brake.

(Problem to be Solved by the Invention) By the way, when the lock-up clutch is engaged during deceleration as described above to sufficiently operate the engine brake, the coefficient of friction of the road surface such as an icy road or snowy road, etc. On a so-called low-μ road, the effectiveness of the engine brake during deceleration becomes excessive relative to the traction coefficient of the road surface, causing the wheels to slip, which may impair driving stability.

SUMMARY OF THE INVENTION Therefore, the present invention aims to suppress wheel slip during deceleration when driving on a low μ road to ensure good running stability in an automatic transmission in which a lock-up clutch is engaged during deceleration. The task is to

(Means for Solving the Problems) In order to solve the above problems, the present invention uses the following means.

That is, the lock-up clutch control device for an automatic transmission according to the present invention is applicable to an automatic transmission in which a lock-up clutch that directly connects the input and output sides of a torque converter is engaged during deceleration. The vehicle is characterized in that it includes a detection means and a control means for controlling the lock-up clutch in the releasing direction when wheel slip is detected by the detection means during deceleration.

(Function) According to the above configuration, when the road surface is in a normal state and the coefficient of friction is not particularly low, and therefore there is no risk of the wheels slipping due to the operation of the engine brake, the lock-up clutch is engaged during deceleration. This allows engine braking to operate effectively.

On the other hand, when the wheels slip due to the operation of the engine brake when driving on a low μ road, the control means receives a signal from the slip detection means that detects this and operates the lock-up clutch in the release direction. As a result, the effectiveness of engine braking is suppressed. As a result, wheel slip is immediately eliminated, and good running stability is ensured during deceleration when running on a low μ road.

(Example) Examples of the present invention will be described below.

First, the structure of a torque converter equipped with a lock-up clutch according to this embodiment will be explained with reference to FIG. It has a pump 12, a turbine 13 rotatably provided on the other side of the case 11 facing the pump 12, and a stator 14 interposed between the turbine 13 and the pump 12. The turbine 13 is driven by the pump 12 that rotates integrally with the engine output shaft 1 through the hydraulic oil in the case 11, and the rotation is transmitted through the turbine shaft 15 to the speed change gear mechanism (not shown) of the automatic transmission. Further, due to the action of the stator 14, when the ratio of the turbine rotation speed to the pump rotation speed is below a predetermined value, the torque is increased and output from the turbine shaft 15.

Further, this torque converter 10 is provided with a lock-up clutch 16 between an end surface 11a of the case 11 on the turbine 13 side and the turbine 13. This lock-up clutch 16 is urged to be engaged with the case end face 11a by the pressure of the hydraulic oil in the case 11, and by coupling the case 11 and the turbine 13, the engine output is directly transmitted to the turbine shaft. 15, and when the hydraulic oil is introduced into the lock-up release chamber 17 provided between the case end face 11a, the pressure causes it to separate from the case end face 11a, separating the case 11 and the turbine 13. By doing so, the original operation of the torque converter as described above is allowed.

There is a hydraulic oil supply line 18 that supplies hydraulic oil from the hydraulic circuit that controls the automatic transmission into the case 11 of the torque converter 10, and a hydraulic oil supply line 18 that is branched from the line 18 and supplies hydraulic oil to the lockup release chamber 17. A lock-up release line 19 is connected to the lock-up release line 19, and a lubrication line 21 is provided to supply hydraulic oil discharged from the case 11 to lubrication points in various parts of the transmission via an oil cooler 20. On line 19,
A lock-up control valve 22 is provided to control supply and discharge of lock-up release hydraulic pressure through the line 19. This lock-up control valve 22 is composed of a spool 22a and a spring 22b disposed at one end of the spool 22a to bias the spool 22a toward the other end. A control line 23 is connected. Further, this control line 23 is provided with a drain hole 24 and is equipped with an ON-OFF type solenoid valve 25 that opens and closes the chain hole 24 . When the drain hole 24 is opened by the solenoid valve 25, the hydraulic oil in the control line 23 is discharged, and the spool 22a in the control valve 22 is moved to the right position as shown in the figure by the spring 22b, thereby locking up. The release line 19 is opened, and thereby the lock-up release hydraulic pressure is introduced into the release chamber 17 in the torque converter 10, and the lock-up clutch 16 is released. Further, when the drain hole 24 is closed by the solenoid valve 25, the hydraulic pressure in the control line 23 acts on the spool 22a of the control valve 22, and moves the spool 22a to the left in the drawing against the spring 22. By this,
The lock-up release line 19 communicates with a drain boat 22c provided in the control valve 22, and the hydraulic oil in the release chamber 17 is discharged, whereby the lock-up clutch 1
6 is now concluded.

A controller 26 is provided to control the operation of the solenoid valve 25, and the controller 26 is connected to a vehicle speed sensor 27 that detects the vehicle speed of the vehicle, a throttle sensor 28 that detects the throttle opening of the engine, and a controller 26 that controls the operation of the solenoid valve 25. Signals are input from various sensors such as a range sensor 29 that detects ranges such as D, S, and L that are set by operating a shift lever provided in the transmission.

This controller 26 controls the engagement and disengagement of the lock-up clutch 16 according to the driving state indicated by the vehicle speed, throttle opening, etc., by operating the solenoid valve 25 ON-OFF in response to signals from each of the above-mentioned sensors. In addition to this control, a rotation sensor 30.3 detects the rotation speed of the driving wheels and driven wheels of the vehicle.
The presence or absence of slip in the drive wheels is determined based on the signal from 1, and the lock-up clutch 16 is controlled in accordance with the determination result.

Next, the control operation of the lock-up clutch 16 by the controller 26 in response to the slip of the driving wheels will be explained with reference to the flowchart shown in FIG.

First, in step S1, the controller 26 reads the vehicle speed, the engine throttle opening, and the operating position of the shift lever, that is, the range, based on the signals from the sensors 27 to 29 shown in FIG. Determine whether the opening is fully open. Then, when the throttle opening is fully open, that is, during deceleration, a control signal is output to the solenoid valve 25 shown in FIG. Based on the signal, it is determined whether a downshift operation using the shift lever has been performed. Here, the downshift operation includes repeated operations from D range to S range or L range, or operations from S range to L range.

When a downshift operation is performed with the lock-up clutch 16 engaged during deceleration, in other words, when the driver requests engine braking,
In step S5, the rotational speed N of the driving wheel and the rotational speed N2 of the driven wheel are read based on the signal from the rotation sensor 30.31, and in step S6 it is determined whether N<N2.

By the way, when the driving wheels slip due to the operation of the engine brake when driving on a low μ road, their rotational speed becomes smaller than the rotational speed of the driven wheels, so these rotational speeds N, , N2
The relationship is N, <N2. Therefore, the above step S6
If it is determined that N and <N2, the controller 26 outputs a control signal to the solenoid valve 25 to release the lock-up clutch 16 in step S7.

As a result, the mechanical connection between the drive wheels and the engine is released, engine braking is suppressed, and in many cases, the slip of the drive wheels is eliminated.

Next, in step S8, the controller 26 reads the rotational speeds N, , N2 of the driving wheels and the driven wheels again, and if N is not <N2, that is, the slip of the driving wheels is eliminated by the release control of the lock-up clutch 16 described above. If so, in steps S, o, and SII, a control signal is outputted to re-engage the lock-up clutch 16 after waiting for the set time to elapse. As a result, the engine brake is activated again with the slip eliminated.

On the other hand, if the slip of the driving wheels is not resolved even though the lock-up clutch is released in step S7, and it is determined in step S that N is less than N2, the controller 26 then changes the speed in step S12. This control performs control to shift up the gear by one gear.
By performing the N-OFF operation, it is performed in the same manner as a normal automatic gear shifting operation. Then, in step SI3, the rotation speeds of the driving wheels and the driven wheels are read again, and in step S14, it is determined whether N l < N 2, that is, whether the slip of the driving wheels has been eliminated, When the engine brake is further reduced and the slip of the driving wheels is eliminated by the above shift-up control, the shift-down control of the gear stage is performed after waiting for the elapse of the set time in step S15+316. In addition, if the slip of the driving wheels is not eliminated despite the shift up control in step SI2, step S14 to step S1
2 is executed again to perform control to further shift up the gear position.

In this way, when driving on a low μ road, if the drive wheels slip due to engine braking,
By controlling the release of the lock-up clutch 16 or controlling the gear shift up, engine braking is suppressed depending on the slip situation, and the slip of the drive wheels is reliably eliminated.

Note that in this embodiment, when a downshift operation is performed with the lock-up clutch 16 engaged during deceleration, there is a risk that the drive wheels will slip due to excessive engine braking, so step 85 described above is performed. Although the following control is performed, simply engaging the lock-up clutch 16 during deceleration may cause the drive wheels to slip, so the control from step 85 onwards is performed regardless of whether or not a downshift operation is performed. You can do it like this.

(Effects of the Invention) As described below, according to the lock-up clutch control device for an automatic transmission according to the present invention, the lock-up clutch is normally engaged during deceleration, thereby providing the required engine braking. , when driving on a low μ road,
When the wheels slip due to the operation of the engine brake, the lock-up clutch is released to suppress the operation of the engine brake, so that the wheel slip is avoided or immediately eliminated. This improves running stability during deceleration on low μ roads.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a diagram showing the structure of a torque converter and a control system for a lock-up clutch, and FIG. 2 is a flowchart showing a control operation of the lock-up clutch. DESCRIPTION OF SYMBOLS 10... Torque converter, 16... Lock-up clutch, 26... Control means (control, U), 3
0.31 slip detection means (rotation sensor). Applicant Mazda Corporation Figure 1 Figure 2

Claims (1)

[Claims] (1) In an automatic transmission in which a lock-up clutch that directly connects the input and output sides of a torque converter is engaged during deceleration, there is provided a slip detection means for detecting wheel slip, and a slip detection means for detecting wheel slip during deceleration. A lock-up clutch control device for an automatic transmission, comprising: control means for controlling the lock-up clutch in a releasing direction when detected.