JPH0754141B2 - Lockup clutch controller for automatic transmission. - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a lockup clutch control device for an automatic transmission, which is configured to release the lockup clutch in a torque converter during a shift.

[Prior art]

An automatic transmission that includes a gear shift mechanism and is configured to selectively switch the engagement state of a friction engagement device by operating a hydraulic control device to achieve one of a plurality of shift stages is provided. It is already widely known. Such an automatic transmission is provided with a fluid clutch (generally a torque converter) in order to reduce the shock at the time of shifting, and the damper effect is utilized. By the way, in recent years, in order to reduce the power loss in the fluid clutch, the one equipped with a lockup clutch that mechanically directly connects the input and output sides of the fluid clutch has become popular. In an automatic transmission equipped with such a lockup clutch, when gearshifting is performed from a state in which the lockup clutch is engaged, the damper function as a fluid clutch cannot be used as it is, so the gearshift It is preferred that a control be implemented in connection with which the lockup clutch is temporarily released. From such a viewpoint, in Japanese Patent Publication No. 60-32063, the timing of releasing and re-engaging the lockup clutch is counted from the output point of the shift signal so as to be set immediately after the shift start and immediately after the shift end, respectively. A technique that employs a timer is disclosed.

[Problems to be Solved by the Invention]

However, when the timing of releasing and re-engaging the lockup clutch is determined by this timer, as shown by the broken line in FIG. 4, for example, when the oil temperature of the automatic transmission is extremely low, the viscosity of the supplied oil becomes large. Since the rise of the hydraulic pressure to the speed change frictional engagement device is delayed, the time from the output of the speed change signal to the actual start of the speed change becomes longer than usual, and the lock-up clutch will start before the speed change starts. There was a problem that it could be released. In this case, the early release of the lockup clutch causes a problem that the engine is blown up and the shift feeling deteriorates. Also, when the lockup clutch is re-engaged, if the lockup clutch re-engages before the shift is completed, the lockup clutch is already engaged at the end of the shift when the output fluctuation becomes the largest. Therefore, the problem that the damper function of the fluid clutch cannot reduce the torque fluctuation of the output shaft at the end of the gear shift is caused. Therefore, the conventional method of grasping the progress state of the shift using the timer has a problem that the lockup clutch may not be properly controlled depending on the traveling state or the traveling environment. By the way, there is already known a technique for detecting a change in the number of revolutions of a member whose rotational speed changes due to a shift and determining the start or end of the shift based on the detected change in the number of revolutions (for example, JP-B-48- 20348 publication). Therefore, a method of using this technique for releasing the lockup clutch or controlling the engagement can be considered. However, when controlling the lockup clutch by detecting the actual change in the number of revolutions, if the means for detecting the change in the number of revolutions fails, for example, the sensor system fails, or the wiring system from the sensor system to the computer. If the wire breaks or is shorted, the lockup clutch cannot be released or controlled. In that case, there is a problem that an extremely large shift shock occurs.

[Object of the Invention]

The present invention has been made in view of such a problem, and can always perform optimum control of the lockup clutch and has a highly reliable lockup clutch for a failure. An object is to provide a control device.

[Means for Solving the Problems]

The present invention, as shown in FIG. 1 for its gist, in a lockup clutch control device for an automatic transmission configured to release the lockup clutch at the time of gear shifting, the rotation of a member whose rotational speed changes depending on the gearshift. Means for detecting a change in the number of revolutions, means for releasing and engaging the lockup clutch based on the detected change in the number of revolutions, timer means for determining a predetermined time from a gear change judgment or a gear change command, and the change in the number of revolutions. When the means for detecting whether a failure has occurred and the means for detecting the change in the number of revolutions fail, the lockup clutch is released based on the confirmation of the predetermined time by the timer means. Means for controlling engagement is provided to achieve the above object. In the present invention, a turbine shaft of a torque converter, one of friction engagement devices, a crankshaft of an engine, or the like can be used as the "member whose rotational speed changes due to gear shift". .

[Operation and effect of the invention]

In the present invention, the disengagement / engagement control of the lockup clutch at the time of gear shift is basically performed by detecting the rotational speed change of the member whose rotational speed changes depending on the gear shift. As a result, for example, the actual gear shift time may vary depending on the oil temperature of the automatic transmission, or the actual gear shift time may vary depending on the change over time of the friction engagement device. Also, following this different shift time, the lockup clutch is released at the optimum timing,
Alternatively, they can be engaged. In addition, in the present invention, a timer means (back-up timer) for determining a predetermined time from the shift judgment or the shift command.
Is provided, and when the means for detecting the change in the number of revolutions fails, the back-up clutch releases and engages the lock-up clutch by the back-up timer. As a result, even if the means for detecting the actual speed change state (change in rotational speed) fails, it becomes possible to control the rockup clutch with a considerable degree of accuracy, and the shift feeling deteriorates extremely. Can be prevented. When the backup timer is used, if a warning to that effect is output, the subsequent inspection can be promptly performed.

【Example】

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 2 is a schematic view showing the vicinity of the lockup clutch of the automatic transmission to which the embodiment of the present invention is applied. The automatic transmission 10 is a torque converter connected to the engine 8 side.
12 and a known gear transmission 14 which is coaxially connected to the torque converter 12 and forms a plurality of gear stages. The torque converter 12 includes a crankshaft 16 of the engine 8.
Pump impeller 18 and one-way clutch 20 connected to
A turbine runner connected to a stator 22 connected to the housing via an input shaft 24 of the gear transmission 14.
26, and a lockup clutch 28. The lockup clutch 28 engages the crankshaft when engaged.
The driving force of 16 is directly transmitted to the input shaft 24 without passing through the fluid in the torque converter 12, and the power of the crankshaft 16 is transmitted to the input shaft 24 side via the fluid in the torque converter 12 when not engaged. The microcomputer 30 for automatic transmission control receives input signals such as throttle opening, vehicle speed (rotation speed of the output shaft 29 of the automatic transmission 10), and a shift pattern selected by the driver, and receives a hydraulic control circuit. 32 solenoids 34A-3
Control 4D. Of these, the solenoid 34A is provided for controlling the lockup clutch 28, and by turning the solenoid 34A ON / OFF, the lockup clutch 28 is hydraulically controlled in a known configuration to be released and engaged. The solenoids 34B to 34D are for selectively releasing and engaging a plurality of friction engagement devices in the gear transmission 14 with a well-known configuration, thereby achieving a predetermined shift speed. You can FIG. 3 shows a flow chart at the time of upshift as an example executed in the above-mentioned microcomputer. Here, as a member whose number of revolutions changes due to gear shifting,
The input shaft 24 of the automatic transmission is adopted, and (the rotation speed Ni of the input shaft 24) <(the low speed side gear ratio i _{L of the} gear transmission 14) ×
(The rotational speed N _O of the output shaft 29 of the automatic transmission 10) -the constant A, the lockup clutch is released at a time. In addition, when the rotation speed Ni of the input shaft 24 <(the gear ratio i _H of the high speed side of the gear transmission 14) x (the rotation speed N _O of the output shaft 29) + a constant B, the lockup clutch is re-established. To engage. Here, the low speed side gear ratio i _L is the gear ratio of the gear stage before the gear shift of the gear transmission 14, and the high speed side gear ratio i _H is the gear ratio of the gear stage after the gear shift. It is the ratio. Further, the constants A and B are constants that are determined in advance depending on the throttle opening degree, the type of gear shift (what speed gear to what speed upshift is). FIG. 3 will be specifically described. First, in step 102, a shift signal (solenoids 34B-34
It is determined whether or not a D-ON-OFF state change command) has been issued. When the shift signal is not issued, it is not necessary to control the lockup clutch based on the shift, and the flow is returned as it is. When it is determined in step 102 that the shift signal has been output, the process proceeds to step 104 and the timers T ₁ and T ₂ are started. Timer T ₁ is a lockup clutch.
The timer T ₂ is for the back-up on the release of 28 and the back-up on the re-engagement of the lock-up clutch 28. If the timer T _1, T ₂ is started at step 104, whether Ni <i _L × N _O -A are satisfied the process proceeds to step 106 it is determined. If it is determined that this condition is established, it is determined that the gear transmission 14 has actually begun to change the rotational speed for gear shifting, and in step 110, the release signal of the lockup clutch 28, that is, the solenoid 34.
The A OFF signal is issued. On the other hand, at step 106, until _{N i <i L × N O} -A is established, the timer T ₁ is compared with a predetermined value t ₁ proceeds to step 108, of the timer T ₁ is less than the predetermined value t ₁ Repeats the judgment at step 106, but if it gets larger,
After that, the process proceeds to step 110 without making the determination of step 106. This is because if Ni <i _L × N _O −A does not hold despite the lapse of a predetermined time t ₁ after the shift signal is output, there is an abnormality in the rotational speed (change) detection system. This is because it can be considered. Therefore, in this case, the release command of the lockup clutch 28, that is, the OFF command of the solenoid 34A is issued irrespective of the change in the rotation speed. At step 112, a determination is made to reengage the lockup clutch 28. That is, it is determined that the gear shift is completed when Ni <i _H × N _O + B is satisfied, and the step
Proceeding to 116, an engagement command for the lockup clutch 28, that is, an ON command for the solenoid 34A is issued. Also in this case, until Ni <i _H × N _O + B is satisfied, the routine proceeds to step 114, where the timer T ₂ is compared with the predetermined value t _2, and T ₂ ≦ t
Of the _two, the determination at step 112 is repeated, but T ₂
In the case of> t ₂ , the process proceeds to step 116 without issuing the determination of step 112, and an instruction to engage the lockup clutch 28 is issued. Since this embodiment is executed as described above, in normal times, the lockup clutch 28 is released and re-engaged depending on the actual shift state. Therefore, the optimum release / engagement control of the lockup clutch 28 can always be executed. Even if a change in the number of revolutions cannot be detected due to a failure, the lockup clutch 28 is released or engaged by the backup timers T ₁ and T ₂ , so that the lockup clutch 28 is engaged. It becomes possible to prevent such a problem that the gear shift is executed while keeping the above condition. In the present invention, how to determine the predetermined values t ₁ and t ₂ for the timers T ₁ and T ₂ is not limited to this. That is, the t ₁ and t ₂ may be fixed, for example, in consideration of the most general gear shift, or may be changed depending on the type of gear shift. Furthermore,
The change may be made more finely depending on the oil temperature of the automatic transmission, the engine load, and the like.

[Brief description of drawings]

FIG. 1 is a block diagram showing the gist of the present invention, and FIG. 2 is
A skeleton diagram showing the vicinity of a rockup clutch of an automatic transmission to which an embodiment of the present invention is applied, FIG. 3 is a flow chart showing a control flow executed by the automatic transmission, and FIG. FIG. 9 is a gear shift transient characteristic diagram for showing a malfunction when the control of the lockup clutch is executed only by the timer. 8 …… Engine, 10 …… Automatic transmission, 12 …… Torque converter, 14 …… Gear transmission, 24 …… Input shaft, 28 …… Lockup clutch, 29 …… Output shaft, T ₁ , T ₂ … … Timer.

Claims (1)

[Claims] 1. A lockup clutch control device for an automatic transmission configured to release a lockup clutch during a gear shift, and a means for detecting a change in the number of revolutions of a member whose number of revolutions changes due to a shift. A means for releasing and engaging the lockup clutch based on a change in the rotation speed, a timer means for determining a predetermined time from a gear change determination or a gear change command, and a means for detecting the change in the rotation speed. When the means for determining and the means for detecting the change in the number of revolutions fail,
A lockup clutch control device for an automatic transmission, comprising: a means for releasing and engaging the lockup clutch based on confirmation of a predetermined time by the timer means.