JPH0823389B2 - Lockup control device for automatic transmission - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lockup control device for an automatic transmission having a lockup clutch.

(Prior Art) Conventionally, in an automatic transmission including a torque converter and a speed change mechanism that is switched according to a speed change pattern, lockup is performed between an input shaft and an output shaft of the torque converter in order to improve torque transmission efficiency. With a clutch,
A device for switching the lockup clutch between an engaged state (a state in which the torque converter is turned on and an output side is directly connected) and an opened state according to the operating region is generally known.

By the way, in an automatic transmission equipped with such a lock-up clutch, if the lock-up clutch is in the engaged state during a gear shift in which the gear is automatically switched, the gear shift is caused by the torque difference between the engine output torque and the wheel side torque. Shock occurs. For this reason, in general, at the time of gear shifting, the lockup clutch is disengaged and the torque is transmitted through the torque converter, so that the torque difference is absorbed and the shift shock is alleviated. However, even if the lockup clutch is disengaged in this way, it is difficult to avoid some shock due to the torque multiplication effect of the torque converter. Further, in the case where the lockup clutch is disengaged at the time of shifting as described above, there is a problem that a shift shock occurs when the lockup clutch is reengaged immediately after shifting.

For example, as disclosed in Japanese Patent Laid-Open No. 57-33253, in order to absorb torque fluctuations and improve fuel consumption, the lockup clutch is put in a slip state (half-clutch state) in a specific operating region, and A lockup control device is also known in which the fastening force of the lockup is feedback-controlled so that the rotational speed difference between the input shaft and the output shaft becomes a set value. However, even in the case of this device, when the gear shift is performed outside the specific region, a shock due to the torque multiplying action or the like occurs, and when the gear shift is performed in the specific region, the difference in the rotational speed is not satisfied. In the feedback control, the engagement force of the lockup clutch is not always maintained at an appropriate value for alleviating the shift shock, and the shift shock has not been sufficiently mitigated.

(Object of the Invention) In view of the above circumstances, the present invention provides a lockup control device capable of appropriately adjusting torque transmission during gear shifting of an automatic transmission and sufficiently reducing shock during gear shifting. .

(Structure of the Invention) The present invention includes a lockup clutch that is hydraulically operated between an input shaft and an output shaft of a torque converter, and adjusts the hydraulic pressure of hydraulic oil supplied to the lockup clutch. In an automatic transmission equipped with an operating hydraulic pressure adjusting means for adjusting the engagement force of a lockup clutch, a shift detecting means for detecting a shift by a speed change mechanism of the automatic transmission, and an oil temperature detecting means for detecting an oil temperature of the working oil. And lock-up clutch engagement force control means for controlling the engagement pressure of the lock-up clutch by receiving the outputs of the shift detection means and the oil temperature detection means and controlling the operating hydraulic pressure adjustment means. The clutch engagement force control means controls the engagement force of the lock-up clutch to be more than the engagement force required to obtain a complete engagement state during shifting. It is configured to control the operating hydraulic pressure adjusting means so as to be a predetermined value that is larger than the fastening force that is a small and completely released state, and correct the control value of the operating hydraulic pressure adjusting means according to the oil temperature. It is what

With this configuration, during shifting of the automatic transmission, a constant engagement force is maintained so as to keep the lock-up clutch in an appropriate half-clutch state, regardless of the rotational speed difference between the input side and the output side of the torque converter. Further, in this case, the control value of the operating oil pressure adjusting means is corrected according to the oil temperature, so that the fluctuation of the lockup clutch engaging force due to the oil temperature is corrected, and an appropriate half-clutch state is secured. In this way, the shift shock is effectively reduced.

(Embodiment) FIG. 1 shows an example of the overall structure of an automatic transmission including the device of the present invention. In this figure, an automatic transmission 2 connected to an engine 1 includes a torque converter 3 incorporating a lock-up clutch described later, various friction elements (various clutches, brakes) for switching a planetary gear mechanism and its power transmission path, and the like. And a hydraulic control circuit 5 for controlling the speed change mechanism 4. The hydraulic control circuit 5 includes shift control solenoids 6a to 6c and a lockup control solenoid 7. The shift control solenoids 6a to 6c are for controlling engagement and disengagement of the friction elements via various control valves and shift valves in a hydraulic control circuit.The shift control solenoids 6a to 6c are turned on. , OFF, the friction element engagement state is changed and the speed change mechanism 4 is switched to a plurality of speed stages. The lockup control solenoid 7 will be described in detail later.

A control signal is output from a control unit (ECU) 10 using a microcomputer or the like to each of the solenoids 6a to 6c, 7 for shift control and lockup control. The control unit 10 includes an engine speed sensor 11 that detects the speed of the engine 1, a turbine speed sensor 12 that detects the turbine speed of the torque converter 3, and a throttle opening sensor 13 that detects the opening of a throttle valve. , Vehicle speed sensor to detect vehicle speed
14, an oil temperature sensor (oil temperature detecting means) 15 for detecting the oil temperature of the hydraulic oil supplied to the lockup clutch, a gear position sensor 16 for detecting the gear position (shift stage) of the speed change mechanism 7, and an operation mode detection Each output signal from the mode lever 17 or the like is input.

FIG. 2 shows the structure of a lockup clutch incorporated in the torque converter 3 and a control system for the lockup clutch. In this figure, a torque converter 3 includes a pump 22 connected to an input shaft (output shaft of the engine 1) 20 via a case 21, a turbine 23 provided to face the pump 22, and a turbine 23 provided between them. An output shaft 25 is coupled to the turbine 23, and a driving force is transmitted from the output shaft 25 to a speed change mechanism (not shown in the drawing). . This torque converter 3
A lock-up clutch 26, which is hydraulically actuated, is incorporated in this.

The lockup clutch 26 is a clutch plate that is connected to the output shaft 25 and can be brought into contact with and separated from the case 21.
A hydraulic working chamber 28 is formed between the clutch plate 27 and the case 21. And the hydraulic working chamber
When the hydraulic pressure of the specified pressure is supplied to 28, the clutch plate
27 is separated from case 21 and is in an open state,
When the hydraulic pressure in 28 is removed, the clutch plate 27 is pressed against the case 21 by a predetermined fastening force by the hydraulic pressure in the torque converter 3 so that the input shaft 20 and the output shaft 25 are directly connected. Is configured.

The hydraulic control circuit for the lockup clutch 26 includes an oil passage 31 and an oil pump 32 communicating with the hydraulic working chamber 28.
A lock-up control valve 35 is provided between the lock-up control valve 35 and the torque converter 3 and an oil passage 34 to which a line pressure is applied from the lock-up control valve 35 to the torque converter 3. An oil passage 36 for providing a constant hydraulic pressure is provided. A lockup control solenoid 7 including a duty solenoid is connected to an oil passage 37 that supplies pilot pressure to the lockup control valve 35. The lockup control solenoid 7 and the lockup control valve 35 constitute an operating hydraulic pressure adjusting means for adjusting the engaging force of the lockup clutch 26 by adjusting the hydraulic pressure of the operating oil supplied to the lockup clutch 26. Has been done.

The lockup control solenoid 7 is for displacing the spool 35a of the lockup control valve 35 by adjusting the pilot pressure according to a control signal (duty signal) from the control unit 10. When the duty of the control signal is minimized and the spool 35a is moved to the one end side, a predetermined hydraulic pressure is supplied to the hydraulic pressure operating chamber 28 to open the lockup clutch 26, and the control signal When the spool 35a moves to the other end side due to the maximum duty, the hydraulic pressure in the hydraulic pressure operating chamber 28 is discharged and the lockup clutch 26 is completely engaged.
Further, when the spool 35a is controlled to the intermediate position by setting the duty of the control signal to an intermediate value, the hydraulic pressure in the hydraulic pressure operating chamber 28 is set so that the lockup clutch 26 is in a semi-engaged state in which it slips to some extent. Is adjusted to control the engagement force of the lockup clutch 26.

For the lockup control solenoid 7, the control unit 10 receives the shift detection means 41 for detecting the shift by the speed change mechanism 4 and the outputs of the shift detection means 41 and the oil temperature sensor 15 to perform the lockup control. The lockup clutch is controlled by controlling the solenoid 7.
Lockup clutch engagement force control means 42 for controlling the engagement force of 26 is included. The lock-up clutch engaging force control means 42 is configured such that, during shifting, the engaging force of the lock-up clutch 26 is smaller than the engaging force required to obtain a complete engaged state, and is larger than the engaging force in a completely released state. The lockup control solenoid 7 is controlled so as to satisfy the above condition, and the duty, which is the control value, is corrected according to the oil temperature.

Memory in the control unit 10 (not shown)
Stored in advance are shift patterns and lockup control patterns as shown in FIG. That is, as the shift pattern, for example, the shift-up lines SU ₁ , SU ₂ , SU ₃ and the shift-down lines SD ₁ , SD ₂ between the first to fourth speeds using the vehicle side and the throttle opening as parameters are set. , SD ₃ are set, and the shift control is performed according to the vehicle speed and the throttle opening according to such a shift pattern. Further, as the lockup control pattern, a slip region in which the lockup clutch engaging force is feedback-controlled so that the lockup clutch 26 is slipped to set the target rotational speed difference between the input side and the output side of the torque converter 3, Lockup clutch 26
Is set to a completely engaged state, and a lock-up clutch 26 is set to a disengaged state (a state in which torque is transmitted via the torque converter 3). For example, the predetermined speed is a specific region slip region A ₁ in the region of each gear _{position, A 2, A 3, A} 4, which a certain region of the high vehicle speed side such as the lock-up region B _1, B _2, B ₃ , B ₄ , so that the other areas become the converter area C, the slip control ON lines SL ₁ , SL ₂ , SL ₃ , SL ₄ and the lockup ON lines LU ₁ , LU ₂ , LU ₃ , LU ₄ , Lockup off line L
U ₁₄ is set. The lockup clutch 26 is controlled in accordance with the region setting except when shifting.

A specific control operation of the lockup control by the control unit 12 will be described with reference to the flowchart of FIG.

In this flowchart, first in step S ₁ ,
The engine speed Ne, the turbine speed Nt of the torque converter 3, the throttle opening, the vehicle speed, and the oil temperature are input, and in step S ₂ , the gear position of the speed change mechanism 4 determined based on the speed change control is determined. The above shift control is performed in another shift control routine (not shown).

In Step S ₃ following step S _2, the engine rotational speed Ne
The actual slip amount S of the lock-up clutch 26 is calculated from the difference between the turbine rotation speed Nt and the turbine rotation speed Nt.
_{At 4} , the deviation (slip amount deviation) ΔS between the slip amount S and the preset target slip amount S ₀ is calculated.

In step S _5, checks whether during the shift. In this determination, the shift start time is checked based on the determination of the gear position, and the shift end time is checked by comparing the change in the engine speed or turbine speed due to the shift with the predicted value. It is determined that shifting is in progress until the end time. NO is the determination in step S ₅
When the (except during shifting), in step S _6, it determines whether the throttle opening and the vehicle speed is in the slip region A ₁ to A ₄ in the lock-up control pattern.

When the Step S ₆ in the slip region A ₁ to A ₄ is determined, at step S ₇ to S _11, the slip amount deviation ΔS a smaller to actual slip amount S of the target slip amount
The engagement force of the lockup clutch 26 is feedback-controlled so as to approach S ₀ . That is, first, the calculated value U for duty correction is calculated by PID control or the like, and the calculated value U is determined according to, for example, the predetermined control parameters A and B, the current slip amount deviation ΔS, and the previous slip amount deviation ΔS ′. Is calculated as U = AΔS + BΔS '(steps S ₇ and S ₈ ). Then, the calculated value U
According to the above, the correction amount Δd of the duty of the control signal output to the lock-up control solenoid is obtained, and the correction amount Δd is increased stepwise as the calculated value U increases as shown in FIG. S ₉ ), this correction amount Δ
The duty d of the current control signal is obtained by adding d to the duty d'of the previous time (step S ₁₀ ). Then, the slip amount deviation ΔS of this time is replaced with the slip amount deviation ΔS ′ of the previous time (step S ₁₁ ), and the process proceeds to step S ₁₂ to output the control signal with the duty d to the lockup control solenoid 7.

When it is determined not to slip region in step S _6, step S in preparation for subsequent slip control
_{In 13} the current slip amount deviation ΔS is replaced with the previous slip amount deviation ΔS ′, and in step S ₁₄ it is determined whether or not it is in the lockup region. And this judgment is YE
If S, the duty d is set to the maximum value d max in step S _15.
After that, the lockup clutch 26 is completely engaged by shifting to step S ₁₂ , and if the above determination is NO, the duty d is set to the minimum value d min in step S ₁₆ and then the lockup is performed by shifting to step S _12. Clutch 2
Open 6.

If the determination in step S ₅ is YES (shifting), the duty d is set to the set value in step S ₁₇ regardless of the region of the lockup control pattern, and then step S ₁₂ To the lock-up control solenoid 7
Output to. That is, during shifting, the engagement force of the lockup clutch 26 is maintained at a predetermined value by maintaining the duty d of the control signal at a set value regardless of the slip amount deviation ΔS. In this case, the set value of the duty d is set so that an appropriate engagement force can be obtained in the range where the lockup clutch 26 is in the half-clutch state between the engaged state and the released state. Desirably, the duty during shifting is set in advance for each shift stage in association with a parameter that determines an engine load state such as an accelerator opening or a throttle opening.
A map as shown in FIG. 6 is stored in the memory of the control unit 10, and the set value of the duty d during the shift is obtained from this map to obtain an appropriate lock according to the gear and accelerator opening. Make sure that the up-clutch engagement force is applied. Furthermore, since the oil temperature of the hydraulic control circuit 5 is also related to the lockup clutch engagement force, a duty correction value corresponding to the oil temperature as shown in FIG. 7 is set and this correction value is added to the duty setting value. To do so.

According to the control device of the present embodiment as described above, except during shifting, according to the lock-up control pattern, the lock-up clutch 26 is in the slip state by the feedback control according to the slip amount deviation, the engaged state, and the released state. However, when shifting is performed, the lockup clutch 26 is set to a half-clutch state,
In addition, the fastening force is appropriately maintained regardless of the slip amount deviation. Therefore, during a shift, the torque difference between the engine side and the wheel side is absorbed, the torque multiplication effect of the torque converter 3 is suppressed, and the engagement force may fluctuate due to the change in the slip amount deviation ΔS accompanying the shift. Instead, the action of absorbing the torque fluctuation is maintained. In this case, when the oil temperature changes, the viscosity of the hydraulic oil changes, which affects the lockup clutch engagement force.However, by correcting the duty according to the oil temperature, the change in the lockup clutch engagement force due to the oil temperature Is corrected.

(Effects of the Invention) As described above, in the present invention, in the automatic transmission provided with the lock-up clutch, the engagement force of the lock-up clutch is smaller than the engagement force required to obtain a complete engagement state during shifting. The lockup clutch can be maintained in an appropriate half-clutch state at the time of gear shifting because it is held at a predetermined value that is larger than the engagement force that results in a proper disengagement state. Since the control value of the operating oil pressure adjusting means for adjusting is corrected according to the oil temperature, it is possible to correct the fluctuation of the lockup clutch engaging force due to the oil temperature and maintain the half-clutch state in good condition. Therefore, both the shift shock due to the torque difference between the engine side and the wheel side and the shock due to the torque multiplication action of the torque converter can be effectively reduced.

[Brief description of drawings]

FIG. 1 is a schematic view of an automatic transmission including the device of the present invention, and FIG.
FIG. 4 is a structural explanatory view of a lockup control device according to an embodiment of the present invention, FIG. 3 is a view showing a shift pattern and a lockup control pattern, FIG. 4 is a flowchart of lockup control, and FIG. FIG. 6 is a characteristic diagram of the duty correction amount of the lockup control signal used for control in the slip region in the control pattern, and FIG. 6 is a characteristic diagram when the duty of the lockup clutch control signal during shifting is set according to the accelerator opening. FIG. 7 is a characteristic diagram of a correction value when the set value of the duty is corrected according to the oil temperature. 2 ... Automatic transmission, 3 ... Torque converter, 7 ... Lockup clutch control solenoid, 10 ... Control unit, 26 ... Lockup clutch, 41 ... Shift detection means, 42 ... Lockup clutch engagement Force control means.

Claims (1)

[Claims] 1. A lock-up clutch that is hydraulically operated is provided between an input shaft and an output shaft of a torque converter, and the hydraulic pressure of hydraulic oil supplied to the lock-up clutch is adjusted to control the lock-up clutch. In an automatic transmission provided with an operating hydraulic pressure adjusting means for adjusting a fastening force, a shift detecting means for detecting a shift by a shift mechanism of the automatic transmission, an oil temperature detecting means for detecting an oil temperature of the working oil, Lockup clutch engagement force control means for controlling engagement pressure of the lockup clutch by controlling outputs of the detection means and the oil temperature detection means, and controlling the operating oil pressure adjusting means. The means is such that, during shifting, the engagement force of the lock-up clutch is less than the engagement force required to obtain a complete engagement state. It is configured to control the operating hydraulic pressure adjusting means so as to have a predetermined value that is larger than the engaging force in the released state, and to correct the control value of the operating hydraulic pressure adjusting means according to the oil temperature. A feature of the lockup control device for automatic transmissions.