JPH0552258A - Controller for automatic transmission - Google Patents

Abstract

PURPOSE:To effectively prevent the engine stall by accelerating the releasing operation for a clutch by compulsorily correcting the line pressure to the value less than the min. line pressure, when a lock-up clutch is controlled to a set tightening force in deceleration operation. CONSTITUTION:A speed change controller is equipped with a lock-up clutch 30 for directly connecting the input shaft and output shaft of a torque converter and a tightening force adjusting means 96 for adjusting the tightening force of the lock-up clutch 30. Further, a deceleration time detecting means 97 for detecting the deceleration operation time of an engine and a tightening force control means 98 for controlling the tightening force adjusting means 96 so that the tightening force of the lock-up clutch 30 is controlled to a set value in deceleration operation are provided. Further, a line pressure correcting means 99 for correcting the line pressure of a hydraulic control circuit lower than the min. line pressure corresponding to the perfect closure of the throttle valve opening degree in the deceleration operation is provided. Accordingly, in the slip control, the releasing operation is accelerated, and the engine stall in the sharp brake application can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an automatic transmission, and more particularly to improvement of engagement force control of a lockup clutch that directly connects an input shaft and an output shaft of a torque converter.

[0002]

2. Description of the Related Art Conventionally, as a control device for an automatic transmission of this type, as disclosed in, for example, Japanese Patent Laid-Open No. 63-195465, a throttle valve opening degree is previously set on a shift diagram of the automatic transmission. A slip region is set in the fully closed region to control the engagement force of the lock-up clutch to an intermediate engagement force between full engagement and full disengagement, and the throttle valve opening is operated to fully close to decelerate the engine. At times, by controlling the engagement force of the lock-up clutch to the intermediate engagement force in the slip region, the engine brake is substantially acted to improve deceleration performance, and fuel is injected into the engine during deceleration. In the case of cut control, the decrease in engine speed is moderated by the action of engine braking, so the cut time of fuel injection is lengthened to improve fuel efficiency. It is known to have.

[0003]

By the way, when the driver applies a large amount of brake on the brake pedal when the throttle valve opening is fully closed as described above, especially on a road surface having a low friction coefficient such as a snow road. In the case where sudden braking is applied, it is desirable that the lockup clutch be immediately released from the engaged state of the intermediate engaging force just before the engine stall (engine stop) occurs.

However, in that case, the engine speed drops sharply during sudden braking, and the oil discharge amount of the oil pump also sharply decreases to a very small amount. Therefore, the amount of oil to be released to be supplied to the lockup clutch is reduced. There are few cases, and it may be difficult to immediately perform the opening operation.

The present invention has been made in view of the above problems, and an object thereof is to provide a case where sudden braking is performed during deceleration operation in which the lock-up clutch is controlled to the set engagement force as described above. Even if there is, the lock-up clutch can be immediately disengaged so as to surely prevent the engine stall.

[0006]

In order to achieve the above object, the present inventors have paid attention to the following points. In other words, in order to immediately disengage the lockup clutch, it is sufficient to supply a large amount of oil to it, but in the hydraulic control circuit provided in the automatic transmission, the pressure regulator valve is generally used to discharge the oil from the oil pump. Is partially bypassed to the other oil passage to generate the line pressure of the hydraulic control circuit, and the line pressure generated by the pressure regulator valve is a relatively high value, that is, the torque input to the speed change mechanism is large. Is set to such a value that the clutch element and the brake element of the speed change mechanism can be engaged sufficiently, and the value usually increases as the opening degree of the throttle valve of the engine increases. Therefore, during deceleration operation when the throttle valve opening is fully closed, the line pressure is set to the lowest value, but even with this lowest line pressure, there is a large amount of leakage from the hydraulic control circuit. The amount of oil required to open the lockup clutch decreases by the amount, and it is difficult to immediately open the clutch. Therefore, in the present invention, during deceleration operation in which the throttle valve opening is fully closed, the line pressure is controlled to be lower than the minimum line pressure to limit the amount of oil leaked from the hydraulic circuit, thereby locking. A large amount of oil for the up clutch is secured and the clutch is immediately opened.

In this case, if the line pressure is controlled to be lower than the minimum line pressure during the deceleration operation, the line pressure is controlled when the operating state on the shift diagram crosses the shift line and a shift is attempted. Is too low so that the friction elements of the speed change mechanism cannot be satisfactorily fastened, and it is also an object of the present invention to take measures against this.

That is, as a concrete solution means of the invention described in claim 1, as shown in FIG. 1, a lockup clutch 30 for directly connecting the input shaft and the output shaft of the torque converter,
Fastening force adjusting means 96 for adjusting the fastening force of the lockup clutch 30 by supplying the residual excess oil that has generated the line pressure of the hydraulic control circuit to the lockup clutch 30, and deceleration for detecting the deceleration operation of the engine. Time detection means 97,
Engaging force control means 9 for controlling the engaging force adjusting means 96 so that the engaging force of the lockup clutch 30 becomes a set value during deceleration operation detected by the deceleration detecting means 97.
And a line pressure correction means 99 for correcting the line pressure of the hydraulic control circuit to be lower than the minimum line pressure corresponding to the fully closed throttle valve opening during deceleration operation detected by the deceleration detection means 97. And are provided.

According to the invention of claim 2, in addition to the structure of the invention of claim 1, shift detecting means for detecting shift during the deceleration operation detected by the deceleration detecting means is provided. Further, there is provided a reduction prohibition means for prohibiting the line reduction correction by the line control means during the shift performed by the shift detection means.

[0010]

With the above construction, in the invention of claim 1,
During deceleration operation in which the lock-up clutch 30 is controlled to the set engagement force, the line pressure is corrected by the line pressure correction means 99 to be lower than the minimum line pressure. As a result, the amount of oil leaking from the hydraulic control circuit is reduced, and the amount of excess oil in the hydraulic control circuit is correspondingly increased, and the amount of oil supplied to the lockup clutch 30 is increased. The opening operation will be performed more quickly than before. Therefore, even if there is sudden braking during this deceleration operation, engine stall due to the fact that the lockup clutch 30 is still in the engaged state is effectively prevented.

Further, when the gear shift is performed during the deceleration operation, the correction of the decrease in the line pressure is prohibited and the line pressure returns to the line pressure according to the opening degree of the throttle valve as usual. The engagement operation of each friction element can be properly secured as expected, and the gear shifting can be performed without trouble.

[0012]

As described above, according to the automatic transmission control device of the present invention, the lockup clutch is controlled to the set engagement force during deceleration operation with the throttle valve opening fully closed. In this case, since the line pressure is forcibly corrected to be lower than the minimum line pressure, it is possible to secure a large amount of oil for the lock-up clutch, speed up the opening operation of the clutch, and effectively prevent engine stall.

In particular, according to the second aspect of the invention, when shifting is performed while the line pressure is being corrected to fall below the minimum line pressure as described above, the control for reducing the line pressure is prohibited, Because I changed the speed with the line pressure of
It is possible to secure desired gear shifting.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows an automatic transmission having four forward gears and one reverse gear, 2 is an engine output shaft, 1 is a pump 4 connected to a case 3 connected to the engine output shaft 2, and a stator. 6 and a turbine 5, the stator 6 being fixed to the case 11 via a one-way clutch 7 for preventing the stator 6 from rotating in the opposite direction to the turbine 5. There is. Further, 10 is a speed change gear device as a speed change mechanism connected to a converter output shaft 8 connected to the turbine 5 of the torque converter 1.

The speed change gear device 10 has a Ravigneaux type planetary gear mechanism 12 therein, and the planetary gear mechanism 12 is
Small diameter sun gear 13 and large diameter sun gear 1 arranged at the front and rear
4, a short pinion gear 15 that meshes with the small diameter sun gear 13, a long pinion gear 16 that meshes with the large diameter sun gear 14 and the short pinion gear 15, and a ring gear 18 that meshes with the long pinion gear 16. The small-diameter sun gear 13 is connected in series to the forward clutch 20 and the clutch 20 arranged behind the first small sun gear 13 to prevent reverse driving of the converter output shaft 8.
It is connected to the output shaft 8 of the torque converter 1 via a one-way clutch 22 and a coast clutch 21 connected in parallel with these. Further, the large-diameter sun gear 14 has a 2-4 brake 23 arranged diagonally rearward thereof.
And, it is connected to the output shaft 8 of the torque converter 1 through a reverse clutch 24 arranged behind the 2-4 brake 23. The 2-4 brake 23 includes a brake drum 23a and a brake band 23b hung on the drum 23a. Further, the low & reverse brake 2 for fixing the long pinion gear 11 to the long pinion gear 16 via the rear carrier 27.
5 and a second one-way clutch 26 that allows rotation of the long pinion gear 16 in the same direction as the engine output shaft 2 are connected in parallel, and the front-side carrier 17 thereof is provided.
Is connected to the output shaft 8 of the torque converter 1 via a 3-4 clutch 27. In addition, ring gear 1
8 is connected to an output gear 19 arranged in front of it. In the figure, 30 is a lock-up clutch that directly connects the engine output shaft 2 and the converter output shaft 8, and 9
Reference numeral 0 denotes an oil pump driven by the engine output shaft 2 via the intermediate shaft 9.

The following table shows the operating states of the clutches and brakes at each shift speed in the above configuration.

[0018]

[Table 1]

Next, a line pressure control circuit in the hydraulic circuit for gear shift control of the automatic transmission will be described with reference to FIG.
In the figure, reference numeral 80 is a reducing valve which is connected to the discharge line 91a of the hydraulic pump 90 and reduces its discharge pressure to a constant set pressure and supplies it to the pressure line 92. Reference numeral 81 is a modulator valve connected to the pressure line 92, and the valve 81 is a spool 81.
The pilot pressure of the pilot passage 93 acts on the right end in the figure of a, and the duty solenoid valve SOL is provided, and the hydraulic pressure acting on the left end of the spool 81a in the figure is controlled by the duty solenoid valve SOL. By adjusting, the hydraulic pressure in the pressure line 93 is reduced, and the hydraulic pressure according to the duty ratio of the duty solenoid valve SOL is supplied to the pilot passage 93.

Reference numeral 82 is a pressure regulator valve. The pilot pressure of the pilot passage 93 acts on the pressure receiving surface at the left end of the spool 82a in the figure, while the spool 82a has a hydraulic pump on the other side. The hydraulic pressure of the discharge line 90b of 90 acts. Then, the movement amount of the spool 82a is adjusted in accordance with the magnitude relationship between the pilot pressure and the pump discharge pressure acting on the left and right ends of the spool 82a to communicate the discharge line 90b with the surplus oil line 94 or to cut off this communication. By this, the discharge line 9
The hydraulic pressure of 0b, that is, the line pressure is adjusted to the hydraulic pressure according to the pilot pressure, and the surplus oil is supplied to the surplus oil line 94. Then, the surplus oil line 9
4, a pressure control valve 95 for maintaining the oil pressure in the line 94 at a constant pressure (torque converter pressure) is arranged, and the oil in the surplus oil line 94 is supplied to the torque converter 1 as described later.
And the lockup clutch 30.

An accumulator 85 for absorbing and mitigating the pulsation of the pilot pressure is connected to the pilot passage 93.

Next, the hydraulic control circuit for the lockup clutch 30 is shown in FIG.

As shown in the figure, the lockup clutch 30 provided in the torque converter 1 includes a converter cover 3 connected to the turbine 5 and the engine output shaft 2.
6 and a torsion damper 31 and a damper piston 32 that rotate integrally with the turbine shaft 8.
And a friction plate (not shown) provided on the converter cover 36 at a position facing the damper piston 32. The damper piston 32 divides the space inside the converter cover 36 into an R chamber (rear chamber) 33 on the turbine 5 side and an F chamber (front chamber) 34 on the converter cover 36 side. The hydraulic pressure in the R chamber 33 becomes the hydraulic fluid pressure on the lock-up engagement side that acts in the direction of pressing the damper piston 32 against the friction plate, and the hydraulic pressure in the F chamber 34 acts in the direction to separate the damper piston 32 from the friction plate. It becomes the hydraulic fluid pressure on the lockup release side. Then, the damper piston 32 is frictionally engaged with the friction plate by a fastening force corresponding to the pressure difference between the hydraulic pressure in the R chamber 33 and the hydraulic pressure in the F chamber 34.

The lockup clutch 30 is completely released according to the hydraulic pressure in the R chamber 33 and the F chamber 34, and the rotation of the engine output shaft 2 is transmitted to the turbine shaft 8 via the pump 4 and the turbine 5. The converter state to be set and the engine output shaft 2 when completely engaged.
Of the engine output shaft 2 through the pump 4 and the turbine 5 to the lockup state in which the rotation of the engine is directly transmitted to the turbine shaft 8 and the semi-fastened state in which the damper piston 32 is slidingly engaged with the friction plate. 8 and a slip state in which the power is transmitted to the turbine shaft 8 even through the lock-up clutch 30 partially.

The hydraulic pressure control circuit 40 for the lock-up clutch 30 controls the lock-up shift valve 50 (hereinafter, simply referred to as the shift valve 50) and the hydraulic pressure supplied to the F chamber 34 via the shift valve 50. Lockup control valve 60 (hereinafter, simply referred to as control valve 60) that pressurizes, and lockup solenoid valve 7 that controls ON / OFF of the first pilot pressure.
1 (hereinafter simply referred to as the solenoid valve 71), the second
And a duty solenoid valve 72 for duty-controlling the pilot pressure of.

The hydraulic control circuit 40 further includes a torque converter line L1 communicating with an excess oil line 94 of the oil discharged from the oil pump 90 shown in FIG. 3, to which excess oil is supplied from the pressure regulator valve 82, and 1st pilot line L2 which supplies 1 pilot pressure
A second pilot line L3 for supplying a second pilot pressure, a line L4 for supplying a constant pressure (for example, 4 kg / cm ² ) to an intermediate portion of the shift valve 50, and a shift valve 5
Line LR connecting port 51R of 0 and R chamber 33
And a line LF or the like connecting the port 51F of the shift valve 50 and the F chamber 34.

The torque converter line L1 is branched into a line L11 and a line L12.
11 communicates with the port 52R of the shift valve 50, and the line L12 communicates with the port 62F of the control valve 60. In addition, port 6 of control valve 60
1F communicates with the port 52F of the shift valve 50 via the line L13. A line L5 communicating with the oil cooler 75 communicates with the port 53 of the shift valve 50.

The first pilot line L2 is the line L
21 and 22 branch to port 5 of shift valve 50
7 and the port 68 of the control valve 60. The drain line L23 communicating with the first pilot line L2 is provided with a solenoid valve 71. When the solenoid valve 71 is OFF, the drain line L23 is closed, and when the solenoid valve 71 is ON, the first pilot line L23 is turned on. L2 is drained. The second pilot line L3 is the line L31,3.
It is branched into two and connected to the port 58 of the shift valve 50 and the port 65 of the control valve 60, respectively.
Drain line L communicating with the second pilot line L3
A duty solenoid valve 72 is provided at 33. The duty solenoid valve 72 closes the drain line L33 in the OFF state, drains the second pilot line L3 in the ON state, and changes the second pilot pressure in accordance with the duty ratio by duty control during that period. The pilot pressure decreases as the duty ratio increases.

In the shift valve 50, the operation of the two spools 54 and 55 according to the pilot pressure switches the communication between the port 51R and the ports 52R and 53, and the port 51F and the port 52F and the drain port. The communication is switched, and the control valve 6
At 0, the communication state of the port 62F and the communication state of the port 61F with the drain port is changed by the movement of the spool according to the pilot pressure.

In the figure, LC is an oil cooler 75 for operating oil in the torque converter via a check valve 76.
The check valve 76 is designed to open above a set pressure.

Next, the structures of the shift valve 50 and the control valve 60 will be described. Shift valve 50
Comprises first and second spools 54, 55 arranged in series within the sleeve, with the first spool 54 on the right in the figure,
The second spool 55 is located on the left side. On the left side of the second sloop 55, a spring 56 for urging both spools 54, 55 in the right direction in the drawing is equipped, and both spools 54, 5 are also provided.
A spring 56a for smoothing the relative movement of both spools 54, 55 is interposed between the five. First above
At the right end of the spool 54, the first pilot line L2
To L21, the pilot pressure introduced into the port 57 acts, and the left end of the second spool 55 is acted on by the pilot pressure introduced from the second pilot line L3 through the line L31 into the port 58. The right end of the first spool 54 is enlarged, and its end surface has a larger pressure receiving area than the left end of the second spool 55.
A constant pressure is introduced from the line L4 to the port 59 located between the spools 54 and 55.

The shift valve 50 is adapted to change to the following first to third positions according to the control of the solenoid valve 71 and the duty solenoid valve 72. That is, when the solenoid valve 71 is OFF, the first pilot pressure increases, so that the shift valve 50 is in the first position in which both spools 54 and 55 are biased to the left side in the drawing. In this first position,
Port 51R communicates with port 53 and port 5
1F communicates with the port 52F. Further, when the solenoid valve 71 is ON and the duty ratio of the duty solenoid valve 72 is a small value (for example, 0%), the first pilot pressure is reduced while the second pilot pressure is compared. By becoming a relatively large value,
The shift valve 50 is in a second position in which both spools 54, 55 are biased to the right side in the drawing. In this second position, the port 51R communicates with the port 52R and
Port 51F communicates with the drain port. Further, when the duty ratio of the duty solenoid valve 72 becomes a predetermined value, for example, 20% or more in the state where the solenoid valve 71 is ON, the second pilot pressure also becomes relatively small, and the pressure acting on the port 59 is reduced. With spool 54,5
When 5 is pushed to both sides, the first spool 54 comes to the right and the second spool 55 comes to the third position which is biased to the left. In this third position, port 51R is
And the port 51F communicates with the port 52F.

On the other hand, the control valve 60 is provided with a spool 63 in the sleeve thereof, which is biased rightward in the drawing by a spring 64. Pilot pressure introduced from the second pilot line L3 to the port 65 via the line L32 acts on the right end surface of the spool 63. Further, the right side step portion 6 of the intermediate land portion of the spool 63
3b, the pressure in the line L13 acts through the line having a fixed orifice and the port 66,
The torque converter pressure, which is the pressure of the line L12, acts on the stepped portion 63c formed on the left side land portion of No. 3 via the line L16 having the fixed orifice and the port 67. Furthermore, on the left end surface of the spool 63,
The pilot pressure introduced from the first pilot line L2 to the port 68 via the line L22 acts.

The control valve 60 controls the spool 6 when the solenoid valve 71 is OFF.
The first pilot pressure acting on the left end face of the spool 3 keeps the spool 63 in a position biased to the right,
Pass 62F. Also, the solenoid valve 71 is turned on.
When the first pilot pressure is 0, the second pilot pressure acting on the right end portion of the spool 63 and the leftward pressing force due to the pressure acting on the step portion 63b and the step portion 63c are applied. The spool 63 moves to a position where the acting pressure and the rightward pressing force by the urging force of the spring 64 are balanced. Then, when the second pilot pressure is high, the spool 63 moves to the left, and the port 61F communicating with the line L13 communicates with the drain port in large numbers,
When the pilot pressure of No. 2 becomes low, the spool 63 moves to the right, and accordingly, the proportion of the port 61F communicating with the port 62F increases. That is, as a correspondence relationship between the second pilot pressure and the hydraulic pressure sent to the line L13, the control valve 60 is configured such that the hydraulic pressure decreases as the second pilot pressure increases.

With the above structure, the fastening force adjusting means 96 is configured to adjust the fastening force of the lockup clutch 30 with the control valve 60 more strongly as the second pilot pressure becomes higher.

Next, the engagement force control of the lockup clutch 30 during deceleration operation will be described based on the control flow of FIGS. 5, the throttle valve opening signal, the vehicle speed signal, and the oil temperature signal of the hydraulic control circuit are read in step S1, and then based on the read throttle valve opening signal and vehicle speed signal in step S2. The shift diagram shown in FIG. 9 is searched for whether or not a shift is in progress or a state in which the lockup clutch 30 should be controlled. If the lock-up clutch 30 is in the lock-up region in which the lock-up clutch 30 is completely engaged in step S3, the lock-up clutch 30 is controlled to be in the completely engaged state in step S4, while in the steady slip region shown in FIG. To step S
In step 6, the engaging force of the lockup clutch 30 is controlled to a predetermined value so that the power transmission path is favorably transferred from the torque converter 1 to the lockup clutch 30.

Next, in step S7 of FIG. 6, it is determined whether or not the current operating region is the fully closed deceleration slip region where the throttle valve opening shown by hatching in FIG. 9 is in the deceleration slip region. If not present, it is in the torque converter region, so the routine proceeds to steps S8 and S9 in FIG. 8 to control the lock-up clutch 30 to the completely released state, and the line pressure of the hydraulic control circuit is set to the normal value according to the throttle valve opening degree and the like. It is calculated based on the line control routine, and the process returns.

On the other hand, when the vehicle is in the deceleration slip region in step S7, the lock-up clutch 30 is pre-determined intermediate engagement in step S15 shown in FIG. 7 only when the following conditions are satisfied in steps S10 to S14 in FIG. Control to the force level. That is, as a condition for controlling the lock-up clutch 30 to the intermediate engagement force value, first, when the shift speed immediately before shifting to the deceleration slip region is the third speed or the fourth speed, that is, 1 → 3 accompanying the accelerator pedal opening operation. Or, assuming the case other than the 2 → 3 back-out shift, (1) the oil temperature is 12
When the temperature is 0 ° C or lower, (2) even if the oil temperature exceeds 120 ° C, when 120 ° C <oil temperature ≤ 130 ° C, the third speed is used and the vehicle speed is less than 120 km / h, or the fourth speed is used. Vehicle speed is 1
The condition is less than 70 km / h.

Under the set engagement force control of the lock-up clutch 30 in step S15 of FIG. 7, it is determined in step S16 whether there is a 3 → 4 shift or a 4 → 3 shift. 3 in step S17.
The duty ratio of the duty solenoid valve SOL for line pressure control shown in is set to 100%, and the line pressure is set to the minimum line pressure (4 kg / cm ² ) set by the normal line pressure setting routine as shown in FIG. The set line pressure value of a low value less than (for example, 3.3 kg / cm ² ) is lowered and corrected, and the process returns.

Therefore, in the control flow of FIG.
In step S7, the deceleration time detecting means 97 for detecting the deceleration operation of the engine by deciding that the operation state of the engine is in the deceleration slip region on the shift diagram of FIG. 9 is configured. Further, in step S15 of FIG. 7, the fastening force control means 98 is configured to perform the deceleration slip control for controlling the fastening force of the lockup clutch 30 to the set value during the deceleration operation detected by the deceleration detection means 97. is doing. Further, in step S17 of FIG. 10, the line pressure of the pressure regulator valve 82 during deceleration operation detected by the deceleration time detecting means 97 is set as shown in FIG.
The set line pressure value (3.) lower than the minimum line pressure (4 kg / cm ² ) corresponding to the fully closed throttle valve opening shown in (3).
Line pressure compensating means 9 adapted to compensate for 3 kg / cm ² )
9 is composed. In addition, step S16 of FIG. 7 configures shift detecting means 100 for detecting 3 → 4 shift or 4 → 3 shift during deceleration operation detected by the deceleration detecting means 97, and Step S in FIG.
By means of 18, the line pressure control based on the normal line pressure control routine according to the throttle valve opening etc. is performed during the shift performed by the shift detecting means 100, and the line correction by the line correcting means 99 is prohibited. Thus, the deterioration prohibition means 101 is configured.

Therefore, in the above embodiment, FIG.
As shown in FIG. 1, during deceleration operation in which the throttle valve opening is fully closed, the lock-up clutch 30 is slip-controlled to the set engagement force, so that the engine speed is more constant than the turbine speed of the torque converter 1. While maintaining a low number of revolutions, it gradually decreases and good engine braking is applied. Now, in this situation, for example, when the driver depresses the brake pedal on a road with a low friction factor on the road surface and the drive wheels are locked, the turbine rotation speed and the engine rotation speed decrease rapidly. As a result, the engine stall is likely to occur as indicated by the chain line in the figure. Moreover, since the oil discharge amount of the oil pump 90 sharply decreases as the engine speed drops sharply, the oil amount supplied to the front chamber 34 of the lockup clutch 30 also sharply decreases.

However, in this case, when the throttle valve opening is fully closed, the line pressure control solenoid SOL.
Is controlled to 100%, the value of the line pressure generated by the pressure regulator valve 82 is the normal minimum value (4 kg
lower in / cm ²⁾ less than setting the line pressure (3.3kg / cm ^2). As a result, the amount of oil leaked from the hydraulic control circuit is reduced, and the flow rate of excess oil supplied from the pressure regulator valve 82 to the excess oil line 94 is correspondingly increased. As a result, the amount of oil supplied from the torque converter line L1 to the front chamber 34 of the lockup clutch 30 via the control valve 60 and the shift valve 50 is secured as much as possible, and the lockup clutch 30 is secured.
Is quickly released from the set engagement force, the engine speed stabilizes at the idle speed as shown by the broken line in the figure, and the engine stall is effectively prevented.

Moreover, as shown in FIG. 12, the characteristic of the differential pressure ΔP between the rear chamber 33 and the front chamber 34 of the lockup clutch 30 with respect to the duty ratio of the duty solenoid valve 72 for controlling the engagement force of the lockup clutch 30. Changes according to the change in engine speed under the normal minimum line pressure (4 kg / cm ² ), but the engine speed decreases below the set line pressure (3.3 kg / cm ² ) corrected for decrease. Since a substantially constant differential pressure ΔP characteristic can be obtained even if it changes, the engaging force of the lockup clutch 30 can be accurately controlled regardless of the engine speed, and the controllability thereof can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an invention according to claim 1.

FIG. 2 is a skeleton diagram of an automatic transmission.

FIG. 3 is a hydraulic circuit diagram for controlling the line pressure.

FIG. 4 is a hydraulic circuit for controlling the engagement force of the lockup clutch.

FIG. 5 is a flowchart showing a part of engagement force control of a lockup clutch during deceleration operation.

FIG. 6 is a flowchart showing a part of engagement force control of a lockup clutch during deceleration operation.

FIG. 7 is a flowchart showing a part of engagement force control of a lockup clutch during deceleration operation.

FIG. 8 is a flowchart showing the remaining part of the lockup clutch engagement force control during deceleration operation.

FIG. 9 is a diagram showing an automatic shift diagram.

FIG. 10 is a diagram showing a line pressure characteristic with respect to a throttle valve opening.

FIG. 11 is an operation explanatory view.

FIG. 12 is a diagram showing a differential pressure characteristic before and after a lockup clutch with respect to a duty ratio of a line pressure control solenoid having an engine speed as a parameter.

[Explanation of symbols]

 30 lock-up clutch 50 lock-up shift valve 60 lock-up control valve 82 pressure regulator valve 96 engaging force adjusting means 97 deceleration detecting means 98 engaging force controlling means 99 line pressure correcting means 100 shifting detecting means 101 lowering prohibiting means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Kurinami 3-1, Shinchi Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Motor Corporation

Claims (2)

[Claims] 1. A lock-up clutch that directly connects an input shaft and an output shaft of a torque converter, and a lock-up clutch that is supplied with residual oil that has generated a line pressure of a hydraulic control circuit to engage the lock-up clutch. A fastening force adjusting means for adjusting the force, a deceleration time detecting means for detecting a deceleration operation of the engine, and a fastening force of the lockup clutch set to a set value during the deceleration operation detected by the deceleration time detecting means. And a fastening force control means for controlling the fastening force adjusting means, wherein the line pressure of the hydraulic control circuit during deceleration operation detected by the deceleration detecting means is set to a minimum line pressure corresponding to a fully closed throttle valve opening. 1. A control device for an automatic transmission, comprising: a line pressure correction means for correcting low. 2. A shift time detecting means for detecting a shift time during deceleration operation detected by the deceleration detecting means, and a line pressure reduction correction by a line pressure control means during the shift performed by the shift detecting means. The control device for an automatic transmission according to claim 1, further comprising: a reduction prohibiting unit that prohibits