JP2000193083A - Method for controlling fluid coupling or torque converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve responsiveness of lockup control during inertia running. SOLUTION: When lockup control is performed during inertia running, a pressure of working fluid fed to a torque converter is boosted through pressure reduction regulation of a secondary regulator 52 or combination of pressure reduction regulation of a primary regulator 50 and the secondary regulator 52. The primary regulator 50 is a valve to regulate a pressure to a value responding to the output of a prime mover and regulate it to a low value during inertial running. With the internal pressure of the torque converter increased, a differential pressure is produced between the surface and the back of a lockup piston 40 by a control valve 56, and the lockup piston 40 is connected. A current differential pressure is a value equal to a differential pressure during drive running.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for transmitting power via a fluid such as a fluid coupling or a torque converter, and more particularly to a device having a lock-up mechanism for mechanically interrupting input and output.

[0002]

2. Description of the Related Art Fluid couplings or torque converters (hereinafter simply referred to as torque converters) transmit power through a working fluid, and therefore loss due to the difference between the input and output rotational speeds, ie, slip loss. And transmission efficiency is low. In order to improve this, a torque converter having a lock-up mechanism that directly connects an input and an output under certain conditions, that is, locks up to eliminate slip loss has been put to practical use.

[0003] A torque converter with a lock-up mechanism has a lock-up piston inside the torque converter and at a position facing the front cover on the input side, and this lock-up piston is connected to the output side. The lock-up piston is intermittently controlled with respect to the front cover by the difference between the fluid pressure on the front cover side and the fluid pressure on the turbine side opposite thereto. That is, when the control fluid pressure supplied to the turbine side is higher than the control fluid pressure supplied to the front cover side, the connection of the lock-up piston to the front cover is controlled, and in the opposite case, the disconnection control is performed. Such a lock-up control is executed when the torque converter does not require the function of amplifying the torque or the function of absorbing the rotation fluctuation, for example, at the time of running at a constant speed, thereby reducing the loss of the driving force.

In recent years, more and more torque converters used for vehicles having an internal combustion engine perform control to lock up the torque converter even during coasting of the vehicle. This is performed to cut off the supply of fuel to the internal combustion engine during coasting.
Even when the fuel supply is cut off, the internal combustion engine can be rotated by the inertia of the vehicle by locking up the torque converter, and the engine does not stop (so-called engine stall). As a result, fuel consumption can be reduced by the amount of fuel supplied to maintain the idling of the internal combustion engine when lock-up is not performed.

[0005]

As described above, when the lock-up control is performed not only when the vehicle is driven but also when the vehicle is coasting, under these circumstances, the lock-up piston is located between the front cover side and the turbine side. Fluid pressure changes. This is because the fluid in the torque converter
This is due to the rotational movement with the torque converter. Although the pressure in the vicinity of the center is reduced by the rotational movement of the fluid in the torque converter, the degree of the reduction is different between the driving travel and the coasting travel. During driving traveling, the rotation speed on the input side is high, and thus the degree of pressure reduction is greater on the front cover side of the lock-up piston. On the other hand, during coasting, on the other hand, the rotation speed on the output side is high, and the degree of pressure reduction on the turbine side is large. That is, the difference between the fluid pressures applied to the front and back of the lock-up piston is different between the driving travel and the coasting travel. For this reason, when connecting the lockup piston to the front cover,
A larger force is required during coasting than during driving. In other words, during coasting, if the same control fluid pressure as during driving is supplied to the turbine side of the lock-up piston, the same responsiveness of lock-up control as during driving may not be obtained. is there.

Japanese Patent Application Laid-Open No. Hei 7-310815 discloses a lock-up control as described above, and particularly, in order to improve control responsiveness during coasting, the front cover side of the lock-up piston and the turbine during coasting. A technique for increasing the difference between the control fluid pressures supplied to the respective sides is disclosed. However, if the difference between the control fluid pressures is large, there is a problem that the shock at the moment when the lock-up piston contacts the front cover is large.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide a control method in which the responsiveness of lock-up control during coasting is good and the shock is small.

[0008]

In order to solve the above-mentioned problems, a lock-up control method for a torque converter according to the present invention is performed as follows.

In the lockup control during coasting, the difference between the control fluid pressure supplied to the turbine side and the front cover side of the lockup piston, ie, the front and back sides, is controlled to the same value as during driving. At the same time, the turbine-side control fluid pressure is controlled to a high value.

By increasing the supply fluid pressure to the turbine side during coasting, the fluid pressure causes the central portion of the front cover to expand in the axial direction. On the other hand, the peripheral portion of the torque converter has a small amount of deformation. The lock-up piston moves following the bulge near the center of the front cover, and its peripheral part moves almost equally. Therefore, in the peripheral portion, the amount of movement of the lock-up piston is larger than the amount of deformation of the front cover, and the gap in this portion is narrowed. By reducing the gap, the moving distance of the lock-up piston can be shortened, and the response is improved. Further, when performing the lock-up operation, since the fluid pressure on the turbine side is high, a flow from the turbine side to the front cover side is formed. However, this flow is restricted by the gap, and a pressure drop occurs. Due to this pressure drop, the pressure difference between the front and back of the lock-up piston increases, the force for moving the lock-up piston increases, and the responsiveness of the lock-up control improves.

Further, the control for increasing the supply fluid pressure to the turbine side, that is, the control for increasing the internal pressure of the torque converter, is stopped when the difference between the input and output rotational speeds of the torque converter becomes equal to or less than a predetermined value. Is controlled so that the pressure of the fluid supplied to the lockup control during driving and traveling is used. Once lockup is completed, control for increasing the turbine-side supply fluid pressure is no longer necessary, and can be stopped. Further, if the control for increasing the turbine-side supply fluid pressure is continued, the responsiveness when the lock-up is released next time is deteriorated. To solve this, after the lock-up is completed, the turbine-side supply is stopped. Preferably, the control for increasing the fluid pressure is stopped.

[0012]

Embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings. FIG. 1 shows a schematic cross section of a vehicle in which a lower half of a torque converter 10 used with an AT (Automatic Transmission) is omitted. Front cover 12
The pump impeller 14 and the pump impeller 14 are welded and joined at the outer peripheral portion, and rotate integrally by the output of the prime mover. A turbine runner 16 is arranged opposite to the pump impeller 14. The turbine runner 16 is connected to a turbine hub 18 and rotates integrally therewith. The turbine hub 18 is an AT
Is spline-coupled to the input shaft 20 of
While rotating together with this, it is relatively movable in the axial direction. The pump impeller 14 has a pump blade 24, which rotates by rotation of the pump impeller 14.
The working fluid is sent to the turbine runner 16. The turbine runner 16 has a turbine blade 26, and rotates by receiving the supplied working fluid. The working fluid discharged from the turbine blade 26 is turned by the stator blade 30 of the stator 28, and is sent again to the pump impeller 14.

The stator 28 includes a one-way clutch 32
And is arranged on the stator shaft 34 via. The stator shaft 34 does not rotate. Pump impeller 14
When the speed ratio of the turbine runner 16 and the clutch is below the clutch point, the working fluid discharged from the turbine runner 16 hits the stator blade 30. At this time, the stator 28 receives a force from the working fluid, and this force is a force in a direction in which the one-way clutch 32 is fixed, and the stator 28
Are fixed on the stator shaft 34 and do not rotate. At this time, the working fluid discharged from the turbine runner 16 is turned by the stator blade 30 and hits the back surface of the pump blade 24, whereby the transmission torque is amplified. After passing the clutch point, the working fluid discharged from the turbine runner 16 is
0 comes from the back side. At this time, the stator 2
8 receives the working fluid from the one-way clutch 32.
Is rotated, so that the stator 28 rotates. At this time, the working fluid discharged from the turbine runner 16 is sent to the pump impeller 14 without being positively changed in direction by the stator 28. In this case, there is no torque amplifying function, and it functions as a simple fluid coupling.

The turbine hub 18 has a torsion damper 36.
Is fixed. The outer peripheral portion of the damper plate 38 is connected to a lockup piston 40 facing the front cover 12. Lock-up piston 40 includes a clutch face 42 provided on an outer peripheral portion of a surface facing the front cover.

When a working fluid is supplied from a fluid passage (refer to an arrow A in FIG. 1) provided between the stator shaft 34 and the oil pump shaft 44, the lock-up piston 40 is provided on the turbine side (hereinafter referred to as a turbine side chamber). ) 46
Supplied to Due to this pressure, the lock-up piston 40 moves to the front cover 12 side, the clutch face 42 is pressed against the front cover 12, and the torque converter 10 is locked. by this,
The rotation of the front cover 12 is the lock-up piston 4
0, via the damper plate 38 and the turbine runner 16 to the input shaft 20. At this time,
The input and output of the front cover 18 and the input shaft 20, that is, the torque converter 10, are mechanically coupled. Therefore, it is possible to suppress the occurrence of the slip loss peculiar to the transmission by the fluid.

In order to release the lock-up state, a working fluid is supplied from a fluid passage (see an arrow B in FIG. 1) provided between the stator shaft 34 and the input shaft 20. The supplied working fluid reaches the front cover side (hereinafter, referred to as a front cover side chamber) 48 of the lock-up piston 40, and the lock-up piston 40 is disconnected from the front cover 12 by this pressure, and the lock-up state is released. .

As described above, the lock-up state of the torque converter 10 is controlled by intermittently connecting the front cover 12 and the lock-up piston 40. Further, from the above description, it is understood that the front cover 12 and the lock-up piston 40 constitute a wet clutch, and these may be collectively referred to as a lock-up clutch.

FIG. 2 shows a simplified configuration of the fluid pressure circuit of the present embodiment, particularly, the configuration of a portion related to lock-up control. The components described with reference to FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. The working fluid supplied from the pump P is supplied to each part of the AT at a predetermined pressure by the primary regulator 50. This pressure is uniquely determined so as to increase as the operation amount of the control operator of the output of the motor, which is the input of the torque converter, for example, the operation amount of the accelerator pedal increases, and the slip of the AT shift clutch occurs due to the increase in the output. Has been prevented. A part of the working fluid sent from the primary regulator 50 is supplied to a secondary regulator 52 and further supplied to a lock-up on / off switching valve 54. The on / off switching valve 54 is a valve for selecting whether to flow the fluid to the fluid path A or the fluid path B. Fluid path A in FIG.
B corresponds to the fluid path indicated by arrows A and B in FIG. When the fluid path A is selected by the on / off switching valve 54, the working fluid is supplied to the turbine side chamber 46 as described above.
On the other hand, when the fluid path B is selected, the working fluid is supplied to the front cover side chamber 48.

When the lock-up control is started, the fluid path A is selected by the on / off switching valve 54, and the differential pressure between the fluid paths A and B is determined by the lock-up control valve 56 to determine the input / output of the torque converter. Control is performed to a predetermined value based on the difference between the rotation speeds and the input rotation speed of the torque converter (that is, the rotation speed of the prime mover) (ON control). This differential pressure is determined based on the shock at the time of connecting the lock-up clutch and the response of the connection. Due to this difference in the control fluid pressure, a pressure difference between the turbine side chamber 46 and the front cover side chamber 48 is generated, and the lockup piston 40 moves to the connection side. When ending the lockup control, the fluid path B is selected by the on / off switching valve 54 and the control valve 56
To generate the same differential pressure as in the ON control (OFF control). This difference in control fluid pressure causes the turbine side chamber 46
And the pressure difference between the front cover side chamber 48 and the lock-up piston 40 moves to the cutting side.

The lock-up piston 40 moves due to the pressure difference between the front and back sides. This pressure difference is said shock,
If the predetermined value based on the responsiveness is not attained, the transient state when connecting the lockup piston 40 to the front cover 12 is not stabilized. As a result, a shock occurs or the responsiveness of the connection is deteriorated. The control valve 56 sets the difference between the control fluid pressures of the fluid passages A and B to the predetermined value in order to adjust and keep the characteristics at the time of lock-up connection constant. by this,
Even if the fluid pressure in the fluid path A changes, the differential pressure is maintained and controlled at the predetermined value.

However, as described above, the pressure in the turbine side chamber 46 and the pressure in the front cover side chamber 48 in the torque converter 10 decrease due to the rotation of the torque converter 10. This reduced pressure is different between the two chambers 46 and 48. In particular, when the vehicle is driven by the prime mover (during driving) and when the vehicle is running with inertia (during inertia), the degree of decompression of the two chambers 46 and 48 is different, so that lock-up occurs. The behavior of the piston will also be different. As described above, during inertia, a force is generated in a direction for moving the lockup piston 40 to the turbine side (to the right in FIG. 1). In order to move the lock-up piston 40 to the front cover 12 side, a greater force is required as compared to when driving.

When connecting the lock-up pistons 40 to the front cover 12, if they are still separated from each other, the clutch face 42 and the front cover 12 are moved from the high pressure turbine side chamber 46 to the low pressure front cover side chamber 48. The working fluid flows through the gap. Both rooms 4
The 6,48 pressure difference is maintained by this gap pressure drop. Immediately before the lock-up piston 40 and the front cover 12 are connected, the gap is extremely narrow, and the pressure drop in this portion is also large. That is, the pressure difference between the turbine side chamber 46 and the front cover side chamber 48 increases,
An attempt is made to move the lock-up piston 40 with a stronger force. Therefore, at the moment of connection, the moving speed of the lock-up piston 40 increases, the lock-up clutch is rapidly connected, and a shock occurs. If the pressure difference between the two chambers 46 and 48 is increased as in the prior art described above, this shock is undesirably promoted.

In the present embodiment, the control fluid pressure supplied to the turbine side chamber 46 and the front cover side chamber 48, that is, the fluid paths A and B, when performing lock-up during coasting.
The control for increasing the fluid pressure in the fluid path A is performed while maintaining the fluid pressure difference at a predetermined value determined from the shock and the response. The pressure difference between the fluid passages A and B is adjusted by the control valve 56 as described above. The fluid path A is used to adjust the pressure of the secondary regulator 52 or reduce the pressure of the primary regulator 50.
And the pressure is increased by a combination of the pressure reduction adjustment of the secondary regulator 52.

By increasing the control fluid pressure supplied from the fluid passage A, the pressure in the torque converter 10 also increases. Although the torque converter 10 expands due to the increase in the internal pressure, since the torque converter 10 has a substantially disk shape, the expansion of the central portion is larger than that of the peripheral portion. If the expansion of the torque converter 10 is regarded as the deformation of the front cover 12, the deformation X near the center of the front cover 12 is larger than the deformation Y at the peripheral portion as shown in FIG.
On the other hand, the turbine hub 18 is urged toward the front cover 12 by the thrust generated by the turbine runner 16 and moves leftward in the figure following the deformation of the central portion of the front cover 12. This is the turbine hub 1
This is because the leftward positioning of 8 is performed by the front cover 12 via the thrust bearing 58. The movement of the turbine hub 18 causes the damper plate 38
And the lock-up piston 40 moves by the same amount.
Therefore, in the clutch face 42, the amount of movement of the lock-up piston 40 is larger than the amount of deformation of the front cover 12. Therefore, the gap between the clutch face 42 and the front cover 12 is reduced.

As described above, the lock-up piston 40
Is moved by the deformation of the front cover 12 in addition to the movement due to the pressure difference between the front and back sides, and the responsiveness of the lock-up control is improved. Further, as the gap between the clutch face 42 and the front cover 12 becomes smaller, the pressure drop in this portion increases, and the pressure difference between the turbine side chamber 46 and the front cover side chamber 48 increases, which also increases the responsiveness of the lock-up control. improves. At this time, the difference between the control fluid pressures supplied to the turbine side chamber 46 and the front cover side chamber 48 is controlled by the differential pressure control valve 56 to a predetermined value obtained from the shock characteristics and the response characteristics. Therefore, the situation immediately before and at the moment when the lock-up piston 40 comes into contact with the front cover 12 is the same as when the predetermined value is determined. Therefore, the response of the lock-up control can have desired characteristics.

FIG. 3 is a flowchart showing lock-up control during coasting. When the accelerator pedal is turned off (S100), it is determined whether the current running state of the vehicle, the driving state of the prime mover and the AT, and the like conform to the conditions for performing the lock-up control (S10).
2). If the conditions are not met, lockup control is not performed. If the condition is satisfied, the fluid pressure supplied to the torque converter 10 is increased by the secondary regulator 52 to increase the pressure in the torque converter 10 (S104). Then, the control valve 56 generates a difference between the control fluid pressures supplied to the turbine side chamber 46 and the front cover side chamber 48, and the lock-up operation starts (S106). And the torque converter 10
When the difference between the input and output rotational speeds (slip speed) becomes equal to or less than a predetermined value (S108), the pressure increase by the secondary regulator 52 is released, and the internal pressure of the torque converter 10 is decreased. The steps S108 and S110 are controlled by
This is to ensure responsiveness when the lockup is turned off. If the primary regulator pressure is kept increased in step S104, the engine speed decreases, and the amount of fluid supplied from the pump decreases. For this reason, the fluid supplied to the secondary regulator 52 also decreases, and the secondary regulator pressure also decreases. At this time, if lock-up is turned off, a predetermined responsiveness may not be obtained because a predetermined secondary regulator pressure cannot be secured.
Therefore, as described above, steps S108 and S110
In the above, when a predetermined slip speed is reached, that is, when the lock-up state is established, the internal pressure of the torque converter is reduced to prevent a decrease in the engine rotation speed and to ensure lock-off responsiveness.

In step S108, the reason why the slip speed is 0, that is, the input and output are not completely coupled, is that when the speed of the vehicle suddenly decreases due to stepping on a brake or the like, the control of the prime mover is adversely affected. Is prevented.

As described above, in the present embodiment, the case where the present invention is applied to the torque converter has been described. However, the present invention can be applied to a fluid coupling having no torque amplifying function.

[0029]

Preferred embodiments of the present invention Preferred embodiments of the present invention are described below.

A lock-up piston disposed at a position facing the front cover in the fluid coupling or the torque converter, wherein the lock-up piston is operated by a difference between a fluid pressure on the turbine side of the lock-up piston and a fluid pressure on the front cover side. A control method for a fluid coupling or a torque converter having a lock-up function for operating and mechanically interrupting input and output, wherein in lock-up control during inertia, a lock-up piston is connected to a front cover. The difference between the control fluid pressure supplied to the turbine side of the up-piston and the control fluid pressure supplied to the front cover side is a predetermined value determined based on the input / output rotational speed difference of the fluid coupling or the torque converter and the input rotational speed. Control fluid pressure and the turbine-side control fluid pressure to the input Controlled to a value higher than the value determined uniquely for the control method of a fluid coupling or torque converter.

A lock-up piston is provided at a position facing the front cover in the fluid coupling or the torque converter, and the lock-up piston is operated by a difference between a fluid pressure on the turbine side of the lock-up piston and a fluid pressure on the front cover side. A fluid coupling or a torque converter control device having a lock-up function that activates and mechanically interrupts input and output, and in lock-up control during coasting, when connecting the lock-up piston to the front cover, The difference between the control fluid pressure supplied to the turbine side of the lock-up piston and the control fluid pressure supplied to the front cover side is a predetermined value determined based on the input / output rotational speed difference and the input rotational speed of the fluid coupling or the torque converter. Means for controlling the pressure to the value of And means for controlling a value higher than the value which is uniquely determined with respect to the operation amount of the control device of the fluid coupling or torque converter.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a schematic structure of a torque converter.

FIG. 2 is a diagram illustrating a main part of a fluid pressure circuit according to the present embodiment.

FIG. 3 is a flowchart illustrating control according to the present embodiment.

[Explanation of symbols]

10 Torque converter, 12 Front cover, 16
Turbine runner, 18 turbine hub, 20 input shaft, 38 damper plate, 40 lock-up piston, 42 clutch face, 46 turbine side chamber, 48 front cover side chamber, 50 primary regulator, 52 secondary regulator, 54 on / off switching valve, 56 control valve.

Claims (2)

[Claims] 1. A lock-up piston disposed at a position facing a front cover in a fluid coupling or a torque converter, and lock-up is performed by a difference between a fluid pressure on a turbine side of the lock-up piston and a fluid pressure on a front cover side. A method of controlling a fluid coupling or a torque converter having a lock-up function that mechanically switches between input and output by operating a piston. In connection with lock-up control during coasting, the lock-up piston is connected to a front cover. The difference between the control fluid pressure supplied to the turbine side of the lock-up piston and the control fluid pressure supplied to the front cover side is controlled to the same value as during driving, and the turbine-side control fluid pressure is controlled to a high value. To control a fluid coupling or a torque converter. 2. The control method for a fluid coupling or a torque converter according to claim 1, wherein the turbine-side control fluid pressure is increased when the difference between the input and output rotational speeds of the fluid coupling or the torque converter becomes a predetermined value or less. A control method for a fluid coupling or a torque converter, wherein the control is stopped.