JPH08334171A - Joint control device for frictional element in automatic transmission - Google Patents

Abstract

PURPOSE: To prevent generation of a jointing shock after holding critical pressure by certainly carrying out control to hold jointing pressure of a frictional element at jointing force generating critical pressure after precharging even at the time of failure. CONSTITUTION: Working pressure Pc is controlled by a pressure reducing valve 11 reacting to electronic control commanding pressure Ps created by duty control of a solenoid 12 at the time of speed change to joint a clutch C3. The clutch C3 is speedily made to lose a stroke by precharging by maximizing the commanding pressure Ps at a speed change initial stage and making the maximum opening between ports 14, 15 of the valve 11. Thereafter, the commanding pressure Ps is made zero, the valve 11 decides the working pressure Pc only by spring force of a spring 13, and the spring force of the spring 13 is decided so that the working pressure Pc becomes critical pressure at this time. Consequently, it is possible to avoid generation of a shock due to critical pressure control impossibility by making the working pressure Pc the critical pressure even at the time of failure when the commanding pressure Ps is not generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for appropriately engaging and controlling fluid-operated friction elements such as a clutch and a brake that control a shift of an automatic transmission.

[0002]

2. Description of the Related Art Automatic transmissions generally include a plurality of fluid operated friction elements (wet friction clutches or wet friction brakes).
Select the corresponding shift speed by the selective hydraulic operation (fastening) of
It is configured to shift to another gear by switching the friction element to be operated.

As a shift control device for controlling the shift of the automatic transmission, conventionally, as described in JP-A-1-299351, the operating pressures of a plurality of friction elements are directly electronically controlled. There has been proposed a gear shift control device which is configured to perform a predetermined gear shift. In this type of shift control device, as a friction element engagement control device that directly electronically controls the operating pressure (engagement pressure) of each friction element, the idea proposed by the applicant of the present application in Japanese Patent Application Laid-Open No. 5-296337 is used. It is conceivable to use the following items.

That is, as shown in FIG. 7, the shift command instant t
_{From 1} to the instant t ₂ after the set time, the fastening pressure command value P
Once _A is made quite high, the friction element is pre-charged so as to fill the friction element rapidly, whereby the loss stroke of the friction element is quickly completed. Then, after the loss stroke end instant t _2, until instant t ₃ when starting the control operation pressure in the engagement progress of the frictional element, the working pressure, aimed at the very limit of the friction element for generating a tightening force Is maintained at a predetermined critical pressure P _X (corresponding to the spring force of the return spring in the friction element), and after the instant t ₃ , the engagement pressure command value P _A of the friction element is set to, for example, the transmission input / output rotation speed N. _i, the effective gear ratio represented by the ratio N _i / N _o of N _o is to produce a temporal change of as intended, is determined by the feedback control in connection with release pressure P _R.

According to the engagement control of the friction element, the loss stroke of the friction element which is not involved in the gear shift shock can be completed promptly, and the response of the gear shift can be improved, and the loss stroke end instant t. By the critical pressure holding control from ₂ to the instant t _{3 of} starting the feedback control, it is possible to prevent a large shift shock from occurring during the progress of engagement of the friction elements after the instant t ₃ .

On the other hand, Japanese Unexamined Patent Publication No. 61-84449 discloses a technical concept of detecting the operating stroke position of a friction element and controlling the operating pressure of the friction element in accordance with the stroke position. Based on this idea, it is possible to perform control such that the loss stroke of the friction element is detected and the operating pressure of the friction element is set to the critical pressure when the loss stroke is detected.

On the other hand, in "Maintenance Manual for FTO Vehicles" issued by Mitsubishi Motors Co., Ltd., the working pressure of the friction element is smoothly made to be a critical pressure by an orifice and an accumulator installed in the working oil passage of the friction element. The technical idea is shown.

[0008]

However, in any case, conventionally, when an abnormality such as a failure occurs, the operating pressure of the friction element cannot be set to the critical pressure. That is, in the technique described in Japanese Patent Laid-Open No. 61-84449 described above, when the sensor for detecting the operating stroke position of the friction element fails, the detection signal from now disappears, so that the operating pressure of the friction element becomes the critical pressure. It becomes impossible to control. In this case, at the time of shifting from the critical pressure holding period to the operating pressure feedback control period, a large shift shock is generated due to improper critical pressure control.

The above-mentioned "F" issued by Mitsubishi Motors Co., Ltd.
In the technology described in "TO vehicle maintenance guideline", when air is mixed in the pipeline downstream of the orifice, the response of the shift is deteriorated, the shift shock is increased, and the shift quality is not good. It causes an adverse effect such as stability.

The present invention provides a fastening pressure control device for a friction element which can surely bring the working pressure of the friction element to the critical pressure during the critical pressure holding period even when an abnormality occurs, thereby solving the above-mentioned problems. The purpose is to

[0011]

To this end, the friction element engagement control device according to the first aspect of the present invention is capable of selectively supplying a working fluid to a friction element corresponding to a selected gear by a shift valve, and an electronic control command. By controlling the supply of the working fluid in time series by the pressure reducing valve that responds to the pressure, the loss stroke of the friction element is initially performed by the precharge of the fluid, and then the working pressure of the friction element is changed to the fastening force. In an automatic transmission in which the critical pressure is set at a predetermined critical point, and then the operating pressure of the friction element is controlled in time series so that the engagement of the friction element proceeds in a predetermined manner. The pressure reducing valve is configured such that the operating pressure of the friction element is set to the critical pressure just when the electronic control command pressure to the pressure reducing valve disappears.

In the friction element engagement control device according to the second aspect of the invention, the pressure reducing valve receives the electronically controlled command pressure and the spring force of a spring in one direction, and the working pressure of the friction element is fed back in the other direction. The operating force of the friction element is controlled so as to balance the forces in both directions, and the spring force of the spring is made to correspond to the critical pressure.

Further, the friction element engagement control device according to the third aspect of the present invention is characterized in that the electronically controlled command pressure is set to a command value such that the pressure reducing valve is set to a maximum opening during an initial set time. It is a thing.

The friction element engagement control device according to the fourth aspect of the present invention is characterized in that the initial set time is determined according to the hydraulic oil temperature of the automatic transmission.

[0015]

In the first aspect of the invention, the automatic transmission can select a predetermined gear stage by selectively supplying the working fluid to the friction element by the shift valve and engaging the friction element.

By the way, at this time, the engagement control device causes the friction elements to be actuated to be engaged as follows. That is, the pressure reducing valve responds to the electronic control command pressure to time-sequentially control the supply of the working fluid, so that the working fluid is precharged toward the friction element to cause the loss stroke of the friction element, and then the friction element The operating pressure of the friction element is maintained at a predetermined critical pressure aiming at a position where the friction element generates the fastening force, and then the operating pressure of the friction element is changed to
The friction elements are controlled in time series so that the engagement of the friction elements proceeds in a predetermined manner.

The above-mentioned precharge can promptly perform a loss stroke that is not involved in the engagement shock of the friction element, and contributes to the improvement of the shift response, and the holding of the critical pressure is maintained at the time of engagement of the friction element thereafter. Prevents gear shift shock from increasing.

By the way, the pressure reducing valve is constructed so that the operating pressure of the friction element is set to the critical pressure just when the electronic control command pressure to the pressure reducing valve disappears. Even when the control command pressure can no longer be generated, the pressure reducing valve can set the operating pressure of the friction element to the critical pressure, and the problem related to the large shift shock caused by the inability to control to this critical pressure at the time of failure. Also, it is possible to solve the problem of unstable shift quality.

In the second invention, the pressure reducing valve receives the electronic control command pressure and the spring force of the spring in one direction, and receives the operating pressure of the friction element in the other direction by being fed back, and the forces in both directions are balanced. To control the operating pressure of the friction element. Since the spring force of the spring corresponds to the critical pressure, when the electronic control command pressure cannot be generated due to an abnormality such as a failure, the pressure reducing valve changes the operating pressure of the friction element to the spring force. The pressure corresponding to the above, that is, the critical pressure is set, and it is possible to solve the problem related to the large shift shock and the problem related to the instability of the shift quality, which have occurred because the control to the critical pressure is impossible at the time of failure.

In the third aspect of the invention, the electronic control command pressure is set to a command value that causes the pressure reducing valve to have a maximum opening during the initial set time. Therefore, the loss stroke speed of the friction element due to the precharge can be increased to the hardware limit, and the shift responsiveness can be maximized.

In the fourth aspect of the invention, since the initial set time is determined according to the hydraulic oil temperature of the automatic transmission, the time required for the loss stroke of the friction element changes depending on the hydraulic oil temperature of the automatic transmission. Shun can also ensure that the precharge period matches the above loss stroke time,
It is possible to achieve the effect of the fourth aspect of the invention, which is to improve the shift responsiveness to the maximum extent, more completely.

[0022]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows a speed change gear mechanism that forms a power transmission train of an automatic transmission equipped with an engagement control device according to an embodiment of the present invention, and FIG. 2 shows a plurality of fluid-operated friction elements in the power transmission train. The conclusion logic table is shown. The transmission train of the transmission gear mechanism shown in FIG. 1 has been developed by the applicant of the present application and is in practical use.
ISSAN Maxima New Car Manual, "Introduction of Changes to J30 Series Cars," issued in August 1991 (FOO7671), similar to that described in the engine ENG crankshaft C / S via the torque converter T / C. A first planetary gear set G1 and a second planetary gear set G2 coaxially provided on the input and output shafts, each of which has an input shaft I / S for transmitting rotational power and an output shaft O / S coaxially arranged with the input shaft I / S.
And various fluid-operated friction elements described later.

The torque converter T / C has a lockup clutch L / C, and when the working fluid is passed through the torque converter T / C, the working fluid is passed from the apply chamber AP to the release chamber RE. When the lockup clutch L / C is engaged, the torque converter T / C enters a lockup state in which the input and output elements are directly connected, and the working fluid flows in the opposite direction.
Is released, the torque converter T / C enters a converter state in which the direct connection between the input and output elements is released.

The first planetary gear set G1 includes a sun gear S1, a ring gear R1, a pinion P1 meshing with these, and a pinion carrier PC1 rotatably supporting the pinion P1.
A normal planetary gear set consisting of a second planetary gear set G
2 is also a simple planetary gear set including a sun gear S2, a ring gear R2, a pinion P2, and a pinion carrier PC2.

Next, the first to third clutches C1, C2 and C3, the first and second brakes B1 and B2, which are various fluid actuated friction elements that control the shift control, and the one-way clutch OWC will be described. The carrier PC1 can be appropriately connected to the input shaft I / S via the second clutch C2, the sun gear S1 can be appropriately fixed by the second brake B2, and can be appropriately connected to the input shaft I / S by the first clutch C1. And The carrier PC1 can be further appropriately fixed by the first brake B1, and the one-way clutch O
Reverse rotation (rotation in the direction opposite to the engine) is blocked via WC. The ring gear R1 is integrally connected to the carrier PC2 and drivingly connected to the output shaft O / S, and the sun gear S2 is connected to the input shaft I / S.
Bind to. The ring gear R2 can be appropriately coupled to the carrier PC1 via the third clutch C3.

First to third clutches C1, C2 and C3,
The first and second brakes B1 and B2 are actuated by the supply of hydraulic pressure to perform the appropriate coupling and fixing, respectively. However, the power transmission train of FIG. 1 includes the first to third clutches C.
1, C2, C3 and first and second brakes B1, B2
2 are operated in various combinations (shown by circles) as shown in the table of FIG. 2 in combination with the appropriate operation (engagement) of the one-way clutch OWC to constitute the planetary gear sets G1 and G2. Of the input shaft I / S
By changing the rotation speed ratio of the output shaft O / S with respect to the rotation speed of, the forward four speeds and the reverse first speed can be obtained. The first brake B1 is operated at the first speed when engine braking is required at the first speed, and when the first brake B1 is not operated, the one-way clutch OWC receives a reaction force. Although the first speed is achieved, engine braking is impossible due to idling of the one-way clutch OWC.

First to third clutches C as shown in FIG.
In this example, FIG. 3 shows a shift control device for selecting a predetermined shift stage by executing the operation / non-operation of C1, C2, C3 and the operation / non-operation of the first and second brakes B1, B2. The shift control is performed by individually and directly controlling the operating pressure of each friction element. However, in FIG. 3, due to space limitations, 3 → 4 upshift shift and 3 ← 4
The third clutch C3 and the second clutch related to downshifting
Only the operating pressure control system of the brake B2 is specified, and the operating pressure control system related to other friction elements is the third clutch C3.
Since it is the same as that of the second brake B2, it is omitted.

A device for controlling the operating pressure P _C of the third clutch C3 and controlling the engagement thereof is composed of a pressure reducing valve 11 and a duty solenoid 12. The pressure reducing valve 11 includes a spool 14 elastically supported at a position shown by a spring 13, and at this spool position, an output port 15 communicating with the third clutch C3 is communicated with an input port 16 so that the shift valve 30 receives the input. It is assumed that the line pressure P _L to the port 16 increases the third clutch operating pressure P _C. Here, the third clutch operating pressure P _C is fed back to the end chamber 17 far from the spring 13, and the spool 14 is pushed back as the third clutch operating pressure P _C rises, thereby connecting the output port 15 to the drain port 18. , 3rd clutch operating pressure P
Limit the rise of _C.

On the other hand, the electronic control command pressure P _S determined by the duty solenoid 12 is supplied to the end chamber 19 on the side where the spring 13 is housed. Duty solenoid 12 is input a constant pilot pressure P _p, gradually assumed to lower the electronic control command pressure P _S from the maximum value of the same value as the pilot pressure P _p as the increase in the drive duty D _C.

The pressure reducing valve 11 receives the electronically controlled command pressure P _S determined as described above and the spring force of the spring 13 in the right direction in the drawing with respect to the spool 14, and in the opposite direction with respect to the spool 14. The third is fed back to the end chamber 17.
Receiving clutch operating pressure P _C. The pressure reducing valve 11 regulates the third clutch operating pressure P _C so that the forces in these two directions are balanced, and therefore the third clutch operating pressure P _C is
Electronic control command pressure P _S , that is, duty solenoid 12
It can be controlled by the drive duty D _C of. Here, the drive duty D _C of the solenoid 12 corresponds to the engagement pressure command value P _A described above with reference to FIG. 7, and is determined by the shift control controller 20 as described later.

The spring force of the spring 13 is the drive duty.
D_C= Electronic control command pressure P by 100%_SBecomes 0
Just when the pressure reducing valve 11 is the third clutch operating pressure P_CThe criticality
Pressure P _XThe spring force is set to Therefore it is shown in Figure 5.
Engaging pressure command value P_AIs the critical pressure P_XWhen is this finger
Electronic control command pressure P_SCorresponds to = 0
Drive duty D to_C= Outputs 100%
And

The device for controlling the engagement pressure by controlling the operating pressure P _B of the second brake B2 is basically the same as the above-mentioned engagement control device for the third clutch C3.
1 and the duty solenoid 22. The pressure reducing valve 21 includes a spool 24 elastically supported at a position shown by a spring 23. At this spool position, an output port 25 communicating with the second brake B2 is communicated with an input port 26, and the shift valve 30 receives the input. Line pressure P to port 26
It is assumed that the operating pressure P _B of the second brake B2 is increased by _L. Here, the second brake operating pressure P _{B is changed} to the spring 23
Feedback from the far end chamber 27, by the spool 24 is pushed back with increasing second braking pressure P _B, through the output port 25 to drain port 28, to limit the rise of the second brake operating pressure P _B I shall.

On the other hand, the electronic control command pressure P _S determined by the duty solenoid 22 is supplied to the end chamber 29 on the side where the spring 23 is housed. Duty solenoid 22 is input a constant pilot pressure P _p, gradually assumed to lower the potential control command pressure P _S from the maximum value of the same value as the pilot pressure P _p as the increase in the drive duty D _B.

The pressure reducing valve 21 receives the electronically controlled command pressure P _S determined as described above and the spring force of the spring 23 in the right direction in the drawing with respect to the spool 24, and in the opposite direction with respect to the spool 14. The second is fed back to the end chamber 27.
Receives brake operating pressure P _B. The pressure reducing valve 21 regulates the second brake operating pressure P _B so that the forces in both directions are balanced, and thus the second brake operating pressure P _B is
Electronic control command pressure P _S , that is, duty solenoid 22
Can be controlled by the drive duty D _B. Here, the drive duty D _B corresponds to the engagement pressure command value P _A described above with reference to FIG.
This is determined by 0 as described later.

The spring force of the spring 23 depends on the driving duty.
D_B= Electronic control command pressure P by 100%_SBecomes 0
Just when the pressure reducing valve 21 is the second brake operating pressure P_BThe criticality
Pressure P _XThe spring force is set to Therefore it is shown in Figure 5.
Engaging pressure command value P_AIs the critical pressure P_XWhen is this finger
Electronic control command pressure P_SCorresponds to = 0
Drive duty D to_B= Outputs 100%
And

The shift valve 30 will now be described. This shift valve selectively supplies the line pressure P _L to the third clutch C3 and the second brake B2, and the third clutch C3 and the second brake B2. Is a 3-4 shift valve that causes a 3 → 4 upshift shift or a 3 ← 4 downshift shift by selectively engaging according to the logic shown in FIG. Therefore, the shift valve 30 is connected to the solenoid 3
When 0a is OFF, the port connection state 30b shown in the figure is established, and although the line pressure P _L is supplied to the third clutch C3 to engage it, the second brake B2 is communicated with the drain to deactivate it. As is apparent from the figure, the third speed can be selected, and when the solenoid 30a is turned on, the inter-port connection state 30c is established, and the line pressure P _L is supplied to the second brake B2 to be engaged. Clutch C3
Through the drain to deactivate it so that the fourth speed can be selected, as is clear from the view shown in FIG.

In addition to the third clutch C3 and the second brake B2, the shift control controller 20 includes the first clutch C3.
1, the second clutch C2, and the first brake B1
Is controlled by a device having a similar configuration, and ON / OFF control of the shift valve solenoid 30a is also performed. Therefore, the controller 20 is provided with a signal from the throttle opening sensor 31 that detects the throttle opening TVO of the engine in the preceding stage of the automatic transmission, a signal from the oil temperature sensor 32 that detects the transmission operating oil temperature T, and a gear shift. output rotation sensor 33 that detects the rotational speed N _o of the machine output shaft
Input signals from each.

The shift control controller 20 includes a sensor 31.
Based on the throttle opening TVO detected in step 3 and the transmission output speed N _o detected by the sensor 33, a shift control program (not shown) is executed to perform predetermined shift control. That is, the throttle opening TVO and the transmission output speed N
_{From o} (vehicle speed), the required shift speed suitable for the current driving state is determined based on the preset shift map, and the friction elements C1, C2, C3, B are set so as to achieve this required shift speed.
1 and B2 are selectively engaged to shift to the required shift speed.

Here, the 3-4 shift will be explained.
When the shift speed is the third speed, the shift valve 30 is set to the solenoid.
When 30a is turned off, the connection between ports is switched to 30b.
Change line pressure P_LIs supplied to the third clutch C3
And connect the second brake B2 to the drain to
Deactivate. Thus the second brake B2 is deactivated
And the third clutch C3 is engaged,
A 3 ← 4 downshift as required occurs. Request again
When the shift speed is the fourth speed, the shift valve 30 is set to the solenoid.
Switching to port-to-port connection state 30c by turning on 30a
Well, line pressure P _LTo the second brake B2
Fasten and connect the third clutch C3 to the drain to disengage it.
Turn it on. Thus, the third clutch C3 is deactivated.
At the same time, the second brake B2 will be engaged, and
It produces the desired 3 → 4 upshift.

At the time of these shifts, the controller 20 controls the engagement pressures of the friction elements that are to be engaged by being supplied with the line pressure P _L as described above.
4 executes the control program of FIG. 4 to determine the engagement pressure command value P _A which changes in time series as shown by the broken line in FIG. 5, and determines the electronic control command pressure P _S corresponding to this. The drive duty D _C or D _B of the solenoid 12 or 22 related to the friction element to be fastened is determined as shown by the solid line.

In FIG. 4, first in step 41,
Then, it is determined whether or not there is a shift command. No gear change command
If so, the shift valve 30 causes the friction element to have the line pressure P._LSupply
Therefore, the friction element is not fastened,
At step 42, the engagement pressure command value P _AThe shift command instant t in FIG.
₁Corresponds to 0, as indicated by earlier values
Electronic control command pressure P_SSet to 0 to achieve this
The solenoid drive duty for
A solenoid (for example, solenoids 12 and 2 shown in FIG. 3)
Output to 2).

Here, the pressure reducing valve 11 (21) supplied with the electronic control command pressure P _S = 0 causes the friction element C3 (B) due to the spring force (set load) of the spring 13 (23).
Although the operating pressure P _C (P _B ) to 2) is made to be a value equivalent to the critical pressure P _X , as described above, the shift valve 30 does not supply the line pressure P _L to the friction element, and therefore the pressure reducing valve. 11
Since there is no input pressure to (21), the operating pressure P
_C (P _B ) is set to 0, which meets the request for the engagement pressure command value P _A = 0.

When it is determined in step 41 that a gear shift command has been issued (instantaneous time t _{1 in} FIG. 5), the transmission operating oil temperature T is detected in step 43, and then in step 44, the detected oil temperature T is used as shown in FIG. The precharge time Δt _p is searched based on the map corresponding to the oil temperature T / precharge time Δt _p characteristic illustrated in FIG. Here, the characteristic of FIG. 6 is that the higher the oil temperature T, the shorter the precharge time Δt _p for the loss stroke, and the reason is that the higher the hydraulic oil temperature, the lower the viscosity and the hydraulic oil to the friction element. Of the precharge time Δ at any oil temperature T, because the inflow of the oil is quick and the time required for the loss stroke is shortened.
It is preferable to match t _p with the actual loss stroke required time.

In steps 45 and 47 of FIG. 4, it is determined whether or not the timer TM for measuring the elapsed time from the shift command instant t ₁ indicates the precharge time Δt _p or less, that is, during the precharge period, that is, in FIG. It is determined whether or not it is during the instants t _{1 to} t ₂ and whether or not the timer TM is during the critical pressure holding period Δt _k during the subsequent instants t _{2 to} t ₃ . When it is determined that the pre-charge time Δt _p is between the instants t _{1 and} t ₂ in FIG. 5, in step 46, the engagement pressure command value P _A = maximum value MAX is commanded as shown in FIG. Corresponding to this, the command pressure P _S is set to the maximum value MAX,
The solenoid drive duty for achieving this is output to the solenoid (for example, the solenoids 12 and 22 shown in FIG. 3) related to the friction element.

As a result, the pressure reducing valve 11 (21) allows the input port, to which the line pressure P _L is supplied, to communicate with the output port at the maximum opening degree so that the friction element is rapidly filled with the working fluid, and the friction element is quickly precharged. If you can do such a loss stroke. Moreover, as described above, the precharge time Δ
Since t _p is changed according to the oil temperature T to match the actual time required for the loss stroke, precharging ends before the loss stroke ends and improvement in gear shift response is hindered, or the loss stroke ends. It is possible to eliminate the harmful effect that a shock is generated because the precharge is continued despite the fact.

If it is determined in step 47 that the critical pressure holding period Δt _k between the instants t _{2 and} t _{3 in} FIG. 5 is being determined, in step 48, the engagement pressure command value P as shown in FIG.
_A = Critical pressure P _X is commanded, electronic control command pressure P _S is set correspondingly to 0, and the solenoid drive duty for achieving this is set to the solenoid relating to the friction element (for example, the solenoid shown in FIG. 3). 12 and 22). As a result, the pressure reducing valve 11 (21) sets the working pressure of the friction element to the critical pressure P _X determined only by the spring force of the built-in spring in response to the electronic control command pressure P _S = 0, and the fastening pressure command value P _A
= Enable operating pressure control that matches the critical pressure P _X.

When it is determined in step 47 that the operating pressure feedback control period is after the instant t _{3 in} FIG. 5, the engaging pressure command value P _A is set in step 49, for example, as shown in FIG.
As shown in, the ratio _Ni / N of the transmission input / output speeds N _i and N _o
A solenoid for determining the effective gear ratio represented by N _o by feedback control so as to cause a desired change over time, setting the electronic control command pressure P _S to a feedback control value corresponding thereto, and achieving this. The drive duty is output to the solenoid (for example, the solenoids 12 and 22 shown in FIG. 3) related to the friction element. As a result, the pressure reducing valve 1
1 (21) can control the operating pressure of the friction element so that the effective gear ratio of the automatic transmission changes with time in a targeted manner, and a gear shift shock can be prevented. The critical pressure holding control described above can reliably prevent a large shock at the time of engaging the friction element immediately after the instant t ₃ in FIG.

When the electronic control command pressure P _S cannot be generated, the pressure reducing valve 11 (21) adjusts the operating pressure of the friction element to a pressure determined only by the spring force of the built-in spring. Since the regulated pressure value is the same as the critical pressure P _X as described above, the critical pressure holding control will not be disabled even during the failure. Therefore, it is possible to prevent the critical pressure holding control from being disabled at the time of this failure, and the shock at the start of the engagement progress of the friction element from increasing.

[0049]

As described above, the friction element engagement control apparatus according to the first aspect of the present invention comprises a pressure reducing valve for controlling the engagement pressure of the friction element in response to the electronic control command pressure. When the pressure disappears, the operating pressure of the friction element is set to the critical pressure, so even when the electronic control command pressure cannot be generated due to an abnormality such as a failure, the pressure reducing valve sets the operating pressure of the friction element to the critical pressure. Therefore, it is possible to solve the problem of a large shift shock and the problem of instability of the shift quality, which have occurred because the control to the critical pressure is impossible at the time of failure.

In the friction element engagement control device according to the second aspect of the present invention, the pressure reducing valve has the following configuration, that is, the electronic control command pressure and the spring force of the spring are received in one direction. , The operating pressure of the friction element is fed back in the other direction, and the operating pressure of the friction element is controlled so that the forces in these two directions are balanced. Furthermore, the spring force of the spring corresponds to the critical pressure. Therefore, when the electronic control command pressure can no longer be generated due to an abnormality such as a failure, the pressure reducing valve sets the operating pressure of the friction element to the pressure corresponding to the above spring force and makes it the critical pressure. It is possible to solve the problem of a large shift shock and the problem of instability of the shift quality, which have occurred because the control to the critical pressure is sometimes impossible.

In the friction element engagement control device according to the third aspect of the present invention, as described in claim 3, the electronic control command pressure is set to a command value such that the pressure reducing valve is maximized during the initial set time. Since it is configured, the loss stroke speed of the friction element due to the precharge can be increased to the hardware limit, and the shift response can be maximized.

In the friction element engagement control device according to the fourth aspect of the present invention, as described in claim 4, the initial set time is determined according to the hydraulic fluid temperature of the automatic transmission. Therefore, the loss stroke of the friction element is lost. When the time required for changes depending on the hydraulic oil temperature of the automatic transmission, the 雛 can also ensure that the precharge period matches the above-mentioned loss stroke time.
It is possible to achieve the effect of the fourth aspect of the invention, which is to improve the gear shift response to the maximum, more completely.

[Brief description of drawings]

FIG. 1 is a skeleton diagram showing a power transmission train of an automatic transmission to which a friction element engagement control device according to an embodiment of the present invention is applied.

FIG. 2 is an explanatory diagram showing a relationship between an engagement logic table of various friction elements in the power transmission train shown in FIG. 1 and a selected shift speed.

FIG. 3 is a system diagram showing a hydraulic circuit and an electronic control system that govern shift control of the transmission train shown in FIG.

FIG. 4 is a flowchart showing a friction element engagement control program in the same example.

FIG. 5 is an operation time chart of the friction element engagement control.

FIG. 6 is a diagram showing a hydraulic oil temperature / precharge time characteristic used in the example.

FIG. 7 is a time chart exemplifying how to give an engagement pressure command value during a shift.

[Explanation of symbols]

 T / C Torque converter I / S Input shaft O / S Output shaft G1 1st planetary gear set G2 2nd planetary gear set C1 1st clutch (friction element) C2 2nd clutch (friction element) C3 3rd clutch (friction element) ) B1 1st brake (friction element) B2 2nd brake (friction element) OWC One-way clutch 11 Pressure reducing valve 12 Duty solenoid 20 Shift control controller 21 Pressure reducing valve 22 Duty solenoid 30 Shift valve 31 Throttle opening sensor 32 Oil temperature sensor 33 Output Rotation sensor

Claims (4)

[Claims] 1. A shift valve can selectively supply a working fluid to a friction element corresponding to a selected gear, and a pressure reducing valve responsive to an electronically controlled command pressure controls the supply of the working fluid in time series. Initially, the loss stroke of the friction element is performed by precharging the fluid, and then the working pressure of the friction element is maintained at a predetermined critical pressure just at the point where the friction element generates the fastening force, and then the friction element is In an automatic transmission, the operating pressure of which is controlled in time series so that the engagement of friction elements proceeds in a predetermined manner, the pressure reducing valve is controlled when the electronic control command pressure to the pressure reducing valve disappears. A fastening control device for a friction element in an automatic transmission, wherein the operating pressure of the friction element is set to a critical pressure. 2. The pressure reducing valve according to claim 1, wherein the pressure reducing valve receives the electronic control command pressure and a spring force of a spring in one direction, and receives the operating pressure of the friction element in another direction by being fed back. Is configured to control the operating pressure of the friction element so that the spring force of the spring corresponds to the critical pressure. 3. The friction in an automatic transmission according to claim 1, wherein the electronically controlled command pressure is set to a command value that causes the pressure reducing valve to have a maximum opening during an initial set time. Element fastening control device. 4. The friction element engagement control device for an automatic transmission according to claim 3, wherein the initial set time is determined according to a hydraulic oil temperature of the automatic transmission.