JP3291979B2 - Device for controlling engagement of friction elements in automatic transmission - Google Patents

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 a fluid-operated friction element such as a clutch or a brake for controlling 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 and wet friction brakes).
Select the corresponding gear by the selective hydraulic operation (engagement) of
The shift to another shift speed is performed by switching the friction element to be operated.

[0003] As a shift control device for controlling the shift of the automatic transmission, conventionally, as described in Japanese Patent Application Laid-Open No. 1-299351, the electronic control of the operating pressures of a plurality of friction elements is performed individually and individually. There has been proposed a shift control device for performing a predetermined shift. In this type of shift control device, a friction element engagement control device that directly and individually electronically controls the operating pressure (engagement pressure) of the friction element is based on the concept proposed by the present applicant in Japanese Patent Application Laid-Open No. 5-296337. The following can be used.

That is, as shown in FIG.
Between ₁ and instant t ₂ after the set time, engagement pressure command value P
Once _A is fairly high, a precharge is performed to quickly fill the friction element with fluid, thereby quickly completing the loss stroke of the friction element. 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 changed 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 shift shock can be quickly completed, and the responsiveness of the shift can be improved. the critical pressure retaining control during the period from ₂ to feedback control start instant t _3, a large shift shock at engagement progression friction element at the instant t ₃ after it is possible to prevent the occurrence.

On the other hand, Japanese Patent Application Laid-Open No. 61-84449 discloses a technical idea of detecting the operation stroke position of a friction element and controlling the operation pressure of the friction element according to the stroke position. Based on this concept, it is possible to detect the loss stroke of the friction element and control the operating pressure of the friction element to a critical pressure from the time of detection of the loss stroke.

On the other hand, the "Maintenance Manual for FTO Vehicles" issued by Mitsubishi Motors Co., Ltd. describes that the operating pressure of a friction element is smoothly brought to a critical pressure by an orifice and an accumulator installed in a hydraulic 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. In other words, according to the technique described in Japanese Patent Application Laid-Open No. 61-84449, when a sensor for detecting the operation stroke position of the friction element fails, the detection signal from the sensor disappears, and the operation pressure of the friction element becomes critical pressure. Control becomes impossible. In this case, when shifting from the critical pressure holding period to the operating pressure feedback control period, a large shift shock occurs due to improper critical pressure control.

Further, "F" issued by Mitsubishi Motors Corporation
According to the technology described in the “TO vehicle maintenance manual”, when air enters the pipeline downstream of the orifice, the response of the gear shift deteriorates, the gear shift shock increases, and the gear shift quality becomes poor. The disadvantage that stability is caused.

The present invention provides a friction element fastening pressure control device capable of reliably setting the operating pressure of a friction element to a critical pressure during the critical pressure holding period even when an abnormality occurs, thereby solving the above-mentioned problems. The purpose is to:

[0011]

SUMMARY OF THE INVENTION For this purpose, a friction element engagement control device according to a first aspect of the present invention can selectively supply working fluid to a friction element corresponding to a selected shift speed by a shift valve. By controlling the supply of the working fluid in a time-series manner by a pressure-reducing valve that responds to the pressure, the loss stroke of the friction element is first performed by precharging the fluid, and then the working pressure of the friction element is increased, and the friction element increases the fastening force. In an automatic transmission in which the critical pressure is kept at a predetermined critical level aiming at a point where the friction occurs, and then the operating pressure of the friction element is controlled in a time-series manner so that the engagement of the friction element proceeds in a predetermined manner. The pressure reducing valve is characterized in that when the electronic control command pressure to the pressure reducing valve disappears, the operating pressure of the friction element is set to the critical pressure.

In a second aspect of the present invention, the pressure reducing valve receives the electronic control command pressure and the spring force of a spring in one direction and feeds back the operating pressure of the friction element in the other direction. The operation pressure of the friction element is controlled so that these forces in both directions are balanced, and the spring force of the spring corresponds to the critical pressure.

Further, the engagement control device for a friction element according to the third invention is characterized in that the electronic control 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. Things.

[0014] Further, the friction element engagement control device according to the fourth invention is characterized in that the initial set time is determined according to the operating oil temperature of the automatic transmission.

[0015]

According to the first aspect of the present invention, the automatic transmission can select a predetermined shift speed by selectively supplying working fluid to the friction element by the shift valve and fastening the friction element.

At this time, the engagement control device causes the friction element to be operated to be engaged as described below. That is, the pressure reducing valve controls the supply of the working fluid in a time-series manner in response to the electronic control command pressure, so that the working fluid is first precharged to the friction element to perform a loss stroke of the friction element, and then to perform the friction stroke. The operating pressure of the element is maintained at a predetermined critical pressure aiming at a point where the friction element generates the fastening force, and then the operating pressure of the friction element is
Control is performed in a time-series manner so that the engagement of the friction element proceeds in a predetermined manner.

The above-described precharge can promptly perform a loss stroke which is not involved in the engagement shock of the friction element, and contributes to improvement of the shift response. The maintenance of the critical pressure is performed when the friction element is subsequently engaged. The shift shock is prevented from increasing.

By the way, the pressure reducing valve is configured 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 is lost. 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 a problem related to a large shift shock caused by the inability to control the critical pressure at the time of failure. In addition, it is possible to solve the problem related to the instability of the 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 by feedback in the other direction, and the forces in these two directions are balanced. The operating pressure of the friction element is controlled to Since the spring force of the spring corresponds to the critical pressure, when the electronic control command pressure cannot be generated due to a failure or the like, the pressure reducing valve changes the operating pressure of the friction element to the spring force. , That is, the critical pressure, and it is possible to solve the problem related to a large shift shock and the problem related to instability of the shift quality, which are caused by the inability to control the critical pressure at the time of failure.

In the third invention, the electronic control 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. Therefore, 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 fourth invention, the initial set time is determined according to the operating oil temperature of the automatic transmission. Therefore, the time required for the loss stroke of the friction element changes according to the operating oil temperature of the automatic transmission. Nevertheless, the precharge period can be reliably matched to the above loss stroke time,
The operation and effect of the fourth invention of maximizing shift response can be more completely achieved.

[0022]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a speed change gear mechanism forming a power transmission line of an automatic transmission having a fastening 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 line. 3 shows a fastening logic table. The transmission train of the speed change gear mechanism shown in FIG.
ISSAN Maxima New Model Manual Introduction of Changes to J30 Series Vehicles "issued in August 1991 (FOO7671), and from the crankshaft C / S of the engine ENG via the torque converter T / C. A first planetary gear set G1 and a second planetary gear set G2 provided with an input shaft I / S to which rotational power is transmitted and an output shaft O / S arranged coaxially with the input shaft I / S, provided coaxially on these input / output shafts.
And various fluid-operated friction elements to be described later.

The torque converter T / C has a lock-up clutch L / C. When the working fluid flows through the torque converter T / C, the working fluid flows from the apply chamber AP to the release chamber RE. When the lock-up clutch L / C is engaged, the torque converter T / C is in a lock-up state in which the input / 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 is composed of a sun gear S1, a ring gear R1, a pinion P1 meshing with the sun gear S1, a ring gear R1, and a pinion carrier PC1 rotatably supporting the pinion P1.
And 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, C3, the first and second brakes B1, B2, and the one-way clutch OWC, which are various fluid-operated friction elements for controlling the shift control, will be described. The carrier PC1 can be appropriately connected to the input shaft I / S via the second clutch C2, and the sun gear S1 can be appropriately fixed to the input shaft I / S by the first clutch C1 in addition to the sun gear S1. And The carrier PC1 can be appropriately fixed by the first brake B1, and the one-way clutch O
Reverse rotation (rotation in the opposite direction to the engine) is prevented via the WC. The ring gear R1 is integrally connected to the carrier PC2 and is drivingly connected to the output shaft O / S, and connects the sun gear S2 to the input shaft I / S.
Tied to The ring gear R2 can be appropriately connected to the carrier PC1 via the third clutch C3.

First to third clutches C1, C2, C3;
The first and second brakes B1 and B2 are respectively operated by supplying hydraulic pressure to perform the above-mentioned proper coupling and fixing. The power transmission train shown in FIG.
1, C2, C3 and the first and second brakes B1, B2
Are operated in various combinations as shown in the table of FIG. 2 (indicated by circles), and together with the appropriate operation (engagement) of the one-way clutch OWC, the elements constituting the planetary gear sets G1, G2 are combined. Of the input shaft I / S
By changing the ratio of the rotation speed of the output shaft O / S to the rotation speed of the first gear, four forward speeds and one reverse 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 and the first brake B1 receives the reaction force. Although the first speed is realized, the engine brake cannot be performed due to the idling of the one-way clutch OWC.

First to third clutches C as shown in FIG.
FIG. 3 shows, in this example, a shift control device that executes the operation and non-operation of the first and second brakes B1 and B2 to select a predetermined shift speed by performing the operation and non-operation of the first and second brakes B1 and B2. The gear 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 and 3 ← 4
Third clutch C3 and 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 the other frictional elements is the third clutch C3.
Since it is the same as that of the second brake B2, it is omitted.

[0028] by controlling the working pressure P _C of the third clutch C3, device which controls the engagement control is constituted by a pressure reducing valve 11 and the duty solenoid 12. The pressure reducing valve 11 includes a spool 14 elastically supported by a spring 13 at a position shown in the drawing. At this spool position, the output port 15 communicating with the third clutch C3 is communicated with the input port 16, and the input from the shift valve 30. the line pressure P _L to the port 16 is assumed to raise the third clutch hydraulic pressure P _C. The third clutch hydraulic pressure P _C, where then fed back to the far end chamber 17 from the spring 13, by the spool 14 is pushed back with increasing third clutch actuation pressure P _C, through the output port 15 to drain port 18 , Third clutch operating pressure P
Limit the rise of _C.

[0029] On the other hand, the end chamber 19 on the side where the spring 13 is accommodated supplies electronic control command pressure P _S which is determined by the duty solenoid 12. 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, and an electronic control command pressure P _S which is determined as described above, receives the spring force of the spring 13 rightward in the drawing with respect to the spool 14, opposite direction relative to the spool 14 The third is fed back to the end chamber 17
Receiving the clutch actuation pressure P _C. Then, the pressure reducing valve 11 regulates the third clutch operating pressure P _C so that these forces in both directions are balanced. Therefore, the third clutch operating pressure P _C is
The electronic control command pressure P _S , that is, the 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 of the aforementioned reference to Figure 7, to determine this on as described later by the shift controller 20.

Note that the spring force of the spring 13 is
D_C= Electronic control command pressure P by 100%_SBecomes 0
Just when the pressure reducing valve 11 reaches the third clutch operating pressure P_CThe critical
Pressure P _XSpring force. Therefore, as shown in FIG.
Thus, the engagement pressure command value P_AIs the critical pressure P_XWhen this finger
The electronic control command pressure P_S= 0
Drive duty D_C= 100% output
And

The device that controls the operating pressure P _B of the second brake B 2 and controls the engagement thereof is basically the same as the above-described engagement control device of the third clutch C 3.
1 and a duty solenoid 22. The pressure reducing valve 21 has a spool 24 elastically supported by a spring 23 at the illustrated position. At this spool position, an output port 25 communicating with the second brake B2 is communicated with an input port 26, and the input from the shift valve 30 is controlled. Line pressure P to port 26
_L By assumed to increase the operating pressure P _B of the second brake B2. Here, the second brake operating pressure P _B is
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 Shall be.

[0033] On the other hand, on the side of the end chamber 29 the spring 23 is accommodated supplies electronic control command pressure P _S which is determined by the duty solenoid 22. 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 electronic control command pressure P _S determined as described above and the spring force of the spring 23 in the right direction in FIG. The second is fed back to the end chamber 27.
Receiving a braking pressure P _B. Then, the pressure reducing valve 21 adjusts the second brake operating pressure P _B so that the forces in these two directions are balanced. Therefore, the second brake operating pressure P _B is
The electronic control command pressure P _S , that is, the duty solenoid 22
It can be controlled by the drive duty D _B of. Here, the drive duty D _B in the case corresponding to the engagement pressure command value P _A of the aforementioned reference to Figure 6, the shift controller 2
0 determines this as described below.

The spring force of the spring 23 depends on the drive duty.
D_B= Electronic control command pressure P by 100%_SBecomes 0
Just when the pressure reducing valve 21 is at the second brake operating pressure P_BThe critical
Pressure P _XSpring force. Therefore, as shown in FIG.
Thus, the engagement pressure command value P_AIs the critical pressure P_XWhen this finger
The electronic control command pressure P_S= 0
Drive duty D_B= 100% output
And

[0036] To explain the shift valve 30, where the shift valve, a line pressure P _L to the third clutch C3 and the second brake B2 by selectively supplying these third clutch C3 and the second brake B2 Are selectively engaged in accordance with the logic shown in FIG. 2 to produce a 3 → 4 upshift or a 3 ← 4 downshift. For this reason, the shift valve 30 is provided with the solenoid 3
When OFF of 0a, port connection status 30b next to the illustrated, is fastened to this line pressure P _L is supplied to the third clutch C3, the second brake B2 deactivated it through the drain, Fig 2 the third speed can be selected is apparent from the method shown in, when oN of the solenoid 30a, port connection status 30c becomes also the line pressure P _L is supplied to the second brake B2 is entered into this third Clutch C3
Through the drain to deactivate it so that the fourth speed can be selected as is apparent from FIG.

The shift control controller 20 includes a first clutch C3 in addition to the third clutch C3 and the second brake B2.
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, a signal from a throttle opening sensor 31 for detecting the throttle opening TVO of the engine at the preceding stage of the automatic transmission, a signal from an oil temperature sensor 32 for detecting the transmission operating oil temperature T, and output rotation sensor 33 that detects the rotational speed N _o of the machine output shaft
Input signals from

The shift control controller 20 includes a sensor 31
Throttle opening TVO, and a transmission output speed N _o detected by the sensor 33 based in the detected performs a predetermined shift control by executing forced gear change control program shown. That is, the throttle opening TVO and the transmission output speed N
_{o From} (vehicle speed), a required shift speed suitable for the current driving state is determined based on a shift map set in advance, and friction elements C1, C2, C3, B are set so that the required shift speed is achieved.
1 and B2 are selectively engaged to shift to the required shift speed.

Here, the 3-4 shift will be described.
When the shift speed is the third speed, the shift valve 30 is connected to the solenoid.
By turning off 30a, it switches to the port connection state 30b.
Replacement, line pressure P_LTo the third clutch C3
And the second brake B2 is passed through the drain to
Deactivate. Thus, the second brake B2 is deactivated.
And the third clutch C3 is engaged,
3. The required 3 ← 4 downshift is performed. Also request
When the shift speed is the fourth speed, the shift valve 30 is connected to the solenoid.
Switch to port connection state 30c by turning on 30a
E, line pressure P _LTo the second brake B2 and
The third clutch C3 is connected to the drain to release
Make it work. Thus, the third clutch C3 is deactivated.
At the same time, the second brake B2 is engaged,
The required 3 → 4 upshift is produced.

[0040] Upon these shift, in order to individually control the engagement pressure of the friction element was to be fastened is supplied with line pressure P _L as described above, the controller 20
Executes a control program in FIG. 4, for example, to determine the engagement pressure command value P _A in a time series change as indicated by a broken line in FIG. 5, FIG electronic control command pressure P _S to correspond to 5 in seeking as indicated by the solid line, shall determine the drive duty D _C or D _B of the solenoid 12 or 22 according to the friction element was to be fastened above.

In FIG. 4, first, in step 41,
It is determined whether or not there has been a shift command. Without shift command
Then, the shift valve 30 applies the line pressure P to the friction element._LSupply
And therefore no friction elements are fastened,
In step 42, the engagement pressure command value P _ATo the shift command instant t in FIG.
₁0 as shown as the earlier value and the corresponding
Electronic control command pressure P_SAchieve this by setting
Of the solenoid drive duty to
Solenoid (for example, the solenoids 12, 2 shown in FIG. 3)
Output to 2).

Here, the pressure reducing valve 11 (21) supplied with the above-mentioned electronic control command pressure P _S = 0 receives the friction element C3 (B) due to the spring force (set load) of the spring 13 (23).
The working pressure P _C (P _B ) to 2) is set to a value equivalent to the critical pressure P _X. However, since the shift valve 30 does not supply the line pressure P _L to the friction element as described above, the pressure reducing valve is used. 11
Since there is no input pressure to (21), the operating pressure P
_C (P _B ) is set to 0, which corresponds to the request for the engagement pressure command value P _A = 0.

When it is determined in step 41 that a shift command has been issued (instantaneous t _{1 in} FIG. 5), the transmission operating oil temperature T is detected in step 43. based on the map corresponding to the exemplified oil temperature T · precharge time Delta] t _p characteristics, to find the precharge time Delta] t _p. Here the characteristics of FIG. 6, the precharge time Delta] t _p is shortened characteristics for loss stroke the higher the oil temperature T, because the viscosity as when a high hydraulic oil temperature is low, the operating oil to the frictional elements In order to match the rapid inflow of oil and the time required for the loss stroke, the precharge time Δ is most preferable at any oil temperature T.
a t _p, is good to match the actual loss stroke required time.

[0044] In step 45 and 47 in FIG. 4, a timer TM for measuring the elapsed time from the shift command instant t ₁ indicates less precharge time Delta] t _p, whether during the precharge period, i.e. in FIG. 5 with determining whether in instant t ₁ ~t _2, the timer TM is equal to or critical pressure holding period or during Delta] t _k between subsequent instant t ₂ ~t _3. When it is determined to be in precharge time Delta] t _p between the instant t ₁ ~t ₂ in FIG. 5, at step 46, it instructs the engagement pressure command value P _A = maximum value MAX as shown in FIG. 5, an electronic control The command pressure P _S is set to the maximum value MAX corresponding to this,
The solenoid drive duty for achieving this is output to the solenoids related to the friction elements (for example, the solenoids 12 and 22 shown in FIG. 3).

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 degree of opening to rapidly fill the friction element with the working fluid, and to quickly charge the friction element by precharging. Enables a large loss stroke. Moreover, as described above, the precharge time Δ
The t _p is changed according to the oil temperature T, since to match the actual loss stroke duration, or improve the shift response ends the precharge is inhibited for a pre-finished loss stroke, stroke loss is finished However, it is possible to eliminate the adverse effect that the precharge is continued in spite of the fact that a shock occurs.

[0046] In step 47, if determined to be critical pressure holding period in Delta] t _k between the instantaneous t ₂ ~t ₃ in FIG. 5, in step 48, engagement pressure command value P as shown in FIG. 5
Commands the _A = critical pressure P _X, the electronic control command pressure P _S is correspondingly set to 0, indicating the solenoid drive duty to accomplish this, the solenoid (for example, FIG. 3 according to the friction element solenoid 12, 22). Accordingly, the pressure reducing valve 11 (21) makes the operating pressure of the friction element a 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 engagement pressure command value P _A
= Makes it possible to operate pressure control were consistent critical pressure P _X.

[0047] In step 47, if determined to be in an instant t ₃ subsequent definitive working pressure feedback control period in Fig. 5, at step 49, the engagement pressure command value P _A, for example, FIG. 7
Transmission output as shown in the rotational speed N _i, the ratio of N _o N _i /
The electronic control command pressure P _S is set to a corresponding feedback control value by a feedback control so that the effective gear ratio represented by N _o changes as intended with time, and a solenoid for achieving this is set. The drive duty is output to a solenoid related to the friction element (for example, the solenoids 12, 22 shown in FIG. 3). Thereby, 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 as intended, and can prevent shift shock. Incidentally, the critical pressure holding control described above, it is possible to reliably prevent the shock at the time of engagement of the friction element immediately after instant t ₃ in FIG. 5 increases.

By the way, when a failure such as no longer obtained to generate an electronic control command pressure P _S is the pressure reducing valve 11 (21) is a hydraulic pressure of the friction elements, by regulating the pressure determined by only the spring force of the internal spring, this pressure value from it is equal to the critical pressure P _X as described above, have never during the fault also becomes impossible critical pressure holding control. Therefore, it is possible to prevent the critical pressure holding control from being disabled at the time of this failure, and prevent the shock at the start of the engagement of the friction element from increasing.

[0049]

Thus, the friction element engagement control device according to the first aspect of the present invention includes an electronic control command pressure control device that controls the friction element engagement pressure in response to the electronic control command pressure. When the operating pressure of the friction element is set to the critical pressure just when the pressure disappears, the pressure reducing valve sets the operating pressure of the friction element to the critical pressure even when the electronic control command pressure cannot be generated due to an abnormality such as a failure. Thus, it is possible to solve a problem relating to a large shift shock and a problem relating to instability of the shift quality, which have occurred due to the inability to control the critical pressure at the time of failure.

According to a second aspect of the present invention, in the friction element engagement control device, the pressure reducing valve has the following structure, that is, receives the electronic control command pressure and the spring force of the spring in one direction. In the other direction, the operating pressure of the friction element is fed back and received, and the operating pressure of the friction element is controlled so that the forces in both directions are balanced, and the spring force of the spring is changed to a configuration corresponding to the critical pressure. Therefore, when it becomes impossible to generate the electronic control command pressure due to an abnormality such as a failure, the pressure reducing valve sets the operating pressure of the friction element to a pressure corresponding to the above spring force, and makes this a critical pressure, and It is possible to solve a problem related to a large shift shock and a problem related to instability of shift quality, which are sometimes caused by the inability to control the critical pressure.

According to the third aspect of the present invention, the electronic control command pressure is set to a command value such that the pressure reducing valve is set to the maximum opening during the initial set time. With the configuration, 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.

According to the fourth aspect of the present invention, the friction element engagement control device is configured such that the initial set time is determined according to the operating oil temperature of the automatic transmission. Although the time required for the automatic transmission changes according to the hydraulic oil temperature of the automatic transmission, the precharge period can be reliably matched with the above loss stroke time,
The operation and effect of the fourth invention of maximizing shift response can be more completely achieved.

[Brief description of the 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 a fastening logic table of various friction elements in a 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 for controlling a shift of the transmission train shown in FIG. 1;

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

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

FIG. 6 is a diagram showing characteristics of hydraulic oil temperature and precharge time used in the example.

FIG. 7 is a time chart illustrating a method of giving an engagement pressure command value at the time of shifting.

[Explanation of symbols]

 T / C Torque converter I / S Input shaft O / S Output shaft G1 First planetary gear set G2 Second planetary gear set C1 First clutch (friction element) C2 Second clutch (friction element) C3 Third 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

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F16H 61/00-61/24

Claims (4)

(57) [Claims] A shift valve is capable of selectively supplying working fluid to a friction element corresponding to a selected shift speed, and the supply of the working fluid is time-sequentially controlled by a pressure reducing valve responsive to an electronic control command pressure. Initially, a loss stroke of the friction element is performed by precharging the fluid, and then the operating pressure of the friction element is maintained at a predetermined critical pressure aiming at a point where the friction element generates a fastening force. In the automatic transmission in which the working pressure of the friction element is controlled in a time series so that the engagement of the friction element proceeds in a predetermined manner, the pressure reducing valve is controlled when the electronic control command pressure to the pressure reducing valve disappears. A friction element engagement control device for an automatic transmission, wherein the operation 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 the spring force of a spring in one direction, and receives the operating pressure of the friction element in the other direction by feedback, and receives the force in both directions. A frictional element engagement control device for an automatic transmission, wherein the operating pressure of the frictional element is controlled so as to balance the force, and the spring force of the spring corresponds to the critical pressure. 3. The friction in an automatic transmission according to claim 1, wherein the electronic control 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. Element fastening control device. 4. The apparatus according to claim 3, wherein the initial set time is determined in accordance with the operating oil temperature of the automatic transmission.