JP2933358B2 - Transmission control device for automatic transmission - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shift control device for an automatic transmission, and more specifically, can reduce a shift shock without impairing a shift response. The present invention relates to a shift control device for an automatic transmission.

[Conventional technology]

2. Description of the Related Art As an automatic transmission mounted on a vehicle, a transmission composed of a torque converter and a multi-gear type transmission mechanism has been widely put to practical use. In such an automatic transmission, a transmission mechanism having a plurality of friction engagement elements is provided.The friction engagement elements include a brake, a servo mechanism for operating the brake, and a hydraulic driven clutch. , A hydraulically driven piston operatively connected to the brake, and a first oil chamber and a second oil chamber formed on both sides of the piston, respectively, and the servo mechanism comprises at least a first oil chamber and a second oil chamber. When the operating oil pressure is supplied to the chamber, the brake is released, when the operating oil pressure is supplied to the first oil chamber, and when the operating oil pressure is released from the second oil chamber, the brake is engaged, 2. Description of the Related Art There is known an automatic transmission configured such that a clutch is engaged when an operating oil pressure is supplied. Such automatic transmissions are generally provided with a shift control device having a hydraulic circuit capable of selectively supplying operating oil pressure to a friction engagement element in order to cause the speed change mechanism to perform a shift speed switching operation.

For example, an automatic transmission disclosed in Japanese Patent Application Laid-Open No. 63-186055 is engaged in a third speed and released in a second speed.
Disengaged at clutch 3 and engaged at clutch 2
-4 brake, and the 2-4 brake is
The servo piston is connected to a servo piston constituting a servo mechanism, and is engaged or released by controlling supply / discharge of a servo apply pressure and a servo release pressure acting respectively on an apply chamber and a release chamber of the servo piston. In such an automatic transmission, switching of a shift valve constituting a hydraulic circuit causes
When the downshift is executed from the third gear to the second gear, as shown in FIG.
Is released to release the 3-4 clutch, the servo release pressure PR acting on the servo piston is released, the servo apply pressure PA is held, and the servo piston is operated by the servo apply pressure PA. 2-4
The brake is engaged.

[Problems to be solved by the invention]

However, in this type of automatic transmission, the release of the servo release pressure PR is set relatively quickly so that the shift response during high-speed running is emphasized. With the release of the PR, the 2-4 brake is relatively quickly applied by the servo apply pressure PA, so that a shift shock is likely to occur particularly during downshifting during low-speed running.

The present invention has been made to solve the above problems, and has as its object to provide a shift control device for an automatic transmission that can reduce shift shock without impairing shift responsiveness. I have.

[Means and actions for solving the problem]

In order to achieve the above object, the present invention provides a transmission mechanism having a friction engagement element, and a hydraulic circuit capable of selectively supplying a hydraulic pressure to the friction engagement element so that the transmission mechanism performs a shift operation. And an engine load detecting means for detecting a value related to the engine load, wherein the frictional engagement element includes a brake, a servo mechanism for operating the brake,
A hydraulically driven clutch, the servomechanism having a hydraulically driven piston operatively connected to the brake, and a first oil chamber and a second oil chamber formed on both sides of the piston, respectively. The brake is released when the operating oil pressure is supplied to the first oil chamber and the second oil chamber.
An operating oil pressure is supplied to the oil chamber, and the brake is engaged when the operating oil pressure is released from the second oil chamber,
In a shift control device provided in an automatic transmission configured to be connected when an operating oil pressure is supplied, a first clutch in which a clutch is engaged and a brake is released.
When the engine load is smaller than a predetermined value when the speed change mechanism is shifted to the second shift speed at which the clutch is released and the brake is engaged from the first shift speed, the clutch and the second shift speed are shifted.
The operating oil pressure in the first oil chamber is also transiently released for a predetermined time simultaneously with the release of the operating oil pressure to the oil chamber, and when the engine load is larger than a predetermined value, the clutch is delayed for a predetermined time from the start of releasing the first hydraulic chamber. And a shift control means for starting release of the second oil chamber.

In the present invention configured as above, when the transmission mechanism shifts from the first gear position where the clutch is engaged and the brake is released to the second gear position where the clutch is released and the brake is engaged. When the engine load is smaller than the predetermined value, the shift control means transiently releases the operating oil pressure in the first oil chamber for a predetermined time simultaneously with the release of the operating oil pressure to the clutch and the second oil chamber. Since the fastening force applied to the brake via the piston of the servo mechanism gradually increases, the shift shock is reduced. Further, since the operating oil pressure for the clutch is released at the same time as the operating oil pressure for the second oil chamber, the speed change mechanism is quickly disengaged from the first speed and a desired speed change response is ensured. Further, when the engine load is larger than the predetermined value, the shift control means delays the release of the first hydraulic chamber by a predetermined time to start the release of the clutch and the second hydraulic chamber. It is possible to prevent the engine from blowing up due to the speed change operation.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is an overall configuration diagram showing an embodiment of an automatic transmission for a vehicle to which a shift control device for an automatic transmission according to the present invention is applied.

In FIG. 1, an automatic transmission 10 has a torque converter
14 and a multi-gear transmission mechanism 20, and the hydraulic pressure used for the operation control thereof is supplied from a hydraulic circuit 41.

The torque converter 14 includes a pump impeller 14a, a turbine runner 14b, a stator 14c, and the case 11,
Engine output shaft 12 to which pump impeller 14a is connected
Is connected to an oil pump 15 via a pump drive shaft 16. The turbine runner 14b has a hollow turbine shaft 17
Is connected to the output shaft 12 via a lock-up clutch 19, and a one-way clutch 18 is interposed between the stator 14c and the case 11, and the stator 14c is It is configured to rotate in the same direction as the pump impeller 14a and the turbine runner 14b.

The transmission mechanism 20 includes a planetary gear unit 21 for obtaining four forward steps and one reverse step. The planetary gear unit 21 includes a small sun gear 22, a large sun gear 23, a long pinion gear 24, a short pinion gear 25, and a ring gear 26.

Between the small-diameter sun gear 22 and the turbine shaft 17, a forward clutch 27 and a coasting clutch 28 for forward traveling are provided.
And a small diameter sun gear 22 and forward clutch 27
A one-way clutch 29 is interposed between the two.
Between the large-diameter sun gear 23 and the turbine shaft 17, a reverse clutch 30 for reverse travel is provided, and a 2-4 brake 31 is arranged. Further, between the long pinion gear 24 and the turbine shaft 17, A 3-4 clutch 32 is provided. The 2-4 brake is connected to the 2-
The rotation of the 4-brake drum is stopped to fix the large-diameter sun gear 23. The 3-4 clutch 32 transmits the driving force of the torque converter 14 to the carrier 33 via the 3-4 clutch drum. It is configured to be.

The long pinion gear 24 is connected to a transmission case 35 via a carrier 33 and a one-way clutch 34, and the carrier 33 and the transmission case 35 are fastened or released by a low reverse brake 36. Furthermore, the ring gear 26
Output gear via the output shaft 37 of the automatic transmission 10
The torque that is connected to the output shaft 37 and is input to the output shaft 37 is transmitted as output torque to drive wheels of the vehicle via a differential gear unit (not shown).

In the multi-gear transmission mechanism 20 having such a configuration, the forward clutch 27, the coasting clutch 28, the reverse clutch 30, and the 2-4 brake 3
The 1, 3-4 clutch 32 and the low reverse brake 36 are selectively selectively engaged or disengaged as appropriate, respectively.
Range (parking range), R range (reverse range), N range (neutral range), and D range and S range (2 ranges) that constitute the forward range
And the L range (1 range) and the first to fourth speeds in the forward range. Each clutch to obtain each of these ranges and gears
27, 28, 32 and 30, and the brakes 31 and 36, and the one-way clutch 29 in each range and speed
And 34 are shown in the table below.

The clutches 27, 28, 32, 30 and the brakes 32, 36
Are formed in the hydraulic circuit 41, and the hydraulic circuit 41 is controlled by the control unit 100 so as to realize the operation relationship as shown in the above table.

The control unit 100 includes a throttle opening signal St from a throttle opening sensor 51 for detecting the opening of a throttle valve (not shown) arranged in the intake passage, and a turbine rotation for detecting the rotation speed of the turbine runner 14b. The rotation speed signal Sr from the number sensor 52, the vehicle speed signal Sv from the vehicle speed sensor 53 for detecting the vehicle speed, the position signal Ss from the shift position sensor 54 for detecting the operating position of the shift lever 55, and the shift lever 55 with a hold signal S _h from Horst scan Itta 56 is input, which is the other predetermined signal Sx required for controlling the automatic transmission 10 is input. The hold switch 56 is turned ON or OFF by pushing and releasing a hold button (not shown) arranged on the side surface of the shift lever 55.

The control unit 100 performs shift control and lock-up control in the automatic transmission 10 based on the various signals described above.

When the shift control and the lock-up control are performed by the control unit 100, the throttle opening signal St and the vehicle speed signal Sv indicate a shift characteristic line previously mapped and stored in a built-in memory in the control unit 100. The throttle opening and the vehicle speed are collated to determine whether a shift-up condition or a shift-down condition is satisfied, and whether a lock-up operation condition or a lock-up release condition is satisfied. Further, when the hold signal S _h is instructed to the ON state of the hold button, the control unit 100 changes the shift characteristic to the shift characteristic line hold mode, performs a shift-up or shift-down determination. The shift characteristic line in the hold mode is as follows. In the S range, the second speed is selected at a predetermined vehicle speed, for example, approximately 100 km / s or less.
It is determined whether the speed is maintained or the downshift from the third speed to the second speed is performed.

When it is determined that the shift-up condition or the shift-down condition is satisfied, the first to third solenoid valves provided in the operating hydraulic pressure supply unit of the hydraulic circuit 41 from the control unit 100.
Drive signals Ca, Cb, and Cc are selectively input to 61, 62, and 63. Thus, various shift valves provided in the hydraulic pressure supply unit is operated, via the oil passage _{L 3, L 4, L 5} , L 6, L 7, L 8, a plurality of friction constituting the transmission mechanism 20 Supply / discharge control of the operating oil pressure is performed for each of the engagement elements, and the predetermined friction engagement elements are selectively engaged or released to achieve the desired gear as shown in the above table.

When it is determined that the lock-up operation condition is satisfied, the drive signal Cd is input from the control unit 100 to the lock-up solenoid valve 64 provided in the operating hydraulic pressure supply unit, and on the other hand, the lock-up release condition is satisfied. If the determination is made, the output of the drive signal Cd to the solenoid valve 64 is stopped. As a result, the operating oil pressure of the hydraulic circuit 41 for the torque converter 14 is controlled to be supplied and discharged via the oil passages L ₁ and L _2, and the lock-up clutch 19 provided in the torque converter 14 is selectively engaged or released. You.

Further, in addition to the above-described control, the control unit 100 inputs a drive signal Ce to a line pressure regulating solenoid valve 65 disposed in the line pressure forming section of the hydraulic circuit 41, and controls the friction engagement element. The line pressure for forming the operating oil pressure is adjusted as desired in accordance with the type of shift speed and the type of shift operation,
The hydraulic circuit 41 is controlled so that an appropriate operating oil pressure according to the type of shift speed and the type of shift operation is supplied from the operating hydraulic pressure supply unit to each friction engagement element. The hydraulic circuit 41
Is substantially the same as that described in Japanese Patent Application Laid-Open No. 63-186055 cited as the prior art, and a detailed description thereof will be omitted.

FIG. 2 is a sectional view showing the structure of a servo mechanism for operating the 2-4 brake 31 shown in FIG.

As shown in FIG. 2, the servo mechanism 70 includes a piston rod 71 connected to the 2-4 brake 31 and a piston rod 71.
A servo piston 72 integrally connected to 71, an apply chamber 73 forming a first oil chamber defined behind the servo piston 72, and a second oil chamber defined in front of the servo piston 72 And a compression spring 75 disposed in the release chamber 74. The urging force of the compression spring 75 acts rearward on the servo piston 72, and the servo piston 72 facing the apply chamber 73.
The rear pressure receiving surface is a servo piston facing the release chamber 44.
It is set smaller than 72 front pressure receiving surfaces. Therefore,
The servo apply pressure, that is, the operating oil pressure PA acts on the apply chamber 73 through the oil passage L ₈ A, and the release chamber 7 is actuated through the oil passage L ₈ R.
4 when the servo release pressure, that is, the operating oil pressure PR is acting, or when the operating oil pressure PA and PR in the apply chamber 73 and the release chamber 74 are both released, or when the apply chamber
The operating oil pressure PA of 73 is released, and the operating oil pressure PR is released to the release chamber 74.
Is acting, the servo piston 72 is retracted and 2
The -4 brake 31 is released. On the other hand, when the operating oil pressure PA acts on the apply chamber 73 and the operating oil pressure PR in the release chamber 74 is released, the servo piston 72 moves forward against the compression spring 75, and the 2-4 brake 31 is engaged. .

In addition, a one-way office 80 is interposed in the oil passage L ₈ A, and the one-way office 80 narrows the oil passage L ₈ A when supplying the working oil pressure PA to the apply chamber 73. Slow down the pressure rise speed in the apply chamber 73,
When the operating oil pressure PA is released from the apply chamber 73, the oil passage L ₈ A
Is quickly opened to enable quick pressure reduction in the application chamber 73. The oil passage L ₈ A also communicates with the accumulator 80 on the downstream side of the servo mechanism 70. Line pressure formed by the line pressure generating unit of the hydraulic circuit 41 is acting as a back pressure to the accumulator 81 via the oil passage L _9, an accumulator 81, by its accumulator action is transmitted through the oil passage L ₈ A The working of the operating oil pressure PA in the application chamber 73 is suppressed by adjusting the change of the operating oil pressure PA.

FIG. 3 shows the output to the first solenoid valve 61, the second solenoid valve 62, and the third solenoid valve 63 in each of the S gear, the first gear, the S gear, the second gear, and the S gear, the third gear. FIG. 6 is a diagram showing output patterns of the driven signals C _a , C _b , and C _c , that is, the solenoid output stage, and the operation relationship of the 3-4 clutch 32 and the 2-4 brake 31 obtained by the output pattern.

In FIG. 3, in the S range and the first speed, the first solenoid valve 61 is set to OFF, and the second and third solenoid valves 6 are turned off.
2, 63 are set to ON. As a result, the 3-4 clutch 32 is released, and the operating oil pressures PA and PR in the apply chamber 73 and the release chamber 74 of the servo mechanism 70 are released.
The brake band of the four-brake 31 (in FIG. 3, simply called a band) is released.

In the S range and the second speed, the first and second solenoid valves 61 and 62 are set to ON, and the third solenoid valve 63 is set to OFF.
Is set to As a result, the 3-4 clutch 32 is released, the operating oil pressure PA acts on the apply chamber 73, and the operating oil pressure PR in the release chamber 74 is released.
Fastened on 31 brake bands.

Further, in the S range and the third speed, the first solenoid valve 61 is
Set to ON, the second and third solenoid valves 62, 62 are OFF
Is set to As a result, the 3-4 clutch 32 is engaged, and the operating oil pressures PA and PR act on the apply chamber 73 and the release chamber 74, so that the brake band of the 2-4 brake 31 is released.

Also, in FIG. 3, the solenoid output stages shown in the columns of transition periods I and II are solenoid output stages that are transiently employed when shifting from the S range / third speed to the S range / second speed. According to the solenoid output stage in the transition period I, the 3-4 clutch 32 is engaged, and the apply chamber 73
Release hydraulic pressure PA, release hydraulic pressure PR to release chamber 74
Act, the brake band of the 2-4 brake 31 is released. Further, the 3-4 clutch 32 is released by the solenoid output stage in the transition period II, and
The operating oil pressures PA and PR are released from the release chamber 73 and the release chamber 74, and the brake band of the 2-4 brake 31 is released.

FIG. 4 shows a method of selecting a solenoid output stage for the first to third solenoid valves 61, 62, 63 executed in the control unit 100 when downshifting from the S range / 3rd speed to the S range / 2nd speed. It is a control flowchart which shows. FIGS. 5A and 5B show an application chamber 73 of the servo mechanism 70 achieved by the control flowchart shown in FIG.
FIG. 3 is a diagram showing a change in a working oil pressure PA in the inside.

Such as by a hold signal S _h from the position signal S _s or hold switch 56 from the shift position sensor 54, the control unit 100, soft down to S Range third gear S Range second speed, i.e., 3 → 2 When the shift is commanded, the control unit 100 compares the throttle opening of the throttle valve (S _t) with the predetermined threshold value T ₀ of the throttle opening (S1), the throttle opening degree (S _t) is When the value is equal to or greater than the predetermined value T ₀ , for example, when the driver depresses the accelerator pedal of the vehicle, the solenoid output stage is selected and the first stage is selected.
Then, all drive signals C _a , C _b , C _c for the third to third solenoid valves 61, 62, 63 are set to OFF for a predetermined time Δt ′ (S
3).

On the other hand, when the throttle opening (S _t ) is smaller than the predetermined value T ₀ , for example, when the vehicle is in the coast operation state, the control unit 100 sets the solenoid output stage in the transient period II shown in FIG. 3 as the solenoid output stage. Is selected, the drive signals C _a and C _c for the first and third solenoid valves 61 and 63 are set to an OFF state for a predetermined time Δt, and the drive signal C _b for the second solenoid valve 62 is turned ON for a predetermined time Δt. Set to (S
2). Note that the solenoid output stage in the transition period II has the same pattern as the solenoid output stage selected in the L range and the first speed, and the first to third solenoid valves 61, 62, 63
Becomes transiently the same as the L range / first speed.

After elapse of the predetermined time Δt or Δt ′, the control unit 100 selects the S-range / second-speed solenoid output stage shown in FIG. 3 and performs all the driving operations on the first to third solenoid valves 61, 62 and 63. Set the signals C _a , C _b , C _c to ON (S
Four).

Thus, when the throttle opening (S _t ) is _{equal to} or greater than the predetermined threshold T and the 3 → 2 shift is designated at the time t ₁ , the solenoid output stage of the transition period I is selected. No.
As shown in FIG. 5A, the hydraulic pressure for the 3-4 clutch 32
The operating oil pressure PR in the release chamber 74 of the PC and the servo mechanism 70 is held, but the operating oil pressure PA in the apply chamber 73 is released,
Step down. At this time, one-way orifice 80 interposed in the oil passage L ₈ A (FIG. 2), since opening the oil passage L ₈ A rapidly, hydraulic pressure PA is rapidly buck some extent buck The accumulator 81 and the hydraulic circuit
The pressure drops relatively slowly due to the pipeline resistance of 41 (a
part).

As described above, the time when the predetermined time Δt has elapsed from the time t ₁
In t _2, since the solenoid output grade of the second speed is selected, with the release pressure PR is released for release chamber 7474 of the 3-4 clutch hydraulic pressure PC and the servo mechanism 70 with respect to the 3-4 clutch 31, the oil passage Hydraulic oil is supplied to the application chamber 74 via L ₈ A. 3-4 clutch operating oil pressure
PC and operating oil pressure PR is relatively rapidly step down, while the working oil pressure PR in the apply chamber 74, the accumulator action of the accumulator 80 interposed in the oil passage L ₈ A, rising moderately (b moiety ), Time when the pressure-lowering effect of accumulator 80 disappears
In t _3, and rapidly increased, stable. As a result,
The 3-4 clutch 32 is immediately released, and the 2-4 brake 31
Is relatively loosely fastened via the above-mentioned part b.

Incidentally, the 2-4 brake 31 and 3-4 clutch 32, since it is respectively held in the released state and the engaged state until time t _2, the timing of the 3 → 2 shift in the shift mechanism 20, as shown in Figure 5A the time t ₂ becomes, the output from the third speed stage is relatively delayed, preventing rising racing of the engine at high load operation of the engine is achieved.

On the other hand, if the throttle opening (S _t ) is smaller than the predetermined threshold value T and a 3 → 2 shift is instructed at time t ₁ , the solenoid output stage in the transitional period II is selected. As shown in FIG. 7, the 3-4 clutch operating oil pressure PC for the 3-4 clutch 32 and the operating oil pressures PA and PR in the apply chamber 73 and the release chamber 74 of the servo machine 70 are simultaneously released, and the pressure drops.
At this time, hydraulic pressure PA is initially one-way orifice 80 interposed in the oil passage L ₈ A (FIG. 2) is, so to open the oil passage L ₈ A rapidly, the 3-4 clutch hydraulic pressure PC The pressure drops relatively sharply with the operating oil pressure PR, but after a certain degree of pressure drop, the pressure drops relatively slowly due to the pipeline resistance of the hydraulic circuit 41 (part a). As a result, the 3-4 clutch 32 is promptly released, and the 2-4 brake 31 is held in the released state.

As described above, the time when the predetermined time Δt ′ has elapsed from the time t ₁
In t _2, since the solenoid output grade of the second speed is selected, 3-4 hydraulic pressure PS release chamber 74 of the 3-4 clutch hydraulic pressure PC and the servo mechanism 70 with respect to the clutch 31 but is directly released, the apply chamber 74, via the oil passage L ₈ a, hydraulic fluid is supplied. Apply pressure PA in the apply chamber 74, by the action of the accumulator 80 interposed in the oil passage L ₈ A, rising moderately (b portion), the accumulator
At time t ₃ when the hypotensive action by 80 disappears, and rapidly increased, it stabilized. As a result, the 2-4 brake 31
It is relatively loosely fastened via the part b.

The speed change mechanism 20 that performs the 3 → 2 speed shift in this manner is
Since substantially shifts to L-range first speed at time t _1, since the transmission mechanism 20 to escape from a relatively early stage to the third speed stage, the desired shift response is ensured. If the predetermined time Δt ′ is long, the gear position is shifted to the S range.
Since the shift is performed in the order of speed, L range / first speed, S range / second speed, the above-mentioned predetermined time is preferably set to a relatively short time so as not to impair the shift feeling.

Thus, in the above embodiment, the throttle opening ( _St )
Is less than the predetermined threshold T, and thus when the engine is in a relatively low load operating state, the control unit 100
From S-range where the 3-4 clutch 32 is engaged and the 2-4 brake 31 is released. From the third speed, the S range where the 3-4 clutch 32 is released and the 2-4 brake 31 brake is engaged. When the transmission mechanism 20 is shifted to the high speed,
The shift control means for transiently releasing the operating oil pressure for the predetermined time Δt ′ from the servo mechanism 70 causes the 2-4 brake via the servo piston 72 of the servo mechanism 70 during the 3 → 2 shift.
The fastening force applied to the brake band 31 does not suddenly increase, and after a lapse of a predetermined time Δt ′,
2-4 brake, since it gradually increases as the pressure of the apply chamber 73 is increased by the hydraulic oil supplied to the 73
The shift shock accompanying the engagement of 31 is reduced. Also, 3-
Since the operating oil pressure for the four clutches 32 is released together with the operating oil pressure for the apply chamber 73, the transmission mechanism 20
Quickly escapes from the S range and the third speed, so that a desired shift responsiveness of the automatic transmission 10 is ensured.

Further, in the above embodiment, when the throttle opening ( _St ) is _{equal to} or larger than the predetermined threshold value T, and the engine is in a relatively heavy overload operation state, the control unit 100 operates in the S range. Since the speed is configured to be maintained for the predetermined time Δt, the automatic transmission 10 can prevent the engine from blowing up due to the speed change operation during the high load operation.

The present invention can be variously modified or modified without being limited to the above-described embodiments, and it is understood that they are also included in the present invention within the scope of the invention described in the claims. Needless to say.

For example, in the above embodiment, the shift from the S range / third speed to the S range / second speed has been described. However, the present invention relates to the shift from the D range / third speed to the D range / second speed, Alternatively, the present invention can be applied to other types of shifts, such as shifting from the third speed to the second speed due to range switching.
Note that, when shifting from the S range or D range / third speed to the L range / second speed, shifting is performed through the L range / first speed state as described above. During the predetermined time Δt ′, the solenoid output stage is set to be the same as the L range / first speed, and the operation relationship and the 5B
As shown by the broken line in the figure, since the operating oil pressure PL is also transiently supplied to the low reverse brake 36 that is engaged in the L range and the first speed, the predetermined time Δt ′ is:
It is preferable that the setting is performed for a relatively short time so that the low reverse brake 36 does not substantially generate a fastening force.

〔The invention's effect〕

As described above, according to the shift control device for an automatic transmission of the present invention, it is possible to reduce shift shock without impairing shift response.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of a vehicle automatic transmission to which an automatic transmission control device according to the present invention is applied. FIG. 2 is a sectional view showing the structure of a servo mechanism for operating the 2-4 brake 31 shown in FIG. FIG. 3 shows S range, first speed, S range, second speed, and S range.
In each of the range and third speed, the first gear shown in FIG.
FIG. 8 is a diagram showing an output pattern (solenoid output stage) of a drive signal output to a third solenoid valve, and an operation state of a 3-4 clutch and an operation state of a 2-4 brake obtained by the output pattern. FIG. 4 shows a method of selecting a solenoid output stage for the first to third solenoid valves, which is executed when the control unit shown in FIG. 1 shifts down from S range / third speed to S range / second speed. It is a control flowchart shown. 5A and 5B are diagrams showing changes in the operating oil pressure in the apply chamber of the servo mechanism achieved by the control flowchart shown in FIG. FIG. 6 is a diagram showing a change in operating oil pressure in an apply chamber of a servo mechanism in a conventional automatic transmission. (Explanation of reference numerals) 10 Automatic transmission 20 Transmission mechanism 27 Forward clutch 28 Coasting clutch 29 One-way clutch 30 Reverse clutch 31 2-4 brake 32 2-4 Clutch 34 One-way clutch 36 Low-reverse brake 41 Hydraulic circuit 42 Operating hydraulic pressure supply unit 44 Line pressure forming unit 51 Throttle opening sensor 52 Turbine speed sensor 53 Vehicle speed Sensor 54 Shift position sensor 55 Shift lever 56 Hold switch 61, 62, 63, 64, 65 Solenoid valve 70 Servo mechanism 71 Piston rod 72 Servo piston 73 Apply chamber 74 ...... release chamber 75 ...... compression spring 80 ...... oneway cage I office 81 ...... accumulator 100 ...... control unit _{L 1 ~L 8, L 8 A} , 1 8 R ...... oil passage

Claims (1)

(57) [Claims] A transmission mechanism having a friction engagement element, a hydraulic circuit capable of selectively supplying a hydraulic pressure to the friction engagement element so as to cause the transmission mechanism to perform a shift operation, and a value related to an engine load. An engine load detecting means for detecting, wherein the friction engagement element includes a brake, a servo mechanism for operating the brake, and a hydraulic driven clutch, wherein the servo mechanism is operatively connected to the brake. And a first oil chamber and a second oil chamber formed on both sides of the piston, respectively, and at least when the operating oil pressure is supplied to the first oil chamber and the second oil chamber. Is configured to release the brake, the operating oil pressure is supplied to the first oil chamber, and the brake is engaged when the operating oil pressure is released from the second oil chamber,
A shift control device provided in an automatic transmission configured to be connected when an operating oil pressure is supplied, wherein the clutch is released from a first shift speed in which the clutch is engaged and the brake is released. And when the engine load is smaller than a predetermined value when the speed change mechanism is shifted to a second shift speed at which the brake is engaged,
At the same time as the release of the operating oil pressure to the clutch and the second oil chamber, the operating oil pressure in the first oil chamber is also transiently released for a predetermined time. A shift control device for an automatic transmission, comprising: shift control means for starting release of the clutch and the second oil chamber with a delay of a predetermined time.