JPH0242257A - Speed change control device of automatic transmission - Google Patents

Abstract

PURPOSE:To prevent no-load stamping by performing disengagement of a brake element of a speed change gearing mechanism in the engagement pressure supply condition in the apply chamber of an actuator while the car is running at a high speed, in the exhaust condition with the temp. in warm range while at a low speed, and in supply condition in cold range. CONSTITUTION:A control circuit 200 engages a 3-4 clutch 27 for speed changing in a speed change gearing mechanism and disengages a 2-4 brake to provide specific high speed position. While the car is running at a high speed, disengagement of this brake 23 is attained in the condition that engaging pressure is supplied to the apply chamber 23d of an actuator 23c. While the car is running at a low speed with the temp. in warm range, it is attained in the condition that the engaging pressure is exhausted from the apply chamber 23d. While at a low speed, also, in the condition that engaging pressure is supplied to the apply chamber 2d. Thus delay in cold range is prevented while response when the car is running at high speed at shifting down into specific shift position and speed change shocks at low speed are reduced to led to prevention of no-load stamping of engine.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is a gear shifting element of a gear shifting tooth III mechanism, which is operated by a hydraulic actuator having a predetermined clutch element, an apply chamber, and a release chamber. The present invention relates to a shift control device for an automatic transmission, which includes a predetermined brake element that is engaged only when engagement pressure is supplied to an apply chamber and release pressure in the release chamber is discharged.

[Conventional technology]

Conventionally, as disclosed in Japanese Patent Application Laid-Open No. 62-233547, a hydraulic actuator having a predetermined clutch element (3-4 clutch), an apply chamber, and a release chamber is used as a friction element for shifting a gear mechanism. and a predetermined brake element (2-4 brake) that is engaged only when the application chamber is supplied with engagement pressure and the release pressure in the release chamber is discharged, the predetermined clutch At a specific high speed stage in which the elements are engaged and a predetermined brake element is released, the release of the predetermined brake element is achieved by supplying the engagement pressure to the apply chamber in the high speed running state, and in the state in which the engagement pressure is supplied to the apply chamber in the low speed running state. A speed change control device is known that achieves this in a state in which engagement pressure is discharged from the engine. According to this device, when downshifting from the specific high speed gear to a specific low gear in which the predetermined clutch element is switched to disengagement and the predetermined brake element is switched to engagement, the predetermined brake element is quickly engaged in the high speed driving state. This is done to improve responsiveness, while at the same time having the advantage of suppressing sudden engagement of the brake elements in low-speed driving conditions and alleviating shift shock.

(Problem to be Solved by the Invention) According to the above conventional device, during the downshift in a low speed running state, hydraulic pressure is gradually supplied to the apply chamber by the action of an accumulator, etc., and the predetermined brake element accordingly shifts to the engaged state. However, in this case, the following problem occurs when the temperature of the hydraulic oil is low. In other words, since the viscosity of the hydraulic oil is high when it is cold, the rise in the hydraulic pressure supplied to the apply chamber via the accumulator etc. is slower than when it is warm, so that the engagement of a predetermined brake element is slower than the release of a predetermined clutch element. There may be significant delays. And if such a delay in engagement of a predetermined brake element occurs,
During this delay period, a situation occurs in which the predetermined clutch element is already released but the predetermined brake element is not engaged, and as a result, the load applied to the engine suddenly decreases, causing the engine to run dry (excessive engine speed). There was a risk that this could lead to an increase in

In view of the above-mentioned circumstances, the present invention achieves both responsiveness in high-speed driving conditions and mitigation of shift shock in low-speed driving conditions when downshifting, and also prevents the engine from revving when the engine is cold. An object of the present invention is to provide a shift control device for an automatic transmission that can prevent such problems.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention is operated by a hydraulic actuator having a predetermined clutch element, an apply chamber, and a release chamber as a gear change *m element of a speed change gear mechanism, and applies fastening pressure to the apply chamber. and a predetermined brake element that is engaged only when the release pressure in the release chamber is discharged, and when downshifting from a specific high speed gear to a specific low gear, the predetermined clutch element switches from engagement to release. In the automatic transmission, the automatic transmission is configured such that the release pressure in the release chamber is discharged and the predetermined brake means is switched from release to engagement. The release of the brake element when in a specific high speed gear is achieved by supplying engagement pressure to the apply chamber at vehicle speeds higher than a predetermined vehicle speed, and exhausting the engagement pressure from the apply chamber at vehicle speeds lower than the predetermined vehicle speed. control means for controlling the hydraulic pressure supply state so as to achieve the state in which the hydraulic pressure is supplied;
Depending on the temperature of the hydraulic fluid detected by the temperature detection means, when the temperature is lower than a predetermined temperature, a fastening pressure is supplied to the apply chamber to release the brake element when the vehicle is in the specific high speed gear even if the vehicle speed is lower than the predetermined vehicle speed. and changing means for changing the hydraulic pressure supply state so as to achieve the desired state.

[Effect]

According to the above configuration, when downshifting from the specific high gear to the specific low gear, engagement pressure is supplied to the apply chamber in advance in a high speed running state, so that the releasing pressure is quickly discharged from the release chamber. The predetermined brake element is engaged, and in a warm, low-speed running state, as hydraulic pressure is gradually supplied to the application chamber, the predetermined brake element shifts to an engaged state, and in a cold, low-speed running state, the predetermined brake element shifts to an engaged state. Similarly, by supplying the engagement pressure to the apply chamber in advance, a delay in engagement of the predetermined brake element due to an increase in the viscosity of the hydraulic oil can be avoided.

〔Example〕

FIG. 1 shows the overall structure of an automatic transmission to which the device of the present invention is applied. This automatic transmission includes a torque converter 2 connected to an output shaft 1 of an engine, and a speed change gear mechanism 10 disposed on the output side of the torque converter 2. The torque converter 2 is connected to the output shaft 1 of the engine.
The engine includes a pump 3 fixed to a pump 3, a turbine 4, and a stator 5 provided on a fixed shaft 7 via a one-way clutch 6.

The speed change gear mechanism 10 includes an oil pump driving solid shaft 12 whose base end is fixed to the output shaft 1 of the engine and whose tip end is connected to the oil pump 100. , a hollow turbine shaft 13 whose base end is connected to the turbine 4 of the torque converter 2,
A Ravigneau-type planetary gear device 14 is provided on the turbine shaft 13 . This planetary gear device 14 includes a small diameter sun gear 15, a large diameter sun gear 16, a long pinion gear 17, a short pinion gear 18, and a ring gear 19.
It consists of The following various friction elements are incorporated into this planetary gear device 14.

On the side far from the engine, the turbine shaft 13
A forward clutch 20 and a coast clutch 21 are arranged in parallel between and the small diameter sun gear 15. The forward clutch 20 connects and disconnects power transmission from the turbine shaft 13 to the small-diameter sun gear 15 via the first one-way clutch 22, and the coast clutch 21 connects the turbine shaft 13 and the small-diameter sun gear 1.
5 and 5 to intermittent mutual power transmission.

A 2-4 brake 23 is arranged radially outward of the coast clutch 21, and includes a brake drum 23a connected to the large-diameter sun gear 16, and a brake band 23b applied to the brake drum 23a1%. When this 2-4 brake 23 is engaged, the large diameter sun gear 16 is fixed. A reverse clutch 24 for backward travel is disposed on the side of the 2-4 brake 23, and connects and disconnects power transmission between the large-diameter sun gear 16 and the turbine shaft 13 via the brake drum 23a. Further, between the carrier 14a of the planetary gear unit 14 and the case 10a of the speed change gear mechanism 10 on the outside in the radial direction of the planetary gear unit 14, the carrier 14
A low reverse brake 25 is disposed to engage and disengage the case 10a and the case 10a, and a second one-way clutch 26 is disposed in parallel thereto.

Furthermore, a 3-4 clutch 27 is disposed on the side of the planetary gear set 14 on the engine side to connect and disconnect power transmission between the carrier 14a and the turbine shaft 13. Also, on the side of this 3-4 clutch 27 is a ring gear 19.
An output gear 28 connected to the
This gear 28 is attached to an output shaft 28a. Note that 29 is a lock-up clutch that directly connects the output shaft 1 of the engine and the turbine shaft 13 without using the torque converter 2.

This transmission gear mechanism 10 has four forward speeds and one reverse speed.
The required gear position can be obtained by appropriately operating the clutches 20.21, 24.27 and the brakes 23.25. Here, Table 1 shows the operational relationship between each gear stage, clutch, and brake.

As can be understood from this Table 1 and FIG.
By changing the states of the 3 and 3-4 clutches 27, the gear ratio changes, and states from 1st to 4th speed can be obtained. Therefore, the 2-4 brake 23 and the 3-4 clutch 27 correspond to a predetermined brake element and a predetermined clutch element for shifting.

FIG. 2 shows a hydraulic control circuit in the automatic transmission. In this figure, the 2-4 brake 23 is
It is actuated by a hydraulic actuator 23c having an apply chamber 23d and a release chamber 23e, and is tightened only when a tightening pressure is supplied to the apply chamber 23d and the releasing pressure in the release chamber 23e is discharged.

Each of the clutches 20, 21, 24, and 27 and the low reverse brake 25 are engaged and released in accordance with the supply and discharge of hydraulic pressure, respectively.

This hydraulic control circuit includes an oil pump 100 driven by the crankshaft 1, and hydraulic oil is discharged from the pump 100 into an oil passage 101.

Hydraulic oil discharged from pump 100 into oil passage 101 is guided to regulator valve 102 . The regulator valve 102 regulates the hydraulic pressure (line pressure) of the hydraulic oil from the pump 100 and supplies it to the boat 9 of the select valve 103 . This select valve 103 is manually operated.
The operation is shifted to N-D, 2, and Lunge, and the hydraulic oil is supplied from the boat 9 to a predetermined boat in each range. The boat 9 is communicated with boats a, d, and e when the select valve 103 is set to lunge, and communicated with boats ac and d when the select valve is set to range 2, and the boat 9 is communicated with boats ac and d when the select valve is set to range 2. Boats a and C
When the select valve is set to the R range, it is communicated with the boat f.

The boat a of the select valve 103 is connected to the 1-2 shift valve 110 via the oil 1i 71, and is also connected to the neutral valve 160 (described later) via an oil passage 172 that bypasses the 1-2 shift valve 110. , the forward clutch 2o is engaged by hydraulic pressure supplied to the forward clutch 20 via the neutral valve 160.

The 1-2 shift valve 110 has a spring 110a.
The pilot pressure that acts against the 1-2 solenoid valve 110b is controlled by the 1-2 solenoid valve 110b, and is switched between 1st speed and 2nd speed, etc., and the hydraulic pressure is applied to the apply chamber 23d of the actuator 23C of the 2-4 brake 23. Supply, discharge, etc.

That is, when the 1-2 solenoid valve 110b is turned off, the line pressure led from the oil passage 101 acts as pilot pressure on the 1-2 shift valve 110, so that the spool moves to the left side in the figure. Apply room 23 above
d is communicated with the drain side via the oil passage 173. Also 1
When the -2 solenoid valve 110b is turned on, the pilot pressure is drained and the spool moves to the right side in the figure, and the line pressure led from the oil passage 171 is transferred to the oil passage 173.
from the apply chamber 23 via the 3-4 shift valve 130.
Send to d. Note that 135 is an accumulator provided for the apply chamber 23d.

Furthermore, when the lunge is in the first speed, the 1-2 shift valve 110 supplies the hydraulic oil supplied from the boat e of the select valve 103 via the low pressure reducing valve 140 to the low reverse brake 25, and at the same time provides throttle backup. Hydraulic pressure is sent to valve 141.

Boat a of the select valve 103 is the 2-3 shift valve 12
0 through an oil passage 174 to provide pilot pressure that opposes the spring 120a of the 2-3 shift valve 120. The pilot pressure of this 2-3 shift valve 120 is controlled by a 2-3 solenoid valve 120b, and the valve is operated to switch between 2nd and 3rd speeds, etc., and supplies and removes hydraulic pressure to and from the 3-4 clutch 27. At the same time, the 2-4 brake 23 is operated in cooperation with the 3-4 shift valve 130.
Release of actuator 23C'! Involved in supplying and removing hydraulic pressure to 23e. That is, when the 2-3 solenoid valve 120b is turned off, the line pressure led from the oil passage 174 is used as the pilot pressure for the 2-3 shift valve 1.
20 moves the spool to the left in the figure. In this state, the line pressure applied from the boat C of the select valve 103 via the oil passage 175 is supplied to the 3-4 clutch 27 via a circuit in which the servo control valve 142 and the 2-3 timing valve 143 are incorporated. It is also sent to an oil line 176 connected to the 3-4 shift valve 130. Further, when the 2-3 solenoid valve 120b is turned on, the pilot pressure is drained and the spool moves to the right side in the figure. In this state, the 3-4 clutch 27 is communicated with the drain side via the oil passage 177, and the oil passage 176 connected to the 3-4 shift valve 130 is connected to the 3-2 capacity valve 14.
9 and 3-2 timing valves 150 are connected to the drain side through a built-in circuit. Note that 148 is an accumulator provided for the 3-4 clutch 27.

The 3-4 shift valve 130 includes the 2-3 shift valve 1
20, the line pressure from the boat a of the select valve 103 via the oil passages 174 and 178 is applied as pilot pressure. The pilot pressure of this 3-4 shift valve 130 is controlled by a 3-4 solenoid valve 130b, and the 3-4 shift valve 130 is operated to switch between 3rd speed and 4th speed.
It is involved in supplying hydraulic pressure to the apply chamber 23d of the brake 23 and supplying and removing hydraulic pressure to the release chamber 23e. That is, when the 3-4 solenoid valve 13ob is turned off, the line pressure acts on the 3-4 shift valve 130 as a pilot pressure, thereby moving the spool to the left side in the figure. In this state, the 1-2 shift valve 11
0 to the 3-4 shift valve 130 through the oil passage 173 is applied via the oil passage 179 to the above-mentioned Apply! 23
An oil passage 176 connected to a circuit connected to the 2-3 shift valve 120 and an oil passage 180 connected to the release chamber 23e are communicated with each other. Further, when the 3-4 shift valve 130 is turned on, the pilot pressure is drained, thereby moving the spool to the right side in the figure. In this state, from the 1-2 shift valve 110 to the 3-4 shift valve 13,
The line pressure sent to the oil passage 18 having an orifice
1 to the apply chamber 23d, and the hydraulic pressure in the release 'J23e is supplied to the 3-4 capacity valve 14.
It is drained through 5.

Furthermore, when the 3-4 renoid valve 130b is off, the 3-4 shift valve 130 transfers the line pressure from the boat a of the select valve 103 through the oil passage 172, 182 to the neutral valve 160 and the N-D accumulator 14.
4 to the coast clutch 21, and when the 3-4 solenoid valve 130b is off, the oil pressure of the coast clutch 21 is drained.

Further, a lock-up control valve 151 is provided in the hydraulic oil path of the lock-up clutch 29.

This lock-up control valve 151 is switched and operated in response to a pilot pressure controlled by a lock-up solenoid 151a, and engages the lock-up clutch 29 when the lock-up solenoid 151a is turned on.

The throttle backup valve 141 receives the hydraulic pressure from the low pressure reducing valve 140 as a pilot pressure against a spring, and supplies or cuts the hydraulic oil from the boat d of the select valve 103 to the regulator valve 102. , and when the select valve 103 is set to range or 2 range and is not receiving pilot pressure,
Hydraulic oil from boat d of select valve 103 is supplied to regulator valve 102 to increase its pressure and ensure engine braking capacity. In addition, the regulator valve 102 is supplied with oil pressure regulated by a throttle valve 146 and a throttle modulator valve 147, and the throttle valve 146 generates oil pressure according to the accelerator opening degree.
7 reduces this oil pressure appropriately and operates the regulator valve 102.
These provide line pressure that matches the engine torque.

Further, the servo control valves 142 and 2-
The 3 timing pulp 143 is for mitigating the shock that occurs when shifting from 2nd speed to 3rd speed, and the servo control valve 142 is for controlling the hydraulic pressure applied to the release chamber 23e of the actuator 23c of the 2-4 brake 23. Adjust the rise of 2-3 timing valve 143.
adjusts the engagement timing of the fourth clutch device [27] according to the accelerator opening degree.

The 3-4 capacity valve 145 is provided to reduce the impact when shifting up from 3rd speed to 4th speed, and is provided to reduce the impact on the actuator 23c of the 2-4 brake 23.
The characteristics of the oil pressure change in the release chamber 23b when hydraulic oil is drained from the release chamber 23d are appropriately adjusted.

The 3-2 capacity valve 149 and the 3-2 timing valve 150 are provided to reduce the impact when shifting from 3rd speed to 2nd speed according to the throttle opening. The capacity valve 149 is 3
Similarly to the -4 capacity valve 145, the characteristic of oil pressure change during draining is adjusted, and the 3-2 timing valve 750 controls the drain delay time according to the throttle modulator pressure.

The neutral valve 160 is operated in accordance with the pilot pressure controlled by the idle cut solenoid valve 161, and communicates the oil passage 183 leading to the forward clutch 20 with the oil passage 172 when the idle cut solenoid valve 161 is off. By doing this, boat a
On the other hand, when the idle cut solenoid valve 161 is on, the line pressure from the oil passage 183 and the oil passage 184 communicating with the boat d is supplied to the first clutch device 20.
communicate with. The boat d has a select valve 10.
3 is set to the D range, and the idle cut solenoid valve 161 is turned on when the brake is operating in a state corresponding to idling operation, so that these conditions are satisfied. When the vehicle is stopped in the D range, the forward clutch 20 is released to prevent the vehicle from being photographed.

According to such a hydraulic control circuit, the states of the 2-4 brake 23 and 3-4 clutch 27, which determine the gear ratio in the forward travel range, are different for 1-2, 2-3, and 3-4. Each shift valve 110.1 of 1-2, 2-3, 3-4 according to on/off of solenoid valves 110b, 120b, 130b
=20.130. That is, 3-4
The clutch 27 is engaged when hydraulic pressure is supplied by turning off the solenoid valve 120b for 2-3, and
-3 solenoid valve 120b is turned on and is opened when hydraulic pressure is drained. -, 2-4 above
As described above, the brake 23 is engaged only when the hydraulic pressure in the release chamber 23e is drained and the hydraulic pressure is supplied to the apply chamber 23d. is released regardless of whether it is in a hydraulic pressure supply state or a drain state, but if hydraulic pressure is supplied to the release chamber 23e, hydraulic pressure is supplied to the drain and apply chambers 23d, and the drain is turned on, each of the solenoid valves 110b, 120b, and 130b is turned on. Varies depending on off combination.

Here, Table 2 shows each of the above solenoid valves (SL in the table).
) 110b, 120b, 130b on/off combinations of 8 patterns and 2-4 brake 23 determined by these patterns. 3-4 clutch 2
7 and the corresponding gears are shown. In this table,
Regarding the 2-4 brake 23 and 3-4 clutch 27, the O mark indicates engagement, and the X mark indicates release.
Regarding the apply chamber 23d and the release chamber 23e of No. 3, the O mark indicates hydraulic pressure supply, and the X mark indicates drain.

The solenoid valves 110b, 120t) and 130b are controlled by a control circuit 200 using a microcomputer or the like shown in FIG. This control circuit 200 includes a turbine rotation speed signal 201 from a turbine sensor, a throttle opening signal 202 from a throttle opening sensor that detects the opening of a throttle valve in the intake passage of the engine,
Selection signal 203 from the range selection sensor, vehicle speed sensor (
a vehicle speed signal 204 from a vehicle speed detection means); an oil temperature signal 2 from an oil temperature sensor (oil temperature detection means) that detects the temperature of hydraulic oil;
05 etc. is input. The control circuit 200 selects a gear position according to the operating state based on predetermined gear shift characteristics, selects a pattern of the solenoid valves 110b, 120b, and 130b corresponding to the selected gear position,
When speed change is required, each solenoid valve 110b,
Shift control is performed by outputting signals to 12ob and 13ob to change the above pattern.

Furthermore, this control circuit 200 achieves the release of the 2-4 brake 23 when the vehicle is in the third gear while supplying the engagement pressure to the apply chamber 23d at vehicle speeds higher than the predetermined vehicle speed. On the low vehicle speed side, the above apply chamber 23d
The control means 200a controls the hydraulic pressure supply state so as to achieve the state in which the engagement pressure is discharged from the control means 200a. and a changing means 200b for changing the hydraulic pressure supply state so that the release of the 2-4 brake 23 is achieved in a state in which the engagement pressure is supplied to the apply chamber 23d.

In other words, in this control circuit 200, the following Table 3 (D
As shown in (Example), a pattern selected from Table 2 above is set for each gear, but especially for the third gear, the pattern is selected for high vehicle speeds or low temperatures. The first pattern (corresponding to pattern B in Table 2)
and a second pattern (second pattern) for use at low vehicle speeds and high temperatures.
(corresponding to pattern A in the table) is set.

Control is then performed based on the flowchart shown in FIG.

To explain this control operation, first, in step S1, the throttle opening θ, oil temperature T, vehicle speed V, range signal, etc. are input. Next, in step S2, it is determined whether the current gear position determined based on a comparison between the shift pattern and the driving state is the third gear position. If the gear is other than the third gear, a pattern corresponding to the gear is selected from Table 3, and each solenoid valve 1101), 12
0b and 130b (step 83).

If the vehicle is in the third gear, it is determined in step S4 whether or not the vehicle speed is higher than a predetermined vehicle speed (for example, 40 km/h). Then, in the high-speed running state, in step S5, the first pattern in the third table is selected and output, and the solenoid valve 110 for 1-2 is
b is turned on, solenoid valves 120b for 2-3 and 3
-4 solenoid valve 130b is turned off.

Further, when it is determined in step S4 that the vehicle speed V is in a low-speed running state lower than a predetermined vehicle speed, it is further checked in step S6 whether or not the oil temperature T is at a warm time higher than a predetermined value T1. Then, during a warm period (step S) in a low speed running state,
6), in step S7, the second pattern in Table 3 is selected and output, that is, all of the solenoid valves 110b, 1201) and 130b are turned off, but at low speed. Even when running when cold (step S)
If the determination in e is No, the process moves to step S5, where the first pattern is selected and output, as in the high-speed running state.

According to the above-described control, when the 3-4 clutch 27 is engaged and the 2-4 brake 23 is released in the third gear, when the vehicle is running at high speed, the first pattern is By being selected, the 2-4 brake 23 is released by the release pressure applied to the release chamber 23e while the engagement pressure is supplied to the apply chamber 23d of the actuator 23c of the 2-4 brake 23 (the third (see table). Therefore, from this state, the 3-4 clutch 27 is released and the 2-4 brake 23 is engaged.
When downshifting to a gear is performed, the release pressure is drained from the release chamber 23e in response to a change in the pattern of the solenoid valves 110b, 120b, and 130b, and the 2-4 brake 23 is quickly brought into the engaged state. It is said that
Downshifts are performed with good responsiveness.

On the other hand, in a warm and low vehicle speed state when driving in the third gear, the second pattern is selected, and the second pattern is selected.
4 Apply chamber 2 of actuator 23C of brake 23
2-4 brake 2 with the engagement pressure drained from 3d.
3 release is achieved (see Table 3). Therefore, when downshifting from this state to the second gear, the apply chamber 23 (j
The supply of hydraulic oil to 2 is started, and the hydraulic pressure supplied to the apply chamber 23d via the accumulator 135 causes
-4 brake 23 will gradually shift to the engaged state, and the shift shock will be alleviated.

By the way, when the above-mentioned downshift is performed in a low-speed running state in a warm state, the engagement speed of the 2-4 brake 23 is appropriately adjusted as shown by the solid line in FIG. 4 due to the above-mentioned action, but in a cold state Since the viscosity of the hydraulic oil increases, if the fastening pressure is drained from the apply chamber 23a in advance, the hydraulic pressure supply to the apply chamber 23 will be delayed compared to when it is warm, as shown by the broken line in FIG. There is a tendency for the engagement of the 2-4 brake 23 to be significantly delayed with respect to the release (hydraulic discharge) of the -4 clutch 27. On the other hand, in the control shown in the flowchart, even in a low-speed running state, when the oil pressure is cold, the oil pressure is supplied to the apply chamber 23d in advance in the third gear, so that the 2-
A delay in the engagement of the four brakes 23 can be avoided.

〔Effect of the invention〕

As described above, the speed change control device for an automatic transmission of the present invention controls the release of the brake element at a high speed in a specific high speed gear in which a predetermined clutch element for speed change in the speed change gear mechanism is engaged and a predetermined brake element is released. In running conditions, this is achieved by supplying the engagement pressure to the apply chamber of the actuator of the brake element, and in low-speed running conditions when warm, this is achieved by discharging the engagement pressure from the apply chamber, while in cold conditions, this is achieved when running at low speeds. Even in this state, this is achieved while the fastening pressure is supplied to the apply chamber. For this reason, when downshifting to a specific gear in which the predetermined clutch element is switched to disengagement and the predetermined brake element is switched to engagement, the responsiveness when in a high speed state and the shift when in a low speed running state are improved. While attempting to alleviate the shock, it is possible to prevent the engagement of the predetermined brake element from being significantly delayed in relation to the release of the predetermined clutch element when the predetermined brake element is engaged in a cold and low speed state, and to prevent the delay in engagement of the predetermined brake element from occurring due to the delay in engagement of the predetermined brake element. This prevents the engine from running dry.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing an outline of a transmission mechanism of an automatic transmission according to an embodiment of the present invention, Fig. 2 is an explanatory diagram of a circuit configuration of a hydraulic control circuit for the transmission mechanism, and Fig. 3 is a flowchart showing a control operation. , FIG. 4 is a time chart showing changes in oil pressure for a predetermined clutch element and a predetermined brake element during downshifting from a specific high speed gear to a specific low speed gear in a low speed running state. 10... Speed change gear mechanism, 14... Planetary gear device, 2
3...2-4 brake (predetermined brake element), 23C
...actuator, 23d...apply chamber, 23
e...Release chamber, 27...3-4 clutch (predetermined clutch element), 110...1-2 shift valve, 120
...2-3 shift valve, 130...3-4 shift valve,
110b... Solenoid valve for 1-2, 120b...
2-3 solenoid valve, 130b...3-4 solenoid valve, 200...control circuit, 200a...control means, 200b...change means. Patent applicant Mazda Co., Ltd. Agent
People Patent Attorney Etsushi Kotani
Patent Attorney Chief 1) Seiyo Patent Attorney
Takao Ito Diagram Diagram

Claims (1)

[Claims] 1. As a friction element for speed change of the speed change gear mechanism, it is operated by a predetermined clutch element and a hydraulic actuator having an apply chamber and a release chamber, so that engagement pressure is supplied to the apply chamber and release pressure in the release chamber is discharged. and a predetermined brake element that is engaged only when the clutch element is engaged, and when downshifting from a specific high speed gear to a specific low gear, the predetermined clutch element is switched from engagement to release and the release pressure in the release chamber is discharged. In an automatic transmission configured such that the predetermined braking means is switched from disengaged to engaged, the braking element is released when the braking element is in the specific high speed gear according to the vehicle speed detected by the vehicle speed detecting means. The hydraulic pressure supply state is controlled so that at vehicle speeds higher than a predetermined vehicle speed, the engagement pressure is supplied to the apply chamber, and at vehicle speeds lower than the predetermined vehicle speed, the engagement pressure is discharged from the apply chamber. and a temperature detection means to control the release of the brake element when the vehicle is in the specific high speed gear even if the vehicle speed is lower than the predetermined vehicle speed when the temperature is lower than a predetermined temperature in accordance with the temperature of the hydraulic fluid detected by the temperature detection device. 1. A shift control device for an automatic transmission, comprising: a changing means for changing a hydraulic pressure supply state so as to achieve a state in which a fastening pressure is supplied.