Hydraulic control apparatus for automatic transmission

In a condition of a vehicle which remains stationary or is about to stop and of a forward second speed having a clutch and a brake engaged, an N range is changed from a D range based on a shift lever operation and a forward range pressure is discharged from a manual shift valve. At this time, an orifice and a check ball are used to delay discharge of oil paths which communicate with a linear solenoid valve relative to discharge of an oil path a1 which communicates with a linear solenoid valve. Specifically, release of the brake is delayed relative to release of the clutch, so that a shift by way of a forward first speed through engagement of a one-way clutch can be prevented.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2007-311253 filed on Nov. 30, 2008 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to hydraulic control apparatuses for automatic transmissions mounted in, for example, vehicles and, in particular, to a hydraulic control apparatus for an automatic transmission having a low speed achieved by engagement of a one-way clutch, forming a neutral condition by discharging a hydraulic pressure when a shift lever operation is performed to change from a forward range of a lower medium speed condition to another shift range.

2. Description of the Related Art

A multi-stage automatic transmission mounted in, for example, vehicles generally forms a shift speed by controlling a rotating condition of each of rotating elements in a speed change gear mechanism that combines together the rotating elements including, for example, a planetary gear. The multi-stage automatic transmission controls the rotating condition of the rotating elements through selective hydraulic engagement of a plurality of clutches or brakes, thereby enabling control of multiple shift speeds.

Among such automatic transmissions, some achieve a forward first speed by engaging an input clutch (C-1) with a one-way clutch (F-1), in addition to engagement of the clutches and brakes (see, for example, Japanese Patent Publication Application No. JP-A-2007-177934 which is hereinafter referred to as Patent Document 1). The one-way clutch performs a smooth automatic engagement to lessen an engagement shock particularly when the forward first speed during a change from a neutral range to a forward range is achieved.

A hydraulic control apparatus used in the automatic transmission includes a solenoid valve regulating and controlling an engagement pressure supplied to a hydraulic servo of the clutches and brakes and a manual shift valve allowing a spool position to be changed based on the shift lever operation. Specifically, the manual shift valve allows supply and discharge of a source pressure (a forward range pressure or a reverse range pressure) of the engagement pressure supplied to the hydraulic servo of the clutches and brakes to be collectively controlled. This reliably forms the neutral condition even if, for example, the solenoid valve fails, thus enhancing reliability and safety as the automatic transmission.

There is, however, the following problem. Specifically, a clutch C-1and a brake B-1are engaged as in, for example, the forward second speed of Patent Document 1 when an input shaft of the speed change gear mechanism is in a condition of being an idle speed or less as when, for example, the vehicle is stationary or is about to stop. In addition, the manual shift valve is changed from a forward range position to a neutral range position through the shift lever operation, forming a neutral condition by discharging a hydraulic pressure. If the engagement pressure of the brake B-1is discharged before the engagement pressure of the clutch C-1under the foregoing condition, the input shaft of the speed change gear mechanism is driven at a higher speed through the idle speed of the engine via, for example, a torque converter. As a result, the one-way clutch is automatically engaged to form, together with the clutch C-1, a forward first speed. Specifically, the forward second speed is changed to the neutral condition via the forward first speed, so that the neutral condition is established after a driving force is transmitted to a drive wheel with amplified torque of a gear ratio being instantaneously the forward first speed. This produces a shift shock not expected by a driver, posing a problem of the driver's not having a good shift feeling.

SUMMARY OF THE INVENTION

In the view of the above, the present invention provides a hydraulic control apparatus for an automatic transmission capable of preventing shock by engagement of a one-way clutch from occurring when a forward range is changed to another shift range based on a shift lever operation in a lower medium speed condition.

According to a first aspect of the present invention, the hydraulic control apparatus for the automatic transmission that achieves a lower medium speed by engaging a first friction engagement element and a second friction engagement element and a low speed lower than the lower medium speed by engaging the first friction engagement element and a one-way clutch, the apparatus includes:

a range pressure generating unit outputting a forward range pressure upon a forward range based on a shift lever operation and discharging the forward range pressure upon another shift range;

a first pressure regulating unit outputting the forward range pressure through pressure regulation to a hydraulic servo of the first friction engagement element;

a second pressure regulating unit outputting the forward range pressure through pressure regulation to a hydraulic servo of the second friction engagement element;

a first oil path providing communication of the forward range pressure of the range pressure generating unit with the first pressure regulating unit;

a second oil path providing communication of the forward range pressure of the range pressure generating unit with the second pressure regulating unit; and

a delay mechanism delaying discharge of the second oil path than discharge of the first oil path when the another shift range is changed from the forward range based on the shift lever operation and the range pressure generating unit discharges the forward range pressure.

Accordingly, the delay mechanism delays the discharge of the forward range pressure in the second oil path that provides communication of a hydraulic pressure of the hydraulic servo of the second friction engagement element via the second pressure regulating unit relative to the discharge of the forward range pressure in the first oil path that provides communication of the hydraulic pressure of the hydraulic servo of the first friction engagement element via the first pressure regulating unit. This allows a release of the second friction engagement element to be delayed relative to the release of the first friction engagement element when the range pressure generating unit changes from the forward range to the another shift range based on the shift lever operation particularly in the lower medium speed. This eliminates engagement of the one-way clutch occurring due to the first friction engagement element left engaged when, for example, the second friction engagement element is released before the first friction engagement element. A shift can therefore be made from the lower medium speed without going through the low speed, specifically, from the lower medium speed directly into a neutral range. A shift shock that otherwise occurs when the forward range is changed to another shift range can thereby be prevented, contributing to a better shift feeling.

According to a second aspect of the present invention, the delay mechanism is disposed on the second oil path.

Since the delay mechanism is disposed on the second oil path, the release of the second friction engagement element achieved by discharging the engagement pressure from the second oil path can be delayed relative to the release of the first friction engagement element achieved by discharging the engagement pressure from the first oil path.

According to a third aspect of the present invention, the delay mechanism includes a first orifice and a one-way valve disposed in parallel with the first orifice.

This allows the delay mechanism to be structured to include the first orifice and the one-way valve. Specifically, the release of the second friction engagement element can be delayed relative to the release of the first friction engagement element using a simple mechanical structure. A shift can therefore be made from the lower medium speed directly into the neutral range upon change of another shift range from the forward range, thereby preventing a shift shock from occurring and contributing to a better shift feeling.

According to a forth aspect of the present invention, the first oil path includes a shared oil path connected to the range pressure generating unit and sharing supply and discharge of the hydraulic pressure with the second oil path; and a first non-shared oil path branched from the shared oil path and connected to the first pressure regulating unit;

the second oil path includes the shared oil path; and a second non-shared oil path branched from the shared oil path and connected to the second pressure regulating unit; and

the delay mechanism is interposed in the second non-shared oil path.

Accordingly, the delay mechanism is interposed in the second non-shared oil path. This allows the discharge of the hydraulic pressure from the second pressure regulating unit to be delayed relative to the discharge of the hydraulic pressure from the first pressure regulating unit. The release of the second friction engagement element can therefore be delayed relative to the release of the first friction engagement element.

According to a fifth aspect of the present invention, the hydraulic control apparatus further includes:

a second orifice interposed in the shared oil path; and

an accumulator disposed on a side closer to the first pressure regulating unit than the second orifice and connected to the shared oil path.

Accordingly, the accumulator is connected to the shared oil path at a point closer to the side of the first pressure regulating unit than the second orifice. Upon change of another shift range from the forward range, therefore, the hydraulic pressure accumulated in the accumulator can prevent, for example, a sudden release shock of the first friction engagement element through a sudden discharge of the forward range pressure. In addition, the release of the second friction engagement element can be delayed relative to the release of the first friction engagement element. While the shock due to sudden release can be prevented, a shift can therefore be made from the lower medium speed directly into the neutral range upon change of another shift range from the forward range. A shift shock can thereby be prevented from occurring, which contributes to a better shift feeling.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention will be described below with reference toFIGS. 1 through 5.

[General Arrangements of the Automatic Transmission]

General arrangements of an automatic transmission3to which the present invention is applicable will be described with reference toFIG. 1. As shown inFIG. 1, the automatic transmission3suitable for use in a vehicle of, for example, an FF type (front engine, front drive) has an input shaft8of the automatic transmission to be connected to an engine (not shown), and includes a torque converter4and an automatic speed change mechanism5disposed about an axis of the input shaft8.

The torque converter4includes a pump impeller4aconnected to the input shaft8of the automatic transmission3and a turbine runner4bto which rotation of the pump impeller4ais transmitted via a hydraulic fluid. The turbine runner4bis connected to an input shaft10of the automatic speed change mechanism5disposed coaxially with the input shaft8. The torque converter4has a lock-up clutch7. When the lock-up clutch7is engaged, rotation of the input shaft8of the automatic transmission3is directly transmitted to the input shaft10of the automatic speed change mechanism5.

The input shaft10of the automatic speed change mechanism5is mounted with a planetary gear SP and a planetary gear unit PU. The planetary gear SP is what is called a single pinion planetary gear including a sun gear S1, a carrier CR1, and a ring gear R1. The carrier CR1has a pinion P1that meshes with the sun gear S1and the ring gear R1.

The planetary gear unit PU is what is called a Ravigneaux type planetary gear including, as four rotating elements, a sun gear S2, a sun gear S3, a carrier CR2, and a ring gear R2. The carrier CR2has a long pinion PL that meshes with the sun gear S2and the ring gear R2and a short pinion PS that meshes with the sun gear S3, the long pinion PL and the short pinion PS being in mesh with each other.

The sun gear S1of the planetary gear SP is connected to a boss portion (not shown) integrally fixed to a transmission case (not shown) and is fixed. In addition, the rotation of the ring gear R1is the same as that of the input shaft10(hereinafter referred to as “input rotation”). Further, the carrier CR1provides a reduced speed rotation that is the input rotation with a reduced speed by the fixed sun gear S1and the ring gear R1providing the input rotation. The carrier CR1is connected to a clutch C-1and a clutch C-3.

The sun gear S2of the planetary gear unit PU is fixable relative to the transmission case by being connected to a brake B-1formed from a band brake. Further, the sun gear S2is connected to the clutch C-3such that the reduced speed rotation of the carrier CR1can be input thereto through the clutch C-3. In addition, the sun gear S3is connected to the clutch C-1and the reduced speed rotation of the carrier CR1can be input thereto.

Additionally, the carrier CR2is connected to a clutch C-2to which the rotation of the input shaft10is input, so that the input rotation can be input thereto via the clutch C-2. The carrier CR2is also connected to a one-way clutch F-1and a brake B-2. Rotation of the carrier CR2in one direction relative to the transmission case is restricted by the one-way clutch F-1. The rotation of the carrier CR2is also fixable via the brake B-2. The ring gear R2is connected to a counter gear11which, in turn, is connected to a drive wheel via a counter shaft and a differential gear (not shown).

[Operation of Each Shift Speed in the Automatic Transmission]

Based on the foregoing arrangements, operations of the automatic speed change mechanism5will be described with reference toFIGS. 1,2, and3. Note that, in a speed diagram shown inFIG. 3, an ordinate direction represents the speed of each rotating element (each gear) and an abscissa direction corresponds to the gear ratio of each rotating element. Further, as for the planetary gear SP of the speed diagram, the ordinate corresponds to the sun gear S1, the carrier CR1, and the ring gear R1in that order from the leftward end inFIG. 3. As for the planetary gear unit PU of the speed diagram, the ordinate corresponds to the sun gear S3, the ring gear R2, the carrier CR2, and the sun gear S2in that order from the rightward end inFIG. 3.

For example, in a forward first speed (1ST) in a D (drive) range, the clutch C-1and the one-way clutch F-1are engaged as shown inFIG. 2. Then, referring toFIGS. 1 and 3, the rotation of the carrier CR1rotated at a reduced speed by the fixed sun gear S1and the input rotation of the ring gear R1is input to the sun gear S3through the clutch C-1. In addition, the rotation of the carrier CR2is restricted to that in one direction only (a forward rotating direction); specifically, the carrier CR2is fixed by being prevented from rotating in a backward direction. The reduced speed rotation input to the sun gear S3is then output to the ring gear R2via the fixed carrier CR2, so that the counter gear11outputs a forward rotation as the forward first speed.

Note that, during engine braking (coasting), the brake B-2is locked to fix the carrier CR2so as to prevent the carrier CR2from rotating forward, thereby maintaining a condition of the forward first speed. Further, in the forward first speed, the one-way clutch F-1prevents the carrier CR2from rotating backward, while permitting forward rotation. The forward first speed can therefore be achieved even more smoothly through an automatic engagement of the one-way clutch F-1when, for example, a non-running range is changed to a running range.

In a forward second speed (2ND), referring toFIG. 2, the clutch C-1is engaged and the brake B-1is locked. Then, referring toFIGS. 1 and 3, the rotation of the carrier CR1rotated at a reduced speed by the fixed sun gear S1and the input rotation of the ring gear R1is input to the sun gear S3through the clutch C-1. The rotation of the sun gear S2is fixed by the locking of the brake B-1. Then, the carrier CR2rotates at a reduced speed lower than the sun gear S3, so that the reduced speed rotation input to the sun gear S3is output to the ring gear R2via the carrier CR2and the counter gear11outputs a forward rotation as the forward second speed.

In a forward third speed (3RD), referring toFIG. 2, the clutch C-1and the clutch C-3are engaged. Then, referring toFIGS. 1 and 3, the rotation of the carrier CR1rotated at a reduced speed by the fixed sun gear S1and the input rotation of the ring gear R1is input to the sun gear S3through the clutch C-1. Further, the engagement of the clutch C-3causes the reduced speed rotation of the carrier CR1to be input to the sun gear S2. Specifically, the reduced speed rotation of the carrier CR1is input to the sun gear S2and the sun gear S3. As a result, the planetary gear unit PU is set into a condition of direct coupling of the reduced speed rotation, so that the reduced speed rotation is directly output to the ring gear R2and the counter gear11outputs a forward rotation as the forward third speed.

In a forward fourth speed (4TH), referring toFIG. 2, the clutch C-1and the clutch C-2are engaged. Then, referring toFIGS. 1 and 3, the rotation of the carrier CR1rotated at a reduced speed by the fixed sun gear S1and the input rotation of the ring gear R1is input to the sun gear S3through the clutch C-1. Further, the engagement of the clutch C-2causes the input rotation to be input to the carrier CR2. Then, the reduced speed rotation input to the sun gear S3and the input rotation input to the carrier CR2causes a reduced speed rotation higher than the forward third speed to be output to the ring gear R2, so that the counter gear11outputs a forward rotation as the forward fourth speed.

In a forward fifth speed (5TH), referring toFIG. 2, the clutch C-2and the clutch C-3are engaged. Then, referring toFIGS. 1 and 3, the rotation of the carrier CR1rotated at a reduced speed by the fixed sun gear S1and the input rotation of the ring gear R1is input to the sun gear S2through the clutch C-3. Further, the engagement of the clutch C-2causes the input rotation to be input to the carrier CR2. Then, the reduced speed rotation input to the sun gear S2and the input rotation input to the carrier CR2causes an accelerated speed rotation slightly higher than the input rotation to be output to the ring gear R2, so that the counter gear11outputs a forward rotation as the forward fifth speed.

In a forward sixth speed (6TH), referring toFIG. 2, the clutch C-2is engaged and the brake B-1is locked. Then, referring toFIGS. 1 and 3, the engagement of the clutch C-2causes the input rotation to be input to the carrier CR2. The rotation of the sun gear S2is fixed by the locking of the brake B-1. Then, the fixed sun gear S2causes the input rotation of the carrier CR2to be output to the ring gear R2as an accelerated speed rotation higher than the forward fifth speed, so that the counter gear11outputs a forward rotation as the forward sixth speed.

In a reverse first speed (REV), referring toFIG. 2, the clutch C-3is engaged and the brake B-2is locked. Then, referring toFIGS. 1 and 3, the rotation of the carrier CR1rotated at a reduced speed by the fixed sun gear S1and the input rotation of the ring gear R1is input to the sun gear S2through the clutch C-3. The rotation of the carrier CR2is fixed by the locking of the brake B-2. Then, the reduced speed rotation input to the sun gear S2is output to the ring gear R2via the fixed carrier CR2and the counter gear11outputs a reverse rotation as the reverse first speed.

It is to be noted that, in a P (parking) range and an N (neutral) range for example, the clutches C-1, C-2, and C-3are released. This disconnects the carrier CR1from the sun gear S2and the sun gear S3; specifically, the planetary gear SP is disconnected from the planetary gear unit PU and the input shaft10is disconnected from the carrier CR2. As a result, power transmission between the input shaft10and the planetary gear unit PU is disconnected; specifically, the power transmission between the input shaft10and the counter gear11is disconnected.

[General Arrangements of the Hydraulic Control Apparatus]

A hydraulic control apparatus1of the automatic transmission3according to the embodiment of the present invention will be described below. Sections of generating pressures such as a line pressure, a secondary pressure, and a modulator pressure which are not shown in drawings showing the hydraulic control apparatus1will be first broadly described. Note that the sections of generating the line pressure, the secondary pressure, and the modulator pressure are the same as those found in common hydraulic control apparatuses for automatic transmissions and well known, and will therefore be only briefly described.

The hydraulic control apparatus1includes, for example, an oil pump, a primary regulator valve, a secondary regulator valve, a solenoid modulator valve, and a linear solenoid valve SLT which are not shown. When, for example, the engine is started, the oil pump rotatably drivably connected to the pump impeller4aof the torque converter4is driven by being operatively connected to rotation of the engine. This generates a hydraulic pressure as oil is pumped up from an oil pan (not shown) via a strainer (not shown).

The hydraulic pressure generated by the oil pump is regulated to a line pressure PL, while being adjusted to be discharged by the primary regulator valve based on a signal pressure PSLTof the linear solenoid valve SLT regulated and output according to a throttle opening. The line pressure PLis supplied, for example, to the solenoid modulator valve, a manual shift valve (a range pressure generating unit)81(seeFIG. 5) to be described in detail later, and a linear solenoid valve SLC3to be described in detail later. Of these, the line pressure PLsupplied to the solenoid modulator valve is regulated to a modulator pressure PMODthat becomes a substantially predetermined pressure, by the valve. The modulator pressure PMODis supplied as a source pressure for, for example, the linear solenoid valve SLT, and solenoid valves S1, S2to be described in detail later.

The pressure discharged from the primary regulator valve is regulated to a secondary pressure PSEC, while being further adjusted to be discharged by, for example, the secondary regulator valve. The secondary pressure PSECis supplied to, for example, a lubricating oil path or an oil cooler. The secondary pressure PSECis also supplied to the torque converter4and used for controlling the lock-up clutch7.

Referring toFIG. 5, the manual shift valve81is structured to include an input port81a, a forward range pressure output port81b, a forward range pressure drain port81c, a reverse range pressure output port81d, and a drain port EX, in addition to a spool81pdriven mechanically (or electrically) by a shift lever disposed at a driver's seat (not shown). An output state or a non-output state (drain) of the line pressure PLinput to the input port81ais set when the position of the spool81pselected according to the shift range (for example, P, R, N, or D) is changed by the shift lever.

More specifically, when the D range is selected through the operation of the shift lever, the input port81ato which the line pressure PLis input based on the position of the spool81pand the forward range pressure output port81bare brought into communication with each other, so that the line pressure PLis output from the forward range pressure output port81bas a forward range pressure (D range pressure) PD. When the R (reverse) range is selected through the operation of the shift lever, the input port81aand the reverse range pressure output port81dare brought into communication with each other based on the position of the spool81p, so that the line pressure PLis output from the reverse range pressure output port81das a reverse range pressure (R range pressure) PREV. In addition, the forward range pressure drain port81cand the drain port EX are brought into communication with each other, so that the D range pressure PDis drained. When the P range or the N range is selected through the operation of the shift lever, the input port81ais shut off from the forward range pressure output port81band the reverse range pressure output port81dby the spool81p, while the forward range pressure drain port81cand the reverse range pressure output port81dare brought into communication with the drain port EX; specifically, the D range pressure PDand the R range pressure PREVare drained (discharged) to be in the non-output state.

[Detailed Arrangements of the Shift Control Section of the Hydraulic Control Apparatus]

A section mainly performing the shift control in the hydraulic control apparatus1according to the embodiment of the present invention will be described below with reference toFIG. 4. Note that, to describe the spool position in the embodiment of the present invention, the position of the right-hand half ofFIG. 4will be referred to as the “right-hand-half position” and that of the left-hand half ofFIG. 4will be referred to as the “left-hand-half position”.

The hydraulic control apparatus1includes four linear solenoid valves SLC1, SLC2, SLC3, and SLB1for supplying an output pressure regulated as an engagement pressure directly to each of a total of five hydraulic servos. The five hydraulic servos are a hydraulic servo41of the clutch C-1, a hydraulic servo42of the clutch C-2, a hydraulic servo43of the clutch C-3, a hydraulic servo44of the brake B-1, and a hydraulic servo45of the brake B-2. The hydraulic control apparatus1further includes, for example, a solenoid valve S1, a solenoid valve S2, a first clutch apply relay valve21, a second clutch apply relay valve22, a C-2relay valve23, and a B-2relay valve24as a portion for achieving a limp-home function and selecting the hydraulic servo42of the clutch C-2or the hydraulic servo45of the brake B-2for the output pressure of the linear solenoid valve SLC2.

The forward range pressure output port81b(and the forward range pressure drain port81c) of the manual shift valve81(seeFIG. 5) are connected to an oil path a1, an oil path a4, and an oil path a5shown inFIG. 4so that the forward range pressure PDcan be input thereto. The reverse range pressure output port81dof the manual shift valve81is connected to an oil path1so that the reverse range pressure PREVis to be input thereto. Further, the line pressure PLfrom the primary regulator valve (not shown) is input to an oil path d and the modulator pressure PMODfrom the modulator valve (not shown) is input to an oil path g1.

Of these, the oil path a1is connected to an input port21eof the first clutch apply relay valve21to be described in detail later via an oil path a2. Further, a check valve50and an orifice (a second orifice)60are disposed on the oil path a1. In addition, the oil path a1is connected to an accumulator30via an oil path a3and to the linear solenoid valve (a first pressure regulating portion) SLC1. The accumulator30is structured to include a case30c, a piston30b, a spring30s, and an oil chamber30a. Specifically, the piston30bis disposed inside the case30c. The spring30surges the piston30b. The oil chamber30ais formed between the case30cand the piston30b.

Referring further toFIG. 5, the oil path a1is connected to the manual shift valve81via oil paths a10, a11. The oil path a5is connected to the manual shift valve81via the oil paths a10, a11and a discharge delay zone90to be described in detail later. An orifice (delay mechanism, a first orifice)71and a check ball (delay mechanism, a one-way valve)72are disposed on the discharge delay zone90.

Referring toFIG. 4, on the other hand, the linear solenoid valve SLC1is a normally closed type that is in the non-output state when deenergized. The linear solenoid valve SLC1has an input port SLC1aand an output port SLC1b. The input port SLC1ainputs the forward range pressure PDvia the oil path a1and the output port SLC1boutputs a control pressure PSLC1to the hydraulic servo41as an engagement pressure PC1by regulating the forward range pressure PD. Specifically, the linear solenoid valve SLC1is structured to be in the non-output state by shutting off the input port SLC1aand the output port SLC1bwhen deenergized and, when energized based on a command value from a control unit (ECU) (not shown), to increase an amount of communication (opening amount) between the input port SLC1aand the output port SLC1baccording to the command value, specifically, to output the engagement pressure PC1in accordance with the command value. Additionally, the output port SLC1bof the linear solenoid valve SLC1is connected to an input port22cof the second clutch apply relay valve22to be described later via an oil path b1.

The linear solenoid valve SLC2is a normally open type that is in the output state when deenergized. The linear solenoid valve SLC2has an input port SLC2aand an output port SLC2b. The input port SLC2ainputs the forward range pressure PDvia, for example, the oil path a4and the output port SLC2boutputs a control pressure PSLC2to the hydraulic servo42as an engagement pressure PC2(or an engagement pressure PB2) by regulating the forward range pressure PD. Specifically, the linear solenoid valve SLC2is structured to be in the output state in which the input port SLC2aand the output port SLC2bare in communication with each other when deenergized and, when energized based on a command value from the control unit (ECU) (not shown), to decrease the amount of communication (specifically, throttle down the opening amount) between the input port SLC2aand the output port SLC2baccording to the command value, specifically, to output the engagement pressure PC2(or PB2) in accordance with the command value. Additionally, the output port SLC2bof the linear solenoid valve SLC2is connected to an input port2fof the second clutch apply relay valve22to be described later via an oil path c1.

The linear solenoid valve SLC3is a normally open type that is in the output state when deenergized. The linear solenoid valve SLC2has an input port SLC3aand an output port SLC3b. The input port SLC3ainputs the line pressure PLvia, for example, the oil path d and the output port SLC3boutputs a control pressure PSLC3to the hydraulic servo43as an engagement pressure PC3by regulating the line pressure PL. Specifically, the linear solenoid valve SLC3is structured to be in the output state in which the input port SLC3aand the output port SLC3bare in communication with each other when deenergized and, when energized based on a command value from the control unit (ECU) (not shown), to decrease the amount of communication (specifically, reduce the opening amount) between the input port SLC3aand the output port SLC3baccording to the command value, specifically, to output the engagement pressure PC3in accordance with the command value. Additionally, the output port SLC3bof the linear solenoid valve SLC3is connected to the hydraulic servo43of the clutch C-3via an oil path e1. A check valve53and an orifice63are disposed on the oil path e1. Further, an oil chamber33aof a C-3damper33is connected to the oil path e1via an oil path e2. Note that the C-3damper33is similar in structure to the accumulator30. The C-3damper33is a commonly found damper and a detailed description thereof will be omitted.

The linear solenoid valve (a second pressure regulating portion) SLB1is a normally closed type that is in the non-output state when deenergized. The linear solenoid valve SLB1has an input port SLB1aand an output port SLB1b. The input port SLB1ainputs the forward range pressure PDvia, for example, the oil path a5and the output port SLB1boutputs a control pressure PSLB1to the hydraulic servo44as an engagement pressure PB1by regulating the forward range pressure PD. Specifically, the linear solenoid valve SLB1is structured to be in the non-output state by shutting off the input port SLB1aand the output port SLB1bwhen deenergized and, when energized based on a command value from the control unit (ECU) (not shown), to increase the amount of communication (opening amount) between the input port SLB1aand the output port SLB1baccording to the command value, specifically, to output the engagement pressure PB1in accordance with the command value. Additionally, the output port SLB1bof the linear solenoid valve SLB1is connected to the hydraulic servo44of the brake B-1via an oil path f1. A check valve54and an orifice64are disposed on the oil path f1. Further, an oil chamber34aof a B-1damper34is connected to the oil path f1via an oil path f2.

The solenoid valve S1is a normally open type that is in the output state when deenergized. The solenoid valve S1has an input port S1aand an output port S1b. The input port S1ainputs the modulator pressure PMODvia the oil path g1and an oil path g2. The output port S1boutputs the modulator pressure PMODsubstantially directly as a signal pressure PS1when deenergized (specifically, when turned OFF). The output port S1bis connected to an oil chamber21aof the first clutch apply relay valve21via oil paths h1, h2, to an oil chamber22aof the second clutch apply relay valve22via oil paths h1, h3, and to an input port24cof the B-2relay valve24via an oil path h4.

The solenoid valve S2is a normally closed type that is in the non-output state when deenergized. The solenoid valve S2has an input port S2aand an output port S2b. The input port S2ainputs the modulator pressure PMODvia the oil path g1and an oil path g3. The output port S2boutputs the modulator pressure PMODsubstantially directly as a signal pressure PS2when energized (specifically, when turned ON). The output port S2bis connected to an oil chamber24aof the B-2relay valve24via an oil path i.

The first clutch apply relay valve21is structured to include two spools21p,21q, a spring21surging the spool21pupward inFIG. 4, and a spring21turging the spools21p,21qin a direction of spacing apart. The first clutch apply relay valve21is structured to include also the oil chamber21adisposed upward of the spool21qinFIG. 4and oil chambers21b,21c,21d. The oil chamber21dis disposed downward of the spool21pinFIG. 4. The oil chamber21cis disposed between the spools21p,21q. The oil chamber21bis formed by a difference in diameter of land portions of the spool21q(difference in pressure receiving area). The first clutch apply relay valve21is structured to include further the input port21e, an input port21f, an input port21g, an input port21h, an output port21i, an output port21j, and a drain port EX.

The first clutch apply relay valve21is structured such that the input port21eand the output port21jare brought into communication with each other and the input port21eand the output port21iare shut off from each other when the spools21p,21qare in the left-hand-half position; and that the input port21eand the output port21iare brought into communication with each other and the output port21jand the drain port EX are brought into communication with each other when the spools21p,21qare in the right-hand-half position. The first clutch apply relay valve21is further structured such that the input port21his shut off when the spool21pis in the left-hand-half position and that the input port21gis shut off when the spool21qis in the right-hand-half position.

As described above, the oil chamber21ais connected to the output port S1bof the solenoid valve S1via the oil paths h1, h2and the oil chamber21bis connected to an output port22iof the second clutch apply relay valve22to be described later via an oil path b4from the input port21f. The forward range pressure PDis input to the input port21evia the oil paths a1, a2. The output port21jthat is brought into communication with the input port21ewhen the spool21pis in the left-hand-half position is connected to an input port22hof the second clutch apply relay valve22via an oil path j. In addition, the output port21ithat is brought into communication with the input port21ewhen the spool21pis in the right-hand-half position is connected to the input port21gvia oil paths k1, k2and to the input port21hvia the oil paths k1, k2, and an oil path k3, respectively. Specifically, the output port21iis connected to the oil chamber21cregardless of the position of the spools21p,21q. Further, the output port21iis connected to an input port22eof the second clutch apply relay valve22to be described later via the oil path k1. In addition, an output port23cof the C-2relay valve23is connected to the oil chamber21dvia an oil path c5. A check valve55and an orifice65are disposed on the oil path c5.

The second clutch apply relay valve22is structured to include a spool22pand a spring22surging the spool22pupward inFIG. 4. The second clutch apply relay valve22is structured to include also the oil chamber22adisposed upward of the spool22pinFIG. 4and an oil chamber22bdisposed downward of the spool22pinFIG. 4. The second clutch apply relay valve22is structured to include further the input port22c, an output port22d, the input port22e, the input port22f, an output port22g, the input port22h, and the output port22i.

The second clutch apply relay valve22is structured such that the input port22cand the output port22d, and the output port22i, are brought into communication with each other; the input port22fand the output port22gare brought into communication with each other; and the input port22eand the input port22hare shut off from each other when the spool22pis in the left-hand-half position. Further, the second clutch apply relay valve22is structured such that the input port22eand the output port22dare brought into communication with each other; the input port22hand the output port22gare brought into communication with each other; and the input port22c, the output port22i, and the input port22fare shut off from each other when the spool22pis in the right-hand-half position.

As described above, the oil chamber22ais connected to the output port S1bof the solenoid valve S1via the oil paths h1, h3and to the input port24cof the B-2relay valve24to be described later via the oil path h4. The input port22cis connected to the output port SLC1bof the linear solenoid valve SLC1via the oil path b1. The output port22dthat is brought into communication with the input port22cwhen the spool22pis in the left-hand-half position is connected to the hydraulic servo41of the clutch C-1via an oil path b2. A check valve51and an orifice61are disposed on the oil path b2. An oil chamber31aof a C-1damper31is connected to the oil path b2via an oil path b3. Similarly, the output port22ithat is brought into communication with the input port22cwhen the spool22pis in the left-hand-half position is connected to the input port21fof the first clutch apply relay valve21via the oil path b4and to the oil chamber22bvia the oil path b4and an oil path b5. The input port22f, on the other hand, is connected to the output port SLC2bof the linear solenoid valve SLC2via the oil path c1. The input port22his connected to the output port21jof the first clutch apply relay valve21via the oil path j. The output port22gthat is brought into communication with the input port22fwhen the spool22pis in the left-hand-half position and with the input port22hwhen the spool22pis in the right-hand-half position is connected to an input port23bof the C-2relay valve23to be described later via an oil path c2. A check valve52and an orifice62are disposed on the oil path c2and an oil chamber32aof a C2-B2damper32is connected to the oil path c2via an oil path c4.

The C-2relay valve23is structured to include a spool23pand a spring23surging the spool23pupward inFIG. 4. The C-2relay valve23is structured to include also an oil chamber23adisposed upward of the spool23pinFIG. 4. The C-2relay valve23is structured to include further the input port23b, the output port23c, an output port23d, an output port23e, and a drain port EX.

The C-2relay valve23is structured such that the input port23band the output port23c, and the output port23e, are brought into communication with each other and the output port23dand the drain port EX are brought into communication with each other when the spool23pis in the left-hand-half position. Further, the C-2relay valve23is structured such that the input port23band the output port23dare brought into communication with each other and the output port23cand the output port23e, and the drain port EX, are brought into communication with each other when the spool23pis in the right-hand-half position.

The oil chamber23ais connected to an output port24bof the B-2relay valve24to be described later via an oil path h5. The input port23bis connected to the output port22gof the second clutch apply relay valve22via the oil path c2and the output port23ethat is brought into communication with the input port23bwhen the spool23pis in the left-hand-half position is connected to the hydraulic servo42of the clutch C-2via an oil path c3. Similarly, the output port23cthat is brought into communication with the input port23bwhen the spool23pis in the left-hand-half position is connected to the oil chamber21dof the first clutch apply relay valve21via the oil path c5. The check valve55and the orifice65are disposed on the oil path c5. Additionally, the output port23dthat is brought into communication with the input port23bwhen the spool23pis in the right-hand-half position is connected to an input port24eof the B-2relay valve24via an oil path m.

The B-2relay valve24is structured to include a spool24pand a spring24surging the spool24pupward inFIG. 4. The B-2relay valve24is structured to include also the oil chamber24adisposed upward of the spool24pinFIG. 4. The B-2relay valve24is structured to include further the output port24b, the input port24c, an input port24d, the input port24e, an output port24f, an output port24g, and a drain port EX.

The B-2relay valve24is structured such that the input port24dand the output port24f, and the output port24g, are brought into communication with each other, the output port24band the drain port EX are brought into communication with each other, and the input port24cis shut off when the spool24pis in the left-hand-half position. Further, the B-2relay valve24is structured such that the input port24cand the output port24bare brought into communication with each other, the input port24eand the output port24gare brought into communication with each other, and the input port24dand the drain port EX are shut off, when the spool24pis in the right-hand-half position.

The oil chamber24ais connected to the output port S2bof the solenoid valve S2via the oil path i. The input port24dis connected to the reverse range pressure output port81dof the manual shift valve81(seeFIG. 5) to which the reverse range pressure PREVis output via the oil path1. The input port24eis connected to the output port23dof the C-2relay valve23via the oil path m. The output port24gthat is brought into communication with the input port24dwhen the spool24pis in the left-hand-half position and with the input port24ewhen the spool24pis in the right-hand-half position is connected to the hydraulic servo45of the brake B-2via an oil path n. Specifically, the hydraulic servo45of the brake B-2is connected to the reverse range pressure output port81dof the manual shift valve81or the output port SLC2bof the linear solenoid valve SLC2. In addition, as described above, the input port24cis connected to the output port S1bof the solenoid valve S1via the oil path h4, the oil chamber22aof the second clutch apply relay valve22, and the oil paths h1, h3, and the output port24bthat is brought into communication with the input port24cwhen the spool24pis in the right-hand-half position is connected to the oil chamber23aof the C-2relay valve23via the oil path h5. Note that the output port24fthat is brought into communication with the input port24dwhen the spool24pis in the left-hand-half position is connected to an oil chamber of the primary regulator valve via an oil path (not shown), so that the reverse range pressure PREVmay act on the primary regulator valve to increase the line pressure PLduring reversing.

[Operations of the Hydraulic Control Apparatus]

Operations of the hydraulic control apparatus1according to the embodiment of the present invention will be described below.

Referring toFIG. 4, when, for example, the driver turns ON the ignition, hydraulic control by the hydraulic control apparatus1is started. If, for example, the shift lever is selected in the P range or the N range, the normally open type linear solenoid valve SLC2, linear solenoid valve SLC3, and solenoid valve S1are energized through an electric command of the control unit (not shown) and the respective input ports and output ports are shut off. When, for example, the engine is next started, a hydraulic pressure is generated through rotation of the oil pump (not shown) based on rotation of the engine. The hydraulic pressure is regulated, respectively, to the line pressure PLand the modulator pressure PMODby the primary regulator valve and the solenoid modulator valve and output as described heretofore. The line pressure PLis then input to the input port81aof the manual shift valve81(seeFIG. 5) and to the input port SLC3aof the linear solenoid valve SLC3via the oil path d, while the modulator pressure PMODis input to the input ports S1a, S2aof the solenoid valves S1, S2, respectively, via the oil paths g1, g2, g3.

[Operation in Shift from N to D Range (Forward First Speed)]

Next, assume, for example, that the driver places the shift lever in the D range position from the N range position. Then, the forward range pressure PDis output from the forward range pressure output port81bof the manual shift valve81(seeFIG. 5) to the oil paths a1, a4, a5. The forward range pressure PDis then input to the linear solenoid valve SLC1via the oil path a1, to the linear solenoid valve SLC2via the oil path a4, to the linear solenoid valve SLB1via the oil path a5, and the first clutch apply relay valve21via the oil paths a1, a2.

The check valve50and the orifice60are disposed on the oil path a1. The forward range pressure PDcauses the check valve50to open, so that supply of the forward range pressure PDfor the linear solenoid valve SLC1is at a more rapid pace as compared with timing during discharge. In addition, the forward range pressure PDsupplied to the oil path a1is input to the oil chamber30aof the accumulator30via the oil path a3. Then, the accumulator30stores therein the forward range pressure PDto be supplied to the linear solenoid valve SLC1and the linear solenoid valve SLB1.

The first clutch apply relay valve21having the input port21eto which the forward range pressure PDis input from the oil path a2is in the left-hand-half position because of an urging force of the spring21sin the beginnings of the D range selected (beginnings of the shift from N to D) for lack of the signal pressure PS1as a result of the solenoid valve S1being energized, so that the forward range pressure PDis output to the oil path j from the output port21j. Similarly, for lack of the signal pressure PS1as a result of the solenoid valve S1being energized, the input port22his shut off in the second clutch apply relay valve22which is in the left-hand-half position by the urging force of the spring22s.

When, for example, the control unit next determines the forward first speed, the linear solenoid valve SLC1is energized through the electric control by the control unit. The forward range pressure PDbeing input to the input port SLC1ais regulated and controlled, and output from the output port SLC1bsuch that the control pressure PSLC1gradually increases as the engagement pressure PC1. The control pressure PSLC1(engagement pressure PC1) is thereby input to the input port22cof the second clutch apply relay valve22via the oil path b1.

The second clutch apply relay valve22which is in the left-hand-half position then outputs the control pressure PSLC1input to the input port22cfrom the output port22i, and also from the output port22d. The control pressure PSLC1output from the output port22iis input to the oil chamber22bvia the oil paths b4, b5to lock the second clutch apply relay valve22in the left-hand-half position. The control pressure PSLC1is also input to the oil chamber21bof the first clutch apply relay valve21via the oil path b4, thereby counteracting the urging force of the spring21sto press the spools21p,21qdownwardly inFIG. 4. The first clutch apply relay valve21is thereby repositioned in the right-hand-half position.

The first clutch apply relay valve21with the spools21p,21qrepositioned in the right-hand-half position uses the control pressure PSLC1output from the output port22iof the second clutch apply relay valve22to counteract the urging force of the spring21t, thereby pressing the spool21qdownwardly inFIG. 4. The forward range pressure PDinput from the input port21eis, however, output from the output port21iand input to the oil chamber21cvia the oil paths k1, k2, k3and the input port21h. The spool21qis therefore repositioned upwardly inFIG. 4by the hydraulic pressure acting on the oil chamber21cand the urging force of the spring21t; specifically, the spools21p,21qare locked in positions spaced apart from each other. Note that the forward range pressure PDinput from the oil path k1to the input port22eof the second clutch apply relay valve22is shut off at the input port22e.

The control pressure PSLC1input from the linear solenoid valve SLC1to the input port22cof the second clutch apply relay valve22as described above is output from the output port22dto the hydraulic servo41via the oil path b2as the engagement pressure PC1, so that the clutch C-1is engaged. This achieves the forward first speed, coupled with the locking of the one-way clutch F-1.

In addition, the check valve51and the orifice61are disposed on the oil path b2. When the engagement pressure PC1(control pressure PSLC1) is to be supplied to the hydraulic servo41, the check valve51is closed and the hydraulic pressure is supplied at a mild pace only via the orifice61. When the engagement pressure PC1is to be discharged from the hydraulic servo41, the check valve51is opened to let the engagement pressure PC1be discharged at a rapid pace as compared with the case of the supply. In addition, the engagement pressure PC1supplied to the oil path b2is input to the oil chamber31aof the C-1damper31via the oil path b3and the C-1damper31prevents pulsation of the engagement pressure PC1supplied to, and discharged from, the hydraulic servo41and absorbs a surge pressure (a sharply fluctuating pressure), for example.

[Operation in Engine Braking of the Forward First Speed]

When, for example, the control unit determines engine braking of the forward first speed, the solenoid valve S2is energized, the solenoid valve S1is deenergized, and the linear solenoid valve SLC2is controlled for pressure regulation through the electric command from the control unit. When the solenoid valve S2is energized, the modulator pressure PMODinput to the input port S2avia the oil paths g1, g3is output from the output port S2bas the signal pressure PS2and input to the oil chamber24aof the B-2relay valve24via the oil path i. Then, the spool24pis repositioned downwardly in the figure against the urging force of the spring24sand the B-2relay valve24is placed in the right-hand-half position.

When the solenoid valve S1is deenergized, the modulator pressure PMODinput to the input port S1avia the oil paths g1, g2is output from the output port S1bas the signal pressure PS1. The signal pressure PS1is then input to the oil chamber21aof the first clutch apply relay valve21via the oil paths h1, h2, to the oil chamber22aof the second clutch apply relay valve22via the oil paths h1, h3, and to the input port24cof the B-2relay valve24via the oil path h4; and further to the oil chamber23aof the C-2relay valve23via the oil path h5from the output port24bof the B-2relay valve24placed in the right-hand-half position.

Then, the C-2relay valve23is placed in the right-hand-half position as the signal pressure PS1input to the oil chamber23acauses the spool23pto counteract the urging force of the spring23sand be repositioned downwardly inFIG. 4. Note that the first clutch apply relay valve21is placed in the right-hand-half position as the signal pressure PS1being input to the oil chamber21acauses the spool21qto be repositioned downwardly inFIG. 4; however, the spool21pis not particularly affected by remaining in the same right-hand-half position as in the forward first speed. In addition, with the second clutch apply relay valve22, though the signal pressure PS1is input to the oil chamber22a, the engagement pressure PC1of the oil chamber22band the urging force of the spring22sovercome the signal pressure PS1to let the spool22premain locked in the left-hand-half position.

When the linear solenoid valve SLC2is then controlled for pressure regulation and the control pressure PSLC2is output from the output port SLC2b, the control pressure PSLC2is input to the input port22fof the second clutch apply relay valve22locked in the left-hand-half position via the oil path c1and output as the engagement pressure PB2from the output port22gto the oil path c2.

The engagement pressure PB2output to the oil path c2is input to the input port23bof the C-2relay valve23placed in the right-hand-half position and output from the output port23d. In addition, the engagement pressure PB2is input to the input port24eof the B-2relay valve24placed in the right-hand-half position via the oil path m, output from the output port24g, and input to the hydraulic servo45via the oil path n, so that the brake B-2is locked. This achieves the engine braking of the forward first speed, coupled with the engagement of the clutch C-1.

Note that the check valve52and the orifice62are disposed on the oil path c2. When the engagement pressure PB2is to be supplied to the hydraulic servo45of the brake B-2, the check valve52is closed and the hydraulic pressure is supplied at a mild pace only via the orifice62. At the time of discharge to be described later, the check valve52is opened to let the hydraulic pressure in the oil path c2be discharged at a rapid pace. In addition, the engagement pressure PB2supplied to the oil path c2is input to the oil chamber32aof the C2-B2damper32via the oil path c4and the C2-B2damper32prevents pulsation of the engagement pressure PB2supplied to, and discharged from, the hydraulic servo45, and absorbs a surge pressure (a sharply fluctuating pressure), for example.

When, for example, the control unit determines a forward drive of the forward first speed, specifically, cancellation of the engine braking, the solenoid valve S2is deenergized and the solenoid valve S1is energized, and in addition, the linear solenoid valve SLC2is closed by being energized and the control pressure PSLC2as the engagement pressure PB2is zeroed and drained. Further, the engagement pressure PB2of the hydraulic servo45of the brake B-2is discharged from the drain port EX of the manual shift valve81(seeFIG. 5) via the input port24d, the oil path1, and the reverse range pressure output port81dof the manual shift valve81, since the B-2relay valve24is repositioned in the left-hand-half position as a result of the deenergization of the solenoid valve S2. This achieves quick draining that is faster than that drained via the linear solenoid valve SLC2, so that the brake B-2is released quickly. Note that the hydraulic pressure in the oil path m is discharged from the drain port EX of the C-2relay valve23repositioned in the left-hand-half position and the hydraulic pressure in the oil paths c1, c2is discharged from the drain port EX of the linear solenoid valve SLC2.

[Operation in the Forward Second Speed]

When, for example, the control unit determines the forward second speed from the condition of the forward first speed, the linear solenoid valve SLB1is controlled for pressure regulation through the electric command from the control unit, while maintaining the pressure regulation condition for the linear solenoid valve SLC1with the solenoid valve S1energized and the solenoid valve S2deenergized in the same manner as in the forward first speed (excepting during the engine braking).

Specifically, when the linear solenoid valve SLB1is controlled for pressure regulation, the control pressure PSLB1is output as the engagement pressure PB1from the output port SLB1band input to the hydraulic servo44via the oil path f1, so that the brake B-1is locked. This achieves the forward second speed, coupled with the engagement of the clutch C-1.

In addition, the check valve54and the orifice64are disposed on the oil path f1. When the engagement pressure PB1is to be supplied to the hydraulic servo44of the brake B-1, the check valve54is closed and the hydraulic pressure is supplied at a mild pace only via the orifice64. When the engagement pressure PB1is to be discharged from the hydraulic servo44, the check valve54is opened to let the engagement pressure PB1be discharged at a rapid pace as compared with the case of the supply. In addition, the engagement pressure PB1supplied to the oil path f1is input to the oil chamber34aof the B-1damper34via the oil path f2and the B-1damper34prevents pulsation of the engagement pressure PB1supplied to, and discharged from, the hydraulic servo44, and absorbs a surge pressure (a sharply fluctuating pressure), for example.

[Operation in the Forward Third Speed]

When, for example, the control unit determines the forward third speed from the condition of the forward second speed, the linear solenoid valve SLB1is closed by being deenergized and the linear solenoid valve SLC3is controlled for pressure regulation through the electric command from the control unit, while maintaining the pressure regulation condition for the linear solenoid valve SLC1with the solenoid valve S1energized and the solenoid valve S2deenergized in the same manner.

Specifically, a release control of the brake B-1is first performed through the control of the linear solenoid valve SLB1for pressure regulation; specifically, the engagement pressure PB1(control pressure PSLB1) of the hydraulic servo44of the brake B-1is controlled to be discharged from the drain port EX of the linear solenoid valve SLB1via the oil path f1, so that the brake B-1is released. Further, the other linear solenoid valve SLC3is controlled for pressure regulation from the condition of being energized to be closed to make a control pressure PSLC3to be zero. The control pressure PSLC3is output as the engagement pressure PC3from the output port SLC3band input to the hydraulic servo43via the oil path e1, so that the clutch C-3is engaged. This achieves the forward third speed, coupled with the engagement of the clutch C-1.

In addition, the check valve53and the orifice63are disposed on the oil path e1. When the engagement pressure PC3is to be supplied to the hydraulic servo43of the clutch C-3, the check valve53is closed and the hydraulic pressure is supplied at a mild pace only via the orifice63. When the engagement pressure PC3is to be discharged from the hydraulic servo43, the check valve53is opened to let the hydraulic pressure be discharged at a rapid pace as compared with the case of the supply. In addition, the engagement pressure PC3supplied to the oil path e1is input to the oil chamber33aof the C-3damper33via the oil path e2and the C-3damper33prevents pulsation of the engagement pressure PC3supplied to, and discharged from, the hydraulic servo43, and absorbs a surge pressure (a sharply fluctuating pressure), for example.

[Operation in the Forward Fourth Speed]

When, for example, the control unit determines the forward fourth speed from the condition of the forward third speed, the linear solenoid valve SLC3is closed by being deenergized and the linear solenoid valve SLC2is controlled for pressure regulation through the electric command from the control unit, while maintaining the pressure regulation condition for the linear solenoid valve SLC1with the solenoid valve S1energized and the solenoid valve S2deenergized in the same manner.

Specifically, a release control of the clutch C-3is first performed through the control of the linear solenoid valve SLC3for pressure regulation; specifically, the engagement pressure PC3(control pressure PSLC3) of the hydraulic servo43of the clutch C-3is controlled to be discharged from the drain port EX of the linear solenoid valve SLC3via the oil path e1, so that the clutch C-3is released. Further, the other linear solenoid valve SLC2is controlled for pressure regulation from the condition of being energized to be closed to make a control pressure PSLC2to be zero. The control pressure PSLC2is output as the engagement pressure PC2from the output port SLC2band input to the input port22fof the second clutch apply relay valve22via the oil path c1.

As described above, the second clutch apply relay valve22is locked in the left-hand-half position because the solenoid valve S1is energized, so that the signal pressure PS1is not being input to the oil chamber22a, and because of the engagement pressure PC1input to the oil chamber22b. The control pressure PSLC2input to the input port22fis therefore output from the output port22gas the engagement pressure PC2. The engagement pressure PC2output from the output port22gis input to the input port23bof the C-2relay valve23via the oil path c2.

In addition, because the solenoid valve S2is deenergized to place the B-2relay valve24in the left-hand-half position and the oil chamber23aand the oil path h5are drained, the C-2relay valve23is placed in the left-hand-half position by the urging force of the spring23s. The engagement pressure PC2input to the input port23bis therefore output from the output port23cand also from the output port23e. The engagement pressure PC2output from the output port23cis input to the oil chamber21dof the first clutch apply relay valve21via the oil path c5. The engagement pressure PC2, coupled with the urging force of the spring21s, places to lock the spool21pof the first clutch apply relay valve21in the left-hand-half position. At this time, the forward range pressure PDinput to the input port22evia the oil path k1is output to the oil path j with the output port21jbeing changed from the output port21i, but is shut off by the input port22hof the second clutch apply relay valve22. Additionally, because the forward range pressure PDsupplied to the oil path k1is shut off, the supply of the forward range pressure PDas a lock pressure relative to the oil chamber21cvia the oil paths k2, k3is canceled.

Note that the check valve55and the orifice65are disposed on the oil path c5. When the engagement pressure PC2is to be supplied to the oil chamber21dof the first clutch apply relay valve21, the check valve55is closed and the hydraulic pressure is supplied at a mild pace only via the orifice65. When the engagement pressure PC2is to be discharged from the oil chamber21d, the check valve55is opened to let the hydraulic pressure be discharged at a rapid pace as compared with the case of supply.

The engagement pressure PC2output from the output port23eof the C-2relay valve23is input to the hydraulic servo42via the oil path c3, so that the clutch C-2is engaged. This achieves the forward fourth speed, coupled with the engagement of the clutch C-1.

Further, as described above, the check valve52and the orifice62are disposed on the oil path c2. In the same manner as in the engine braking of the forward first speed, when the engagement pressure PC2is to be supplied to the hydraulic servo42of the clutch C-2, the check valve52is closed and the hydraulic pressure is supplied at a mild pace only via the orifice62. At the time of discharge of the engagement pressure PC2from the hydraulic servo42, the check valve52is opened to let the hydraulic pressure be discharged at a rapid pace as compared with the case of the supply. In addition, the engagement pressure PC2supplied to the oil path c2is input to the oil chamber32aof the C2-B2damper32via the oil path c4and the C2-B2damper32prevents pulsation of the engagement pressure PC2supplied to, and discharged from, the hydraulic servo42, and absorbs a surge pressure (a sharply fluctuating pressure), for example.

[Operation in the Forward Fifth Speed]

When, for example, the control unit determines the forward fifth speed from the condition of the forward fourth speed, the linear solenoid valve SLC1is closed by being deenergized and the linear solenoid valve SLC3is controlled for pressure regulation through the electric command from the control unit, while maintaining the pressure regulation condition for the linear solenoid valve SLC2with the solenoid valve S1energized and the solenoid valve S2deenergized in the same manner.

Specifically, a release control of the clutch C-1is first performed through the control of the linear solenoid valve SLC1for pressure regulation; specifically, the engagement pressure PC1(control pressure PSLC1) of the hydraulic servo41of the clutch C-1is controlled to be discharged from the drain port EX of the linear solenoid valve SLC1via the oil paths b1, b2, so that the clutch C-1is released. Further, the other linear solenoid valve SLC3is controlled for pressure regulation from the condition of being energized to be closed to make a control pressure PSLC3to be zero in the same manner as in the forward third speed. The control pressure PSLC3is output as the engagement pressure PC3from the output port SLC3band input to the hydraulic servo43via the oil path e1, so that the clutch C-3is engaged. This achieves the forward fifth speed, coupled with the engagement of the clutch C-2.

[Operation in the Forward Sixth Speed]

When, for example, the control unit determines the forward sixth speed from the condition of the forward fifth speed, the linear solenoid valve SLC3is closed by being energized and the linear solenoid valve SLB1is controlled for pressure regulation through the electric command from the control unit, while maintaining the pressure regulation condition for the linear solenoid valve SLC2with the solenoid valve S1energized and the solenoid valve S2deenergized in the same manner.

Specifically, a release control of the clutch C-3is first performed through the control of the linear solenoid valve SLC3for pressure regulation; specifically, the engagement pressure PC3(control pressure PSLC3) of the hydraulic servo43of the clutch C-3is controlled to be discharged from the drain port EX of the linear solenoid valve SLC3via the oil path e1, so that the clutch C-3is released. Further, the other linear solenoid valve SLB1is energized and controlled for pressure regulation from the condition of being deenergized to be closed to make a control pressure PSLB1to be zero in the same manner as in the forward second speed. The control pressure PSLB1is output as the engagement pressure PB1from the output port SLB1band input to the hydraulic servo44via the oil path f1, so that the brake B-1is engaged. This achieves the forward sixth speed, coupled with the engagement of the clutch C-2.

[Operation in Shift from D to N Range]

Assume, for example, that the driver thereafter decelerates the vehicle and brings the vehicle to a stop at the forward first speed through downshifting thereto according to the vehicle speed. When the shift lever is then placed in the N range position from the D range position, the forward range pressure output port81bof the manual shift valve81(seeFIG. 5) is shut off from the input port81a, while the forward range pressure output port81band the drain port EX are brought into communication with each other, specifically, the forward range pressure PDis drained.

At the same time, a shift lever sensor (not shown) detects that the shift lever is in the N range position and the control unit determines the N range based on the shift lever position. Then, the linear solenoid valve SLC2and the linear solenoid valve SLC3are first energized and the linear solenoid valve SLB1is deenergized to drain the control pressures PSLC2, PSLC3, PSLB1thereof to zero pressures (the non-output state). Specifically, the hydraulic pressure of each of the hydraulic servos42,43,44,45is drained and the clutches C-2, C-3and the brakes B-1, B-2are released. Note that the solenoid valve S1is retained in the energized condition and the solenoid valve S2is retained in the deenergized condition; specifically, the signal pressures PS1, PS2are not output from the solenoid valves S1, S2.

The linear solenoid valve SLC1, on the other hand, is controlled for pressure regulation such that the control pressure PSLC1is gradually decreased to prevent a release shock from being produced when, for example, the clutch C-1is released rapidly. The control pressure PSLC1is thus finally drained to zero pressures (the non-output state) and the clutch C-1is released at a mild pace. When the clutch C-1is also released, the automatic transmission3is placed in the neutral condition with all clutches and brakes released.

During the release control with the linear solenoid valve SLC1, the accumulator30connected to the input port SLC1aof the linear solenoid valve SLC1via, for example, the oil path a3releases, for maintaining pressure, a hydraulic pressure accumulated during the D range to the oil paths a1, a3on a side closer to the linear solenoid valve SLC1than the orifice60. This permits a mild release control of the clutch C-1using the linear solenoid valve SLC1, which prevents a release shock from being produced during the D-N shift operation from the forward first speed condition.

[Operation in the Reverse First Speed]

If, for example, the shift lever is placed in the R range position through a shift lever operation performed by the driver, the reverse range pressure PREVfrom the reverse range pressure output port81dof the manual shift valve81(seeFIG. 5) is output as described above and the reverse range pressure PREVis input to the input port24dof the B-2relay valve24via, for example, the oil path1.

At the same time, the shift lever sensor (not shown) detects that the shift lever is in the R range position and the control unit determines the R range as the shift lever position. Then, the solenoid valve S1is retained in the energized condition and the solenoid valve S2is retained in the deenergized condition; specifically, the signal pressure PS2is not output, so that the B-2relay valve24is maintained in the left-hand-half position by the urging force of the spring24s. This causes the reverse range pressure PREVinput to the input port24cto be supplied to the hydraulic servo45of the brake B-2via the output port24gand the oil path n, so that the brake B-2is engaged.

Further, the control unit controls the linear solenoid valve SLC3for pressure regulation so that the linear solenoid valve SLC3gradually outputs the control pressure PSLC3. The control pressure PSLC3is then output as the engagement pressure PC3from the output port SLC3band input to the hydraulic servo43via the oil path e1. Specifically, the clutch C-3is engaged at a mild pace. This achieves the reverse first speed, coupled with the locking of the brake B-2.

Note that, when the N range (or the P range) is changed from the R range, the same conditions as in the N range are established. Specifically, the engagement pressure PB2of the hydraulic servo45of the brake B-2is drained via the oil path n, the B-2relay valve24, the oil path1, and the manual shift valve81(seeFIG. 5) and the engagement pressure PC3of the hydraulic servo43of the clutch C-3is drained from the linear solenoid valve SLC3.

Additionally, if the vehicle speed is detected to be a predetermined speed or more in the forward direction when, for example, the driver places the shift lever in the R range position, the control unit energizes the solenoid valve S2and keeps the linear solenoid valve SLC3in the energized condition; specifically, the B-2relay valve24is used to achieve a shutoff so that the reverse range pressure PREVis not supplied to the hydraulic servo45of the brake B-2and the engagement pressure PC3(control pressure PSLC3) is not supplied to the hydraulic servo43of the clutch C-3. This works as, what is called, a reverse inhibit function that prevents the reverse first speed from being achieved.

Operations during a solenoids-all-deenergized failure in the hydraulic control apparatus1will be described below. If all solenoid valves (the linear solenoid valve SLC1, the linear solenoid valve SLC2, the linear solenoid valve SLC3, the linear solenoid valve SLB1, the solenoid valve S1, and the solenoid valve S2) run into a deenergized failure (hereinafter referred to as “all-deenergized failure”) due to, for example, a short-circuit or an open circuit in the battery during ordinary running with the shift lever placed in the D range, the linear solenoid valve SLC1, the linear solenoid valve SLB1, and the solenoid valve S2, which are of the normally closed type, do not output any hydraulic pressure, while the linear solenoid valve SLC2, the linear solenoid valve SLC3, and the solenoid valve S1, which are of the normally open type, outputs respective hydraulic pressures.

During normal running covering from the forward first speed through the forward third speed, the first clutch apply relay valve21has the spool21plocked in the right-hand-half position by the forward range pressure PDinput to the oil chamber21cas described above. Accordingly, the forward range pressure PDoutput from the output port21iis input to the input port22eof the second clutch apply relay valve22via the oil path k1and shut off by the second clutch apply relay valve22positioned in the left-hand-half position.

If the all-deenergized failure occurs under this condition, the second clutch apply relay valve22is repositioned in the right-hand-half position by the signal pressure PS1output from the solenoid valve S1being input to the oil chamber22avia the oil paths h1, h3and the forward range pressure PDinput to the input port22eis output from the output port22dand input to the hydraulic servo41via the oil path b2, so that the clutch C-1is engaged. In addition, PSLC2(engagement pressure PC2) output from the normally open linear solenoid valve SLC2is shut off by the input port22fof the second clutch apply relay valve22repositioned in the right-hand-half position. Further, with the normally open linear solenoid valve SLC3, the line pressure PLinput to the input port SLC3ais substantially directly output as the engagement pressure PC3from the output port SLC3band input to the hydraulic servo43via the oil path e1, so that the clutch C-3is engaged. This engages the clutch C-1and the clutch C-3to achieve the forward third speed (seeFIG. 2). Specifically, the running condition by the forward third speed is achieved when the all-deenergized failure occurs during running from the forward first speed to the forward third speed.

During normal running covering from the forward fourth speed through the forward sixth speed, the engagement pressure PC2of the clutch C-2is input, as described above, to the oil chamber21dof the first clutch apply relay valve21via the oil path c1, the second clutch apply relay valve22, the oil path c2, the C-2relay valve23, and the oil path c5, so that the spools21p,21qare locked in the left-hand-half position. Consequently, the forward range pressure PDoutput from the output port21jis input to the input port22hof the second clutch apply relay valve22via the oil path j and thus shut off by the second clutch apply relay valve22positioned in the left-hand-half position.

If the all-deenergized failure occurs under this condition, the second clutch apply relay valve22is repositioned in the right-hand-half position by the signal pressure PS1output from the solenoid valve S1being input to the oil chamber22avia the oil paths h1, h3; and the solenoid valve S2is deenergized to keep the B-2relay valve24in the left-hand-half position, which results in the oil path h4being shut off, so that the signal pressure PS1of the solenoid valve S1is not output to the oil path h5; as a result, the C-2relay valve23is also kept in the left-hand-half position. The forward range pressure PDinput to the input port22hof the second clutch apply relay valve22is therefore output from the output port22gand input to the hydraulic servo42via the oil path c2, the C-2relay valve23, and the oil path c3, so that the clutch C-2is engaged. In addition, PSLC2(engagement pressure PC2) output from the normally open linear solenoid valve SLC2is shut off by the input port22fof the second clutch apply relay valve22repositioned in the right-hand-half position. The forward range pressure PDoutput to the oil path c2is, however, output also to the oil path c5via the C-2relay valve23and then input to the oil chamber21dof the first clutch apply relay valve21, so that the first clutch apply relay valve21remains locked in the left-hand-half position. Further, with the normally open linear solenoid valve SLC3, the line pressure PLinput to the input port SLC3ais substantially directly output as the engagement pressure PC3from the output port SLC3band input to the hydraulic servo43via the oil path e1, so that the clutch C-3is engaged. This engages the clutch C-2and the clutch C-3to achieve the forward fifth speed (seeFIG. 2). Specifically, the running condition by the forward fifth speed is achieved when the all-deenergized failure occurs during running from the forward fourth speed to the forward sixth speed.

When the vehicle is brought to a stop and the shift lever is temporarily placed in the N range position as the all-deenergized failure occurs during the normal running covering from the forward fourth speed through the forward sixth speed, the manual shift valve81(seeFIG. 5) suspends the output of, and drains, the forward range pressure PDand, particularly, drains the forward range pressure PDrelative to the normally open linear solenoid valve SLC2and the input port21eof the first clutch apply relay valve21. Then, the forward range pressure PDinput to the oil chamber21dvia the oil paths j, c2, c5is drained to release the lock by the forward range pressure PD. In addition, since the signal pressure PS1continuously remains output from the normally open solenoid valve S1, the first clutch apply relay valve21has the spools21p,21qrepositioned in the right-hand-half position by the signal pressure PS1input to the oil chamber21a.

Note that, under the condition of the N range having the all-deenergized failure, the line pressure PLis the source pressure and the control pressure PSLC3(engagement pressure PC3) substantially equivalent to the line pressure PLis output from the normally open linear solenoid valve SLC3, so that the clutch C-3is in the engaged condition. In addition, the clutches C-1, C-2and the brakes B-1, B-2are released, though the clutch C-3is engaged, so that the sun gear S3and the carrier CR2turn idly despite the input of reduced speed rotation of the sun gear S2. Therefore, the input shaft10and the counter gear11are substantially in the neutral condition (seeFIG. 1).

If, for example, the driver places the shift lever in the D range position again, the forward range pressure PDis output from the manual shift valve81(seeFIG. 5). The forward range pressure PDis then input to the input port21eof the first clutch apply relay valve21repositioned in the right-hand-half position. The forward range pressure PDis also output from the output port21ito the oil path k1and input to the hydraulic servo41of the clutch C-1via the input port22eand the output port22dof the second clutch apply relay valve22placed in the right-hand-half position and the oil path b2, and the clutch C-1is engaged; specifically, the same condition is established as in the all-deenergized failure during the running from the forward first speed to the forward third speed and the forward third speed is achieved. Consequently, the vehicle can be restarted even after the temporary stop following the all-deenergized failure, thus achieving the limp-home function that permits, for example, moving to a safe place or a service garage.

DESCRIPTION OF THE PRESENT INVENTION

A principal portion of the present invention will be described below with reference toFIG. 5.

In the hydraulic control apparatus1according to the embodiment of the present invention, the linear solenoid valve SLC1has the input port SLC1aconnected to the forward range pressure output port81bof the manual shift valve81via the oil paths a1, a10, a11(a first oil path). The linear solenoid valve SLB1has the input port SLB1a connected to the forward range pressure output port81bof the manual shift valve81via the oil path a5, oil paths a6, a7, a8, a9, and the oil paths a10, a11(a second oil path). Accordingly, in the embodiment of the present invention, the oil path for supplying and discharging the forward range pressure to/from the linear solenoid valve SLC1and the linear solenoid valve SLB1is shared across a portion between the forward range pressure output port81band a branch point C. At this time, the oil paths a10, a11shared therebetween are a shared oil path. Further, the oil path a1between the branch point C and the input port SLC1aof the linear solenoid valve SLC1is a first non-shared oil path and the oil paths a5, a6, a7, a8, a9between the branch point C and the input port SLB1aof the linear solenoid valve SLB1are a second non-shared oil path. In addition, the oil paths a6, a7, a8, a9between the branch point C and a point A of the second non-shared oil path are the discharge delay zone90.

The discharge delay zone90is structured to include the oil path a6, the oil path a7, the oil path8, and the oil path a9. Specifically, the oil path a6is connected at the point A to the oil path a5. The oil path a7, on which the orifice71is disposed, is connected to the oil path a6. The oil path a9is connected to the oil path a7and to the branch point C. The oil path a8is disposed to extend in parallel with the oil path a7and connected to the oil paths a6, a9. Further, the check ball72is disposed on the oil path a8. Note that the oil path a9may be connected to the oil paths a1and a11at any point other than the branch point C, as long as the point is between the linear solenoid valve SLC1and the orifice60.

In accordance with the foregoing arrangements, if, for example, the shift lever is placed in the D range position from the N range position, the forward range pressure PDis output from the forward range pressure output port81bof the manual shift valve81to the oil path a10. The forward range pressure PDis then input to the linear solenoid valve SLC1via the oil paths a10, a11, a1and to the linear solenoid valve SLB1via the oil paths a10, a11, a9, a7, a8, a6, a5, respectively. In addition, the check ball72is disposed on the oil path a8and the orifice71is disposed on the oil path a7, respectively. Accordingly, the check ball72is opened by the forward range pressure PD, so that the supply of the forward range pressure PDto the linear solenoid valve SLB1is at a rapid pace as compared with the case of the discharge. Note that, as described above, the forward range pressure PDsupplied to the oil paths a10, a11is input to the oil chamber30aof the accumulator30via the oil path a3. Then, the accumulator30stores therein the forward range pressure PDto be supplied to the linear solenoid valve SLC1and the linear solenoid valve SLB1.

After the vehicle has run, the vehicle may, for example, be decelerated and brought to a stop or made to be about to stop through downshifting to the forward second speed according to the vehicle speed. When the shift lever is then placed in the N range position from the D range position, the forward range pressure output port81bof the manual shift valve81is shut off from the input port81a, while the forward range pressure output port81band the drain port EX are brought into communication with each other, specifically, the forward range pressure PDis drained.

At the same time, the shift lever sensor (not shown) detects that the shift lever is in the N range position and the control unit determines the N range based on the shift lever position. Then, the linear solenoid valve SLC2and the linear solenoid valve SLC3are first energized and the control pressures PSLC2, PSLC3thereof are drained to zero pressures (the non-output state). Specifically, the hydraulic pressure of each of the hydraulic servos42,43,45is drained and the clutches C-2, C-3and the brake B-2are completely released.

The linear solenoid valve SLC1and the linear solenoid valve SLB1, on the other hand, are controlled for pressure regulation such that the control pressure PSLC1and the control pressure PSLB1are gradually decreased. The control pressure PSLC1and the control pressure PSLB1are thus finally drained to zero pressures (the non-output state) and the clutch C-1and the brake B-1are released at a mild pace.

During the release control with the linear solenoid valve SLC1and the linear solenoid valve SLB1, the accumulator30connected to the input port SLC1aof the linear solenoid valve SLC1and the input port SLB1aof the linear solenoid valve SLB1via, for example, the oil path a3releases, for maintaining pressure, the hydraulic pressure accumulated during the D range to the oil paths a3, a1, a9, a7, a8, a6, a5on the side closer to the linear solenoid valve SLC1than the orifice60. This permits a mild release control of the clutch C-1and the brake B-1using the linear solenoid valve SLC1and the linear solenoid valve SLB1, which prevents a release shock from being produced during the D-N shift operation from the forward second speed condition.

In a known arrangement, for example, having no discharge delay zone90, specifically, in an oil path configuration directly connecting the point A on the oil path a5with a point B on the oil path a1, the forward range pressure PDsupplied to the linear solenoid valve SLB1is rapidly drained when the shift lever is placed in the D range position from the N range position. This invites engagement of the one-way clutch F-1due to the clutch C-1left engaged, producing a shift shock by way of the forward first speed.

In this hydraulic control apparatus1, however, through the simple mechanical arrangement of the orifice71interposed in the oil path a7and the check ball72interposed in the oil path a8, the forward range pressure PDto be discharged is discharged by way of the orifice71of the oil path a7because of the check ball72disposed on the oil path a8being closed by the hydraulic pressure. This allows discharge of the forward range pressure PDin the oil paths a5, a6, a7, a8, a9supplying and discharging the hydraulic pressure of the hydraulic servo44of the brake B-1through the linear solenoid valve SLB1to be delayed relative to discharge of the forward range pressure PDin the oil path a1supplying and discharging the hydraulic pressure of the hydraulic servo41of the clutch C-1through the linear solenoid valve SLC1.

Consequently, in, for example, the forward second speed, release of the brake B-1can be delayed relative to release of the clutch C-1when the manual shift valve81is placed in the N range from the D range based on the shift lever operation. This eliminates the engagement of the one-way clutch F-1due to the clutch C-1left engaged when, for example, the brake B-1is released before the clutch C-1. This allows the N range to be directly changed from the forward second speed without going through the forward first speed from the forward second speed. This prevents a shift shock from being produced when the N range is changed from the D range, contributing to a better shift feeling.

Further, the accumulator30is connected to the oil paths a10, a11(the shared oil path) at a point closer to the side of the linear solenoid valve SLC1than the orifice60. This not only, upon change of the N range from the D range, prevents a sudden release shock of the clutch C-1from occurring as a result of a sudden discharge of, for example, the forward range pressure PDusing the hydraulic pressure accumulated in the accumulator30, but also delays the release of the clutch C-1than the release of the brake B-1.

The foregoing has been described for the case in which the N range is changed from the D range. Nonetheless, the forward range pressure PDis drained likewise even in a case in which the R range or the P range is changed from the D range. Understandably, the present invention that delays the release of the brake B-1is also effective even in the case of changing from the D range to the R range to establish the reverse first speed, since the reverse first speed is established after being temporarily in the neutral condition.

The embodiment of the present invention described heretofore has been described as an exemplary case in which the hydraulic control apparatus1of the automatic transmission is applied to the automatic transmission3capable of achieving the forward six speeds and the reverse one speed. The automatic transmission3is not the only one to which the embodiment of the present invention can be applied; rather, the automatic transmission may be of any type as long as the type achieves a shift speed higher than that achieved by the engagement of the clutch C-1and the one-way clutch by the engagement of the clutch C-1and another friction engagement element (a clutch or a brake). The present invention is useful even in a case, in which, for example, the forward first speed and the forward second speed are both achieved by the engagement of the clutch C-1and the one-way clutch (e.g. F-1or F-2) and the forward third speed is achieved by the engagement of the clutch C-1and another friction engagement element (e.g. C-3), and the shift is made from D to N range in the condition of the forward third speed.

The embodiment of the present invention described heretofore has been described as having the orifice71and the check ball72as the delay mechanism. Discharge of the hydraulic pressure may nonetheless be delayed only through an electric control using, for example, a linear solenoid valve. In this case, a control mechanism issuing an electric control command corresponds to the delay mechanism on the assumption that a period of time is allowed during which at least the source pressure of the linear solenoid valve to be delayed is delayed.

The embodiment of the present invention described heretofore has been described for the case in which the N range is changed from the forward second speed in which the clutch C-1and the brake B-1are engaged. For example, assume a condition in which the N range is changed from the forward third speed in which the clutch C-1and the clutch C-3are engaged. Since the source pressure of the linear solenoid valve SLC3that controls the clutch C-3is the line pressure PL, in particular, the above-referenced condition can be achieved by using, as the delay mechanism, an electric control mechanism that controls pressure reduction of the control pressure PSLC3of the linear solenoid valve SLC3is delayed relative to pressure reduction of the control pressure PSLC1of the linear solenoid valve SLC1.

The embodiment of the present invention described heretofore has been described so that the discharge delay zone90is disposed across the branch point C and the point A. The discharge delay zone90may nonetheless even be disposed, for example, across the point A and the input port SLB1aof the linear solenoid valve SLB1. Specifically, the present invention can be applied as long as the discharge delay zone is disposed on the second non-shared oil path.

The hydraulic control apparatus for the automatic transmission according to the some aspects of the present invention is applicable to automatic transmissions mounted in vehicles, such as passenger cars, trucks, buses, and agricultural machinery and particularly suitable for use in an automatic transmission having a low speed achieved by engagement of a friction engagement element and a one-way clutch. For example, the hydraulic control apparatus is suitable, for example, for one that is required to prevent shock as a result of engagement of the one-way clutch from occurring.