JP4926670B2 - Hydraulic control device for automatic transmission - Google Patents

Description

  The present invention relates to a hydraulic control device for an automatic transmission including a hydraulically controlled friction engagement element that is released when a select lever is switched from a drive range to a neutral range.

  In general, in a multi-speed automatic transmission or the like, switching to each gear is performed by selectively disengaging a plurality of friction engagement elements such as clutches and brakes through transmission oil (ATF) hydraulic control. It is realized by.

  By the way, the viscosity of ATF used in this type of automatic transmission varies greatly with temperature. That is, ATF has a high viscosity at low temperatures and is difficult to drain. Therefore, for example, when switching from the drive range (D range) to the neutral range (N range), the drain time of the fastening hydraulic pressure with respect to the friction engagement element may become long, and dragging of the friction engagement element may occur.

  On the other hand, if the drain oil passage is designed based on the viscosity of the ATF at a low temperature, the friction engagement element is instantaneously released by a rapid drain of the fastening hydraulic pressure at a high temperature of the ATF, and a large torque shock (D− N select shock) may occur.

To cope with this, for example, Patent Document 1 discloses that a solenoid valve capable of introducing oil into the clutch at the first shift stage of the D range and draining the oil from the clutch at the N range, and bypassing the solenoid valve The drain oil path that can drain the clutch oil, the position is switched according to the D range and N range switching, the drain oil path is closed at the D range position, and the drain oil path at the N range position In an automatic transmission equipped with a manual valve that opens the valve, when the oil temperature detected in the N range is high, the drain of the clutch oil is controlled to the decreasing side through the solenoid valve, and to the increasing side when the oil temperature is low. Technology is disclosed.
Japanese Patent Laid-Open No. 10-252876

  However, as in the technique disclosed in Patent Document 1 described above, even when the drain opening degree of the engagement hydraulic pressure is controlled, the high engagement hydraulic pressure (clutch pressure) needs to be drained within a predetermined time. In some cases, it is difficult to gently change the fastening hydraulic pressure in the vicinity of the region where the torque capacity becomes zero.

  The present invention has been made in view of the above circumstances. When the select lever is switched from the drive range to the neutral range, the automatic friction engagement element can be quickly released without generating a select shock. An object of the present invention is to provide a hydraulic control device for a transmission.

A hydraulic control device for an automatic transmission according to an aspect of the present invention includes a hydraulic control for an automatic transmission that includes a hydraulically controlled friction engagement element that drains a fastening hydraulic pressure when the select lever is switched from a drive range to a neutral range. A line pressure oil passage through which control oil regulated to line pressure flows, a drive range pressure oil passage connected to the hydraulic chamber of the friction engagement element, and a drain oil passage connected to the hydraulic chamber When the drive range is selected, the drive range pressure oil passage is communicated with the line pressure oil passage, and the drive range pressure oil passage is connected to the line pressure oil in conjunction with the start of the switching operation from the drive range to the neutral range. A manual valve that is disconnected from the road to open the drain, and is interposed between the hydraulic chamber, the drive range pressure oil passage, and the drain oil passage, Pressure adjusting means for controlling the communication amount of the drive range pressure oil passage and the drain oil passage to the pressure chamber to regulate the fastening hydraulic pressure supplied to the friction engagement element, and engine output detection for detecting the output state of the engine And the pressure regulating means detects the drive range pressure with respect to the hydraulic chamber when a preset low output state of the engine is detected when the friction engagement element for which the drive range is selected is engaged. The communication amount of the oil passage and the drain oil passage is controlled to a preset communication amount, and the drain oil passage is opened in conjunction with the completion of the switching operation from the drive range to the neutral range. .

  According to the hydraulic control device for an automatic transmission of the present invention, when the select lever is switched from the drive range to the neutral range, the corresponding friction engagement element can be quickly released without generating a select shock. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The drawings relate to an embodiment of the present invention, FIG. 1 is a skeleton diagram showing a main part of an automatic transmission, FIG. 2 is an explanatory diagram showing an engagement state between a shift position and a friction engagement element, and FIG. FIG. 4 is an explanatory diagram conceptually showing a hydraulic state when a forward brake is engaged by normal running control, showing a control system, FIG. 4 is an explanatory diagram conceptually showing a hydraulic state during lap control, and FIG. FIG. 6 is an explanatory diagram conceptually showing the hydraulic pressure state in the middle of the transition from the range to the N range, FIG. 6 is an explanatory diagram conceptually showing the hydraulic pressure state in the N range, and FIG. 7 is a flowchart showing the control routine of the forward brake solenoid valve; FIG. 8 is a map showing the relationship between the ATF oil temperature and solenoid current during lap control, and FIG. 9 is an explanatory diagram showing the transition of brake pressure when shifting from the D range to the N range. .

  In FIG. 1, reference numeral 1 denotes an automatic transmission connected to an engine (not shown). The automatic transmission 1 is disposed at a torque converter 16 having a lock-up clutch 15 and a rear portion of the torque converter 16. Main transmission unit 20.

  In this embodiment, the main transmission unit 20 is mainly composed of a skeleton in which three sets of planetary gears of a front planetary gear 21, a mid planetary gear 22, and a rear planetary gear 23 are connected in series. It is composed of a transmission unit with 5 forward gears and 1 reverse gear equipped with a coupling element.

  As friction engagement elements of the main transmission unit 20, a front brake (FR / B) 24 and a one-way clutch (3rdOWC) 25 are provided for the front planetary gear 21. Further, with respect to the mid planetary gear 22 and the rear planetary gear 23, an input clutch (I / C) 26, a high & low reverse clutch (H & LR / C) 27, a one-way clutch (1stOWC) 28, a direct clutch (D / C) 29, A reverse brake (REV / B) 30 and a forward brake (FWD / B) 31 are provided.

  Specifically, a front brake 24 and a one-way clutch 25 are interposed in parallel between the sun gear 21 a of the front planetary gear 21 and the case side which is a fixed member, and the carrier 21 b of the front planetary gear 21 is connected to the rear planetary gear 23. It is connected to the internal gear 23c. Further, an internal gear 21 c of the front planetary gear 21 is connected to the input shaft 2, and further connected to an internal gear 22 c of the mid planetary gear 22 via the input clutch 26.

  The mid planetary gear 22 has a forward brake 31 interposed between the sun gear 22 a and the case side, and an internal gear 22 c is connected to the carrier 23 b of the rear planetary gear 23. The carrier 22 b of the mid planetary gear 22 is connected to the output shaft 3.

  In the rear planetary gear 23, a direct clutch 29 is interposed between the sun gear 23a and the carrier 23b, and a reverse brake 30 is interposed between the carrier 23b and the case side. Further, between the sun gear 23a of the rear planetary gear 23 and the sun gear 22a of the mid planetary gear 22, a high & low reverse clutch 27 and a one-way clutch 28 are interposed in parallel.

  Each of these friction engagement elements is supplied and discharged with control oil (ATF) by a control valve body (not shown) housed in an oil pan based on a control signal from a transmission control unit (TCU) 71. Individually engaged and disengaged, as shown in FIG. 2, it is possible to obtain five forward speeds and one reverse speed.

  In FIG. 2, ◯ indicates fastening, ◎ indicates that it is involved in torque transmission at power-on, and ◇ indicates that it is involved in torque transmission during coasting. Further, Δ indicates that the hydraulic pressure is supplied but there is no effect on the output, and Δ * indicates that the engagement is performed in a predetermined vehicle speed region.

  Schematically, in the first speed of the drive (D) range, the forward brake 31 is engaged to lock the sun gear 22a of the mid planetary gear 22, and the internal gear 22c, carrier 22b, rear 22b of the front planetary gear 21 from the input shaft 2 are locked. The power is transmitted to the output shaft 3 through the internal gear 23c and the carrier 23b of the planetary gear 23 and the internal gear 22c and the carrier 22b of the mid planetary gear 22.

  In the second speed in the D range, the direct clutch 29 is engaged in addition to the forward brake 31, and the sun gear 23a and the carrier 23b of the rear planetary gear 23 rotate together to output power that is increased more than in the first speed.

  In the third speed of the D range, the forward brake 31 is released with respect to the second speed, the sun gear 22a of the mid planetary gear 22 is unlocked, and instead the high & low reverse clutch 27 is engaged, and the sun gear 22a of the mid planetary gear 22 is engaged. Is integrally rotated with the sun gear 23a and the carrier 23b of the rear planetary gear 23, the speed is increased from the second speed.

  In the fourth speed of the D range, the input clutch 26 is further engaged with the third speed, the internal gear 22c of the mid planetary gear 22 rotates integrally with the sun gear 22a, and the input shaft 2 and the output shaft 3 are directly connected. Further, in the fifth speed of the D range, the front brake 24 is engaged with the fourth speed, the sun gear 22a of the front planetary gear 21 is locked, and the rotation of the input shaft 2 is accelerated and transmitted to the output shaft 3.

  In the reverse (R) range, the sun gear 21a of the front planetary gear 21 is locked when the front brake 24 is engaged, and the internal gear 22c of the mid planetary gear 22 and the carrier 23b of the rear planetary gear 23 are locked when the reverse brake 30 is engaged. . Further, since the sun gear 22a of the mid planetary gear 22 and the sun gear 22a of the rear planetary gear 23 are connected by the high & low reverse clutch 27 being engaged, the rear planetary gear 23 reverses with respect to the front planetary gear 21, and the carrier of the mid planetary gear 22 is reversed. Reverse rotation power having a large gear ratio is output via 22 b and transmitted to the output shaft 3.

  Next, a hydraulic control system of the forward brake 31 that is engaged in the 1st and 2nd speeds of the D range and released in the N range will be described with reference to FIGS.

  As shown in the figure, the hydraulic control system of the forward brake 31 includes a manual valve 50 mechanically interlocked with the switching operation of the select lever 51 by the driver, and a drive range pressure oil path (D range pressure oil path) to the manual valve 50. And a forward brake control valve 60 (hereinafter simply referred to as a control valve) 60 connected through 56.

  In the present embodiment, a line pressure oil passage 55 is connected to the valve body 50 b of the manual valve 50. Then, ATF discharged from the oil pump 5 (see FIG. 1) and adjusted to the line pressure by a primary regulator (not shown) is introduced into the valve body 50b through the line pressure oil passage 55. Further, a D range pressure oil passage 56, a drain oil passage 57, a reverse range pressure oil passage (R range pressure oil passage) 53, and a parking range drain oil passage (P range drain oil passage) 59 are connected to the valve body 50b. ing.

  Further, the manual valve 50 has a manual valve spool 50a that moves forward and backward in the valve body 50b in conjunction with the select lever 51. Depending on the position of the manual valve spool 50a, the communication states of the oil passages 55 to 59 are changed. Switch.

  More specifically, as shown in FIGS. 3 and 4, when the select lever 51 is in the D range position, the manual valve 50 communicates the line pressure oil passage 55 with the D range pressure oil passage 56 and the R range. The pressure oil passage 58 is communicated with the P range drain oil passage 59, and the drain oil passage 57 is blocked.

  As shown in FIG. 6, when the select lever 51 is in the N range position, the manual valve 50 blocks the line pressure oil passage 55, the R range pressure oil passage 58, and the P range drain oil passage 59, and D range pressure oil passage 56 is connected to drain oil passage 57 (D range pressure oil passage 56 is drained).

  Here, as shown in FIG. 5, in the manual valve 50 of the present embodiment, the D range pressure oil passage 56 is the line pressure oil passage during the transition when the select lever 51 is switched from the D range position to the N range position. It is configured so as to be immediately shut off from 55 and to open the drain.

  In addition, description is abbreviate | omitted about the communication state of each oil path 55-59 in R range position and P range position.

  A hydraulic chamber 31a of the forward brake 31 is connected to the valve body 60b of the control valve 60 via a brake pressure oil passage 65, and a D range pressure oil passage 56 and a drain oil passage 66 are connected.

  The valve body 60b includes a spool 60a. Further, a forward brake solenoid valve (solenoid valve) 70 for supplying pilot oil pressure to the spool 60 a is connected to one end side of the valve body 60 b via a pilot pressure oil passage 67. On the other hand, a spring 60c that urges the spool 60a toward one end is built in the other end side of the valve body 60b, and a feedback pressure oil passage 65a branched from the brake pressure oil passage 65 is connected.

  The control valve 60 fully opens the D-range pressure oil passage 56 and shuts off the drain oil passage 66 in accordance with the relative relationship between the pilot oil pressure, the feedback oil pressure, and the biasing force of the spring 60c. The spool 60a is moved forward and backward from the D range pressure fully open position to the drain fully open position where the D range pressure oil passage 56 is shut off and the drain oil passage 66 is fully opened. The forward / backward movement of the spool 60a is controlled by the TCU 71 via the solenoid valve 70, so that the control valve 60 uses the line pressure as the source pressure, and the fastening hydraulic pressure P supplied to the hydraulic chamber 31a. Adjust pressure. Thus, in the present embodiment, the control valve 60, the solenoid valve 70, and the TCU 71 realize a function as a pressure adjusting unit.

  Here, the control valve 60 has a region where the spool 60a simultaneously wraps with the D range pressure oil passage 56 and the drain oil passage 66 while the spool 60a moves from the D range pressure fully open position to the drain fully open position. Is set. Even in this simultaneous lap region, a slight communication amount can be secured between the D-range pressure oil passage 56, the drain oil passage 66, and the hydraulic chamber 31a by the clearance between the spool 60a and the valve body 60b. It has become. In other words, by wrapping the spool 60a in both the passages 56 and 66 in a predetermined state, it is possible to realize throttle control equivalent to the case where an orifice is interposed in each passage 56 and 66. In this case, the throttle amount of each of the oil passages 56 and 66 can be finely adjusted by the position of the spool 60a, and the spool 60a wraps around both the passages 56 and 66 at a position biased to one end side. If there is, the throttle amount of the drain oil passage 66 is relatively larger than the throttle amount of the D-range pressure oil passage 56 (the communication amount of the drain oil passage 66 is relatively small), and the spool 60a is the other In the case of wrapping in both the passages 56 and 66 at a position biased to the end side, the throttle amount of the D range pressure oil passage 56 is relatively larger than the throttle amount of the drain oil passage 66 (D range pressure oil). The communication amount of the path 56 is relatively small).

  The solenoid valve 70 is a linear solenoid valve that generates a pilot hydraulic pressure corresponding to a control signal (solenoid current I) supplied from the TCU 71 using the line pressure supplied from the branch oil passage 55a of the line pressure oil passage 55 as a source pressure. It is configured.

  Further, the TCU 71 includes an inhibitor switch 52 for detecting a current selection position by the selection lever 51, and a throttle opening sensor 72 (engine output detecting means) for detecting a throttle opening which is one of parameters indicating an output state of the engine. Various sensors and switches such as an oil temperature sensor 73 (oil temperature detecting means) for detecting the oil temperature of the ATF are connected. In this embodiment, the inhibitor switch 52 is connected to the manual valve spool 50a, for example, and detects the signal at the corresponding select position when the select position switching operation by the select lever 51 is substantially completed. It is supposed to be. Therefore, as is clear from FIGS. 5 and 6, for example, when the select position is switched from the D range to the N range, in the manual valve 50, the communication states of the oil passages 55 to 59 are one when the switching operation is transient. In contrast, the TCU 71 recognizes a new select position at a timing when the switching operation is substantially completed, and a predetermined time lag occurs between them.

  Next, drive control of the forward brake solenoid valve 70 executed by the TCU 71 will be described with reference to the flowchart shown in FIG.

  This routine is repeatedly executed every set time. When the routine starts, the TCU 71 first selects the range currently selected through the select lever 51 based on the input signal from the inhibitor switch 52 in step S101. A determination is made regarding (select position).

  As a result, if it is determined in step S101 that the D range is selected, the TCU 71 proceeds to step S102 and checks whether the engine output is in a low output state. In the present embodiment, the TCU 71 monitors the output state of the engine based on, for example, a signal from the throttle opening sensor 72. For example, after the engine is warmed up, the throttle opening becomes substantially zero. When the engine is in the idle state, it is determined that the engine output is in the low output state.

  If it is determined in step S102 that the engine output is not in the low output state, the TCU 71 proceeds to step S105. On the other hand, if it is determined in step S102 that the engine output is in the low output state, the TCU 71 is highly likely that the vehicle is in a stopped state, and the driver switches the select lever 51 from the D range to the N range. It is determined that there is a high possibility of performing the process, and the process proceeds to step S103.

  When the process proceeds from step S102 to step S103, the TCU 71 checks whether or not the forward brake 31 is currently engaged. As a result, if it is determined in step S103 that the forward brake 31 is in the released state, the process proceeds to step S105, and if it is determined that the forward brake 31 is in the engaged state, the process proceeds to step S104.

  When the process proceeds from step S103 to step S104, the TCU 71 checks whether the ATF oil temperature is, for example, 10 ° C. or higher based on the signal from the oil temperature sensor 73. As a result, when it is determined that the ATF oil temperature is lower than 10 ° C., it is determined that the viscosity of the ATF is high and the process proceeds to step S105. When it is determined that the ATF oil temperature is 10 ° C. or higher, the ATF is It is determined that the viscosity is low, and the process proceeds to step S106.

  Then, when the process proceeds from step S102, step S103, or step S104 to step S105, the TCU 71 exits the routine after performing the normal running time control. That is, for example, the TCU 71 performs a shift determination with reference to a known shift map based on the vehicle speed and the throttle opening, and if the shift to the first speed or the second speed is determined, the forward brake 31 is engaged. When the shift to another gear stage is determined, the forward brake 31 is released. In this case, when the forward brake 31 is engaged, a sufficient torque capacity necessary for traveling is generated. Therefore, the TCU 71 increases the engagement hydraulic pressure P supplied to the hydraulic chamber 31 a by controlling the control valve 60 through the solenoid valve 70. The pressure is adjusted to a hydraulic pressure P1 (for example, 722 KPa).

  On the other hand, when the process proceeds from step S104 to step S106, the TCU 71 exits the routine after performing throttle control of the communication amount with respect to the D range pressure oil passage 56 and the drain oil passage 66. That is, the TCU 71 controls the control valve 60 through the solenoid valve 70 to perform throttle control for wrapping the spool 60a with respect to the D-range pressure oil passage 56 and the drain oil passage 66, and the fastening hydraulic pressure P supplied to the hydraulic chamber 31a. Is reduced to a set hydraulic pressure P2 (for example, 281 KPa). The set oil pressure P2 is higher than the fastening oil pressure P (torque release oil pressure P0) at which the torque capacity of the forward brake 31 becomes zero.

  Here, for example, as shown in FIG. 8, a map indicating the relationship between the ATF oil temperature and the solenoid current I during throttle control is set in the TCU 71, and the TCU 71 has a higher ATF oil temperature. Then, the solenoid current I is decreased, the spool 60a is biased to one end side, and the communication amount on the D range pressure oil passage 56 side is controlled to be small. As a result, the fastening hydraulic pressure P for the hydraulic chamber 31a is regulated to the set hydraulic pressure P2 regardless of the viscosity of the ATF.

  If it is determined in step S101 that the N range, R range, or P range is selected, the TCU 71 proceeds to step S107 and sets the solenoid current I to zero to fully open the drain oil passage 66. Thus, after releasing the engagement of the forward brake 31, the routine is exited.

  Thus, for example, as shown by a solid line in FIG. 9, when the D range is selected, the engagement hydraulic pressure P when the forward brake 31 is engaged when the engine output is other than the low output state (idle state) is high. It is controlled to P1 which is a proper fastening hydraulic pressure. That is, as shown in FIG. 3, by the control of the control valve 60 through the solenoid valve 70, the D range pressure oil passage 56 side is mainly opened with respect to the hydraulic chamber 31a, and the high-pressure fastening hydraulic pressure P1 is regulated.

  When the low output state of the engine is detected, the engagement hydraulic pressure P is controlled to the engagement hydraulic pressure P2 that is lower than P1. That is, as shown in FIG. 4, the D range pressure oil passage 56 and the drain oil passage 66 are controlled by the control of the control valve 60 through the solenoid valve 70, and the flow rate of the ATF supplied to the hydraulic chamber 31a and the hydraulic chamber 31a. The fastening hydraulic pressure P is adjusted to P2 by suppressing the flow rate of the ATF drained from.

  When the switching operation of the select lever 51 from the D range to the N range is started, the fastening hydraulic pressure P gradually decreases to a hydraulic pressure equal to or lower than the set hydraulic pressure P2. That is, as shown in FIG. 5, when the switching operation of the select lever 51 is started, the manual valve 50 is disconnected from the D range pressure oil passage 56 and the line pressure oil passage 55 and at the same time the D range pressure oil passage. The drain 56 is opened, and the supply of the line pressure to the hydraulic chamber 31a is cut off. On the other hand, when the switching operation of the select lever 51 is in transition, the N range is not detected by the inhibitor switch 52, so that the throttle control of the D range pressure oil passage 56 and the drain oil passage 66 is maintained. As a result, the ATF in the hydraulic chamber 31a is gradually drained through the D-range pressure oil passage 56 and the drain oil passage 66, and the fastening oil pressure P gradually decreases. Here, in this embodiment, each part is tuned so that the fastening hydraulic pressure P is less than the torque release hydraulic pressure P0 by the drain of the ATF at the time of the transition operation of the select lever 51.

  When the switching operation of the select lever 51 from the D range to the N range is completed, the fastening hydraulic pressure P is released at once. That is, as shown in FIG. 6, when the switching operation of the select lever 51 is completed, the selection state of the N range is detected by the inhibitor switch 52, so that the drain oil passage 66 is controlled by the control valve 60 through the solenoid valve 70. Is fully opened. At this time, the engagement hydraulic pressure P is already lower than the torque release hydraulic pressure P0, and the forward brake has no torque capacity. Therefore, even when the engagement hydraulic pressure P is released suddenly, no select shock occurs.

  According to such an embodiment, when the low output state of the engine is detected, throttle control is performed on the D-range pressure oil passage 56 and the drain oil passage 66, so that the engagement hydraulic pressure P for the forward brake 31 is normally engaged. By reducing the hydraulic pressure P1 to the set hydraulic pressure P2 and maintaining the throttle control until the switching operation of the select lever 51 is completed, the engagement hydraulic pressure P can be gradually changed in the vicinity of the torque release hydraulic pressure P0. It can be accurately prevented. Moreover, since the fastening hydraulic pressure P has decreased to the set hydraulic pressure P2 before the selection lever 51 is switched, the forward brake 31 can be quickly released when the selection lever 51 is switched.

  Here, the change of the fastening hydraulic pressure P when the throttle control is not performed on the D range pressure oil passage 56 and the drain oil passage 66 is indicated by a broken line in FIG. 9. In this case, since the hydraulic chamber 31a is released from the fastening hydraulic pressure P1 at once by the switching operation of the select lever 51, the fastening hydraulic pressure P changes abruptly in the vicinity of the torque release hydraulic pressure P0, making it difficult to suppress the selection shock.

  Of course, the friction engagement element to which the present invention is applied is not limited to the forward brake described above.

  Further, the throttling control for the D-range pressure oil passage 56 and the drain oil passage 66 is not limited to the one using the spool 60a, and, of course, an orifice or the like may be used.

  Of course, the detection of the output state of the engine is not limited to that using the throttle opening.

Skeleton diagram showing main parts of automatic transmission Explanatory drawing which shows the engagement state of a gear shift position and a friction engagement element Explanatory drawing showing the hydraulic control state of the forward brake and conceptually showing the hydraulic state when the forward brake is engaged by the normal running control Explanatory diagram conceptually showing the hydraulic state during lap control Explanatory drawing which shows notionally the oil pressure state in the middle of a shift lever shifting from D range to N range Explanatory drawing which shows the oil pressure state in N range notionally Flowchart showing control routine of forward brake solenoid valve Map showing the relationship between ATF oil temperature and solenoid current during lap control Explanatory drawing which shows transition of brake pressure when shifting from D range to N range

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Automatic transmission 20 ... Main transmission part 31 ... Forward brake (friction engagement element)
31a ... Hydraulic chamber 50 ... Manual valve 50a ... Manual valve spool 50b ... Valve body 51 ... Select lever 52 ... Inhibitor switch 55 ... Line pressure oil passage 55a ... Branch oil passage 56 ... Drive range pressure oil passage 60 ... Forward brake control valve ( Pressure regulating means)
60a ... Spool 60b ... Valve body 60c ... Spring 65 ... Brake pressure oil passage 65a ... Feedback pressure oil passage 66 ... Drain oil passage 67 ... Pilot pressure oil passage 70 ... Forward brake solenoid valve (pressure adjusting means)
71 ... Transmission control unit 72 ... Throttle opening sensor (engine output detection means)
73 ... Oil temperature sensor (oil temperature detecting means)

Claims (2)

A hydraulic control device for an automatic transmission having a hydraulically controlled frictional engagement element that drains a fastening hydraulic pressure when switching from a drive range of a select lever to a neutral range,
A line pressure oil passage through which the control oil regulated to the line pressure flows,
A drive range pressure oil passage connected to the hydraulic chamber of the friction engagement element;
A drain oil passage connected to the hydraulic chamber;
When the drive range is selected, the drive range pressure oil passage is connected to the line pressure oil passage, and the drive range pressure oil passage is connected to the line pressure oil passage in conjunction with the start of the switching operation from the drive range to the neutral range. A manual valve that shuts off and opens the drain;
Friction engagement is provided between the hydraulic chamber and the drive range pressure oil passage and the drain oil passage, and controls the communication amount of the drive range pressure oil passage and the drain oil passage to the hydraulic chamber. Pressure regulating means for regulating the fastening hydraulic pressure supplied to the element;
Engine output detecting means for detecting the output state of the engine,
The pressure adjusting means is configured to detect the drive range pressure oil path and the drain oil to the hydraulic chamber when a preset low output state of the engine is detected when the friction engagement element for which a drive range is selected is engaged. controlled aperture to a preset communication amount communication of road, the automatic transmission according to claim Rukoto to opening the drain oil passage in conjunction from the drive range to the completion of the switching operation to the neutral range Hydraulic control device. Having oil temperature detecting means for detecting the oil temperature of the control oil;
2. The hydraulic control device for an automatic transmission according to claim 1, wherein the pressure adjusting means reduces the amount of communication with the hydraulic chamber when the drive range pressure oil path is throttled as the oil temperature increases. .

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