JP2019148296A - Hydraulic circuit of automatic transmission - Google Patents

Abstract

An object of the present invention is to improve a situation in which a delay in engagement of a start clutch or an engagement shock is caused at the time of next driving of a vehicle due to oil drop. A hydraulic circuit constitutes a hydraulic circuit of an automatic transmission that supplies oil adjusted by a clutch solenoid valve to a forward clutch FWD / C as a starting clutch via a manual valve. The manual valve 125 is provided in the air, and the hydraulic circuit 12 includes a hydraulic pressure adjusting valve 130 that supplies oil at a set pressure to a drain oil passage 128 of the clutch solenoid valve 124. [Selection diagram] FIG.

Description

  The present invention relates to a hydraulic circuit for an automatic transmission.

  Patent Document 1 discloses a belt-type continuously variable transmission that includes a main hydraulic control system disposed at a lower portion of a transmission casing and a manual valve disposed at an upper portion of the transmission casing separately from the main hydraulic control system. Is disclosed.

JP 7-174198 A

  When the switching valve is provided in the air above the clutch pressure adjusting valve, if the supply of oil from the clutch pressure adjusting valve is stopped, the oil may fall from the switching valve in a short time. As a result, there is a possibility that the start clutch is delayed or a shock is applied when the vehicle is driven next time. In order to cope with such a situation, for example, it is conceivable to provide a pressure holding valve for preventing oil drop. However, in this case, when a long time elapses, there is a possibility that the same situation may be caused by oil dropping.

  The present invention has been made in view of such a problem, and an object of the present invention is to improve the fact that an oil drop causes a delay in engagement of a start clutch and an engagement shock when the vehicle is driven next time.

  A hydraulic circuit of an automatic transmission according to an aspect of the present invention is a hydraulic circuit of an automatic transmission that supplies oil adjusted by a clutch pressure adjusting valve to a starting clutch via a switching valve. And a hydraulic pressure adjusting valve that is provided therein and supplies oil of a predetermined pressure to a drain oil passage of the clutch pressure adjusting valve.

  According to the said aspect, the oil pressure of the oil path between a clutch pressure adjustment valve and a switching valve can be raised by supplying the oil of predetermined pressure to the drain oil path of a clutch pressure adjustment valve. For this reason, it is possible to improve the delay in engagement of the start clutch and the engagement shock due to oil spilling during the next vehicle drive.

It is a figure which shows the principal part of a vehicle. It is a schematic block diagram of a hydraulic circuit. It is a figure which shows the principal part of a hydraulic circuit. It is FIG. 1 of the figure explaining the state of the principal part of a hydraulic circuit. It is FIG. 2 of the figure explaining the state of the principal part of a hydraulic circuit. It is FIG. 3 of the figure explaining the state of the principal part of a hydraulic circuit.

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

  FIG. 1 is a diagram illustrating a main part of a vehicle. The vehicle includes an engine ENG, a transmission TM, and drive wheels DW. The engine ENG constitutes a drive source for the vehicle. The power of the engine ENG is transmitted to the drive wheels DW via the transmission TM. In other words, the transmission TM is provided in a power transmission path from the engine ENG to the drive wheel DW.

  The transmission TM is an automatic transmission, for example, a belt-type continuously variable transmission. The transmission TM has a drive (D) range, a reverse (R) range, a neutral (N) range, a parking (P) range, etc. as a range, and any one of them can be set as a set range. . The D range and the R range constitute a travel range, and the N range and the P range constitute a non-travel range. The D range constitutes the forward range, and the R range constitutes the reverse range.

  The transmission TM includes a torque converter TC, a forward / reverse switching mechanism SWM, and a variator VA. The forward / reverse switching mechanism SWM and the variator VA constitute a transmission mechanism SIM that is a transmission mechanism of the transmission TM. The transmission mechanism SIM constitutes a transmission mechanism as a whole in the transmission TM, for example.

  The torque converter TC transmits power through a fluid. In the torque converter TC, the power transmission efficiency is improved by engaging the lockup clutch LU.

  The forward / reverse switching mechanism SWM is provided in a power transmission path that connects the engine ENG and the variator VA. The forward / reverse switching mechanism SWM switches the forward / reverse travel of the vehicle by switching the rotational direction of the input rotation. The forward / reverse switching mechanism SWM includes a forward clutch FWD / C that is engaged when the D range is selected, and a reverse brake REV / B that is engaged when the R range is selected. When the forward clutch FWD / C and the reverse brake REV / B are released, the speed change mechanism SIM is in a neutral state, that is, a power cut-off state.

  Both the forward clutch FWD / C and the reverse brake REV / B are an example of an engaging element of the speed change mechanism SIM, and an example of a starting clutch.

  The variator VA constitutes a belt-type continuously variable transmission mechanism including a primary pulley PRI, a secondary pulley SEC, and a belt BLT wound around the primary pulley PRI and the secondary pulley SEC. A primary pressure Ppri is supplied to the primary pulley PRI, and a secondary pressure Psec is supplied to the secondary pulley SEC from a hydraulic circuit 12 described later.

  An oil pump 10 is provided in the transmission TM. The oil pump 10 is a mechanical oil pump that is driven by the power of the engine ENG and pumps oil to the hydraulic circuit 12. For example, the power of the engine ENG is transmitted to the oil pump 10 via a power transmission mechanism that extracts power from the impeller of the torque converter TC.

  The transmission TM further includes an ATCU 11 and a hydraulic circuit 12.

  The ATCU 11 is a controller for the transmission TM, and for example, a signal from the sensor switch group 15 is also input to the ATCU 11.

  The sensor switch group 15 includes, for example, a vehicle speed sensor that detects the vehicle speed VSP, an accelerator opening sensor that detects the accelerator opening APO, a throttle opening sensor that detects the throttle opening TVO, a brake sensor that detects the brake pedaling force BPF, an engine An engine rotation speed sensor for detecting the rotation speed NE of the ENG is included.

The sensor switch group 15 further includes, for example, a primary pressure sensor that detects the primary pressure Ppri, a secondary pressure sensor that detects the secondary pressure Psec, a PRI rotation speed sensor that detects the rotation speed Npri that is the input side rotation speed of the primary pulley PRI, SEC rotation speed sensor that detects the rotation speed Nsec that is the output side rotation speed of the secondary pulley SEC, turbine rotation speed sensor that detects the rotation speed Nt of the turbine of the torque converter TC, and oil that detects the oil temperature T _OIL of the transmission TM Includes temperature sensor.

  The rotational speed Npri is, for example, the rotational speed of the primary pulley PRI, and the rotational speed Nsec is, for example, the rotational speed of the secondary pulley SEC. The rotational speed Nt constitutes the input rotational speed of the forward clutch FWD / C, and the rotational speed Npri constitutes the output rotational speed of the forward clutch FWD / C. In addition, the ATCU 11 receives a torque information signal of the engine ENG from, for example, an engine controller for controlling the engine ENG.

  The ATCU 11 controls the transmission TM based on these signals. For example, the ATCU 11 controls the hydraulic circuit 12 based on these signals. The hydraulic circuit 12 performs hydraulic control of the lockup clutch LU, the forward clutch FWD / C, the reverse brake REV / B, the primary pulley PRI, the secondary pulley SEC, and the like based on an instruction from the ATCU 11.

  FIG. 2 is a schematic configuration diagram of the hydraulic circuit 12. The hydraulic circuit 12 includes a line pressure adjusting valve 121, a pressure reducing valve 122, a line pressure solenoid valve 123, a clutch solenoid valve 124, a manual valve 125, a line pressure oil passage 126, a secondary pressure supply oil passage 127, a drain oil passage 128, a clutch. A pressure supply oil passage 129, a hydraulic pressure adjusting valve 130, a forward clutch oil passage 131, a reverse brake oil passage 132, and the like are provided. In controlling the hydraulic circuit 12, the ATCU 11 controls, for example, the line pressure solenoid valve 123 and the clutch solenoid valve 124.

  The line pressure adjusting valve 121 adjusts the hydraulic pressure generated by the oil pump 10 to generate the line pressure PL. The oil that is relieved when the line pressure regulating valve 121 regulates the pressure is supplied to the lubrication system. The pressure reducing valve 122 is connected to the oil pump 10 via the line pressure oil passage 126 to reduce the line pressure PL. The hydraulic pressure reduced by the pressure reducing valve 122 is supplied to the line pressure solenoid valve 123, the clutch solenoid valve 124, and the hydraulic pressure adjusting valve 130 via the secondary pressure supply oil passage 127. The secondary pressure supply oil passage 127 is branched from the pressure reducing valve 122 to the line pressure solenoid valve 123, the clutch solenoid valve 124, and the hydraulic pressure adjustment valve 130.

  The line pressure solenoid valve 123 is a linear solenoid valve and generates a control hydraulic pressure corresponding to the control current. The control oil pressure generated by the line pressure solenoid valve 123 is supplied to the line pressure adjustment valve 121, and the line pressure adjustment valve 121 adjusts the pressure by operating according to the control oil pressure. For this reason, the command value of the line pressure PL can be set by the control current to the line pressure solenoid valve 123.

  The clutch solenoid valve 124 is a control valve that controls the hydraulic pressure supplied to the engagement element, and performs hydraulic control of the forward clutch FWD / C and the reverse brake REV / B. The clutch solenoid valve 124 is a linear solenoid valve, for example, and generates a clutch pressure PCL corresponding to the control current.

  The clutch pressure PCL generated by the clutch solenoid valve 124 is supplied to the forward clutch FWD / C and the reverse brake REV / B via the clutch pressure supply oil passage 129 and the manual valve 125. The clutch pressure PCL supplied to the forward clutch FWD / C constitutes the forward clutch pressure Pfwd, and the clutch pressure PCL supplied to the reverse brake REV / B constitutes the reverse brake pressure Prev. The clutch solenoid valve 124 constitutes a clutch pressure adjustment valve.

  The manual valve 125 operates in response to a driver shift operation. The manual valve 125 is driven by the operating force of the driver. The manual valve 125 may be an actuator drive type.

  When the setting range is the N range or the P range, that is, the non-traveling range, the valve position of the manual valve 125 is the P range position or the N range position, that is, the non-traveling range position corresponding to the non-traveling range of the transmission TM. When the set range is the D range or R range, that is, the travel range, the valve position of the manual valve 125 is the D range position or R range position, that is, the travel range position corresponding to the travel range of the transmission TM.

  The manual valve 125 does not perform hydraulic control of the forward clutch FWD / C and the reverse brake REV / B itself, and switches the valve position according to the shift operation, so that the hydraulic supply destination is the forward clutch FWD / C and the reverse brake REV / B. A switching valve to be switched with B is configured.

  The manual valve 125 is provided above the clutch solenoid valve 124 of the hydraulic circuit 12. The manual valve 125 is provided in this way by being provided above the main part MC of the hydraulic circuit 12.

  In addition to the clutch solenoid valve 124, the main part MC includes, for example, a line pressure adjusting valve 121, a pressure reducing valve 122, a line pressure solenoid valve 123, a line pressure oil passage 126, a secondary pressure supply oil passage 127, a drain oil passage 128, and a hydraulic pressure adjustment. A valve 130 is included. The main part MC further includes an adjustment valve for the primary pressure Ppri, an adjustment valve for the secondary pressure Psec, and the like.

  The main part MC is provided so as to be immersed in the casing of the variator VA. On the other hand, the manual valve 125 is provided in the air by being provided above the main part MC immersed in oil. By providing the manual valve 125 in the air, the degree of freedom of arrangement of the manual valve 125 is increased. The manual valve 125 can be provided outside the casing of the variator VA. The main part MC constitutes the hydraulic circuit 12 together with the manual valve 125.

  By the way, when the manual valve 125 is provided above the clutch solenoid valve 124, there is a concern that if the supply of oil from the clutch solenoid valve 124 is stopped, the oil will drop from the manual valve 125 in a short time. As a result, there is a concern that the engagement of the forward clutch FWD / C and the reverse brake REV / B may be delayed or an engagement shock may occur during the next vehicle drive.

  For this reason, in this embodiment, as shown in FIG. 2, the hydraulic pressure adjustment valve 130 is connected to the clutch solenoid valve 124 via the drain oil passage 128 of the clutch solenoid valve 124. Next, the hydraulic circuit 12 configured as described above will be further described with reference to FIGS. 3 and 4A to 4C.

  FIG. 3 is a diagram showing a main part of the hydraulic circuit 12. 4A to 4C are diagrams for explaining a state of a main part of the hydraulic circuit 12. FIG. In these drawings, the clutch solenoid valve 124, the manual valve 125, and the hydraulic pressure adjusting valve 130 are shown as the main parts of the hydraulic circuit 12 together with the forward clutch FWD / C and the reverse brake REV / B.

  As shown in FIG. 3, an oil passage is connected to each port of the clutch solenoid valve 124 as follows. That is, the secondary pressure supply oil passage 127 is connected to the input port. A clutch pressure supply oil passage 129 is connected to the output port. The clutch pressure supply oil passage 129 is also branchedly connected to the feedback port. A drain oil passage 128 is connected to the drain port.

  An oil passage is connected to each port of the manual valve 125 as follows. That is, the clutch pressure supply oil passage 129 is connected to the input port. A forward clutch oil passage 131 is connected to the first output port. A reverse brake oil passage 132 is connected to the second output port. The first drain oil passage and the second drain oil passage of the manual valve 125 are connected to the first drain port communicated with the first output port and the second drain port communicated with the second output port. .

  The manual valve 125 switches the oil path when the forward clutch FWD / C is engaged, when the reverse brake REV / B is engaged, and when the forward clutch FWD / C and the reverse brake REV / B are released. .

  When the forward clutch FWD / C is engaged, the manual valve 125 connects the clutch pressure supply oil passage 129 and the forward clutch oil passage 131, and thus the clutch pressure supply oil passage 129 and the forward clutch FWD / C.

  When the reverse brake REV / B is engaged, the manual valve 125 connects the clutch pressure supply oil passage 129 and the reverse brake oil passage 132, and thus the clutch pressure supply oil passage 129 and the reverse brake REV / B.

  When releasing the forward clutch FWD / C and the reverse brake REV / B, the manual valve 125 closes the clutch pressure supply oil passage 129. Further, in this case, the manual valve 125 includes the forward clutch oil passage 131 and the reverse brake oil passage 132 and the drain oil passage of the manual valve 125, and accordingly, the forward clutch FWD / C and the reverse brake REV / B and the first drain oil of the manual valve 125. The passage and the second drain oil passage are communicated.

  The connection state of the oil passage to each port of the hydraulic pressure regulating valve 130 is as follows. That is, the secondary pressure supply oil passage 127 is connected to the input port. A drain oil passage 128 is connected to the output port. The drain oil passage 128 is also branchedly connected to the feedback port. The drain port of the hydraulic pressure regulating valve 130 is connected to the drain port. For example, a supply oil passage other than the secondary pressure oil passage 127 such as the line pressure oil passage 126 may be connected to the input port. That is, the oil pressure adjusting valve 130 may be supplied with oil from a supply oil path other than the secondary pressure supply oil path 127 that constitutes a common supply oil path with the clutch solenoid valve 124 in the present embodiment.

  The hydraulic adjustment valve 130 is a mechanical hydraulic adjustment valve, and includes a valve body 130a, a spool 130b, and a spring 130c. The valve body 130a accommodates the spool 130b. The spool 130b switches between communication and blocking states of the oil passage in the hydraulic pressure adjustment valve 130. The spring 130c biases the spool 130b in the valve opening direction.

  In the hydraulic pressure adjusting valve 130, the spool 130b moves according to the acting force generated by the hydraulic pressure acting on the spool 130b and the urging force of the spring 130c. As a result, the hydraulic pressure adjustment valve 130 adjusts the pressure to a set pressure that is a predetermined pressure, and supplies oil at the set pressure. The set pressure is set to a pressure lower than the engagement pressure of the forward clutch FWD / C. The set pressure can be set in advance by setting the pressure receiving area of the spool 130b, the spring constant of the spring 130c, and the like.

  In the hydraulic circuit 12 configured as described above, hydraulic pressure is supplied as shown in FIGS. 4A to 4C in accordance with the state of the set range of the transmission TM and further the engagement and disengagement states of the forward clutch FWD / C. . 4A to 4C, the engine ENG is in operation and the oil pump 10 is supplying oil, that is, the line pressure PL is secured. When the transmission TM is provided with an electric oil pump, the line pressure PL may be secured by the electric oil pump with the engine ENG stopped, for example.

  FIG. 4A shows a first case where the set range is the N range or the P range. In this case, the manual valve 125 shuts off the clutch pressure supply oil passage 129 and communicates the forward clutch FWD / C and the reverse brake REV / B with the drain oil passage of the manual valve 125. As a result, the supply of oil from the clutch solenoid valve 124 is stopped, and the forward clutch FWD / C and the reverse brake REV / B are released.

  The ATCU 11 sets the command pressure of the clutch solenoid valve 124 to the drain pressure. For example, the drain pressure is zero in gauge pressure, that is, atmospheric pressure. As a result, the clutch solenoid valve 124 communicates the drain oil path 128 and the clutch pressure supply oil path 129.

  In the hydraulic adjustment valve 130, the spool 130b moves according to the applied force, and the pressure is adjusted to the set pressure. As a result, oil having a set pressure is supplied from the hydraulic pressure adjusting valve 130 to the drain oil passage 128, and the pressures in the drain oil passage 128 and the clutch pressure supply oil passage 129 become the set pressure. For this reason, even if the supply of oil from the clutch solenoid valve 124 is stopped, oil drop from the manual valve 125 is prevented.

  FIG. 4B shows a second case where the set range is the D range and the forward clutch FWD / C is engaged. In this case, the manual valve 125 connects the clutch pressure supply oil passage 129 and the forward clutch FWD / C.

  The ATCU 11 sets the instruction pressure of the clutch solenoid valve 124 to the engagement pressure. Thus, the clutch solenoid valve 124 regulates the engagement pressure, and supplies the engagement pressure oil from the clutch pressure supply oil passage 129 to the forward clutch FWD / C through the manual valve 125 and the forward clutch oil passage 131. . As a result, the forward clutch FWD / C is engaged.

  In the clutch solenoid valve 124, oil is appropriately discharged from the clutch pressure supply oil passage 129 to the drain oil passage 128 in accordance with the adjustment to the engagement pressure. Further, in the hydraulic adjustment valve 130, oil is appropriately discharged from the drain oil passage 128 to the drain oil passage of the hydraulic adjustment valve 130 in accordance with the adjustment to the set pressure. For this reason, the provision of the hydraulic pressure regulating valve 130 does not hinder the engagement of the forward clutch FWD / C. In the second case, the oil in the clutch pressure supply oil passage 129 becomes the engagement pressure, and the oil in the drain oil passage 128 becomes the set pressure.

  FIG. 4C shows a third case where the set range is the D range and the forward clutch FWD / C is released. The forward clutch FWD / C is released even when the sailing idle is performed, for example, even if the set range is the D range.

  In sailing idle, the engine ENG is in a driving state, while the transmission TM is in a neutral state. For this reason, coasting with the transmission TM in a neutral state is performed by performing sailing idle. If the line pressure PL can be secured by the electric oil pump, such inertia traveling can be performed with the engine ENG stopped.

  In the third case, as in the second case, the manual valve 125 communicates the clutch pressure supply oil passage 129 and the forward clutch FWD / C. On the other hand, the ATCU 11 sets the command pressure of the clutch solenoid valve 124 to the drain pressure. As a result, the clutch solenoid valve 124 communicates the clutch pressure supply oil passage 129 and the drain oil passage 128.

  The hydraulic adjustment valve 130 adjusts the pressure to the set pressure in such a state. For this reason, as a result of the supply of the set pressure oil from the hydraulic pressure adjusting valve 130 to the drain oil passage 128, the pressure in the drain oil passage 128, the clutch pressure supply oil passage 129, and further the forward clutch oil passage 131 becomes the set pressure. Oil drop from the valve 125 is prevented.

  As described above, the set pressure is set to a pressure lower than the engagement pressure of the forward clutch FWD / C. For this reason, even when the oil in the clutch pressure supply oil passage 129 and the forward clutch oil passage 131 reaches the set pressure, the forward clutch FWD / C is not engaged but is released.

  Next, main effects of the present embodiment will be described.

  The hydraulic circuit 12 constitutes a hydraulic circuit of an automatic transmission that supplies oil adjusted by the clutch solenoid valve 124 to the forward clutch FWD / C via the manual valve 125. The manual valve 125 is provided in the air, and the hydraulic circuit 12 includes a hydraulic pressure adjustment valve 130 that supplies oil of a set pressure to the drain oil passage 128 of the clutch solenoid valve 124.

  According to such a configuration, the oil pressure of the clutch pressure supply oil passage 129 can be increased by supplying the set pressure oil to the drain oil passage 128. For this reason, it is possible to improve the delay of engagement of the forward clutch FWD / C and the engagement shock at the time of the next vehicle driving due to oil drop (effect corresponding to claim 1).

  In the present embodiment, the hydraulic pressure adjusting valve 130 supplies oil having a pressure lower than the engagement pressure of the forward clutch FWD / C to the drain oil passage 128 as set pressure oil.

  According to such a configuration, it is possible to prevent the forward clutch FWD / C from being fastened by supplying the set pressure oil when the forward clutch FWD / C is not fastened (effect corresponding to claim 2).

  In the present embodiment, when the manual valve 125 is in the P range position or the N range position, the hydraulic pressure adjustment valve 130 supplies the set pressure oil with the indicated pressure of the clutch solenoid valve 124 being the drain pressure. By supplying the drain oil passage 128, the pressure of the clutch pressure supply oil passage 129 is set to the set pressure.

  According to such a configuration, even if the supply of oil from the clutch solenoid valve 124 is stopped to release the clutch in the P range or the N range, oil drop from the manual valve 125 can be prevented (corresponding to claim 3). Effect).

  In the present embodiment, the hydraulic pressure adjusting valve 130 uses the command pressure of the clutch solenoid valve 124 as the drain pressure when the valve position of the manual valve 125 is in the D range position and the transmission TM is coasting in the neutral state. In this state, the pressure of the clutch pressure supply oil path 129 and the forward clutch oil path 131 is set to the set pressure by supplying the set pressure oil to the drain oil path 128.

  According to such a configuration, even if the supply of oil from the clutch solenoid valve 124 is stopped along with the inertia running, the oil drop from the manual valve 125 can be prevented (effect corresponding to claim 4).

  The embodiment of the present invention has been described above. However, the above embodiment only shows a part of application examples of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. Absent.

  In the above-described embodiment, the description has been given mainly using the forward clutch FWD / C as the starting clutch. However, the starting clutch may be, for example, the reverse brake REV / B.

  In the above-described embodiment, the case where the hydraulic adjustment valve 130 is a mechanical hydraulic adjustment valve has been described. However, the hydraulic pressure adjusting valve 130 may be an electronically controlled hydraulic pressure adjusting valve such as a linear solenoid valve.

12 Hydraulic circuit 124 Clutch solenoid valve (clutch pressure adjusting valve)
125 Manual valve (switching valve)
128 Drain oil passage 129 Clutch pressure supply oil passage 130 Hydraulic adjustment valve 131 Forward clutch oil passage ENG Engine FWD / C Forward clutch (starting clutch)
REV / B Reverse brake (start clutch)
SIM transmission mechanism SWM forward / reverse switching mechanism TM transmission VA variator

Claims (4)

A hydraulic circuit of an automatic transmission that supplies oil adjusted by a clutch pressure adjusting valve to a starting clutch via a switching valve,
The switching valve is provided in the air,
A hydraulic adjustment valve that supplies oil of a predetermined pressure to a drain oil passage of the clutch pressure adjustment valve;
A hydraulic circuit for an automatic transmission. A hydraulic circuit for an automatic transmission according to claim 1,
The hydraulic pressure regulating valve supplies oil having a pressure lower than a fastening pressure of the start clutch to the drain oil passage as the oil having the predetermined pressure;
A hydraulic circuit for an automatic transmission. A hydraulic circuit for an automatic transmission according to claim 1 or 2,
When the valve position of the switching valve is in a non-traveling range position corresponding to a non-traveling range of the automatic transmission, the hydraulic pressure adjusting valve is in a state where the indicated pressure of the clutch pressure adjusting valve is a drain pressure, By supplying oil of a predetermined pressure to the drain oil passage, the pressure of the oil passage from the clutch pressure adjustment valve to the switching valve is set as the predetermined pressure.
A hydraulic circuit for an automatic transmission. A hydraulic circuit for an automatic transmission according to claim 1 or 2,
The hydraulic pressure adjusting valve is configured to control the clutch pressure adjusting valve when the valve position of the switching valve is in a travel range position corresponding to a travel range of the automatic transmission and when the automatic transmission is coasting in a neutral state. The oil pressure at the predetermined pressure is supplied to the drain oil passage in the state where the drain pressure is the drain pressure, so that the pressure in the oil passage from the clutch pressure adjusting valve to the starting clutch is the predetermined pressure.
A hydraulic circuit for an automatic transmission.

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