HYDRAULIC CONTROL UNIT OF A VEHICLE DRIVE SYSTEM

Abstract

Hydraulic control unit (50) of a drive system (12) of a vehicle (10) with an automatic transmission (24) having a plurality of hydraulic actuators (C1a, 34) and an oil pump device (36; 36, 90) which is designed to pressurise a working fluid for controlling the hydraulic actuators, which comprises: a first solenoid valve (SL1) configured to generate a first hydraulic pressure (Pc1) to operate a first clutch device (C1) by operating a first hydraulic actuator (C1a) from the plurality of hydraulic actuators; a second solenoid valve (SL2) configured to generate a second hydraulic pressure (Ps1) to operate a second clutch device (D1) by operating a second hydraulic actuator (34) from the plurality of hydraulic actuators; a first oil passage (56) connected to the first solenoid valve (SL1) so that a reserve pressure for the first hydraulic pressure is applied to the first solenoid valve (SL1); a second oil passage (58) connected to the second solenoid valve (SL2) so that a reserve pressure for the second hydraulic pressure is applied to the second solenoid valve (SL2); a third oil passage (52) connected to the oil pump device (36; 36, 90) and the second oil passage (58) such that a pressure (PL) of the working fluid delivered by the oil pump device (36; 36, 90) and flowing through the third oil passage (52) is regulated to a predetermined value; a manual valve (62) provided in the first oil passage (56) and not in the second oil passage (58) so that the line pressure (PL) is applied directly to the second electromagnetic valve (SL2) without flow of the pressurized working fluid through the manual valve (62), and operated to connect and disconnect the first oil passage (56), the third oil passage (52), and a drain oil passage (60) in response to an operation of a switching device (70) manually operated by an operator of the vehicle (10), so that the first oil passage (56) is connected to the third oil passage (52) when the switching device (70) is set to a first operating position, while the first oil passage (56) is connected to the drain oil passage (60) when the switching device (70) is set to a second operating position; an accumulator (64) connected to the first oil passage (56); and a check valve (66) provided in the second oil passage (58) for preventing flow of the working fluid in a direction from the second solenoid valve (SL2) toward the third oil passage (52).

Description

Technical area

[0001] The present invention relates to a hydraulic control unit of a drive system of a vehicle with an automatic transmission and an oil pump. Background of the invention

[0002] A hydraulic control unit of a drive system of a vehicle with an automatic transmission, including a plurality of hydraulic actuators and an oil pump operable to pressurize a working fluid for controlling the hydraulic actuators, is known in the art. An example of such a hydraulic control unit for an automatic transmission is disclosed in JP 2014-202348 A. The hydraulic control unit disclosed in this document includes electromagnetic valves for generating hydraulic pressures for operating the respective hydraulic actuators by adjusting or regulating a predetermined target line pressure of a working fluid generated by the oil pump. The hydraulic control unit further includes an accumulator connected to a line pressure oil passage through which the working fluid flows at the regulated hydraulic pressure.

[0003] Furthermore, it is conceivable to provide the hydraulic control unit with a manual valve that receives the line pressure and is actuated by a vehicle operator in response to the operation of a manually actuated (or hand-operated) switching device. The switching device is actuated by a vehicle operator in response to the operation of a manually actuated switching device to selectively connect and disconnect oil passages (or oil channels). The pressurized working fluid is supplied to the above-described solenoid valves and the accumulator (or reservoir) through the manual valve. When the manually actuated switching device is moved (or engaged) to a first operating position, oil passages connected to the solenoid valves and the accumulator are kept in communication (or fluid communication) with the line pressure oil passage.When the manually operated shift device is placed in a second operating position, the oil passages connected to the solenoid valves and the accumulator are kept in communication with a drain oil passage. It is also contemplated to apply the line pressure directly to a second solenoid valve without any flow of the pressurized working fluid through the manual valve, so that the line pressure is regulated (or controlled) into a second hydraulic pressure to be applied to a second hydraulic actuator. In this case, the second hydraulic actuator is operated independently of the operating position of the manually operated shift device. However, when the manually operated shift device is switched from the second operating position to the first operating position, the line pressure may temporarily drop (or increase).reduced) due to a lower delivery rate of the pressurized working fluid from the oil pump compared to a flow rate of the working fluid into the accumulator (or reservoir) for charging the accumulator. Accordingly, the line pressure to be applied to the second solenoid valve is temporarily reduced, thereby increasing the risk that the second hydraulic actuator, driven by the second hydraulic pressure generated by the second solenoid valve, will temporarily be placed in an inadequate or undesirable operating state.

[0004] DE 10 2004 035 504 A1 discloses a control device for starting a vehicle equipped with an automatic transmission, which has an engagement element that is engaged when the vehicle starts from a standstill, which executes a neutral state control that releases the engagement element when the automatic transmission is in an operating state associated with forward travel and the vehicle is stopped, a predetermined condition being met, and which executes a neutral state cancellation control that cancels the neutral state control when a predetermined condition different from the said condition is met.In a first variant, the control device comprises: a detection means for detecting the braking state of the vehicle, and a decision means that decides, based on the braking state detected by the detection means during the cancellation of the neutral state control, to complete the cancellation of the neutral state control. In a second variant, the control device comprises: a detection means for detecting a moving state of the vehicle, and a decision means that is suitable for initiating the completion of the cancellation of the neutral state control based on the moving state determined by the detection means during the cancellation of the neutral state control. Summary of the invention

[0005] The present invention was made in view of the prior art described above. It is therefore an object of the present invention to provide a hydraulic control unit of a vehicle drive system that enables the second hydraulic actuator to be maintained in the sufficient or desired operating state even when the second hydraulic actuator is operated with the second hydraulic pressure generated by the second solenoid valve, without causing the pressurized working fluid to flow through the manual valve as a result of switching the manually operated switching device from the second operating position to the first operating position.

[0006] The above object is achieved according to claim 1; the subclaims relate to preferred embodiments of the present invention: According to a first aspect of the invention, there is provided a hydraulic control unit of a drive system of a vehicle having an automatic transmission having a plurality of hydraulic actuators and an oil pump device configured to pressurize a working fluid for controlling the hydraulic actuators, the hydraulic control unit comprising: a first solenoid valve for generating a first hydraulic pressure for operating a first hydraulic actuator among the plurality of hydraulic actuators; a second solenoid valve for generating a second hydraulic pressure for operating a second hydraulic actuator among the plurality of hydraulic actuators; a first oil passage (or oil channel) connected to the first solenoid valve so that a reserve pressure (or pressure source) for the first hydraulic pressure is applied to the first solenoid valve.a second oil passage connected to the second solenoid valve so that a reserve pressure for the second hydraulic pressure is applied to the second solenoid valve; a third oil passage connected to the oil pump device and the second oil passage so that a pressure of the working fluid delivered by the oil pump device and flowing through the third oil passage is regulated to a predetermined value; a manual valve operated to connect and disconnect the first oil passage, the third oil passage, and a drain oil passage in response to an operation of a switching device manually operated by an operator of the vehicle, so that the first oil passage is connected to the third oil passage when the switching device is set to a first operating position.switched, offset), while the first oil passage is connected to the drain oil passage when the switching device is set to a second operating position; an accumulator connected to the first oil passage; and a check valve provided in the second oil passage for preventing a flow of the working fluid in a direction from the second solenoid valve toward the third oil passage.

[0007] According to a second aspect of the invention, the hydraulic control unit according to the first aspect of the invention is provided with the oil pump device having a mechanical oil pump driven by an engine provided as a drive power supply of the vehicle to deliver the pressurized working fluid.

[0008] According to a third aspect of the invention, the hydraulic control unit according to the second aspect of the invention is provided with the oil pump device, which further comprises an electric oil pump arranged in parallel with the mechanical oil pump and driven by an oil pump drive electric motor for delivering the pressurized working fluid.

[0009] According to a fourth embodiment of the invention, the hydraulic control unit according to one of the first to third embodiments of the invention is designed to control the first hydraulic actuator for operating a first clutch device and the second hydraulic actuator for operating a second clutch device, so that an engagement effect (or an engagement process, coupling process) of the second clutch device is preferably initiated before a time of initiation of an engagement effect of the first clutch device.

[0010] According to a fifth aspect of the invention, the hydraulic control unit according to any one of the first to third aspects of the invention is configured to control the first hydraulic actuator for operating a friction clutch device and the second hydraulic actuator for operating a dog clutch, so that the friction clutch device and the dog clutch are both brought into closed (or engaged) states to establish a power transmission path through the automatic transmission.

[0011] According to a sixth embodiment of the invention, the hydraulic control unit according to one of the first five embodiments of the invention is configured to control the automatic transmission such that the automatic transmission is set or displaced into a power transmission state in which a power transmission path is formed by the automatic transmission in the first operating position of the manually operable or hand-operated switching device, and is displaced into a switch-off state in which the power transmission path is not formed by the automatic transmission in the second operating position of the manually operable switching device.

[0012] As described above, the hydraulic control unit according to the first aspect of the invention includes: the first oil passage connected to the first solenoid valve so that the first hydraulic pressure is applied to the first solenoid valve; the second oil passage connected to the second solenoid valve so that the second hydraulic pressure is applied to the second solenoid valve; the third oil passage connected to the oil pump device and the second oil passage so that the pressure of the working fluid discharged from the oil pump device and flowing through the third oil passage is regulated to the predetermined value; the manual valve operated to connect and disconnect the first oil passage, the third oil passage, and the drain oil passage depending on the operation of the switching device manually operated by the vehicle operator;such that the first oil passage is connected to the third oil passage when the switching device is set to the first operating position, while the first oil passage is connected to the drain oil passage when the switching device is set to the second operating position; the accumulator connected to the first oil passage; and the check valve provided in the second oil passage to prevent the flow of the working fluid in the direction from the second solenoid valve toward the third oil passage. Accordingly, even if the pressure of the working fluid flowing through the third oil passage drops below the above-specified predetermined value due to a flow of the working fluid into the accumulator when the switching device is switched from the second operating position to the first operating position,The check valve prevents a drop in the pre-pressure for the second hydraulic pressure to be built up by the second solenoid valve. Thus, the present hydraulic control unit makes it possible to maintain the second hydraulic actuator in the sufficient or desired operating state, even when the second hydraulic actuator is operated with the second hydraulic pressure generated by the second solenoid valve, without a flow of the pressurized working fluid through the manual valve occurring as a result of the switching of the manually operated switching device from the second operating position to the first operating position. The present hydraulic control unit makes it possible to maintain a device actuated by the second hydraulic actuator in a sufficient or desired operating state when the switching device is switched from the second operating position to the first operating position.

[0013] The hydraulic control unit according to the second aspect of the invention is provided with the oil pump device comprising the mechanical oil pump driven by the engine serving as the vehicle's power source to deliver the pressurized working fluid. In this aspect of the invention, there is a risk that the pressure of the working fluid flowing through the third oil passage cannot be quickly raised to the predetermined value when an engine idle stop control configured to temporarily stop the idle operation of the engine is terminated. However, during the execution of the engine idle stop control, the reserve pressure for the second hydraulic pressure to be generated by the second solenoid valve is maintained unchanged in the presence of the check valve.Accordingly, the device to be operated by the second hydraulic actuator can be maintained in the desired operating state after the engine idle stop control is terminated. Furthermore, the need to increase the size of the mechanical oil pump for quickly raising the hydraulic pressure in the third oil passage to the predetermined value upon termination of the engine idle stop control can be reduced.

[0014] In the hydraulic control unit according to the third aspect of the invention, the oil pump device further includes the electric oil pump arranged in parallel with the mechanical oil pump and driven by an oil pump-driving electric motor to supply the pressurized working fluid. For example, the electric oil pump can supply the pressurized working fluid even during the engine idle stop control process. On the other hand, when the switching device is operated from the second operating position to the first operating position during the engine idle stop control process, the pressure of the working fluid flowing through the third oil passage can be temporarily lowered below the predetermined value. However, the check valve prevents a drop in the pressure applied to the second solenoid valve despite the temporary drop in the pressure of the working fluid flowing through the third oil passage.This can reduce the need to increase the size of the electric oil pump to cope with the temporary drop in pressure in the third oil passage.

[0015] The hydraulic control unit according to the fourth aspect of the invention is configured to control the first hydraulic actuator for operating the first clutch device and the second hydraulic actuator for operating the second clutch device, such that the engagement action of the second clutch device is preferably initiated before the time of initiation of the engagement action of the first clutch device. Accordingly, there is a risk of a delayed switching of the first clutch device to its engaged state due to the initiation of the engagement action of the first clutch device in the engaged state of the second clutch device after the pressure of the third oil passage rises to the predetermined value following the switching of the switching device from the second operating position to the first operating position.However, the check valve provided in the present hydraulic control unit prevents a decrease in the pre-pressure applied to the second solenoid valve despite a temporary drop in the pressure of the third oil passage below the predetermined value, so that it is possible to initiate the engagement action of the first clutch device in the engaged state of the second clutch device without having to increase the pressure of the third oil passage to the predetermined value, so that the risk of delayed switching of the first clutch device to its engaged state can be reduced.

[0016] The hydraulic control unit according to the fifth aspect of the invention is configured to control the first and second hydraulic actuators to respectively operate the friction clutch device and the dog clutch, so that the friction clutch device and the dog clutch are both brought into closed states (or engaged states, engaged states) to establish the power transmission path through the automatic transmission. Accordingly, it is desirable to initiate the engagement action of the friction clutch device in the engaged state of the dog clutch, in view of a risk of failure of the dog clutch, which is to be brought into its engaged state when the engagement action of the dog clutch is initiated in the engaged state of the friction clutch device.However, the check valve provided in the present hydraulic control unit prevents a decrease in the pre-pressure applied to the second solenoid valve despite a temporary drop in the pressure of the third oil passage below the predetermined value when switching the switching device from the second operating position to the first operating position, so that it is possible to keep the second clutch device in its engaged state and thus reduce the risk of delayed switching of the first clutch device to its engaged state, even if the engagement action of the first clutch device is initiated in the closed (or engaged) state of the second clutch device.

[0017] The hydraulic control unit according to the sixth aspect of the invention is configured to control the automatic transmission such that the automatic transmission is placed in the power transmission state and the disengagement state in the respective first and second operating positions of the manually operated shifting device. Accordingly, the second hydraulic actuator is operated with the second hydraulic pressure generated by the second solenoid valve due to the pre-pressure applied to the second solenoid valve through the third and second oil passages, without flow of the pressurized working fluid through the manual valve, so that the second solenoid valve can be maintained in the sufficient or desired operating state. Short description of the drawings Fig. 1 is a schematic diagram showing an arrangement of a vehicle drive system having a hydraulic control unit constructed according to a first embodiment of the invention; Fig. 2 is a view showing portions of the hydraulic control unit associated with control hydraulic pressures applied to a friction clutch and a dog clutch, and a hydraulic pressure source device (or reserve pressure device) provided for supplying a pressurized working fluid to the hydraulic control unit; and Fig. Fig. 3 is a view showing a hydraulic control unit constructed according to a second embodiment of the present invention and a hydraulic pressure source device (or reserve pressure device) different from the first embodiment of Fig. 2 differs. Detailed description of the preferred embodiments

[0018] With reference to the drawings, preferred embodiments of the present invention will be described in detail. First embodiment

[0019] First, Fig. 1, which is a schematic view of an arrangement of a drive system 12 of a vehicle 10 provided with a hydraulic control unit 50 constructed according to a first embodiment of the present invention. As shown in Fig. 1, the vehicle drive system 12 includes an engine 14, drive wheels 16, and a power transmission device 18 disposed in a power transmission path between the engine 14 and the drive wheels 16.

[0020] The engine 14 is a vehicle drive power supply, which is a known internal combustion engine such as a gasoline engine or a diesel engine. The vehicle 10 is provided with an electronic control device 100 and an engine control device 40 including a throttle actuator, a fuel injection device, and an ignition device, which are controlled by the electronic control device 100 to control an output torque Te of the engine 14.

[0021] The power transmission device 18 includes a torque converter 22 connected to the engine 14, an automatic transmission 24 connected to the torque converter 22, a reduction gear 28 connected to an output rotary member in the form of an output gear 26 of the automatic transmission 24, and a differential gear 30 connected to the reduction gear 28. The torque converter 22, the automatic transmission 24, the reduction gear 28, and the differential gear 30 are arranged within a stationary component in the form of a housing 20 attached to a body of the vehicle 10. The power transmission device 18 further includes right and left drive shafts 32 connected to the differential gear 30.In the power transmission device 18, the driving force generated by the engine 14 is transmitted to the drive wheels 16 via the torque converter 22, the automatic transmission 24, the speed reducer 28, the differential gear 30, and the drive shafts 32, in this order of description. The aforementioned driving force corresponds to torque or power, unless otherwise distinguished.

[0022] The automatic transmission 24 has a power transmission path PT that is established when both a friction clutch C1 and a dog clutch D1 are placed in their engaged states. The friction clutch C1 is a known hydraulically actuated friction clutch device that is selectively placed in its closed (or engaged) and released (or uncoupled) states by operation of a hydraulic actuator C1a, as described with reference to Fig. 2. The dog clutch D1 is arranged in a power transmission path between the friction clutch C1 and the output gear 26 and selectively places this power transmission path into a power transmission state or a disengagement state. The dog clutch D1 is provided with a synchronous engagement mechanism S1 for synchronizing rotational movements of its input and output rotary members (or input and output rotary elements) when the dog clutch D1 is placed in its engaged state. The dog clutch D1 is selectively placed into its closed and released states by actuating a hydraulic actuator 34 provided in the automatic transmission 24.The friction clutch C1 and the dog clutch D1 are switched between their closed and released states by the respective hydraulic actuators C1a and C1b, each operated with a C1 control hydraulic pressure Pc1 and a synchronization control hydraulic pressure Ps1, as described with reference to FIG. Fig. 2. These C1 and synchronization control hydraulic pressures Pc1 and Ps1 are generated by the hydraulic control unit 50 provided for controlling the vehicle drive system 12. Thus, the automatic transmission 24 is provided with the two hydraulic actuators C1a and 34. Specifically, the hydraulic actuator C1a, provided as the first clutch device for the friction clutch C1, is a first hydraulic actuator, while the hydraulic actuator 34, provided as the second clutch device for the dog clutch D1, is a second hydraulic actuator.

[0023] When the power transmission path PT is established with both the friction clutch C1 and the dog clutch D1 in their engaged states, the automatic transmission 24 is placed in its power transmission state, in which the driving force of the engine 14 is transmitted to the driven gear 26 via the power transmission path PT. On the other hand, when the power transmission path PT is not established with at least one of the friction and dog clutches C1 and D1 in its released state, the automatic transmission 24 is placed in its cut-off state, namely, its neutral state, in which the driving force cannot be transmitted via the power transmission path PT.

[0024] The vehicle drive system 12 is provided with an oil pump device operable to pressurize a working fluid, that is, to deliver a pressurized working fluid, so that the pressurized working fluid is supplied to the hydraulic control unit 50. In the present embodiment, an MOP 36, which is a mechanical oil pump, is provided as the oil pump device. The MOP 36 is driven by the engine 14 to deliver the pressurized working fluid.

[0025] For example, the above-mentioned electronic control device 100 is a so-called microcomputer including a CPU, a ROM, a RAM, and an input / output interface. The CPU performs various controls of the vehicle 10 by implementing various input signal processing operations according to control programs stored in the ROM, using a temporary data storage function of the RAM. The various controls of the vehicle 10 include output control of the engine 14 and hydraulic controls of the operating states of the clutch devices (friction clutch C1 and dog clutch D1).

[0026] The electronic control device 100 receives output signals from various sensors provided on the vehicle 10, such as: a signal indicating an operating speed of the engine 14; a signal indicating a traveling speed of the vehicle 10; a signal indicating an operating amount of an accelerator pedal; and a signal indicating a currently selected operating position POSsh of a manually operated shifting device in the form of a shift lever 70. The electronic control device 100 generates various output signals to be applied to various devices provided on the vehicle 10, such as the engine control unit 40 and the hydraulic control unit 50. The various output signals include: engine control command signals Se for controlling the engine 14 and hydraulic control command signals Scd for controlling the operating states of the clutch devices.

[0027] The shift lever 70 has a plurality of operating positions such as a park position P, a reverse position R, a neutral position N, and a forward drive position D, one of which is selected as the currently selected operating position POSsh to place the automatic transmission 24 in a selected operating position. When the shift lever 70 is placed in the park position P, the automatic transmission 24 is placed in its neutral state in which the output gear 26 is mechanically locked to be held stationary. When the shift lever 70 is placed in the reverse drive position R, the automatic transmission 24 is placed in its reverse drive state in which the vehicle 10 can be driven in the reverse direction. When the shift lever 70 is placed in the neutral position N, the automatic transmission 24 is placed in its neutral state in which the output gear 26 is not mechanically locked.When the shift lever 70 is placed in the forward drive position D, the automatic transmission 24 is placed in its forward drive state, in which the vehicle 10 can be driven in the forward direction. In the reverse drive state and the forward drive state of the automatic transmission 24, the driving power can be transmitted through the automatic transmission 24. In the neutral state of the automatic transmission 24 engaged in the park position P or the neutral position N, the driving power cannot be transmitted through the automatic transmission 24. Both the forward drive position D and the reverse drive position R of the shift lever 70 are considered a first operating position selected to place the automatic transmission 24 in its power-transmitting state, while both the park position P and the neutral position N of the shift lever 70 are considered a second operating position selected to place the automatic transmission 24 in its power-off state.

[0028] Subsequently, reference is made to Fig. 2 as the view showing portions of the hydraulic control unit 50 assigned to control hydraulic pressures to be applied to the friction clutch C1 and the dog clutch D1, and a hydraulic pressure source device (or reserve pressure device) provided to supply the pressurized working fluid to the hydraulic control unit 50.

[0029] As in Fig. 2, the MOP 36 is operated to suck, through a strainer 82, the working fluid returned from the hydraulic control unit 50 to an oil pan 80 disposed in a lower portion of the housing 20, to pressurize the working fluid, and to discharge the pressurized working fluid into the hydraulic control unit 50 via a discharge oil passage 84. The discharge oil passage 84 is directly connected to a line pressure oil passage 52 in the hydraulic control unit 50. The working fluid having a line pressure PL flows through the line pressure oil passage 52. Thus, the pressurized working fluid discharged from the MOP 36 has the line pressure PL, which is a lead pressure to be controlled into a C1 control hydraulic pressure Pc1 and a synchronization control hydraulic pressure Ps1 for switching the operating states of the friction clutch C1 and the dog clutch D1, as described in detail below.The pressurized working fluid delivered by the MOP 36 also serves to lubricate various sections (or parts) of the power transmission device 18.

[0030] The hydraulic control unit 50 is provided with a pressure control valve 54, a C1 control solenoid valve SL1, a D1 control solenoid valve SL2, a C1 reserve pressure oil passage 56, a D1 reserve pressure oil passage 58, a drain oil passage 60, a manual valve 62, and an accumulator 64, in addition to the above-mentioned line pressure oil passage 52.

[0031] The pressure control valve 54 serves to regulate the hydraulic pressure of the pressurized working fluid delivered from the MOP 36 to the line pressure PL. Thus, the line pressure PL is a predetermined target hydraulic pressure (or desired hydraulic pressure) that is set by regulating the hydraulic pressure of the pressurized working fluid delivered from the MOP 36.

[0032] The C1 control solenoid valve SL1 is a first solenoid valve configured to generate a first hydraulic pressure in the form of a C1 control hydraulic pressure Pc1 for operating the hydraulic actuator C1a of the friction clutch C1, while the D1 control solenoid valve SL2 is a second solenoid valve configured to generate a second hydraulic pressure in the form of a D1 control hydraulic pressure Ps1 for operating the hydraulic actuator 34 of the dog clutch D1. These C1 control solenoid valves SL1 and D1 control solenoid valves SL2 are, for example, linear solenoid valves.

[0033] The C1 pre-pressure oil passage 56 is a first oil passage connected to an input port SL1in of the C1 control solenoid valve SL1 and is an oil passage for flowing the working fluid having a pre-pressure for the C1 control hydraulic pressure Pc1, namely, a C1 pre-pressure applied to the C1 control solenoid valve SL1, while the D1 pre-pressure oil passage 58 is a second oil passage connected to an input port SL2in of the D1 control solenoid valve SL2 and is an oil passage for flowing the working fluid having a pre-pressure for the synchronization control hydraulic pressure Ps1, namely, a D1 pre-pressure applied to the D1 control solenoid valve SL2. The line pressure oil passage 52 is a third oil passage to which the D1 reserve pressure oil passage 58 is connected and which is an oil passage for flowing the working fluid having the line pressure PL.The drain oil passage 60 is an oil passage open to the atmosphere through which the working fluid is discharged from the hydraulic control unit 50 and returned to the oil pan 80.

[0034] The manual valve 62 is mechanically connected to the shift lever 70 and is actuated upon (or in response to) operation of the shift lever 70 to selectively connect and disconnect the C1 reserve pressure oil passage 56, the line pressure oil passage 52 (D1 reserve pressure oil passage 58), and the drain oil passage 60. When the shift lever 70 is set to the above-specified first operating position (forward drive position D or reverse drive position R), the manual valve 62 is actuated to connect the C1 reserve pressure oil passage 56 to the line pressure oil passage 52. The first operating position is the forward driving position D, when the drive force for driving the vehicle 10 is transmitted in the forward direction, namely through the power transmission path PT which is established in the engaged states of the friction clutch C1 and the dog clutch D1.That is, when the shift lever 70 is set to the forward drive position D, the line pressure PL received by the manual valve 62 is output as the forward drive pressure PD to the C1 pre-pressure oil passage 56. The first operating position is the reverse drive position R, when the driving force for driving the vehicle 10 is transmitted in the reverse direction (or reverse direction) via the power transmission path PT. That is, when the shift lever 70 is set to the reverse drive position R, the line pressure PL received by the manual valve 62 is output as the reverse drive pressure PR to the C1 pre-pressure oil passage 56.

[0035] When the shift lever 70 is operated to the above-mentioned second operating position (parking position P or neutral position N), the manual valve 62 is operated to isolate the C1 reserve pressure oil passage 56 and the line pressure oil passage 52 from each other and to connect the C1 reserve pressure oil passage 56 to the drain oil passage 60. Specifically, when the shift lever 70 is operated to the second operating position (parking position P or neutral position N), the manual valve 62 is operated so that the working fluid having the forward drive pressure PD or the reverse drive pressure PR is discharged from the C1 reserve pressure oil passage 56 of the hydraulic control unit 50 through the drain oil passage 60.

[0036] The accumulator 64 is connected to the C1 reserve pressure oil passage 56. The accumulator 64 is a known pressure storage device provided with a spring and a sealing element for preventing leakage of the working fluid, and is configured to store and supply the pressurized working fluid. When the C1 reserve pressure in the C1 reserve pressure oil passage 56 is higher than the hydraulic pressure within the accumulator 64, the working fluid is supplied from the C1 reserve pressure oil passage 56 into the accumulator 64. When the hydraulic pressure within the accumulator 64 is higher than the C1 reserve pressure in the C1 reserve pressure oil passage 56, the working fluid is supplied from the accumulator 64 into the C1 reserve pressure oil passage 56.

[0037] Furthermore, when the shift lever 70 is shifted from the second operating position (parking position P or neutral position N) to the first operating position (forward drive position D or reverse drive position R), the accumulator 64 is automatically charged with the pressurized working fluid. During the charging process of the accumulator 64, a flow rate of the working fluid received by the hydraulic control unit 50 is likely to be greater than a flow rate of the working fluid delivered to the hydraulic control unit 50, resulting in a risk of a temporary drop in the line pressure PL. Accordingly, the D1 lead pressure applied to the D1 control solenoid valve SL2 may be temporarily reduced, posing a risk that the dog clutch D1, operated by the synchronization control hydraulic pressure Ps1 generated by the D1 control solenoid valve SL2, may temporarily enter an inadequate or undesirable operating state.For example, there is a risk that the dog clutch D1, which is intended to be held in its engaged state, will temporarily fall (or be displaced) into its disengaged state. Furthermore, when establishing the power transmission path PT with the engagement effects (or engagement processes) of the friction clutch C1 and the dog clutch D1, there is a risk that the dog clutch D1 cannot be brought into its engaged state if an engagement effect of the dog clutch D1, which is held in its disengaged state, is initiated while the friction clutch C1 is engaged.

[0038] In view of the above-described problem, the present embodiment is arranged such that the engagement action of the dog clutch D1 is preferably initiated before a time point at which an engagement action of the friction clutch C1 is initiated. Specifically, when the shift lever 70 is shifted from the second operating position to the first operating position, the engagement action of the friction clutch C1 is initiated only after the dog clutch D1, once in the released state, has been returned to its engaged state due to an increase in the line pressure PL. However, this arrangement of the present embodiment entails the risk of a delayed switching of the friction clutch C1 to its engaged state.A probability of the above-described undesirable phenomenon increases with a reduction in the size of the MOP 36 to improve the fuel efficiency of the engine 14, and is relatively high when an operating speed Ne of the engine 14 is kept relatively low to improve its fuel efficiency and reduce its operating noise.

[0039] To prevent the above-described undesirable phenomenon, the hydraulic control unit 50 is further provided with a check valve 66 in the D1 reserve pressure oil passage 58. This check valve 66 prevents the flow of the working fluid in the direction from the D1 control solenoid valve SL2 toward the line pressure oil passage 52. More specifically, the D1 reserve pressure oil passage 58 consists of an SL2-side portion 58a connected to the D1 control solenoid valve SL2 and an MOP-side portion 58b connected to the line pressure oil passage 52. The check valve 66 prevents the flow of the working fluid from the SL2-side portion 58a toward the MOP-side portion 58b.

[0040] The electronic control device 100 controls the vehicle drive system 12 to execute (or implement) a known engine idle stop control for temporarily stopping the engine 14 when a predetermined engine stop condition is met while the shift lever 70 is set, for example, in the forward drive position D. The engine stop condition is met when the vehicle 10 is held stationary with the accelerator pedal in its unapplied position and a brake pedal in an applied position. When the engine 14 is automatically stopped by the engine idle stop control, the MOP 36 is not operated to deliver the pressurized working fluid. As a result, in the absence of the check valve 66 in the hydraulic control unit 50, the dog clutch D1, which is in the engaged state, is brought into the disengaged state.Upon termination of the engine idle stop control, the line pressure PL cannot be quickly raised to a predetermined appropriate value due to a flow of the pressurized working fluid into the accumulator 64. Accordingly, the engagement action of the dog clutch D1 may be delayed due to the synchronization control hydraulic pressure Ps1 not being sufficiently high to allow the dog clutch D1 to be returned to its engaged state. To quickly raise the line pressure PL after termination of the engine idle stop control, it is necessary to increase the size of the MOP 36. In contrast, the hydraulic control unit 50 provided with the check valve 66 according to the invention does not suffer from the undesirable phenomenon described above when the engine idle stop control is executed by the electronic control device 100.

[0041] The electronic control device 100 can terminate the engine idle stop control executed by operating the shift lever 70 to the second operating position (parking position P or neutral position N) while the vehicle 10 is stopped when the shift lever 70 is returned to the first operating position (forward drive position D or reverse drive position R). In the absence of the check valve 66 in the hydraulic control unit 50, the above-mentioned undesirable phenomenon may occur, such as in the engine idle stop control executed in the forward drive position D of the shift lever 70 when the engine idle stop control is executed in response to operating the shift lever 70 to the second operating position. The present embodiment, in which the hydraulic control unit 50 is provided with the check valve 66, does not suffer from the above-mentioned undesirable phenomenon.

[0042] As described above, the hydraulic control unit 50 according to the first embodiment of the invention includes: the C1 lead pressure oil passage 56 connected to the C1 control solenoid valve SL1 so that the C1 lead pressure for the C1 control hydraulic pressure Pc1 is applied to the C1 control solenoid valve SL1; the D1 lead pressure oil passage 58 connected to the D1 control solenoid valve SL2 so that the synchronization control hydraulic pressure Ps1 is applied to the D1 control solenoid valve SL2; the line pressure oil passage 52 connected to the MOP 36 and the D1 lead pressure oil passage 58 so that the pressure PL of the working fluid discharged from the MOP 36 and flowing through the line pressure oil passage 52 is regulated to the predetermined value; the manual valve 62, which is operated to connect and disconnect the C1 reserve pressure oil passage 56, the line pressure oil passage 52 and the drain oil passage 60, depending on (orin response) to the operation of the shift lever 70 manually operated by the operator of the vehicle 10, such that the C1 reserve pressure oil passage 56 is connected to the line pressure oil passage 52 when the shift lever 70 is set to the first operating position (forward drive position D or reverse drive position R), while the C1 reserve pressure oil passage 56 is connected to the drain oil passage 60 when the shift lever 70 is set to the second operating position (park position P or neutral position N); the accumulator 64 connected to the C1 reserve pressure oil passage 56; and the check valve 66 provided in the D1 reserve pressure oil passage 58 to prevent the flow of the working fluid in the direction from the D1 control solenoid valve SL2 to the line pressure oil passage 52.Accordingly, even if the line pressure PL is lowered below the predetermined value due to a flow of the working fluid into the accumulator 64, as soon as the shift lever 70 is switched from the second operating position to the first operating position, the check valve 66 prevents a drop in the D1 reserve pressure for the synchronization control hydraulic pressure Ps1 to be generated by the D1 control solenoid valve SL2.Thus, the present hydraulic control unit 50 allows the hydraulic actuator 34 to be maintained in the sufficient or desired operating state even when the hydraulic actuator 34 is operated with the synchronization control hydraulic pressure Ps1 generated by the D1 control solenoid valve SL2 based on the D1 pre-load pressure applied thereto without a flow of the pressurized working fluid through the manual valve 62 as a result of switching the shift lever 70 from the second operating position to the first operating position. Namely, the present hydraulic control unit 50 allows the dog clutch D1 actuated by the hydraulic actuator 34 to be maintained in the sufficient or desired operating state when the shift lever 70 is switched from the second operating position to the first operating position.Furthermore, it is possible to reduce the need for enlarging (the size) the MOP 36 to cope with a temporary drop in the line pressure PL when switching the shift lever 70 from the second operating position to the first operating position while the engine idle stop control is not being executed. Furthermore, it is possible to reduce the need for increasing the operating speed Ne of the engine 14 to cope with the temporary drop in the line pressure PL, and thus it is possible to improve the fuel efficiency of the engine 14 and reduce the operating noise of the engine 14.

[0043] The present hydraulic control unit 50 is further configured such that the D1 lead pressure to be generated by the D1 control solenoid valve SL2 for the synchronization control hydraulic pressure Ps1 can be maintained unchanged in the presence of the check valve 66. Accordingly, the dog clutch D1 to be operated by the hydraulic actuator 34 can be maintained in the desired operating state after the engine idle stop control is terminated. Furthermore, it is possible to reduce the need to increase the size of the MOP 36 for the purpose of quickly raising the line pressure PL to the predetermined value upon termination of the engine idle stop control.

[0044] In addition, the present hydraulic control unit 50 is provided with the check valve 66 which prevents a drop in the D1 pre-pressure applied to the D1 control solenoid valve SL2 despite a temporary drop in the line pressure PL, so that it is possible to initiate an engagement action of the friction clutch C1 in the closed state of the dog clutch D1 without having to raise the line pressure PL to the predetermined value, so that the risk of delayed switching of the friction clutch C1 to its engaged state can be reduced.

[0045] Furthermore, the check valve 66 can prevent the drop in the D1 lead pressure applied to the D1 control solenoid valve SL2 even if the line pressure PL is temporarily lowered when the shift lever 70 is switched from its second operating position to its first operating position, so that it is possible to keep the dog clutch D1 in its engaged state and thus reduce the risk of delayed switching of the friction clutch C1 to its engaged state even if the engagement action of the friction clutch C1 is initiated in the engaged state of the dog clutch D1.

[0046] A second embodiment of the present invention will now be described. It should be understood that the same reference numerals as in the first embodiment are used to designate corresponding elements, which is not intended to be redundant. Second embodiment

[0047] In the first embodiment described above, the MOP 36 is provided as an oil pump device for supplying the pressurized working fluid to the hydraulic control unit 50. In the present second embodiment, the oil pump device includes the MOP 36 and an EOP 90, which is an electric oil pump.

[0048] It will now Fig. 3, which shows the view of the hydraulic control unit 50 according to the second embodiment of the present invention and a Fig. 2 different hydraulic pressure source devices (or reserve pressure devices). The hydraulic pressure source device includes the oil pump device. As shown in Fig.3, in the vehicle drive system 12, an oil pump drive electric motor 92 is provided as part of the hydraulic pressure source device. The EOP 90 is driven by the electric motor 92 to deliver the pressurized working fluid. The EOP 90 is arranged in parallel with the MOP 36, and the EOP 90 is connected to a discharge oil passage 94, which merges with the discharge oil passage 84 connected to the MOP 36. The discharge oil passages 84 and 94 are both connected to the line pressure oil passage 52. The EOP 90 is controlled according to an EOP control command signal Seop generated by the electronic control device 100.

[0049] The MOP 36 and EOP 90, arranged in parallel, draw the working fluid stored in the oil pan 80 through the common strainer 82, so that the pressurized working fluid is delivered from the MOP 36 and the EOP 90 to the respective discharge oil passages 84 and 94, both of which are connected to the line pressure oil passage 52 as described above. Specifically, the discharge oil passage 84 connected to the MOP 36 is directly connected to the line pressure oil passage 52, while the discharge oil passage 94 connected to the EOP 90 is connected to the line pressure oil passage 52 via an EOP check valve 96. The EOP check valve 96 is arranged in an oil passage between the discharge oil passages 84 and 94 to prevent flow of the working fluid in the direction from the discharge oil passage 84 toward the discharge oil passage 94.The EOP 90 can be operated to deliver the pressurized working fluid regardless of the operating state of the engine 14. For example, the EOP 90 is operated while the engine 14 is automatically stopped (or held at rest) in the process of engine idle stop control. The EOP 90 is temporarily operated in place of the stopped MOP 36. The EOP 90 is a comparatively small pump whose maximum discharge rate is smaller than that of the MOP 36. The pressure regulating valve 54 regulates the line pressure PL based on the pressure of the pressurized working fluid discharged (or delivered) from the MOP 36 and / or the EOP 90.

[0050] In the present second embodiment, the line pressure PL can be generated based on the pressure of the pressurized working fluid discharged from the EOP 90 while the engine idle stop control is being executed, so that the dog clutch D1 can be maintained in the engaged state even when the check valve 66 is not provided. Furthermore, the provision of the EOP 90 makes it possible to keep the accumulator 64 charged with the pressurized working fluid during the execution of the engine idle stop control in the forward drive position D of the shift lever 70. Accordingly, the risk that the line pressure PL cannot be quickly raised to the predetermined value upon termination of the engine idle stop control can be reduced. However, there is a risk of a temporary drop in the line pressure PL when the engine idle stop control is performed upon shifting the shift lever 70 from the second drive position (parking position P or [the like]).Neutral position N) to the first operating position (forward drive position D or reverse drive position R) is terminated during the process of the engine idle stop control executed in the second operating position of the shift lever 70. This temporary drop in the line pressure PL also occurs when the shift lever 70 is switched from the second operating position to the first operating position during operation of the engine 14. However, the hydraulic control unit 50 according to the second embodiment is also provided with the check valve 66, so that the undesirable phenomenon that the dog clutch D1 is temporarily placed in the released state due to a temporary drop in the D1 lead pressure applied to the D1 control solenoid valve SL2 can be avoided.

[0051] As described above, the hydraulic control unit 50 according to the second embodiment of the invention is provided with the oil pump device, which further includes the EOP 90 arranged in parallel with the MOP 36 and cooperating with the MOP 36 to supply the pressurized working fluid. For example, the EOP 90 may supply the pressurized working fluid even during the engine idle stop control process. However, the pressure of the working fluid flowing through the third oil passage may be temporarily lowered below the predetermined value when the switching device is operated from the second operating position to the first operating position during the engine idle stop control process.Furthermore, the check valve 66 prevents the D1 pre-pressure applied to the D1 control solenoid valve SL2 from dropping below the predetermined value despite the temporary drop in the line pressure PL when the shift lever 70 is shifted from the second operating position to the first operating position in the engine idle stop control sequence. This can reduce the need to increase the size of the EOP 90 to cope with the temporary drop in the line pressure PL.

[0052] While the preferred embodiments of the present invention have been described in detail with reference to the drawings, it should be understood that the present invention may be embodied in other ways.

[0053] In the illustrated embodiments, the hydraulic control unit 50 is designed to control a plurality of hydraulic actuators in the form of the hydraulic actuator C1a for the friction clutch C1 and the hydraulic actuator 34 for the dog clutch D1. However, the hydraulic control unit according to the invention is also applicable to a plurality of any other hydraulic actuators, for example, to hydraulic actuators for a plurality of friction clutch devices such as friction clutches or brakes, or to hydraulic actuators each designed to generate a thrust force to change an effective width of a groove as defined by and between stationary and movable rotating members or rotating elements of a corresponding one of a pair of such pulleys of a known continuously variable transmission of a belt or chain type.In other words, the automatic transmission with the plurality of hydraulic actuators can be: a step-variable (or continuously variable) automatic transmission with a plurality of operating positions selectively constructed with engagement effects (or engagement operations, clutch engagement operations) of selected combinations of a plurality of clutch devices, or an automatic transmission with a first power transmission path through which input and output rotary members (or input and output rotary elements) are connected to each other via a transmission, and with a second power transmission path through which the input and output rotary members are connected to each other via a continuously variable transmission constructed as described above.For example, the first power transmission path is established with engagement effects of a first friction clutch device and a dog clutch, while the second power transmission path is established with an engagement effect of a second friction clutch device arranged in series with the continuously variable transmission.

[0054] In the illustrated embodiments, the pressure of the pressurized working fluid delivered by the MOP 36 and / or the EOP 90 is regulated to the line pressure PL. However, the line pressure PL is further regulated to a predetermined modulator pressure (or converter pressure) by a modulator valve (or throttle valve).

[0055] In the illustrated first embodiment, the MOP 36 is provided as the oil pump device for conveying the pressurized working fluid to the hydraulic control unit 50. In the illustrated second embodiment, the MOP 36 and the EOP 90 are provided as the oil pump device. However, the oil pump device provided for conveying the pressurized working fluid to the hydraulic control unit 50 can be replaced by any other arrangement (or configuration), for example, by an oil pump device having at least the EOP 90.

[0056] In the illustrated embodiments, the manual valve 62 is mechanically connected to the shift lever 70c. However, the manual valve 62 can be replaced by a manual valve that is not mechanically connected to the shift lever 70c. In this case, the manual valve is moved into a selected one of its operating positions by an actuator that is electrically controlled according to the currently selected operating position POSsh of the shift lever 70c.

[0057] Furthermore, it is to be understood that the present invention may be embodied with various changes and modifications as would be apparent to those skilled in the art. List of reference symbols 12 (Vehicle) drive system 14 Motor (drive power supply) 24 automatic transmissions 34 hydraulic actuator (second hydraulic actuator) 36 MOP (mechanical oil pump) 50 hydraulic control unit 52 Line pressure oil passage (third oil passage) 56 C1-Pre-pressure oil passage (first oil passage) 58 D1-Pre-pressure oil passage (second oil passage) 60 Drain oil passage 62 manual valve 64 accumulator 66 Check valve 70 gear lever (manually operated gearshift device) 90 EOP (electric oil pump) 92 Electric motor (oil pump drive electric motor) C1 Friction clutch (first clutch device; friction clutch device) C1a hydraulic actuator (first hydraulic actuator) D1 Claw coupling (second coupling device Pc1 C1-Control hydraulic pressure (first hydraulic pressure) Ps1 Synchronization control hydraulic pressure (second hydraulic pressure) PL line pressure (predetermined hydraulic pressure) PT power transmission path SL1 C1 control solenoid valve (first solenoid valve) SL2 D1 control solenoid valve (second solenoid valve)

Claims

[1] Hydraulic control unit (50) of a drive system (12) of a vehicle (10) with an automatic transmission (24) having a plurality of hydraulic actuators (C1a, 34) and an oil pump device (36; 36, 90) which is configured to pressurize a working fluid for controlling the hydraulic actuators, which has: a first solenoid valve (SL1) which is configured to generate a first hydraulic pressure (Pc1) in order to operate a first coupling device (C1) from the plurality of hydraulic actuators by operating a first hydraulic actuator (C1a); a second solenoid valve (SL2) configured to generate a second hydraulic pressure (Ps1) to operate a second coupling device (D1) from the plurality of hydraulic actuators by operating a second hydraulic actuator (34); a first oil passage (56) which is connected to the first solenoid valve (SL1) so that a holding pressure for the first hydraulic pressure is applied to the first solenoid valve (SL1); a second oil passage (58) which is connected to the second solenoid valve (SL2) so that a holding pressure for the second hydraulic pressure is applied to the second solenoid valve (SL2); a third oil passage (52) which is connected to the oil pump device (36; 36, 90) and the second oil passage (58) in such a way that a pressure (PL) of the working fluid pumped by the oil pump device (36; 36, 90) and flowing through the third oil passage (52) is regulated to a predetermined value; a manual valve (62) provided in the first oil passage (56) and not in the second oil passage (58), so that the line pressure (PL) is applied directly to the second solenoid valve (SL2) without any flow of pressurized working fluid through the manual valve (62), and is operated to connect and disconnect the first oil passage (56), the third oil passage (52) and a drain oil passage (60), depending on the operation of a switching device (70) manually operated by a vehicle operator (10), such that the first oil passage (56) is connected to the third oil passage (52) when the switching device (70) is set to a first operating position, while the first oil passage (56) is connected to the drain oil passage (60) when the switching device (70) is set to a second operating position; an accumulator (64) connected to the first oil passage (56); and a check valve (66) provided in the second oil passage (58) to prevent flow of the working fluid in one direction from the second solenoid valve (SL2) towards the third oil passage (52). [2] Hydraulic control unit according to claim 1, wherein the oil pump device (36; 36, 90) comprises a mechanical oil pump (36) which is operated by a motor (14) provided as a drive energy supply for the vehicle (10) to pump the pressurized working fluid. [3] Hydraulic control unit according to claim 2, wherein the oil pump device (36; 36, 90) further comprises an electric oil pump (90) arranged in parallel to the mechanical oil pump (36) and driven by an oil pump drive electric motor (92) to pump the pressurized working fluid. [4] Hydraulic control unit according to one of claims 1 to 3, which is configured to control the first hydraulic actuator (C1a) for operating the first coupling device (C1) and the second hydraulic actuator (34) for operating the second coupling device (D1) in such a way that an engagement effect of the second coupling device (D1) is preferably initiated before a point in time of initiation of an engagement effect of the first coupling device (C1). [5] Hydraulic control unit according to one of claims 1 to 3, which is configured to control the first hydraulic actuator (C1a) for operating a friction clutch device as the first clutch device (C1) and the second hydraulic actuator (34) for operating a dog clutch as the second clutch device (D1) such that the friction clutch device (C1) and the dog clutch (D1) are both brought into closed states to form a power transmission path (PT) through the automatic transmission (24). [6] Hydraulic control unit according to one of claims 1 to 5, which is configured to control the automatic transmission (24) such that the automatic transmission (24) is put into a power transmission state in which a power transmission path (PT) is formed through the automatic transmission (24) in the first operating position of the manually actuated shifting device (70), and is put into a shutdown state in which the power transmission path (PT) is not formed through the automatic transmission (24) in the second operating position of the manually actuated shifting device (70).

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