Abstract:
A solenoid valve device includes a solenoid valve that has a solenoid portion, a valve element that drivingly slides using electromagnetic force generated by the solenoid portion and regulates and outputs fluid pressure supplied from a fluid pressure source, a spring that biases the valve element in the sliding direction, and a spring chamber that accommodates the spring; an accumulating portion that accumulates operation fluid; an intake check valve that permits the flow of operation fluid from the accumulating portion to the spring chamber; and a discharge check valve that permits the flow of operation fluid from the spring chamber to an operation destination different from the accumulating portion.

Description:
INCORPORATION BY REFERENCE 
     The disclosure of Japanese Patent Application No. 2009-072198 filed on Mar. 24, 2009 including the specification, drawings and abstract is incorporated herein by reference in its entirety. 
     BACKGROUND 
     The present invention relates to a solenoid valve device. 
     A conventional solenoid valve device of this type includes a sleeve, a spool, and a solenoid that moves the spool in the axial direction. The sleeve has a cylindrical valve chamber that is formed with an input port, an output port, a drain port, and a feedback port as various ports through which operation oil flows in and out. The spool is a shaft-like member accommodated in the valve chamber, and has a plurality of lands with a cylindrical shape whose outer diameter is generally equal to the inner diameter of the valve chamber, as well as a communication portion that has a cylindrical shape whose outer diameter is smaller than the outer diameter of the lands and communicates between the ports. (See Japanese Patent Application Publication No. JP-A-2004-176895, for example.) 
     An electromagnetic pump has also been proposed that pressure feeds fluid by repeated excitation and non-excitation of an electromagnetic coil. (See Japanese Patent Application Publication No. JP-A-2007-126974, for example.) This electromagnetic pump has a spring member that uses elastic force to press a piston that forms a pump chamber, and is also provided with an electromagnetic coil that generates a suction force in a direction opposite the elastic force of the spring member. Non-excitation (an off state) of the electromagnetic coil causes the elastic force of the spring member to move the piston, whereby fluid is intaken. Excitation (an on state) of the electromagnetic coil causes the suction force of the electromagnetic coil to move the piston, whereby the intaken fluid is discharged. 
     SUMMARY 
     However, there may be limited mounting space for a device that incorporates the pump in addition to the solenoid valve, for example, a device that incorporates a solenoid valve (linear solenoid) for regulating a clutch pressure in a hydraulic circuit that is used to turn on and off a clutch (brake) in an automatic transmission for a vehicle and also incorporates a pump for generating fluid pressure. Therefore, the device should be downsized as much as possible. 
     A solenoid valve device of the present invention downsizes the overall device. 
     The solenoid valve device of the present invention employs the following to achieve the above. 
     A solenoid valve device of the present invention includes: a solenoid valve that has a solenoid portion, a valve element that drivingly slides using electromagnetic force generated by the solenoid portion and regulates and outputs fluid pressure supplied from a fluid pressure source, a spring that biases the valve element in the sliding direction, and a spring chamber that accommodates the spring; an accumulating portion that accumulates operation fluid; an intake check valve that permits the flow of operation fluid from the accumulating portion to the spring chamber; and a discharge check valve that permits the flow of operation fluid from the spring chamber to an operation destination different from the accumulating portion, wherein the spring chamber includes one inflow/outflow port through which operation fluid from the intake check valve enters and operation fluid from the discharge check valve exits. 
     According to the solenoid valve device of the present invention, the spring chamber of the solenoid valve includes one inflow/outflow port through which operation fluid from the intake check valve enters and operation fluid from the discharge check valve exits. Therefore, one solenoid portion can be used to function as both a pressure regulating valve and as a pump. Consequently, a more downsized device overall can be achieved compared to one that separately provides a pressure regulating valve and an electromagnetic pump. 
     In the solenoid valve device of the present invention described above, the valve element may have a hollow sleeve formed with an input port and an output port, and a spool that with the sleeve forms a pressure regulating chamber therebetween such that pressure regulation performed by sliding the spool inside the sleeve causes fluid pressure that is input from the input port to be output from the output port. The spring chamber may also be formed as a space cut off from the pressure regulating chamber. Thus, one sleeve and spool can impart function as a pressure regulating valve and as a pump, which enables further downsizing of the device. 
     The solenoid valve device of the present invention may further include: a switching valve that switches between a first state that drains operation fluid inside the spring chamber, and a second state that prohibits the drainage of operation fluid inside the spring chamber, wherein the discharge check valve is built into the switching valve. Thus, further downsizing of the device can be achieved. When the solenoid valve functions as a pressure regulating valve, the switching valve is used to drain operation fluid inside the spring chamber, which can prevent operation fluid from remaining inside the spring chamber and having an adverse impact on pressure regulating precision. In the solenoid valve device of the present invention according to this aspect, the switching valve may include: a hollow portion that is connected to an output flow passage through which operation fluid output from the valve element of the solenoid valve flows, a spring chamber flow passage that is connected to the inflow/outflow port, an operation destination flow passage that is connected to the operation destination, and a drain flow passage that drains operation fluid inside the spring chamber; a spool that slides inside the hollow portion; and the discharge intake valve disposed inside the hollow portion. When the spool is in a first position, as the first state, the output flow passage communicates with the operation destination flow passage, communication between the spring chamber flow passage and the operation destination flow passage is cut off, and the spring chamber flow passage communicates with the drain flow passage. When the spool is in a second position, as the second state, communication between the output flow passage and the operation destination flow passage is cut off, communication between the spring chamber flow passage and the drain flow passage is cut off, and the spring chamber flow passage communicates with the operation destination flow passage through the discharge check valve. In such case, the spool and the discharge check valve may also be coaxially disposed in the switching valve. 
     In the solenoid valve device of the present invention according to an aspect where the spool and the discharge check valve are coaxially disposed, the discharge check valve may include: a body wherein an axial center thereof is formed with a center hole that communicates with the spring chamber flow passage, and the body is also formed with a through hole that communicates with the center hole in the radial direction; and an opening/closing member that opens and closes the center hole. The switching valve cuts off communication between the through hole and the operation destination flow passage when the spool is in the first position, and communicates the through hole with the operation destination flow passage when the spool is in the second position. Thus, a relatively simple constitution enables the drainage of operation fluid inside the spring chamber through the switching valve. In the solenoid valve device of the present invention according to this aspect, the switching valve may communicate the spring chamber flow passage with the drain flow passage through the through hole when the spool is in the first position. In addition, the body of the discharge check valve may be formed with a reduced-diameter portion whose diameter is smaller than the diameter of the hollow portion, and the switching valve may communicate the spring chamber flow passage with the drain flow passage through the reduced-diameter portion when the spool is in the first position. Furthermore, in the solenoid valve device of the present embodiment according to these aspects, the discharge check valve may be formed such that the body integratedly operates with the spool. In such case, the body of the discharge check valve may be integratedly cast with the spool, or the discharge check valve may be installed by threadedly fastening the body to the spool and clamping a threadedly fastened portion. 
     In the solenoid valve device of the present invention according to an aspect where the discharge check valve is formed such that the body integratedly operates with the spool, the opening/closing member may be formed from a ball, and a spring that uses the spool as a spring receiver and closes the center hole by biasing the ball. Thus, the switching valve can be made smaller than one that provides a separate spring receiver. 
     The solenoid valve device of the present invention may further include: a switching valve that switches between a first state that drains operation fluid inside the spring chamber, and a second state that prohibits the drainage of operation fluid inside the spring chamber, wherein the intake check valve and the discharge check valve are formed as separate from the solenoid valve and the switching valve. In the solenoid valve device of the present invention according to this aspect, the intake check valve and the discharge check valve may also be incorporated into a valve body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a structural diagram that shows an outline of the constitution of a power transmission apparatus  20  provided with a solenoid valve device serving as an embodiment of the present invention; 
         FIG. 2  is an operation chart for an automatic speed change mechanism  28 ; 
         FIG. 3  is a collinear diagram that shows relationships among rotational speeds of rotational elements in the automatic speed change mechanism  28 ; 
         FIG. 4  is a structural diagram that shows an outline of the constitution of a hydraulic circuit  30 ; 
         FIGS. 5A and 5B  are structural diagrams that show an outline of the constitution of a switching valve  60 ; 
         FIGS. 6A and 6B  are structural diagrams that show an outline of the constitution of a switching valve  160  according to a modification; and 
         FIG. 7  is a structural diagram that shows an outline of the constitution of a hydraulic circuit  230  according to a modification. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Next, an embodiment will be used to describe a best mode for carrying out the present invention. 
       FIG. 1  is a structural diagram that shows an outline of the constitution of a vehicle  10  installed with a power transmission apparatus  20  that is provided with a solenoid valve device serving as an embodiment of the present invention.  FIG. 2  is an operation chart for an automatic speed change mechanism  28 . 
     As shown in the figures, the power transmission apparatus  20  of the embodiment is structured so as to be installed in a front-engine, front-wheel-drive (FF) type vehicle  10 . The power transmission apparatus  20  includes a torque converter  26  with a lock-up clutch, the automatic speed change mechanism  28 , and an automatic transmission electronic control unit (AT ECU)  29  that controls the overall apparatus. The torque converter  26  amplifies torque and transmits power from an engine  12 , which is subjected to an operation control executed by an engine electronic control unit (EG ECU)  16 . The automatic speed change mechanism  28  changes the speed of power from the torque converter  26  and transmits such power to wheels  18   a ,  18   b . The AT ECU  29  is communicably connected to the EG ECU  16  and a main electronic control unit (main ECU)  90  that controls the overall vehicle, and exchanges control signals and data pertaining to operating conditions. Note that the main ECU  90  is input with a shift position SP from a shift position sensor  92  that detects an operation position of a shift lever  91 ; and accelerator opening Acc from an accelerator pedal position sensor  94  that detects a depression amount of an accelerator pedal  93 ; a brake switch signal BSW from a brake switch  96  that detects depression of a brake pedal  95 ; and a vehicle speed V from a vehicle speed sensor  98 . 
     The torque converter  26  includes a pump impeller  26   a , which is connected to a crankshaft  14  of the engine  12 , and a turbine runner  26   b , which is connected to an input shaft  22  of the automatic speed change mechanism  28  and disposed facing the pump impeller  26   a . The torque converter  26  transmits torque by the pump impeller  26   a  converting engine torque into a flow of operation oil, and the turbine runner  26   b  converting this flow of operation oil into torque for the input shaft  22 . The torque converter  26  also has a built-in lock-up clutch  26   c , and engagement of the lock-up clutch  26   c  directly connects the crankshaft  14  of the engine  12  and the input shaft  22  of the automatic speed change mechanism  28  so that engine torque is directly transmitted. 
     The automatic speed change mechanism  28  has a planetary gear unit PU; three clutches C 1 , C 2 , C 3 ; two brakes B 1 , B 2 ; and a one-way clutch F 1 . The planetary gear unit PU is structured as a Ravigneaux type planetary gear mechanism, and has two sun gears S 1 , S 2  with external teeth; a ring gear R with internal teeth; a plurality of short pinion gears PS that mesh with the sun gear S 1 ; a plurality of long pinion gears PL that mesh with the sun gear S 2  and the plurality of short pinion gears PS, and also mesh with the ring gear R; and a carrier CR that is connected to and also rotatably and revolvably holds the plurality of short pinion gears PS and the plurality of long pinion gears PL. The sun gear S 1  is connected to the input shaft  22  through the clutch C 1 . The sun gear S 2  is connected to the input shaft  22  through the clutch C 3 , and the rotation of the sun gear S 2  is permitted or held stationary by the brake B 1 . The ring gear R is connected to an output shaft  24 . The carrier CR is connected to the input shaft  22  through the clutch C 2 . The rotation of the carrier CR is restricted to one direction by the one-way clutch F 1 , and also permitted or held stationary by the brake B 2 , which is provided in parallel with the one-way clutch F 1 . Note that power output to the output shaft  24  is transmitted to the wheels  18   a ,  18   b  through a counter gear and a differential gear not shown in the figures. 
     As shown in the operation chart of  FIG. 2 , the automatic speed change mechanism  28  can switch among first to fourth forward speeds and one reverse speed by combinations of engaging and disengaging the clutches C 1  to C 3  and the brakes B 1 , B 2 .  FIG. 3  is a collinear diagram that shows relationships among rotational speeds of the sun gears S 1 , S 2 , the ring gear R, and the carrier CR at each shift speed of the automatic speed change mechanism  28 . 
     Engaging and disengaging of the clutches C 1  to C 3  and the brakes B 1 , B 2  of the automatic speed change mechanism  28  is performed by a hydraulic circuit  30 .  FIG. 4  is a structural diagram that shows an outline of the constitution of the hydraulic circuit  30 .  FIGS. 5A and 5B  are structural diagrams that mainly show an outline of the constitution of a solenoid valve  50  and a switching valve  60 . As shown the figures, the hydraulic circuit  30  includes: a mechanical oil pump  34 , a regulator valve  36 , a linear solenoid SLT, a manual valve  38 , a solenoid valve  50 , and a switching valve  60 . The mechanical oil pump  34  pressure feeds operation oil through a strainer  32  based on power from the engine  12 . The regulator valve  36  regulates operation oil pressure fed from the mechanical oil pump  34  to generate a line pressure PL. The linear solenoid SLT regulates a modulator pressure PMOD that is generated from the line pressure PL through a modulator valve (not shown) and outputs the modulator pressure PMOD as a signal pressure so as to drive the regulator valve  36 . The manual valve  38  is formed with an input port  38   a  that is input with the line pressure PL, a Drive-position (D-position) output port  38   b , and a Reverse-position (R-position) output port  38   c , and the like. The manual valve  38  opens and closes each port in association with the operation of a shift lever  91 . The solenoid valve  50  functions as a pressure regulating valve that is input with operation oil output from the D-position output port  38   b  of the manual valve  38  and regulates pressure by discharge to a first drain port  52   c . The solenoid valve  50  also functions as an electromagnetic pump that intakes operation oil from an intake oil passage  48  between the strainer  32  and the mechanical oil pump  34 , and discharges such operation oil. The switching valve  60  switches between the following two states: a state that causes the solenoid valve  50  to function as a pressure regulating valve to deliver hydraulic pressure to the clutch C 1 ; and a state that causes the solenoid valve  50  to function as an electromagnetic pump to deliver hydraulic pressure from the electromagnetic pump to the clutch C 1 . Note that  FIG. 4  only shows the hydraulic system of the clutch C 1 , and does not show the hydraulic systems for the clutches C 2 , C 3  or the brakes B 1 , B 2  because they are not central to the present invention. These hydraulic systems may be configured using common linear solenoids or the like. 
     As shown in  FIG. 5 , the solenoid valve  50  is structured as a linear solenoid valve formed from a solenoid portion  51 , a sleeve  52 , a spool  54 , and a spring  56 . The solenoid portion  51  drives a plunger  51   a  by generating a suction force using a magnetic circuit, which is formed by applying an electric current to a coil. The sleeve  52  is hollow and formed with an input port  52   a , an output port  52   b , the first drain port  52   c , and a second drain port  52   d . The spool  54  slides inside the sleeve  52  due to driving of the plunger  51   a  of the solenoid portion  51 , and forms a pressure regulating chamber  58  that enables and cuts off communication between the input port  52   a , the output port  52   b , and the first drain port  52   c . The spring  56  is disposed in a spring chamber  59  that is spatially cut off from the pressure regulating chamber  58  and communicates with the second drain port  52   d , and biases the spool  54  from a side opposite the solenoid portion  51 . 
     As shown in  FIG. 5 , the switching valve  60  includes a spool  64 , an intake check valve  70 , a discharge check valve  80 , and a spring  66 . The spool  64  slides inside a cylindrical cavity  62  that is connected to the following: a line pressure oil passage  42  connected to the mechanical oil pump  34 ; an output port oil passage  45  connected to the output port  52   b  of the solenoid valve  50 ; clutch oil passages  49   a ,  49   b  connected to the clutch C 1 ; the intake oil passage  48  between the mechanical oil pump  34  and the strainer  32 ; spring chamber oil passages  46   a ,  46   b  connected to the spring chamber  59  (second drain port  52   d ) of the solenoid valve  50 ; and a drain oil passage  68 . The intake check valve  70  is disposed inside the cylindrical cavity  62 . The discharge check valve  80  is similarly disposed inside the cylindrical cavity  62 , and connected by threaded fastening to the spool  64 . The spring  66  biases the spool  64 . In the switching valve  60 , the spool  64 , the discharge check valve  80 , and the intake check valve  70  are arranged in that order, with the spring  66  provided between the discharge check valve  80  and the intake check valve  70 . The spring  66  thus uses the intake check valve  70  as a spring receiver, and biases the spool  64  through the discharge check valve  80 . Note that the cylindrical cavity  62  may be directly formed in the valve body or formed using a separate member. 
     The intake check valve  70  includes: a hollow cylindrical body  72  whose axial center is formed with a center hole  72   a  having large diameter and small diameter steps; a ball  74  that is inserted from the large diameter side into the center hole  72   a ; a spring  76  that presses the ball  74  against the body  72 ; and a hollow cylindrical spring receiver  78  that is connected by threaded fastening from the large diameter side to the center hole  72   a  of the body  72 , and receives the spring  78  on an end surface. When there is positive pressure downstream, the biasing force of the spring  76  causes the ball  74  to block the center hole  72   a  to close the valve. When there is negative pressure downstream, contraction of the spring  76  unblocks the center hole  72   a  to open the valve. Note that a connecting portion of the body  72  and the spring receiver  78  is clamped from an outer surface toward a diameter reducing direction so that the connection does not weaken. 
     The discharge check valve  80  includes: a hollow cylindrical body  82  wherein the axial center thereof is formed with a center hole  82   a  having large diameter and small diameter steps, and the body  82  is also formed with a through hole  82   b  that communicates with the center hole  82   a  in the radial direction; a ball  84  that is inserted from the large diameter side into the center hole  82   a ; and a spring  86  that uses the spool  64  threadedly fastened from the large diameter side to the center hole  82   a  of the body  82  as a spring receiver, and presses the ball  84  against the body  82 . When there is positive pressure downstream, the biasing force of the spring  86  causes the ball  84  to block the center hole  82   a  to close the valve. When there is negative pressure downstream, contraction of the spring  86  unblocks the center hole  82   a  to open the valve. Note that a connecting portion of the body  82  and the spool  64  is clamped from an outer surface toward a diameter reducing direction so that the connection does not weaken. 
     When the line pressure PL is input to the line pressure oil passage  42 , in the switching valve  60  contraction of the spring  66  causes the spool  64  and the discharge check valve  80  to move downward in the figure. Consequently, the output port oil passage  45  connects with the clutch oil passage  49   a , and the spring chamber oil passage  46   a  connects with the drain oil passage  68  through the through hole  82   b  (see  FIG. 5A ). Causing the solenoid valve  50  to function as a pressure regulating valve thus allows operation oil output from the output port  52   b  as the result of pressure regulation to act on the clutch C 1 . When the line pressure PL is not input to the line pressure oil passage  42 , in the switching valve  60  extension of the spring  66  due to its biasing force causes the spool  64  and the discharge check valve  80  to move upward in the figure. Consequently, the connection between the output port oil passage  45  and the clutch oil passage  49   a  is cut off, the connection between the spring chamber oil passage  46   b  and the clutch oil passage  49   b  is cut off, the intake oil passage  48  is connected to the spring chamber oil passage  46   a  through the intake check valve  70  (through hole  72   b , center hole  72   a ), and the spring chamber oil passage  46   a  is connected to the clutch oil passage  49   b  through the discharge check valve  80  (center hole  82   a , through hole  82   b ) (see  FIG. 5B ). In the solenoid valve  50 , when driving of the solenoid portion  51  is stopped following a state in which the spool  54  is pushed out by driving of the solenoid portion  51 , the spring  56  presses the spool  54  back. Therefore, negative pressure is generated inside the spring chamber  59 , which opens the intake check valve  70  and closes the discharge check valve  80 . Consequently, operation oil is guided to the spring chamber  59  through the intake oil passage  48 , the intake check valve  70 , and the spring chamber oil passage  46   a  in that order. Subsequent driving of the solenoid portion  51  pushes out the spool  54 . Therefore, positive pressure is generated inside the spring chamber  59 , which closes the intake check valve  70  and opens the discharge check valve  80 . Consequently, operation oil guided to the spring chamber  59  is delivered to the clutch C 1  through the spring chamber oil passage  46   a , the discharge check valve  80 , and the clutch oil passage  49   b  in that order. By thus repeatedly driving and stopping the solenoid portion  51  in a constant cycle, the solenoid valve  50  functions as an electromagnetic pump and can supply operation oil to the clutch C 1 . 
     Furthermore, when the vehicle  10  of the embodiment thus formed is running with the shift lever  91  in the Drive (D) running position, the engine  12  automatically stops when all preset automatic stop conditions are satisfied. Such automatic stop conditions include the vehicle speed V being zero, the accelerator off, and the brake switch signal BSW on. Once the engine  12  automatically stops, if preset automatic start conditions such as the brake switch signal BSW being off are subsequently satisfied, the automatically stopped engine  12  is automatically started. 
     When the automatic stop conditions are satisfied in the vehicle  10  of the embodiment and the engine  12  automatically stops, the mechanical oil pump  34  also stops accordingly. Therefore, the line pressure PL escapes and the spool  64  of the switching valve  60  cuts off the connection between the output port oil passage  45  and the clutch oil passage  49   a , cuts off the connection between the spring chamber oil passage  46   b  and the clutch oil passage  49   b , connects the intake oil passage  48  with the spring chamber oil passage  46   a  through the intake check valve  70 , and connects the spring chamber oil passage  46   a  with the clutch oil passage  49   b  through the discharge check valve  80 . Thus, the solenoid valve  50  functioning as an electromagnetic pump causes hydraulic pressure to act on the clutch C 1 . When the automatic start conditions are subsequently satisfied and the engine  12  automatically starts, the mechanical oil pump  34  also operates accordingly. Therefore, the line pressure PL is delivered and the spool  64  of the switching valve  60  connects the output port oil passage  45  with the clutch oil passage  49   a , and connects the spring chamber oil passage  46   b  with the drain oil passage  68 . Thus, the solenoid valve  50  functioning as a pressure regulating valve causes complete engagement of the clutch C 1  to start off the vehicle. At such time, the switching valve  60  connects the spring chamber oil passage  46   b  with the drain oil passage  68  so that operation oil remaining inside the spring chamber  59  is drained. There is thus no adverse impact on the pressure regulating precision of the solenoid valve  50 . By making the solenoid valve  50  function as an electromagnetic pump so that hydraulic pressure acts on the clutch C 1  while the engine  12  is automatically stopped, the clutch C 1  can be rapidly engaged when the solenoid valve  50  functions as a pressure regulating valve immediately after the engine  12  automatically restarts. Therefore, the vehicle can smoothly start off. Note that in this embodiment, the solenoid valve  50  is designed with a pressure feeding performance as an electromagnetic pump capable of replenishing only an amount of operation oil leakage from a seal ring or the like provided between the piston and drum of the clutch C 1 . 
     According to the solenoid valve device of the embodiment described above, the second drain port  52   d , which communicates with the spring chamber  59  of the solenoid valve  50  that functions as a pressure regulating valve, is connected to the spring chamber oil passage  46   a . The spring oil passage  46   a  is further connected to the intake oil passage  48  through the intake check valve  70  and connected to the clutch oil passage  49   b  through the discharge check valve  80 . Therefore, the solenoid valve  50  can use the spring chamber  59  to also function as an electromagnetic pump. Consequently, a smaller hydraulic circuit  30  can be achieved compared to one that separately provides a pressure regulating valve and an electromagnetic pump, thus achieving a more downsized device. When the solenoid valve  50  functions as a pressure regulating valve, that is, when the mechanical oil pump  34  drives to generate the line pressure PL, the switching valve  60  causes the spring chamber oil passage  46   b  to connect to the drain oil passage  68  so as to drain operation oil inside the spring chamber  59 . It is thus possible to prevent operation oil from remaining inside the spring chamber  59  and having an adverse impact on pressure regulating precision. In addition, because the intake check valve  70  and the discharge check valve  80  that connect to the spring chamber  59  (second drain port  52   d ) of the solenoid valve  50  are built into the switching valve  60 , the device can be further downsized. 
     In the solenoid valve device of the embodiment, a switching valve  60  is provided in which the cylindrical cavity  62  is connected to the line pressure oil passage  42 , the output port oil passage  45 , the clutch oil passages  49   a ,  49   b , the intake oil passage  48 , the spring chamber oil passages  46   a ,  46   b , and the drain oil passage  68 , and communication and non-communication among these oil passages is switched by the spool  64 . However, the present invention is not limited to this example, and a switching valve  160  illustrated in  FIG. 6  may be used. As shown in the figure, the switching valve  160  is formed from a sleeve  162 , a spool  164  that slides in the axial direction inside the sleeve  162  and is integrated with a discharge check valve  180 , a spring  166  that biases the spool  164  in the axial direction, and an intake check valve  170  installed inside the sleeve  162 . The sleeve  162  is formed with the following ports: a signal pressure input port  162   a  that is connected to the line pressure oil passage  42 ; an input port  162   b  that is connected to the output port oil passage  45 ; output ports  162   c ,  162   d  that are connected to the clutch oil passage  49 ; an input port  162   e  and an output port  162   f  that are connected to the spring chamber oil passages  46   b ,  46   a , respectively; an input port  162   g  that is connected to the intake oil passage  48 ; and drain ports  162   h ,  162   i  that are connected to the drain oil passages  168 ,  169 , respectively. 
     The intake check valve  170  includes: a hollow cylindrical body  172  whose axial center is formed with a center hole  172   a  having large diameter and small diameter steps; a spring  176  that is inserted from the large diameter side and uses a step of the center hole  172   a  as a spring receiver; a ball  174  that is inserted from the large diameter side into the center hole  172   a  after insertion of the spring  176 ; a hollow cylindrical ball receiver  178  that is inserted into the center hole  172   a  and receives the ball  174 ; and a snap ring  179  for fixing the ball receiver  178  to the body  172 . Meanwhile, the discharge check valve  180  includes: a body  182  that is integratedly cast with the spool  164 , wherein the axial center of the body  182  is formed with a center hole  182   a  having a recess shape, and the body  182  is also formed with a through hole  182   b  that runs through the center hole  182   a  in the radial direction; a spring  186  that is inserted into the center hole  182   a  and uses the bottom of the center hole  182   a  as a spring receiver; a ball  184  that is inserted into the center hole  182   a  after insertion of the spring  186 ; a hollow cylindrical ball receiver  188  that is inserted into the center hole  182   a  and receives the ball  184 ; and a snap ring  189  for fixing the ball receiver  188  to the body  182 . In addition, the body  182  of the discharge check valve  180  is formed with a reduced-diameter portion  182   c  of which a portion of the outer diameter is reduced. 
     When the line pressure PL is input to the signal pressure input port  162   a , in the switching valve  160  described above contraction of the spring  166  due to the line pressure PL causes the spool  164  to move downward in the figure. Consequently, the input port  162   b  communicates with the output port  162   c , and the input port  162   e  communicates with the drain port  162   i  through the reduced-diameter portion  182   c . Therefore, the solenoid valve  50  functioning as a pressure regulating valve causes hydraulic pressure from the output port  52   b  to act on the clutch C 1 . At such time, operation oil remaining inside the spring chamber  59  is drained through the second drain port  52   d , the spring chamber oil passage  46   b , the input port  162   e , the reduced-diameter portion  182   c , and the drain port  162   i  in that order. There is thus no adverse impact on the pressure regulating precision of the solenoid valve  50 . In addition, the body  172  of the intake check valve  170  is formed with a through hole  172   b  at a portion that contacts the body  182  of the discharge check valve  180 . Operation oil remaining in a space between the intake check valve  170  and the discharge check valve  180  is thus also drained through the output port  162   f , the spring chamber oil passage  46   a ,  46   b , the input port  162   e , the reduced-diameter portion  182   c , and the drain port  162   i  in that order. When the line pressure PL is not input to the signal pressure input port  162   a , extension of the spring  166  due to its biasing force causes the spool  164  to move upward in the figure. Consequently, communication between the input port  162   b  and the output port  162   c  is cut off, the input port  162   g  communicates with the output port  162   f  through the intake check valve  170  (center hole  172   a , through hole  172   b ), the input ports  162   e ,  162   f  communicate with the output port  162   d  through the discharge check valve  180  (center hole  182   a , through hole  182   b ), and communication between the input port  162   e  and the drain ports  162   h ,  162   i  is cut off. Therefore, the solenoid valve  50  functioning as an electromagnetic pump causes operation oil to be intaken by the spring chamber  59  through the input port  162   g  of the switching valve  160 , the intake check valve  170 , the output port  162   f , and the spring chamber oil passage  46   a  in that order. The solenoid valve  50  functioning as an electromagnetic pump also causes the intaken operation oil to be delivered to the clutch C 1  through the spring chamber oil passages  46   b ,  46   a , the input ports  162   e ,  162   f  of the switching valve  160 , the discharge check valve  180 , and the output port  162   d  in that order. 
     In the solenoid valve device of the embodiment, the intake check valve  70  and the discharge check valve  80  are built into the switching valve  60 . However, the discharge check valve may be built into the switching valve while the intake check valve is incorporated into a valve body other than the switching valve, or the intake check valve built into the switching valve while the discharge check valve is incorporated into a valve body other than the switching valve, or both the intake check valve and the discharge check valve incorporated into a valve body other than the switching valve.  FIG. 7  shows an example of a hydraulic circuit  230  in which the intake check valve and the discharge check valve are incorporated into a valve body. An intake check valve  270  and a discharge check valve  280  are structured such that a ball and a spring are disposed in a cylindrical housing, and incorporated by fitting into a recess portion formed in the valve body. The switching valve  260  is formed from a sleeve  262 , a spool  264  that slides in the axial direction inside the sleeve  262 , and a spring  266  that biases the spool  264  in the axial direction. The sleeve  262  is formed with the following ports: a signal pressure input port  262   a  that is connected to the line pressure oil passage  42 ; an input port  262   b  that is connected to the output port oil passage  45 ; an input port  262   c  that is connected to the spring chamber oil passage  46  through the discharge check valve  280 ; an output port  262   d  that is connected to the clutch oil passage  49 ; an input port  262   e  that is connected to the intake oil passage  48 ; an output port  262   f  that is connected to the spring chamber oil passage  46  through the intake check valve  270 ; an input port  262   h  that is connected to the spring chamber oil passage  46 ; and a drain port  262   i . When the line pressure PL is input to the signal pressure input port  262   a , in the switching valve  260  contraction of the spring  266  causes the spool  264  to move to a position shown on the right-hand side of the valve in the figure. Consequently, the input port  262   b  communicates with the output port  262   d , communication is cut off between the input port  262   c  and the output port  262   d , and the input port  262   h  communicates with the drain port  262   i . Therefore, the solenoid valve  50  functioning as a pressure regulating valve causes hydraulic pressure from the output port  52   b  to act on the clutch C 1 . At such time, operation oil remaining inside the spring chamber  59  is drained through the second drain port  52   d , the spring chamber oil passage  46 , the input port  262   h , and the drain port  262   i  in that order. There is thus no adverse impact on the pressure regulating precision of the solenoid valve  50 . When the line pressure PL is not input to the signal pressure input port  262   a , extension of the spring  266  due to its biasing force causes the spool  264  to move to a position shown on the left-hand side of the valve in the figure. Consequently, communication between the input port  262   b  and the output port  26   dc  is cut off, the input port  262   c  communicates with the output port  262   d , the input port  262   e  communicates with the output port  262   f , and communication between the input port  262   h  and the drain port  262   i  is cut off. Therefore, the solenoid valve  50  functioning as an electromagnetic pump causes operation oil to be intaken by the spring chamber  59  through the intake oil passage  48 , the input port  262   e  of the switching valve  60 , the output port  262   f , the intake check valve  270 , and the spring chamber oil passage  46  in that order. The solenoid valve  50  functioning as an electromagnetic pump also causes the intaken operation oil to be delivered to the clutch C 1  through the spring chamber oil passage  46 , the discharge check valve  280 , and the input ports  262   c ,  262   d  of the switching valve  60  in that order. 
     In the solenoid valve device of the embodiment, the switching valve  60  is driven using the line pressure PL. However, the switching valve  60  may be driven using a modulator pressure PMOD achieved by lowering the line pressure PL with a modulator valve (not shown). Alternatively, the line pressure PL or a modulator pressure may be supplied to the switching valve  60  through a solenoid valve, and the solenoid valve used to drive the switching valve  60 . 
     In the solenoid valve device of the embodiment, the solenoid valve  50  is formed by combining a linear solenoid SLC 1  that regulates the hydraulic pressure of the clutch C 1  with an electromagnetic pump. However, the present invention is not limited to this example. The solenoid valve  50  may combine the linear solenoid SLT that drives the regulator valve  36  with an electromagnetic pump, or combine an on-off solenoid valve instead of a linear solenoid with the electromagnetic pump. 
     The embodiment incorporates a four-speed automatic speed change mechanism  28  with first to fourth forward speeds. However, the present invention is not limited to this example, and an automatic speed change mechanism with any number of speeds may be incorporated, such as an automatic speed change mechanism with two speeds, three speeds, or five or more speeds. 
     Here, the correspondence relation will be described between main elements in the embodiment and main elements of the invention as listed in the Disclosure of the Invention. In the embodiment, the solenoid portion  51  corresponds to a “solenoid portion”; the sleeve  52  and the spool  54  that form the pressure regulating chamber  58  to a “valve element”; the spring chamber  59  to a “spring chamber”; the intake oil passage  48  to a “reservoir portion”; the intake check valve  70  to an “intake check valve”; the discharge check valve  80  to a “discharge check valve”; and the second drain port  52   d  to an “inflow/outflow port”. The switching valve  60  corresponds to a “switching valve”. 
     The above embodiment was used to describe a mode for carrying out the present invention. However, the present invention is not particularly limited to such an example, and may obviously be carried out using various embodiments without departing from the scope of the present invention. 
     The present invention may be used in the automobile industry.