JP2010238205A - Variable hydraulic system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variable hydraulic system that improves reliability in switching a valve opening pressure, in the variable hydraulic system provided with a relief valve for switching the valve opening pressure by displacing a movable member slidably provided in a bore in accordance with the mode of oil pressure applied from a back pressure chamber. <P>SOLUTION: In the variable hydraulic system for switching supply pressure to a supply object by changing the pressure stage of valve opening pressure by switching the mode of oil pressure application in the back pressure chamber 35, the relief valve 20 for regulating the valve opening pressure includes a bore 23 provided with a sleeve 26 slidable in the axial direction and circumferential direction thereof, and a return path 26E recessed on the outer circumferential surface of the sleeve 26 to connect an intake side of a pump communicate with the back pressure chamber 35 by the displacement of the sleeve 26 by increasing the pressure of the back pressure chamber 35. The return path 26E is configured so as to rotate the sleeve 26 in the circumferential direction thereof using oil flowing therethrough. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a variable hydraulic system including a relief valve that makes a valve opening pressure variable.

  As a variable hydraulic system that varies the pressure of oil supplied to an internal combustion engine, for example, a variable hydraulic system including a relief valve whose valve opening pressure is controlled in two stages as in Patent Document 1 is known. In a variable hydraulic system equipped with such a relief valve, the opening pressure of the relief valve is set to a low pressure stage when the engine starts, for example, when the engine does not require high supply pressure, thereby reducing the load on the oil pump. As a result, fuel efficiency can be improved. In recent years, as one of such variable hydraulic systems, a variable hydraulic system has been developed that switches a relief valve opening pressure between a low pressure stage and a high pressure stage higher than the low pressure stage through a switching valve that switches an oil flow path. Has reached the point. An example of such a variable hydraulic system will be described below. FIG. 8 shows a schematic configuration of such a variable hydraulic system together with a sectional structure of a relief valve. FIG. 8 shows a state when the engine is stopped.

  As shown in FIG. 8, in the variable hydraulic system 50, oil is sucked and discharged in the middle of a supply passage 52 that connects between each part of an internal combustion engine as an oil supply target and the oil pan 51. An engine-driven pump 53 and an oil strainer 54 for removing relatively large foreign matters contained in the oil on the suction side of the pump 53 are provided. A relief passage 55 connected to the discharge side and the suction side of the pump 53 is provided in the middle of the supply passage 52, and the pressure of the oil discharged from the pump 53 is in the middle of the relief passage 55. A relief valve 60 is provided for releasing a part of the oil to the suction side of the pump 53 when a predetermined valve opening pressure is exceeded.

  The valve body 61 constituting the relief valve 60 has a bore 61a which is a circular hole extending in one direction, one end of which is connected to the suction side of the relief passage 55 and the other end is closed by a closing member 62. Is provided. The bore 61a has a multi-stage shape in which the inner diameter increases from the inlet passage 64 connected to the relief passage 55 toward the closing member 62, and the closing member 62 forming the bottom of the bore 61a extends in the inlet passage 64. 62a is separated from the peripheral surface of the bore 61a. And the accommodation chamber 63 is comprised in the form enclosed by these entrance channel | paths 64, the closing member 62, and the bore | bore 61a.

  Near the center in the longitudinal direction of the bore 61a, an outlet passage 65 extending in a direction crossing the longitudinal direction has one end connected to the storage chamber 63 and the other end connected to the discharge side of the relief passage 55. It is provided in the form to be done. Inside the bore 61a, a cylindrical sleeve 66 into which the closing portion 62a is inserted is slidably provided between the inlet passage 64 and the closing member 62. While the sleeve 66 slides in the bore 61a, the closing portion 62a continues to be fitted into the sleeve 66, and the back pressure chamber 71 is surrounded between the sleeve 66 and the closing member 62 and the bore 61a. Continue to form.

The back pressure chamber 71 having such a configuration is connected to the discharge side of the pump 53 and the suction side of the pump 53 via the back pressure passage 72 and the switching valve 73 to which the back pressure passage 72 is connected. When the connection destination of the back pressure chamber 71 is switched to the discharge side of the pump 53 by the switching valve 73, oil from the discharge side of the pump 53 is supplied to the back pressure chamber 71, and the pressure of the back pressure chamber 71 is increased. One end of the sleeve 66 in the longitudinal direction is displaced to a low pressure stage control position that is a position where the end of the housing chamber 63 abuts on the end on the inlet passage 64 side. In contrast, the back pressure chamber 71 is connected to the pump 5 by the switching valve 73.
3, part of the oil in the back pressure chamber 71 is discharged to the suction side of the pump 53, the pressure in the back pressure chamber 71 is reduced, and the other end in the longitudinal direction of the sleeve 66 is the accommodation chamber 63. It moves to the high-pressure stage control position, which is a position that contacts the end of the closing member 62 side.

  Inside the sleeve 66 is provided a valve body sliding hole 68 which is a multi-stage circular hole extending from the inlet passage 64 side to the closing portion 62a side. A cylindrical valve body 67 is provided so as to be slidable in the central axis direction of the valve body sliding hole 68. A biasing spring 70 that biases the valve body 67 toward the inlet passage 64 is provided between the valve body 67 and the closing portion 62a. A relief hole 69 communicating with the outlet passage 65 is provided in the vicinity of the center in the longitudinal direction of the peripheral wall of the sleeve 66. When the oil pressure from the inlet passage 64 acts on the valve body 67 through the valve body sliding hole 68, the valve body 67 is caused by a force based on the hydraulic pressure in the valve body sliding hole 68 and an urging spring against the force. It is displaced along the axial direction of the valve body sliding hole 68 within a range crossing the relief hole 69 according to the urging force of 70.

  According to the relief valve 60 having such a configuration, whether or not the valve body 67 opens the relief hole 69, that is, whether or not the oil is relieved, and the position of the valve body 67 and the relief hole 69 (sleeve 66). It will be defined by the position of. In other words, depending on whether or not the hydraulic pressure that defines the position of the valve body 67 is the valve opening pressure, whether or not the oil is relieved is switched, and the back pressure chamber 71 that defines the position of the sleeve 66 is switched. Therefore, the above-described valve opening pressure is switched to two stages.

JP-A-6-4141

  By the way, when the valve opening pressure of the relief valve 60 is switched from the high pressure stage to the low pressure stage in the variable hydraulic system 50 described above, the oil flows into the back pressure chamber 71, and even bubbles and foreign matters mixed in the oil are back. It will be carried to the pressure chamber 71. On the other hand, when the valve opening pressure of the relief valve 60 is switched from the low pressure stage to the high pressure stage, the oil is discharged from the back pressure chamber 71, but the back pressure chamber 71 is only the amount of pressure fluctuation in the back pressure chamber 71. The oil cannot flow. For this reason, when most of the bubbles and foreign substances as described above once enter the back pressure chamber 71, the stagnation of oil and the complicated structure of the back pressure chamber 71 make it difficult to discharge them, and as a result, these bubbles Or foreign matter continues to be accumulated in the back pressure chamber 71.

  Some of the bubbles and foreign substances accumulated in this way are not only a factor that causes the sliding of the sleeve 66 to become unstable due to being carried along with the oil to the clearance between the outer peripheral surface of the sleeve 66 and the inner peripheral surface of the bore 61a. May cause the outer peripheral surface of the sleeve 66 and the inner peripheral surface of the bore 61a to adhere to each other with foreign matter. Even when such foreign matter does not enter, since the sleeve 66 is configured to reciprocate between the low pressure stage control position and the high pressure stage control position, the reciprocation of the sleeve 66 is repeated. There is a possibility that uneven wear occurs on the outer peripheral surface of the sleeve 66 and the inner peripheral surface of the bore 61a, and the smooth wear of the sleeve 66 may be hindered by such uneven wear. Such a decrease in reliability related to the switching of the valve opening pressure is not a problem limited to the above-described configuration, and a movable member that is displaced in accordance with the application mode of the hydraulic pressure to the back pressure chamber is provided in the bore. This is a problem that can generally occur in a variable hydraulic system having the above-described configuration.

The present invention has been made in view of the above-described situation, and an object of the present invention is to open a valve by displacing a movable member slidably mounted in a bore in accordance with an application mode of hydraulic pressure from a back pressure chamber. An object of the present invention is to provide a variable hydraulic system capable of improving the reliability of the switching operation of the valve opening pressure in the variable hydraulic system having a relief valve for switching pressure.

In the following, means for achieving the above object and its effects are described.
According to the first aspect of the present invention, there is provided a relief valve provided on the discharge side of the pump having a columnar movable member that changes the valve opening pressure by axial displacement according to the hydraulic pressure applied from the back pressure chamber. And a switching valve that switches an application mode of hydraulic pressure in the back pressure chamber, and a variable hydraulic system that changes a supply pressure to a supply target by switching a pressure stage of the valve opening pressure by switching the application mode. The relief valve is recessed in one of a bore that slidably houses the movable member in its axial direction and circumferential direction, and an outer peripheral surface of the movable member and an inner peripheral surface of the bore, A return passage that communicates the suction side of the pump and the back pressure chamber by displacement of the movable member due to the pressure increase of the back pressure chamber, and the return passage has a flow of oil in the return passage around the movable member. Direction And summarized in that configured in a shape to be rotated in.

  In a variable hydraulic system in which the opening pressure of the relief valve is switched by switching the mode of application of hydraulic pressure in the back pressure chamber, oil is mixed into the back pressure chamber when the oil flows into the back pressure chamber and the back pressure chamber is pressurized. Even bubbles and foreign objects that are generated are carried to the back pressure chamber. On the other hand, when oil is discharged from the back pressure chamber and the back pressure chamber is depressurized, the oil can flow in the back pressure chamber only by the pressure fluctuation in the back pressure chamber. Therefore, many of the bubbles and foreign matters carried to the back pressure chamber continue to accumulate in the back pressure chamber. As described above, some of the bubbles and foreign substances accumulated in this way enter the clearance between the movable member that receives the hydraulic pressure in the back pressure chamber and the bore surrounding it, and make the sliding of the movable member unstable. In addition, there is a possibility that the outer peripheral surface of the movable member and the inner peripheral surface of the bore are fixed by foreign matter. In addition to this, even if the above-mentioned foreign matter does not enter the clearance, the movable member slides in the axial direction every time the valve opening pressure is switched. There is a possibility that uneven wear occurs on the inner peripheral surface of the bore, and such uneven wear may prevent smooth sliding of the movable member in the axial direction.

  In this regard, according to the first aspect of the present invention, since the return passage is opened when the back pressure chamber is pressurized, bubbles and foreign matters carried to the back pressure chamber The oil that continues to flow is discharged from the back pressure chamber to the suction side of the pump. In addition, when oil flows through the return passage, the movable member itself rotates in the circumferential direction due to the oil flowing therethrough, and the return passage rotates in the circumferential direction with respect to the outer peripheral surface of the movable member or the inner peripheral surface of the bore. It will be. Therefore, even if bubbles or foreign matter enters the clearance between the movable member and the bore, these bubbles and foreign matter are sequentially trapped in the rotating return passage, and are thereby discharged to the suction side of the pump. Become. Moreover, since the outer peripheral surface of the movable member rotates with respect to the inner peripheral surface of the bore, the above-described uneven wear is also reduced.

  Further, according to the above-described configuration, the return passage is opened upon receiving the pressure increase in the back pressure chamber. Therefore, the pressure increase in the back pressure chamber required for switching the valve opening pressure precedes the opening of the return passage. As a result, the return passage is opened from the state in which the back pressure chamber starts to be pressurized. Therefore, if the back pressure chamber communicates with the return passage immediately before the back pressure chamber is increased, the oil supplied to the back pressure chamber is likely to flow out of the return passage, and the back pressure chamber is difficult to be pressurized. Even the state is avoided, and the switching of the application mode of the hydraulic pressure in the back pressure chamber is smoothly executed. Therefore, according to the above-described configuration, the reliability of the switching operation of the valve opening pressure is improved.

The gist of the invention described in claim 2 is that the flow path direction of the return passage intersects the axial direction.
According to the second aspect of the present invention, since the flow path direction in which the oil flows in the return passage intersects the axial direction, when the oil flows in such a return passage, the viscosity exerted by the oil that is a viscous fluid is exerted. The stress acts stably in the direction of the flow path, that is, the direction crossing the axial direction. Therefore, when oil flows in such a return passage, the rotational force in the circumferential direction is given to the movable member with high reproducibility. As a result, the effect of discharging bubbles and foreign matters entering the relief valve and the effect of reducing the above-described uneven wear are more reliably exhibited.

  According to a third aspect of the present invention, there is provided a relief hole that has an outlet in the peripheral wall of the movable member and relieves oil from the discharge side of the pump to the suction side of the pump, and the suction side and relief hole of the pump And an outlet passage that communicates with the outlet of the bore through an opening over the entire circumference of the inner surface of the bore.

  As described above, when oil flows through the return passage, the relief holes that form the relief passage also rotate in the circumferential direction as the movable member rotates. When there is a period in which the outlet of the relief hole rotating in this way is temporarily closed by the peripheral surface of the movable member or the inner surface of the bore, excess oil on the discharge side of the pump becomes difficult to be relieved during that period. The relief function of the valve itself is impaired. In this respect, according to the third aspect of the present invention, since the outlet passage communicating with the suction side of the pump has an opening extending in the entire circumferential direction on the inner surface of the bore, the movable member rotates in the circumferential direction. Even so, the outlet of the relief hole and the outlet passage always communicate with each other, and the relief function of the relief valve is always maintained.

  According to a fourth aspect of the present invention, there is provided a relief hole having an outlet in a recess extending over the entire outer peripheral surface of the movable member to relieve oil from the discharge side of the pump to the suction side of the pump, and the movable member The present invention is characterized in that an opening that communicates with the suction side of the pump is provided on the inner surface of the bore.

  According to the fourth aspect of the present invention, since the relief hole outlet is provided in the recess extending over the entire outer peripheral surface of the movable member, even if the movable member rotates, the relief hole and the outlet are passed through the recess. The passage is always in communication, and the relief function of the relief valve is always maintained.

  According to a fifth aspect of the invention, the movable member is disposed in the bore and is displaced between a first position and a second position defined according to the pressure stage of the valve opening pressure. The back pressure chamber is defined in the bore by one end portion of the sleeve in the sliding direction, and the volume of the back pressure chamber is increased by the displacement of the sleeve from the first position to the second position. The return passage is configured to expand and displace from the second position to the first position to reduce the volume thereof, and the return passage is configured so that the sleeve is in the second position. The gist is that the suction side of the pump communicates with the back pressure chamber.

  According to the fifth aspect of the present invention, when the sleeve is disposed at the second position, the switching of the pressure stage of the valve opening pressure is completed, and the return passage is opened. In such a variable hydraulic system, when the movable member moves to the second position, the movable member receives the hydraulic pressure in the back pressure chamber and moves. Therefore, the back pressure chamber and the suction side of the pump are not always in communication. Even if oil is supplied to the back pressure chamber so that the valve opening pressure of the relief valve is switched, a part of the oil in the back pressure chamber always flows out to the suction side of the pump, so the hydraulic pressure in the back pressure chamber is increased. It will be difficult. In this regard, according to the invention described in claim 5, when the movable member is disposed at the second position, the return passage is configured in a manner in which the back pressure chamber communicates with the suction side of the pump. The hydraulic pressure in the back pressure chamber is quickly increased, and the response of the movable member to the switching of the valve opening pressure is not impaired.

The schematic block diagram which showed the schematic structure of the variable hydraulic system concerning this invention centering on the cross section of the relief valve. The side view which shows the side structure of a sleeve. Explanatory drawing for demonstrating operation | movement of the sleeve when oil flows through a return channel | path. It is a figure in case the valve opening pressure of a relief valve is selected to the low pressure stage, (a) The figure which showed the flow of oil centering on the cross-sectional structure of the relief valve in a valve closing state, (b) Valve opening The figure which showed the flow of oil centering on the cross-section of the relief valve in a state. It is a figure in case the valve opening pressure of a relief valve is selected to the high pressure stage, (a) The figure which showed the flow of oil centering on the cross-sectional structure of the relief valve in a valve closing state, (b) Valve opening The figure which showed the flow of oil centering on the cross-section of the relief valve in a state. Sectional drawing of the valve main body which shows an example at the time of providing a return channel | path in the inner surface of a bore. (A) (b) (c) The side view of the sleeve which shows the shape of the return channel | path in the example of a change. The schematic block diagram which showed the schematic structure of the conventional variable hydraulic system centering on the cross section of the relief valve.

  Hereinafter, an embodiment embodying a variable hydraulic system according to the present embodiment will be described with reference to FIGS. FIG. 1 is a schematic configuration diagram showing a schematic configuration of a variable hydraulic system centered on a cross section of a relief valve, and shows a state before an engine to be supplied with oil is started.

  As shown in FIG. 1, the variable hydraulic system 10 is provided with a supply passage 12 that supplies oil stored in an oil pan 11 to each part of the internal combustion engine. An engine driven pump 13 that sucks and discharges oil is provided in the middle of the supply passage 12, and relatively large impurities contained in the oil are removed from the suction side end of the supply passage 12. An oil strainer 14 is provided. When the pump 13 is driven along with the operation of the internal combustion engine, the oil stored in the oil pan 11 is sucked up by the pump 13 and driven from the supply passage 12 by each part of the internal combustion engine, for example, the pressure of the oil. Oil is supplied to various hydraulically driven devices, and further, the oil is injected into the piston for taking out the engine output and cooled to the piston jet mechanism for cooling the piston and the oil to be lubricated parts of the engine Will be supplied. A relief passage 15 connected to the discharge side and the suction side of the pump 13 is provided in the middle of the supply passage 12. In the middle of the relief passage 15, the pressure of the oil discharged from the pump 13 is provided. A relief valve 20 is provided for releasing a part of the oil when a predetermined valve opening pressure is exceeded.

  A bore 23 which is a circular hole having an opening on the lower surface of the valve main body 21 is provided at one end of the valve main body 21 constituting the relief valve 20 (lower end 21B in FIG. 1). The opening of the bore 23 is closed by a fixing member 22, whereby a storage chamber corresponding to the internal space of the bore 23 is defined in the valve body 21. The fixing member 22 constituting the housing chamber is provided with a substantially cylindrical valve body support portion 22A having a diameter smaller than the diameter of the bore 23 and projecting into the bore 23 on the same axis as the bore 23. . A gap is formed between the outer peripheral surface of the valve body support portion 22 </ b> A and the inner surface of the bore 23 so that the distance between them is substantially equal. Further, a stopper 22B protruding in the radial direction is provided on a part of the outer peripheral surface of the valve body support portion 22A. Hereinafter, the direction along the central axis C of the bore 23 described above is referred to as an axial direction.

An inlet passage 24 having a diameter smaller than the diameter of the above-described bore 23 is provided on the same axis as the bore 23 at the other end portion (upper end portion 21 </ b> A in FIG. 1) of the valve body 21. The relief passage 15 connected to the discharge side of the pump 13 communicates with the above-described storage chamber via the inlet passage 24. Further, an axially wide outlet passage 25 is provided in the vicinity of the axial center position of the bore 23 so as to open over the entire circumference of the inner surface of the bore 23. The relief passage 15 connected to the suction side of the pump 13 communicates with the above-described storage chamber via the outlet passage 25.

  Inside the bore 23 thus configured, a sleeve 26, which is a cylindrical movable member extending along the axial direction, is mounted on the same axis so as to be slidable along the axial direction and the circumferential direction. The length of the sleeve 26 in the axial direction is shorter than the length of the storage chamber in the same axial direction, and the lower end of the sleeve 26 is the outer peripheral surface of the valve body support portion 22A and the inner surface of the bore 23. It is fitted in the gap between. That is, the gap between the outer peripheral surface of the valve body support portion 22 </ b> A and the inner surface of the bore 23 is partitioned in the axial direction by the back pressure surface 26 </ b> C that is the lower end surface of the sleeve 26. The back pressure chamber 35 surrounded by the outer peripheral surface of the valve body support portion 22A, the inner surface of the bore 23, and the back pressure surface 26C of the sleeve 26 can be expanded and contracted in the axial direction. It is defined in the above gap.

  At a position facing the stopper 22B across the central axis C, a lead-out hole 36 that opens to the inner surface of the bore 23 and communicates with the back pressure chamber 35 is provided in the valve body 21. The other end of the lead-in / in passage 41 whose one end is connected to the switching valve 40 is connected to the lead-in / out hole 36. In addition to the lead-in / out passage 41, the switching valve 40 is connected to an introduction passage 42 connected to the supply passage 12 on the discharge side of the pump 13 and a discharge passage 43 connected to the suction side of the pump 13. Yes. When the switching valve 40 performs the switching operation, the connection destination of the lead-in / out passage 41 (back pressure chamber 35) is switched between the introduction passage 42 and the discharge passage 43. Such a switching operation of the switching valve 40 is executed by the electronic control unit 45 electrically connected to the switching valve 40 in accordance with the engine operating state of the internal combustion engine. The switching valve 40 is, for example, a three-way solenoid valve. When the switching valve 40 is energized, a passage communicating with the back pressure chamber 35 through the lead-in / out passage 41 is selected as the introduction passage 42, and the back pressure chamber 35 is selected. The hydraulic pressure at is increased. When the energization of the switching valve 40 is interrupted, a passage communicating with the back pressure chamber 35 through the lead-in / out passage 41 is selected as the discharge passage 43, and the hydraulic pressure in the back pressure chamber 35 is reduced. In the variable hydraulic system 10 in the present embodiment, the application mode of the hydraulic pressure to the back pressure chamber 35 is switched in this way.

  In the sleeve 26 described above, a multi-stage circular hole penetrating in the axial direction of the sleeve 26 is provided so that the upper end portion 26A of the sleeve 26 is thick. An inlet communication hole 28 having a hole diameter smaller than the diameter of the inlet passage 24 is provided. The sleeve 26 having such a structure receives the hydraulic pressure corresponding to the difference between the diameter of the inlet passage 24 and the diameter of the inlet communication hole 28 from the inlet passage 24 to the upper end portion 26A, and is opposed to the hydraulic pressure. The hydraulic pressure in the back pressure chamber 35 is received by the back pressure surface 26C, and the sleeve 26 itself slides along the axial direction according to the difference between the force acting on the upper end portion 26A and the force acting on the back pressure surface 26C. It will be.

  More specifically, when the back pressure chamber 35 and the introduction passage 42 communicate with each other by the switching operation of the switching valve 40, the hydraulic pressure in the back pressure chamber 35 is increased and the sleeve 26 itself is pushed up along the axial direction. It becomes. Such an upward movement of the sleeve 26 itself is regulated by the increase of the hydraulic pressure in the back pressure chamber 35 or by the mechanical locking of the sleeve 26 itself. Incidentally, in the relief valve 20 having the above-described configuration, the upward movement of the sleeve 26 is restricted in such a manner that the upper end portion 26 </ b> A of the sleeve 26 is locked to the inlet passage 24. Hereinafter, the position of the sleeve 26 where the upper end portion 26A of the sleeve 26 contacts the inlet passage 24 is referred to as a low pressure stage control position as the second position.

  On the other hand, when the back pressure chamber 35 and the discharge passage 43 communicate with each other by the switching operation of the switching valve 40, the hydraulic pressure in the back pressure chamber 35 is reduced, and the sleeve itself is pushed down along the axial direction. It becomes. Such downward movement of the sleeve 26 itself is regulated by the reduction of the hydraulic pressure in the back pressure chamber 35 or by mechanical locking of the sleeve 26 itself. Incidentally, in the relief valve 20 having the above-described configuration, the downward movement of the sleeve 26 is restricted in such a manner that the back pressure surface 26C of the sleeve 26 is locked to the stopper 22B of the fixing member 22. In a state where the downward movement of the sleeve 26 is restricted, the back pressure chamber 35 defined in the circumferential direction of the stopper 22 </ b> B communicates only with the lead-in / out hole 36. As a result, the oil in the back pressure chamber 35 flows to the suction side of the pump 13 through the lead-in / in hole 36 by the reduced amount of the back pressure chamber 35. Hereinafter, the position of the sleeve 26 where the back pressure surface 26C and the stopper 22B come into contact is referred to as a high pressure stage control position as the first position.

  A relief hole 29 having a diameter smaller than the axial width of the outlet passage 25 is provided in a portion of the peripheral wall of the sleeve 26 facing the outlet passage 25 so as to penetrate the peripheral wall of the sleeve 26. The relief hole 29 is an oil passage that is displaced in the axial direction along with the displacement of the sleeve 26, and is provided at a position communicating with the outlet passage 25 in the entire movement range of the sleeve 26. When the sleeve 26 is disposed at the low pressure stage control position, the relief hole 29 is furthest away from the valve body support portion 22A in the movement range, and when the sleeve 26 is disposed at the high pressure stage control position, The hole 29 is closest to the valve body support portion 22A in the moving range. Further, as shown in FIG. 2, the relief hole 29 is provided so as to open to the bottom surface of a recess 26 </ b> D provided over the entire outer periphery of the sleeve 26. The recess 26D is provided so as to face the outlet passage 25 of the valve body 21 when the sleeve 26 is disposed at the low-pressure stage control position.

  Further, the back pressure chamber 35 and the outlet passage 25 communicate with the lower end portion 26B, which is the outer peripheral surface of the sleeve 26 and is below the concave portion 26D, when the sleeve 26 is disposed at the low pressure stage control position. A spiral return passage 26 </ b> E extending in the axial direction is recessed. The opening on the outlet passage 25 side in the return passage 26E communicates with the outlet passage 25 in a state where the sleeve 26 is disposed at the low pressure stage control position in the process of moving the sleeve 26 from the high pressure stage control position to the low pressure stage control position. In the state where the sleeve 26 is disposed at the low pressure stage control position, the opening is provided in a fully open state. Further, the opening on the back pressure chamber 35 side in the return passage 26E is provided in the back pressure surface 26C of the sleeve 26, and the communication between the return passage 26E and the back pressure chamber 35 is always maintained by such a configuration. The return passage 26 </ b> E is formed such that the opening area of the outlet passage 25 is smaller than the opening area of the lead-in / out hole 36 in the back pressure chamber 35.

  When the sleeve 26 is disposed at the low pressure stage control position, the lead-in / out hole 36, the back pressure chamber 35, and the outlet passage 25 communicate with each other through the return passage 26E. As a result, in the back pressure chamber 35, a part of the oil flows out to the outlet passage 25 through the return passage 26E, and the oil that has flowed out through the introduction passage 42, the outlet / inlet passage 41, and the outlet / inlet hole 36 sequentially Will be supplied. As a result, oil from the switching valve 40 flows to the outlet passage 25 through the back pressure chamber 35, and bubbles and foreign matter that have entered the back pressure chamber 35 and the lead-in / in passage 41 are discharged to the outlet passage 25. The Rukoto. Therefore, bubbles and foreign matters carried into the back pressure chamber 35 are less likely to stay in the back pressure chamber 35 due to the flow of oil.

In addition, the return passage 26E is provided in such a manner that the opening area in the outlet passage 25 is smaller than the opening area of the lead-in / out hole 36 in the back pressure chamber 35. This acts as a large flow path resistance with respect to the outlet passage 25, the amount of oil flowing out from the back pressure chamber 35 is limited, and the hydraulic pressure in the back pressure chamber 35 is generally maintained. In other words, the axially upward force continues to act on the sleeve 26 disposed at the low pressure stage control position from the back pressure chamber 35, and the position is the low pressure stage control even when the return passage 26E is opened. Will be held in position.

  The return passage 26E that connects the back pressure chamber 35 and the outlet passage 25 is arranged at the low pressure stage control position in the process of moving the sleeve 26 from the high pressure stage control position to the low pressure stage control position. It is sometimes provided in communication with the exit passage 25. Here, if the return passage 26E is provided in such a way that the back pressure chamber 35 and the outlet passage 25 are always in communication, the oil supplied to the back pressure chamber 35 will flow out into the outlet passage 25 at any time. In addition, the hydraulic pressure in the back pressure chamber 35 is hardly increased. As a result, the responsiveness of the sleeve 26 to the switching of the switching valve 40 is deteriorated, and there is a possibility that the sleeve 26 may not easily move to the low pressure stage control position. In this respect, in the present embodiment, oil does not flow out from the back pressure chamber 35 to the outlet passage 25 until immediately before the sleeve 26 is disposed at the low pressure stage control position. The pressure in the chamber 35 is quickly increased. As a result, the response of the sleeve 26 when the valve opening pressure of the relief valve 20 is switched from the high pressure stage to the low pressure stage is improved, and the sleeve 26 can be quickly and reliably guided to the low pressure stage control position. .

  When the sleeve 26 is disposed at the high pressure stage control position, the opening on the outlet passage 25 side in the return passage 26E is closed by the inner surface of the bore 23. As a result, the back pressure chamber 35 and the outlet passage 25 are not communicated with each other, and the back pressure chamber 35 defined in the circumferential direction of the stopper 22B communicates with only the lead-in / out hole 36. As a result, the oil in the back pressure chamber 35 flows to the suction side of the pump 13 through the lead-in / in hole 36 by the reduced amount of the back pressure chamber 35.

  Here, as described above, in the process in which the sleeve 26 reciprocates between the low pressure stage control position and the high pressure stage control position, the reciprocating motion is repeated, so that the deviation between the sleeve 26 and the valve body 21 occurs. Wear may occur. When such uneven wear occurs, the worn portion of the sleeve 26 prevents the sleeve 26 from moving when the sleeve 26 reciprocates, making it difficult to realize a smooth reciprocation of the sleeve 26.

  In this regard, in this embodiment, as shown in FIG. 4, a return passage 26E recessed in the outer peripheral surface of the sleeve 26 has a spiral shape extending in the axial direction, and the oil flows in the return passage 26E. That is, the flow path direction includes a vector component in the tangential direction of the outer peripheral surface of the sleeve 26. When oil flows through the return passage 26E, the viscous stress exerted by the oil, which is a viscous fluid, is applied to each side surface of the return passage 26E (sleeve 26) that is an object placed in the oil flow. It will act in the road direction. Therefore, when oil flows through the return passage 26E, a rotational force in the circumferential direction is applied to the sleeve 26. Since the sleeve 26 is slidably mounted in the circumferential direction in the above-described configuration, the sleeve 26 rotates in the circumferential direction when the valve opening pressure of the relief valve 20 is in the low pressure stage. . Furthermore, even when the valve opening pressure is switched from the low pressure stage to the high pressure stage, the sleeve 26 slides downward in the axial direction while rotating due to the inertia of the rotary motion.

Therefore, in the process in which the sleeve 26 reciprocates between the low pressure stage control position and the high pressure stage control position, the rotation of the sleeve 26 causes the outer peripheral surface of the sleeve 26 and the inner surface of the bore 23 to rotate relatively. Uneven wear between the sleeve 26 and the valve body 21 is suppressed. Not only this, even if a bubble or a foreign object enters the clearance between the outer peripheral surface of the sleeve 26 and the inner peripheral surface of the bore 23, such a bubble or foreign material is rotated along the inner surface of the bore 23. 26E is sequentially captured by this, and is thereby discharged to the suction side of the pump 13, so that bubbles and foreign matter are less likely to stagnate even during clearance.

  If there is a period in which the outlet passage 25 and the relief hole 29 are temporarily disconnected due to such rotation of the sleeve 26, the relief passage 15 is closed during that period, and the relief valve 20 The function itself will be lost. Further, when there is a period in which the outlet passage 25 and the return passage 26E are temporarily disconnected in a state where the valve opening pressure is switched to the low pressure stage, oil does not flow through the return passage 26E during that period. The efficiency of discharging bubbles and foreign matters sent into the back pressure chamber 35 is reduced, and the effect of suppressing uneven wear between the sleeve 26 and the valve body 21 is also reduced.

  In this respect, in the present embodiment, the valve body 21 is configured in such a manner that the outlet passage 25 is opened over the entire inner periphery of the bore 23, and further, a relief hole is formed in the recess 26D provided in the outer peripheral surface of the sleeve 26. A sleeve 26 is formed in such a manner that 29 opens. By doing so, even if the sleeve 26 is in a rotating state, the outlet passage 25 and the relief hole 29 can always maintain communication with each other, and a flow path for oil flowing out from the relief hole 29 is always secured. Will be. Similarly, if the valve opening pressure is switched to the low pressure stage, the outlet passage 25 and the return passage 26E can always maintain their communication, and the back pressure chamber 35 and the outlet passage 25 are connected to each other. An oil passage is secured. As a result, the relief function of the relief valve 20 is stably expressed, and the discharge efficiency of bubbles and foreign matters and the effect of suppressing uneven wear are surely expressed.

  Inside the sleeve 26 having such a configuration, a valve body 27 that has a cylindrical shape with a lid and can close the relief hole 29 by the outer peripheral surface thereof is relatively axially and circumferentially relative to the sleeve 26. The interior is slidable. The valve body 27 is connected to the valve body support portion 22 </ b> A via an urging spring 30 that is also housed inside the sleeve 26, and is urged upward by the urging force of the urging spring 30. The valve body 27 having such a configuration receives a force for pushing down the valve body 27 based on the hydraulic pressure in the inlet communication hole 28, and pushes up the valve body 27 based on a biasing force corresponding to the amount of contraction of the biasing spring 30. You will receive power. That is, as the force based on the hydraulic pressure increases, the valve body 27 approaches the valve body support portion 22A, and as the force based on the hydraulic pressure decreases, the valve body 27 moves away from the valve body support portion 22A.

  In the variable hydraulic system 10 having such a configuration, whether or not the valve body 27 opens the relief hole 29, that is, whether or not the oil is relieved is defined by the relative position of the valve body 27 and the relief hole 29. The Rukoto. That is, depending on whether the hydraulic pressure that defines the position of the valve body 27 is the valve opening pressure, whether or not the oil is relieved is switched, and the hydraulic pressure of the back pressure chamber 35 that defines the position of the relief hole 29 is switched. Since the application state is in two stages, the above-described valve opening pressure is switched to two stages.

More specifically, when the sleeve 26 is disposed at the low pressure stage control position, the valve body 27 continues to close the relief hole 29 until the hydraulic pressure on the discharge side of the pump 13 reaches the valve opening pressure of the low pressure stage. It becomes. When the hydraulic pressure on the discharge side of the pump 13 reaches the valve opening pressure of the low pressure stage, the valve element 27 opens the relief hole 29 in a state where the contraction amount of the biasing spring 30 is relatively small. On the other hand, when the sleeve 26 is disposed at the high pressure stage control position, the valve element 27 continues to close the relief hole 29 until the hydraulic pressure on the discharge side of the pump 13 reaches the valve opening pressure of the high pressure stage. . That is, even if the hydraulic pressure on the discharge side of the pump 13 becomes the valve opening pressure of the low pressure stage, the amount of contraction of the urging spring 30 is small, so that the valve element 27 continues to close the relief hole 29. When the hydraulic pressure on the discharge side of the pump 13 reaches the valve opening pressure of the high pressure stage, the valve element 27 opens the relief hole 29 in a situation where the amount of contraction of the biasing spring 30 is relatively large.

Next, the operation mode of the relief valve 20 in the variable hydraulic system 10 will be described.
First, the case where the valve opening pressure of the relief valve 20 is selected to the low pressure stage will be described with reference to FIG. FIG. 4A shows a schematic configuration of the variable hydraulic system 10 centering on the sectional structure of the relief valve in the closed state. FIG. 4B shows a schematic configuration of the variable hydraulic system 10 centering on the cross-sectional structure of the relief valve 20 in the opened state.

  As shown in FIG. 4A, when the switching valve 40 is energized by the electronic control unit 45 based on the engine operating state, the lead-in / out passage 41 and the introduction passage 42 communicate with each other from the pump 13. Part of the discharged oil is supplied to the back pressure chamber 35 through the introduction passage 42, the lead-in / out passage 41, and the lead-in / out hole 36. When oil is supplied to the back pressure chamber 35, the oil pressure in the back pressure chamber 35 is increased to a pressure substantially equal to the oil pressure in the inlet passage 24, and the back pressure surface 26 </ b> C of the sleeve 26 corresponds to the oil pressure in the back pressure chamber 35. Force acts. At this time, since the lower end portion 26B of the sleeve 26 has a larger outer diameter than the upper end portion 26A, the back surface is a pressure receiving area of the lower end portion 26B rather than the pressure receiving area of the upper end portion 26A of the sleeve 26. The area of the pressure surface 26C is larger, so that the force that pushes the sleeve 26 upward in the axial direction is larger than the force that pushes the sleeve 26 downward on the axial direction acting on the upper end portion 26A of the sleeve 26. The resultant force F <b> 1 pushed upward in the direction acts on the sleeve 26. When the sleeve 26 receives the resultant force F1, the sleeve 26 moves upward in the axial direction and is displaced to the low pressure stage control position.

  At this time, as described above, the return passage 26E is opened when the sleeve 26 is disposed at the low pressure stage control position, and the oil from the switching valve 40 flows to the outlet passage 25 through the back pressure chamber 35. Air bubbles and foreign matter that have entered the back pressure chamber 35 and the lead-in / out passage 41 are discharged to the outlet passage 25. Further, the opening portion of the return passage 26E acts as a large flow resistance against the outlet passage 25, and even when the return passage 26E is opened, the position is held at the low pressure stage control position. In addition, when the oil flows in the return passage 26E, the sleeve 26 rotates in the circumferential direction, and the effect of suppressing uneven wear is exhibited.

  In such a state, when the hydraulic pressure on the discharge side of the pump 13 is increased as the engine rotational speed increases, the force that pushes the valve body 27 downward in the axial direction increases. As a result, the valve body 27 It will be displaced downward in the axial direction. Then, as shown in FIG. 4B, when the hydraulic pressure on the discharge side of the pump 13 becomes the valve opening pressure of the low pressure stage, the valve body 27 is connected to the inlet passage 24, the inlet communication hole 28, the relief hole 29, and the outlet passage. 25 is displaced to a position where it communicates. Accordingly, excess oil on the downstream side of the pump 13 is relieved to the upstream side of the pump 13 through the relief passage 15, and the hydraulic pressure on the discharge side of the pump 13 is held in the low pressure stage. In such a state, since the position of the relief hole 29 is relatively on the upper side in the movement range, the oil is relieved in a situation where the amount of contraction of the biasing spring 30 is relatively small. As a result, the hydraulic pressure on the discharge side of the pump 13 is controlled to the low pressure stage.

  As described above, in the relief valve 20 of the present embodiment, since the valve body 27 and the sleeve 26 are configured to be relatively slidable in the circumferential direction, the sleeve 26 is in the low pressure stage control position. Although the sleeve 26 surrounding the valve body 27 continues to rotate in the circumferential direction during the period in which the valve body 27 is disposed, the relief hole 29 can be opened and closed smoothly regardless of the rotation of the sleeve 26. Will be implemented.

  Next, a case where the valve opening pressure of the relief valve 20 is selected as the high pressure stage will be described with reference to FIG. FIG. 5A shows a schematic configuration of the variable hydraulic system 10 centering on the cross-sectional structure of the relief valve in the closed state. FIG. 5B shows a schematic configuration of the variable hydraulic system 10 centering on the cross-sectional structure of the relief valve 20 in the valve open state.

  When the valve opening pressure of the relief valve 20 is switched from the low pressure stage to the high pressure stage based on the engine operating state, the electronic controller 45 first cuts off the energization to the switching valve 40. When the switching valve 40 is de-energized, as shown in FIG. 5 (a), the lead-in / out passage 41 and the introduction passage 42 are disconnected and the supply of oil to the back pressure chamber 35 is prohibited. The lead-in / out passage 41 and the discharge passage 43 communicate with each other. As a result, the hydraulic pressure in the back pressure chamber 35 is reduced, and the force that pushes down the sleeve 26 becomes larger than the force that pushes up the sleeve 26, and the resultant force F <b> 2 that pushes the sleeve 26 downward in the axial direction acts on the sleeve 26. Become. When the sleeve 26 receives the resultant force F2, the sleeve 26 is displaced downward in the axial direction from the low-pressure stage control position, and the displacement of the sleeve 26 causes the back pressure chamber 35 and the outlet passage 25 to communicate with each other through the return passage 26E. Will be blocked. Further, the relief hole 29 is moved axially below the valve body 27 due to the displacement of the sleeve 26 to block the relief passage 15, and the sleeve 26 and the valve body 27 undergo a relative displacement to move the sleeve 26. The valve body 27 comes into contact with the upper end portion 26A of the valve.

  When the hydraulic pressure on the discharge side of the pump 13 is increased by blocking the relief passage 15, the valve body 27 is further displaced downward in the axial direction against the urging force of the urging spring 30. As a result, the sleeve 26 is further displaced downward in the axial direction, and is eventually disposed at the high-pressure stage control position. When the volume of the back pressure chamber 35 is reduced due to the displacement from the low pressure stage control position to the high pressure stage control position, the oil contained in the back pressure chamber 35 and the lead-in / in passage 41 is equivalent to the reduced volume. It will be discharged to the relief passage 15 through the discharge passage 43. Even during the period in which the sleeve 26 is displaced from the low-pressure stage control position to the high-pressure stage control position, the sleeve 26 is slid downward in the axial direction while rotating due to the inertia of the rotary motion, and the effect of suppressing uneven wear is obtained. Will be expressed.

  In such a state, when the hydraulic pressure on the discharge side of the pump 13 is increased as the engine rotational speed increases, the force that pushes the valve body 27 downward in the axial direction increases. As a result, the valve body 27 It will be displaced downward in the axial direction. As shown in FIG. 5B, when the hydraulic pressure on the discharge side of the pump 13 becomes the valve opening pressure of the high-pressure stage, the valve body 27 has the inlet passage 24, the inlet communication hole 28, the relief hole 29, and the outlet passage. 25 is displaced to a position where it communicates. In such a state, since the position of the relief hole 29 is relatively on the lower side in the axial direction within the movement range, the oil is relieved in a situation where the amount of contraction of the biasing spring 30 is relatively large. As a result, the hydraulic pressure on the discharge side of the pump 13 is controlled to the high pressure stage.

  Incidentally, switching of the valve opening pressure from the high pressure stage to the low pressure stage is executed after the engine operating state of the internal combustion engine shifts to an operating state suitable for low pressure stage control. That is, the engine rotational speed decreases, the hydraulic pressure on the discharge side of the pump 13 becomes equal to or lower than the valve opening pressure of the low pressure stage, the valve body 27 is displaced upward in the axial direction, and the relief passage 15 is shut off. Is switched.

As described above, according to the variable hydraulic system in the present embodiment, the following effects can be obtained.
(1) According to the above embodiment, since the return passage 26E is opened when the back pressure chamber 35 is pressurized, air bubbles and foreign matter carried to the back pressure chamber 35 The oil that continues to circulate is discharged from the back pressure chamber 35 to the suction side of the pump 13. In addition, when oil flows through the return passage 26E, the sleeve 26 itself rotates in the circumferential direction by the oil flowing therethrough, and the return passage 26E rotates in the circumferential direction with respect to the inner surface of the bore 23. Therefore, even if bubbles or foreign matter enters the clearance between the sleeve 26 and the bore 23, the bubbles and foreign matter are sequentially captured by the rotating return passage 26E, and are thereby discharged to the suction side of the pump 13. The Rukoto. Moreover, since the outer peripheral surface of the sleeve 26 rotates with respect to the inner surface of the bore 23, uneven wear associated with the sleeve 26 and the bore 23 is also reduced.

  (2) According to the above embodiment, since the return passage 26E is opened upon receiving the pressure increase in the back pressure chamber 35, the pressure increase in the back pressure chamber 35 required for switching the valve opening pressure is the return passage. As a result, the return passage 26E is opened from the state in which the back pressure chamber 35 starts to be pressurized. Therefore, if the back pressure chamber 35 and the return passage 26E communicate with each other immediately before the back pressure chamber 35 is increased, the oil supplied to the back pressure chamber 35 easily flows out from the return passage 26E. Thus, the state in which the pressure is hardly increased is avoided, and the application of the hydraulic pressure in the back pressure chamber 35 is smoothly switched. Therefore, according to the above-described configuration, the reliability of the switching operation of the valve opening pressure is improved.

  (3) According to the above embodiment, the return passage 26E is formed in a spiral shape extending in the axial direction, and the flow path direction, in which the oil flows in the return passage 26E, intersects the axial direction. When oil flows through the return passage 26E, the viscous stress exerted by the oil, which is a viscous fluid, acts stably in the flow path direction, that is, in the direction intersecting the axial direction. Therefore, when oil flows in the return passage 26E, the rotational force in the circumferential direction is given to the sleeve 26 with high reproducibility. As a result, the effect of discharging bubbles and foreign matters entering the relief valve 20 and the effect of reducing the above-described uneven wear are more reliably exhibited.

  (4) According to the above embodiment, since the outlet passage 25 communicating with the suction side of the pump 13 has the opening in the entire circumferential direction on the inner surface of the bore 23, the sleeve 26 is rotated in the circumferential direction. Even so, the outlet of the relief hole 29 and the outlet passage 25 always communicate with each other, and the relief function of the relief valve 20 is always maintained. In addition, since the outlet of the relief hole 29 is provided in the recess 26D over the entire outer periphery of the sleeve 26, the relief hole 29 and the outlet passage 25 always communicate with each other through the recess 26D even if the sleeve 26 rotates. As a result, the relief function of the relief valve 20 is more reliably maintained.

In addition, you may change the said embodiment as follows.
In the above embodiment, the sleeve 26 is displaced to the high-pressure stage control position along with the pressure decrease in the back pressure chamber 35 (reduction of the back pressure chamber 35), and the pressure increase in the back pressure chamber 35 (enlargement of the back pressure chamber 35). The relief valve 20 is configured in such a manner that the sleeve 26 is displaced to the low pressure stage control position. By changing this, for example, a back pressure chamber is provided between the upper end portion of the sleeve 26 and the inlet passage 24, and the sleeve is moved upward as the hydraulic pressure in the back pressure chamber is lowered and displaced to the low pressure stage control position. The relief valve may be configured in such a manner that the sleeve is moved downward and displaced to the high pressure stage control position as the hydraulic pressure in the back pressure chamber is increased. Even in such a configuration, the same effect as described above can be obtained when the return passage is opened due to the displacement of the sleeve due to the pressure increase in the back pressure chamber and the sleeve rotates due to the oil flow therein. .

In the above embodiment, the return passage 26E is configured such that the back pressure chamber 35 and the outlet passage 25 communicate with each other when the sleeve 26 is displaced to the low pressure stage control position. Not limited to this, if the sleeve 26 reliably reaches the low-pressure stage control position in a state where the back pressure chamber 35 and the outlet passage 25 communicate with each other, the return passage 26E is opened by the pressure increase of the back pressure chamber 35. There may be.

  In the above embodiment, the relief hole 29 constituting the relief passage 15 has an opening in the recess 26 </ b> D that extends over the entire outer peripheral surface of the sleeve 26. Even if there is a period when the outlet passage and the relief hole are temporarily disconnected by changing such a configuration, the fluctuation of the hydraulic pressure on the discharge side of the pump 13 is sufficiently small with respect to the supply target during this period. If so, a configuration in which the recess 26D of the sleeve 26 is omitted may be employed.

  In the above embodiment, the outlet passage 25 has an opening over the entire circumference of the inner surface of the bore 23. Even if there is a period in which the outlet passage and the relief hole are temporarily disconnected by changing such a configuration, as described above, the fluctuation of the hydraulic pressure on the discharge side of the pump 13 is the same as the supply target in this period. As long as it is sufficiently small, the outlet passage may be configured in such a manner that an opening is provided only in a part of the inner surface of the bore 23.

  In the above embodiment, the return passage 26E is recessed in the outer peripheral surface of the sleeve 26. However, the present invention is not limited to this, and as shown in FIG. The return passage 21 </ b> C may be recessed in the inner surface of the bore 23. In the figure, the sleeve 26 when it is disposed at the low-pressure stage control position is indicated by a two-dot chain line. Even in such a configuration, oil flows from the switching valve 40 to the outlet passage 25 through the back pressure chamber 35, and bubbles and foreign matter fed into the back pressure chamber 35 are discharged to the suction side of the pump 13. It becomes. The oil flowing through the return passage exerts a viscous stress on the outer peripheral surface of the sleeve 26, and the sleeve 26 is rotated so as to be guided by the oil flow.

  In the above embodiment, the return passage 26E is formed in a spiral shape extending in the axial direction. However, the present invention is not limited to this, and for example, a part of the return passage 26E is a shaft like the return passage 26F shown in FIG. The cross-sectional area (flow-path area) in the flow-path direction is gradually reduced, for example, like a return path 26G shown in FIG. 7B. May be. Further, for example, a part of the lower end portion 26B of the sleeve 26 may be cut away as in a return passage 26H shown in FIG. In these return passages, in addition to the above-described viscous stress, it is possible to obtain rotational force by oil colliding with the side wall of the notched portion.

  In other words, whether the side surface constituting the flow path is a side surface along the axial direction or the flow path area is different along the flow path direction, the direction intersecting the axial direction on the side surface constituting the flow path If the flow of oil to the surface is expressed, the flow channel shape, flow channel area, flow channel length, etc. are appropriately determined according to the required rotational force and the shape of the back pressure chamber 35 and the outlet passage 25. It can be changed. Even in such a configuration, the same effect as described above can be obtained.

  In the above embodiment, the back pressure surface 26 </ b> C, which is the lower end surface of the sleeve 26, is fitted in the gap between the valve body support portion 22 </ b> A and the bore 23 (stepped portion provided at the bottom of the bore 23). A back pressure chamber 35 is defined in the gap. For example, if the valve body 27 is connected to the inlet passage 24 via an urging spring, the low-cylindrical sleeve is adopted by omitting the valve body support portion 22A from the fixing member 22. The back pressure chamber 35 may be constituted by the gap itself between the bottom surface of the sleeve and the fixing member. Such a configuration facilitates simplification of the shape of the back pressure chamber, and the degree of freedom in designing the configuration of the return passage communicating with the back pressure chamber is expanded.

In the above embodiment, the cylindrical sleeve 26 is embodied as a hollow cylindrical movable member. The shape of the columnar movable member is not limited to this. For example, the shape of the cylindrical movable member is not hollow as long as the valve opening pressure can be switched according to the application mode of the hydraulic pressure in the back pressure chamber. Can also be embodied.

  C ... central shaft, 10 ... variable hydraulic system, 11 ... oil pan, 12 ... supply passage, 13 ... pump, 14 ... oil strainer, 15 ... relief passage, 20 ... relief valve, 21 ... valve body, 22 ... closing member, 22A ... Valve body support, 22B ... Stopper, 23 ... Bore, 24 ... Inlet passage, 25 ... Outlet passage, 26 ... Sleeve, 26A ... Upper end, 26B ... Lower end, 26C ... Back pressure surface, 26D ... Recess, 21C, 26E, 26F, 26G, 26H ... return passage, 27 ... valve body, 28 ... inlet communication light, 29 ... relief hole, 30 ... biasing spring, 35 ... back pressure chamber, 36 ... lead-in / out hole, 40 ... switching valve, DESCRIPTION OF SYMBOLS 41 ... Lead-in / in passage, 42 ... Introduction passage, 43 ... Discharge passage, 45 ... Electronic control unit, 50 ... Variable hydraulic system, 51 ... Oil pan, 52 ... Supply passage, 53 ... Pump, 54 ... Oil strainer 55 ... Relief passage, 60 ... Relief valve, 61 ... Valve body, 61a ... Bore, 62 ... Closing member, 62a ... Closing part, 63 ... Storage chamber, 64 ... Inlet passage, 65 ... Outlet passage, 66 ... Sleeve, 67 ... Valve body 68 ... Valve body sliding hole 69 ... Relief hole 70 ... Energizing spring 71 ... Back pressure chamber 72 ... Back pressure passage 73 ... Switching valve

Claims (5)

A relief valve provided on the discharge side of the pump having a cylindrical movable member that changes the valve opening pressure by axial displacement according to the hydraulic pressure applied from the back pressure chamber, and the hydraulic pressure in the back pressure chamber A variable hydraulic system comprising a switching valve for switching an application mode, and changing a supply pressure to a supply target by switching a pressure stage of the valve opening pressure by switching the application mode,
The relief valve is
A bore that slidably houses the movable member in its axial and circumferential directions;
It is recessed in either one of the outer peripheral surface of the movable member and the inner peripheral surface of the bore, and the suction side of the pump communicates with the back pressure chamber by the displacement of the movable member due to the pressure increase of the back pressure chamber. A return passage,
The return passage is
A variable hydraulic system, wherein the flow of oil in the return passage is configured to rotate the movable member in the circumferential direction. The variable hydraulic system according to claim 1, wherein a flow path direction of the return passage is a direction intersecting the axial direction. A relief hole having an outlet in the peripheral wall of the movable member and relieving oil from the discharge side of the pump to the suction side of the pump;
3. The variable hydraulic system according to claim 1, further comprising an outlet passage that communicates the suction side of the pump and the outlet of the relief hole through an opening over the entire circumference of the inner surface of the bore. A relief hole that has an outlet in a recess extending over the entire circumference of the outer peripheral surface of the movable member to relieve oil from the discharge side of the pump to the suction side of the pump;
4. The outlet passage according to claim 1, further comprising an outlet passage having an opening communicating with the concave portion of the movable member on an inner surface of the bore and communicating with a suction side of the pump. Variable hydraulic system. The movable member is a sleeve that is housed in the bore and is displaced between a first position and a second position defined according to a pressure stage of the valve opening pressure;
The back pressure chamber is defined in the bore by one end portion of the sleeve in the sliding direction, and the volume of the back pressure chamber is increased by the displacement of the sleeve from the first position to the second position. The volume is reduced by displacing from the second position to the first position,
5. The variable according to claim 1, wherein the return passage communicates the suction side of the pump and the back pressure chamber when the sleeve is in the second position. 6. Hydraulic system.

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