JP5453911B2 - Variable hydraulic system - Google Patents

Description

  The present invention relates to a variable hydraulic system including a relief valve whose relief pressure is changed by a switching valve.

  As a variable hydraulic system that changes the pressure of oil supplied to an internal combustion engine, for example, a variable hydraulic system that includes a relief valve that controls a relief pressure in two stages as in Patent Document 1 is known. In a variable hydraulic system equipped with such a relief valve, the relief pressure of the relief valve is set to a low pressure stage when the engine is operated without high supply pressure, for example, when the engine is started, thereby reducing the load on the oil pump. Improved fuel economy can be realized. In recent years, as one of such variable hydraulic systems, a variable hydraulic system has been developed that switches the relief pressure of a relief valve into two stages, 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. An example of such a variable hydraulic system will be described below. FIG. 4A shows a schematic configuration of such a variable hydraulic system together with a sectional structure of a relief valve. FIG. 4A shows a state when the valve is opened when the relief pressure is selected as the high pressure stage.

  As shown in FIG. 4, 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 the 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 the pressure exceeds a predetermined relief pressure.

  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. The closing member 62 that closes the bottom of the bore 61a extends to the inlet passage 64. A cylindrical closing portion 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 housing chamber 63 and the other end connected to the suction 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 through the introduction passage 74, and the hydraulic pressure in the back pressure chamber 71 is reached. Is boosted. As a result, one end in the longitudinal direction of the sleeve 66 is displaced to the low-pressure stage control position, which is a position where the sleeve 66 comes into contact with the end on the inlet passage 64 side. On the other hand, when the connection destination of the back pressure chamber 71 is switched to the suction side of the pump 53 by the switching valve 73, part of the oil in the back pressure chamber 71 is discharged to the suction side of the pump 53 through the discharge passage 75. The hydraulic pressure in the back pressure chamber 71 is reduced. As a result, the other end of the sleeve 66 in the longitudinal direction moves to the high pressure stage control position, which is a position where the other end of the housing chamber 63 contacts the end of the closing member 62.

  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 coil spring 70 that urges 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 has a force based on the hydraulic pressure in the valve body sliding hole 68 and a coil spring 70 against the force. In accordance with the restoring force of the valve body, the valve body is displaced along the axial direction of the valve body sliding hole 68 within a range crossing the relief hole 69.

  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 a relief 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. Since the application state of the hydraulic pressure is in two stages, the above-described relief pressure is switched to two stages.

Japanese Utility Model Publication 4-105676

  By the way, as shown in FIG. 4A, when the relief pressure of the relief valve 60 is controlled to the high pressure stage, the engine speed is significantly reduced, that is, the back pressure chamber 71 is discharged via the switching valve 73. When the engine rotational speed is significantly reduced while communicating with the use passage 75, the hydraulic pressure in the supply passage 52 is significantly reduced as the rotational speed of the engine-driven pump 53 is significantly reduced. In the relief valve 60 in such a process, first, the valve body 67 moves toward the inlet passage 64 by the biasing force of the coil spring 70. Next, the valve body 67 abuts against the sleeve 66, and the valve body 67 and the sleeve 66 move integrally toward the inlet passage 64. Finally, as shown in FIG. Displaces to the control position.

  When the sleeve 66 is displaced to the low pressure stage control position as described above, the volume of the back pressure chamber 71 is forcibly expanded in a state where oil is not supplied from the introduction passage 74 to the back pressure chamber 71. As a result, in accordance with the negative pressure in the back pressure chamber 71 generated by the forced expansion of the volume, the oil flows back toward the back pressure chamber 71 from the flow path that normally drains the oil in the back pressure chamber 71. Will do. That is, the oil flows back toward the back pressure chamber 71 through the pair of back pressure passages 72 and the discharge passage 75 configured to sandwich the switching valve 73.

When the variable hydraulic system is driven in a state where such a backflow does not occur, oil is supplied only from the introduction passage 74 to the back pressure passage 72 and from only the back pressure passage 72 to the discharge passage 75. Oil is supplied, and eventually all the passages are filled with oil from the introduction passage 74. Therefore, the switching valve 73 sandwiched between the back pressure passage 72 and the discharge passage 75 is cleaned by the oil supplied from the introduction passage 74, that is, by the filter provided on the pump or the discharge side of the pump. Only the collected oil will flow in.

  On the other hand, when the above-described backflow occurs, the oil flows back from the back pressure passage 72 and the discharge passage 75 toward the back pressure chamber 71, and thus the back flowing oil is supplied. It is supplied from the passage 52. Therefore, in the switching valve 73 sandwiched between the back pressure passage 72 and the discharge passage 75, oil supplied from the supply passage 52, that is, oil containing a relatively small foreign matter that has passed through the oil strainer 54 is contained. Will flow in. Each time the forcible expansion of the back pressure chamber 71 is repeated, oil containing such foreign matter is introduced, and foreign matter is accumulated in the switching valve 73 or in the back pressure chamber 71 side thereof. In this way, the foreign matter that flows into the back pressure chamber 71 through the switching valve 73 or through the switching valve 73 causes clogging of the flow path in the switching valve 73 or malfunction of the valve body at the subsequent switching of the relief pressure. There is a risk that the reliability of the relief pressure switching operation in the relief valve may be impaired.

  The present invention has been made in view of the above circumstances, and the purpose thereof is a variable hydraulic system including a relief valve in which a relief pressure is changed by switching an application mode of hydraulic pressure in a back pressure chamber by a switching valve. An object of the present invention is to provide a variable hydraulic system in which the reliability of the relief pressure switching operation in the relief valve is improved.

In the following, means for achieving the above object and its effects are described.
According to the first aspect of the present invention, the displacement of the back pressure chamber is increased and reduced in accordance with the difference between the hydraulic pressure in the back pressure chamber and the hydraulic pressure on the discharge side of the pump. A relief valve having a movable member that changes the relief pressure, a communication destination that communicates with the back pressure chamber, a discharge passage that connects an oil supply target and the pump, an intake tank that connects an oil tank and the pump A switching valve that switches to a passage, and changes the hydraulic pressure in the back pressure chamber by switching the communication destination by the switching valve, and changes the relief pressure of the relief valve by the displacement of the movable member according to the hydraulic pressure. a variable hydraulic system, the volume of the discharge passage connecting the switching valve and with said suction passage much larger than the maximum change in volume of the back pressure chamber, said suction passage While positioned in the direction of gravity than the selector valve, it is summarized in that the discharge passage is a passage extending to said suction passage along the direction of gravity from said switching valve.

According to the first aspect of the present invention, the volume of the discharge passage connecting the switching valve and the suction side of the pump is larger than the maximum amount of change in the volume of the back pressure chamber. The volume is always larger than the volume of oil sucked into the back pressure chamber. When the hydraulic pressure on the discharge side of the pump is lower than the hydraulic pressure on the back pressure chamber, the movable member is displaced in such a way that the volume of the back pressure chamber increases even if the communication destination of the back pressure chamber is on the suction side of the pump. Can do. When the volume of the back pressure chamber is forcibly expanded in this way, the oil on the suction side of the pump that is the communication destination of the back pressure chamber, that is, the oil in the discharge passage flows back into the back pressure chamber. Become. With the configuration as described above, even if the oil in the discharge passage flows back into the back pressure chamber, the capacity of the oil that flows back (inhales) into the back pressure chamber is larger than the oil capacity in the discharge passage. Since it is always small, the oil in the suction passage, which is the connection destination of the discharge passage, does not reach the switching valve. This makes it difficult for foreign matter contained in the oil in the suction passage to flow into the switching valve. As a result, the malfunction of the switching valve due to foreign matter is less likely to occur, and the reliability of the relief pressure switching operation in the relief valve can be improved.
Further, since the suction passage is positioned in the direction of gravity with respect to the switching valve, the foreign matter flowing into the discharge passage connecting them receives a force (self-weight) that returns to the suction passage. That is, since the discharge passage becomes longer in the direction of gravity, it is difficult for foreign matter in the suction passage to flow into the switching valve, and the degree of freedom of the shape of the discharge passage can be expanded.
In addition, since the discharge passage is configured to extend in the direction of gravity over its entire length, foreign matter that has flowed into the discharge passage is more effective due to its own weight when the discharge passage is isolated from the oil distribution route. Will move to the end of the suction passage. Therefore, the foreign matter in the suction passage is less likely to flow into the switching valve, and the reliability of the relief pressure switching operation in the relief valve can be further improved.

The gist of the invention described in claim 2 is that the volume of the discharge passage is larger than the maximum volume of the back pressure chamber.
According to the second aspect of the present invention, even if the oil in the discharge passage flows back into the back pressure chamber, the capacity of the oil that flows back (inhales) into the back pressure chamber is the capacity of the oil in the discharge passage. Therefore, the oil in the suction passage, which is the connection destination of the discharge passage, does not reach the switching valve. Therefore, the reliability of the relief pressure switching operation is further improved.

The schematic block diagram which showed the structure of the variable hydraulic system concerning this invention centering on the cross section of the relief valve. The relief pressure of the relief valve is selected as a low pressure stage, and (a) a diagram showing the flow of oil centering on the sectional structure of the relief valve in the closed state, and (b) in the opened state. The figure which showed the flow of oil centering on the cross-section of a relief valve. The relief pressure of the relief valve is selected in the high pressure stage, (a) a diagram showing the flow of oil centering on the sectional structure of the relief valve in the closed state, and (b) in the opened state. The figure which showed the flow of oil centering on the cross-section of a relief valve. In the conventional variable hydraulic system, when the relief pressure is selected in the high pressure stage, (a) a diagram showing the flow of oil centering on the sectional structure of the relief valve in the valve open state, (b) the sleeve is The figure which showed the flow of the oil at the time of displacing to a low voltage | pressure stage control position.

Hereinafter, an embodiment embodying a variable hydraulic system according to the present invention will be described with reference to FIGS. FIG. 1 is a configuration diagram showing a schematic configuration of a variable hydraulic system centering on a sectional structure 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. Hereinafter, the supply passage 12 on the suction side of the pump 13 is referred to as a suction passage 12a, and the supply passage 12 on the discharge side of the pump 13 is referred to as a discharge passage 12b. An oil strainer 14 for removing relatively large impurities contained in the oil is provided at the end of the suction passage 12a on the suction side.

  When the pump 13 is driven in accordance with the engine operation of the internal combustion engine, the oil stored in the oil pan 11 is sucked up by the pump 13 through the oil strainer 14 and the suction passage 12a, and each part of the internal combustion engine is discharged from the discharge passage 12b. For example, the oil is supplied to various hydraulically driven devices driven by the oil pressure. Further, the oil is injected into a piston for taking out the engine output, and the oil is supplied to a piston jet mechanism that cools the piston and a lubricated portion of the engine. A relief passage 15 connected to the discharge side and the suction side of the pump 13 is provided in the middle of the discharge passage 12b. 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 the pressure exceeds a predetermined relief pressure.

  A bore 23 which is a circular hole having an opening on the end surface of the valve main body 21 is provided at one end (left end shown in FIG. 1) of the valve main body 21 constituting the relief valve 20. The opening of the bore 23 is closed by a closing member 22, whereby a storage chamber corresponding to the internal space of the bore 23 is defined in the valve body 21. The closing member 22 constituting the housing chamber is provided with a substantially cylindrical valve body support portion 22 </ b> A 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 22A and the inner peripheral surface of the bore 23 so that the distance between them is substantially equal to the entire inner peripheral surface of the bore 23. Yes. 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.

  The other end of the valve body 21 is provided with an inlet opening 24 having a diameter smaller than the diameter of the bore 23 described above on the same axis as the bore 23. The relief passage 15 connected to the discharge side of the pump 13 and the above-described storage chamber communicate with each other via the inlet opening 24. An axially wide outlet passage 25 is provided in the vicinity of the axial center position of the bore 23 so as to open to the inner peripheral 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. The axial length of the sleeve 26 is formed shorter than the axial length of the storage chamber, and one end portion 26B of the sleeve 26 is formed between the outer peripheral surface of the valve body support portion 22A and the bore 23 described above. It is fitted in the gap between the inner peripheral surface. That is, the gap between the outer peripheral surface of the valve body support portion 22A and the inner surface of the bore 23 is partitioned in the axial direction by the back pressure surface 26C which is the end surface on the one end portion 26B side of the sleeve 26. The back pressure chamber 35 surrounded by the outer peripheral surface of the valve body support portion 22A, the inner peripheral surface of the bore 23, and the back pressure surface 26C of the sleeve 26 has its volume increased when the sleeve 26 is displaced in the axial direction. The gap is defined in the above-described gap around the entire circumference of the bore 23 in such a manner that it can be enlarged and reduced.

  At a position facing the stopper 22B across the central axis C, a lead-out hole 36 that opens to the inner peripheral 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 back pressure passage 41 whose one end is connected to the switching valve 40 is connected to the lead-in / out hole 36. The switching valve 40 is configured such that the suction passage 12a is positioned in the gravity direction of the switching valve 40. The switching valve 40 includes a discharge passage 12b on the discharge side of the pump 13 in addition to the back pressure passage 41. Are connected to a suction passage 43 connected to the suction side of the pump 13 and a discharge passage 43 as a passage extending in the direction of gravity. The discharge passage 43 has an oil flow path having a volume V1 larger than the maximum change amount ΔV of the volume of the back pressure chamber 35 that can be expanded and contracted. When the switching valve 40 performs the switching operation, the connection destination of the back pressure 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 back pressure 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 switching valve 40 is de-energized, the passage communicating with the back pressure chamber 35 through the back pressure passage 41 is selected as the discharge passage 43, and the hydraulic pressure in the back pressure chamber 35 is reduced. In this manner, the application mode of the hydraulic pressure to the back pressure chamber 35 is switched.

  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 other end portion 26A of the sleeve 26 is thick, and the other end portion 26A of the sleeve 26 is provided. Is provided with an inflow hole 28 having a smaller diameter than the diameter of the inlet opening 24. The sleeve 26 having such a configuration receives the hydraulic pressure corresponding to the difference between the diameter of the inlet opening 24 and the diameter of the inflow hole 28 from the inlet opening 24 to the end face of the other end 26A. The oil pressure in the back pressure chamber 35 is received by the back pressure surface 26C in a manner opposite to the oil pressure. Then, the sleeve 26 itself slides along the axial direction according to the difference between the force acting on the end face of the other end portion 26A and the force acting on the back pressure face 26C.

  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 enters the inlet opening along the axial direction. Displacement to the 24 side. With such displacement of the sleeve 26, oil on the discharge side of the pump 13 is supplied to the back pressure chamber 35 through the switching valve 40, and the volume of the back pressure chamber 35 is expanded. The displacement of the sleeve 26 itself toward the inlet opening 24 is restricted by the other end 26 </ b> A of the sleeve 26 being locked to the inlet opening 24. Hereinafter, the position of the sleeve 26 where the other end 26A of the sleeve 26 and the inlet opening 24 come into contact is referred to as a low-pressure stage control position.

  Note that when the back pressure chamber 35 and the introduction passage 42 are in communication with each other, the oil stays in the discharge passage 43 because there is almost no oil flow. Since the specific gravity of the foreign matter contained in the oil is larger than that of the oil, the foreign matter moves toward the direction of gravity in the oil in the staying state due to its own weight. Since the discharge passage 43 of the present embodiment is a passage extending along the direction of gravity, the foreign matter in the discharge passage 43 moves in a direction away from the switching valve 40 in the discharge passage 43 and is eventually discharged. It will be discharged from the passage 43. By doing so, foreign matter contained in the oil in the discharge passage 43 is reduced, and foreign matter is prevented from accumulating in the discharge passage 43.

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 closed along the axial direction. It will be displaced to the 22 side. With such displacement of the sleeve 26, the oil in the back pressure chamber 35 is discharged to the lead-in / out hole 36, and the volume of the back pressure chamber 35 is reduced. The displacement of the sleeve 26 itself toward the closing member 22 is restricted by the back pressure surface 26 </ b> C of the sleeve 26 being locked to the stopper 22 </ b> B of the closing member 22. Hereinafter, the position of the sleeve 26 where the back pressure surface 26C contacts the stopper 22B is referred to as a high pressure stage control position.

  Even when the sleeve 26 continues to be positioned at the high pressure stage control position, the oil remains in the discharge passage 43 because the oil hardly flows. As described above, the foreign matter contained in the oil in such a staying state moves in the discharge passage 43 in the direction away from the switching valve 40 and is discharged from the discharge passage 43.

  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 a passage that is displaced in the axial direction along with the displacement of the sleeve 26, and is provided at a position that communicates with the outlet passage 25 in the entire movement range of the sleeve 26. When the sleeve 26 is positioned at the low pressure stage control position, the relief hole 29 is furthest away from the valve body support portion 22A in the moving range, and when the sleeve 26 is positioned at the high pressure stage control position, the relief hole 29 is positioned. Is closest to the valve body support 22A within the moving range.

  Inside the sleeve 26, a valve body 27 which is formed in a cylindrical shape with a lid and which can close the relief hole 29 by its outer peripheral surface is slidably mounted along the axial direction. The valve body 27 is connected to the valve body support portion 22 </ b> A via a coil spring 30 that is also housed inside the sleeve 26, and is urged toward the inflow hole 28 by the restoring force of the coil spring 30. . The valve body 27 having such a configuration receives a force for pushing the valve body 27 toward the closing member 22 based on the hydraulic pressure in the inflow hole 28, and based on a restoring force corresponding to the stroke of the coil spring 30. The force which pushes out from the closing member 22 is received. 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 oil is relieved, is defined by the position of the valve body 27 and the position of the relief hole 29. Will be. That is, depending on whether or not the hydraulic pressure that defines the position of the valve body 27 is the relief pressure, whether or not the oil is relieved is switched, and the application of the hydraulic pressure in the back pressure chamber 35 that defines the position of the relief hole 29 is applied. Since the state is in two stages, the above-described relief pressure is switched to two stages.

  More specifically, when the sleeve 26 is positioned at the low 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 relief pressure of the low pressure stage. When the hydraulic pressure on the discharge side of the pump 13 reaches the relief pressure at the low pressure stage, the valve element 27 opens the relief hole 29 in a state where the stroke of the coil spring 30 is relatively small. On the other hand, when the sleeve 26 is positioned at the high-pressure stage control position, the valve element 27 that receives the restoring force from the coil spring 30 is provided in the relief hole until the hydraulic pressure on the discharge side of the pump 13 reaches the relief pressure of the high-pressure stage. 29 will continue to be closed. That is, even if the hydraulic pressure on the discharge side of the pump 13 becomes the relief pressure at the low pressure stage, the relief hole 29 is closed by the valve element 27 because the stroke of the coil spring 30 is small. When the hydraulic pressure on the discharge side of the pump 13 reaches the relief pressure of the high pressure stage, the valve element 27 opens the relief hole 29 in a situation where the stroke of the coil spring 30 is relatively large.

By the way, when the relief pressure of the relief valve 20 is selected as a high pressure stage, that is, when the back pressure chamber 35 and the discharge passage 43 are in communication with each other, if the engine rotational speed is remarkably reduced, the engine is driven. As a result, the discharge pressure of the pump 13 is reduced, and the oil pressure in the discharge passage 12b is also reduced. In the relief valve 20 in such a case, the valve element 27 is displaced toward the inlet opening 24 by the urging force of the coil spring 30, and the displacement is continued until the sleeve 26 eventually reaches the low pressure stage control position. Become. That is, although the communication destination of the back pressure chamber 35 is the discharge passage 43, the volume of the back pressure chamber 35 is expanded by such forced displacement of the sleeve 26. At this time, oil is introduced into the back pressure chamber 35 by the expanded volume, and when the sleeve 26 is displaced from the high pressure stage control position to the low pressure stage control position, the maximum change amount ΔV is increased. The amount of oil is introduced into the back pressure chamber 35 from the suction passage 12a side.

  Here, in the case where the total volume of the lead-in / out hole 36, the back pressure passage 41, the switching valve 40, the discharge passage 43, and the volume thereof is smaller than the maximum change amount ΔV of the back pressure chamber 35, oil in the suction passage 12a Flows into the back pressure chamber 35 as well as the switching valve 40. In such a case, a minute foreign matter that has passed through the oil strainer 14 flows into the back pressure chamber 35 together with the oil in the suction passage 12a. When the sleeve 26 is positioned at the high-pressure stage control position, the oil stays in the lead-in / out hole 36, the back pressure passage 41, the switching valve 40, and the discharge passage 43, while the oil in the supply passage 12 is pumped. It always flows by 13 discharge operations. Therefore, when the displacement of the sleeve 26 by the valve body 27 described above is repeated, foreign matter contained in the oil in the suction passage 12a newly flows into the switching valve 40 and the back pressure chamber 35 each time. The amount of foreign matter flowing into the inside will increase. As a result, in the back pressure chamber 35, for example, foreign matter accumulates on the stopper 22B and the sleeve 26 cannot be displaced to the high pressure stage control position, and the relief pressure of the relief valve 20 may become unstable. Further, in the switching valve 40, for example, there is a possibility that the smooth switching of the oil flow path may be hindered by foreign matter.

  On the other hand, the discharge passage 43 of the present embodiment has a volume V1 that is larger than the maximum change amount ΔV of the back pressure chamber 35. With such a configuration, even if the volume of the back pressure chamber 35 is repeatedly increased by the maximum change amount ΔV, only the oil remaining in the discharge passage 43 is introduced into the switching valve 40. become. Thus, the oil in the suction passage 12a is not introduced into the back pressure chamber 35 as well as the switching valve 40, and foreign matter contained in the oil in the suction passage 12a flows into the switching valve 40 and the back pressure chamber 35. It becomes difficult. As a result, the malfunction of the switching valve 40 and the back pressure chamber 35 due to foreign matter is less likely to occur, and the relief pressure reliability of the relief valve 20 can be improved.

  In addition, since the discharge passage 43 is a passage extending along the direction of gravity, the foreign matter contained in the oil in the discharge passage 43 passes through the discharge passage 43 by its own weight while the oil remains. It moves in a direction away from the switching valve 40 and is eventually discharged from the discharge passage 43. As a result, foreign matter staying in the discharge passage 43 itself is reduced, and inflow of foreign matter is further reduced in the switching valve 40 and the back pressure chamber 35 into which oil flows from the discharge passage 43.

Next, the operation mode of the relief valve 20 in the variable hydraulic system 10 will be described.
First, the case where the relief pressure of the relief valve 20 is selected as the low pressure stage will be described with reference to FIG. FIG. 2A 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. 2B 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. 2A, when the switching valve 40 is energized by the electronic control unit 45 based on the engine operating state, the introduction passage 42 and the back pressure passage 41 are brought into communication, and the pump Part of the oil discharged from 13 is supplied to the back pressure chamber 35 through the introduction passage 42, the back pressure 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, and the sleeve 26 moves toward the inlet opening 24 along the axial direction and is displaced to the low pressure stage control position.

  At this time, the oil stays in the discharge passage 43 that is isolated from the oil distribution route. Therefore, the foreign matter contained in the oil in the discharge passage 43 moves in a direction away from the switching valve 40 by its own weight, and is eventually discharged to the suction passage 12a.

  On the other hand, when the pressure of the oil discharged from the pump 13 increases as the engine speed increases, the force that pushes the valve body 27 toward the closing member 22 increases, and as a result, the valve body 27 moves toward the closing member 22. Will be displaced. As shown in FIG. 2B, when the hydraulic pressure on the discharge side of the pump 13 reaches the relief pressure of the low pressure stage, the valve element 27 has the inlet opening 24, the inflow hole 28, the relief hole 29, and the outlet passage 25. Is displaced to the position where the communication state is established. As a result, excess oil on the discharge side of the pump 13 is relieved to the suction side of the pump 13 through the relief passage 15, and the pressure of the oil discharged from the pump 13 is held at the relief pressure of the low pressure stage. In such a state, since the relief hole 29 is relatively away from the closing member 22 in the movement range, the oil is relieved in a situation where the stroke of the coil spring 30 is relatively small. As a result, the discharge side of the pump 13 is controlled to the low pressure stage.

  Next, the case where the relief pressure of the relief valve 20 is selected as the high pressure stage will be described with reference to FIG. FIG. 3A shows the variable hydraulic system 10 centering on the sectional structure of the relief valve in the closed state. FIG. 3B 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 relief 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 power supply to the switching valve 40. When the energization to the switching valve 40 is interrupted, as shown in FIG. 3A, the back pressure passage 41 and the introduction passage 42 are disconnected and the supply of oil to the back pressure chamber 35 is prohibited. The back pressure passage 41 and the discharge passage 43 are in communication with each other. As a result, the pressure of the oil in the back pressure chamber 35 is reduced, and the sleeve 26 is displaced from the low pressure stage control position toward the closing member 22 along the axial direction. Further, the relief hole 29 is moved closer to the closing member 22 than the valve body 27 by the displacement of the sleeve 26 and the relief passage 15 is blocked, and the other displacement of the sleeve 26 is caused by the relative displacement between the sleeve 26 and the valve body 27. The valve element 27 comes into contact with the end portion 26A.

  When the hydraulic pressure on the discharge side of the pump 13 is increased by blocking the relief passage 15, the valve element 27 is further displaced toward the closing member 22 against the restoring force of the coil spring 30, and follows this. As a result, the sleeve 26 is further displaced toward the closing member 22 and is eventually positioned at the high-pressure stage control position. When the volume of the back pressure chamber 35 is reduced by the displacement from the low pressure stage control position to the high pressure stage control position, the oil in the back pressure chamber 35 and the back pressure passage 41 is discharged by the reduced volume. 43 is discharged to the suction passage 12a.

As shown in FIG. 3B, when the sleeve 26 is positioned at the high pressure stage control position, the relief hole 29 of the sleeve 26 communicates with the outlet passage 25 on the closing member 22 side in the outlet passage 25 of the valve body 21. As the engine speed increases, the pressure of oil discharged from the pump 13 increases, and when the hydraulic pressure on the discharge side of the pump 13 eventually reaches the relief pressure of the high-pressure stage, the valve element 27 has the inlet opening 24 and the inflow hole. 28, the relief hole 29, and the outlet passage 25 are displaced to a position where they are in communication. As a result, excess oil on the discharge side of the pump 13 is relieved to the suction 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 high pressure stage. That is, when the switching valve 40 is de-energized, the sleeve 26 is displaced to the high pressure stage control position, and the relief hole 29 of the sleeve 26 communicates with the closing member 22 side in the outlet passage 25 of the valve body 21; That is, since the oil is relieved when the stroke of the coil spring 30 is relatively large, the relief pressure of the relief valve 20 becomes the high pressure stage.

  While the sleeve 26 is positioned at the high-pressure stage control position, the oil is in the staying state in the discharge passage 43. Therefore, the foreign matter contained in the oil moves away from the switching valve 40 by its own weight. It moves and eventually is discharged into the suction passage 12a. Further, when the engine rotational speed is remarkably lowered from this state and the discharge pressure of the pump 13 is lowered, the valve body 27 moves to the inlet opening 24 side, and the valve body 27 moves the sleeve 26 to the low pressure stage control position. Displace. At this time, the oil in the suction passage 12a is not introduced into the switching valve 40 and the back pressure chamber 35, and even if the displacement of the sleeve 26 by the valve body 27 described above is repeated, the switching valve 40 and Inflow of new foreign matter into the back pressure chamber 35 is avoided. Therefore, the malfunction of the switching valve 40 and the back pressure chamber 35 caused by the foreign matter is less likely to occur, and the reliability of the subsequent relief pressure switching operation in the relief valve 20 can be improved.

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, the volume V1 of the discharge passage 43 connecting the switching valve 40 and the suction passage 12a on the suction side of the pump 13 is set to be larger than the maximum change amount ΔV of the volume of the back pressure chamber 35. Increased. By doing so, even if the volume of the back pressure chamber 35 is increased when the communication destination of the back pressure chamber 35 is the discharge passage 43, the foreign matter contained in the oil in the suction passage 12a is transferred to the switching valve 40 and the back pressure. Mixing into the chamber 35 is avoided. Therefore, the amount of foreign matter mixed into the switching valve 40 and the back pressure chamber 35 is reduced by the amount by which foreign matter contained in the oil in the suction passage 12a is avoided. As a result, the malfunction of the switching valve 40 and the back pressure chamber 35 due to the foreign matter is less likely to occur, and the reliability of the relief pressure switching operation in the relief valve 20 can be improved.

  (2) According to the above embodiment, the discharge passage 43 is a passage extending along the direction of gravity. As a result, when the oil in the discharge passage 43 is in a staying state, the foreign matter contained in the oil in the discharge passage 43 moves in the direction of gravity due to its own weight, and is eventually discharged into the suction passage 12a. Will be. As a result, the foreign matter contained in the oil in the discharge passage 43 is reduced, and the foreign matter is prevented from accumulating in the discharge passage 43. Therefore, even if the volume of the back pressure chamber 35 is increased when the back pressure chamber 35 and the discharge passage 43 are communicated with each other, the accumulation of foreign matter in the discharge passage 43 is suppressed. Foreign matter mixed in the switching valve 40 and the back pressure chamber 35 can be further reduced.

In addition, you may change the said embodiment as follows.
In the above embodiment, the suction passage 12a is positioned in the gravity direction of the switching valve 40. However, for example, the switching valve 40 is positioned in the gravity direction of the suction passage 12a. However, it suffices if the direction of the passage from the switching valve 40 toward the suction passage 12a includes a component in the gravitational direction in a part of the discharge passage 43. Further, for example, the discharge passage may extend from the switching valve 40 toward the suction passage 12a in the direction intersecting the direction of gravity, or may be a discharge passage bent in the middle. Even with such a configuration, an effect similar to the above (1) can be obtained, and in a passage including a component in the gravity direction, foreign matter in the oil moves in a direction away from the switching valve 40 by its own weight. It is possible to reduce foreign matter flowing into the switching valve 40.

  The volume of the discharge passage may be larger than the maximum volume of the back pressure chamber 35 as long as it is larger than the maximum change amount of the volume of the back pressure chamber 35. According to such a configuration, the same effects as in the above (1) and (2) can be obtained, and the volume of oil that flows back from the suction passage 12a toward the back pressure chamber 35 is greater than the volume of oil in the discharge passage 43. Therefore, the reliability of the relief pressure switching operation is further improved. Further, the discharge passage may be a passage extending in the horizontal direction orthogonal to the direction of gravity, for example, as long as the volume thereof is larger than the maximum change amount ΔV of the back pressure chamber 35.

  In the variable hydraulic system 10 of the above-described embodiment, an oil filter that removes foreign matters smaller than the oil strainer 14 may be provided in the discharge passage 12b. Even with such a configuration, the above-described effects can be obtained. In particular, when the oil filter described above is provided between the pump 13 and the connection portion to the introduction passage 42, the oil supplied from the discharge passage 12b to the switching valve 40 is in a state in which foreign matter is removed therefrom. The effects described above can be obtained more remarkably.

  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. By changing this, for example, if the valve body 27 is connected to the inlet opening 24 via a coil spring, the bottomed cylindrical sleeve is adopted by omitting the valve body support 22A from the closing member 22. The back pressure chamber 35 may be constituted by the gap itself between the bottom surface of the sleeve and the closing member. With such a configuration, it is possible to simplify the shape of the back pressure chamber.

  In the above embodiment, the movable member is embodied as the cylindrical sleeve 26, but the shape of the movable member is not limited to this, and the relief pressure is switched according to the application mode of the hydraulic pressure in the back pressure chamber. Any configuration that can be displaced as much as possible can be embodied in, for example, a rectangular cylindrical configuration or other shapes.

  C: central axis, ΔV: maximum change amount, V1: volume, 10: variable hydraulic system, 11: oil pan, 12: supply passage, 12a ... suction passage, 12b ... discharge passage, 13 ... pump, 14 ... oil strainer, DESCRIPTION OF SYMBOLS 15 ... Relief passage, 20 ... Relief valve, 21 ... Valve main body, 22 ... Closing member, 22A ... Valve body support part, 22B ... Stopper, 23 ... Bore, 24 ... Inlet opening part, 25 ... Outlet passage, 26 ... Sleeve, 26A ... the other end, 26B ... one end, 26C ... the back pressure surface, 27 ... the valve body, 28 ... the inflow hole, 29 ... the relief hole, 30 ... the coil spring, 35 ... the back pressure chamber, 36 ... the lead-in / out hole, 40 ... Switching valve, 41 ... back pressure passage, 42 ... introduction passage, 43 ... discharge passage, 45 ... electronic control device, 50 ... variable hydraulic system, 51 ... oil pan, 52 ... supply passage, 53 ... pump, 54 ... oil strainer , DESCRIPTION OF SYMBOLS 5 ... Relief passage, 60 ... Relief valve, 61 ... Valve body, 61a ... Bore, 62 ... Closing member, 62a ... Closure part, 63 ... Storage chamber, 64 ... Inlet passage, 65 ... Outlet passage, 66 ... Sleeve, 67 ... Valve body 68... Valve body sliding hole 69. Relief hole 70. Coil spring 71 71 Back pressure chamber 72 Back pressure passage 73 Switching valve 74 Introduction passage 75 Discharge passage

Claims (2)

There is a movable member that changes the relief pressure on the discharge side of the pump by displacing the back pressure chamber in a manner that the volume of the back pressure chamber expands and contracts according to the difference between the hydraulic pressure in the back pressure chamber and the hydraulic pressure on the discharge side of the pump. Relief valve,
A switching valve for switching a communication destination with which the back pressure chamber communicates to a discharge passage that connects an oil supply target and the pump, and a suction passage that connects an oil tank and the pump;
A variable hydraulic system that changes the hydraulic pressure in the back pressure chamber by switching the communication destination by the switching valve and changes the relief pressure of the relief valve by displacement of the movable member according to the hydraulic pressure,
The volume of the discharge passage connecting the switching valve and with said suction passage much larger than the maximum change in volume of the back pressure chamber,
The variable hydraulic system characterized in that the suction passage is located in the direction of gravity relative to the switching valve, and the discharge passage is a passage extending from the switching valve to the suction passage along the direction of gravity. . The variable hydraulic system according to claim 1, wherein a volume of the discharge passage is larger than a maximum volume of the back pressure chamber.

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