Relief valve, negative control relief valve and control valve

Abstract

To provide a relief valve, a negative control relief valve and a control valve capable of reducing noise, improving temperature characteristics and reducing influence of fluid force.SOLUTION: A negative control relief valve 10 comprises a case 2, and a relief valve body 20 that is attached to the case 2 and through which hydraulic oil passes. The relief valve body 20 has at least a first diaphragm 43 and a second diaphragm 55 that gives resistance to the hydraulic oil passing through the relief valve body 20.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a relief valve, a negative control relief valve, and a control valve. [Background technology]

[0002] Some control valves are known to be equipped with a so-called negative control relief valve that generates a negative control type pump flow control pressure (hereinafter sometimes referred to as negative control pressure). Some negative control relief valves, for example, have two throttles, a first throttle and a second throttle, provided in two separate locations and connected in series. Each throttle provides resistance to the hydraulic oil (fluid) passing through the negative control relief valve.

[0003] By providing two throttles in series at two separate locations, the flow rate of the hydraulic oil flowing through the first throttle and the flow rate of the hydraulic oil flowing through the second throttle can be slower than when a single throttle is provided. By slowing down the flow rates of the first throttle and the second throttle, it is possible to reduce, for example, noise generated by jets spouting from the two throttles (see Patent Document 1, for example). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3690839 Summary of the Invention [Problem to be solved by the invention]

[0005] In the above-mentioned conventional technology, the second orifice is formed long in the lift direction of the poppet at the sliding portion between the cap and the poppet. If the length of the second orifice is long, it is difficult to keep the pressure difference between the front and rear of the orifice small. Therefore, it is difficult to keep the jet velocity from the second orifice low, and there is a possibility that the noise caused by the jet from the second orifice will be large. In addition, when the restriction is long, the pressure loss characteristics change more greatly due to the oil temperature than when the restriction is short. Therefore, the negative control pressure from the negative control relief valve can change significantly due to the temperature characteristics of the oil temperature.

[0006] The present invention provides a relief valve, a negative control relief valve, and a control valve that can reduce noise and have good temperature characteristics. [Means for solving the problem]

[0007] As a means for solving the above problems, the present invention has the following configuration. A relief valve according to one embodiment of the present invention comprises a case and a relief valve body attached to the case and through which a fluid passes, the relief valve body having at least two orifices that provide resistance to the fluid passing through the relief valve body.

[0008] In this way, the throttle of the relief valve is divided into at least two, and the length of the throttle can be shortened by the amount of division. In other words, the fluid can be made to flow continuously through each divided throttle. This makes it possible to keep the pressure difference between the front and rear of the fluid flowing through the divided throttle small, and to slow down the flow velocity of the fluid flowing through the throttle. Therefore, it is possible to reduce noise caused by the jets of fluid ejected from the at least two throttles. By shortening the length of at least two of the throttles, the change in the temperature of the fluid can be kept small, and the temperature characteristics of the fluid can be improved.

[0009] In the above configuration, the relief valve body may be formed in a cylindrical shape, and the throttle may be formed in a radial direction of the relief valve body. Furthermore, at least two throttles are formed in the radial direction of the relief valve body. Therefore, the at least two throttles can be perpendicular to the lift direction of the relief valve body. This can reduce the effect of the fluid force on the relief valve body.

[0010] In the above configuration, the relief valve body may include a cap fixed to the case and a poppet housed in the cap, and the cap and the poppet may each have the orifice.

[0011] Here, the cap is fixed to the case and has a hollow storage portion. A poppet is stored in the storage portion of the cap. The poppet is arranged so as to be slidable in a lift direction away from the valve seat of the case. The poppet has a communication passage (i.e., a hollow portion) that penetrates in the lift direction. Thus, at least two throttles can be provided radially in the hollow portion of the cap and the hollow portion of the poppet. This allows the at least two throttles to be formed in a simple configuration and in a short length.

[0012] In the above configuration, the cap and the poppet may each have one or more of the orifices, and a first orifice among the orifices may be provided on the cap, and a second orifice among the orifices may be provided on the poppet.

[0013] With this configuration, at least two throttles, a first throttle and a second throttle, are provided in the cap and the second throttle in the poppet, which allows greater freedom in determining the locations of the first throttle and the second throttle.

[0014] In the above configuration, the poppet comprises a poppet body housed within the cap and provided with the second orifice, and a guide housed within the poppet body, and the poppet may further have the orifice, and the guide may be provided with a third orifice among the orifices.

[0015] With this configuration, the first throttle is provided in the cap, the second throttle is provided in the poppet body, and the third throttle is provided in the guide, which increases the degree of freedom when setting the throttle.

[0016] In the above configuration, the relief valve body includes a cap fixed to the case and a poppet housed in the cap, the poppet includes a poppet body and a guide housed in the poppet body, and selected two of the cap, the poppet body, and the guide may have the orifice.

[0017] With this configuration, the throttle is provided in two selected from the cap, the poppet body, and the guide, which allows for greater freedom in setting the throttle.

[0018] In the above configuration, adjacent ones of the first diaphragm, the second diaphragm, and the third diaphragm may be provided at positions spaced apart from each other.

[0019] With this configuration, it is possible to provide a gap between adjacent orifices, and therefore the velocity of the jet flow emitted from one of the adjacent orifices can be kept low at the gap between the adjacent orifices, thereby effectively reducing noise caused by the jet flow emitted from the orifices.

[0020] In the above configuration, the first throttle, the second throttle, and the third throttle may each be provided on an outlet side of the fluid, and may include a wall portion that intersects with an axial direction of the first throttle, the second throttle, and the third throttle.

[0021] With this configuration, the jets ejected from the outlets of the first throttle, the second throttle, and the third throttle can be made to hit the wall, thereby keeping the ejected jet velocity low, thereby suitably reducing noise caused by the jets ejected from the throttle.

[0022] A negative control relief valve according to another aspect of the present invention is a negative control relief valve that is provided at the most downstream of an unloading passage and generates a pressure for controlling a pump flow rate by a negative control method, and comprises a case and a relief valve body attached to the case and through which a fluid passes, and the relief valve body has at least two orifices for providing resistance to the fluid passing through the relief valve body and generating the pressure for controlling the pump flow rate.

[0023] By configuring in this manner, noise caused by the jet of water ejected from the throttle can be reduced in the negative control relief valve. In addition, the temperature characteristics of the fluid can be improved. This makes it possible to minimize changes in pressure loss characteristics when the fluid passes through the throttle, thereby minimizing changes in the pump flow rate control pressure due to the temperature characteristics of the fluid. Furthermore, the effect of the fluid force on the relief valve body can be reduced, thereby making it possible to keep changes in the pump flow rate control pressure small.

[0024] A control valve according to another aspect of the present invention is a negative control relief valve that is provided at the most downstream of an unloading passage and generates a pressure for controlling a pump flow rate by a negative control method, and comprises a case and a relief valve body attached to the case and through which a fluid passes, and the relief valve body has at least two orifices for providing resistance to the fluid passing through the relief valve body and generating the pressure for controlling the pump flow rate.

[0025] In this way, by providing the control valve with a negative control relief valve, the noise of the control valve can be reduced. In addition, the temperature characteristics of the negative control relief valve can be improved and the influence of fluid force can be reduced. This makes it possible to suppress changes in the pump flow rate control pressure to a minimum. As a result, the discharge rate of the variable displacement pump can be suitably controlled based on the pump flow rate control pressure. Effect of the Invention

[0026] According to the present invention, the noise of the relief valve, the negative control relief valve, and the control valve can be reduced, and the temperature characteristics can be improved. [Brief description of the drawings]

[0027] [Figure 1] 1 is a hydraulic circuit diagram illustrating an outline of a control valve according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view showing a negative control relief valve in an embodiment of the present invention. [Diagram 3] 3 is an enlarged cross-sectional view of part III in FIG. 2, showing the flow of hydraulic oil in the second throttle and the first throttle. [Figure 4] 13 is a graph showing changes in negative control pressure in an embodiment of the present invention. [Diagram 5] FIG. 11 is a cross-sectional view showing a negative control relief valve according to a modified example of the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Next, an embodiment of the present invention will be described with reference to the drawings.

[0029] <Control valve> Fig. 1 is a hydraulic circuit diagram showing an outline of a control valve 1. Fig. 2 is a cross-sectional view showing a negative control relief valve 10. In the following description, the upstream side in the flow direction of hydraulic oil may be simply referred to as the upstream side, and the downstream side in the flow direction of hydraulic oil may be simply referred to as the downstream side. In Fig. 2, the upstream side may be referred to as the "front" and the downstream side as the "rear". As shown in Figures 1 and 2, the control valve 1 includes, for example, a case 2, a plurality of directional control valves 4, 5, and 6 provided in the case 2, a variable displacement pump 8 that supplies hydraulic oil to each of the directional control valves 4, 5, and 6, and a negative control relief valve 10 provided downstream of each of the directional control valves 4, 5, and 6.

[0030] The first directional control valve 4 is connected to, for example, a hydraulic motor 12 as a first actuator. The first directional control valve 4 controls the drive of the hydraulic motor 12. The second directional control valve 5 is connected to, for example, a first hydraulic cylinder 13 as a second actuator. The second directional control valve 5 controls the drive of the first hydraulic cylinder 13. The third directional control valve 6 is connected to, for example, a second hydraulic cylinder 14 as a second actuator. The third directional control valve 6 controls the drive of the second hydraulic cylinder 14.

[0031] The variable displacement pump 8 is connected to the unloading passage 16 and the supply passage 17. The variable displacement pump 8 supplies the discharged hydraulic oil (an example of the fluid in the claims) to the first direction switching valve 4, the second direction switching valve 5, and the third direction switching valve 6 via the unloading passage 16 and the supply passage 17. The variable displacement pump 8 includes, for example, a pump flow rate controller 8a. The pump flow rate controller 8a is connected to a negative control relief valve 10. The pump flow rate controller 8a changes the inclination angle of the movable swash plate 8b based on the negative control pressure (pump flow rate control pressure) applied from the negative control relief valve 10. In this way, the discharge rate of the variable displacement pump 8 is controlled.

[0032] <Negative control relief valve> The negative control relief valve 10 is a valve used in a negative control system that controls the discharge volume of the variable displacement pump 8. The negative control relief valve 10 is provided downstream of the first directional control valve 4, the second directional control valve 5, and the third directional control valve 6. In other words, the negative control relief valve 10 is provided on the most downstream side of the unloading passage 16. In this way, the negative control relief valve 10 generates a negative control pressure for the negative control system (details will be described later). The negative control relief valve 10 includes a case 2, a relief valve body (an example of the relief valve body in the claims) 20 attached to the case 2, and a spring 25 provided in the relief valve body 20.

[0033] <Case> The case 2 has a front pressure chamber 31 communicating with the downstream side of the control valve 1, and a case passage 32 communicating with the front pressure chamber 31 and also communicating with the tank line 18. The case passage 32 has an inner circumferential surface 32a (an example of a wall portion in the claims). The tank line 18 is communicated with the tank 19.

[0034] <Relief valve body> The relief valve body 20 is formed in a cylindrical shape. The relief valve body 20 has at least two throttles formed in a radial direction with the central axis of the relief valve body 20 as the center. The relief valve body 20 includes a cap 21 fixed to the case 2 and a poppet 22 housed in the cap 21. In the embodiment, a first aperture 43 and a second aperture 55, which will be described later, will be taken as examples of at least two apertures.

[0035] In the following description, the center of the poppet 22 in the lift direction in which the poppet 22 moves away from the valve seat 33 of the case 2 is referred to as the lift axis O. The lift axis O is the same as the central axis of the relief valve body 20 (i.e., the cap 21 and the poppet 22). In the following description, the radial direction about the lift axis O may be simply referred to as the radial direction, and the circumferential direction about the lift axis O may be simply referred to as the circumferential direction.

[0036] <Cap> FIG. 3 is an enlarged cross-sectional view of part III in FIG. 2, showing the flow of hydraulic oil through the second throttle 55 and the first throttle 43. As shown in FIG. 2 and 3, the cap 21 has a male thread 35 formed on the outer periphery on the front end side. The male thread 35 is coupled to a female thread 36 of the case 2, thereby fixing the cap 21 to the case 2. An O-ring 37 is provided between the cap 21 and the case 2. The cap 21 has a storage portion 41 formed in a hollow space centered on the lift axis O, a protruding portion 42 formed at the front end, and a first aperture 43 formed in the protruding portion 42.

[0037] The storage section 41 has an open front end. The storage section 41 is formed hollow along the lift axis O to the rear end. The storage section 41 communicates with a communication passage 51 of the poppet 22, which will be described later. The storage section 41 communicates with a port 46 via a through hole 45 formed at the rear end. The storage section 41 has an inner circumferential surface 41a (an example of a wall in the claims). The protruding portion 42 forms an opening of the storage portion 41. The protruding portion 42 is formed hollow with a relatively thin wall thickness in the radial direction centered on the lift axis O. A first aperture 43 is formed in the protruding portion 42.

[0038] A plurality of first orifices 43 are formed in the circumferential direction around the lift axis O. In the embodiment, an example will be described in which two first orifices 43 are provided as shown in Fig. 2. The number of the first orifices 43 is not limited to two and can be arbitrarily selected. The first orifice 43 is formed in a radial direction perpendicular to the lift axis O and is an orifice that penetrates from the inner peripheral surface to the outer peripheral surface of the protruding portion 42. An inlet on the inner peripheral surface side of the first orifice 43 opens to a guide groove 54, which will be described later. An outlet on the outer peripheral surface side of the first orifice 43 opens to the case passage 32.

[0039] The outlet of the first throttle 43 on the outer peripheral surface side is disposed at a position facing the inner peripheral surface 32a of the case passage 32. Therefore, the inner peripheral surface 32a of the case passage 32 is provided as a wall portion on the outlet side of the first throttle 43. The inner peripheral surface 32a of the case passage 32 is disposed slightly spaced radially outward from the outlet of the first throttle 43. The inner peripheral surface 32a of the case passage 32 is formed along the lift axis O. That is, the inner peripheral surface 32a of the case passage 32 is formed so as to intersect with the axial direction of the first throttle 43. Preferably, the inner peripheral surface 32a of the case passage 32 is formed so as to be perpendicular to the first throttle 43.

[0040] <Poppet> The poppet 22 is housed in the storage portion 41 of the cap 21 through an opening. The poppet 22 is formed in a cylindrical shape along the lift axis O. The poppet 22 is disposed in the storage portion 41 of the cap 21 so as to be slidable along the lift axis O. The storage portion 41 has a rear pressure chamber 48 formed between the rear end portion of the storage portion 41 and the poppet 22. The poppet 22 has a communicating passage 51 that runs through from the front end to the rear end, a seat surface 52 formed at the front end, a rear pressure-receiving surface 53 formed at the rear end, a guide groove 54 formed on the outer circumferential surface, and a second orifice 55 that communicates with the guide groove 54.

[0041] The communication passage 51 penetrates the poppet 22 along the lift axis O from the front end to the rear end. The front end side of the communication passage 51 is communicated with the front pressure chamber 31 of the case 2, and the rear end side is communicated with the rear pressure chamber 48. In other words, the front pressure chamber 31 and the rear pressure chamber 48 communicate with each other along the lift axis O via the communication passage 51.

[0042] The seat surface 52 is formed so as to be able to come into contact with the valve seat 33 at the front end of the poppet 22. When the seat surface 52 comes into contact with the valve seat 33, the front pressure chamber 31 is blocked from the case passage 32. When the poppet 22 is lifted and the seat surface 52 moves away from the valve seat 33, the front pressure chamber 31 of the case 2 is connected to the case passage 32. The rear pressure receiving surface 53 faces the rear pressure chamber 48. The rear pressure receiving surface 53 is smaller than the pressure receiving area of ​​the seat surface 52. In other words, the pressure receiving area of ​​the seat surface 52 is larger than the rear pressure receiving surface 53. The rear pressure receiving surface 53 is in contact with the front end of a spring 25, which will be described later.

[0043] The guide groove 54 is, for example, formed in an annular shape in the circumferential direction on the outer circumferential surface of the poppet 22. The guide groove 54 has a constant groove width in the direction of the lift axis O. The guide groove 54 has an inlet of the first throttle 43 open therein. A second throttle 55 is provided in the guide groove of the poppet 22. The outlet of the second throttle 55 opens into the guide groove . A plurality of second orifices 55 are formed in the circumferential direction around the lift axis O. In the embodiment, an example will be described in which two second orifices 55 are provided as shown in Fig. 2. The number of the second orifices 55 is not limited to two and can be selected arbitrarily.

[0044] The second orifice 55 is formed in a radial direction perpendicular to the lift axis O. The second orifice 55 is an orifice that penetrates from the inner peripheral surface of the poppet 22 to the bottom surface 54a of the guide groove 54. The second orifice 55 is provided at a position separated (displaced) from the first orifice 43 in the direction of the lift axis O. In the embodiment, an example in which the first orifice 43 and the second orifice 55 are provided at positions separated from each other in the direction of the lift axis O will be described, but it is also possible to provide the first orifice 43 and the second orifice 55 at positions separated from each other in the radial direction.

[0045] The inlet on the inner peripheral surface side of the second throttle 55 opens to the communication passage 51. The outlet on the outer peripheral surface side of the second throttle 55 opens to the guide groove 54. The outlet on the outer peripheral surface side of the second throttle 55 is disposed at a position facing the inner peripheral surface 41a of the storage section 41. For this reason, the inner peripheral surface 41a of the storage section 41 is provided as a wall on the outlet side of the second throttle 55. The inner peripheral surface 41a of the storage section 41 is disposed slightly apart from the outlet of the second throttle 55 radially outward. The inner peripheral surface 41a of the storage section 41 is formed along the lift axis O. That is, the inner peripheral surface 41a of the storage section 41 is formed so as to intersect with the axial direction of the second throttle 55. Preferably, the inner peripheral surface 41a of the storage section 41 is formed so as to be perpendicular to the second throttle 55.

[0046] The poppet 22 is housed in the cap 21. Therefore, a second orifice 55 is formed in the poppet 22, and the second orifice 55 is formed in the cap 21. Therefore, the first orifice 43 and the second orifice 55 are connected in series via the guide groove 54. In other words, the orifice of the negative control relief valve 10 is divided into the first orifice 43 and the second orifice 55 in series. In this way, the divided first orifice 43 and second orifice 55 are connected in series via the guide groove 54 at two locations, the cap 21 and the poppet 22.

[0047] Therefore, the hydraulic oil flows from the communication passage 51 into the second throttle 55 as indicated by arrow A. The hydraulic oil that flows into the second throttle 55 jets into the guide groove 54 and hits the inner circumferential surface (i.e., the wall portion) 41a of the storage portion 41. The hydraulic oil that hits the inner circumferential surface 41a flows into the guide groove 54 as indicated by arrow B. The hydraulic oil that has flowed into the guide groove 54 flows into the first orifice 43 as indicated by arrow C. The hydraulic oil that has flowed into the first orifice 43 is jetted into the case passage 32 and hits the inner circumferential surface (i.e., the wall portion) 32a of the case passage 32. The hydraulic oil that has hit the inner circumferential surface 32a flows into the case passage 32 of the case 2 as indicated by arrow D.

[0048] <Spring> A spring 25 is housed in the rear pressure chamber 48. The spring 25 is a compression coil spring interposed between the rear pressure receiving surface 53 of the poppet 22 and the rear wall surface 48a of the rear pressure chamber 48. The spring 25 is compressed by the rear pressure receiving surface 53 and the rear wall surface 48a of the rear pressure chamber 48. Therefore, the pressing force of the spring 25 causes the seat surface 52 of the poppet 22 to contact the valve seat 33 of the case 2. Therefore, the front pressure chamber 31 of the case 2 and the case passage 32 are blocked by the poppet 22.

[0049] Next, the operation of the negative control relief valve 10 when applied to the control valve 1 will be described with reference to FIGS. 1 and 2, hydraulic oil is discharged from variable displacement pump 8. The first directional control valve 4, the second directional control valve 5, and the third directional control valve 6 of control valve 1 are disposed in neutral positions. Therefore, the hydraulic oil discharged from variable displacement pump 8 is supplied to front pressure chamber 31 via the first directional control valve 4, the second directional control valve 5, and the third directional control valve 6 of control valve 1. The hydraulic oil supplied to the front pressure chamber 31 is supplied to the case passage 32 of the case 2 via the communication passage 51, the second orifice 55, the guide groove 54, and the first orifice 43. The hydraulic oil supplied to the case passage 32 of the case 2 is returned to the tank 19 via the tank line 18.

[0050] FIG. 4 is a graph showing changes in negative control pressure, with the vertical axis representing the negative control pressure and the horizontal axis representing the flow rate of hydraulic oil. 4, when the hydraulic oil discharged from the variable displacement pump 8 passes through the relief valve body 20 of the negative control relief valve 10, resistance is applied by the orifices 43, 55. As a result, a flow rate control pressure (hereinafter sometimes referred to as negative control pressure) PC is generated in the front pressure chamber 31 in accordance with the flow rate Q of the hydraulic oil discharged from the variable displacement pump 8.

[0051] 1 and 2, the negative control pressure PC generated in the front pressure chamber 31 is output to the pump flow rate controller 8a via the communication passage 51, the rear pressure chamber 48, the through hole 45, and the port 46. The pump flow rate controller 8a controls the movable swash plate 8b of the variable displacement pump 8 by the output negative control pressure PC. As a result, by applying the negative control relief valve 10 to the control valve 1, the discharge rate of the variable displacement pump 8 can be controlled in accordance with the negative control pressure PC detected by the negative control relief valve 10.

[0052] For example, while the variable displacement pump 8 is discharging hydraulic oil, an excessive flow rate Q may flow through the second orifice 55 or the first orifice 43. In this case, the excessive flow rate Q increases the pressure of the hydraulic oil supplied to the front pressure chamber 31. The increased pressure acts on the pressure-receiving area of ​​the seat surface 52, lifting the poppet 22 against the biasing force of the spring 25. As the poppet 22 lifts, the seat surface 52 moves away from the valve seat 33.

[0053] Therefore, the hydraulic oil in the front pressure chamber 31 can flow from between the seat surface 52 and the valve seat 33 into the case passage 32 in the case 2, and can be returned from the case passage 32 to the tank 19 via the tank line 18. This makes it possible to prevent excessive pressure P from being generated in the front pressure chamber 31.

[0054] As described above, in the negative control relief valve 10 according to the embodiment, as shown in Fig. 3, the throttle of the negative control relief valve 10 is divided into the first throttle 43 and the second throttle 55, and the first throttle 43 and the second throttle 55 are formed in the radial direction. This makes it possible to shorten the length of the first throttle 43 and the length of the second throttle 55. The throttle length refers to the axial length of the throttle (hole) (hereinafter the same). Furthermore, the first orifice 43 and the second orifice 55 are provided in series via a guide groove 54. Therefore, the hydraulic oil can flow continuously from the second orifice 55 to the first orifice 43 in the order of arrows A, B, C, and D. This makes it possible to keep small the differential pressure before and after the hydraulic oil flowing through the second orifice 55 and the first orifice 43. As a result, it is possible to keep the flow speed of the hydraulic oil flowing through the first orifice 43 and the second orifice 55 low. Therefore, it is possible to reduce noise caused by the jets ejected from the second orifice 55 and the first orifice 43.

[0055] By shortening the length of the second orifice 55 and the length of the first orifice 43, the change in the oil temperature of the hydraulic oil can be kept small. Therefore, the temperature characteristics of the hydraulic oil can be maintained good. Therefore, the change in the pressure loss characteristics when the hydraulic oil passes through the second orifice 55 and the first orifice 43 can be kept small. As a result, for example, the change in the negative control pressure due to the temperature characteristics of the oil temperature can be kept small.

[0056] The second orifice 55 and the first orifice 43 are formed in the radial direction. Therefore, the second orifice 55 and the first orifice 43 can be perpendicular to the lift axis O. This makes it possible to reduce the effect of the fluid force of the hydraulic oil on the cap 21 and the poppet 22 (particularly the poppet 22). Therefore, for example, the change in negative control pressure caused by the fluid force of the hydraulic oil can be reduced.

[0057] The cap 21 is fixed to the case 2 and has a hollow storage portion 41. The poppet 22 is stored in the storage portion 41 of the cap 21. The poppet 22 is arranged to be slidable along the lift axis O in a direction away from the valve seat 33 of the case 2. The poppet 22 has a communication passage 51 (i.e., a hollow portion) that penetrates along the lift axis O. Therefore, the first orifice 43 and the second orifice 55 can be provided radially in the hollow portion of the cap 21 and the hollow portion of the poppet 22. This allows the first orifice 43 and the second orifice 55 to be formed short with a simple configuration.

[0058] Furthermore, the first orifice 43 is provided in the cap 21, and the second orifice 55 is provided in the poppet 22. This allows greater freedom in determining the locations of the first orifice 43 and the second orifice 55.

[0059] The first orifice 43 and the second orifice 55 are provided at positions separated from each other (shifted positions) in the direction of the lift axis O. This allows a gap to be provided between the first orifice 43 and the second orifice 55. This allows the velocity of the jet ejected from the second orifice 55 to be kept low in the gap between the first orifice 43 and the second orifice 55. This allows the noise caused by the jets ejected from the first orifice 43 and the second orifice 55 to be suitably reduced.

[0060] The storage section 41 has an inner circumferential surface (i.e., a wall portion) 41a on the outlet side of the second orifice 55 that is perpendicular to the second orifice 55. The inner circumferential surface 41a of the storage section 41 is disposed slightly spaced radially outward from the outlet of the second orifice 55. Therefore, by making the jet flow ejected from the outlet of the second orifice 55 hit the inner circumferential surface 41a of the storage section 41 at a short distance, the speed of the ejected jet flow can be kept low.

[0061] In addition, the case passage 32 has an inner circumferential surface (i.e., a wall portion) 32a on the outlet side of the first orifice 43, which is perpendicular to the first orifice 43. The inner circumferential surface 32a of the case passage 32 is disposed slightly spaced radially outward from the outlet of the first orifice 43. Therefore, by making the jet flow ejected from the outlet of the first orifice 43 hit the inner circumferential surface 32a of the case passage 32 at a short distance, the ejected jet speed can be kept low. In this way, it is possible to keep low the velocity of the jets ejected from the outlet of the second orifice 55 and the outlet of the first orifice 43. Therefore, it is possible to suitably reduce noise caused by the jets ejected from the second orifice 55 and the first orifice 43.

[0062] As shown in Fig. 1, the control valve 1 can reduce noise. In addition, the temperature characteristics of the negative control relief valve 10 can be improved and the influence of fluid force can be reduced. This makes it possible to keep changes in the negative control pressure small. As a result, the discharge volume of the variable displacement pump 8 provided in the control valve 1 can be suitably controlled according to the negative control pressure detected by the negative control relief valve 10.

[0063] [Variations] Next, a modified relief valve will be described with reference to Fig. 5. In the modified example, the same or similar configurations as those of the relief valve of the above-described embodiment are denoted by the same reference numerals and detailed description thereof will be omitted.

[0064] FIG. 5 is a cross-sectional view showing a modified negative control relief valve 100. As shown in FIG. 5, the difference between the negative control relief valve 10 of the embodiment and the negative control relief valve 100 of the modified example is that the poppet 22 of the negative control relief valve 10 of the embodiment is different from the poppet 102 of the negative control relief valve 100 of the modified example. Other configurations of the negative control relief valve 100 of the modified example are generally similar to those of the negative control relief valve 10 of the embodiment. The modified example will be described taking as an example the first orifice 43, the second orifice 55, and a third orifice 116 described later as at least two orifices.

[0065] The poppet 102 includes a poppet body 103 housed within the cap 21, and a guide 104 housed within the poppet body 103. The port 46 of the cap 21 is closed by a plug 106. The poppet body 103 is disposed in the storage portion 41 of the cap 21 so as to be slidable along the lift axis O. The poppet body 103 is formed in a manner generally similar to that of the poppet 22 of the above-described embodiment. The poppet body 103 has a first guide groove 107 and a second orifice 108 instead of the guide groove 54 and the second orifice 55 in the poppet 22 of the above-described embodiment. The other configurations of the poppet body 103 are similar to those of the poppet 22 of the above-described embodiment. The second orifice 108 is formed in front of the first orifice 43. The second orifice 108 and the first orifice 43 are connected by the first guide groove 107.

[0066] An inner circumferential surface 41a of the storage section 41 is provided as a wall on the outlet side of the second iris 108. The inner circumferential surface 41a of the storage section 41 is disposed slightly away from the outlet of the second iris 108 radially outward in the radial direction. The inner circumferential surface 41a of the storage section 41 is formed so as to intersect with the axial direction of the second iris 108. Preferably, the inner circumferential surface 41a of the storage section 41 is formed so as to be perpendicular to the second iris 108.

[0067] The guide 104 is disposed in the communication passage 51 of the poppet body 103 so as to be slidable along the lift axis O. The guide 104 has a deep hole 112 opening at the front end, a flange 114 formed at the rear end, a second guide groove 115 formed on the outer circumferential surface, and a third aperture 116 communicating with the second guide groove 115. The deep hole 112 is formed along the lift axis O from the front end to the center. The flange 114 projects radially outward from the rear end of the guide 104. The flange 114 is disposed in the storage portion 41 of the cap 21 so as to be slidable along the lift axis O. A spring 25 is interposed between the flange 114 and the poppet body 103.

[0068] The second guide groove 115 is formed in an annular shape around the entire outer circumferential surface of the guide 104. An inlet of a second aperture 108 opens in the second guide groove 115. A third aperture 116 is provided in the second guide groove 115 of the guide 104. The third aperture 116 has an inlet that opens into the deep hole 112 and an outlet that opens into the second guide groove 115. A plurality of third apertures 116 are formed along the circumferential direction. In this modified example, two third apertures 116 as shown in Fig. 5 will be described as an example. The number of the plurality of third apertures 116 is not limited to two and can be selected arbitrarily.

[0069] An inner circumferential surface 51a (one example of a wall in the claims) of the communicating passage 51 is provided as a wall on the outlet side of the third orifice 116. The inner circumferential surface 51a of the communicating passage 51 is disposed slightly away from the outlet of the third orifice 116 radially outward. The inner circumferential surface 51a of the communicating passage 51 is formed so as to intersect with the axial direction of the third orifice 116. Preferably, the inner circumferential surface 51a of the communicating passage 51 is formed so as to be perpendicular to the third orifice 116. The lengths of the third orifice 116 and the second orifice 108 are formed to be short, similar to the length of the first orifice 43.

[0070] The first orifice 43 and the third orifice 116 are disposed at the same position in the direction of the lift axis O. The second orifice 108 is disposed forward and away from the first orifice 43 and the third orifice 116. Therefore, the adjacent first orifice 43 and the second orifice 108 are provided at positions spaced apart from each other (shifted positions) in the direction of the lift axis O. The adjacent second orifice 108 and the third orifice 116 are provided at positions spaced apart from each other (shifted positions) in the direction of the lift axis O. In other words, adjacent orifices among the first orifice 43, the second orifice 108, and the third orifice 116 are provided at positions spaced apart from each other. In the modified example, an example will be described in which adjacent throttles are provided at positions spaced apart from each other in the direction of the lift axis O, but they may also be provided at positions spaced apart from each other in the radial direction.

[0071] The negative control relief valve 100 outputs the negative control pressure PC generated in the front pressure chamber 31 from the front pressure chamber 31 to the pump flow rate controller 8a. Therefore, like the negative control relief valve 10 of the embodiment, the negative control relief valve 100 can control the discharge rate of the variable displacement pump 8 in accordance with the negative control pressure PC. Moreover, the negative control relief valve 100 can prevent the occurrence of excessive pressure P in the front pressure chamber 31, similar to the negative control relief valve 10 of the embodiment.

[0072] Therefore, the negative control relief valve 100 in the above-described modified example has the same effects as those of the first embodiment. That is, like the negative control relief valve 10 in the above-described embodiment, noise caused by the jets ejected from the third orifice 116, the second orifice 108, and the first orifice 43 can be reduced.

[0073] By shortening the length of the third throttle 116, the length of the second throttle 108, and the length of the first throttle 43, it is possible to maintain good temperature characteristics of the hydraulic oil. By forming the third orifice 116, the second orifice 108, and the first orifice 43 in the radial direction, the effect of the fluid force of the hydraulic oil on the cap 21 and the poppet 102 (particularly the poppet 102) can be reduced.

[0074] The first orifice 43 is provided in the cap 21, and the second orifice 108 is provided in the poppet body 103. In addition, the guide 104 is provided with a third orifice 116. This allows for greater freedom in providing the orifices.

[0075] Adjacent throttles among the first throttle 43, the second throttle 108, and the third throttle 116 are provided at positions spaced apart from each other. Specifically, the adjacent second throttle 108 and the third throttle 116 are provided at positions spaced apart from each other. This makes it possible to provide a gap between the adjacent second throttle 108 and the third throttle 116. This makes it possible to keep the jet velocity ejected from the third throttle 116 low in the gap provided between the adjacent second throttle 108 and the third throttle 116.

[0076] The adjacent first orifices 43 and second orifices 108 are provided at positions spaced apart from each other. This allows a gap to be provided between the adjacent first orifices 43 and second orifices 108. This makes it possible to keep the jet velocity ejected from the second orifice 108 low in the gap provided between the adjacent first orifices 43 and second orifices 108. In this way, by keeping the velocity of the jet ejected from the third orifice 116 low and keeping the velocity of the jet ejected from the second orifice 108 low, it is possible to suitably reduce noise caused by the jets ejected from the orifices.

[0077] In addition, the first throttle 43 is formed so as to be perpendicular to the inner peripheral surface (wall portion) 32a of the case passage 32. Therefore, by making the jet flow ejected from the outlet of the first throttle 43 hit the inner peripheral surface 32a, the ejected jet flow velocity can be kept low. The second throttle 108 is formed so as to be perpendicular to the inner peripheral surface (wall portion) 41a of the storage section 41. Therefore, by making the jet flow ejected from the outlet of the second throttle 108 hit the inner peripheral surface 41a, the ejected jet speed can be kept low. Furthermore, the third throttle 116 is formed so as to be perpendicular to the inner peripheral surface (wall portion) 51a of the communication passage 51. By making the jet flow ejected from the outlet of the third throttle 116 hit the inner peripheral surface 51a, the ejected jet speed can be kept low. This makes it possible to suitably reduce noise caused by the jet flow ejected from the orifice.

[0078] In the modified example, an example has been described in which the first orifice 43 is provided in the cap 21, the second orifice 108 is provided in the poppet body 103, and the third orifice 116 is provided in the guide 104. However, this is not limited to this, and as another example, orifices may be provided in two members selected from the cap 21, the poppet body 103, and the guide 104. In this case, the other members not provided with orifices may be provided with, for example, communication holes or the like instead of orifices. In this way, by providing the throttle in two members selected from the cap 21, the poppet body 103, and the guide 104, the degree of freedom in providing the throttle can be further increased.

[0079] The present invention is not limited to the above-described embodiment, and includes various modifications to the above-described embodiment without departing from the spirit of the present invention. For example, in the above-described embodiment and modified example, hydraulic oil is used as an example of the fluid. However, the present invention is not limited to this, and may be applied to fluids other than hydraulic oil. The fluid is not limited to liquid, and may be gas.

[0080] In the above-mentioned embodiment and modified example, the negative control relief valve 10, 100 that generates a pressure for controlling the pump flow rate of a negative control type has been described as a relief valve. However, the present invention is not limited to this, and the configuration of the negative control relief valve 10, 100 can be applied to the configuration of other relief valves. Even in such a case, it is possible to reduce noise, improve the temperature characteristics, and reduce the influence of fluid force.

[0081] In the above-described embodiment and modified examples, the first direction switching valve 4, the second direction switching valve 5, and the third direction switching valve 6 are used as examples of the multiple direction switching valves 4, 5, and 6. However, the present invention is not limited to this, and the number of the multiple direction switching valves can be selected arbitrarily.

[0082] Among the embodiments disclosed in this specification, those that are composed of multiple objects may be integrated, and conversely, those that are composed of one object may be divided into multiple objects. Regardless of whether they are integrated or not, it is sufficient that they are configured to achieve the object of the invention. [Explanation of symbols]

[0083] 1...Control valve 2. Case 4,5,6...1st to 3rd directional control valves (directional control valves) 8...Variable displacement pump 8a…Pump flow controller 10,100...Negative control relief valve (relief valve) 20...Relief valve body 21. Cap 22,102…Poppet 32…Case aisle 32a…Inner surface (wall) of case passage 41…Storage section 41a...Inner circumferential surface (wall) of the storage section 43…1st aperture (at least 2 apertures) 51...Communication path 51a...Inner circumferential surface (wall portion) of the communication passage 55,108…2nd stop (at least 2 stops) 103…Poppet body 104…Guide 116…3rd stop (at least 2 stops)

Claims

1. Case and a relief valve body attached to the case and through which a fluid passes; Equipped with The relief valve body has at least two restrictions that provide resistance to the fluid passing through the relief valve body. Relief valve.

2. The relief valve body is formed in a cylindrical shape, The throttle is formed in the radial direction of the relief valve body. The relief valve according to claim 1 .

3. The relief valve body includes: A cap fixed to the case; A poppet housed within the cap; Equipped with The cap and the poppet each have the restriction. The relief valve according to claim 1 or 2.

4. the cap and the poppet each have one of the orifices; A first restriction of the restrictors is provided on the cap, and a second restriction of the restrictors is provided on the poppet. The relief valve according to claim 3.

5. The poppet is A poppet body housed in the cap and provided with the second throttle; A guide housed within the poppet body; Equipped with The poppet further includes the restriction. The guide is provided with a third aperture of the apertures. The relief valve according to claim 4.

6. The relief valve body includes: A cap fixed to the case; A poppet housed within the cap; Equipped with The poppet is A poppet body; A guide housed within the poppet body; Equipped with selected two of the cap, the poppet body, and the guide include the restriction; The relief valve according to claim 1 .

7. Adjacent ones of the first aperture, the second aperture, and the third aperture are provided at positions spaced apart from each other. The relief valve according to claim 5.

8. a wall portion provided on an outlet side of the fluid of each of the first throttle, the second throttle, and the third throttle, the wall portion intersecting an axial direction of the first throttle, the second throttle, and the third throttle; The relief valve according to claim 7.

9. A negative control relief valve is provided at the most downstream of an unloading passage and generates pressure for controlling the flow rate of a negative control type pump. Case and a relief valve body attached to the case and through which a fluid passes; Equipped with the relief valve body has at least two restrictors for applying resistance to the fluid passing through the relief valve body and generating the pump flow rate control pressure; Negative control relief valve.

10. a plurality of directional control valves provided in an unloading passage through which a fluid discharged from a variable displacement pump passes, the plurality of directional control valves being supplied with the fluid; a negative control relief valve provided in the unloading passage downstream of the directional control valve and configured to generate a negative control type pump flow rate control pressure downstream of the directional control valve; Equipped with a discharge amount of the variable displacement pump is controlled based on the pump flow rate control pressure; Control valve.

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