Overflow valve, negative control overflow valve and control valve

Abstract

The invention relates to an overflow valve, a negative control overflow valve and a control valve. A negative control relief valve (10) according to an embodiment is provided with: a housing (2); and a relief valve body (20) which is attached to the housing (2) and through which hydraulic oil passes. The relief valve main body (20) has at least a first throttle section (43) and a second throttle section (55) that apply resistance to hydraulic oil passing through the relief valve main body (20).

Description

Technical Field

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

[0002] A control valve including a so-called negative control relief valve for generating a pump flow control pressure (hereinafter sometimes referred to as negative control pressure) of a negative control method is known.

[0003] As a negative control relief valve, for example, there is known a negative control relief valve in which two throttling parts, a first throttling part and a second throttling part, are provided at two locations and the two throttling parts are connected in series. The two throttling parts apply resistance to the working oil (fluid) passing through the negative control relief valve.

[0004] By dividing the two throttling parts into two places and setting them in series, the flow rate of the working oil flowing in the first throttling part and the flow rate of the working oil flowing in the second throttling part can be set to be lower than the case where one throttling part is set. By setting the flow rate at the first throttling part and the flow rate at the second throttling part to be lower, noise can be reduced. For example, the noise generated by the jets ejected from the two throttling parts can be reduced (for example, refer to Patent Document 1).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent No. 3690839 Summary of the invention

[0008] Problem that the invention aims to solve

[0009] In the above-mentioned prior art, the second throttle portion is formed long in the lifting direction of the poppet at the sliding portion between the valve cap and the poppet. When the length of the second throttle portion is long, it is difficult to suppress the pressure difference before and after the throttle portion to be small. Therefore, there is a possibility that it is difficult to suppress the jet speed from the second throttle portion to a low speed, and the noise generated by the jet ejected from the second throttle portion becomes large.

[0010] In addition, when the throttle portion is long, the pressure loss characteristics change more due to the oil temperature of the working oil than when the throttle portion is short. Therefore, there is a possibility that the negative control pressure generated by the negative control relief valve changes greatly due to the temperature characteristics of the oil temperature.

[0011] The present invention provides a relief valve, a negative control relief valve and a control valve which can reduce noise and improve temperature characteristics.

[0012] Solutions for solving problems

[0013] A relief valve according to one aspect of the present invention comprises: a housing; and a relief valve body mounted on the housing and allowing fluid to pass through. The relief valve body has at least two throttle parts that apply resistance to the fluid passing through the relief valve body.

[0014] Thus, by setting a structure in which the throttling part of the relief valve is divided into at least two, the length of the throttling part can be shortened in accordance with the division. That is, the fluid can flow continuously to each of the divided throttling parts. Thus, the front-to-rear pressure difference of the fluid flowing to the divided throttling parts can be suppressed to be small, and the flow velocity of the fluid flowing to the throttling part can be set to a low speed. Therefore, the noise generated by the jets ejected from the at least two throttling parts can be reduced.

[0015] By shortening the lengths of at least two throttle portions, changes in the fluid temperature of the fluid can be suppressed to be small, and the temperature characteristics of the fluid can be improved.

[0016] In the above configuration, the relief valve body may be formed in a cylindrical shape, and the throttle portion may be formed along a radial direction of the relief valve body.

[0017] In this case, at least two throttle portions are formed along the radial direction of the relief valve body, so that the at least two throttle portions can be orthogonal to the lifting direction of the relief valve body, thereby reducing the influence of the fluid force from the fluid on the relief valve body.

[0018] In the above structure, the relief valve body may include: a valve cap fixed to the housing; and a poppet accommodated in the valve cap. The valve cap and the poppet may each include the throttle portion.

[0019] In this case, the valve bonnet can be fixed to the housing, for example, it can have a hollow housing portion. Furthermore, the poppet can be housed in the housing portion of the valve bonnet. In addition, the poppet can be configured to be slidable in a lifting direction to separate from the valve seat of the housing. In addition, a communication path (hollow portion) that passes through in the lifting direction can be provided in the poppet.

[0020] In this case, at least two throttle portions can be provided in the hollow portion of the valve cap and the hollow portion of the poppet along the radial direction. Thus, at least two throttle portions can be formed shorter with a simple structure.

[0021] In the above structure, the valve bonnet and the poppet may each have one throttling portion. The valve bonnet may be provided with a first throttling portion as the throttling portion. The poppet may be provided with a second throttling portion different from the first throttling portion as the throttling portion.

[0022] In this case, at least two throttle parts can be set as the first throttle part and the second throttle part, the first throttle part is set on the valve cap, and the second throttle part is set on the poppet. Thus, the degree of freedom in determining the configuration of the first throttle part and the second throttle part can be increased.

[0023] In the above structure, the poppet may include: a poppet body housed in the valve cap and provided with the second throttle portion; and a guide member housed in the poppet body. The guide member may be provided with a third throttle portion different from the first throttle portion and the second throttle portion as the throttle portion.

[0024] In this case, the first throttle portion can be provided on the valve cap, the second throttle portion can be provided on the poppet body, and the third throttle portion can be provided on the guide. Thus, the degree of freedom in setting the throttle portion can be increased.

[0025] In the above structure, the relief valve body may include: a valve cap fixed to the housing; and a poppet accommodated in the valve cap. The poppet may include: a poppet body; and a guide accommodated in the poppet body. Two selected members among the valve cap, the poppet body, and the guide may each include the throttling portion.

[0026] In this case, the throttle portion is provided on two members selected from the bonnet, the poppet body, and the guide, thereby further improving the degree of freedom in setting the throttle portion.

[0027] In the above configuration, in the first throttle portion, the second throttle portion, and the third throttle portion, adjacent throttle portions may be provided at positions separated from each other.

[0028] In this case, a gap can be provided between adjacent throttle sections. Therefore, the gap provided between adjacent throttle sections can be used to suppress the velocity of the jet ejected from one of the adjacent throttle sections to be low. Therefore, the noise generated by the jet ejected from the throttle section can be reduced.

[0029] In the above structure, a wall portion intersecting the axial direction of the first throttling portion may be provided on the outlet side of the fluid in the first throttling portion, a wall portion intersecting the axial direction of the second throttling portion may be provided on the outlet side of the fluid in the second throttling portion, and a wall portion intersecting the axial direction of the third throttling portion may be provided on the outlet side of the fluid in the third throttling portion.

[0030] In this case, the jets ejected from the outlets of the first throttle portion, the second throttle portion, and the third throttle portion can be made to collide with the wall portion, and the jet speed can be suppressed to be low. Thus, the noise generated by the jets ejected from the throttle portions can be well reduced.

[0031] A negative control relief valve according to another technical solution of the present invention is arranged at the most downstream of the unloading passage to generate a negative control pump flow control pressure, wherein the negative control relief valve comprises: a housing; and a relief valve body, which is mounted on the housing and allows fluid to pass through. The relief valve body has at least two throttle parts for applying resistance to the fluid passing through the relief valve body to generate the pump flow control pressure.

[0032] With such a configuration, in the negative control relief valve, it is possible to reduce the noise generated by the jet flow ejected from the throttle portion.

[0033] In addition, the temperature characteristics of the fluid can be improved. Therefore, the change in the pressure loss characteristics of the fluid when passing through the throttle portion can be suppressed to be small. As a result, the change in the pump flow control pressure caused by the temperature characteristics of the fluid temperature can be suppressed to be small.

[0034] Furthermore, the influence of the fluid force from the fluid on the relief valve body can be reduced, thereby suppressing the change in the pump flow control pressure to be small.

[0035] A control valve according to another technical solution of the present invention comprises: a plurality of reversing valves disposed in the middle of an unloading passage through which a fluid ejected from a variable capacity pump passes, and supplying the fluid to the plurality of reversing valves; and a negative control relief valve disposed at a position on the downstream side of the unloading passage relative to the reversing valve, and generating a negative control method pump flow control pressure on the downstream side of the reversing valve. The negative control relief valve comprises: a housing; and a relief valve body mounted on the housing through which a fluid passes. The relief valve body has at least two throttling parts for applying resistance to the fluid passing through the relief valve body to generate the pump flow control pressure. Moreover, the negative control relief valve controls the discharge volume of the variable capacity pump based on the pump flow control pressure.

[0036] Thus, by providing the negative control relief valve in the control valve, the noise of the control valve can be reduced.

[0037] In addition, the temperature characteristics of the negative control relief valve can be improved and the influence of fluid force can be reduced. Therefore, the change of the pump flow control pressure can be suppressed to a small level. As a result, the discharge amount of the variable capacity pump can be well controlled based on the pump flow control pressure.

[0038] Effects of the Invention

[0039] 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

[0040] Figure 1 This is a hydraulic circuit diagram schematically showing a control valve in an embodiment of the present invention.

[0041] Figure 2 It is a cross-sectional view showing a negative control relief valve in an embodiment of the present invention.

[0042] Figure 3 Is magnification Figure 2 2 is a sectional view of the III portion of FIG. 1 , and is a view showing a state in which the working oil flows toward the second throttle portion and the first throttle portion.

[0043] Figure 4 This is a graph showing changes in negative control pressure in the embodiment of the present invention.

[0044] Figure 5 It is a cross-sectional view showing a negative control relief valve according to a modified example of the embodiment of the present invention.

[0045] Description of Reference Numerals

[0046] 1. Control valve; 2. Shell; 4, 5, 6. 1st to 3rd reversing valves (reversing valves); 8. Variable capacity pump; 8a. Pump flow controller; 10. 100. Negative control relief valve (relief valve); 20. Relief valve body; 21. Valve bonnet; 22. 102. Poppet; 32. Shell passage; 32a. Inner circumference (wall) of shell passage; 41. Receiving part; 41a. Inner circumference (wall) of receiving part; 43. 1st throttling part (at least two throttling parts); 51. Communication path; 51a. Inner circumference (wall) of communication path; 55. 108. 2nd throttling part (at least two throttling parts); 103. Poppet body; 104. Guide; 116. 3rd throttling part (at least two throttling parts). DETAILED DESCRIPTION

[0047] Next, embodiments of the present invention will be described based on the drawings.

[0048] <Control valve>

[0049] Figure 1 1 is a hydraulic circuit diagram schematically showing the control valve 1 . Figure 2 1 is a cross-sectional view showing the negative control relief valve 10. In the following description, the upstream side in the flow direction of the working oil is sometimes referred to as the upstream side, and the downstream side in the flow direction of the working oil is sometimes referred to as the downstream side. In addition, the upstream side is sometimes referred to as the "front", and the downstream side is sometimes referred to as the "rear" for description.

[0050] like Figure 1 , Figure 2 As shown, the control valve 1 includes, for example: a housing 2; a plurality of switching valves 4, 5, 6, which are arranged in the housing 2; a variable displacement pump 8, which supplies hydraulic oil to each switching valve 4, 5, 6; and a negative control relief valve 10, which is arranged on the downstream side of each switching valve 4, 5, 6. Figure 1 In the figure, the housing 2 is omitted.

[0051] like Figure 1 As shown, the first switching valve 4 is connected to, for example, a hydraulic motor 12 as a first actuator. The first switching valve 4 controls the driving of the hydraulic motor 12.

[0052] The second switching valve 5 is connected to, for example, the first hydraulic cylinder 13 as a second actuator. The second switching valve 5 controls the driving of the first hydraulic cylinder 13.

[0053] The third switching valve 6 is connected to, for example, the second hydraulic cylinder 14 as a third actuator. The third switching valve 6 controls the driving of the second hydraulic cylinder 14.

[0054] 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 fluid in the claims) to the first switching valve 4, the second switching valve 5, and the third switching valve 6 via the unloading passage 16 and the supply passage 17, respectively.

[0055] The variable displacement pump 8 has a built-in pump flow controller 8a, for example. The pump flow controller 8a is connected to the negative control relief valve 10. The pump flow controller 8a changes the inclination angle of the movable swash plate 8b based on the negative control pressure (pump flow control pressure) applied by the negative control relief valve 10. Thus, the discharge amount of the variable displacement pump 8 is controlled.

[0056] <Negative control relief valve>

[0057] like Figure 1 and Figure 2 As shown, the negative control relief valve 10 is a valve used in the negative control method for controlling the discharge amount of the variable displacement pump 8. The negative control relief valve 10 is provided on the downstream side of the first switching valve 4, the second switching valve 5, and the third switching valve 6. Therefore, the negative control relief valve 10 is provided on the most downstream side of the unloading passage 16. The negative control relief valve 10 generates a negative control pressure of the negative control method (details will be discussed later).

[0058] The negative control relief valve 10 includes: a housing 2 ; a relief valve body (an example of a relief valve body in the claims) 20 attached to the housing 2 ; and a spring 25 provided on the relief valve body 20 .

[0059] <Housing>

[0060] The housing 2 includes a front pressure chamber 31 that communicates with the downstream side of the first switching valve 4, the second switching valve 5, and the third switching valve 6, and a housing passage 32 that communicates with the front pressure chamber 31 and with the tank line 18. The housing passage 32 includes an inner peripheral surface (an example of a wall in the claims) 32a. The tank line 18 communicates with the tank 19.

[0061] <Relief valve body>

[0062] The relief valve body 20 is formed in a cylindrical shape and has at least two throttle portions formed along the radial direction with the central axis of the relief valve body 20 as the center.

[0063] The relief valve body 20 includes a bonnet 21 fixed to the housing 2 and a poppet 22 accommodated in the bonnet 21 .

[0064] In the embodiment, as at least two throttle portions, a first throttle portion 43 and a second throttle portion 55 to be described later will be described as examples.

[0065] In the following description, the center of the poppet 22 is referred to as the lifting axis O. The poppet 22 can be separated from the valve seat 33 of the housing 2 along the lifting axis O. The direction in which the poppet 22 separates from the valve seat 33 is referred to as the lifting direction. The lifting axis O is the same as the central axis of the relief valve body 20 (i.e., the bonnet 21 and the poppet 22). In the following description, the radial direction centered on the lifting axis O is sometimes referred to as simply the radial direction, and the circumferential direction centered on the lifting axis O is sometimes referred to as simply the circumferential direction.

[0066] <Bonnet>

[0067] Figure 3 Is magnification Figure 2 2 is a cross-sectional view of the III portion of FIG. 1 , and shows a state in which the working oil flows toward the second throttle portion 55 and the first throttle portion 43 .

[0068] like Figure 2 , Figure 3 As shown in FIG. 1 , the valve bonnet 21 is formed with an external thread 35 on the outer periphery of the front end side. The external thread 35 is combined with the internal thread 36 of the housing 2, so that the valve bonnet 21 is fixed to the housing 2. An O-ring 37 is provided between the valve bonnet 21 and the housing 2. The valve bonnet 21 has: a housing portion 41 formed to be hollow with the lifting axis O as the center; a protrusion 42 formed at the front end; and a first throttle portion 43 formed at the protrusion 42.

[0069] The front end of the storage portion 41 is open toward the front (upstream side). The storage portion 41 is formed to be hollow from the front end to the rear end along the lifting axis O. The storage portion 41 communicates with a communication path 51 of the poppet 22 to be discussed later. The storage portion 41 communicates with the port 46 via a through hole 45 formed at the rear end. The storage portion 41 has an inner peripheral surface (an example of a wall portion in the claims) 41a.

[0070] The protruding portion 42 forms an opening of the housing portion 41 . The protruding portion 42 is formed into a hollow structure having a relatively thin wall thickness in the radial direction centered on the lift axis O. A first throttle portion 43 is formed in the protruding portion 42 .

[0071] A plurality of first throttle portions 43 are formed in a manner that they are arranged at intervals in the circumferential direction of the protruding portion 42 with the lifting axis O as the center. Figure 2 The description will be given by taking two first throttle portions 43 as an example. However, the number of the plurality of first throttle portions 43 is not limited to two, and can be arbitrarily selected.

[0072] The first throttle portion 43 is a throttle hole formed along a radial direction orthogonal to the lifting axis O and penetrating from the inner peripheral surface to the outer peripheral surface of the protrusion 42. The inlet of the first throttle portion 43 opened on the inner peripheral surface of the protrusion 42 opens to the guide groove 54 discussed later. The outlet of the first throttle portion 43 opened on the outer peripheral surface of the protrusion 42 opens to the housing passage 32.

[0073] The outlet of the first throttle portion 43 is arranged at a position opposite to the inner peripheral surface 32a of the housing passage 32. Therefore, the inner peripheral surface 32a of the housing passage 32 is provided as a wall portion on the outlet side of the first throttle portion 43. The inner peripheral surface 32a of the housing passage 32 is arranged in a manner slightly separated from the outlet of the first throttle portion 43 toward the radial outer side. The inner peripheral surface 32a of the housing passage 32 is formed along the lifting axis O. That is, the inner peripheral surface 32a of the housing passage 32 is formed in a manner intersecting with the axial direction of the first throttle portion 43. Preferably, the inner peripheral surface 32a of the housing passage 32 is formed in a manner orthogonal to the first throttle portion 43.

[0074] <Pop head>

[0075] The poppet 22 is housed in the housing portion 41 of the bonnet 21 via an opening of the housing portion 41. The poppet 22 is formed in a cylindrical shape along the lifting axis O. The poppet 22 is arranged to be slidable along the lifting axis O relative to the housing portion 41 of the bonnet 21. A rear pressure chamber 48 is formed between the rear end portion of the housing portion 41 and the poppet 22.

[0076] The poppet 22 has: a connecting path 51 formed in a manner that passes through the poppet 22 from the front end to the rear end; a seat surface 52 formed at the front end; a rear pressure-bearing surface 53 formed at the rear end; a guide groove 54 formed on the outer peripheral surface; and a second throttling portion 55 communicating with the guide groove 54.

[0077] The communication path 51 is formed from the front end portion to the rear end portion of the poppet 22 and penetrates the poppet 22 along the lift axis O. The communication path 51 communicates with the front pressure chamber 31 of the housing 2 and communicates with the rear pressure chamber 48. Therefore, the front pressure chamber 31 and the rear pressure chamber 48 communicate along the lift axis O via the communication path 51.

[0078] The seat surface 52 is formed so as to be contactable with the valve seat 33 at the front end of the poppet 22. The front pressure chamber 31 is blocked from the housing passage 32 by the contact between the seat surface 52 and the valve seat 33. In contrast, by lifting the poppet 22, the seat surface 52 and the valve seat 33 are separated, and the front pressure chamber 31 of the housing 2 is communicated with the housing passage 32.

[0079] The rear pressure receiving surface 53 is arranged to face the rear pressure chamber 48. The rear pressure receiving surface 53 is formed so that the pressure receiving area 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 pressure receiving area of ​​the rear pressure receiving surface 53. The front end portion of the spring 25 discussed later contacts the rear pressure receiving surface 53.

[0080] The guide groove 54 is formed in an annular shape, for example, on the outer peripheral surface of the poppet 22 and continuously extends in the circumferential direction of the poppet 22 . The guide groove 54 has a constant groove width along the lift axis O. The inlet of the first throttle portion 43 opens in the guide groove 54 .

[0081] The second throttle portion 55 is provided in the guide groove 54 of the poppet 22. The second throttle portion 55 is formed so that an outlet opens in the guide groove 54.

[0082] A plurality of second throttle portions 55 are formed in a manner that they are arranged at intervals in the circumferential direction of the poppet 22 with the lift axis O as the center. Figure 2 The description will be given by taking two second throttle portions 55 as an example. However, the number of the second throttle portions 55 is not limited to two, and can be arbitrarily selected.

[0083] The second throttle portion 55 is formed along a radial direction orthogonal to the lifting axis O. The second throttle portion 55 is a throttle hole penetrating from the inner peripheral surface of the poppet 22 to the bottom surface 54a of the guide groove 54. The second throttle portion 55 is provided at a position separated from the first throttle portion 43 along the lifting axis O (offset position).

[0084] In the embodiment, an example is described in which the first throttle portion 43 and the second throttle portion 55 are provided at positions separated from each other along the lift axis O. However, the first throttle portion 43 and the second throttle portion 55 may be provided at positions separated from each other in the radial direction.

[0085] The inlet of the second throttle portion 55, which opens on the inner circumferential surface of the poppet 22, opens to the connecting path 51. The outlet of the second throttle portion 55 opens to the guide groove 54. The outlet of the second throttle portion 55 is arranged at a position opposite to the inner circumferential surface 41a of the housing portion 41. Therefore, the inner circumferential surface 41a of the housing portion 41 is provided as a wall portion on the outlet side of the second throttle portion 55. The inner circumferential surface 41a of the housing portion 41 is arranged in a manner slightly separated from the outlet of the second throttle portion 55 toward the radial outside. The inner circumferential surface 41a of the housing portion 41 is formed along the lifting axis O. That is, the inner circumferential surface 41a of the housing portion 41 is formed in a manner intersecting with the axial direction of the second throttle portion 55. Preferably, the inner circumferential surface 41a of the housing portion 41 is formed in a manner orthogonal to the second throttle portion 55.

[0086] The poppet 22 is partially housed in the bonnet 21. In addition, the second throttle portion 55 is formed in the poppet 22, and the first throttle portion 43 is formed in the bonnet 21. Therefore, the first throttle portion 43 and the second throttle portion 55 are connected in series via the guide groove 54. Therefore, the throttle portion of the negative control relief valve 10 is divided into the first throttle portion 43 and the second throttle portion 55 in series. In this way, the divided first throttle portion 43 and the second throttle portion 55 are connected in series at two locations of the bonnet 21 and the poppet 22 via the guide groove 54.

[0087] Therefore, if Figure 3 As shown, the working oil flows from the communication path 51 into the second throttle portion 55 as indicated by arrow A. The working oil flowing into the second throttle portion 55 flows toward the guide groove 54 and hits the inner peripheral surface (wall portion) 41a of the housing portion 41. The working oil hitting the inner peripheral surface 41a flows into the guide groove 54 as indicated by arrow B.

[0088] The hydraulic oil flowing into the guide groove 54 flows into the first throttle portion 43 as indicated by arrow C. The hydraulic oil flowing into the first throttle portion 43 flows toward the case passage 32 and hits the inner peripheral surface (wall portion) 32a of the case passage 32. The hydraulic oil hitting the inner peripheral surface 32a flows into the case passage 32 as indicated by arrow D.

[0089] <Spring>

[0090] like Figure 2 and Figure 3As shown in FIG. 1 , the rear pressure chamber 48 contains a spring 25. The spring 25 is a compression coil spring disposed 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 between the rear pressure receiving surface 53 and the rear wall surface 48a of the rear pressure chamber 48. Therefore, under the force (elastic restoring force) of the spring 25, the seat surface 52 of the poppet 22 is pressed against and contacts the valve seat 33 of the housing 2. As a result, the front pressure chamber 31 of the housing 2 and the housing passage 32 are blocked by the poppet 22.

[0091] (Action of negative control relief valve)

[0092] Next, based on Figure 1 , Figure 2 , Figure 4 The operation when the negative control relief valve 10 is applied to the control valve 1 will be described.

[0093] like Figure 1 , Figure 2 As shown in FIG. 1 , the working oil is ejected from the variable displacement pump 8. The first reversing valve 4, the second reversing valve 5, and the third reversing valve 6 of the control valve 1 are arranged in the neutral position. Therefore, the working oil ejected from the variable displacement pump 8 is supplied to the front pressure chamber 31 via the first reversing valve 4, the second reversing valve 5, and the third reversing valve 6 of the control valve 1.

[0094] The hydraulic oil supplied to the front pressure chamber 31 is supplied to the case passage 32 of the case 2 via the communication path 51, the second throttle portion 55, the guide groove 54 and the first throttle portion 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.

[0095] Figure 4 This is a graph showing changes in negative control pressure when the vertical axis represents the negative control pressure and the horizontal axis represents the flow rate of the hydraulic oil.

[0096] like Figure 4 As shown, the hydraulic oil ejected from the variable displacement pump 8 is subjected to resistance by the throttle portions 43 and 55 when passing through the relief valve body 20 of the negative control relief valve 10. As a result, a flow control pressure (negative control pressure) PC is generated in the front pressure chamber 31 in accordance with the flow rate Q of the hydraulic oil ejected from the variable displacement pump 8.

[0097] like Figure 1 , Figure 2As shown in FIG. 1 , the negative control pressure PC generated in the front pressure chamber 31 is output to the pump flow controller 8a via the communication path 51, the rear pressure chamber 48, the through hole 45, and the port 46. The pump flow controller 8a controls the movable swash plate 8b of the variable displacement pump 8 using the output negative control pressure PC. Thus, by applying the negative control relief valve 10 to the control valve 1, the discharge amount of the variable displacement pump 8 can be controlled in accordance with the negative control pressure PC discharged from the negative control relief valve 10.

[0098] For example, during the ejection of the working oil by the variable displacement pump 8, there is a possibility that an excessive flow rate Q flows to the second throttle portion 55 and the first throttle portion 43. In this case, the pressure of the working oil supplied to the front pressure chamber 31 increases due to the excessive flow rate Q. In this case, the increased pressure acts on the pressure receiving area of ​​the seat surface 52. As a result, the poppet 22 can be lifted against the force of the spring 25. As the poppet 22 is lifted, the seat surface 52 and the valve seat 33 are separated.

[0099] Therefore, the hydraulic oil in the front pressure chamber 31 can flow directly from between the seat surface 52 and the valve seat 33 to the housing passage 32 of the housing 2 and can return from the housing passage 32 to the tank 19 via the tank line 18. Thus, the generation of excessive pressure P in the front pressure chamber 31 can be prevented.

[0100] like Figure 3 As shown, the negative control relief valve 10 in the embodiment is configured in such a way that the throttle portion of the negative control relief valve 10 is divided into the first throttle portion 43 and the second throttle portion 55, and the first throttle portion 43 and the second throttle portion 55 are formed in the radial direction. Therefore, it is possible to shorten the length of the first throttle portion 43 and the length of the second throttle portion 55. In addition, the length of the throttle portion refers to the length of the throttle portion (hole) in the axial direction (the same applies hereinafter).

[0101] Furthermore, the first throttle portion 43 and the second throttle portion 55 are provided in series via the guide groove 54. Therefore, the hydraulic oil can flow continuously to the second throttle portion 55 and the first throttle portion 43 in the order of arrow A, arrow B, arrow C, and arrow D.

[0102] Thus, the pressure difference between the front and rear of the working oil flowing to the second throttle portion 55 and the first throttle portion 43 can be suppressed to be small. As a result, the flow rate of the working oil flowing to the first throttle portion 43 and the second throttle portion 55 can be suppressed to a low speed. Therefore, the noise generated by the jet flow ejected from the second throttle portion 55 and the first throttle portion 43 can be reduced.

[0103] By shortening the length of the second throttle portion 55 and the length of the first throttle portion 43, the change in the oil temperature of the working oil can be suppressed to be small. Therefore, the temperature characteristics of the working oil can be well maintained. Therefore, the change in the pressure loss characteristics when the working oil passes through the second throttle portion 55 and the first throttle portion 43 can be suppressed to be small. As a result, for example, the change in the negative control pressure caused by the temperature characteristics of the oil temperature can be suppressed to be small.

[0104] The second throttle portion 55 and the first throttle portion 43 are formed in the radial direction. Therefore, the second throttle portion 55 and the first throttle portion 43 can be made orthogonal to the lift axis O. As a result, the influence of the fluid force from the working oil on the bonnet 21 and the poppet 22 (especially the poppet 22) can be suppressed to be small. Therefore, for example, the change of the negative control pressure caused by the fluid force of the working oil can be suppressed to be small.

[0105] The valve bonnet 21 is fixed to the housing 2 and has a hollow housing portion 41. The poppet 22 is housed in the housing portion 41 of the valve bonnet 21. The poppet 22 is arranged to be slidable along the lifting axis O and can be separated from the valve seat 33 of the housing 2. The poppet 22 has a communication path 51 (hollow portion) along the lifting axis O. Therefore, the first throttle portion 43 and the second throttle portion 55 can be radially arranged in the hollow portion of the valve bonnet 21 and the hollow portion of the poppet 22. As a result, the first throttle portion 43 and the second throttle portion 55 can be formed shorter with a simple structure.

[0106] Furthermore, the first throttle portion 43 is provided on the bonnet 21, and the second throttle portion 55 is provided on the poppet 22. Thus, the degree of freedom in determining the arrangement of the first throttle portion 43 and the second throttle portion 55 can be improved.

[0107] The first throttle portion 43 and the second throttle portion 55 are arranged at mutually separated positions (offset positions) along the lifting axis. Therefore, a gap can be provided between the first throttle portion 43 and the second throttle portion 55. Therefore, the velocity of the jet ejected from the second throttle portion 55 can be suppressed to a low level by utilizing the gap provided between the first throttle portion 43 and the second throttle portion 55. Therefore, the noise generated by the jet ejected from the first throttle portion 43 and the second throttle portion 55 can be reduced well.

[0108] The inner peripheral surface (wall portion) 41a of the housing portion 41 orthogonal to the second throttle portion 55 is provided on the outlet side of the second throttle portion 55. The inner peripheral surface 41a of the housing portion 41 is arranged so as to be slightly separated from the outlet of the second throttle portion 55 toward the radially outer side. Therefore, the jet ejected from the outlet of the second throttle portion 55 can hit the inner peripheral surface 41a of the housing portion 41 at a relatively short distance, and the jet velocity ejected can be suppressed to be relatively low.

[0109] In addition, an inner peripheral surface (wall portion) 32a of the housing passage 32 orthogonal to the first throttle portion 43 is provided on the outlet side of the first throttle portion 43. The inner peripheral surface 32a of the housing passage 32 is arranged so as to be slightly separated from the outlet of the first throttle portion 43 toward the radial outer side. Therefore, the jet ejected from the outlet of the first throttle portion 43 can hit the inner peripheral surface 32a of the housing passage 32 at a relatively short distance, and the jet velocity ejected can be suppressed to be relatively low.

[0110] Thus, the jet flow velocity ejected from the outlet of the second throttle portion 55 and the outlet of the first throttle portion 43 can be suppressed low. Therefore, the noise generated by the jet flow ejected from the second throttle portion 55 and the first throttle portion 43 can be reduced well.

[0111] Through the above content, according to Figure 1 The control valve 1 shown 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. Therefore, the change of the negative control pressure can be suppressed to be small. As a result, the discharge amount of the variable capacity pump 8 provided in the control valve 1 can be well controlled in accordance with the negative control pressure discharged by the negative control relief valve 10.

[0112] [Modifications]

[0113] Next, based on Figure 5 A relief valve according to a modified example will be described. In the modified example, the same reference numerals are given to the same or similar structures as those of the relief valve according to the above-described embodiment, and detailed descriptions thereof will be omitted.

[0114] Figure 5 1 is a cross-sectional view showing a negative control relief valve 100 according to a modified example.

[0115] like Figure 5 As shown, 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. In the negative control relief valve 100 of the modified example, the other structures are substantially the same as those of the negative control relief valve 10 of the embodiment.

[0116] In the modification, the first throttle portion 43, the second throttle portion 108, and the third throttle portion 116 are described as examples of the throttle portion.

[0117] The poppet 102 includes a poppet body 103 housed in the bonnet 21 and a guide 104 housed in the poppet body 103. The port 46 of the bonnet 21 is closed by a plug 106.

[0118] The poppet body 103 is arranged in the housing portion 41 of the valve bonnet 21 in a manner that it can slide along the lifting axis O in the housing portion 41 of the valve bonnet 21. The poppet body 103 is formed substantially the same as the poppet 22 of the above-mentioned embodiment. The poppet body 103 has a first guide groove 107 and a second throttle portion 108 instead of the guide groove 54 and the second throttle portion 55 in the poppet 22 of the above-mentioned embodiment. The second throttle portion 108 is formed in front of the first throttle portion 43. The second throttle portion 108 and the first throttle portion 43 are connected via the first guide groove 107.

[0119] The inner peripheral surface 41a of the housing portion 41 is provided as a wall portion on the outlet side of the second throttle portion 108. The inner peripheral surface 41a of the housing portion 41 is arranged so as to be slightly separated from the outlet of the second throttle portion 108 toward the outside in the radial direction. The inner peripheral surface 41a of the housing portion 41 is formed so as to intersect with the axial direction of the second throttle portion 108. Preferably, the inner peripheral surface 41a of the housing portion 41 is formed so as to be orthogonal to the second throttle portion 108.

[0120] The guide 104 is arranged in the communication path 51 of the poppet body 103 in a manner that it can slide in the communication path 51 of the poppet body 103 along the lifting axis O. The guide 104 has: a deep hole 112 that opens toward the front; a flange 114 that is formed at the rear end; a second guide groove 115 that is formed on the outer peripheral surface; and a third throttle portion 116 that communicates with the second guide groove 115.

[0121] The deep hole 112 is formed from the front end portion to the center portion of the poppet body 103 along the lifting axis O. The flange 114 is formed so as to protrude radially outward from the rear end portion of the guide 104. The flange 114 is arranged in the housing portion 41 of the bonnet 21 so as to be slidable in the housing portion 41 of the bonnet 21 along the lifting axis O. A spring 25 is arranged between the flange 114 and the poppet body 103.

[0122] The second guide groove 115 is formed in an annular shape over the entire circumference of the outer peripheral surface of the guide 104. The inlet of the second throttle portion 108 opens to the second guide groove 115. The third throttle portion 116 is provided in the second guide groove 115 of the guide 104.

[0123] The third throttle portion 116 is formed in such a manner that the inlet is opened on the inner peripheral surface of the deep hole 112 and the outlet is opened in the second guide groove 115. A plurality of third throttle portions 116 are formed in such a manner that they are spaced apart along the circumferential direction of the guide member 104. Figure 5 The description will be given by taking two third throttle portions 116 as an example. However, the number of the third throttle portions 116 is not limited to two, and can be arbitrarily selected.

[0124] The inner peripheral surface (an example of the wall portion in the claims) 51a of the communication path 51 is provided as a wall portion on the outlet side of the third throttle portion 116. The inner peripheral surface 51a of the communication path 51 is arranged in a manner slightly separated from the outlet of the third throttle portion 116 toward the radial outside. The inner peripheral surface 51a of the communication path 51 is formed in a manner intersecting with the axial direction of the third throttle portion 116. Preferably, the inner peripheral surface 51a of the communication path 51 is formed in a manner orthogonal to the third throttle portion 116. The length of the third throttle portion 116 and the length of the second throttle portion 108 are formed to be shorter in the same manner as the length of the first throttle portion 43.

[0125] The first throttle portion 43 and the third throttle portion 116 are arranged in such a manner that their positions along the lifting axis O become the same position. The second throttle portion 108 is arranged in such a manner that it is separated forward from the first throttle portion 43 and the third throttle portion 116. Therefore, the first throttle portion 43 and the second throttle portion 108 adjacent in the radial direction are arranged at positions separated from each other (offset positions) along the lifting axis O. The second throttle portion 108 and the third throttle portion 116 adjacent in the radial direction are arranged at positions separated from each other (offset positions) along the lifting axis O. Therefore, in the first throttle portion 43, the second throttle portion 108, and the third throttle portion 116, the throttle portions adjacent in the radial direction are arranged at positions separated from each other.

[0126] In the modification, an example is described in which the throttle portions adjacent in the radial direction are provided at positions separated from each other along the lift axis O, but they may be provided at positions separated from each other in the radial direction.

[0127] The negative control relief valve 100 outputs the negative control pressure PC generated in the front pressure chamber 31 to the pump flow controller 8a. Therefore, the negative control relief valve 100 can control the discharge amount of the variable displacement pump 8 according to the negative control pressure PC, similarly to the negative control relief valve 10 of the embodiment.

[0128] In addition, the negative control relief valve 100 can prevent the excessive pressure P from being generated in the front pressure chamber 31 in the same manner as the negative control relief valve 10 of the embodiment.

[0129] Therefore, the negative control relief valve 100 in the modified example has the same effect as the embodiment. That is, the noise generated by the jets ejected from the third throttle portion 116, the second throttle portion 108, and the first throttle portion 43 can be reduced in the same manner as the negative control relief valve 10 in the above-mentioned embodiment.

[0130] By shortening the length of the third throttle portion 116 , the length of the second throttle portion 108 , and the length of the first throttle portion 43 , it is possible to maintain favorable temperature characteristics of the hydraulic oil.

[0131] By forming the third throttle portion 116 , the second throttle portion 108 , and the first throttle portion 43 in the radial direction, the influence of the fluid force from the hydraulic oil on the bonnet 21 and the poppet 102 (particularly the poppet 102 ) can be suppressed to be small.

[0132] The first throttle portion 43 is provided on the bonnet 21, and the second throttle portion 108 is provided on the poppet body 103. In addition, the third throttle portion 116 is provided on the guide 104. Thus, the degree of freedom in providing the throttle portion can be increased.

[0133] In the first throttle portion 43, the second throttle portion 108, and the third throttle portion 116, the throttle portions adjacent in the radial direction are arranged at positions separated from each other. Specifically, the adjacent second throttle portion 108 and the third throttle portion 116 are arranged at positions separated from each other. Therefore, a gap can be provided between the adjacent second throttle portion 108 and the third throttle portion 116. Thus, the jet velocity ejected from the third throttle portion 116 can be suppressed to a low level by utilizing the gap provided between the adjacent second throttle portion 108 and the third throttle portion 116.

[0134] Furthermore, the adjacent first throttle portion 43 and the second throttle portion 108 are disposed at positions separated from each other. Therefore, a gap can be provided between the adjacent first throttle portion 43 and the second throttle portion 108. Thus, the jet velocity ejected from the second throttle portion 108 can be suppressed to a low level by utilizing the gap provided between the adjacent first throttle portion 43 and the second throttle portion 108.

[0135] In this way, the velocity of the jet flow ejected from the third throttle portion 116 can be suppressed to be low, and the velocity of the jet flow ejected from the second throttle portion 108 can be suppressed to be low, so that the noise generated by the jet flow ejected from the throttle portion can be reduced well.

[0136] In addition, the first throttle portion 43 is formed to be orthogonal to the inner peripheral surface (wall portion) 32a of the housing passage 32. Therefore, by making the jet ejected from the outlet of the first throttle portion 43 hit the inner peripheral surface 32a, the jet velocity can be suppressed low.

[0137] The second throttle portion 108 is formed in a manner orthogonal to the inner peripheral surface (wall portion) 41a of the storage portion 41. Therefore, by causing the jet ejected from the outlet of the second throttle portion 108 to hit the inner peripheral surface 41a, the jet velocity can be suppressed to a low level. In addition, the third throttle portion 116 is formed in a manner orthogonal to the inner peripheral surface (wall portion) 51a of the communication path 51. By causing the jet ejected from the outlet of the third throttle portion 116 to hit the inner peripheral surface 51a, the jet velocity can be suppressed to a low level.

[0138] This can effectively reduce the noise generated by the jet flow ejected from the throttle portion.

[0139] In the modified example, an example is described in which the first throttle portion 43 is provided in the bonnet 21, the second throttle portion 108 is provided in the poppet body 103, and the third throttle portion 116 is provided in the guide 104. However, the invention is not limited thereto, and as another example, for example, throttle portions may be provided in two members selected from the bonnet 21, the poppet body 103, and the guide 104. In this case, for example, a connecting hole or the like may be provided in other members that are not provided with a throttle portion, instead of the throttle portion.

[0140] In this way, by providing the throttle portion in two members selected from the bonnet 21 , the poppet body 103 , and the guide 104 , the degree of freedom in providing the throttle portion can be further increased.

[0141] The present invention is not limited to the above-described embodiment, and includes embodiments in which various modifications are added to the above-described embodiment within a scope that does not depart from the gist of the present invention.

[0142] For example, in the above-mentioned embodiments and modified examples, hydraulic oil is exemplified as the fluid. However, the present invention is not limited to this, and the present invention can also be applied to fluids other than hydraulic oil. The fluid is not limited to liquids, and can also be gas.

[0143] In the above-mentioned embodiments and modified examples, the negative control relief valves 10 and 100 that generate the pump flow control pressure in the negative control method are described as relief valves. However, this is not limited to this, and the structure of the negative control relief valves 10 and 100 can also be applied to the structure of other relief valves. In this case, noise can also be reduced, and in addition, the temperature characteristics can be improved and the influence of fluid force can be reduced.

[0144] In the above-mentioned embodiment and modification, the first switching valve 4, the second switching valve 5 and the third switching valve 6 are used as the plurality of switching valves 4, 5 and 6. However, the present invention is not limited thereto, and the number of the plurality of switching valves can be arbitrarily selected.

[0145] In the embodiments disclosed in this specification, for a component composed of multiple objects, the multiple objects may be integrated, and conversely, for a component composed of one object, it can be divided into multiple objects. Regardless of whether they are integrated or not, they can be constructed in a manner that can achieve the purpose of the invention.

Claims

1. A relief valve, wherein: The relief valve has: a housing; and The relief valve body is mounted on the housing and allows the fluid to pass through. The relief valve body has at least two throttle parts that apply resistance to the fluid passing through the relief valve body.

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

3. The relief valve according to claim 1 or 2, wherein: The relief valve body comprises: a valve cap fixed to the housing; and A poppet is received in the valve cap, The bonnet and the poppet each have the throttle portion.

4. The relief valve according to claim 3, wherein: The valve cap and the poppet each have a throttling portion, The valve cap is provided with a first throttle portion as the throttle portion, The poppet is provided with a second throttle portion different from the first throttle portion as the throttle portion.

5. The relief valve according to claim 4, wherein: The poppet has: a poppet body, which is accommodated in the valve bonnet and is provided with the second throttling portion; and a guide member received in the poppet body, The guide is provided with a third throttle portion as the throttle portion, which is different from the first throttle portion and the second throttle portion.

6. The relief valve according to claim 1, wherein: The relief valve body comprises: a valve cap fixed to the housing; and A poppet is received in the valve cap, The poppet has: a poppet body; and a guide member received in the poppet body, Selected two of the bonnet, the poppet body, and the guide each have the throttle portion.

7. The relief valve according to claim 5, wherein: In the first throttle portion, the second throttle portion, and the third throttle portion, adjacent throttle portions are provided at positions separated from each other.

8. The relief valve according to claim 7, wherein: A wall portion intersecting the axial direction of the first throttling portion is provided on the outlet side of the fluid in the first throttling portion, a wall portion intersecting the axial direction of the second throttling portion is provided on the outlet side of the fluid in the second throttling portion, and a wall portion intersecting the axial direction of the third throttling portion is provided on the outlet side of the fluid in the third throttling portion.

9. A negative control relief valve, which is arranged at the most downstream of the unloading passage, and generates a negative control pump flow control pressure, wherein: The negative control relief valve has: case; as well as The relief valve body is mounted on the housing and allows the fluid to pass through. The relief valve body has at least two throttle parts for applying resistance to the fluid passing through the relief valve body to generate the pump flow control pressure.

10. A control valve, wherein: The control valve has: a plurality of reversing valves disposed in the middle of an unloading passage through which the fluid ejected from the variable capacity pump passes, and to which the fluid is supplied; as well as a negative control relief valve disposed on the unloading passage at a position downstream of the switching valve, and generating a negative control method pump flow control pressure on the downstream side of the switching valve; The negative control relief valve has: case; as well as The relief valve body is mounted on the housing and allows the fluid to pass through. The relief valve body has at least two throttle parts for applying resistance to the fluid passing through the relief valve body to generate the pump flow control pressure. Furthermore, the negative control relief valve controls the discharge amount of the variable displacement pump based on the pump flow rate control pressure.

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