Relief valve

Abstract

To suppress occurrence of chattering phenomenon while further miniaturizing a direct acting-type relief valve.SOLUTION: An inflow hole 21a is formed on a peripheral wall portion 21 of a valve housing 2 for housing a valve element 5. An outflow hole 21b is formed on one end portion of the valve housing 2. A small-diameter portion 50, a large-diameter portion 51 and a pressure receiving surface 52 are formed on an outer peripheral surface of the valve element 5, and a fluid flowing from the inflow hole 21a makes a pressure act on the pressure receiving surface 52. A contact surface 50a of the valve element 5 on a closing position, is kept into contact with a valve seat 22a disposed on an inner peripheral surface of the valve housing 2. An inclination angle of the valve seat 22a and an inclination angle of the contact surface 50a are different from each other.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a relief valve provided in, for example, a positive displacement coolant pump. [Background technology]

[0002] For example, a pump that delivers liquid may be provided with a relief valve to suppress an excessive increase in pressure on the high-pressure side. This type of relief valve may be of the pilot type or direct acting type.

[0003] A pilot-operated relief valve, as disclosed in Patent Documents 1 and 2, for example, is equipped with a pilot section that operates by detecting the secondary pressure. This pilot section creates a pressure difference between the primary pressure and the pressure inside the valve, and this pressure difference is used to operate the main valve.

[0004] Furthermore, as disclosed in Patent Documents 3 and 4, for example, a direct-acting relief valve does not have a pilot portion, and is configured such that a valve element that is constantly biased by a spring directly receives the pressure of the liquid to open and close. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Utility Model Application Publication No. 54-94634 [Patent Document 2] Patent No. 3676727 [Patent Document 3] Japanese Utility Model Application Publication No. 1-144575 [Patent Document 4] Patent No. 5938818 Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, when providing a relief valve in a pump or the like, there are limitations on layout and the need to avoid interference with other components, and there is a demand to make the relief valve itself as small as possible.

[0007] Therefore, comparing the pilot type relief valves of Patent Documents 1 and 2 with the direct acting type relief valves of Patent Documents 3 and 4, the pilot type has a pilot section that detects the secondary pressure and operates, so the number of parts is greater than that of the direct acting type, resulting in a larger size. On the other hand, the direct acting type can be made smaller than the pilot type because it requires fewer parts. However, in order to accommodate large volumes and high pressures, the bore size must be increased and the spring load must be increased, resulting in a larger size. Therefore, if the direct acting type is used under relatively low operating conditions, such as a coolant pump that supplies coolant to a machine tool, the direct acting type has the advantage of being smaller than the pilot type and easier to incorporate into the pump casing.

[0008] Therefore, it is considered preferable to use the direct acting relief valves disclosed in Patent Documents 3 and 4 under low pressure conditions. However, in the relief valve of Patent Document 3, the axial tip surface of the valve body becomes the pressure receiving surface, and a spring load acts on the opposite base end surface. When the pressing force of the liquid acting on the pressure receiving surface becomes larger than the spring load, the valve body retreats and releases the fluid from a relief hole formed in the peripheral wall of the valve housing. In such a structure, the spring load is determined by the product of the pressure receiving area and the pressure of the fluid, but since the pressure receiving surface is wide, almost the entire tip surface of the valve body, it is necessary to increase the spring load, and as a result, a large spring must be installed, and there is room for further improvement in terms of miniaturization of the relief valve.

[0009] Therefore, it is conceivable to adopt a structure in which an inlet hole is formed in the peripheral wall of the valve housing and the pressure of the fluid is applied to a concave portion formed on the outer peripheral surface of the valve disc, as in the relief valve of Patent Document 4. In this way, the side surface of the concave portion becomes the pressure-receiving surface, so the load that pushes the valve disc in the opening direction is the load obtained by subtracting the area of ​​the side surface of the concave portion from the area of ​​the tip surface of the valve disc and multiplying this by the pressure of the fluid, and therefore the spring load can be reduced compared to the structure of Patent Document 3 in which the tip surface of the valve disc is the pressure-receiving surface. Reducing the spring load means that a smaller spring can be incorporated, so this is advantageous in terms of miniaturizing the relief valve compared to the one in Patent Document 3.

[0010] However, in the relief valve of Patent Document 4, chattering may easily occur due to a small spring load. That is, at the moment when the valve disc opens due to the pressure of the fluid flowing in from the side, the fluid flows through the gap between the valve disc and the valve seat at high speed, so the pressure drops according to Bernoulli's theorem and the valve disc tries to close. When the valve disc tries to close, the pressure rises again and tries to open the valve disc. In particular, when the spring load is small, this process is repeated due to small pressure changes, and as a result, the valve disc vibrates violently and collides with the valve seat repeatedly in a short period of time, causing a phenomenon called chattering, which makes it easy to generate noise.

[0011] The present invention has been made in view of the above-mentioned points, and an object of the present invention is to suppress the occurrence of chattering while achieving further miniaturization of a direct-acting relief valve. [Means for solving the problem]

[0012] In order to achieve the above object, a first aspect of the present disclosure can be based on a relief valve including a cylindrical valve housing, an axially shaped valve element that is axially movable within the valve housing between a closed position and an open position and is held coaxially with the valve housing, and a biasing member that biases the valve element toward the closed position, wherein the valve element is switched to the open position by a fluid of a predetermined pressure or higher that flows in through an inlet hole of the valve housing, causing the fluid to flow out through an outlet hole of the valve housing. The inlet hole is formed in a peripheral wall of the valve housing, and the outlet hole is formed at one axial end of the valve housing. An annular valve seat that protrudes radially inward and extends continuously in the circumferential direction is formed between the inlet hole and the outlet hole on the inner peripheral surface of the valve housing, the valve seat is inclined relative to the axis of the valve housing so as to be positioned radially inward as it approaches the outlet hole, and an annular abutment surface that extends continuously in the circumferential direction is formed at one axial end of the valve disc and is inclined relative to the axis of the valve disc so as to abut against the valve seat when the valve disc is in a closed position, and the inclination angle of the valve seat relative to the axis of the valve housing and The inclination angles of the abutment surfaces relative to the axis of the valve body are different from each other, and a small diameter section is formed at a portion of the outer peripheral surface of the valve body closer to the other axial end than the abutment surface, the small diameter section being positioned to correspond to the downstream end opening of the inlet hole opening into the inner peripheral surface of the valve housing, a large diameter section connected to the other axial end of the small diameter section, and a pressure-receiving surface extending from the end of the small diameter section on the large diameter section side to the end of the large diameter section on the small diameter section side, and the biasing member is configured to bias the valve body toward one end side relative to the other axial end side of the valve body.

[0013] According to this configuration, fluid flowing out from a high pressure side of, for example, a pump, flows into an inlet hole formed in a peripheral wall of the valve housing. The fluid that flows into the inlet hole flows toward a portion of the valve housing that corresponds to the small diameter portion of the valve disc, and exerts pressure on the pressure-receiving surface. When a load calculated by multiplying the area of ​​the pressure-receiving surface by the pressure of the fluid becomes greater than the load caused by the biasing member, the valve disc, which is in the closed position, moves axially to switch to the open position, the abutment surface of the valve disc separates from the valve seat, and the valve is in an open state, and the fluid flows out from the outlet hole.

[0014] In this way, because part of the outer circumferential surface of the valve disc is used as the pressure-receiving surface, the load that urges the valve disc in the opening direction is calculated by subtracting the area of ​​the pressure-receiving surface from the area of ​​one axial end face of the valve disc, and multiplying this by the pressure of the fluid. Therefore, the load from the biasing member is smaller than in a structure in which one end face of the valve disc is the pressure-receiving surface. This allows a smaller biasing member to be installed, making it possible to reduce the size of the relief valve.

[0015] In addition, because the inclination angle of the valve seat and the inclination angle of the abutment surface of the valve disc are different from each other, the valve seat and the abutment surface are in a state of contact close to line contact even when the valve disc is in the completely closed position. This avoids surface contact between the valve seat and the abutment surface and forms a minute gap between them, so that when the valve disc opens, the fluid flows at high speed through the gap between the abutment surface and the valve seat, and at the moment when the pressure drops according to Bernoulli's theorem and the valve disc begins to close, the fluid can be present in the gap between the valve seat and the abutment surface. The fluid present in this gap exerts a cushioning effect, preventing the valve disc from colliding with the valve seat.

[0016] In the second aspect of the present disclosure, an inclination angle of the valve seat is set to be larger than an inclination angle of the contact surface.

[0017] According to this configuration, a gap can be reliably formed between the valve seat and the contact surface.

[0018] In a third aspect of the present disclosure, an annular surface is formed on an inner surface of the valve housing, extending along the axis of the valve housing from the end of the valve seat on the outlet hole side toward the downstream side of the outlet hole and continuing circumferentially, and one axial end of the valve body is provided with a tip insertion portion that enters a space surrounded by the annular surface when in a closed position, an outer peripheral surface of the tip insertion portion extends approximately parallel to the annular surface, and a gap of a predetermined size is formed between the outer peripheral surface of the tip insertion portion and the annular surface.

[0019] In a fourth aspect of the present disclosure, the gap can be set to a size that applies a reverse force to the valve body when the valve body in the open position switches to the closed position and the tip insertion portion enters the space surrounded by the annular surface at a speed greater than or equal to a predetermined speed.

[0020] That is, when the valve body is switched from the open position to the closed position, if the speed is equal to or faster than a predetermined speed, the contact surface of the valve body may collide with the valve seat with force, which may cause noise. In contrast, according to the present configuration, when the tip insertion part of the valve body enters the space surrounded by the annular surface of the valve housing at a speed equal to or faster than a predetermined speed, the flow path is almost instantly closed immediately before the valve body is inserted, so that the inflow pressure increases instantaneously and a force acts on the valve body in the reverse direction (opening direction). In addition, a gap of a predetermined size is formed between the outer circumferential surface of the tip insertion part and the annular surface at this point, so that the contact surface of the valve body does not contact the valve seat, and no collision noise is generated. After that, as the inflow pressure decreases, the valve body moves to the closed position and the contact surface contacts the valve seat. At this time, a force in the reverse direction is temporarily acting on the valve body, so the impact when the valve seat contacts is mitigated. This further enhances the effect of suppressing the chattering phenomenon.

[0021] In a fifth aspect of the present disclosure, the tip insertion portion has an insertion length into the space surrounded by the annular surface set to be equal to or greater than a predetermined length.

[0022] According to this configuration, the tip insertion portion is inserted into the space surrounded by the annular surface by at least a predetermined length, so that even if some pressure fluctuation occurs, the impact when the valve disc abuts against the valve seat is mitigated. Effect of the Invention

[0023] As explained above, by making part of the outer circumferential surface of the valve disc into the pressure-receiving surface, the load applied by the biasing member can be reduced, allowing a smaller biasing member to be incorporated, thereby making the relief valve more compact. Furthermore, since the inclination angle of the valve seat and the inclination angle of the contact surface of the valve disc are different from each other, the fluid present in the gap between them exerts a buffering effect, thereby suppressing the occurrence of chattering. [Brief description of the drawings]

[0024] [Figure 1] 1 is a side view of a coolant pump equipped with a relief valve according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a partial cross-sectional view of the coolant pump. [Diagram 3] FIG. 2 is a perspective view of a relief valve. [Figure 4] FIG. 2 is a cross-sectional view showing a portion of a relief valve with a valve body in a closed position. [Diagram 5] 5 is a view equivalent to FIG. 4 when the valve body is in an open position. [Figure 6] FIG. 4 is a side view of a tip housing component. [Figure 7] FIG. 4 is a cross-sectional view of a tip housing component. [Figure 8] 8 is a cross-sectional view taken along line VIII-VIII in FIG. 6. [Figure 9] FIG. 4 is a view of the tip side housing component as seen from the tip side. [Figure 10] 13 is a view of the distal housing component as viewed from the proximal end side. FIG. [Figure 11] FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. Note that the following description of the preferred embodiments is merely illustrative in nature and is not intended to limit the present invention, its applications, or its uses.

[0026] 1 is a side view of a coolant pump 100 including a relief valve 1 according to an embodiment of the present invention. The coolant pump 100 is for supplying coolant (one example of a fluid) to a machine tool (not shown), and can be disposed, for example, in a coolant filtering device that filters the coolant, or in a coolant storage device (not shown) that stores the coolant. The coolant pump 100 includes a pump body 102 and a motor 101 that drives the pump body 102. The motor 101 is disposed above the pump body 102. A rotating shaft (not shown) of the motor 101 is disposed in an orientation that extends in the vertical direction.

[0027] The pump body 102 is configured as a positive displacement pump. Examples of the positive displacement pump include a gear pump and a vane pump. The discharge pressure of the pump body 102 is set to about 2 to 7 MPa, but this is only an example, and the discharge pressure may be outside this range. The pump body 102 includes a pump casing 103 and a rotor (not shown) housed in the pump casing 103 and driven to rotate by a motor 101. A suction port 104 for sucking in a coolant is provided on the lower side of the pump casing 103. A discharge port 105 is formed on the side of the pump casing 103. A coolant passage (not shown) of a machine tool is connected to the discharge port 105. The coolant is a well-known liquid that is used when cutting various metals.

[0028] 2, a discharge passage 106 is formed inside the pump casing 103, through which the coolant sucked into the pump casing 103 is discharged. The upstream end of the discharge passage 106 is connected to the high pressure side (discharge side) in the space in which the rotor is housed. The downstream end of the discharge passage 106 is connected to the discharge port 105.

[0029] A branch passage 107 branched off from the middle of the discharge passage 106 is formed in the pump casing 103. The branch passage 107 extends downward, and its lower end is blocked by a blocking member 108. A relief passage 109 is also formed in the pump casing 103 at a portion horizontally separated from the branch passage 107. The relief passage 109 extends in the vertical direction like the branch passage 107. The upper end of the relief passage 109 is blocked, while the lower end of the relief passage 109 is open to the outside of the pump casing 103. The horizontal cross-sectional area of ​​the relief passage 109 is set to be larger than the horizontal cross-sectional area of ​​the branch passage 107.

[0030] As described above, since the coolant pump 100 is a positive displacement pump, if the discharge side (high pressure side) is blocked for some reason and the coolant pump 100 enters shutoff operation, the pressure continues to rise, causing an increase in the current value due to overload, which may lead to burning of the motor 101 and damage to the pump body 102. To prevent this, the coolant pump 100 is provided with a relief valve 1 for releasing excess pressure. That is, the pump casing 103 is formed with a mounting hole 110 to which the relief valve 1 is attached. The mounting hole 110 extends horizontally, and the tip end of the mounting hole 110 communicates with the relief passage 109. The middle part of the mounting hole 110 communicates with the discharge passage 106. The base end of the mounting hole 110 opens to the side surface of the pump casing 103.

[0031] As shown in FIG. 3, the relief valve 1 is generally columnar. As also shown in FIG. 4 and FIG. 5, the relief valve 1 includes a cylindrical valve housing 2, a valve body 5, a spring (biasing member) 6, an adjustment screw 7, and a nut 8 (shown in FIG. 2 and FIG. 3). As shown in FIG. 3, the valve housing 2 can be divided into three members in the axial direction, and is composed of a tip-side housing component member 20, an intermediate housing component member 30, and a base-side housing component member 40. The axial direction of the relief valve 1 is a horizontal direction in a state where it is attached to the pump casing 103, and is, for example, a left-right direction in FIG. 2 to FIG. 5. In addition, in the description of this embodiment, the axial tip (corresponding to one axial end) of the relief valve 1 is on the left in FIG. 2 to FIG. 5, and the axial base end (corresponding to the other axial end) of the relief valve 1 is on the right in FIG. 2 to FIG. 5, but this is defined only for convenience of description and does not limit the posture during actual use or during manufacturing. For example, the relief valve 1 may be disposed so that its axial direction is in the vertical direction.

[0032] The tip-side housing component 20 is a cylindrical member constituting the axial tip-side portion of the valve housing 2. The intermediate housing component 30 is a cylindrical member constituting the axial middle portion of the valve housing 2. The base-side housing component 40 is a cylindrical member constituting the axial base-side portion of the valve housing 2. The tip-side housing component 20, the intermediate housing component 30, and the base-side housing component 40 are made of, for example, a highly rigid metal member and basically have a circular cross section. By forming the valve housing 2 from three members, the valve body 5, the spring 6, etc. can be easily accommodated therein, and the valve housing 2 can be easily molded into a complex shape. The number of members constituting the valve housing 2 is not limited to three, and may be two or less, or may be four or more.

[0033] As shown in Figs. 6 and 7, a plurality of inlet holes 21a are formed in the peripheral wall 21 constituting the tip-side housing component 20 so as to penetrate the peripheral wall 21 in the thickness direction. The position of the inlet holes 21a is closer to the tip than the axial center of the tip-side housing component 20. As shown in Fig. 8, the plurality of inlet holes 21a are arranged at approximately equal intervals in the circumferential direction of the tip-side housing component 20. In this embodiment, six inlet holes 21a are formed, but the number of inlet holes 21a may be five or less, or seven or more. The number of inlet holes 21a may be one. When a plurality of inlet holes 21a are formed, they may be formed at unequal intervals.

[0034] The inlet hole 21a has a substantially circular shape and extends radially from the axis A (shown in FIG. 7) of the tip side housing component 20. The axis A of the tip side housing component 20 is the axis of the valve housing 2. When the relief valve 1 is attached to the pump casing 103, the inlet hole 21a is arranged inside the branch passage 107 as shown by the imaginary line in FIG. 4. Therefore, the coolant discharged to the discharge passage 106 shown in FIG. 2 flows into the inlet hole 21a via the branch passage 107, and then can flow into a portion of the tip side housing component 20 closer to the tip than the axial center.

[0035] As shown in FIG. 7, the tip end (one axial end) of the tip end housing component 20 is formed with an outflow hole 21b for letting the coolant out. The outflow hole 21b is circular and opens over almost the entire tip end surface of the tip end housing component 20, and has a diameter larger than that of each of the inflow holes 21a. As will be described later, when the valve body 5 advances to the open position, the coolant that has flowed into the tip end housing component 20 from each of the inflow holes 21a flows through the outflow hole 21b toward the tip end and can flow out of the outflow hole 21b. When the relief valve 1 is attached to the pump casing 103, the downstream end opening of the outflow hole 21b is arranged in the relief passage 109, as shown by the imaginary line in FIG. 4. Therefore, the coolant that has flowed out of the relief valve 1 from the outflow hole 21b can flow through the relief passage 109.

[0036] As shown in Fig. 7, a protrusion 21c is formed in the axially middle portion of the outer circumferential surface of the peripheral wall 21 of the tip-side housing component 20. The protrusion 21c is located closer to the base end than the inlet hole 21a, and as shown in Figs. 9 and 10, protrudes radially outward and extends continuously in the circumferential direction. A male screw portion (not shown) is provided on the outer circumferential surface of the peripheral wall 21 of the tip-side housing component 20 closer to the base end than the protrusion 21c.

[0037] A tip groove 21d is formed on the outer circumferential surface of the peripheral wall portion 21 of the tip-side housing component member 20. The tip groove 21d is positioned between the inlet hole 21a and the outlet hole 21b, and extends continuously in the circumferential direction. A first seal member S1 constituted by an O-ring or the like is fitted into this tip groove 21d, as shown in FIG. 4. When the relief valve 1 is attached to the pump casing 103, the first seal member S1 comes into close contact with a portion between the branch passage 107 and the relief passage 109 on the inner circumferential surface of the mounting hole 110 of the pump casing 103. This separates the branch passage 107 and the relief passage 109, thereby suppressing the movement of coolant. When attaching the relief valve 1 to the pump casing 103, it is sufficient to screw a male threaded portion (not shown) formed on the outer peripheral surface of the intermediate housing component 30 into a female threaded portion (not shown) formed on the inner peripheral surface of the mounting hole 110, but the relief valve 1 can also be attached to the pump casing 103 by a method other than this.

[0038] An annular valve seat 22a that protrudes radially inward and extends continuously in the circumferential direction is formed on the inner circumferential surface of the peripheral wall portion 21 of the tip-side housing component member 20. The valve seat 22a extends from the peripheral edge of the inlet hole 21a or its vicinity on the inner circumferential surface of the peripheral wall portion 21 toward the tip side, and is formed of a smooth surface without irregularities. Specifically, when the base end of the valve seat 22a is the end on the inlet hole 21a side and the tip end of the valve seat 22a is the end on the outlet hole 21b side, the base end of the valve seat 22a is disposed so as to be continuous with the edge on the tip side in the axial A direction of the inlet hole 21a.

[0039] The valve seat 22a is inclined so as to approach the axis A toward the tip side in the direction of the axis A. That is, the valve seat 22a is inclined so as to be located radially inward toward the outlet hole 21b side with respect to the axis A of the valve housing 2, and the inclination angle α of the valve seat 22a with respect to the axis A of the valve housing 2 can be set arbitrarily according to the use conditions. For example, it can be set in the range of 45° to 75°. It is more preferable to set the inclination angle α in the range of 60° to 63° so as to be slightly larger than the inclination angle β described later. The inclination angle α can also be said to be the intersection angle between the extension line of the valve seat 22a (shown by a dashed line) and the axis A. In addition, since the valve seat 22a is inclined as described above, the inner diameter of the peripheral wall portion 21 is minimum at the tip of the valve seat 22a.

[0040] An annular surface 22b is formed on the inner peripheral surface of the peripheral wall portion 21 of the tip-side housing component member 20. The annular surface 22b extends from the tip of the valve seat 22a toward the downstream side (tip side) of the outflow hole 21b along the axis A of the valve housing 2 and continues to extend in the circumferential direction. The annular surface 22b and the axis A are approximately parallel to each other. The dimension of the annular surface 22b in the direction of the axis A is set, for example, in the range of 0.5 mm to 3.0 mm. It is more preferable that the dimension of the annular surface 22b in the direction of the axis A is set in the range of 1.0 mm to 2.0 mm.

[0041] A tip-side inclined surface 22c is formed on the inner peripheral surface of the peripheral wall portion 21 of the tip-side housing component member 20. The tip-side inclined surface 22c extends from the tip portion (the tip portion in the direction of axis A) of the annular surface 22b toward the downstream side of the outflow hole 21b and is inclined so as to be positioned radially outward as it approaches the tip side in the direction of axis A, i.e., so as to be away from the axis A. The inclination direction of the tip-side inclined surface 22c is opposite to the inclination direction of the valve seat 22a. The tip-side inclined surface 22c is also continuous in the circumferential direction.

[0042] The valve seat 22a, the annular surface 22b, and the tip side inclined surface 22c form a protrusion 22 on the inner circumferential surface of the peripheral wall portion 21 of the tip side housing component member 20. This protrusion 22 is positioned between the inlet hole 21a and the outlet hole 21b, and is continuous in the circumferential direction of the peripheral wall portion 21. The width (dimension in the direction of axis A) of the protrusion 22 becomes shorter toward the tip of the protrusion 22 in the protruding direction.

[0043] A base end chamfer 23a is formed on the inner circumferential surface of the base end of the tip side housing component 20. Also, a tip side chamfer 23b is formed on the inner circumferential surface of the tip end of the tip side housing component 20.

[0044] As shown in FIG. 4 and other figures, a small diameter cylindrical portion 31 is formed on the tip side of the intermediate housing component 30. The base end side of the tip side housing component 20 is inserted into the small diameter cylindrical portion 31. That is, a female thread portion (not shown) is formed on the inner peripheral surface of the small diameter cylindrical portion 31, which is screwed into a male thread portion formed on the outer peripheral surface of the peripheral wall portion 21 of the tip side housing component 20. By screwing the male thread portion of the tip side housing component 20 into the female thread portion of the intermediate housing component 30, the tip side housing component 20 and the intermediate housing component 30 are liquid-tightly connected and integrated. In the connected state of the tip side housing component 20 and the intermediate housing component 30, the tip portion of the intermediate housing component 30 is adapted to abut against the protruding portion 21c.

[0045] An intermediate groove 31a is formed on the outer circumferential surface of the small diameter cylindrical portion 31. A second seal member S2, such as an O-ring, is fitted into the intermediate groove 31a. When the relief valve 1 is attached to the pump casing 103, the second seal member S2 comes into close contact with a portion of the inner circumferential surface of the mounting hole 110 of the pump casing 103 that is closer to the base end side than the branch passage 107. This prevents the coolant from leaking from the branch passage 107.

[0046] A large diameter cylindrical portion 32 having a diameter larger than the small diameter cylindrical portion 31 is formed on the base end side of the small diameter cylindrical portion 31 of the intermediate housing component member 30. Furthermore, a tool engagement portion 33 having a hexagonal cross section is provided on the base end side of the large diameter cylindrical portion 32 of the intermediate housing component member 30. When the male threaded portion of the intermediate housing component member 30 is screwed into the female threaded portion of the mounting hole 110, a tool (not shown) can be engaged with the tool engagement portion 33 to tighten the relief valve 1. The tool engagement portion 33 can also be used when removing the relief valve 1.

[0047] 2, the base-end housing component 40 is attached to the base end of the intermediate housing component 30. Specifically, a female thread portion (not shown) is formed on the inner peripheral surface on the tip side of the base-end housing component 40, while a male thread portion (not shown) is formed on the outer peripheral surface on the base side of the intermediate housing component 30. By screwing the female thread portion of the base-end housing component 40 into the male thread portion of the intermediate housing component 30, the base-end housing component 40 and the intermediate housing component 30 are liquid-tightly connected and integrated.

[0048] As shown in Fig. 11, the valve element 5 is made of a highly rigid member such as metal, and is formed into an axis shape as a whole. The valve element 5 is movable in the axial direction between a closed position (shown in Fig. 4) and an open position (shown in Fig. 5) within the valve housing 2, and is held coaxially with the valve housing 2. "Coaxially" means that when the valve element 5 is accommodated in the tip-side housing component 20 of the valve housing 2, the axis B of the valve element 5 coincides with the axis A of the valve housing 2, and the valve element 5 is movable within a predetermined range in the direction of the axis A relative to the valve housing 2.

[0049] As shown in Fig. 4, the spring 6 is a member for biasing the valve body 5 towards the tip side, and is made of an elastic member such as a coil spring. The spring 6 is accommodated in the intermediate housing component member 30. A tip side member 60a is provided at the tip of the spring 6, and the biasing force of the spring 6 acts on the valve body 5 via this tip side member 60a. As shown in Fig. 2, a base end member 60c is provided at the base end of the spring 6.

[0050] A screw hole 40a into which the adjustment screw 7 is screwed is formed on the base end side of the base end housing component 40 of the valve housing 2. When the adjustment screw 7 is screwed into the screw hole 40a, the base end side of the valve housing 2 is closed. The base end member 60c abuts on the tip of the adjustment screw 7. Therefore, the valve body 5 is biased toward the closed position by the spring 6, and the biasing force of the spring 6 against the valve body 5 by tightening the adjustment screw 7 increases, while the biasing force of the spring 6 against the valve body 5 by loosening the adjustment screw 7 decreases. The biasing force of the spring 6 is set so that the valve body 5 is advanced and switched to the open position by the fluid with a predetermined pressure or more that flows in from the inlet hole 21a. A nut 8 is screwed into the adjustment screw 7, and the adjustment screw 7 can be prevented from loosening by using this nut 8.

[0051] As shown in FIG. 11, the valve body 5 has a tip end (one axial end) in the axial direction thereof with a contact surface 50a that contacts the valve seat 22a when the valve body 5 is in the closed position, and the contact surface 50a is formed in a ring shape that extends continuously in the circumferential direction. The contact surface 50a is formed as an inclined surface inclined with respect to the axial line B of the valve body 5. The inclination angle β of the contact surface 50a with respect to the axial line B of the valve body 5 can be set arbitrarily according to the use conditions. For example, the inclination angle β can be set in the range of 45° to 75°, and more preferably in the range of 59° to 62°. The inclination angle α of the valve seat 22a with respect to the axial line A of the valve housing 2 and the inclination angle β of the contact surface 50a are different from each other. The inclination angle α of the valve seat 22a is set to be larger than the inclination angle β of the contact surface 50a. Specifically, the inclination angle α of the valve seat 22a is set to be larger than the inclination angle β of the contact surface 50a by 1° or more. The upper limit of the difference between the inclination angle α of the valve seat 22a and the inclination angle β of the contact surface 50a is preferably 3° or less, and more preferably 2° or less. The inclination angle β of the contact surface 50a can also be regarded as the intersection angle between an extension line of the contact surface 50a (shown by a dashed line) and the axis B.

[0052] The tip of the valve body 5 in the direction of the axis B is provided with a tip insertion part 50b that enters the space surrounded by the annular surface 22b of the tip housing component 20 when the valve body 5 is in the closed position. The tip insertion part 50b protrudes in the direction of the axis B from the edge part on the tip side of the abutment surface 50a. The tip surface of the tip insertion part 50b is composed of a flat surface that is approximately perpendicular to the axis B and has an approximately circular shape. The outer peripheral surface of the tip insertion part 50b extends approximately parallel to the annular surface 22b of the tip housing component 20, that is, along the axis B. The dimension of the tip insertion part 50b in the direction of the axis B is set so that it enters the space surrounded by the annular surface 22b when the valve body 5 advances to the closed position, and exits from the space surrounded by the annular surface 22b when the valve body 5 retreats to the open position.

[0053] The inner diameter of the annular surface 22b of the tip side housing component 20 is set to be slightly larger than the outer diameter of the tip insertion portion 50b of the valve body 5. As a result, a gap (micro gap) of a predetermined size is formed between the outer circumferential surface of the tip insertion portion 50b and the annular surface 22b. This gap is set to a size that applies a force in the opposite direction to the valve body 5 when the tip insertion portion 50b enters the space surrounded by the annular surface 22b at a speed equal to or greater than a predetermined speed when the valve body 5 in the open position switches to the closed position.

[0054] That is, when the valve body 5 switches from the open position to the closed position, it moves toward the tip side, and if the speed of movement at that time is equal to or faster than a predetermined speed, the tip insertion part 50b of the valve body 5 enters the space surrounded by the annular surface 22b of the tip side housing component 20 at a speed equal to or faster than the predetermined speed. At this time, the flow path is almost instantly closed by the valve body 5, so that the inflow pressure increases instantaneously and a force acts on the valve body 5 in the reverse direction (opening direction). The size of the gap is set so as to exert such an effect, and as an example, the gap can be set in the range of 0.005 mm to 0.025 mm. The predetermined speed is a speed at which the chattering phenomenon can occur when the force in the reverse direction does not act.

[0055] The dimension of the tip insertion part 50b in the direction of axis B is set so that the insertion length into the space surrounded by the annular surface 22b is equal to or greater than a predetermined length. The predetermined length can be set to the same length as the dimension of the annular surface 22b in the direction of axis A, and can be set, for example, in the range of 1.0 mm to 2.0 mm.

[0056] A small diameter portion 50 is formed in a portion of the outer circumferential surface of the valve body 5 closer to the base end (the other axial end) than the abutment surface 50a. As shown in FIG. 4, the outer diameter of the small diameter portion 50 is set smaller than the inner diameter of the portion of the tip-side housing component 20 where the inlet hole 21a is formed, and a gap through which the coolant can flow is formed between the outer circumferential surface of the small diameter portion 50 and the inner circumferential surface of the portion of the tip-side housing component 20 where the inlet hole 21a is formed. The small diameter portion 50 is positioned so as to correspond to the downstream end opening of the inlet hole 21a opening in the inner circumferential surface of the tip-side housing component 20, and thus the outer circumferential surface of the small diameter portion 50 faces the inner circumferential surface of the portion of the tip-side housing component 20 where the inlet hole 21a is formed.

[0057] A large diameter portion 51 is formed on the outer peripheral surface of the valve body 5, which is continuous with the base end (the other axial end) of the small diameter portion 50. The outer diameter of the large diameter portion 51 is set to be larger than the outer diameter of the small diameter portion 50, and is set to be substantially equal to or slightly smaller than the inner diameter of the tip-side housing component 20 on the base end side than the inlet hole 21a. The large diameter portion 51 slides against the inner peripheral surface of the tip-side housing component 20, so that the valve body 5 is guided in the direction of the axis A. Two grooves 51a having a V-shaped cross section are formed on the outer peripheral surface of the large diameter portion 51 at an interval from each other in the direction of the axis B. The grooves 51a extend continuously in the circumferential direction.

[0058] A pressure receiving surface 52 is formed on the outer peripheral surface of the valve body 5. That is, since the small diameter portion 50 and the large diameter portion 51 have different diameters, a step is formed on the outer peripheral surface of the valve body 5. The pressure receiving surface 52 is formed by utilizing this step, and extends from the end of the small diameter portion 50 on the large diameter portion 51 side to the end of the large diameter portion 51 on the small diameter portion 50 side. The pressure receiving surface 52 is composed of an annular surface that is continuous in the circumferential direction of the valve body 5, and extends in a direction approximately perpendicular to the axis B. It should be noted that the pressure receiving surface 52 may be inclined with respect to the axis B.

[0059] An intermediate portion 53 is formed on the outer circumferential surface of the valve body 5, closer to the base end than the large diameter portion 51. The outer diameter of the intermediate portion 53 is set smaller than the outer diameter of the large diameter portion 51. A gap is formed between the outer circumferential surface of this intermediate portion 53 and the inner circumferential surface of the tip side housing component member 20.

[0060] A first ridge portion 54 and a second ridge portion 55 are provided on the outer peripheral surface of the valve body 5 at a distance from each other in the direction of axis B, closer to the base end than the intermediate portion 53. The first ridge portion 54 and the second ridge portion 55 extend continuously in the circumferential direction. The outer diameters of the first ridge portion 54 and the second ridge portion 55 are set to be the same as the outer diameter of the large diameter portion 51. The first ridge portion 54 and the second ridge portion 55 come into sliding contact with the inner peripheral surface of the tip side housing component member 20, thereby guiding the valve body 5 in the direction of axis A.

[0061] A groove 56 is formed between the first protrusion 54 and the second protrusion 55. A third seal member S3 constituted by an O-ring or the like is fitted into this groove 56. The third seal member S3 is in sliding contact with the inner circumferential surface of the tip-side housing component member 20. This prevents the coolant from leaking between the base end side of the valve body 5 and the tip-side housing component member 20.

[0062] An insertion portion 57 that is inserted into an insertion hole 60b formed in the tip side member 60a is provided at the base end of the valve body 5. By inserting the insertion portion 57 into the insertion hole 60b, radial positional deviation between the valve body 5 and the tip side member 60a is suppressed.

[0063] The valve body 5 is formed with a small diameter hole portion 56a and a large diameter hole portion 56b passing through the axis B. The small diameter hole portion 56a is formed on the base end side of the valve body 5 and opens at the base end surface of the valve body 5. The large diameter hole portion 56b is formed on the tip side of the valve body 5 and opens at the tip surface of the valve body 5. The small diameter hole portion 56a and the large diameter hole portion 56b communicate with each other. The small diameter hole portion 56a also communicates with a through hole 60d formed in the tip side member 60a. The through hole 60d communicates with the space in which the spring 6 is housed.

[0064] (Action and effect of relief valve 1) When the motor 101 rotates during operation, the coolant pump 100 sucks in coolant from an inlet 104 of a pump casing 103 and then discharges it to a discharge passage 106. The high-pressure coolant discharged to the discharge passage 106 is normally continuously supplied to a machine tool. Coolant at normal pressure flows into the inlet hole 21a of the relief valve 1 disposed in a branch passage 107 branching off from the discharge passage 106, and the coolant that flows into the inlet hole 21a flows toward a portion of the valve body 5 corresponding to the small diameter portion 50 in the valve housing 2, and applies pressure to the pressure-receiving surface 52. The biasing force of the spring 6 is set so that the valve body 5 does not move to the open position under normal pressure (less than a predetermined pressure), so that the coolant does not flow out to the relief passage 109.

[0065] On the other hand, even if the amount of coolant used in the machine tool decreases, the motor 101 continues to rotate at a constant rotation speed, so that the pressure of the coolant in the discharge passage 106 rises. The pressure of the coolant in the branch passage 107 branching off from the discharge passage 106 also rises, and high-pressure coolant flows into the inlet hole 21a of the relief valve 1 arranged in the branch passage 107, exerting a pressure of a predetermined pressure or more on the pressure-receiving surface 52. When the load obtained by multiplying the area of ​​the pressure-receiving surface 52 by the pressure of the coolant becomes greater than the load of the spring 6, the valve body 5 in the closed position moves in the axial direction and switches to the open position, the abutment surface 50a of the valve body 5 separates from the valve seat 22a, and the coolant flows out from the outlet hole 21b. Since the relief valve 1 is of a direct acting type, it has good responsiveness when switching from the closed position to the open position.

[0066] In this way, because part of the outer circumferential surface of the valve disc 5 is used as the pressure-receiving surface 52, the load that pushes the valve disc 5 in the opening direction is the load obtained by subtracting the area of ​​the tip surface of the valve disc 5 from the area of ​​the pressure-receiving surface 52 and multiplying this by the pressure of the coolant, and therefore the load from the spring 6 is smaller than in a structure in which the tip surface of the valve disc 5 is the pressure-receiving surface. This allows a smaller spring 6 to be installed, allowing the relief valve 1 to be made smaller.

[0067] In addition, since the inclination angle of the valve seat 22a and the inclination angle of the abutment surface 50a of the valve body 5 are different from each other, the valve seat 22a and the abutment surface 50a are in a state of contact close to line contact even when the valve body 5 is in the completely closed position. As a result, the surface contact between the valve seat 22a and the abutment surface 50a is avoided and a minute gap is formed between them, so that when the valve body 5 opens, the coolant flows at high speed through the gap between the abutment surface 50a and the valve seat 22a, and at the moment when the pressure drops according to Bernoulli's theorem and the valve body 5 tries to close, the coolant can be present in the gap between the valve seat 22a and the abutment surface 50a. The coolant present in this gap exerts a cushioning effect, so that the valve body 5 can be prevented from colliding with the valve seat 22a.

[0068] In addition, when the valve element 5 in the open position is switched to the closed position, a gap of a predetermined size is formed between the outer peripheral surface of the tip insertion portion 50b of the valve element 5 and the annular surface 22b of the tip side housing component 20, so that a force in the opposite direction can be applied to the valve element 5. This prevents the valve element 5 from immediately contacting the valve seat 22a, so that no impact noise is generated. After that, when the valve element 5 moves to the closed position with a decrease in the inflow pressure and the contact surface 50a contacts the valve seat 22a, the force in the opposite direction is temporarily applied to the valve element 5, so that the impact when the valve seat 22a contacts is mitigated. Therefore, the direct acting relief valve 1 can be further miniaturized while suppressing the occurrence of the chattering phenomenon.

[0069] The above-described embodiment is merely illustrative in all respects and should not be construed as limiting. Furthermore, all modifications and variations within the scope of the claims are within the scope of the present invention. [Industrial Applicability]

[0070] As described above, the relief valve according to the present invention can be provided in, for example, a coolant pump that supplies coolant to a machine tool. [Explanation of symbols]

[0071] 1 Relief valve 2 Valve housing 5 Valve body 6 Spring (biasing member) 21 Peripheral wall section 21a Inflow hole 21b Outflow hole 22a valve seat 22b Annular surface 50 Small diameter section 50a Contact surface 50b Tip insertion part 51 Large diameter section 52 Pressure surface

Claims

1. A cylindrical valve housing; a shaft-shaped valve body that is axially movable between a closed position and an open position within the valve housing and is held coaxially with the valve housing; a biasing member that biases the valve body toward a closed position, A relief valve configured such that the valve element is switched to an open position by a fluid of a predetermined pressure or more that flows in through an inlet hole of the valve housing, thereby allowing the fluid to flow out through an outlet hole of the valve housing, The inlet hole is formed in a peripheral wall portion of the valve housing, The outlet hole is formed at one axial end of the valve housing, an annular valve seat is formed between the inlet hole and the outlet hole on the inner circumferential surface of the valve housing, the valve seat protruding radially inward and extending continuously in a circumferential direction; the valve seat is inclined radially inwardly with respect to the axis of the valve housing toward the outlet hole, a contact surface inclined with respect to the axis of the valve body so as to contact the valve seat when the valve body is in the closed position, the contact surface being formed in an annular shape extending continuously in a circumferential direction; an inclination angle of the valve seat relative to an axis of the valve housing and an inclination angle of the abutment surface relative to an axis of the valve body are different from each other, a small diameter portion located in a portion of the outer peripheral surface of the valve body closer to the other end in the axial direction than the contact surface, the small diameter portion being positioned so as to correspond to a downstream end opening of the inlet hole opening into the inner peripheral surface of the valve housing, a large diameter portion connected to the other end in the axial direction of the small diameter portion, and a pressure-receiving surface extending from an end of the small diameter portion on the large diameter portion side to an end of the large diameter portion on the small diameter portion side, the biasing member is provided to bias the valve body toward one end side relative to the other axial end side of the valve body, an annular surface is formed on an inner peripheral surface of the valve housing, the annular surface extending from an end of the valve seat on the outlet hole side toward a downstream side of the outlet hole along an axis of the valve housing and continuously extending in a circumferential direction, a tip insertion portion that is inserted into a space surrounded by the annular surface when the valve body is in a closed position, the tip insertion portion being provided at one axial end of the valve body; The outer circumferential surface of the tip insertion portion extends substantially parallel to the annular surface, A relief valve, characterized in that a gap of a predetermined size is formed between an outer circumferential surface of the tip insertion portion and the annular surface.

2. 2. The relief valve according to claim 1, A relief valve, wherein an inclination angle of the valve seat is set larger than an inclination angle of the contact surface.

3. 2. The relief valve according to claim 1, a relief valve characterized in that the gap is set to a size that applies a reverse force to the valve body when the valve body, which is in an open position, switches to a closed position and the tip insertion portion enters the space surrounded by the annular surface at a speed equal to or greater than a predetermined speed.

4. 2. The relief valve according to claim 1, A relief valve characterized in that the length of insertion of the tip insertion portion into the space surrounded by the annular surface is set to be equal to or greater than a predetermined length.

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