Valve body and casting method thereof

Abstract

To improve productivity of a valve body.SOLUTION: A second case 20 is manufactured by using a first core 51 for forming a first storage hole 21 to accommodate a spool of a counterbalance valve C and valve ports P1 and P2 of the counterbalance valve C and a second core 52 for forming first and second supply and discharge ports 23 and 24 that open on a plane 25 opposite a cylinder block 3 and are connected to valve ports P1 and P2 of the counterbalance valve C.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a valve body and a casting method thereof. [Background technology]

[0002] Patent Document 1 discloses a hydraulic motor that includes a motor housing that accommodates a cylinder block, and a suction port and a discharge port that are formed in a valve body that constitutes a part of the motor housing.

[0003] In the hydraulic motor described in Patent Document 1, a counterbalance valve is provided in a flow path leading to a suction port and a discharge port formed in a valve body. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 3-9080 Summary of the Invention [Problem to be solved by the invention]

[0005] In the hydraulic motor described in Patent Document 1, the inner discharge port and the inner suction port are each in communication with a valve port of a counterbalance valve.

[0006] An example of the casting method for the valve body described in Patent Document 1 will now be described with reference to Fig. 5. Fig. 5 is a cross-sectional view of the vicinity of an accommodation hole 121 that accommodates a spool of a counterbalance valve in the direction of the rotation axis of a hydraulic motor.

[0007] When manufacturing the valve body 120 shown in FIG. 5, first, a core 151 that forms the flow path 126 from the first supply / discharge port (suction port) 123 to the valve port P11 of the counterbalance valve, and a core 152 that forms the flow path 127 from the second supply / discharge port (discharge port) 124 to the valve port P12 of the counterbalance valve are manufactured, and these cores 151, 152 are further integrated with a core 153 that forms the accommodation hole 121 to manufacture a core 154.

[0008] Thereafter, the valve body 120 is cast using the core 154 and a core 155 that forms the flat surface 125 that faces the cylinder block (not shown).

[0009] As described above, when casting the valve body 120, it is necessary to manufacture the cores 151 and 152, and then manufacture the core 154 by integrating it with the core 153 that forms the receiving hole 121. For this reason, two work steps are required to manufacture the core 154, and it takes time and costs to manufacture the cores.

[0010] The present invention has been made in consideration of the above problems, and has an object to improve the productivity of valve bodies. [Means for solving the problem]

[0011] The present invention is a casting method for manufacturing a valve body of a hydraulic motor including a cylinder block that is rotationally driven by working fluid discharged from a pump, a housing that accommodates the cylinder block, a spool valve provided in a flow path that connects the pump and the cylinder block, and a valve body that accommodates the spool valve and closes an opening of the housing, and is characterized by including the steps of manufacturing a first core for forming a hole that accommodates a spool of the spool valve and a valve port of the spool valve, manufacturing a second core for forming an inlet / outlet port that opens on a plane opposite the cylinder block and is connected to the valve port of the spool valve, and manufacturing the valve body using the first core and the second core.

[0012] In this invention, the valve body is manufactured using a first core and a second core. The first core forms a first receiving hole that receives the spool of the spool valve and a valve port of the spool valve, while the second core opens to a plane facing the cylinder block and forms the first and second supply and discharge ports. By configuring the first and second cores in this way, the first core can be manufactured in a single work process. This reduces the time required to manufacture the cores, thereby improving the productivity of the valve body.

[0013] The present invention is also characterized in that the second core is formed integrally with the core that forms the flat surface facing the cylinder block.

[0014] In this invention, there is no need to provide a separate member for supporting the second core, so an increase in costs can be suppressed.

[0015] The present invention is also characterized in that the second core is disposed offset from the first core in the radial direction of the rotation shaft of the hydraulic motor.

[0016] In this invention, even if the second core is positioned offset from the first core in the radial direction of the rotation shaft of the hydraulic motor, no undercut occurs, and the valve body can be manufactured using the first core and the second core.

[0017] The present invention is also characterized in that a step is formed by the first core and the second core at a location where the first core and the second core come into contact with each other.

[0018] In this invention, a step is formed where the first core and the second core come into contact, so that it is possible to prevent an undercut from occurring where the first core and the second core come into contact.

[0019] The present invention is also characterized in that the spool valve is a counterbalance valve.

[0020] The present invention also provides a valve body for use in a hydraulic motor, which includes a cylinder block that is rotationally driven by working fluid discharged from a pump, a housing that accommodates the cylinder block, a spool valve provided in a flow path connecting the pump and the cylinder block, and a valve body that accommodates the spool valve and closes an opening in the housing, wherein the valve body has an accommodating hole that accommodates a spool of the spool valve, a valve port that opens into the accommodating hole, and an inlet / outlet port that opens on a flat surface facing the cylinder block and communicates with the valve port, and a step is formed in the flow path connecting the valve port and the inlet / outlet port.

[0021] In this invention, the valve body can be formed from a first core that forms an accommodation hole that accommodates the spool of the spool valve and a valve port of the spool valve, and a second core that opens to a plane facing the cylinder block and forms the first and second supply / discharge ports. [Effects of the Invention]

[0022] According to the present invention, the core is composed of a first core for forming the first accommodating hole that accommodates the spool of the spool valve and the valve port of the spool valve, and a second core that opens on a plane facing the cylinder block and forms the first and second supply / discharge ports, so the first core can be manufactured in a single process, which reduces the time required to manufacture the core and improves the productivity of the valve body. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a cross-sectional view of a hydraulic motor according to an embodiment of the present invention. [Figure 2] FIG. 2 is a plan view of a second case according to an embodiment of the present invention. [Figure 3] FIG. 3 is a cross-sectional view of the second case according to the embodiment of the present invention in a cast state taken along line III-III in FIG. [Figure 4]FIG. 4 is a cross-sectional view of the second case according to the embodiment of the present invention in a cast state taken along line IV-IV in FIG. [Figure 5] FIG. 5 is a cross-sectional view of a valve body according to a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0024] A hydraulic motor 100 as a hydraulic motor according to an embodiment of the present invention will now be described with reference to the drawings. FIG.

[0025] The hydraulic motor 100 is used in a travel drive device of a working machine that is driven by fluid pressure, such as a power shovel or a wheel loader. In this embodiment, an example will be described in which hydraulic oil is used as the working fluid, but other fluids such as hydraulic water may also be used as the working fluid.

[0026] As shown in FIG. 1 , the hydraulic motor 100 is, for example, a swash plate-type axial piston motor with a variable displacement. The hydraulic motor 100 is driven to rotate by receiving a supply of hydraulic oil discharged from a pump (not shown) serving as a hydraulic source. The hydraulic motor 100 is switched between forward and reverse rotation by a directional control valve (not shown) provided in a flow path connecting the pump and the hydraulic motor 100. When the hydraulic motor 100 rotates forward, the working machine moves forward, and when the hydraulic motor 100 rotates reverse, the working machine moves backward. The hydraulic motor 100 is not limited to being a swash plate-type axial piston motor with a variable displacement, and may also be a swash plate-type axial piston motor with a fixed displacement.

[0027] Next, a specific configuration of the hydraulic motor 100 will be described with reference to FIGS.

[0028] The hydraulic motor 100 includes an output shaft 2 connected to a load (not shown), a cylinder block 3 connected to the output shaft 2 and rotating integrally therewith, and a metal case 1 that houses the output shaft 2 and the cylinder block 3. The output shaft 2 is rotatably supported by the case 1 via bearings 17 and 18. Hereinafter, the direction in which the rotation axis O of the output shaft 2 extends will be referred to as the axial direction, and the direction perpendicular to the rotation axis O of the output shaft 2 will be referred to as the radial direction.

[0029] As shown in FIG. 1, the case 1 has a first case 10 as a housing that accommodates the cylinder block 3, and a second case 20 that is joined to the first case 10 via bolts.

[0030] 1, the first case 10 is formed in a cylindrical shape with a bottom. A bottom portion 11 of the first case 10 is provided with a through hole 12 through which the output shaft 2 is inserted.

[0031] 1, the second case 20 is attached to the first case 10 so as to cover the opening 13 of the first case 10. The second case 20 is formed with a first housing hole 21 that houses a spool C1 of a counterbalance valve C serving as a spool valve, and a second housing hole 22 that houses a spool S1 of a two-speed switching valve S. As described above, the second case 20 functions as a cover that covers the opening 13 of the first case 10, and also functions as a valve body for the counterbalance valve C and the two-speed switching valve S.

[0032] The second case 20 is also provided with a first supply / discharge port 23 and a second supply / discharge port 24 (see FIGS. 2 and 3) that communicate with valve ports P1, P2 (see FIG. 3), respectively, which open into the first housing hole 21 of the counterbalance valve C. Note that FIG. 2 is a plan view of the second case 20 as seen from a flat surface 25 side that faces the cylinder block 3.

[0033] As shown in FIG. 2, the first supply / discharge port 23 and the second supply / discharge port 24 are formed at positions facing each other across the central axis of the second case 20 (the rotation axis O of the output shaft 2) and open in an arc shape on a plane 25.

[0034] 1, a valve plate 8, which is in sliding contact with the base end surface of the cylinder block 3, is attached between the second case 20 and the cylinder block 3. The valve plate 8 has communication holes (not shown) which communicate with the valve ports P1 and P2 of the counterbalance valve C, respectively.

[0035] As shown in Fig. 1, a plurality of cylinders 4 are provided in a cylinder block 3 on a concentric circle centered on an output shaft 2 and parallel to the output shaft 2. A piston 5 forming a volume chamber 4a is inserted in each cylinder 4 so as to be able to reciprocate and slide freely.

[0036] A shoe 6 is connected to the tip of each piston 5 via a spherical seat 5a. The shoe 6 is in surface contact with a swash plate 7 provided inside a first case 10. In the hydraulic motor 100, as the cylinder block 3 rotates, each shoe 6 comes into sliding contact with the swash plate 7, causing each piston 5 to reciprocate with a stroke amount corresponding to the tilt angle of the swash plate 7.

[0037] The hydraulic motor 100 further includes a friction braking device 40 that prevents the cylinder block 3 from rotating when it is stopped, and a tilt angle control piston 9 that changes the tilt angle of the swash plate 7.

[0038] 1, the brake device 40 includes a disc plate 41 that rotates together with the cylinder block 3, a brake piston 42 that presses the disc plate 41 against the first case 10, and a spring 43 that urges the brake piston 42 in a direction in which the disc plate 41 presses against the first case 10. In this embodiment, the hydraulic motor 100 is used in a traveling device, and therefore the brake device 40 that brakes the hydraulic motor 100 functions as a parking brake device.

[0039] 1, the brake piston 42 has a main body 42a and a tip end 42b that is provided on the tip side and has an outer diameter smaller than that of the main body 42a. A brake release chamber 44 is defined by the main body 42a and tip end 42b of the brake piston 42 and the inner circumferential surface of the first case 10.

[0040] In the hydraulic motor 100, when the directional control valve is switched to the forward or reverse position, hydraulic pressure is supplied to the brake release chamber 44. As a result, the brake piston 42 moves against the biasing force of the spring 43, thereby releasing the brake and allowing the output shaft 2 and cylinder block 3 to rotate. Note that the brake device 40 may also include a friction plate that is non-rotatable relative to the first case 10 and abuts against the disc plate 41. In this case, the brake piston 42 presses the disc plate 41 against the friction plate, generating a braking force on the cylinder block 3.

[0041] The tilt angle control piston 9 is slidably disposed in a hole 11a formed in the bottom 11 of the first case 10. When hydraulic pressure is supplied to a pressure chamber 11b defined by the hole 11a and the tilt angle control piston 9, the tilt angle control piston 9 pushes up the swash plate 7, reducing the tilt angle of the swash plate 7. This reduces the stroke of the piston 5, thereby increasing the rotation speed of the output shaft 2. The supply of hydraulic pressure to and from the pressure chamber 11b is controlled, i.e., the tilt angle of the swash plate 7 is controlled by switching the two-speed selector valve S.

[0042] In the hydraulic motor 100 configured in this manner, each piston 5 protrudes from the cylinder 4 due to the hydraulic pressure (hydraulic pressure) that is guided from the pump to each volume chamber 4a through the directional control valve and the counterbalance valve C. The protruding piston 5 then pushes the swash plate 7 via the shoe 6, causing the cylinder block 3 to rotate, and the rotation of the cylinder block 3 is transmitted to the load via the output shaft 2.

[0043] Next, a method for manufacturing the second case 20 will be described with reference to Figures 3 and 4. Figure 3 is a cross-sectional view of the second case 20 in a cast state taken along line III-III in Figure 1. Figure 4 is a cross-sectional view of the second case 20 in a cast state taken along line IV-IV in Figure 1.

[0044] Second case 20 is formed by casting, for example, from an aluminum alloy or an iron-based alloy. When forming second case 20 by casting, first core 51 for forming first housing hole 21 and second core 52 for forming first supply / discharge port 23 and second supply / discharge port 24 are produced.

[0045] Specifically, the first core 51 is a core for integrally forming the first accommodation hole 21 that accommodates the spool C1 of the counterbalance valve C, the flow path 26 that connects the valve port P1 of the counterbalance valve C to the first supply / discharge port 23, and the flow path 27 that connects the valve port P2 of the counterbalance valve C to the second supply / discharge port 24. The second core 52 is a core for forming the first and second supply / discharge ports 23, 24, and is also a core for forming the flat surface 25.

[0046] As described above, when casting the valve body 120 of the comparative example shown in Fig. 5, first the cores 151, 152 are produced, and then these cores 151, 152 are further integrated with the core 153 that forms the receiving hole 121 using a mold, or by baking and hardening them to produce the core 154. As described above, when casting the valve body 120 of the comparative example shown in Fig. 5, two work steps are required to produce the core 154, which requires time and cost to produce the core 154.

[0047] Therefore, in the comparative example shown in FIG. 5 , in order to shorten the production time of the core for casting the valve body 120, it is conceivable to form the core 155 and the cores 151, 152 as a single unit. However, as shown in FIG. 5 , the width of the first and second supply / discharge ports 123, 124 is narrower than the width of the valve ports P11, P12, and the first and second supply / discharge ports 123, 124 are radially outward relative to the valve ports P11, P12, that is, radially offset relative to the rotation axis O of the hydraulic motor 100. This results in the presence of a recessed portion, as shown as region A in FIG. 5 . If the core 155 and the cores 151, 152 are integrally formed, and an attempt is made to manufacture this integrated core using a mold divided vertically as shown in FIG. 5 , the recessed portion (region A) becomes a so-called undercut, and the integrated core cannot be pulled out from the lower mold.

[0048] For this reason, it is conceivable to manufacture the valve body 120 using a mold divided in the depth direction as shown in Fig. 5. However, because the first and second supply / discharge ports 123, 124 are formed in an arc shape like the first and second supply / discharge ports 23, 24 of this embodiment (see Figs. 2 and 3), the recessed portion (area A) also becomes a so-called undercut in this case, and therefore, even if a mold divided in the vertical direction as shown in Fig. 3 is used, the valve body 120 cannot be pulled out from the mold.

[0049] Therefore, it is difficult to integrate core 151 for integrally forming first supply / discharge port 123, flow path 126, and valve port P11, as in the comparative example shown in Figure 5, or core 152 for integrally forming second supply / discharge port 124, flow path 127, and flow path 127 leading to valve port P12, with other cores or molds.

[0050] Therefore, in this embodiment, instead of using core 151 for integrally forming first supply / discharge port 123, flow path 126, and valve port P11, or core 152 for integrally forming second supply / discharge port 124, flow path 127, and flow path 127 leading to valve port P12, as in the comparative example, second case 20 is manufactured by dividing the core at the connection portion between first and second supply / discharge ports 23, 24 and flow paths 26, 27, as shown in Fig. 4. Specifically, second case 20 is manufactured using first core 51 for integrally forming first housing hole 21, valve ports P1, P2, and flow paths 26, 27, and second core 52 for forming first and second supply / discharge ports 23, 24 and flat surface 25.

[0051] By configuring the core to be divided in this way, there are no undercuts, and therefore the first core 51 and the second core 52 can be manufactured easily.

[0052] Moreover, in the comparative example shown in FIG. 5, first, cores 151 and 152 are produced, and then core 151 and 152 are integrated with core 153 that forms accommodation hole 121 to produce core 154. Therefore, in addition to a mold for producing core 154, another mold for producing cores 151 and 152 is required, and the work process for producing core 154 becomes two-stage.

[0053] In contrast, in this embodiment, the core for integrally forming the first housing hole 21, the valve ports P1, P2, and the flow paths 26, 27 is configured as a single first core 51. The first core 51 of this embodiment can be manufactured in a single work process, so the time required to manufacture the core can be shortened compared to the comparative example shown in FIG. 5. Furthermore, by adopting the configuration of the first core 51, it is possible to eliminate the need for a mold for making a core in a stage prior to making the final core, as in the comparative example shown in FIG. 5. This allows for a reduction in the number of molds.

[0054] Furthermore, even if the first and second supply / discharge ports 23, 24 are offset radially from the rotation axis O of the hydraulic motor 100 relative to the valve ports P1, P2, undercuts do not occur by using the first core 51 and the second core 52.

[0055] 4, in the manufacturing method of this embodiment, where first core 51 and second core 52 abut, that is, on flow path 26 connecting valve port P1 and first supply / discharge port 23, and on flow path 27 connecting valve port P2 and second supply / discharge port 24, steps 28a, 28b, 29a, and 29b are formed by first core 51 and second core 52. This makes it possible to prevent undercuts from occurring where first core 51 and second core 52 abut.

[0056] Although not described in the above embodiment, when manufacturing the second case 20, a core for forming the second accommodating hole 22 for accommodating the spool S1 of the two-speed switching valve S is prepared separately. In this case, the core for forming the second accommodating hole 22 may be integral with the first core 51 or may be separate from it.

[0057] Furthermore, in the hydraulic motor 100 of the above embodiment, the two-speed switching valve S is provided in the second case 20, but the two-speed switching valve S does not necessarily have to be provided.

[0058] Furthermore, the second core 52 has been described as an example in which the core that forms the first and second supply / discharge ports 23, 24 and the core that forms the flat surface 25 are integrated together. However, if there is another core that can be formed at the same time as the core that forms the first and second supply / discharge ports 23, 24, then the core formed by integrating these may also be used as the second core 52.

[0059] The configuration, operation, and effects of the embodiment of the present invention configured as above will be described below.

[0060] The hydraulic motor 100 (hydraulic motor) comprises a cylinder block 3 that is rotationally driven by the working fluid discharged from the pump, a first case 10 (housing) that accommodates the cylinder block 3, a counterbalance valve C (spool valve) that is provided in a flow path that connects the pump and the cylinder block 3, and a second case 20 (valve body) that accommodates the counterbalance valve C (spool valve) and closes an opening 13 in the first case 10 (housing). The casting method for manufacturing the second case 20 (valve body) includes the steps of manufacturing a first core 51 for forming the first accommodating hole 21 that accommodates the spool C1 of the counterbalance valve C (spool valve) and the valve ports P1, P2 of the counterbalance valve C (spool valve), a step of manufacturing a second core 52 for forming the first and second supply and discharge ports 23, 24 that open to a flat surface 25 facing the cylinder block 3 and are connected to the valve ports P1, P2 of the counterbalance valve C (spool valve), and a step of manufacturing the second case 20 (valve body) using the first core 51 and the second core 52.

[0061] In this configuration, the second case 20 (valve body) is manufactured using a first core 51 and a second core 52 that are configured separately. The first core 51 forms the first housing hole 21 that houses the spool C1 of the counterbalance valve C (spool valve) and the valve ports P1 and P2 of the counterbalance valve C (spool valve), while the second core 52 forms the first and second supply and discharge ports 23 and 24 that open to a flat surface 25 facing the cylinder block 3. By configuring the first core 51 and the second core 52 in this way, the first core 51 can be manufactured in a single work process. This shortens the time and cost required to manufacture the cores, thereby improving the productivity of the second case 20 (valve body).

[0062] Furthermore, for example, if the size (characteristics) of the pump or counterbalance valve C (spool valve) is changed, the positions of the first and second supply / discharge ports 23, 24 and the valve ports P1, P2 must be changed. Changing the positions of the first and second supply / discharge ports 23, 24 and the valve ports P1, P2 changes their relative positions. Conventionally, when a core is manufactured in a two-stage process, the shapes of the molds for each stage, i.e., the two molds, must be changed. In contrast, with this configuration, the steps 28a, 28b, 29a, 29b formed in the flow paths 26, 27 can absorb changes in the positions of the first and second supply / discharge ports 23, 24 and the valve ports P1, P2. This allows changes to be made by changing the shape of either the first core 51 or the second core 52. In other words, with this configuration, if the size (characteristics) of the pump or the counterbalance valve C (spool valve) is changed, the changes can be made by changing the shape of only one of the molds used to mold the first core 51 or the second core 52.

[0063] Furthermore, by adopting the configuration of the first core 51 and the second core 52, it is possible to eliminate the need for a mold for making a core in a stage prior to making the final core, as in the comparative example shown in Fig. 5. This allows the number of molds to be reduced.

[0064] In the casting method for the second case 20 (valve body), the second core 52 is formed integrally with the core that forms the flat surface 25 that faces the cylinder block 3.

[0065] In this configuration, there is no need to provide a separate member for supporting the second core 52, which can prevent costs from increasing.

[0066] In the casting method for the second case 20 (valve body), the second core 52 is disposed offset from the first core 51 in the radial direction with respect to the rotation axis O of the hydraulic motor 100 (hydraulic motor).

[0067] In this configuration, even if the second core 52 is positioned radially offset relative to the first core 51 with respect to the rotation axis O of the hydraulic motor 100 (hydraulic motor), no undercut occurs, so the second case 20 (valve body) can be manufactured using the first core 51 and the second core 52.

[0068] In the casting method for the second case 20 (valve body), where the first core 51 and the second core 52 abut against each other, the first core 51 and the second core 52 form steps 28a, 28b, 29a, and 29b.

[0069] In this configuration, step portions 28a, 28b, 29a, 29b are formed at the points where the first core 51 and the second core 52 abut, thereby preventing undercuts from occurring at the points where the first core 51 and the second core 52 abut.

[0070] In the casting method for the second case 20 (valve body), the spool valve is a counterbalance valve C.

[0071] The hydraulic motor 100 (hydraulic motor) comprises a cylinder block 3 that is rotationally driven by the working fluid discharged from the pump, a first case 10 (housing) that accommodates the cylinder block 3, a counterbalance valve C (spool valve) that is provided in a flow path that connects the pump and the cylinder block 3, and a second case 20 (valve body) that accommodates the counterbalance valve C (spool valve) and closes an opening 13 in the first case 10 (housing). The second case 20 (valve body) has a housing hole (first housing hole 21) that houses the spool C1 of the counterbalance valve C (spool valve), valve ports P1 and P2 that open into the housing hole (first housing hole 21), and supply and discharge ports (first supply and discharge port 23, second supply and discharge port 24) that open into a flat surface 25 facing the cylinder block 3 and communicate with the valve ports P1 and P2, and step portions 28a, 28b, 29a, 29b are formed in flow paths 26 and 27 that connect the valve ports P1 and P2 to the supply and discharge ports (first supply and discharge port 23, second supply and discharge port 24).

[0072] In this configuration, the second case 20 (valve body) can be formed by a first core 51 that forms a housing hole (first housing hole 21) that houses the spool C1 of the counterbalance valve C (spool valve) and the valve ports P1, P2 of the counterbalance valve C (spool valve), and a second core 52 that opens to a flat surface 25 facing the cylinder block 3 and forms the first and second supply and discharge ports 23, 24.

[0073] Furthermore, for example, if the size (characteristics) of the pump or counterbalance valve C (spool valve) is changed, the positions of the first and second supply / discharge ports 23, 24 and the valve ports P1, P2 must be changed. Changing the positions of the first and second supply / discharge ports 23, 24 and the valve ports P1, P2 changes their relative positions. Conventionally, when a core is manufactured in a two-stage process, the shapes of the molds for each stage, i.e., the two molds, must be changed. In contrast, with this configuration, the steps 28a, 28b, 29a, 29b formed in the flow paths 26, 27 can absorb changes in the positions of the first and second supply / discharge ports 23, 24 and the valve ports P1, P2. This allows changes to be made by changing the shape of either the first core 51 or the second core 52. In other words, with this configuration, if the size (characteristics) of the pump or the counterbalance valve C (spool valve) is changed, the changes can be made by changing the shape of only one of the molds used to mold the first core 51 or the second core 52.

[0074] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments.

[0075] In the above embodiment, the hydraulic motor 100 is used for traveling, but the hydraulic motor 100 may be a swing motor, a motor for driving a winch, or the like.

[0076] Furthermore, in the above embodiment, the counterbalance valve C is used as an example of the spool valve, but the spool valve is not limited to this, and may be, for example, a low pressure selection valve.

[0077] The first and second supply / discharge ports 23, 24 may be offset radially inward relative to the valve ports P1, P2. In this case, too, by using the first core 51 and the second core 52, undercuts do not occur. [Explanation of symbols]

[0078] 100 hydraulic motor (fluid pressure motor), 1 case, 2 output shaft, 3 cylinder block, 4 cylinder, 5 piston, 7 swash plate, 10 first case (housing), 11 bottom, 20 second case (valve body), 21 first housing hole, 22 second housing hole, 23 first supply / discharge port, 24 second supply / discharge port, 25 flat surface, 26 flow path, 27 flow path, 51 first core, 52 second core

Claims

1. a cylinder block that is rotationally driven by the working fluid discharged from the pump; a housing that accommodates the cylinder block; a spool valve provided in a flow path connecting the pump and the cylinder block; a valve body that houses the spool valve and closes an opening of the housing, manufacturing a first core for forming a hole for receiving a spool of the spool valve and a valve port of the spool valve; a step of manufacturing a second core for forming an inlet / outlet port that opens on a plane facing the cylinder block and is connected to the valve port of the spool valve; and manufacturing the valve body using the first core and the second core.

2. 2. The method for casting a valve body according to claim 1, a second core formed integrally with a core forming the flat surface facing the cylinder block;

3. 3. The method for casting a valve body according to claim 1 or 2, a valve body casting method, characterized in that the second core is disposed offset from the first core in a radial direction of the rotation shaft of the hydraulic motor.

4. 4. A method for casting a valve body according to claim 1, further comprising the steps of: a step is formed by the first core and the second core at a location where the first core and the second core come into contact with each other.

5. 5. A method for casting a valve body according to claim 1, further comprising the steps of:

2. The method for casting a valve body, wherein the spool valve is a counterbalance valve.

6. a cylinder block that is rotationally driven by the working fluid discharged from the pump; a housing that accommodates the cylinder block; a spool valve provided in a flow path connecting the pump and the cylinder block; a valve body for accommodating the spool valve and closing an opening of the housing, an accommodation hole for accommodating a spool of the spool valve; a valve port that opens into the receiving hole; an intake / exhaust port that opens on a plane facing the cylinder block and communicates with the valve port; A valve body characterized in that a step portion is formed in a flow path connecting the valve port and the supply / discharge port.

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