Piston pump

Abstract

A piston pump according to an embodiment of the present invention comprises, as one example: a motor that has a motor shaft extending in a first axial direction along the central axis, and is disposed such that the first axial direction intersects with the vertical direction; and a housing that has a first inner surface defining a cam chamber and a second inner surface defining a liquid storage chamber linked with the lower end of the cam chamber. The first inner surface has an inner circumferential surface extending around the central axis. The liquid storage chamber has a first room that is open to the lower end of the inner circumferential surface, and a second room that is open to the lower end of the inner circumferential surface and is linked with the end of the first room in the first axial direction. The first room extends further downward as compared to the second room from the lower end of the inner circumferential surface, and the maximum length around the central axis is larger than that of the second room.

Description

Piston pump

[0001] An embodiment of the present invention relates to a piston pump.

[0002] Conventionally, a piston pump is known that includes a housing provided with a cam chamber and a piston chamber, a cam disposed in the cam chamber, a piston disposed in the piston chamber, and a motor that drives the cam. When the motor rotates the cam, the cam pushes the piston, and the piston reciprocates in the piston chamber. As a result, the piston pump sucks liquid into the piston chamber and pumps the liquid out of the piston chamber.

[0003] Liquid may leak from the piston chamber into the cam chamber. For this reason, a liquid reservoir chamber communicating with the cam chamber is provided in the housing. The liquid reservoir chamber extends downward from the cam chamber and stores the liquid that has leaked into the cam chamber (Patent Document 1).

[0004] Japanese Patent No. 4830338

[0005] However, in the conventional configuration, it may be difficult to form a large-capacity liquid reservoir chamber in the housing due to various manufacturing constraints.

[0006] Therefore, the present invention has been made in view of the above, and provides a piston pump capable of easily forming a large-capacity liquid reservoir chamber.

[0007] A piston pump according to an embodiment of the present invention includes, as an example, a motor having a motor body and a motor shaft extending from the motor body in a first axial direction along a central axis, the first axial direction being arranged to intersect with the vertical direction and configured to rotate the motor shaft around the central axis; a housing having an outer surface, a first inner surface defining a cam chamber recessed from the outer surface in the first axial direction, and a second inner surface recessed from the outer surface in the first axial direction and defining a liquid reservoir chamber communicating with the lower end of the cam chamber around the central axis, with a piston chamber extending from the cam chamber in a direction intersecting the central axis, and the cam chamber being covered by the motor body; and the motor being eccentrically positioned with respect to the central axis. The device comprises a cam located in the cam chamber and provided on the drive shaft, and a piston located in the piston chamber and configured to be pressed by the cam, which rotates relative to the housing around a central axis, wherein the first inner surface has an inner circumferential surface extending around the central axis, and the liquid reservoir chamber has a first chamber opening at the lower end of the outer surface and the inner circumferential surface around the central axis, and a second chamber opening at the lower end of the inner circumferential surface around the central axis and communicating with the end of the first chamber in the first axial direction, wherein the first chamber extends longer downward from the lower end of the inner circumferential surface around the central axis than the second chamber, and its maximum length around the central axis is greater than that of the second chamber. For example, the second chamber, located at the back of the liquid reservoir chamber, has a smaller maximum length around the central axis than the first chamber. For this reason, the first and second chambers can be formed by moving a common end mill of a general shape in a direction along the central axis and in a vertical direction. For example, by inserting the end mill deeply into the housing in the first axial direction such that the distance between the central axis and the lower end of the end mill is shortened, a second chamber with a small length around the central axis can be formed. On the other hand, by inserting the end mill shallowly into the housing in the first axial direction such that the distance between the central axis and the lower end of the end mill is longer, a first chamber with a large length around the central axis can be formed. In this way, a common end mill can form a liquid reservoir chamber including the first and second chambers with simple and short movements.Therefore, a piston pump can easily form a large-capacity liquid reservoir.

[0008] Figure 1 is a cross-sectional view showing a part of a brake system according to one embodiment. Figure 2 is a perspective view showing the housing block of the above embodiment. Figure 3 is a cross-sectional view showing the housing block of the above embodiment along the line F3-F3 in Figure 1. Figure 4 is a cross-sectional view showing a part of the housing block of the above embodiment. Figure 5 is a schematic cross-sectional view showing the housing block and end mill of the above embodiment. Figure 6 is a schematic front view showing the housing block in which the rear chamber of the above embodiment is formed. Figure 7 is a schematic front view showing the housing block in which the front chamber of the above embodiment is formed.

[0009] An embodiment will be described below with reference to Figures 1 to 7. Note that in this specification, the components of an embodiment and their descriptions may be described using multiple expressions. The components and their descriptions are examples and are not limited by the expressions used herein. Components may also be identified by names different from those used herein. Furthermore, components may also be described using expressions different from those used herein.

[0010] In the following explanation, “suppress” is defined, for example, to prevent the occurrence of an event, action, or effect, or to reduce the degree of an event, action, or effect. Also, in the following explanation, “restrict” is defined, for example, to prevent movement or rotation, or to permit movement or rotation within a predetermined range while preventing movement or rotation beyond that predetermined range.

[0011] Figure 1 is a cross-sectional view showing a part of the brake system 10 according to this embodiment. The brake system 10 is mounted on a vehicle 1 such as a four-wheeled automobile. Note that the brake system 10 is not limited to this example. The brake system 10 brakes the vehicle 1.

[0012] The brake system 10 includes a wheel cylinder 11 and a brake fluid pressure control device 12. The wheel cylinder 11 generates braking force by the pressure of the brake fluid, which is the pressure medium. The brake fluid pressure control device 12 is connected to the wheel cylinder 11 and controls the pressure of the brake fluid in the wheel cylinder 11.

[0013] As shown in each drawing, the X-axis, Y-axis, and Z-axis are defined herein for convenience. The X-axis, Y-axis, and Z-axis are orthogonal to each other. The X-axis is provided along the width of the brake fluid pressure control device 12. The Y-axis is provided along the depth of the brake fluid pressure control device 12. The Z-axis is provided along the height of the brake fluid pressure control device 12.

[0014] Furthermore, the X, Y, and Z directions are defined herein. The X direction is the direction along the X axis and includes the +X direction indicated by the X-axis arrow and the -X direction which is the opposite direction of the X-axis arrow. The Y direction is the direction along the Y axis and includes the +Y direction indicated by the Y-axis arrow and the -Y direction which is the opposite direction of the Y-axis arrow. The Z direction is the direction along the Z axis and includes the +Z direction indicated by the Z-axis arrow and the -Z direction which is the opposite direction of the Z-axis arrow.

[0015] In this embodiment, when the vehicle 1 is on a horizontal surface, the +Z direction is substantially vertically upward, and the -Z direction is substantially vertically downward. That is, the -Z direction is an example of a downward direction. Note that the +Z and -Z directions may be deviated from the vertical direction.

[0016] The brake fluid pressure control device 12 includes a reservoir 21, a piston pump 22, and an electronic control unit (ECU) 23. The brake fluid pressure control device 12 further includes various components such as solenoid valves. Note that the piston pump 22 is not limited to the brake fluid pressure control device 12 and may be mounted in other devices.

[0017] The reservoir 21 temporarily stores brake fluid. The reservoir 21 is, for example, open to the atmosphere to maintain the pressure of the stored brake fluid at atmospheric pressure. Note that the reservoir 21 is not limited to this example.

[0018] The piston pump 22 includes a motor 31, a housing 32, a bearing 33, a cam 34, and two pistons 35. The piston pump 22 may have other components, and the bearing 33 may be omitted. Furthermore, the number of pistons 35 is not limited to two.

[0019] The motor 31 has a motor body 41 and a motor shaft 42. The motor body 41 has a motor case 45. Furthermore, the motor body 41 has a stator and a rotor housed in the motor case 45. The motor shaft 42 extends from the motor body 41 along the central axis Ax1 in the +Y direction.

[0020] The central axis Ax1 is essentially the central axis of the motor shaft 42 and extends in the Y direction. Therefore, the +Y direction is one direction along the central axis Ax1 and is an example of a first axial direction. The -Y direction is the opposite direction to the +Y direction and is an example of a second axial direction.

[0021] The motor 31 extends in a direction that intersects the vertical direction with its central axis Ax1, and is positioned such that the +Y and -Y directions intersect the vertical direction. In this embodiment, the +Y and -Y directions are substantially perpendicular to the vertical direction. That is, the +Y and -Y directions are substantially horizontal. Note that the +Y and -Y directions may also be oblique to the horizontal direction.

[0022] For convenience, the direction perpendicular to the central axis Ax1 is defined as the radial direction, and the direction around the central axis Ax1 is defined as the circumferential direction. The radial direction includes multiple directions perpendicular to the central axis Ax1. For example, the radial direction includes the +Z direction (up) and the -Z direction (down).

[0023] The motor shaft 42 has a base shaft 47 and an eccentric shaft 48. The base shaft 47 is formed in a substantially cylindrical shape extending along the central axis Ax1 and is coupled to the rotor of the motor body 41. The eccentric shaft 48 protrudes in the +Y direction from the end of the base shaft 47 in the +Y direction.

[0024] The eccentric shaft 48 is formed in a substantially cylindrical shape extending along the eccentric axis Ax2. The eccentric axis Ax2 is the central axis of the eccentric shaft 48 and extends in the Y direction. The eccentric axis Ax2 is radially spaced away from the central axis Ax1. That is, the eccentric axis Ax2 extends parallel to the central axis Ax1.

[0025] The housing 32 forms multiple passages through which brake fluid flows. The housing 32 has a housing block 51 and two plugs 52. Note that the housing 32 is not limited to this example. Figure 1 shows one of the two plugs 52.

[0026] Figure 2 is a perspective view showing the housing block 51 of this embodiment. The housing block 51 is made of, for example, metal and is formed in a substantially rectangular parallelepiped shape. Note that the housing block 51 is not limited to this example.

[0027] Figure 3 is a cross-sectional view of the housing block 51 of this embodiment, taken along the line F3-F3 in Figure 1. The housing block 51 has a front surface 51a and a rear surface 51b as shown in Figure 3, and a right surface 51c as shown in Figure 2. The front surface 51a is an example of an outer surface.

[0028] As shown in Figure 2, the front surface 51a is a roughly square plane. The front surface 51a faces the -Y direction. As shown in Figure 3, the back surface 51b is located on the opposite side of the front surface 51a and faces the roughly +Y direction. As shown in Figure 2, the right surface 51c is a roughly rectangular plane extending in the Z direction. The right surface 51c is located at the end of the housing block 51 in the -X direction and faces the -X direction. Note that the front surface 51a, back surface 51b, and right surface 51c are not limited to this example.

[0029] As shown in Figure 1, the housing block 51 is provided with a cam chamber 61, two piston chambers 62, two intake passages 63, and two discharge passages 64. Figure 1 shows one of the two intake passages 63 and one of the two discharge passages 64.

[0030] The cam chamber 61 is recessed in the +Y direction along the central axis Ax1 from the front surface 51a. The cam chamber 61 in this embodiment includes a plurality of substantially cylindrical spaces. The diameter of these plurality of cylindrical spaces decreases in stages toward the +Y direction.

[0031] The housing block 51 further has an inner surface 65 that defines the cam chamber 61. The inner surface 65 is an example of a first inner surface. As shown in Figure 2, the inner surface 65 has an end face 65a, a first inner circumferential surface 65b, a stepped surface 65c, and a second inner circumferential surface 65d. The first inner circumferential surface 65b is an example of an inner circumferential surface.

[0032] The end face 65a is a plane provided at the end of the cam chamber 61 in the +Y direction. The end face 65a is formed in a substantially circular shape perpendicular to the central axis Ax1 and faces in the -Y direction.

[0033] The first inner circumferential surface 65b extends from the end face 65a toward the front face 51a. The first inner circumferential surface 65b is a substantially cylindrical curved surface extending around the central axis Ax1. Note that the central axis of the first inner circumferential surface 65b may be different from the central axis Ax1. The end of the first inner circumferential surface 65b in the +Y direction is connected to the end face 65a, for example, via a substantially conical slope that tapers in the +Y direction.

[0034] The stepped surface 65c is a substantially annular plane or curved surface extending in the circumferential direction. The stepped surface 65c is oriented approximately in the -Y direction. The end of the first inner circumferential surface 65b in the -Y direction is connected to the inner edge of the stepped surface 65c via, for example, a substantially conical slope that tapers in the +Y direction.

[0035] The second inner circumferential surface 65d extends from the outer edge of the stepped surface 65c toward the front surface 51a. The second inner circumferential surface 65d is a substantially cylindrical curved surface extending around the central axis Ax1. The end of the second inner circumferential surface 65d in the +Y direction is connected to the outer edge of the stepped surface 65c, for example, via a substantially conical slope that tapers in the +Y direction.

[0036] As shown in Figure 1, the two piston chambers 62 each open to the first inner circumferential surface 65b of the cam chamber 61. One of the two piston chambers 62 extends from the cam chamber 61 in approximately the -X direction. The other of the two piston chambers 62 extends from the cam chamber 61 in approximately the +X direction. In other words, the two piston chambers 62 each extend from the cam chamber 61 in a direction intersecting the central axis Ax1.

[0037] A hole forming one piston chamber 62 communicates with the outside of the housing block 51. The plug 52 is fitted into this hole, for example by crimping, thereby closing and sealing the end of the piston chamber 62.

[0038] One intake passage 63 and one discharge passage 64 communicate with one piston chamber 62. The end of the intake passage 63 communicating with the piston chamber 62 is closer to the cam chamber 61 than the end of the discharge passage 64 communicating with the piston chamber 62. The reservoir 21 is connected to the piston chamber 62 through the intake passage 63. The wheel cylinder 11 is connected to the piston chamber 62 through the discharge passage 64. Note that the discharge passage 64 is not limited to the wheel cylinder 11 and may communicate with other devices.

[0039] As shown in Figure 2, a liquid reservoir chamber 70 is further provided in the housing block 51. The liquid reservoir chamber 70 is recessed in the +Y direction from the front surface 51a of the housing block 51 and communicates with the lower end of the cam chamber 61 around the central axis Ax1. The lower end of the cam chamber 61 around the central axis Ax1 includes not only the lowest part of the cam chamber 61, but also multiple parts that are the lowest at each position of the cam chamber 61 in the Y direction.

[0040] The liquid reservoir chamber 70 is spaced apart from the two piston chambers 62. The liquid reservoir chamber 70 is located below the two piston chambers 62. However, the liquid reservoir chamber 70 may be adjacent to the piston chambers 62.

[0041] In this embodiment, the liquid reservoir chamber 70 extends from the cam chamber 61 in the -Z direction (downward). The liquid reservoir chamber 70 has a front chamber 71 and a rear chamber 72. The front chamber 71 is an example of a first chamber. The rear chamber 72 is an example of a second chamber.

[0042] The front chamber 71 opens to the front surface 51a of the housing block 51, the lower end of the first inner circumferential surface 65b around the central axis Ax1, the stepped surface 65c, and the lower end of the second inner circumferential surface 65d around the central axis Ax1. In this embodiment, the front chamber 71 is recessed in the -Z direction (downward) from the lower end of the first inner circumferential surface 65b around the central axis Ax1 and the lower end of the second inner circumferential surface 65d around the central axis Ax1.

[0043] The back chamber 72 opens at the lower end of the first inner peripheral surface 65b around the central axis Ax1 and communicates with the end of the front chamber 71 in the +Y direction. The back chamber 72 is spaced apart from the end surface 65a of the inner surface 65 in the -Y direction. Note that the back chamber 72 may be adjacent to the end surface 65a.

[0044] The front chamber 71 extends longer downward than the back chamber 72 from the lower end of the first inner peripheral surface 65b around the central axis Ax1. That is, the length of the liquid reservoir chamber 70 in the vertical direction increases stepwise in the -Y direction.

[0045] The housing block 51 further has an inner surface 75 that defines the liquid reservoir chamber 70. The inner surface 75 is an example of a second inner surface. The inner surface 75 has a front concave surface 76 that defines the front chamber 71 and a back concave surface 77 that defines the back chamber 72. The front concave surface 76 is an example of a first concave surface. The back concave surface 77 is an example of a second concave surface.

[0046] The front concave surface 76 has an end surface 76a, a lower inclined surface 76b, two side inclined surfaces 76c, and two side surfaces 76d. FIG. 2 shows one of the two side inclined surfaces 76c and one of the two side surfaces 76d. The end surface 76a is an example of a first end surface. The lower inclined surface 76b is an example of a first inclined surface.

[0047] FIG. 4 is a cross-sectional view showing a part of the housing block 51 of the present embodiment. As shown in FIG. 4, the end surface 76a is a flat surface provided at the end of the front chamber 71 in the +Y direction. The end surface 76a extends in the Z direction and faces the -Y direction. Note that the end surface 76a may face in other directions.

[0048] The lower inclined surface 76b extends from the end surface 76a toward the front surface 51a. The lower inclined surface 76b is a semi-conical (truncated cone-shaped) curved surface that tapers in the +Y direction. Therefore, the lower inclined surface 76b is inclined with respect to the end surface 76a. The end of the lower inclined surface 76b in the +Y direction is connected to the end of the end surface 76a in the -Z direction.

[0049] As shown in Figure 2, the end face 76a has an arc-shaped edge 76e. The edge 76e is an example of a first edge. The edge 76e is the boundary between the end face 76a and the lower slope 76b. That is, the end of the lower slope 76b in the +Y direction is connected to the edge 76e of the end face 76a.

[0050] The two lateral slopes 76c extend from the end face 76a toward the front face 51a. The ends of the two lateral slopes 76c in the +Y direction are connected to both ends of the end face 76a in the X direction. The ends of the two lateral slopes 76c in the -Z direction are connected to both ends of the semiconical lower slope 76b.

[0051] Each of the two sides 76d extends toward the front surface 51a from one of the two lateral slopes 76c. The ends of each of the two sides 76d in the +Y direction are connected to the end of one of the lateral slopes 76c in the -Y direction. The two sides 76d extend parallel to each other in the Y direction and face each other.

[0052] The recessed surface 77 has an end face 77a, an inclined surface 77b, and a bottom surface 77c. The end face 77a is an example of a second end face. The inclined surface 77b is an example of an inclined surface and a second inclined surface. The end face 77a is a plane provided at the end of the recessed chamber 72 in the +Y direction. The end face 77a faces the -Y direction. The end face 77a may face other directions.

[0053] The inclined surface 77b is located at the lower end of the inner chamber 72 around the central axis Ax1, and extends from the end face 77a toward the end face 76a of the concave front surface 76. The inclined surface 77b is a semi-conical (semi-frustum-shaped) curved surface that tapers in the +Y direction. That is, the inclined surface 77b extends diagonally downward toward the front chamber 71. For this reason, the inclined surface 77b is inclined with respect to the end face 77a.

[0054] The end face 77a has an arc-shaped edge 77e. The edge 77e is an example of a second edge. The edge 77e is the boundary between the end face 77a and the inclined surface 77b. That is, the end of the inclined surface 77b in the +Y direction is connected to the edge 77e of the end face 77a.

[0055] The base surface 77c extends in the -Y direction from the end of the inclined surface 77b in the -Y direction. The base surface 77c is a semi-cylindrical curved surface extending in the Y direction. The end of the base surface 77c in the -Y direction is connected, for example, to the end surface 76a of the concave front surface 76.

[0056] As shown in Figure 4, the angle between the end face 76a of the front concave surface 76 and the lower slope 76b is substantially equal to the angle between the end face 77a of the back concave surface 77 and the slope 77b. Note that there may be some error between the angle between the end face 76a of the front concave surface 76 and the lower slope 76b, and the angle between the end face 77a of the back concave surface 77 and the slope 77b.

[0057] As shown in Figure 2, the curvature of the edge 76e of the front concave surface 76 is substantially equal to the curvature of the edge 77e of the back concave surface 77. However, there may be an error between the curvature of the edge 76e of the front concave surface 76 and the curvature of the edge 77e of the back concave surface 77.

[0058] In the X direction, the maximum length of the front chamber 71 is greater than the maximum length of the back chamber 72. The lengths of the front chamber 71 and the back chamber 72 in the X direction are approximately equal to the lengths of the front chamber 71 and the back chamber 72 in the circumferential direction. Therefore, in the circumferential direction, the maximum length of the front chamber 71 is greater than the maximum length of the back chamber 72.

[0059] In this embodiment, the maximum length of the front chamber 71 in the circumferential direction is, for example, the distance between the two sides 76d in the circumferential direction. Also in this embodiment, the maximum length of the back chamber 72 in the circumferential direction is, for example, the distance between the two ends of the bottom surface 77c in the circumferential direction.

[0060] Furthermore, in the circumferential direction, the minimum length of the front chamber 71 is approximately equal to the maximum length of the back chamber 72. In this embodiment, the minimum length of the front chamber 71 in the circumferential direction is the width of the end face 76a in the circumferential direction.

[0061] As shown in Figure 4, the housing block 51 has a boundary line 80 between the first inner circumferential surface 65b and the inner surface 75. The boundary line 80 has a front boundary line 81 and a back boundary line 82. The front boundary line 81 is the boundary line between the first inner circumferential surface 65b and the front concave surface 76. The back boundary line 82 is the boundary line between the first inner circumferential surface 65b and the back concave surface 77, and is an example of a second boundary line.

[0062] The front boundary line 81 has an inclined boundary line 81a and a horizontal boundary line 81b. The inclined boundary line 81a is the boundary line between the first inner surface 65b and the lateral slope 76c, and is an example of the first boundary line. The horizontal boundary line 81b is the boundary line between the first inner surface 65b and the side surface 76d.

[0063] The inclined boundary line 81a extends diagonally downward from its end in the -Y direction to its end in the +Y direction. The horizontal boundary line 81b extends in the -Y direction from its end in the -Y direction. That is, the horizontal boundary line 81b extends approximately horizontally. The inclined boundary line 81a and the horizontal boundary line 81b may each be straight lines or curves.

[0064] The inner boundary line 82 has an inclined boundary line 82a and a horizontal boundary line 82b. The inclined boundary line 82a is the boundary line between the first inner surface 65b and the slope 77b. The horizontal boundary line 82b is the boundary line between the first inner surface 65b and the bottom surface 77c.

[0065] The inclined boundary line 82a extends diagonally downward from its end in the -Y direction to its end in the +Y direction. The horizontal boundary line 82b extends in the -Y direction from its end in the -Y direction. That is, the horizontal boundary line 82b extends approximately horizontally. The inclined boundary line 82a and the horizontal boundary line 82b may each be straight lines or curves.

[0066] The end of the horizontal boundary line 82b in the -Y direction is connected to the inclined boundary line 81a of the front boundary line 81. In other words, the end of the rear boundary line 82 in the -Y direction is connected to the inclined boundary line 81a of the front boundary line 81. The rear boundary line 82 may be connected to the end of the inclined boundary line 81a in the +Y direction, or to any other position on the inclined boundary line 81a.

[0067] As described above, the boundary line 80 extends horizontally or diagonally downward toward the first end 80a in the entire area between the first end 80a of the boundary line 80 in the +Y direction and the second end 80b of the boundary line 80 in the -Y direction. In other words, the boundary line 80 does not have a portion that extends diagonally upward toward the first end 80a. However, the boundary line 80 may partially extend diagonally upward toward the first end 80a.

[0068] The boundary line 80 extends at least partially in a diagonal downward direction toward the first end 80a. In this embodiment, the inclined boundary lines 81a and 82a extend diagonally downward toward the first end 80a. Therefore, the first end 80a is located below the second end 80b.

[0069] A flow path 85 is further provided inside the housing block 51. The flow path 85 may communicate with the intake flow path 63, the discharge flow path 64, or any other flow path. The flow path 85 is located below the inner chamber 72 and is spaced apart from the front chamber 71 in the +Y direction. The flow path 85 overlaps the inner chamber 72 vertically and the front chamber 71 horizontally.

[0070] As shown in Figure 1, the motor body 41 of the motor 31 is attached to the front surface 51a of the housing block 51, for example, by screws. In this way, the motor body 41 covers the cam chamber 61. Furthermore, the motor body 41 may also cover the liquid reservoir chamber 70.

[0071] At least a portion of the motor shaft 42 is located in the cam chamber 61. The first inner circumferential surface 65b of the inner surface 65 faces the eccentric shaft 48 at a distance. The second inner circumferential surface 65d faces the base shaft 47 at a distance.

[0072] The bearing 33 is, for example, a ball bearing. However, the bearing 33 may be of other types. The bearing 33 is interposed between the base shaft 47 and the second inner circumferential surface 65d. That is, the second inner circumferential surface 65d supports the motor shaft 42 so that it can rotate around the central axis Ax1 via the bearing 33.

[0073] The cam 34 is, for example, a ball bearing. However, the cam 34 is not limited to this example. The cam 34 is mounted on the eccentric shaft 48. For this reason, the cam 34 is mounted on the motor shaft 42 eccentrically with respect to the central axis Ax1 and is located in the cam chamber 61.

[0074] The first inner circumferential surface 65b of the inner surface 65 faces the cam 34 at a distance. The outer diameter of the cam 34 is smaller than the diameter of the first inner circumferential surface 65b. Even when the cam 34 rotates around the central axis Ax1, it remains separated from the first inner circumferential surface 65b.

[0075] Two pistons 35 are located in two piston chambers 62. Each of the two pistons 35 has a piston member 91, an outer spring 92, a retainer 93, a ball 94, an inner spring 95, and two ring seals 96.

[0076] The piston member 91 is formed in a substantially cylindrical shape extending in the X direction. The piston member 91 is housed in the piston chamber 62 so as to be slidable in the X direction. The piston member 91 has two end faces 91a and 91b.

[0077] End face 91a is provided at one end of the piston member 91 in the X direction. End face 91a faces the cam 34. End face 91b is provided at the other end of the piston member 91 in the X direction. End face 91b faces the plug 52.

[0078] The piston member 91 is provided with a vertical hole 97 and a horizontal hole 98. The vertical hole 97 extends in the X direction. One end of the vertical hole 97 opens to the end face 91b. The other end of the vertical hole 97 communicates with the horizontal hole 98. The horizontal hole 98 penetrates the piston member 91 in the Z direction, for example, and communicates with the suction passage 63.

[0079] The outer spring 92 is interposed between the piston member 91 and the plug 52. The outer spring 92 biases the piston member 91 toward the cam 34. As a result, the end face 91a of the piston member 91 is pressed against the cam 34.

[0080] The retainer 93 is attached to the piston member 91 so as to cover the end face 91b of the piston member 91. The retainer 93 is provided with a through hole through which, for example, brake fluid can flow.

[0081] The ball 94 is positioned between the end face 91b of the piston member 91 and the retainer 93. By contacting the end face 91b, the ball 94 closes the vertical hole 97. The ball 94 can move away from the end face 91b, opening the vertical hole 97.

[0082] The internal spring 95 is interposed between the retainer 93 and the ball 94. The internal spring 95 biases the ball 94 toward the end face 91b of the piston member 91. As a result, the ball 94 is pressed against the end face 91b.

[0083] The two ring seals 96 are spaced apart from each other in the X direction. The two ring seals 96 are fitted into, for example, two grooves provided in the piston member 91 and attached to the piston member 91. The lateral hole 98 is located between the two ring seals 96.

[0084] The ECU 23 is mounted, for example, on the rear surface 51b of the housing block 51. The ECU 23 may be located in other positions. The ECU 23 drives the motor 31 by, for example, supplying an electrical signal (current) to the stator of the motor body 41.

[0085] The ECU 23 drives the motor 31, causing the motor shaft 42 to rotate around the central axis Ax1 relative to the housing 32. As a result, the cam 34 rotates (revolves) around the central axis Ax1 relative to the housing 32, pushing one of the pistons 35.

[0086] The cam 34 pushes the end face 91a of the piston member 91 toward the plug 52. This causes the piston member 91 to move toward the plug 52. At this time, the ball 94 comes into contact with the end face 91b of the piston member 91 and closes the vertical hole 97. As a result, the brake fluid in the space between the piston member 91 and the plug 52 is compressed and sent from the discharge passage 64.

[0087] As the cam 34 rotates further, it moves away from the plug 52. The piston member 91 is pushed by the outer spring 92 and moves toward the central axis Ax1. At this time, the ball 94 moves away from the end face 91b of the piston member 91 and opens the vertical hole 97. As a result, the brake fluid from the reservoir 21 is supplied to the space between the piston member 91 and the plug 52 through the intake passage 63, the horizontal hole 98, the vertical hole 97, and the through hole of the retainer 93.

[0088] The ring seal 96 provides a watertight seal between the cam chamber 61 and the piston chamber 62, limiting the outflow of brake fluid from the piston chamber 62 into the cam chamber 61. However, brake fluid may still leak from the piston chamber 62 into the cam chamber 61.

[0089] Brake fluid flows down from the piston chamber 62 along the first inner circumferential surface 65b through which the piston chamber 62 opens. The fluid reservoir chamber 70 is located below the piston chamber 62. Therefore, the brake fluid reaches the boundary line 80 between the first inner circumferential surface 65b and the inner surface 75 of the fluid reservoir chamber 70. The brake fluid adheres to the boundary line 80, for example, due to surface tension.

[0090] As described above, the boundary line 80 extends horizontally or diagonally downward toward the first end 80a throughout the entire area between the first end 80a and the second end 80b. Therefore, the brake fluid flows along the boundary line 80 toward the first end 80a.

[0091] For example, when the brake fluid reaches the inclined boundary line 81a, gravity causes the brake fluid to flow diagonally downward along the inclined boundary line 81a towards the rear boundary line 82. In other words, the brake fluid moves away from the motor body 41 and flows towards the horizontal boundary line 82b of the rear boundary line 82.

[0092] When the brake fluid reaches the horizontal boundary line 82b of the inner boundary line 82, the brake fluid flows along the horizontal boundary line 82b toward the inclined boundary line 82a. Due to gravity, the brake fluid flows diagonally downward along the inclined boundary line 82a toward the first end 80a of the boundary line 80. In other words, the brake fluid moves away from the motor body 41.

[0093] When the brake fluid reaches the first end 80a of the boundary line 80, it flows down into the inner chamber 72, for example, along the end surface 77a or the slope 77b of the inner concave surface 77. Due to gravity, the brake fluid flows diagonally downward along the slope 77b.

[0094] The brake fluid flows along the bottom surface 77c from the end of the inclined surface 77b in the -Z direction toward the end surface 76a of the front concave surface 76. When the brake fluid reaches the end surface 76a of the front concave surface 76, it flows down the end surface 76a into the front chamber 71.

[0095] The brake fluid flows diagonally downward along the lower slope 76b from the end of the end face 76a in the -Z direction due to gravity. The brake fluid may be stored in a space further below the front chamber 71, or it may be discharged to the outside through the flow path.

[0096] As described above, the brake fluid flows away from the motor body 41 before flowing down into the fluid reservoir chamber 70. For this reason, the brake fluid is less likely to flow into the motor case 45, which houses the stator and rotor, for example. Note that the brake fluid is not limited to the above example; for example, it may flow down from the front boundary line 81 into the front chamber 71.

[0097] The following examples illustrate a method for forming the liquid reservoir chamber 70, which is part of the manufacturing method of the piston pump 22, with reference to Figures 5 to 7. Note that the method for forming the liquid reservoir chamber 70 is not limited to the methods described below; other methods may also be used.

[0098] Figure 5 is a schematic cross-sectional view showing the housing block 51 and end mill 100 of this embodiment. As shown in Figure 5, the liquid reservoir chamber 70 is formed by cutting with a rotary cutting tool such as the end mill 100.

[0099] For example, the end mill 100 is formed in a substantially cylindrical shape extending along the rotation axis Ax3. The rotation axis Ax3 is the central axis of the end mill 100 and extends in the Y direction. The end mill 100 has an end face 100a, an inclined surface 100b, and an outer circumferential surface 100c.

[0100] The end face 100a is located at the end of the end mill 100 in the +Y direction. The end face 100a is a plane formed in a substantially circular shape. The end face 100a faces in the +Y direction. The inclined surface 100b is formed in a substantially conical (frustoconical) shape that tapers toward the +Y direction. The end of the inclined surface 100b in the +Y direction is connected to the end face 100a. The outer circumferential surface 100c is a substantially cylindrical curved surface that extends in the -Y direction from the end of the inclined surface 100b in the -Y direction. The diameter of the outer circumferential surface 100c is smaller than the diameter of the first inner circumferential surface 65b of the housing block 51.

[0101] The end mill 100 has cutting edges extending across its end face 100a, inclined surface 100b, and outer circumferential surface 100c. The end mill 100 rotates around the rotation axis Ax3 and cuts the housing block 51.

[0102] Figure 6 is a schematic front view showing the housing block 51 in which the inner chamber 72 of this embodiment is formed. As shown in Figure 6, the end mill 100 is inserted into the cam chamber 61. The cam chamber 61 is formed in advance, for example, before the liquid reservoir chamber 70 is formed.

[0103] The end mill 100 moves in the -Z direction while rotating around the rotation axis Ax3. The end mill 100 cuts the housing block 51 by contacting the first inner circumferential surface 65b, forming the inner chamber 72.

[0104] The end face 100a of the end mill 100 forms the end face 77a of the recessed surface 77, the inclined surface 100b forms the inclined surface 77b, and the outer circumferential surface 100c forms the bottom surface 77c. Therefore, the angle between the end face 77a of the recessed surface 77 and the inclined surface 77b is approximately equal to the angle between the end face 100a of the end mill 100 and the inclined surface 100b.

[0105] The end mill 100 forms a recessed chamber 72 by shallowly cutting the first inner circumferential surface 65b. That is, the length of the recessed chamber 72 in the vertical direction is shorter than the radius of the outer circumferential surface 100c of the end mill 100. Therefore, the length of the recessed chamber 72 in the X direction is smaller than the diameter of the outer circumferential surface 100c.

[0106] As shown by the arrows in Figure 5, the end mill 100 moves in the -Z direction to form the inner chamber 72, and then moves in the -Y direction, for example. After that, the end mill 100 moves in the -Z direction and cuts the housing block 51 from the bottom surface 77c of the inner concave surface 77.

[0107] Figure 7 is a schematic front view showing the housing block 51 in which the front chamber 71 of this embodiment is formed. As shown in Figure 7, the end mill 100 forms the front chamber 71 by cutting the housing block 51 from the bottom surface 77c.

[0108] The end face 100a of the end mill 100 forms the end face 76a of the front concave surface 76, the inclined surface 100b forms the lower inclined surface 76b and the lateral inclined surface 76c, and the outer peripheral surface 100c forms the side surface 76d. Therefore, the angle between the end face 76a of the front concave surface 76 and the lower inclined surface 76b is approximately equal to the angle between the end face 100a of the end mill 100 and the inclined surface 100b.

[0109] The formation of the liquid reservoir chamber 70 is completed when the end mill 100 is withdrawn from the housing block 51 in the -Y direction. The end mill 100 may continue cutting the housing block 51, for example, to form a space that communicates with the front chamber 71.

[0110] The end mill 100 forms the front chamber 71 by cutting the housing block 51 in the -Z direction from the bottom surface 77c of the recessed surface 77. The length of the front chamber 71 in the vertical direction is longer than the radius of the outer surface 100c of the end mill 100. Therefore, the length of the front chamber 71 in the X direction is approximately equal to the diameter of the outer surface 100c.

[0111] Since the first inner surface 65b is a cylindrical curved surface extending around the central axis Ax1, the rear boundary line 82 between the first inner surface 65b and the rear concave surface 77 is located below the front boundary line 81 between the first inner surface 65b and the front concave surface 76. For this reason, the brake fluid on the boundary line 80 flows from the front boundary line 81 to the rear boundary line 82 due to gravity.

[0112] In the piston pump 22 according to the embodiment described above, the inner surface 65 defines a cam chamber 61 that is recessed in the +Y direction from the front surface 51a. The inner surface 75 defines a liquid reservoir chamber 70 that is recessed in the +Y direction from the front surface 51a and communicates with the lower end of the cam chamber 61 around the central axis Ax1. The inner surface 65 of the cam chamber 61 has a first inner circumferential surface 65b that extends around the central axis Ax1. The liquid reservoir chamber 70 has a front chamber 71 that opens to the front surface 51a and the lower end of the first inner circumferential surface 65b around the central axis Ax1, and a back chamber 72 that opens to the lower end of the first inner circumferential surface 65b around the central axis Ax1 and communicates with the end of the front chamber 71 in the +Y direction. The front chamber 71 extends longer downward than the back chamber 72 from the lower end of the first inner surface 65b around the central axis Ax1, and its maximum length around the central axis Ax1 is greater than that of the back chamber 72.

[0113] When brake fluid flows from the piston chamber 62 into the cam chamber 61, the brake fluid flows into a fluid reservoir chamber 70 which is connected to the lower end of the cam chamber 61. The fluid reservoir chamber 70 holds the brake fluid, preventing it from entering the motor body 41.

[0114] Of the liquid reservoir chambers 70, the inner chamber 72, located at the back, is shorter vertically than the front chamber 71. Therefore, the piston pump 22 can, for example, provide a flow path 85 below the inner chamber 72 inside the housing 32, while in the vicinity of the front surface 51a, where it is difficult to provide an internal space such as a flow path 85, the volume of the front chamber 71 can be set to be larger. In other words, the piston pump 22 can set a larger overall volume for the liquid reservoir chambers 70.

[0115] The brake fluid flows from the inner chamber 72 to the deeper front chamber 71 and does not easily remain in the inner chamber 72. Therefore, the piston pump 22 can prevent the rotating cam 34 from scooping up the brake fluid from the inner chamber 72.

[0116] Of the liquid reservoir chambers 70, the inner chamber 72, located at the back, has a smaller maximum length around the central axis Ax1 than the front chamber 71. Therefore, the front chamber 71 and the inner chamber 72 can be formed by moving a common end mill 100 of a general shape in the Y direction and the vertical direction. For example, by inserting the end mill 100 deeper into the housing 32 in the +Y direction so that the distance between the central axis Ax1 and the lower end of the end mill 100 is shortened, the inner chamber 72 with a smaller length around the central axis Ax1 can be formed. On the other hand, by inserting the end mill 100 shallower into the housing 32 in the +Y direction so that the distance between the central axis Ax1 and the lower end of the end mill 100 is longer, the front chamber 71 with a larger length around the central axis Ax1 can be formed. In this way, a common end mill 100 can form the liquid reservoir chamber 70, including the front chamber 71 and the inner chamber 72, with simple and short movements. Therefore, the piston pump 22 can reduce the manufacturing time and cost of the front chamber 71 and the rear chamber 72, and can easily form a large-capacity liquid reservoir chamber 70.

[0117] Because the first inner surface 65b extends around the central axis Ax1, the inner boundary line 82 between the first inner surface 65b and the inner chamber 72 is located below the outer boundary line 81 between the first inner surface 65b and the outer chamber 71. Therefore, the piston pump 22 can direct the brake fluid that has flowed out of the piston chamber 62 into the cam chamber 61 to the inner chamber 72 located further inside, via the outer boundary line 81. Thus, the piston pump 22 can keep the brake fluid away from the motor body 41. Furthermore, the piston pump 22 can set a longer distance between the inner chamber 72 and the piston chamber 62. As a result, the piston pump 22 can more reliably prevent brake fluid from entering the motor body 41.

[0118] The boundary line 80 between the first inner circumferential surface 65b and the inner surface 75 extends horizontally or diagonally downward toward the first end 80a in the entire area between the first end 80a of the boundary line 80 in the +Y direction and the second end 80b of the boundary line 80 in the -Y direction. The first end 80a is located below the second end 80b. In other words, the boundary line 80 extends diagonally downward overall toward the back of the fluid reservoir chamber 70. Due to surface tension, brake fluid tends to flow along ridges such as the boundary line 80. Therefore, when brake fluid flows out of the piston chamber 62 to the boundary line 80, it moves away from the motor body 41 along the boundary line 80. Consequently, the piston pump 22 can more reliably prevent brake fluid from entering the motor body 41.

[0119] The inner surface 75 has a front concave surface 76 defining the front chamber 71 and a rear concave surface 77 defining the rear chamber 72. The boundary line 80 has an inclined boundary line 81a between the first inner circumferential surface 65b and the front concave surface 76, and a rear boundary line 82 between the first inner circumferential surface 65b and the rear concave surface 77. The inclined boundary line 81a extends diagonally downward from its end in the -Y direction to its end in the +Y direction. The end of the rear boundary line 82 in the -Y direction is connected to the inclined boundary line 81a.

[0120] As the brake fluid flows out of the piston chamber 62 to the front boundary line 81, it moves away from the motor body 41 along the inclined boundary line 81a. Furthermore, the brake fluid flows smoothly from the inclined boundary line 81a to the rear boundary line 82, and moves even further away from the motor body 41 along the rear boundary line 82. Finally, the brake fluid falls from the rear boundary line 82 into the rear chamber 72. Therefore, the piston pump 22 can more reliably prevent the brake fluid from entering the motor body 41.

[0121] The recessed surface 77 is located at the lower end of the inner chamber 72 around the central axis Ax1 and has a slope 77b that extends diagonally downward toward the front chamber 71. As a result, the slope 77b can efficiently direct the brake fluid from the inner chamber 72 to the deeper front chamber 71. Therefore, the piston pump 22 can maintain a low fluid level of brake fluid in the inner chamber 72 and prevent the rotating cam 34 from scooping up the brake fluid from the inner chamber 72.

[0122] The front concave surface 76 has an end face 76a provided at the end of the front chamber 71 in the +Y direction, and a downward sloping surface 76b extending from the end face 76a toward the front surface 51a and tapering in the +Y direction. The rear concave surface 77 has an end face 77a provided at the end of the rear chamber 72 in the +Y direction, and a sloping surface 77b extending from the end face 77a toward the end face 76a and tapering in the +Y direction. The angle between the end face 76a and the downward sloping surface 76b is equal to the angle between the end face 77a and the sloping surface 77b. Thus, the front chamber 71 and the rear chamber 72 can be formed by moving a common end mill 100 in a direction along the central axis Ax1 and in a vertical direction. In other words, the front chamber 71 and the rear chamber 72 can be formed by a common end mill 100 such that the angle between the end face 76a and the lower slope 76b, and the angle between the end face 77a and the slope 77b, are equal to the angle between the end face 100a and the slope 100b of the end mill 100. Therefore, the piston pump 22 can reduce the manufacturing time and cost of the front chamber 71 and the rear chamber 72, and can easily form a large-capacity liquid reservoir chamber 70.

[0123] The end face 76a has an arc-shaped edge 76e. The end face 77a has an arc-shaped edge 77e with the same curvature as the edge 76e. As a result, the front chamber 71 and the rear chamber 72 can be formed by moving a common end mill 100 in the Y direction and the vertical direction. That is, the front chamber 71 and the rear chamber 72 can be formed by a common end mill 100 such that the curvature of the edge 76e and the curvature of the edge 77e are equal to the curvature of the end face 100a of the end mill 100. Therefore, the piston pump 22 can reduce the manufacturing time and cost of the front chamber 71 and the rear chamber 72, and can easily form a large-capacity liquid reservoir chamber 70.

[0124] A piston pump according to at least one embodiment described above includes, as an example, a motor having a motor body and a motor shaft extending from the motor body in a first axial direction along a central axis, the first axial direction being arranged to intersect with the vertical direction and configured to rotate the motor shaft about the central axis; a housing having an outer surface, a first inner surface defining a cam chamber recessed from the outer surface in the first axial direction, and a second inner surface defining a liquid reservoir chamber recessed from the outer surface in the first axial direction and communicating with the lower end of the cam chamber about the central axis, the cam chamber being provided with a piston chamber extending from the cam chamber in a direction intersecting the central axis, and the cam chamber being covered by the motor body; and an eccentric with respect to the central axis The motor shaft is provided with a cam located in the cam chamber, and a piston located in the piston chamber is configured to be pressed by the cam, which rotates relative to the housing around a central axis. The first inner surface has an inner circumferential surface extending around the central axis, and the liquid reservoir chamber has a first chamber opening at the lower end of the outer surface and the inner circumferential surface around the central axis, and a second chamber opening at the lower end of the inner circumferential surface around the central axis and communicating with the end of the first chamber in the first axial direction. The first chamber extends longer downward from the lower end of the inner circumferential surface around the central axis than the second chamber, and its maximum length around the central axis is greater than that of the second chamber. For example, if liquid flows out of the piston chamber into the cam chamber, the liquid flows into the liquid reservoir chamber which communicates with the lower end of the cam chamber. The liquid reservoir chamber prevents the liquid from entering the motor body by accumulating liquid. In the liquid reservoir chamber, the second chamber, located at the back, is shorter vertically than the first chamber. Therefore, the piston pump can, for example, create a flow path below the second chamber inside the housing, while allowing for a larger volume in the vicinity of the outer surface where a flow path is difficult to create. The liquid flows from the second chamber to the deeper first chamber and does not easily remain in the second chamber. This prevents the rotating cam from scooping up the liquid from the second chamber. Furthermore, the second chamber, located at the back of the liquid reservoir chamber, has a smaller maximum length around its central axis than the first chamber.Therefore, the first and second chambers can be formed by moving a common end mill of a general shape along the central axis and vertically. For example, by inserting the end mill deeply into the housing in the first axial direction so that the distance between the central axis and the lower end of the end mill is shortened, a second chamber with a small length around the central axis can be formed. On the other hand, by inserting the end mill shallowly into the housing in the first axial direction so that the distance between the central axis and the lower end of the end mill is longer, a first chamber with a large length around the central axis can be formed. In this way, a common end mill can form a liquid reservoir chamber including the first and second chambers with simple and short movements. Therefore, the piston pump can reduce the manufacturing time and cost of the first and second chambers and can easily form a large-capacity liquid reservoir chamber. Because the inner circumferential surface extends around the central axis, the boundary line between the inner circumferential surface and the second chamber is located below the boundary line between the inner circumferential surface and the first chamber. Therefore, the piston pump can direct the liquid that has flowed from the piston chamber into the cam chamber through the boundary line between the inner surface and the first chamber to the second chamber located further inside. Thus, the piston pump can keep the liquid away from the motor body. Furthermore, the piston pump can set a longer distance between the second chamber and the piston chamber. As a result, the piston pump can more reliably prevent the liquid from entering the motor body.

[0125] In the piston pump described above, as an example, the boundary line between the inner circumferential surface and the second inner surface extends horizontally or diagonally downward toward the first end over the entire area between the first end of the boundary line in the first axial direction and the second end of the boundary line in the second axial direction opposite to the first axial direction, with the first end located below the second end. Therefore, as an example, the boundary line between the inner circumferential surface and the second inner surface extends diagonally downward overall toward the back of the liquid reservoir chamber. Due to surface tension, liquid tends to flow along ridges such as this boundary line. Therefore, when liquid flows out of the piston chamber to the boundary line between the inner circumferential surface and the second inner surface, it moves away from the motor body along this boundary line. Consequently, the piston pump can more reliably prevent liquid from entering the motor body.

[0126] In the piston pump described above, as an example, the second inner surface has a first concave surface defining the first chamber and a second concave surface defining the second chamber, and the boundary line has a first boundary line between the inner circumferential surface and the first concave surface and a second boundary line between the inner circumferential surface and the second concave surface, and the first boundary line extends diagonally downward from one end of the first boundary line in the second axial direction to the other end of the first boundary line in the second axial direction, and the end of the second boundary line in the second axial direction is connected to the first boundary line. Therefore, as an example, when liquid flows out of the piston chamber to the first boundary line, it moves away from the motor body along the first boundary line. Furthermore, the liquid flows smoothly from the first boundary line to the second boundary line and moves further away from the motor body along the second boundary line. Finally, the liquid falls from the second boundary line into the second chamber. Therefore, the piston pump can more reliably prevent liquid from entering the motor body.

[0127] In the piston pump described above, for example, the second inner surface is provided at the lower end of the second chamber around the central axis and has a slope that extends diagonally downward toward the first chamber. Therefore, for example, the slope can efficiently flow the liquid from the second chamber to the deeper first chamber. Consequently, the piston pump can maintain a low liquid level in the second chamber and prevent the rotating cam from scooping up the liquid from the second chamber.

[0128] In the piston pump described above, as an example, the second inner surface has a first concave surface defining the first chamber and a second concave surface defining the second chamber, the first concave surface has a first end face provided at the end of the first chamber in the first axial direction and a first inclined surface extending from the first end face toward the outer surface and tapering in the first axial direction, the second concave surface has a second end face provided at the end of the second chamber in the first axial direction and a second inclined surface extending from the second end face toward the first end face and tapering in the first axial direction, and the angle between the first end face and the first inclined surface is equal to the angle between the second end face and the second inclined surface. Therefore, as an example, the first chamber and the second chamber can be formed by moving a common end mill in a direction along the central axis and in a vertical direction. In other words, the first and second chambers can be formed by a common end mill such that the angle between the first end face and the first inclined plane, and the angle between the second end face and the second inclined plane, are equal to the angle between the end face and the inclined plane of the end mill. Therefore, the piston pump can reduce the manufacturing time and cost of the first and second chambers, and can easily form a large-capacity liquid reservoir chamber.

[0129] In the piston pump described above, as an example, the second inner surface has a first end face provided at the end of the first chamber in the first axial direction, and a second end face provided at the end of the second chamber in the first axial direction, the first end face having an arc-shaped first edge, and the second end face having an arc-shaped second edge with the same curvature as the first edge. Thus, as an example, the first and second chambers can be formed by moving a common end mill in a direction along the central axis and in a vertical direction. That is, the first and second chambers can be formed by a common end mill such that the curvature of the first edge and the curvature of the second edge are equal to the curvature of the end face of the end mill. Thus, the piston pump can reduce the manufacturing time and cost of the first and second chambers, and can easily form a large-capacity liquid reservoir chamber.

[0130] Although embodiments of the present invention have been illustrated above, these embodiments and modifications are merely examples and are not intended to limit the scope of the invention. The above embodiments and modifications can be implemented in various other forms, and various omissions, substitutions, combinations, and changes can be made without departing from the spirit of the invention. Furthermore, the configurations and shapes of each embodiment and modification can be partially replaced.

Claims

1. A motor comprising: a motor body and a motor shaft extending from the motor body in a first axial direction along a central axis, the first axial direction being arranged to intersect with the vertical direction and configured to rotate the motor shaft around the central axis; a housing comprising: an outer surface, a first inner surface defining a cam chamber recessed from the outer surface in the first axial direction, and a second inner surface defining a liquid reservoir chamber recessed from the outer surface in the first axial direction and communicating with the lower end of the cam chamber around the central axis, a piston chamber extending from the cam chamber in a direction intersecting the central axis, and the cam chamber being covered by the motor body; a cam provided on the motor shaft eccentrically with respect to the central axis and located in the cam chamber; and a piston located in the piston chamber and configured to be pressed by the cam rotating relative to the housing around the central axis, wherein the first inner surface has an inner circumferential surface extending around the central axis. The piston pump wherein the liquid reservoir chamber has a first chamber opening at the lower end of the outer surface and the inner circumferential surface around the central axis, and a second chamber opening at the lower end of the inner circumferential surface around the central axis and communicating with the end of the first chamber in the first axial direction, wherein the first chamber extends longer downward from the lower end of the inner circumferential surface around the central axis than the second chamber, and its maximum length around the central axis is greater than that of the second chamber.

2. The piston pump according to claim 1, wherein the boundary line between the inner circumferential surface and the second inner surface extends horizontally or diagonally downward toward the first end over the entire area between the first end of the boundary line in the first axial direction and the second end of the boundary line in the second axial direction opposite to the first axial direction, and the first end is located below the second end.

3. The piston pump according to claim 2, wherein the second inner surface has a first concave surface defining the first chamber and a second concave surface defining the second chamber, the boundary line has a first boundary line between the inner circumferential surface and the first concave surface and a second boundary line between the inner circumferential surface and the second concave surface, the first boundary line extends diagonally downward from one end of the first boundary line in the second axial direction to the other end of the first boundary line in the first axial direction, and the end of the second boundary line in the second axial direction is connected to the first boundary line.

4. The second inner surface is provided at the lower end of the second chamber around the central axis and has a slope extending diagonally downward toward the first chamber, a piston pump according to any one of claims 1 to 3.

5. The piston pump according to claim 1, wherein the second inner surface has a first concave surface defining the first chamber and a second concave surface defining the second chamber, the first concave surface has a first end face provided at the end of the first chamber in the first axial direction and a first inclined surface extending from the first end face toward the outer surface and tapering in the first axial direction, the second concave surface has a second end face provided at the end of the second chamber in the first axial direction and a second inclined surface extending from the second end face toward the first end face and tapering in the first axial direction, and the angle between the first end face and the first inclined surface is equal to the angle between the second end face and the second inclined surface.

6. The piston pump according to claim 1, wherein the second inner surface has a first end face provided at the end of the first chamber in the first axial direction and a second end face provided at the end of the second chamber in the first axial direction, the first end face having an arc-shaped first edge, and the second end face having an arc-shaped second edge having the same curvature as the first edge.

Images