rotary pump

Abstract

As an example, a rotary pump is obtained that does not require a lubricant other than fluid between the shaft and the seal. [Solution] A rotary pump according to the embodiment includes, as an example, a rotating body rotatable about a rotation axis, a housing having an inner circumferential surface facing the rotation axis, a shaft extending along the rotation axis and having a first outer circumferential surface facing the inner circumferential surface, connected to the rotating body, a plug having a passage, the first end of the passage opening to the second outer circumferential surface, and the second end of the passage opening to the inner surface, a first seal sealing the gap between the first outer circumferential surface and the inner surface, and closer to the rotating body than the second end, a second seal sealing the gap, and further from the rotating body than the second end, and a third seal sealing the passage between the first end and the second end.

Description

Technical Field

[0001] Embodiments of the present invention relate to a rotary pump.

Background Art

[0002] Conventionally, rotary pumps such as gear pumps are known. A rotary pump includes a housing, a plug housed in the housing, a shaft extending through the plug, and a rotating body such as an inner gear connected to the shaft. The rotary pump transports fluid, for example, by rotating the rotating body. <​​​​​​​​​​​​​​​​​​​​​​​​​​​​Therefore, the present invention has been made in view of the above, and provides a rotary pump that does not require a lubricant other than fluid between the shaft and the seal. [Means for solving the problem]

[0007] A rotary pump according to an embodiment of the present invention includes, as an example, a rotating body rotatable around a rotation axis; a housing having an inner circumferential surface facing the rotation axis and housing the rotating body; a shaft extending along the rotation axis and having a first outer circumferential surface facing the inner circumferential surface, connected to the rotating body, and configured to transport fluid to the rotating body by rotating together with the rotating body around the rotation axis relative to the housing; a plug having a passage into which the fluid can be injected, with a first end of the passage opening to the second outer circumferential surface and a second end of the passage opening to the inner surface; a first seal sealing the gap between the first outer circumferential surface and the inner surface and closer to the rotating body than the second end; a second seal sealing the gap and further from the rotating body than the second end; and a third seal sealing the passage between the first end and the second end. Therefore, as an example, before the third seal seals the passage, the second end of the passage communicates with the space between the first seal and the second seal (the intermediate chamber) in the gap. For this reason, before the plug is assembled inside the inner circumferential surface of the housing, fluid can be supplied from outside the plug to the intermediate chamber through the passage. The fluid can lubricate the shaft and the second seal as they rotate around the axis by entering the tiny gap between the first outer circumferential surface of the shaft and the second seal from the intermediate chamber. For this reason, the rotary pump does not require a lubricant other than the fluid to lubricate the shaft and the second seal. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic circuit block diagram showing a brake control device according to the first embodiment. [Figure 2]Figure 2 is a cross-sectional view showing a gear pump device according to the first embodiment. [Figure 3] Figure 3 is a cross-sectional view showing a part of the gear pump device of the first embodiment. [Figure 4] Figure 4 is a cross-sectional view showing a part of the gear pump device according to the second embodiment. [Figure 5] Figure 5 is a cross-sectional view showing a part of a gear pump device according to the third embodiment. [Modes for carrying out the invention]

[0009] (First embodiment) The first embodiment will be described below with reference to Figures 1 to 3. In this specification, the vertically upward direction is generally defined as the upward direction, and the vertically downward direction as the downward direction. Furthermore, in this specification, the components of the 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 in this specification. Components may also be identified by names different from those used in this specification. Furthermore, components may also be described using expressions different from those used in this specification.

[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 schematic circuit block diagram showing a brake control device 10 according to a first embodiment. The brake control device 10 is mounted on a vehicle 1, such as an automobile, and controls the braking force of the vehicle 1's brakes. As shown in Figure 1, the brake control device 10 includes, for example, four wheel cylinders 11, a pressurizing device 12, an actuator 13, and an electronic control unit (ECU) 14.

[0012] The brake control device 10 generates braking force by adjusting the fluid pressure in the four wheel cylinders 11. The fluid may also be referred to as brake fluid or brake oil. Each of the four wheel cylinders 11 brakes the corresponding wheel by using the fluid pressure to, for example, press the brake pads against the disc rotor.

[0013] The pressurizing device 12 includes, for example, a brake pedal, a master cylinder, a reservoir, a stroke sensor, a pump, a stroke simulator, multiple pipes, multiple valves, and multiple pressure sensors. However, the pressurizing device 12 is not limited to this example.

[0014] The master cylinder of the pressurizing device 12 pressurizes the fluid, for example, in response to the driver's operation of the brake pedal. The ECU 14 may detect the operation of the brake pedal using the stroke simulator of the pressurizing device 12 and pressurize the fluid using the pump of the pressurizing device 12 in response to that operation. The ECU 14 can switch between pressurization by the master cylinder and pressurization by the pump by controlling a valve.

[0015] The actuator 13 is installed between each of the four wheel cylinders 11 and the pressurizing device 12. The actuator 13 adjusts the pressure in each of the four wheel cylinders 11 based on the pressure supplied from the pressurizing device 12.

[0016] The actuator 13 includes a first piping system 21, a second piping system 22, and a gear pump device 23. The gear pump device 23 is an example of a rotary pump. The actuator 13 itself may also be an example of a rotary pump.

[0017] The first piping system 21 is provided between the pressurizing device 12 and two of the four wheel cylinders 11, and adjusts the pressure of the two wheel cylinders 11. The second piping system 22 is provided between the pressurizing device 12 and the other two of the four wheel cylinders 11, and adjusts the pressure of the two wheel cylinders 11.

[0018] The gear pump device 23 has a first gear pump 25 and a second gear pump 26. The first gear pump 25 is incorporated into the first piping system 21. The second gear pump 26 is incorporated into the second piping system 22.

[0019] The actuator 13 further has a plurality of valves and a plurality of pressure sensors. The ECU 14 can adjust the pressure of each of the four wheel cylinders 11 by controlling the valves of the actuator 13 and driving the gear pump device 23. The actuator 13 may be an ABS actuator capable of performing anti-skid control (ABS control), or an ESC actuator capable of performing anti-slip control (ESC control).

[0020] The ECU 14 has, for example, a CPU, a memory, a circuit board, a drive circuit, and various electronic components. The ECU 14 controls the pressurizing device 12 and the actuator 13 based on information from various sensors such as a stroke sensor of the pressurizing device 12 and a plurality of pressure sensors of the pressurizing device 12 and the actuator 13.

[0021] Figure 2 is a cross-sectional view showing the gear pump device 23 of the first embodiment. The gear pump device 23 of the present embodiment is an internal gear pump (trochoid pump). Note that the gear pump device 23 is not limited to this example.

[0022] The gear pump device 23 includes, in addition to the first gear pump 25 and the second gear pump 26, a motor 31, a shaft 32, two bearings 33, 34, a housing 35, a cylinder 36, a plug 37, a stopper 38, an intermediate seal 41, two seal structures 42, 43, a ring seal 44, a seal shaft 45, an oil seal 46, and a plug 47. The seal shaft 45 is an example of a first seal. The oil seal 46 is an example of a second seal. The plug 47 is an example of a third seal.

[0023] The motor 31 rotates the shaft 32 around the central axis Ax with respect to the housing 35 based on, for example, an electrical signal input from the ECU 14. The central axis Ax is an example of a rotation axis and is, for example, the central axis of the shaft 32. Note that the center (rotation axis) of the rotation of the shaft 32 may be different from the central axis of the shaft 32.

[0024] For convenience in this specification, an axial direction, a radial direction, and a circumferential direction are defined. The axial direction is the direction along the central axis Ax and includes an inner direction Di and an outer direction Do. The inner direction Di is a direction along the central axis Ax. The outer direction Do is the opposite direction of the inner direction Di. The radial direction is the direction orthogonal to the central axis Ax. The circumferential direction is the direction around the central axis Ax.

[0025] The shaft 32 is formed in a substantially cylindrical shape extending along the central axis Ax. The shaft 32 has an outer peripheral surface 32a. The outer peripheral surface 32a is an example of a first outer peripheral surface. The outer peripheral surface 32a is a substantially cylindrical curved surface extending along the central axis Ax and facing outward in the radial direction.

[0026] The shaft 32 is supported by the cylinder 36 via the bearing 33 and by the plug 37 via the bearing 34 so as to be rotatable around the central axis Ax with respect to the housing 35. The first gear pump 25 is located between the two bearings 33, 34.

[0027] The motor 31 drives the first gear pump 25 and the second gear pump 26 by rotating the shaft 32 relative to the housing 35. The first gear pump 25 and the second gear pump 26 each have an inner gear 51, a key 52, and an outer gear 53. The inner gear 51 is an example of a rotating body.

[0028] The inner gear 51 is a spur gear. The shaft 32 extends through the inner gear 51. The key 52 fits into a groove provided on the outer circumferential surface 32a of the shaft 32, as well as into a groove provided on the inner gear 51. As a result, the shaft 32 is connected to the inner gear 51 and can rotate together with the inner gear 51 around the central axis Ax.

[0029] The outer gear 53 is an internal gear and surrounds the inner gear 51. The multiple teeth of the inner gear 51 and the multiple teeth of the outer gear 53 mesh with each other while being eccentric to one another. As a result, a gap is formed between the multiple teeth of the inner gear 51 and the multiple teeth of the outer gear 53.

[0030] The inner gear 51 is rotated around its central axis Ax relative to the outer gear 53 by the motor 31 and shaft 32, thereby changing the volume of the gap, drawing fluid into the gap, and discharging fluid from the gap. In other words, the shaft 32 rotates together with the inner gear 51 around its central axis Ax relative to the housing 35, thereby transporting fluid to the inner gear 51.

[0031] The housing 35 is made of a metal such as an aluminum alloy. However, the housing 35 may be made of other materials. The housing 35 also serves as the housing for the actuator 13. Therefore, the housing 35 is provided with the piping for the actuator 13, and several valves of the actuator 13 are attached to it. Note that the housing 35 is not limited to this example.

[0032] The housing 35 has an outer surface 35a facing outward in the direction Do. The housing 35 is provided with a housing hole 55 that is recessed inward in the direction Di along the central axis Ax from the outer surface 35a. The housing 35 further has an inner circumferential surface 55a that defines the housing hole 55. The inner circumferential surface 55a is a substantially cylindrical curved surface that extends along the central axis Ax. The inner circumferential surface 55a faces the central axis Ax.

[0033] The housing 35 accommodates the first gear pump 25, the second gear pump 26, the shaft 32, the bearings 33 and 34, the cylinder 36, the plug 37, the stopper 38, the intermediate seal 41, the seal structures 42 and 43, the ring seal 44, the seal shaft 45, the oil seal 46, and the plug 47 in the housing hole 55. For this reason, the inner circumferential surface 55a of the housing 35 and the outer circumferential surface 32a of the shaft 32 face each other. Note that the shaft 32, the bearings 34, the plug 37, and the stopper 38 may be partially located outside the housing hole 55.

[0034] The cylinder 36 and the plug 37 are each formed in a substantially annular shape that extends in the circumferential direction. Therefore, a hole 61 is provided on the inside of the cylinder 36, and a hole 62 is provided on the inside of the plug 37. Hole 61 penetrates the cylinder 36 along the central axis Ax. Hole 62 penetrates the plug 37 along the central axis Ax. The shaft 32 extends axially through the hole 61 in the cylinder 36 and the hole 62 in the plug 37.

[0035] The cylinder 36 has an inner surface 61i that defines the hole 61. The inner surface 61i has four inner circumferential surfaces 61a, 61b, 61c, and 61d, and three side surfaces 61e, 61f, and 61g.

[0036] The four inner surfaces 61a, 61b, 61c, and 61d are each substantially cylindrical curved surfaces extending along the central axis Ax and facing radially inward. The three inner surfaces 61a, 61b, 61c, and 61d each face the outer surface 32a of the shaft 32.

[0037] The diameter of the inner circumferential surface 61a is smaller than the diameters of the inner circumferential surfaces 61b, 61c, and 61d. Also, the diameter of the inner circumferential surface 61a is larger than the diameter of the outer circumferential surface 32a of the shaft 32. For this reason, the inner circumferential surface 61a is spaced apart from the shaft 32. However, the inner circumferential surface 61a may temporarily come into contact with the shaft 32 due to vibrations of the vehicle 1, for example. In the axial direction, the inner circumferential surface 61a is located between the two inner circumferential surfaces 61b and 61c.

[0038] The diameter of the inner circumferential surface 61b is smaller than the diameters of the inner circumferential surfaces 61c and 61d. In the axial direction, the inner circumferential surface 61b is located between the two inner circumferential surfaces 61a and 61d. The diameters of the two inner circumferential surfaces 61c and 61d are approximately the same. However, the diameters of the two inner circumferential surfaces 61c and 61d may be different.

[0039] Side surface 61e extends radially between the end of the inner circumferential surface 61a in the inward direction Di and the end of the inner circumferential surface 61b in the outward direction Do, and is oriented in the inward direction Di. Side surface 61f extends radially between the end of the inner circumferential surface 61a in the outward direction Do and the end of the inner circumferential surface 61c in the inward direction Di, and is oriented in the outward direction Do. Side surface 61g extends radially between the end of the inner circumferential surface 61b in the inward direction Di and the end of the inner circumferential surface 61d in the outward direction Do, and is oriented in the inward direction Di.

[0040] The first gear pump 25 is positioned inside the inner circumferential surface 61c of the cylinder 36. The second gear pump 26 is positioned inside the inner circumferential surface 61d of the cylinder 36. The bearing 33 and the intermediate seal 41 are provided between the outer circumferential surface 32a of the shaft 32 and the inner circumferential surface 61b of the cylinder 36, respectively.

[0041] The intermediate seal 41 seals the gap between the outer circumferential surface 32a of the shaft 32 and the inner circumferential surface 61b of the cylinder 36. In other words, the intermediate seal 41 restricts the flow of fluid between the space housing the first gear pump 25 (first pump chamber RP1) and the space housing the second gear pump 26 (second pump chamber RP2).

[0042] The seal structure 42 presses the first gear pump 25 against the side surface 61f of the cylinder 36 by elastic force. Furthermore, the seal structure 42 and the mechanical seal provided on the side surface 61f seal the gap between the high-pressure side space and the low-pressure side space in the first pump chamber RP1.

[0043] The seal structure 43 presses the second gear pump 26 against the side surface 61g of the cylinder 36 by elastic force. Furthermore, the seal structure 43 and the mechanical seal provided on the side surface 61g seal the gap between the high-pressure space and the low-pressure space in the second pump chamber RP2.

[0044] The plug 37 is attached to the cylinder 36 by press-fitting it, for example, into the end of the cylinder 36 in the outward direction Do. The plug 37 has an outer peripheral surface 37a and a support surface 37b. The outer peripheral surface 37a is an example of a second outer peripheral surface.

[0045] The outer circumferential surface 37a is a substantially cylindrical curved surface extending along the central axis Ax and facing radially outward. The outer circumferential surface 37a of the plug 37 and the inner circumferential surface 55a of the housing 35 face each other. The support surface 37b extends radially inward from, for example, the end of the outer circumferential surface 37a in the outward direction Do. The support surface 37b faces outward in the direction Do.

[0046] Figure 3 is a cross-sectional view showing a part of the gear pump device 23 of the first embodiment. As shown in Figure 3, the plug 37 further has an inner surface 62i that defines the hole 62. The inner surface 62i is located on the opposite side of the outer surface 37a. The inner surface 62i has three inner surfaces 62a, 62b, and 62c and two sides 62d and 62e.

[0047] The three inner surfaces 62a, 62b, and 62c are each substantially cylindrical curved surfaces extending along the central axis Ax and facing radially inward. The three inner surfaces 62a, 62b, and 62c each face the outer surface 32a of the shaft 32.

[0048] The diameter of the inner circumferential surface 62a is smaller than the diameter of the inner circumferential surface 62b and also smaller than the diameter of the inner circumferential surface 62c. Furthermore, the diameter of the inner circumferential surface 62a is larger than the diameter of the outer circumferential surface 32a of the shaft 32. For this reason, the inner circumferential surface 62a is spaced apart from the shaft 32. However, the inner circumferential surface 62a may temporarily come into contact with the shaft 32 due to vibrations of the vehicle 1, for example.

[0049] The inner circumferential surface 62a is located in the axial direction between the two inner circumferential surfaces 62b and 62c. The side surface 62d extends radially between the end of the inner circumferential surface 62a in the inward direction Di and the end of the inner circumferential surface 62b in the outward direction Do, and faces inward direction Di. The side surface 62e extends radially between the end of the inner circumferential surface 62a in the outward direction Do and the end of the inner circumferential surface 62c in the inward direction Di, and faces outward direction Do.

[0050] The plug 37 is further provided with a groove 65 and a passage 66. The groove 65 is provided on the outer circumferential surface 37a of the plug 37 and extends in the circumferential direction. The ring seal 44 is fitted into the groove 65. The ring seal 44 contacts the inner circumferential surface 55a of the housing 35, thereby sealing the gap between the inner circumferential surface 55a of the housing 35 and the outer circumferential surface 37a of the plug 37.

[0051] The passage 66 has a first end 66a and a second end 66b. The first end 66a opens to the outer circumferential surface 37a. The second end 66b opens to the inner surface 62i, for example, the inner circumferential surface 62a and the side surface 62e. In other words, a part of the passage 66 is a notch opening to the side surface 62e. Note that the passage 66 is not limited to this example.

[0052] The first end 66a opens, for example, to the upper end of the outer circumferential surface 37a. The second end 66b opens, for example, to the upper end of the inner circumferential surface 62a. The passage 66 extends upward from the upper end of the inner circumferential surface 62a toward the upper end of the outer circumferential surface 37a. Note that the passage 66 is not limited to this example.

[0053] The stopper 38 is formed in a substantially annular shape that extends in the circumferential direction. The stopper 38 is attached to the housing 35 by fitting, for example, a male screw provided on the stopper 38 with a female screw provided on the inner circumferential surface 55a of the housing 35. The stopper 38 holds the cylinder 36 and the plug 37 in the housing 35 by contacting the support surface 37b of the plug 37.

[0054] The seal shaft 45 and the oil seal 46 each seal the gap G between the outer circumferential surface 32a of the shaft 32 and the inner surface 62i of the plug 37. The seal shaft 45 and the oil seal 46 are spaced apart from each other in the axial direction. Therefore, the gap G has an intermediate chamber RI, a fluid chamber RF, and an atmospheric chamber RA, which are partitioned by the seal shaft 45 and the oil seal 46.

[0055] The intermediate chamber RI is located between the seal shaft 45 and the oil seal 46. The intermediate chamber RI includes the space between at least the outer circumferential surface 32a of the shaft 32 and the inner circumferential surface 62a of the plug 37 within the gap G. Therefore, the intermediate chamber RI communicates with the second end 66b of the passage 66. The first end 66a of the passage 66 is located above the entirety of the intermediate chamber RI.

[0056] The seal shaft 45 is closer to the inner gears 51 of the first gear pump 25 and the second gear pump 26 than the second end 66b of the passage 66. The oil seal 46 is further from the inner gears 51 of the first gear pump 25 and the second gear pump 26 than the second end 66b of the passage 66. The seal shaft 45 and the oil seal 46 do not cover the second end 66b. However, the second end 66b may be partially covered by the seal shaft 45 and the oil seal 46.

[0057] The fluid chamber RF is spaced inward (Di) from the intermediate chamber RI. The fluid chamber RF communicates with the first pump chamber RP1. Therefore, the fluid chamber RF is filled with fluid during the operation of the gear pump device 23. Note that the fluid chamber RF is not limited to this example.

[0058] The atmospheric chamber RA is spaced outward (Do) from the intermediate chamber RI. The atmospheric chamber RA communicates with the outside of the gear pump device 23. The atmospheric chamber RA is basically filled with air. Note that the atmospheric chamber RA is not limited to this example.

[0059] The seal shaft 45 is located between the intermediate chamber RI and the fluid chamber RF, and separates the intermediate chamber RI from the fluid chamber RF. The seal shaft 45 is also located between the outer circumferential surface 32a of the shaft 32 and the inner circumferential surface 62b of the plug 37. The seal shaft 45 has, for example, a holder 71 and a cup 72.

[0060] The holder 71 is made of, for example, synthetic resin and is formed in a substantially annular shape that extends circumferentially. The shaft 32 extends through the inside of the holder 71. The holder 71 is spaced apart from the inner circumferential surface 62b of the plug 37.

[0061] A recess 75 is provided in the holder 71. The recess 75 is recessed from the radially outer end of the holder 71 and extends in the circumferential direction. The cup 72 is fitted into the recess 75.

[0062] The cup 72 is made of an elastomer such as synthetic rubber and is formed in a substantially annular shape that extends circumferentially. The cup 72 has a base 76, an inner lip 77, and an outer lip 78.

[0063] The base 76 is supported by the holder 71 so as to restrict its movement in the outward direction Do. The base 76 also abuts against the inner circumferential surface 62b of the plug 37. A groove 79 is provided at the radially outer end of the base 76. The groove 79 extends, for example, in the axial direction.

[0064] The inner lip 77 protrudes inward Di from the base 76 along the holder 71. The inner lip 77 is supported by the holder 71 so as to restrict its radial inward movement. The base 76 and inner lip 77 of the cup 72 press the holder 71 against the outer circumferential surface 32a of the shaft 32, for example by elastic force. This causes the holder 71 to contact the outer circumferential surface 32a of the shaft 32.

[0065] The outer lip 78 protrudes obliquely from the base 76 between the radially outward and inward directions Di. The outer lip 78 is spaced radially outward from the inner lip 77. The outer lip 78 is elastically deformed and contacts the inner circumferential surface 62b of the plug 37. That is, the cup 72 presses the outer lip 78 against the inner circumferential surface 62b by elastic force.

[0066] The pressure in the fluid chamber RF expands the gap between the inner lip 77 and the outer lip 78. This causes the inner lip 77 to press the holder 71 against the outer surface 32a of the shaft 32, and the outer lip 78 to press against the inner surface 62b of the plug 37. Therefore, as the pressure in the fluid chamber RF and the first pump chamber RP1 increases, the sealing performance of the seal shaft 45 improves.

[0067] The oil seal 46 is located between the intermediate chamber RI and the atmospheric chamber RA, and separates the intermediate chamber RI from the atmospheric chamber RA. The oil seal 46 is also located between the outer circumferential surface 32a of the shaft 32 and the inner circumferential surface 62c of the plug 37. The oil seal 46 includes, for example, a frame 81, an elastic member 82, and a spring 83.

[0068] The frame 81 is made of, for example, metal and is formed in a substantially annular shape that extends circumferentially. The frame 81 has a substantially L-shaped cross-section and has an outer wall 85 and side walls 86. The outer wall 85 is formed in a substantially cylindrical shape that extends along the central axis Ax. The outer wall 85 contacts, for example, the inner circumferential surface 62c of the plug 37. The side walls 86 extend radially inward from the end of the outer wall 85 in the inward direction Di. The side walls 86 are spaced apart from the shaft 32.

[0069] The elastic member 82 is made of an elastomer such as rubber and is formed in a substantially annular shape that extends in the circumferential direction. The elastic member 82 has a base 87 and a lip 88. The base 87 is formed integrally with the side wall 86 of the frame 81, for example by insert molding. In this way, the frame 81 reinforces the base 87. The base 87 is located between the side wall 86 and the side surface 62e of the plug 37. The base 87 abuts against the inner circumferential surface 62c of the plug 37.

[0070] The lip 88 protrudes diagonally downward from the end of the base 87 on the radially inward side, between the radially inward side and the outward direction Do. The lip 88 abuts against the outer circumferential surface 32a of the shaft 32.

[0071] The spring 83 surrounds the lip 88. The oil seal 46 presses the lip 88 against the outer surface 32a of the shaft 32 due to the elastic force of the lip 88 and the elastic force of the spring 83.

[0072] The plug 47 is made of an elastomer, such as synthetic rubber. Alternatively, the plug 47 may be made of a rigid material such as metal, or another material. The plug 47 is fitted into the passage 66 of the plug 37. The plug 47 is located between the first end 66a and the second end 66b of the passage 66, sealing the passage 66.

[0073] The plug 47 is formed, for example, in a roughly cylindrical shape extending radially. In its natural state, when no external force acts on the plug 47, the diameter of the plug 47 is larger than the diameter of the passage 66. That is, the plug 47 is compressed and fitted into the passage 66, and pushes the plug 37 by elastic force. In this way, the plug 47 can reliably seal the passage 66. The plug 47 may be formed in other shapes.

[0074] The plug 47 is located near the first end 66a of the passage 66. The plug 47 is supported by the inner circumferential surface 55a of the housing 35. That is, the inner circumferential surface 55a of the housing 35 restricts the plug 47 from exiting the passage 66 radially outward.

[0075] In this embodiment, the intermediate chamber RI and the passage 66 are filled with fluid F. Figure 3 shows the fluid F in the intermediate chamber RI with hatching, but omits the fluid in the fluid chamber RF.

[0076] The fluid F in the intermediate chamber RI penetrates, for example, into the minute gap between the outer circumferential surface 32a of the shaft 32 and the holder 71 of the seal shaft 45. Furthermore, the fluid F in the intermediate chamber RI penetrates into the minute gap between the inner circumferential surface 62b of the plug 37 and the cup 72 of the seal shaft 45. This improves the sealing and sliding properties of the seal shaft 45. In other words, the fluid F lubricates the shaft 32 and the seal shaft 45.

[0077] The fluid F in the intermediate chamber RI penetrates, for example, into the minute gap between the outer surface 32a of the shaft 32 and the lip 88 of the oil seal 46. This improves the sealing and sliding properties of the oil seal 46. In other words, the fluid F lubricates the shaft 32 and the oil seal 46.

[0078] As the shaft 32 rotates around its central axis Ax relative to the housing 35, fluid may flow from the fluid chamber RF into the intermediate chamber RI through a small gap between the outer circumferential surface 32a of the shaft 32 and the seal shaft 45. The pressure in the intermediate chamber RI may increase due to the fluid flowing in from the fluid chamber RF.

[0079] When the pressure in the intermediate chamber RI exceeds a predetermined pressure (deformation pressure), the plug 47 undergoes elastic deformation due to this pressure. This mitigates the pressure increase in the intermediate chamber RI and the passage 66 compared to when the plug 47 does not deform. The deformation pressure is an example of a third threshold.

[0080] When the pressure in the intermediate chamber RI rises further and exceeds a predetermined pressure (relief pressure), this pressure causes the outer lip 78 of the seal shaft 45 to separate from the inner circumferential surface 62b of the plug 37. As a result, the fluid F in the intermediate chamber RI flows through the groove 79 of the cup 72 and over the outer lip 78 into the fluid chamber RF. In other words, the seal shaft 45 connects the intermediate chamber RI to the outside of the intermediate chamber RI (fluid chamber RF) when the pressure in the intermediate chamber RI exceeds the relief pressure. This relief pressure related to the seal shaft 45 is an example of a first threshold.

[0081] The deformation pressure is lower than the relief pressure. Therefore, before the seal shaft 45 connects the intermediate chamber RI to the fluid chamber RF, the plug 47 elastically deforms, mitigating the pressure rise in the intermediate chamber RI. In other words, the plug 47 can delay the opening of the seal shaft 45.

[0082] The deformation pressure is determined, for example, by the stress-strain properties of the plug 47. On the other hand, the relief pressure is determined, for example, by the difference between the pressure in the intermediate chamber RI and the pressure in the fluid chamber RF. For example, the relief pressure is the pressure in the fluid chamber RF.

[0083] Even when the pressure in the intermediate chamber RI reaches the relief pressure, the lip 88 of the oil seal 46 continues to contact the outer circumferential surface 32a of the shaft 32. In other words, the oil seal 46 maintains its sealing performance and can suppress the leakage of fluid F to the outside of the gear pump device 23. Furthermore, when the pressure in the intermediate chamber RI exceeds a predetermined threshold (second threshold) that is higher than the relief pressure (first threshold), the oil seal 46 is configured to connect the intermediate chamber RI with the outside of the gear pump device 23 via the outside of the intermediate chamber RI in the gap G.

[0084] The relief pressure decreases due to the aging of the cup 72 of the seal shaft 45. In other words, the relief pressure is relatively high before the gear pump device 23 starts operation. However, the plug 47 can alleviate the pressure acting on the oil seal 46 even when the relief pressure is high by mitigating the rise in pressure in the intermediate chamber RI. Note that the relief pressure and deformation pressure are not limited to the above examples.

[0085] The following is an example of a part of the manufacturing method of the gear pump device 23. Note that the manufacturing method of the gear pump device 23 is not limited to the method described below, and other methods may be used. First, bearings 33 and 34, a cylinder 36, a plug 37, an intermediate seal 41, seal structures 42 and 43, a seal shaft 45, and an oil seal 46 are attached to the shaft 32.

[0086] Next, fluid F is supplied from outside the plug 37 to the passage 66 and the intermediate chamber RI. That is, fluid F is injected into the passage 66. Fluid F flows through the passage 66 and fills the intermediate chamber RI. Furthermore, fluid F fills the passage 66.

[0087] Next, a plug 47 is inserted into the passage 66. This plug 47 seals the passage 66, preventing the fluid F in the intermediate chamber RI and passage 66 from being discharged from the first end 66a of the passage 66. The plug 47 is located radially inward from the outer circumferential surface 37a of the plug 37. On the other hand, a portion of the ring seal 44 protrudes radially outward from the outer circumferential surface 37a of the plug 37.

[0088] Next, the shaft 32, bearings 33, 34, cylinder 36, plug 37, intermediate seal 41, seal structures 42, 43, seal shaft 45, and oil seal 46 are inserted into the housing hole 55 of the housing 35. This causes the inner circumferential surface 55a of the housing 35 to cover the first end 66a of the passage 66.

[0089] When the plug 37 is inserted into the housing hole 55, the ring seal 44 comes into contact with the inner circumferential surface 55a of the housing 35. On the other hand, since the plug 47 does not protrude from the outer circumferential surface 37a of the plug 37, interference with the housing 35 can be suppressed.

[0090] Next, the stopper 38 is attached to the housing 35, holding the cylinder 36 and plug 37 in the housing 35. With this, the manufacturing of the gear pump device 23 is completed. Even before the gear pump device 23 starts operation, the fluid F in the intermediate chamber RI lubricates the shaft 32 and seal shaft 45, and also lubricates the shaft 32 and oil seal 46.

[0091] In the gear pump device 23 according to the first embodiment described above, the gear pump device 23 comprises an inner gear 51, a housing 35, a shaft 32, a plug 37, a seal shaft 45, an oil seal 46, and a stopper 47. The inner gear 51 is rotatable about a central axis Ax. The housing 35 has an inner circumferential surface 55a facing the central axis Ax and houses the inner gear 51. The shaft 32 extends along the central axis Ax and has an outer circumferential surface 32a facing the inner circumferential surface 55a, and is connected to the inner gear 51. It is configured to rotate together with the inner gear 51 about the central axis Ax relative to the housing 35, thereby transporting fluid to the inner gear 51. The plug 37 has an outer circumferential surface 37a facing the inner circumferential surface 55a and an inner surface 62i located on the opposite side of the outer circumferential surface 37a. The plug 37 is provided with a passage 66 into which fluid F can be injected. The first end 66a of the passage 66 opens to the outer circumferential surface 37a, and the second end 66b of the passage 66 opens to the inner surface 62i. The seal shaft 45 seals the gap G between the outer circumferential surface 32a and the inner surface 62i, and is closer to the inner gear 51 than the second end 66b. The oil seal 46 seals the gap G, and is further from the inner gear 51 than the second end 66b. The plug 47 seals the passage 66 between the first end 66a and the second end 66b.

[0092] Before the plug 47 seals the passage 66, the second end 66b of the passage 66 communicates with the space between the seal shaft 45 and the oil seal 46 (intermediate chamber RI) in the gap G. Therefore, before the plug 37 is assembled inside the inner circumferential surface 55a of the housing 35, fluid F can be supplied from outside the plug 37 to the intermediate chamber RI through the passage 66. The fluid F enters the minute gap between the outer circumferential surface 32a of the shaft 32 and the oil seal 46 from the intermediate chamber RI, thereby lubricating the shaft 32 and the oil seal 46 as they rotate around the central axis Ax. As a result, the gear pump device 23 does not need expensive lubricants such as fluorine grease to lubricate the shaft 32 and the oil seal 46, and thus costs can be reduced. Furthermore, after the plug 37 is assembled inside the inner circumferential surface 55a of the housing 35, the inner circumferential surface 55a of the housing 35 closes the first end 66a of the passage 66. Therefore, the inner circumferential surface 55a of the housing 35 can prevent the plug 47 from coming out of the passage 66. In other words, the gear pump device 23 does not require a large seal, such as an annular seal extending around the central axis Ax, and the plug 37 can be made smaller.

[0093] The plug 47 is made of elastomer. Therefore, the plug 47 can be elastically deformed by the pressure in the intermediate chamber RI. By elastically deforming, the plug 47 can mitigate the increase in pressure in the intermediate chamber RI. Thus, the gear pump device 23 can prevent fluid F from leaking to the outside through the oil seal 46 due to an increase in pressure in the intermediate chamber RI. Note that the plug 47 made of elastomer may be less securely fixed to the plug 37 compared to a metal plug that seals the passage 66 by press-fitting, for example. However, the plug 47 is supported by the inner circumferential surface 55a of the housing 35 at the first end 66a of the passage 66. Thus, the gear pump device 23 can prevent the plug 47 from coming out of the passage 66.

[0094] The gap G is located between the seal shaft 45 and the oil seal 46 and has an intermediate chamber RI that communicates with the second end 66b. The seal shaft 45 is configured to seal the gap G when the pressure in the intermediate chamber RI is less than or equal to the relief pressure (first threshold) and to communicate the intermediate chamber RI with the outside of the intermediate chamber RI in the gap G when the pressure in the intermediate chamber RI exceeds the relief pressure (first threshold). The oil seal 46 is configured to seal the gap G when the pressure in the intermediate chamber RI is less than or equal to a predetermined threshold (second threshold) that is the same as or higher than the relief pressure and to communicate the intermediate chamber RI with the outside of the intermediate chamber RI in the gap G when the pressure in the intermediate chamber RI exceeds the threshold (second threshold). The plug 47 is configured to elastically deform when the pressure in the intermediate chamber RI exceeds a deformation pressure that is lower than the relief pressure. That is, the plug 47 elastically deforms before the seal shaft 45 communicates the intermediate chamber RI with the outside. As a result, the plug 47 elastically deforms until the seal shaft 45 connects the intermediate chamber RI to the outside, thereby mitigating the rise in pressure in the intermediate chamber RI. Therefore, the gear pump device 23 can prevent fluid F from leaking out of the gear pump device 23 through the oil seal 46 due to the rise in pressure in the intermediate chamber RI.

[0095] The first end 66a is located above the entire intermediate chamber RI. Therefore, when the gear pump device 23 supplies fluid F to the intermediate chamber RI through the passage 66, it can prevent the fluid F from leaking out of the first end 66a of the passage 66 due to gravity before it fills the intermediate chamber RI to the top. In other words, the gear pump device 23 can easily fill the intermediate chamber RI and the passage 66 with fluid F.

[0096] (Second embodiment) A second embodiment will be described below with reference to Figure 4. In the following descriptions of multiple embodiments, components having the same function as those already described will be denoted by the same reference numerals as those previously described, and their descriptions may be omitted. Furthermore, multiple components denoted by the same reference numerals do not necessarily share all functions and properties, and may have different functions and properties depending on the embodiment.

[0097] Figure 4 is a cross-sectional view showing a part of the gear pump device 23 according to the second embodiment. As shown in Figure 4, in the second embodiment, the intermediate chamber RI and a part of the passage 66 contain fluid F. On the other hand, the other part of the passage 66 contains air A between the plug 47 and the fluid F in the intermediate chamber RI.

[0098] When the pressure in the intermediate chamber RI increases, the plug 47 undergoes elastic deformation, and the air A located between the plug 47 and the fluid F in the passage 66 is compressed. This mitigates the pressure increase in the intermediate chamber RI and the passage 66.

[0099] In the second embodiment, the stopper 47 may be a rigid body. Even in this case, the air A located between the stopper 47 and the fluid F in the passage 66 is compressed, which mitigates the pressure rise in the intermediate chamber RI and the passage 66.

[0100] In the gear pump device 23 of the second embodiment described above, the intermediate chamber RI contains fluid F. The passage 66 contains air A between the plug 47 and the fluid F in the intermediate chamber RI. When the pressure in the intermediate chamber RI rises, the air A between the plug 47 and the fluid F in the intermediate chamber RI is compressed. This allows the gear pump device 23 to mitigate the rise in pressure in the intermediate chamber RI like an air damper. Furthermore, because the first end 66a is located above the entirety of the intermediate chamber RI, the gear pump device 23 can easily leave air A between the plug 47 and the fluid F in the intermediate chamber RI.

[0101] (Third embodiment) A third embodiment will be described below with reference to Figure 5. Figure 5 is a cross-sectional view showing a part of the gear pump device 23 according to the third embodiment. As shown in Figure 5, the gear pump device 23 of the third embodiment has a plug 100 instead of a plug 47. The plug 100 is substantially equivalent to the plug 47, except as described below.

[0102] The plug 100 has a base portion 101 and a tapered portion 102. The base portion 101 is formed in a substantially cylindrical shape, similar to the plug 47 of the first embodiment. The tapered portion 102 protrudes from the base portion 101 toward the second end 66b of the passage 66.

[0103] The tapered portion 102 narrows towards the second end 66b of the passage 66. For example, the tapered portion 102 is formed in a conical shape that narrows towards the second end 66b. The tapered portion 102 may also be formed in other shapes, such as a triangular pyramid.

[0104] When the stopper 100 is inserted into the passage 66, the air and fluid F in the passage 66 flow along the outer surface of the tapered portion 102 and are discharged from the passage 66. In other words, the stopper 100 of the third embodiment suppresses the retention of air in the passage 66 and can be easily inserted into the passage 66.

[0105] In each of the above embodiments, the pressure relationship of the intermediate chamber RI when the seal shaft 45 and the oil seal 46 communicate the intermediate chamber RI with the outside of the intermediate chamber RI in the gap G is such that the pressure related to the oil seal 46 is set higher than the pressure related to the seal shaft 45, but this is not limited to this. For example, the pressure related to the oil seal 46 may be set to be equal to or lower than the pressure related to the seal shaft 45. In this case, the pressure related to the oil seal 46 corresponds to the relief pressure (first threshold) of the intermediate chamber RI, and the pressure related to the seal shaft 45 may correspond to a predetermined threshold (second threshold) that is higher than or equal to the above relief pressure (first threshold).

[0106] A rotary pump according to at least one embodiment described above, as an example, comprises: a rotating body rotatable about a rotation axis; a housing having an inner circumferential surface facing the rotation axis and housing the rotating body; a shaft extending along the rotation axis and having a first outer circumferential surface facing the inner circumferential surface, connected to the rotating body and configured to transport fluid to the rotating body by rotating together with the rotating body about the rotation axis relative to the housing; a plug having a passage into which the fluid can be injected, with the first end of the passage opening to the second outer circumferential surface and the second end of the passage opening to the inner surface; a first seal sealing the gap between the first outer circumferential surface and the inner surface and closer to the rotating body than the second end; a second seal sealing the gap and further from the rotating body than the second end; and a third seal sealing the passage between the first end and the second end. Therefore, for example, before the third seal seals the passage, the second end of the passage communicates with the space between the first seal and the second seal (intermediate chamber) in the gap. As a result, before the plug is assembled inside the inner surface of the housing, fluid can be supplied from outside the plug to the intermediate chamber through the passage. The fluid enters the minute gap between the first outer surface of the shaft and the second seal from the intermediate chamber, lubricating the shaft and the second seal as they rotate around the axis of rotation. As a result, the rotary pump does not require a lubricant other than the fluid to lubricate the shaft and the second seal, thereby reducing costs. Furthermore, after the plug is assembled inside the inner surface of the housing, the inner surface of the housing closes the first end of the passage. As a result, the inner surface of the housing prevents the third seal from coming out of the passage. In other words, the rotary pump does not require a large seal, such as an annular seal extending around the axis of rotation, and the plug can be made smaller.

[0107] In the rotary pump described above, for example, the third seal is made of elastomer. Therefore, for example, the third seal can be elastically deformed by the pressure in the space (intermediate chamber) between the first seal and the second seal. By elastically deforming, the third seal can mitigate the rise in pressure in the intermediate chamber. Thus, the rotary pump can prevent fluid from leaking to the outside through the second seal due to a rise in pressure in the intermediate chamber. Note that the third seal made of elastomer may be less securely fixed to the plug compared to, for example, a metal plug that seals the passage by press-fitting. However, the third seal is supported by the inner circumferential surface of the housing at the first end of the passage. Thus, the rotary pump can prevent the third seal from coming out of the passage.

[0108] In the rotary pump described above, as an example, the gap has an intermediate chamber located between the first seal and the second seal and communicating with the second end, and one of the first seal and the second seal is configured to seal the gap when the pressure in the intermediate chamber is below a first threshold and to communicate the intermediate chamber to the outside of the intermediate chamber in the gap when the pressure in the intermediate chamber exceeds the first threshold, and the other of the first seal and the second seal is configured to seal the gap when the pressure in the intermediate chamber is below a second threshold that is the same as or higher than the first threshold and to communicate the intermediate chamber to the outside of the intermediate chamber in the gap when the pressure in the intermediate chamber exceeds the second threshold, and the third seal is configured to elastically deform when the pressure in the intermediate chamber exceeds a third threshold that is lower than the first threshold. Therefore, as an example, the third seal elastically deforms before one of the first seal and the second seal communicates the intermediate chamber to the outside. As a result, the third seal can mitigate the pressure rise in the intermediate chamber by elastically deforming until either the first or second seal opens the intermediate chamber to the outside. Therefore, the rotary pump can prevent fluid from leaking out through the second seal due to the pressure rise in the intermediate chamber.

[0109] In the rotary pump described above, for example, the gap has an intermediate chamber located between the first seal and the second seal and communicating with the second end, and the first end is located above the entirety of the intermediate chamber. Therefore, for example, when fluid is supplied to the intermediate chamber through the passage, the rotary pump can prevent the fluid from leaking out from the first end of the passage due to gravity before the fluid fills the intermediate chamber to the upper end. In other words, the rotary pump can easily fill the intermediate chamber and passage with fluid.

[0110] In the rotary pump described above, for example, the intermediate chamber contains the fluid, and the passage contains air between the third seal and the fluid in the intermediate chamber. Therefore, for example, when the pressure in the intermediate chamber rises, the air between the third seal and the fluid in the intermediate chamber is compressed. This allows the rotary pump to mitigate the rise in pressure in the intermediate chamber, like an air damper. Also, because the first end is located above the entirety of the intermediate chamber, the rotary pump can easily leave air between the third seal and the fluid in the intermediate chamber.

[0111] 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. [Explanation of symbols]

[0112] 23...Gear pump device (rotary pump), 32...Shaft, 32a...Outer surface (first outer surface), 35...Housing, 37...Plug, 37a...Outer surface (second outer surface), 45...Seal shaft (first seal), 46...Oil seal (second seal), 47,100...Plug (third seal), 51...Inner gear (rotating body), 62i...Inner surface, 66...Passage, 66a...First end, 66b...Second end, Ax...Central axis (rotating axis), G...Gap, RI...Intermediate chamber, F...Fluid, A...Air.

Claims

1. A rotating body that can rotate around its axis of rotation, A housing having an inner circumferential surface facing the rotation axis and housing the rotating body, A shaft extending along the rotation axis and having a first outer surface facing the inner surface, connected to the rotating body, and configured to rotate together with the rotating body around the rotation axis relative to the housing to transport fluid to the rotating body, A plug having a second outer surface facing the inner surface and an inner surface located opposite the second outer surface, with a passage into which the fluid can be injected, the first end of the passage opening to the second outer surface and the second end of the passage opening to the inner surface, The gap between the first outer surface and the inner surface is sealed, and the first seal is closer to the rotating body than the second end, A second seal that seals the gap and is further from the rotating body than the second end, A third seal that seals the passage between the first end and the second end, A rotary pump equipped with the following features.

2. The third seal is made of elastomer. A rotary pump according to claim 1.

3. The gap is located between the first seal and the second seal and has an intermediate chamber that communicates with the second end. One of the first seal and the second seal is configured to seal the gap when the pressure in the intermediate chamber is below a first threshold, and to communicate the intermediate chamber with the outside of the gap when the pressure in the intermediate chamber exceeds the first threshold. The other of the first seal and the second seal is configured to seal the gap when the pressure in the intermediate chamber is equal to or less than a second threshold that is higher than the first threshold, and to communicate the intermediate chamber with the outside of the gap when the pressure in the intermediate chamber exceeds the second threshold. The third seal is configured to elastically deform when the pressure in the intermediate chamber exceeds a third threshold that is lower than the first threshold. A rotary pump according to claim 2.

4. The gap is located between the first seal and the second seal and has an intermediate chamber that communicates with the second end. The first end is located above the entirety of the intermediate chamber. A rotary pump according to claim 1.

5. The intermediate chamber contains the fluid, The passage contains air between the third seal and the fluid in the intermediate chamber. A rotary pump according to claim 4.

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