Internal gear pump

Abstract

To provide an internal gear pump which can suppress an increase of drive torque for rotationally driving a gear while suppressing reduction of volume efficiency by reducing leakage from a discharge port to a suction port.SOLUTION: In both gears 5, 6, recesses 5C, 6C are formed by recessing axial one-end faces in an axial direction. In the recesses 5C, 6C, a plurality of beams 5G, 6G are formed with clearances in a circumferential direction. Radially outer ends of the beams 5G, 6G are connected to external peripheral sides of both the gears 5, 6, and radially inner ends are connected to internal peripheral sides of both the gears 5, 6. In the beams 5G, 6G, intersections 5I, 6I at which the axial one-end faces and side faces 5H, 6H of both the gears 5, 6 intersect at a front side in a rotation direction A are formed in circular arc shapes.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an internal gear pump that houses an external gear eccentrically inside a ring-shaped internal gear and rotates both gears to suck in and discharge liquid. [Background technology]

[0002] This type of internal gear pump houses an external gear eccentrically inside a ring-shaped internal gear, and the rotation of both gears draws in liquid through a suction port and discharges it through a discharge port. The external gear has annular recesses on both ends in the axial direction, making it lightweight. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-122548 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in such conventional internal gear pumps, the outer edges of the recesses are sealed to prevent communication between the arc-shaped suction and discharge ports in the pump housing. Because the outer edges are thin, the seal between the ports and the recesses is unsatisfactory, increasing leakage from the discharge port to the suction port via the recesses and potentially reducing volumetric efficiency. To address this issue, the applicant developed an invention disclosed in Japanese Patent Application No. 2020-208197, in which one axial end face of each gear is recessed to form a recess, and multiple beams are formed in the recess with gaps in the circumferential direction to reduce leakage from the discharge port to the suction port. However, the pressure from the discharge port acts on the flat axial end face of each gear, which faces the axial end face with the recesses, while an intermediate pressure lower than the pressure from the discharge port but higher than the pressure from the suction port acts on the axial end face. This causes the gears to be pressed against the one axial end face and pressed against the pump housing, potentially increasing the drive torque that rotates the gears.

[0005] An object of the present invention is to provide an internal gear pump that can reduce leakage from the discharge port to the suction port, thereby suppressing a decrease in volumetric efficiency, while suppressing an increase in the drive torque that rotates the gears. [Means for solving the problem]

[0006] In order to achieve this object, the present invention takes the following measures: A ring-shaped internal gear having internal teeth is rotatably accommodated in an accommodation hole of the pump housing, and an external gear having external teeth that internally mesh with the internal teeth of the internal gear is accommodated eccentrically inside the internal gear, and an intake area space is formed between both gears, communicating with an intake port that draws in liquid in an area where the meshing gap between both teeth increases as both gears rotate, and a discharge area space is formed between both gears, communicating with a discharge port that discharges liquid in an area where the meshing gap between both teeth decreases as both gears rotate, and a pump chamber is defined by the internal teeth of the internal gear and the external teeth of the external gear, and the pump chamber increases in volume in the intake area space as both gears rotate, drawing in liquid from the intake port, and decreases in volume in the discharge area space, discharging liquid to the discharge port, and one axial end face of both gears is recessed in the axial direction to form a recess. and the other axial end face opposite to the one axial end face is formed flat, and an intake port and a discharge port are opened on the other face of the pump housing with which the other axial end faces of both gears slide.This internal gear pump is characterized in that multiple beams are formed in the recess with gaps in the circumferential direction, and each beam has its radial outer end connected to the outer periphery of both gears and its radial inner end connected to the inner periphery of both gears, and the intersection of one axial end face of each beam and the front side face in the rotational direction of both gears is formed in an arc shape.

[0007] In this case, the intersecting portions of the beams of the two gears may be formed in a chamfered shape instead of the arc shape. [Effects of the Invention]

[0008] As described above in detail, in the invention described in claim 1, each gear has one axial end face recessed in the axial direction to form a recess, and multiple beams are formed in the recess with gaps in the circumferential direction, and each beam has a radially outer end connected to the outer periphery of each gear and a radially inner end connected to the inner periphery of each gear, and each beam has an arc-shaped intersection where one axial end face intersects with a side face on the front side in the rotational direction of each gear. Therefore, liquid leaking from the discharge port can be prevented from leaking to the suction port by the multiple beams, and liquid can be easily introduced between the axial end faces of each gear and the opposing surface of the pump housing through the arc-shaped intersection of each beam when the gears are rotated. This facilitates liquid introduction, creating a wedge effect on the gears and preventing the gears from being pressed toward their axial end faces. This reduces leakage from the discharge port to the suction port, thereby preventing a decrease in volumetric efficiency and an increase in drive torque for rotating the gears. Furthermore, both gears have flat axial end faces that face the opposite axial end faces, and the suction port and discharge port are opened on the other side of the pump housing where the other axial end faces of both gears slide. As a result, the flat other axial end faces of both gears slide on the other side of the pump housing where the suction port and discharge port are opened, and the suction port and discharge port are not exposed to the recesses formed in the one axial end faces of both gears, which further reduces leakage from the discharge port to the suction port and further suppresses a decrease in volumetric efficiency.

[0009] In the invention described in claim 2, the intersections of the beams of both gears are chamfered instead of arcuate, so that the multiple beams can prevent liquid leaking from the discharge port from leaking into the suction port, and the rotation of both gears can make it easier for liquid to flow between the axial end faces of both gears and the opposing surface of the pump housing through the chamfered intersections of the beams. This facilitates the introduction of liquid, creating a wedge effect on the gears and preventing the gears from being pressed toward their axial end faces. This reduces leakage from the discharge port to the suction port, suppresses a decrease in volumetric efficiency, and suppresses an increase in the drive torque that rotates the gears. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view of an internal gear pump according to an embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged cross-sectional view taken along line AA in FIG. [Figure 3] FIG. 3 is an enlarged cross-sectional view taken along line BB in FIG. 2. [Figure 4] FIG. 4 is an enlarged cross-sectional view corresponding to FIG. 3 showing another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In Figures 1 and 2, reference numeral 1 denotes a pump body 1, which forms a bottomed accommodation hole 2. Reference numeral 3 denotes a cover member attached to the pump body 1 so as to close the opening of the accommodation hole 2. The pump body 1 and cover member 3 are made of metal, and together they form a pump housing 4. Reference numeral 5 denotes a ring-shaped internal gear 5 having seven internal teeth 5A and rotatably housed in the accommodation hole 2. Reference numeral 6 denotes an external gear 6 having six external teeth 6A that internally mesh with the internal teeth 5A and is housed eccentrically inside the internal gear 5. Both gears 5 and 6 are molded from synthetic resin. One axial end face 5B of the internal gear 5 and one axial end face 6B of the external gear 6 are able to slide against the bottom surface of the accommodation hole 2, and this bottom surface forms one surface 4A of the pump housing 4 and is formed flat.

[0012] Each of the gears 5 and 6 has a plurality of recesses 5C, 6C formed by axially recessing one end face 5B, 6B. The recesses 5C of the internal gear 5 are formed in each internal tooth 5A, with seven recesses, the same number as the internal teeth 5A. The outer periphery of each recess 5C has a slightly smaller diameter than the outer periphery of the internal gear 5, and its inner periphery is shaped to follow the internal teeth 5A and is slightly outward of the internal teeth 5A. The axial depth of each recess 5C is slightly smaller than the width of the internal gear 5. The internal gear 5 has an outer peripheral thin-walled portion 5D on the outer periphery of each recess 5C, an inner peripheral thin-walled portion 5E on the inner periphery of each recess 5C, and a bottom thin-walled portion 5F on the bottom of each recess 5C. This gives each recess 5C a slightly smaller planar shape similar to the internal teeth 5A.

[0013] Seven beams 5G are formed in the recesses 5C, and are evenly spaced circumferentially. Each beam 5G extends radially outward from the radial center of the internal gear 5, passing through the circumferential center of each recess 5C. Its radially outer end is connected to the outer peripheral thin-walled portion 5D on the outer periphery of the internal gear 5, and its radially inner end is connected to the tips of the internal teeth 5A in the inner peripheral thin-walled portion 5E on the inner periphery of the internal gear 5. The axial width of each beam 5G is approximately the same as the axial depth of the recesses 5C. As shown in FIG. 3 , each beam 5G has an arc-shaped intersection 5I where one axial end face 5B intersects with a side face 5H on the front side in the rotational direction A of both gears 5, 6.

[0014] Reference numeral 5J denotes a separation wall between two adjacent recessed portions 5C, and seven of these are provided at equal intervals in the circumferential direction of the internal gear 5. Each separation wall 5J has an arc-shaped intersection 5L where one axial end face 5B intersects with a side face 5K on the front side in the rotational direction A of both gears 5, 6. The internal gear 5 has the recessed portions 5C and the separation walls 5J alternately provided at equal intervals in the circumferential direction.

[0015] The recess 6C formed in the external gear 6 is annular, with its outer periphery shaped to follow the external teeth 6A and be slightly smaller than the external teeth 6A. The inner periphery of the recess 6C is larger in diameter than the through-hole 7 that penetrates the axial direction from the radial center. The axial depth of the recess 6C is slightly smaller than the width of the external gear 6. The external gear 6 has a thin-walled outer peripheral portion 6D on the outer periphery of the recess 6C, a boss portion 6E on the inner periphery of the recess 6C, and a thin-walled bottom portion 6F on the bottom of the recess 6C. The through-hole 7 has a substantially two-flat shape in vertical cross section, and a drive shaft 8 with a vertical cross section at its tip that is substantially two-flat is fitted into it. The drive shaft 8 is sealed by a seal member 9 disposed in the pump body 1 and drives the external gear 6 to rotate.

[0016] 6G are beams formed in the recess 6C, and 12 of them are provided at equal intervals in the circumferential direction. Each beam 6G is formed radially outward from the radial center of the external gear 6. Six beams 6G1 have their radial outer ends connected to the tips of the external teeth 6A in the outer peripheral thin-walled portion 6D on the outer periphery of the external gear 6, and six beams 6G2 have their radial outer ends connected to the roots of the external teeth 6A in the outer peripheral thin-walled portion 6D on the outer periphery of the external gear 6. The radial inner ends of each beam 6G1 and 6G2 are connected to the boss portion 6E on the inner periphery of the external gear 6, and the beams 6G1 and 6G2 are arranged alternately in the circumferential direction. The axial width of each beam 6G1 and 6G2 is approximately the same as the axial depth of the recess 6C. The intersection 6I of each beam 6G1, 6G2, where one axial end face 6B intersects with the front side face 6H in the rotation direction A of both gears 5, 6, is formed in an arc shape that is approximately the same shape as the intersection 5I of the beam 5G of the internal gear 5 shown in Figure 3.

[0017] Both gears 5, 6 have flat end faces 5M, 6M opposite one end face 5B, 6B. The other end faces 5M, 6M of both gears 5, 6 slide against the side of the cover member 3 that closes the opening of the accommodation hole 2. This side is the other face 4B of the pump housing 4 and is also flat. S denotes the suction area space, and P denotes the discharge area space, both located between the gears 5, 6. The suction area space S is formed as an area where the meshing gap between the teeth 5A, 6A increases as the gears 5, 6 rotate. The discharge area space P is formed as an area where the meshing gap between the teeth 5A, 6A decreases as the gears 5, 6 rotate. T denotes multiple pump chambers, defined by the internal teeth 5A of the internal gear 5 and the external teeth 6A of the external gear 6. The rotation of the gears 5, 6 increases the volume of the suction area space S and decreases the volume of the discharge area space P.

[0018] Reference numeral 10 denotes an intake port that communicates with the intake area space S, and is opened by forming a semicircular recess on the other surface 4B of the pump housing 4. Reference numeral 11 denotes an intake flow path that connects to the intake port 10, and is formed in the cover member 3, through which the liquid that is drawn in from the low-pressure side flows. Reference numeral 12 denotes a discharge port that communicates with the discharge area space P, and is formed as a semicircular recess on the other surface 4B of the pump housing 4, and is opened at a position radially symmetrical to the intake port 10. Reference numeral 13 denotes a discharge flow path that connects to the discharge port 12, and is formed in the cover member 3, through which the liquid that is discharged to the load side flows.

[0019] In the discharge area space P, each recess 5C introduces a small amount of liquid to be discharged to the discharge port 12 into the interior through the gap between the tip of the inner thin-walled portion 5E and one surface 4A of the pump housing 4, and in the suction area space S, a portion of the liquid inside is guided to the suction port 10 through the gap between the tip of the inner thin-walled portion 5E and one surface 4A of the pump housing 4. Therefore, in the discharge area space P, each recess 5C has an intermediate pressure that is slightly lower than the pressure of the discharge port 12, and in the suction area space S, it has an intermediate pressure that is slightly higher than the pressure of the suction port 10.

[0020] In the discharge area space P, each recess 6C introduces a small amount of liquid to be discharged to the discharge port 12 into the interior through the gap between the tip of the outer circumferential thin portion 6D and one surface 4A of the pump housing 4, and in the suction area space S, a portion of the liquid inside is guided to the suction port 10 through the gap between the tip of the outer circumferential thin portion 6D and one surface 4A of the pump housing 4. Therefore, in the discharge area space P, each recess 6C has an intermediate pressure that is slightly lower than the pressure of the discharge port 12, and in the suction area space S, it has an intermediate pressure that is slightly higher than the pressure of the suction port 10.

[0021] Next, the operation of this configuration will be described. When the external gear 6 is driven to rotate by the drive shaft 8, the internal gear 5 that is in mesh with the external gear 6 is driven to rotate, and liquid flows from the low-pressure side through the intake passage 11, is sucked into the intake area space S through the intake port 10, is transported to the discharge area space P, and is discharged through the discharge passage 13 from the discharge port 12.

[0022] At this time, a small amount of liquid flowing from the discharge area space P through the discharge port 12 is introduced into the recess 5C located in the discharge area space P through the gap between the tip of the inner thin portion 5E of the internal gear 5 and one sliding contact surface 4A of the pump housing 4, and is also introduced into the recess 6C located in the discharge area space P through the gap between the tip of the outer thin portion 6D of the external gear 6 and one sliding contact surface 4A of the pump housing 4. Therefore, the recesses 5C and 6C located in the discharge area space P have an intermediate pressure that is slightly lower than the pressure of the discharge port 12.

[0023] Meanwhile, a small amount of liquid in recess 5C located in suction area space S is guided from suction area space S to suction port 10 through the gap between the tip of inner thin-walled portion 5E and one surface 4A of pump housing 4. A small amount of liquid in recess 6C located in suction area space S is guided to suction port 10 through the gap between the tip of outer thin-walled portion 6D and one surface 4A of pump housing 4. Therefore, recesses 5C and 6C located in suction area space S have an intermediate pressure that is slightly higher than the pressure at suction port 10.

[0024] In addition, liquid is introduced between the axial end faces 5B, 6B of each beam 5G, 6G and one face 4A of the pump housing 4 through the intersections 5I, 6I of each beam 5G, 6G, creating a wedge effect and preventing both gears 5, 6 from being pressed toward the axial end faces 5B, 6B.

[0025] In this operation, the gears 5, 6 have one axial end face 5B, 6B recessed in the axial direction to form recesses 5C, 6C, and the recesses 5C, 6C have gaps in the circumferential direction to form multiple beams 5G, 6G, with the radial outer end of each beam 5G, 6G connected to the outer periphery of the gears 5, 6 and the radial inner end connected to the inner periphery of the gears 5, 6, and each beam 5G, 6G forms an arc-shaped intersection 5I, 6I where the axial end face 5B, 6B intersects with the front side face 5H, 6H in the rotational direction A of the gears 5, 6. Therefore, the multiple beams 5G, 6G can prevent liquid leaking from the discharge port 12 from leaking into the suction port 10, and the rotation of the gears 5, 6 can facilitate liquid introduction between the axial end faces 5B, 6B of the beams 5G, 6G and the surface 4A of the pump housing 4 facing these end faces 5B, 6B through the arc-shaped intersections 5I, 6I of the beams 5G, 6G. This facilitates liquid introduction, creating a wedge effect on the gears 5, 6 and preventing the gears 5, 6 from being pressed toward the axial end faces 5B, 6B. This reduces leakage from the discharge port 12 to the suction port 10, prevents a decrease in volumetric efficiency, and prevents an increase in the drive torque that rotates the gears 5, 6. The strength of the gears 5, 6 can also be improved by the multiple beams 5G, 6G formed in the recesses 5C, 6C.

[0026] Furthermore, both gears 5, 6 have flat end faces 5B, 6B and flat opposite end faces 5M, 6M, and the pump housing 4 has flat one face 4A with which the end faces 5B, 6B of both gears 5, 6 slide, and the suction port 10 and the discharge port 12 are formed on the other face 4B with which the end faces 5M, 6M of both gears 5, 6 slide. Therefore, the flat other end faces 5M, 6M of both gears 5, 6 slide on the other face 4B of the pump housing 4 with the suction port 10 and the discharge port 12 opened therein, so that the suction port 10 and the discharge port 12 are not exposed to the recesses 5C, 6C recessed in the end faces 5B, 6B of both gears 5, 6. This further reduces leakage from the discharge port 12 to the suction port 10 and further suppresses a decrease in volumetric efficiency.

[0027] FIG. 4 shows another embodiment of the present invention, and the same parts as those in the first embodiment are given the same reference numerals and their explanations are omitted, and only the different parts will be explained. An intersection 55I where one axial end face 5B of each beam 5G of the internal gear 5 intersects with the front side face 5H is formed in a chamfered shape. Furthermore, although not shown, the intersection 6I of each beam 6G of the external gear 6 is formed in a chamfered shape having substantially the same shape as the intersection 55I.

[0028] The operation is substantially the same as in the first embodiment, in which the external gear 6 is rotationally driven by the drive shaft 8, and the liquid is sucked in through the suction port 10 and discharged from the discharge port 12.

[0029] In this operation, the intersection 55I of the beams 5G, 6G of both gears 5, 6 is chamfered. Therefore, similar to the first embodiment, a wedge effect is generated in both gears 5, 6, and the gears 5, 6 are prevented from being pressed toward the axial end faces 5B, 6B. This reduces leakage from the discharge port 12 to the suction port 10, suppresses a decrease in volumetric efficiency, and suppresses an increase in the drive torque that rotates the gears 5, 6.

[0030] In the above-described embodiments, the pump housing 4 is composed of the pump body 1 and the cover member 3, but the pump housing may also be composed of three members: a first member that penetrates and forms an accommodation hole that accommodates both gears, a second member that is attached to one side of the first member and against which one end faces of both gears slide, and a third member that is attached to the other side of the first member and against which the other end faces of both gears slide. Furthermore, the through hole 7 that fits the drive shaft 8 that rotates and drives the external gear 6 is formed into a substantially two-face shape in vertical cross section, but it goes without saying that the through hole may be formed into a substantially D-shape or a spline shape in vertical cross section. [Explanation of symbols]

[0031] 2: Storage hole 4: Pump housing 5: Internal gear 5A: Internal teeth 5B, 6B: One end surface 5C, 6C: Recessed 5G, 6G, 6G1, 6G2: Beam 5H, 6H: Side 5I, 6I, 55I: Intersection 6: External gear 6A: External teeth 10: Intake port 12: Discharge port S: Suction area space P:Discharge area space T: Pump room

Claims

1. A ring-shaped internal gear with internal teeth is rotatably housed in an accommodation hole in the pump housing, and an external gear with external teeth that internally mesh with the internal teeth of the internal gear is housed eccentrically inside the internal gear, and an intake area space is formed between the two gears, which communicates with an intake port that draws in liquid in an area where the meshing gap between the teeth increases as the two gears rotate, and a discharge area space is formed between the two gears, which communicates with a discharge port that discharges liquid in an area where the meshing gap between the teeth decreases as the two gears rotate, and a pump chamber is defined by the internal teeth of the internal gear and the external teeth of the external gear, and the pump chamber increases in volume in the intake area space as the two gears rotate, drawing in liquid from the suction port. and a discharge port, wherein the volume of the discharge area space is reduced to discharge the liquid to the discharge port, and one axial end face of each of the gears is recessed in the axial direction to form a recess, and the other axial end face opposite the one axial end face is formed flat, and an intake port and a discharge port are opened on the other side of the pump housing where the other axial end faces of the gears slide against each other, and a plurality of beams are formed in the recess with gaps in the circumferential direction, and each beam has a radial outer end connected to the outer periphery of both gears and a radial inner end connected to the inner periphery of both gears, and the intersection of each beam's one axial end face and the side face on the front side in the rotational direction of both gears is formed in an arc-shaped shape.

2. 2. The internal gear pump according to claim 1, wherein the intersecting portions of the beams of the two gears are formed into chamfered shapes instead of the arc shapes.

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