External gear pump

Abstract

To suppress the generation of erosion.SOLUTION: An external gear pump comprises: a first gear rotationally driven by a drive source; a second gear engaged with the first gear, and driven-rotated; a third gear engaged with the second gear, and driven-rotated; a body having a first inside face part which faces one of side faces of the first gear, the second gear and the third gear; and a cover having a second inside face part which faces the other of the side faces of the first gear, the second gear and the third gear. A suction port into which oil is sucked, and a discharge port from which the oil is discharged are formed at the body. The first gear, the second gear and the third gear are constituted so as to pressure-send the oil from the suction port toward the discharge port by the mutual engagement and rotation, at least either of the first inside face part and the second inside face part has a discharge end edge being an end edge of the discharge port at a bulkhead part for partitioning the suction port and the discharge port, and a notched groove is formed at the discharge end edge.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an external gear pump. [Background technology]

[0002] External gear pumps include a double oil pump in which two pump gears mesh with each other, and a triple oil pump in which three pump gears mesh with each other. Patent Document 1 discloses a double external gear pump. The external gear pump in Patent Document 1 includes side plates arranged on both sides of each pump gear. The side plates have suction side relief portions and discharge side relief portions formed by inclined surfaces that extend in a straight line connecting the rotation axes of the pump gears. Patent Document 1 does not disclose a triple external gear pump. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-113916 A Summary of the Invention [Problem to be solved by the invention]

[0004] In triple-type external gear pumps, it is difficult to ensure a sufficient length in the section where oil is pumped from the suction port to the discharge port. Therefore, when pumping oil, the pressure in the tooth grooves may rise suddenly when the gears are released. In this case, there is a high possibility that so-called cavitation will occur, in which bubbles are generated and disappeared in a short time due to the pressure difference in the oil flow. If cavitation occurs, there is a risk of erosion (mechanical wear) occurring at the bottom of the gear chamber. Therefore, there is room for improvement in suppressing the occurrence of erosion due to cavitation.

[0005] SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide an external gear pump capable of suppressing the occurrence of erosion due to cavitation. [Means for solving the problem]

[0006] An external gear pump according to one embodiment of the present invention comprises a first gear that is rotated by a drive source, a second gear that meshes with the first gear and rotates in a driven manner, a third gear that meshes with the second gear and rotates in a driven manner, a body having a first inner surface portion facing one side of the first gear, the second gear, and the third gear, and a cover having a second inner surface portion facing the other side of the first gear, the second gear, and the third gear, wherein the body is formed with a suction port through which oil is sucked in and a discharge port through which the oil is discharged, and the first gear, the second gear, and the third gear are configured to rotate in a driven manner while meshing with each other, thereby pressurizing the oil from the suction port to the discharge port, and at least one of the first inner surface portion and the second inner surface portion has a discharge edge that becomes the edge of the discharge port at a partition portion separating the suction port and the discharge port, and a notched groove is formed in the discharge edge. Effect of the Invention

[0007] According to the above aspect, it is possible to suppress the occurrence of erosion due to cavitation. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view of an external gear pump according to an embodiment. [Diagram 2] FIG. 2 is an exploded perspective view of the external gear pump according to the embodiment. [Diagram 3] 1 is a perspective view of an engine equipped with an external gear pump according to an embodiment; [Figure 4] FIG. 4 is a perspective view illustrating an oil flow in the external gear pump according to the embodiment. [Diagram 5] FIG. 4 is a perspective view illustrating an oil flow in an internal flow path of the external gear pump according to the embodiment. [Figure 6] 5A and 5B are diagrams illustrating an oil flow in a gear chamber of the external gear pump according to the embodiment. [Figure 7]FIG. 4 is a perspective view illustrating a flow of bearing lubricating oil in the external gear pump according to the embodiment. [Figure 8] FIG. 4 is a perspective view illustrating a flow of lubricating oil for a bearing of a first gear according to the embodiment. [Figure 9] FIG. 4 is a perspective view illustrating a flow of lubricating oil for a bearing of a second gear according to the embodiment. [Figure 10] FIG. 6 is a perspective view illustrating a flow of lubricating oil for a bearing of a third gear according to the embodiment. [Figure 11] 1 is a cross-sectional view of an external gear pump according to an embodiment, taken along a plane including a rotation axis of each pump gear. [Figure 12] FIG. 4 is a view of the body according to the embodiment as seen from the inside in the axial direction. [Figure 13] FIG. 4 is a view of the cover according to the embodiment as viewed from the inside in the axial direction. [Figure 14] 5A and 5B are diagrams showing cutout grooves formed in a body according to the embodiment. [Figure 15] 6A and 6B are diagrams illustrating inner grooves formed in a cover according to an embodiment. [Figure 16] 5A to 5C are diagrams illustrating the outer shape of a cutout groove formed in a body according to the embodiment. [Figure 17] 6 is a diagram illustrating a change in the high-pressure oil pressing area accompanying rotation of the second gear according to the embodiment. FIG. [Figure 18] FIG. 18 is a diagram illustrating the variation in the high-pressure oil pressing area following FIG. 17 . [Figure 19] FIG. 19 is a diagram illustrating the variation in the high-pressure oil pressing area following FIG. 18 . [Figure 20] FIG. 16 is an explanatory diagram of the operation of the external gear pump according to the embodiment, including a cross section taken along line XX-XX in FIG. [Figure 21] FIG. 15 is an explanatory diagram of the operation of the external gear pump according to the embodiment, including a cross section taken along line XXI-XXI of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the embodiment, an external gear pump mounted on a diesel engine (one example of an engine) will be described as an external gear pump.

[0010] In the following description, expressions indicating relative or absolute arrangements, such as "parallel," "orthogonal," "center," and "coaxial," do not only mean such arrangements or states strictly, but also include arrangements or states in which there is a relative displacement with an angle or distance to the extent that the same function can be obtained with a tolerance. In the drawings used in the following description, the scale of each component may be appropriately changed to show each component with a recognizable size.

[0011] <External gear pump> Fig. 1 is a perspective view of an external gear pump 1 according to an embodiment of the present invention. Fig. 2 is an exploded perspective view of the external gear pump 1 according to an embodiment of the present invention. 1 and 2, the external gear pump 1 is a triple oil pump in which three pump gears 10, 20, and 30 mesh with each other. The three pump gears 10, 20, and 30 are composed of a first gear 10, a second gear 20, and a third gear 30. The external gear pump 1 includes the first gear 10 that is driven to rotate by a drive source, a second gear 20 that meshes with the first gear 10 and rotates in a driven manner, a third gear 30 that meshes with the second gear 20 and rotates in a driven manner, a body 40 having a first inner surface portion 41 that faces one side surface of the first gear 10, the second gear 20, and the third gear 30, and a cover 50 having a second inner surface portion 51 that faces the other side surface of the first gear 10, the second gear 20, and the third gear 30. Hereinafter, the first inner side surface portion 41 of the body 40 will also be referred to as the "gear chamber bottom surface," and the second inner side surface portion 51 of the cover 50 will also be referred to as the "cover mounting surface."

[0012] For example, the pump gears 10, 20, 30 may be arranged along a vertical line. For example, the pump gears 10, 20, 30 may be arranged in the order of the first gear 10, the second gear 20, and the third gear 30 from vertically above. For example, the pump gears 10, 20, 30 may be arranged along a horizontal line, without being limited to the above. For example, the first gear 10, which is a drive gear, may be arranged on the center side, without being limited to being arranged on the side side of the oil pump. For example, the arrangement of the pump gears 10, 20, 30 may be changed according to design specifications.

[0013] For example, the pump gears 10, 20, and 30 each have the same shape. For example, the pump gears 10, 20, and 30 are not limited to the above, and may have at least a part of a different shape from each other. For example, the shape of each of the pump gears 10, 20, and 30 can be changed according to design specifications.

[0014] In the illustrated example, the number of teeth of the pump gears 10, 20, 30 is 8. The number of teeth of the pump gears 10, 20, 30 is not limited to the above, and may be 7 or less, or 9 or more. For example, the number of teeth of the pump gears 10, 20, 30 can be changed according to design specifications.

[0015] <Engine> FIG. 3 is a perspective view of an engine 100 equipped with the external gear pump 1 according to the embodiment. 3, the circumscribing gear pump 1 is disposed under a crankcase 101 of an engine 100. A pump drive gear 103 rotates in conjunction with a crankshaft 102 of the engine 100, which is a drive source. The rotational force of the pump drive gear 103 rotates pump gears 10, 20, and 30, which mesh with each other. The rotation of the pump gears 10, 20, and 30 pumps oil from an oil pan 104 located under the crankcase 101. The pumped oil is sucked into an internal flow path 2 of the circumscribing gear pump 1 through a suction port of the circumscribing gear pump 1.

[0016] In this way, the circumscribing gear pump 1 changes the spatial volume of the meshing portion by the rotation of each of the pump gears 10, 20, 30, and draws oil from the oil pan 104 into the internal flow path 2 of the circumscribing gear pump 1. The drawn oil is pumped to the discharge port of the circumscribing gear pump 1 by the rotation of the pump gears 10, 20, 30. The pumped oil is sent to each sliding portion (for example, the sliding portions of the cylinder 105 and piston 106 of the engine 100).

[0017] <Oil flow> Fig. 4 is a perspective view explaining the oil flow in the external gear pump 1 according to the embodiment. Fig. 5 is a perspective view explaining the oil flow in the internal flow passage 2 of the external gear pump 1 according to the embodiment. Fig. 6 is a diagram explaining the oil flow in the gear chamber of the external gear pump 1 according to the embodiment. 4 to 6, suction ports 3A, 3B through which oil is sucked and discharge ports 4A, 4B through which oil is discharged are formed in the body 40. The first gear 10, the second gear 20, and the third gear 30 are configured to rotate while meshing with one another, thereby pressure-feeding the oil from the suction ports 3A, 3B to the discharge ports 4A, 4B.

[0018] For example, oil sucked from the oil pan 104 through the suction ports 3A and 3B is divided and flows toward each pump gear 10, 20, and 30. For example, a part of the divided oil flows from the suction port 3A to the discharge port 4A in the direction of the arrow W1 in FIG. 6 due to the rotation of the first gear 10 in the direction of the arrow R1 in FIG. 6 (clockwise). For example, a part of the divided oil flows from the suction port 3B to the discharge port 4A in the direction of the arrow W2 in FIG. 6 due to the rotation of the second gear 20 in the direction of the arrow R2 in FIG. 6 (counterclockwise), and also flows from the suction port 3A to the discharge port 4B in the direction of the arrow W3 in FIG. 6. For example, a part of the divided oil flows from the suction port 3B to the discharge port 4B in the direction of the arrow W4 in FIG. 6 due to the rotation of the third gear 30 in the direction of the arrow R3 in FIG. 6 (clockwise).

[0019] For example, the oil pumped to each of the discharge ports 4A, 4B joins together and is sent out to the outside of the external gear pump 1. For example, the pumped oil is used for lubrication or cooling of each sliding part. For example, when the oil pressure in the internal flow path 2 of the external gear pump 1 reaches a specified value due to the pumping of the oil, the relief valve 60 opens and the oil is made to flow to a bypass flow path (not shown).

[0020] <Bearing lubricating oil flow> Fig. 7 is a perspective view illustrating the flow of bearing lubricating oil in the external gear pump 1 according to the embodiment. Fig. 8 is a perspective view illustrating the flow of bearing lubricating oil in the first gear 10 according to the embodiment. Fig. 9 is a perspective view illustrating the flow of bearing lubricating oil in the second gear 20 according to the embodiment. Fig. 10 is a perspective view illustrating the flow of bearing lubricating oil in the third gear 30 according to the embodiment. Fig. 11 is a view including a cross section of the external gear pump 1 according to the embodiment cut along a plane including the rotation axes of the pump gears 10, 20, and 30. The bearing lubricating oil flows to lubricate the bearings to prevent seizure of the rotating parts due to the rotation of the pump gears 10, 20, and 30. The bearing lubricating oil flows from the high pressure side to the low pressure side. The bearing lubricating oil flows into the oil groove on the discharge side (high pressure side), flows through the oil groove of the bearing, and flows out to the oil groove on the suction side (low pressure side).

[0021] Referring also to Figures 7 to 11, the external gear pump 1 further includes shafts 11, 21, 31 (first shaft 11, second shaft 21 and third shaft 31) that run along the rotation axes of the pump gears 10, 20, 30, and bearings 13, 23, 33 (first bearing 13, second bearing 23 and third bearing 33) that support the shafts 11, 21, 31 and have oil grooves formed therein.

[0022] The central axes of the three shafts 11, 21, 31 are arranged parallel to each other. For example, the central axes of the shafts 11, 21, 31 may be arranged on the same vertical plane. For example, the shafts 11, 21, 31 may be arranged in the order of the first shaft 11, the second shaft 21, and the third shaft 31 from vertically above. For example, the central axes of the shafts 11, 21, 31 are not limited to the above, and may be arranged on different vertical planes. For example, the central axes of the shafts 11, 21, 31 may be arranged on a horizontal plane. For example, the arrangement of the shafts 11, 21, 31 can be changed according to the design specifications.

[0023] The first shaft 11 extends in the axial direction along the rotation axis of the first gear 10. One end of the first shaft 11 is fixed to the pump drive gear 103. The first shaft 11 is longer in the axial direction than the second shaft 21 and the third shaft 31 by an amount corresponding to the length of the first shaft 11 that is fixed to the pump drive gear 103.

[0024] The first bearing 13 is disposed between the inner peripheral surface of the through hole of the body 40 and the outer peripheral surface of the first shaft 11, and between the inner peripheral surface of the through hole of the cover 50 and the outer peripheral surface of the first shaft 11. The first shaft 11 and the first gear 10 rotate integrally by the rotation of the pump drive gear 103. The first gear 10, the first shaft 11, and the first bearing 13 on the body 40 side are configured to allow oil to flow through the oil groove 12 from the discharge ports 4A, 4B toward the body 40 in the direction of the arrow W11. The first gear 10, the first shaft 11, and the first bearing 13 on the cover 50 side are configured to allow oil to flow through the oil groove 12 from the cover 50 side to the outside of the external gear pump 1 in the direction of the arrow W12.

[0025] The second shaft 21 extends in the axial direction along the rotation axis of the second gear 20. One end of the second shaft 21 is fixed to the body 40. The other end of the second shaft 21 is fixed to the cover 50. The second bearing 23 is disposed between the inner peripheral surface of the second gear 20 and the outer peripheral surface of the second shaft 21. The second gear 20 rotates about the second shaft 21 by meshing with the first gear 10. The second gear 20, the second shaft 21 and the second bearing 23 are configured to allow oil to flow through the oil groove 22 in the direction of arrow W13 from the cover 50 side toward the body 40 side.

[0026] The third shaft 31 extends in the axial direction along the rotation axis of the third gear 30. One end of the third shaft 31 is fixed to the body 40. The other end of the third shaft 31 is fixed to the cover 50. The third bearing 33 is disposed between the inner peripheral surface of the third gear 30 and the outer peripheral surface of the third shaft 31. The third gear 30 is rotated around the third shaft 31 by meshing with the second gear 20. The third gear 30, the third shaft 31 and the third bearing 33 are configured to allow oil to flow through the oil groove 32 in the direction of arrow W14 from the body 40 side toward the cover 50 side.

[0027] In the illustrated example, the bearings 13, 23, and 33 have the same shape. However, the shapes of the bearings 13, 23, and 33 are not limited to those described above and can be changed according to design specifications. In the illustrated example, two bearings 13, 23, and 33 are disposed on each of the shafts 11, 21, and 31. Note that the number of bearings 13, 23, and 33 is not limited to the above, and can be changed according to design specifications. In the illustrated example, the oil grooves 12, 22, and 32 are formed in a spiral shape along the axial direction on the inner or outer circumferential surfaces of the bearings 13, 23, and 33, respectively. Note that the shapes of the oil grooves 12, 22, and 32 are not limited to those described above and can be changed according to design specifications.

[0028] <Notched groove> FIG. 12 is a view of the body 40 according to the embodiment as seen from the inside in the axial direction. FIG. 13 is a view of the cover 50 according to the embodiment as seen from the inside in the axial direction. FIG. 14 is a view showing the notch groove 45 formed in the body 40 according to the embodiment. FIG. 15 is a view showing the inner groove 52 formed in the cover 50 according to the embodiment. FIG. 16 is a view explaining the outer shape of the notch groove 45 formed in the body 40 according to the embodiment. In FIG. 12 and FIG. 13, the arrows W11 to W14 indicate the flow direction of the bearing lubricating oil flowing through the oil groove of the shaft insertion part on the gear chamber bottom surface or the cover mounting surface. In FIG. 14, the area where the second gear 20 and the notch groove 45 overlap as viewed from the axial direction is shown by hatching. In FIG. 15, the formation area of ​​the inner groove 52 as viewed from the axial direction is shown by hatching. In FIG. 16, the formation area of ​​the notch groove 45 as viewed from the axial direction is shown by hatching. 12 to 16, the first inner side surface portion 41 (gear chamber bottom surface) has a partition wall portion 42 that separates the suction ports 3A, 3B from the discharge ports 4A, 4B.

[0029] The partition 42 is formed in a portion separating the suction port 3A on one side and the discharge port 4B on the other side, and in a portion separating the suction port 3B on the other side and the discharge port 4A on the other side, as viewed in the axial direction. The partition 42 is formed in an area overlapping a part of the second gear 20 as viewed in the axial direction. The partition 42 is formed in two areas sandwiching the insertion part of the second shaft 21 as viewed in the axial direction. The partition 42 has a discharge edge 44 which becomes the edge of the discharge ports 4A, 4B. The discharge edge 44 extends along a direction perpendicular to the central axis of the second shaft 21 as viewed in the axial direction. A notched groove 45 is formed in the discharge edge 44.

[0030] 16, when viewed from the axial direction along the rotation axis of the second gear 20, a part of the notched groove 45 is disposed on the inner peripheral side of the bottom circle Dc of the second gear 20. The bottom circle Dc means a circle that passes through the roots of the teeth of the second gear 20 and is concentric with the pitch circle Pc when viewed from the axial direction. The pitch circle Pc means a circle whose radius is the distance from the center of the second gear 20 to the point where the second gear 20 contacts the first gear 10 or the third gear 30 when viewed from the axial direction.

[0031] When viewed from the axial direction, a part of the outer shape of the notched groove 45 overlaps with the pitch circle Pc of the second gear 20. When viewed from the axial direction, a part of the outer shape of the notched groove 45 overlaps with a bisection point Bp that bisects the distance between the bottom circle Dc and the outer shape of the second bearing 23 in a radial direction perpendicular to the axial direction.

[0032] Fig. 17 is a diagram for explaining the variation in the high-pressure oil pressing area accompanying the rotation of the second gear 20 according to the embodiment. Fig. 18 is a diagram for explaining the variation in the high-pressure oil pressing area following Fig. 17. Fig. 19 is a diagram for explaining the variation in the high-pressure oil pressing area following Fig. 18. Fig. 17 corresponds to a diagram when the first surface F1 of the tooth of the second gear 20 facing downstream in the rotation direction of the second gear 20 overlaps with the discharge edge 44 as viewed from the axial direction. 17 to 19, when viewed from the axial direction, when a first surface F1 of the tooth of the second gear 20 facing downstream in the rotation direction of the second gear 20 overlaps with the discharge edge 44, a part of the outer shape of the notched groove 45 overlaps with an intersection point Ip where a second surface F2 of the tooth of the second gear 20 facing upstream in the rotation direction of the second gear 20 intersects with the pitch circle Pc. When viewed from the axial direction, the outer shape of the notched groove 45 includes a curved shape that overlaps with the pitch circle Pc, the bisection point Bp, and the intersection point Ip.

[0033] Partition wall portion 42 has suction edge 43 which becomes the edge of suction ports 3A, 3B. Part of notch groove 45 is formed in partition wall portion 42 from a portion between suction edge 43 and discharge edge 44 to discharge edge 44. The opening area of ​​part of notch groove 45 increases as second gear 20 rotates. Also, the depth of part of notch groove 45 increases as second gear 20 rotates.

[0034] When viewed from the axial direction, the opening area of ​​a portion of the notched groove 45 changes. In the example shown in the figure, when viewed from the axial direction, the opening area of ​​a portion of the notched groove 45 changes in a radial direction perpendicular to the axial direction of the second shaft 21, and the opening area changes in the rotation direction of the second gear 20 (the circumferential direction around the second shaft 21). Note that the manner in which the opening area of ​​a portion of the notched groove 45 changes when viewed from the axial direction is not limited to the above, and can be changed according to design specifications.

[0035] In a cross-sectional view of the notched groove 45 cut along a plane parallel to the axial direction, the opening area of ​​a portion of the notched groove 45 changes. For example, in a cross-sectional view, the opening area of ​​a portion of the notched groove 45 may change in a radial direction perpendicular to the axial direction. Note that the manner in which the opening area of ​​a portion of the notched groove 45 changes in a cross-sectional view is not limited to the above and can be changed according to design specifications.

[0036] <Inner groove> 15, an inner groove 52 through which oil flows is formed in the second inner side surface portion 51 (cover mounting surface). Also referring to FIG. 16, the cutout groove 45 is formed in the first inner side surface portion 41 so that the high-pressure oil pressing area as viewed in the axial direction is approximately the same as that of the inner groove 52.

[0037] 15, the inner groove 52 is composed of an annular portion that follows the outer periphery of the shaft insertion portion on the cover mounting surface, and an extending portion that extends radially from a part of the annular portion. The entire inner groove 52 is located on the inner periphery side of the bottom circle Dc when viewed in the axial direction. Therefore, on the cover 50 side where the inner groove 52 is formed, the area pressed against the high-pressure oil does not change with the rotation of the second gear 20.

[0038] As described above, a part of the notched groove 45 is disposed on the outer circumferential side of the bottom circle Dc when viewed in the axial direction. Therefore, on the body 40 side where the notched groove 45 is formed, the area pressed against the high-pressure oil varies with the rotation of the second gear 20.

[0039] <Regarding pump gear misalignment> For example, bearing lubricating oil flows in from the oil groove on the discharge side (high pressure side), flows through the oil groove of the bearing, and flows out to the oil groove on the suction side (low pressure side). At that time, the high pressure oil flows through the gaps on the side of the pump gears 10, 20, 30, and presses the pump gears 10, 20, 30 in one direction. This causes the pump gears 10, 20, 30 to become biased (misaligned in the axial direction).

[0040] The second gear 20, the second shaft 21, and the second bearing 23 are configured to allow oil to flow from the cover 50 side toward the body 40 side through the oil groove 22. Therefore, the second gear 20 is pressed toward the body 40 side and biased toward the body 40 side.

[0041] This narrows the gap between the second gear 20 and the body 40, and when the oil is discharged, the high-pressure oil flows through the tiny gap at high speed and is released into the low-pressure area (cavitation area), making cavitation and erosion due to cavitation more likely to occur.

[0042] In this embodiment, in order to suppress the occurrence of erosion due to cavitation, a notched groove 45 is formed on the side of the body 40 (first inner side surface portion 41). For example, the notched groove 45 is formed on the side of the body 40 so as to be equal to the pressing area of ​​the second gear 20 by the high-pressure oil on the cover 50 side. This allows equal pressing forces to be applied from both sides of the second gear 20, and the second gear 20 can be balanced to ensure a gap on the side of the second gear 20. For example, in order to ensure a gap on both sides of the second gear 20 by applying equal pressing forces from both sides of the second gear 20, it is preferable to make the volumes of the grooves formed in the body 40 and the cover 50 equal to each other.

[0043] Hereinafter, the high-pressure oil pressing area of ​​the cutout groove 45 as viewed in the axial direction is designated as A1, and the high-pressure oil pressing area of ​​the inner groove 52 as viewed in the axial direction is designated as A2. For example, it is preferable to set the high-pressure oil pressing area ratio A1 / A2 within the range of 0.98 to 1.02. This allows the second gear 20 to be pressed with equal force in a balanced manner from both sides in the axial direction. For example, the high-pressure oil pressing area ratio A1 / A2 is not limited to the above and can be changed according to design specifications.

[0044] <Action and effect> As described above, the external gear pump 1 of this embodiment includes the first gear 10 that is driven by the drive source, the second gear 20 that meshes with the first gear 10 and rotates, the third gear 30 that meshes with the second gear 20 and rotates, the body 40 having the first inner side surface portion 41 that faces one side surface of the first gear 10, the second gear 20, and the third gear 30, and the cover 50 having the second inner side surface portion 51 that faces the other side surface of the first gear 10, the second gear 20, and the third gear 30. The body 40 is formed with the suction ports 3A and 3B through which oil is sucked and the discharge ports 4A and 4B through which oil is discharged. The first gear 10, the second gear 20, and the third gear 30 are configured to rotate while meshing with each other to pump the oil from the suction ports 3A and 3B to the discharge ports 4A and 4B. The first inner side surface portion 41 has a partition wall portion 42 separating the suction ports 3A, 3B from the discharge ports 4A, 4B, and has a discharge edge 44 which becomes the edge of the discharge ports 4A, 4B. A notched groove 45 is formed in the discharge edge 44. For example, in the triple-type external gear pump 1, it is difficult to ensure a sufficient length in the section where oil is pumped from the suction ports 3A, 3B to the discharge ports 4A, 4B. Therefore, when pumping oil, the pressure in the tooth grooves may suddenly rise when the second gear 20 is opened. In this case, the possibility of cavitation occurring increases. If cavitation occurs, there is a risk of erosion occurring on the bottom surface of the gear chamber. In contrast, according to the present configuration, the notch groove 45 is formed in the discharge edge 44 of the partition wall portion 42 separating the suction ports 3A, 3B and the discharge ports 4A, 4B, so that the tooth grooves communicate with the notch groove 45 before communicating with the discharge ports 4A, 4B during the course of the rotation of the second gear 20. Therefore, when the pumped oil flows to the discharge ports 4A, 4B, the flow rate of the oil decreases, and a sudden pressure rise in the tooth grooves of the second gear 20 can be suppressed. Therefore, the occurrence of erosion due to cavitation can be suppressed.

[0045] In this embodiment, a part of the cutout groove 45 is disposed on the inner peripheral side of the bottom circle Dc of the second gear 20 when viewed in the axial direction along the rotation axis of the second gear 20. For example, if the entire cutout groove 45 is located on the outer periphery side of the bottom circle Dc of the second gear 20 as viewed in the axial direction, the high-pressure oil pressing area will fluctuate with the rotation of the second gear 20. In contrast, according to the present configuration, a part of the cutout groove 45 is located on the inner periphery side of the bottom circle Dc of the second gear 20 as viewed in the axial direction, thereby making it possible to suppress fluctuations in the high-pressure oil pressing area.

[0046] In this embodiment, a part of the outer shape of the cutout groove 45 overlaps with the pitch circle Pc of the second gear 20 when viewed in the axial direction. According to this configuration, it is possible to prevent the outer shape of the cutout groove 45 from becoming larger than necessary.

[0047] In this embodiment, when viewed from the axial direction, a portion of the outer shape of the cutout groove 45 overlaps with a bisection point Bp that bisects the distance between the bottom circle Dc and the outer shape of the bearing of the second gear 20 in a radial direction perpendicular to the axial direction. According to this configuration, it is possible to suppress the variation in the area pressed by the high-pressure oil, while preventing the outer shape of the cutout groove 45 from becoming larger than necessary.

[0048] In this embodiment, when viewed from the axial direction, when the first surface F1 of the tooth of the second gear 20 facing downstream in the rotational direction of the second gear 20 overlaps with the discharge edge 44, a part of the outer shape of the cutout groove 45 overlaps with the intersection point Ip where the second surface F2 of the tooth of the second gear 20 facing upstream in the rotational direction of the second gear 20 intersects with the pitch circle Pc. According to this configuration, it is possible to prevent the outer shape of the cutout groove 45 from becoming larger than necessary.

[0049] In this embodiment, the outer shape of the cutout groove 45 when viewed from the axial direction includes a curved shape that overlaps with the pitch circle Pc, the bisection point Bp, and the intersection point Ip. With this configuration, oil can flow more smoothly within the cutout groove 45 compared to a case in which the outer shape of the cutout groove 45 when viewed from the axial direction includes a straight line shape that overlaps with the pitch circle Pc, the bisection point Bp, and the intersection point Ip.

[0050] In this embodiment, partition portion 42 has suction edges 43 which become the edges of suction ports 3A, 3B. A portion of notched groove 45 is formed in partition portion 42 from a portion between suction edge 43 and discharge edge 44 to discharge edge 44. The opening area of ​​the portion of notched groove 45 increases with the rotation of second gear 20. With this configuration, compared to a case where the opening area of ​​the entire cutout groove 45 is constant from the portion between the suction edge 43 and the discharge edge 44 in the partition wall 42 to the discharge edge 44, the oil flow rate decreases more slowly when the oil flows to the discharge ports 4A, 4B. This makes it possible to more effectively suppress a sudden increase in pressure in the tooth grooves of the second gear 20. This makes it possible to more effectively suppress the occurrence of erosion due to cavitation.

[0051] In this embodiment, the opening area of ​​a part of the cutout groove 45 changes when viewed in the axial direction. According to this configuration, the degree of freedom in designing the opening area of ​​the cutout groove 45 can be improved.

[0052] In this embodiment, in a cross-sectional view of the notched groove 45 cut along a plane parallel to the axial direction, the opening area of ​​a part of the notched groove 45 changes. According to this configuration, the degree of freedom in designing the opening area of ​​the cutout groove 45 can be improved.

[0053] In this embodiment, the external gear pump 1 further includes a second shaft 21 that extends in the axial direction along the rotation axis of the second gear 20 and has one end fixed to the body 40 and the other end fixed to the cover 50, and a second bearing 23 that is disposed between the inner peripheral surface of the second gear 20 and the outer peripheral surface of the second shaft 21 and has an oil groove 22 formed therein. The second gear 20, the second shaft 21, and the second bearing 23 are configured to allow oil to flow from the cover 50 side toward the body 40 side through the oil groove 22. For example, when high-pressure oil presses the second gear 20 from the cover 50 side toward the body 40 side, the second gear 20 is biased toward the body 40 side in the axial direction. Then, the gap between the second gear 20 and the body 40 narrows, and when the oil is discharged, the high-pressure oil flows through the minute gap at high speed and is released to the low-pressure part (cavitation part). Therefore, erosion due to cavitation is likely to occur. In this embodiment, the notch groove 45 is formed on the body 40 side (first inner side surface part 41) as described above, which is highly beneficial in suppressing the occurrence of erosion due to cavitation.

[0054] In this embodiment, an inner groove 52 through which oil flows is formed in the second inner side surface portion 51. The notched groove 45 is formed in the first inner side surface portion 41 so that the high-pressure oil pressing area as viewed in the axial direction is approximately the same as that of the inner groove 52. According to this configuration, the second gear 20 can be pushed with equal and well-balanced forces from both sides in the axial direction. Therefore, a gap can be secured between both side surfaces of the second gear 20 and each of the first inner side surface portion 41 and the second inner side surface portion 51. Therefore, the occurrence of erosion due to cavitation can be more effectively suppressed.

[0055] The external gear pump 1 of this embodiment is mounted on a diesel engine 100. According to this configuration, in the external gear pump 1 mounted on the diesel engine 100, the occurrence of erosion due to cavitation can be suppressed.

[0056] Conventionally, diesel engine oil pumps mainly use external gear pumps in which a pump drive gear rotates in conjunction with the engine crankshaft, and the torque of the pump drive gear rotates and drives the meshing pump gears. In external gear pumps, oil is introduced into the tooth grooves from the suction port by the rotation of the pump gear, and the oil is pumped to the discharge port by rotating the pump gear. The oil is pumped out when the pressure in the tooth grooves of the pump gear changes from suction pressure to discharge pressure. To prevent a decrease in pump efficiency, there are very small gaps between both sides of the meshing pump gears and the bottom surface of the gear chamber and the cover mounting surface.

[0057] However, in conventional external gear pumps, when the oil introduced into the tooth grooves from the suction port is pressurized and sent to the discharge port by the rotation of the pump gears that mesh with each other, the high-pressure oil on the discharge side is likely to flow into the suction port side, which is at low pressure, through the gaps between both sides of the pump gear and the bottom surface of the gear chamber and the cover mounting surface. In addition, since the oil inside the external gear pump is lubricated to lubricate the bearing part of the pump gear, the pump gear tends to be biased to one side depending on the direction of the oil flow, and the gaps on the sides of the pump gear tend to become small. Therefore, the gaps between both sides of the pump gear and the bottom surface of the gear chamber and the cover mounting surface tend to become extremely small. As a result, the oil flowing through the gaps becomes high-speed (low-pressure spots are generated), and cavitation tends to occur. In addition, when the oil is pumped from the suction port to the discharge port by the rotation of the pump gear, the high-pressure oil on the discharge side tends to enter the tooth grooves of the pump gear when it is sent to the discharge port. In particular, in triple external gear pumps, the pumping section from the suction port to the discharge port cannot be made to have a sufficient length, which causes the pressure in the tooth grooves of the second gear to rise suddenly, making erosion due to cavitation more likely to occur.

[0058] In contrast, in the external gear pump 1 of this embodiment, a notched groove 45 is formed in the discharge edge 44 of the partition wall 42 separating the suction ports 3A, 3B from the discharge ports 4A, 4B, thereby making it possible to prevent a decrease in pump efficiency and suppress the occurrence of cavitation in the gaps between the side surface of the second gear 20 and the first inner side surface portion 41 (gear chamber bottom surface) and the second inner side surface portion 51 (cover mounting surface). In addition, it is possible to suppress the occurrence of cavitation due to a sudden increase in pressure in the tooth grooves of the second gear 20 that occurs when pressure-fed oil is sent to the discharge ports 4A, 4B, and to suppress the occurrence of erosion due to cavitation.

[0059] Specifically, referring to Fig. 16 to Fig. 19, the high-pressure oil is introduced into the notched groove 45 that communicates with the discharge ports 4A and 4B, and the side surface of the second gear 20 on the inner periphery side of the bottom circle Dc is filled with high-pressure oil. The high-pressure oil pushes back the second gear 20 that is biased to one side in the axial direction, thereby ensuring a large gap between both sides of the second gear 20 and the gear chamber bottom and cover mounting surface. Therefore, the flow velocity of the high-pressure oil flowing through the above gaps can be kept low, and the drop in oil pressure becomes slow due to the decrease in the flow velocity of the high-pressure oil when it is released to the low-pressure side. This makes it possible to suppress cavitation occurring in the gaps with the side surfaces of the second gear 20.

[0060] In addition, the oil introduced into the tooth groove of the second gear 20 from the suction ports 3A and 3B moves to the discharge ports 4A and 4B with the rotation of the pump gears 10, 20 and 30. In the process in which the pressure in the tooth groove of the second gear 20 changes from the suction pressure to the discharge pressure, the notch groove 45 is communicated with the high-pressure side discharge ports 4A and 4B. Therefore, as shown in FIG. 17, when the tooth groove portion of the second gear 20 reaches the notch groove 45, the pressure in the tooth groove gradually increases. In the initial stage when the tooth groove portion of the second gear 20 reaches the notch groove 45, most of the notch groove 45 is covered by the second gear 20. Therefore, the pressure in the tooth groove of the second gear 20 gradually increases. That is, the pressure in the tooth groove of the second gear 20 communicating with the notch groove 45 increases gently.

[0061] 18 and 19, as the rotation of the pump gears 10, 20, 30 progresses, the notched groove 45 that opens into the tooth groove portion of the second gear 20 expands, and the pressure further increases and approaches the discharge pressure. This suppresses a sudden increase in pressure in the tooth groove of the second gear 20 that occurs when the pumped oil is sent to the discharge ports 4A, 4B. This makes it possible to suppress the occurrence of cavitation and erosion due to cavitation.

[0062] In this embodiment, a portion of the notched groove 45 is formed in the partition wall 42 from a portion between the suction edge 43 and the discharge edge 44 to the discharge edge 44. Therefore, the gaps between the side surface of the second gear 20 and the bottom surface of the gear chamber and the cover mounting surface are not communicated with the suction ports 3A and 3B. Therefore, a decrease in pump efficiency due to the formation of the notched groove 45 can be avoided.

[0063] Therefore, according to this embodiment, it is possible to prevent a decrease in pump efficiency and suppress the occurrence of cavitation in the gaps between the side surface of the second gear 20 and the bottom surface of the gear chamber and the cover mounting surface. In addition, it is possible to suppress the occurrence of cavitation caused by a sudden increase in pressure in the tooth grooves of the second gear 20 when the pumped oil is delivered to the discharge ports 4A and 4B, and to suppress the occurrence of erosion caused by cavitation.

[0064] <Modification> In the above-described embodiment, an example has been described in which a portion of the notched groove is disposed on the inner circumferential side of the bottom circle of the second gear as viewed from the axial direction, but this is not limited thereto. For example, the entire notched groove may be disposed on the outer circumferential side of the bottom circle of the second gear as viewed from the axial direction. For example, at least a portion of the notched groove may be disposed on the inner circumferential side of the bottom circle of the second gear as viewed from the axial direction. For example, the arrangement of the notched groove with respect to the bottom circle of the second gear can be changed according to design specifications.

[0065] In the above embodiment, an example has been described in which a part of the outer shape of the notched groove overlaps with the pitch circle of the second gear when viewed from the axial direction, but this is not limited thereto. For example, a part of the outer shape of the notched groove does not have to overlap with the pitch circle of the second gear when viewed from the axial direction. For example, the arrangement of the outer shape of the notched groove with respect to the pitch circle of the second gear can be changed according to design specifications.

[0066] In the above embodiment, an example has been described in which a part of the outer shape of the notched groove, as viewed from the axial direction, overlaps with a bisection point that divides the distance between the root circle and the outer shape of the bearing of the second gear in half in a radial direction perpendicular to the axial direction, but this is not limited to the above. For example, a part of the outer shape of the notched groove does not have to overlap with the bisection point as viewed from the axial direction. For example, the arrangement of the outer shape of the notched groove with respect to the bisection point can be changed according to design specifications.

[0067] In the above embodiment, an example has been described in which, when the first surface of the tooth of the second gear facing downstream in the rotation direction of the second gear overlaps with the discharge edge as viewed from the axial direction, a part of the outer shape of the notched groove overlaps with the intersection point where the second surface of the tooth of the second gear facing upstream in the rotation direction of the second gear intersects with the pitch circle, but this is not limited to this. For example, when the first surface of the tooth of the second gear facing downstream in the rotation direction of the second gear overlaps with the discharge edge as viewed from the axial direction, a part of the outer shape of the notched groove does not have to overlap with the intersection point. For example, the arrangement of the outer shape of the notched groove with respect to the intersection point can be changed according to design specifications.

[0068] In the above-described embodiment, an example has been described in which the outer shape of the notched groove when viewed from the axial direction includes a curved shape that overlaps with the pitch circle, the bisection point, and the intersection point, but this is not limited thereto. For example, the outer shape of the notched groove when viewed from the axial direction may include a linear shape that overlaps with the pitch circle, the bisection point, and the intersection point. For example, the arrangement of the outer shape of the notched groove with respect to the pitch circle, the bisection point, and the intersection point can be changed according to design specifications.

[0069] In the above-described embodiment, the partition has an inlet edge that is an edge of the inlet port, and a part of the notch groove is formed in the partition from a portion between the inlet edge and the discharge edge to the discharge edge, and the opening area increases with the rotation of the second gear. However, the present invention is not limited to this. For example, the opening area of ​​the entire notch groove may be constant from a portion between the inlet edge and the discharge edge to the discharge edge in the partition. For example, at least a portion of the notch groove may be formed in the partition from a portion between the inlet edge and the discharge edge to the discharge edge, and the opening area may increase with the rotation of the second gear. For example, the size of the opening area of ​​the notch groove with the rotation of the second gear can be changed according to the design specifications.

[0070] In the above-described embodiment, an example has been described in which the opening area of ​​a portion of the notched groove changes when viewed from the axial direction, but this is not limited thereto. For example, the opening area of ​​the entire notched groove may not change when viewed from the axial direction. For example, the opening area of ​​at least a portion of the notched groove may change when viewed from the axial direction. For example, the manner in which the opening area of ​​the notched groove changes when viewed from the axial direction can be changed according to design specifications.

[0071] In the above-described embodiment, an example has been described in which the opening area of ​​a portion of the notched groove changes in a cross-sectional view taken along a plane parallel to the axial direction, but this is not limiting. For example, the opening area of ​​the entire notched groove may not change in a cross-sectional view. For example, the opening area of ​​at least a portion of the notched groove may change in a cross-sectional view. For example, the manner in which the opening area of ​​the notched groove changes in a cross-sectional view can be changed according to design specifications.

[0072] In the above-described embodiment, an example has been described in which the notch groove is formed in the first inner side surface portion and not formed in the second inner side surface portion, but this is not limited thereto. For example, the notch groove may be formed in each of the first inner side surface portion and the second inner side surface portion. With this configuration, it is possible to suppress the occurrence of erosion due to cavitation in each inner side surface portion of the body and the cover.

[0073] In the above-described embodiment, the external gear pump further includes a shaft extending in the axial direction along the rotation axis of the second gear, one end of which is fixed to the body and the other end of which is fixed to the cover, and a bearing disposed between the inner peripheral surface of the second gear and the outer peripheral surface of the shaft, in which an oil groove is formed. The second gear, the shaft, and the bearing are configured to allow oil to flow from the cover side to the body side through the oil groove, but the present invention is not limited to this. For example, the second gear, the shaft, and the bearing may be configured to allow oil to flow from the body side to the cover side through the oil groove. For example, the flow direction of the oil through the oil groove can be changed according to design specifications.

[0074] In the above-described embodiment, an example has been described in which the second inner side surface portion is formed with an inner groove through which oil flows, and the notched groove is formed in the first inner side surface portion so that the high-pressure oil pressing area as viewed from the axial direction is substantially the same as that of the inner groove, but this is not limited thereto. For example, the notched groove may be formed in the first inner side surface portion so that the high-pressure oil pressing area as viewed from the axial direction is different from that of the inner groove. For example, the relationship between the high-pressure oil pressing area of ​​the notched groove and that of the inner groove as viewed from the axial direction can be changed according to design specifications.

[0075] In the above embodiment, the external gear pump is described as being mounted on a diesel engine, but the present invention is not limited thereto. For example, the external gear pump may be mounted on an engine other than a diesel engine. For example, the external gear pump may be mounted on a power source other than an engine. For example, the target on which the external gear pump is mounted may be changed depending on the design specifications.

[0076] Although the embodiments of the present invention have been described above, the present invention is not limited to these, and additions, omissions, substitutions, and other modifications of the configuration are possible without departing from the spirit of the present invention, and the above-described embodiments can also be combined as appropriate.

[0077] (Appendix 1) a first gear that is rotationally driven by a drive source; a second gear that meshes with the first gear and rotates in a driven manner; a third gear that meshes with the second gear and rotates in a driven manner; a body having a first inner surface portion facing one side surface of the first gear, the second gear, and the third gear; a cover having a second inner side surface portion facing the other side surfaces of the first gear, the second gear, and the third gear, The body is formed with a suction port through which oil is drawn and a discharge port through which the oil is discharged, the first gear, the second gear, and the third gear are configured to rotate while meshing with each other, thereby pressure-feeding the oil from the suction port toward the discharge port, At least one of the first inner side surface portion and the second inner side surface portion has a discharge edge that becomes an edge of the discharge port in a partition portion that separates the suction port and the discharge port, A notched groove is formed on the discharge edge. External gear pump.

[0078] (Appendix 2) When viewed from an axial direction along the rotation shaft of the second gear, at least a part of the notched groove is disposed on an inner peripheral side with respect to a bottom circle of the second gear. 2. An external gear pump as defined in claim 1.

[0079] (Appendix 3) When viewed from the axial direction, a part of an outer shape of the notched groove overlaps with a pitch circle of the second gear. 2. An external gear pump as defined in claim 2.

[0080] (Appendix 4) When viewed from the axial direction, a part of an outer shape of the notched groove overlaps with a bisection point that bisects a distance between the bottom circle and an outer shape of the bearing of the second gear in a radial direction perpendicular to the axial direction. 4. An external gear pump as defined in claim 3.

[0081] (Appendix 5) When viewed from the axial direction, when a first surface of the tooth of the second gear facing downstream in a rotation direction of the second gear overlaps with the discharge edge, a part of an outer shape of the notched groove overlaps with an intersection point where a second surface of the tooth facing upstream in the rotation direction of the second gear intersects with the pitch circle. 5. An external gear pump as defined in claim 4.

[0082] (Appendix 6) When viewed from the axial direction, an outer shape of the notched groove includes a curved shape overlapping with the pitch circle, the bisection point, and the intersection point. 5. An external gear pump as defined in claim 5.

[0083] (Appendix 7) The partition portion has a suction edge that becomes an edge of the suction port, At least a portion of the notch groove is formed in the partition wall from a portion between the suction edge and the discharge edge to the discharge edge, and an opening area of ​​the notch groove increases with rotation of the second gear. 6. An external gear pump as defined in claim 6.

[0084] (Appendix 8) When viewed from the axial direction, the opening area of ​​at least a part of the notch groove changes. 8. An external gear pump as defined in claim 7.

[0085] (Appendix 9) In a cross-sectional view of the notched groove taken along a plane parallel to the axial direction, the opening area of ​​at least a portion of the notched groove changes. 9. The external gear pump according to claim 7 or 8.

[0086] (Appendix 10) The notch groove is formed in each of the first inner side surface portion and the second inner side surface portion. 10. An external gear pump according to any one of claims 1 to 9.

[0087] (Appendix 11) a shaft extending in an axial direction along the rotation axis of the second gear, one end of which is fixed to the body and the other end of which is fixed to the cover; A bearing is disposed between an inner circumferential surface of the second gear and an outer circumferential surface of the shaft, and has an oil groove formed therein. The second gear, the shaft, and the bearing are configured to flow the oil through the oil groove from the cover side toward the body side. 11. The external gear pump according to any one of claims 1 to 10.

[0088] (Appendix 12) The second inner side surface portion is formed with an inner groove through which the oil flows, The notched groove is formed in the first inner surface portion so that a high-pressure oil pressing area as viewed in the axial direction is substantially the same as that of the inner groove. 12. The external gear pump according to claim 11.

[0089] (Appendix 13) The external gear pump is mounted on an engine. 13. The external gear pump according to any one of claims 1 to 12. [Explanation of symbols]

[0090]

[0033] 1... circumscribed gear pump, 3A, 3B... suction port, 4A, 4B... discharge port, 10... first gear, 20... second gear, 21... second shaft (shaft of second gear), 22... oil groove (oil groove of second bearing), 23... second bearing (bearing of second gear), 30... third gear, 40... body, 41... first inner surface portion, 42... partition wall portion, 43... suction edge, 44... discharge edge, 45... notched groove, 50... cover, 51... second inner surface portion, 52... inner groove, 100... engine (driving source), A1... high-pressure oil pressing area of ​​notched groove, A2... high-pressure oil pressing area of ​​inner groove, Bp... bisection point, Dc... tooth root circle, F1... first tooth surface, F2... second tooth surface, Ip... intersection point, Pc... pitch circle

Claims

1. a first gear that is rotationally driven by a drive source; a second gear that meshes with the first gear and rotates in a driven manner; a third gear that meshes with the second gear and rotates in a driven manner; a body having a first inner surface portion facing one side surface of the first gear, the second gear, and the third gear; a cover having a second inner side surface portion facing the other side surfaces of the first gear, the second gear, and the third gear, The body is formed with a suction port through which oil is drawn and a discharge port through which the oil is discharged, the first gear, the second gear, and the third gear are configured to rotate while meshing with each other, thereby pressure-feeding the oil from the suction port toward the discharge port, At least one of the first inner side surface portion and the second inner side surface portion has a partition portion separating the suction port and the discharge port, the partition portion having a discharge edge that becomes an edge of the discharge port, A notched groove is formed on the discharge edge. External gear pump.

2. When viewed in an axial direction along a rotation shaft of the second gear, at least a part of the notched groove is disposed on an inner peripheral side with respect to a bottom circle of the second gear.

2. The external gear pump according to claim 1.

3. When viewed from the axial direction, a part of an outer shape of the notched groove overlaps with a pitch circle of the second gear.

3. The external gear pump according to claim 2.

4. When viewed from the axial direction, a part of an outer shape of the notched groove overlaps with a bisection point that bisects a distance between the bottom circle and an outer shape of a bearing of the second gear in a radial direction perpendicular to the axial direction.

4. The external gear pump according to claim 3.

5. when viewed from the axial direction, when a first surface of the tooth of the second gear facing downstream in a rotational direction of the second gear overlaps with the discharge edge, a part of an outer shape of the notched groove overlaps with an intersection point where a second surface of the tooth facing upstream in the rotational direction of the second gear intersects with the pitch circle.

5. The external gear pump according to claim 4.

6. When viewed from the axial direction, an outer shape of the notched groove includes a curved shape overlapping with the pitch circle, the bisection point, and the intersection point.

6. The external gear pump according to claim 5.

7. The partition portion has a suction edge that becomes an edge of the suction port, At least a portion of the notch groove is formed in the partition wall from a portion between the suction edge and the discharge edge to the discharge edge, and an opening area of ​​the notch groove increases with rotation of the second gear.

7. The external gear pump according to claim 6.

8. When viewed from the axial direction, the opening area of ​​at least a part of the notch groove changes.

8. The external gear pump according to claim 7.

9. In a cross-sectional view of the notched groove taken along a plane parallel to the axial direction, the opening area of ​​at least a portion of the notched groove changes.

9. The external gear pump according to claim 7 or 8.

10. The notch groove is formed in each of the first inner side surface portion and the second inner side surface portion.

9. The external gear pump according to claim 1 .

11. a shaft extending in an axial direction along the rotation axis of the second gear, one end of which is fixed to the body and the other end of which is fixed to the cover; a bearing disposed between an inner circumferential surface of the second gear and an outer circumferential surface of the shaft, the bearing having an oil groove formed therein; The second gear, the shaft, and the bearing are configured to flow the oil through the oil groove from the cover side toward the body side.

9. The external gear pump according to claim 1 .

12. The second inner side surface portion is formed with an inner groove through which the oil flows, the notched groove is formed in the first inner side surface portion so that a high-pressure oil pressing area as viewed in the axial direction is substantially the same as that of the inner groove.

12. The external gear pump according to claim 11.

13. The external gear pump is mounted on an engine.

9. The external gear pump according to claim 1 .

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