External gear pump

Abstract

This external gear pump comprises: a first gear that is rotationally driven by a drive source; a second gear that meshes with the first gear and rotates following the first gear; a third gear that meshes with the second gear and rotates following the second gear; a body having a first inner side surface part facing one side surface of the first gear, the second gear and the third gear; and a cover having a second inner side surface part facing another side surface of the first gear, the second gear and the third gear. The body is formed with a suction port from which oil is sucked in, and a discharge port from which the oil is discharged. The first gear, the second gear, and the third gear are configured to rotate in mesh with each other to pressure-feed the oil from the suction port toward the discharge port. At least one of the first inner side surface part and the second inner side surface part has a discharge edge serving as an edge of the discharge port in a partition wall part that separates the suction port from the discharge port, and a notch groove is formed at the discharge edge.

Description

External gear pump

[0001] The present invention relates to an external gear pump. The present invention claims priority to Japanese Patent Application No. 2023-096865, filed on June 13, 2023, the contents of which are incorporated herein by reference.

[0002] External gear pumps include dual oil pumps in which two pump gears mesh, and triple oil pumps in which three pump gears mesh. Patent Document 1 discloses a dual external gear pump. The external gear pump in Patent Document 1 includes side plates disposed on both sides of each pump gear. The side plates have inclined surfaces that define a suction-side relief portion and a discharge-side relief portion that extend in a linear direction connecting the rotation axes of the pump gears. Patent Document 1 does not disclose a triple external gear pump.

[0003] Japanese Patent Application Publication No. 2016-113916

[0004] In triple-type external gear pumps, it is difficult to ensure a sufficient length for pumping oil 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. This increases the likelihood of cavitation, in which bubbles appear and disappear in a short period of time due to pressure differences in the oil flow. Cavitation can cause erosion (mechanical wear) at the bottom of the gear chamber. Therefore, there is room for improvement in suppressing erosion caused by cavitation.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an external gear pump that can suppress the occurrence of erosion due to cavitation.

[0006] An external gear pump according to one aspect of the present invention comprises: a first gear that is driven to rotate 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. The body is formed with an intake port through which oil is drawn and an outlet port through which the oil is discharged. The first gear, the second gear, and the third gear are configured to mesh with each other and rotate to pressurize the oil from the intake port to the outlet port. At least one of the first inner surface portion and the second inner surface portion has an outlet edge that forms the edge of the outlet port at a partition portion separating the intake port and the outlet port, and the outlet edge has a notched groove formed in the outlet edge.

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

[0008] 1 is a perspective view of an external gear pump according to an embodiment; an exploded perspective view of an external gear pump according to an embodiment; a perspective view of an engine equipped with an external gear pump according to an embodiment; a perspective view illustrating an oil flow in the external gear pump according to an embodiment; a perspective view illustrating an oil flow in an internal flow path of the external gear pump according to an embodiment; a diagram illustrating an oil flow in a gear chamber of the external gear pump according to an embodiment; a perspective view illustrating a bearing lubricating oil flow in the external gear pump according to an embodiment; a perspective view illustrating a bearing lubricating oil flow in the first gear according to an embodiment; a perspective view illustrating a bearing lubricating oil flow in the second gear according to an embodiment; a perspective view illustrating a bearing lubricating oil flow in the third gear according to an embodiment; a view including a cross section of the external gear pump according to an embodiment, cut along a plane including the rotation axes of the pump gears; a view of a body according to an embodiment, as viewed from the inner axial direction; a view of a cover according to an embodiment, as viewed from the inner axial direction; a view showing a notched groove formed in the body according to an embodiment; a view showing an inner groove formed in the cover according to an embodiment; a view illustrating an outer shape of a notched groove formed in the body according to an embodiment. 15. A diagram for explaining the fluctuation of the high-pressure oil pressing area with rotation of the second gear according to the embodiment. A diagram for explaining the fluctuation of the high-pressure oil pressing area following Fig. 17. A diagram for explaining the fluctuation of the high-pressure oil pressing area following Fig. 18 ... operation of the external gear pump according to the embodiment, including a cross section taken along XX-XX in Fig. 15. A diagram for explaining the operation of the external gear pump according to the embodiment, including a cross section taken along XXI-XXI in Fig. 14.

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below 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 in the strict sense, but also include arrangements or states in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. In the drawings used in the following description, the scale of each component may be changed as appropriate to make each component recognizable.

[0011] <External Gear Pump> Fig. 1 is a perspective view of an external gear pump 1 according to an embodiment. Fig. 2 is an exploded perspective view of the external gear pump 1 according to an embodiment. As shown in Figs. 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 a first gear 10 that is rotationally driven by a drive source, a second gear 20 that meshes with the first gear 10 and rotates accordingly, a third gear 30 that meshes with the second gear 20 and rotates accordingly, a body 40 having a first inner surface portion 41 that faces one side 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 of the first gear 10, the second gear 20, and the third gear 30. Hereinafter, the first inner surface portion 41 of the body 40 will also be referred to as the "gear chamber bottom surface," and the second inner 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 first gear 10, second gear 20, and third gear 30 from the top vertically. 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 the drive gear, may be arranged on the center side of the oil pump, 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 depending on the design specifications.

[0013] For example, the pump gears 10, 20, and 30 may have the same shape. For example, the pump gears 10, 20, and 30 may have at least a portion of a different shape from each other, without being limited to the above. For example, the shape of each of the pump gears 10, 20, and 30 may be changed according to design specifications.

[0014] In the illustrated example, the number of teeth of the pump gears 10, 20, and 30 is 8. However, the number of teeth of the pump gears 10, 20, and 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, and 30 can be changed depending on the design specifications.

[0015] <Engine> Figure 3 is a perspective view of an engine 100 equipped with an external gear pump 1 according to an embodiment. Referring also to Figure 3, the external gear pump 1 is disposed below a crankcase 101 of the engine 100. A pump drive gear 103 rotates in conjunction with a crankshaft 102 of the engine 100, which is the 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 below the crankcase 101. The pumped oil is sucked into an internal flow path 2 of the external gear pump 1 through an inlet port of the external gear pump 1.

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

[0017] <Oil Flow> Figure 4 is a perspective view illustrating the flow of oil in the external gear pump 1 according to the embodiment. Figure 5 is a perspective view illustrating the flow of oil in the internal flow path 2 of the external gear pump 1 according to the embodiment. Figure 6 is a diagram illustrating the flow of oil in the gear chamber of the external gear pump 1 according to the embodiment. Referring to Figures 4 to 6 together, the body 40 is formed with suction ports 3A, 3B through which oil is sucked and discharge ports 4A, 4B through which oil is discharged. The first gear 10, the second gear 20, and the third gear 30 are configured to mesh with each other and rotate, thereby pressure-feeding oil from the suction ports 3A, 3B toward the discharge ports 4A, 4B.

[0018] For example, oil drawn 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 portion 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 portion 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 portion 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 and 4B joins together and is sent out to the outside of the external gear pump 1. For example, the pumped oil is used for lubricating or cooling 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 pumped oil, the relief valve 60 opens and the oil is forced to flow into a bypass flow path (not shown).

[0020] <Flow of Bearing Lubricating Oil> 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 cross-sectional view of the external gear pump 1 according to the embodiment, taken along a plane including the rotation axes of the pump gears 10, 20, and 30. Bearing lubricating oil flows to lubricate the bearings to prevent seizure of the rotating parts due to 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] 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, and 30, and bearings 13, 23, 33 (first bearing 13, second bearing 23, and third bearing 33) that support the shafts 11, 21, and 31 and have oil grooves formed therein.

[0022] The central axes of the three shafts 11, 21, and 31 are arranged parallel to one another. For example, the central axes of the shafts 11, 21, and 31 may be arranged on the same vertical plane. For example, the shafts 11, 21, and 31 may be arranged in the order of first shaft 11, second shaft 21, and third shaft 31 from vertically above. For example, the central axes of the shafts 11, 21, and 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, and 31 may be arranged on a horizontal plane. For example, the arrangement of the shafts 11, 21, and 31 can be changed according to 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 bearings 13 are disposed between the inner circumferential surface of the through hole in the body 40 and the outer circumferential surface of the first shaft 11, and between the inner circumferential surface of the through hole in the cover 50 and the outer circumferential surface of the first shaft 11. Rotation of the pump drive gear 103 causes the first shaft 11 and first gear 10 to rotate integrally. 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 side in the direction of 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 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 circumferential surface of the second gear 20 and the outer circumferential surface of the second shaft 21. The second gear 20 is rotated around 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 circumferential surface of the third gear 30 and the outer circumferential 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. 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 shaft 11, 21, and 31. The number of bearings 13, 23, and 33 is not limited to those described above and can be changed according to design specifications. In the illustrated example, the oil grooves 12, 22, and 32 are formed spirally along the axial direction on the inner or outer peripheral surfaces of the bearings 13, 23, and 33, respectively. 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 viewed from the inside in the axial direction. FIG. 13 is a view of the cover 50 according to the embodiment, as viewed from the inside in the axial direction. FIG. 14 is a view showing the notched 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 illustrating the outer shape of the notched groove 45 formed in the body 40 according to the embodiment. In FIGS. 12 and 13, arrows W11 to W14 indicate the flow direction of bearing lubricating oil flowing through the oil groove in the shaft insertion portion on the gear chamber bottom surface or the cover mounting surface. In FIG. 14, the area where the second gear 20 and the notched groove 45 overlap as viewed from the axial direction is indicated by hatching. In FIG. 15, the area where the inner groove 52 is formed as viewed from the axial direction is indicated by hatching. In FIG. 16, the area where the notched groove 45 is formed as viewed from the axial direction is indicated 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 wall 42 is formed in a portion separating one suction port 3A and the discharge port 4B, and in a portion separating the other suction port 3B and the discharge port 4A, as viewed in the axial direction. The partition wall 42 is formed in a region overlapping with a portion of the second gear 20, as viewed in the axial direction. The partition wall 42 is formed in two regions sandwiching the insertion portion of the second shaft 21, as viewed in the axial direction. The partition wall 42 has a discharge edge 44 that forms the edge of the discharge ports 4A, 4B. The discharge edge 44 extends in 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 portion of the notched groove 45 is located more inward than the root circle Dc of the second gear 20. The root circle Dc is a circle that passes through the roots of the teeth of the second gear 20 when viewed from the axial direction and is concentric with the pitch circle Pc. The pitch circle Pc is 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 portion 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 portion of the outer shape of the notched groove 45 overlaps with a bisection point Bp that bisects the distance between the root circle Dc and the outer shape of the second bearing 23 in the radial direction perpendicular to the axial direction.

[0032] FIG. 17 is a diagram illustrating fluctuations in the high-pressure oil pressing area accompanying rotation of the second gear 20 according to the embodiment. FIG. 18 is a diagram illustrating fluctuations in the high-pressure oil pressing area following FIG. 17 . FIG. 19 is a diagram illustrating fluctuations in the high-pressure oil pressing area following FIG. 18 . FIG. 17 corresponds to a diagram illustrating a state in which, as viewed from the axial direction, a first surface F1 of a tooth of the second gear 20 facing downstream in the rotation direction of the second gear 20 overlaps with the discharge edge 44. Referring to FIGS. 17 to 19 together, when, as viewed from the axial direction, 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, a portion of the outer shape of the notched groove 45 overlaps with an intersection Ip between a second surface F2 of the tooth of the second gear 20 facing upstream in the rotation direction of the second gear 20 and the pitch circle Pc. When viewed from the axial direction, the contour 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] The partition wall 42 has an inlet edge 43 that forms the edge of the inlet ports 3A, 3B. A portion of the notched groove 45 is formed in the partition wall 42 from a portion between the inlet edge 43 and the discharge edge 44 to the discharge edge 44. The opening area of ​​the portion of the notched groove 45 increases as the second gear 20 rotates. Furthermore, the depth of the portion of the notched groove 45 increases as the 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 the radial direction perpendicular to the axial direction of the second shaft 21, and also 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 taken 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> Referring also to Figure 15, an inner groove 52 through which oil flows is formed in the second inner side surface portion 51 (cover mounting surface). Referring also to Figure 16, 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.

[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 part of the annular portion. The entire inner groove 52 is located on the inner periphery side of the root 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 as the second gear 20 rotates.

[0038] As described above, part of the notched groove 45 is located on the outer circumferential side of the root 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 as the second gear 20 rotates.

[0039] <Regarding pump gear misalignment> For example, 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). At that time, the high-pressure oil flows through the gaps on the sides of the pump gears 10, 20, and 30, pressing the pump gears 10, 20, and 30 to one side. This causes the pump gears 10, 20, and 30 to become misaligned (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, causing high-pressure oil to flow through the tiny gap at high speed and be released into the low-pressure section (cavitation section) when the oil is discharged, making it more likely that cavitation and erosion due to cavitation will 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 that the area of ​​the notched groove 45 is equal to the area of ​​the second gear 20 pressed 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, balancing the second gear 20 and ensuring clearances on the sides of the second gear 20. For example, in order to apply equal pressing forces from both sides of the second gear 20 and ensure clearances on 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 notched groove 45 as viewed from the axial direction is referred to as A1, and the high-pressure oil pressing area of ​​the inner groove 52 as viewed from the axial direction is referred to 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 and balanced forces 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] <Operation and Effect> As described above, the external gear pump 1 of this embodiment includes the first gear 10 that is rotationally driven by a drive source, the second gear 20 that meshes with the first gear 10 and rotates accordingly, the third gear 30 that meshes with the second gear 20 and rotates accordingly, the body 40 having a first inner surface portion 41 that faces one side of the first gear 10, the second gear 20, and the third gear 30, and the cover 50 having a second inner surface portion 51 that faces the other side of the first gear 10, the second gear 20, and the third gear 30. The body 40 is formed with suction ports 3A and 3B through which oil is sucked and discharge ports 4A and 4B through which oil is discharged. The first gear 10, the second gear 20, and the third gear 30 mesh with each other and rotate, thereby pressure-feeding oil from the suction ports 3A and 3B toward the discharge ports 4A and 4B. The first inner 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 that forms the edge of the discharge ports 4A, 4B. A notched groove 45 is formed in the discharge edge 44. For example, in a triple-type external gear pump 1, it is difficult to ensure a sufficient length for the section through which 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 increase when the second gear 20 opens. In this case, the possibility of cavitation occurring increases. If cavitation occurs, erosion may occur on the bottom surface of the gear chamber. In contrast, according to the present configuration, the notched grooves 45 are formed in the discharge edge 44 of the partition wall 42 separating the suction ports 3A, 3B and the discharge ports 4A, 4B, so that as the second gear 20 rotates, the tooth grooves communicate with the notched grooves 45 before they communicate with the discharge ports 4A, 4B. Therefore, when the pressurized oil flows to the discharge ports 4A, 4B, the oil flow rate decreases, which can suppress a sudden increase in pressure in the tooth grooves of the second gear 20. This can suppress the occurrence of erosion due to cavitation.

[0045] In this embodiment, as viewed from the axial direction along the rotation axis of the second gear 20, a portion of the notched groove 45 is located more inward than the root circle Dc of the second gear 20. For example, if the entire notched groove 45 were located more outward than the root circle Dc of the second gear 20 as viewed from the axial direction, fluctuations in the high-pressure oil pressing area would occur as the second gear 20 rotates. In contrast, according to the present configuration, by arranging a portion of the notched groove 45 more inward than the root circle Dc of the second gear 20 as viewed from the axial direction, fluctuations in the high-pressure oil pressing area can be suppressed.

[0046] In this embodiment, when viewed from the axial direction, a part of the outer shape of the cutout groove 45 overlaps with the pitch circle Pc of the second gear 20. This configuration can 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 part of the outer shape of the notched groove 45 overlaps with a bisection point Bp that halves the distance in the radial direction perpendicular to the axial direction between the root circle Dc and the outer shape of the bearing of the second gear 20. This configuration can suppress fluctuations in the high-pressure oil pressing area while preventing the outer shape of the notched 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 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 the intersection point Ip where the 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. This configuration makes it possible to prevent the outer shape of the notched groove 45 from becoming larger than necessary.

[0049] In the present embodiment, the contour of the notched groove 45, as 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. This configuration allows oil to flow more smoothly within the notched groove 45, compared to when the contour of the notched groove 45, as viewed from the axial direction, includes a linear shape that overlaps with the pitch circle Pc, the bisection point Bp, and the intersection point Ip.

[0050] In this embodiment, the partition wall 42 has a suction edge 43 that defines the edge of the suction ports 3A and 3B. A portion of the notched groove 45 extends from the portion between the suction edge 43 and the discharge edge 44 in the partition wall 42 to the discharge edge 44. The opening area of ​​the portion of the notched groove 45 increases as the second gear 20 rotates. With this configuration, the oil flow velocity decreases more slowly as the oil flows to the discharge ports 4A and 4B, compared to when the entire notched groove 45 has a constant opening area from the portion between the suction edge 43 and the discharge edge 44 in the partition wall 42 to the discharge edge 44. This configuration more effectively suppresses a sudden increase in pressure within the tooth grooves of the second gear 20. This more effectively suppresses erosion due to cavitation.

[0051] In this embodiment, when viewed from the axial direction, the opening area of ​​a portion of the notched groove 45 changes. This configuration improves design freedom in optimizing the opening area of ​​the notched groove 45.

[0052] In the present embodiment, the opening area of ​​a portion of the notched groove 45 changes in a cross section of the notched groove 45 cut along a plane parallel to the axial direction. This configuration improves design freedom in optimizing the opening area of ​​the notched groove 45.

[0053] In this embodiment, the external gear pump 1 further includes a second shaft 21 extending axially along the rotation axis of the second gear 20, one end of which is fixed to the body 40 and the other end of which is fixed to the cover 50, and a second bearing 23 disposed between the inner circumferential surface of the second gear 20 and the outer circumferential surface of the second shaft 21 and having 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 through the oil groove 22 from the cover 50 side toward the body 40 side. For example, if high-pressure oil presses the second gear 20 from the cover 50 side toward the body 40 side, the second gear 20 will be biased axially toward the body 40 side. This narrows the gap between the second gear 20 and the body 40, and high-pressure oil will flow through the small gap at high speed during oil discharge and be released into a low-pressure section (cavitation section). This makes erosion due to cavitation more likely to occur. In this embodiment, as described above, the notched groove 45 is formed on the side of the body 40 (first inner side surface portion 41), which has a great practical benefit 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 surface portion 51. The notched groove 45 is formed in the first inner surface portion 41 so that the area of ​​the notched groove 45 that presses against the high-pressure oil as viewed in the axial direction is approximately the same as that of the inner groove 52. With this configuration, the second gear 20 can be pressed with equal and balanced force from both sides in the axial direction. Therefore, gaps can be secured between both sides of the second gear 20 and each of the first inner surface portion 41 and the second inner surface portion 51. This makes it possible to more effectively suppress the occurrence of erosion due to cavitation.

[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] Conventional diesel engine oil pumps mainly use external gear pumps, in which a pump drive gear rotates in conjunction with the engine's crankshaft, driving meshing pump gears in rotation with the rotational force. In external gear pumps, the rotation of the pump gear introduces oil from the suction port into the tooth grooves, which then rotates the pump gear and pumps the oil to the discharge port. The oil is delivered by changing the pressure in the pump gear grooves from suction pressure to discharge pressure. To prevent a decrease in pump efficiency, extremely small gaps are configured between the sides of the meshing pump gears and the bottom of the gear chamber and the cover mounting surface.

[0057] However, in conventional external gear pumps, when the rotation of the meshing pump gears pressurizes oil introduced into the tooth grooves from the suction port and delivers it to the discharge port, the high-pressure oil on the discharge side easily passes between the sides of the pump gear and the bottom of the gear chamber and the cover mounting surface, flowing into the low-pressure suction port. Furthermore, because the oil inside the external gear pump is used to lubricate the pump gear bearings, the pump gear tends to shift to one side depending on the direction of oil flow, narrowing the gaps on the sides of the pump gear. This tends to result in extremely narrow gaps between the sides of the pump gear and the bottom of the gear chamber and the cover mounting surface. This causes the oil to flow through the gaps at a high flow rate (creating low-pressure areas), making cavitation more likely. Furthermore, when the pump gear rotates to pump oil from the suction port to the discharge port and deliver it to the discharge port, the high-pressure oil on the discharge side easily invades the tooth grooves of the pump gear. In particular, triple-type external gear pumps do not have sufficient length for the pumping section from the suction port to the discharge port, which causes the pressure in the tooth groove 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 and the discharge ports 4A, 4B, thereby preventing a decrease in pump efficiency and suppressing the occurrence of cavitation in the gaps between the side of the second gear 20 and the first inner side surface 41 (gear chamber bottom surface) and the second inner side surface 51 (cover mounting surface).In addition, the occurrence of cavitation due to a sudden increase in pressure in the tooth grooves of the second gear 20 when pressurized oil is delivered to the discharge ports 4A, 4B is suppressed, and the occurrence of erosion due to cavitation is also suppressed.

[0059] 16 to 19 , high-pressure oil is introduced into the notched groove 45, which communicates with the discharge ports 4A and 4B, filling the side of the second gear 20 on the inner circumferential side of the root circle Dc with high-pressure oil. The high-pressure oil pushes back the second gear 20, which is biased to one side in the axial direction, thereby ensuring large gaps between both sides of the second gear 20 and the gear chamber bottom and cover mounting surface. This allows the flow velocity of the high-pressure oil flowing through these gaps to be kept low, and the decrease in the flow velocity of the high-pressure oil when released to the low-pressure side reduces the drop in oil pressure. This suppresses cavitation that occurs in the gaps with the side of the second gear 20.

[0060] Furthermore, oil introduced into the tooth grooves of the second gear 20 from the suction ports 3A and 3B moves to the discharge ports 4A and 4B as the pump gears 10, 20, and 30 rotate. As the pressure in the tooth grooves of the second gear 20 transitions from suction pressure to discharge pressure, the notched grooves 45 communicate with the high-pressure discharge ports 4A and 4B. Therefore, as shown in FIG. 17 , once the tooth grooves of the second gear 20 reach the notched grooves 45, the pressure in the tooth grooves gradually increases. In the initial stage when the tooth grooves of the second gear 20 reach the notched grooves 45, most of the notched grooves 45 are covered by the second gear 20. Therefore, the pressure in the tooth grooves of the second gear 20 gradually increases. That is, the pressure in the tooth grooves of the second gear 20, which communicate with the notched grooves 45, increases slowly.

[0061] 18 and 19, as the rotation of the pump gears 10, 20, and 30 progresses, the notched grooves 45 that open into the tooth grooves of the second gear 20 expand, and the pressure further increases and approaches the discharge pressure. This suppresses the sudden increase in pressure in the tooth grooves of the second gear 20 that occurs when the pumped oil is sent to the discharge ports 4A and 4B. This therefore suppresses the occurrence of cavitation and erosion due to cavitation.

[0062] In this embodiment, a portion of the notched groove 45 extends from the portion of the partition wall 42 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 in communication with the suction ports 3A and 3B. This makes it possible to avoid a decrease in pump efficiency due to the formation of the notched groove 45.

[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 due to a sudden increase in pressure in the tooth grooves of the second gear 20 that occurs when pressurized oil is delivered to the discharge ports 4A, 4B, and it is also possible to suppress the occurrence of erosion due to cavitation.

[0064] <Modifications> In the above-described embodiment, an example has been described in which some of the notched grooves are located more inward than the root circle of the second gear when viewed from the axial direction, but this is not limiting. For example, all of the notched grooves may be located more outward than the root circle of the second gear when viewed from the axial direction. For example, at least some of the notched grooves may be located more inward than the root circle of the second gear when viewed from the axial direction. For example, the arrangement of the notched grooves relative to the root circle of the second gear can be changed depending on the design specifications.

[0065] In the above-described embodiment, an example has been described in which a portion 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 to this. For example, a portion 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 relative to the pitch circle of the second gear can be changed according to design specifications.

[0066] In the above-described embodiment, an example has been described in which, as viewed from the axial direction, a portion of the outer shape of the notched groove 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. However, this is not limited to this. For example, as viewed from the axial direction, a portion of the outer shape of the notched groove does not have to overlap with the bisection point. For example, the arrangement of the outer shape of the notched groove relative to the bisection point can be changed according to design specifications.

[0067] In the above-described embodiment, when the first surface of the tooth of the second gear facing downstream in the rotational direction of the second gear overlaps with the discharge edge as viewed from the axial direction, a portion of the contour of the notched groove overlaps with the intersection point where the second surface of the tooth of the second gear facing upstream in the rotational direction of the second gear intersects with the pitch circle. However, this is not limited to this. For example, when the first surface of the tooth of the second gear facing downstream in the rotational direction of the second gear overlaps with the discharge edge as viewed from the axial direction, a portion of the contour of the notched groove does not have to overlap with the intersection point. For example, the arrangement of the contour of the notched groove relative to the intersection point can be changed depending on the design specifications.

[0068] In the above-described embodiment, an example has been described in which the outer shape of the notched groove, as 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, as 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 relative 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 wall has an inlet edge that defines the inlet port, and a portion of the notched groove extends from a portion between the inlet edge and the outlet edge of the partition wall to the outlet edge, increasing its opening area as the second gear rotates. However, this is not limiting. For example, the entire notched groove may have a constant opening area from a portion between the inlet edge and the outlet edge of the partition wall to the outlet edge. For example, at least a portion of the notched groove may extend from a portion between the inlet edge and the outlet edge of the partition wall to the outlet edge, increasing its opening area as the second gear rotates. For example, the size of the opening area of ​​the notched groove as the second gear rotates may be changed according to 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 to this. For example, the opening area of ​​all of the notched grooves may not change when viewed from the axial direction. For example, the opening area of ​​at least a portion of the notched grooves 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 of the notched groove, 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 was described in which the notched grooves were formed in the first inner side surface portion but not in the second inner side surface portion, but this is not limited thereto. For example, the notched grooves may be formed in both the first inner side surface portion and the second inner side surface portion. This configuration can suppress the occurrence of erosion due to cavitation in the inner side surface portions 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 fixed to the body, and the other end fixed to the cover, and a bearing disposed between the inner circumferential surface of the second gear and the outer circumferential surface of the shaft, with an oil groove formed therein. The second gear, the shaft, and the bearing are configured to allow oil to flow from the cover side toward the body side through the oil groove. However, this is not limiting. For example, the second gear, the shaft, and the bearing may be configured to allow oil to flow from the body side toward the cover side through the oil groove. For example, the direction of oil flow through the oil groove can be changed depending on design specifications.

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

[0075] In the above-described embodiment, the external gear pump is described as being mounted on a diesel engine, but this is not limiting. 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 to the configuration are possible within the scope of the spirit of the present invention, and the above-described embodiments can also be combined as appropriate.

[0077] (Supplementary Note 1) An external gear pump comprising: a first gear driven to rotate by a drive source; a second gear meshing with the first gear and rotating in a driven manner; a third gear meshing with the second gear and rotating 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 and a discharge port through which the oil is discharged, 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 that separates the suction port and the discharge port, and a notched groove is formed in the discharge edge.

[0078] (Supplementary Note 2) The external gear pump according to Supplementary Note 1, wherein at least a portion of the notched groove is disposed on an inner peripheral side of a root circle of the second gear when viewed in an axial direction along the rotation axis of the second gear.

[0079] (Supplementary Note 3) The external gear pump according to Supplementary Note 2, wherein a part of an outer shape of the notched groove overlaps with a pitch circle of the second gear when viewed from the axial direction.

[0080] (Supplementary Note 4) The external gear pump according to Supplementary Note 3, wherein, as viewed from the axial direction, a part of an outer shape of the notched groove overlaps with a bisection point that divides equally a distance between the root circle and an outer shape of a bearing of the second gear in a radial direction perpendicular to the axial direction.

[0081] (Supplementary Note 5) The external gear pump according to Supplementary Note 4, wherein when a first surface of a 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 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.

[0082] (Supplementary Note 6) The external gear pump according to Supplementary Note 5, wherein an outer shape of the notched groove, as viewed from the axial direction, includes a curved shape that overlaps with the pitch circle, the bisection point, and the intersection point.

[0083] (Supplementary Note 7) The external gear pump according to Supplementary Note 6, wherein the partition wall has a suction edge that forms an edge of the suction port, and at least a portion of the notched 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 increases as the second gear rotates.

[0084] (Supplementary Note 8) The external gear pump according to Supplementary Note 7, wherein the opening area of ​​at least a part of the notched groove changes when viewed from the axial direction.

[0085] (Supplementary Note 9) The external gear pump according to Supplementary Note 7 or 8, wherein the opening area of ​​at least a part of the notched groove changes in a cross section of the notched groove cut along a plane parallel to the axial direction.

[0086] (Supplementary Note 10) The external gear pump according to any one of Supplementary Notes 1 to 9, wherein the notched groove is formed in each of the first inner side surface portion and the second inner side surface portion.

[0087] (Appendix 11) The external gear pump according to any one of Appendices 1 to 10, further comprising: a shaft extending in an axial direction along the rotation axis of the second gear, one end fixed to the body and the other end fixed to the cover; and a bearing arranged between the inner peripheral surface of the second gear and the outer peripheral surface of the shaft, the bearing having an oil groove formed therein, wherein the second gear, the shaft, and the bearing are configured to cause the oil to flow from the cover side toward the body side through the oil groove.

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

[0089] (Supplementary Note 13) The external gear pump according to any one of Supplementary Notes 1 to 12, wherein the external gear pump is mounted on an engine.

[0090] DESCRIPTION OF SYMBOLS 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... root circle, F1... first surface of tooth, F2... second surface of tooth, Ip... intersection point, Pc... pitch circle

Claims

1. An external gear pump comprising: a first gear rotated by a drive source; a second gear meshing with the first gear and rotating in a driven manner; a third gear meshing with the second gear and rotating 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, 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 which 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.

2. The external gear pump according to claim 1, wherein at least a portion of the notched groove is positioned on the inner peripheral side of a bottom circle of the second gear when viewed in an axial direction along the rotation axis of the second gear.

3. The external gear pump according to claim 2, wherein a part of an outer shape of the notched groove overlaps with a pitch circle of the second gear when viewed from the axial direction.

4. The external gear pump according to claim 3, wherein, as viewed from the axial direction, a part of the outer shape of the notched groove overlaps with a bisection point that halves the distance between the bottom circle and the outer shape of the bearing of the second gear in a radial direction perpendicular to the axial direction.

5. The external gear pump according to claim 4, wherein when a first surface of a tooth of the second gear facing downstream in the 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, as viewed in the axial direction.

6. The external gear pump according to claim 5, wherein an 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.

7. The external gear pump as set forth in claim 6, wherein the partition has a suction edge which forms the edge of the suction port, and at least a portion of the cutout groove is formed in the partition from a portion between the suction edge and the discharge edge to the discharge edge, and an opening area increases as the second gear rotates.

8. The external gear pump according to claim 7, wherein the opening area of ​​at least a part of the notched groove changes when viewed in the axial direction.

9. The external gear pump according to claim 7 or 8, wherein the opening area of ​​at least a part of the notched groove changes in a cross section taken along a plane parallel to the axial direction of the notched groove.

10. The external gear pump according to any one of claims 1 to 8, wherein the notched groove is formed in each of the first inner side surface portion and the second inner side surface portion.

11. An external gear pump as described in any one of claims 1 to 8, further comprising: a shaft extending in an axial direction along the rotation axis of the second gear, one end fixed to the body and the other end fixed to the cover; and a bearing arranged between the inner surface of the second gear and the outer surface of the shaft, the bearing having an oil groove formed therein, wherein the second gear, the shaft and the bearing are configured to cause the oil to flow from the cover side to the body side through the oil groove.

12. The external gear pump as described in claim 11, wherein an inner groove through which the oil flows is formed on the second inner surface portion, and the notched groove is formed on the first inner surface portion so that the high-pressure oil pressing area as viewed in the axial direction is approximately the same as that of the inner groove.

13. The external gear pump according to any one of claims 1 to 8, wherein the external gear pump is mounted on an engine.

Images