Gear pump

Abstract

To reduce manufacturing costs of a gear pump.SOLUTION: A gear pump 100 includes: a drive gear 1 having a first rotary shaft 3 connected to a power source; a driven gear 2 which is rotatably supported by a second rotary shaft 4 and meshes with the drive gear 1 to be rotated by the drive gear 1; a body 10 which houses the drive gear 1 and the driven gear 2; and a cover 30 which covers an opening of the body 10. The first rotary shaft 3 is rotatably supported by the body 10 and the cover 30 and the second rotary shaft 4 is formed separately from the body 10 and the cover 30 and provided eccentrically with respect to a center axis O1 of the driven gear 2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a gear pump in which a pair of gears rotate while meshing with each other to discharge a fluid. The gear pump includes a body having a pair of gear chambers in which the pair of gears are respectively installed, and a pair of housings disposed on either side of the body and rotatably supporting the rotation shafts of the pair of gears. The body and housing are positioned with a positioning pin and fastened together with a bolt as a fastening member. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] WO2010 / 013354A1 Summary of the Invention [Problem to be solved by the invention]

[0004] In a gear pump such as that described in Patent Document 1, it is conceivable that the meshing state of the pair of gears may change due to manufacturing tolerances of the pair of gears, which could result in a deterioration in the performance of the gear pump due to, for example, hydraulic oil flowing back from the high-pressure side to the low-pressure side of the gear chamber through the meshing portion of the pair of gears.

[0005] The present invention has been made in view of the above problems, and has an object to improve the performance of gear pumps. [Means for solving the problem]

[0006] The present invention is a gear pump comprising: a drive gear having a first rotating shaft connected to a power source; a driven gear rotatably supported on a second rotating shaft and meshing with the drive gear so as to be rotated by the drive gear; a body that houses the drive gear and driven gear; and a cover that covers an opening of the body, wherein the first rotating shaft is rotatably supported by the body and the cover, and the second rotating shaft is formed separately from the body and the cover and is disposed eccentrically with respect to the central axis of the driven gear.

[0007] In this invention, when the second rotating shaft, which is formed separately from the body and the cover, is attached, the second rotating shaft is rotated to adjust its circumferential position, thereby adjusting the position of the driven gear so as to reduce backlash between the drive gear and the driven gear. In other words, the position of the driven gear can be adjusted according to the manufacturing tolerances of the drive gear and the driven gear, thereby improving the performance of the gear pump.

[0008] The present invention is also characterized in that the gear pump further comprises a plurality of positioning pins provided between the body and the cover for positioning the cover relative to the body, and the second rotation shaft of the driven gear constitutes one of the positioning pins.

[0009] In this invention, the positioning pin that positions the cover relative to the body also serves as the second rotation shaft of the driven gear, thereby reducing the number of parts in the gear pump.

[0010] The present invention is also characterized in that the second rotary shaft of the driven gear is provided with a rotation stopper that restricts relative rotation of the second rotary shaft with respect to the body or the cover.

[0011] In this invention, the rotation stopper restricts the relative rotation of the second rotary shaft with respect to the body and the cover, thereby making it possible to stabilize the operation of the gear pump.

[0012] The present invention is also characterized in that the second rotary shaft is fitted into one of the body and the cover to position the cover relative to the body.

[0013] In this invention, the second rotating shaft of the driven gear positions the cover relative to the body. In other words, in the gear pump, the second rotating shaft of the driven gear also serves as a positioning member that positions the cover relative to the body. Therefore, since the second rotating shaft has two functions, that is, positioning the cover relative to the body and serving as the rotating shaft of the driven gear, the number of parts in the gear pump can be reduced. [Effects of the Invention]

[0014] According to the present invention, the performance of the gear pump can be improved. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a cross-sectional view of a gear pump according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Figure 3] 10A and 10B are schematic diagrams illustrating a rotation stopper according to a modified example of the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] A gear pump 100 according to an embodiment of the present invention will now be described with reference to the drawings. The gear pump 100 is mounted on hydraulic machinery such as a forklift or a hydraulic excavator, and discharges hydraulic oil as a working fluid to drive actuators and other components of the hydraulic machinery. The gear pump 100 may also discharge fluids other than hydraulic oil, such as water. The use of the gear pump 100 is not limited to driving actuators and other components, and it can also be used for cooling or lubricating equipment.

[0017] Fig. 1 is a cross-sectional view of gear pump 100, and Fig. 2 is a cross-sectional view taken along line III-III in Fig. 1, showing a cross section including a pair of gears, namely, a drive gear 1 and a driven gear 2. In Fig. 2, the positions of a suction port 25 and a discharge port 27, which are not visible in the drawing and will be described later, are indicated by dotted lines.

[0018] As shown in FIG. 1, the gear pump 100 includes a drive gear 1 having a first rotating shaft 3 connected to a power source (not shown), a driven gear 2 rotatably supported on a second rotating shaft 4 and meshing with the drive gear 1 so as to be rotated by the drive gear 1, a body 10 that houses the drive gear 1 and the driven gear 2, a cover 30 that covers an opening 10a of the body 10, bolts 40 as multiple fastening members that secure the body 10 and the cover 30, and a positioning pin 45 that is provided between the body 10 and the cover 30 and that positions the cover 30 relative to the body 10.

[0019] The gear pump 100 discharges hydraulic oil as a result of the rotation of a drive gear 1 and a driven gear 2. When the first rotating shaft 3 is rotated by the power of a power source, the drive gear 1 rotates, and the driven gear 2 meshing with the drive gear 1 also rotates. In the gear pump 100 of this embodiment, the second rotating shaft 4 of the driven gear 2 is formed separately (as a separate member) from the body 10 and the cover 30, as will be described later, and is provided eccentrically with respect to the central axis O1 of the driven gear 2. The driven gear 2 is rotatably supported on the second rotating shaft 4 via a bushing 50. The first rotating shaft 3 and the second rotating shaft 4 are provided to extend parallel to each other. Note that, hereinafter, the axial direction of the first rotating shaft 3 and the second rotating shaft 4 will also be simply referred to as the "axial direction."

[0020] In this embodiment, the body 10 is formed by casting using a metal such as iron. As shown in Figures 1 and 2, the body 10 has a gear chamber 21 having an opening 10a and accommodating the drive gear 1 and the driven gear 2, an intake port 25 (see Figure 2) that sucks in hydraulic oil and directs it to the low-pressure side of the gear chamber 21, and a discharge port 27 (see Figure 2) that directs hydraulic oil discharged from the high-pressure side of the gear chamber 21. The body 10 is formed in a substantially rectangular parallelepiped shape, and a cover 30 is attached to it.

[0021] 1 and 2, the gear chamber 21 is formed into an elliptical shape in a cross section including the drive gear 1 and the driven gear 2 (see FIG. 2), and the teeth 1a of the drive gear 1 and the teeth 2a of the driven gear 2 are in sliding contact with the inner peripheral surface 21a. The body 10 is subjected to the pressure of the hydraulic oil in the gear chamber 21, but because it is formed by casting using a metal such as iron and has high strength, damage to the body 10 is prevented.

[0022] As shown in FIG. 1 , the bottom 21b of the gear chamber 21 is formed with an accommodation hole 21c that accommodates one end of the first rotating shaft 3 of the drive gear 1, and an accommodation hole 21d that accommodates one end of the second rotating shaft 4. The cover 30 is also formed with a through-hole 30a coaxial with the accommodation hole 21c, through which the first rotating shaft 3 of the drive gear 1 is inserted, and with an accommodation hole 30b coaxial with the accommodation hole 21d, through which the end of the second rotating shaft 4 of the driven gear 2 is accommodated. The first rotating shaft 3 is disposed between the accommodation hole 21c and the through-hole 30a, and is rotatably supported by the body 10 and the cover 30 via a bearing 61. The second rotating shaft 4 is fitted into the accommodation hole 21d of the body 10 and into the accommodation hole 30b of the cover 30. As a result, the second rotating shaft 4, together with a positioning pin 45, determines the position of the cover 30 relative to the body 10, as will be described later. A seal member 38 is provided between the outer peripheral surface of the first rotating shaft 3 and the inner peripheral surface of the through hole 30a.

[0023] 2, suction port 25 and discharge port 27 are formed in body 10 in symmetrical shapes. Suction port 25 has an opening 25a that opens to side surface 10b of body 10 and a passage 25b that connects opening 25a to gear chamber 21. Discharge port 27 similarly has an opening 27a that opens to side surface 10c of body 10 opposite side surface 10b and a passage 27b that connects opening 27a to gear chamber 21. Suction port 25 has a piping (not shown) or the like connected to opening 25a to draw in hydraulic oil from the outside, and discharge port 27 has a piping (not shown) or the like connected to opening 27a to supply hydraulic oil to the outside.

[0024] The body 10 is formed with a plurality of insertion holes 15 through which bolts 40 are inserted. In the gear pump 100 of this embodiment, the body 10 and the cover 30 are fixed together by a plurality of bolts 40 provided, for example, at each of the four corners of the body 10. The bolts 40 are fastened from the body 10 side (the left side in FIG. 1 ), and the insertion holes 15 are formed by penetrating the body 10. No female thread is formed on the inner circumferential surface of the insertion holes 15, and the bolts 40 are inserted into the insertion holes 15 without being threadedly coupled to the insertion holes 15. The male threads 40a of the bolt 40 may be formed only at the tip of the shaft portion, or may be formed along the entire shaft portion.

[0025] In this embodiment, the cover 30 is made of aluminum and is formed into a shape by die casting. As shown in Fig. 1, the cover 30 has a main body 35 and an attachment portion 31 formed by partially protruding radially from the main body 35.

[0026] The main body 35 is formed with an annular fitting portion 36 that protrudes from the main body 35 toward the mounting target and fits into a recess in the mounting target. When mounting the gear pump 100 to the mounting target, the fitting portion 36 is fitted into the recess in the mounting target, thereby aligning the gear pump 100 (cover 30) with the mounting target. Then, with the two aligned, bolts (not shown) are inserted into notches (not shown) in the main body 35 and fastened to the mounting target, thereby fixing the two together. The mounting portion 31 is formed in a shape corresponding to the body 10. The mounting portion 31 is formed with a plurality of fastening holes 37 (see FIG. 1 ) into which bolts 40 are inserted and fastened. The fastening holes 37 are each formed to penetrate the mounting portion 31. An internal thread 37a is formed on the inner peripheral surface of the fastening hole 37, and each bolt 40 is threadedly coupled to the fastening hole 37.

[0027] As shown in FIG. 1 , the positioning pin 45 is inserted into pin holes 46 and 47 formed in the mounting portion 31 of the body 10 and the cover 30, respectively. The positioning pin 45 is fitted into the pin holes 46 and 47, and the second rotating shaft 4 of the driven gear 2 is fitted into the housing hole 21d of the body 10 and the housing hole 30b of the cover 30. This restricts relative movement between the body 10 and the cover 30, thereby positioning the cover 30 relative to the body 10. In other words, the second rotating shaft 4 also serves as a positioning member that positions the cover 30 relative to the body 10, and has two functions: positioning the cover 30 relative to the body 10 and serving as the rotation shaft of the driven gear 2. In other words, the second rotating shaft 4 constitutes one of the multiple positioning pins 45 that position the cover 30 relative to the body 10. This allows for a reduction in the number of positioning pins 45, thereby reducing the number of parts in the gear pump 100. Furthermore, the manufacturing cost of the gear pump 100 can be reduced because the effort required for machining the pin holes 46, 47 and for inserting the positioning pin 45 is reduced. Only one positioning pin 45 may be provided, or multiple positioning pins 45 may be provided at intervals in the circumferential direction. As long as the positioning pin 45 can position the cover 30 relative to the body 10, the second rotating shaft 4 does not necessarily have to be fitted into the housing hole 21d of the body 10 and the housing hole 30b of the cover 30, and the second rotating shaft 4 does not necessarily have to function as a positioning member that positions the cover 30 relative to the body 10. Once the cover 30 is positioned relative to the body 10, the bolts 40 are attached to secure the cover 30 to the body 10.

[0028] In this gear pump 100, the drive gear 1 and the driven gear 2 are rotated in the direction of the arrows shown in Fig. 2 by the power of the drive source while meshing with each other. When the drive gear 1 and the driven gear 2 rotate, the hydraulic oil is guided from the suction port 25 to the low-pressure side (right side in Fig. 2) of the gear chamber 21, is guided between adjacent teeth 1 a of the drive gear 1 and between adjacent teeth 2 a of the driven gear 2, moves along the inner circumferential surface 21 a of the gear chamber 21, is guided to the high-pressure side (left side in Fig. 2) of the gear chamber 21, and is discharged through the discharge port 27.

[0029] Next, the second rotary shaft 4 of the driven gear 2 will be described in detail.

[0030] As shown in FIG. 1, the second rotating shaft 4 has a large-diameter portion 4a formed at one end (the left end in FIG. 1) and having the largest diameter, a medium-diameter portion 4b formed continuously with the large-diameter portion 4a and having a smaller diameter than the large-diameter portion 4a, and a small-diameter portion 4c formed at the other end (the right end in FIG. 1) and having the smallest diameter. Between the large-diameter portion 4a and the medium-diameter portion 4b, a sloped portion 4d is formed in a portion of the circumferential direction, so that the center of the medium-diameter portion 4b is eccentric with respect to the center of the large-diameter portion 4a (in FIG. 1, it is eccentric above the center of the large-diameter portion 4a). Between the medium-diameter portion 4b and the small-diameter portion 4c, a sloped portion 4e is formed on the opposite side of the sloped portion 4d in the circumferential direction, so that the center of the small-diameter portion 4c is eccentric with respect to the center of the medium-diameter portion 4b (in FIG. 1, it is eccentric below the center of the medium-diameter portion 4b), so that the large-diameter portion 4a and the small-diameter portion 4c are coaxial. That is, only the medium diameter portion 4b of the second rotating shaft 4 is formed eccentrically. In other words, the central axis O2 of the second rotating shaft 4 is the same as the central axes of the large diameter portion 4a and the small diameter portion 4c, but is different from the central axis of the medium diameter portion 4b. The driven gear 2 is provided on the outer peripheral surface of the medium diameter portion 4b. This makes the second rotating shaft 4 eccentric with respect to the driven gear 2 (the central axis O1 of the driven gear 2). Note that the sizes of the inclined portions 4d and 4e are exaggerated in FIG. 2.

[0031] The large-diameter portion 4a of the second rotating shaft 4 is formed with a tool hole 4f for fitting with a tool such as a hex wrench, and the bottom surface 10d of the body 10 is formed with an adjustment hole 10h that communicates with the accommodation hole 21d. In the gear pump 100 of this embodiment, when the second rotating shaft 4 is attached, the second rotating shaft 4 is rotated to adjust its circumferential position, thereby adjusting the position of the driven gear 2 (in other words, the distance between the drive gear 1 and the driven gear 2) so as to reduce backlash between the drive gear 1 and the driven gear 2. Specifically, the circumferential position of the second rotating shaft 4 is adjusted by inserting a tool into the tool hole 4f of the second rotating shaft 4 through the adjustment hole 10h and rotating the tool after the second rotating shaft 4 is accommodated in the accommodation hole 21d.

[0032] The second rotating shaft 4 is provided with a rotation stopper 60 that restricts relative rotation of the second rotating shaft 4 with respect to the body 10. The rotation stopper 60 is, for example, a pin-shaped member. Specifically, an insertion hole 4g ​​into which the tip of the rotation stopper 60 is inserted is formed in one end (the end on the body 10 side) of the second rotating shaft 4, and a through hole 10f that can communicate with the insertion hole 4g ​​(in other words, the gear chamber 21) is formed in the bottom surface 10d of the body 10. The through hole 10f and the insertion hole 4g ​​are formed, for example, by adjusting the circumferential position of the second rotating shaft 4 as described above, and then machining from the bottom surface 10d of the body 10 to the second rotating shaft 4 with a drill or the like.

[0033] To attach the second rotating shaft 4, first, the second rotating shaft 4 is accommodated in the accommodation hole 21d, and then the circumferential position is adjusted using a tool so that backlash between the drive gear 1 and the driven gear 2 is reduced. Then, the through hole 10f and the insertion hole 4g ​​are formed using a drill or the like, and the rotation stopper 60 is inserted through the through hole 10f from the body 10 side into the through hole 10f and the insertion hole 4g. This restricts the relative rotation of the second rotating shaft 4 with respect to the body 10, and the second rotating shaft 4 is attached. Alternatively, the insertion hole 4g ​​may be formed at the other end (the end on the cover 30 side) of the second rotating shaft 4, and a through hole 10f may be formed in the cover 30 so as to communicate with the insertion hole 4g, and the rotation stopper 60 may be inserted through the through hole 10f from the cover 30 side into the insertion hole 4g ​​and the insertion hole 4g. In this case, the relative rotation of the second rotating shaft 4 with respect to the cover 30 is restricted. Furthermore, in cases where the second rotary shaft 4 is press-fitted, the rotation stopper 60 does not have to be provided, and the rotation stopper 60 is not an essential component of the gear pump 100.

[0034] In this way, in the gear pump 100, the position of the driven gear 2 can be adjusted to reduce backlash between the drive gear 1 and the driven gear 2. In other words, the position of the driven gear 2 can be adjusted according to the manufacturing tolerances of the drive gear 1 and the driven gear 2. This makes it possible to prevent hydraulic oil from flowing back from the high-pressure side to the low-pressure side of the gear chamber 21 through the meshing portion between the drive gear 1 and the driven gear 2, for example. This therefore improves the performance of the gear pump 100.

[0035] Furthermore, in the gear pump 100, the rotation stopper 60 restricts the relative rotation of the second rotary shaft 4 with respect to the body 10 and the cover 30, thereby making it possible to stabilize the operation of the gear pump 100.

[0036] According to the present embodiment described above, the following effects are achieved.

[0037] In the gear pump 100, when the second rotating shaft 4 is attached, the position of the driven gear 2 can be adjusted to reduce backlash between the drive gear 1 and the driven gear 2. In other words, the position of the driven gear 2 can be adjusted according to the manufacturing tolerances of the drive gear 1 and the driven gear 2, thereby improving the performance of the gear pump 100.

[0038] Next, modified examples of this embodiment will be described. The following modified examples are also within the scope of the present invention, and it is possible to combine the configurations shown in the modified examples with the configurations described in the above embodiment, or to combine the configurations described in the different modified examples below.

[0039] <Modification> In the gear pump 100 of the above embodiment, a pin-shaped rotation stopper 60 is provided to restrict the rotation of the second rotating shaft 4 relative to the body 10. However, the configuration for restricting the rotation of the second rotating shaft 4 relative to the body 10 is not limited to the above. For example, as shown in FIG. 3(a), in a gear pump 200, a tip end 160a of a bolt 160 may be coupled to a tool hole 4f of the second rotating shaft 4 as a rotation stopper. FIG. 3(a) is an enlarged view showing a state in which the bolt 160 is attached, and FIG. 3(b) is a plan view showing a head 160b of the bolt 160 before attachment. As shown in FIG. 3(b), the head 160b of the bolt 160 has an annular portion 160c formed with approximately the same diameter as the adjustment hole 10h, a plurality of wedges 160d formed on the outer peripheral surface of the annular portion 160c at intervals in the circumferential direction, and a tool hole 160e into which a tool (not shown) for attaching the bolt 160 is inserted. The tip portion 160a of the bolt 160 is formed with approximately the same outer shape as the tool hole 4f of the second rotating shaft 4. The wedge 160d protrudes radially from the outer circumferential surface of the annular portion 160c and is formed with a diameter larger than the inner diameter of the adjustment hole 10h. The wedge 160d is plastically deformable so as to be crushed radially inward, and four wedges 160d are formed in this modified example. To restrict the relative rotation of the second rotating shaft 4, first, a tool is attached to the tool hole 160e of the bolt 160, and a portion of the tip portion 160a of the bolt 160 (the end on the right side in FIG. 3(a)) is inserted through the adjustment hole 10h so as to fit into the tool hole 4f of the second rotating shaft 4. At this time, the head 160b of the bolt 160 is inserted into the adjustment hole 10h up to a region where the wedge 160d is not formed, and the tip portion 160a of the bolt 160 is not entirely inserted into the tool hole 4f. The tool is then rotated to rotate the bolt 160, thereby circumferentially aligning the second rotating shaft 4. The tool is then used to further press the bolt 160 into the adjustment hole 10h, and the entire tip portion 160a of the bolt 160 is inserted into the tool hole 4f. As a result, the wedge 160d, which has a diameter larger than that of the adjustment hole 10h, is press-fit into the adjustment hole 10h while undergoing plastic deformation, thereby restricting the relative rotation of the second rotating shaft 4 with respect to the body 10. With this configuration, the relative rotation of the second rotating shaft 4 can be easily restricted.

[0040] The configuration, operation, and effects of the embodiment of the present invention will be described below.

[0041] The gear pump 100, 200 comprises a drive gear 1 having a first rotating shaft 3 connected to a power source, a driven gear 2 rotatably supported on a second rotating shaft 4 and meshing with the drive gear 1 so as to be rotated by the drive gear 1, a body 10 in which the drive gear 1 and driven gear 2 are housed, and a cover 30 that covers an opening 10a of the body 10, wherein the first rotating shaft 3 is rotatably supported by the body 10 and the cover 30, and the second rotating shaft 4 is formed separately from the body 10 and the cover 30 and is disposed eccentrically with respect to the central axis O1 of the driven gear 2.

[0042] In this configuration, when attaching the second rotating shaft 4, which is formed separately from the body 10 and the cover 30, the second rotating shaft 4 is rotated to adjust its circumferential position, thereby adjusting the position of the driven gear 2 so as to reduce backlash between the drive gear 1 and the driven gear 2. In other words, the position of the driven gear 2 can be adjusted according to the manufacturing tolerances of the drive gear 1 and the driven gear 2, thereby improving the performance of the gear pumps 100, 200.

[0043] In addition, the gear pumps 100, 200 further include a plurality of positioning pins 45 that are provided between the body 10 and the cover 30 and position the cover 30 relative to the body 10, and the second rotating shaft 4 of the driven gear 2 constitutes one of the positioning pins 45.

[0044] In this configuration, the positioning pin 45 that positions the cover 30 relative to the body 10 also serves as the second rotation shaft 4 of the driven gear 2. Therefore, the positioning pin 45 has two functions: to position the cover 30 relative to the body 10 and to serve as the second rotation shaft 4 of the driven gear 2, which reduces the number of parts in the gear pumps 100 and 200. As a result, the manufacturing costs of the gear pumps 100 and 200 can be reduced.

[0045] In the gear pumps 100 and 200, the second rotary shaft 4 of the driven gear 2 is provided with a rotation stopper 60 (bolt 160) that restricts the relative rotation of the second rotary shaft 4 with respect to the body 10 or the cover 30.

[0046] In this configuration, the rotation stopper 60 (bolt 160) restricts the relative rotation of the second rotary shaft 4 with respect to the body 10 and the cover 30, thereby making it possible to stabilize the operation of the gear pumps 100, 200.

[0047] In the gear pumps 100 and 200, the second rotary shaft 4 is fitted into one of the body 10 and the cover 30, thereby positioning the cover 30 relative to the body 10.

[0048] In this configuration, the second rotating shaft 4 of the driven gear 2 positions the cover 30 relative to the body 10. In other words, in the gear pump 100, the second rotating shaft 4 of the driven gear 2 also serves as a positioning member that positions the cover 30 relative to the body 10. Therefore, since the second rotating shaft 4 has two functions, that is, to position the cover 30 relative to the body 10 and to serve as the rotating shaft of the driven gear 2, the number of parts in the gear pumps 100 and 200 can be reduced.

[0049] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments. [Explanation of symbols]

[0050] 1 drive gear, 2... driven gear, 3... first rotating shaft, 4... second rotating shaft, 10... body, 10a... opening, 30... cover, 45... positioning pin, 60... rotation stopper, 160... bolt (rotation stopper), 100, 200... gear pump

Claims

1. a drive gear having a first rotation shaft connected to a power source; a driven gear that is rotatably supported on a second rotation shaft, and that meshes with the drive gear and is rotated by the drive gear; a body in which the drive gear and the driven gear are housed; a cover that covers the opening of the body, the first rotation shaft is rotatably supported by the body and the cover, The gear pump, wherein the second rotation shaft is formed separately from the body and the cover, and is disposed eccentrically with respect to a central axis of the driven gear.

2. 2. The gear pump according to claim 1, a plurality of positioning pins provided between the body and the cover for positioning the cover relative to the body; The gear pump, wherein the second rotation shaft of the driven gear constitutes one of the positioning pins.

3. 2. The gear pump according to claim 1, The gear pump according to claim 1, wherein the second rotary shaft of the driven gear is provided with a rotation stopper that restricts relative rotation of the second rotary shaft with respect to the body or the cover.

4. 2. The gear pump according to claim 1, The gear pump according to claim 1, wherein the second rotating shaft is fitted into one of the body and the cover to position the cover relative to the body.

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