Gear pump

Abstract

This gear pump (100) comprises: a pair of gears (drive gear (1), driven gear (2)) that rotate while meshing with each other; a body (10) that accommodates the pair of gears; a cover (30) that rotatably supports rotating shafts (3, 4) of the pair of gears; and a plurality of bolts (40) that each have a shaft part (40a) and fix the body (10) and the cover (30) to each other. The body (10) has a gear chamber (21) in which the pair of gears are accommodated while each making sliding contact with an inner peripheral surface (21a) of the gear chamber, a suction port (25) that suctions a working fluid and guides the working fluid to a low-pressure side of the gear chamber (21), and a discharge port (27) that guides the working fluid discharged from a high-pressure side of the gear chamber (21). One among the plurality of bolts (40) is fastened such that at least a part of at least one among the suction port (25) and the discharge port (27) is positioned on an extension line of the shaft part (40a).

Description

gear pump

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

[0002] WO 2010 / 013354 A1 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 mounted, and a pair of housings arranged on either side of the body and rotatably supporting the rotation shafts of the pair of gears. The body and housings are positioned with positioning pins and fastened together with bolts as fastening members. The bolts are fastened from the side of the pair of housings that is farthest from the target to which the gear pump is attached, and the housing has a low-pressure (suction) port that sucks in fluid and directs it to the gear chambers.

[0003] In the gear pump described in WO2010 / 013354 A1, bolts are fastened to a housing in which a suction port is formed, and therefore the bolts must be installed to avoid the suction port, which increases the radial size of the housing to provide space for the bolts, potentially resulting in an increase in the size of the gear pump.

[0004] An object of the present invention is to reduce the size of a gear pump.

[0005] According to one aspect of the present invention, a gear pump comprises a pair of gears that rotate while meshing with each other, a body having an opening formed therein and housing the pair of gears, a cover that covers the opening of the body and rotatably supports the rotating shafts of the pair of gears, and a plurality of fastening members having shaft portions and fastening the body and the cover, wherein the body has a gear chamber in which the pair of gears are housed, each in sliding contact with its inner surface, an intake port that sucks in working fluid and directs it to the low-pressure side of the gear chamber, and an exhaust port that directs working fluid discharged from the high-pressure side of the gear chamber, and one of the plurality of fastening members is fastened so that at least a portion of at least one of the intake port and the discharge port is positioned on an extension line of the shaft portion.

[0006] Fig. 1 is a cross-sectional view of a gear pump according to an embodiment of the present invention. Fig. 2 is a front view of the gear pump as viewed in the direction of arrow II in Fig. 1. Fig. 3 is a front view of the gear pump as viewed in the direction of arrow III in Fig. 1. Fig. 4 is a cross-sectional view taken along line IV-IV in Fig. 1. Fig. 5 is a cross-sectional view taken along line V-V in Fig. 3.

[0007] A gear pump 100 according to an embodiment of the present invention will be described below with reference to the drawings. The gear pump 100 is mounted on a hydraulic machine 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 machine. The gear pump 100 may also discharge fluids other than hydraulic oil, such as water. The gear pump 100 is not limited to being used to drive actuators and other components, and can also be used for cooling or lubricating equipment.

[0008] FIG. 1 is a cross-sectional view of the gear pump 100, FIG. 2 is a front view of the gear pump 100 as viewed in the direction of arrow II in FIG. 1, and FIG. 3 is a front view of the gear pump 100 as viewed in the direction of arrow III in FIG. 1. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 1, showing a cross section including a pair of gears, namely, a drive gear 1 and a driven gear 2. FIG. 5 is a cross-sectional view taken along line V-V in FIG. 3, showing the positional relationship between an intake port 25 (described later) and a bolt 41. The cross-sectional view in FIG. 4 is shown in the same orientation as FIG. 3. Note that FIG. 1 is also a cross-sectional view taken along line I-I in FIG. 4. Furthermore, in FIGS. 1 to 4, the positions of the intake port 25 and the discharge port 27 (described later), which are not visible in the figures, are indicated by dotted lines.

[0009] 1, the gear pump 100 includes a drive gear 1 and a driven gear 2 that rotate while meshing with each other, a body 10 that has an opening 10a formed therein and that houses the drive gear 1 and the driven gear 2, a cover 30 that covers the opening 10a of the body 10 and rotatably supports the rotary shafts 3, 4 of the drive gear 1 and the driven gear 2, and a plurality of bolts 40 as fastening members that secure the body 10 and the cover 30. The gear pump 100 discharges hydraulic oil as the drive gear 1 and the driven gear 2 rotate.

[0010] A rotating shaft 3 is connected to the drive gear 1, and a rotating shaft 4 is connected to the driven gear 2. The rotating shaft 3 is connected to a power source and is rotated by the power of the power source. This causes the drive gear 1 to rotate, and also causes the driven gear 2, which meshes with the drive gear 1, to rotate. Note that hereinafter, the axial direction of the rotating shafts 3 and 4 will also be simply referred to as the "axial direction."

[0011] 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 main body portion 11 and a flange portion 12 that is larger in diameter than the main body portion 11. The flange portion 12 has a rectangular shape with one corner removed (see Figure 2), and a cover 30 is attached to the flange portion 12. The body 10 has a gear chamber 21 that houses the drive gear 1 and the driven gear 2, a suction port 25 that sucks in hydraulic oil and directs it to the low-pressure side of the gear chamber 21, and a discharge port 27 that directs hydraulic oil discharged from the high-pressure side of the gear chamber 21.

[0012] The gear chamber 21 is formed continuous with the opening 10a. As shown in Figures 1 and 4, the gear chamber 21 is formed in an elliptical shape in a cross section including the drive gear 1 and the driven gear 2 (see Figure 4), 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.

[0013] As shown in Figure 1, the bottom 21b of the gear chamber 21 is formed with accommodation holes 21c and 21d that accommodate one end of the rotary shaft 3 of the drive gear 1 and one end of the rotary shaft 4 of the driven gear 2, respectively. In addition, the cover 30 is formed with a through hole 30a, through which the rotary shaft 3 of the drive gear 1 is inserted, coaxially with the accommodation hole 21c, and with an accommodation hole 30b, through which the other end of the rotary shaft 4 of the driven gear 2 is accommodated, coaxially with the accommodation hole 21d. The rotary shaft 3 is rotatably supported between the accommodation hole 21c and the through hole 30a via a bearing 60, and the rotary shaft 4 is rotatably supported between the accommodation hole 21d and the accommodation hole 30b via a bearing 61. A seal member 38 is provided between the outer peripheral surface of the rotary shaft 3 and the inner peripheral surface of the through hole 30a.

[0014] 2 and 5, the body 10 has raised portions 26 and 28 that rise from the flange portion 12 and are formed symmetrically opposite each other. The raised portions 26 and 28 are formed to rise higher than the bottom surface 11a of the main body portion 11 (in other words, to protrude to the left in FIGS. 1 and 5). An opening 25a (described later) of the suction port 25 is formed in a side surface 26a of the raised portion 26, and an opening 27a (described later) of the discharge port 27 is formed in a side surface 28a of the raised portion 28.

[0015] The suction port 25 and the discharge port 27 are formed symmetrically to each other. The suction port 25 has an opening 25a that opens to a side surface 26a of the raised portion 26 and a passage 25b (see FIGS. 3 to 5) that connects the opening 25a to the gear chamber 21. Similarly, the discharge port 27 has an opening 27a that opens to a side surface 28a of the raised portion 28 and a passage 27b (see FIGS. 3 to 5) that connects the opening 27a to the gear chamber 21. The suction port 25 has a piping (not shown) or the like connected to the opening 25a to draw in hydraulic oil from the outside, and the discharge port 27 has a piping (not shown) or the like connected to the opening 27a to supply hydraulic oil to the outside. As shown in Figures 3 to 5, the passage 25b of the suction port 25 is formed from a passage extending from the opening 25a perpendicular to the axial direction of the rotary shafts 3 and 4 and a passage opening to the gear chamber 21 and extending axially (see Figure 5). The same is true for the passage 27b of the discharge port 27. As described above, in the gear pump 100, the openings 25a, 27a of the suction port 25 and the discharge port 27 are offset from the radial outside of the gear chamber 21 toward the bottom surface 11a of the main body 11 (see Figures 1 and 5), and the openings 25a, 27a communicate with the gear chamber 21 through the passages 25b, 27b, respectively. This ensures the strength of the radial outside of the gear chamber 21 and prevents damage to the body 10 due to the pressure of the hydraulic oil in the gear chamber 21.

[0016] A plurality of fastening holes 15 into which bolts 40 are inserted and fastened are formed in the flange portion 12 of the body 10. The configuration of the fastening holes 15 will be described in detail later.

[0017] In this embodiment, the cover 30 is made of aluminum and is formed into a shape by die casting. As shown in Figures 1 and 3, the cover 30 has a main body 35 and an attachment portion 31 that is formed by partially protruding radially from the main body 35.

[0018] The main body 35 faces the mounting target and, as shown in FIGS. 2 and 3 , extends in the linear direction connecting the suction port 25 and the discharge port 27 (the left-right direction in FIGS. 2 and 3 ). A notch 35a is formed at each end of this linear direction, through which a bolt (not shown) is inserted. The main body 35 is formed with a fitting portion 36 that protrudes from the main body 35 toward the mounting target and fits into a recess in the mounting target. Because the fitting portion 36 protrudes further toward the mounting target than the bolt 40, the bolt 40 does not interfere with the fitting of the fitting portion 36. When mounting the gear pump 100 to the mounting target, the gear pump 100 (cover 30) is aligned with the mounting target by fitting the fitting portion 36 into the recess in the mounting target. Then, with the gear pump 100 and cover 30 aligned, a bolt is inserted through the notch 35a of the main body 35 and fastened to the mounting target, thereby fixing the gear pump 100 and cover 30 together. The mounting portion 31 is formed in a shape corresponding to the flange portion 12 of the body 10. The cover 30 is fixed to the body 10 by attaching a bolt 40 across the mounting portion 31 and the flange portion 12.

[0019] A plurality of insertion holes 37 through which bolts 40 are inserted are formed in the cover 30. The configuration of the insertion holes 37 will be described in detail later.

[0020] 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. 4 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 of the gear chamber 21 (left side in Fig. 4) and 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, and is guided to the high-pressure side of the gear chamber 21 (right side in Fig. 4) and discharged through the discharge port 27.

[0021] Next, the fastening of the bolt 40 and the configuration of the fastening hole 15 and the insertion hole 37 will be described in detail.

[0022] In the gear pump 100 of this embodiment, three bolts 40 fasten the body 10 and the cover 30. Each bolt 40 has a shaft portion 40a on which a male thread is formed and a head portion 40b formed with a larger diameter than the shaft portion 40a and to which a tool is fastened. As shown in FIG. 3 , the cover 30 is divided into two imaginary regions A1 and A2 by an imaginary plane A passing through the axes O1 and O2 of both the drive gear 1 and the driven gear 2 (rotating shafts 3 and 4). One bolt 40 is provided on the cover 30 closer to the suction port 25 than the imaginary plane A (imaginary region A1), and two bolts 40 are provided on the cover 30 closer to the discharge port 27 than the imaginary plane A (imaginary region A2).

[0023] Specifically, in the imaginary area A1, a bolt 41 is provided across the main body portion 35 and the fitting portion 36 of the cover 30. The bolt 41 is fastened so that at least a portion of the suction port 25 is located on an extension of the shaft portion 40a. The bolt 41 is fastened from the cover 30 side so that the head portion 40b contacts the cover 30. Although the bolt 41 is provided across the flange portion 12 of the body 10, it does not interfere with the gear chamber 21, the suction port 25, or the discharge port 27. Specifically, as shown in FIG. 5 , the axial length L1 between the seating portion 50 on which the head portion 40b of the bolt 41 is seated in the cover 30 and the suction port 25 (passage 25b) is greater than the length of the shaft portion 40a of the bolt 41.

[0024] In the imaginary area A2, a bolt 42 is provided in the mounting portion 31 of the cover 30, and a bolt 43 is provided in the main body portion 35. The bolts 42, 43 are provided on the cover 30, sandwiching the discharge port 27. The bolts 42, 43 are fastened from the cover 30 side so that their heads 40b contact the cover 30, and although the bolts 42, 43 are provided across the flange portion 12 of the body 10, the gear chamber 21, the suction port 25, and the discharge port 27 are not located on an extension line of the shaft portion 40a, and do not interfere with these.

[0025] As shown in Fig. 2, fastening holes 15a, 15b, and 15c are formed in the flange portion 12 of the body 10 corresponding to the positions of the bolts 41, 42, and 43, respectively. Fastening holes 15b and 15c are formed to pass through the flange portion 12, while fastening hole 15a is formed without passing through the raised portion 26. Note that the position of fastening hole 15a is indicated by a dotted line in Fig. 2. Female threads (not shown) are formed on the inner circumferential surfaces of fastening holes 15a, 15b, and 15c, and are threadedly coupled to the respective bolts 41, 42, and 43.

[0026] Insertion holes 37 are formed in the cover 30 corresponding to the positions of the bolts 41, 42, and 43. Only the insertion hole 37b corresponding to the bolt 42 is shown in Fig. 1. The insertion holes 37 are formed so as to penetrate the cover 30. No female threads are formed on the inner peripheral surface of the insertion hole 37, and the bolt 40 is inserted into the insertion hole 37 without being threadedly coupled to the insertion hole 37.

[0027] As described above, in the gear pump 100 of this embodiment, the bolt 40 is fastened so that the head 40b contacts the cover 30. In the gear pump 100, the suction port 25 and the discharge port 27 are formed on the bottom surface 11a side of the main body portion 11 of the body 10 (in other words, the side opposite the cover 30). Furthermore, in the gear pump 100, the axial length L1 between the seating portion 50 in the cover 30, on which the head 40b of the bolt 41 sits, and the suction port 25 (passage 25b) is longer than the length of the shank 40a of the bolt 41. Therefore, by fastening the bolt 40 from the cover 30 side, which is away from the suction port 25 and the discharge port 27, rather than from the body 10 side, the bolt 40 does not interfere with the suction port 25 and the discharge port 27 regardless of the positions of the suction port 25 and the discharge port 27. Therefore, in the gear pump 100 of this embodiment, the bolt 40 (bolt 41) can be provided so that at least a portion of the suction port 25 is located on its extension. This eliminates the need to install the bolt 40 around the suction port 25, as opposed to fastening the bolt 40 from the body 10 side. Therefore, the bolt 40 can be positioned closer to the suction port 25 (see FIG. 3 ). Therefore, as shown in FIGS. 2 and 3 , the flange portion 12 of the body 10 and the mounting portion 31 of the cover 30 can be reduced in size radially inward to a degree that can support the load of each bolt 40. Specifically, the bolts can be shaped like a rectangle with some corners removed, thereby partially reducing the radial outward projection of the body 10 and the cover 30. This allows the gear pump 100 to be made more compact.

[0028] Furthermore, in the gear pump 100, two bolts 40 are provided in the area of ​​the cover 30 where high pressure acts (virtual area A2) and one bolt 40 is provided in the area where low pressure acts (virtual area A1), so that the body 10 and the cover 30 can be fixed with a smaller number of bolts 40. Therefore, compared to the case where two bolts 40 are provided in the virtual area A1, the body 10 and the cover 30 can be made smaller in the radial direction, and the gear pump 100 can be made smaller.

[0029] Furthermore, if the gear pump 100 were configured such that the bolts 40 were fastened from the body 10 side, the bolts 40 would need to be positioned to avoid the suction port 25 and the discharge port 27, as described above. Furthermore, the body 10, which is formed by casting, has large dimensional tolerances. Therefore, machining of the bolt 40 bearing surfaces in the body 10 would be necessary. Furthermore, the large dimensional tolerances would require a large distance between the bolts 40 (fastening holes 15) and the outer circumferential surface of the main body 11 of the body 10, making it difficult to miniaturize the gear pump 100. In contrast, the gear pump 100 of this embodiment, in which the bolts 40 are fastened from the cover 30 side, allows the body 10 and the cover 30 to be miniaturized in the radial direction, as described above. Furthermore, the cover 30, which is formed by die casting, has high machining accuracy and small dimensional tolerances. Therefore, machining of the bolt 40 bearing surfaces in the cover 30 is unnecessary. Furthermore, because the insertion holes 37 in the cover 30 are not internally threaded, the cover 30 can be machined in one step by die casting, facilitating the manufacture of the gear pump 100. Furthermore, since the dimensional tolerance of the cover 30 formed by die casting is small, there is no need to increase the distance between the bolt 40 (fastening hole 15) and the outer surface of the main body portion 11 of the body 10, making it possible to make the gear pump 100 even more compact.

[0030] 4, in the gear pump 100, the pressure of the hydraulic oil conveyed by the drive gear 1 and the pressure of the hydraulic oil conveyed by the driven gear 2 (in other words, the pressure inside the gear chamber 21) are balanced on the bisector of the distance between the drive gear 1 and the driven gear 2 (the dashed-dotted line B in FIG. 4). Therefore, by arranging the bolts 40 so that at least a portion of the suction port 25 is located on the extension line of the bolts 40, the body 10 and the cover 30 can be fixed by the bolts 40 near the point where the pressure inside the gear chamber 21 is balanced. This allows the body 10 and the cover 30 to be fixed efficiently with fewer bolts 40. Furthermore, since the number of parts is reduced, the cost and weight of the gear pump 100 can be reduced.

[0031] Each bolt 40 may have a configuration in which the head 40b is in indirect contact with the cover 30 via a washer or the like. Furthermore, each bolt 40 is not limited to a configuration in which the shank 40a and the head 40b are formed from the same member as in the above embodiment, but may be formed from separate members. For example, the shank 40a may be formed from a fully threaded bolt or a stud bolt, and the head 40b may be formed from a nut.

[0032] According to the present embodiment described above, the following effects are achieved.

[0033] In the gear pump 100, the bolt 40 (bolt 41) is fastened so that at least a portion of the suction port 25 is positioned on an extension line of the shaft portion 40a, so that the bolt 40 does not interfere with the suction port 25 and the discharge port 27. Therefore, it is not necessary to provide the bolt 40 so as to avoid the suction port 25, and the gear pump 100 can be made smaller.

[0034] 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.

[0035] <Modification 1> In the above embodiment, the body 10 is formed from a single member. However, the present invention is not limited to this, and the body 10 may be formed from multiple members. For example, the body 10 may be divided into a ring member that surrounds the gear chamber 21 and a member that is closer to the bottom surface 11a of the main body 11 than the gear chamber 21. The ring member is formed from a high-strength member to receive the pressure of the hydraulic oil in the gear chamber 21.

[0036] <Modification 2> In the above embodiment, three bolts 40 are provided. However, the number and locations of the bolts 40 are not limited to those described above, as long as each bolt 40 is provided so that at least a portion of the suction port 25 is located on an extension of its shank 40a. For example, two bolts 40 may be provided in the imaginary region A1 so that at least a portion of the suction port 25 is located on an extension of their respective shanks 40a. Furthermore, two bolts 40 may be provided in the imaginary region A2 so that at least a portion of the discharge port 27 is located on an extension of their respective shanks 40a, or one bolt 40 may be provided in the imaginary region A2 so that at least a portion of the discharge port 27 is located on an extension of its shank 40a. In other words, it is sufficient that one of the multiple bolts 40 is fastened so that its head 40b contacts the cover 30 and at least a portion of at least one of the suction port 25 and the suction port 25 is located on an extension of its shank 40a. Even with this configuration, the same effects as those of the above embodiment are achieved.

[0037] The configuration, operation, and effects of the embodiment of the present invention will be described below.

[0038] The gear pump 100 comprises a pair of gears (drive gear 1, driven gear 2) that rotate while meshing with each other, a body 10 that has an opening 10a formed therein and that houses the pair of gears, a cover 30 that covers the opening 10a of the body 10 and rotatably supports the rotating shafts 3, 4 of the pair of gears, and a plurality of bolts 40 that have shaft portions 40a and serve as fastening members that secure the body 10 and the cover 30. The body 10 has a gear chamber 21 in which the pair of gears are housed, each in sliding contact with its inner surface 21a, an intake port 25 that sucks in working fluid and directs it to the low-pressure side of the gear chamber 21, and a discharge port 27 that directs working fluid discharged from the high-pressure side of the gear chamber 21. One of the plurality of bolts 40 is fastened so that at least a portion of at least one of the intake port 25 and the discharge port 27 is positioned on an extension line of the shaft portion 40a.

[0039] In this configuration, by fastening the bolt 40 so that at least a portion of at least one of the suction port 25 and the discharge port 27 is positioned on an extension line of the shaft portion 40a, the bolt 40 does not interfere with the suction port 25 and the discharge port 27. Therefore, it is not necessary to provide the bolt 40 so as to avoid at least one of the suction port 25 and the discharge port 27, and the gear pump 100 can be made smaller.

[0040] In addition, in the gear pump 100, the cover 30 is divided into two imaginary regions A1 and A2 by an imaginary plane A that passes through both axis centers O1 and O2 of the pair of gears, and one bolt 40 is provided on the extension line of the shaft portion 40a on the suction port 25 side of the imaginary plane A on the cover 30, and two bolts 40 are provided on the discharge port 27 side of the imaginary plane A on the cover 30.

[0041] In this configuration, two bolts 40 are provided in the area of ​​the cover 30 where high pressure acts and one bolt 40 is provided in the area where low pressure acts, so that the body 10 and the cover 30 can be fixed with a small number of bolts 40, and the gear pump 100 can be made smaller.

[0042] 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.

[0043] This application claims priority based on Japanese Patent Application No. 2024-58000, filed with the Japan Patent Office on March 29, 2024, the entire contents of which are incorporated herein by reference.

Claims

1. A gear pump comprising: a pair of gears that rotate while meshing with each other; a body having an opening formed therein and accommodating the pair of gears; a cover that covers the opening of the body and rotatably supports the rotation shafts of the pair of gears; and a plurality of fastening members having shaft portions and fastening the body and the cover, wherein the body has a gear chamber in which the pair of gears are accommodated, each in sliding contact with the inner circumferential surface thereof; an intake port that sucks in working fluid and directs it to the low-pressure side of the gear chamber; and a discharge port that directs working fluid discharged from the high-pressure side of the gear chamber, and one of the plurality of fastening members is fastened so that at least a portion of at least one of the intake port and the discharge port is positioned on an extension line of the shaft portion.

2. A gear pump as claimed in claim 1, wherein the cover is divided into two imaginary regions by an imaginary plane passing through both axes of the pair of gears, and one fastening member is provided on the cover closer to the suction port than the imaginary plane, on an extension of the shaft portion, and two fastening members are provided on the cover closer to the discharge port than the imaginary plane.

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