External gear pump
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- JTEKT FLUID POWER SYST CORP
- Filing Date
- 2024-12-13
- Publication Date
- 2026-06-25
Smart Images
Figure 2026103922000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to an external gear pump that rotationally drives a driving gear and a driven gear that are in meshing engagement with each other to suck and discharge a liquid, and more particularly to an external gear pump suitable for sucking and discharging a liquid having low lubricity such as water.
Background Art
[0002] This type of external gear pump houses a driving gear and a driven gear that are in meshing engagement with each other inside a casing, and sucks a liquid from a suction passage and discharges it from a discharge passage by rotationally driving both gears. The casing is formed of a resin material to reduce wear and adhesion at locations where both gears are in sliding contact with the casing.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] However, in such a conventional external gear pump, since the acting force based on the discharge pressure of the liquid to be sucked and discharged acts in the axial direction separating from both gears on the main body member (second main body member) constituting the casing, the gap between the side surfaces of both gears and the main body member expands, and there is a risk that the leakage amount of the liquid leaking from this gap increases and the volumetric efficiency of the pump decreases.
[0005] An object of the present invention is to provide an external gear pump capable of suppressing a reduction in the volumetric efficiency of the pump even when the liquid to be sucked and discharged is a liquid having low lubricity such as water.
Means for Solving the Problems
[0006] To achieve such problems, the present invention takes the following means. That is, An external gear pump that rotatably houses a drive gear and a driven gear that mesh with each other inside a casing, and sucks in and discharges liquid by the rotational drive of both gears, wherein the casing comprises a main body member that slides against one side of both gears, the sliding surface of the main body member that slides against one side of both gears defines a discharge pressure acting region where the force based on the discharge pressure of the liquid being sucked in and discharged acts in the axial direction away from both gears, and an suction pressure acting region where the suction pressure of the liquid being sucked in and discharged acts, the back surface of the main body member which is the back side of the sliding surface defines a back discharge pressure acting region where the force based on the discharge pressure of the liquid being sucked in and discharged acts in the axial direction approaching both gears, opposite to the force acting in the discharge pressure acting region, and the back discharge pressure acting region is shaped to overlap with the discharge pressure acting region in a plan view, but not overlap with the suction pressure acting region.
[0007] In this case, the main body member may have an introduction hole for introducing the discharge pressure from the discharge pressure acting area to the back discharge pressure acting area. [Effects of the Invention]
[0008] As described in detail above, the invention described in claim 1 comprises a casing comprising a main body member that slides against one side surface of both gears, wherein the main body member divides the sliding surface that slides against one side surface of both gears into a discharge pressure acting region where the force based on the discharge pressure of the liquid being drawn in and drawn out acts in the axial direction away from both gears, and an suction pressure acting region where the suction pressure of the liquid being drawn in and drawn out acts, and further divides the back surface of the main body member which is the back side of the sliding surface into a back discharge pressure acting region where the force based on the discharge pressure of the liquid being drawn in and drawn out acts in the axial direction approaching both gears, opposite to the force acting in the discharge pressure acting region, and the back discharge pressure acting region is shaped to overlap with the discharge pressure acting region in a plan view, but not to overlap with the suction pressure acting region. Therefore, the main body member is pressed axially toward both gears by the force acting on the rear discharge pressure acting region, which suppresses the widening of the gap between the sides of both gears and the main body member. This suppresses the amount of liquid leakage from this gap, and even if the liquid being sucked in and discharged is a liquid with low lubricity such as water, it is possible to suppress a reduction in the volumetric efficiency of the pump. Furthermore, the rear discharge pressure acting region is shaped to superimpose the discharge pressure acting region in a plan view, but not to superimpose the suction pressure acting region. Therefore, the main body member is not pressed axially toward both gears in the suction pressure acting region, so the main body member is not excessively pressed toward both gears, and an increase in the driving torque that rotates both gears can be suppressed.
[0009] Furthermore, the invention described in claim 2 has an introduction hole formed in the main body member for introducing discharge pressure from the discharge pressure acting region to the back discharge pressure acting region. For this reason, the introduction hole only needs to connect the sliding surface and the back surface of the main body member and can be easily formed by penetrating the main body member. [Brief explanation of the drawing]
[0010] [Figure 1] This is a longitudinal cross-sectional view along line DD in Figure 2 of an external gear pump showing one embodiment of the present invention. [Figure 2] This is a cross-sectional view along line AA in Figure 1. [Figure 3] This is a cross-sectional view along line BB in Figure 1. [Figure 4] This is a cross-sectional view along line CC in Figure 1. [Figure 5] This is a cross-sectional view corresponding to Figure 4, which shows another embodiment. [Figure 6] This is a cross-sectional view corresponding to Figure 4, which shows yet another embodiment. [Modes for carrying out the invention]
[0011] One embodiment of the present invention will be described below with reference to the drawings. In Figures 1 and 2, 1 is the casing, which consists of a first main body member 2, a second main body member 3, a flange member 4, and a cover member 5. The first main body member 2 is made of glass fiber-reinforced polyphenylene sulfide resin (commonly known as PPS) as the resin material. 6 is the first through hole, and 7 is the second through hole. Both through holes 6 and 7 are formed through the first main body member 2, spaced radially apart and parallel to the axial direction. 8 is the gear housing hole, which is formed by creating a recess in one axial end face of the first main body member 2, and its cross-section is roughly figure-eight shaped. Both through holes 6 and 7 open at the bottom of the gear housing hole 8.
[0012] The second main body member 3 is made of the same material as the first main body member 2, formed from glass fiber-reinforced polyphenylene sulfide resin and provided in a plate shape. Its other axial end face is joined to one axial end face of the first main body member 2 to close the gear housing hole 8. The flange member 4 is made from a metal material such as aluminum alloy and is joined to the other axial end face of the first main body member 2 opposite to one axial end face, closing the through hole 7. An insertion hole 9 is formed through the flange member 4 in the axial direction, and the insertion hole 9 is formed to be larger in diameter than the first through hole 6 and is connected concentrically to the first through hole 6.
[0013] The lid member 5 is formed from a metal material such as carbon steel for machine structures and is joined to one axial end face of the second main body member 3 that is opposite to the other axial end face. 10 are four bolt members that are inserted through the second main body member 3 and the first main body member 2 from the outside of the lid member 5 and screwed into the flange member 4, thereby integrally joining the first main body member 2, the second main body member 3, the flange member 4, and the lid member 5.
[0014] 11 is a drive gear and 12 is a driven gear. They are identical in shape, forming a pair, and have multiple external teeth 11A and 12A that mesh with each other on their outer circumference. They are housed in a gear housing hole 8, with the tips of the teeth 11A and 12A positioned to slide against the inner circumferential surface of the gear housing hole 8. One axial side of each gear is positioned to slide against the other axial end surface of the second main body member 3, and the other axial side opposite to the axial side of each gear is positioned to slide against the bottom surface of the gear housing hole 8. Both gears 11 and 12 have their surfaces coated with DLC (Diamond-Like Carbon). 13 is an intake passage for drawing in liquid, formed in the first main body member 2 and connected to one radial side of the gear housing hole 8. 14 is a discharge channel for discharging liquid, formed in the first main body member 2, and connected to the other radial side which is symmetrical to one radial side via a meshing point × where the external teeth 11A and 12A of both gears 11 and 12 of the gear housing hole 8 mesh.
[0015] The meshing point × is the point where the tooth side of the external teeth 11A of the drive gear 11 abuts against the tooth side of the external teeth 12A of the driven gear 12, transmitting the rotational driving force of the drive gear 11 to the driven gear 12. Y is the first partition point, where the drive gear 11 is pushed radially toward the intake passage 13 by a force based on the discharge pressure on the discharge passage 14 side, causing the tooth tips of the external teeth 11A to abut against the inner circumferential surface of the gear housing hole 8. Z is the second partition point, where the driven gear 12 is pushed radially toward the intake passage 13 by a force based on the discharge pressure on the discharge passage 14 side, causing the tooth tips of the external teeth 12A to abut against the inner circumferential surface of the gear housing hole 8, and is located approximately symmetrically to the first partition point Y via the meshing point ×.
[0016] The sliding contact surface 3A of the second main body member 3 is divided into a discharge pressure acting region 15, which applies a force based on the discharge pressure of the liquid being drawn in and discharged, in a direction that moves the second main body member 3 away from both gears 11 and 12, and an suction pressure acting region 16, which applies a force based on the suction pressure of the liquid being drawn in and discharged. More specifically, the discharge pressure acting region 15 is the region demarcated by the inner circumferential surface of the gear housing hole 8 and the external teeth 11A and 12A of both gears 11 and 12, on the discharge flow path 14 side from the first partition Y, the meshing location ×, and the second partition Z when viewing the gear housing hole 8 which houses both gears 11 and 12 in plan view, and is indicated by ... in Figure 2. The suction pressure acting region 16 is the region demarcated by the inner circumferential surface of the gear housing hole 8 and the external teeth 11A and 12A of both gears 11 and 12, respectively, on the suction passage 13 side from the first partition Y, the meshing location ×, and the second partition Z, when viewed from above the gear housing hole 8 which houses both gears 11 and 12, and is indicated by / / / in Figure 2.
[0017] 17 is a first sealing member formed from an elastic material, which is positioned on the sliding contact surface 3A and closely adheres to one axial end surface of the first main body member 2 so as to surround the gear housing hole 8, sealing the discharge pressure acting area 15 and the suction pressure acting area 16 from the outside. As shown in Figure 3, the first sealing member 17 consists of a straight first straight section 17A located on the suction passage 13 side of the gear housing hole 8, a straight second straight section 17B located on the discharge passage 14 side of the gear housing hole 8, an arc-shaped section 17C on the drive gear 11 side of the gear housing hole 8 that is slightly larger in diameter than the gear housing hole 8 and connects one end of both straight sections 17A and 17B to each other, and an arc-shaped section 17D on the driven gear side 12 of the gear housing hole 8 that is slightly larger in diameter than the gear housing hole 8 and connects the other end opposite to one end of both straight sections 17A and 17B to each other, and is formed in an oval shape.
[0018] The second body member 3 is provided with a second sealing member 18 formed of an elastic material on the back surface 3B on the back side of the sliding contact surface 3A to define and form a back discharge pressure acting region 19. The second sealing member 18 adheres to the lid member 5 to seal the back discharge pressure acting region 19 from the outside. Reference numeral 20 is an introduction hole formed to penetrate the second body member 3 in the axial direction, which connects the discharge pressure acting region 15 and the back discharge pressure acting region 19 and introduces the discharge pressure of the liquid to be sucked and discharged from the discharge pressure acting region 15 to the back discharge pressure acting region 19. The back discharge pressure acting region 19 acts in the axial direction approaching the two gears 11 and 12 against the acting force acting on the discharge pressure acting region 15 of the second body member 3 based on the discharge pressure. The back discharge pressure acting region 19 forms a depression in the back surface 3B of the second body member 3 to facilitate the introduction of the discharge pressure of the liquid to be sucked and discharged from the introduction hole 20.
[0019] The back discharge pressure acting region 19 is provided in a shape that overlaps the discharge pressure acting region 15 in plan view and does not overlap the suction pressure acting region 16. Specifically, as shown in FIG. 4, the back discharge pressure acting region 19 includes an inner diameter portion 19A having substantially the same shape as an arc shape sequentially connecting a first partition portion Y, an engagement portion ×, and a second partition portion Z, an arc shape having a larger diameter than the inner diameter portion 19A and located slightly outside the second straight portion 17B of the first sealing member 17, a large diameter portion 19B, an end portion 19C connecting one circumferential end of the small diameter portion 19A and the large diameter portion 19B to each other and located slightly outside the one end arc portion 17C of the first sealing member 17, and an other end portion 19D connecting the circumferential other end, which is the end opposite to the one circumferential end of the small diameter portion 19A and the large diameter portion 19B, to each other and located slightly outside the other end arc portion 17D of the first sealing member 17, and is formed in a semi-arc shape. The back discharge pressure acting region 19 has a larger area than the discharge pressure acting region 15.
[0020] Reference numeral 21 denotes a drive shaft formed of a metallic material, which is engaged in the rotational direction with a drive gear 11 by means of a key 22, passes through a first through hole 6 and an insertion hole 9, and has its tip exposed to the outside. The tip is coupled to a motor (not shown) to rotationally drive the drive gear 11. Reference numeral 23 denotes a bush press-fitted into the first through hole 6, which is in sliding contact with the drive shaft 21 and rotatably supports the drive shaft 21. Reference numeral 24 denotes a sealing member provided in the insertion hole 9, which is in sliding contact with the drive shaft 21 and seals the inside of the pump housing 1. Reference numeral 25 denotes a ball bearing provided axially outward of the sealing member 24 in the insertion hole 9, which rotatably supports the drive shaft 21. The drive shaft 21 is supported by the bush 23 and the ball bearing 25 on one axial side of the drive gear 11.
[0021] Reference numeral 26 denotes a driven shaft formed of a metallic material, which is engaged in the rotational direction with a driven gear 12 by means of a key 27 and passes through a second through hole 7. Reference numeral 28 denotes a bush press-fitted into the second through hole 7, which is in sliding contact with the driven shaft 26 and rotatably supports the driven shaft 26. The driven shaft 26 is supported by the bush 28 on one axial side of the driven gear 12.
[0022] Next, the operation of such a configuration will be described. When the drive shaft 21 rotationally drives the drive gear 11 in the direction of arrow E, the driven gear 12 meshing with the drive gear 11 is rotationally driven in the direction opposite to the direction of arrow E. The liquid on the low-pressure side flows through the suction passage 13, is sucked between the respective outer teeth 11A of the drive gear 11 and between the respective outer teeth 12A of the driven gear 12, and is conveyed to the discharge side along the inner periphery of the gear accommodation hole 8, and then flows through the discharge passage 14 and is discharged. At this time, a part of the liquid flowing to the discharge side is introduced into a back discharge pressure acting region 19 partitioned and formed on the back surface 3B on the back side of the sliding contact surface 3A through the introduction hole 20.
[0023] In this operation, the casing 1 is provided with a main body member 3 that slides against one side of both gears 11 and 12. The main body member 3 divides the sliding contact surface 3A that slides against one side of both gears 11 and 12 into a discharge pressure acting region 15, which acts in the axial direction away from both gears 11 and 12 based on the discharge pressure of the liquid being drawn in and drawn out, and an suction pressure acting region 16, which acts on the suction pressure of the liquid being drawn in and drawn out. The main body member 3 divides the back surface 3B, which is the back side of the sliding contact surface 3A, into a back discharge pressure acting region 19, which acts in the axial direction approaching both gears 11 and 12, opposite to the force acting on the discharge pressure of the liquid being drawn in and drawn out, and the back discharge pressure acting region 19 is shaped to overlap with the discharge pressure acting region 15 in a plan view, but not with the suction pressure acting region 16. Therefore, the main body member 3 is pressed axially toward both gears 11 and 12 by the force acting on the rear discharge pressure acting area 19, and the gap between the sides of both gears 11 and 12 and the main body member 3 is suppressed from widening. As a result, the amount of liquid leaking out from this gap is suppressed, and even if the liquid being sucked in and discharged is a liquid with low lubricity such as water, a reduction in the volumetric efficiency of the pump can be suppressed.
[0024] Furthermore, the rear discharge pressure acting region 19 is shaped to superimpose the discharge pressure acting region 15 in a plan view, but not to superimpose the suction pressure acting region 16. As a result, the second main body member 3 is not pressed in the axial direction approaching both gears in the suction pressure acting region 16, so that the second main body member 3 is not excessively pressed against both gears 11 and 12, and an increase in the driving torque that rotates both gears 11 and 12 can be suppressed.
[0025] Furthermore, the main body member 3 has an introduction hole 20 for introducing discharge pressure from the discharge pressure acting area 15 to the rear discharge pressure acting area 19. For this reason, the introduction hole 20 only needs to connect the sliding surface 3A and the rear surface 3B of the main body member 3, and can be easily formed by penetrating the main body member 3. Also, the rear discharge pressure acting area 19 is formed as a recess in the rear surface 3B of the main body member 3. This makes it easier to introduce the discharge pressure of the liquid being sucked in and discharged through the introduction hole 20.
[0026] Figure 5 shows another embodiment of the present invention. Parts identical to those in one embodiment are denoted by the same reference numerals and their descriptions are omitted; only the different parts will be described. In one embodiment, the rear discharge pressure acting region 191 is provided with a straight section 191B located outward from the second straight section 17B of the first sealing member 17, instead of the large diameter section 19B. One end of the straight section 191B is linearly connected to the first end 19C, and the other end, opposite to the first end, is linearly connected to the other end 19D, forming a roughly trapezoidal recess on the back of the main body member 3. As the rear discharge pressure acting region 191 is formed in a roughly trapezoidal shape, the second sealing member 181 that partitions the rear discharge pressure acting region 191 is also formed in a roughly trapezoidal shape. In a plan view, the rear discharge pressure acting region 191 overlaps with the discharge pressure acting region 15 and has a larger area than the discharge pressure acting region 15. In a plan view, this larger area faces one axial end face of the first main body member 2 and does not face the gear housing hole 8 that houses both gears 11 and 12.
[0027] The operation is the same as in one embodiment, and in this operation, the main body member 3 is pressed axially toward both gears 11 and 12 by the force acting on the rear discharge pressure acting region 191, thereby suppressing the amount of liquid leakage and preventing a reduction in the volumetric efficiency of the pump. Furthermore, since the rear discharge pressure acting region 191 overlaps with the discharge pressure acting region 15 in a plan view and does not overlap with the suction pressure acting region 16, the main body member 3 is not excessively pressed toward both gears 11 and 12, and an increase in the driving torque that rotates both gears 11 and 12 is suppressed. In addition, the introduction hole 20 for introducing discharge pressure from the discharge pressure acting region 15 to the rear discharge pressure acting region 191 can be easily formed by penetrating the main body member 3. Furthermore, the rear discharge pressure acting region 191 is formed as a recess on the back of the main body member 3, making it easier to introduce the discharge pressure of the liquid being sucked in and discharged through the introduction hole 20.
[0028] Figure 6 shows yet another embodiment of the present invention. Parts identical to those in one embodiment are denoted by the same reference numerals and their descriptions are omitted, while only the different parts are described. The rear discharge pressure acting region 192 is provided with a curved section 192B that follows the inner circumferential surface (shown in Figure 2) of the gear housing hole 8 on the discharge passage 14 side, instead of the large diameter section 19B in one embodiment. One end of the curved section 192B is linearly connected to the end 19C, and the other end, which is the opposite end, is linearly connected to the other end 19D, forming a semi-circular arc shape. As the rear discharge pressure acting region 192 is formed in a semi-circular arc shape, the second sealing member 182 that partitions the rear discharge pressure acting region 192 is also formed in a semi-circular arc shape. In a plan view, the rear discharge pressure acting region 192 overlaps with the discharge pressure acting region 15 to increase its area.
[0029] The operation is the same as in one embodiment, and in this operation, the main body member 3 is pressed axially toward both gears 11 and 12 by the force acting on the rear discharge pressure acting region 192, thereby suppressing the amount of liquid leakage and preventing a reduction in the volumetric efficiency of the pump. Furthermore, since the rear discharge pressure acting region 192 overlaps with the discharge pressure acting region 15 in a plan view and does not overlap with the suction pressure acting region 16, the main body member 3 is not excessively pressed toward both gears 11 and 12, and an increase in the driving torque that rotates both gears 11 and 12 is suppressed. In addition, the introduction hole 20 for introducing discharge pressure from the discharge pressure acting region 15 to the rear discharge pressure acting region 192 can be easily formed by penetrating the main body member 3. Furthermore, the rear discharge pressure acting region 192 is formed as a recess on the back of the main body member 3, making it easier to introduce the discharge pressure of the liquid being sucked in and discharged through the introduction hole 20.
[0030] In the embodiment described above, the first main body member 2 and the second main body member 3 were formed from a resin material, but they may also be formed from a metal material. Furthermore, although the drive shaft 21 and driven shaft 26 were pivotally supported on one axial side of both gears 11 and 12, it goes without saying that both shafts 21 and 26 may be pivotally supported protruding from both axial sides of both gears 11 and 12. [Explanation of Symbols]
[0031] 1: Casing 2, 3: Main body components 3A: Sliding surface 3B: Back 11: Drive gear 12: Driven gear 15: Discharge pressure action area 16: Inhalation pressure action area 19, 191, 192: Rear discharge pressure action area
Claims
1. An external gear pump that rotatably houses a drive gear and a driven gear that mesh with each other inside a casing, and sucks in and discharges liquid by the rotational drive of both gears, wherein the casing comprises a main body member that slides against one side of both gears, the sliding surface of the main body member that slides against one side of both gears defines a discharge pressure acting region where the force based on the discharge pressure of the liquid being sucked in and discharged acts in the axial direction away from both gears, and an suction pressure acting region where the suction pressure of the liquid being sucked in and discharged acts, the back surface of the main body member which is the back side of the sliding surface defines a back discharge pressure acting region where the force based on the discharge pressure of the liquid being sucked in and discharged acts in the axial direction approaching both gears, opposite to the force acting in the discharge pressure acting region, and the back discharge pressure acting region is shaped to overlap with the discharge pressure acting region in a plan view, but not overlap with the suction pressure acting region.
2. The external gear pump according to claim 1, characterized in that the main body member has an introduction hole formed therein for introducing the discharge pressure from the discharge pressure acting region to the rear discharge pressure acting region.