Internal gear pump

Abstract

To restrain noise of an internal gear pump, and restrain a decrease in pump efficiency at the same time.SOLUTION: An internal gear pump 1 comprises a pinion gear 3, a ring gear 4, a housing 10 rotatably housing the pinion gear and the ring gear, and a crescent 54 comprising a first arc wall 541 with which external teeth 31 come into contact, and a second arc wall 542 with which internal teeth 41 come into contact. Both the first arc wall and the second arc wall are fixed walls that do not move to the external teeth and the internal teeth. A pressure transmission oil passage 91 extending from a discharge port is formed in the housing, only in a ring gear side region out of the ring gear side region and a pinion gear side region across the crescent. The pressure transmission oil passage establishes communication between the discharge port and a space between teeth of the ring gear.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The technology disclosed herein relates to an internal gear pump.

Background Art

[0002] Patent Document 1 describes an internal gear pump (1). This internal gear pump (1) has a separating member (7) (so-called crescent). The tooth tips of the internal gear (2) and the pinion (3) respectively abut against the separating member (7).

[0003] The separating member (7) has an inner part (13), an outer part (14), and a spring (16). The spring (l6) presses the inner part (13) against the tooth tip of the pinion (3) and the outer part (14) against the tooth tip of the internal gear (2). The separating member (7) has a movable structure. The movable separating member (7) suppresses the leakage flow in the internal gear pump (1) and improves the pump efficiency.

[0004] The separating member (7) also has an intermediate space (17) between the inner part (13) and the outer part (14). The intermediate space (17) communicates with the pressurized region (9) of the internal gear pump (1). The inner part (13) and the outer part (14) have through-holes (19). The through-holes (19) penetrate the inner part (13) and the outer part (14) in the radial direction, and connect the intermediate part (17) to the space between the teeth of the pinion (3) and the internal gear (2). Since the intermediate space (17) has the same pressure as the pressurized region (9) during the operation of the internal gear pump (1), the pressure in the space between the teeth of the pinion (3) and the internal gear (2) increases through the through-holes (19). The high pressure in the space between the teeth suppresses the rapid pressure change at the pump discharge part and suppresses the noise of the internal gear pump (1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] In the internal gear pump (1) of Patent Document 1, the through-hole (19) supplies liquid from the pump discharge to both the space between the separating member (7) and the pinion (3), and the space between the separating member (7) and the internal gear (2), in order to suppress noise. However, this supply of liquid increases leakage flow within the internal gear pump (1). Conventional internal gear pumps suppress noise but lead to a decrease in pump efficiency.

[0007] The technology disclosed herein achieves both noise reduction in an internal gear pump and suppression of a decrease in pump efficiency. [Means for solving the problem]

[0008] The internal gear pump (1) described in Patent Document 1 has a structure in which the crescent is movable. In contrast, internal gear pumps with a non-movable crescent are known.

[0009] The inventors of this invention have discovered that in a structure where the crescent is not movable, the pressure in the space between the teeth of the pinion gear is relatively high. This is thought to be because the wall of the crescent is not pressed against the outer teeth of the pinion gear, resulting in a minute gap between the teeth of the pinion gear and the wall of the crescent. This minute gap allows leakage flow from the discharge port, and this leakage flow increases the pressure in the space between the teeth of the pinion gear.

[0010] Even if a structure is added to an internal gear pump to supply hydraulic fluid from the discharge port into the space between the teeth of the pinion gear for the purpose of noise reduction, this only increases leakage flow and reduces pump efficiency, and does not substantially improve the noise reduction effect of the internal gear pump.

[0011] Therefore, the inventors of the present invention decided to form only the pressure transmission oil passage extending from the discharge port to the space between the teeth of the ring gear within the housing of an internal gear pump having a non-movable crescent structure.

[0012] Specifically, the technology disclosed herein relates to an internal gear pump. This internal gear pump is, A pinion gear having external teeth, A ring gear having internal teeth that mesh with the external teeth, A housing having an intake port and a discharge port, and rotatably housing the pinion gear and the ring gear, The crescent is located at a point where the meshing of the pinion gear and the ring gear separates, and has a first arc-shaped wall in contact with the external teeth and a second arc-shaped wall in contact with the internal teeth, Both the first and second arc-shaped walls are fixed walls that do not move toward the external and internal teeth. Of the region on the pinion gear side and the region on the ring gear side, the pressure transmission oil passage extending from the discharge port is formed within the housing only in the region on the ring gear side. The pressure transmission oil passage connects the discharge port to the space between the teeth of the ring gear.

[0013] Furthermore, the space between the teeth of a ring gear is the space between adjacent teeth in the ring gear.

[0014] This internal gear pump has a structure in which the crescent is not movable. As mentioned above, the pressure in the space between the teeth of the pinion gear is relatively high.

[0015] The pressure transmission oil passage is formed within the housing only in the ring gear side of the crescent, between the pinion gear side and the ring gear side. The pressure transmission oil passage extending from the discharge port allows a portion of the hydraulic fluid to flow from the discharge port to the low-pressure side. The pressure transmission oil passage connects the discharge port to the space between the teeth of the ring gear, so a portion of the high-pressure hydraulic fluid from the discharge port flows into the space between the teeth of the ring gear. The pressure in the space between the teeth of the ring gear increases. The high pressure in the space between the teeth suppresses rapid pressure changes at the discharge port.

[0016] The pressure in the space between the teeth of the pinion gear is high even without a pressure transmission oil passage. On the pinion gear side, rapid pressure changes at the discharge port are suppressed.

[0017] By forming a pressure transmission oil passage only in the ring gear side region, which is flanked by a non-movable crescent, abrupt pressure changes at the discharge port are suppressed on both the ring gear side and the pinion gear side, thereby reducing noise from the internal gear pump.

[0018] Furthermore, while pressure transmission oil passages promote leakage flow in the internal gear pump, these passages are formed only in the ring gear side region and not in the pinion gear side region. This suppresses the increase in leakage flow in the internal gear pump, thus preventing a decrease in pump efficiency.

[0019] Therefore, the aforementioned internal gear pump achieves both noise reduction and suppression of a decrease in pump efficiency.

[0020] The housing has a sliding surface on which the outer circumferential surface of the ring gear slides, The internal gear pump is equipped with a high-pressure oil supply unit that supplies high-pressure hydraulic fluid between the outer circumferential surface and the sliding surface through an inlet opening that opens to the sliding surface. The inlet may be located on the opposite side of the crescent from the ring gear.

[0021] The high-pressure oil supply section supplies high-pressure hydraulic oil between the outer peripheral surface of the ring gear and the sliding surface of the housing. The supplied high-pressure hydraulic oil pushes the ring gear toward the rotation axis of the ring gear. Since the inlet is located on the side opposite to the crescent sandwiching the ring gear, the internal teeth of the ring gear are pressed against the second arc wall of the crescent. Leakage of hydraulic oil between the internal teeth and the second arc wall is suppressed. The high-pressure oil supply section increases the pump efficiency of the internal gear pump.

[0022] The fact that the internal teeth of the ring gear are pressed against the second arc wall of the crescent increases the pump efficiency while suppressing the pressure increase in the space between the teeth of the ring gear due to the leakage flow from the discharge port. The low pressure in the space between the teeth of the ring gear increases the noise of the internal gear pump.

[0023] [ The internal gear pump has a pressure transmission oil passage formed in the housing in the region on the ring gear side. As described above, the pressure transmission oil passage increases the pressure in the space between the teeth of the ring gear. The combination of the high-pressure oil supply section and the pressure transmission oil passage on the ring gear side enables high-level compatibility between noise suppression of the internal gear pump and suppression of a decrease in pump efficiency.

[0024] The housing has a first support surface and a second support surface that respectively support two side surfaces orthogonal to the rotation axis, which are side surfaces of the ring gear. The discharge port is formed in each of the first support surface and the second support surface. The pressure transmission oil passage is formed so as to be recessed from the first support surface, the second support surface, or both the first support surface and the second support surface. The pressure transmission oil passage may overlap with the space between the teeth of the ring gear when viewed in the direction of the rotation axis.

[0025] Since the pressure transmission oil passage formed in the first support surface and / or the second support surface overlaps with the space between the teeth of the ring gear when viewed in the direction of the rotation axis, hydraulic oil can be supplied from the discharge port to the space between the teeth of the ring gear. The pressure in the space between the teeth of the ring gear increases.

[0026] The cross-section of the pressure transmission oil passage formed on the first support surface and / or the second support surface may be triangular. The cross-section of the pressure transmission oil passage formed on the first support surface and / or the second support surface may be quadrilateral.

[0027] The pressure transmission oil passage may be a groove formed in the first support surface and / or the second support surface.

[0028] The pressure transmission oil passage may be straight. The pressure transmission oil passage may be curved.

[0029] The pressure transmission oil passage may be formed to recess from the second circular arc wall of the crescent.

[0030] The pressure transmission oil passage may be formed by cutting out the surface of the crescent.

[0031] The pressure transmission oil passage formed in the second arc wall of the crescent communicates with the space between the teeth of the ring gear. The pressure transmission oil passage can supply hydraulic fluid from the discharge port to the space between the teeth of the ring gear. The pressure in the space between the teeth of the ring gear increases.

[0032] The depth of the pressure transmission oil passage may gradually decrease as it moves away from the discharge port. The depth of the pressure transmission oil passage may be constant. The width of the pressure transmission oil passage may gradually decrease as it moves away from the discharge port. The width of the pressure transmission oil passage may be constant.

[0033] The tip of the pressure transmission oil passage may be located within a range of an angle θ1 or greater from the edge of the discharge port, corresponding to the tooth width of the ring gear, and an angle θ2 or less from the midpoint of the crescent extending from the discharge port to the suction port, with respect to the rotation axis of the ring gear.

[0034] An appropriately sized pressure transmission oil passage allows for both noise reduction in the internal gear pump and prevention of a decrease in pump efficiency.

[0035] If the tip of the pressure transmission oil passage is located at a position less than θ1, the pressure transmission oil passage is too short. In other words, a pressure transmission oil passage that is too short cannot raise the pressure in the space between the teeth of the ring gear before that space is opened to the discharge port.

[0036] Even if the tip of the pressure transmission oil passage is located beyond θ2, the noise suppression effect is substantially the same as when it is below θ2. On the other hand, an excessively long pressure transmission oil passage increases the leakage flow of hydraulic fluid, leading to a decrease in pump efficiency.

[0037] When the tip of the pressure transmission oil passage is located within the range of an angle θ1 or greater and an angle θ2 or less, noise suppression and suppression of pump efficiency reduction can be achieved simultaneously. [Effects of the Invention]

[0038] The aforementioned internal gear pump can achieve both noise reduction and suppression of pump efficiency degradation. [Brief explanation of the drawing]

[0039] [Figure 1] Figure 1 is an exploded view of an internal gear pump. [Figure 2] Figure 2 is a cross-sectional view of an internal gear pump. [Figure 3] Figure 3 illustrates a pressure transmission oil passage. [Figure 4] Figure 4 shows a modified example of a pressure transmission oil passage. [Figure 5] Figure 5 shows a modified example of a pressure transmission oil passage. [Modes for carrying out the invention]

[0040] The following describes an embodiment of the internal gear pump with reference to the drawings. The internal gear pump described here is illustrative.

[0041] (Overall structure of an internal gear pump) Figures 1 and 2 illustrate an internal gear pump 1. The internal gear pump 1 comprises a shaft 2, a pinion gear 3, a ring gear 4, a gear housing 5, and a front cover 6. The gear housing 5 and the front cover 6 constitute the housing 10 of the internal gear pump 1. Figure 1 is an exploded view with the front cover 6 removed from the gear housing 5.

[0042] Shaft 2 extends in the left-right direction in Figure 2. Shaft 2 consists of a first shaft 21 and a second shaft 22. The first shaft 21 and the second shaft 22 are coupled coaxially and rotate together. The second shaft 22 protrudes from the housing 10 and is connected to a prime mover, which is not shown in the figure. The prime mover is, for example, an electric motor.

[0043] The pinion gear 3 is integrally formed at the midpoint of the first shaft 21. The pinion gear 3 and the shaft 2 are coaxial. The pinion gear 3 rotates together with the shaft 2. The pinion gear 3 has external teeth 31.

[0044] The ring gear 4 meshes with the pinion gear 3. The ring gear 4 is positioned eccentrically with respect to the shaft 2. In Figure 1, C1 is the axis of rotation of the pinion gear 3, and C2 is the axis of rotation of the ring gear 4. Internal teeth 41 are formed on the inner surface of the ring gear 4. In the right-hand view of Figure 1, in the area on the right side of the paper, a portion of the external teeth 31 of the pinion gear 3 meshes with a portion of the internal teeth 41 of the ring gear 4.

[0045] The gear housing 5 accommodates the pinion gear 3 and the ring gear 4. An inner bore 53 is formed in the gear housing 5. The end of the first shaft 21 is located inside the inner bore 53.

[0046] The pinion gear 3 and the ring gear 4 are rotatably housed in the gear housing 5. The gear housing 5 has a sliding surface 51 on which the outer circumferential surface 42 of the ring gear 4 slides. The outer circumferential surface 42 of the ring gear 4 has a circular cross-section. The sliding surface 51 of the gear housing 5 also has a circular cross-section. The sliding surface 51 is eccentric with respect to the shaft 2.

[0047] The gear housing 5 has a first support surface 52 perpendicular to the sliding surface 51. The sliding surface 51 and the first support surface 52 form a space 50 that houses the pinion gear 3 and the ring gear 4. This space 50 is open to the left side of the paper in Figure 2. The first side surface 32 of the pinion gear 3 and the first side surface 43 of the ring gear 4 are supported by the first support surface 52 of the gear housing 5 and slide on the first support surface 52. The first side surface 32 of the pinion gear 3 is the surface perpendicular to the rotation axis C1 of the pinion gear 3 and is the right side surface in Figure 2. The first side surface 43 of the ring gear 4 is the surface perpendicular to the rotation axis C2 of the ring gear 4 and is the right side surface in Figure 2.

[0048] The front cover 6 is positioned adjacent to the gear housing 5. The front cover 6 and the gear housing 5 are integrated by being fixed to each other. The front cover 6 has a second support surface 61 that contacts the gear housing 5 and closes the space 50. The second side surface 33 of the pinion gear 3 and the second side surface 44 of the ring gear 4 are supported by the second support surface 61 of the front cover 6 and slide on the second support surface 61. The second side surface 33 of the pinion gear 3 is the surface perpendicular to the rotation axis C1 of the pinion gear 3, and is the left side surface in Figure 2. The second side surface 44 of the ring gear 4 is the surface perpendicular to the rotation axis C2 of the ring gear 4, and is the left side surface in Figure 2.

[0049] The front cover 6 has a support hole 62 through which the shaft 2 passes. The shaft 2 is rotatably supported by the front cover 6 and the gear housing 5 via a bearing 63 and a bearing member 64. The opening of the support hole 62 is sealed by a sealing member 621.

[0050] Suction ports 11 are formed in the front cover 6 and the gear housing 5. The suction ports 11 are ports that draw hydraulic fluid into the internal space 50 of the housing 10. The inlet of the suction port 11 opens to the outer circumferential surface of the front cover 6, as shown in Figure 2. The outlet of the suction port 11 opens to the second support surface 61 of the front cover 6 and the first support surface 52 of the gear housing 5, respectively, as shown in Figures 1 and 2. The outlet of the suction port 11 also extends circumferentially along the rotational direction of the shaft 2.

[0051] Discharge ports 12 are also formed in the front cover 6 and the gear housing 5. The discharge port 12 is a port that discharges hydraulic fluid from the space 50 inside the housing 10. The outlet of the discharge port 12 opens to the outer surface of the gear housing 5, as shown in Figure 2. The direction of the inlet of the suction port 11 and the direction of the outlet of the discharge port 12 may be different, as illustrated in Figure 2, or they may be the same, although this is not shown.

[0052] The inlet of the discharge port 12 opens into the second support surface 61 of the front cover 6 and the first support surface 52 of the gear housing 5, respectively. The inlet of the discharge port 12 also extends circumferentially along the rotational direction of the shaft 2, on the opposite side of the shaft 2 from the suction port 11, as shown in Figure 1.

[0053] A crescent 54 is provided in the gear housing 5. The crescent 54 is positioned where the meshing between the pinion gear 3 and the ring gear 4 separates. The crescent 54 separates the second region and the first region, which will be described later.

[0054] The crescent 54 extends circumferentially over a predetermined angular range along the rotational direction of the shaft 2. As shown in Figure 1, the crescent 54 has a crescent shape when viewed in the axial direction of the shaft 2. The crescent 54 has two arcuate walls, a first arcuate wall 541 and a second arcuate wall 542, and the first arcuate wall 541 and the second arcuate wall 542 are erected on the first support surface 52 of the gear housing 5.

[0055] The tips of the external teeth 31 of the pinion gear 3 substantially contact the first arcuate wall 541 of the crescent 54. The tips of the internal teeth 41 of the ring gear 4 substantially contact the second arcuate wall 542 of the crescent 54. Both the first arcuate wall 541 and the second arcuate wall 542 are fixed walls that do not move toward the external teeth 31 and internal teeth 41.

[0056] The inside of the housing 10 can be divided into three regions in the circumferential direction around the rotation axis C2 of the ring gear 4: a first region where the suction port 11 opens, a second region where the discharge port 12 opens, and a third region between the first and second regions where the crescent 54 is located. The first region is a low-pressure region, and the second region is a high-pressure region.

[0057] Next, the operation of the internal gear pump 1 will be briefly explained. When the prime mover rotates the shaft 2 in the clockwise direction shown in the right-hand diagram of Figure 1, the pinion gear 3 and the ring gear 4 rotate in the direction from the first region, through the third region, to the second region, respectively.

[0058] In the first region within the housing 10, as the external teeth 31 of the pinion gear 3 and the internal teeth 41 of the ring gear 4 separate, hydraulic fluid is drawn in from the suction port 11 between the external teeth 31 and the internal teeth 41. The drawn-in hydraulic fluid is transported from the first region through the third region to the second region as the pinion gear 3 and ring gear 4 rotate.

[0059] In the second region within the housing 10, the external teeth 31 of the pinion gear 3 and the internal teeth 41 of the ring gear 4, which were previously separated, gradually move closer together and mesh. As a result, the hydraulic fluid is discharged from between the external teeth 31 and the internal teeth 41 through the discharge port 12.

[0060] (Structure designed to improve pump efficiency) The internal gear pump 1 is equipped with a high-pressure oil supply unit 8. The high-pressure oil supply unit 8 supplies high-pressure hydraulic fluid between the outer circumferential surface 42 of the ring gear 4 and the sliding surface 51 of the gear housing 5. Note that the high-pressure oil supply unit 8 is shown only in Figure 1.

[0061] The high-pressure oil supply unit 8 uses high-pressure hydraulic fluid to push and move the ring gear 4 from the outer circumference of the third region toward the rotation axis C2. Since the teeth of the ring gear 4 are pressed against the second arcuate wall 542 of the crescent 54, leakage of hydraulic fluid from the high-pressure side to the low-pressure side within the housing 10 is suppressed.

[0062] The high-pressure oil supply unit 8 has an inlet 81 that opens into the sliding surface 51 and a supply passage 82 that connects the discharge port 12 and the inlet 81.

[0063] As shown in Figure 1, the inlet 81 is located in the third region. More specifically, the inlet 81 faces the crescent 54 radially, with the ring gear 4 in between. The inlet 81 introduces a portion of the high-pressure hydraulic fluid discharged from the discharge port 12 into the housing 10. In order to efficiently press the teeth of the ring gear 4 against the crescent 54, it is preferable that the inlet 81 is located facing the crescent 54. Furthermore, in order to prevent the high-pressure hydraulic fluid introduced into the housing 10 from flowing into the low-pressure first region, it is preferable that the inlet 81 is located in the high-pressure region in the third region, which is divided into a low-pressure region and a high-pressure region.

[0064] The supply passage 82 is formed within the gear housing 5. The supply passage 82 connects the discharge port 12, which opens to the first support surface 52 of the gear housing 5, to the inlet 81. The supply passage may also be formed in the front cover 6 and the gear housing 5 so as to connect the discharge port 12, which opens to the second support surface 61 of the front cover 6, to the inlet 81. Alternatively, the supply passage may connect the discharge port 12 opening to the first support surface 52 to the inlet 81, and also connect the discharge port 12 opening to the second support surface 61 to the inlet 81.

[0065] As described above, during operation of the internal gear pump 1, a portion of the high-pressure hydraulic fluid from the discharge port 12 is introduced between the outer circumferential surface of the ring gear 4 and the sliding surface 51 of the gear housing 5 through the supply passage 82 and the inlet 81. The high-pressure hydraulic fluid pushes the ring gear 4 from the outer circumference of the third region toward the rotation axis C2. The teeth of the ring gear 4 are pressed against the second arcuate wall 542 of the crescent 54. In the third region, leakage of hydraulic fluid from the high-pressure side to the low-pressure side through the space between the teeth of the ring gear 4 and the second arcuate wall 542 of the crescent 54 is suppressed. By suppressing leakage flow within the housing 10, the pumping efficiency of the internal gear pump 1 is improved.

[0066] Furthermore, the high-pressure oil supply unit 8 may have a throttle in the middle of the supply passage 82. The throttle adjusts the pressure of the hydraulic fluid introduced between the outer circumferential surface of the ring gear 4 and the sliding surface 51 of the gear housing 5.

[0067] In the internal gear pump 1, the high-pressure oil supply unit 8 may be omitted. The high-pressure oil supply unit 8 is not an essential element in the internal gear pump 1.

[0068] (Noise-reducing structure) In the internal gear pump 1, noise is generated due to the pressure difference between the pressure at the discharge port 12 and the pressure in the spaces between the teeth when the spaces between the teeth of the pinion gear 3 and the ring gear 4 pass through the third region and are opened to the discharge port 12. The larger the pressure difference between the pressure at the discharge port 12 and the pressure in the spaces between the teeth, the greater the pressure fluctuation when the spaces between the teeth are opened to the discharge port 12, and therefore the louder the noise from the internal gear pump. The internal gear pump 1 has a pressure transmission oil passage 91 that suppresses noise.

[0069] The pressure transmission oil passage 91 utilizes the high pressure of the discharge port 12 to pre-increase the pressure of the hydraulic fluid trapped in the space between the teeth in the third region, thereby reducing the pressure difference between the pressure at the discharge port 12 and the pressure in the space between the teeth. A smaller pressure difference reduces the pressure fluctuation when the space between the teeth is opened to the discharge port 12, thus suppressing noise from the internal gear pump.

[0070] In the internal gear pump 1 illustrated in Figures 1 and 3, the pressure transmission oil passage 91 is formed to be recessed from the second support surface 61 of the front cover 6. In the right-hand diagram of Figure 1 and Figure 3, the pressure transmission oil passage 91 shown by the dashed line is projected onto the gear housing 5 from the pressure transmission oil passage 91 formed on the front cover 6 in order to clarify the positional relationship between the pressure transmission oil passage 91, the ring gear 4, and the crescent 54.

[0071] The pressure transmission oil passage 91 is a groove formed in the second support surface 61. As shown in Figure 3, the cross-sectional shape of the pressure transmission oil passage 91 is triangular. However, the cross-sectional shape of the pressure transmission oil passage 91 is not limited to a triangle. The cross-sectional shape may be, for example, a rectangle.

[0072] The pressure transmission oil passage 91 extends straight from the edge of the discharge port 12 toward the low-pressure side in the third region. As shown in Figure 3, the depth of the pressure transmission oil passage 91 gradually decreases as it moves away from the discharge port 12, and the width of the pressure transmission oil passage 91 gradually narrows as it moves away from the discharge port 12. The depth of the pressure transmission oil passage may be constant, and the width of the pressure transmission oil passage may be constant.

[0073] The pressure transmission oil passage 91, when viewed in the direction of the rotation axis C2 of the ring gear 4, in other words, in the right diagram of Figure 1 or Figure 3, overlaps with the space between the teeth of the ring gear 4. Since the pressure transmission oil passage 91 is linear while the crescent 54 is crescent-shaped, the base end of the pressure transmission oil passage 91 (i.e., the connection end between the pressure transmission oil passage 91 and the discharge port 12) is located near the radially outermost edge of the discharge port 12, the middle part of the pressure transmission oil passage 91 is located near the second arcuate wall 542 of the crescent 54, and the tip of the pressure transmission oil passage 91 is located away from the second arcuate wall 542 of the crescent 54. The pressure transmission oil passage 91 can extend while avoiding interference with the crescent 54.

[0074] In the third region, the space between the teeth of the ring gear 4 is closed because the tooth tips of the ring gear 4 are pressed against the second arcuate wall 542 of the crescent 54. The pressure transmission oil passage 91 communicates with the space between the teeth of the ring gear 4 in a direction perpendicular to the plane of the paper in Figure 1 or 3. A portion of the high-pressure hydraulic fluid from the discharge port 12 flows into the space between the teeth of the ring gear 4 through the pressure transmission oil passage 91, increasing the pressure in that space. According to the results of actual pressure measurements taken by the inventors of the present invention, when the pressure transmission oil passage 91 is not formed, the pressure in the space between the teeth of the ring gear 4 on the ring gear 4 side of the crescent 54 in the third region decreases relative to the discharge pressure, while the formation of the pressure transmission oil passage 91 increases the pressure in that space. Since the pressure in the space between the teeth of the ring gear 4 is increased in advance in the third region, the pressure difference between the pressure at the discharge port 12 and the pressure in the space between the teeth becomes small. Since pressure fluctuations are suppressed when the space is opened to the discharge port 12, the noise of the internal gear pump 1 is suppressed. According to the inventors' studies, a reduction in noise level due to the formation of the pressure transmission oil passage 91 was confirmed, and it was found that the noise level improvement effect is higher the higher the discharge pressure of the internal gear pump 1.

[0075] The internal gear pump 1 is formed within the housing 10 only in the region on the ring gear 4 side of the third region, which is separated by the crescent 54 by the pinion gear 3 side and the ring gear 4 side. No pressure transmission oil passage is formed in the region on the pinion gear 3 side.

[0076] According to the inventors' investigation, the pressure in the space between the teeth of the pinion gear 3 is relatively high even without a pressure transmission oil passage, and is equal to or higher than the pressure on the ring gear 4 side when the pressure transmission oil passage 91 is formed. The pressure fluctuation when the space between the teeth of the pinion gear 3 is opened to the discharge port 12 is relatively small. This is because the crescent 54 has a structure in which the first arcuate wall 541 and the second arcuate wall 542 are not movable, and a minute gap exists between the tooth tips of the pinion gear 3 and the first arcuate wall 541. On the pinion gear 3 side, leakage flow occurs from the discharge port 12 to the space between the teeth of the pinion gear 3 through this gap. As a result, in the third region, the pressure in the space between the teeth of the pinion gear 3 is relatively high.

[0077] Because the pressure in the space between the teeth of the pinion gear 3 is relatively high, even if a pressure transmission oil passage is formed in the region on the pinion gear 3 side, the pressure in that space will not increase further. The noise suppression effect of the internal gear pump 1 will not improve easily. On the other hand, if a pressure transmission oil passage is formed, leakage flow will increase accordingly. There is a risk that the pumping efficiency of the internal gear pump 1 will decrease.

[0078] Therefore, in the internal gear pump 1, the pressure transmission oil passage 91 is formed within the housing only in the region on the ring gear 4 side, and no pressure transmission oil passage is formed in the region on the pinion gear 3 side. This achieves both noise suppression of the internal gear pump 1 and improved pump efficiency.

[0079] Next, we consider the preferred length of the pressure transmission oil passage 91. Here, the length of the pressure transmission oil passage 91 is determined by the position of the tip of the pressure transmission oil passage 91 within the third region of the housing 10. The length of the pressure transmission oil passage 91 referred to here is not the length along a straight pressure transmission oil passage 91.

[0080] As mentioned above, the pressure transmission oil passage 91 has the function of increasing the pressure in the space between the teeth of the ring gear 4 before it communicates with the discharge port 12. If the pressure transmission oil passage 91 is too short, it is difficult to pre-increase the pressure in the space between the teeth of the ring gear 4 before it communicates with the discharge port 12. There is a minimum length for the pressure transmission oil passage 91 in order for it to function properly.

[0081] Specifically, as shown in Figure 3, the tip of the pressure transmission oil passage 91 is positioned at an angle θ1 or greater from the edge of the discharge port 12, with respect to the rotation axis C2 of the ring gear 4, corresponding to the tooth width TW of the ring gear 4. Since the pressure transmission oil passage 91 extends to a position of angle θ1 or greater, it can extend beyond at least one tooth of the ring gear 4, enabling communication between the discharge port 12 and the space between the teeth. The pressure transmission oil passage 91 can supply high-pressure hydraulic fluid into the space between the teeth before it reaches the discharge port 12. In other words, the pressure transmission oil passage 91 can pre-increase the pressure in the space between the teeth of the ring gear 4 before it communicates with the discharge port 12.

[0082] Lengthening the pressure transmission oil passage 91 is advantageous in increasing the pressure in the space between the teeth of the ring gear 4. However, once the pressure transmission oil passage 91 reaches a certain length, further lengthening will not increase the pressure in the space between the teeth. On the other hand, the longer the pressure transmission oil passage 91 becomes, the greater the leakage flow within the housing 10. Therefore, the tip of the pressure transmission oil passage 91 is located within an angle θ2 or less from the edge of the discharge port 12 to the midpoint of the crescent 54. In the illustrated example, the tip of the pressure transmission oil passage 91 is located at the midpoint of the crescent 54. The midpoint of the crescent 54 is the midpoint in the circumferential direction of the crescent 54 that extends circumferentially from the discharge port 12 to the suction port 11. By keeping the pressure transmission oil passage 91 from being too long, the pressure in the space between the teeth of the ring gear 4 can be sufficiently increased while suppressing the increase in leakage flow.

[0083] (Modified example of a pressure transmission oil passage) In the internal gear pump 1 shown in Figure 1, the pressure transmission oil passage 91 is formed in the second support surface 61 of the front cover 6. The pressure transmission oil passage 91 may also be formed recessed from the first support surface 52 of the gear housing 5. The pressure transmission oil passage 91 may be formed in both the second support surface 61 of the front cover 6 and the first support surface 52 of the gear housing 5.

[0084] The pressure transmission oil passage is not limited to a straight shape. Figure 4 shows a curved pressure transmission oil passage 92. The pressure transmission oil passage 92, like the pressure transmission oil passage 91, is formed on the second support surface 61 of the front cover 6. Note that, as with Figure 3, the pressure transmission oil passage 92 in Figure 4 is shown projected onto the gear housing 5 from the pressure transmission oil passage 92 formed on the front cover 6.

[0085] The pressure transmission oil passage 92 extends in an arc shape, following the curve of the second arc-shaped wall 542 of the crescent 54. When viewed in the direction of the rotation axis C2 of the ring gear 4, the pressure transmission oil passage 92 overlaps with the space between the teeth of the ring gear 4. The pressure transmission oil passage 92 communicates with the space between the teeth of the ring gear 4. Because the pressure in the space between the teeth of the ring gear 4 increases in the third region, the pressure difference between the pressure at the discharge port 12 and the pressure in the space between the teeth is small when the space is opened to the discharge port 12. Noise from the internal gear pump 1 is suppressed.

[0086] Note that the arc shape of the pressure transmission oil passage 92 shown in Figure 4 is illustrative. The curved pressure transmission oil passage 92 is not limited to an arc shape. The depth of the pressure transmission oil passage 92 may gradually become shallower as it moves away from the discharge port 12, or it may be a constant depth. The width of the pressure transmission oil passage 92 may gradually become narrower as it moves away from the discharge port 12, or it may be a constant width. Furthermore, the position of the tip of the pressure transmission oil passage 92 can be arbitrarily set within the range of θ1 to θ2 as described above. The pressure transmission oil passage 92 may be formed on the first support surface 52 of the gear housing 5 instead of being formed on the second support surface 61 of the front cover 6, or in addition to being formed on the second support surface 61.

[0087] Furthermore, the pressure transmission oil passages formed on the first support surface 52 and / or the second support surface 61 may be bent along their course.

[0088] The pressure transmission oil passage is not limited to being formed in the first support surface 52 and / or the second support surface 61. Figure 5 is a perspective view of the internal gear pump 1 with the front cover 6 removed. This internal gear pump 1 has a pressure transmission oil passage 93 formed in the crescent 54.

[0089] The pressure transmission oil passage 93 is formed at the upper end of the second arcuate wall 542 of the crescent 54. The pressure transmission oil passage 93 is formed by cutting out the surface of the crescent 54. The upper end referred to here is the end of the crescent 54 that is erected from the first support surface 52 of the gear housing 5, on the side opposite to the first support surface 52. The upper end of the second arcuate wall 542 is the end that abuts against the second support surface 61 of the front cover 6.

[0090] The pressure transmission oil passage 93 extends from the high-pressure side end of the crescent 54 (i.e., the left end in Figure 5) to the middle position of the crescent 54. The pressure transmission oil passage 93 communicates with the discharge port 12 which opens into the second support surface 61 of the front cover 6. The length of the pressure transmission oil passage 93 can be arbitrarily set within the range of θ1 to θ2 as described above. In the configuration example in Figure 5, the width / depth of the pressure transmission oil passage 93 gradually narrows / shallows as it moves away from the discharge port 12. The width / depth of the pressure transmission oil passage 93 may also be constant.

[0091] The pressure transmission oil passage 93 formed in the crescent 54 also connects the space between the teeth of the ring gear 4 to the discharge port 12, similar to the pressure transmission oil passages 91 and 92 described above. Because the pressure in the space between the teeth of the ring gear 4 increases in the third region, the pressure difference between the pressure at the discharge port 12 and the pressure in the space between the teeth is small when this space is opened to the discharge port 12. Since pressure fluctuations are suppressed, the noise of the internal gear pump 1 is suppressed.

[0092] Furthermore, the pressure transmission oil passage formed in the crescent 54 is not limited to being formed at the upper end of the crescent 54. The pressure transmission oil passage may be formed at an intermediate vertical position in the second arcuate wall 542 of the crescent 54. The pressure transmission oil passage may also be formed at the lower end of the crescent 54. [Explanation of Symbols]

[0093] 1. Internal gear pump 10 Housing 11 Intake port 12 discharge ports 3 Pinion gear 31 External teeth 4 Ring gear 41 Inner teeth 42 Outer surface 43 First aspect 44 Second aspect 5. Gear Housing (Housing) 51 Sliding surface 52 1st support surface 54 Crescent 541 First Circular Wall 542 Second Circular Wall 6. Front cover (housing) 61 Second support surface 8. High-pressure oil supply unit 81 Inlet 91 Pressure transmission oil passage 92 Pressure transmission oil passage 93 Pressure transmission oil passage C2 Rotation axis

Claims

1. A pinion gear having external teeth, A ring gear having internal teeth that mesh with the external teeth, A housing having an intake port and a discharge port, and rotatably housing the pinion gear and the ring gear, The crescent is located at a point where the meshing of the pinion gear and the ring gear separates, and has a first arc-shaped wall in contact with the external teeth and a second arc-shaped wall in contact with the internal teeth. The first and second arc-shaped walls are both fixed walls that do not move toward the external and internal teeth. Of the region on the pinion gear side and the region on the ring gear side, the pressure transmission oil passage extending from the discharge port is formed within the housing only in the region on the ring gear side. The pressure transmission oil passage is an internal gear pump that connects the discharge port and the space between the teeth of the ring gear.

2. In the internal gear pump according to claim 1, The housing has a sliding surface on which the outer circumferential surface of the ring gear slides, The system includes a high-pressure oil supply unit that supplies high-pressure hydraulic fluid between the outer circumferential surface and the sliding surface through an inlet opening that opens to the sliding surface, The inlet is located on the opposite side of the crescent from the ring gear in the internal gear pump.

3. In the internal gear pump according to claim 1 or 2, The housing has a first support surface and a second support surface that support two sides of the ring gear that are perpendicular to the rotation axis of the ring gear, respectively. The discharge ports are formed on the first support surface and the second support surface, The pressure transmission oil passage is formed to be recessed from the first support surface, the second support surface, or the first support surface and the second support surface. An internal gear pump in which the pressure transmission oil passage overlaps with the space between the teeth of the ring gear when viewed in the direction of the rotating shaft.

4. In the internal gear pump according to claim 1 or 2, The pressure transmission oil passage is formed to recess from the second circular arc wall of the crescent, in an internal gear pump.

5. In the internal gear pump according to claim 1 or 2, An internal gear pump in which the tip of the pressure transmission oil passage is located within a range of an angle θ1 or greater from the edge of the discharge port, corresponding to the tooth width of the ring gear, and an angle θ2 or less from the midpoint of the crescent extending from the discharge port to the suction port, with respect to the rotation axis of the ring gear.

Images