Internal gear pump

Abstract

An internal gear pump (1) is provided with: a shaft (2); a gear set (13) that includes a ring gear (4) and a pinion gear (3) which is integrally rotated with the shaft; and a casing (10) that has a suction part (11) and a discharge part (12) for hydraulic oil and rotatably accommodates the gear set. The casing has a support surface (52, 61) that intersects the shaft and supports a side surface (32, 33) of the pinion gear, the side surface sliding in conjunction with the rotation of the pinion gear. The casing has a groove (lubrication groove 7) that is recessed from the support surface and in which the hydraulic oil accumulates.

Description

Internal gear pump

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

[0002] Patent Document 1 describes a conventional internal gear pump. This conventional internal gear pump includes an inner gear, an outer gear, and a housing that accommodates the inner gear and the outer gear. The inner gear corresponds to a pinion gear, and the outer gear corresponds to a ring gear. Two oil grooves extending in the rotational axis direction are provided on the inner peripheral surface of a gear accommodating portion of the housing. The two oil grooves are connected to a discharge port. Hydraulic oil flows between the outer peripheral surface of the outer gear and the inner peripheral surface of the gear accommodating portion through the oil grooves. The hydraulic oil flowing between the outer peripheral surface of the outer gear and the inner peripheral surface of the gear accommodating portion prevents seizure from occurring on the outer peripheral surface of the outer gear.

[0003] JP 2010-190161 A

[0004] The conventional internal gear pump described above can suppress seizure on the outer peripheral surface of the outer gear. Seizure in an internal gear pump does not occur only on the outer peripheral surface of the outer gear. Research by the present inventors has newly discovered that seizure can also occur in other locations, such as between the side surface of the pinion gear, which rotates integrally with the shaft, and the support surface of the casing against which the side surface of the pinion gear slides.

[0005] The technology disclosed herein suppresses seizure between the side surface of the pinion gear and the support surface of the casing in an internal gear pump.

[0006] The technology disclosed herein relates to an internal gear pump comprising: a shaft; a gear set including a pinion gear having external teeth and rotating integrally with the shaft and a ring gear having internal teeth meshing with the external teeth; and a casing having a hydraulic oil intake section and a discharge section and rotatably housing the gear set, wherein the casing has a support surface that intersects the shaft and supports a side surface of the pinion gear, the side surface sliding against the rotation of the pinion gear, and a groove recessed from the support surface in which the hydraulic oil accumulates.

[0007] In an internal gear pump, as the gear set rotates, the pinion gear and ring gear gradually disengage from each other at the suction section. As the pinion gear and ring gear disengage, hydraulic oil is drawn from the suction section into the tooth grooves of the pinion gear and the ring gear. The tooth grooves are the spaces between the gear teeth. The drawn hydraulic oil is transported from the suction section to the discharge section as the gear set rotates. Then, as the pinion gear and ring gear, which had been separated, gradually approach each other and mesh together at the discharge section, the hydraulic oil in the tooth grooves of the pinion gear and the ring gear is discharged to the discharge section.

[0008] When the gear set rotates, the side of the pinion gear slides on the support surface of the casing. The casing has a groove formed in the support surface. The groove is recessed from the support surface and hydraulic oil accumulates in the groove. The groove allows a sufficient amount of hydraulic oil to be supplied between the side of the pinion gear and the support surface of the casing. The lubricating effect of the hydraulic oil prevents seizure between the side of the pinion gear and the support surface of the casing.

[0009] The casing may include a gear housing having an accommodating portion in which the gear set is accommodated, and a cover adjacent to the gear housing and closing the opening of the accommodating portion, wherein the gear housing has a first support surface against which a first side surface of the pinion gear slides, and the cover has a second support surface against which a second side surface of the pinion gear opposite to the first side surface slides, and the groove may be formed in at least one of the first support surface and the second support surface.

[0010] Seizure between the pinion gear and the casing can occur between the first side surface of the pinion gear and the first support surface of the gear housing and / or between the second side surface of the pinion gear and the second support surface of the cover. If a groove is formed in at least one of the first support surface and the second support surface, seizure is suppressed between the first side surface of the pinion gear and the first support surface of the gear housing and / or between the second side surface of the pinion gear and the second support surface of the cover.

[0011] The groove may be formed only in the first support surface.

[0012] The groove may be formed in both the first support surface and the second support surface.

[0013] The groove in the first support surface of the gear housing holds hydraulic oil between the first support surface and the first side surface of the pinion gear, maintaining a distance between the first support surface and the first side surface.

[0014] The groove in the second support surface of the cover holds hydraulic oil between the second support surface and the second side surface of the pinion gear, maintaining a distance between the second support surface and the second side surface.

[0015] By forming grooves on both the first support surface and the second support surface, seizure between the first support surface and the first side surface, and seizure between the second support surface and the second side surface are stably suppressed.

[0016] The groove formed in the first support surface and the groove formed in the second support surface may have the same groove width and the same groove depth.

[0017] If the groove width and groove depth of the two grooves are the same, the spacing retention function on the first side surface of the pinion gear and the spacing retention function on the second side surface will be the same, so that seizure between the first side surface and the first support surface and seizure between the second side surface and the second support surface can both be suppressed.

[0018] The groove formed in the first support surface and the groove formed in the second support surface may be positioned at the same position in a radial direction centered on the shaft.

[0019] If the radial positions of the two grooves are the same, the spacing retention function of the first side surface of the pinion gear and the spacing retention function of the second side surface will be the same, so that seizure between the first side surface and the first support surface and seizure between the second side surface and the second support surface can both be suppressed.

[0020] The support surface may have an opening for the suction section and an opening for the discharge section, with an insertion hole through which the shaft is inserted between them, and the groove may be located midway between the insertion hole and the opening for the suction section and the opening for the discharge section on the support surface of the casing.

[0021] The portions of the casing support surface between the insertion hole and the openings of the suction and discharge ports are the portions on which the side of the pinion gear slides. The grooves located in the middle of these portions effectively prevent the side of the pinion gear from seizing. Furthermore, because the grooves filled with hydraulic oil come into contact with the side of the pinion gear, the side of the pinion gear is prevented from adhering to the casing support surface. Furthermore, the edges of the openings of the suction port and the openings of the discharge port coincide or nearly coincide with the root circle of the pinion gear. Therefore, the grooves located between the openings of the suction port and the openings of the discharge port and the insertion hole do not come into contact with the tooth grooves of the pinion gear. The grooves do not increase leakage from the internal gear pump.

[0022] The groove may have a continuous annular shape surrounding the insertion hole.

[0023] The continuous annular groove supplies hydraulic oil uniformly or almost uniformly to the entire area between the side surface of the rotating pinion gear and the support surface of the casing, thereby enhancing the effect of suppressing seizure of the side surface of the pinion gear.

[0024] The pinion gear may have a second groove recessed from the side surface, in which the hydraulic oil is stored.

[0025] Forming a second groove on the side surface of the pinion gear in addition to the groove on the support surface of the casing allows a sufficient amount of hydraulic oil to be supplied between the side surface of the pinion gear and the support surface of the casing, thereby suppressing the occurrence of seizure between the side surface of the pinion gear and the support surface of the casing.

[0026] The internal gear pump disclosed herein also comprises: a shaft; a gear set including a pinion gear having external teeth and rotating integrally with the shaft, and a ring gear having internal teeth that mesh with the external teeth; and a casing having a hydraulic oil suction section and a discharge section and rotatably housing the gear set, wherein the casing has a surface that intersects the shaft and supports a side surface of the pinion gear, the support surface being a surface against which the side surface slides as the pinion gear rotates, and the pinion gear has a groove recessed from the side surface in which the hydraulic oil collects.

[0027] The pinion gear has a groove on its side surface that is recessed from the side surface and in which hydraulic oil is accumulated. A sufficient amount of hydraulic oil is supplied between the pinion gear side surface and the support surface of the casing, thereby suppressing seizure between the pinion gear side surface and the support surface of the casing.

[0028] The casing may include a gear housing having an accommodating portion in which the gear set is accommodated, and a cover adjacent to the gear housing and closing the opening of the accommodating portion, wherein the gear housing has a first support surface against which a first side surface of the pinion gear slides, and the cover has a second support surface against which a second side surface of the pinion gear opposite to the first side surface slides, and the groove may be formed on at least one of the first side surface and the second side surface.

[0029] If a groove is formed on at least one of the first and second sides of the pinion gear, the occurrence of seizure between the first side of the pinion gear and the first support surface of the gear housing, and / or between the second side of the pinion gear and the second support surface of the cover, is suppressed.

[0030] The groove may be located on the side surface of the pinion gear midway between the outer peripheral surface of the shaft and the tooth bottom.

[0031] The grooves located on the side of the pinion gear between the outer circumferential surface of the shaft and the tooth root effectively prevent the pinion gear from seizing. Furthermore, since the grooves do not contact the pinion gear tooth grooves, the grooves do not increase leakage from the internal gear pump.

[0032] The groove may have a continuous annular shape surrounding the shaft.

[0033] The continuous annular groove supplies hydraulic oil uniformly or almost uniformly to the entire area between the side surface of the rotating pinion gear and the support surface of the casing, thereby enhancing the effect of suppressing seizure of the side surface of the pinion gear.

[0034] The housing may have a guide portion that communicates with the groove and guides the hydraulic oil to the groove.

[0035] The hydraulic oil is guided to the groove through the guide portion, so that the groove can supply a sufficient amount of hydraulic oil between the side surface of the pinion gear and the support surface of the casing, further suppressing the occurrence of seizure between the side surface of the pinion gear and the support surface of the casing.

[0036] The guide portion may connect at least one of the suction portion and the discharge portion to the groove.

[0037] The guide portion can stably guide the hydraulic oil from the suction portion and / or the discharge portion to the groove.

[0038] The guide portion may connect an insertion hole for the shaft formed in the casing and the groove to each other.

[0039] Hydraulic oil used to lubricate the shaft bearings flows along the shaft through the insertion hole, and the guide portion can stably guide the hydraulic oil from the insertion hole to the groove.

[0040] The groove formed on the first support surface and the groove formed on the second support surface have a continuous annular shape centered on the rotation axis of the pinion gear; the casing has a guide portion that connects at least one of the groove formed on the first support surface and the groove formed on the second support surface to an insertion hole for the shaft formed in the casing; the pinion gear has a through hole that opens to the first side surface and the second side surface and passes through the pinion gear; and the through hole is always in communication with the groove on the first support surface and the groove on the second support surface.

[0041] The groove formed in the first support surface and the groove formed in the second support surface are always in communication with each other through the through hole of the pinion gear. Because the groove formed in the first support surface and the groove formed in the second support surface are annular, the through hole can maintain communication with the groove formed in the first support surface and the groove formed in the second support surface even while the pinion gear is rotating.

[0042] The guide portion connects at least one of the grooves formed in the first support surface and the second support surface with a shaft insertion hole formed in the casing. The hydraulic oil is guided from the shaft insertion hole to the groove through the guide portion. The hydraulic oil is also guided from the groove formed in the first support surface to the groove formed in the second support surface, or vice versa, through the through hole of the pinion gear. Seizing between the first support surface and the first side surface and between the second support surface and the second side surface are stably suppressed.

[0043] The groove formed in the first support surface and / or the second support surface may have a continuous ring shape surrounding the insertion hole, the casing may have a guide section that communicates with the groove and guides the hydraulic oil to the groove, and the guide section may connect at least one of the suction section and the discharge section to the groove, but may not connect the insertion hole of the shaft formed in the casing to the groove.

[0044] The hydraulic oil is guided from at least one of the suction and discharge sections through the guide section to the annular groove. This allows the hydraulic oil to be supplied uniformly or almost uniformly to the entire area between the side surface of the rotating pinion gear and the support surface of the casing, effectively preventing the side surface of the pinion gear from seizing.

[0045] The internal gear pump described above can suppress seizure between the side surface of the pinion gear and the support surface of the casing.

[0046] FIG. 1 is a longitudinal cross-sectional view of an internal gear pump. FIG. 2 is a side view of the internal gear pump with the front cover removed. FIG. 3 shows a gear housing and cover with lubrication grooves, and a pinion gear. FIG. 4 is an enlarged view of the first support surface of the gear housing. FIG. 5 shows a gear housing, cover, and pinion gear with lubrication grooves. FIG. 6 shows a gear housing with a guide portion. FIG. 7 shows a gear housing and cover, and a pinion gear with lubrication grooves. FIG. 8 is a longitudinal cross-sectional view of an internal gear pump in which the pinion gear has a lubrication groove. FIG. 9 shows a gear housing and cover with a guide portion, and a pinion gear with lubrication grooves. FIG. 10 shows combinations of locations where lubrication grooves are formed in an internal gear pump. FIG. 11 shows modified guide portions. FIG. 12A shows modified examples of the relative positions of the through holes in the pinion gear and the lubrication grooves. Fig. 12B shows a modification of the relative position of the through hole of the pinion gear and the lubrication groove, and Fig. 13 shows a modification of the shape of the lubrication groove.

[0047] Hereinafter, an embodiment of an internal gear pump will be described with reference to the drawings. The internal gear pump described here is an example.

[0048] (Overall Structure of the Inscribed Gear Pump) Figures 1 and 2 illustrate an inscribed gear pump 1. Figure 1 corresponds to a cross-sectional view (i.e., a longitudinal cross-sectional view) taken along the shaft 2 of the inscribed gear pump 1. Figure 2 is a side view of the inscribed gear pump 1 as seen along the shaft 2 with the front cover 6 removed from the gear housing 5. The gear housing 5 and the front cover 6 form a casing 10 of the inscribed gear pump 1.

[0049] The internal gear pump 1 includes a shaft 2. The shaft 2 extends in the left-right direction of the paper in Fig. 1. The tip of the shaft 2, i.e., the left end in Fig. 1, protrudes from a casing 10. The tip of the shaft 2 is connected to a prime mover (not shown). The prime mover is, for example, an electric motor.

[0050] The internal gear pump 1 includes a pinion gear 3. The pinion gear 3 is integrated with the shaft 2 at an intermediate position of the shaft 2 via a spline (see also FIG. 3 ). 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.

[0051] The internal gear pump 1 includes a ring gear 4. The ring gear 4 meshes with a pinion gear 3. The ring gear 4 is eccentric with respect to the shaft 2. In FIG. 2, C1 denotes the rotation axis of the pinion gear 3, and C2 denotes the rotation axis of the ring gear 4. Internal teeth 41 are formed on the inner circumferential surface of the ring gear 4. In FIG. 2, 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 in the region on the left side of the page.

[0052] The pinion gear 3 and the ring gear 4 form a gear set 13 of the internal gear pump 1 .

[0053] The gear housing 5 accommodates the pinion gear 3 and the ring gear 4. An inner hole 53 is formed in the gear housing 5. The base end of the shaft 2, i.e., the right end in FIG. 1, is located within the inner hole 53. The inner hole 53 is an insertion hole through which the shaft 2 is inserted.

[0054] The pinion gear 3 and the ring gear 4 are rotatably housed in a gear housing 5. The gear housing 5 has a sliding surface 51 on which the outer peripheral surface 42 of the ring gear 4 slides. The outer peripheral 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.

[0055] The gear housing 5 has a first support surface 52 that is perpendicular to the sliding surface 51. The first support surface 52 is a surface that intersects, or more precisely, is perpendicular to, the shaft 2. The sliding surface 51 and the first support surface 52 form an accommodation portion 50 that accommodates the pinion gear 3 and the ring gear 4. The accommodation portion 50 is open to the left side of the paper in FIG. 1 . The first side surface 32 of the pinion gear 3 and the first side surface 43 of the ring gear 4 are each 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 a surface that intersects, or more precisely, is perpendicular to, the rotation axis C1 of the pinion gear 3, and is the side surface on the right side of the paper in FIG. 1 . The first side surface 43 of the ring gear 4 is a surface that intersects, or more precisely, is perpendicular to the rotation axis C2 of the ring gear 4, and is the side surface on the right side of the paper in FIG. 1 .

[0056] The front cover 6 is disposed adjacent to the gear housing 5. The front cover 6 and the gear housing 5 are fixed to each other and integrated. The front cover 6 has a second support surface 61. The second support surface 61 is a surface that intersects, or more precisely, is perpendicular to, the shaft 2. The second support surface 61 contacts the gear housing 5 and closes the opening of the accommodating portion 50. The second side surface 33 of the pinion gear 3 and the second side surface 44 of the ring gear 4 are each supported by and slide on the second support surface 61 of the front cover 6. The second side surface 33 of the pinion gear 3 is a surface that intersects, or more precisely, is perpendicular to, the rotation axis C1 of the pinion gear 3, and is the side surface opposite to the first side surface 32. The second side surface 33 of the pinion gear 3 is the side surface on the left side of the paper in FIG. 1 . The second side surface 44 of the ring gear 4 is a surface that intersects with, or more precisely, is perpendicular to, the rotation axis C2 of the ring gear 4, and is the side surface on the left side of the paper in FIG.

[0057] A support hole 62 through which the shaft 2 passes is formed in the front cover 6. The support hole 62 is an insertion hole 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 closed by a sealing member 621.

[0058] The front cover 6 and the gear housing 5 have a suction portion 11. The suction portion 11 includes a suction portion 11a formed in the gear housing 5 and a suction portion 11b formed in the front cover 6. The suction portion 11a and the suction portion 11b are connected by a connection portion 11c. The connection portion 11c is also a part of the suction portion 11.

[0059] Hydraulic oil is sucked from the suction portion 11 into the storage portion 50 inside the casing 10. The inlet of the suction portion 11 opens to the outer peripheral surface of the front cover 6, as shown in Figure 1. The outlet of the suction portion 11 opens to the second support surface 61 of the front cover 6 and the first support surface 52 of the gear housing 5, as shown in Figures 1 and 2. The outlet of the suction portion 11 extends in the circumferential direction along the rotation direction of the shaft 2. The edge of the outlet of the suction portion 11, more specifically the radially inner edge of the outlet of the suction portion 11, substantially coincides with the root circle of the pinion gear 3, as shown in Figure 2.

[0060] The front cover 6 and the gear housing 5 also have a discharge portion 12. The discharge portion 12 includes a discharge portion 12a formed in the gear housing 5 and a discharge portion 12b formed in the front cover 6. The discharge portion 12a and the discharge portion 12b are independent of each other.

[0061] Hydraulic oil is discharged from the storage section 50 inside the casing 10 through the discharge section 12. The outlet of the discharge section 12 opens to the outer peripheral surface of the gear housing 5, as shown in Figure 1. The direction of the inlet of the suction section 11 and the direction of the outlet of the discharge section 12 may be different directions as shown in Figure 1, or may be the same direction.

[0062] The inlet of the discharge portion 12 opens to each of the second support surface 61 of the front cover 6 and the first support surface 52 of the gear housing 5. As shown in Figure 2, the inlet of the discharge portion 12 also extends in the circumferential direction along the rotation direction of the shaft 2, on the opposite side of the shaft 2 from the suction portion 11. An edge of the inlet of the discharge portion 12, more specifically, a radially inner edge of the inlet of the discharge portion 12, substantially coincides with the root circle of the pinion gear 3.

[0063] The hydraulic oil discharged to the discharge port 12a of the gear housing 5 is discharged through the outlet to the outside of the internal gear pump 1. The hydraulic oil discharged to the discharge port 12b of the front cover 6 is not discharged to the outside of the internal gear pump 1.

[0064] The gear housing 5 is provided with a crescent 54. The crescent 54 is disposed at a position where the pinion gear 3 and the ring gear 4 disengage from each other. The crescent 54 suppresses leakage flow from the discharge portion 12 to the suction portion 11.

[0065] The crescent 54 extends circumferentially over a predetermined angular range along the rotation direction of the shaft 2. As shown in Figure 2, the crescent 54 has an arc-shaped or crescent-shaped configuration when viewed in the axial direction of the shaft 2. The tips of the external teeth 31 of the pinion gear 3 abut against the inner arc-shaped wall of the crescent 54. The tips of the internal teeth 41 of the ring gear 4 abut against the outer arc-shaped wall of the crescent 54. The arc-shaped wall of the crescent 54 is a fixed wall that does not move toward the external teeth 31 and the internal teeth 41.

[0066] Next, we will briefly explain the operation of the internal gear pump 1. When the shaft 2 is rotated counterclockwise in Figure 2 by the prime mover, the pinion gear 3 and the ring gear 4 each rotate in a direction from the suction port 11 to the discharge port 12 via the crescent 54.

[0067] In the suction section 11 inside the casing 10, as the meshed external teeth 31 of the pinion gear 3 and the internal teeth 41 of the ring gear 4 separate, hydraulic oil is sucked into the gap between the external teeth 31 and the internal teeth 41 from the outlet of the suction section 11. As the pinion gear 3 and the ring gear 4 rotate, the sucked hydraulic oil is transported from the suction section 11 through the crescent 54 to the discharge section 12.

[0068] In the discharge section 12 inside the casing 10, the external teeth 31 of the pinion gear 3 and the internal teeth 41 of the ring gear 4, which had been separated, gradually approach each other and mesh together. As a result, the hydraulic oil is discharged from between the external teeth 31 and the internal teeth 41 through the inlet of the discharge section 12.

[0069] The crescent 54 contacts the tips of the teeth of the pinion gear 3 and the ring gear 4 between the suction portion 11 and the discharge portion 12, thereby suppressing leakage flow within the accommodation portion 50. The internal gear pump 1 is, for example, a high-pressure hydraulic pump with a relatively high discharge pressure, and the crescent 54 increases the efficiency of the high-pressure hydraulic pump.

[0070] (Lubrication Groove of Internal Gear Pump) The internal gear pump 1 has a lubrication groove 7. The lubrication groove 7 suppresses seizure between the side surfaces 32, 33 of the pinion gear 3 and the support surfaces 52, 61 of the casing 10 mainly by the lubricating effect of the hydraulic oil.

[0071] FIG. 3 shows the gear housing 5, front cover 6, and pinion gear 3 in an exploded view. In FIG. 3, the gear housing 5 is oriented so that the first support surface 52 is visible, and the front cover 6 is oriented so that the second support surface 61 is visible. The pinion gear 3 is oriented so that the first side surface 32 that slides on the first support surface 52 is visible. The gear housing 5 has a first lubrication groove 71 as the lubrication groove 7, and the front cover 6 has a second lubrication groove 72 as the lubrication groove 7 (see also FIG. 1 ). The first lubrication groove 71 stores hydraulic oil. The first lubrication groove 71 supplies a sufficient amount of hydraulic oil between the first side surface 32 of the pinion gear 3 and the first support surface 52 of the gear housing 5. Similarly, the second lubrication groove 72 stores hydraulic oil. The second lubrication groove 72 supplies a sufficient amount of hydraulic oil between the second side surface 33 of the pinion gear 3 and the second support surface 61 of the front cover 6.

[0072] Figure 4 shows an enlarged view of the first lubrication groove 71. The upper view of Figure 4 is an end view showing an enlarged view of the A-A end face. The structure of the second lubrication groove 72 is substantially the same as the structure of the first lubrication groove 71. Below, the structure of the first lubrication groove 71 will be described with reference to Figure 4, and a description of the structure of the second lubrication groove 72 may be omitted.

[0073] The first lubrication groove 71 is recessed from the first support surface 52. The first lubrication groove 71 opens to the first support surface 52. The first lubrication groove 71 is annular and surrounds the periphery of the inner hole 53. The first lubrication groove 71 is continuous and endless. In the illustrated example, the first lubrication groove 71 is circular and centered on the rotation axis C1 of the pinion gear 3. Note that the first lubrication groove 71 is not limited to a circular shape. The first lubrication groove 71 may be, for example, elliptical, or polygonal, such as triangular or rectangular. Similarly, the second lubrication groove 72 is recessed from the second support surface 61. The second lubrication groove 72 is annular and surrounds the periphery of the support hole 62, or more precisely, a circle centered on the rotation axis C1 of the pinion gear 3.

[0074] The first lubrication groove 71 is located midway between the inner hole 53 and the outlet of the suction portion 11, and is also located midway between the inner hole 53 and the inlet of the discharge portion 12. In the example of Fig. 4, the first lubrication groove 71 is located at a position of a radius r1 centered on the rotation axis C1 of the pinion gear 3. The first lubrication groove 71 may be located midway between the edge of the inner hole 53 and the edge of the outlet of the suction portion 11, or may be shifted from the center toward the inner hole 53 or toward the suction portion 11.

[0075] 3, the second lubrication groove 72 is located midway between the support hole 62 and the outlet of the suction portion 11, and is also located midway between the support hole 62 and the inlet of the discharge portion 12. Similar to the first lubrication groove 71, the second lubrication groove 72 is located at a position of a diameter r1 centered on the rotation axis C1 of the pinion gear 3. The second lubrication groove 72 may be located in the center between the edge of the support hole 62 and the edge of the inlet of the discharge portion 12, or may be shifted from the center toward the support hole 62 or toward the discharge portion 12.

[0076] The cross-sectional shape of the first lubrication groove 71 is rectangular, as shown in the upper diagram of FIG. 4 . The width W1 of the first lubrication groove 71 is constant in the depth direction. The width W1 of the first lubrication groove 71 can be set to an appropriate width. For example, the width W1 may be set to 1 / 3 or approximately 1 / 3 of the distance W2 between the edge of the inner hole 53 and the edge of the outlet of the suction portion 11. If the width W1 is too narrow, the hydraulic oil storage capacity of the first lubrication groove 71 will be reduced. If the width W1 is too wide, hydraulic oil leakage from the internal gear pump 1 will increase. Note that the width of the lubrication groove 7 is not limited to being constant around the entire circumference of the lubrication groove 7. The width of the lubrication groove 7 may be changed depending on the positional relationship with the suction portion 11 or the discharge portion 12.

[0077] The depth D of the first lubrication groove 71 can be set to any appropriate depth. The depth D may be, for example, in the range of 0.1 to 0.5 mm. If the depth D is too shallow, the hydraulic oil storage capacity of the first lubrication groove 71 will be reduced. If the depth D is too deep, hydraulic oil leakage from the internal gear pump 1 will increase.

[0078] The cross-sectional shape of the second lubrication groove 72 is rectangular, similar to the first lubrication groove 71. The width of the second lubrication groove 72 may be the same as or approximately the same as the width W1 of the first lubrication groove 71. The depth of the second lubrication groove 72 may be the same as or approximately the same as the depth D of the first lubrication groove 71.

[0079] The pinion gear 3 has through holes 361 and 362. The through holes 361 and 362 each open to the first side surface 32 and the second side surface 33. The through holes 361 and 362 axially penetrate the pinion gear 3. A portion of the hydraulic oil that flows along the axis of the shaft 2 and contributes to lubrication of the shaft 2 passes through the through holes 361 and 362.

[0080] 4 , the through hole 361 is located at a position of a radius r1 centered on the rotation axis C1 of the pinion gear 3. The through hole 361 mainly supplies hydraulic oil between the first support surface 52 and the first side surface 32, and between the second support surface 61 and the second side surface 33.

[0081] For example, when an external force causes the pinion gear 3 to move in a direction in which the first side surface 32 comes into contact with the first support surface 52, the hydraulic oil between the second support surface 61 and the second side surface 33 is supplied to between the first support surface 52 and the first side surface 32 through the through hole 361. Seizure between the first support surface 52 and the first side surface 32 is suppressed.

[0082] Conversely, when the pinion gear 3 moves in a direction in which the second side surface 33 comes into contact with the second support surface 61, the hydraulic oil between the first support surface 52 and the first side surface 32 is supplied through the through hole 361 to between the second support surface 61 and the second side surface 33. Seizing between the second support surface 61 and the second side surface 33 is suppressed.

[0083] The through hole 361 is located at a radial position (i.e., the position of the radius r1) where seizure on the side surfaces 32, 33 of the pinion gear 3 can be effectively suppressed.

[0084] The through hole 362 is located at a position of radius r2 centered on the rotation axis C1 of the pinion gear 3. The radius r2 is smaller than the radius r1. As shown imaginarily in Figure 4, a portion of the through hole 362 overlaps with the edge of the inner hole 53, and therefore the through hole 362 overlaps with the bearing member 64. The through hole 362 mainly supplies hydraulic oil to each of the two bearing members 64, 64 that sandwich the pinion gear 3 therebetween.

[0085] For example, when an external force causes the pinion gear 3 to move in a direction in which the first side surface 32 comes into contact with the first support surface 52, the hydraulic oil between the second support surface 61 and the second side surface 33 is supplied to the bearing member 64 on the first side surface 32 side through the through hole 362. This prevents the bearing member 64 from seizing.

[0086] Conversely, when the pinion gear 3 moves in a direction in which the second side surface 33 comes into contact with the second support surface 61, the hydraulic oil between the first support surface 52 and the first side surface 32 is supplied to the bearing member 64 on the second side surface 33 side through the through hole 362. This prevents the bearing member 64 from seizing.

[0087] The through-hole 362 is located at a radial position where the hydraulic oil can be effectively supplied to the bearing member 64 (i.e., the position of the radius r2).

[0088] The pinion gear 3 in the illustrated example has two through holes 361. The two through holes 361 are positioned at a distance from each other in the circumferential direction. The through holes 361 are positioned at a point where the total tooth depth is high in the circumferential direction of the pinion gear 3. If the through holes 361 are positioned at the tooth bottom, the distance between the through holes 361 and the tooth bottom is narrow, which may reduce the strength of the pinion gear 3. The angle between the two through holes 361 is approximately 180°.

[0089] The pinion gear 3 in the illustrated example has two through holes 362. The two through holes 362 are positioned at a distance from each other in the circumferential direction, and are also positioned at a distance from the through hole 361. The through hole 362 is positioned relatively close to the tooth bottom in the circumferential direction of the pinion gear 3. Because the through hole 362 is positioned radially inward of the through hole 361, the distance between the through hole 362 and the tooth bottom of the pinion gear 3 is greater. The angle between the two through holes 362 is approximately 180°, and the angle between the through hole 361 and the through hole 362 is approximately 90°.

[0090] The pinion gear 3 has a plurality of through holes 361, 362 that are distributed in the circumferential direction, which stabilizes the rotation of the pinion gear 3. This prevents unstable behavior such as vibration from occurring during operation of the internal gear pump 1.

[0091] Because the through hole 361 is located at a position of diameter r1, as shown imaginarily in FIG. 4 , the through hole 361 communicates with the first lubrication groove 71. Although not shown, the through hole 361 also communicates with the second lubrication groove 72. Even when the pinion gear 3 rotates, the through hole 361 maintains communication with the annular first lubrication groove 71 and second lubrication groove 72. As shown in the upper diagram of FIG. 4 , the diameter φ1 of the through hole 361 is larger than the width W1 of the first lubrication groove 71 and second lubrication groove 72. The through hole 361 can supply hydraulic oil to the first lubrication groove 71 and second lubrication groove 72.

[0092] The through hole 362 is located at a position of diameter r2 and therefore does not communicate with the first lubrication groove 71 and the second lubrication groove 72. The diameter of the through hole 362 is the same as the diameter φ1 of the through hole 361. The diameter of the through hole 362 may be different from the diameter φ1 of the through hole 361.

[0093] When the gear set 13 rotates due to operation of the internal gear pump 1, the first side surface 32 of the pinion gear 3 slides on the first support surface 52 of the gear housing 5, and the second side surface 33 slides on the second support surface 61 of the front cover 6. As described above, the first lubrication groove 71 supplies a sufficient amount of hydraulic oil between the first side surface 32 of the pinion gear 3 and the first support surface 52, and the second lubrication groove 72 supplies a sufficient amount of hydraulic oil between the second side surface 33 of the pinion gear 3 and the second support surface 61. The lubricating effect of the hydraulic oil suppresses the occurrence of seizure between the first side surface 32 and the first support surface 52 and between the second side surface 33 and the second support surface 61.

[0094] Since hydraulic oil is stored in the first lubrication groove 71 or the second lubrication groove 72 recessed from the support surfaces 52, 61 of the casing 10, the entire side surfaces 32, 33 of the pinion gear 3 do not contact the support surfaces 52, 61, but rather a portion of the side surfaces 32, 33 always contacts the groove in which hydraulic oil is stored. This prevents the side surfaces 32, 33 from adhering to the support surfaces 52, 61.

[0095] Furthermore, the first lubrication groove 71 is located midway between the inner bore 53 and the outlet of the suction portion 11 and the inlet of the discharge portion 12, and the second lubrication groove 72 is located midway between the inner bore 53 and the outlet of the suction portion 11 and the inlet of the discharge portion 12. Therefore, the first lubrication groove 71 and the second lubrication groove 72 can effectively suppress seizure of the side surfaces 32, 33 of the pinion gear 3. The first lubrication groove 71 and the second lubrication groove 72 are also radially offset from the tooth grooves of the pinion gear 3, as shown imaginarily in FIG. 4 . The fact that the first lubrication groove 71 and the second lubrication groove 72 do not contact the tooth grooves of the pinion gear 3 suppresses leakage from the internal gear pump 1. The first lubrication groove 71 and the second lubrication groove 72 do not reduce the efficiency of the internal gear pump 1.

[0096] Furthermore, the continuous annular first lubrication groove 71 or second lubrication groove 72 supplies hydraulic oil uniformly or almost uniformly to the entire area between the side surfaces 32, 33 of the rotating pinion gear 3 and the support surfaces 52, 61 of the casing 10. The continuous annular first lubrication groove 71 or second lubrication groove 72 enhances the effect of suppressing seizure of the side surfaces 32, 33 of the pinion gear 3.

[0097] Furthermore, the through holes 361, 362 of the pinion gear 3 supply the hydraulic oil flowing along the axis of the shaft 2 between the first support surface 52 and the first side surface 32, and between the second support surface 61 and the second side surface 33. In particular, since the through hole 361 is constantly in communication with each of the first lubrication groove 71 and the second lubrication groove 72, the hydraulic oil can be sufficiently supplied between the first support surface 52 and the first side surface 32, and between the second support surface 61 and the second side surface 33.

[0098] Furthermore, the internal gear pump 1 is provided with two lubrication grooves 7, the first lubrication groove 71 and the second lubrication groove 72, on either side of the pinion gear 3 in the axial direction, so that hydraulic oil is held between the first side surface 32 of the pinion gear 3 and the first support surface 52 of the gear housing 5, and hydraulic oil is held between the second side surface 33 of the pinion gear 3 and the second support surface 61 of the front cover 6. Axial pressure is balanced on the pinion gear 3. Having the same diameter for the first lubrication groove 71 and the second lubrication groove 72 is advantageous in balancing axial pressure on the pinion gear 3.

[0099] Changing the width or depth of the first lubrication groove 71 or the second lubrication groove 72 increases or decreases the hydraulic pressure supplied between the first support surface 52 and the first side surface 32, or between the second support surface 61 and the second side surface 33. Adjusting the magnitude of the hydraulic pressure on both sides of the pinion gear 3 in the axial direction makes it possible to adjust the axial positions of the pinion gear 3 and the ring gear 4 during operation of the internal gear pump 1. Adjusting the width or depth of the first lubrication groove 71 or the second lubrication groove 72 makes it possible to stabilize the behavior of the pinion gear 3 and the ring gear 4 during operation of the internal gear pump 1. The width or depth of the first lubrication groove 71 and the width or depth of the second lubrication groove 72 may be the same or different from each other.

[0100] The internal gear pump 1 is not limited to having both the first lubrication groove 71 and the second lubrication groove 72. For example, as shown in FIG. 5 , as a modified example of the internal gear pump, the internal gear pump 1 may have only the first lubrication groove 71 formed in the first support surface 52 of the gear housing 5. The internal gear pump 1 does not have the second lubrication groove in the second support surface 61 of the front cover 6. Because the discharge portion 12b of the front cover 6 is not connected to an outlet, the hydraulic oil discharged to the discharge portion 12b tends to accumulate between the second support surface 61 and the second side surface 33. The second lubrication groove in the second support surface 61 of the front cover 6 can be omitted.

[0101] (Guidance portion that guides hydraulic oil to lubrication groove) Fig. 6 shows the guidance portion 81. The guidance portion 81 guides hydraulic oil to the lubrication groove 7. The guidance portion 81 in Fig. 6 connects the first lubrication groove 71 and the discharge portion 12 on the first support surface 52 of the gear housing 5. The guidance portion 81 in Fig. 6 is a part of a circle recessed from the first support surface 52. The shape of the guidance portion 81 is arbitrary.

[0102] As shown in the B-B end view of FIG. 6 , the guide portion 81 opens to the first lubrication groove 71 and also opens to the discharge portion 12. The guide portion 81 can be formed by cutting the first support surface 52 from a direction perpendicular to the first support surface 52 using, for example, an end mill. The front cover 6 has a guide portion on the second support surface 61 that connects the second lubrication groove 72 and the discharge portion 12. Note that the guide portion of the front cover 6 can be omitted. Furthermore, if the front cover 6 has a guide portion, the guide portion of the gear housing 5 can be omitted.

[0103] The hydraulic oil is supplied from the discharge portion 12 through the guide portion 81 to the first lubrication groove 71 or the second lubrication groove 72. The first lubrication groove 71 or the second lubrication groove 72 can supply a sufficient amount of hydraulic oil between the side surfaces 32, 33 of the pinion gear 3 and the support surfaces 52, 61 of the casing 10. The occurrence of seizure between the side surfaces 32, 33 of the pinion gear 3 and the support surfaces 52, 61 of the casing 10 is suppressed.

[0104] The guide portion 81 communicating with the discharge portion 12 can stably supply hydraulic oil from the discharge portion 12 , which is at a relatively high pressure, to the first lubrication groove 71 or the second lubrication groove 72 .

[0105] (Lubrication Groove of Pinion Gear) The lubrication groove 7 does not necessarily have to be formed in the casing 10. The lubrication groove 7 may be formed in the first side surface 32 or the second side surface 33 of the pinion gear 3. Fig. 7 shows a third lubrication groove 73 formed in the pinion gear 3. Fig. 8 shows the third lubrication groove 73 and the fourth lubrication groove 74 formed in the pinion gear 3. Fig. 7 corresponds to Fig. 3, and the pinion gear 3 is oriented so that the first side surface 32 is visible. Fig. 8 shows an enlarged longitudinal cross-sectional view of a portion of the internal gear pump 1.

[0106] The third lubrication groove 73 is formed in the first side surface 32 of the pinion gear 3. As shown in FIG. 8 , the third lubrication groove 73 is recessed from the first side surface 32. The third lubrication groove 73 opens to the first side surface 32. The third lubrication groove 73 has an annular shape that surrounds the periphery of the shaft 2. In the illustrated example, the third lubrication groove 73 is a circle centered on the rotation axis C1 of the pinion gear. Note that the third lubrication groove 73 is not limited to a circle. The third lubrication groove 73 may be, for example, an ellipse, or a polygon such as a triangle or a rectangle.

[0107] The fourth lubrication groove 74 is formed in the second side surface 33 of the pinion gear 3. The fourth lubrication groove 74 is recessed from the second side surface 33. The fourth lubrication groove 74 opens to the second side surface 33. The fourth lubrication groove 74 is annular and surrounds the periphery of the shaft 2. More precisely, the shape of the fourth lubrication groove 74 is a circle centered on the rotation axis C1 of the pinion gear. The fourth lubrication groove 74 may also be elliptical or polygonal.

[0108] As shown in Fig. 7 , the third lubrication groove 73 is located midway between the outer circumferential surface of the shaft 2 and the tooth bottom of the pinion gear 3. The third lubrication groove 73 may be located in the center between the outer circumferential surface of the shaft 2 and the tooth bottom of the pinion gear 3, or may be shifted toward the shaft 2 from the center or toward the tooth bottom from the center. Similarly, the fourth lubrication groove 74 may be located in the center between the outer circumferential surface of the shaft 2 and the tooth bottom of the pinion gear 3, or may be shifted toward the shaft 2 from the center or toward the tooth bottom from the center. Here, as shown in Fig. 8 , the diameter of the third lubrication groove 73 and the diameter of the fourth lubrication groove 74 are the same.

[0109] The width and depth of the third lubrication groove 73 or the fourth lubrication groove 74 may be approximately the same as the width and depth of the first lubrication groove 71 or the second lubrication groove 72.

[0110] 8 , the through hole 361 of the pinion gear 3 communicates with the third lubrication groove 73. The through hole 361 also communicates with the fourth lubrication groove 74. The through hole 362 does not communicate with the third lubrication groove 73 or the fourth lubrication groove 74.

[0111] The third lubrication groove 73 opens between the first side surface 32 of the pinion gear 3 and the first support surface 52 of the gear housing 5, and the fourth lubrication groove 74 opens between the second side surface 33 of the pinion gear 3 and the second support surface 61 of the front cover 6. The third lubrication groove 73 supplies a sufficient amount of hydraulic oil between the first side surface 32 of the pinion gear 3 and the first support surface 52, and the fourth lubrication groove 74 supplies a sufficient amount of hydraulic oil between the second side surface 33 of the pinion gear 3 and the second support surface 61. The occurrence of seizure between the first side surface 32 and the first support surface 52 and between the second side surface 33 and the second support surface 61 is suppressed.

[0112] Furthermore, the through holes 361, 362 of the pinion gear 3 supply hydraulic oil flowing along the axis of the shaft 2 to between the first support surface 52 and the first side surface 32, and between the second support surface 61 and the second side surface 33. In particular, the through hole 361 is constantly in communication with each of the third lubrication groove 73 and the fourth lubrication groove 74, so that hydraulic oil can be sufficiently supplied between the first support surface 52 and the first side surface 32, and between the second support surface 61 and the second side surface 33.

[0113] Furthermore, since the pinion gear 3 has both the third lubrication groove 73 and the fourth lubrication groove 74, the axial pressure is balanced on the pinion gear 3. The diameter of the third lubrication groove 73 and the diameter of the fourth lubrication groove 74 are the same, which is advantageous in terms of balancing the axial pressure on the pinion gear 3.

[0114] 9, a guide portion 81 may be formed on the first support surface 52 of the gear housing 5 and the second support surface 61 of the front cover 6. The guide portion 81 connects the discharge portion 12 with the third lubrication groove 73 or the fourth lubrication groove 74, which are shown imaginarily in FIG. 9. The guide portion 81 can supply hydraulic oil from the discharge portion 12 to the third lubrication groove 73 or the fourth lubrication groove 74. The guide portion 81 may be formed only on the gear housing 5, or only on the front cover 6.

[0115] (Combination of Lubrication Grooves) As described above, the lubrication grooves 7 may be formed in the casing 10 or in the pinion gear 3. Fig. 10 shows examples of combinations of lubrication grooves 7 formed in various parts of the internal gear pump 1. A check mark in Fig. 10 indicates that a lubrication groove 7 is formed, and a cross mark indicates that a lubrication groove 7 is not formed.

[0116] Example (1) is an example in which lubrication grooves 7 are formed on all of the second support surface 61 of the front cover 6, the first side surface 32 and the second side surface 33 of the pinion gear 3, and the first support surface 52 of the gear housing 5.

[0117] Example (2) is an example in which the lubrication grooves 7 are formed on the second support surface 61 of the front cover 6 and the first side surface 32 and second side surface 33 of the pinion gear 3. Example (3) is an example in which the lubrication grooves 7 are formed on the second support surface 61 of the front cover 6, the second side surface 33 of the pinion gear 3, and the first support surface 52 of the gear housing 5. Example (4) is an example in which the lubrication grooves 7 are formed on the second support surface 61 of the front cover 6, the first side surface 32 of the pinion gear 3, and the first support surface 52 of the gear housing 5. Example (5) is an example in which the lubrication grooves 7 are formed on the first side surface 32 and second side surface 33 of the pinion gear 3, and the first support surface 52 of the gear housing 5.

[0118] In Example (6), lubrication grooves 7 are formed on the second support surface 61 of the front cover 6 and the first support surface 52 of the gear housing 5. Example (6) is shown in FIGS.

[0119] In the example (7), the lubrication grooves 7 are formed on the first side surface 32 and the second side surface 33 of the pinion gear 3. The example (7) is shown in FIGS.

[0120] Example (8) is an example in which the lubrication grooves 7 are formed on the second support surface 61 of the front cover 6 and the first side surface 32 of the pinion gear 3. Example (9) is an example in which the lubrication grooves 7 are formed on the second support surface 61 of the front cover 6 and the second side surface 33 of the pinion gear 3. Example (10) is an example in which the lubrication grooves 7 are formed on the first side surface 32 of the pinion gear 3 and the first support surface 52 of the gear housing 5. Example (11) is an example in which the lubrication grooves 7 are formed on the second side surface 33 of the pinion gear 3 and the first support surface 52 of the gear housing 5.

[0121] Example (12) is an example in which the lubrication groove 7 is formed only on the first support surface 52 of the gear housing 5. Example (12) is shown in Fig. 5. Example (13) is an example in which the lubrication groove 7 is formed only on the first side surface 32 of the pinion gear 3. Example (14) is an example in which the lubrication groove 7 is formed only on the second side surface 33 of the pinion gear 3. Example (15) is an example in which the lubrication groove 7 is formed only on the second support surface 61 of the front cover 6.

[0122] In each of the above-described examples (1) to (15), the guide portion 81 or the guide portions 82 and 83 described below may be formed, or no guide portion may be formed.

[0123] In addition, in examples (1) to (5) and examples (8) to (11), the diameter of the lubrication groove 7 formed in the casing 10 may be the same as or different from the diameter of the lubrication groove 7 formed in the pinion gear 3. In examples (1) to (5), (9), and (10), if the diameter of the lubrication groove 7 formed in the casing 10 is the same as the diameter of the lubrication groove 7 formed in the pinion gear 3, the lubrication groove 7 formed in the casing 10 and the lubrication groove 7 formed in the pinion gear 3 face each other in a direction along the shaft 2.

[0124] Furthermore, in examples (1) to (5) and examples (8) to (11), the groove width or groove depth of the lubrication groove 7 formed in the casing 10 may be the same as or different from the groove width or groove depth of the lubrication groove 7 formed in the pinion gear 3.

[0125] In all of the examples (1) to (15), seizure of the first side surface 32 and / or the second side surface 33 of the pinion gear 3 of the internal gear pump 1 is suppressed.

[0126] Here, the first lubrication groove 71 retains hydraulic oil between the first side surface 32 of the pinion gear 3 and the first support surface 52 of the gear housing 5, thereby maintaining the distance between the first side surface 32 and the first support surface 52. Furthermore, the second lubrication groove 72 retains hydraulic oil between the second side surface 33 of the pinion gear 3 and the second support surface 61 of the front cover 6, thereby maintaining the distance between the second side surface 33 and the second support surface 61. The first lubrication groove 71 and the second lubrication groove 72 have a spacing maintaining function, which also contributes to suppressing seizure between the first side surface 32 and the first support surface 52 and between the second side surface 33 and the second support surface 61. Furthermore, the third lubrication groove 73 and the fourth lubrication groove 74 of the pinion gear 3 also have a spacing maintaining function.

[0127] Depending on the operating conditions (pressure or rotation speed) of the internal gear pump 1, the effect of the spacing retention function of the first lubrication groove 71 and / or the third lubrication groove 73 may become too strong, causing the second side surface 33 of the pinion gear 3 to be pressed against the second support surface 61 of the front cover 6, which may result in seizure between the second side surface 33 and the second support surface 61. Conversely, if the effect of the spacing retention function of the second lubrication groove 72 and / or the fourth lubrication groove 74 becomes too strong, the first side surface 32 of the pinion gear 3 may be pressed against the first support surface 52 of the gear housing 5, which may result in seizure between the first side surface 32 and the first support surface 52.

[0128] The combination of lubrication grooves 7 can be appropriately selected from examples (1) to (15) so that seizure between the first side surface 32 and the first support surface 52 and seizure between the second side surface 33 and the second support surface 61 are stably suppressed regardless of the operating conditions of the internal gear pump 1. Furthermore, changing the position, width, depth, or shape of the lubrication groove 7 changes the effectiveness of the spacing function. In the selected examples (1) to (15), by changing the position, width, depth, or shape of the first lubrication groove 71, the second lubrication groove 72, the third lubrication groove 73, and / or the fourth lubrication groove 74, and / or by changing the presence or absence of guide portions 81, 82, and 83, seizure between the first side surface 32 and the first support surface 52 and seizure between the second side surface 33 and the second support surface 61 can both be suppressed.

[0129] (Modifications of the Guide Portion) FIG. 11 shows modifications of the guide portion. The guide portion 82 in the upper part 101 of FIG. 11 communicates the first lubrication groove 71 and the suction portion 11 on the first support surface 52. The shape of the guide portion 82 is a part of a circle recessed from the first support surface 52, similar to the guide portion 81, but the shape of the guide portion 82 is not limited to this. The hydraulic oil is supplied from the suction portion 11 to the first lubrication groove 71 through the guide portion 82. The guide portion 82 may also communicate the third lubrication groove 73 of the pinion gear 3 with the suction portion 11. Furthermore, a guide portion communicating the second lubrication groove 72 with the suction portion 11 or communicating the fourth lubrication groove 74 with the suction portion 11 may be formed on the second support surface 61.

[0130] The guide portion 83 in the lower diagram 102 of Figure 11 communicates between the first lubrication groove 71 and the inner hole 53 on the first support surface 52. As described above, hydraulic oil flows through the support hole 62 and the inner hole 53 along the shaft 2 to lubricate the bearing of the shaft 2. The guide portion 83 can supply hydraulic oil from the inner hole 53 to the first lubrication groove 71. Like the guide portion 81, the shape of the guide portion 83 is a portion of a circle recessed from the first support surface 52, but the shape of the guide portion 83 is not limited to this shape.

[0131] The guide portion 83 is located between the discharge portion 12 and the suction portion 11 in the circumferential direction of the inner hole 53. The guide portion 83 is not easily affected by the discharge portion 12 or the suction portion 11.

[0132] The guide portion 83 can effectively utilize the empty space between the discharge portion 12 and the suction portion 11. Furthermore, the guide portion 83 allows the hydraulic oil to accumulate at a location away from the discharge portion 12 or the suction portion 11, thereby achieving a high effect of preventing seizure. Furthermore, when the internal gear pump 1 rotates in both the first and second directions, the guide portion 83 located between the discharge portion 12 and the suction portion 11 can achieve the same effect of preventing seizure, regardless of whether the rotation direction of the internal gear pump 1 is the first direction or the second direction.

[0133] The induction portion located between the discharge portion 12 and the suction portion 11 is not limited to being located on the side away from the crescent 54, as shown in the lower diagram 102 of Figure 11, but may also be located between the discharge portion 12 and the suction portion 11 on the side closer to the crescent 54. Even on the side closer to the crescent 54, the induction portion can effectively utilize the empty space between the discharge portion 12 and the suction portion 11, and the induction portion can exert its seizure prevention effect regardless of the rotational direction of the internal gear pump 1.

[0134] Furthermore, since the distance between the discharge portion 12 and the suction portion 11 on the side closer to the crescent 54 is relatively long, the guide portion at this position is advantageous in preventing the internal gear pump 1 from seizing.

[0135] The guide portion 83 may connect the third lubrication groove 73 of the pinion gear 3 to the inner hole 53. Also, a guide portion may be formed on the second support surface 61 that connects the second lubrication groove 72 to the support hole 62 or that connects the fourth lubrication groove 74 to the support hole 62.

[0136] It should be noted that a plurality of guide portions out of the guide portion 81 , the guide portion 82 , and the guide portion 83 may be formed on the first support surface 52 and / or the second support surface 61 .

[0137] The guide portions 81, 82, 83 are not limited to having a shape recessed from the first support surface 52. A communication passage may be formed inside the gear housing 5 or the front cover 6, connecting the discharge portion 12, the suction portion 11, the inner hole 53, or the support hole 62 with the lubrication groove 7.

[0138] (Modifications of Lubrication Groove) FIGS. 12A and 12B show modifications regarding the relative positions of the through holes 361 and 362 of the pinion gear 3 and the lubrication groove 7 formed in the casing 10 or the lubrication groove 7 formed in the pinion gear 3. FIG.

[0139] 12A, a portion of the lubrication groove 7 may overlap the through hole 361. The diameter of the lubrication groove 7 is larger than the diameter r1 of the through hole 361.

[0140] 12A , a portion of the lubrication groove 7 may overlap the through hole 361. The diameter of the lubrication groove 7 is smaller than the diameter r1 of the through hole 361. Note that the lubrication groove 7 does not overlap with the through hole 362.

[0141] 12A , the lubrication groove 7 may overlap the through hole 362. The diameter of the lubrication groove 7 is the same as the diameter r2 of the through hole 362. Note that the lubrication groove 7 does not overlap with the through hole 361.

[0142] 12B, a portion of the lubrication groove 7 may overlap the through hole 362. The diameter of the lubrication groove 7 is larger than the diameter r2 of the through hole 362.

[0143] As shown in the middle diagram 1205 of FIG. 12B, the lubrication groove 7 may overlap both the through hole 361 and the through hole 362.

[0144] As shown in the lower diagram 1206 of FIG. 12B, the lubrication groove 7 does not have to overlap with the through holes 361 and 362.

[0145] FIG. 13 shows modified cross-sectional shapes of the lubrication groove 7. The cross-sectional shape of the lubrication groove 7 is not limited to the rectangle shown in the upper diagram of FIG. 4. The cross-sectional shape of the lubrication groove 7 may be trapezoidal, as shown in the upper diagram 111 of FIG. 13. The lubrication groove 7 may have a cross-sectional shape that widens toward the opening. The cross-sectional shape of the lubrication groove 7 may be triangular, as shown in the middle diagram 112 of FIG. 13. The cross-sectional shape of the lubrication groove 7 may be semicircular, as shown in the lower diagram 113 of FIG. 13.

[0146] The lubrication groove 7 is not limited to being a continuous ring. The lubrication groove 7 may be discontinuous. A plurality of lubrication grooves 7 having ends may be arranged, for example, evenly around the inner hole 53, the support hole 62, or the shaft 2.

[0147] The lubrication grooves 7 may also be located around the inner bore 53, the support bore 62 or the shaft 2, for example in double.

[0148] (Modifications of Casing and Pinion Gear) With respect to the casing 10 of the internal gear pump 1, the first support surface 52 of the gear housing 5 does not necessarily have to be perpendicular to the shaft 2. The first support surface 52 may be a surface that is approximately perpendicular to the shaft 2. Similarly, the second support surface 61 of the front cover 6 may be a surface that is approximately perpendicular to the shaft 2. In this case, the first side surface 32 and the second side surface 33 of the pinion gear 3 also are aligned with the first support surface 52 and the second support surface 61 and are therefore approximately perpendicular to the shaft 2.

[0149] Furthermore, the first support surface 52 and the second support surface 61 may be surfaces that curve as they expand radially outward from the shaft 2. Furthermore, the first support surface 52 and the second support surface 61 may be surfaces that expand radially outward from the shaft 2 and intersect with the shaft 2 at an angle other than 90°. The first side surface 32 and the second side surface 33 of the pinion gear 3 have shapes that correspond to the first support surface 52 and the second support surface 61.

[0150] REFERENCE SIGNS LIST 1 internal gear pump 10 casing 11 suction portion 12 discharge portion 13 gear set 2 shaft 3 pinion gear 31 external teeth 32 first side surface 33 second side surface 4 ring gear 41 internal teeth 5 gear housing 50 accommodation portion 52 first support surface 53 inner hole (insertion hole) 6 front cover (cover) 61 second support surface 62 support hole (insertion hole) 7 lubrication groove 71 first lubrication groove (groove) 72 second lubrication groove (groove) 73 third lubrication groove (groove, second groove) 74 fourth lubrication groove (groove, second groove) 81 guiding portion 82 guiding portion 83 guiding portion

Claims

1. An internal gear pump comprising: a shaft; a gear set including a pinion gear having external teeth and rotating integrally with the shaft, and a ring gear having internal teeth that mesh with the external teeth; and a casing having a hydraulic oil suction section and a discharge section and rotatably housing the gear set, wherein the casing has a support surface that intersects the shaft and supports a side surface of the pinion gear, the side surface sliding as the pinion gear rotates, and the casing has a groove recessed from the support surface in which the hydraulic oil accumulates.

2. An internal gear pump according to claim 1, wherein the casing includes a gear housing having a storage section in which the gear set is stored, and a cover adjacent to the gear housing and closing the opening of the storage section, the gear housing having a first support surface against which a first side surface of the pinion gear slides, the cover having a second support surface against which a second side surface of the pinion gear opposite to the first side surface slides, and the groove is formed in at least one of the first support surface and the second support surface.

3. The internal gear pump according to claim 2, wherein the groove is formed only in the first support surface.

4. An internal gear pump according to claim 2, wherein the grooves are formed in both the first support surface and the second support surface.

5. An internal gear pump according to claim 4, wherein the groove formed in the first support surface and the groove formed in the second support surface have the same groove width and groove depth.

6. An internal gear pump according to claim 4 or 5, wherein the groove formed in the first support surface and the groove formed in the second support surface are located at the same position in the radial direction around the shaft.

7. An internal gear pump according to any one of claims 1 to 6, wherein an opening for the suction section and an opening for the discharge section are formed on the support surface, with an insertion hole for inserting the shaft therebetween, and the groove is located midway between the insertion hole and the opening for the suction section and the opening for the discharge section on the support surface of the casing.

8. An internal gear pump according to claim 7, wherein the groove has a continuous annular shape surrounding the insertion hole.

9. An internal gear pump according to any one of claims 1 to 8, wherein the pinion gear has a second groove recessed from the side surface, in which the hydraulic oil is stored.

10. An internal gear pump comprising: a shaft; a gear set including a pinion gear having external teeth and rotating integrally with the shaft, and a ring gear having internal teeth that mesh with the external teeth; and a casing having a hydraulic oil suction section and a discharge section and rotatably housing the gear set, wherein the casing has a surface that intersects the shaft and supports a side surface of the pinion gear, the support surface against which the side surface slides as the pinion gear rotates, and the pinion gear has a groove recessed from the side surface in which the hydraulic oil collects.

11. An internal gear pump according to claim 10, wherein the casing includes a gear housing having a storage section in which the gear set is stored, and a cover adjacent to the gear housing and closing the opening of the storage section, the gear housing having a first support surface against which a first side surface of the pinion gear slides, the cover having a second support surface against which a second side surface of the pinion gear opposite to the first side surface slides, and the groove is formed in at least one of the first side surface and the second side surface.

12. An internal gear pump according to claim 10 or 11, wherein the groove is located midway between the outer peripheral surface of the shaft and the tooth bottom on the side surface of the pinion gear.

13. An internal gear pump according to claim 12, wherein the groove has a continuous annular shape surrounding the shaft.

14. An internal gear pump according to any one of claims 1 to 13, wherein the casing has a guide portion that communicates with the groove and guides the hydraulic oil to the groove.

15. An internal gear pump according to claim 14, wherein the induction section connects at least one of the suction section and the discharge section to the groove.

16. An internal gear pump according to claim 14, wherein the guide portion connects the groove to an insertion hole for the shaft formed in the casing.

17. An internal gear pump as claimed in claim 4, wherein the groove formed in the first support surface and the groove formed in the second support surface have a continuous annular shape centered on the rotation axis of the pinion gear, the casing has a guide portion that connects at least one of the groove formed in the first support surface and the groove formed in the second support surface with an insertion hole for the shaft formed in the casing, and the pinion gear has a through hole that opens to the first side surface and the second side surface and passes through the pinion gear, and the through hole is always in communication with the groove in the first support surface and the groove in the second support surface.

18. An internal gear pump as claimed in claim 3 or 4, wherein the groove has a continuous ring shape surrounding the insertion hole, the casing has a guide section that communicates with the groove and guides the hydraulic oil to the groove, and the guide section communicates at least one of the suction section and the discharge section with the groove, but does not communicate the insertion hole of the shaft formed in the casing with the groove.

Images