Oil pump

Abstract

Provided is an oil pump (10) in which a screen (12b) is provided protruding toward a pump drive shaft (11) on a portion of a bearing part (12a) of a pump cover (12) through which the pump drive shaft (11) passes, the portion being on the side of the bearing part (12a) opposite to a rotor accommodating part (13) side, and an oil retention part (18) is formed between the pump drive shaft (11) and a portion of the bearing part (12a) of the pump cover (12) on the rotor accommodating part (13) side, whereby, in an oil discharge side region, most oil passing through a side clearance of an inner rotor (14) is retained in the oil retention part (18), thereby suppressing oil leakage, and in an oil suction side region, suction of air is suppressed by the oil retained in the oil retention part (18).

Description

oil pump

[0001] The present invention relates to an oil pump for an engine.

[0002] Some vehicle engines, such as automobiles, are equipped with a trochoid oil pump, which serves as a lubricating oil supply source for sending engine oil to various parts inside the engine. The pump drive shaft is fixed to the outer periphery of the engine's crankshaft (drive shaft), an inner rotor is fixed to the outer periphery of the pump drive shaft, and an outer rotor that meshes with the inner rotor.

[0003] The trochoid oil pump described above may be mounted integrally with the chain case that covers the engine's timing chain. In this case, a pump cover having a bearing for the pump drive shaft is disposed inside the chain case, and the inner and outer rotors (hereinafter collectively referred to as "pump rotors") are housed in an annular rotor housing formed by the chain case and pump cover. An oil pump mounted integrally with the chain case in this manner will be referred to as a "chain case-integrated oil pump."

[0004] In order to ensure pump efficiency, a certain amount of axial clearance (hereinafter referred to as "side clearance") must be provided between the pump rotor and the pump cover to reduce friction on the pump rotor. However, this can easily cause oil to leak into the engine through the side clearance and the radial clearance between the pump cover's bearing and the pump drive shaft (perpendicular to the extension direction of the pump drive shaft), particularly in the oil discharge area. This oil leakage can reduce discharge efficiency and cause friction in the timing chain that passes near the inside of the pump cover (the side opposite the rotor housing section). Furthermore, in the oil suction area, negative pressure in the rotor housing section can easily cause air to be sucked into the engine via the opposite route to the oil leakage, resulting in the oil being mixed in.

[0005] In response to this, Patent Document 1 proposes reducing the amount of oil leakage while suppressing friction of the outer rotor by making the side clearance of the inner rotor smaller than the side clearance of the outer rotor.

[0006] JP 2013-44254 A

[0007] In the oil pump of Patent Document 1, the dimensional relationship between the side clearance of the inner rotor and the side clearance of the outer rotor is specified, but there is no mention of the radial gap between the bearing portion of the pump cover and the pump drive shaft.

[0008] Therefore, even if the side clearance of the inner rotor is reduced to a certain extent, problems of oil leakage and air entrapment may still occur.

[0009] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an oil pump that can suppress oil leakage and prevent air from entering the oil pump.

[0010] In order to solve the above problems, the oil pump of the present invention employs a configuration (configuration 1) that includes a pump drive shaft fixed to the outer periphery of an engine crankshaft, a rotor fixed to the outer periphery of the pump drive shaft, and a pump cover that forms a rotor storage section in which the rotor is stored, the pump cover being formed by an opening through which the pump drive shaft is inserted and having a bearing section that rotatably supports the pump drive shaft, and the bearing section has an oil storage section in which oil stores between the bearing section and the pump drive shaft, the oil storage section being provided around the entire circumference of the bearing section.

[0011] In the above-mentioned configuration 1, the oil stagnation section can be formed by providing a partition protruding toward the pump drive shaft on the side of the bearing section opposite the rotor housing section (configuration 2).

[0012] When the above-mentioned configuration 2 is adopted, it is preferable that the partition has a first surface extending from the bearing portion toward the pump drive shaft and a second surface extending from the first surface along the outer periphery of the pump drive shaft, and the boundary between the bearing portion and the first surface is formed into a concave R-shape (Configuration 3). Furthermore, in the configuration 3, the boundary can be formed so that the radius of curvature of the concave R-shape is smaller in the oil suction side region of the bearing portion than in the oil discharge side region in the circumferential direction (Configuration 4).

[0013] In addition, in the above-mentioned configuration 3 or 4, it is preferable that the pump drive shaft has a tapered portion at the end on the rotor housing portion side where the diameter of the pump drive shaft becomes smaller, and the first surface is formed on the rotor housing portion side of the tapered portion (configuration 5).

[0014] In any of the above configurations 1 to 5, it is preferable that the oil reservoir be formed so that its dimension in the axial direction of the pump drive shaft is larger than its dimension in the radial direction of the pump drive shaft (configuration 6).

[0015] By adopting the above-described configuration, the present invention can suppress oil leakage and prevent air from entering the oil pump.

[0016] 1 is an enlarged cross-sectional view of the vicinity of the oil pump in FIG. 1; FIG. 2 is a view taken from the direction of arrow A in FIG. 2 (with the timing chain and sprocket removed); and FIG. 2 is an enlarged cross-sectional view of a main part of FIG. 2. An explanatory diagram of the oil leakage suppression effect of the oil pump in FIG. 1; An explanatory diagram of oil leakage in an oil pump with a conventional structure; and FIG. 1 is a cross-sectional view showing a modified partition shape of the oil pump in FIG. 1.

[0017] An embodiment of the present invention will now be described with reference to the drawings. An oil pump 10 of this embodiment is attached to an engine 1 as shown in FIGS. 1 and 2. The engine 1 has a cylinder block having a plurality of cylinders, pistons 8 provided for each of the cylinders, a crankshaft 2 extending in the direction in which the cylinders are aligned, and connecting rods 9 connecting the pistons 8 to the crankshaft 2. A timing chain 3 is attached to the outer side of the cylinder block in the direction in which the cylinders are aligned (on the side of the cylinder block). A chain case 4 is attached to the side of the cylinder block, and the timing chain 3 is housed between the side of the cylinder block and the chain case 4. The oil pump 10 of this embodiment is an oil pump integrated with a chain case, attached to the surface of the chain case 4 facing the cylinder block. The oil pump 10 comprises a pump drive shaft 11 that is rotated by the rotation of the crankshaft 2, a pump cover 12 that is attached to the cylinder block side surface of the chain case 4, an inner rotor 14 that is housed in a rotor housing section 13 that is the space formed between the chain case 4 and the pump cover 12 and that is rotated by the rotation of the pump drive shaft 11, and an outer rotor 15 that is housed in the rotor housing section 13 so as to be positioned radially outward of the inner rotor 14 and that meshes with the inner rotor 14. In this embodiment, the inner rotor 14 and outer rotor 15 constitute the "rotor" in the claims.

[0018] The pump drive shaft 11 is fixed to the outer periphery of the crankshaft 2. The pump cover 12 has an opening through which the pump drive shaft 11 is inserted, and the inner surface of this opening (the surface facing the pump drive shaft 11) forms a bearing portion 12a that rotatably supports the pump drive shaft 11. The chain case 4 has a recess that is recessed on the side opposite the cylinder block, and the pump cover 12 has a recess that is recessed on the cylinder block side. The recesses in the chain case 4 and the pump cover 12 form a rotor housing portion 13. The inner rotor 14 is fixed to the outer periphery of the pump drive shaft 11, and the outer rotor 15 is located within the rotor housing portion 13.

[0019] The crankshaft 2 is fitted with, in order from its tip end, a crank pulley 5, a pump drive shaft 11, and a sprocket 6 around which the timing chain 3 is wound.

[0020] The reciprocating motion of the piston 8 of the engine 1 is converted into rotational motion by the connecting rod 9 and transmitted to the crankshaft 2, and the rotation is transmitted to the auxiliary machinery via a belt (not shown) wrapped around the crank pulley 5, driving the oil pump 10 and the timing chain 3.

[0021] As shown in Figure 3, the oil pump 10 is divided into an oil suction side region a having an intake port 16 on one side (the right side in Figure 3) and an oil discharge side region b having an outlet port 17 on the other side (the left side in Figure 3), with the lateral (radial) center line C of the pump drive shaft 11 as the boundary. When driven by the crankshaft 2, the oil sucked in from the intake port 16 is discharged from the outlet port 17.

[0022] As shown in Figure 4, the pump cover 12 of this oil pump 10 has a partition 12b that protrudes toward the pump drive shaft 11 on the side of the bearing portion 12a opposite the rotor storage portion 13 (the side opposite the chain case 4, i.e., the cylinder block side).This forms an oil storage portion 18, which is a space in which oil accumulates, between the rotor storage portion 13 side of the bearing portion 12a of the pump cover 12 and the pump drive shaft 11.

[0023] Specifically, the partition 12b has a first surface 12c that rises from the bearing portion 12a toward the pump drive shaft 11, and a second surface 12d that extends from the end of the first surface 12c on the pump drive shaft 11 side in the axial direction of the pump drive shaft 11 to the end of the pump cover 12 opposite to the rotor housing portion 13 side. The partition 12b is provided around the entire circumferential direction of the bearing portion 12a.

[0024] By providing the oil retention section 18 as described above, oil leaking from between the pump cover 12 and the inner rotor 14 (side clearance) is retained in the oil retention section 18, thereby preventing oil from leaking from between the bearing section 12a and the pump drive shaft 11 and preventing air from being sucked into the oil pump 10 from between the bearing section 12a and the pump drive shaft 11.

[0025] Here, the pump drive shaft 11 has a tapered portion 11a formed at its tip on the cylinder block side. The pump drive shaft 11 is inserted into the bearing portion 12a from the chain case 4 side toward the cylinder block side. The tapered portion 11a is formed by a step portion 11b that extends toward the center axis of the pump drive shaft 11 and the cylinder block side so that the diameter of the pump drive shaft 11 decreases, and an extension portion 11c that extends from the tip of the step portion 11b along the center axis of the pump drive shaft 11. A first surface 12c of the partition 12b on the rotor housing portion 13 side is formed closer to the rotor housing portion 13 than the tapered portion 11a of the pump drive shaft 11. In other words, the first surface 12c is located closer to the chain case 4 than the step portion 11b. This ensures that the width (seal width) S of the gap between the pump drive shaft 11 and the bearing portion 12a of the pump cover 12 is smaller than the oil retention portion 18, preventing oil from escaping from the tapered portion 11a of the pump drive shaft 11.

[0026] The oil reservoir 18 has a radial dimension L of the pump drive shaft 11. １ The axial dimension L of the pump drive shaft 11 is ２ This allows the seal length L of the side clearance to be increased. Ｓ By ensuring sufficient sealing, the amount of oil leakage from the side clearance is reduced and the size of the oil retention portion 18 is ensured so that the oil can easily be retained.

[0027] The boundary between the first surface 12c and the surface of the bearing portion 12a (the surface where the partition 12b is not provided) is formed in a concave R-shape, which also makes it easier for oil to accumulate in the oil accumulation portion 18, as described below.

[0028] The oil pump 10 of this embodiment has the above-described configuration, and its sealing performance will now be described in comparison with that of a conventional configuration, based on Figures 5A and 5B. Figure 5A shows the oil pump 10 of the above-described configuration, and Figure 5B shows an oil pump 20 of the conventional configuration. The oil pump 20 of the conventional configuration differs from the oil pump 10 of the embodiment only in that the bearing portion 12a does not have a partition 12b.

[0029] First, in the oil discharge side region b shown in Figure 3, in the oil pump 20 of the conventional structure, as shown in Figure 5B, oil that passes through the side clearance and the gap between the bearing portion 12a and the pump drive shaft 11 is likely to leak into the engine 1. This reduces the discharge efficiency. Furthermore, the leaked oil may fly toward the piston 8 and hit the timing chain 3, increasing friction.

[0030] In contrast, in the oil pump 10 of the embodiment, as shown in FIG. 5A , much of the oil that passes through the side clearance is blocked by a partition 12b provided in the bearing portion 12a and accumulates in an oil accumulation portion 18 formed on the rotor housing portion 13 side of the partition 12b. Here, the boundary between the first surface 12c of the partition 12b and the surface of the bearing portion 12a is formed with a concave R-shape. As a result, oil flowing from the rotor housing portion 13 side toward the first surface 12c collides with the first surface 12c, changes direction, and flows toward the rotor housing portion 13 side along the outer peripheral surface of the pump drive shaft 11. This reflux makes it easier for the oil to accumulate in the oil accumulation portion 18. By having the oil accumulate in the oil accumulation portion 18 in this way, the amount of oil leakage can be reduced compared to conventional structures, improving discharge efficiency. In addition, the partition 12b prevents oil leaking through the gap between the bearing portion 12a and the pump drive shaft 11 from flying toward the piston 8 and hitting the timing chain 3, thereby suppressing an increase in friction.

[0031] Furthermore, in the oil suction side region a shown in Figure 3, the rotor housing section 13 becomes negative pressure, so in the oil pump 20 of the conventional structure, air inside the engine 1 is easily sucked in and mixed into the oil via a route opposite to the oil leakage described above.

[0032] In contrast, in the oil pump 10 of the embodiment, the oil that has accumulated in the oil retention section 18 in the oil discharge side area b flows into the oil retention section 18 in the oil suction side area a, and the oil that has accumulated in the oil retention section 18 suppresses the intake of air, thereby preventing air from mixing with the oil in the rotor storage section 13.

[0033] As described above, the oil pump 10 of the embodiment has a partition 12b on the side of the bearing portion 12a of the pump cover 12 opposite the rotor housing portion 13, forming an oil reservoir portion 18 between the rotor housing portion 13 side of the bearing portion 12a of the pump cover 12 and the pump drive shaft 11. Compared to conventional structures, this reduces oil leakage in the oil discharge side region b, improving discharge efficiency, and suppresses air suction in the oil suction side region a, preventing air from mixing into the oil. Furthermore, if the oil pump 10 is an oil pump with an integrated chain case, it can prevent oil from hitting the timing chain 3 and suppress an increase in friction.

[0034] In the above example, the boundary between the first surface 12c of the partition 12b and the surface of the bearing portion 12a is formed with a constant concave R-shape around the entire circumference of the bearing portion 12a. However, as a modified example, the radius of curvature of the concave R-shape in the oil suction-side region a may be smaller than that in the oil discharge-side region b. As an example, in FIG. 6 , the boundary between the first surface 12c of the partition 12b and the surface of the bearing portion 12a in the oil suction-side region a is formed at a substantially right angle. The position of the end of the first surface 12c on the pump drive shaft 11 side (the position in the axial direction of the pump drive shaft 11) is the same in both the oil suction-side region a and the oil discharge-side region b. In this modified example, the concave R-shape at the boundary between the first surface 12c and the surface of the bearing portion 12a in the oil suction-side region a is smaller than in the above example, thereby increasing the volume of the oil reservoir 18. This improves the effectiveness of preventing air from being ingested and mixing with the oil. In addition, in the oil discharge side region b, the concave R portion at the boundary between the first surface 12c and the surface of the bearing portion 12a is sufficiently ensured, so that oil can easily be retained.

[0035] The pump cover may be formed such that the pump cover body and the partition are integrally formed by casting or the like, or the partition is formed separately and attached to the pump cover body. Alternatively, an intermediate product having a bearing portion with a constant inner diameter in the axial direction may be produced by casting or the like, and then the oil reservoir 18 may be formed by cutting the bearing portion of the intermediate product on the rotor housing portion 13 side. The oil reservoir 18 may also be formed by a recess formed in the axial middle of the bearing portion 12a of the pump drive shaft 11.

[0036] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. Therefore, the scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0037] REFERENCE SIGNS LIST 1 engine 2 crankshaft 3 timing chain 4 chain case 6 sprocket 10 oil pump 11 pump drive shaft 11a tapered portion 12 pump cover 12a bearing portion 12b partition 12c first surface 12d second surface 13 rotor storage portion 14 inner rotor 15 outer rotor 16 suction port 17 discharge port 18 oil retention portion a suction side area b discharge side area

Claims

1. a pump drive shaft fixed to the outer periphery of the engine crankshaft; a rotor fixed to the outer periphery of the pump drive shaft; a pump cover that forms a rotor housing portion in which the rotor is housed, the pump cover is formed with an opening through which the pump drive shaft is inserted, and has a bearing portion that rotatably supports the pump drive shaft; an oil reservoir in which oil is retained is provided around the entire circumference of the bearing between the bearing and the pump drive shaft; the oil reservoir is formed by providing a partition protruding toward the pump drive shaft on a portion of the bearing portion opposite the rotor housing portion, A gap is provided between the partition and the pump drive shaft, the partition has a first surface extending from the bearing portion toward the pump drive shaft and a second surface extending from the first surface along an outer periphery of the pump drive shaft, The pump drive shaft has a tapered portion at the end on the rotor housing portion side where the diameter of the pump drive shaft is reduced, and the first surface is formed on the rotor housing portion side of the tapered portion.

2. (delete)

3. The oil pump according to claim 1 , wherein a boundary between the bearing portion and the first surface is formed in a concave R shape.

4. 4. The oil pump according to claim 3, wherein the boundary portion is formed so that the radius of curvature of the concave R-shape is smaller in an oil suction side region of the bearing portion than in an oil discharge side region of the bearing portion in the circumferential direction.

5. (delete)

6. 5. The oil pump according to claim 1, wherein the oil reservoir is formed so that its dimension in the axial direction of the pump drive shaft is larger than its dimension in the radial direction of the pump drive shaft.