JP7772605B2 - Bearing structure for internal combustion engines - Google Patents

Description

The present invention relates to a bearing structure for an internal combustion engine.

Internal combustion engines are known in which the oil pump is driven by the rotation of a balance shaft.

JP 2014-88807 A

However, in conventional technology, the rotation of the balance shaft is transmitted to the oil pump via a power transmission mechanism including a chain, and bearings for the balance shaft and oil pump are provided separately, resulting in a large number of parts and a complicated internal combustion engine.

The present invention was made in consideration of the above, and one of its objectives is to reduce the complexity of internal combustion engines.

In order to solve the above-mentioned problems and achieve the objectives, the bearing structure for an internal combustion engine according to the present invention comprises a base, a first cover fixed to the base, a first bearing provided on the base, a second bearing provided on the first cover, a balance shaft, a rotating shaft that is a separate part from the balance shaft and is connected to the balance shaft and rotates integrally with the balance shaft, and an oil pump driven by the rotating shaft, wherein the first bearing rotatably supports the connecting portion between the balance shaft and the rotating shaft, and the second bearing rotatably supports the rotating shaft.

With this configuration, the first bearing is shared by both the balance shaft and the rotating shaft, so the bearing structure can be realized without having to consider the positional accuracy or tolerances between the balance shaft and the rotating shaft that are associated with the first bearing.

The bearing structure for the internal combustion engine includes a second cover that is positioned on the balance shaft side of the first cover, is fixed to the first cover, and has a hole through which the rotating shaft is inserted. A gap is provided between the circumferential surface of the second cover that forms the hole and the rotating shaft. The oil pump has a casing formed by the first cover and the second cover.

With this configuration, there is a gap between the second cover and the rotating shaft, which allows for relaxed positional accuracy between the first bearing and the second bearing from the balance shaft to the first cover.

In the bearing structure of the internal combustion engine, for example, the rotating shaft is rotatably supported only by the first bearing and the second bearing.

With this configuration, the positional accuracy of the rotating shaft can be relaxed compared to a configuration in which the rotating shaft is supported by three or more bearings.

This invention makes it possible to reduce the complexity of internal combustion engines.

FIG. 1 is a cross-sectional view showing a part of an internal combustion engine according to an embodiment. FIG. 2 is a cross-sectional perspective view showing a part of the internal combustion engine according to the embodiment.

Embodiments are described below with reference to Figures 1 and 2. Note that in this specification, components according to embodiments and descriptions of those components may be described using multiple expressions. The components and their descriptions are merely examples and are not limited by the expressions in this specification. Components may also be identified by names different from those used in this specification. Furthermore, components may also be described using expressions different from those used in this specification.

Figure 1 is a cross-sectional view showing a portion of an internal combustion engine 10 according to an embodiment. Figure 2 is a cross-sectional perspective view showing a portion of an internal combustion engine 10 according to an embodiment. The internal combustion engine 10 is, for example, a reciprocating engine mounted on a vehicle. Note that the internal combustion engine 10 may be another type of internal combustion engine, or may be mounted on another device.

As shown in each drawing, for convenience, the X-axis, Y-axis, and Z-axis are defined in this specification. The X-axis, Y-axis, and Z-axis are perpendicular to each other. The X-axis extends along the width of the vehicle. The Y-axis extends along the length of the vehicle. The Z-axis extends along the height of the vehicle.

Furthermore, the X direction, Y direction, and Z direction are defined herein. The X direction is the direction along the X axis, and includes the +X direction indicated by the X axis arrow and the -X direction, which is the opposite direction of the X axis arrow. The Y direction is the direction along the Y axis, and includes the +Y direction indicated by the Y axis arrow and the -Y direction, which is the opposite direction of the Y axis arrow. The Z direction is the direction along the Z axis, and includes the +Z direction indicated by the Z axis arrow and the -Z direction, which is the opposite direction of the Z axis arrow.

In the following description, the +Z direction is defined as the vertically upward direction, and the -Z direction is defined as the vertically downward direction. Note that the Z direction may differ from the vertical direction depending on various conditions, such as the location of the vehicle and the condition of the tires.

The internal combustion engine 10 comprises a crankcase 11, a chain cover 12, a balance shaft 13, a rotating shaft 15, an oil pump 14, a first bearing 16, and a second bearing 17. In addition to the above, the internal combustion engine 10 also comprises a cylinder block, an oil pan, a crankshaft, a chain, etc. The crankcase 11, the chain cover 12, the first bearing 16, the second bearing 17, the balance shaft 13, and the oil pump 14 constitute the bearing structure of the internal combustion engine 10.

The crankcase 11 has an outer surface 11a. The crankcase 11 also has an internal space 11b that opens to the outer surface 11a. The crankcase 11 also has a support portion 11c that supports the first bearing. The crankcase 11 is an example of a base. Note that the base may also be a cylinder block, etc.

The chain cover 12 is placed on the outer surface 11a of the crankcase 11. The chain cover 12 is fixed to the crankcase 11 with fasteners 22 (Figure 2), such as bolts. The chain cover 12 covers a chain (not shown) located between the crankcase 11 and the chain cover 12. The inner surface 12a of the chain cover 12 has a recess 12b. The recess 12b opens to the inner surface 12a. The chain cover 12 also has a bottomed hole 12c. The hole 12c opens to the bottom of the recess 12b. A second bearing 17 is provided on the peripheral surface 12d of the chain cover 12, which forms the hole 12c. The second bearing 17 is a sliding bearing. That is, the second bearing 17 is formed by a portion of the peripheral surface 12d.

At least a portion of the balance shaft 13 is housed inside the crankcase 11. The balance shaft 13 is supported by two bearings (one of which is not shown), including a first bearing 16, so that it can rotate around the central axis of rotation Ax. One end 13a of the balance shaft 13 is rotatably supported by the first bearing 16. Hereinafter, unless otherwise specified, the axial, radial, and circumferential directions refer to the axial, radial, and circumferential directions of the central axis of rotation Ax.

The first bearing 16 is a rolling bearing and has an outer ring 16a, an inner ring 16b, and rolling elements 16c.

The rotating shaft 15 has one end 15a and the other end 15b. The rotating shaft 15 has a large diameter portion 15c and a small diameter portion 15d. The large diameter portion 15c includes the one end 15a. The small diameter portion 15d includes the other end 15b and has a smaller diameter than the large diameter portion 15c.

The rotating shaft 15 is connected to the balance shaft 13 with a different diameter, and rotates integrally with the balance shaft 13 around the central rotation axis Ax.

Specifically, the rotating shaft 15 and balance shaft 13 are splined together. A male spline 15e is provided on the large-diameter portion 15c of the rotating shaft 15. The male spline 15e is configured with external teeth. Meanwhile, a hole 13b is provided on one end 13a of the balance shaft 13, and a female spline 13d is provided on the surface 13c of the balance shaft 13 that forms the hole 13b. The female spline 13d is configured with internal teeth. The large-diameter portion 15c of the rotating shaft 15 is inserted into the hole 13b of the balance shaft 13, and the male spline 15e and female spline 13d mesh with each other. The male spline 15e and female spline 13d form a joint 21 between the balance shaft 13 and the rotating shaft 15. The joint 21 is also referred to as a spline joint.

The oil pump 14 is, for example, a trochoid oil pump, and has a casing 31, an outer rotor 32, and an inner rotor 33. The oil pump 14 draws oil stored in the oil pan through an intake port by rotating the inner rotor 33, and discharges the oil from an exhaust port. The oil discharged from the oil pump 14 is supplied to each part of the internal combustion engine 10 via passages, etc. The oil supplied to each part falls due to the action of gravity and returns to the oil pan.

The casing 31 has a base portion 34 provided on the chain cover 12 and a pump cover 35. The base portion 34 is the portion of the chain cover 12 that includes the recess 12b, and is formed integrally with the chain cover 12. In other words, part of the chain cover 12 constitutes the base portion 34.

The pump cover 35 is fixed to the chain cover 12 with fasteners 23, such as screws, while covering the recess 12b. The pump cover 35 is fixed to the crankcase 11 via the chain cover 12, and is not fixed directly to the crankcase 11. The pump cover 35 constitutes the bearing structure of the internal combustion engine 10.

The pump cover 35 has one surface 35a and the other surface 35b. The one surface 35a is placed on the inner surface 12a of the chain cover 12. The pump cover 35 also has a hole 35c. The hole 35c penetrates the pump cover 35 in the thickness direction of the pump cover 35. That is, the hole 35c is open to the one surface 35a and the other surface 35b. The small diameter portion 15d of the rotating shaft 15 is inserted into the hole 35c. The circumferential surface 35d that forms the hole 35c in the pump cover 35 is spaced apart from the outer peripheral surface 15f of the rotating shaft 15, and a gap Sa is formed between the circumferential surface 35d of the pump cover 35 and the outer peripheral surface 15f of the rotating shaft 15.

The outer rotor 32 has multiple recesses formed in a trochoidal curve or the like. The inner rotor 33 has one fewer protrusion than the outer rotor 32's recesses. It is positioned inside the outer rotor 32 and engages with the outer rotor 32. The inner rotor 33 has a hole 33a formed therein. The hole 33a penetrates the inner rotor 33 in the axial direction. The small-diameter portion 15d of the rotating shaft 15 is press-fitted into the hole 33a. In other words, the inner rotor 33 rotates around the rotation center axis Ax integrally with the rotating shaft 15 and balance shaft 13. The tips of the protrusions of the inner rotor 33 slide along the inner surfaces of the recesses in the outer rotor 32 as it rotates. This allows oil to be sucked in and discharged. Note that the oil pump 14 is not limited to the above configuration.

Two guide portions 36, 37 are provided on the other surface 35b of the pump cover 35. The guide portion 36 protrudes from the pump cover 35 toward the joint 21 between the balance shaft 13 and the rotating shaft 15. The guide portion 36 guides oil from the oil pump 14 that leaks from the gap Sa between the peripheral surface 35d of the pump cover 35 and the outer peripheral surface 15f of the rotating shaft 15 to the first bearing 16. The guide portion 36 protrudes from the pump cover 35 toward the joint 21 between the balance shaft 13 and the rotating shaft 15. The guide portion 37 guides oil that drops from an oil hole 51 located above the joint 21 to the joint 21.

In the internal combustion engine 10 configured as described above, the rotating shaft 15 rotates in conjunction with the rotation of the balance shaft 13, and an oil pump driving method is implemented in which the rotation of the rotating shaft 15 drives the oil pump 14.

As described above, in this embodiment, the bearing structure of the internal combustion engine 10 includes the crankcase 11 (base), the chain cover 12 (first cover), the first bearing 16, the second bearing 17, the balance shaft 13, and the oil pump 14. The chain cover 12 is fixed to the crankcase 11. The first bearing 16 is provided on the crankcase 11. The second bearing 17 is provided on the chain cover 12. The rotating shaft 15 is a separate part from the balance shaft 13 and is connected to the balance shaft 13 to rotate integrally therewith. The oil pump 14 is driven by the rotating shaft 15. The first bearing 16 rotatably supports the connecting portion 21 between the balance shaft 13 and the rotating shaft 15, and the second bearing 17 rotatably supports the rotating shaft 15.

With this configuration, the first bearing 16 is shared by the balance shaft 13 and the rotating shaft 15. Therefore, compared to a configuration in which the balance shaft 13 and the rotating shaft 15 are connected by a chain or the like and bearings corresponding to the first bearing 16 are provided on the balance shaft 13 and the rotating shaft 15, for example, this configuration can be configured without considering positional accuracy or tolerances, thereby reducing the complexity of the internal combustion engine 10.

The bearing structure of the internal combustion engine 10 also includes a pump cover 35 (second cover). The pump cover 35 is positioned on the balance shaft 13 side of the chain cover 12 and is fixed to the chain cover 12. The pump cover 35 has a hole 35c into which the rotating shaft 15 is inserted. A gap Sa is provided between the rotating shaft 15 and the peripheral surface 35d that forms the hole 35c in the pump cover 35.

With this configuration, there is a gap Sa between the pump cover 35 and the rotating shaft 15, so the positional accuracy requirements between the first bearing 16 and the second bearing 17 from the balance shaft 13 to the chain cover 12 can be relaxed. This makes it easier to assemble the internal combustion engine 10.

Furthermore, the rotating shaft 15 is rotatably supported only by the first bearing 16 and the second bearing 17.

With this configuration, the positional accuracy of the rotating shaft 15 can be relaxed compared to a configuration in which the rotating shaft 15 is supported by three or more bearings. This makes it easier to assemble the internal combustion engine 10.

In addition, the only moving part provided between the first bearing 16 and the second bearing 17 is the oil pump 14. This allows the length of the rotating shaft 15 to be shortened, thereby reducing the moment in the oil pump 14.

In the above embodiment, an example was shown in which the pump cover 35 was fixed to the crankcase 11 via the chain cover 12, but this is not limited to this. For example, the chain cover 12 may be fixed to the crankcase 11 via the pump cover 35. In this case, the second bearing 17 is provided in the pump cover 35. In other words, the second bearing 17 is provided in a member that is directly fixed to the crankcase 11.

The above-described embodiments of the present invention do not limit the scope of the invention, but are merely examples within the scope of the invention. Certain embodiments of the present invention may be modified, omitted, or added to the above-described embodiments, for example, with respect to at least some of the specific uses, structures, shapes, actions, and effects, as long as they do not deviate from the gist of the invention.

10...internal combustion engine, 11...crankcase (base), 12...chain cover (first cover), 13...balance shaft, 14...oil pump, 16...first bearing, 17...second bearing, 35...pump cover (second cover), 35c...hole, 35d...circumferential surface, Sa...gap.

Claims (2)

With the base,
a first cover fixed to the base;
a first bearing provided on the base;
a second bearing provided in the first cover;
A balance shaft and
a rotating shaft that is a separate part from the balance shaft, is coupled to the balance shaft, and rotates integrally with the balance shaft;
an oil pump driven by the rotating shaft;
a second cover that is disposed on the balance shaft side of the first cover, is fixed to the first cover, and has a hole into which the rotating shaft is inserted;
Equipped with
the first bearing rotatably supports a joint between the balance shaft and the rotary shaft,
the second bearing rotatably supports the rotary shaft ;
a gap is provided between a peripheral surface of the second cover that forms the hole and the rotary shaft;
Bearing structure for internal combustion engines. the rotating shaft is rotatably supported only by the first bearing and the second bearing;
2. A bearing structure for an internal combustion engine according to claim 1 .