JPH0140357Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to the structure of a balancer shaft attached to an engine for the purpose of damping engine vibration.

(Prior Art) Engines have been known in which vibrations are damped by attaching a balancer shaft to the engine. In this case, the balancer shaft is provided primarily for the purpose of reducing secondary vibrations of the engine, and is usually driven to rotate via a drive gear meshing with a crank gear. For this purpose, the balancer shaft must be rotated at a high speed approximately twice that of the crankshaft, and therefore the drive gear of the balancer shaft should be configured to have a small diameter, approximately half the diameter of the crankshaft. There must be. On the other hand, the balancer shaft has a structure in which a pair of balancers are provided eccentrically from the rotating shaft, and are inserted into and supported in the opening of the cylinder block in the axial direction. Therefore, in order to enable this insertion, the bearing portion of the balancer shaft must be configured to have a larger diameter than the outer diameter of the balancer shaft. Further, the balancer shaft drive gear is attached to one end portion of the balancer shaft protruding from the bearing portion in a fitted state.
In such a structure, as mentioned above, there is a constraint that the bearing part must have a large diameter and the drive gear must have a small diameter.Also, since the balancer shaft rotates at high speed, it is necessary to support the balancer shaft in the thrust direction. The problem is the structure and the support structure of the drive gear. In the balancer shaft structure disclosed in Japanese Patent Publication No. 58-28456, a thrust plate is attached to the outer surface of the cylinder block, a step is formed outside the bearing section of the balancer shaft, and the thrust plate is extended to the step. The thrust bearing is configured to support the balancer shaft in the axial direction, and a shoulder is further formed outside of this step, and the drive gear, which is tightened in the axial direction by a bolt, is attached to this shoulder. It is sandwiched and supported between the bolt-side washer and thereby prevents relative rotation between the drive gear and the balancer shaft.

(Problem to be Solved) In the structure disclosed in the above-mentioned Japanese Patent Publication No. 58-28456, the inner end surface of the drive gear is pressed against the outer end surface of the shoulder formed on the balancer shaft by tightening the bolt. The rotational power transmitted to the drive gear is
The driving force is transmitted to the balancer shaft by the frictional engagement force generated between the two end faces. However, in this structure, a step part for accommodating the thrust plate is continuously formed around the shoulder part, so the shoulder part cannot be formed to extend in the radial direction. This means that a sufficiently large contact area with the inner end surface of the drive gear cannot be secured. As a result, the frictional engagement force generated between the two end surfaces is reduced, and shearing force is applied to the positioning key inserted in the axial direction between the drive gear and the shaft, which may impair the durability of the key. be. In order to solve this problem, if the shoulders are formed to extend greatly in the radial direction to ensure a sufficient contact area, the support area of the thrust plate will be reduced and the problem that the thrust plate must be made stronger will arise. arise.

(Means for solving the problem) The present invention was constructed in order to solve the above problem, and it is possible to reliably support the drive gear of the balancer shaft so that an excessive load is not applied to the positioning key. Moreover, it is an object of the present invention to provide a balancer shaft structure that can effectively restrict the axial movement of a balancer shaft rotating at high speed.

The present invention provides an engine balancer shaft that is equipped with a bearing that is rotatably supported by an engine block, and a drive gear that is fitted to one end of the shaft, and that is rotationally driven by crankshaft power via the drive gear. The structure includes a thrust plate having an opening larger than the outer diameter of the drive gear and attached to the engine block, and a thrust collar that comes into pressure contact with the outer surface of the thrust plate and the inner end surface of the drive gear. It is characterized by

According to the structure of the present invention, the balancer shaft is
Displacement in the axial direction is regulated by a thrust plate attached to the cylinder block on the outer surface of the bearing portion which is rotatably supported by the cylinder block. Further, a drive gear is fitted to one end of the balancer shaft to transmit power from the crankshaft and drive the balancer shaft. A thrust collar is disposed between the drive gear and the thrust plate. In one embodiment of the assembly of the structure of the present invention, the balancer shaft is first inserted into an opening formed in the cylinder block and supported in the bearing section, and then the thrust plate controls the axial movement of the outer end of the bearing section. It is attached to the outer surface of the cylinder block so as to regulate it. Then, the thrust collar is inserted from the end of the shaft and brought into contact with the outer surface of the thrust plate. Next, the drive gear is inserted and positioned with a positioning key, and then tightened in the axial direction with a bolt. By this,
The drive gear is axially sandwiched between the bolt and the thrust collar.

The inner end of the thrust collar is supported by a step formed on the balancer shaft, and when crankshaft power is transmitted to the drive gear, the thrust collar rotates together with the drive gear and balancer shaft. . Therefore, the outer end surface of the thrust plate fixed to the cylinder block, the inner end surface of the thrust collar, the inner end surface of the thrust plate, and the outer surface of the balancer shaft come into sliding contact. In a preferred embodiment of the present invention, the oil supplied to the rotation bearing portion of the balancer shaft is introduced into the inner and outer end surfaces of the thrust collar to lubricate the sliding portion. Although it is conceivable to form the thrust collar integrally with the drive gear, this would make it impossible to cut the gears of the drive gear.

(Effects of the invention) According to the invention, a thrust collar is provided separately from the thrust plate that constitutes the thrust bearing of the balancer shaft, thereby supporting the drive gear in the axial direction. The collar is adapted to contact the entire inner end surface of the drive gear. Therefore, sufficient frictional engagement force between the drive gear thrust collar, that is, the balancer shaft can be ensured. As a result, it is possible to eliminate excessive load from being applied to the positioning key arranged in the axial direction between the drive gear and the balancer shaft. That is, according to the present invention, it is possible to easily and reliably support a balancer shaft that is subject to various restrictions.

(Description of Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Referring to FIGS. 1 and 2, the engine 1 of this example includes a pair of balancer shafts 2, each of which is inserted into a through hole formed in a cylinder block 3 and has a liner 4. It is rotatably supported through. balancer shaft 2
A drive gear 5 for rotationally driving the balancer shaft is attached to one end of the balancer shaft, and this drive gear is driven by a crank gear 8 via idle gears 6 and 7. The drive gear 5 has a diameter that is half the diameter of the crank gear 8, so the balancer shaft 2 rotates at twice the speed of the crankshaft.

The drive gear may be a sprocket gear wheel, which may be chain driven, or a timing belt gear, which may be belt driven.

Referring to FIGS. 2 and 3 together, a thrust plate 9 is provided on the side of the cylinder block 3.
is fixed with bolts 10. The outer surface 2b of the end bearing portion 2a of the balancer shaft 2 is in contact with the inner end surface 9a of the thrust plate 9.
A thrust collar 11 is disposed between the drive gear 5 and the thrust plate 9. The thrust collar 11 has a disc structure having a hole 11a that accommodates a small diameter portion at the tip of the balancer shaft 2. The drive gear 5 is fitted to the tip of the balancer shaft 2, and a positioning key 12 is inserted between the balancer shaft 2 and the drive gear 5. A holding member 13 is arranged at the outer end of the drive gear 5, and the driving gear 5 is tightened to the balancer shaft 2 in the axial direction with a bolt 14 via the holding member 13. As a result, the drive gear 5 is firmly clamped between the pressing member 13 and the thrust collar 11. Further, the thrust collar 11 is in pressure contact with the drive gear 5 and a stepped portion 2c formed on the balancer shaft 2. As a result, the inner end surface of the drive gear 5 is pressed against the outer end surface of the thrust collar 11 over the entire surface, and a large frictional engagement force is generated between the two. Therefore, when the drive gear 5 is rotated by the power of the crank gear 8, the thrust collar 11 and the balancer shaft 2 rotate together. Therefore, the thrust plate 9 has the outer surface 2b of the balancer shaft bearing portion and the thrust collar 11 on both end surfaces.
It comes into sliding contact with the inner end surface of. The rotating surface of the bearing portion 2a of the balancer shaft 2 is provided through an oil passage 15 formed in the cylinder block 3.
Oil is being introduced. Further, an oil passage 16 passing through the thrust plate 9 is formed at a sliding contact portion between the thrust collar and the bearing side end surface 2b of the thrust plate 9. As a result, a portion of the oil that has lubricated the rotating surface of the bearing portion 2a enters between the thrust plate 9 and the outer surface 2b of the bearing portion, and a portion of the oil also passes through the oil passage 15 and contacts the thrust plate 9. Lubricate the sliding surface with the thrust collar 11.

According to the above structure, the thrust plate 9 can be supported by bolts at a position extremely close to the sliding contact portion with the side end surface 2b of the balancer shaft bearing portion that functions as a thrust bearing, and is simple and stable. It can provide a good supporting effect. Moreover, the drive gear 5 covers the entire inner end surface,
Since it is supported by the thrust collar, sufficient frictional engagement force can be obtained, and problems regarding the durability of the positioning key can be solved.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of an engine having a balancer shaft structure according to an embodiment of the present invention, Fig. 2 is a detailed sectional view of the balancer shaft structure, and Fig. 3 is a side view of the structure of Fig. 2. be. 1...Engine, 2...Balancer shaft, 3
...Cylinder block, 5...Drive gear, 8...
Crank block, 9... Thrust plate, 1
1...Thrust collar.

Claims (1)

[Scope of utility model registration request] A balancer shaft structure for an engine, comprising a bearing part rotatably supported by an engine block, and a driving gear fitted to one end part, and rotationally driven by crankshaft power via the driving gear. A balancer shaft structure for an engine, comprising: a thrust plate attached to an engine block; and a thrust collar that presses against an outer surface of the thrust plate and an inner end surface of the drive gear.