JPH03219145A - Balance shaft fitting structure for internal - Google Patents

Abstract

PURPOSE:To prevent the damage of a cylinder block, improve the assembling performance of balance shafts and reduce the number of parts by fitting balance shafts respectively on both side parts relatively opposed to each other on one side of a plate integrally fitted at a cylinder block. CONSTITUTION:Centrifugal force generated at balance shafts 15 is received by the compression and tension of a plate 11 in a case of being in the right- angled direction to the stroke of a piston. The centrifugal force is received by the bending of the plate 11 in a case of being in the same direction as the piston stroke, at a section in its thickness direction having sufficiently rigidity so as to enable the support of the balance shafts 15. As a result, the flank parts of a cylinder block 10 does not receive centrifugal force caused by the unbalance quantity of the balance shafts 15, and therefore even a cylinder block made of a light alloy of comparatively weak structure used on the flank parts of the cylinder block 10 or a skeltonized cylinder block for the purpose of lightweight is prevented from resulting in damage.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a balance shaft mounting structure for an internal combustion engine.

<Prior art> As this type of balance shaft mounting structure, conventionally, the 6th
There is one shown in the figure (see Japanese Patent Laid-Open No. 5868532).

That is, in the figure, a cylinder block 1 is formed with a bearing portion, and a bearing cap 2 is attached to the bearing portion. A balance shaft 4 having an unbalanced portion 3 is rotatably supported by the bearing portion.

The balance shaft 4 rotates in synchronization with the crankshaft 5 at twice the rotational speed of the crankshaft 5.

As a result, the 2
The unbalance of the couple or inertial force of the following or more is canceled out by the centrifugal force due to the unbalance amount of the balance shaft 4, thereby reducing the vibration of the internal combustion engine.

In the figure, 7 is a cylinder head, 8 is an intake pipe, and 9 is an exhaust pipe.

<Problems to be Solved by the Invention> However, the conventional balance shaft mounting structure as described above has the following problems.

That is, since the balance shaft 4 is configured to be attached to the side surface of the cylinder block 1, a cylinder block using a light alloy with a relatively weak structure on the side surface or a cylinder block made into a skeleton to reduce weight cannot be used. When the side portion is subjected to centrifugal force due to the unbalanced amount of the balance shaft 4, it may vibrate greatly and even break.

Also, conventionally, Utility Model Application Publication No. 163643/1983 and Utility Model Application Publication No. 5
A balance shaft mounting structure as shown in Japanese Patent No. 8-20750 is known.

In the former type, a balance shaft housing including a balance shaft is clamped and fixed between a flange of a skirt portion of a cylinder block and an oil pan.

In addition, in l-1-later, a balancer case that rotatably supports the balance shaft is detachably connected to the lower end of the intermediate bearing wall on the crankcase side, into which the bearing section that holds the crankshaft is inserted. be.

However, the former type has drawbacks such as poor assembling of the balance shaft, increased number of parts, and increased overall height of the engine.

In addition, the latter requires a balance case, and has the disadvantage that it is difficult to assemble because the balancer is installed inside the crankcase, and the disadvantage is that oil is constantly applied to the gear part, causing increased friction. .

Therefore, in view of the above conventional problems, the present invention aims to improve the mounting structure of the balance shaft, thereby preventing damage to the cylinder block, improving the ease of assembling the balance shaft, and reducing the number of parts. The purpose is to

Means for Solving the Problems> For this reason, the balance shaft mounting structure for an internal combustion engine of the present invention has a structure in which the bearing cap of the bearing portion of the crankshaft is integrally molded and is integrally attached to the cylinder block. A plate is provided, and balance shafts are attached to both sides facing one side of the plate, respectively.

<Function> In such a configuration, the centrifugal force generated by the balance shaft can be received by the compression and tension of the plate when the centrifugal force is perpendicular to the piston stroke, and when it is in the same direction (up and down) as the piston stroke. In some cases, bending in a sufficiently rigid through-thickness section of the plate can be accommodated to allow support of the balance shaft.

As a result, the side surface of the cylinder block is not subjected to centrifugal force due to the unbalanced amount of the balance shaft, and the structure of the side surface of the cylinder block is made of relatively weak light alloy, or the cylinder block is replaced with a skeleton to reduce weight. Even if the product becomes damaged, it will not lead to damage.

Furthermore, since the balance shaft is attached to the plate, the balance shaft is easy to assemble, the number of parts can be reduced, and the overall height of the engine does not increase.

Furthermore, no balance case is required and no increase in friction occurs.

<Example> Embodiments of the present invention will be described below based on the drawings.

In FIGS. 1, 3, and 5 described below, the same elements as those in FIG. 6 are given the same reference numerals to simplify the explanation.

In FIG. 1, a plate 11 is integrally attached to the side surface of the skeletonized cylinder block with bolts 12. As shown in FIG.

As shown in FIG. 2, this plate 11 is formed into a substantially rectangular shape, and includes a bearing cap portion 13 of the bearing portion of the crankshaft 5 integrally molded therein, and five hair ring support portions. 14 is formed. Balance shafts 15 are attached to the side surfaces of both opposing sides of the plate 11 in the longitudinal direction, respectively.

That is, the balance shaft 15 is rotatably supported by a bearing part, and bearing camps 17 fixed by bolts 16 are provided on both sides of the plate 110.

The mounting position of the bolt 16 is set to correspond to the same position as the bearing cap portion 13 in order to sufficiently maintain the centrifugal force of the balance shaft 15.

In this embodiment, #2 and #3 bearing cap parts 1
The position of the bolt 16 is set at a position corresponding to position 3.

A sprocket 18 for driving a shaft is attached to the outer end of each balance shaft 15.

Note that the balance shaft 15 is similar to the crankshaft 5.
The piston 6 rotates in synchronization with the crankshaft 5 at twice the rotation speed of the piston 6, and the 2
This is the same as in the prior art in that the unbalance of the couple or inertial force of the following order or more is canceled out by the centrifugal force due to the unbalance amount of the balance shaft 15, and vibrations of the internal combustion engine are reduced.

As explained above, as a result of attaching the Harance shafts 15 to both sides facing one side of the plate 11 which is integrally attached to the lower part of the cylinder block 10, the following functions and effects are achieved.

That is, the centrifugal force generated by the balance shaft 15 is
If it is in the direction perpendicular to the piston stroke, it can be supported by compression or tension of the plate 11, and if it is in the same direction (up or down) as the piston stroke, it can be received in the thickness direction of the plate 11 with sufficient rigidity. The balance shaft 15 can be supported by bending the cross section of the balance shaft 15.

As a result of the above, the side surface of the cylinder block 1o is not subjected to centrifugal force due to the unbalanced amount of the balance shaft 15, and the side surface of the cylinder block 1o is made of a light alloy with a relatively weak structure, resulting in a lightweight cylinder block. Therefore, even if the Cylinder Pro is made into a skeleton, it will not cause damage.

Furthermore, since the balance shaft 15 is attached to the play 1-11, the balance shaft 15 is easy to assemble, the number of parts can be reduced, and the overall height of the engine does not increase.

Furthermore, no balance case is required and no increase in friction occurs.

Next, another embodiment of the present invention is shown in FIG.

That is, in this figure, the plate 1 is integrally attached to the lower part of the cylinder block 10 with bolts 12.
9 is formed into a substantially rectangular body shape, and rectangular step portions 20 are formed on the upper surfaces of both opposing sides in the longitudinal direction, and each of the step portions 20 has a balance shaft 15.
can be installed.

That is, a bearing cap 21 is fixed to the stepped portion of the plate I9 by bolts 16.

According to this configuration, the position of the joint surface between the bearing camp 21 and the stepped portion 20 does not have an adverse effect on the upper and lower bearing loads generated by the balance shaft 15.

To explain this in detail, the inertial force of the reciprocating part in an internal combustion engine increases as the rotation speed increases, and in particular, in Figure 4 (a)
) is maximum at top dead center. The deformation of the plate 19 at this time is as shown in FIG. 4B, and an inertial force is exerted downward by the balance shaft 15. Therefore, in response to forces in the vertical direction, the fastening strength is higher when the fastening is performed in the vertical direction.

Incidentally, if the bearing cap is fastened laterally, it will be subjected to shearing force and the fastening strength will be weak.

Further, in this configuration in which the bearing cap 21 is fastened from above, the fastening work is easy to perform (and has excellent workability).

Next, still another embodiment of the present invention is shown in FIG.

That is, in this figure, the plate 22 is formed into a substantially rectangular shape, and the balance shaft 15 is attached to the upper surface of each opposing side portion in the longitudinal direction.

Then, the bearing cap 23 is integrally molded on a lower part of the lower part of the cylinder block 10, and the cough bearing cap 23 is fastened to the upper surface of the plate 22 with the bolts 16.

This configuration has the advantage of reducing the disadvantages of weight reduction and improving the mounting rigidity of the balance shaft 15.

Note that the configuration of the above embodiment does not indicate any structural limitations of the present invention (in short, it is a configuration in which the bearing cap of the bearing portion of the crankshaft is integrally molded and is integrally attached to the cylinder block). Any configuration may be used as long as a plate is provided, and balance shafts are attached to both sides facing the plate, respectively.

<Effects of the Invention> As explained above, according to the balance shaft mounting structure for an internal combustion engine according to the present invention, the bearing camp of the bearing portion of the crankshaft is integrally molded and is integrally formed with the cylinder block. Since the balance shaft is attached to each side of the plate that is attached to the plate, it is possible to prevent damage to the cylinder block, improve the ease of assembling the balance shaft, reduce the number of parts, reduce the overall height of the engine, and reduce friction. It is possible to reduce the In particular, the present invention is extremely useful when applied to a cylinder block using a light alloy whose side part structure is relatively weak, or a cylinder block made into a skeleton to reduce weight.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view of an internal combustion engine showing one embodiment of the balance shaft mounting structure according to the present invention, Fig. 2 is a perspective view showing the structure of the plate in the same embodiment, and Fig. 3 is a diagram showing another embodiment. A vertical cross-sectional view of the internal combustion engine shown in Fig. 4(a), [with]
FIG. 5 is a longitudinal sectional view of an internal combustion engine showing still another embodiment, and FIG. 6 is a longitudinal sectional view of an internal combustion engine showing an example of a conventional balance shaft mounting structure. It is. 5... Crank shirt 11... Play 13... Bearing cap part 16... Holt cap 19,2 10... Cylinder pro 12... Bolt 15... Balance shirt 17.21. 23... Bearing 2... Plate Todo

Claims (1)

[Claims] The structure includes a bearing cap for the bearing portion of the crankshaft integrally molded, and a plate is provided which is integrally attached to the cylinder block, and a balance shaft is attached to each side of the plate opposite to one side. A balance shaft mounting structure for an internal combustion engine, which is characterized by: