JPH0639081Y2 - Cylinder body structure - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention enhances the rigidity of the skirt portion of the cylinder body,
The present invention relates to a cylinder body structure that suppresses vibration noise.

[Prior Art] As a cylinder body structure, as shown in FIG.
"Cylinder block partition structure" in which the rib c of the partition b formed between the adjacent crank chambers a has a large area and a thin structure to reduce the step difference on the partition surface.
839 publication).

That is, the proposal is to increase the area of the rib in order to reduce the step by reducing the thickness of the rib and to maintain a constant strength.

However, when the vibration stress analysis for the combustion excitation force of this type of cylinder body structure is performed, FIG.
As shown in (B), it was confirmed that the vibration in the axial direction of the cylinder becomes large in the normal frequency band (1.5 to 3 KHz), and as a result, the coupled vibration is likely to occur in the direction of opening and closing the skirt.

Therefore, as a solution to this kind of problem, as shown in FIG. 6, an "engine cylinder block structure" in which a lower deck f which is convex downward is bridged over a skirt portion e of a cylinder body d ( Japanese Utility Model Publication No. Sho 62-126538) was proposed.

[Problems to be solved by the invention] However, because the lower end of the lower deck is naturally limited due to the relationship with the track of the counterweight of the crankshaft, the positions of both ends of the lower deck to be bridged are also lower than the skirt of the cylinder body. There is the inconvenience of being restricted upward. That is, although the rigidity of the cylinder body above the skirt portion is improved, the effect of improving the torsional rigidity of the skirt portion is small, and as a result, it is not sufficient to increase the rigidity of the entire cylinder body.

[Means for Solving the Problems] The present invention is intended to solve the above-mentioned problems, and the present invention hangs a lower deck, which is arched and protrudes upward in the radial direction of the cylinder, on the upper portion of the skirt portion of the cylinder body. Is a cylinder body structure.

[Operation] The lower deck, which is hung on the upper part of the skirt in an arch shape, has significantly improved rigidity as compared to the lower deck that is laid flat, and also has a fundamentally increased rigidity when the skirt is opened and closed. Increases the overall stiffness strength of the cylinder body against torsional vibrations. As a result, the natural vibration moves to the high frequency side and the vibration propagated to the skirt portion in the normal operation band is substantially prevented.

As a result, vibration in the direction in which the skirt is opened and closed is prevented, so that vibration noise can be significantly reduced.

[Embodiment] A preferred embodiment of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, the skirt portion 2 that forms the lower portion of the cylinder body 1 is configured so that the inner walls 4 and 5 facing each other in a direction intersecting the column direction of the cylinder 3 have strengths along the axial direction of the cylinder 3. The strength member 6 is formed by being connected by the member 6, and a bearing portion that fits into the crankshaft 7 is formed in the lower portion of the strength member 6.

Now, the purpose of this invention is the cylinder body 1
To increase the overall rigidity of the skirt to prevent vibration of the skirt portion 2. Therefore, in this embodiment, as shown in FIG. 1 and FIG. ,
The lower deck 8 is integrally formed so as to extend in an arch shape in a direction intersecting the column direction of the cylinders 3. In this embodiment, the lower deck 8 has both ends laid across the portion of the skirt portion 2 where the oil gallery 10 is formed, and the upper portion of the skirt portion 2 is connected to the opposite skirt portion 2 It is laid so as to form an almost continuous arch with inner walls 4 and 5. Therefore, the arch direction of the lower deck 8 is formed so as to be convex upward, that is, to be convex toward the cylinder head (not shown) side.

Therefore, the lower deck 8 can have a semi-circular cross section that is substantially effective in the load direction for the substantially strong cross section of the skirt portion 2 with respect to the flat deck. As a result, the rigidity of the cylinder body 1 is increased overall, and it becomes possible to fundamentally suppress the skirt opening / closing vibration.

By the way, it has been confirmed that the combustion excitation force with respect to the frequency of the cylinder body 1 changes as shown in FIG. 3, and that the combustion excitation force becomes smaller on the higher frequency side.
Since noise can be reduced by moving the natural vibration of (1) to the high frequency side, the curvature and the plate thickness of the lower deck 8 are properly determined based on this relationship so as to move the natural vibration to the high frequency side. Further, if necessary, it is possible to form ribs on the lower deck 8 surface or boss portions 9 for fixing to the partition walls between the cylinders by bolts.

[Effect of the Invention] As is clear from the above description, the present invention exhibits the following excellent effects.

(1) A lower deck that is arched and convex upward in the radial direction of the cylinder is laid over the upper portion of the skirt of the cylinder body to improve the rigidity of the cylinder body as a whole. It is possible to suppress the vibration of the and reduce the vibration noise.

(2) The structure is simple and can be provided at low cost.

[Brief description of drawings]

FIG. 1 is a sectional view showing a preferred embodiment of the present invention, FIG. 2 is a schematic view showing a mounting position of a lower deck, FIG. 3 is a view showing a relation between frequency and combustion exciting force, and FIG. 5 is a sectional view showing a partition wall structure of a cylinder body as a conventional technique, FIGS. 5 (A) and 5 (B) are vibration stress analysis diagrams, and FIG. 6 is a sectional view showing a related technique. In the figure, 1 is a cylinder body, 2 is a skirt portion, 3 is a cylinder, and 8 is a lower deck.

Claims (1)

[Scope of utility model registration request] 1. A cylinder body structure in which a lower deck having an arch shape and a convex shape in a radial direction of the cylinder is provided on an upper portion of a skirt portion of the cylinder body.