JPH05118249A - Device of fixing cylinder head to cylinder block for engine - Google Patents

Abstract

PURPOSE:To prevent excessive consumption of oil by reducing irregularities in the circumferential direction of the inner peripheral surface of a cylinder, thereby preventing seizing of an engine to reduce the quantity of blowby gas. CONSTITUTION:At the upper part of a cylinder block 1 of an engine, plural head mounting bosses 14 are formed integrally with the cylinder block 1 at suitable intervals on the outer periphery of a cylinder 10. Head mounting tapped holes 15 are drilled in the respective head mounting bosses 14 so as to fix a cylinder head 2 to the cylinder block 1 with plural head bolts 13. Respective head mounting screws 15 and bolt inserting holes 25 are arranged nearly along the circumferential direction of the cylinder 10, and inclined to the axis-line of the cylinder 10. Thus, stresses in the axial direction of the cylinder 10 are elliptically spread along the circumferential direction of the cylinder 10, and since compressive stresses become nearly constant over the full peripheral length of the cylinder 10, irregularities in the circumferential direction of the inner peripheral surface of the cylinder can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder head fixing device for fixing a cylinder head of an engine to a cylinder block.

[0002]

2. Description of the Related Art The basic structure of this type of cylinder head fixing device is constructed as shown in FIG. That is,
In the upper portion of the cylinder block 1 of the engine E, a plurality of head mounting bosses 14 are integrally formed with the cylinder block 1 at appropriate intervals on the outer circumference of the cylinder 10, and a head mounting screw is attached to each head mounting boss 14. Hole 15
The cylinder head 2 and insert a plurality of bolt insertion holes 2
5 by penetrating the head mounting screw holes 15 concentrically, inserting a plurality of head bolts 13 into the bolt insertion holes 25, and tightening the head mounting screw holes 15 into the head mounting screw holes 15. The cylinder head 2 is fixed to the cylinder block 1. And traditionally,
Each head mounting screw hole 15 and each bolt insertion hole 2
5 was formed parallel to the axis of the cylinder 10.

[0003]

In the above-mentioned conventional technique, the piston 3 may be burned on the cylinder 10 after the amount of blow-by gas becomes large at the time of high rotation and high load operation.
After investigating the cause, it can be understood that the reason is as follows. The seizure of the piston 3 occurs intermittently along the circumferential direction of the cylinder 10, and all the seizure points are near the head mounting screw hole 15. Judging from this phenomenon, the cylinder 10 is deformed in a meandering shape along the circumferential direction, as exaggeratedly drawn by an imaginary line in FIG. 6, and this meandering deformation causes the cylinder 10 to tighten the head bolts 13. This is because the cylinder head 2 receives a non-uniform restraining force due to the force.

That is, the amount of thermal expansion in the cylinder radial direction due to the operation of the engine is maximum in the piston 3 and then in the cylinder 1.
0, and the cylinder head 2 becomes the minimum. Due to this difference in thermal expansion, the cylinder 10 receives a compressive stress σ in the axial Z direction from the cylinder head 2 due to the tightening force of the head bolt 13. This compressive stress σ is, for example, a constant stress line g in FIG.
As indicated by, the head bolt 13 is large in the portion close to each head bolt 13 and is small in the far portion.

Here, the restraining force F for restraining the thermal expansion of the upper side portion 10a of the cylinder 10 is, as shown in FIG. 7, the compressive stress σ in the axial Z direction and the sectional area A of the upper side portion 10a. It is defined by the product of and That is, each head bolt 1
The binding force F is large in the portion close to 3, and is small in the portion far. Therefore, the amount of thermal expansion in the radial direction of the cylinder 10 is small in the portion near the head bolts 13 where the binding force F is strong, and conversely expands outward in the portion far from the head bolts 13 where the binding force is weak. .. Therefore, as shown in FIG. 6, irregularities are formed in the circumferential direction of the cylinder inner peripheral surface 10A.

The unevenness of the cylinder inner peripheral surface 10A induces seizure of the engine when the piston 3 locally contacts with the unevenness. Further, the unevenness increases the amount of blow-by gas and consumes oil excessively. The present invention has been made in consideration of such circumstances. To reduce the unevenness on the inner peripheral surface of the cylinder to prevent engine seizure due to local contact of the piston. The technical problem is to reduce the amount of blow-by gas due to the unevenness and to prevent excessive consumption of oil.

[0007]

In order to solve the above-mentioned problems in the above-mentioned basic structure, the present invention has, for example, FIGS.
As shown in FIG. 5, the head mounting screw holes 15 and the bolt insertion holes 25 are formed so as to be substantially aligned with the circumferential direction of the cylinder 10 and be inclined with respect to the axis of the cylinder 10. It is what

[0008]

[Operation] The present invention operates as follows. The upper portion 10a of the cylinder 10 is constrained by the compressive stress σ in the axial direction of the cylinder 10 that accompanies the fixing of the head bolt 13 tilted as described above. That is, the stress σ in the axial Z direction of the cylinder 10 is such that the major axis of the equal stress ellipse g spreads in an elliptical shape along the circumferential direction of the cylinder 10, as shown by the equal stress ellipse g in FIG. The compressive stress σ becomes substantially constant over the entire circumference of the cylinder 10. Here, the restraining force F that restrains the thermal expansion of the upper portion 10a of the cylinder 10 is
As shown in FIG. 4, it is defined by the product of the compressive stress σ in the Z-axis direction and the cross-sectional area A of the upper side portion 10a.

In the present invention, since the compressive stress σ is substantially constant as described above, the restraining force (F = σA) is substantially constant over the entire circumference of the cylinder 10, and the cylinder 10 has its entire circumference. It becomes difficult to meander and deform. As a result, it is possible to reduce the unevenness of the inner peripheral surface of the cylinder in the circumferential direction. Therefore, it is possible to prevent the seizure of the engine due to the unevenness of the inner peripheral surface of the cylinder and reduce the excessive consumption of oil due to the increase of the blow-by gas amount.

[0010]

Embodiments of the present invention will now be described in more detail with reference to the drawings. FIG. 1 is a vertical sectional view of an engine showing an embodiment according to the present invention, and FIG. 2 is a partial transverse plan view of a cylinder block. That is, the upper half of FIG. 2 is a cross-sectional view taken along the line V-V of FIG. 1, and the lower half is an end view of the fixed side of the cylinder block. Further, FIG. 3 shows the cylinder 10 of FIG.
FIG. 6 is a cross-sectional plan view taken along the line V-arrow. The cross section of the cylinder 10 in FIG. 3 is not shown because it is easily visible.

As shown in FIGS. 1 and 2, this cylinder head fixing device is provided with a plurality of head mounting bosses 14 at the upper part of the cylinder block 1 of the engine E at appropriate intervals on the outer circumference of the cylinder 10. Is integrally formed with the cylinder block 1, head mounting screw holes 15 are formed in each head mounting boss 14, and a plurality of bolt insertion holes 25 are formed in the cylinder head 2 concentrically with the head mounting screw holes 15. The cylinder head 2 is fixed to the cylinder block 1 by penetrating and inserting a plurality of head bolts 13 into the bolt insertion holes 25 and tightly fitting the head mounting screw holes 15. Is configured to. In these drawings, reference numeral 3 is a piston,
4 is a water jacket, 4a is a jacket communication hole, 5
Is a cam shaft, 6 is a tappet, 7 is a push rod, and 8 is a head jacket.

In the present invention, as shown in FIGS. 1 to 3, the head mounting screw holes 15 and the bolt insertion holes 25 are provided.
Are formed so as to be substantially aligned with the circumferential direction of the cylinder 10 and inclined with respect to the axis of the cylinder 10, and the head bolts 13 are also substantially aligned with the circumferential direction of the cylinder 10. It should be noted that the head bolt 13 is thickened by an amount corresponding to the inclination to secure a required tightening force. This allows
As described above, the compressive stress σ becomes substantially constant over the entire circumference of the cylinder 10. That is, the upper portion 10 of the cylinder 10
The constraint force (F = σA) that constrains the thermal expansion of a is
It becomes almost constant over the entire circumference of 0, and the cylinder 10 is less likely to meander and deform over the entire circumference. As a result, it is possible to reduce the irregularities that have conventionally been generated in the circumferential direction of the cylinder inner peripheral surface. Therefore, it is possible to prevent the seizure of the engine due to the unevenness and reduce the excessive consumption of oil due to the increase of the blow-by gas amount.

[0013]

According to the present invention, each head mounting screw hole and each bolt insertion hole are formed so as to be substantially aligned with the circumferential direction of the cylinder and inclined with respect to the axis of the cylinder. Since the restraint force by the head bolt is almost constant over the entire circumference, the following effects are achieved. I. Since the cylinder is less prone to meandering deformation over the entire circumference, unevenness in the circumferential direction of the cylinder inner peripheral surface can be reduced. As a result, it is possible to prevent the seizure of the engine due to the unevenness of the inner peripheral surface of the cylinder. B. It is possible to eliminate the increase in the amount of blow-by gas due to the unevenness of the inner peripheral surface of the cylinder and reduce the excessive consumption of oil.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an engine showing an embodiment according to the present invention.

FIG. 2 is a partial cross-sectional plan view of a cylinder block according to an embodiment of the present invention.

FIG. 3 is a cross-sectional plan view of the cylinder according to the embodiment of the present invention taken along the line VV in FIG.

FIG. 4 is a graph showing the relationship between the axial stress, the cross-sectional area, and the restraining force of the cylinder according to the present invention.

FIG. 5 is a vertical sectional view of an engine according to a conventional example.

FIG. 6 is a cross-sectional plan view of the cylinder according to the conventional example taken along the line V-V in FIG.

FIG. 7 is a graph showing the relationship between the axial stress, the cross-sectional area, and the restraining force of the cylinder according to the conventional example.

[Explanation of symbols]

E ... Engine, 1 ... Cylinder block, 2 ... Cylinder head, 10 ... Cylinder,
10a ... Top part of cylinder, 13 ... Head bolt,
14 ... Head mounting boss, 15 ... Head mounting screw hole, 25 ... Bolt insertion hole.

Claims (1)

[Claims] 1. A plurality of head mounting bosses (14) are provided at the upper portion of the cylinder block (1) of the engine E at appropriate intervals on the outer circumference of the cylinder (10).
(1) Formed integrally with each head mounting boss
Drill a head mounting screw hole (15) in (14) and insert a plurality of bolt insertion holes (25) in the cylinder head (2).
Through each of the head mounting screw holes (15) concentrically, and insert a plurality of head bolts (13) into the bolt insertion holes.
A cylinder head for a cylinder block of an engine configured to fix the cylinder head (2) to the cylinder block (1) by inserting the same into the head mounting screw holes (15) through the (25). In the fixing device, the head mounting screw holes (15) and the bolt insertion holes
(25) is a device for fixing a cylinder head to a cylinder block of an engine, characterized in that it is formed substantially along the circumferential direction of the cylinder (10) and is inclined with respect to the axis of the cylinder (10). ..