JPH11117802A - Cylinder head structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the deformation quantity of a guide hole so as to reduce the stress of a peripheral part by providing a rigidity lowered part facilitating deformation in a diameter contracting direction, at the outer peripheral part of a valve guide including a part opposed to a thin-walled part between a guide hole and a port. SOLUTION: Cylindrical seal parts 12 for sealing gas and oil are provided at both axial end parts of a valve guide 10, and a rigidity lowered part 13 lowered in rigidity in a diameter contracting direction so as to facilitate deformation in the diameter contracting direction is provided at the axial intermediate part of the valve guide 10. This rigidity lowered part 13 is formed including the outer peripheral part of the valve guide 10 opposed to a thin-walled part between a guide hole and an intake port or an exhaust port. The rigidity lowered part is provided with a large number of axial groove parts 15 at the outer peripheral part. The deformation quantity of the guide hole in press-fitting is therefore suppressed so as to reduce the stress of the thin-walled part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder head structure which relieves stress concentration around a cylinder head side of a valve guide which slidably supports a valve stem such as an exhaust valve or an intake valve of an internal combustion engine. is there.

[0002]

2. Description of the Related Art In an internal combustion engine of an automobile or the like, an aluminum alloy is used for a cylinder or a cylinder head to reduce the weight, but a valve guide through which a valve stem such as an exhaust valve or an intake valve is inserted has friction. In consideration of the durability of the cast iron, a cast iron cylindrical shape having a higher Young's modulus than the aluminum alloy is used.

The valve guide made of cast iron is press-fitted into a valve hole 9 formed in the cylinder head 1 as shown in FIG. This press-fitting is performed by using a slightly larger diameter valve guide 10 having a press-fit allowance of about several tens μm larger than the diameter of the guide hole 9.
Is firmly fixed and supported. On the other hand, in recent engines, the intake port 4
A tumble port for generating a vertical vortex (tumble) in the combustion chamber is adopted.

[0004]

However, when this tumble port is adopted, as shown in FIG.
The intake port 4 is provided at a large angle close to the vertical with respect to the cylinder head lower surface 1b, and the angle θ between the guide hole 9 of the portion holding the valve guide 10 and the intake port 4 becomes small, The thin portion (port guide portion) 8 of this portion has a sharp edge shape.

Therefore, when the valve guide 10 is press-fitted into the guide hole 9, the guide hole 9 of the aluminum alloy portion having a lower rigidity than the valve guide 10 made of cast iron has a press fitting allowance of 7 mm.
As a result, the deformation of the guide hole 9 is increased, so that a high stress is generated in the thin portion 8 and a crack is generated. To avoid this problem, Japanese Unexamined Patent Publication No. 62-96707 discloses a method of providing a gap near the port side of a valve guide to eliminate the influence of a press-fit margin. hand,
A valve holding device for reducing the generated stress has been proposed.

However, in this device, since there is a gap on the port side of the valve guide, it is not possible to support the valve stem or the valve guide in this gap, and the supporting portion is shortened accordingly. for that reason,
There is a problem that vibration occurs in the valve stem or the valve guide and the valve stem or the valve guide is easily damaged. The present invention has been made to solve the above-described problem, and an object of the present invention is to reduce the amount of deformation of a guide hole generated in connection with a press-fitting margin when press-fitting a valve guide, thereby reducing the amount of guide hole. An object of the present invention is to provide a highly durable cylinder head structure in which stress generated in a peripheral portion is reduced.

[0007]

In order to achieve the above object, a cylinder head structure is provided with a guide hole formed obliquely to a suction / exhaust port of an aluminum alloy cylinder head of an engine. In a cylinder head structure in which a cylindrical valve guide is press-fitted and a valve stem is slidably inserted into an inner peripheral surface of the valve guide, at least a thin portion between the guide hole and the port is opposed. The outer periphery of the valve guide including a portion to be deformed is provided with a reduced rigidity portion that is easily deformed in the diameter reducing direction.

Further, the rigidity reducing portion is constituted by providing a plurality of grooves along the axial direction on the outer peripheral portion. Alternatively, the reduced rigidity portion is formed of a soft metal member. As the soft metal member, a metal softer than cast iron, for example, copper, a copper alloy, aluminum, an aluminum alloy, or the like can be used. Casting or winding, fitting of a cylinder having a slit, processing such as lining, etc. It can be formed by a method.

As described above, by providing the rigidity reducing portion in a part of the valve guide, the amount of deformation on the guide hole side due to the press-fitting is reduced. The stress generated in a thin portion between the relatively weak guide hole and the port can be reduced.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. The cylinder head structure of the engine according to the present invention is formed of an aluminum alloy in a structure as shown in FIGS. 5 and 6, and an intake port 4 and an exhaust port (not shown) are provided in the cylinder head 1. A valve 2 and an exhaust valve (not shown) are provided. The intake valve 2 is configured such that a valve stem 2 a is guided by a valve guide 10 and is opened and closed by an upper cam 7 and a valve spring 6.

The valve guide 10 is made of cast iron and is formed in a cylindrical shape.
a is inserted and slidably supported. Further, a guide hole 9 into which the valve guide 10 is press-fitted with a predetermined press-fitting margin is formed so as to open obliquely to the intake port 4 or the exhaust port in the cylinder head 1.

At both ends in the axial direction of the valve guide 10, as shown in FIGS. 1 to 4, cylindrical seal portions 12 for sealing gas and oil are provided. A rigidity reducing portion 13 is provided at an intermediate portion in the axial direction to reduce rigidity in the diameter reducing direction to facilitate deformation in the diameter reducing direction. At least the guide hole 9
The outer peripheral portion of the valve guide 10 is opposed to the thin portion (port guide portion) 8 between the intake port 4 and the exhaust port (not shown).

The position of the seal portion 12 does not necessarily have to be at both ends, and any structure may be used as long as it can seal between both ends of the guide hole 9. Therefore, the rigidity reducing portion 13 is not limited to the intermediate portion. Is also good. This rigidity reducing part 13 is shown in FIGS.
As shown in (1), a large number of axial grooves 15 are provided in the outer peripheral portion, and the stress of the thin portion 8 is reduced by suppressing the amount of deformation of the guide hole 9 at the time of press fitting. In this configuration, by changing the minimum diameter D shown in the AA cross section perpendicular to the axis of FIG. 2 and the width M and depth N of the contact surface 14 and the width L of the root of the tooth profile, the press-fitting is performed. The amount of decrease in rigidity in the diameter reduction direction can be adjusted. Further, by setting the direction of the groove 15 to be the axial direction, it is possible to reduce a decrease in the structural strength of the valve guide 10 in the axial direction.

On the other hand, since the inner peripheral surface 11 of the valve guide 10 is a sliding surface of the valve stem 2a, the minimum diameter D at the root of the tooth profile in FIG. Maintain an appropriate size to ensure rigidity. The inner peripheral surface 11 of the valve guide 10 is cut to a specified size after the valve guide 10 is press-fitted, and even if it is slightly deformed at the time of press-fitting, the sliding of the valve stem 2a is adversely affected. Not to be.

In order to prevent the valve guide 10 from falling out of the guide hole 9, a gripping force that overcomes the gas pressure in the cylinder and the frictional force accompanying the sliding of the valve stem 2a is required. The contact surface 14 where the guide 10 and the guide hole 9 are in contact with each other is appropriately sized to secure a contact force necessary for supporting and fixing. As an example of the embodiment of FIGS. 1 and 2, for example, the length of the valve guide 10 is 40 mm, the outer diameter is 22 mm, the inner diameter is 14 mm, and the length of the guide hole 9 is 40 mm.
In the case where the maximum press-fitting allowance is 0.055 mm, the results of a structural analysis and comparison between the case where the rigidity reducing portion 13 formed by the groove portion 15 is provided and the case where the rigidity reducing portion 13 is formed by the groove 15 are compared. It has been found that when the contact area is reduced to half by providing the lowering portion 13, the deformation amount of the guide hole 9 can be reduced by 20%, and the stress of the thin portion 8 can be reduced by 20%.

Further, the force for gripping the valve guide 10 is significantly greater than the force for pulling out the valve guide 10 generated by the gas pressure of the combustion in the cylinder.
It was also confirmed that there was no risk of falling off. Further, according to this structural analysis, the relationship between the amount of deformation of the guide hole 9 and the valve guide 10 in the diameter increasing and reducing directions and the contact force generated on the contact surface is such that the weaker the rigidity of the valve guide 10 is, The amount of deformation on the side of the guide hole 9 decreases, and the contact force on the contact surface also decreases in proportion thereto, and the contact force on the contact surface and the magnitude of the generated stress around the guide hole 9 are in a proportional relationship. Do you get it.

Further, the rigidity reducing portion 13 can be realized not only by changing the shape but also by changing the material. That is, as shown in FIG. 3, the rigidity reducing portion 13 is formed by casting a soft metal member 17, for example, a cylindrical member 17 made of copper, a copper alloy, aluminum, an aluminum alloy, or the like, by lining, or by using a retaining ring. It may be formed by fitting a cylindrical member 17 provided with a slit, or by winding a soft metal wire 18 or the like as shown in FIG.

According to the cylinder head structure having the above-described structure, the rigidity reducing portion 13 is provided on the outer peripheral portion of the valve guide 10 to reduce the rigidity in the diameter-reducing direction to facilitate the deformation. The amount of diameter reduction deformation of the outer peripheral surface of the valve guide 10 can be increased, and conversely, the amount of diameter expansion deformation of the guide hole 9 on the cylinder head 1 side can be reduced. As a result, the surface contact force can be reduced, so that the peripheral portion of the guide hole 9 on the cylinder head 1 side, particularly the structurally weak guide hole 9 and the port 4
The stress of the thin portion 8 can be reduced.

The rigidity reducing portion 13 is formed by providing a large number of axial grooves 15 in the outer peripheral portion, and the rigidity can be easily reduced by making the cross-sectional shape of the valve guide 10 substantially gear-shaped. Can be. The groove 15 is provided in the valve guide 10
Is made of cast iron, and can be easily provided at the time of casting. In addition, by forming the rigidity reducing portion 13 with the soft metal members 17 and 18, the contact area with the guide hole 9 is kept to a maximum, and the rigidity of the guide hole 9 is increased while securing the rigid support. Stress can be reduced.

[0020]

As described above, according to the cylinder structure of the present invention, at least the diameter of the outer peripheral portion of the valve guide including the portion opposed to the thin portion between the guide hole and the intake port or the exhaust port is reduced. A rigidity reduction part that facilitates deformation in the direction is provided to increase the amount of deformation on the valve guide side with respect to the press-fitting margin at the time of pressure fitting, so the amount of deformation of the guide hole on the cylinder head side can be reduced and the surrounding area can be reduced. The stress on the part can be reduced.

Accordingly, the stress in the thin portion between the guide hole and the port, which are structurally weak, can be reduced, and the durability of the cylinder head can be improved. The rigidity can be easily reduced by forming the rigidity reducing portion by providing a large number of axial grooves in the outer peripheral portion and forming the cross-sectional shape of the valve guide into a gear shape.

Further, by forming the reduced rigidity portion with a soft metal member, the contact area with the guide hole can be kept to a maximum, so that the amount of deformation of the guide hole and the peripheral portion can be maintained while securing firm support. Stress can be reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a valve guide having a cylinder head structure according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a perspective view including a partial cross section showing another valve guide of the cylinder head structure according to the present invention.

FIG. 4 is a perspective view including a partial cross section showing another valve guide of the cylinder head structure according to the present invention.

FIG. 5 is a sectional view showing a cylinder head structure.

FIG. 6 is a partial sectional view showing a structure of a valve guide and a guide hole portion.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Cylinder head 2 Intake valve 4 Intake port 6 Spring 7 Cam 8 Thin part 9 Guide hole 10 Valve guide 11 Inner peripheral surface 12 Seal part 13 Rigidity decreasing part 14 Contact part 15 Groove 17 Soft metal member 18 Soft metal wire

Claims (3)

[Claims] 1. A cylindrical valve guide made of cast iron is press-fitted into a guide hole opened obliquely to a suction / exhaust port of an aluminum alloy cylinder head of an engine, and an inner peripheral surface of the valve guide is provided. In the cylinder head structure in which the valve stem is slidably inserted, the outer peripheral portion of the valve guide including at least a portion opposed to the thin portion between the guide hole and the port can be easily deformed in the diameter reducing direction. Cylinder head structure with a reduced rigidity section. 2. The cylinder head structure according to claim 1, wherein said rigidity reducing portion is formed by providing a plurality of grooves along an axial direction in an outer peripheral portion. 3. The cylinder head structure according to claim 1, wherein said reduced rigidity portion is formed of a soft metal member.