JPS6119527A - Method of tightening bolt on cylinder head - Google Patents

Abstract

PURPOSE:To uniformly tighten bolts on the cylinder head of an internal-combustion engine, by providing angle reference signs on the bolt seats of the cylinder head and angle graduations on the heads of the bolts to additionally tighten the bolts to a prescribed angle after previously tightening them. CONSTITUTION:After a plurality of bolts 11 are tentatively tightened uniformly in prescribed tightening order, the bolts are additionally tightened by torque of about 7.8-8.0kg.m with a tightening wrench. Each bolt 11 is thereafter still additionally tightened from the current position so that the reading of an angle graduation a to an angle reference signal c becomes a prescribed angle of 60- 90 deg.. The bolts 11 are thus uniformly and sufficiently tightened to enhance the degrees of sealing and reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to a method for tightening bolts for attaching a cylinder head of an internal combustion engine to a cylinder block.

As is well known in the art, a cylinder head is attached to a cylinder block by tightening a plurality of bolts, and these bolts 1 generally have heads 2 as shown in FIG.
A type having a flange portion 4 between the shaft portion 3 and the shaft portion 3 is used. As a conventional method for tightening this bolt 1, that is, a method for controlling the tightening axial force, the torque method is usually used. After temporarily tightening with a torque of 5 to 5.0 kg-m, use a torque φ wrench to tighten approximately 7.0 to B, O.
k! The cylinder head is installed by retightening with a torque of 9-m (see page 19 of Gasoline Vehicle Maintenance, published by Hyoryo Shoten, June 5, 1966).

Problems to be solved by the invention In the conventional torque method mentioned above,
1 Due to variations in the coefficient of friction between the threaded part and the bearing surface of the bolt 1, even if the torque wrench is used to retighten it to the specified torque value, if the coefficient of friction deviates to the larger side,
This large frictional resistance consumes the specified torque, making it impossible to obtain sufficient tightening force. On the other hand, if the friction coefficient deviates to the smaller side, the bolt may break due to excessive axial force. That is, the surface pressure between the flange portion 4 and the bolt seating surface of the cylinder head is not constant, making it impossible to ensure a strong and uniform tightening state of the bolt 1. As a result, the sealing performance of the gasket deteriorated, leading to gas leaks, oil leaks, etc. The above situation also occurs when dirt or the like adheres to the threaded portion or the seat surface.

Means for Solving the Problems This invention provides that at least one angular reference mark is formed around the seating surface of each bolt of the cylinder head, and a plurality of angular reference marks are formed on the outer periphery of the upper surface of the bolt on the head side, corresponding to the above-mentioned angular reference markings. An angle scale is formed, and it is recommended that each bolt be tightened to the specified torque value at the beginning of tightening, then rotated from the current rotation position to the specified angle while reading the angle reference mark against the angle reference mark, and further tightened. It is a feature.

Function Generally speaking, there is a rotation angle method in addition to the so-called torque method as a method for managing axial force when tightening bolts. The variation in bolt axial force according to the torque method is 2 for M 10 x 1.5 bolts.
．． 3 t ~ 4.1 t (tightening torque 6 kg -m
), whereas in the rotation angle method it is 2.8t to 3.7t.
(Tightening condition: 3 kl!-m torque and then temporarily tightening the bolt and then rotating it by 60°), and the rotation angle method has less variation in axial force and is more reliable in tightening accuracy. .

This invention uses the torque method and rotation angle method in combination, and first tightens the torque to a specified torque value using the torque method.
Then, while reading the angle scale formed on the upper outer periphery of the bolt head with respect to the angle reference mark formed on the end of the bolt seating surface of the cylinder head, rotate the bolt to a certain angle and tighten it to prevent over-tightening. This prevents the bolt from breaking due to torque, and also provides strong surface pressure between the bolt seating surface of the cylinder head and the lower surface of the bolt, so that the bolt can be evenly and firmly tightened to the cylinder head.

Example Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a plan view showing a state in which a bolt is tightened to a cylinder head used in the present invention, and FIGS. 2 and 3 are enlarged views of the bolt. Head 12 and shaft portion 1 of hexagonal bolt 11
A head 12 is provided on the upper surface of the outer periphery of the flange portion 14 formed between 3 and 3.
12 at equal intervals with an angle θ of 30° from the center line 0 of
angle scales a are formed. Also, the head 1 on the line connecting the axis P of the bolt 11 to the one angle scale a mentioned above.
A check mark b is formed on the top surface of 2 to prevent miscounting on the angle scale a.

On the other hand, the cylinder head 15 is made of cast iron and is integrally cast, and as shown in FIG.
One angle reference mark C corresponding to the angle scale a of the bolt 110 is formed on the peripheral edge of the seating surface 17 on which the lower surface 16 of the first flange portion 140 is seated.

In addition, the cylinder head 150 angle and reference mark C are as follows:
It may be stamped with a punch or the like, or it may be formed into a convex shape during casting. In addition, the angle scale a formed on the flange portion 14 of the bolt 11 has a notch 14a on the outer upper surface of the flange portion 14 as shown in FIG. The recess 14b or the same figure (Q
It is also possible to form a convex portion 14c as shown in FIG.

Therefore, in addition to the torque method, the flange portion 1 of the port 11
The axial force can also be managed by the bolt 110 rotation angle method using the angle scale a formed on the cylinder head 4 and the angle reference mark C formed on the cylinder head 15.

That is, first, after temporarily tightening the plurality of bolts 11 according to the specified tightening order, tighten them approximately 7 times with a torque wrench.
．． Retighten with a torque of 8 to 8.0 kl-m, then use a wrench etc. to adjust the specified angle (600 to
900), then tighten each bolt 11.

In addition, when reading the number on the angle scale a above, check mark b
Reading based on this will prevent misreading of numbers. In addition, the angle reference mark C is not limited to just one, but also has an angle scale a.
A plurality of them may be formed as long as it is easy to read them.

Effects of the Invention As is clear from the above explanation, the cylinder head bolt tightening method according to the present invention uses the torque method in combination with the narrow-end angle method as an axial force management method when tightening the bolts, and tightens by the torque method. After that, the bolts are further tightened to the specified angle using the rotational angle method, which equalizes the surface pressure between the bolt seating surface of the cylinder head and the bottom surface of the bolt that seats on the seating surface, ensuring uniform and sufficient tightening of all bolts. , the tightening accuracy is increased. As a result, the sealing performance of the gasket is improved and leakage of gas and lubricating oil is completely prevented.

On the other hand, by restricting the rotation to a specified angle, problems such as bolt breakage due to over-tightening are reliably prevented.

[Brief explanation of drawings]

Fig. 1 is a plan view showing a state in which a bolt is tightened to a cylinder head used in the present invention, Fig. 2 is a plan view of the bolt used in the present invention, and Fig. 3 is a side view of the bolt.
Fig. 4 (5), (BL (C) is a sectional view taken along the line ■-■ in Fig. 2 showing different examples of angle scales, Fig. 5 is a side view showing a conventional bolt. 11...Bolt, 12...Head, 14...Flange part, 15...Cylinder head, a...Angle scale,
C...Angle reference mark. 2 people outside

Claims (1)

[Claims] (1) In a method of tightening a cylinder head attached to a cylinder block with a plurality of bolts, at least one angle reference mark is formed around the seating surface of each bolt of the cylinder head, while the A plurality of angle scales corresponding to the angle reference mark are formed, and at the beginning of tightening, each bolt is tightened to the specified torque value, and then rotated from the current rotation position to the above angle reference mark to the specified angle while reading the angle scale. A method for tightening bolts on a cylinder head, characterized in that the bolts are tightened after the bolts are tightened.