JPH08145039A - Fastening device and fastening method - Google Patents

Abstract

PURPOSE: To prevent variation in frictional coefficient when a workpiece is fastened by a fastening member so as to stabilize the axial force of the fastening member. CONSTITUTION: When a plurality of workpieces 10a, 10b are fastened together by means of a bolt 12 (fastening means), a treated washer 16 subjected to a seizure preventing process is interposed between a washer 14 arranged on the workpiece 10a and the head part 12a of the bolt 12. With this arrangement, variation in frictional coefficient between the head part 12a and the washer 14 is restrained so as to stabilize the frictional force effected on the surface of the washer, thereby it is possible to obtain a predetermined axial force in accordance with the fastening torque.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fastening device and a fastening method using fastening members such as bolts and nuts, and in particular, a fastening device and a method capable of obtaining a stable fastening force (axial force) when fastening the fastening members. Regarding

[0002]

2. Description of the Related Art When a plurality of works are fastened to each other,
For example, fastening members such as bolts and nuts are often used when attaching a wheel of an automobile to a wheel hub or fixing an engine to a frame. When the works are fastened to each other by the fastening member, whether or not the fastening is stable is a problem. The degree of this fastening is determined by the magnitude of the axial force acting in the axial direction of the fastening member. That is, if the axial force can be maintained within a predetermined range, good fastening can be performed.

However, since it is difficult to directly detect and manage the axial force during the work fastening work, the fastening end portion (the head portion of the bolt or the nut) of the fastening member is usually tightened by a tightening tool such as a torque wrench. By controlling the tightening torque T at the time of tightening and rotating, it is used as a substitute for the management of the axial force. In this case, the axial force N can be expressed by the following formula using the tightening torque T.

N = μ × T (μ is the friction coefficient between the fastening member and the fastening seat surface) Therefore, under the assumption that the friction coefficient does not change, the fastening torque T of the fastening tool is measured by a torque sensor or the like in the work assembly process or the like. By detecting and managing, approximate axial force management (management of fastening state) can be performed.

[0005]

However, generally, the coefficient of friction between the fastening member and the fastening seat surface, for example, between the head portion of the bolt and the washer and between the washer and the work is substantially constant in the region where the pressing load is low. However, the friction coefficient significantly fluctuates and becomes large when a very large load is involved, such as in the case of bolt fastening. Here, the washer is interposed between the work and the fastening end for the purpose of preventing scratches and loosening of the work surface. Originally, the coefficient of friction is defined by the shear strength of the material and the indentation hardness of the material regardless of the load.
When a load is applied, the metal members undergo plastic deformation at their contact surfaces and cause adhesion. The force required to shear the adhered portion is a frictional force, and alloying, work hardening, etc. due to the adhesion change the mechanical properties of the material (particularly the shear strength), and the friction coefficient greatly fluctuates. In particular, the friction coefficient sharply increases depending on the micro level state difference of the metal surface and the way of applying a load.

As means for preventing an increase in the coefficient of friction, the roughness of the screw surface and seat surface of the fastening member, the surface of the washer, and the like are made uniform and the actual opening is reduced.
As disclosed in JP-A-1-79022, it is conceivable to use a washer having a large number of small-diameter recesses to reduce the contact area and reduce the friction coefficient. However, it is not possible to prevent the fluctuation of the friction coefficient itself. When the friction coefficient changes, the frictional force when slip occurs on the fastening seat surface changes, and the relationship between the fastening torque of the fastening tool and the actual fastening force does not correspond. In other words, although the tightening tool tightens with a predetermined tightening torque, the tightening torque rises to a predetermined value due to the frictional force generated in the washer part, etc., and the tightening member is not actually sufficiently tightened. Or, conversely, although the tightening torque is set in consideration of the frictional force, there is a problem that the expected frictional force does not occur and the tightening member or the work is destroyed due to excessive tightening. Since the friction coefficient fluctuates in this way, it is difficult to manage the axial force only with the tightening torque, and it is impossible to eliminate the variation in the axial force.

The present invention has been made to solve the above problems, and it is possible to prevent the variation of the friction coefficient at the time of fastening a workpiece by the fastening member and to stabilize the axial force of the fastening member. An object of the present invention is to provide a fastening device and a fastening method capable of performing the above.

[0008]

In order to achieve such an object, the present invention is, firstly, that a fastening tool is used to fasten a fastening end portion on one end side of a screw portion which is inserted through fastening holes of a plurality of works. A fastening member that fastens a plurality of works to each other by rotating inward, and a hole through which a screw portion is inserted, and the work is disposed between the work and the fastening end portion. And a treated washer having at least one of its surfaces subjected to anti-adhesion treatment on its side.

Secondly, in the first invention,
The anti-adhesion process of the treated washer is an oil impregnation process in which oil is impregnated.

Thirdly, in the first invention,
The anti-adhesion process of the treated washer is a surface hardening process.

Fourthly, in the first, second or third invention, a washer having substantially the same material and substantially the same surface roughness as the fastening end is interposed between the work and the processing washer. It is characterized by

Further, the fifth and the fifth inventions are fastening methods in which a plurality of works are fastened to each other by tightening the fastening end portion of the fastening member having the screw portion inserted in the fastening hole of the work with a fastening tool and rotating the work. Then, at least one surface of the fastening end portion and the work which are in contact with each other is subjected to anti-adhesion processing and tightened.

[0013]

According to the structure of the present invention, when the plurality of works are fastened to each other by the fastening member, the treatment washer having the anti-adhesion treatment is interposed between the works and the fastening end portion. On at least one side of the above, the adhesion of the metals does not occur, and it is possible to suppress the fluctuation of the friction coefficient. As a result, a stable slip is generated on the seat surface based on a constant frictional force, and the tightening tool tightens the fastening member until a predetermined torque is detected. Therefore, it is possible to obtain a predetermined axial force according to the tightening torque.

Further, since the anti-adhesion processing of the treated washer is oil impregnation processing or surface hardening processing which is impregnated with oil, variation of the friction coefficient is suppressed by easy processing.
At this time, a stable slip is generated on the seat surface based on a constant frictional force, and the tightening tool tightens the fastening member until a predetermined torque is detected. Therefore, it is possible to obtain a predetermined axial force according to the tightening torque.

Further, since a washer having substantially the same material and surface roughness as that of the fastening end is interposed between the work and the processing washer, it depends on the material and surface condition of the work. Since it is possible to obtain a stable sliding action between at least one of the fastening end portion and the processing washer and between the processing washer and the washer, the tightening tool should tighten the fastening member until a predetermined torque is detected. You can

Furthermore, when a plurality of workpieces are fastened to each other by the fastening member, at least one of the fastening ends and the workpieces that come into contact with each other is subjected to anti-adhesion processing, so that the fastening members directly fasten the workpieces. Even when the friction coefficient is suppressed from varying, the tightening tool can tighten the fastening member until a predetermined torque is detected.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a state in which a plurality of works 10a and 10b are fastened using fastening members, which are bolts 12 in this embodiment. In FIG. 1, the work 10a and the bolt 12
2 between the head portion 12a (the portion for tightening the bolt 12 by engaging a tightening tool such as a torque wrench).
There are some types of washers. The washer 14 on the work surface side is a generally used annular plate, which prevents the surface of the work 10a from being scratched by fastening, and relaxes the contact pressure by taking a large contact area to secure the work pressure at the time of fastening. It is used to prevent deformation of the work 10a.

The characteristic feature of this embodiment is that a processing washer 16 further processed to prevent adhesion is interposed between the washer 14 and the head portion 12a.

The processing washer 16 is made of, for example, an iron-based material such as SS41 or S45C impregnated with an oil such as machine oil or an oil-impregnated bearing alloy. Washer 14
By forming the oil-lubricated surface by interposing the processing washer 16 between the head and the head portion 12a, seizure due to adhesion of metals is prevented, and as described above, the friction coefficient of the contact surface depends on the shear strength of the material. And the indentation hardness of the material, independent of load. Therefore, the friction coefficient μ of the surface in contact with the processing washer 16 becomes constant, the frictional force generated on the contacting surface becomes a known value, and the resistance force (friction force) based on the completion of tightening of the bolt 12 and the known frictional force. It becomes possible to set the tightening torque of the bolt 12 based on the above.

In FIG. 1, the oil-containing state of the processing washer 16 is substantially uniform, the material of the washer 14 and the head portion 12a.
When the surface state in contact with the head portion 12a is substantially the same as the material and the surface state of the head portion 12a, the friction coefficient μ 1 acting between the head portion 12a and the processing washer 16 and the friction acting between the processing washer 16 and the washer 14 The coefficient μ2 has a relationship of μ1 = μ2. On the other hand, the friction coefficient μ3 acting between the washer 14 and the work 10a depends on the material and surface condition of the work 10a.
Since the treatment washer 16 has no effect of preventing adhesion, it increases as the tightening of the bolt 12 progresses, and the relationship of μ3> μ1 = μ2 is established. For example, μ1 = μ2 = 0.15, μ3 =
When each material, surface condition, and oil impregnation state are selected to about 0.6, as the bolt 12 is tightened, the friction coefficient μ3 between the washer 14 and the workpiece 10a is larger than the friction coefficients μ1 and μ2, and The seizure due to adhesion occurs because it increases with the tightening of 12. On the other hand, between the head portion 12a and the processing washer 16 or between the processing washer 16 and the washer 14, the friction coefficients μ1 and μ2 are equal to the friction coefficient μ3.
Since the coefficient of friction is smaller and the coefficient of friction does not fluctuate due to the action of the processing washer 16, slippage occurs without adhesion.

Therefore, the frictional force on the fastening seat surface during tightening of the bolt 12 does not exceed a certain value, and the fastening torque detected by the fastening tool with a torque sensor or the like is only the resistance force based on the completion of the fastening of the bolt 12. The fastening tool recognizes the end of tightening due to the variation. As described above, by using the two types of washers, the tightening torque T of the fastening tool is controlled without considering the material and surface condition of the work, so that N =
With μ × T, the axial force N can be accurately controlled.

In the above-described embodiment, the treatment washer 16 is impregnated with oil to improve the lubricity of the contact surface to prevent the adhesion, but another method, for example, a quenching treatment on the surface of the treatment washer. It is also possible to prevent sticking by performing surface hardening treatment such as anodic oxidation treatment, plating treatment and shot beaning treatment to prevent seizure. In particular, the surface hardening treatment can be applied directly to the work or the head part of the bolt, so if it is required to reduce the weight or the number of parts as much as possible, the surface hardening treatment can be applied directly to the contact surface of the work or the head part. By performing the process, it becomes possible to eliminate the processing washer and the ordinary washer, and it is possible to obtain the same axial force stabilizing effect as that of the above-described embodiment.

Further, as shown in FIG.
To have a two-layer structure, and the head portion 12a side is an adhesion preventing layer 18a made of an oil-containing layer or a surface-hardened layer.
The side is the untreated layer 18b. Then, by suppressing the fluctuation of the friction coefficient μ1 acting between the head portion 12a and the processing washer 18, it is possible to obtain the same axial force stabilizing effect as that of the embodiment shown in FIG. Even if the anti-adhesion layer 18a and the untreated layer 18b are arranged in the opposite manner, the axial force stabilizing effect can be obtained. However, the anti-adhesion layer 18a is formed on the head portion 12a side, and when the tightening is performed, If the slip is generated on the side of the head portion 12a, the axial force stabilizing effect can be obtained without causing a scratch on the surface of the work 10a. Further, if necessary, even when both surfaces of the processing washer are processed, different friction coefficients (including untreated one side) may be provided on the upper surface side and the lower surface side of the processing washer. At this time, the diameter of the processing washers 18 should be increased to some extent so as to increase the mutual contact areas, and the friction coefficient on the upper surface side, that is, the head portion 12a side should be smaller than that on the lower surface side, that is, the work 10a side. For example, the head portion 12a and the work 10
It is possible to achieve the original purpose of the washer, which is to prevent the deformation of the work 10a at the time of fastening by relaxing the contact pressure with a, and to suppress the variation of the friction coefficient μ1 acting between the head portion 12a and the processing washer 18. Therefore, the axial force stabilizing effect can be obtained.

In this embodiment, the bolts are used as the fastening members, but the same effect can be obtained by using the nuts.

[0026]

According to the present invention, when a plurality of works are fastened to each other by a fastening member, a processing washer having an anti-sticking treatment is interposed between the work and the fastening end portion. At least one side of the treated washer does not cause adhesion of metals to each other, and it is possible to suppress variation in friction coefficient. As a result, a stable slip is generated on the seat surface based on a constant frictional force, and the tightening tool tightens the fastening member until a predetermined torque is detected. Therefore, it becomes possible to obtain a predetermined axial force according to the tightening torque, and it is possible to accurately manage the axial force by the tightening torque.

Further, since the anti-adhesion processing of the treated washer is oil impregnation processing or surface hardening processing of oil impregnation, fluctuations in the friction coefficient are suppressed, and the seat surface is stabilized based on a constant friction force. The slipping occurs and the tightening tool tightens the fastening member until a predetermined torque is detected. Therefore, it becomes possible to obtain a predetermined axial force according to the tightening torque, and it is possible to accurately manage the axial force by the tightening torque.

Further, since a washer having substantially the same material and surface roughness as the fastening end is interposed between the work and the processing washer, it depends on the material and surface condition of the work. Since it is possible to obtain a stable sliding action between at least one of the fastening end portion and the processing washer and between the processing washer and the washer, the tightening tool should tighten the fastening member until a predetermined torque is detected. It is possible to accurately control the axial force due to the tightening torque.

Furthermore, when a plurality of workpieces are fastened to each other by the fastening member, at least one of the fastening ends and the workpieces that come into contact with each other is subjected to anti-adhesion processing, so that the fastening members directly fasten the workpieces. Even when the variation of the friction coefficient is suppressed, the tightening tool can tighten the fastening member until the predetermined torque is detected.
It is possible to accurately control the axial force based on the tightening torque.

[Brief description of drawings]

FIG. 1 is an explanatory diagram illustrating an embodiment of a fastening device and a fastening method according to the present invention.

FIG. 2 is an explanatory view illustrating another embodiment of the fastening device and the fastening method according to the present invention.

[Explanation of symbols]

 10a, 10b Work 12 Bolt (fastening member) 12a Head 14 Washer 16, 18 Processing washer

Claims (5)

[Claims] 1. A fastening member for fastening a plurality of works to each other by tightening and rotating a fastening end portion on one end side of a screw portion inserted in a fastening hole of a plurality of works with a fastening tool, and a screw portion is inserted. A processing washer having a hole, disposed between the work and the fastening end, and having at least one of the fastening end side surface and the work side surface subjected to anti-adhesion processing, A fastening device characterized by the above. 2. The fastening device according to claim 1, wherein the anti-adhesion process of the processing washer is an oil impregnation process impregnated with oil. 3. The fastening device according to claim 1, wherein the anti-adhesion processing of the processing washer is surface hardening processing. 4. Claim 1 or claim 2 or claim 3.
The fastening device according to claim 1, wherein a washer having substantially the same material and surface roughness as the fastening end is interposed between the work and the processing washer. 5. A fastening method for fastening a plurality of works to each other by tightening and rotating a fastening end portion of a fastening member having a threaded portion inserted in a fastening hole of the work with a fastening tool, wherein the plurality of works are in contact with each other. A fastening method characterized in that at least one of the fastening end portion and the work is subjected to anti-adhesion processing and tightened.