JP2001179645A - Method of controlling screw tightening in proportional range - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of controlling axial tension for properly tightening a screw. SOLUTION: The screw rotational angle or tightening torque is detected with the progress of screw tightening work, it is read that the tightened body of the screw enters a proportional range to determine a proportional origin. Using the proportional constant known beforehand in the screw system of the tightened body of the screw, the rotational angle of the screw is divided into the elongation component of the screw system and the contraction component of a member to be tightened. A tightening diagram indicated with a triangle in which axial tension is taken as its strut is determined to control the tightening axial tension of the screw with the tightening diagram.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shaft which is actually generated by using a tightening diagram (hereinafter, referred to as a tightening triangle) represented by a triangle having an axial force as a main column in a tightening operation of a screw fastener. The present invention relates to a technique for calculating a force to make proper tightening not only of a new screw fastener but also of a used screw fastener. Applications include manual hand tools, power nutrunners, impact wrenches (including impact wrenches and oil pulse wrenches),
It is a hydraulically driven torque wrench or the like. As an impact wrench, for example, Japanese Utility Model 4-32225, US.PAT.
285,638, US.PAT. 2,160,150, US.PA
T. 3,661,217, US.PAT. 3,174,59
7, US.PAT. 3,428,137, US.PAT. 3,55
2,499, and other similar clutch structures. As a hydraulic drive type torque wrench, for example, U
S.PAT. 4,524,651, US.PAT. 4,619,1
60 and other similar structures. Power sources include manual, electric, pneumatic, engine, and hydraulic drives.

[0002]

BACKGROUND OF THE INVENTION Screws are the basic mechanical element that supports modern machine civilization. Now, in the era of recycling, its role is considered to be increasingly important.
However, in spite of such an important role of the screw, there is a reality that various problems remain in the tightening control method and its execution. Apart from the case of assembling a new machine under quality control, in the case of disassembly, maintenance and repair of used equipment, facilities and equipment, the construction of necessary screw tightening work methods and means is extremely delayed. It is the current situation.
JIS B 1083 1084 "General rules for tightening screws" and "Test methods for tightening screw parts"
It can also be understood from the fact that the provisions of the significance, basis and tightening management method of screw tightening are specially established. However, this rule is based on the quality control of parts and the like, and it is impossible to apply it to widely existing unmanaged workplaces. There are three methods of screw tightening management indicated in the JIS standard: a torque method, a rotation angle method, and a torque gradient method.

[0003]

Among them, the torque gradient method is not widely used in equipment and facilities, and the execution of this method is limited. Therefore, in the general screw tightening work, at present, the remaining two methods, particularly the torque method, have become widespread. Therefore, in the following:
Only in connection with these two methods, outlines and problems are described. The purpose of the screw tightening control is to create a strong screw tightening body, and the main problem for that is to apply a specified tightening force (axial force). The point in this case is that insufficient tightening must be avoided. However, it can be said that it is structurally impossible to directly measure the tightening force (axial force) at the stage of the tightening operation of the screw fastener. Therefore, both the torque method and the rotation angle method
It is an indirect method from the viewpoint of axial force management.
From this point of view, the significance of the incidental condition that the torque coefficient under the control of the JIS regulation is controlled is heavy.

[0004] In the field of screw tightening work, the torque method is overwhelmingly widespread. This method mainly determines the axial force through the frictional resistance of the tightening frictional surface. Therefore, the control of the tightening force (axial force) cannot be realized unless the torque coefficient mainly composed of the friction of the sliding surfaces is known. This is a major problem with this method. This is because it is extremely difficult to control the torque coefficient at the site of most screw tightening operations.

The rotation angle method is a method capable of controlling a tightening force regardless of a torque coefficient. However, this method has a drawback in the accuracy of measuring the rotation angle. It is difficult to determine the starting point for measuring the tightening rotation angle of a screw (bolt or nut). In this method, the starting point (snag point) at which the screw fastener enters the linear region (proportional region) in the elastic region must be rationally set as the angle measurement starting point.
The elasticity is unstable at the beginning of tightening of the screw fastening body, and a method and a device that can easily and accurately set a snag point are not yet known.

Next, the screw tightening operation will be considered from the viewpoint of the work site. When a product having a screw fastening portion is assembled in a factory, screws and members to be fastened are new, and are generally quality-controlled to ensure standard quality. In addition, there are equipment and devices required for fastening, and the performance is also managed. This means that the conditions necessary for the implementation of the JIS regulations have been met. Therefore, there is little possibility that a problem in assembly quality will occur. However, the situation at the work site where the used products are disassembled and maintained is very different. The quality of screws and parts is second-hand, so that it has deteriorated and individualized due to its use history. In particular, a change in the coefficient of friction due to a change in the surface condition and a change in the elasticity due to the deformation of the component are considered. Unless the change can be determined visually or by a simple method, it is practically difficult to perform the determination by precise measurement in terms of facilities and costs.
At such a work site, J
Although the method specified by the IS can be applied mutatis mutandis, quality assurance lacks its prerequisites, so the quality of used screw fasteners has great anxiety. There are many such work sites worldwide, and this is considered to be a major problem in the age of recycling.

Next, an actual example of the screw fastening of a used product will be described. As an example, the tightening of hub bolts and nuts that fasten tire wheels to axle hubs of passenger cars familiar to consumers is given. The standard dimensions of hub bolts for domestic passenger cars are generally 12 mm outside diameter and 40 mm long. There are various types of wheels, such as materials, shapes, and shapes of fastening seat surfaces. The specified tightening torque is around 100 N · m, though there is a slight difference depending on the vehicle type. Usually, there is no specification of the tightening force. However, the design axial force may be about 40,000N or more. The reason is that the yield strength of 12mm bolt of intermediate load bearing steel is about 70,000N, 60% of which is 42,000N.

The inventors have made an experimental bench substantially similar to the actual vehicle structure, and have repeatedly tightened various kinds of new and old wheels. As a result, the apparent torque coefficient was found to vary unexpectedly over a wide range. The low value was measured from about 0.1 generation when the lubricant was applied, and the maximum was measured to about 1. In terms of rotation angle, the rotation angle up to a torque of 100 N · m for iron bolts for five bolts varied from 40 degrees to 129 degrees depending on the tightening location.
Thus, it can be seen that the screw fastening is unexpectedly individualized with the second-hand use. Such instability of the torque coefficient means that the variation in the tightening force is about 10 times even with the tightening with the same torque value. It should be noted that when the torque coefficient is high, the tightening force is considerably lower than the design value in the torque method. Most notable is the problem of weak tightening forces that occur when high torque coefficients and low torque tightening overlap. It is conceivable that the tightening axial force does not reach 10,000N, and in such a case, the mission as a screw fastener has not been fulfilled significantly.

[0009] In addition to the problem of the torque coefficient, there is another problem in the screw fastener that is the difference in elasticity of the member to be fastened which cannot be distinguished by the operator. Most screw fasteners consist of a plurality of screw fasteners. In this case, when the screws are sequentially tightened one by one, the elastic modulus of the member to be fastened varies depending on the tightening order in addition to the inherent deviation. In used screw fasteners, in addition to individualizing the members to be fastened,
Because of this change in environment, it is difficult to set a target not only for the torque method but also for the rotation angle method. Therefore, in the past, the countermeasures were in a state of being left unchecked. For reference, in the United States, Lost wheel crisis and Torque
The word gremlin appears. It has been pointed out that the cause of this problem is largely related to the quality of screw fastening.

The present invention proposes a method that satisfies the requirements of both the torque method and the rotation angle method and enables the control of the tightening axial force.

According to a first aspect of the present invention, a screw rotation angle or a tightening torque is detected as the screw fastening operation progresses, and the fact that the screw fastener has entered a proportional range is read. The origin is determined, the screw rotation angle is divided into the elongation component of the screw system and the contraction component of the member to be fastened using the proportional constant known in advance in the screw system of the screw fastening body, and the axial force is determined by the main column. A proportional area screw tightening control method is characterized in that a tightening diagram represented by a triangle is determined, and the tightening axial force of the screw is controlled using the tightening diagram. However, the screw system refers to a combination system of a bolt and a nut or an alternative female screw.
According to a second aspect of the present invention, in the screw tightening control using static force, the screw rotation angle and the tightening torque are detected in parallel with the progress of the screw tightening operation, and the screw tightened body enters the proportional range. By reading the fact, determining the proportional origin, using the proportional constant known in advance in the screw system of the screw fastener, the screw rotation angle is divided into the elongation component of the screw system and the contraction component of the member to be fastened, A proportional area screw tightening control method is characterized in that a tightening diagram represented by a triangle having an axial force as a main column is determined, and the tightening axial force of the screw is controlled using the tightening diagram. However, screw tightening using static force means screw tightening with a static force using a manual wrench or a power wrench. According to the third aspect of the invention, when both the tightening torque and the screw rotation angle cannot be simultaneously read simultaneously, both the tightening torque and the screw rotation angle are partially read, and the tightening torque of the screw fastener is converted to the screw rotation angle. A proportional area screw tightening control method is characterized in that a tightening diagram represented by a triangle is determined by conversion, and the tightening axial force of the screw is controlled using the tightening diagram. The invention according to claim 4 is a proportional area screw tightening control method, wherein the quality of the fastening operation is determined based on a torque coefficient calculated from a tightening torque and an axial force in screw fastening. According to a fifth aspect of the present invention, the elasticity coefficient Ka of the screw system, the elasticity angle coefficient Kb of the member to be fastened, and the elasticity angle coefficient K of the screw fastening body in a fastening diagram represented by a triangle with the axial force as the main column
And based on the value of Kb / Ka or K / Ka,
A proportional area screw tightening method characterized by judging the quality of a fastening operation.

<1> Principle of the Invention-Part 1 The principle of the tightening control according to the present invention is basically based on the rotation angle method. However, the torque method also includes methods that can be used. The principles of the torque method and the rotation angle method for screw tightening in the proportional range are simple and known. The explanation will be slightly added below. First, a description will be given of a fastening diagram that is a classic theory of the proportional area screw fastening and has not been replaced by a classical theory at present. The present invention is a practical application of the theory of the tightening diagram by the mechatronics technology.

(1) Tightening Diagram The first principle is that a “tightening triangle” generated from a fastening diagram
Shape ". This is proportional range screw fastening
The principle of the body shows that there is a relationship between proportion and equilibrium.
is there. Fig. 1 shows a typical ACD.
Was. This line segment AB of the height of ACD indicates the axial force.
You. △ ABC on the left side of line segment AB is
It is a diagram showing that the screw system is extended by λa by the axial force F.
Are shown. △ ABD on the right shows the change of the member to be fastened
FIG. 3 is a diagram showing that the shaft is contracted by λb by an axial force F.
are doing. Line segment AC is the process of change of λa with respect to axial force F
It is shown. Angle CAB (= angle α) is this screw system
Is the elastic angle representing the elasticity of
It is. This is due to the inherent elasticity of this screw system due to tan α.
It can be expressed as an angle coefficient and expressed as Ka. Also,
In the case, in accordance with practical convenience, stretch and shrink
It is expressed by the rotation angle of the same system. △ Horizontal line in ABC
A shown₁Is the intermediate rotation of the screw system caused by the elongation of the screw system
Angle and intermediate axial force f₁It corresponds to. Intermediate shaft
Force f ₁And intermediate rotation angle a₁Is related to a₁= F₁× Ka
Becomes Also, the elongation of the screw system at that time is λa₁To be
And λa₁= A₁× p / 360. In addition, p
It is the same pitch.

△ ABD on the right side of the line segment AB is for the member to be fastened. The relationship between axial force and elongation in ΔABC is ΔA
In BD, the relationship is between axial force and contraction. The elastic angle of the proportional area screw is β, and the elastic angle coefficient is tan β = Kb. Intermediate rotation angle of the screw system caused shrinkage of the fastening member relative to the intermediate shaft force f ₁ is b _1, when the full rotation angle of the screw system at this time is theta _1, the θ ₁ = a ₁ + b ₁ . The tightening triangle shows that all changes change linearly, i.e. proportionally. With respect to a certain screw fastening body, this proportional relationship is established among the axial force F, the torque T, the extension λa of the screw system, and the contraction λb of the member to be fastened. That is, the axial force, the torque, and the rotation angle are in a proportional relationship, respectively.

The second principle is another important principle represented by the tightening triangle, that is, the equilibrium relationship of the screw fastener. The work of elongation of the screw system and the work of compression of the member to be fastened have an equivalent relationship, which means that the work is completed at all stages of tightening. That is, △ ABC and △ A in FIG.
Although the apparent area is different from that of the BD, the amount of work is equal. This equilibrium does not change even during the tightening. FIG. 2 illustrates this. △ AB ₁ C ₁ and △ AB _{1 in the} figure
D ₁ is equivalent in terms of work load. Naturally, the quadrilateral B ₁ B ₂ C ₂ C ₁ and the quadrilateral B ₁ B ₂ D ₂ C
_{1 is} also equivalent in workload.

(2) Uniqueness and Diversity The screw fastener has a uniqueness portion and a diversity portion. The characteristic portion is the relationship between the axial force of the screw system and the rotation angle or elongation. That is, the relationship between the axial force F of △ ABC and the elongation λa or the rotation angle is unique to a screw-fastened body using the same material and the same size screw regardless of the member to be fastened. That is, the elastic angle coefficient Ka of the screw system is a constant for a screw system of the same material and the same dimensions. The elastic angle coefficient ka is a constant that is generally referred to as being proportional to the reciprocal of the tension spring constant of the screw system. On the other hand, various types of members to be fastened are conceivable. For example, even though the hub bolts of passenger cars are the same type, there are various types of tire wheels. In addition, there are differences among individuals of the same type of member to be fastened. This is shown in FIG. In the tightening triangle, the structure of the screw system, that is, the shape of △ ABC does not change, but the △ ABD of the member to be fastened changes for each design specification. In summary, one screw fastening member is made up of an elastic angle coefficient Ka unique to the screw system and an elastic angle coefficient Kb of the member to be fastened that changes for each individual. The elastic angle coefficient K of the screw fastener obtained by combining the two is expressed as K = Ka + Kb. In FIG. 1, since a ₁ = f ₁ × Ka and b ₁ = f ₁ × Kb, θ ₁ = a ₁ + b ₁ = f ₁ × (Ka + Kb) = f ₁ ×
It becomes K.

(3) Independence The screw fastener has a fastening triangle which is a mechanical pattern independent of each individual. The feature of the tightening triangle is that it is a dynamic pattern of screw fastening and is independent of the screw fastening method (torque method, rotation angle method, etc.) and means (tool type, etc.). There are various types of screw fastening methods and tools used, but it is not possible to change the pattern of the tightening triangle. Conversely, in the screw fastening operation of the axial force control, it is necessary to read the tightening triangle pattern and execute the operation while confirming the soundness of the screw fastener. This is especially necessary when reassembling used screw fasteners.

<2> Principle of the Invention-Part 2 The most important feature of the present invention is that the progress of the screw fastening generated by the fastening input is read by the rotation angle of the screw system, and the fastening triangle of the screw fastening body is read from the value. On the point.
Needless to say, half of the tightening triangle is formed by the elastic angle coefficient Ka of the screw system (the rotation angle of the screw system due to the elongation of the screw system per load). Since the coefficient Ka is a coefficient obtained in advance, axial force control can be performed using the coefficient Ka as a reference. The data necessary for the control and its calculation may be performed in a digital manner. For this purpose, a small dedicated computer is mounted on the tool. The point of the control method of the present invention is to recognize the purpose of screw fastening,
It is to read out the snag point of the screw fastening body and read out the fastening triangle.

(1) Recognition of Purpose of Screw Fastening The purpose of screw fastening is to apply a necessary axial force to a screw system. To do so, recognize the performance and quality of the screw system used, know the design axial force, check the quality of related members and eliminate abnormalities, recognize the functions of the tools used, and meet the objectives. It is necessary to perform necessary learning and setup, such as determining whether or not it is a thing.

(2) Snag Point What has been described above is that the elongation of the screw system and the shrinkage of the member to be fastened have a completely proportional relationship. However, in reality, both the screw system and the member to be fastened usually have no proportional relationship at the beginning of fastening. In actual screw fastening, the contact of the fastening surface partially starts, progresses and expands in order, and reaches a state of seating. That is, the snug point of the screw fastener cannot be clearly determined by the actual one. Therefore, in order to execute the tightening of the axial force control based on the principle of the tightening triangle, it is necessary to determine the snag point as accurately as possible.

Therefore, in the present invention, the following method is proposed for determining a snag point.・ How to determine the snug point of the used screw system. The first method is a method that is determined by actual measurement. Bolts and nuts of the same material and dimensions as the thread system to be controlled
This method measures the relationship between axial force and elongation and specifies the proportional relationship by regression. 4 (a) and 4 (b) show the outline. The second method is a method of calculating and determining from various dimensions of a screw system to be used. Various calculation methods have been published. -About the snag point of the member to be fastened The snag point of the member to be fastened is generally difficult to determine, except for a simple shape.・ About the snag point of the entire screw fastener The snag point of the entire screw fastener satisfies the snug points of both the screw system and the member to be fastened, and the deformation of the entire screw fastener has a proportional relationship with the axial force. It is considered a point in time. Therefore, the determination at this time is performed by executing the tightening of the screw fastener and reading the time when the total rotation angle of the screw system by the tightening becomes proportional to the axial force.

(3) Reading of Tightening Triangle and Tightening Control The actual method of reading the progress of screw tightening by the rotation angle of the screw system and drawing the tightening triangle of the screw tightening body from the value is a practical method of the present invention. The most important factor to decide. Therefore, the basic concept and procedure of this method will be described first. This method is based on the rotation angle method. In order to control the axial force by the rotation angle method, the elasticity of the screw fastener is required. According to the present invention, the elasticity value of the screw fastening body is read from the value of the screw rotation angle itself resulting from the execution of the screw fastening, and the rotation angle method is executed based on the elasticity value. There is a slight difference in the procedure for reading the tightening triangle between a static wrench (refers to a manual wrench or a power wrench that tightens by static force) and an impact wrench. It relates to a technique for reading the proportional area of the screw fastener from the screw rotation angle. This will be described later.

Hereinafter, the description will be made with a focus on the case of the static wrench. First, the steps for reading the tightening triangle will be described mainly with reference to FIGS. 5, 6, and 7. FIG. First, as described above, the elastic angle coefficient Ka of the screw system used and the snug point are obtained in advance. Next, the tightening of the screw fastener is performed, and the rotation angle is read. When directly reading the tightening rotation angle, the value is used as control data. In the case of the torque method, it is necessary to convert a torque value into a rotation angle value. The specific method will be described later. Next, an operation of specifying the proportional start point and setting the proportional origin and the rotation angle line Lθ of the screw fastener is performed. Specifically, progression (the vertical axis rotation angle, the horizontal axis represents the input process.) Of the total rotation angle of the screw system to read a curve O-Aθ ₁ -Aθ ₂ in FIG. At the same time, the read rotation angle is divided by the elastic angle constant Ka of the screw system. Rate of change of the divided value identifies a first time constant and become point (intersection of the line segment X-X and angle line) A.theta. _1. Aθ ₁ is a point that none other than the proportional zone transition point. Then, to determine the proportional region determination point A.theta. _2. Then, the intersection A with the horizontal axis is determined by extending the line segment Aθ ₁ -Aθ ₂ . Point A is the proportional origin of the entire screw fastener. Then, the line segment A-Aθ ₁ -Aθ ₂ is the linear Lθ is determined.

Then, the positioning of the snug point, the rotation angle line La of the screw system, and the axial force line of the horizontal axis are performed. As shown in FIG. 6, the snug point of the screw system (vertical axis is the screw rotation angle, horizontal axis is the axial force) is aligned with the vertical line XX, and the axial force at the snag point and the screw at that time are adjusted. A point indicating the rotation angle is set below the vertical axis. This point does not deviate from the position of the snug point of the screw system.
This point is designated as point S. The straight line connecting the point S and the proportional origin A is the La line. At this time, the scale of the axial force is given to the horizontal axis. In this process, the ratio Kb / Ka is obtained, and the soundness of the screw fastener is verified. If the soundness of the screw fastener is confirmed, the pattern of the tightening triangle can be determined. In this manner, the determined Lθ, La lines are formed in FIG. 6, and the tightening control can be performed. The rotation angle line Lb due to the contraction of the member to be fastened is calculated as the difference between the Lθ line and the La line. FIG. 7 shows a tightening triangle in which the elements are determined in this manner.

Then, tightening control is performed. When the positioning of the snug point is completed, a proportional constant between the axial force and the tightening rotation angle is determined. The tightening control is configured to only apply a target axial force to the wrench, and the wrench is automatically stopped when a rotation angle corresponding to the axial force is reached.

(4) Synchronization of snag point According to a fastening test of a tire wheel for a passenger car (outer diameter of a used screw is 12 mm), a snag point of a screw system almost coincides with a snag point of a member to be fastened. Appears almost coincident with the starting point of the proportional region of the screw rotation angle as the whole screw fastener, and has synchronism. As shown in FIG. 7, the XX line at which the screw fastening body shifts to the proportional range includes a snag point S of the screw diameter and a point Ds at which the threaded member enters the proportional range. Axial force at that time is f _1, between the two, holds a proportional relationship between the screw fastener. This holds true in general as long as the proportionality of the tightening triangle is based. FIG. 8 shows that the elastic angle coefficient of the member to be fastened is various (Kb _{1 to} Kb ₁ ).
The case ₄ ) will be described below. If the elastic angular coefficient of Kb _4, may be treated with a rotation angle caused by the shrinkage of the workpieces "0". That is, it is a case where the member can be regarded as a rigid body, and in this case, the deformation of the member to be fastened can be ignored. In other words, only the screw system is deformed (rotation angle due to the elongation of the screw system to the axial force f ₁ is ax). This indicates that this point is the snug point itself. Similarly,
When the elastic angle coefficients are Kb ₁ , Kb ₂ , and Kb ₃ , the rotation angles resulting from the contraction of the member to be fastened in proportion to the axial force f ₁ are bx ₁ , bX ₂ , bX ₃ , and X -Do not deviate from X-rays. Also, for example, an iron (taper seat) wheel has a spring structure at the tightening portion,
This is a soft joint in which Kb / Ka has a large value.
In this case, the member to be fastened is subject to the snug point of the screw system. That is, the snag point of the screw system becomes the snag point of the screw fastener. Kb / K made of light alloy (flat seat)
The value of a is a small hard joint. It is considered that such a member having high rigidity does not clearly have a snug point. In an extreme case, the member to be fastened is close to a rigid body. In this case, the screw system is controlled by the member to be fastened, and its snag point is the snug point of the screw system itself.

(5) Variation in Snag Point Alignment and Tightening Accuracy The snag point of the screw system can be roughly determined by a bench test or the like. However, the elastic angle coefficients of the members to be fastened vary widely. In particular, used ones are striking and individual. Therefore, a certain degree of variation must be tolerated in order to specify the transition point (XX line) of the screw fastener in the proportional region in the fastening operation process and to treat it at the same time as the snag point of the screw system. . However, according to the present invention, the error rate of snag point alignment is sharply improved as the tightening progresses. FIG. 6 shows an example of a fastening triangle for a tire wheel of a passenger car. Screw outer diameter is 12mm, proper axial force is about
40,000N, but at least 30,000N is required. The axial force at the snug point of this screw system is 10,000N.
The error of ± 20% at the stage of snag point alignment is ± 2,000 N in terms of axial force. It is considered that this error range of the axial force value is maintained as it is even when the tightening proceeds. Therefore,
Tightening accuracy is ± 2,000 N, 40,0 for axial force of 30,000N.
± 2,000 N for 00N, ie ±± for proper axial force
5%. It can be said that such tightening accuracy is extremely excellent.

(6) Verification of Soundness of Screw Fastened Body and Detection of Abnormal Tightening In the present invention, when the measured value indicating the proportional relationship of the screw fastened body is out of an allowable range, or when the tightening axial force increases normally. If not, a function for issuing an alarm as loss of soundness of the screw fastener or abnormal tightening can be provided. The main cases are as follows: (a) When the screw fastening body does not have a proportional range, detection is performed based on the degree of increase of the Lθ line. (B) When the tightening hardness of the screw fastener is outside the allowable value, it is detected by the value of Kb / Ka. (C) When the increase in the axial force is low (such as co-rotation),
In the case of screw tightening by static force, it is detected that the torque does not increase normally. In the case of an impact wrench, detection is made based on a low rebound value.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS <First Embodiment> In the case of a torque wrench A torque wrench as a first embodiment of the present invention will be described in detail below with reference to the drawings.

7 (a) and 7 (b), the drive lever 14 of the torque wrench 13 of the present invention comprises a first lever 1 and a second lever 2. First lever 1
Is rotatable with respect to the main shaft 9 and the second lever 2
Is configured to rotate integrally with the main shaft 9 via a set screw 10. The rotational force applied to the first lever 1 is
The rotational force transmitted to the second lever 2 via the intermediate structure 15 composed of the coil spring 5, the metal fittings 3, 6, and the spring mounting metal 4 is tightened via the main shaft 9. Rotate the target screw. The function of the intermediate structure 15 is composed of the following two steps. The function of the first stage is to transmit the rotational force via the spring 5 and to give the screw a certain rotation angle. The stroke of the first stage is until the end faces 5 ′, 6 ′ of the metal fittings 3, 6 come into contact with each other. The torque value and the rotation angle value during this time are read by the displacement sensor 7 as electric signals. The read electrical signals of the torque value and the rotation angle value are sent to the calculation / display device 11.

The function of the second stage is to transmit the rotation by the contact of the metal fittings 3 and 6 without the action of the spring 5.
At this stage, it is a movement as a normal torque wrench in which the first and second levers 1 and 2 work integrally. Since the torque value appears as a compression strain of the metal fitting 6, the compression strain is read as an electric signal by a strain gauge 16 attached to the metal fitting 6. The electric signal of the torque value thus read is sent to the calculation / display device 11.

The spring 5 is preliminarily provided with a compressive force slightly larger than a force corresponding to a torque when the screw fastening member generates an axial force falling within the proportional range. Until the proportional range is reached, the spring 5 does not contract, and the screw is tightened with the first and second levers 1 and 2 remaining unchanged. Before the first stage starts, a snug point alignment is performed with a screw system serving as a control standard. That time is shortly after the fastener enters the proportional range, and is represented by line XX in FIG. After passing this line, the first stage starts. That is, X
-X-ray is the same movement as a general hand wrench,
Not controlled.

In the first step described above, the reading of the fastening triangle elements of the screw fastener is performed. For this reason, the rotation angle (screw rotation angle) at this stage is limited to a certain angle δ. The torque value during this period is determined both for the initial value and the final value. This can be achieved by systematically setting the pre-applied compression force of the spring 5 and adjusting it to suit the intended use.

From the rotation angle value and the torque value in the first stage,
The proportional relationship of the screw fastener is read, and a tightening triangle of the screw fastener is determined. This is because the two small △ A ₂ B ₂ D ₂ and △ A ₁ B ₁ C ₁ determined in the first stage are similar to △ ABD and △ ABC, respectively. If the proportional relationship cannot be read,
It is necessary to reconsider the initial setting of the tool (the first stage angle and torque).

The second step is to determine the target torque or the target rotation angle with respect to the target axial force by using the proportional relationship of the tightening triangle read out in the first step, and realize it. In this tool, the torque method and the rotation angle method are compatible as one tightening action.

FIG. 11 is a diagram for explaining the control operation, and the basic principle is exactly the same as in FIGS. In a general screw fastening body, a proportional relationship among the axial force f, the torque T, and the screw rotation angle θ does not hold up to the snag point, and cannot be a controlled object. The position of the snug point is considered to be unique to each screw fastener. In general, it is considered that the time point (XX line) at which the snag point is reached is within about 30% of the target axial force (or torque).

Axial force f in FIG.₀Initial tightening up to
Is out of control. XX line is the line of the snug point
The axial force f₁Is the starting line of the first stage. And
Axial force f _TwoIs the end line of the first stage. This start line
And the torque value at the end line, and the rotational angle difference δ between them
Is set in advance in this torque wrench. That
Therefore, the spring mounting bracket 4 is adjustable.

The Lθ line in FIG. 11 shows the rate of change of the rotation angle with respect to the axial force, which is obtained by converting the read torque value into a rotation angle value. This rate of change is based on the small ΔAθ ₁ Aθ ₂ D ₂ in the first stage, Δ
Obtained from θ / ΔT. Here, Δθ has the same value as δ. Further, the torque coefficient of the fastening body can be determined from the triangle. The torque coefficient is ΔT / Δf / thread diameter.

If a tightening triangle is obtained and the torque coefficient and the rotation angle value Δθ / ΔT with respect to the torque are known, the torque and the rotation angle corresponding to the target axial force can be obtained, so that the axial force can be controlled. When the torque coefficient can be read, it is preferable to determine whether to continue the tightening operation or to use the torque coefficient stabilizer depending on the value of the read torque coefficient.

<Second Embodiment> In the case of a nutrunner A nutrunner 30 as shown in FIGS.
An example in which the present invention is applied to will be described below. This nut
Also in the case of the runner 30, the tightening control method is basically the same as in FIG.
Therefore, the differences will be mainly described. (1) Starting point of control The feed state before the screw is seated and the non-proportional area at the beginning of tightening
Is a process that is not necessary for tightening control. Therefore, control
Do not read data for For that,
Control to about 30% of the target axial force as in the case of the Lucent's wrench
Starting line (axial force f ₀Is set. This start
Start reading the torque value and the rotation angle value from the line.

(2) Regarding the torque value Here, as shown in FIG.
An example is shown in which the strain gauge 32 is attached and the torque value is read. However, the present invention is not limited to such a configuration. For example, a configuration in which a reaction force is read from components inside the nut runner is possible. The internal component is, for example, the outer surface of the internal gear 33 of the planetary reduction gear device. As another method, if the performance of the motor 34 is stable, it can be determined by an experiment similarly to the gear device. Further, depending on the condition of the member to be fastened, it can be determined from the force for stopping the rotation of the member to be fastened. Since the reaction force receiver 31 is also necessary for reading the screw rotation angle, the example in which the strain gauge 32 is attached to the reaction force receiver 31 has been described with reference to FIG. Further, as in the case of the first embodiment, it is possible to determine the converted values of the torque value and the rotation angle value by partial measurement in the proportional range.

(3) Reading of the rotation angle The rotation angle of the hand-held power wrench utilizing the static force is read by combining the screw rotation angle and the hand movement angle of the wrench if the wrench body shakes. . Therefore, as shown in FIG. 12A, the camera shake is prevented from occurring in the reaction force receiver 31, or the rotation angle of the screw fixed to the member to be fastened (or integrated with the member to be fastened) is read. Means are needed. Also, the partial measurement method using the torque wrench of the first embodiment can be used. The tightening triangle for the nutrunner is shown in FIG.

<Third Embodiment> In the case of an impact wrench An embodiment in which the present invention is applied to an impact wrench such as an impact wrench or an oil pulse wrench will be described using the impact wrench 40 in FIG. 14 as an example.

FIG. 14 is a longitudinal sectional side view of a main part of the impact wrench of the third embodiment. The impact wrench and impact wrench described below are all hand-held.
In the figure, an air motor 41 is provided inside a casing of a handle on the rear lower surface of the impact wrench 40. A rotary cylindrical member 44 is integrally connected to a front end of a drive shaft 43 of the air motor 41. The central portion of the rotating cylindrical member 44 in the disk-shaped rear wall plate is integrally connected to the drive shaft 43 by a fitting structure of square irregularities.

As is well known, the air motor 41 supplies compressed air from the outside through an air supply passage (not shown) provided in the handle, and operates an operation lever and a switching valve (not shown). Is operated to rotate rightward or leftward by compressed air at a high speed. Then, as is well known, the tip of the casing projects forward from the front end of the casing via a striking force transmission mechanism 45 described below, through a striking force transmission mechanism 45 which rotates integrally with the rotation of the drive shaft 43 of the air motor 41. By transmitting the light to a driven shaft 46 called an anvil, the screw attached to a socket body (not shown) attached to the tip of the driven shaft 46 is tightened.

The rear portion of the driven shaft 46 is formed in a large-diameter body portion, which is provided at the center of the rotary cylindrical member 44. The rotating cylindrical member 44 rotates around the body of the driven shaft 46, and as described above, the striking force transmitting mechanism 45
The torque is transmitted to the driven shaft 46 through the shaft. 14 and FIG.
As shown in FIG. 6, the striking projection 45 a protruding inward at an appropriate position on the inner peripheral surface of the rotary cylindrical member 44 and the semicircular support groove formed on the body of the driven shaft 46 swing right and left. And an anvil piece 45b freely supported.
The rotation force of the rotary cylindrical member 44 is transmitted to the driven shaft 46 by causing the hitting protrusion 45a to collide with the upper end surface of the anvil piece 45b while tilting the anvil piece 45b in the left-right direction. ing.

As shown in FIG. 17, when the cam plate 45c is located at the front end of the anvil piece 45b on the inner peripheral surface of the front end of the rotary cylindrical member 44, the anvil piece 45b is located in a concave portion having a constant arc length in the circumferential direction. In addition, while maintaining the neutral posture in which the striking projection 45a is not engaged, and moving while contacting the inner peripheral surface of the rotating cylindrical member 44 outside the concave portion, the inclined posture is such that it collides with the striking projection 45a. Further, the anvil piece 45b is an anvil piece pressing member provided in the body of the driven shaft 46, a spring,
A force is always applied by the spring receiving member in the direction of the neutral position, and the spring receiving member is in contact with the inner peripheral cam surface of the rotary cylindrical member 44. Further, on the inner peripheral surface of the rotating cylindrical member 44, concave portions are formed on both sides of the striking projection 45a to allow the anvil piece 45b to tilt. Since the structure of such an impact wrench is known, detailed description is omitted. Also, here, the description has been given of a configuration in which one impact is generated per rotation. However, a hand-held impact having a configuration in which two impacts are generated per rotation or a configuration in which three or more impacts are generated is performed. It goes without saying that the same can be applied to a wrench.

On the outer peripheral surface of the rear end of the rotary cylindrical member 44, a detection rotary member 47 composed of a gear body provided with a predetermined number of teeth 47a as shown in FIG. 15 is integrally fixed. On the other hand, a pair of detection sensors 48a and 48b composed of semiconductor magnetoresistive elements are attached to the inner peripheral surface of the casing on the non-rotating side facing the detection rotator 47 at a constant interval in the circumferential direction. ing. The rotation of the detection rotator 47 is detected by a detection sensor 48.
a, 48b, and the output signal is detected by the detection sensor 48.
It is configured to input to an input circuit 50 that is electrically connected to a and b. The input circuit 50 supplies compressed air via an amplification unit 51, a waveform shaping unit 52, a central processing unit 53, a rotation angle signal output unit 54, a screw tightening completion detection unit 55, a solenoid valve control unit 56, and an output circuit 57. Solenoid valve provided in hose 58
Connected to 59.

In the impact wrench configured as described above, the rotation angles of the screws such as bolts and nuts are read as follows. First, a screw (not shown) to be tightened is mounted on a socket body attached to the tip end of the driven shaft 46, and a predetermined screw tightening angle is input to the screw tightening completion detecting unit 55 in advance. After that, the solenoid valve 59
The compressed air is supplied to the impact wrench 40 by pressing the operation lever of the impact wrench 40, and the air motor 41 is rotated in the screw tightening direction (clockwise in the case of a right-handed screw). The cylindrical member 44 rotates integrally. And, by the rotation, the cam plate 45C
Moves while contacting the inner peripheral surface of the rotating cylindrical member 44 from the concave portion, the anvil piece 45b tilts, and the frictional resistance between the spring receiving member and the inner peripheral cam surface causes the rotating cylindrical member 44 and the driven shaft 46 Rotate integrally and rotate the screw in the tightening direction at a high speed to advance.

While the screw is rotating and moving forward, that is,
Until seating on the bearing surface, almost no load is applied to the driven shaft 46 side, and the detection rotating body 47 composed of a gear body that rotates integrally with the rotating cylindrical member 44 also rotates at a high speed in the screw tightening direction. The teeth 47a continuously pass over the detection sensors 48a and 48b. At this time, the detection sensors 48a and 48b generate a pulse signal having a waveform shifted in phase, but this pulse signal is not used for calculation for angle detection until the user is seated.

When the driven shaft 46 rotates at high speed integrally with the rotary cylindrical member 44 via the striking force transmitting mechanism 45 composed of the striking projection 45a and the anvil piece 45b, and when the screw is seated on the tightening seat surface, the driven shaft is rotated. When a resistance torque (load) is generated in the driven shaft 46, the rotation of the driven shaft 46 rapidly approaches the stop, and the striking projection 45a
And the anvil piece 45b collide with each other, and hitting is started. After the impact is completed, the elastic force of the spring pressing the anvil piece 45b overcomes the engaging force between the impact projection 45a and the anvil piece 45b, and the engagement is released, and the rotary cylindrical member 44 is released.
Runs free around the body of the driven shaft 46. During the free running, the rotating cylindrical member 44 is accelerated by the rotational driving force of the air motor 41, while
8. As shown in FIG. 19, the cam plate 45C contacts the inner peripheral surface of the rotary cylindrical member 44, and the anvil piece 45b is tilted.
After free running, as shown in FIG. 20, the striking projection 45a is impactedly engaged with the anvil piece 45b, and the striking force transmits the rotating force of the rotary cylindrical member 44 to the driven shaft 46 to thereby drive the driven shaft 46. The shaft 46 is rotated by a certain angle in the tightening direction. The tightening angle at this time is detected by the detection rotator 47 and the detection sensors 48a and 48b.

When the screw is tightened, a resistance force greater than the rotation force of the air motor 41 is generated on the driven shaft 46 side.
At the moment when the driven shaft 46 has been rotated in the tightening direction by a certain angle by the impact force of the impact projection 45a, the rotating cylindrical member
After 44 rebounds in the direction opposite to the tightening direction as shown in FIG. 21, free-runs in the tightening direction by the rotational driving force of the air motor 41, and again strikes the striking projection 45a with the anvil piece 45b in the same manner as described above. Then, the driven shaft 46 is further rotated in the tightening direction. The screw rotation angle at this time is read by the detection rotator 47 and the detection sensors 48a and 48b, and thereafter, every time the impact projection 45a collides with the anvil piece 45b after the rotating cylindrical member 44 performs free running, the screw at that time is used. Detect the rotation angle. In addition, the applicant,
A method for reading a screw rotation angle which is hardly affected by hand shake in a hand-held impact wrench for reading the screw rotation angle having the above-described configuration has already been filed.
1-229277). The influence of camera shake on the screw rotation angle detected by this method is extremely small. Therefore, a tightening triangle is read based on the screw rotation angle, and axial force control is performed based on the read tightening triangle in the same manner as in the case of static tightening.

[0052]

According to the tightening control method of the present invention, the elastic angle coefficient and the snug point of the screw system are obtained prior to the tightening operation using the tightening triangle, and these are used as the standard of the axial force control. Since the tightening is controlled, the axial force can be controlled regardless of the elasticity of the member to be fastened. It also provides guidelines for determining the appropriateness and probability of fastening work. In this way, for the first time, practical axial force control of screw tightening became possible. As long as the elastic angle coefficient of the screw system is known, the axial force control can be performed on the screw fastener whose elastic angle coefficient is unknown while reading the elastic angle coefficient in real time. Further, it becomes possible to control the tightening of the screw while avoiding the difficulty of knowing the torque coefficient for a used screw fastener. Further, it has become easy to easily perform fastening of a screw having an outer diameter of about 18 mm or more under control. In addition, it has become possible to prevent insufficient tightening, which is the biggest problem in screw tightening. Further, by specifying the design axial force of the screw, it is possible to contribute to a design for reducing the size and weight of the device and the screw structure. It is also a useful tool for raising awareness of the purpose of screw tightening work. In addition, because of the axial force control, it is possible to provide the tightening control means to a repair / maintenance market where quality control is not perfect. And
Since the control is performed based on the tightening result, it is possible to eliminate the influence on the tightening due to a defect on the tool side. A tool-side defect is a mismatch of capabilities, where the capabilities are too high or too low. In addition, it is possible to eliminate the influence on the tightening due to the fluctuation of the supplied voltage and air pressure, the deterioration state of the tool, and the level of skill of the operator. In addition, it is possible to determine whether or not it is necessary to use a larger tool by verifying the nonconformity state on the tool side.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a typical tightening triangle.

FIG. 2 is an explanatory view of a typical tightening triangle.

FIG. 3 is an explanatory view of a typical tightening triangle.

FIG. 4 is a view showing actual measured values of bolts and nuts;

FIG. 5 is a diagram illustrating a process of forming a fastening triangle.

FIG. 6 is a diagram illustrating a process of forming a fastening triangle.

FIG. 7 is a diagram illustrating a process of forming a fastening triangle.

FIG. 8 is a diagram illustrating a process of forming a tightening triangle.

FIG. 9 is a view for explaining tightening accuracy.

FIG. 10 is a schematic explanatory view of a torque wrench used in the present invention.

FIG. 11 is an explanatory view of a tightening triangle in the case of a torque wrench.

FIG. 12 is a schematic explanatory view of a nut runner used in the present invention.

FIG. 13 is an explanatory diagram of a tightening triangle in the case of a nut runner.

FIG. 14 is a vertical sectional side view of an impact wrench.

FIG. 15 is a longitudinal sectional front view of a main part of FIG. 14;

FIG. 16 is a longitudinal sectional front view of a striking force transmission mechanism including a striking projection and an anvil piece.

FIG. 17 is a longitudinal sectional front view of a cam plate portion for operating an anvil piece.

FIG. 18 is a longitudinal sectional front view of a striking force transmission mechanism during free running.

FIG. 19 is an operation state diagram of the cam plate.

FIG. 20 is a vertical sectional front view at the time of impact.

FIG. 21 is a longitudinal sectional front view at the time of rebound.

[Explanation of symbols]

 11 Calculation / display device 13 Torque wrench 14 Drive lever 15 Intermediate structure 7 Displacement sensor 30 Nut runner 40 Impact wrench

Claims (5)

[Claims] The present invention detects a screw rotation angle or a tightening torque with the progress of a screw fastening operation, reads that the screw fastening body has entered a proportional area, determines a proportional origin, and determines a proportional origin. Using the proportional constant known in advance in the screw system, the screw rotation angle is divided into the elongation component of the screw system and the shrinkage component of the member to be fastened, and a tightening diagram is displayed in the form of a triangle with the axial force as the main column. A proportional area screw tightening control method, wherein the tightening axial force of the screw is controlled using the tightening diagram. (However, the thread system refers to a combination system of a bolt and a nut or an alternative female screw.) 2. In a screw tightening control using a static force, a screw rotation angle and a tightening torque are detected in parallel with a progress of a screw tightening operation, and it is determined that the screw tightened body has entered a proportional range. Read, determine the origin of proportionality, and divide the screw rotation angle into an elongation component of the screw system and a contraction component of the member to be fastened using the proportional constant known in advance in the screw system of the screw fastening body, A proportional area screw tightening control method, comprising: determining a tightening diagram represented by a triangle having a main column as a main column; and controlling the tightening axial force of the screw using the tightening diagram. (However, screw tightening using static force refers to screw tightening with static force using a manual wrench or power wrench.) 3. When both the tightening torque and the screw rotation angle cannot be read simultaneously and continuously, both the tightening torque and the screw rotation angle are partially read, and the tightening torque of the screw fastener is converted into the screw rotation angle. 3. The proportional area screw tightening control method according to claim 2, wherein a tightening diagram represented by a triangle is determined thereby, and the tightening axial force of the screw is controlled using the tightening diagram. 4. The method according to claim 1, wherein the quality of the fastening operation is determined based on a torque coefficient calculated from a tightening torque and an axial force in the screw fastening. Proportional area screw tightening control method. 5. An elastic coefficient Ka of a screw system, an elastic angle coefficient Kb of a member to be fastened, and an elastic angle coefficient K of a screw fastener in a tightening diagram represented by a triangle having an axial force as a main column.
4. The proportional area screw tightening method according to claim 1, wherein the quality of the fastening operation is determined based on the value of b / Ka or K / Ka.