JP3754542B2 - Screw tightening method, screw tightening device, attachment and recording medium - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention prevents the rotation of the non-rotating screw member that is one of the two screw members and rotates the rotating screw member that is the other of the two screw members in a state where the male screw member and the female screw member are screwed together. Thus, the present invention relates to a method and an apparatus for fastening both screw members with an object to be fastened in between, and in particular, to improvement of management accuracy of fastening force.
[0002]
[Prior art]
When the object to be tightened is tightened by the male screw member and the female screw member, there are a case where there are a plurality of objects to be tightened and a case where there is a single object. For example, when a bolt (this is a male screw member) passing through a through-hole of an object to be tightened is tightened into a member in which an internal thread hole is formed (this is an internal thread member), the object to be tightened becomes an internal thread. When tightened to a member, the number of objects to be tightened is often singular. However, when tightening is performed using a headed bolt and nut as male and female screw members, respectively, multiple objects are to be tightened. It becomes a piece. In addition, when a to-be-tightened member is fastened with a nut to the member to which the stud bolt is attached, the member to which the stud bolt is attached is considered as a male screw member. In this case, the number of objects to be tightened is often singular. In tightening, the male screw member may be rotated and the female screw member may be rotated, and the screw member on the opposite side needs to be prevented from rotating. In this specification, the screw member on the side to be rotated is referred to as a rotating screw member, and the screw member on the side to be prevented from rotating is referred to as a non-rotating screw member.
[0003]
When tightening the screw member, the tightening force that is the axial force of the male screw member should be managed. However, since it is difficult to detect the tightening force, the “screw tightening” of JIS B 1083 is usually used. It is managed by the “torque method”, “rotation angle method”, “torque gradient method”, etc. defined in “General Rules”. Among these, in the case of the “torque gradient method”, the tightening force management accuracy is such that the friction coefficient between the screw surfaces of the male and female screw members (referred to as the friction coefficient between the screw surfaces) and the bearing surface of the rotary screw member. Although it is not affected by the coefficient of friction with the bearing surface of the object to be tightened (referred to as the coefficient of friction between the bearing surfaces), when the “torque method” and “rotation angle method” are used, the friction coefficient to be influenced. Conventionally, the coefficient of friction between the screw surfaces and the coefficient of friction between the bearing surfaces have been measured in advance, and the tightening force has been managed using them. It depends. It is affected by the surface roughness and hardness of the threaded surface and the bearing surface, and the lubrication status. Since these are usually not constant, the variation in the tightening force becomes large and the reliability of the tightening force management is sufficient. I could not say.
[0004]
At the time of screw tightening, at least one of a spring washer and a flat washer is usually disposed between the seat surface of the rotating screw member and the seat surface of the object to be tightened. Normally, slip occurs between the rotating screw member and the washer during the rotation of. Therefore, in the following description, the washer is regarded as a part of the object to be tightened, the seat surface of the washer is regarded as the seat surface of the object to be tightened, and the presence of the washer will be ignored. In addition, the spring washer may rotate integrally with the rotating screw member, and in this case, the seating surface that contacts the seating surface of the spring washer to be tightened should be regarded as the rotating screw member. However, in practice, there is no problem even if it is assumed that the sliding is between the rotating screw member and the washer.
[0005]
[Problems to be Solved by the Invention, Problem Solving Means, Functions and Effects]
In view of the above circumstances, the present invention has been made with the object of improving the reliability of tightening force management.
According to the present invention, there are provided a screw tightening method, a screw tightening device, an attachment for tightening force management, a recording medium for tightening force management, a friction coefficient related amount acquisition method, a friction coefficient related amount acquisition device, etc. can get. As with the claims, each aspect is divided into sections, each section is numbered, and is described in a form that cites the numbers of other sections as necessary. This is to clarify the possibility of combining the features described in each section.
(1) In a state where the male screw member and the female screw member are screwed together, the rotation of the non-rotating screw member which is one of the two screw members is prevented, and the rotating screw member which is the other of the two screw members is rotated. The method of tightening both screw members with the object to be fastened in between,
In an initial stage in which the seat surface of the rotating screw member does not contact the seat surface of the object to be tightened, the rotating screw member is rotated while applying a first axial force to the rotating screw member, and a rotational resistance torque is detected. A screw that determines a tightening end condition based on at least the detected initial stage torque that is the initial stage rotational resistance torque and the first axial force, and that ends the tightening when the tightening end condition is satisfied Tightening method (Claim 1).
Here, “the seating surface of the rotating screw member” and “the seating surface of the object to be tightened” are literally their seating surfaces when the rotating screw member and the object to be tightened are in direct contact with each other. If at least one of a spring washer and a flat washer is provided, two seat surfaces that cause slip when the rotating screw member rotates (the seat surface of the rotating screw member and the seat surface of the rotating screw member as described above), unless otherwise specified. It is assumed that the bearing surface of the washer that comes into contact is the “seat surface of the rotating screw member” and “the seat surface of the object to be fastened”, respectively. However, a washer (especially a spring washer) is provided mainly for the purpose of preventing loosening of the screw, whereas when the screw is tightened by the method of the present invention, the tightening force is not increased. Proper management makes it difficult for screws to loosen, reducing the need for washers. In some cases, the washer can be omitted.
The initial stage torque detected as described above is affected by the coefficient of friction between the screw surfaces of both screw members. If the nominal diameter (or effective diameter) and lead angle (or pitch) of both screw members are the same and the first axial force applied to the rotating screw member is the same, the larger the coefficient of friction between the screw faces, the earlier the stage The torque increases. And, the larger the friction coefficient between screw surfaces, the larger the tightening torque required to obtain the same tightening force. Therefore, when managing the tightening force using the torque method, the larger the initial stage torque, the higher the target If the tightening torque (tightening torque at which tightening should be finished) is set large, the influence of the friction coefficient between screw surfaces can be reduced. When the tightening force is managed by the rotation angle method, the effect of the coefficient of friction between screw surfaces is increased by setting the starting point torque, such as the snag point, which is the starting point for measuring the rotation angle, as the initial stage torque increases. Can be reduced. According to the experiment, the evaluation accuracy of the coefficient of friction between the screw surfaces improves as the first axial force applied to the rotating screw member increases. In particular, when a spring washer is provided between the seating surfaces of the rotating screw member and the article to be fastened, it is desirable that the first axial force is large enough to bring the spring washer into close contact.
In determining the tightening end condition, the initial stage torque itself is used as a kind of friction coefficient related quantity related to the friction coefficient between the screw faces, and the tightening end condition is determined from the initial stage torque. The friction coefficient may be estimated, and the tightening end condition may be determined using the estimated friction coefficient. Even if the coefficient of friction between screw surfaces is evaluated, it is not always necessary to estimate the coefficient of friction between screw surfaces.
(2) The screw tightening method according to item (1), wherein the first axial force is a force in a direction in which the seat surface of the rotating screw member approaches the seat surface of the article to be tightened.
Rotational resistance torque of the rotary screw member is detected while applying a first axial force (referred to as tensile force) in a direction to separate the seat surface of the rotary screw member from the seat surface of the object to be fastened. However, although the coefficient of friction between the screw surfaces can be evaluated, as in this embodiment, the rotating screw member
In many cases, it is desirable to detect the rotational resistance torque of the rotating screw member while applying a first axial force (referred to as a compressive force) in a direction that causes the seat surface to approach the seat surface of the object to be tightened. For example, in order to apply a compressive force to a rotating screw member, a screw engaging portion (referred to as a wrench member) of a screw tightening device may be brought into contact with the rotating screw member. Sockets, hexagonal bars, etc. can be used as they are, but in order to apply a tensile force, it is necessary to use a wrench member having a special structure as will be described later in the section of the embodiment. . Further, depending on the structure of the wrench member, the shape of the rotating screw member needs to be different from the normal shape. Furthermore, when a compressive force is applied, the friction coefficient between the seating surfaces of the rotating screw member and the object to be tightened can be evaluated as described below, but this is evaluated when a tensile force is applied. Can not do it.
(3) The rotational resistance torque is detected even in an intermediate stage where the seating surface of the rotating screw member is in contact with the seating surface of the object to be fastened and the screw surfaces of both screw members are not substantially in contact. The screw tightening method according to item (2), wherein the tightening end condition is determined based on the detected intermediate stage torque.
As in this aspect, if the coefficient of friction between the seating surfaces is evaluated in addition to the coefficient of friction between the screw surfaces, and it is taken into consideration in determining the tightening end condition, the management accuracy of the tightening force can be further enhanced. The configuration of the axial force applying device is simplified by making the magnitude and direction of the first axial force applied to the rotating screw member in the initial stage and the second axial force applied in the intermediate stage the same. Desirable but not essential. At least one of the magnitude and direction of the axial force may be changed between the initial stage and the intermediate stage. In the initial stage, the axial force is used as the tensile force, and the reaction force is easily transmitted to the non-rotating screw member. An example is a mode of being received by itself.
In order to apply an axial force to the rotating screw member, various axial force applying devices described later can be used. However, when a screw is tightened by a screw tightening device that is held in hand, the screw It is also possible to apply an axial force depending on the weight of the tightening device, or to apply an axial force to the rotating screw member by an operator applying an axial force to the screw tightening device. If the axial force and the rotational resistance torque at the same time are used, the coefficient of friction between the thread surface and the seating surface can be evaluated without hindrance, and the axial force does not necessarily have to be kept constant.
Further, the axial force may be intentionally changed during one screw tightening. For example, the rotational resistance torque for each magnitude of axial force is detected while changing the axial force, and the coefficient of friction between the threaded surface and the seating surface for each of a plurality of combinations of axial force and rotational resistance torque. And the average value can be used to determine the tightening end condition. Also, the friction coefficient may change according to changes in the axial force. In this case, the friction coefficient-related quantities for a plurality of axial forces are acquired, and extrapolation (extrapolation) based on them. Alternatively, the friction coefficient related quantity for the desired axial force can be acquired by interpolation (interpolation). Furthermore, after evaluating the friction coefficient, it is possible to change the axial force in consideration of workability and the like, such as releasing or reducing the axial force.
As described above, when the friction coefficient varies depending on the axial force, the closer the axial force applied to the initial stage and the intermediate stage is to the target tightening force, the more accurate the tightening force management is. Since an increase in the axial force often leads to an increase in the size of the apparatus and a decrease in workability, it is desirable to determine the axial force in consideration of both.
In addition, it is not always necessary to keep the rotational speed of the rotating screw member constant. For example, in the initial stage or the intermediate stage (especially in the intermediate stage where the time during which the rotational resistance torque can be detected is short), the rotational speed can be reduced to facilitate the evaluation of the friction coefficient, or conversely, the speed reduction of the speed reducer Instead of increasing the ratio and decreasing the rotational speed, a large tightening torque can be obtained.
(4) The tightening end condition is that the actual rotational resistance torque is equal to a target tightening torque determined based on at least the initial stage torque, according to any one of (1) to (3) The described screw tightening method.
This aspect corresponds to management of the tightening force by the “torque method”.
(5) The rotation angle of the rotating screw member from when the actual rotation resistance torque reaches the starting point torque determined based on the initial stage torque as the tightening end condition is determined by the male screw member and the object to be tightened. The screw tightening method according to any one of (1) to (3), which is equal to a target rotation angle determined on the basis of an elastic coefficient and a target tightening force.
This aspect corresponds to management of the tightening force by the “rotation angle method”. However, the starting point torque is not limited to the snag point in the conventional “rotation angle method”, and the bearing surfaces of the rotating screw member and the object to be tightened and the screw surfaces of both screw members are in contact with each other. It is also possible to use the rotational resistance torque at the end of the intermediate stage, which is the boundary point between the final stage where the tightening force increases and the intermediate stage, or the rotational resistance torque set slightly higher than the snag point as the starting torque. .
The management accuracy of the tightening force by the screw tightening method of this aspect greatly depends on the setting accuracy of the starting point torque. Although it is desirable to set the starting point torque to the lower limit of a range in which the rotation angle and the rotational resistance torque are certain to be in a proportional relationship, it is relatively difficult to accurately detect the lower limit of the proportional range. is there. Therefore, first, a lower limit value of the tightening force that is guaranteed to be in the proportional range (for example, a tightening force that ensures that the contact state between the screw surfaces and between the bearing surfaces reaches a stable state) is determined. By setting the starting point torque based on at least the former of the lower limit value of the tightening force and the initial stage torque as the friction coefficient related amount between the screw surfaces and the intermediate stage torque as the friction coefficient related amount between the bearing surfaces, The screw tightening method of this aspect is to improve the accuracy of tightening force management by the “rotation angle method”.
(6) A casing that rotatably holds a wrench member that engages with the rotary screw member in a relatively non-rotatable manner is applied to the object to be tightened, and a reaction force of an axial force from the wrench member to the rotary screw member is applied. The screw tightening method according to any one of (1) to (5), wherein the tightening is performed by engaging in a transmittable state.
If the axial force applied to the rotating screw member is a tensile force, the reaction force of the tensile force can be reduced by simply bringing the casing or an integral member into contact with the surface of the object to be tightened. Via the non-rotating screw member. On the other hand, when the axial force applied to the rotating screw member is a compressive force, the casing or an integral member is engaged with the object to be tightened so that the casing is not separated from the object to be tightened. is required. In addition, the object to be tightened must not move to the casing side together with the casing (this is called lifting of the object to be tightened). This is because a sufficient compressive force cannot be applied to the rotating screw member once the object to be tightened is lifted. If the weight of the object to be tightened is greater than the compressive load to be applied to the rotating screw member, place the casing above the object to be tightened and place the casing on the object to be tightened against the object to be tightened. If it is engaged so as not to move relatively upward, the object to be fastened will not be lifted even if a sufficient compression force is applied to the rotating screw member. However, if the object to be tightened is light in weight, for example, temporarily tighten the object to be tightened as in the next section, or hold it with a special jig or another heavy object so that it does not rise. Is required. The above has been described assuming that the object to be tightened is tightened downward, but if the object to be tightened is temporarily tightened or pressed with a dedicated jig as described above, the object to be tightened is It can also be tightened.
Note that the term wrench member includes not only a narrow wrench member such as a socket or a hexagonal bar that directly engages with a rotating screw member, but also an output shaft that includes an angular drive of a screw tightening device such as an impact wrench. Used as a broad term. It is also possible to paraphrase the wrench member as the output member of the screw tightening device. In this case, the output member is an output shaft having a socket part or a hexagonal bar part having a hexagonal hole at the tip, and a direct rotation screw member. When engaging with a hexagonal head or a hexagonal hole, the output shaft can be said to be a wrench member in a narrow sense. On the other hand, when the output member is an output shaft only having a mounting part such as a socket such as a square drive part at the tip, it can only indirectly engage with the rotating screw member via the socket, It is hard to say that it is a wrench member in a narrow sense. However, if the indirect engagement with the rotating screw member is also considered to be engagement, the output shaft itself can be considered as a wrench member in a broad sense, and one in which a socket or the like is attached to the output shaft is one. When considered as a member, a member in which these output shafts and sockets are combined can be said to be a wrench member in a narrow sense.
(7) The object to be tightened is tightened by a plurality of pairs of the screw members.
A to-be-tightened object is temporarily tightened by at least one of the plurality of pairs of screw members, and a wrench member engaged with the rotating screw member in a relatively non-rotatable manner is rotatably held on the to-be-fastened object. The casing is engaged in a state in which the reaction force of the axial force from the wrench member to the rotating screw member can be transmitted, and at least one of the plurality of pairs of screw members is (2) to (5) After tightening by any one of the methods, once tightened the screw members that were temporarily tightened,
Screw tightening method to retighten by any one of the methods of (2) to (5).
According to this method, it is possible to fasten a lightweight article to be fastened in a lateral direction or an upward direction without using a dedicated jig. In general, since the object to be tightened is tightened by a plurality of pairs of screw members, the tightening method of this aspect can be employed in most cases. When a plurality of female screw holes are formed in one member, it is assumed that the single member is formed by integrally forming a plurality of female screw members.
(8) In a state where the male screw member and the female screw member are screwed together, the rotation of the non-rotating screw member which is one of the two screw members is prevented, and the rotating screw member which is the other of the two screw members is rotated. Is a device for tightening both screw members with an object to be fastened in between,
A rotary drive device for rotating the rotary screw member;
The rotary screw member is being rotated at least at an initial point when the rotary screw member is rotating by the rotary drive device and the seat surface of the rotary screw member does not contact the seat surface of the article to be tightened. An axial force applying device for applying a first axial force;
A torque detector for detecting a rotational resistance torque of the rotary screw member;
At least an initial stage torque that is a rotational resistance torque detected by the torque detection device in the initial stage and in a state where the first axial force is applied by the axial force application device, and the first shaft A tightening end condition determining means for determining a tightening end condition based on the directional force;
Stop command means for issuing a stop command for the rotary drive device when the tightening end condition determined by the tightening end condition determining means is satisfied;
A screw fastening device comprising: (Claim 2).
According to the apparatus of this aspect, the screw tightening method described in the above item (1) can be performed. The axial force applying device may continue to apply the first axial force throughout the initial stage, or may be applied discretely one or more times. The torque detecting device can detect the rotational resistance torque only once. However, if it is detected a plurality of times, the rotational resistance torque with high reliability can be acquired. Further, if automatic stop means for automatically stopping the rotation drive device is provided based on the stop command issued by the stop command means, the tightening is automatically terminated when the tightening force reaches the target tightening force. Ideal, but not indispensable. For example, an alarm such as a buzzer that rings based on a stop command is provided, and the operator stops the rotation drive device in response to the alarm notification. It is also possible to make it.
(9) In the item (8), the axial force applying device applies the first axial force in a direction in which the seat surface of the rotating screw member approaches the seat surface of the article to be tightened. The screw fastening apparatus according to claim 3.
(10) The axial force applying device may be an intermediate stage in which the seat surface of the rotating screw member is in contact with the seat surface of the article to be tightened and the screw surfaces of both screw members are not substantially in contact with each other. A second axial force is applied at least at a temporary point, and the torque detecting device detects an intermediate stage torque that is a rotational resistance torque at least at the temporary point, and the tightening end condition determining means includes: The screw tightening device according to (9), wherein the tightening end condition is determined based on the intermediate stage torque and the second axial force.
(11) The tightening end condition is that an actual rotation resistance torque is equal to a target tightening torque determined based on the initial stage torque. A screw tightening device (claim 7).
(12) The rotation angle of the rotating screw member from when the actual rotation resistance torque reaches the starting point torque determined based on the initial stage torque as the tightening end condition is determined by the male screw member and the article to be tightened. To be equal to the target rotation angle determined on the basis of the elastic modulus and target tightening force
The screw fastening device according to any one of (8) to (10) (claim 8).
(13) The screw tightening device according to any one of (10) to (12), including an intermediate stage detecting means for detecting at least a temporary point of the intermediate stage.
(14) The screw tightening device according to (13), wherein the intermediate stage detecting means detects at least a temporary point of the intermediate stage based on the rotation resistance torque detected by the torque detector.
Since the rotational resistance torque is usually different between the initial stage and the intermediate stage, the intermediate stage can be detected based on the rotational resistance torque. For example, since the rotational resistance torque changes suddenly at the boundary between the two stages, the start time of the intermediate stage can be detected based on the sudden change as in the next section. However, it is not essential to be based on the rotational resistance torque. For example, as described later in the section of the embodiment, at the moment when the seat surface of the rotating screw member abuts on the seat surface of the object to be fastened, Since the force fluctuates (particularly when the rotational speed is high or when the spring washer is not used), the start point of the intermediate stage can be detected based on this fluctuation.
(15) The intermediate stage detection means includes intermediate stage start time detection means for detecting a start time of the intermediate stage by detecting a sudden change in the rotational resistance torque at the time of transition from the initial stage to the intermediate stage ( The screw fastening device according to item 14) (claim 5).
(16) The intermediate stage detecting means
Torque storage means for storing the rotation resistance torque detected moment by moment by the torque detection device;
(14) an intermediate stage end time determination unit that determines an end point of the intermediate stage based on a group of rotation resistance torques stored in the torque storage unit after the rotation resistance torque reaches a set torque; Or the screw fastening apparatus as described in any one of (15) term (Claim 6).
At the time of transition from the intermediate stage to the final stage, the change in the rotational resistance torque is more gradual than at the transition from the initial stage to the intermediate stage, so the transition from the intermediate stage to the final stage is based on the rotational resistance torque. It is not impossible to detect in real time, but it is difficult to detect accurately. On the other hand, it is possible to store the rotational resistance torque every moment in the torque storage means, and later specify the transition point from the intermediate stage to the final stage, that is, the end stage of the intermediate stage, based on the group of the rotational resistance torques. Easy. However, before the tightening force reaches the target tightening force, the corresponding target tightening torque (in the case of the “torque method”) or the target rotation angle (in the case of the “rotation angle method”) is determined. Because it is necessary, it is desirable to determine the end point of the intermediate stage as early as possible. Therefore, it is desirable that the set torque is set as small as possible within a range in which the transition from the intermediate stage to the final stage can be specified. The intermediate stage end time determination means, for example, when the change gradient of the rotational resistance torque with respect to the rotation angle is examined in the direction opposite to the elapsed direction of time, the time point when the change gradient starts to become a set gradient (for example, 0) or less in the middle It is determined at the end of the stage, the point at which the rotational resistance torque reaches the minimum value is determined as the end of the intermediate stage, or is separated in both positive and negative directions in time from the end of the intermediate stage. The time point at which two straight lines defined by a plurality of rotational resistance torques apparently belonging to the stage intersect may be determined as the end point of the intermediate stage.
(17) The tightening end condition determining means may determine the distance between the thread surfaces of the screw members based on the rotational resistance torque detected by the torque detector and the axial force applied by the axial force applying device. Friction coefficient estimating means for estimating at least one of a friction coefficient and a friction coefficient between seating surfaces of the rotary screw member and the object to be tightened, and determining the tightening end condition based on the estimated friction coefficient The screw fastening device according to any one of items (8) to (16) (claim 9).
(18) An axial force detecting device that detects an axial force applied by the axial force applying device, and the friction coefficient estimating means includes the detected axial force and the torque detecting device. The screw tightening device according to (17), wherein at least one of the friction coefficients is estimated based on the detected rotational resistance torque.
If the axial force applied by the axial force application device is a predetermined constant value, the axial force detection device can be omitted, but if an axial force detection device is provided, the axis detected at the same point Since the friction coefficient can be estimated based on the directional force and the rotational resistance torque, it is not necessary to keep the axial force constant, and the effect of increasing the degree of freedom in tightening work can be obtained. Even when the axial force applied by the axial force applying device is a predetermined constant value, the effect of improving the estimation accuracy of the friction coefficient can be obtained by providing the axial force detecting device.
(19) The rotary drive device includes a wrench member that engages with the rotary screw member so as not to rotate relative to the rotary screw member, and a rotary drive source that rotates the wrench member. Any one of (8) to (18) The screw fastening device described in 1.
(20) The axial force applying device is
A reaction force receiving member that cannot move relative to the non-rotating screw member in the axial direction of the screw members at least when tightening the screws;
An axial drive device disposed between the reaction force receiving member and the wrench member and relatively moving the reaction force reception member and the wrench member in the axial direction of the screw members;
A screw tightening device according to item (19), comprising:
A typical reaction force receiving member is the reaction force transmitting member described in the next section. For example, an object on which a screw member is to be tightened is supported by a support base installed on the floor, while the reaction force receiving member. Is fixed to a support frame or ceiling separate from the support base, or is supported via a lifting device such as a hydraulic cylinder as described later in the embodiment section, the reaction force receiving member is not necessarily It is not necessary to engage with either the non-rotating screw member or the object to be tightened in the mode described in the next item.
(21) The reaction force receiving member can transmit a reaction force of the axial force applied to the rotating screw member by the wrench member to one of the non-rotating screw member and the tightened object. The screw member fastening device according to item (20), including a reaction force transmitting member to be engaged.
(22) The screw tightening according to (21), wherein the reaction force transmission member includes a mechanical engagement portion that mechanically engages either the non-rotating screw member or the tightened object. apparatus.
As the mechanical engagement portion, a collet chuck described later in the section of the embodiment, a contact portion of the caliper with the non-rotating screw member, or the like can be employed.
(23) The screw tightening device according to (21), wherein the reaction force transmission member includes a negative pressure adsorbing portion that adsorbs to one of the non-rotating screw member and the article to be tightened by negative pressure.
According to this aspect and the aspect described in the next section, the reaction force transmission member can be engaged with the flat surface of the non-clamped object or the non-rotating screw member so as not to be separated.
(24) The screw tightening device according to (21), wherein the reaction force receiving member includes a magnetic attracting portion that attracts to one of the non-rotating screw member and the tightened object by a magnetic force.
Although it is possible to provide the magnetic attracting portion with a permanent magnet, if it is equipped with an electromagnet, the work of attracting and separating the non-rotating screw member and the object to be fastened can be easily performed.
(25) The axial force applying device is
A load balancer that lifts all the members with a force substantially equal to the weight of all the members that move integrally with the wrench member;
A balancer releasing device for releasing the action of the load balancer;
The screw fastening apparatus according to item (19), including:
At all times, the weight of all the members that move integrally with the wrench member and the acting force of the load balancer are balanced, and the operator can easily move the wrench member to engage the rotating screw member. If the load balancer is released by the balancer releasing device after the engagement, the weight of all the members that move integrally with the wrench member is applied to the rotating screw member as a compressive force. If the weight of all the members that move integrally with the wrench member is increased, a large compressive force can be applied to the rotating screw member, and the weight is always received by the load balancer. Can be avoided.
(26) The axial force applying device is
A length changing device provided between at least a part of the screw tightening device and the wrench member, the length changing device;
A length changer control device for changing the length of the length changer at least once in at least one of the initial stage and the intermediate stage;
The screw fastening apparatus according to item (19), including:
If the length of the length changing device is changed, the wrench member and at least a part of the screw tightening device (referred to as inertia mass part) are separated from each other, but the wrench member is engaged with the rotating screw member. Therefore, it cannot move and the inertial mass part is moved. As a result, an inertial force, which is the product of the acceleration of the movement and the mass of the inertial mass portion, is applied to the rotating screw member as an axial force via the wrench member. If the length of the length changing device is increased, the compressive force is applied to the rotating screw portion, and if the length changing device is decreased, the tensile force is applied to the rotating screw portion. Since the inertia force can be easily made larger than the weight of all the members that move integrally with the wrench member of the screw tightening device, a large axial force can be applied while making the screw tightening device relatively light. It can be added to the rotating screw member. In order to increase the axial force, it is only necessary to increase at least one of the mass and acceleration of the inertial mass part, but in order to accurately evaluate the coefficient of friction between the thread surfaces and between the seat surfaces. The inertial force is preferably maintained for a certain period of time, and the acceleration is preferably maintained at a large value for a relatively long time. However, since this is not so easy, it is desirable that the mass of the inertial mass portion be as large as possible. The length changing device is provided as close to the wrench member as possible, and the screw fastening device can be as much as possible. It is desirable that many parts be made to function as inertial mass parts.
(27) The screw tightening device according to any one of (19) to (26), wherein the rotational drive source is an electric motor.
(28) The screw tightening device according to (27), wherein the torque detection device includes a current-based torque detection device that detects the rotation resistance torque based on a current of the electric motor.
(29) The screw tightening device according to any one of (19) to (26), wherein the rotational drive source is an air motor.
(30) Any one of (19) to (29), wherein the rotational drive device includes an impact torque imparting device that imparts impact torque to the wrench member while transmitting the rotation of the rotational drive source to the wrench member. The screw fastening device described in 1.
In general, when the wrench member is rotated at a constant speed, the evaluation accuracy of the coefficient of friction between the screw surfaces and between the seat surfaces becomes higher, but even when impact torque is applied to the wrench member and the rotational speed of the wrench member fluctuates. There is a certain relationship between the friction coefficient and the rotational resistance torque, and it is possible to evaluate the friction coefficient based on the rotational resistance torque. A larger tightening force can be realized more easily by the impact torque than by the substantially constant tightening torque. However, in order to improve the evaluation accuracy of the coefficient of friction in the initial stage and the intermediate stage, it is desirable to prevent the impact torque from being applied to the wrench member. Therefore, it is desirable that the impact torque applying device does not apply impact torque to the initial stage and the intermediate stage but applies it to the final stage.
(31) The screw tightening device according to any one of (8) to (30), further including a screwing abnormality detecting unit that detects a screwing abnormality of the two screw members based on the initial stage torque.
If a foreign matter is caught between the screw surfaces of both screw members, or if a screwing abnormality occurs such that the screw surfaces of both screw members are not properly screwed, the initial stage torque becomes larger than usual. Accordingly, for example, an allowable range setting means for setting an allowable range of the initial stage torque based on data such as the nominal diameter and pitch of the screw, and when the initial stage torque deviates from the allowable range, it is determined that there is a screwing abnormality. If a screwing abnormality detecting unit including a screwing abnormality determining unit is provided, a screwing abnormality can be detected at an early stage, and an abnormality that stops the rotation driving device according to the determination result of the screwing abnormality determining unit. If the stop means is provided, it is possible to satisfactorily avoid that the tightening is forcibly performed despite the occurrence of the screwing abnormality.
(32) A casing, a wrench member rotatably held in the casing, and a lens
A rotational drive source for rotating the member, and an axial force applying device for applying an axial force to the wrench member, wherein the wrench member is a screw member to be rotated among the male screw member and the female screw member. The rotating screw member is engaged with the rotating screw member so as not to rotate relative to the rotating screw member, and the rotating screw member is rotated so that both screw members are clamped with an object to be tightened between them, and the seating surface of the rotating screw member is tightened. An attachment that is used by being attached to a screw tightening device that applies a first axial force to the rotating screw member by the axial force applying device at least at a temporary point in the initial stage where the attachment surface does not contact. ,
An auxiliary casing attached to the casing;
Rotation that is rotatably supported by the auxiliary casing, has a connecting portion that engages with the wrench member in a relatively non-rotatable manner at the rear end, and a wrench portion that engages in a relatively non-rotatable manner with the rotating screw member at the front end portion. A transmission member;
A torque detection device for detecting torsional torque of the rotation transmission member;
A control device connected to at least the torque detection device, wherein (a) at least
Based on the initial stage torque that is the torsional torque detected by the torque detector at the time when the first axial force is applied by the axial force applying apparatus in the initial stage and the first axial force. Tightening condition determining means for determining the tightening condition, and (b) determining the tightening condition.
A stop command means for issuing a stop command for the rotary drive device when the tightening end condition determined by the fixing means is satisfied;
An attachment for tightening torque management, comprising:
If the attachment of this aspect is attached to a normal screw fastening device, the screw fastening device according to the present invention can be obtained.
(33) In a state where the male screw member and the female screw member are screwed together, the rotation of the non-rotating screw member which is one of the two screw members is prevented, and the rotating screw member which is the other of the two screw members is rotated. According to the control program for managing the tightening torque by a computer when tightening both screw members with the object to be tightened in between,
This is the rotational resistance torque of the rotating screw member in the initial stage in which the seating surface of the rotating screw member does not contact the seating surface of the object to be fastened and the first axial force is applied to the rotating screw member. An initial stage torque detection step for detecting the initial stage torque;
A tightening end condition determining step for determining a tightening end condition based on at least the initial stage torque detected in the initial stage torque detecting step and the first axial force;
A tightening end instruction step for instructing the end of tightening when the tightening end condition determined in the tightening end condition determining step is satisfied;
And a tightening torque management program recorded in a readable manner by the computer (claim 13).
(34) In a state where the male screw member and the female screw member are screwed together, the rotation of the non-rotating screw member which is one of the two screw members is prevented, and the rotating screw member which is the other of the two screw members is rotated. By this, when tightening both screw members with the object to be fastened in between, the friction coefficient related quantity related to the friction coefficient between both screw parts is obtained,
In an initial stage where the seat surface of the rotating screw member does not contact the seat surface of the object to be tightened, the rotating screw member is rotated while applying a first axial force to the rotating screw member, and the rotational resistance torque is detected. A friction coefficient related quantity acquisition method including a process.
An example of how to use this friction coefficient related quantity acquisition method is to acquire the friction coefficient related quantity for one or more appropriate number of rotary screw members by the method of this mode at the beginning of the tightening work of a large number of rotary screw members. Using the acquired friction coefficient related quantity, the conventional “torque method” is used to manage the tightening force of all the rotating screw members.
(35) In a state where the male screw member and the female screw member are screwed together, the rotation of the non-rotating screw member which is one of the two screw members is prevented, and the rotating screw member which is the other of the two screw members is rotated. By this, when tightening both screw members with the object to be fastened in between, the apparatus obtains a friction coefficient related quantity related to the friction coefficient between both screw parts,
A rotary drive device for rotating the rotary screw member;
When the rotary screw member is rotating by the rotary drive device and the seat surface of the rotary screw member is not in contact with the seat surface of the article to be fastened, the rotary screw member is An axial force applying device for applying a uniaxial force;
A torque detecting device for detecting a rotational resistance torque of the rotating screw member in a state where the first axial force is applied by the axial force applying device;
Friction coefficient related quantity acquisition device including
(36) In a state where the male screw member and the female screw member are screwed together, the rotation of the non-rotating screw member which is one of the two screw members is prevented, and the rotating screw member which is the other of the two screw members is rotated. The method of tightening both screw members with the object to be fastened in between,
In the intermediate stage where the seating surface of the rotating screw member is in contact with the seating surface of the member to be fastened and the screw surfaces of both screw members are not substantially in contact, the seating of the rotating screw member is placed on the rotating screw member. The rotational resistance torque is measured by rotating the rotating screw member while applying a second axial force equal to or greater than the set value in the direction in which the surface is pressed against the seat surface of the object to be tightened, and the measurement result of the rotational resistance torque A snag point torque determining step of determining a snag point torque that is a rotational resistance torque of the snag point based on the second axial force;
When the rotation angle of the rotation screw member after the rotation resistance torque of the rotation screw member reaches the snag point torque reaches a rotation angle determined so that the tightening force reaches a desired magnitude A step of stopping the rotation of the rotating screw member;
Screw tightening method including.
In this aspect, in the intermediate stage, the rotating screw member is rotated while applying a sufficient and sufficient compressive force to keep the seating surface between the rotating screw member and the object to be fastened in a stable contact state. By measuring the resistance torque, it is possible to detect the snug point with high accuracy and improve the accuracy of tightening force management by the “rotation angle method”. The technical idea is basically different from each of the above-described aspects in which the management accuracy of the tightening force is improved by evaluating the coefficient. Therefore, the set value of the second axial force is set to a magnitude that is necessary and sufficient for the contact state of the seating surface between the rotating screw member and the article to be tightened to reach a stable state. For example, when a spring washer is provided between the seating surfaces of the rotating screw member and the article to be tightened, the spring washer is set to a size that is necessary and sufficient to bring the spring washer into close contact. When a flat washer is provided between the seating surfaces of the rotating screw member and the object to be tightened, the seating surface of the rotating screw member and the seating surface of the flat washer, the seating surface of the flat washer and the object to be tightened The seating surfaces of each of the seating surfaces are crushed completely by minute projections that may be present on each seating surface and foreign matter that may be caught between the seating surfaces, and contact in substantially the same state as the final tightening state. Is set to a size that is necessary and sufficient.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EMBODIMENTS Hereinafter, a screw tightening apparatus and method according to some embodiments of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 10 denotes a main body frame of the screw tightening device, which is provided with a support base 12 and a bracket 14 attached thereto. A lifting member 18 is attached to the bracket 14 via a linear guide 16 and can be lifted and lowered by a hydraulic cylinder 20. An electric motor with a reduction gear (hereinafter abbreviated as a motor) 22 and a detector 24 are attached to the elevating member 18. The detector 24 includes a torque detection unit and a compression force detection unit. The torque detection unit includes a detection shaft 30 connected to the rotation shaft of the motor 22 as shown in FIG. The four strain gauges 32 are fixed at an inclination of +45 degrees and −45 degrees, and a bridge circuit 34 is formed. A DC power supply 38 is connected to the bridge circuit 34 by two pairs of slip rings 36, and is connected to a voltage detection circuit 42 by another two pairs of slip rings 40. If a torsional torque is applied to the detection shaft 30, a voltage proportional to the torsional torque appears in the voltage detection circuit 42. Although the illustration of the compressive force detector is omitted, two of the four strain gauges are fixed parallel to the axial direction of the detection shaft 30, and the remaining two are fixed parallel to the circumferential direction, It has the same configuration as the torque detector. The compression force may be obtained by calculation by detecting the hydraulic pressure of the hydraulic cylinder 20 with a hydraulic pressure detector. A socket 44, which is a kind of wrench member, is attached to the tip of the detection shaft 30. The operation and operation force of the hydraulic cylinder 20 are controlled by an operation control valve such as the electromagnetic direction switching valve 46 and an operation force control valve such as the electromagnetic pressure control valve 48 shown in FIG.
[0007]
The electromagnetic direction switching valve 46, the electromagnetic pressure control valve 48, the motor 22, the detector 24, and the like are connected to a control device 50. The control device 50 includes an input device 52 and a microcomputer 54 as a processing unit, and the microcomputer 54 is connected to the motor 22, the electromagnetic direction switching valve 46, and the electromagnetic pressure control via drivers 56, 57, and 58. While controlling the valve 48, the detection result is read from the torque detector 60 and the compression force detector 62 of the detector 24. For this purpose, the microcomputer 54 includes a PU 66, a ROM 68, a RAM 70, and an I / O port 72. The ROM 68 stores various control programs including a tightening torque control program shown in FIG. The PU 66 uses the RAM 70 to execute these control programs, and automatically manages the tightening force.
[0008]
As shown in FIG. 1, the present screw tightening device is suitable for tightening a first member 76 and a second member 78 that can be placed on the support base 12 with a rotating screw member such as a bolt 80. In the illustrated example, the first member 76 is a non-rotating screw member, and the second member 78 is an object to be tightened. Prior to the start of the tightening operation, data such as the target tightening force, screw nominal diameter, screw pitch, and set torque of the bolt 80 are input from the input device 52 by the operator or host computer and stored in the RAM 70. Next, the first member 76 and the second member 78 are placed on the support base 12, and the bolt 80 passes through the bolt hole of the second member 78 and is screwed into the female screw hole of the first member 76. . When the preparation for tightening is completed and the start button of the input device 52 of the screw tightening device is pressed, the screw is automatically tightened.
[0009]
First, in step 1 (hereinafter simply represented by S1, the same applies to other steps), the target tightening force F3 is read from the RAM 70, and the compression force Q to be applied to the bolt 80 is calculated in S2. The compression force Q is preferably equal to the target tightening force F3 from the viewpoint of the evaluation accuracy of the friction coefficient, but an increase in the compression force tends to lead to an increase in the size of the apparatus and a decrease in workability. Usually, it is made smaller than the compressive force Q. The compression force Q is desirably increased as the screw nominal diameter d is increased, and the target tightening force F3 is also increased as the screw nominal diameter d is increased. Therefore, in this embodiment, the compression force Q is the target tightening force F3. It is calculated so that it may become the magnitude | size corresponding to the value selected beforehand from 3 to 30% of range. Subsequently, in S3, the compression force Q is set to 0 and tightening is started. Specifically, the electromagnetic pressure control valve 48 is set to a state in which the hydraulic pressure supplied to the hydraulic cylinder 20 is controlled to a very small value, and the electromagnetic direction switching valve 46 is switched to a position where the hydraulic cylinder 20 is extended. The motor 22 is rotated at a low speed. Accordingly, the socket 44 descends while rotating at a low speed, engages with the head of the bolt 80 so as not to be relatively rotatable, and thereafter the bolt 80 is rotated.
[0010]
After elapse of a predetermined time, in S4, the output signal of the torque detector 60 is read. In S5, whether or not the rotational resistance torque is substantially 0, specifically, a small set value or less. If the determination result is NO, the rotation of the motor 22 is stopped in S6, and a buzzer (not shown) is sounded in S7 to notify the operator of the screwing abnormality. .
[0011]
On the other hand, if the determination result in S5 is YES, the electromagnetic pressure control valve 48 is controlled in S8, and the compression force Q calculated in S2 is applied by the hydraulic cylinder 20. At this time, as shown in FIG. 5, the male screw portion 82 is screwed into the female screw hole 84 in the bolt 80, but the seat surface 88 of the head 86 is an unfastened object of the second member 78. The thread surfaces 92 and 94 are pressed against each other as shown in an enlarged view in FIG. In this state, S9 and S10 are repeatedly performed every predetermined minute time, and the rotational resistance torque T until reaching the set torque Tb is stored in the torque memory of the RAM 70.
[0012]
While S9 and S10 are repeatedly performed, the seating surface 88 of the head portion 86 of the bolt 80 is seated on the seating surface 90 of the tightened object 78 as shown in FIG. 7, and thereafter, as shown in FIG. As described above, the threaded surface 92 of the bolt 80 is not substantially in contact with the threaded surface 94 of the female threaded hole 84. Transition to an intermediate stage takes place. In this case, “the state of not substantially contacting” means that “the screw surfaces 92 and 94 may be slightly in contact with each other due to the eccentricity of the bolt 80 and the female screw hole 84, but as in the initial stage, It means "not pressed". If the bolt 80 is further rotated by a predetermined angle after the transition to the intermediate stage, as shown in FIGS. 9 and 10, the threaded surface 92 of the bolt 80 and the threaded surface 94 of the female threaded hole 84 are in the initial stage. Are in contact on the opposite side. The transition to the final stage takes place. As the above-described stage shifts, the rotational resistance torque T detected by the torque detector 60 changes as shown in FIG.
[0013]
If the rotational resistance torque T reaches the set torque Tb, the initial stage torque T1 is stored in the initial stage torque memory of the RAM 70 in S11, and then the intermediate stage torque T2 is determined in S12 and stored in the intermediate stage torque memory of the RAM 70. Stored. The initial stage torque T1 is obtained as an average value of a plurality of rotational resistance torques T acquired during the initial stage. The intermediate stage torque T2 is obtained as a minimum value of the plurality of rotational resistance torques T stored in the torque memory. More specifically, the difference between adjacent rotation resistance torques T stored in the torque memory is calculated from the time when the rotation resistance torque T reaches the set torque Tb. One of the set of rotational resistance torques T when it becomes negative is set as an intermediate stage torque.
[0014]
Subsequently, the target tightening torque T3 is determined in S13. This determination is performed by the calculation of the later-described equation (3) based on the following facts.
5 and 6, the friction torque ξ that is the product of a coefficient ξ that is proportional to the friction coefficient between the thread surfaces 92 and 94 and the compression force Q that is applied to the head of the bolt 80 by the hydraulic cylinder 20. -Although Q generate | occur | produces, the following torque Tq of the direction which tightens the volt | bolt 80 based on the effect of the slope of the screw surfaces 92 and 94 is also generated simultaneously.
Tq = ζ · Q
Where ζ = (p / 2π)
Therefore, the initial stage torque T1, which is a tightening torque required to rotate the bolt 80 in the tightening direction, is expressed by the following equation.
T1 = ξ · Q−ζ · Q (1)
[0015]
7 and 8, the friction is a product of a coefficient η proportional to the friction coefficient between the seating surfaces 88 and 90 and the compressive force Q applied to the head of the bolt 80 by the hydraulic cylinder 20. Torque η · Q is generated, and this is balanced with an intermediate stage torque T2, which is a tightening torque required to rotate the bolt 80 in the tightening direction, as expressed by the following equation.
T2 = η · Q (2)
[0016]
In the final stage shown in FIGS. 9 and 10, if F is the tightening force with which the bolt 80 tightens the second member 78, the force acting between the seating surfaces 88 and 90 is F + Q, which is based on this force. The friction torque generated between the seating surfaces 88 and 90 is η · (F + Q). Further, the rotational resistance torque generated based on the friction coefficient between the thread surfaces 92 and 94, the effect of the inclined surface, and the tightening force F is ξ · F + ζ · F. Since the friction torque η · (F + Q) and the rotational resistance torque ξ · F + ζ · F are the tightening torque T necessary to rotate the bolt 80 in the tightening direction,
T = η · (F + Q) + ξ · F + ζ · F (3)
[0017]
The coefficients ξ and η can be calculated from the above expressions (1) and (2), the compression force Q in the expression (3) is detected, the tightening force F is set in S1, and the coefficient Since ζ can be calculated from the screw pitch p set in S1, the tightening torque T3 required to obtain a desired tightening force F3 can be calculated from the equation (3). In S13, this calculation is performed. Thereafter, S14 and S15 are repeatedly executed to wait for the rotational resistance torque T to reach the target tightening torque T3, and if it reaches, a motor stop command is issued in S16. In response to this command, the driver 56 stops the motor 22 and the tightening is automatically terminated.
[0018]
As described above, in the present embodiment, based on the initial stage torque T1, which is the rotational resistance torque T in the initial stage, it is a kind of the inter-thread surface friction coefficient related quantity related to the friction coefficient between the thread surfaces 92 and 94. The coefficient ξ is acquired, and the coefficient η, which is a kind of the friction coefficient between the seating surfaces related to the friction coefficient between the seating surfaces 88 and 90, is acquired based on the intermediate stage torque T2 that is the rotational resistance torque T in the intermediate stage. Is done. Then, the target tightening torque T3 is determined based on both the coefficients ξ and η, and when the rotation resistance torque in the final stage becomes equal to the target tightening torque T3, the tightening is automatically terminated. Therefore, for example, even if the friction coefficient between the screw faces and the friction coefficient between the seating faces change depending on whether oil is attached or not, and the roughness of the surface, it is not affected by the change, and is always almost constant. The bolt 80 can be tightened with a tightening force.
[0019]
As is apparent from the above description, in the present embodiment, the hydraulic cylinder 20 constitutes an axial force applying device, the motor 22, the socket 44, etc. constitute a rotational drive device, and the torque detector 60 of the detector 24. Constitutes a torque detector. Moreover, the part which performs S11-S13 of the microcomputer 54 comprises the fastening completion | finish condition determination means, and the part which performs S14-S16 comprises the stop command means.
[0020]
As another embodiment of the present invention, the intermediate stage torque T2 may be determined based on a change gradient of a plurality of rotational resistance torques stored in the torque memory. In this case, S12 in the flowchart of FIG. 4 is changed to S12 ′ shown in FIG. In S12 ′, the difference between adjacent ones of the plurality of rotational resistance torques stored in the torque memory is sequentially calculated backward from the time when the rotational resistance torque T reaches the set torque Tb. When the plurality of change gradients to be obtained first become equal to or less than the set gradient, the rotational resistance torque T at that time is set as the intermediate stage torque T2.
[0021]
It is also possible to determine the initial stage torque T1 and the intermediate stage torque T2 by executing the program represented by the flowchart shown in FIG. In FIG. 13, S1 to S8 and S13 to S16 are the same as the corresponding steps in FIG. 4, and S21 to S23 are different. S21 and S22 are repeatedly executed, and a sudden change in the rotational resistance torque T appears. For example, it is awaited that the difference between the two rotational resistance torques T that follow each other exceeds a preset torque difference. If a sudden change occurs, the two rotational resistance torques T before and after the sudden change are determined as the initial stage torque T1 and the intermediate stage torque T2, respectively, and stored in the initial stage torque memory and the intermediate stage torque memory in S23.
[0022]
Furthermore, the initial stage torque T1 and the intermediate stage torque T2 can be determined by executing the program represented by the flowchart shown in FIG. In the flowchart of FIG. 14, the initial stage torque T1 and the intermediate stage torque T2 are determined by repeatedly executing S31 to S38 every predetermined minute time. First, the rotational resistance torque T is read in S31 and stored in the torque memory, and it is determined whether or not the flag is turned on in S32. This flag is turned ON in S35 after the determination of the initial stage torque T1, and is initially OFF, so in S33, it is determined whether or not a sudden change in the rotational resistance torque T has occurred. For example, as in S22, it is determined whether or not the difference between the two successive rotational resistance torques T exceeds a predetermined set torque difference. If the determination result is NO, the execution of the program is returned to S31. If YES, the program is stored in the torque memory so far in S34 as the end of the initial stage or the start of the intermediate stage. Among the plurality of rotational resistance torques T, the average value of the set number of rotational resistance torques T closest to the end point of the initial stage is determined as the initial stage torque T1. After that, since the determination of S32 is YES, S33 to S35 are bypassed, S36, S38, S31, and S32 are repeatedly executed, and it is waited for the gradient of the rotational resistance torque to be equal to or greater than the set torque gradient. If it is greater than or equal to the gradient, it is determined that it is the end time of the intermediate stage or the start time of the final stage, and in S37, the average value of the set number of rotational resistance torques T closest to the end time of the intermediate stage is determined as the intermediate stage torque T2. . Next, if the rotational resistance torque T reaches the set torque Tb, S13 and subsequent steps in FIG. 4 are executed. In the present embodiment, the sudden change in the rotational resistance torque and the fact that the rotational resistance torque gradient is equal to or greater than the set torque gradient are used to determine the start time and end time of the intermediate stage, respectively, and the initial stage torque T1. And the intermediate stage torque T2 are determined on the basis of the set number of rotation resistance torques T that are apparent to belong to the initial stage and the intermediate stage, respectively. Therefore, the highly reliable initial stage torque T1 and intermediate stage torque T2 are To be acquired.
[0023]
Another embodiment of the present invention is shown in FIG. This embodiment is suitable for fastening a large-sized object to be fastened, as in the case where a cylinder head 102 is fastened to a cylinder block 100 of an engine by a plurality of bolts 104. The cylinder block 100 and the cylinder head 102 are overlapped as shown in the drawing, and the bolts 104 pass through the bolt holes of the cylinder head 102 and are screwed to the female screw holes of the cylinder block 100 to some extent. It is conveyed to. Above the tightening station, an elevating frame 112 holding a plurality of screw tightening device main bodies 110 is disposed and supported by a ceiling or a fixed support frame via an elevating device such as a hydraulic cylinder 114. Of course, it is desirable that the elevating frame 112 is guided up and down by a guide. Each of the screw tightening device main portions 110 is similar to the main portion of the screw tightening device shown in FIG. 1 except that the linear guide 16 is attached to the lifting frame 112 and the hydraulic cylinder 20 is a diaphragm type. The difference is that the fluid pressure actuator 116 is changed. The working fluid for operating the fluid pressure actuator may be liquid or gas, but according to the former, the fluid pressure actuator can be miniaturized. When the cylinder block 100 and the cylinder head 102 are conveyed to the tightening station, the lifting frame 112 that has been kept in the raised position is lowered to the lowered position by the hydraulic cylinder 114. In this state, the socket 118 of each screw fastening device main body 110 is only close to the head of the bolt 104 and is not engaged. Subsequently, the fluid pressure actuator 116 is actuated at a low pressure, and each socket 118 is engaged with the head of each bolt 104. The subsequent operation of each screw fastening device main body 110 is the same as that of the screw fastening device of FIG.
[0024]
Another embodiment is shown in FIG. This embodiment is suitable for the case where the large second member 124 is fastened to the large first member 122 by the bolt 126. The screw tightening device main body 130 includes the motor 22 and the detector 24, similarly to the main body of the screw tightening device of FIG. 1, and the fitting portion 132 of the motor 22 is connected to the fitting portion 136 of the caliper 134. It is fitted with a spline, a key or the like so that it cannot be rotated relative to the shaft but can move in the axial direction. An air cylinder 140 is attached to the caliper 134 via a bracket 138, and the motor 22, the detector 24, and the like are moved relative to the caliper 134 in the axial direction. A suspension member such as an eyebolt 142 is attached to the air cylinder 140 or the caliper 134 and can be suspended by a load balancer (not shown) disposed above. In tightening, the air cylinder 140 is operated with the engaging portion 144 of the caliper 134 being in contact with the back side of the first member 122, and a compressive force is applied from the socket 145 to the bolt 126, and the reaction force Is transmitted to the first member 122 via the bracket 138, the caliper 134, and the like. Thereby, a compressive force of a desired magnitude can be applied to the bolt 126. The operation of the screw tightening device main body 130 is the same as that of the screw tightening device of FIG.
[0025]
Yet another embodiment is shown in FIG. In the present embodiment, the axial force applying device applies a compressive force to rotating screw members such as bolts and nuts by the weight of the motor 22, the detector 24, and the like. The axial force applying device includes an air-type load balancer 146 that suspends the motor 22 and the like, and an electromagnetic direction switching valve 148 as a kind of action releasing device that releases the action. Until a wrench member such as a socket rotated by the motor 22 is engaged with the bolt, the electromagnetic direction switching valve 148 causes the pressure chamber 150 of the load balancer 146 to communicate with the air source 152, and the load balancer 146 is in an operating state. The weight of the motor and the like is not burdened on the operator, but after the wrench member is engaged with the bolt, the pressure chamber 150 is switched to a state where the pressure chamber 150 is communicated with the atmosphere. Be applied as a compression force to the bolt.
[0026]
The screw tightening device shown in FIG. 16 includes an engaging portion 144 of a caliper 134 as a mechanical engaging portion that mechanically engages with a non-rotating screw member. FIG. 18 shows a screw tightening device having an engaging portion. This mechanical engagement part engages with the article to be tightened. This screw tightening device is provided with a motor 22 and a detector 24 in the same manner as the screw tightening device of FIG. 1, but its output shaft 160 has a hexagonal bar portion 162 as a wrench at the tip. Yes. The motor 22 and the detector 24 are accommodated in the casing 164 so as to be relatively movable in the axial direction and not to be relatively rotatable. A fluid pressure cylinder 165 is disposed between the casing 164 and the motor 22 so that the motor 22, the detector 24, the output shaft 160, and the like can be moved forward and backward relative to the casing 164. The tip of the casing 164 is a small diameter portion 166, and a ring-shaped first cylinder 168 is fitted and fixed therein, and a ring-shaped first piston 170 is disposed in the first cylinder 168. Provided, and are fitted fluidly and slidably on the inner peripheral surface of the first cylinder 168 and the outer peripheral surface of the small-diameter portion 166, respectively. As a result, the space in the first cylinder 168 is divided into two pressure chambers 172 and 174. A ring-shaped second cylinder 176 is formed integrally with the first piston 170, and the ring-shaped second piston 178 is fitted into the second cylinder 176 so as to be liquid-tight and slidable. As a result, the space in the second cylinder is divided into two pressure chambers 180 and 182. A collet 184 is fixed to the tip of the second cylinder 176, a cylindrical taper member 186 is fixed to the second piston 178, and the taper member 186 is fitted inside the collet 184. The collet 184 has an inner peripheral tapered surface 190 corresponding to the outer peripheral tapered surface 188 of the tapered member 186, and a plurality of axially parallel slits formed from the tip to the middle. The tip is divided into a plurality of parts. Therefore, if the taper member 186 is moved to the tip side relative to the collet 184, the diameter of the tip portion of the collet 184 is increased. An engaging protrusion 192 is formed on the outer peripheral surface of the tip portion.
[0027]
Normally, pressure fluid (hydraulic oil, compressed air, etc.) is supplied to the pressure chambers 172 and 182 so that the first piston 170 is kept at the forward end position, while the second piston 178 is kept at the backward end position. . In this state, the tip of the collet 184 is inserted between the inner peripheral surface of the counterbore 202 formed in the article to be tightened 200 and the head of the bolt 198. Subsequently, the pressure fluid is supplied to the pressure chamber 180 to advance the second piston 178, and the diameter of the collet 184 is increased by the taper member 186. As a result, the engagement protrusion 192 bites into the inner peripheral surface of the counterbore 202, and the casing 164 is engaged with the article to be tightened 200 via the collet 184, the second cylinder 176, the first piston 170, the first cylinder 168, and the like. Can be combined. The collet 184, the taper member 186, and the two hydraulic cylinders that drive them constitute a mechanical engagement portion. In order to enable the engagement of the mechanical engagement portion, the counterbore 202 needs to be slightly larger in diameter than the conventional counterbore. If an annular engagement groove that engages with the engagement protrusion 192 is formed on the inner peripheral surface of the counterbore 202, the engagement can be further ensured. After the engagement, while the motor 22 is rotated, the fluid pressure cylinder 165 advances the motor 22, the detector 24 and the output shaft 160 relative to the casing 164, and the hexagonal bar portion 162 is engaged with the hexagonal hole of the bolt 198. Can be combined.
[0028]
In this state, if the operating force of the fluid pressure cylinder 165 is increased, a compressive force is applied to the bolt 198 by the hexagonal bar 162, and the reaction force is transmitted to the object to be tightened 200 via the casing 164, the collet 184, and the like. Is done. At this time, if the weight of the object to be tightened 200 is sufficiently large compared to the compression force to be applied to the bolt 198 by the hexagonal bar 162, the object to be tightened 200 is lifted from the female screw member 204 which is a non-rotating screw member. Absent. On the other hand, if the weight is small, the article to be fastened 200 is lifted from the female screw member, and a sufficient compressive force cannot be applied to the bolt 198 by the hexagonal bar 162. In that case, a part of a plurality of bolts 198 for fastening the article to be fastened 200 to the female screw member 204 (one piece is sufficient if the piece to be fastened 200 is small, and a plurality of bolts are large. Is preferably temporarily tightened by an ordinary method not according to the present invention, and the remaining bolts 198 may be tightened by the method of the present invention in that state. Finally, once the bolt 198 that has been tightened is once loosened and retightened by the method of the present invention, the operation of tightening the object 200 to the female screw member 204 is completed.
[0029]
Instead of the mechanical engagement portion described above, a magnetic attraction portion 210 shown in FIG. 19 can be adopted. The magnetic attraction unit 210 is provided with an electromagnet 214 at the tip of the casing 164. The electromagnet 214 is obtained by winding a coil 218 around an iron core 216. The electromagnet 214 is magnetized when a current is supplied to the coil 218 and demagnetized when the current is cut off. Can be easily performed. Although the illustrated electromagnet 214 is annular, a plurality of independent electromagnets can be fixed to the casing 164 to form a magnetic attracting portion. In the screw tightening device of FIG. 19, the detector 24 is separated into a torque detector 220 and an axial force detector 222. The screw tightening device of the present embodiment is for applying a compressive force to the bolt 198 to evaluate the friction coefficient between the screw surfaces and the friction coefficient between the seating surfaces. 27, 28 By changing to a special head and a wrench member as shown in FIGS. 27 and 28, a tensile force is applied to the bolt 198 to be used as an apparatus for evaluating the friction coefficient between the screw surfaces and the friction coefficient between the bearing surfaces. Is possible.
[0030]
As shown in FIG. 20, the magnetic adsorption unit 210 can be changed to a negative pressure adsorption unit 228. The negative pressure adsorbing part 228 includes a plurality of cup-shaped adsorbing part main bodies 230 fixed to the casing 164 and a sealing member such as a suction cup 232 attached to each opening thereof. Is connected to a negative pressure source 236 through a negative pressure control device such as an electromagnetic direction switching valve 234. The negative pressure adsorbing unit 228 can be easily switched between an adsorbing operating state and a non-adsorbing non-operating state by controlling the electromagnetic direction switching valve 234. It should be noted that both the negative pressure adsorbing portion 228 and the magnetic adsorbing portion 210 may be directly adsorbed to the female screw member 204 when the article to be tightened 200 is small. Moreover, a through-hole or a notch may be provided in the article to be tightened 200, and the magnetic attracting part 210 and the negative pressure attracting part 228 may be directly attracted to the female screw member 204 through them.
[0031]
All of the above embodiments were configured as the screw tightening device according to the present invention from the beginning. However, as shown in FIG. 21, an attachment 242 is attached to an impact wrench 240 as a normal screw tightening device. It is also possible to attach the screw tightening device according to the present invention. The impact wrench 240 is a known one and will not be described in detail. However, the impact wrench 240 includes an air supply unit 244, a motor unit 246, and a striking unit 248. The motor unit 246 composed of an air motor such as the above operates to rotate the output shaft 252, and the striking unit 248 strikes the output shaft 252 in the rotational direction. An attachment casing 256 as an auxiliary casing is attached to the casing 254 of the impact wrench 240. In the attachment casing 256, the detector 24 similar to that shown in FIG. 1 is provided, and the connection portion 260 at the rear end of the detection shaft 258 of the detector 24 serves as an engagement portion at the front end of the output shaft 252. The angular drive 262 is engaged with the angular drive 262 such that the relative rotation is impossible and the compression force can be transmitted. The tip end of the detection shaft 258 is a corner drive 264, and a rotary screw member can be rotated by attaching a socket or a hexagonal bar thereto. Although not shown, the detector 24 is connected to a control device similar to the screw tightening device of FIG. 1, and when the detected rotational resistance torque becomes equal to the target tightening torque, an alarm device such as a buzzer. Is notified to the operator. When the operator releases the operation member 250 in response to this notification, the motor unit 246 stops. A control valve such as an electromagnetic on-off valve is provided in the air supply passage connected to the air supply unit 244. When the rotation resistance torque becomes equal to the target tightening torque, the air supply passage is shut off, and the tightening is automatically performed. It is also possible to be terminated.
[0032]
Although the screw tightening device has been configured using an impact wrench, the screw tightening device according to the present invention can be obtained even if the attachment 242 is attached to a screw tightening device having no striking portion. Conversely, the motor 22 in each of the above embodiments can be changed to an air motor, and an impact wrench can be provided by providing a striking portion. Further, it is possible to provide an impact wrench by providing a striking portion between the motor 22 and the output shaft. However, in order to increase the evaluation accuracy of the friction coefficient between the screw surfaces and the friction coefficient between the bearing surfaces, it is desirable that the striking portion does not act in the initial stage and the intermediate stage.
[0033]
FIG. 22 shows still another embodiment. In this screw tightening device, a speed reducer 272 and a detector 24 are attached to a motor unit 270, and a length changing device 278 is provided between a detection shaft 274 of the detector 24 and a wrench member 276. is there. The length changing device 278 includes an actuator unit 280 and a displacement enlarging unit 282. The actuator unit 280 is mainly composed of a laminated piezoelectric element 284, and this laminated piezoelectric element 284 is connected to a large-diameter support portion 286 formed at one end of the output shaft 274 and a large-diameter piston 288 of the displacement expanding portion 282. It is sandwiched. A cylinder 290 is fixed to the support portion 286, and a large-diameter piston 288 is fitted into the cylinder 290 so as to be liquid-tight and slidable. The displacement enlarging unit 282 includes a small-diameter piston 292 together with the large-diameter piston 288 and the cylinder 290, and a closed space 293 surrounded by these is filled with hydraulic fluid. Therefore, when the large-diameter piston 288 is advanced relative to the cylinder 290 due to the extension of the laminated piezoelectric element 284, the small-diameter piston 292 is advanced by a distance larger than the advance distance. The displacement expanding portion 282 is a hydraulic type. A ball spline shaft 294 is provided integrally with the small diameter piston 292, and a ball spline hole 296 is provided integrally with the cylinder 290. The ball spline shaft 294 and the ball spline hole 296 are formed of a plurality of balls. By engaging through 298 without backlash, the relative rotation of the small diameter piston 292 with respect to the cylinder 290 is well prevented.
[0034]
When a voltage is applied to the laminated piezoelectric element 284 with the wrench member 276 engaged with the rotating screw member, the laminated piezoelectric element 284 expands to advance the large-diameter piston 288 relative to the cylinder 290. The small diameter piston 294 is advanced a greater distance. This is because the length from the support portion 286 of the length changing device 278 to the ball spline shaft 294 extends. At this time, since the wrench member 276 is engaged with the rotating screw member, the wrench member 276 cannot move forward. Instead, the inertia mass portion including the motor portion 270, the speed reducer 272, the detector 24, and the like is retracted. As a result, an inertial force corresponding to the product of the mass of the inertial mass portion and the acceleration is applied to the wrench member 276. In the present embodiment, the inertial mass portion and the length changing device 278 constitute an axial force applying device.
[0035]
If the laminated piezoelectric element 284 is repeatedly extended at a short cycle in the initial stage and the intermediate stage, and the rotational resistance torque is detected by the detector 24 in synchronization with the extension, the screw surfaces are connected to each other. In addition, the coefficient of friction between the thread surfaces and the coefficient of friction between the seat surfaces can be evaluated in a state where the bearing surfaces are pressed with a force larger than the weight of the inertial mass portion. Therefore, it is possible to improve the evaluation accuracy of the coefficient of friction between the screw surfaces and the coefficient of friction between the seating surfaces while reducing the weight of the screw tightening device and improving the workability.
[0036]
It is also possible for the laminated piezoelectric element 284 to be extended once in the initial stage and in the intermediate stage. Since the initial stage is long in time, it is easy to make the laminated piezoelectric element 284 extend once in the initial stage. However, since the intermediate stage is short, in order to allow the laminated piezoelectric element 284 to be extended once in the intermediate stage, it is detected that the transition to the intermediate stage has occurred, and the laminated piezoelectric element 284 is moved once in response to the detection. It is necessary to elongate. This detection can be performed as follows, for example. Even when the length changing device 278 is not operated, the weight of the inertial mass portion is added to the rotating screw member. Therefore, a sudden change in the rotational resistance torque due to the contact between the seating surfaces is caused by the torque detecting portion of the detector 24. Can be detected from a sudden change in the output signal. Further, at the moment when the seat surface of the rotating screw member comes into contact with the seat surface of the object to be fastened, the axial movement of the rotating screw member, that is, the axial movement of the inertial mass portion is suddenly stopped. The compressive force applied to 278 increases. By detecting this increase by the laminated piezoelectric element 284, the transition to the intermediate stage can be detected. A part of the piezoelectric elements of the laminated piezoelectric element 284 is dedicated to compressive force detection, or the entire laminated piezoelectric element 284 is normally functioned as an element for detecting compressive force to detect an increase in compressive force. Then, after the transition to the intermediate stage is detected, a voltage is applied to the laminated piezoelectric element 284 to expand it, and the compressive force to the rotating screw member is temporarily increased by the inertial force of the inertial mass portion, If the friction coefficient between the seating surfaces is evaluated based on the detected value of the rotational resistance torque, the evaluation accuracy can be improved. As described above, a part of the laminated piezoelectric element 284 or the whole laminated piezoelectric element 284 can be used as the compressive force detecting means, and therefore the axial force detecting unit of the detector 24 can be omitted. It is.
[0037]
Another embodiment of the length changing device is shown in FIG. The length changing device 300 is mainly composed of a hydraulic cylinder 301 and includes a hydraulic chamber formed by a cylinder 302 and a piston 303. The cylinder 302 and the piston 303 are respectively received by a motor shaft 305 and an output shaft 306 via a thrust bearing 304 so as to be rotatable relative to each other. The rotation of the motor shaft 305 is transmitted to the output shaft 306 by a gear mechanism 307. Transmission of axial force between the motor shaft 305 and the output shaft 306 is performed via the thrust bearing 304 and the hydraulic cylinder 301, and transmission of rotational torque is performed via the gear mechanism 307. The gear mechanism 307 constitutes a rotation transmission device that transmits rotational torque while allowing relative movement in the axial direction between the motor shaft 305 and the output shaft 306. When the screw is tightened, the output shaft 306 is pushed toward the motor shaft 305 by the reaction force applied to the rotating screw member by the wrench member, and the hydraulic cylinder 301 is in the most contracted state. The length changing device 300 is in the shortest state. When the length changing device 300 needs to be extended, a current is supplied to the electromagnetic direction switching valve 308 as a control valve for a certain minute time, and a certain amount of hydraulic oil is supplied from an external hydraulic power source (not shown). The length changing device 300 is extended by a certain amount by the extension of the hydraulic cylinder 301. Subsequently, the flow of hydraulic oil from the hydraulic cylinder 301 is permitted by cutting off the current to the electromagnetic direction switching valve 308, and the length of the length changing device 300 is returned to the original length.
[0038]
In each of the embodiments described above, the tightening force is managed by the “torque method”, but may be performed by the “rotation angle method”. For example, an encoder 309 is added as shown in FIG. 24 to the motor 22 of the screw fastening apparatus shown in FIG. 1, and the tightening force is managed by the program shown in the flowchart of FIG. Steps up to S23 are the same as those in the flowchart of FIG. After the initial stage torque T1 and the intermediate stage torque T2 are determined, the starting point torque Ts is determined in S41. The starting point torque Ts is calculated by substituting the coefficients ξ, η, ζ and the starting point axial force Fs into the equation (3). The starting point axial force Fs is, for example, a value obtained by multiplying the target tightening force F3 by a certain ratio, and the certain ratio is selected from a range of 3 to 30%, preferably 5 to 15%. Then, in S42 and S43, it is waited that the rotational resistance torque T reaches the starting point torque Ts. If it reaches, the rotating screw starting from the point where the target rotational angle θ3, that is, the starting point torque Ts is applied, is obtained in S44 by the following equation. The rotation angle θ3 of the member is determined.
θ3 = (F3−Fs) / φ
Fs = (Ts + η · Q) / (η + ξ + ζ)
φ = (p · Kb · Kc) / [2π · (Kb + Kc)]
Where Kb is the tension spring constant of the bolt system, and Kc is the tension spring constant of the system to be tightened
Thereafter, in S45, the actual rotation angle θ of the socket 44 is calculated based on the output signal of the encoder 309, and it is repeatedly determined in S46 whether or not the actual rotation angle θ has reached the target rotation angle θ3. When the actual rotation angle θ reaches the target rotation angle θ3, a stop command for the motor 22 is issued in S47. In this embodiment, the starting point tightening force Fs for determining the starting point torque Ts is a snag point in the conventional rotation angle method (θ-F line indicating the relationship between the rotation angle θ and the tightening force F). It is assumed that the value is as small as possible in the straight line portion of the figure).
[0039]
In the above embodiment, the starting point torque is determined based on the coefficient ξ as the friction coefficient related amount between the screw surfaces and the coefficient η as the friction coefficient related amount between the bearing surfaces. By rotating the rotating screw member while applying a compressive force equal to or greater than the set value and measuring the rotational resistance torque during the rotation, the point where the rotational resistance torque begins to increase, that is, the boundary between the intermediate stage and the final stage can be clearly defined. The starting point torque can also be determined by using the fact that it can be detected. For example, as shown in FIG. 28, when the spring washer 334 is disposed between the seating surfaces 330 and 332 of the bolt 326 as the rotating screw member and the article to be tightened 328, the spring washer 334 is formed into a flat plate shape. If the rotation resistance torque T is measured by rotating the bolt 326 while applying a sufficient compressive force to the bolt 326 to apply both of the seating surfaces 336 and 338 to the seating surfaces 330 and 332, respectively. The rotational resistance torque T changes as shown in FIG. Then, the change from the state in which the rotational resistance torque T is maintained at the substantially constant intermediate torque T2 to the state in which the rotational resistance torque T increases increases more rapidly than in the conventional case where a large compressive force is not applied. Therefore, the snag point that is a point near the starting point of the increase of the rotational resistance torque (for example, the point at which the rotational resistance torque first exceeds the set torque gradient, or the point at which the rotational resistance torque has increased by the set increment) is accurate. It can be determined well and the accuracy of tightening force management by the “rotation angle method” can be improved. The screw tightening device described in FIG. 1, FIG. 15, FIG. 16, FIG. 18 and the like can be used as a screw tightening device for performing the screw tightening method of the present embodiment.
A sudden change in the rotational resistance torque during the transition from the initial stage to the intermediate stage is also detected, and if the rotational resistance torque increases after the sudden change (or within a certain period of time after the sudden change), that point is the intermediate stage. If it is the time of transition from to the final stage, the snag point can be detected more reliably.
[0040]
In each of the above embodiments, the rotating screw member is rotated in a state where a compressive force is applied and the friction coefficient between screw surfaces is evaluated. It is also possible to evaluate the coefficient of friction between the surfaces. For example, as shown in FIG. 26, the head 312 of the bolt 310 has an axial groove 314 extending in the axial direction from the top surface of the head and a downstream in the rotational direction when the bolt 310 is tightened from the tip of the axial groove 314. An L-shaped engagement notch 318 having a circumferential groove 316 extending to the side is formed (preferably, a plurality of axially symmetrical notches 318 are formed). On the other hand, as shown in FIG. An engaging portion 322 having a shape that can be engaged with the circumferential groove 316 is provided, and the engaging portion 322 is engaged with the circumferential groove 316 so that a tensile force and a tightening torque can be applied to the bolt 310. To. Then, as the screw tightening device, for example, as shown in FIG. 19, a device having a contact portion (electromagnet 214 in the embodiment of FIG. 19) that contacts the object to be tightened 200 is used, and the fluid pressure cylinder 165 is used. The motor 22 is rotated in the direction in which the bolt 310 is tightened while operating in the contraction direction, the rotational resistance torque is detected by the torque detector 220, and the friction coefficient between the screw surfaces is evaluated based on the detected rotational resistance torque.
[0041]
In the above-described embodiment, the rotational resistance torque T is detected in a state where the axial force Q is substantially zero, and if it is not substantially zero, it is detected that a screwing abnormality such as a foreign object biting has occurred. However, it is also possible to detect the screwing abnormality without making the axial force Q substantially zero. For example, as shown in FIG. 29, the axial force Q is changed to a plurality of values such as Qe and Qf to obtain rotational resistance torques Te and Tf and the like, and extrapolation is performed from the plurality of rotational resistance torques Te and Tf. To calculate the rotational resistance torque Tg when the axial force Q is 0, and if the absolute value of the calculated rotational resistance torque Tg is a value within a relatively narrow setting region across 0, it is determined that there is no screwing abnormality. If it is out of the set area, it is determined that a screwing abnormality has occurred. Since the rotational resistance torque resulting from the screwing abnormality does not change depending on the change in the value of the axial force Q, and is often almost constant, the rotational resistance torque Te ′ corresponding to the axial forces Qe and Qf. , Tf ′ is obtained by translating the straight line defined by the rotational resistance torques Te, Tf when there is no screwing abnormality upward, and the rotational resistance torque when the axial force Q is zero. Since Tg ′ deviates from the setting region that sandwiches 0, the occurrence of screwing abnormality can be detected.
[0042]
In each of the embodiments described above, a dedicated microcomputer is provided for each screw tightening device. However, the computer portion of the control device for a plurality of screw tightening devices is configured by a shared personal computer or workstation. It is also possible to manage the tightening force in a centralized manner. It is also possible to employ an electric circuit that performs the same function instead of the microcomputer.
In addition, the present invention can be implemented in various modifications and improvements based on the knowledge of those skilled in the art.
[Brief description of the drawings]
FIG. 1 is a front view showing a screw tightening apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram conceptually showing a torque detector in the screw tightening device.
FIG. 3 is a block diagram showing a control device of the screw tightening device.
FIG. 4 is a flowchart showing a part of a control program of the control device.
FIG. 5 is a diagram showing an initial stage of screw tightening by the screw tightening device.
6 is an enlarged view of a part of FIG.
FIG. 7 is a diagram showing an intermediate stage of screw tightening by the screw tightening device.
8 is an enlarged view of a part of FIG.
FIG. 9 is a diagram showing a final stage of screw tightening by the screw tightening apparatus.
10 is an enlarged view of a part of FIG. 9;
FIG. 11 is a graph showing changes in rotational resistance torque during screw tightening by the screw tightening device.
12 is a diagram showing only a part different from the flowchart of FIG. 4 in the flowchart of the control program of the screw tightening apparatus which is another embodiment of the present invention.
FIG. 13 is a flowchart showing a part of a control program for a screw tightening apparatus according to still another embodiment of the present invention.
FIG. 14 is a diagram showing only a part different from the flowchart of FIG. 13 in the flowchart of the control program of the screw tightening apparatus which is still another embodiment of the present invention.
FIG. 15 is a front view (partially cross-sectional view) showing a screw fastening device according to still another embodiment of the present invention.
FIG. 16 is a front view (partially cross-sectional view) showing a screw tightening device according to still another embodiment of the present invention.
FIG. 17 is a front sectional view showing only an axial force applying device of a screw tightening device which is still another embodiment of the present invention.
FIG. 18 is a front sectional view showing a screw tightening device according to still another embodiment of the present invention.
FIG. 19 is a front sectional view showing a screw tightening device according to still another embodiment of the present invention.
FIG. 20 is a front sectional view showing a screw tightening device according to still another embodiment of the present invention.
FIG. 21 is a front sectional view showing a screw tightening device according to still another embodiment of the present invention.
FIG. 22 is a front view (partially cross-sectional view) showing a screw tightening device according to still another embodiment of the present invention.
FIG. 23 is a front view (partially cross-sectional view) conceptually showing a length changing device in a screw fastening device according to still another embodiment of the present invention.
FIG. 24 is a front view showing a screw tightening device according to still another embodiment of the present invention.
FIG. 25 is a flowchart showing a control program for a screw tightening apparatus according to still another embodiment of the present invention.
FIG. 26 is a front view showing a bolt tightened by a screw tightening device according to still another embodiment of the present invention.
FIG. 27 is a front sectional view showing a state in which the bolt is tightened.
FIG. 28 is a front view showing a bolt and a spring washer tightened by the screw tightening method according to the present invention.
FIG. 29 is a graph for explaining detection of screwing abnormality by a screw tightening device according to still another embodiment of the present invention.
[Explanation of symbols]
10: Main body frame 12: Support base 16: Linear guide 18: Lifting member 20: Hydraulic cylinder 22: Electric motor with reduction gear 24: Detector
50: Control device 76: First member 78: Second member 80: Bolt
88, 90: Seat surface 92, 94: Screw surface 110: Screw tightening device main part
112: Lifting frame 114: Hydraulic cylinder 116: Fluid pressure actuator 118: Socket 130: Screw tightening device main part 134: Caliper 140: Air cylinder 146: Load balancer 148: Electromagnetic direction switching valve 152: Air source 162: Hexagonal bar 164: Casing 165: Fluid pressure cylinder 184: Collet 186: Taper member 192: Engagement protrusion 202: Counterbore 210: Magnetic adsorption part 228: Negative pressure adsorption part 240: Impact wrench 242: Attachment 256: Attachment casing 258: Detection shaft 260: Connection unit 262, 264: Square drive 270: Motor unit 272: Reducer 274: Output shaft
276: Wrench member 278: Length changing device 280: Actuator section
282: Displacement expansion part 284: Multilayer piezoelectric element 309: Encoder
318: engagement notch 320: wrench member 322: engagement portion

Claims (13)

In a state where the male screw member and the female screw member are screwed together, the rotation of the non-rotating screw member, which is one of the two screw members, is prevented, and the rotating screw member, which is the other of the two screw members, is rotated. A method of tightening a screw member with an object to be fastened in between,
In an initial stage in which the seat surface of the rotating screw member does not contact the seat surface of the object to be tightened, the rotating screw member is rotated while applying a first axial force to the rotating screw member, and a rotational resistance torque is detected. A tightening end condition is determined based on at least the detected initial stage torque that is the initial stage rotational resistance torque and the first axial force, and the tightening is terminated when the tightening end condition is satisfied. A screw tightening method characterized by the above. In a state where the male screw member and the female screw member are screwed together, the rotation of the non-rotating screw member which is one of the two screw members is prevented, and both the screw members are rotated by rotating the rotating screw member which is the other of the both screw members. A device for fastening a screw member with an object to be fastened in between,
A rotary drive device for rotating the rotary screw member;
The rotary screw member is being rotated at least at an initial point when the rotary screw member is rotating by the rotary drive device and the seat surface of the rotary screw member does not contact the seat surface of the article to be tightened. An axial force applying device for applying a first axial force;
A torque detector for detecting a rotational resistance torque of the rotary screw member;
At least an initial stage torque that is a rotational resistance torque detected by the torque detection device in the initial stage and in a state where the first axial force is applied by the axial force application device, and the first shaft A tightening end condition determining means for determining a tightening end condition based on the directional force;
A screw tightening device comprising stop command means for issuing a stop command for the rotary drive device when the tightening end condition determined by the tightening end condition determining means is satisfied.   3. The axial force applying device applies the first axial force in a direction in which a seat surface of the rotating screw member approaches a seat surface of the object to be tightened. The screw fastening device described in 1. The axial force imparting device has at least a temporary point at which the seat surface of the rotating screw member is in contact with the seat surface of the article to be fastened and the screw surfaces of both screw members are not substantially in contact with each other. The second axial force is applied, and the torque detecting device detects an intermediate stage torque that is a rotational resistance torque at least at a temporary point, and the tightening end condition determining means The screw tightening device according to claim 3, wherein the tightening end condition is determined based on a step torque and the second axial force.   Intermediate stage detection means for detecting at least a temporary point of the intermediate stage, and the intermediate stage detection means detects a sudden change of the rotational resistance torque detected by the torque detection device at the time of transition from the initial stage to the intermediate stage. 5. The screw tightening device according to claim 4, further comprising an intermediate stage start point detecting means for detecting a start point of the intermediate stage by detecting. An intermediate stage detecting means for detecting at least a temporary point of the intermediate stage, the intermediate stage detecting means,
Torque storage means for storing the rotation resistance torque detected moment by moment by the torque detection device;
5. An intermediate stage end time determination unit that determines an end point of the intermediate stage based on a group of rotation resistance torques stored in the torque storage unit after the rotation resistance torque reaches a set torque. 5. A screw tightening device according to 5. 7. The tightening end condition is that the actual rotational resistance torque is equal to a target tightening torque determined based on at least the initial stage torque and the first axial force. Screw tightening device as described. The rotation angle of the rotating screw member from the time when the actual rotation resistance torque reaches the starting point torque determined based on at least the initial stage torque and the first axial force as the tightening end condition is the male screw member The screw tightening device according to any one of claims 2 to 6, wherein the screw tightening device is equal to a target rotation angle determined based on an elastic coefficient of the object to be tightened and a target tightening force.   Based on the rotational resistance torque detected by the torque detecting device and the axial force applied by the axial force applying device, the tightening end condition determining means determines the friction coefficient between the screw surfaces of the screw members. Including a friction coefficient estimating means for estimating at least one of the friction coefficient between the bearing surfaces of the rotating screw member and the object to be tightened, and determining the tightening end condition based on the estimated friction coefficient. The screw fastening apparatus according to any one of claims 2 to 8.   An axial force detecting device for detecting an axial force applied by the axial force applying device, and the friction coefficient estimating means is detected by the detected axial force and the torque detecting device. The screw fastening apparatus according to claim 9, wherein at least one of the friction coefficients is estimated based on a rotational resistance torque. The rotational drive device is
A wrench member engaged with the rotary screw member in a relatively non-rotatable manner;
A rotational drive source for rotating the wrench member, the axial force applying device,
A reaction force receiving member that cannot move relative to the non-rotating screw member in the axial direction of the screw members at least when tightening the screws;
11. An axial drive device that is disposed between the reaction force receiving member and the wrench member and moves the reaction force reception member and the wrench member relative to each other in the axial direction of the screw members. The screw fastening apparatus in any one of. A casing, a wrench member rotatably held in the casing, a rotation drive source that rotates the wrench member, and an axial force applying device that applies an axial force to the wrench member, The rotary screw member, which is a screw member to be rotated among the male screw member and the female screw member, is engaged with the rotary screw member so as not to rotate relative to each other, thereby rotating the rotary screw member so that the two screw members are sandwiched between the objects to be tightened. And at least a temporary point in the initial stage where the seating surface of the rotating screw member does not contact the seating surface of the object to be fastened, the first axial force is applied to the rotating screw member by the axial force applying device. An attachment that is used by being attached to a screw tightening device that provides
An auxiliary casing attached to the casing;
Rotation that is rotatably supported by the auxiliary casing, has a connecting portion that engages with the wrench member in a relatively non-rotatable manner at the rear end, and a wrench portion that engages in a relatively non-rotatable manner with the rotating screw member at the front end portion. A transmission member;
A torque detection device for detecting torsional torque of the rotation transmission member;
A control device connected to at least the torque detection device, and (a) detected by the torque detection device at least when the first axial force is applied by the axial force application device in the initial stage. Tightening end condition determining means for determining a tightening end condition based on the initial stage torque that is the torsional torque and the first axial force, and (b) determined by the tightening end condition determining means A fastening torque management attachment comprising: a stop command means for issuing a stop command for the rotary drive device when a tightening end condition is satisfied. In a state where the male screw member and the female screw member are screwed together, the rotation of the non-rotating screw member, which is one of the two screw members, is prevented, and the rotating screw member, which is the other of the two screw members, is rotated. A control program for managing a tightening torque by a computer when tightening a screw member with an object to be tightened in between,
This is the rotational resistance torque of the rotating screw member in the initial stage in which the seating surface of the rotating screw member does not contact the seating surface of the object to be fastened and the first axial force is applied to the rotating screw member. An initial stage torque detection step for detecting the initial stage torque;
A tightening end condition determining step for determining a tightening end condition based on at least the initial stage torque detected in the initial stage torque detecting step and the first axial force;
A tightening torque management program including a tightening end command step for instructing the end of tightening when the tightening end condition determined in the tightening end condition determining step is satisfied is recorded so as to be readable by the computer. A recording medium characterized by the above.

Images