JP2003025163A - Screw tightening device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manage a tightening amount of a screw by detecting a height of the screw to be tightened surely to eliminate erroneous tightening. SOLUTION: This screw tightening device tightens the screw automatically by a screw tightening tool engaged with a screw member such as a bolt, a nut, etc. It is provided with a height detection means 14 for detecting a height of the screw 2, a rotation means 8 for rotating the screw tightening tool 3, a moving means 9 for moving the rotation means 8 in the direction parallel with the direction of advance of the screw, and a joint 6 for connecting the screw tightening tool 3 and the rotation means 8 mutually so as to slide in the direction of advance of the screw 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw tightening device which is used for assembling various devices and automatically tightens screw members such as bolts and nuts.

[0002]

2. Description of the Related Art In a screw tightening operation using a screw tightening device, in order to determine the screw tightening state, a mechanical torque limiting mechanism such as a slip clutch or an electric torque detecting means is used. Mechanisms based on torque control are widely used. Each of these has a structure in which the strength of screw tightening is controlled by limiting the rotation torque of the screw tightening device.

On the other hand, Japanese Patent Laid-Open No. 4-109101 discloses that
A screw tightening device incorporating a screw height detecting device that controls the strength of screw tightening by the screw tightening amount is disclosed.

FIG. 6 shows this screw tightening device, which includes a driver bit 103 for tightening the screw 110 against the member 120 to be fastened, a motor 104 for rotating the driver bit 103, and a joint for connecting the motor 104 and the driver bit 103. A screw tightening mechanism is constituted by 105. As a mechanism for detecting the height of the screw 110, a sensor 109 attached to the frame 101 supporting the motor 104, a dog 107 attached to the driver bit 103, a dog 107 and the sensor 109.
And a lever 108 disposed between and.

In this device, the sensor 109 detects the tail end 108b of the lever 108 to determine that the screw height is a predetermined value. The lever 108 is designed to rotate about a rotation center 108c, and the spring 102 causes the tip 108a of the lever 108 to rotate.
Biased to contact 7. As a result, the height change of the driver bit 103 is transmitted to the lever 108 via the dog 107.

Further, the length of the lever 108 to the tail end 108b is several times larger than the length from the rotation center 108c to the tip end 108a side. Therefore, driver bit 1
When the change in height of 03 is transmitted to the lever 108 via the dog 107, the tail end 108b of the lever 108 moves largely with respect to the small movement of the dog 107 depending on the lever ratio. Therefore, the sensor 109 can detect a small movement change of the dog 107 or the bit 103 from the large movement of the tail end 108b, and can accurately detect the minute height of the screw 110 tightened by the driver bit 103.

[0007]

However, in the structure in which the strength of screw tightening is controlled by limiting the rotational torque,
Even if there are factors such as the screws not fitting or foreign substances on the screws, the specified tightening torque is reached and screw tightening is erroneously completed. Further, there is a drawback that a predetermined tightening torque cannot be reached unless the driver bit of the screw tightening device is inserted into the screw. If an electrical or mechanical avoidance means is provided to compensate for these drawbacks, there is a problem in that the structure is complicated, the operation is troublesome, and the cost is high. In addition, there is also a problem that it is impossible to control the direction in which the screw is loosened.

On the other hand, in Japanese Unexamined Patent Publication No. 4-109101, the screw height is detected via the driver bit 103. Therefore, an error in the screw insertion height of the driver bit 103 and an error in the height of the fastened member 120 are corrected. Since it is detected as it is, there is a problem that the exact screw-in amount cannot be known. Further, when the shape of the head of the screw 110 is changed, the driver bit 103 is also replaced, but at the time of this replacement, the sensor 109 needs to be adjusted each time, which makes adjustment difficult and lacks versatility. have.

From the above, according to the prior art, when the screw is tightened, the screw may not be able to fulfill its original function, and the product may be defective due to defective tightening. It has an adverse effect such as the inability to work in the process.

The present invention has been made in consideration of such conventional problems, and it is possible to manage the screw tightening amount of the screw itself and to freely control the screw tightening amount. The purpose is to provide.

[0011]

The invention according to claim 1 is a screw tightening device for automatically tightening a screw by means of a screw tightener engaging a screw member such as a bolt or a nut, and detecting the height of the screw. Height detecting means, rotating means for rotating the screw fastener, moving means for moving the rotating means in a direction parallel to the traveling direction of the screw, and the screw fastener and the rotating means can slide in the traveling direction of the screw And a joint connected to.

In the present invention, the height detecting means detects the height of the screw head before tightening the screw. Then, the screw tightening operation is performed by rotating the screw tightening tool by the rotating means and moving the rotating means by the moving means. After that, the height of the screw head is detected by the height detecting means, and the calculated value is compared with the preset reference value of the screw head height after tightening the screw. Tighten. After that, the above operation is continuously repeated, and the screw tightening operation is terminated when the comparison calculation result falls within the range of the reference value. As a result, stable screw tightening work can be performed under predetermined screw tightening conditions.

When tightening the screw, if the screw fastener is not accurately engaged with the screw, the joint pushes up the screw fastener, so that no unreasonable force is applied to the screw and careless tightening is performed. Can be avoided.

In this case, when the screw head height is lower than the lower limit of the reference value range depending on the object to be assembled, it is necessary to loosen the screw, but even in such a case, the screw fastener is rotated in the reverse direction by the rotating means. You can deal with it.

A second aspect of the present invention is the screw tightening device according to the first aspect, wherein the height detecting means detects the height of the screw at a portion other than where the screw fastener is engaged with the screw. It is characterized by doing.

By detecting the screw in this way,
Since the screw fastener does not interfere with the height detection, the screw height can be detected easily and accurately.

According to a third aspect of the present invention, in the screw tightening device according to the first or second aspect, the height detecting means adjusts the height of the screw according to a light blocking amount of light emitted in a width parallel to the traveling direction of the screw. It is a light transmissive sensor for detecting the height.

By emitting and detecting light having a width parallel to the traveling direction of the screw, the light shielded by the screw becomes the height of the screw. In such detection, the height of the screw is detected in a non-contact manner, so that the screw and other members are not damaged and the detection can be performed with a simple structure.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below with reference to the embodiments shown in the drawings. In the respective embodiments, the same members are designated by the same reference numerals and correspond to each other.

(Embodiment 1) FIGS. 1 to 4 show Embodiment 1 of the present invention, and FIG. 1 shows the overall structure thereof.

In this embodiment, the screw 2 is screwed to the screw receiving member 1 by rotating a driver bit 3 as a screw fastener. A bolt is used as the screw 2. Therefore, the tip of the driver bit 3 as the screw fastener (the end on the screw side) is inserted into the head of the screw (bolt) 2 and engages with the bit. The part 3a is formed.

The screw receiving member 1 is placed on a base (not shown) and is provided below the driver bit 3. A light transmissive sensor 14 as height detecting means is arranged around the screw receiving member 1 in a non-contact state with the screw receiving member 1, the screw 2, and the driver bit 3.

The light transmission type sensor 14 is provided with a light projecting portion 4 and a light receiving portion 5, which are arranged so as to sandwich the screw receiving member 1. The light projecting unit 4 and the light receiving unit 5 are sensors that respectively project and receive band-shaped light, and when the light is blocked by the light blocking object (screw receiving member 1 and screw 2) therebetween, the light is proportional to the light blocking amount. The voltage output changes, and the tightening height of the screw 2 is detected based on this light shielding amount. Light transmission type sensor 14
The optical axis C of is parallel to the traveling direction of the screw 2 when the screw 2 is tightened. This allows
As the screw 2 advances due to tightening, the light to be shielded changes as shown in FIGS. 3 to 4, and the height of the screw can be detected by detecting the amount of change in the shielded light.

The driver bit 3 is connected to the shaft of a motor 8 as a rotating means through a joint 6, and
Rotate by rotating. A spring mechanism is built in the joint 6, and the driver bit 3 is slidable in the joint 6 in the traveling direction of the screw 2. Normally, it is pressed against the screw 2 side by the spring force, but when the driver bit 3 comes into contact with the screw 2, the shock is absorbed and the spring is changed so that the driver bit 3 at the time of screw tightening is screwed. The pressing force for the screw 2 is selected. The motor 8 is preferably a pulse motor or a servomotor that can easily control the rotation angle.

The motor 8 is a vertical moving shaft 9 as moving means.
Is attached via a motor mount 7. The vertical movement shaft 9 has a built-in motor, and the built-in motor moves the motor mount 7 in a direction parallel to the traveling direction of the screw 2. That is, by operating the vertical movement shaft 9, the motor 8 and the driver bit 3 can move in parallel with the traveling direction of the screw 2.

The controller 10 includes a light transmission type sensor 1
The light projecting unit 4 and the light receiving unit 5 of No. 4 are connected to the motor 8 and the vertical movement shaft 9, and the read signal from the light transmission type sensor 14 is input and the motor 8 and the vertical movement shaft 9 are connected.
Control the behavior of. In addition, the controller 10 has
Parameters such as the number of command pulses required for one rotation of the motor 8, the operating speed, the pitch of the screw 2 and the screw tightening condition (screw tightening amount) can be input. These are set in advance before the automatic screw tightening work.

Next, the operation of the above configuration will be described.

First, the screw receiving member 1 with the screws 2 attached in a temporarily tightened state is installed in advance so that the center thereof coincides with the center of the driver bit 3. FIG. 3 shows the state of the screw receiving member 1, the screw 2, and the light projecting portion 4 and the light receiving portion 5 of the light transmissive sensor 14 at this time. The light quantity input to the light receiving section 5 is D, and the light quantity D from the light receiving section 5 is D.
The voltage corresponding to is output. The controller 10 calculates the height of the screw 2 at the present time by reading the output voltage from the light receiving unit 5 of the light transmission type sensor 14 and performing conversion calculation.

Next, the controller 10 calculates the calculated current value of the height of the screw 2 and a preset target value of the height of the screw 2 after tightening the screw to calculate the tightening amount. Further, the controller 10 calculates the required rotation amount of the motor 8 from the tightened amount.

Next, the vertical moving shaft 9 moves the driver bit 3 to a position where it is inserted into the head of the screw 2. At this time, even if the driver bit 3 is not accurately inserted into the head of the screw 2, the driver bit 3 is pushed up in the direction of the motor 8 by the sliding of the joint 6, so that the screw receiving member 1 and the screw 2 cannot be forced. If no force is applied and the motor 8 is rotated in the screw tightening direction B from this state, the bit portion 3a of the driver bit 3 is eventually inserted into the head of the screw 2 and engages with the screw 2. As a result, when the screw 2 is tightened, no unreasonable force acts on the screw 2,
It is possible to avoid careless tightening.

Next, after the motor 8 completes the rotation required for screw tightening, the vertical moving shaft 9 is moved to the driver bit 3
Moves the light transmission type sensor in a direction away from the screw 2 to a position where it does not block the light transmission type sensor. FIG. 4 shows the screw receiving member 1 at this time,
The states of the screw 2 and the light projecting portion 4 and the light receiving portion 5 of the light transmission type sensor 14 are shown. At this time, in the same manner as described above, the height of the screw 2 at that time is calculated from the amount of light E input to the light receiving unit 5.

If the calculated height of the screw 2 is higher than the upper limit value of the target height, the vertical moving shaft 9 is lowered again, and the screw tightening operation, the height detection, and the calculation operation are repeated. When the calculated height of the screw 2 is lower than the lower limit of the target height, the screw tightening can be loosened by rotating the motor 8 in the opposite direction. As a result, it is possible to prevent excessive tightening. Then, when the height of the screw 2 calculated by the controller 10 falls within the range of the target height, the screw tightening work is completed.

According to such an embodiment, the height of the head of the screw 2 can be reliably detected regardless of the shape of the screw 2, so that accurate and error-free screw tightening work can be performed. You can Therefore, the original function of the screw can be achieved, and there is no tightening failure, and the generation of defective products can be prevented.

(Second Embodiment) FIG. 5 shows a second embodiment of the present invention. Also in this embodiment, the optical axes C2 of the light projecting section 4 and the light receiving section 5 of the light transmissive sensor 14 are such that the width direction of the band is parallel to the traveling direction of the screw 2 when tightening. In addition to this, the optical axis C2 is arranged at a position where the driver bit 3 is not detected. That is, in this embodiment, the head of the screw 2 is larger than the outer shape of the driver bit 3, and the optical axis C2 is attached to the head of the screw 2 at a position deviated from the part where the driver bit 3 is engaged. Are provided so as to run.

Also in this embodiment, the screw receiving member 1 in which the screw 2 is preliminarily tightened and attached is installed so that the center thereof coincides with the center of the driver bit 3.

Next, the vertical moving shaft 9 moves the driver bit 3 to a position where it is inserted into the head of the screw 2. At this time, similarly to the first embodiment, even if the driver bit 3 is not accurately inserted into the head of the screw 2, the driver bit 3 is pushed up in the direction of the motor 8 by the sliding of the joint 6, and the screw receiver No excessive force is applied to the member 1 and the screw 2. From this state, by rotating the motor 8 in the screw tightening direction B, the bit portion 3a of the driver bit 3 is eventually inserted into and engaged with the head portion of the screw 2.

In this embodiment, the head of the screw 2 is larger than the outer shape of the driver bit 3, and the optical axis C2 is aligned with a portion other than where the driver bit 3 is engaged with the screw 2 and the height of the screw 2 is increased. Can be detected. Therefore, the height of the screw 2 can be detected even when the driver bit 3 is inserted in the head of the screw 2.

Since the detection and calculation of the head of the screw 2 are the same as in the first embodiment, the description thereof will be omitted.

After the head of the screw 2 is detected and calculated, the controller 10 simultaneously calculates the height of the screw 2 while rotating the motor 8 in the screw tightening direction, and sets the preset screw tightened screw. Comparing with the target value of height of 2. The screw tightening work is completed by stopping the rotation of the motor 8 when the calculated height of the screw 2 falls within the target height range.

In this embodiment, the same operation and effect as in the first embodiment can be obtained, and in addition, the tightening amount of the screw can be detected while the driver bit 3 is still inserted in the screw 2. . Therefore, it is not necessary to move the vertical movement shaft 9 to detect the tightening amount, so that the screw tightening work can be performed in a short time.

In the above embodiments, the case where the bolt is used as the screw has been described, but the present invention can be similarly applied to the nut. In this case, the bit portion at the tip of the driver bit 3 is used. Can be shaped to fit on the outer circumference of the nut.

[0042]

According to the first aspect of the invention, the screw tightening amount of the screw can be directly controlled, the screw tightening amount can be freely controlled, and the screw tightening result can be surely grasped. . Therefore, defective products such as insufficient tightening and excessive tightening do not flow out to the subsequent process.

According to the invention of claim 2, in addition to the effect of the invention of claim 1, since the screw fastener does not participate in the height detection, the screw height can be detected easily and accurately. it can.

According to the invention of claim 3, claims 1 and 2
In addition to the effect of the present invention, since the height of the screw is detected without contact, the screw and other members are not damaged, and the detection can be performed with a simple structure.

[Brief description of drawings]

FIG. 1 is an overall front view of a first embodiment of the present invention.

FIG. 2 is a side view showing a screw and a driver bit according to the first embodiment.

FIG. 3 is a front view showing a state in which the height of a screw is detected according to the first embodiment.

FIG. 4 is a front view showing a state in which the height of a screw is detected according to the first embodiment.

FIG. 5 is a side view showing a screw and a driver bit according to the second embodiment.

FIG. 6 is a front view of a conventional device.

[Explanation of symbols]

2 screws 3 driver bits (screw fastener) 6 joints 8 motors (rotating means) 9 Vertical movement axis (moving means) 14 Light transmission type sensor

Claims (3)

[Claims] 1. A screw tightening device for automatically tightening a screw by means of a screw tightener engaging a screw member such as a bolt or a nut, the height detecting means for detecting a height of the screw, and the screw tightener. A rotating means for rotating; a moving means for moving the rotating means in a direction parallel to the moving direction of the screw; and a joint for slidably connecting the screw fastener and the rotating means in the moving direction of the screw. Characteristic screw tightening device. 2. The screw tightening device according to claim 1, wherein the height detecting means detects the height of the screw at a portion other than where the screw fastener is engaged with the screw. 3. The height detecting means is a light transmissive sensor that detects the height of the screw based on the amount of light shielded from light emitted in a width parallel to the traveling direction of the screw.
Or the screw tightening device described in 2.