JP2688810B2 - Screw tightening method and screw tightening device used for implementing this method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw tightening method capable of tightening an individual screw with a torque most suitable for the screw and a screw tightening device used for implementing this method.

[0002]

2. Description of the Related Art As a screw tightening device for tightening a screw to a mating member, several examples have been proposed and are known. However, in these examples, in order to set the tightening force when tightening the screw on the mating member, a timer is set so that the tightening time is constant, or the height of the screw head is set to a predetermined height. However, the tightening torque is regulated by a torque limiter, but all of them are uniformly tightened under the condition of a preset value (for example, Japanese Patent Laid-Open No. 6-11465).
No. 1).

[0003]

In such a method,
When tightening a plurality of screws, not all screws are tightened with an appropriate tightening torque. Because,
This is because even if screws of the same size are fastened to the same mating member, the friction coefficient and the like differ depending on their precision, surface roughness, or foreign matter biting. Therefore, of course, the loosening torque when loosening a screw once tightened is also different, and whether or not the screw is tightened with an appropriate torque should be considered after considering the loosening torque when loosening this screw. Can be said.

The present invention addresses such a problem and considers the loosening torque in the calculation of the torque required for tightening the screws, so that each screw has an appropriate torque that does not loosen naturally. So that it can be tightened,
As a result, in the case where the fully tightened screws are forcibly loosened, the screws of the same type can be loosened with substantially the same torque.

[0005]

In order to achieve the above object, the present invention provides a screw tightening method characterized by being carried out by the following operations (a) to (d). (A) A temporary tightening torque T ₁ based on the specifications of the screw and the mating member is set and input to a controller that controls the drive of the screw tightening driver, and the driver is driven with the temporary tightening torque T ₁ to drive the screw. Is temporarily fastened to the mating member. (B) The temporary tightening loosening torque T _{2 in} which the friction coefficient between the screw and the mating member required for loosening the temporary tightening is added is detected by the torque sensor attached to the driver, and is input to the controller. (C) Assumed torque T _{3 for} tightening the main tightening, which is already known and is required when loosening the screw when the main tightening is performed.
To the controller. (D) The controller calculates the final tightening torque T ₅ required for the final tightening based on the temporary tightening torque T _{1, the} temporary tightening loosening torque T ₂ , and the final tightening loosening expected torque T ₃ , and the driver is operated with the final tightening torque T _5. Drive to fully tighten the screws to the mating member.

Further, according to the present invention, in the above method, temporary tightening and temporary tightening loosening operations are performed a plurality of times to cause the screw and the mating member to become familiar with each other, and each temporary tightening loosening torque T _{2 is set} to the torque. Provided is a screw tightening method, which is detected by a sensor and an average value thereof is adopted as a temporary tightening and loosening torque T ₂ .

Furthermore, the present invention provides a screw tightening device used for carrying out the above-mentioned method, which includes a driver forcibly driven to rotate a screw, a torque sensor capable of detecting a driving torque of the driver, and a torque sensor. Provided is a screw tightening device having a controller having a predetermined arithmetic function based on a detected value or input data and capable of controlling driving of a driver.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings, but this is for explaining the present invention and the present invention is not limited to this embodiment. FIG. 1 is a partially cutaway vertical sectional view for explaining a configuration of a main part for performing a screw tightening operation of a screw tightening device according to a preferred embodiment of the present invention. In the figure, the screw tightening motor 1
0 indicates a forward rotation, a reverse rotation, a stop, etc. based on an instruction from the controller 12, and the screw tightening motor 1
A torque sensor 18, a ball spline 20, and a bit (driver) 22 are provided on a shaft connected to an external main shaft of No. 0, and a jaw 2 capable of holding a screw is provided at the tip thereof.
4 are provided.

The screw 28 is set on the jaw 24, but this setting is usually performed automatically by using the screw pressure feeding means 26. This screw pressure feeding means 26
Uses a pneumatic screw to feed a screw 28 through a tube. For example, in Japanese Patent Laid-Open No. 28574/1993.
Since it is already well known in Japanese Patent Publication No. 8 etc., its detailed description is omitted here. The torque sensor 18 is for detecting the torque applied to the driver 22 and the like.

A driver 22 and a jaw 24 are connected to the tip of the torque sensor 18 via a ball spline 20. The ball spline 20 has a pressing cylinder 30.
Thus, even if the driver 22 moves up and down, the power of the screw tightening motor 10 and the torque for tightening or loosening the screw 28 'are always freely transmitted to each other. Although the torque sensor 18 of the present embodiment uses a strain gauge, the present invention is not limited to this example, and the light amount sensor may detect that the amount of light passing through the slits changes due to torque.

In the pressing cylinder 30, when the tip of the driver 22 is located above the tip of the screw pressure feeding means 26, the screw 28 'is set from the screw pressure feeding means 26 as shown in FIG. As shown in FIG. 1, 22 is pushed down to the tip of the jaw 24, and the pneumatic cylinder is used in this embodiment, but the invention is not limited to this, and an electric cylinder may be used.

A commercially available personal computer 16 (14 is its keyboard), which is relatively easy to obtain, is used as a device responsible for the calculation and data input of the controller 12, and the personal computer 16 and the controller 12 are connected to each other. It was connected by a cable 34 (RS232C). FIG. 4 is a perspective view schematically showing this connection state. Then, each component including the screw tightening motor 10 is controlled via the controller 12.

In addition to the above, a so-called multi-joint robot 36, which is also a commercially available product, is used as a means for positionally controlling the portion shown in FIG. 1 of the screw tightening device, and the personal computer 16 is also a brain department. It was controlled by the controller 12.
A detailed description of the method and means for controlling the articulated robot 36 has nothing to do with the gist of the present invention, so that it will be omitted here, but the configuration is generally as shown in FIG.

Next, the screw tightening by the screw tightening device having the above construction will be described. First, a temporary tightening torque T ₁ based on the specifications of the screw and the mating member is set and input to the controller, and the driver is driven by this temporary tightening torque T ₁ to temporarily tighten the screw to the mating member. What is temporary tightening?
The tightening does not reach the final tightening, and the temporary tightening torque T ₁ is set appropriately based on empirical rules.

Next, this temporary tightening is loosened, the temporary tightening loosening torque T ₂ required at that time is detected by the torque sensor, and this is input to the controller. This temporary tightening and loosening torque T
No. ₂ takes into consideration a unique coefficient such as a coefficient of friction between the screw and the mating member, and is different for each screw.
Since the controller calculates these specific coefficients from the difference between the temporary tightening torque T ₁ and the temporary tightening loosening torque T ₂ , these data are used as the final tightening torque T described later.
_It can be used for various purposes including the setting of ₅ .

Further, an estimated full tightening / loosening torque T ₃ required when the screw is fully tightened and loosened is input to the controller. The assumed tightening / loosening torque T ₃ is based on the fact that the screw is not loosened naturally during use and is in an optimum tightening state in which a sufficient axial force is obtained, and this is temporarily forcibly loosened. Is the inherent torque required in the case of, and this value is theoretically or empirically known from the diameter, length, material of the screw, surface roughness, and the tightening state with the mating member. It is a thing.

Then, the final tightening torque T ₅ required for the final tightening is calculated based on the temporary tightening torque T ₁ , the temporary tightening loosening torque T ₂ and the final tightening loosening expected torque T ₃ , and the driver is calculated with the final tightening torque T ₅ . 22 is driven to fasten the screw to the mating member.

The final tightening torque T ₅ is calculated as follows. As an example, M4 × 16 nickel-plated screws were adopted. In this case, the temporary tightening torque T ₁ is 6.0k.
4.5 g when the torque sensor measures the temporary tightening and loosening torque T ₂ when loosening it by temporarily setting it to gf · cm.
gf · cm.

The following relationship is approximately established between the two data T ₁ and T ₂ and the assumed tightening / loosening torque T _{3 of} 7.0 kgf · cm which is input to the controller in advance. T ₁ : T ₂ ≈T ₅ : T ₃ (T ₅ = T ₁ × T ₃ / T ₂ ) Therefore, 6.0: 4.5≈T ₅ : 7.0, and the final tightening torque T ₅ is about 9 .3 (kgf · cm) is obtained.

This final tightening torque T ₅ ≈9.3 kgf · c
In order to test whether or not m is appropriate, the screw which was finally tightened with this torque was forcibly loosened, and the torque (actual torque for actual tightening and loosening) T ₄ was measured with a torque sensor.
The actual tightening and loosening actual torque T _{4 at} this time is 7. ₁ kgf · c
m was measured.

As is apparent from this, when the screw is tightened by the screw tightening method according to the present invention, the actual tightening / loosening actual torque T ₄ is very close to the actual tightening / loosening expected torque T _3. It is always stable.

The first embodiment will be shown below, but in this embodiment,
Prepare a 3mm-thick iron plate with 20 threaded holes, and use the above-mentioned 20 screws to the mating member made of 20mm-thick iron material. After the operation, in order to confirm the action and effect of the present invention, it is forcibly loosened again, and then the actual tightening and loosening actual torque T ₄
Was measured. As a result, the torques of T _{1 to} T ₅ were as follows (three examples were extracted and described). The unit of torque used here is “kgf · cm”, but the shift to SI unit can be converted by “kgf · cm” = “9.8N (Newton) · cm”.

T₁~ T₅The meaning of each is as described above
But just in case, I'll re-write it here. T₁: Temporary tightening torque T₂: Temporary tightening and loosening torque T₃: Assumed torque for final tightening T₄: Actual tightening and loosening torque T₅: Final tightening torque. Screw number T₁ T₂ T₃ T₄ T₅  1 6.0 4.8 5.7 5.7 7.2 5 6.0 6.0 4.4 5.7 5.7 7.7 7 6.0 4.2 5.7 5.7 8.2

For 20 screws including these three examples, T
T _{4 and} T ₅ when ₁ is 6.0 and T ₃ is 5.7
The torque of was as follows.

As another embodiment of the present invention, the above-mentioned temporary tightening is performed.
And perform temporary tightening and loosening operations multiple times (3 times each).
The final tightening operation should be performed after the fitting between
went. An example of each torque data at that time is as follows.
there were. T₁ T₂ T₂(Average) T₃ T₄ T₅  4.4 6.0 4.5 4.8 5.7 5.7 7.7 5.4

Regarding 20 screws including this example, T ₄ and T when T ₁ is 6.0 and T ₃ is 5.7.
The torque of ₅ was as follows.

In each of these two embodiments, in order to confirm the operation and effect of the present invention, once the screw which has been fully tightened is loosened again, all the torques of T _{1 to} T ₅ are measured and data is collected. However, when the present invention is put to practical use, only two points, that is, the temporary tightening torque T ₁ and the final tightening loosening expected torque T ₃ need be input to the controller, and it is necessary to loosen the screw once tightened again. Needless to say

[0028]

By implementing the present invention, the following excellent operational effects can be expected. When tightening a screw to a mating member, a very stable tightening result that is most suitable for each screw can be obtained even if the friction coefficient etc. are different for each screw (If the fully tightened screw is loosened, When the actual tightening is loosened, the actual torque becomes stable). Temporary tightening causes the contact surface between the screw and the mating member to become familiar with each other, and then by final tightening, it is extremely unlikely that the surface roughness of the contact surface will change after the final tightening. A stable tightening result can be obtained. As described above, the result of tightening is not sufficient in the conventional screw tightening method that is generally performed. However, when tightening is performed by the method of controlling the loosening torque of the screw as in the present invention, The most suitable high-precision tightening is possible for each screw.

[Brief description of the drawings]

FIG. 1 is a partially cutaway vertical cross-sectional view for explaining the configuration of a main part that performs a screw tightening operation of a screw tightening device according to a preferred embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view illustrating a state in which a screw is set on a jaw.

FIG. 3 is a side view of a state in which a main part of the screw tightening device is configured by an articulated robot.

FIG. 4 is a perspective view schematically showing a state in which a personal computer and a controller are connected by a connection cable.

[Explanation of symbols]

 10 screw tightening motor 12 controller 14 keyboard 16 personal computer 18 torque sensor 20 ball spline 22 driver (bit) 24 jaw 26 screw pressure feeding means 28 screw 28 'screw 30 pressing cylinder 34 connection cable 36 articulated robot 36

Claims (3)

(57) [Claims] 1. A screw tightening method characterized by being carried out by the following operations (a) to (d). (A) A temporary tightening torque T ₁ based on the specifications of the screw and the mating member is set and input to a controller that controls the drive of the screw tightening driver, and the driver is driven with the temporary tightening torque T ₁ to drive the screw. Is temporarily fastened to the mating member. (B) The temporary tightening loosening torque T _{2 in} which the friction coefficient between the screw and the mating member required for loosening the temporary tightening is added is detected by the torque sensor attached to the driver, and is input to the controller. (C) Assumed torque T _{3 for} tightening the main tightening, which is already known and is required when loosening the screw when the main tightening is performed.
To the controller. (D) Based on the temporary tightening torque T _{1, the} temporary tightening loosening torque T _{2 and the} final tightening loosening expected torque T ₃ , the final tightening torque T ₅ required for the final tightening is the final tightening torque T ₅ = the temporary tightening torque T
₁ x assumed tightening / loosening torque T ₃ / temporary tightening / loosening torque T ₂
The value is calculated by the controller using the following formula, and the driver is driven by this final tightening torque T ₅ to fully tighten the screw to the mating member. 2. The temporary tightening and the temporary tightening / loosening operation are performed a plurality of times to make the screw become compatible with the mating member, and
The screw tightening method according to claim 1, wherein each temporary tightening / loosening torque T ₂ is detected by a torque sensor, and an average value thereof is adopted as the temporary tightening / loosening torque T ₂ . 3. A driver having a forced drive capable of rotating a screw, a torque sensor capable of detecting a drive torque of the driver, and a driver having a predetermined calculation function based on a detected value of the torque sensor and input data. 3. A screw tightening device used for carrying out the screw tightening method according to claim 1, further comprising a controller capable of controlling the driving of the screw tightener.