JPH05116074A - Clamping torque detecting method in torque wrench - Google Patents

Abstract

PURPOSE:To detect a clamping torque with high accuracy by computing a clamping characteristics value according to the change rate of intake air pressure supplied to a torque wrench and the peak value of the intake pressure change rate at the time of impact, and then converting the clamping characteristic value to a clamping torque. CONSTITUTION:In a test device, an impact wrench 3 is connected to an air source 1 through a pressure reducing valve 2. Further, a pressure sensor 4 is interposed on the intake side of the impact wrench 3, and a torque transducer 5 is installed on the output shaft side in the similar way. Further, the output of the pressure sensor 4 is input to FFC 6, and the change rate waveform of the intake air pressure is input to a personal computer 7. On the other hand, the output of the torque transducer 5 is input to another personal computer 9 via an amplifier 8. According to the change rate of intake air pressure supplied to the impact wrench 3 and the peak value of the intake air pressure change rate at the time of impact of the impact wrench 3, a clamping characteristic value is computed, and then the clamping characteristic value is converted to a clamping torque.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tightening torque detecting method for a torque wrench such as an impact wrench or a hydraulic wrench.

[0002]

2. Description of the Related Art In an impact wrench, in order to perform accurate tightening torque control, it is necessary to detect a hit state. Conventionally, this hit state is detected by mounting a sensor on the main shaft of an air motor, It is performed by a method of detecting the inversion of the main axis. However, this method has a drawback in that the size of the device and the cost are increased because it is necessary to dispose a sensor for detecting normal rotation and reverse rotation inside the impact wrench.

Therefore, it is conceivable to adopt a method of detecting the supply pressure, and assuming that the impact wrench is operating when the supply pressure drops below a reference value, the striking state is detected. However, this method has a drawback in that it is impossible to distinguish whether the impact wrench is in the no-load rotation state or the striking state. This is because the pressure difference that occurs between the unloaded rotation state and the striking state is smaller than the pressure fluctuation that inevitably occurs in the air supply source, and it is impossible to identify the difference.

Therefore, for example, in Japanese Patent Application Laid-Open No. 2-198772, the rate of change of the supply pressure supplied to the torque wrench is detected, and when the rate of change reaches a reference value, a batting signal is output and the batting signal is When the set count value is reached,
Alternatively, when the output of the striking signal reaches the set time, it is assumed that the target tightening torque is obtained, and the operation is stopped.

[0005]

In the tightening control system for the impact wrench described above, it is possible to perform tightening torque control with considerably high accuracy, but from the viewpoint of further improving the torque management accuracy, this is not the case. There is also a demand for more highly accurate torque control.

Therefore, an object of the present invention is to provide a tightening torque detecting method in a torque wrench which can detect a tightening torque with higher accuracy than in the conventional art, and therefore enables highly accurate tightening torque control. ..

[0007]

Therefore, a tightening torque detecting method for a torque wrench according to a first aspect of the present invention detects the rate of change of the supply pressure supplied to the torque wrench, and the peak value of the rate of change of the supply pressure at the time of impact. It is characterized in that a tightening characteristic value is calculated based on the above, and this tightening characteristic value is converted into a tightening torque.

The tightening torque detection method for a torque wrench according to a second aspect of the invention is characterized in that the tightening characteristic value is obtained as a sum of peak values of the supply pressure change rate at each impact.

In the method for detecting the tightening torque in the torque wrench according to the third aspect of the invention, the tightening characteristic value is obtained as the sum of the peak values above the reference level among the peak values of the supply pressure change rate at each impact. It is characterized by

A tightening torque detection method for a torque wrench according to a fourth aspect of the present invention is such that the tightening characteristic value exceeds a reference level when the tightening characteristic value is a peak value which is equal to or higher than a reference level among the peak values of the supply pressure change rate at each impact. The tightening torque detecting method for a torque wrench according to claim 1, wherein the tightening torque is obtained as a total sum of the minutes.

According to a fifth aspect of the present invention, there is provided a method for detecting a tightening torque in a torque wrench, wherein the tightening characteristic value is a peak value that is equal to or higher than the highest value of the peak values of the supply pressure change rate at each impact. It is characterized in that it is obtained as the sum of peak values equal to or higher than a predetermined ratio of the highest value up to that point.

[0012]

The impact force of a torque wrench, for example, an impact wrench, increases as the velocity at the moment of impact increases, and the reversal amount and reversal speed increase accordingly. At this time, on the air motor side, the pressure increase amount of the supply pressure and the pressure increase speed become large.
On the other hand, the magnitude of the change rate of the supply pressure is proportional to the change amount and the change rate of the supply pressure itself. Therefore, the striking force and the magnitude of the supply pressure change rate are in a proportional relationship.

The tightening torque detecting method for the torque wrench according to the first aspect is based on the above principle, and therefore, the tightening torque can be detected with higher accuracy than ever before.

When carrying out the method, the tightening characteristic value may be calculated by any one of the methods of claims 2 to 5 according to the characteristics of the object to be tightened.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A concrete embodiment of a tightening torque detecting method for a torque wrench according to the present invention will be described in detail with reference to the drawings.

First, the relationship between the striking force and the rate of change in supply pressure will be examined. The test apparatus is shown in FIG. 1. In the figure, 1 is an air source, 2 is a pressure reducing valve, 3 is an impact wrench, and a pressure sensor 4 is provided on the air supply side of the impact wrench 3. Further, a torque transducer 5 is attached to its output shaft. The sensor 4
Is output to the FFC 6, and the change rate waveform of the supply pressure is input to the personal computer 7. The output of the torque transducer 5 is input to the personal computer 9 different from the above through the amplifier 8.

FIG. 2 shows the output waveform of the pressure sensor 4 (FIG. 2A) and the output waveform of the supply pressure change rate from the FFC 6 (AC component of the output waveform of the pressure sensor 4) (FIG. b)) is shown. This air pressure change rate signal does not fluctuate when stopped, a large negative fluctuation level is obtained when the lever is opened, and there are small positive and negative fluctuations during free running (no load rotation). It has the characteristic of repeating fluctuations and small negative fluctuations.

FIG. 3 shows a comparison between the output signal from the torque transducer 5 and the supply pressure change rate signal. Comparing the magnitudes of the signals for each impact in the same figure, although there are variations due to the peak value reading resolution in the test device, the impact force (the same figure (a)) and the supply pressure change rate (the same figure (b)) It can be said that the magnitude (peak value) has a substantially proportional relationship.

A similar test was performed on the hydraulic pulse wrench, but as shown in FIG.
It was confirmed that the generated torque per pulse ((a) in the figure) and the magnitude (peak value) of the change rate of the supply pressure ((b) in the figure) have a substantially proportional relationship.

From the above, it is clear that the tightening torque can be accurately detected by using the magnitude of the change rate of the supply pressure, but the specific procedure will be described below. First, the tightening characteristic value T is grasped by one of the following methods (1) to (4) based on the magnitude of the supply pressure change rate.

Method of grasping tightening characteristic value T (1) ... FIG. 5
As shown in, the sum of the peak values of all the change rates of the supply pressure is obtained, and this is set as the tightening characteristic value T (T = a + b + c +.
・ ・).

Method of grasping tightening characteristic value T (2) ... FIG. 6
As shown in FIG. 5, only the waveform having the peak value equal to or higher than the reference level B is valid, and the total sum of the valid peak values is used as the tightening characteristic value
(T = a + b + c + ...).

Method of grasping tightening characteristic value T (3) ... FIG. 7
As shown in FIG. 7, only the waveform having a peak value equal to or higher than the reference level B is valid, and the sum of values obtained by subtracting the reference level B from the peak value of the valid waveform is set as the tightening characteristic value T (T = (a-
B) + (b-B) + (c-B) + ...).

Method of grasping tightening characteristic value T (4) ... After the start of striking, the peak value of the change rate waveform is stored. When a waveform having a peak value equal to or greater than the stored peak value is output, the value is updated. Waveforms having a peak value less than a fixed ratio (X%) of the stored peak values are invalid,
The tightening characteristic value T is the sum of the effective peak values (T = a + b
+ C + ..., see FIG. 8).

Next, the relationship between the tightening characteristic value T obtained as described above and the actual tightening torque will be determined. This is because the tightening test is repeated a plurality of times while detecting the tightening characteristic value T, each tightening torque Q is measured after tightening, and both (T-
The correlation of Q) is obtained by the method of least squares as shown in FIG.

According to the above method, the tightening torque Q can be estimated from the tightening characteristic value T, or the tightening torque Q can be set to obtain the tightening characteristic value T required for the tightening torque Q. By the way, the impact force of the impact wrench increases as the velocity at the moment of impact increases, and the reversal amount and reversal velocity accordingly increase. At this time, on the air motor side, the pressure increase amount of the supply pressure and the pressure increase speed become large. On the other hand, the magnitude of the change rate of the supply pressure is proportional to the change amount and the change rate of the supply pressure itself. Therefore, the striking force and the magnitude of the supply pressure change rate are in a proportional relationship. Since the tightening characteristic value T is obtained based on the magnitude (peak value) of the supply pressure change rate as described above, the tightening characteristic value T and the tightening torque Q have good correlation. As described above, based on the characteristic value T having a very good correlation with the tightening torque Q, the accuracy of detecting the tightening torque Q is also improved.

The following are examples of applications of the tightening torque detection method in the torque wrench.
First, when tightening, the first one detects the rate of change in air pressure in the same manner as in the past, and counts the number of effective hits that produce a peak value above the reference level, and when the count value reaches the set value. While the tightening operation is completed, the tightening characteristic value T up to that time is known, and this is converted into the tightening torque Q, which is obtained at the time of tightening after the tightening is completed. This is a method of displaying as an attached torque. This makes it possible to determine whether the work is appropriate. For the second one, set the target tightening torque Q,
This is a method of ending the tightening operation when the tightening characteristic value T detected while performing the tightening work becomes a value corresponding to the target tightening torque Q. In any of these methods, as described above, highly accurate torque display or tightening control can be performed.

[0028]

As described above, in the tightening torque detecting method for the torque wrench according to the first aspect, the tightening torque is detected based on the tightening characteristic value having a good correlation with the tightening torque. It is possible to detect the applied torque with higher accuracy than before.

In implementing the above method, the method according to claim 2
The method of any one of claims 5 to 5 may be adopted, and the detection operation can be facilitated due to the simplicity of each method.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a test device that obtains a relationship between a rate of change in supply pressure and a tightening torque in an impact wrench.

FIG. 2 is an explanatory diagram showing, in contrast, changes in the supply pressure and the supply pressure change rate obtained in the above apparatus.

FIG. 3 is an explanatory diagram showing the change states of the supply pressure change rate and the impact force obtained in the above in comparison.

FIG. 4 is an explanatory diagram showing, in contrast, change rates of a supply pressure change rate and generated pulses in a hydraulic pulse wrench.

FIG. 5 is an explanatory diagram for explaining a first embodiment of a method of grasping a tightening characteristic value.

FIG. 6 is an explanatory diagram for explaining a second embodiment of a method of grasping a tightening characteristic value.

FIG. 7 is an explanatory diagram for explaining a third embodiment of a method of grasping a tightening characteristic value.

FIG. 8 is an explanatory diagram for explaining a fourth embodiment of a method of grasping a tightening characteristic value.

FIG. 9 is an explanatory diagram for explaining a relationship between a tightening characteristic value T and a tightening torque Q.

[Explanation of symbols]

 1 Air source 3 Impact wrench 4 Pressure sensor 7 PC

Claims (5)

[Claims] 1. A change rate of supply pressure supplied to a torque wrench is detected, and a tightening characteristic value is calculated based on a peak value of the change rate of supply pressure at the time of impact, and the tightening characteristic value is tightened. A method for detecting tightening torque in a torque wrench, characterized by converting to torque. 2. The tightening torque detection method for a torque wrench according to claim 1, wherein the tightening characteristic value is obtained as a sum of peak values of the supply pressure change rate at each impact. 3. The torque wrench according to claim 1, wherein the tightening characteristic value is obtained as a sum of peak values above a reference level among the peak values of the supply pressure change rate at each impact. Tightening torque detection method. 4. The tightening characteristic value is obtained as a total sum of excesses of a reference level at a peak value equal to or higher than a reference level among the peak values of the supply pressure change rate at each impact. A method for detecting tightening torque in the torque wrench of Item 1. 5. The tightening characteristic value is a peak value that is equal to or higher than the highest value up to that point, or a peak value that is equal to or higher than a predetermined ratio, of the peak values of the supply pressure change rate at each impact. The tightening torque detecting method for the torque wrench according to claim 1, wherein