JP2572808B2 - Torque detector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque detection device, and more particularly to a torque detection device suitable for high-speed rotation or detection of a small torque.

[Conventional technology]

A conventional torque detecting device for a rotating shaft system is disclosed in Japanese Patent Application Laid-Open No. 57-1940.
In general, an elastic body having a strain gauge attached thereto is inserted into a torque transmission shaft system and a signal is taken out via a slip ring.

In addition, as a method of detecting torque in a non-contact manner, a method of measuring that when the torque is added causes a decrease in the rotation speed of the rotating shaft is disclosed in the 1984 Annual Meeting of the Japan Society of Precision Engineers Autumn Meeting, page 723. It is discussed on page 726 and is an effective method when a relatively large torque is applied or when the number of revolutions is small.

Further, there is a method for detecting deformation of an elastic body by a non-contact sensor as disclosed in Japanese Patent Application Laid-Open No. 62-247222 filed by the applicant of the present invention. It leaves room for improvement.

[Problems to be solved by the invention]

In the conventional torque detecting device based on slipping, since a contact point exists, noise is increased due to heat generation at the contact point at high speed rotation, and accurate measurement becomes difficult.

In a device that measures a decrease in the spindle speed due to the torque acting on the spindle and detects the torque in a non-contact manner, the inertia of the spindle causes the torque from acting on the spindle until the spindle speed decreases. There were problems such as a large time delay and poor response.

Further, in the method of detecting the deformation of the elastic body by the non-contact sensor, the detection of the deformation accompanying the addition of the torque is performed irrespective of the rotation phase.

The present invention has been made in view of the above points, and an object of the present invention is to provide a torque detection device which has high responsiveness and enables highly accurate torque measurement even at high speed rotation.

[Means for solving the problem]

In order to achieve the above object, the present invention detects a deformation amount of an elastic body in a device for extracting a torque signal from a rotating shaft system provided with an elastic body that deforms in a radial direction according to the magnitude of torque. A first non-contact sensor, a second sensor for detecting a rotation phase of each rotation of the rotation shaft, and a torque obtained by sampling an output signal based on the first sensor by an output signal based on the second sensor. Means for obtaining a signal, and means for obtaining a predetermined threshold value for the sampled torque signal as a corrected threshold value based on the output signal based on the first sensor in the latest non-negative sampling period of the rotating shaft. Means for setting the corrected threshold value as a threshold value of a torque signal in a sampling cycle at the time of load for each rotation.

[Action]

 The operation of the present invention will be specifically described with reference to embodiments of the present invention.

In FIG. 1, a cylindrical elastic body 5 attached to a lower side of a drive shaft 3 of a drilling machine elastically deforms in a radial direction following a cutting torque by a drill 9 as described later.

After the amount of deformation is detected by the non-contact type sensor 6, sampling is performed using the rotation phase signal of the non-contact type sensor 4 for detecting the presence or absence of the marker 2 engraved on the circumference of the drive shaft 3 at a predetermined angle. Thus, a temporal change in the cutting torque generated in the drill 9 can be detected.

This signal includes the mechanical initial eccentricity of the elastic body 5 and the initial voltage, the temperature of the sensor system, and the time drift due to the mounting position of the non-contact type sensor 6 arranged facing the outer peripheral surface of the elastic body 5. Therefore, a signal processing circuit for storing and holding the same signal and detecting a cutting torque equal to the set value of the threshold value setter 13 to superimpose the drift signal is provided.

Also, to increase the number of times the torque signal is sampled,
The torque detection response speed can be improved by using the symmetry of the drift signal or by performing the correction calculation while considering the waveform as a sine waveform.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a schematic configuration of an embodiment of the present invention, in which a spindle rotating motor 1 mounted on a drilling machine is rotated at a high speed (5 rpm).
(100,000 to 100,000 rotations) while lowering the entire shaft system at a predetermined speed, and the hole diameter φ0.3mm to 0.5mm in the multilayer printed circuit board 10.
A processing unit 7 for detecting and processing a cutting torque generated in the drill 9 is provided for a mechanism for making a minute hole.

The rotational force of the motor 1 is transmitted to the drive shaft 3 and a rotational phase sensor 4 for detecting the presence or absence of the marker 2 marked at a predetermined interval on the coaxial circumference is disposed facing the coaxial outer peripheral surface. A rotation phase signal for each rotation is detected.

On the other hand, the elastic body 5 attached to the lower side of the drive shaft 3 has a drill 9
Has the function of being elastically deformed in the radial direction by the cutting torque transmitted through the chuck 8 holding the shaft.

2 (a) and 2 (b) show the detailed configuration and principle thereof. As shown in FIG. 3A, the elastic members 5 are provided with slits 51, 52.
Is divided into three parts, 53, 54, and 55.
When a load torque is applied via the, it is elastically deformed as shown in FIG. 2 (b). (B) is a vertical cross-sectional view of the center of the slit 51 with respect to the center line of the cylinder.
However, when a load torque 61 is applied, the shape changes to an ellipse like 65. It has been confirmed that this deformation is proportional to the torque. If the radial displacement is detected by the torque sensor 6, the cutting torque can be detected. Therefore, the torque sensor 6 is arranged to face the outer peripheral surface of the elastic body 5.

As shown in FIG. 1, the signals detected by the rotation phase sensor 4 and the torque sensor 6 are amplified to an appropriate magnification via an amplifier 11 and an amplifier 12, and sent to a signal processing device 7.

Here, as the non-contact sensors 4 and 6, known capacitance displacement meters are used, and specifically, the following ones are applied.

Capacitance type non-contact displacement meter using two metal bodies as a capacitor plate and utilizing the fact that the capacitance of the capacitor changes in inverse proportion to the distance between the objects.

An eddy-current type non-contact displacement meter that measures the gap between the sensor and the object according to the strength of the eddy current generated when the head of the sensor to which high-frequency AC is applied is opposed to the object.

A laser-type measuring device that measures displacement from a reference measurement point.

An optical fiber type non-contact displacement meter constituted by a set of light emitting and light receiving elements.

Among them, the measurement accuracy is as high as 0.1 μ or less, but the system is large and the price is expensive, so that it is generally suitable for high-grade measuring instruments. ,, Are almost the same in terms of performance and price, but are particularly susceptible to surface contamination due to the reflectance of the measurement object, and are likely to cause errors in the measurement results.

, Have excellent compactness and wide application range.

In the signal processing device 7, the torque signal of the torque sensor 6 is sampled by the rotation phase signal of the rotation phase sensor 4, and the torque can be detected corresponding to the phase. Therefore, the change with time of the signal can be detected as the cutting torque. In this case, a threshold value equal to the cutting torque to be released is previously set in the threshold value setting unit 13.
When the value becomes equal to the set value, a signal indicating that over-torque is applied to the drill 9 is output. At this time, there is provided a driving device for vertically moving the shaft system, which rapidly raises the tip of the drill 9 to the upper side of the printed circuit board 10, thereby releasing the cutting torque. In this way, the drilling of the printed circuit board 10 is performed while the cutting and the torque release by the drill 9 are repeated.

Next, a method of processing signals detected by the rotation phase sensor 4 and the torque sensor 6 will be described in detail with reference to FIGS.

In FIG. 3, the change over time of the signal generated in the torque sensor 6 takes a form in which the amplitude of a sine waveform having a constant cycle changes as indicated by 61 in FIG.

This DC offset voltage due to the initial set gap δ of the AC drift signal V _D and the elastic body 5 and the torque sensor 6 by mechanical initial eccentricity of the elastic body 5 as shown in (b) V8
The signal 62 corresponding to the sum of. Numeral 61 denotes a signal obtained by adding a signal 63 equal to the amount of deformation generated by the cutting torque given to the elastic body 5 to the signal including the temperature and the time drift of the sensor amplifier 12 as shown in FIG. It is.

Therefore, when no torque is applied to the rotating elastic body 5, only the sine waveform 62 due to the drift signal appears, and when a torque is applied by drill cutting, the sum of the drift signal and the signal due to pure cutting torque is obtained. In (b), the amplitude of the signal (b) is gradually reduced by canceling the signal in the opposite phase by the signal (c). Further, when the cutting torque increases, as shown in FIG. 3A, the cutting torque signal appears strongly and the phase of the signal is reversed.

Next, a method of extracting only the cutting torque signal from the signal appearing on the torque sensor 6 will be described with reference to FIG.

In FIG. 4, the detection signal of the torque sensor 6 appears as a change in the amplitude of a sinusoidal waveform having a constant period as shown in FIG. 3A as in the case of FIG. It cannot be determined, compared, or determined.

In the present embodiment, this is made possible by focusing on a certain fixed point during one rotation of the elastic body 5 and monitoring the change over time at that point. As a basic method for realizing this, one rotation phase marker is attached on the circumference of the drive shaft, and a sensor 4 for detecting the rotation phase marker is installed, so that the rotation phase signal is generated once per main shaft rotation. The signal of the torque sensor 6 is sampled by the rotation phase signal. FIG. 4 (c) shows a temporal change in the torque signal at a fixed point detected during one rotation which changes every one rotation. Furthermore, in order to improve the detection response speed of the torque signal, two rotation phase markers are attached on the circumference of the drive shaft at 180 degrees apart from each other, and the rotation phase signal is generated twice per rotation, and the sampling of the torque sensor 6 is performed. By comparing and judging the increasing / decreasing tendency of the signal with the set threshold value every half cycle, a double detection response speed as shown in FIG. 4D can be realized.

Thus, upon reaching the set threshold value with the torque signal V _T which is obtained by sampling at the rotational phase signal, as a torque over, or display it, further raising thereby the tip of the drill rapidly torque It sends a release signal. However, at this time, due to the AC drift due to the initial eccentricity of the elastic body 5 and the offset signal such as the mounting position of the torque sensor 6, etc., (c) and (d) in FIG.
In this embodiment, the set threshold value is changed every time the rotational phase is measured.

Next, this will be described in detail. Here intended to set in relation to the maximum value of the absolute value rather than simply detected only that whether reaches the set threshold, the set threshold A ₀ itself cutting torque of the torque signal Thereby, the influence of the drift signal can be eliminated. That is, the signal of the torque sensor 6 when no torque is applied, that is, the drift signals of V ₁ and V ₂ are stored and held, and a set threshold value A ₀ equal to the cutting torque signal to be released is added or subtracted from this value. Then, when this value and the signal of the torque sensor 6 to which the torque is added become a predetermined value, a torque release signal is issued.

Expressing this as an equation, Set upper and lower limits. In contrast, the torque signal V _r after torque addition When bets has fallen, detects that the set threshold A ₀ which is heavy nourishment to the drift signal cutting torque exceeds.

Next an example of a setting method of the threshold A _0. Figure 5 (a) is a result of measurement by a crystal piezoelectric effect type cutting dynamometer load torque T ₀ of the drill in setting the threshold A ₀ of the present invention, the (b) figure the T ₀ It illustrates an example of the experimental data of the amplification results V _H of the detected value by the sensor 6.

In this case, the drill diameter is 0.5φ and the drill rotation speed is 30,000 rpm. However, as shown in the figure, the actual cutting torque T ₀ and the sensor signal V _H are almost proportional. The limit value of the drill cutting loss of the actual cutting torque is T _M (eg, 0.98 N · cm), and the corresponding amplification result of the sensor output is V _M (eg, 2.2 V).
When calculating the torque-voltage ratio R at this limit value, Becomes T _M differs depending on the drill diameter, and is 0.98 Ncm as described above for 0.5 φ, but 0.15 Ncm for 0.3 φ
It is. T _MD shows the value of cutting torque for any drill diameter
Then, the corresponding output voltage V _HD is V _HD = R · T _MD (4) The threshold value A ₀ is selected as a value close to the drill Setsuson limit, defined as for example A ₀ = 0.8 V _H.
Here, 0.8 is a kind of safety factor.

Next, the specific circuit configuration of the above torque detection method will be described in the sixth.
This will be described with reference to the drawings. In the figure, the signal processing device 7 is shown as a dedicated processing device, but may be a general-purpose microprocessor.

In FIG. 6, the signal of the torque sensor 6 is amplified by the sensor amplifier 12, the output of the rotational phase sensor 4 detected from the drive shaft is amplified by 11, and the rotational phase signal is used as the timing signal of the timing generator 20 by the hold unit 18. To a sampling signal.

The timing generator 20 is used to adjust the timing of each function based on the output of the eleventh function.

Among the signals of the hold 18, and converted into a digital signal by the torque signal (= drift signal) on the half cycle and the lower half cycle A / D converter 19 that occurs when torque no load, DV ₁ each data , DV ₂ in the initial value memory 17.

This data is updated at any time when no torque is applied, for example, immediately before drilling to minimize the influence of the drift.

On the other hand, the value obtained by converting the set value A ₀ of the threshold value setting device 13 into a binary number by the binary device 15, which is equal to the upper limit of the above-described cutting torque, for example, 0.8 T _M , is subtracted from the data of the initial memory 17, or The values are added and stored in the drift corrector 16 as α ₁ and α ₂ described above.

Next, the digital value DV _T of the alpha ₁ or alpha ₂ and the torque-added torque _{signal, D VT ≦ α 1, θ} = π / 2 + 2nπ (n = 1,2, ...) or D _VT ≧ α _2, Since θ = 3 / 2π + 2nπ (n = 1, 2,...), the comparator 21 detects that a cutting torque equal to or more than the set threshold has occurred.

 FIG. 7 shows another embodiment of the present invention.

As a method for further improving the torque detection response speed,
As shown in the figure, 4 rotations per elastic body rotation
The sampling of the torque signal is performed twice. Here, the rotational phase mark attached to the drive shaft is represented by θ, π-θ, π + θ, 2π-
At the position of θ. In this case, data of the initial memory for storing the drift signal was extracted at the points of θ and π + θ.
Data obtained by adding and subtracting the threshold value B ₀ to the data of V ₃ and V ₄ respectively
The values are stored in the drift corrector as β ₂ and β ₁ . And
When the torque signal D _VT after the addition of torque satisfies D _VT ≦ β ₁ or D _VT ≧ β _2, it is detected that a cutting torque equal to or greater than the set threshold value has been generated.

In yet another embodiment, as shown in FIG. 8 rotated, as a method for further increasing the torque signal detection point, at a position to detect the voltage V _5, V ₆ of maximum / minimum amplitude point of a torque unloaded signal the phase signal is provided, acceleration vital threshold C ₀ to V _5, V _6, in order to correct the sine wave wave, as _{(V 5 -C 0) = γ} 1 (V 6 + C 0) = γ 2 cutting stored drift corrector, the torque signal V _T after torque addition, the comparator _{21, V T ≦ γ 1 ·} sinθ or when there was summer and V _T ≧ γ ₂ · sinθ, exceeds the set threshold value The occurrence of torque can be detected.

As a result, the number of times of sampling for torque detection can be increased as much as possible within the permissible range of the signal processing time, and minute torque generated on the high-speed rotating shaft can be detected with good responsiveness.

However, since the amplitude change amount of the antinode portion of the sine wave and the portion near the node is small, the number and setting of sampling points such as not being used as torque signal data are determined by comprehensively determining the change amount of the amplitude. It needs to be adopted.

By but those giving appropriate threshold A ₀ from the outside to store the equation (4) to the threshold setting unit 13 in the above embodiment, thresholds for drill diameter used Can be automatically generated.

〔The invention's effect〕

According to the present invention, it is possible to obtain a torque detecting device which has a good response even at a high speed rotation and has a high resolution even for a small torque.

For example, when the number of rotations is tens of thousands (50,000 to 100,000) and the drill diameter is φ0.3, φ0.4, φ0.5, noise is generated due to the contact point as in the conventional slipping method. Accurate measurement is not possible, and responsiveness is not bad due to the inertia of the spindle as in the method of detecting a decrease in the rotation speed of the spindle due to torque. In addition, the accuracy is higher than that of the conventional elastic body deformation method, and in a prototype experiment, the accuracy such as the minimum detection torque of 0.1 Ncm and the resolution of 0.02 Ncm was obtained.

[Brief description of the drawings]

1 is an overall configuration diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram showing deformation of an elastic body of the torque sensor of the present invention, and FIGS. 3 and 4 illustrate a signal processing method of the present invention. FIG. 5 is a diagram showing an example of a torque measurement result according to the present invention, FIG. 6 is a circuit configuration diagram showing one embodiment of the present invention,
FIG. 7 is a signal waveform diagram for explaining another embodiment of the present invention, and FIG. 8 is an explanatory diagram for explaining still another embodiment of the present invention. 2 Marker 4 Rotation phase sensor 5 Elastic body
6: Torque sensor, 7: Signal processing device, 9: Drill, 13: Threshold setting device, 16: Drift correction device, 17
...... Initial value memory, 18 Hold device, 19 A / D converter, 21 Comparator.

Claims (2)

(57) [Claims] An apparatus for extracting a torque signal from a rotating shaft system provided with an elastic body which deforms in a radial direction according to the magnitude of a torque, wherein the first non-contact detecting means detects a deformation amount of the elastic body. A type sensor, a second sensor for detecting a rotation phase of each rotation of the rotation shaft, and means for obtaining a torque signal obtained by sampling an output signal based on the first sensor by an output signal based on the second sensor. Means for obtaining a predetermined threshold value for the sampled torque signal as a corrected threshold value based on the output signal based on the first sensor in the latest no-load sampling period of the rotating shaft; and the corrected threshold value. Means for setting a threshold of a torque signal in a sampling cycle at the time of load for each rotation. 2. The amount of deformation of an elastic body in a drilling bar having a device for extracting a torque signal of a drill from a rotating shaft system provided with an elastic body which deforms in the radial direction according to the magnitude of the torque. A first non-contact type sensor for detecting the rotation, a second sensor for detecting the rotation phase of each rotation of the rotating shaft,
Means for obtaining a torque signal obtained by sampling an output signal based on the first sensor by an output signal based on the second sensor; and setting a predetermined threshold value for the sampled torque signal at the time of the latest no-load of the rotating shaft. Means for obtaining a corrected threshold value based on the output signal based on the first sensor in the sampling cycle, and means for setting the corrected threshold value as a threshold value of a torque signal in a sampling cycle at the time of load for each rotation; Means for pulling up the drill from the cutting portion when the sampled torque signal exceeds the corrected threshold value during cutting by the drill.