JPS6310766B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a contact type encoder for a measuring instrument, and particularly to a contact type encoder for a measuring instrument suitable for small measuring instruments such as low current consumption battery-driven devices.

2. Description of the Related Art Encoders that detect the mechanical displacement of a probe as an electrical digital signal are well known, and are applied in various measurement fields as length measuring machines, position detectors, and the like. This type of encoder electrically detects the length of the object to be measured as a scale or other displacement amount, and the electrical detection means include electromagnetic type,
Various types of encoders are known, such as electrostatic type and photoelectric type. In particular, photoelectric conversion type encoders are used as micrometers, calipers, coordinate measuring machines, etc. due to their advantages such as miniaturization and high-precision measurement. It has been widely put into practical use.

However, conventional devices of this type have the drawbacks of being relatively expensive and consuming a relatively large amount of current. In particular, batteries are used as a driving source for recent compact length measuring machines and the like, and for this reason there is a demand for low current consumption and long life spans. The digital displacement detection device has the advantage that its electrical processing is formed from a C-MOS circuit, and the current consumption in these electrical processing circuits is extremely small. In photoelectric devices, a light emitting device for photoelectric conversion, such as a light emitting diode, consumes a large amount of current, resulting in a problem that the overall current consumption increases.

In contrast to the non-contact type encoders mentioned above, contact type encoders have been known that detect electrical digital signals from opening/closing operations by contacting contacts, and can electrically detect mechanical displacement with a simple structure. It has the advantage of being highly accurate and has been put to practical use in certain fields, but it has only been used as a positioning mechanism that does not require precision or as a rotational position detection device for large drive mechanisms. Its use was not considered at all, especially in length measuring machines that require small size and high precision. In other words, this type of contact type had fundamental drawbacks such as low contact reliability, extremely unstable contact state, and extremely easy contact state change after long-term use. It was considered impossible to use it in length measuring machines, etc., where poor contact directly causes errors.

However, one aspect of this device is that it can convert mechanical displacement into electrical digital pulses only by applying voltage, and basically does not require current consumption. We focused on the application of this method to a small length measuring machine that can be driven by a battery with low current consumption by combining it with a voltage type element such as a C-MOS transistor.

However, with such a contact encoder,
There is a drawback that various noises are mixed into the input voltage that changes as the detection contact opens and closes, and as a result, the accuracy and reliability of the measuring device are significantly impaired. This type of noise is mainly caused by the surface condition of the contacts, such as dirt, the presence of high resistance parts, and other surface deterioration due to long-term use, and it has been impossible to completely prevent the incorporation of these noises.

FIG. 1 shows a schematic configuration of the above-mentioned contact type encoder, which includes a group of slit contacts 10 and 12 made up of a plurality of conductors arranged at a predetermined interval, and a measuring probe connected to the group of slit contacts 10 and 12. A sliding contact 14 that moves in the AB direction in response to mechanical displacement is provided, a battery 18 serving as a DC power source is connected to the sliding contact 14 via a resistor 16, and the slit contact group 1
A detection voltage is applied between 0 and 12 and the sliding contact 14. Both slit contact groups 10 and 12 can be formed, for example, from slit electrodes formed by vapor deposition on the side surface of a disk, or from linear slit electrode groups, and the sliding contact 14
can be formed from a brush contact that rotates or moves linearly in conjunction with the probe. Therefore, as the sliding contact 14 moves in the direction of the arrow AB, the opening/closing operation between the slit contact 10 or 12 and the sliding contact 14 causes the sliding contact 14 to be removed from the terminals 20 and 22.
A digital signal corresponding to the amount of movement can be detected. By arranging the slit contact groups 10 and 12 with a predetermined phase difference, 90 degrees in FIG. It becomes possible to obtain a square wave signal.

However, as described above, when the detection contact is formed from the simple slit contacts 10, 12 and the brush contact 14, noise due to disturbances enters the terminals 20, 22, and especially in the opening/closing critical state of the detection contact, the contact It is known that incomplete contact causes non-negligible noise, and
The figure shows a state in which disturbance noise or critical noise occurs before and after a predetermined measurement signal, that is, region T. Therefore, in the conventional device, these noises, particularly noises caused by poor contact between the contacts, cause counting errors in digital measurement signals, resulting in a drawback that the accuracy of the measuring device is significantly reduced.

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to reduce the occurrence of contact failures, and even if noise caused by contact failure occurs, it can distinguish between noise and signals and generate correct signals. An object of the present invention is to provide an improved contact type encoder for a measuring instrument that only counts.

In order to achieve the above object, the present invention provides a resistance band that extends continuously in a predetermined direction, and a contact that slides directly and constantly relative to the resistance band in conjunction with the mechanical displacement of a probe. at least one pair of sliding contacts;
a detection circuit that electrically detects a resistance value between a pair of sliding contacts, and a detection circuit that electrically detects a resistance value between a pair of sliding contacts; It is characterized in that the resistance value between the moving contacts changes periodically along the extending direction of the resistor along with the sliding movement thereof.

Preferred embodiments of the present invention will be described below based on the drawings.

FIG. 3 shows a preferred embodiment of the encoder according to the present invention, which has a configuration in which the displacement detectors 24 and 26 of the encoder move relative to each other in conjunction with the mechanical displacement of the measuring head in a caliper or other length measuring device. Become,
In the embodiment, the first displacement detector 24 is fixed to an encoder board (not shown), and the other displacement detector 26 is linked to the measuring element of the length measuring machine to detect the first displacement detector 24.
can be moved relative to the displacement detector 24 of.

The first displacement detector 24 is made of a plastic or other insulating plate, and on one surface thereof is provided a resistance band 28 that extends continuously in a predetermined direction, in the embodiment, in the direction of the arrow CD in the figure. Obi 2
Reference numeral 8 is a thin film resistor attached to the surface of the displacement detector 24 in the embodiment.

A pair of sliding contacts 30 and 32 are fixed to the other displacement detector 26, and both sliding contacts 3
0 and 32 are in sliding contact with the resistance band 28 at predetermined intervals, respectively. Therefore, sliding contact 3
This means that a partial resistance of the resistance band 28 between them is connected between 0 and 32.

The resistance value between the sliding contacts 30 and 32 is
It is electrically detected by a detection circuit 34 connected to terminals 0 and 32.

The characteristic feature of the present invention is that the resistance band 2
8 changes continuously and periodically along the extension direction CD, and as a result, when the resistance band 28 and the sliding contacts 30, 32 move relative to each other, the contact points 30, 32 change continuously and periodically. A continuous and periodic change occurs in the resistance value between the probes, and from this, the mechanical displacement of the probe can be electrically detected.

The resistance band 28 in this embodiment has a substantially sinusoidal shape at both ends thereof, and the spacing between the sliding contacts 30 and 32 is set to be the same as the sine wave pitch of the resistance band 28. Therefore, a resistance value that changes approximately sinusoidally in response to the mechanical displacement of the probe is obtained between the contacts 30 and 32. This change in resistance value is converted into an electrical signal by a detection circuit 34, which includes a bridge circuit 36, a voltage comparator 38, and a poor contact alarm circuit 4.
Contains 0. Both ends of the sliding contacts 30 and 32 are connected to one side of the bridge circuit 36, and the output of the bridge circuit 36 is supplied from a comparator to an AD converter 38, where it is compared with a threshold voltage _V1 , and the output terminal 42 is connected to one side of the bridge circuit 36. The signal is supplied to a subsequent stage counting circuit (not shown). Similarly, the output of the bridge circuit 36 is supplied to a poor contact alarm circuit 40 consisting of a comparator, which connects either of the sliding contacts 30, 32 and the resistance band 28.
It is possible to warn that a poor contact has occurred between the

The first embodiment of the present invention has the above configuration, and its operation will be explained below.

In the present invention, the resistance band 28 is a resistor that is continuously extended and formed on the first displacement detector 24,
Sliding contacts 30 and 32, which are in relative sliding contact with the resistance band 28 in conjunction with the mechanical displacement of the probe, both maintain constant contact with the resistance band 28, and the amount of relative movement between them is equal to the sliding contact 30. , 32 is detected from the change in resistance value. That is, the resistance value of the resistance band 28 is equal to the resistance value of the contact point 3.
0 and 32, and as the contact position of both sliding contacts 30 and 32 with respect to the resistance band 28 changes, both contacts 3
The resistance value between 0 and 32 changes significantly, and by electrically detecting the change in resistance value corresponding to the amount of movement of the probe by the detection circuit 34, unlike conventional contact contact type encoders, the resistance value changes significantly. It is possible to obtain the type encoding. Both sliding contacts 30, 3
2 does not leave the resistance band 28 under normal measurement conditions and is always in a contact state with a predetermined contact pressure.
8, there is almost no contact failure. In particular, conventional contact failures tend to occur as critical noise in the detection contacts, and this critical noise occurs when the contacts connect or disconnect, so the encoder of the present invention, which is a constant contact type that does not have such contact or disconnection, has a higher level of noise than the conventional one. It is possible to significantly increase its reliability. The periodic resistance value change of the resistance band 28 in the embodiment is almost determined by the resistance band width in the direction perpendicular to the stretching direction CD, and such a contact band width pattern can be arbitrarily selected. By providing a substantially sinusoidal contact band width pattern, it is possible to obtain an electrical detection signal that changes substantially sinusoidally between the sliding contacts 30 and 32 when the probe is mechanically displaced.

FIG. 4 shows waveforms of various parts in the detection circuit 34, and the resistance value between the sliding contacts 30 and 32 detected by the bridge circuit 36 is equal to the bridge output 100.
As is clear from FIG. 4, the bridge output 100 is obtained as a sinusoidally varying voltage signal approximately following the pattern of the resistance band 28.
And this bridge output 100 is the AD converter 3
8, it is compared with the threshold voltage V ₁ and outputted from the output terminal 42 as a digital signal 102 to a subsequent counter circuit, and by counting this digital pulse signal, it is possible to accurately determine the amount of mechanical displacement of the probe. It becomes possible.

Further, according to the always-contact type encoder of the present invention, the bridge output 100 has a voltage value within a predetermined range unless the contacts 30 and 32 are opened, but if the contacts 30 and 32 are not opened for some reason. If it is opened, the output 100 will show an abnormal value that is significantly different from the normal voltage value, and in the present invention, such characteristics are utilized to detect poor contact between the sliding contacts 30, 32 and the resistance band 28. It becomes possible to reliably warn that something has occurred. That is, at time t in FIG.
0, 32 causes a contact failure with the resistance band 28, the bridge output 100 becomes a significantly large value far from the normal voltage indication range, and from this, the contact failure alarm circuit 40 detects that this abnormal value exceeds the comparison voltage Vo. When this occurs, an alarm signal 104 can be output to invalidate the measured value or to perform re-measurement.

As described above, in the embodiment, it is possible to reliably detect the displacement of the probe that changes linearly, and in particular, the contact pressure of the detection contact is approximately constant, so noise or contact that has conventionally occurred can be detected. It becomes possible to reliably prevent defects.

FIG. 5 shows another resistance band width pattern suitable for the present invention, in which a triangular wave pattern is adopted.

FIG. 6 further shows another embodiment of the present invention,
In this embodiment, a disk-shaped first detector 2
Two ring-shaped resistance bands 28a, 28b on the sides of 4
is pasted, and each resistance band 28a, 28b has a sinusoidal resistance band width pattern along its extending direction, which in the embodiment is a circular direction. Each resistance band 28a, 28b has a pair of sliding contacts 30.
a, 32a, 30b, and 32b are arranged correspondingly, and the inter-contact resistance value can be detected from each contact pair.

In FIG. 6, both resistance bands 28a and 28b have different phases in their patterns, or by providing a phase in the arrangement of each contact pair, it becomes possible to detect resistance value changes as sine wave and cosine wave signals. The subsequent counter can perform accurate signal division based on these two types of detection signals.

Figure 6 is suitable for electrically detecting spindle rotation, such as in a micrometer, and can be easily incorporated into such a small length measuring device and used as an inexpensive high-precision encoder. becomes.

FIG. 7 shows still another embodiment of the present invention,
The resistance bands 28a, 28b are formed on the side surface of the cylindrical first displacement detector 24, and the two pairs of sliding contacts 30a, 32a, 30 are formed similarly to the embodiment shown in FIG.
b and 32b, it is possible to detect resistance value changes in different phases.

As explained above, according to the present invention, the contacts of the contact type encoder are always in contact, so that the contact pressure is maintained at an extremely stable predetermined value, and the occurrence of disturbance noise or critical noise is significantly reduced. becomes possible. Therefore, according to the present invention, a highly accurate and highly reliable encoder can be provided. Further, according to the present invention, when a contact failure occurs between the sliding contact and the resistance band, it is possible to issue a warning immediately, and it is possible to reliably eliminate errors mixed in the measured values.

Note that the conductor according to the present invention can also be formed from conductive plastic or other materials, and is extremely suitable for a low-cost, small-sized, portable length measuring machine.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an example of a contact encoder, FIG. 2 is a detection waveform diagram of the encoder of FIG. 1, and FIG. 3 is a preferred embodiment of the contact encoder for measuring instruments according to the present invention. 4 is a waveform diagram of each part of FIG. 3, FIG. 5 is an explanatory diagram showing another pattern of the resistance band in FIG. 3, and FIG. 6 is a schematic diagram showing another embodiment of the present invention. A partial plan view, FIG. 7 is a schematic explanatory diagram showing another embodiment according to the present invention. 28...Resistance band, 30, 32...Sliding contact, 3
4...detection circuit, 40...poor contact alarm circuit.

Claims (1)

[Scope of Claims] 1. A resistance band that continuously extends in a predetermined direction, and at least one pair of sliding members that are in relative direct sliding contact with the resistance band at all times in conjunction with the mechanical displacement of the probe. and a detection circuit that electrically detects a resistance value between a pair of sliding contacts, and continuously and periodically changes the width of the resistance band along its extending direction. 1. A contact type encoder for a measuring instrument, characterized in that a resistance value between a pair of sliding contacts is continuously and periodically changed along an extending direction of the resistance band in accordance with the sliding operation thereof. 2. The encoder according to claim 1, wherein the width of the resistance band changes approximately sinusoidally.