JP2629833B2 - Composite rotary encoder - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a rotary encoder used for detecting a rotation angle.

[Prior Art] Conventionally, as a rotary encoder used for detecting a rotation angle of a shaft, an incremental type and an absolute type are generally used.

An incremental type rotary encoder forms an equally spaced binary code pattern on a rotating disk coupled to a shaft, and detects this binary code pattern as a pulse signal with the rotation of the rotating disk. By integrating the pulse signals, the rotation angle of the shaft is detected.

In this incremental type rotary encoder, it is relatively easy to form a pattern on a rotating disk, and higher resolution can be achieved by multiplying a detected pulse signal.

However, when the rotation speed of the shaft is low, there are disadvantages that the pulse interval becomes long and accurate control cannot be performed, and a detection error easily occurs due to electric noise or the like.

Absolute encoders are known as those capable of instantaneously detecting an absolute position corresponding to a rotation angle from a sensor without using a counter.

A typical detection panel of this absolute encoder employs a rotating disk configuration, and on its surface, a ring pattern is formed concentrically with a number corresponding to the number of code bits,
The detected pattern binary-coded by the ring pattern is formed.

By doing so, the number of divisions can be 2 ⁿ where n is the number of code bits. For example, if ¹⁰ sensors are used, a rotary encoder of 2 ¹⁰ = 1024 divisions can be obtained.

However, increasing the resolution requires a large number of sensors and a finer annular pattern, which is expensive.

Also, when the rotating disk is made smaller, the diameter of the ring pattern in the diameter direction becomes narrower, and it becomes difficult to reliably detect information of each ring pattern, so that downsizing is difficult.

Further, as a combination of both, there is a rotary encoder provided with both an incremental code pattern and an absolute code pattern on a rotating disk (Japanese Patent Laid-Open No. 60-15015).

However, this rotary encoder detects the rotational speed of the shaft using an incremental code pattern, and detects the rotational angle of the shaft using an absolute pattern.

Therefore, the signal detected from the incremental pattern and the signal detected from the absolute pattern are separately processed.

Therefore, in order to detect the rotation angle of the shaft with high resolution, it is necessary to increase the number of absolute annular patterns. In addition, the detection error of each signal, the missing pulse, etc. may overlap and the detection result of the rotation angle may differ between these signals.

[Problems to be Solved by the Invention] In recent years, with the advance of technology, a rotary encoder having a smaller size, high resolution, and high accuracy has been required.

An object of the present invention is to provide a rotary encoder satisfying such a condition.

[Means for Solving the Problems] The gist of the present invention for solving such problems is as follows. In a rotary encoder that detects the rotation angle of a shaft as an n-bit digital signal, a rotary disk has m bits ( However, 1 <m
<N) an absolute code pattern to be an absolute signal is provided, and an absolute signal detecting means having a detecting portion for detecting the absolute signal on a fixed plate; and 2 ^m pulses per rotation on the rotating disk. A timing pulse code pattern for providing the plurality of timing pulse signals, a timing pulse signal detecting means provided with the timing pulse signal detecting section on the fixed plate, and a timing pulse detected by the timing pulse signal detecting means. Absolute signal determining means for determining the absolute signal detected by the absolute signal detecting means in synchronization with the signal; l bits of the rotation angle signal (where l = nm)
The rotating disk is provided with an incremental code pattern so as to output an incremental signal used to detect the phase difference, and a detection unit for detecting a two-phase signal having a phase shifted from the incremental code pattern is provided on the fixed plate. Incremental signal detection means provided in the above, Rotation direction determination means for determining whether the rotating disk is rotating forward or reverse based on the two layers of incremental signals detected by the incremental signal detection means, The rotation direction If the determination means determines that the rotation is normal, the l-bit signal is all set to 0 in synchronization with the timing pulse signal, and then the l-bit signal is incremented in synchronization with the detection timing of the incremental signal. When it is determined that the rotation direction is reversed by the rotation direction determination means, Incremental to determine the l-bit incremental signal by setting all the l-bit signals to 1 in synchronization with the pulse signal and then decrementing the l-bit signal in synchronization with the detection timing of the incremental signal A signal determination unit, and an n-bit digital signal that sets the m-bit absolute signal determined by the absolute signal determination unit as upper bits and the l-bit incremental signal determined by the incremental signal determination unit as lower bits and n-bit signal forming means.

[Operation and Effect] According to the present invention, the absolute signal is determined in synchronization with the timing pulse signal generated at least 2 ^m pulses per rotation, so that the influence of the rising and falling edges of the absolute signal waveform and the noise Absolute signals whose values change at equal angular intervals can be determined without being affected. In addition, since the two-phase signals having different phases are detected as the incremental signals, the rotation direction can be determined from the manner in which these two-phase signals change. Then, the lower l bits are set to 00 according to the rotation direction.
... Counting method incrementing from 0, 11 ・
.. Since the counting method for decrementing from 1 is switched, the lower 1-bit signal can be determined with high accuracy.

Therefore, it is not necessary to represent all n bits only with the absolute signal, and even if the detection accuracy of the absolute signal itself is rough, sufficient accuracy is assured by determining the absolute signal using the timing pulse. be able to. In addition, since the incremental signal is switched between increment and decrement according to the rotation direction while being initialized in synchronization with the timing pulse, the absolute signal and the incremental signal can be accurately synchronized.

As a result, according to the present invention, it is possible to obtain not only a small size and high resolution but also an n-bit angle signal with high accuracy while being small.

Further, since an absolute code pattern having a sufficiently large width in the diameter direction can be obtained, the output of the absolute signal increases, and a stable output can be obtained.

[Embodiment] An optical composite rotary encoder according to an embodiment of the present invention will be described below with reference to the drawings.

This rotary encoder detects the rotation angle as a 15-bit digital signal (2 ¹⁵ = 32768 divisions). The upper 8 bits of the rotation angle are detected by an absolute code pattern, and the lower 7 bits are detected by an incremental code pattern. I do.

FIG. 3 is a view showing a cross section of the composite type rotary encoder 2 of the present embodiment.

The encoder 2 includes a housing 8 including a base 4 and a cover 6.
Is housed inside.

A rotor shaft 10 projects from the base 4, and the rotor shaft 10 is supported by a bearing 12 attached to the base 4.

A rotating disk 14 is attached to the rotor shaft 10, and the rotating disk 14 rotates with the rotor shaft 10.

As will be described later, an absolute code pattern and an incremental code pattern are formed on the rotating disk 14.

A light emitting element 16 is arranged on the back surface (upper side in the figure) of the rotating disk 14, and the light emitting element 16 is mounted on a waveform shaping circuit board 18. Note that the waveform shaping circuit board 18 is supported by the housing 8 and fixed to the rotating disk 14.

Further, the waveform shaping circuit board 18 is formed so as to extend to the surface of the rotating disk 14 with the outer peripheral portion of the rotating disk 14 crotch, and the fixed slit plate 20 is fixed.

The fixed slit plate 20 is disposed on the surface (lower side in the figure) of the rotating disk 14 so as to face the rotating disk 14, and a plurality of slits are formed on the surface as described later.

Further, a light receiving element 22 is arranged for each slit on the surface of the fixed slit plate 20 opposite to the side facing the rotating disk 14.

Then, an absolute signal and an incremental signal are detected by a detection unit in which each slit of the fixed slit plate 20 and the corresponding light receiving element 22 are combined.

The output of the light receiving element 22 is input to the waveform shaping circuit board 18, and the output of the waveform shaping circuit board 18 is taken out of the housing 8 via the lead wire 24.

As shown in FIG. 1, the rotating disk 14 has an incremental code pattern 30 composed of slits at equal intervals on the outer peripheral portion.
Eight annular patterns 32A to 3 concentrically arranged on the inner circumference
Absolute code pattern 32 consisting of 2H, incremental code pattern 30 and absolute code pattern 32
And the timing code pattern. Each of these patterns is a slit array formed in accordance with a predetermined rule, and these slit arrays are formed, for example, by forming a light-shielding vapor-deposited film on a transparent disk surface serving as a rotating disk 14, and forming the slits. The deposited film corresponding to the formation region is formed by selective etching by a photolithography technique or the like.

Also, the ring pattern of the absolute code pattern 32
Light amount correction tracks 36A and 36B are provided between 32D and 32E and between the ring pattern 32H and the timing code pattern 34.

The absolute code pattern 32 includes eight ring patterns 32A to 32H concentrically arranged as described above,
These are constituted by areas indicating logical levels, for example, made of gray codes in the same direction as the circumference from a predetermined diameter serving as a reference.

Here, a 4-bit gray code is shown below as an example.

As described above, each of the annular patterns 32A to 32H has a logical level formed by a light and dark pattern in a slit row.

On the other hand, as shown in FIG. 2, the fixed slit plate 20 has incremental signal detection slits 40A and 40B, timing signal detection slit 42, absolute signal detection slits 44A to 44H, and light amount correction slits 46A and 46B. .

The slits 40A and 40B for detecting incremental signals cooperate with the incremental code pattern 30 of the rotating disk 14 to generate the incremental signals A and B whose output phases are shifted by 90 degrees.

The slit 42 for detecting the timing signal is a rotating disk.
A timing signal is generated in cooperation with the 14 timing code patterns 34. Since this timing signal requires a sharp rise and fall, the width of the slit 42 in the circumferential direction is as very small as 30 μm. Then, in order to secure the light amount, the light emitting device is constituted by five slits.

On the other hand, slits 44A-44H for detecting absolute signals
Are the absolute code patterns 32A to 32H of the rotating disk 14.
And generate absolute signals A to H. Since the absolute signals A to H are based on timing pulses as described later, the width of the slits 44A to 44H can be widened to 240 μm, and a sufficient light amount can be secured.

The rotating disk 14 and the fixed slit plate 20 are attached to the housing 8 such that the annular pattern for each signal corresponds to the slit.

Then, when the slits of the rotating disk 14 and the slits of the fixed slit plate 20 match, the transmitted light from the light emitting element 16 is detected by the light receiving element 22.

FIG. 4 shows each output signal of the light receiving element 22 as the rotating disk 14 rotates. These output signals are converted into 15-bit digital signals representing the rotation angle by the circuit shown in FIG.

That is, first, the timing signal and the timing signal delayed by the gate are input to the anti-coincidence circuit (EX-OR) 50 to obtain a timing pulse.

Then, when the absolute signals A to H are input to D-
When this timing pulse is input to the clock terminal CK of the flip-flop circuit 52, the upper 8 bits b8 to b15 of the rotation angle signal are output.

On the other hand, the A of the incremental signal 90 degrees out of phase
The up / down discrimination circuit 54 discriminates whether the rotation direction of the rotating disk 14 is positive or reverse, and outputs an up / down signal. The up-down signal is "0" for forward rotation and "1" for reverse rotation.

The A-phase and B-phase of the incremental signal are input to the pulse quadrupler circuit 56, and a quadrupled pulse signal is output.

The up / down signal is input to the up / down terminals D / and preset terminals A1 to A4 of the 4-bit up / down counters 58 and 60, and the pulse signal is input to the clock terminal CK of the up / down counter 58.

Therefore, when the above-mentioned timing pulse is input to the load terminal L of the up / down counters 58 and 60, each bit of the counters 58 and 60 is set to "0" when the rotating disk 14 is rotating forward.
Is set, and in the case of reverse rotation, "1" is set in each bit. Each time one pulse signal is input, it is incremented or decremented by one.

As a result, the lower 7 bits b1 of the rotation angle signal are output from the output terminals B1 to B4 of the counter 58 and the output terminals B1 to B3 of the counter 60.
To b7 are output.

Then, by adding b8 to b15 obtained from the absolute signal and b1 to b7 obtained from the incremental signal, a 15-bit digital signal b1 to b15 is obtained. In this embodiment, the output of the output terminal B4 of the counter 60 is not used.

That is, in this embodiment, when a timing pulse is generated, an absolute signal is captured,
Initialization of the incremental signal count is performed.
Therefore, rotation angle detection using an incremental signal can be performed with high resolution and high accuracy.

In the conventional absolute type rotary encoder, at least 15 ring patterns are required to output a rotation angle as a 15-bit digital signal.

However, in this embodiment, by combining the absolute code pattern and the incremental code pattern, the rotation angle can be output as a highly accurate 15-bit digital signal with a very small annular pattern.

Since the number of ring patterns is reduced as described above, the rotary encoder of the present embodiment can be reduced in size. In addition, since the number of ring patterns is small, the width of each ring pattern in the diameter direction can be widened, and each signal can be detected stably.

In the present embodiment, each signal is detected optically. However, a magnetic recording pattern may be used as each code pattern, and a magnetic type configured to detect each signal by a magnetic detection element may be used. Also, some code patterns may be optical and others may be magnetic.

Further, the absolute code pattern of the present embodiment is:
Although it is based on the gray code, it is not necessarily limited to this and may be based on another code.

[Brief description of the drawings]

FIG. 1 is a plan view illustrating each code pattern formed on a rotating disk of a composite rotary encoder according to an embodiment of the present invention, and FIG. 2 illustrates an arrangement of slits formed on a fixed slit plate thereof. FIG. 3 is a cross-sectional view showing the overall configuration, FIG. 4 is an explanatory diagram of an output signal of the light receiving element, and FIG. 5 is an explanatory diagram of the waveform shaping circuit. 14 ... rotating disk, 16 ... light emitting element, 20 ... fixed slit plate, 22 ... light receiving element, 30 ... incremental code pattern, 32A to 32H ... absolute code pattern, 40A,
40B: Incremental signal detection slit, 44A-44
H: Absolute signal detection slit.

Claims (1)

(57) [Claims] In a rotary encoder for detecting a rotation angle of a shaft as an n-bit digital signal, a rotating disk has m bits of a rotation angle signal (where 1 <m <
n) an absolute code pattern for forming an absolute signal, and an absolute signal detecting means provided on a fixed plate with a detecting section for detecting the absolute signal; and 2 ^m or more pulses per rotation on the rotating disk. A timing pulse code pattern for providing a plurality of timing pulse signals, a timing pulse signal detecting means provided with a timing pulse signal detecting section on the fixed plate; and a timing pulse signal detected by the timing pulse signal detecting means. An absolute signal determining means for determining the absolute signal detected by the absolute signal detecting means in synchronism with the above, and outputting an incremental signal used to detect 1 bit (l = nm) of the rotation angle signal To the rotating disk Incremental signal detection means provided with a fixed code plate and a detection unit for detecting a two-phase signal having a phase shifted from the incremental code pattern, and detecting the incremental signal pattern by the incremental signal detection means. Rotation direction determining means for determining whether the rotating disk is rotating forward or reverse based on the phase incremental signal; and when the rotating direction determining means determines that the rotating disk is rotating forward, the rotation direction is synchronized with the timing pulse signal. The l-bit signal is all set to 0, and then the l-bit signal is incremented in synchronization with the detection timing of the incremental signal. When the rotation direction determining means determines that the rotation is reverse, the timing pulse signal is used. In synchronization with
An incremental signal determining means for determining the l-bit incremental signal by setting all the bit signals to 1 and decrementing the l-bit signal in synchronization with the detection timing of the incremental signal; and the absolute signal M determined by the determination means
And n-bit signal forming means for forming an n-bit digital signal for lowering the l-bit incremental signal determined by the incremental signal determining means, wherein the absolute signal of the bit is set as an upper bit. Type rotary encoder.