JPH0226459B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a speed frequency generator for sensing the rotational speed of a motor.

[Prior Art] This type of generator has traditionally been constructed by, for example, cutting slits at evenly spaced intervals on the outer circumference of a disk fixed to the rotor, and sandwiching the outer circumference with a projector on one side and a receiver on the other. In this conventional device, as the rotor rotates, the input to the receiver changes AC depending on the presence or absence of the slit, and since the frequency of this AC is proportional to the speed, the rotational speed of the motor changes. It is used to detect.

Also, it is a conventionally known method to use a magnetoresistive element instead of the light emitter/receiver and a magnet instead of the slit. However, in these conventional devices, since the AC signal is extracted from one location (or several locations), the detected AC signal may have periodic irregularities, that is, frequency irregularities, due to the influence of mechanical manufacturing errors in the slit or attached magnet. occurs.

Conventionally, the first method for removing the above-mentioned periodic unevenness is
A speed generator called a full-circumference integral type as shown in Figures a and b has been considered. First, in FIG. 1A, a rotor magnet 20 for a speed generator is assumed, which is attached to a rotor and magnetized with multiple poles at approximately equal pitches (equivalently expanded in a straight line in the figure). Next, a coil plate 21 is assumed, which is provided at a position on the stator opposite to the rotor magnet 20 and has a coil (equivalently developed linearly in the figure) having a coil provided at approximately equipolar pitch with the rotor magnet 20. In this conventional example, as the rotor magnet 20 rotates, the coil plate 21
The voltage induced in the coil changes alternately, and the frequency of this alternating signal is proportional to the speed of the motor.

In this conventional method, since the coil plate 21 is arranged almost all around the motor in the peripheral direction, the sum of the voltages on each coil side becomes the AC signal output. As a result, even if there is unevenness in the magnetized magnetic pole pitch of the rotor magnet 20, there is almost no unevenness in the total AC signal corresponding to the entire circumference of the coil plate 21, and as a result, an accurate AC signal, that is, a speed signal can be obtained. In this case, even if there is unevenness not only in the magnetic poles of the rotor magnet 20 but also in the arrangement of the coils on the coil plate 21, the output will be a signal synthesized over the entire circumference, so the signal frequency unevenness will be extremely reduced.

In addition to the AC power generation system shown in Figure 1a above, conventional
The variable reluctance type frequency generator shown in Figure b is also frequently used.

In the figure, the magnet 23 on the stator is magnetized as a single pole, and the soft magnetic plate 24 has an uneven inner circumference.
The stator magnetic path of the speed generator is constituted by the soft magnetic yoke 26, and in the space between these, a signal detection coil 25 is arranged, and this is constituted by a wire wound in a large number in a circular shape. . Further, the rotor plate 22 has irregularities carved on its outer periphery, and these irregularities are made at the same pitch as the irregularities of the soft magnetic plate 24.

In this conventional example, when the rotor plate 22 rotates as the motor rotates, an AC signal having a frequency proportional to the pitch of the unevenness and proportional to the rotational speed is induced into the coil 25 using the magnet 23 as a magnetomotive force source. Ru. However, the conventionally known
In the case of a full-circle integral type configuration as shown in Figures a and b, a magnetomotive force source dedicated to a single-pole or multi-pole speed generator is required.

In view of this, there has conventionally been a device shown in FIG. 2 that can eliminate the need for a magnetomotive force source dedicated to the speed generator. This is an example of a rotating magnet field type flat motor, and figure a shows a magnet 1 attached to a soft magnetic disc 2, a soft magnetic ring 3 facing the unevenness carved on the inner circumferential surface, and a signal detecting ring 3. coil 6
FIG. FIG. 2b is a sectional view taken along the line a-a in FIG. 2a, in which the soft magnetic yoke 7 and the armature flat winding 8, which are not shown in FIG. The soft magnetic ring 3 and the coil 5 are attached to the dotted line portion by a pedestal 6, and constitute a stator. The soft magnetic ring 3 has irregularities of uniform pitch τ carved all over its outer surface in the circumferential direction. On the other hand, the inner circumferential surface of the magnet 1 is also carved with unevenness at the same pitch τ, but the unevenness phase is reversed between the mutual polarity of the N and S poles that are magnetized to drive the motor. It is configured to do so. For example, when the convex part of the soft magnetic ring 3 and the convex part of the N (or S) pole part face each other, the concave part of the S (or N) pole part and the convex part of the soft magnetic ring 3 face each other.
They are in such a relationship that the convex portions are facing each other.

If we assume that the upper surface of the magnet 1 is the N pole and that the convex part on the inner circumferential side faces the convex part of the soft magnetic ring 3, then in FIG. The path is magnet 1, soft magnetic ring 3,
It is formed between the soft magnetic disk 2 and the soft magnetic disk 2. The amount of magnetic flux in this magnetic path varies depending on the magnitude of the magnetic flux of the magnet 1 and depending on the location. In this way, on the inner circumferential side of the magnet 1, which is originally provided to supply only magnetic flux in the direction of the rotation axis, there is a so-called leakage magnetic flux that is sufficient to extract a signal, and this leakage magnetic flux is not utilized in this conventional example. ing.

Now, in the structure configured as above, the second
In the state shown in figure a, the magnetic flux density Bf between the soft magnetic ring 3 and the inner peripheral side of the magnet 1 in the θ direction from the point Po
Looking at this, this magnetic flux density Bf has a distribution as shown by the solid line in FIG. 3a. This can be considered to be because the magnetic flux density distribution Bs (dotted chain line in the figure), which would normally exist in the case where there is no unevenness, is modulated by the mechanical unevenness. Here, all the magnetic flux densities of the convex portions of the soft magnetic ring 3 correspond to the upwardly convex portions of the Bf waveform. The magnetic flux density distribution of the soft magnetic ring 3 as a whole is obtained by adding and averaging the magnetic flux densities of each convex part of the entire circumference, and in this case, this is at the level shown by the straight line B3 in Figure 3a. Become. In other words, the basic Bs component is averaged to 0 over the entire circumference, and the convex parts of the soft magnetic ring 3 are all more positive than this Bs, so the average of the positive values is +B3. It is expressed as Now, if we assume that the rotor magnet 1 changes its position as the rotor moves and has moved by τ/2 pitch compared to the previous state, the convex part of the soft magnetic ring 3 will be concave (convex) with N (S) pole.
You will be facing the department. In other words, Bf in Figure 3 a
Regarding the waveform, all magnetic flux densities at the convex portions correspond to the downwardly convex portions. At this time, in the same way as before, the overall average magnetic flux density of the soft magnetic ring 3 is −
The level will be as shown in B ₃ .

In this manner, the overall magnetic flux density of the soft magnetic ring 3 changes between positive and negative depending on whether the convex portion of the soft magnetic ring 3 faces the convex or concave portion of the magnet 1. Therefore, as the rotor rotates, the density B3 of the magnetic flux passing through the soft magnetic ring 3 changes between positive and negative, and if this change is converted into a change in the amount of magnetic flux φ, φ=B3
×S (S is the area of the convex part of the soft magnetic ring 3),
An alternating current electromotive force of e≒Ndφ/dt is already obtained in the coil 5 wound with N turns, and the frequency of this voltage is proportional to the rotational speed of the rotor.In the end, the configuration shown in Fig. 2 is a speed generator. It will function as In this case, the AC electromotive force will be as shown in Figure 3b, and a stable electromotive force with constant voltage peak value and constant period can be obtained during constant speed rotation, and there is no need for a dedicated magnetomotive force source for the speed generator. Can be done.

Note that the overall magnetic flux density of the soft magnetic ring 3 also requires consideration of the concave portions on its outer periphery. Taking this into account, the actual output voltage of the coil 5 will be lower than the above value, but since the magnetic flux density is relatively higher in the convex portion than in the concave portion, it can be considered that it is already close to the above value.

Further, the reason why the phase of the unevenness on the inner circumferential side surface of the magnet 1 is reversed between the north pole and the south pole is because if the phase is not reversed, no alternating current voltage will appear in the coil 5. That is, when not inverted, the magnetic flux density at the convex portion of the soft magnetic ring 3 matches the waveform of Bf under the N pole in FIG. 3a, for example, but
At the bottom of the S pole, the unevenness of the waveform has an inverted relationship with Bf, as shown by the dotted line. As a result, soft magnetic ring 3
When considering mainly the magnetic flux density of the convex part, the overall magnetic flux density becomes 0, just as the basic Bs component becomes 0 as a result of average addition, and the change in ±B3 due to the rotation of the rotor becomes 0. I can't get it and it always becomes 0. Therefore, as the N and S polarities of the main field of the motor change, the phases of the concavities and convexities must also be reversed.

Note that the magnetic flux in the direction of the rotating shaft in both the convex and concave portions of the inner circumference of the magnet 1 interlinks with the armature winding 8 in the same way as in the portions where there are no concavities and convexities, and acts as a component to generate effective torque, thereby increasing the speed. It goes without saying that the use of the radial magnetic flux for the detection generator does not impair the basic functionality. It goes without saying that the arrangement of the unevenness on the side surface of the magnet on the outer periphery of the magnet and the arrangement of the soft magnetic ring 3 in a position opposite thereto is equivalent to that described above.

[Problem that the invention seeks to solve]

The problem to be solved by the present invention is the above-mentioned first problem.
The problem with the conventional devices shown in FIGS. a and b is that a magnetomotive force source dedicated to the speed generator is required, resulting in a complicated structure and a large device.

The present invention was made in such a conventional situation, and even though it has a completely different structure from that shown in FIG.
By using part of the magnetomotive force source for driving the motor, we provide a speed generator that eliminates the need for a magnetomotive force source dedicated to the speed generator, simplifies the structure, and allows the entire device to be made smaller. It is intended to.

[Problem that the invention seeks to solve]

In addition, in order to solve the problem of the conventional device shown in Fig. 1a and b, in which a magnetomotive force source dedicated to the speed generator is required, the structure becomes complicated, and the device becomes large. -46576 and Japanese Patent Application Laid-open No. 53-115012,
The former is a speed generator for a general DC machine, in which a part of the magnetic flux of a permanent magnet field is used to construct a magnetic circuit, and a detection coil is provided in a part of the magnetic circuit. However, in this case, since the detection coil is provided on a part of the stationary side facing the magnetic circuit, there is a problem that point detection is performed and periodic irregularities are likely to occur depending on the machining accuracy of the rotating gear.

In addition, in the latter case, in a speed generator for a brushless motor with a rotor magnet, the structure is simplified and compacted by using leakage magnetic flux of the rotor magnet, which is the main magnetic flux source of the motor, as the magnetic flux generation source of the speed generator. Similarly to the conventional example shown in FIG. 2, phase inversion teeth are used to prevent rotational unevenness signals from being generated. However, this was for brushless motors and could not be applied to general DC machines.

In such a conventional situation, the present invention is a speed generator that can be applied to any general DC machine, does not require a rotating magnetomotive force source exclusively for the speed generator, makes the entire device compact, and has high output accuracy without periodic irregularities. The purpose is to provide something.

[Means for solving problems]

The present invention provides a speed generator for a general DC machine with a soft magnetic ring having mechanical concavo-convex reversal teeth on the same stationary side as the field magnetic flux source, in order to make the generator a full-circumference integral type with no periodic irregularities. A shield ring on the rotating side is provided with concave-convex teeth opposite to the concave-convex reversal teeth on the stationary side, and a detection coil detects changes in magnetic flux between the field magnetic flux source and the soft magnetic ring passing through the shield ring. It is.

[Effect]

In the present invention, a soft magnetic ring having reversible concavo-convex teeth is provided on the stationary side, and a shield ring is provided on the rotating side with reversible teeth facing the reversible concave-convex teeth. The phase changes continuously and smoothly, providing highly accurate output with no periodic irregularities. Furthermore, since a rotating magnetomotive force source dedicated to speed detection is not required, the configuration is simple and the entire device can be made smaller.

〔Example〕

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

FIG. 4 shows an embodiment of the present invention. In the figure, a magnet 1 and a soft magnetic material 2 supporting the same constitute the main body of the stator, and a soft magnetic ring 3 is attached to the soft magnetic material 2.
and a coil 5 wound therein are attached. The shield ring 10 is integrally fixed to the rotor shaft 4, and has concave and convex teeth carved at a uniform pitch τ on its outer periphery. The concave and convex teeth are set so as to rotate through the gap between the lower surface of the magnet 1 and the soft magnetic ring 3. In addition, on the side of the soft magnetic ring 3 that faces the uneven teeth of the shield ring 10, uneven teeth are similarly carved with an even pitch τ, and the uneven teeth are formed on the part facing the north pole of the magnet 1 and the south pole. It is made so that the phase of the unevenness is reversed between the opposite part and the opposite part.

In the device of this embodiment, the shield ring 10 also rotates as the rotor shaft 4 rotates. At this time, when the concave part of the shield ring 10 and the convex part of the soft magnetic ring 3 face each other, the path 9 shown by the broken line in the figure The amount of magnetic flux passing through increases, and conversely, when the convex portion of shield ring 10 faces the convex portion of soft magnetic ring 3, the amount of magnetic flux decreases.

In this way, in the device of this embodiment, since the shield ring 10 and the soft magnetic ring 3 are provided with uneven teeth, the magnetic flux passing through the soft magnetic ring 3 as the shield ring 10 rotates is similar to that of the conventional example shown in FIG. Similarly, it changes with a frequency proportional to the rotational speed, and this is detected by the alternating current voltage induced in the coil 5, so that the rotational speed of the rotor can be picked up as a voltage.

In addition, in the above explanation, when extracting the change in density of magnetic flux, only an example was given in which the soft magnetic ring 3 or a corresponding one is provided at a width of a positive integer x pole pair pitch, but for example, for a motor rotating at a predetermined speed does not have to be a positive integer multiple. In this case, since it is only necessary to extract the AC signal output associated with a predetermined rotation speed, the fundamental wave Bs is
This purpose can be achieved by electrically removing the portion corresponding to .

Although the description has been made using only a magnet as a source of magnetomotive force, it goes without saying that this can be replaced by a field magnetic flux source excited by a coil.

〔Effect of the invention〕

As described above, according to the present invention, in a speed generator for a general DC machine, a soft magnetic ring having concave-convex reversal teeth is provided on the same stationary side as the field magnetic flux source, and the soft magnetic ring is provided opposite to the concavo-convex inverting teeth on the stationary side. Concave and convex teeth are provided on the shield ring of the rotating shaft, and changes in the magnetic flux passing through this shield ring are detected by a detection coil, which eliminates the need for an independent source of magnetomotive force for speed detection and allows the device to be made more compact. At the same time, highly accurate detection output with no periodic irregularities can be obtained, which is extremely effective in the field of micromotors.

[Brief explanation of drawings]

Fig. 1 a, b and Fig. 2 a, b are block diagrams showing a conventional full-circumference integral type speed generator, and Fig. 3 a, b explain the operation of an embodiment of the present invention and a conventional device. Figures 4a and 4b are block diagrams of a speed generator according to an embodiment of the present invention. In the figure, 1 is a magnet (field magnetic flux source), 3 is a soft magnetic ring, 4 is a rotor shaft, 5 is a coil, and 10 is a shield ring. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1. A speed generator for a general DC machine, comprising: a field magnetic flux source provided on the stator side and serving as a main magnetic flux source for rotation of the DC machine; , a shield ring having concave and convex teeth facing the field magnetic flux source carved on its periphery at a uniform pitch finer than the magnetic pole pitch of the field magnetic flux source, and a pitch of the concave and convex teeth of the shield ring is equal;
The same pole of the field magnetic flux source has uneven teeth that form a magnetic flux that changes in density and density with an even pitch in the rotational circumferential direction, and the phase of the density and density is reversed between poles of different polarity. A soft magnetic ring is provided on the stator side so that the magnetic path of the magnetic flux formed by the teeth is blocked by the convex portions of the uneven teeth of the shield ring, and a change in magnetic flux is detected through the soft magnetic ring provided on the stator side. A speed generator characterized by being equipped with a coil.