JPH04347558A - Motor - Google Patents

Abstract

PURPOSE:To sufficiently reduce a noise level and also reduce a cost by simplifying a structure to realize such low level noise. CONSTITUTION:In a motor comprising a stator 1 which is formed by providing a winding 3 to a stator core 2 and a motor drive circuit for feeding electrical power to the winding 3, a piezoelectric element is provided to teeth 4 of the stator core 2 and this piezoelectric element is vibrated in the reverse phase against vibration of tooth 4 generated when an electrical power is supplied to the winding 3.

Description

[Detailed description of the invention]

[Object of the invention]

0002

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor having windings wound around a stator core.

0003

2. Description of the Related Art When rotating a DC brushless motor as this type of motor, for example, a so-called PWM (Pulse Width Motion) is used to change its rotational speed.
The windings are energized by a control method (duration). In this case, there is a problem in that the tooth portion of the stator core vibrates when the winding is energized, causing noise.

[0004] As a structure to solve this problem, there has conventionally been a structure in which the tooth portion of the stator core is made of a so-called vibration damping steel plate, which is a material that does not easily vibrate, thereby making the tooth portion difficult to vibrate. It was significantly reduced.

On the other hand, as a configuration for actively reducing noise, conventionally, the frequency of the generated noise is analyzed, and a sound that vibrates in the opposite direction for the main frequency components is generated from a speaker. There was a configuration in which the generated sound canceled out the noise.

[0006]

However, among the conventional configurations described above, in which noise is passively reduced, a damping steel plate is used, which increases material costs, processing costs, etc. In addition, it could not be said that the noise reduction effect was sufficient considering the increase in cost.

[0007] Furthermore, in a configuration that actively reduces noise,
In addition to analyzing the frequency of the generated noise, it is necessary to generate a sound that vibrates from the speaker so that the main frequency components have opposite phases and have the necessary amplitude, so complex calculations can be processed at high speed. A control device is required. Therefore, there is a drawback that the electrical configuration becomes complicated and the cost increases.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a motor which can sufficiently reduce noise, and which can also be simplified in construction and reduced in cost.

[Configuration of the invention]

0010

[Means for Solving the Problems] A motor of the present invention includes a stator formed by winding a winding around a stator core, and a motor drive circuit that supplies current to the winding, in which a piezoelectric element is attached to the teeth of the stator core. The piezoelectric element is characterized in that the piezoelectric element is driven to vibrate in a phase opposite to the vibration generated in the teeth by energizing the winding.

[0011] In this case, the piezoelectric element is energized and driven by a motor drive circuit via a delay circuit for correcting a time delay from when the winding is energized until the teeth vibrate due to the energization. It may be configured as follows.

0012

[Operation] According to the above means, piezoelectric elements are provided in the teeth of the stator core, and when the teeth vibrate and generate noise due to energization of the windings, they vibrate in a phase opposite to the vibration generated in the teeth. The piezoelectric element is driven to do this. Therefore, the sound generated by the vibration of the piezoelectric element cancels out the noise caused by the vibration of the teeth, and the noise is reduced as a whole.

In this case, in order to vibrate the piezoelectric element in the opposite phase, it is sufficient to synchronize the energization timing of the motor drive circuit to the winding. Therefore, since it is only necessary to provide a piezoelectric element on the teeth and to have an electrical configuration synchronized with the energization timing of the motor drive circuit, the configuration can be simplified and the cost can be reduced compared to the conventional configuration.

[0014] Furthermore, the piezoelectric element is energized and driven by a motor drive circuit via a delay circuit to correct a time delay from when the winding is energized until the teeth vibrate due to the energization. Therefore, a dedicated drive circuit for driving the piezoelectric element is not required separately, and the electrical configuration can be simplified accordingly.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a DC brushless motor will be described below with reference to the drawings. First, in FIGS. 1 and 2, a stator 1 includes a stator core 2 and, for example, three-phase windings 3 wound around the stator core 2. The stator core 2 has a substantially cylindrical shape, and has a plurality of teeth 4 protruding inward on its inner peripheral surface, and slots 5 are formed between each of the teeth 4. The winding 3 is accommodated in this slot 5.

Further, the rotor 7 having the rotor magnet 6 is housed in the stator 1, and the rotor 7 has its rotating shaft 8.
is supported by a bearing (not shown). In this case, the rotor 7 is rotationally driven by energizing the winding 3 using a well-known so-called PWM control method.

A piezoelectric element unit 9 is provided along the axial direction at both ends of the tip side of each of the teeth 4, for example, by being glued. This piezoelectric element unit 9 is
A plurality of piezoelectric elements 10 whose vibration direction is the radial direction (direction shown by arrow A in FIG. 2) and piezoelectric elements 11 whose vibration direction is the circumferential direction (direction shown by arrow B in FIG. 2) are arranged alternately. It is composed of These plurality of piezoelectric elements 10 and 11 are connected in parallel.

Furthermore, in FIG. 3 showing the electrical configuration, 3
The phase windings 3 each have one end connected to a common connection point O, and each other end connected to output terminals P, Q, and R of the motor drive circuit. The motor drive circuit has a switching element (not shown) for performing PWM control. The three-phase piezoelectric element unit 9 corresponding to the three-phase winding 3 has one end connected to the common connection point T, and the other end connected to the output terminal of the motor drive circuit via the delay circuit 12. Connected to P, Q, and R.

The delay circuit 12, as shown in FIG.
It is constituted by a first-order lag filter consisting of a resistor 13 and a capacitor 14. In this case, the connection point between one end of the resistor 13 and one end of the capacitor 14 is connected to the other end of the piezoelectric element unit 9, the other end of the resistor 13 is connected to the output terminals P, Q, and R of the motor drive circuit, and the other end of the resistor 13 is connected to the output terminals P, Q, and R of the motor drive circuit. The other end of the piezoelectric element unit 9 is connected to a common connection point T, which is one end of the piezoelectric element unit 9 .

Next, the operation of the above structure will be explained with reference to FIGS. 5 and 6. Assume that a voltage having a waveform as shown in FIG. 5A is applied to the winding 3 by the motor drive circuit. In this case, the teeth 4 of the stator core 2 vibrate due to the magnetic flux generated from the winding 3. The vibration of the teeth 4 has a component in the radial direction (direction indicated by arrow A in FIG. 2),
The main component is the component in the circumferential direction (direction indicated by arrow B in FIG. 2). These vibration components are generated by the winding 3 housed in the slot 5 and the winding 3 at the coil end portion.

[0021] Here, changes in vibration, that is, mechanical displacement of the teeth 4 are shown in FIG. 5(b). From this FIG. 5(b) and FIG. 5(a) showing the voltage waveform applied to the winding 3, it is clear that the time from when the winding 3 is energized until the teeth 4 vibrate due to the energization is It can be seen that there is a delay.

[0022]In order to cancel the noise caused by the vibration of the teeth 4, it is sufficient to vibrate the piezoelectric element unit 9, that is, the piezoelectric elements 10 and 11, in a phase opposite to the vibration of the teeth 4. . Specifically, the piezoelectric element 10
, 11 may be vibrated so that the mechanical displacements of the components change as shown in FIG. 5(c).

In the case of this embodiment, as shown in FIG. 3, the piezoelectric element unit 9 is connected to the delay circuit 12 by a motor drive circuit.
The time constant of the delay circuit 12 is set to correspond to the time delay from when the winding 3 is energized until the teeth 4 vibrate due to the energization. Therefore, the piezoelectric element unit 9 vibrates in a phase opposite to the vibration of the teeth 4, as shown in FIG. 5(c).

As a result, the overall vibration of the teeth 4 and the piezoelectric element unit 9 becomes as shown in FIG. 5(d).
It can be seen that the vibration peak has decreased compared to (b). Then, the sound generated by the vibration of the piezoelectric element unit 9 cancels out the noise caused by the vibration of the teeth 4,
Noise is reduced overall. The results of measuring noise for this example are shown in broken lines in FIG. Note that in FIG. 6, the solid line indicates the result of measuring noise for a configuration in which the piezoelectric element unit 9 is not provided. Comparing the two, it can be seen that the loudness of the harmonic components of the noise can be reduced.

According to this embodiment having such a configuration, in order to cause the piezoelectric element unit 9 to vibrate in a phase opposite to the vibration of the teeth 4, it is necessary to synchronize the energization timing of the motor drive circuit to the winding 3. That's all you need. Therefore, it is only necessary to provide the piezoelectric element unit 9 on the teeth 4 and to have a simple electrical configuration that is synchronized with the energization timing of the motor drive circuit. The electrical configuration can be significantly simplified and the cost can be reduced accordingly compared to a configuration that reduces noise.

In this embodiment, the piezoelectric element unit 9 is energized and driven by the motor drive circuit via the delay circuit 12, and from the time when the winding 3 is energized until the teeth 4 vibrate due to the energization. Since the structure is configured to correct the time delay of , there is no need for a separate drive circuit for driving the piezoelectric element.
Therefore, the electrical configuration can be further simplified.

Further, in the above embodiment, the delay circuit 12 was composed of the resistor 13 and the capacitor 14, but instead of this, as in the second embodiment of the present invention shown in FIG. 16 and a capacitor 17.

[0028]

[Effects of the Invention] Since the present invention is as explained above, the following effects can be obtained.

In the motor according to the first aspect, a piezoelectric element is provided in the teeth of the stator core, and the piezoelectric element is driven to vibrate in a phase opposite to the vibration generated in the teeth by energizing the winding. With this configuration, the noise can be reduced as a whole, and the configuration can be simplified and the cost can be reduced.

In the motor of the second aspect, the piezoelectric element is energized and driven by a motor drive circuit via a delay circuit,
The structure is designed to compensate for the time delay between when the winding is energized and when the teeth vibrate due to the energization.
A separate drive circuit for driving the piezoelectric element is not required, and the electrical configuration can be further simplified.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a motor showing a first embodiment of the present invention.

[
Figure 2: Partial perspective view enlarging the area around the teeth of the stator

[Figure 3] Overall electrical circuit diagram

[Figure 4] Electrical circuit diagram of delay circuit

FIG. 5 is a time chart, in which (a) shows the voltage waveform applied to the winding, (b) shows the displacement of the vibration of the teeth, and (c) shows the displacement of the vibration of the piezoelectric element unit. , (d) shows the displacement amount of the entire vibration of the teeth and the piezoelectric element unit.

[Figure 6] Graph showing noise measurement results

FIG. 7 is an electrical circuit diagram of a delay circuit showing a second embodiment of the present invention.

[Explanation of symbols]

1 is a stator, 2 is a stator core, 3 is a winding, 4 is a tooth, 9 is a piezoelectric element unit, 10 and 11 are piezoelectric elements,
12 and 15 indicate delay circuits.

Claims (2)

[Claims] 1. A motor comprising a stator formed by winding a winding around a stator core, and a motor drive circuit that energizes the winding, wherein a piezoelectric element is provided in the teeth of the stator core, and the piezoelectric element is connected to the winding. A motor characterized in that the motor is driven to vibrate in a phase opposite to the vibration generated in the teeth by energizing the wire. [Claim 2] The piezoelectric element is energized and driven by a motor drive circuit via a delay circuit for correcting a time delay from when the winding is energized until the teeth vibrate due to the energization. The motor according to claim 1, characterized in that it is configured as follows.