JP3441798B2 - Motor position detector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting device for a moving element in a motor, and more particularly to a position detecting device capable of increasing an output signal. 2. Description of the Related Art For example, a video tape recorder (VTR)
Since a reference position during one rotation needs to be always detected in a cylinder motor for a motor or the like, a rotation position detection device is incorporated. FIG. 5 shows an example of such a VTR cylinder motor. In FIG. 5, reference numeral 12 denotes a lower fixed cylinder. On the lower surface side of the fixed cylinder 12, a stator core 15 is fixed by an appropriate fixing means with a substrate 17 for a frequency generator (hereinafter referred to as "FG") and a position signal generator (hereinafter referred to as "PG") interposed. Have been.
The stator core 15 has a plurality of salient poles radially, and a driving coil 16 is wound around each salient pole. Stator core 1
5, a driving coil 16, a substrate 17, and the like constitute a stator. The fixed cylinder 12 has a center hole into which outer rings of two bearings 13 and 14 are press-fitted and fixed vertically, and a shaft 11 is press-fitted into inner rings of the bearings 13 and 14 and fixed. , Shaft 11 are rotatably supported. A rotating cylinder 18 is fixed to the upper end of the shaft 11 protruding from the upper bearing 14. There is an appropriate gap between the outer peripheral edge of the lower surface of the rotating cylinder 18 and the outer peripheral edge of the upper surface of the fixed cylinder 12, and the magnetic head attached to the outer peripheral edge of the lower surface of the rotating cylinder 18 rotates in the above-mentioned gap. The flat cup-shaped rotor case 1 is fixed to the lower end of the shaft 11 protruding from the lower bearing 13 via a boss or the like.
The rotor case 1 covers the stator core 15 from below. A ring-shaped drive magnet 2 is fixed to the inner surface of the peripheral wall of the rotor case 1, and the inner surface of the drive magnet 2 faces the distal end surface of each salient pole, which is the outer peripheral surface of the stator core 15, with an appropriate gap. I have. An FG magnet 3 is fixed to an upper end surface of the driving magnet 2. FIG. 6 shows drive magnet 2 and F
This shows an example of the G magnet 3, and when the magnetizing pitch of the drive magnet 2 is one pitch, the magnetizing pitch of the FG magnet 3 is 1/2 pitch. Two magnetic poles of the FG magnet 3 are further arranged in four poles at a half pitch to form a PG magnet 4. Therefore, the PG magnet 4 is arranged corresponding to one magnetic pole of the drive magnet 2. In FIG. 5, the upper end surface of the FG magnet 3 faces the lower surface of the substrate 17 with an appropriate gap. A well-known FG pattern for generating a FG signal and a PG pattern for generating a PG signal are formed on the surface of the substrate 17 facing the FG magnet 3 by etching or the like. The magnetic pole of the drive magnet 2 is detected by a Hall element or the like, and the energization of each drive coil 16 is switched in accordance with the detection signal. It is driven to rotate. As the FG magnet 3 rotates together with the drive magnet 2 and its magnetic flux crosses the FG pattern, the FG pattern outputs an FG signal having a frequency corresponding to the rotation speed of the rotor, as is well known. The rotation speed is controlled to be constant based on the FG signal. PG magnet 4
When the magnetic flux crosses the PG pattern, the PG pattern outputs a PG signal as is well known. This PG signal is a reference signal for one rotation. [0006] Like the motor described above, there is provided a position detecting device comprising a PG magnet 4 provided integrally with the driving magnet 2 and a PG pattern opposed thereto. For example, the PG pattern is affected by the magnetic flux of the driving magnet 2 and the PG power generation output is low, and the signal-to-noise ratio (S / N) deteriorates. The present invention has been made to solve the above-mentioned problems of the prior art. By devising the structure of the position detecting magnet, the PG pattern can reduce the influence of the magnetic flux of the driving magnet. Accordingly, it is an object of the present invention to provide a motor position detecting device capable of increasing the PG power generation output and improving the signal-to-noise ratio. In order to achieve the above object, according to the present invention, a drive magnet is provided with a position detecting magnet, and a position signal generating wire element is arranged to face the position detecting magnet. The position detecting magnet is disposed within one magnetic pole of the drive magnet and
The magnetic poles are arranged in the form of magnetic poles. Of these magnetic poles, the magnetic pole at the tip of the moving element in the moving direction is the same as the magnetic pole of the corresponding drive magnet. When the magnetic flux of the position detecting magnet crosses the position signal generating wire element, the position signal generating wire element generates electric power.
A signal having the same cycle as the cycle at which the magnetic pole of the position detecting magnet passes through each position signal generating wire element is generated. The signals generated in each position signal generating element are combined, and the first rising signal of the combined signals is used as a position signal. Since the magnetic poles are of the same polarity as the magnetic poles of the corresponding drive magnets, the influence of the magnetic flux of the drive magnets on the position signal generating wire element acts to increase the signal that rises first among the composite signals. , A large position signal can be obtained. An embodiment of a motor position detecting apparatus according to the present invention will be described below with reference to the drawings. In addition,
The basic configuration of the motor is the same as that of the example of FIG. 5, and the common components are denoted by the same reference numerals. Here, the features characteristic of the present invention will be mainly described. In FIG. 1, a ring-shaped drive magnet 2 is fixed to the inner surface of the peripheral wall of the rotor case 1. The drive magnet 2 has eight magnetic poles arranged at regular intervals in the circumferential direction. An FG magnet 3 is fixed to an axial end surface of the drive magnet 2. The FG magnets 3 are arranged with magnetic poles at a half pitch with respect to the magnetic pole pitch of the drive magnet 2. Therefore, the number of magnetic poles of the FG magnet 3 to the number of magnetic poles of the drive magnet 2 is 2: 1. A portion corresponding to two adjacent magnetic poles among the magnetic poles of the FG magnet 3, that is, a portion corresponding to one magnetic pole of the drive magnet 3 is divided into four equal parts in the circumferential direction to form magnetic poles respectively. A position detecting magnet (hereinafter, referred to as a “PG magnet”) 4 having a magnetic pole arrangement is configured. Thus, the magnetic pole width of the PG magnet 4 is 1/4 of the magnetic pole width of the driving magnet 2 and 1 / of the magnetic pole width of the FG magnet 3.
It is 2. Further, of the four magnetic poles of the PG magnet 4, the magnetic pole at the tip in the rotation direction of the rotor is the PG magnet 4.
Are the same as the magnetic poles of the corresponding drive magnet 2. In the example shown in FIG. 1, a PG magnet 4 having a magnetic pole arrangement of four poles corresponding to one N pole of the drive magnet 2 is provided.
When the rotation direction of the rotor is set in the counterclockwise direction indicated by the arrow, the magnetic pole at the tip of the PG magnet 4 in the rotation direction is the same N pole as the corresponding magnetic pole of the drive magnet 2. The FG magnet 3 including the PG magnet 4 may be made separately from the driving magnet 2 and fixed to the driving magnet 2, or the magnetized FG magnet 3 may be attached to the end of the driving magnet 2 and the PG magnet 4 May be performed. FIGS. 2A and 2B show examples of an FG pattern and a PG pattern arranged to face the FG magnet 3 and the PG magnet 4, respectively. 2A and 2B, the FG pattern 5 is provided on one surface side of the substantially circular substrate 10.
Are formed. The FG pattern 5 is composed of the FG signal generating line elements 5a radially formed at the same pitch as the magnetic pole pitch of the FG magnet 3 and at regular intervals in the circumferential direction, and the adjacent FG signal generating line elements 5a. It has a conducting wire 5b connecting the peripheral ends and a conducting wire 5c connecting the outer peripheral ends of adjacent FG signal generating wire elements 5a. Line element 5 for FG signal generation
a is formed into a single continuous rectangular wave by connecting its inner and outer ends alternately with conductors 5b and 5c, and is formed in a substantially arc-shaped circuit. Is connected to terminals 7 and 9. A PG pattern 6 is arranged so as to overlap a part of the FG pattern 5. The PG pattern 6 includes four position signal generating line elements a, b, c, d, a conductor 6b connecting the inner ends of the line elements a, b and the inner ends of the line elements c, d, and line elements b, c is formed in a continuous rectangular wave shape by a conducting wire 6c connecting the outer ends of the terminals 9a and 9b.
(Plus side). The terminal 9 is a common terminal of the FG pattern 5 and the PG pattern 6. The line signals a, b, c, d of the position signal generation of the PG pattern 6 are formed radially at the same pitch as the magnetic pole pitch of the PG magnet 4 and at regular intervals in the circumferential direction. The PG pattern 6 is formed with an appropriate insulator interposed between the PG pattern 6 and the FG pattern 5. For example, the PG pattern 6 may be formed on a flexible circuit board, and the flexible circuit board may be laminated on the substrate 10 on which the FG pattern 5 is formed and bonded. The PG magnet 4 and the PG pattern 6 described above constitute a position detecting device. Therefore, next, the operation of the position detecting device will be described. By energizing the drive coil 16 described with reference to FIG. 5 and switching the energization to the drive coil 16 in accordance with the rotational position of the drive magnet 2, the drive magnet 2 forming part of the motor and the stator core 15 The driving magnet 2 is biased by the magnetic force generated between the driving magnet 2 and the
At the same time, the rotor case 1, the FG magnet 3, and the PG magnet 4 rotate counterclockwise in FIG. When the FG magnet 3 and the PG magnet 4 rotate, their magnetic flux causes the position signal generating line elements a,
b, c, and d, and each position signal generating line element a, b,
Sinusoidal signals are generated at c and d. FIGS. 3A and 3B
(C) and (d) show the position signal generating line elements a, b, c,
The signal generated at d is shown. The portion of each of these signals that changes in a short period from time t1 to time t2 is P
The signal generated by the G magnet 4 is generated by the FG magnet 3, and the portion that changes at twice the period is the signal generated by the FG magnet 3. In FIG. 3A, a waveform indicated by a broken line A1 shows a power generation waveform of the position signal generating line element a when the magnetic flux of the driving magnet 2 is not affected. However, the waveform B1
There is a leakage magnetic flux of the drive magnet 2 as shown by the following, and under the influence of this, the line element a actually outputs a signal having a waveform shown by a line C1. The same applies to the output signals of the position signal generating line elements b, c, and d shown in FIGS. 3B, 3C, and 3D, which are not affected by the magnetic flux of the drive magnet 2 of each line element. The power generation waveforms are indicated by A2, A3, and A4, and the leakage flux waveforms of the drive magnet 2 received by the respective line elements are indicated by B2, B3, and B4, and the position signal generating line element b affected by these leakage fluxes , C, d are indicated by C2, C3, C4. Since the position signal generating line elements a, b, c, and d are connected in series by the conductors 6b and 6c, the waveforms of FIGS. 3A, 3B, 3C, and 3D are combined with the PG. The pattern 6 is output. FIG. 4 shows the output of the PG pattern 6.
By synthesizing the signals generated by the position signal generating wire elements a, b, c and d, the signals corresponding to the FG magnets 3 are mutually canceled, and only the signals corresponding to the PG magnets 4 are shown in FIG. It is output as a signal having two peaks on the positive side. In FIG. 4, a broken line A shows a waveform in the case where the magnetic flux of the driving magnet 2 does not affect, and the two peak values are the same. On the other hand, the solid line C shows the actual output waveform affected by the magnetic flux of the drive magnet 2, and the first peak value is higher than the first peak value of the waveform A by U. Therefore, the second peak value is lower than the second peak value of the waveform A. The reason is that the PG magnet 4 is arranged corresponding to one magnetic pole of the drive magnet 2 and has an arrangement of four magnetic poles. Of these magnetic poles, the magnetic pole at the tip end in the rotation direction of the rotor corresponds to the above-mentioned drive magnet. This is because the magnetic pole of the magnet 2 is the same. That is, the magnetic pole of the drive magnet 2 corresponding to the PG magnet 4 acts in a direction to increase the magnetic flux emitted from the magnetic pole at the tip of the PG magnet 4 in the rotor rotation direction, and the peak value of the first signal of the PG pattern output increases. Is what you do. The output of the PG pattern is used as a position detection signal by shaping the waveform of the first appearing signal.
By increasing the peak value of the signal appearing first in the PG pattern output as described above, the signal-to-noise ratio of the position detection signal is improved, and a highly accurate position detection signal can be obtained. Here, for reference, as shown in FIG.
Consider a case in which the magnetic pole at the tip of the rotor in the rotation direction of the magnet 4 is the reverse of the magnetic pole of the corresponding drive magnet 2. The PG pattern facing the rotation surface of the PG magnet 4 is the same as that shown in FIG.
FIG. 7 shows a waveform obtained by synthesizing signals generated in each position signal generating line element in this case. In FIG. 7, a broken line A shows a waveform when the influence of the magnetic flux of the driving magnet 2 is not exerted, and the two peak values are the same. On the other hand, the solid line C shows the actual output waveform affected by the magnetic flux of the driving magnet 2, and the peak value of the first appearing signal is lower than the peak value of the waveform of the broken line A by the value indicated by D. are doing. Therefore, when this signal is used as the position detection signal, it is understood that the noise component is large and the signal-to-noise ratio is deteriorated. Although the embodiment of the present invention has been described with reference to an example of a cylinder motor for a VTR, the present invention is not limited to this, and is applicable to any motor requiring a position detection signal, such as a disk drive motor. Can also be applied. In the illustrated embodiment, a rotary motor is used. However, the present invention can be applied to a linear motor in which a rotor case, magnets, and an FG pattern and a PG pattern opposed thereto are linearly developed. In the case of a rotary motor, the rotor is the moving element. In the illustrated embodiment, the range of the position detecting magnet having the four-pole magnetic pole arrangement coincides with the range of one magnetic pole of the drive magnet. A magnet may be formed. The relationship between the magnetized pitch of the drive magnet and the magnetized pitch of the FG magnet is not particularly limited. According to the present invention, the position detecting magnet is arranged corresponding to one magnetic pole of the drive magnet and has a four-pole magnetic pole array. Since the magnetic pole at the tip of the direction is the same as the magnetic pole of the corresponding drive magnet, the magnetic pole of the drive magnet corresponding to the position detecting magnet generates magnetic flux from the magnetic pole at the tip of the position detecting magnet in the rotor rotation direction. Acting in an increasing direction, the peak value of the position detection signal that appears first increases, and a position detection signal with a good signal-to-noise ratio can be obtained by using the signal that appears first as a position detection signal.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view showing an example of a drive magnet, a frequency power generation magnet, and a position detection magnet applicable to the device of the present invention. FIG. 2 is a plan view and a perspective view showing an example of a frequency power generation pattern and a position detection pattern corresponding to the drive magnet, the frequency power generation magnet, and the position detection magnet. FIG. 3 is a waveform diagram showing an example of a power generation signal of each position signal generating line element of the position detection pattern. FIG. 4 is a waveform diagram in which power generation signals are combined. FIG. 5 is a front sectional view showing a conventional example of a motor with a position detecting device. FIG. 6 is a plan view showing a drive magnet, a frequency power generation magnet, and a position detection magnet of the motor. FIG. 7 is a waveform diagram of a position detection signal obtained from the motor position detection device. [Description of Signs] 1 Rotor case 2 as mover Drive magnet 4 Position detecting magnet a Position signal generating line element b Position signal generating line element c Position signal generating line element d Position signal generating line element

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ identification code FI H02K 29/14 H02K 11/00 C (58) Field surveyed (Int.Cl. ⁷ , DB name) H02K 29/08 G01B 7 / 30 101 G01D 5/245 G01D 5/245 101 H02K 11/00 H02K 29/14

Claims (1)

(57) The present invention relates to a motor having a stator, a mover that moves with respect to the stator, and a drive magnet provided on the mover and arranged with a plurality of magnetic poles. The magnet has a position detecting magnet, and a position signal generating wire element is arranged to face the position detecting magnet. The position detecting magnet is one of the driving magnets.
The magnetic poles are arranged correspondingly within the magnetic poles, and have a four-pole magnetic pole arrangement, and the magnetic pole at the tip of the mover in the moving direction of these magnetic poles is the same as the magnetic pole of the corresponding drive magnet. Motor position detection device.