JPS6198178A - Servo motor - Google Patents

Abstract

PURPOSE:To perform stable rotating speed switching by providing a plurality of oscillators, and switching the speed by the connection switching of its PLL type servo IC. CONSTITUTION:A PLL type servo IC 5 which does not includes an oscillator is used, and two oscillators 6, 7 are connected through a changeover switch 4 with the IC 5. The oscillators 6, 7 are set to different oscillating frequencies by oscillation elements X1, X2. Thus, it is not necessary to finely regulate the oscillating frequency, and it can prevent a spurious vibration at rotating speed switching time.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to servo motors used in floppy disk drives and the like.

Conventional technology In general, this type of servo motor has a fixed rotation speed, but recently two or more different rotation speeds are required. FIG. 3 shows a conventional system in which two types of rotational speed can be switched. This is based on the PLL method using a PLL method servo IC, and the phase of the field coil 2 of the motor and the rotation speed that is attached to the motor shaft are adjusted so that the rotation speed required for a certain fundamental frequency is achieved. Control is performed by comparing the frequencies of a frequency generator (FG) 3 that generates pulse signals based on a detection plate (not shown). In order to vary the fundamental frequency and change the rotation speed, two types of oscillators Xi and X2 are connected to the servo ICI, and which oscillator X1. X
2 is connected or not by switching a changeover switch 4 such as an analog switch using a rotational speed switching signal SP.

Problems to be Solved by the Invention In the conventional system, the oscillators XL and X2 must be directly connected to the PLL servo IC 1 which has one built-in oscillation circuit. Fine adjustment capacitors C1 and C2 must be connected in series with X2 to match the required rotation speed.

Another disadvantage is that when the number of revolutions is changed by one rotation, spurious vibrations are likely to occur due to the characteristics of the oscillators Xi and X2. In other words, a ceramic oscillator (CERALOCK) is used as the oscillators Xl and X2, but since this CERALOCK is a type of mechanical resonator, in addition to the fundamental vibration, it can also generate odd-order vibrations and different vibration modes. It will have .

This vibration is called spurious vibration.2 For example, it is not known what kind of vibration will occur the moment the power is turned on.Therefore, as shown in Figure 3, the oscillators Xs and X2 are connected directly to the PLL system ICI. If the switching is performed after the change is made, spurious vibration phenomena like this will occur.

At the moment of switching, there may be a time when it is not known which vibration will be generated.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to obtain a servo motor that can change the rotation speed without causing fine adjustment or spurious vibration due to a capacitor.

Means for Solving the Problems In order to solve the above problems, the present invention provides oscillation circuits 6 and 7 set to different oscillation frequencies, and connects the P
A configuration is adopted in which the LL type servo IC 5 is connected.

1 by connecting one of the oscillation circuits 6 or 7 to the PLL type servo IC 5 using the operating rotation speed switching signal SP.
Although the rotation speed can be changed, PLL type servo IC has a more stable oscillation output than when one resonator is directly connected.
Because it will be entered in 5.

This also eliminates the need for fine adjustment using a capacitor.

It is also possible to eliminate the occurrence of spurious vibrations when changing the rotational speed.6 Embodiment A first embodiment of the present invention will be described with reference to FIG. Parts that are the same as those shown in Figure 3 are indicated using the same symbols 6
This example is a PLL type servo IC that does not include a single oscillation circuit.
5, and selector switch 4 is used for this servo IC5.
Two oscillation circuits 6 and 7 are connected via the oscillation circuit.

The oscillation circuits 6.7 each have oscillators Xi and X2, and are set to different oscillation frequencies. More specifically, these oscillation circuits 6 and 7 oscillate at an oscillation frequency several times the required oscillation frequency, and the feedback resistors Rf1 . It has inverting amplifiers 8 and 9 to which a bias voltage is applied by Rf2, and inverters 10 and 11 for buffer and waveform shaping.

Further, Rdl and Rdz are resistors for preventing spurious vibrations.

In such a configuration, one of the oscillation circuits 6 and 7 is connected to the PLL servo IC 5 by setting the rotation speed switching signal SP to H level or L level and switching the changeover switch 4.

As a result, the oscillation output produced by the oscillation circuit 6 or 7 is P
The signal is input to the LL type servo IC5. This causes current to flow through coil 2, receives the timing, and then the PLL
It controls and applies servo.

As in this embodiment, by providing one oscillation circuit 6.7 externally to the PLL type servo IC 5 instead of directly providing one oscillator, there is no need to fine-tune the one oscillation frequency by switching the rotation speed. Oscillation output can be input to the PLL type servo IC 5 in a stable state without generating spurious vibrations when changing the rotation speed. or.

Although one oscillation circuit 6.7 is provided instead of a single oscillator, the structure is simple because the PLL type servo IC 5 does not need to include an oscillation circuit.

Note that in this embodiment, two oscillation circuits 6 and 7 are provided,
Although the rotation speed is switched between two types, it is also possible to add oscillation circuits with different oscillation frequencies and switch between a plurality of rotation speeds.

Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, the oscillation circuits 6, 7 and changeover switch 40 circuit in the previous embodiment are replaced with one IC. That is, in the oscillation circuit 6.7, the NAND circuit 12.1 which forms an inverting amplifier like the inverters 8 and 9
3 is provided.

The output is inputted via a NAND circuit 14 to an I.C. 5 which operates in a PLL system. On the other hand, the rotational speed switching signal SP is directly input to the oscillation circuit 6, and the rotational speed switching signal SP is inputted to the oscillation circuit 7 after being inverted by the NAND circuit 15.

In such a configuration, the rotation speed switching signals S and P are H.
If it is at the level, the oscillation circuit 6 outputs an oscillation frequency based on the oscillator Xl. At this time, NAND circuit 15
Since the output of the oscillation circuit 7 is at the L level and the output of the oscillation circuit 7 is at the H level, the oscillation output from the oscillation circuit 6 is applied from the NAND circuit 14 to the PLL type servo IC 5. On the other hand, when the rotation speed switching signal SP becomes L level, the oscillation circuit 7 becomes effective, and the output of the oscillation frequency based on the oscillator X2 is input to the PLL type servo IC 5.

Here, the NAND circuits 12 to 15 are packaged with four
Since there are two ICs included, only one IC is required, resulting in a simple configuration with fewer parts and no changeover switch 4 required.

Effects of the Invention In the present invention, as described above, a plurality of oscillation circuits are provided, and the rotation speed is changed by switching the connection to the PLL type circuit. This eliminates the need for fine adjustment and does not generate spurious vibrations when switching the number of revolutions, allowing stable switching of the number of revolutions.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention. FIG. 2 is a circuit diagram showing a second embodiment of the present invention, and FIG. 3 is a circuit diagram showing a conventional example. 5...PLL type servo IC16~7...Oscillation circuit product Requester Tokyo Electric Co., Ltd. SP/Rotation speed reno change +, +

Claims (1)

[Claims] In a servo motor whose rotation speed is controlled using a PLL type servo IC, multiple oscillation circuits set to different oscillation frequencies are provided, and one oscillation circuit is changed to the PLL type servo IC in response to a rotation speed switching signal. A servo motor characterized by switching to a rotation speed determined by its oscillation frequency in a connected state.