JPH0428237Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a brushless linear motor drive device, and particularly to a brushless linear motor drive device that provides uniform torque to the brushless linear motor and is simple and economically constructed.

As shown in FIG. 1, the thrust-position characteristics of a brushless linear motor having two-phase windings change periodically, and there is a phase difference of 1/4 period between the first phase and the second phase.
For this reason, for example, when the movable part is made to travel in a fixed direction, an excitation mode is used in which the winding current is made positive in section T and negative in section T'. However, in this case, as shown in Figure 2, ripples occur in the combined thrust F of the 1st and 2nd phases, causing speed fluctuations, etc., so conventionally, the magnitude of the winding current at the location where the ripples occur is determined to compensate for the ripples. In response to changes, measures were taken to reduce ripple, such as forcing changes from the outside. However, this method requires expensive circuit components such as a ROM to store changes in the winding current and a multiplier to change the winding current according to the conduction angle, which poses an economical problem. Ta.

In order to eliminate such drawbacks, the present invention aims to provide a drive device that utilizes an inexpensive digital switch or analog switch by switching the excitation of the winding using a small section of thrust ripple as an excitation unit. This will be explained in detail below.

FIG. 3 shows the excitation mode of the winding in the present invention. When running at a constant speed, one excitation cycle is, for example,
It changes in the order of T ₁ , T ₂ , T′ ₁ , T′ ₂ , T ₁ , T ₂ , T′ ₁ ,
A different excitation state is created every T′ ₂ .
The interval between each excitation state is equal to 1/4 of the period λ of the thrust-position characteristic, and there is a phase difference of ±λ/8 between the point P ₁ where the thrust is zero and the point P ₂ where the excitation cycle begins. have In this case, the thrust ripple at each interval becomes small.

Here, for each excitation state, T ₁ is a section where a positive current flows through the 1-phase winding, T ₂ is a section where a positive current flows through the 2-phase winding, and T ₃ is a section where a negative current flows through the 1-phase winding. _T4 is defined by the selection of windings and the polarity of the current, such as the period in which negative current is passed through the two-phase winding.

FIG. 4 shows an embodiment of the present invention which embodies such excitation switching of the windings and drives a brushless linear motor according to a drive signal from a control system.
In the figure, A-1 and A-2 are analog switches, C
is a control circuit that creates an excitation state, AMP-1,
AMP-2 is a power amplifier, D/A is digital.
It is an analog converter. In the linear motor system, 1 is a movable part, 2 is a fixed part, 3 is a movable part side member of a position detector, and 4 is a stator side member of a position detector. As the movable part moves, the position pulse S-1 output from the movable part side member 3 is sent to the control circuit C.
The signals are counted and output as binary position signals to the servo processing system, and are also converted into excitation switching signals φ ₁ , φ ₂ , φ′ ₁ , φ′ ₂ as shown in FIG. 5, for example.
Signals φ ₁ and φ ₂ are 2×n(n
= 1, 2...), and the signals φ ₁ and φ ₂ are in opposite states. Furthermore, the signals φ' ₁ and φ' ₂ are set to have the same phase and twice the period as the signals φ ₁ and φ ₂ , respectively.

Note that the control circuit C can be easily realized by a combination of a binary counter, a latch circuit, etc. In FIG. 5, φ ₁ and φ ₁ ' are the outputs of a binary counter with S-1 as input, while φ ₂ and φ ₂ ' are φ ₁ and φ ₁ ', respectively.
may be delayed by a period of S-1 using a latch circuit. The relationship between the period conditions and phase conditions of these φ ₁ , φ ₂ , φ ₁ ', and φ ₂ ' can be uniquely defined from the period of S-1. Here, S- which is the output signal of the position detector 3
The number of pulses 1 corresponds to the distance of the movable part from the fixed part reference point (the reference point is point p2 of the thrust-position characteristic in Figure 3), so if this number of pulses is counted with a counter, the position of the movable part can be found, φ ₁ , φ ₂ , φ ₁ ′, and φ ₂ ′, which change depending on the position, are determined. Further, point P2 shown in FIG. 3 is selected as the reference point for counting S-1. That is, P2 is a position shifted by λ/8 (λ: period of thrust characteristic) from the stable point (point where thrust = 0) p1, and when excitation switching is performed based on this point, the excitation switching interval T ₁ , T ₂ , T ₁ ′, T ₂ ′
(The section is λ/4), the thrust force is constant and the thrust value is maximum. P2 is the midpoint between the stable point of 1-phase thrust and the stable point of 2-phase thrust, and the phase difference between the two thrust characteristics is λ/4, so the excitation cycle and thrust -
The difference in positional characteristics is ±λ/8. Since such intermediate points between stable points exist with a period λ, it is usually sufficient to set the intermediate point between the ends as P2.

With the above four types of signals, T ₁ ,
Create states T ₂ , T′ ₁ , and T′ ₂ . That is, φ ₁ =
When φ' ₁ = 1, it becomes T ₁ , when φ ₂ = φ' ₂ = 1, it becomes T ₂ , and φ ₁ =
1, T' ₁ when φ' ₁ = 0, T' when φ ₂ = 1, φ' ₂ = 0
₂
It is made to be. If φ ₁ and φ ₂ are zero,
The 1-phase winding and the 2-phase winding are respectively in the OFF state.

If such a relationship is shown in FIG. 4, φ ₁
=1, φ ₂ =1, analog switch A-
1 and A-2 are in the ON state, and the analog switches A-1 and A-2 directly receive the drive signal S-2 via the converter D/A when φ' ₁ =1 and φ' ₂ =1. When φ' ₁ =0 and φ' ₂ =0, the sign of S-2 is inverted and output to the power amplifier side. Needless to say, the analog switches A-1 and A-2 having the above-mentioned functions can be easily realized using an integrated circuit differential amplifier.

If the drive circuit shown in FIG. 4 is used, the current in the winding will flow as shown in FIG. 6. In FIG. 6, I ₁ is the current in the one-phase winding, and I ₂ is the current in the two-phase winding. For example, the load current generates a thrust in the opposite direction to the polarity of the thrust constant, so a thrust as shown by F in the figure is generated, and the movable part moves in one direction.

FIG. 7 shows a second embodiment using an electronic switch with digital elements. D-1 and D-2 are digital switches and output signals ψ ₁ , ψ ₂ , ψ′ ₁ , ψ′ ₂
Based on the opening/closing of the drive signal S-2 and the signal S
-2 sign setting. Signals ψ ₁ , ψ ₂ , ψ′ ₁ , ψ′ ₂
The functions of are exactly the same as those of the signals φ ₁ , φ ₂ , φ′ ₁ , and φ′ ₂ described above, so a detailed explanation will be omitted.

As described above, according to the present invention, the circuit for switching the excitation of the windings can be realized using inexpensive circuit components, so that a driving device for a brushless linear motor can be provided extremely economically.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram explaining the conventional excitation mode, Fig. 2 is an explanatory diagram showing the relationship between winding current and thrust, Fig. 3 is an explanatory diagram explaining the excitation state in the present invention, and Fig. 4 is an explanatory diagram explaining the excitation state in the present invention. The configuration of the first embodiment of the present invention, FIG. 5 is an explanatory diagram explaining the signals that define the excitation state in the first embodiment, and FIG. 6 shows the relationship between current and thrust in the first embodiment. The explanatory diagram, FIG. 7, shows the configuration of a second embodiment of the present invention. T, T′, T ₁ , T ₂ , T′ ₁ , T′ ₂ ...excitation state, λ
...Pitch of thrust-position characteristics, 1...Movable part, 2
...Fixed part, 3...Movable part of position detector, 4...
Fixed part of position detector, AMP-1, AMP-2...
Power amplifier, A-1, A-2...Analog switch, D/A...Digital-analog converter, C
...Control circuit, φ ₁ , φ ₂ , φ′ ₁ , φ′ ₂ , ψ ₁ , ψ ₂ , ψ
′ ₁ ,
ψ′ ₂ ... Signal that defines the excitation state, S-1 ... Pulse, S-2 ... Drive signal, D-1, D-2 ...
Digital switch.

Claims (1)

[Scope of utility model registration request] A fixed part having a field made of permanent magnets arranged in a uniaxial direction on a plane, a movable part having windings that can independently form two closed electric circuits, and position information of the movable part in the running axis direction. In a brushless linear motor that switches the current to the windings based on the driving shaft, the control means determines the selection of the windings and the polarity of the current in units of 1/4 period of the thrust-position characteristic that periodically changes with respect to the traveling axis, and switching means for producing an excitation cycle consisting of four different excitation states in one period of the thrust-position characteristic based on the control means, switching means for switching the current to the winding by the control means and the switching means; A drive device for a brushless linear motor, characterized in that the phase difference between the and thrust-position characteristics is set to be shifted by ±1/8 cycle.