The present invention relates a driving controlling apparatus of a reciprocating compressor using resonance, and more particularly, to a driving controlling apparatus of a reciprocating compressor using resonance with high current counteracting characteristics by offsetting an inductance value of a coil wound inside a motor by employing a capacitor.

In general, in a reciprocating compressor, power supplied to a coil wound at a polyphase stator is switched off by using a switching device to thereby generate a rotational torque. In this respect, by sequentially varying an excitation state between a rotor and a stator, a forward rotational torque can be generated by a magnetic suction force.

If a specific excitation state is not varied, the rotor can be stopped at a certain position, and by controlling a phase of an input pulse signal applied to the switching device by taking a maximum inductance as a starting point, a reverse-rotational force can be generated

With such various driving control availability, the reciprocating compressor is adopted for use to electric products requiring a direction control of the motor.

Especially, the reciprocating compressor used for a refrigerator or air-conditioner, a compression ratio can be varied by a voltage applied to the motor, and accordingly, a cooling force can be varied according to a user's intention.

The reciprocating motor will now be described in detail with reference to Figure 1.

Figure 1 is a block diagram showing the construction of a driving controlling apparatus of a general reciprocating compressors as disclosed e.g. in JP-A-09112439.

As shown in Figure 1, the general reciprocating compressor includes: a reciprocating compressing unit (L.COMP) for varying a stroke by piston's movement to control a cooling force by a voltage applied to an internal motor according to a stroke command value; a voltage detector 30 for detecting a voltage generated at the reciprocating compressing unit (L.COMP) as the stroke is increased by the applied voltage; a current detector 20 for detecting a current applied to the reciprocating compressing unit (L.COMP) as the stroke is increased by the applied voltage; a microcomputer 40 for calculating a stroke with the voltage and the current detected by the voltage detector 30 and the current detector 20, comparing the stroke with the stroke command value and outputting a corresponding switching control signal; and an electric circuit unit 10 for switching off an AC power with a triac according to the switching control signal of the microcomputer 40 to apply a voltage to the reciprocating compressing unit (L.COMP).

The operation of the conventional reciprocating motor constructed as described will now be explained.

First, in the reciprocating compressing unit (L.COMP), the piston is moved by the voltage applied according to the stroke command value set by a user, and accordingly, a stroke is varied to control a cooling force.

Meanwhile, as the turn-on period of the triac (Tr1) of the electric circuit unit 10 is lengthened by the switching control Signal of the microcomputer 40, the stroke of the reciprocating compressing unit (L.COMP) is increased. At this time, the voltage and current applied to the motor (M) of the reciprocating compressing unit (L.COMP) are detected by the voltage detector 30 and the current detector 20 and applied to the microcomputer 40.

Then, the microcomputer 40 calculates a stroke by using the voltage and current detected by the voltage detector 30 and the current detector 20.

The stroke is compared with the stroke command value to output a corresponding switching control signal.

That is, if the calculated stroke is smaller than the stroke command value, the microcomputer 40 outputs a switching control signal for lengthening the ON period of the triac (Tr1) in order to increase the voltage applied to the reciprocating compressing unit (L.COMP).

If, however, the calculated stroke is greater than the stroke command value, the microcomputer 40 outputs a switching control signal for shortening the ON period of the triac (Tr1) to reduce the voltage applied to the reciprocating compressing unit (L.COMP).

The relation between the voltage applied to the motor (M) and the stroke can be expressed by the following equation (1)$$\mathit{\text{V}}\text{=}\mathit{\text{L}}\frac{\mathit{\text{di}}}{\mathit{\text{dt}}}\text{+}\mathit{\text{R}}\text{·}\mathit{\text{i}}\text{+ α ·}\overrightarrow{\mathit{\text{S}}}$$ wherein α indicates a motor constant for converting an electric force to a mechanic force, $\overrightarrow{\mathit{\text{S}}}$ indicates a stroke, 'R' is a internal resistance of the motor, and 'L' indicates an inductance of the motor (M) itself.

The inductance voltage (L $\frac{\mathit{\text{di}}}{\mathit{\text{dt}}}$) is almost similar to a back electromotive force (α ·$\overrightarrow{\mathit{\text{S}}}$), and the voltage by the internal resistance (R) can be negligible compared with the back electromotive force (α ·$\overrightarrow{\mathit{\text{S}}}$).

Accordingly, the voltage (V) applied to the motor (M) is determined by sum of the inductance voltage (L $\frac{\mathit{\text{di}}}{\mathit{\text{dt}}}$) and the back electromotive force (α ·$\overrightarrow{\mathit{\text{S}}}$), and in order to generate a required stroke, the voltage (V) applied to the motor should be increased.

At this time, in order to improve an efficiency of the reciprocating compressor, the inductance (L) value of the coil wound on the motor (M) itself should be small, and the inductance (L) value of the coil becomes small as the size of the motor (magnet) is increased.

Thus, in order to improve the efficiency of the reciprocating motor, if the size of the mover (the thickness of the magnet) is increased, an air gap is increased, causing a problem that the overall size and cost of the reciprocating compressor is increased.

Meanwhile, if the size of the mover (the thickness of the magnet) is reduced, the inductance (L) value of the coil wound at the motor (M) is increased. Then, the current according to the voltage value for the stroke control of the reciprocating compressor would slowly work, so that the stroke is not smoothly controlled.

Therefore, an object of the present invention is to provide a driving controlling apparatus of a reciprocating compressor which has an excellent current counteracting capacity by offsetting a quality which slows current operation characteristics as an inductance value of a coil wound inside a motor is increased by employing a capacitor.

In order to achieve the above objects, there is provided a driving controlling apparatus of a reciprocating compressor having a reciprocating compressing unit controlling a cooling force by varying a stroke according to a piston's movement by a voltage applied to an internal motor according to a stroke command value and an electric circuit unit for switching an AC power with a triac and applying it to the motor of the reciprocating compressing unit, wherein the electric circuit unit includes a capacitor for offsetting an inductance of a coil wound at a motor itself of the reciprocating compressing unit.

• Figure 1 is a block diagram showing the construction of a driving controlling apparatus of a conventional reciprocating compressor; and
• Figure 2 is a block diagram showing the construction of a driving controlling apparatus of a reciprocating compressor using a resonance according to the present invnetion.

The operation and effect of a driving controlling apparatus of a reciprocating compressor will now be described in detail with reference to the accompanying drawings.

Figure 2 is a block diagram showing the construction of a driving controlling apparatus of a reciprocating compressor using a resonance according to the present invnetion.

As shown in Figure 2, a driving controlling apparatus of a reciprocating compressor includes: a reciprocating compressing unit (L.COMP) for varying a stroke by piston's movement to control a cooling force by a voltage applied to an internal motor according to a stroke command value; a voltage detector 30 for detecting a voltage generated at the reciprocating compressing unit (L.COMP) as the stroke is increased by the applied voltage; a current detector 20 for detecting a current applied to the reciprocating compressing unit (L.COMP) as the stroke is increased by the applied voltage; a microcomputer 40 for calculating a stroke with the voltage and the current detected by the voltage detector 30 and the current detector 20, comparing the stroke with the stroke command value and outputting a corresponding switching control signal; and an electric circuit unit 10 having a capacitor (C) to offset an inductance of a coil (L) wound at the motor (M) itself of the reciprocating compressing unit (L.COMP) and switching off an AC power with a triac according to the switching control signal of the microcomputer 40 to apply a voltage to the reciprocating compressing unit (L.COMP).

The operation of the driving controlling apparatus of a reciprocating compressor will now be described in detail.

First, the piston is moved by an applied voltage according to a stroke command value set by a user, and accordingly, a stroke is varied to control a cooling force.

Meanwhile, as the turn-on period of the triac (tr1) of the electric circuit unit 10 is lengthened by the switching control signal of the microcomputer 40, the stroke of the reciprocating compressing unit (L.COMP) is increased. At this time, the voltage and current applied to the motor (M) of the reciprocating compressing unit (L.COMP) are detected by the voltage detector 30 and the current detector 20 and applied to the microcomputer 40.

Then, the microcomputer 40 calculates a stroke by using the voltage and current detected by the voltage detector 30 and the current detector 20.

The stroke is compared with the stroke command value to output a corresponding switching control signal.

In this respect, in the present invention, the capacitor (C) is connected in series to the motor (M) to offset an inductance (L) of a coil wound at the motor (M), which will now be described in detail.

First, a voltage (V) applied to both ends of the motor (M) and the capacitor (C) can be deduced to the following equation (2):$$\mathit{\text{V}}\text{=}\mathit{\text{L}}\frac{\mathit{\text{di}}}{\mathit{\text{dt}}}\text{+}\frac{\text{1}}{\mathit{\text{C}}}\text{∫}\mathit{\text{idt}}\text{+}\mathit{\text{R}}\text{·}\mathit{\text{i}}\text{+ α ·}\overrightarrow{\mathit{\text{S}}}$$

At this time, a capacitance can be set by the following equation (3):$$\mathit{\text{C}}\text{=}\frac{\text{1}}{\text{(2}\mathit{\text{πf}}{\text{)}}^{\text{2}}\mathit{\text{L}}}$$

At this time, the capacitance (C) and the inductance (L) are previously set with values causing a resonance.

Accordingly, since the capacitance (C) and the inductance (L) are mutually resonated and offset, so that the voltage (V) applied to both ends of the motor (M) and the capacitor is deduced to the following equation (4):$$\mathit{\text{V}}\text{=}\mathit{\text{R}}\text{·}\mathit{\text{i}}\text{+ α ·}\overrightarrow{\mathit{\text{S}}}$$

In equation (4), the applied voltage (V) has the similar size to the back electromotive force (α · $\overrightarrow{\mathit{\text{S}}}$) as the inductance voltage (L $\frac{\mathit{\text{di}}}{\mathit{\text{dt}}}$) is offset by the capacitor voltage ($\frac{\text{1}}{\mathit{\text{C}}}$∫idt), and accordingly, a required stroke is generated at the low applied voltage (V).

In addition, since the voltage filled in the capacitor (C) is applied to the motor (M) like the applied voltage (V), a big stroke is generated with the small applied voltage. Thus, an overload counteracting capacity is improved.

As so far described, according to the driving controlling apparatus of a reciprocating compressor, since the current operation characteristics according to the increase in the inductance of the coil inside the motor is offset by employing the capacitor, the load of the applied voltage to inductance is reduced, and thus, a required stroke can be generated with the low applied voltage.

In addition, since the current change makes a little influence on the stroke variation, even though a load change occurs, the stroke variation is small, so that stable load characteristics are obtained.