JPH06105074B2 - Excitation method of electromagnetically driven reciprocating compressor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic drive type reciprocating compressor in which a piston reciprocates by an electromagnetic force, and relates to an excitation system of a driver coil of a compressor.

[Conventional technology]

In a reciprocating compressor, since a piston reciprocates linearly, pulsating vibration is generated during operation, which is a major cause of noise and shortened life. For this reason, various anti-vibration measures have been taken conventionally. As one of the measures, a method of electromagnetically driving the piston with a linear motor is adopted.Moreover, in terms of structure, the working medium is stored in a single cylinder with both ends open. A pair of pistons are placed opposite to each other across the compression space, and the driver coil connected to each piston is placed in the magnetic field of the constant magnetic field magnet device, and each drive is given a phase difference of 180 degrees. An electromagnetically driven reciprocating compressor in which a child coil is AC-excited to electromagnetically drive a piston has already been proposed by the same applicant as Japanese Patent Laid-Open No. 61-210276.

According to the configuration proposed above, since a pair of pistons reciprocate in opposite directions in synchronization with each other with respect to a single cylinder, the inertial forces of the pistons cancel each other out, and vibration generation in the entire compressor is suppressed to a low level. You can

[Problems to be Solved by the Invention]

By the way, in the compressor, a clearance seal system is generally adopted in order to suppress sliding friction between the cylinder and the piston. This clearance seal method is a method in which a gas, which is a working medium, is discharged from the compression space side of the cylinder into a minute gap between the cylinder and the piston, and the gas is sealed by viscous resistance of the gas flow. In this case, in order to improve the efficiency of the compressor, it is necessary to make the fitting gap between the cylinder and the piston as small as possible so as to suppress the amount of gas discharged as the seal gas.

On the other hand, when machining a piston and a cylinder, there is a machining error in terms of accuracy of circularity and cylindricity, and this machining error causes the piston and the cylinder to locally contact each other during operation of the compressor. There is a so-called bitterness in this part,
This bite acts as a frictional resistance force on the movement of the piston. However, since the bite occurrence points of the piston and the cylinder generated due to such a processing error are random, in the compressor in which a pair of pistons are combined in a single cylinder as described above, both pistons There is a difference in frictional resistance between the two. Moreover, the difference in frictional resistance that acts on both pistons greatly affects the acceleration and deceleration when driving the pistons. In addition to the loss of synchronization, the stroke amplitude of the reciprocating motion of each piston also becomes different. As a result, in addition to the reduction in the effective discharge amount of the compressor, there arises a problem that large vibration and noise are generated due to the difference in the inertial force of the piston.

The present invention has been made in view of the above points, by improving the excitation method of the driver coil coupled to the piston, to reduce the frictional force between the piston and the cylinder to maintain the performance of the compressor, and It is an object of the present invention to provide an excitation system for an electromagnetically driven reciprocating compressor that is designed to reduce generated vibration.

[Means for Solving the Problems]

In order to solve the above-mentioned problems, the present invention is directed to the electromagnetically driven reciprocating compressor described above, wherein a fundamental wave having a frequency corresponding to the reciprocating motion of the compressor has a higher frequency than the fundamental wave and an amplitude. The driver coil is excited by an alternating current superposed with a small superimposed wave of.

[Action]

Due to the above, between the driver coil and the constant magnetic field magnet device, in addition to the large alternating electromagnetic force that reciprocates the piston corresponding to the frequency of the fundamental wave, a small amount of a superposed wave having a frequency higher than that of the fundamental wave is generated. Alternate electromagnetic force (electromagnetic force due to superposed waves is set to a low value so as not to affect the piston reciprocating motion of the compressor) is generated. As a result, the piston is reciprocated in the cylinder at a cycle corresponding to the fundamental wave, and at the same time, the upper and lower dead centers of the stroke end in the reciprocating stroke (at this position, the movement direction of the piston is reversed, so the movement is temporary. Even when the piston is stopped, a slight vibration force due to the excitation of the superposed wave is always applied to the piston.

Therefore, as described above, even if there is a bite portion where the piston and the cylinder locally contact with each other due to the machining error during the production as described above, at the stroke top and bottom dead center position in the reciprocating stroke of the piston, the above-mentioned superimposed wave is generated. Since a slight vibration force is applied, static friction does not act between the piston and the cylinder, and it is always in a state of dynamic friction.

On the other hand, as is well known, the dynamic friction coefficient is much smaller than the static friction coefficient. Therefore, as described above, a minute exciting force is applied to the piston by the exciting current of the superimposed wave applied to the driver coil, and the dynamic friction is always applied to the contact surface between the piston and the cylinder to operate. The frictional resistance between the piston and the cylinder is extremely small, and the difference in the frictional resistance generated between the pair of pistons mounted on the cylinder is also small. This allows the compressor to operate stably.

〔Example〕

FIG. 1 is a configuration diagram of an embodiment of the present invention, and FIG. 2 is a waveform diagram of a fundamental wave and a superimposed wave applied as an exciting current. First, the configuration of an electromagnetically driven reciprocating compressor will be described with reference to FIG. To do.

In the figure, in a case 1, a single cylinder 2 having a working medium compression space 2a formed therein is installed, and dimensions are provided on both the left and right sides of the cylinder with the compression space 2a sandwiched therebetween. , A pair of pistons 3 with the same weight specifications
A and 3B are deployed oppositely. A suction pipe 5 and a discharge pipe 6 for the working medium are opened in the case 1 through the center of the cylinder 2 and a suction valve 7 and a discharge valve 8 are provided therein.

Further, electromagnetic drive mechanisms 4A and 4B are attached to the pistons 3A and 3B. The electromagnetic drive mechanisms 4A and 4B are driver coils that are wound around a sleeve 10 made of a non-magnetic material and connected to a piston shaft 9.
11A and 11B, cylindrical magnetic yokes 12 and 13 arranged opposite to the inner and outer circumferences of the driver coil (however, in the illustrated embodiment, the cylinder 2 also serves as the inner yoke 12), and the yokes.
It is composed of a constant magnetic field magnet device including a permanent magnet 14 interposed between 12 and 13. In addition, the driver coil 11A
And 11B are opposite to each other in the winding direction of the coil, and the lead wire drawn from each driver coil is connected to the external power supply 16 via the power supply terminal 15 provided in the case 1. In addition,
Reference numeral 17 is a spring member for holding each of the pistons 3A and 3B in a neutral position in a stopped state.

On the other hand, the power supply 16 includes a fundamental wave generation circuit 18, a superimposed wave generation circuit 19, and a summing amplification circuit 20. Here, the fundamental wave generation circuit 18
Outputs a fundamental wave signal having a frequency corresponding to the reciprocating cycle of the compressor, and the superposed wave generation circuit 19 outputs a superposed wave signal having a higher frequency and an extremely small amplitude as compared with the fundamental wave. The superimposed wave signal is amplified by the addition amplifier circuit 20 and fed to the driver coil 11A, 11B of the compressor to be excited. In addition,
The waveforms of the fundamental wave and the superposed wave are shown in FIG.

In such a structure, the driver coils 11A and 11B are supplied from the power source 16.
When an alternating current is supplied to and excited by a constant magnetic field, an alternating electromagnetic force is generated by the Fleming's law, and the pistons 3A and 3B receive this electromagnetic force and have a 180-degree phase difference between them, and the pistons 3A and 3B reverse inside the cylinder 2. Reciprocates in the direction. The reciprocating motion of the piston is described in the above-mentioned Japanese Patent Laid-Open No. 61-210276, and its explanation is omitted here.

By the way, the driver coils 11A, 11A supplied by the power supply 16
The electromagnetic force generated by the excitation of B is a large electromagnetic force corresponding to the frequency of the fundamental wave, and a small high-frequency excitation force due to the superimposed wave. And the pistons 3A, 3B
Is driven so as to reciprocate inside the cylinder 2 at a cycle corresponding to the frequency of the fundamental wave, and at the same time, in the entire stroke stroke of the piston including the top and bottom dead center of the reciprocating motion, the frequency of the superposed wave is very small. Vibratory force is added. The amplitude of the superimposed wave is selected to be sufficiently smaller than the fundamental wave so that this exciting force does not affect the basic piston reciprocation of the compressor.

As a result, the pistons 3A and 3B do not become completely stationary even at the top and bottom dead center positions at the stroke end in the reciprocating stroke of the piston, and the fine movement state continues. Therefore, even if there is a mechanical contact between the cylinder 2 and the pistons 3A, 3B, no static friction force is applied between them, and only a kinetic frictional force with a small resistance acts. As pistons 3A, 3 accompanying the reciprocating motion of the compressor
The frictional resistance acting between B and the cylinder 2 can be suppressed to a slight extent. This also allows the pair of pistons 3A and 3B to
There is almost no difference in frictional force between the two pistons, and both pistons are stably reciprocated while maintaining a predetermined phase difference (180 degrees) and stroke amplitude.

Although the illustrated example illustrates a general gas compressor, it can also be applied to a reverse Stirling cycle refrigerator configured by combining this compressor with a displacer serving as a separation type expansion cylinder.

〔The invention's effect〕

As described above, the following effects are exhibited by the excitation system of the electromagnetically driven reciprocating compressor according to the present invention.

(1) The friction acting between the piston and the cylinder, including the position of the top and bottom dead centers of the stroke end in the reciprocating stroke of the piston, can always be maintained in a dynamic friction state with a small friction resistance.

(2) As a result, the difference in frictional force between the pistons of a pair of pistons mounted on a single cylinder becomes small, so that stable operation of the compressor, maintenance of performance, and reduction of generated vibration can be achieved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention, and FIG. 2 is a waveform diagram of a fundamental wave and a superposed wave of an exciting current. In the figure, 2: cylinder, 2a: compression space, 3A, 3B: piston, 4A, 4B: electromagnetic drive mechanism, 11A, 11B: driver coil, 14: permanent magnet, 16:
Power supply, 18: fundamental wave generation circuit, 19: superposed wave generation circuit.

Claims (1)

[Claims] 1. A pair of pistons are arranged opposite to each other across a compression space of a working medium in a single cylinder whose both ends are open, and a driver coil connected to each piston is placed in a magnetic field of a constant magnetic field magnet device. It corresponds to the reciprocating motion of the compressor for the electromagnetically driven reciprocating compressor, which is arranged at the same time and gives a phase difference of 180 degrees to each other to excite each driver coil by alternating current to drive the piston. An excitation method for an electromagnetically driven reciprocating compressor, characterized in that the driver coil is excited by an alternating current in which a high frequency having a frequency smaller than the fundamental wave and a small amplitude is superposed on the fundamental wave of the frequency.