JPH09287558A - Driving device for linear compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a driving device for a linear compressor which attains high efficiency. SOLUTION: A position commanding value Pref of a piston is output by means of a position commanding part 31 according to a formula A*sinωt. A velocity commanding value Vref is computed by means of a position controlling part 33 by multiplying the difference between the position commanding value Pref and a present position value Pnow by a constant Gv. A current commanding value Iref is computed by means of a velocity controlling part 35 by multiplying the difference between the velocity commanding value Vref and a present velocity value Vnow by a constant Gi. A power source is so controlled that a present current value Inow i s agreed with the current commanding value Iref by means of a current controlling part 37. The values ωand Gi are so adjusted that a phase difference between the present velocity value Vnow and the current commanding value Iref is eliminated by means of a phase controlling part 38. Thrust of a linear motor can be directly and properly controlled according to a load condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device for a linear compressor, and more particularly to a driving device for a linear compressor in which a piston is reciprocated in a cylinder by a linear motor to generate compressed gas.

[0002]

2. Description of the Related Art In recent years, a linear compressor has been developed as a mechanism for compressing expanded refrigerant gas in a cooling device such as a refrigerator. In this linear compressor, gas compression is performed by driving a piston by a linear motor and a mechanical spring for resonance.

[0003]

In such a linear compressor, a non-linear force (gas spring force) accompanying the suction, compression and discharge of gas is generated in the compression chamber, and the non-linear force is a load at the time of starting or the like. It fluctuates due to fluctuations.

However, in a conventional linear compressor,
There is no means for controlling the thrust of the linear motor, and a constant power is supplied to the linear motor even when there is a load change. Therefore, the ratio of output energy to input energy (hereinafter referred to as efficiency) is low. Was. Further, a method of controlling a voltage applied to a coil of a linear motor in accordance with a load change has been studied for higher efficiency, but is not satisfactory.

[0005] Therefore, a main object of the present invention is to provide a drive device for a linear compressor which can obtain high efficiency.

[0006]

The invention according to claim 1 is
A linear compressor drive device that reciprocally moves a piston in a cylinder by a linear motor to generate compressed gas. A power supply capable of controlling an output current for driving the linear motor, a position of the piston in the cylinder according to a sine function. Position commanding means for commanding the position of the piston in the cylinder, position commanding means for detecting the position of the piston in the cylinder, commanding the piston speed based on the difference between the position commanded by the position commanding means and the position detected by the position detecting means. Speed commanding means, speed detecting means for detecting the speed of the piston, current commanding means for commanding the output current of the power supply based on the difference between the speed commanded by the speed commanding means and the speed detected by the speed detecting means, and the power supply Current detecting means for detecting the output current of the Current control means for controlling the output current of the power supply so as to match the current commanded by the command means, and the phase difference between the piston speed detected by the speed detection means and the output current of the power supply commanded by the current command means. And a frequency adjusting means for adjusting the frequency of the sine function used in the position commanding means so as to eliminate the phase difference.

In the invention according to claim 2, the speed detecting means of the invention according to claim 1 differentiates the detection result of the position detecting means to detect the speed of the piston.

In the invention according to claim 3, the speed command means of the invention according to claim 1 or 2 uses the first gain for the difference between the position commanded by the position command means and the position detected by the position detection means. The constant is multiplied to calculate the command value of the speed of the piston, the speed of the piston is commanded based on the calculated value, and the current command means is the speed commanded by the speed command means and the speed detected by the speed detection means. The difference between and is multiplied by the second gain constant to calculate the output current of the power supply, and the output current of the power supply is commanded based on the calculated value.
Gain adjusting means for adjusting at least one of the first gain constant used in the speed commanding means and the second gain constant used in the current commanding means so that the phase difference detected by the phase difference detecting means disappears. Further provided.

[0009]

FIG. 1 is a block diagram showing a configuration of a driving device 2 of a linear compressor 1 according to an embodiment of the present invention.

In FIG. 1, the driving device 2 includes a power supply 3, a current sensor 4, a position sensor 5, and a control device 6. The power supply 3 supplies a drive current I to the linear motor of the linear compressor 1. The current sensor 4 detects a current value Inow of the output current of the power supply 3. The position sensor 5 directly or indirectly detects the current position value Pnow of the piston of the linear compressor 1. The control device 6 outputs a control signal φc to the power supply 3 based on the current current value Inow detected by the current sensor 4 and the position current value Pnow detected by the position sensor 5 to control the output current I of the power supply 3. To do.

FIG. 2 is a sectional view showing the structure of the linear compressor 1. 2, the linear compressor 1 includes two cylinders 11a and 11b provided at an upper end and a lower end of a cylindrical casing 10, respectively.
And 2 fitted in the cylinders 11a and 11b, respectively.
Pistons 12a and 12b,
a, two compression chambers 1 formed facing the heads 12b
3a, 13b and two sets of suction valves 14a, 14b that open and close according to the gas pressure in the compression chambers 13a, 13b, respectively.
And discharge valves 15a and 15b.

The two pistons 12a and 12b are provided at one end and the other end of one shaft 16, respectively. The shaft 16 is made up of the casing 10 and the cylinders 11a, 11b by two sets of linear ball bearings 17a, 17b and coil springs 18a, 18b.
It is reciprocally supported inside. Pistons 12a, 1
Gas leak holes 19a and 19b for preventing irreversible compression are provided in the space formed by the back side of the head 2b and the cylinders 11a and 11b.

Further, the linear compressor 1 has a linear motor 20 for reciprocating the shaft 16 and the pistons 12a and 12b. The linear motor 20 is a voice coil motor with high controllability,
a and a movable part including a coil 23 and a cylindrical support member 24. The yoke part 10a forms a part of the casing 10.
The permanent magnet 21 is provided on the inner peripheral wall of the yoke part 10a. One end of the support member 24 is reciprocally inserted between the permanent magnet 21 and the outer peripheral wall of the cylinder 11b, and the other end is fixed to the center of the shaft 16. Coil 23
Is provided to face the permanent magnet 21 at one end of the support member. The power supply 3 and the coil 24 are connected via a coil spring-shaped electric wire 25.

The linear compressor 1 has a piston 1
It has a resonance frequency determined by the weights of the shafts 2a and 12b, the shaft 16, the coil 23 and the support member 24, the spring constant of the gas in the compression chambers 13a and 13b, the spring constant of the coil springs 18a and 18b, and the like. By driving the linear motor 20 at this resonance frequency, the upper and lower two compression chambers 13 are driven.
The compressed gas can be generated with high efficiency by a and 13b.

FIG. 3 is a block diagram showing a configuration of the control device 6 shown in FIG. In FIG. 3, the control device 6
Are a PV converter 30, a position commander 31, three subtractors 32, 34, 36, a position controller 33, a speed controller 35,
It includes a current controller 37 and a phase controller 38. The PV converter 30 differentiates the current position value Pnow detected by the position sensor 5 to obtain the current speed value Vnow. The position command unit 31 gives the position command value Pref to the subtractor 32 according to the mathematical expression Pref = A * sinωt (where A is the amplitude and ω is the angular frequency). The subtractor 32 calculates the difference Pref-Pnow between the position command value Pref given from the position command unit 31 and the position current value Pnow detected by the position sensor 5, and calculates the calculation result Pref-Pn.
ow is given to the position control unit 33.

The position control unit 33 calculates the equation Vref = Gv *
The speed command value Vref is calculated based on (Pref-Pnow) (where Gv is a gain constant), and the calculation result Vref is given to the subtractor 34. The subtractor 34 calculates the speed command value Vref given by the position control unit 33 and the P-V
Difference Vr from current speed value Vnow generated by converter 30
ef-Vnow is calculated, and the calculation result Vref-Vnow is calculated.
Is given to the speed control unit 35.

The speed control unit 35 calculates the equation Iref = Gi *
The current command value Iref is calculated based on (Vref-Vnow) (where Gi is a gain constant), and the calculation result Iref is given to the subtractor 36. The subtractor 36 calculates a difference I between the current command value Iref given from the speed control unit 35 and the current current value Inow detected by the current sensor 4.
ref-Inow is calculated, and the calculation result Iref-Ino is calculated.
w is given to the current control unit 37.

The current control unit 37 outputs the output Ir of the subtractor 36.
Control signal φc is supplied to power supply 3 so that ef-Inow becomes 0.
To control the output current I of the power supply 3. The control of the output current I of the power supply 3 is performed by, for example, a PWM method or a PAM method.

The phase control unit 38 detects the phase difference between the current speed value Vnow generated by the P-V conversion unit 30 and the current command value Iref generated by the speed control unit 35 so that the phase difference disappears. Equation P used in the position command unit 31
The angular frequency ω of ref = A * sinωt and the speed control unit 35
Equation Iref = Gi * (Vref−Vno)
The gain constant Gi of w) is adjusted.

FIG. 4 is a flow chart showing the operation of the control device 6 shown in FIG. According to this flowchart, the operation of the linear compressor 1 and the driving device 2 thereof shown in FIGS. 1 to 3 will be briefly described.

First, in step S1, the position command unit 3
At 1, the position command value Pref is generated, the position control unit 33 generates the speed command value Vref, and the speed control unit 35 generates the current command value Iref. When a current is supplied to the coil 23 of the linear motor 20, the movable portion of the linear motor 20 starts reciprocating, thereby starting generation of compressed gas.

In step S2, the current position value Pnow is detected by the position sensor 5, and the detected current position value Pnow is given to the subtractor 32 and the PV converter 30. In step S3, the velocity command value Vref = Gv * (Pref-Pno) is
w) is calculated, and in step S4, the current position value Pnow is converted by the PV conversion unit 30 into the current speed value Vnow.
Is converted to The current speed value Vnow is provided to the subtractor 34 and the phase control unit 38.

In step S5, the speed control unit 35 controls the current command value Iref = Gi * (Vref-Vno).
w) is calculated, and the calculated value Iref is provided to the subtractor 36 and the phase control unit 38. The current control unit 37 controls the power supply 3 so that the current current value Inow matches the current command value Iref.

In step S6, the phase controller 38 detects the phase difference between the current speed value Vnow and the current command value Iref. In step S7, the phase controller 3
8 indicates each frequency ω of the position command value Pref so that there is no phase difference between the current speed value Vnow and the current command value Iref.
And the gain constant Gi are adjusted.

Thereafter, steps S1 to S7 are repeated,
The operating state of the linear compressor 1 stabilizes rapidly. Further, even when there is a load change after the start, the thrust of the linear motor 20, that is, the drive current I is directly and appropriately controlled in accordance with the load change, and high efficiency is obtained.

In this embodiment, the position sensor 4
The current position value Pnow is detected according to the following formula, and the detected value is differentiated to obtain the current speed value Vnow. However, a speed sensor is provided instead of the position sensor 4 and the detected value Vnow is integrated to obtain the current position value Pnow. You may. Further, both the position sensor 4 and the speed sensor may be provided.

Further, in this embodiment, the phase controller 3
8 is the gain constant Gv of the position control unit 33 and the speed control unit 35
Although only the gain constant Gi among the gain constants Gi is adjusted, only the gain constant Gv among them may be adjusted, or both of them may be adjusted.

[0028]

As described above, the first aspect of the present invention employs a multiplex control configuration including position control, speed control, and current control, and eliminates the phase difference between the current speed value and the current command value. Adjust the frequency of the position command value. Therefore, the thrust of the linear motor can be directly and appropriately controlled according to the load condition, and high efficiency can be achieved.

Further, in the invention according to claim 2, since the speed detecting means detects the speed of the piston by differentiating the detection result of the position detecting means, it is not necessary to separately provide a speed detecting sensor.

In the invention according to claim 3, the speed command means calculates the speed command value by multiplying the difference between the position command value and the current position value by the first gain constant, and the current command means calculates the current command value. And the current current value are multiplied by a second gain constant to calculate a current command value, and the gain adjusting means sets the first and second gain constants so that the phase difference between the current speed value and the current command value is eliminated. Adjust at least one of them. Therefore, the responsiveness of the current control can be adjusted according to the load condition, and the thrust of the linear motor can be controlled more appropriately.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a control device for a linear compressor according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a configuration of the linear compressor shown in FIG.

3 is a block diagram showing a configuration of a control device 6 shown in FIG.

FIG. 4 is a flowchart showing an operation of the control device shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Linear compressor 2 Drive device 3 Power supply 4 Current sensor 5 Position sensor 6 Control device 11a, 11b Cylinder 12a, 12b Piston 20 Linear motor 30 PV conversion part 31 Position command part 32, 34, 36 Subtractor 33 Position control part 35 Speed controller 37 Current controller 38 Phase controller

Claims (3)

[Claims] 1. A drive device for a linear compressor that reciprocates a piston in a cylinder by a linear motor to generate compressed gas, the power supply capable of controlling an output current for driving the linear motor, and a sine function Position command means for commanding the position of the piston in the cylinder, position detection means for detecting the position of the piston in the cylinder, position commanded by the position command means and detected by the position detection means. Speed command means for commanding the speed of the piston based on the difference with the position, speed detection means for detecting the speed of the piston, speed commanded by the speed command means and speed detected by the speed detection means Current command means for commanding the output current of the power supply based on the difference; A current detection unit that detects a current, a current control unit that controls the output current of the power supply so that the current detected by the current detection unit matches the current commanded by the current command unit, and the speed detection unit. Detects the phase difference between the detected speed of the piston and the output current of the power source commanded by the current command means, and adjusts the frequency of the sine function used by the position command means so as to eliminate the phase difference. A drive device for a linear compressor, which is provided with a frequency adjusting means for controlling. 2. The speed detecting means differentiates the detection result of the position detecting means to detect the speed of the piston.
The drive device for the linear compressor according to claim 1. 3. The speed command means is configured to multiply the difference between the position commanded by the position command means and the position detected by the position detection means by a first gain constant to command the speed of the piston. Is calculated, and the speed of the piston is commanded based on the calculated value, and the current command means sets the difference between the speed commanded by the speed command means and the speed detected by the speed detection means to a second value. The output current of the power supply is calculated by multiplying by a gain constant, and the output current of the power supply is commanded based on the calculated value, and the drive device of the linear compressor further detects the position detected by the phase difference detection means. At least one of the first gain constant used in the speed command means and the second gain constant used in the current command means is adjusted so that there is no phase difference. To comprise a gain adjusting means, the linear compressor driving apparatus according to claim 1 or 2.