JP3177448B2 - Drive unit for linear compressor - Google Patents

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 a 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) associated with 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 drive device for a linear compressor that generates a compressed gas by reciprocating a piston in a cylinder by a linear motor, comprising a power supply, a position command unit, a position detection unit, a speed command unit, a speed detection unit, a current command unit, and a current detection unit. ,
Current control means, phase difference detection means, peak value difference detection means,
The apparatus includes frequency adjusting means and gain adjusting means. The power supply is provided for driving the linear motor, and its output current is controllable. The position command means commands the position of the piston in the cylinder according to a sine function. The position detecting means detects a position of the piston in the cylinder. The speed command means calculates a command value of the piston speed by multiplying a difference between the position commanded by the position command means and the position detected by the position detection means by a first gain constant, and calculates a command value of the piston speed based on the calculated value. Command piston speed. The speed detecting means detects the speed of the piston. The current command means multiplies the difference between the speed commanded by the speed command means and the speed detected by the speed detection means by a second gain constant to calculate a command value of the output current of the power supply. The output current of the power supply is instructed based on this. The current detecting means detects an output current of the power supply. The current control means controls the output current of the power supply so that the current detected by the current detection means matches the current commanded by the current command means. The phase difference detection means detects a phase difference between the speed of the piston detected by the speed detection means and the output current of the power supply commanded by the current command means. The peak value difference detection means detects a difference between the peak value of the position of the piston in the cylinder instructed by the position command means and the peak value of the position detected by the position detection means. The frequency adjusting means adjusts the frequency of the sine function used by the position command means so that the phase difference detected by the phase difference detecting means disappears. The gain adjusting means includes at least one of a first gain constant used by the speed command means and a second gain constant used by the current command means so that the peak value difference detected by the peak value difference detecting means disappears. To adjust.

According to a second aspect of the present invention, the phase difference detecting means according to the first aspect of the present invention includes a zero-cross point of the piston speed detected by the speed detecting means and an output current of the power supply commanded by the current commanding means. A zero-cross point is detected, and a phase difference is detected based on the detection result.

According to a third aspect of the present invention, the phase difference detecting means according to the first aspect of the present invention comprises a peak point of the piston speed detected by the speed detecting means and the output current of the power supply commanded by the current commanding means. A peak point is detected, and a phase difference is detected based on the detection result.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment] FIG. 1 is a block diagram showing a configuration of a driving device 2 of a linear compressor 1 according to a first 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 current position value Pnow detected by the position sensor 5, and controls the output current I of the power supply 3. I 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 supported so that it can reciprocate 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.

The linear compressor 1 includes 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 and the phase control unit 38 according to the formula Pref = A * sin ωt (where A is the amplitude and ω is the angular frequency). The subtractor 32 calculates a difference Pref-Pnow between the position command value Pref given from the position command unit 31 and the current position value Pnow detected by the position sensor 5, and outputs the calculation result Pref-Pnow to the position control unit 33. give.

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 control gain), and the calculation result Vref is provided 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 control gain), and the calculation result Iref is provided 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.

As shown in FIG. 4, the phase controller 38 includes zero point detectors 41 and 42, a phase difference detector 43, a frequency controller 44, peak value detectors 45 and 46, a subtractor 47, and a gain controller. 48.

The zero point detector 41 detects a zero cross point of the current speed value Vnow generated by the PV converter 30. The zero point detector 42 detects a zero cross point of the current command value Iref given from the speed controller 35. The zero point detection unit 41 samples the current speed value Vnow at a cycle sufficiently smaller than the current speed value Vnow, for example, where the product of the previous sampled value and the current sampled value is a negative value, and By detecting that the value is a positive value, it is detected that the current speed value Vnow has passed the zero cross point. The same applies to the zero point detection unit 42.

The phase difference detection unit 43 determines the current speed based on the zero cross point of the current speed value Vnow detected by the zero point detection unit 41 and the zero cross point of the current command value Iref detected by the zero point detection unit 42. Value Vnow and current command value I
The phase difference of ref is detected. The frequency control unit 44 controls the position command unit 3 so that the phase difference between the current speed value Vnow detected by the phase difference detection unit 43 and the current command value Iref is eliminated.
Adjust the angular frequency ω of the formula Pref = A * sin ωt used in (1).

The peak value detecting section 45 includes a phase difference detecting section 43.
Current speed value Vnow detected at step S1 and current command value Iref
And the position command value Pr calculated by the position command unit 31
ef and the position command value Pre when the phase difference is zero.
The peak value of f is detected. The peak value detection unit 46 receives the current speed value Vnow detected by the phase difference detection unit 43, the phase difference between the current command value Iref, and the current position value Pnow detected by the position sensor 5, and when the phase difference is zero. The peak value of the current position value Pnow is detected.

The subtracter 47 calculates the difference between the peak value of the position command value Pref detected by the peak value detection unit 45 and the peak value of the current position value Pnow detected by the peak value detection unit 46. The gain control unit 48 adjusts the control gain Gi of the formula Iref = Gi * (Vref-Vnow) used in the speed control unit 35 so that the operation value of the subtractor 47 becomes zero.

FIG. 5 is a flowchart showing the operation of the control device 6 shown in FIGS. 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 supplied to the PV conversion unit 30, the subtractor 32, and the phase control unit 38. In step S3, the velocity command value Vref = Gv * (P
ref-Pnow) is calculated, and in step S4, the PV current value Pnow is converted by the PV conversion unit 30 into the current speed value Vnow. The current speed value Vnow is provided to the subtractor 34 and the phase control unit 38.

In step S5, the current control 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 zero point detector 4
1, 42, the zero cross point of the current speed value Vnow and the current command value Iref is detected.
The phase difference of f is detected.

In step S7, the frequency control unit 44
Thus, the angular frequency ω of the position command value Pref is controlled such that the phase difference between the current speed value Vnow and the current command value Iref becomes zero. Current speed value Vnow and current command value I
In response to the phase difference of ref becoming zero, the peak value detectors 45 and 46 detect the peak value (target value) of the position command value Pref and the peak value of the current position value Pnow, respectively. The gain control unit 48 checks whether the peak value of the current position value Pnow is equal to the target value.

When the peak value of the current position value Pnow is smaller than the target value in step S8, the gain control unit 48 increases the control gain Gi. In step S9, the peak value of the current position value Pnow is larger than the target value. In this case, the control gain Gi is reduced.

Steps S6 to S9 correspond to the current position value Pno.
The process is repeated until the peak value of w matches the target value. If the peak value of the current position value Pnow matches the target value in step S10, the process returns to step S1.

Thereafter, steps S1 to S10 are repeated, and the operating state of the linear compressor 1 is rapidly stabilized. 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.

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

[Second Embodiment] FIG. 6 is a diagram showing a configuration of a phase control section 38 'of a driving device of a linear compressor 1 according to a second embodiment of the present invention, which is compared with FIG. is there.

Referring to FIG. 6, this phase control section 38 'is different from phase control section 38 of FIG.
1 and 42 are replaced by peak point detection units 51 and 52, respectively.

The peak point detecting section 51 includes a PV converting section 30.
The peak point of the current speed value Vnow generated in step (1) is detected. The peak point detection section 52 detects a peak point of the current command value Iref given from the speed control section 35. For example, the peak point detection unit 51 samples the current speed value Vnow at a cycle sufficiently smaller than the current speed value Vnow, and the previous sampled value is larger than the sampled value two times before, and is larger than the previous sampled value. By detecting that the current sampling value is smaller, it is detected that the current speed value Vnow has passed the peak point. The same applies to the peak point detection unit 52.

The phase difference detector 43, as shown in FIG.
In step S6, the phase difference between the current speed value Vnow and the current command value Iref is detected based on the peak point of the current speed value Vnow and the peak point of the current command value Iref. The other configurations and operations are the same as those in the first embodiment, and thus description thereof is omitted.

In this embodiment, the same effect as in the first embodiment can be obtained.

[0040]

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,
The gain constant is adjusted so that the peak value difference between the position command value and the current position value disappears. Therefore, the thrust of the linear motor can be directly and appropriately controlled according to the load condition, and high efficiency can be achieved.

In the invention according to claim 2, the phase difference detecting means detects the zero cross point of the current speed value and the zero cross point of the current command value, and detects the phase difference based on the detection result. Therefore, the phase difference detecting means can be easily configured.

In the invention according to claim 3, the phase difference detecting means detects the peak point of the current speed value and the peak point of the current command value, and detects the phase difference based on the detection result. Therefore, the phase difference detecting means can be easily configured.

[Brief description of the drawings]

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

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

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

FIG. 4 is a block diagram illustrating a configuration of a phase control unit illustrated in FIG. 3;

FIG. 5 is a flowchart showing an operation of the control device shown in FIG. 3;

FIG. 6 is a block diagram showing a configuration of a phase control unit of a linear compressor drive device according to Embodiment 2 of the present invention.

FIG. 7 is a flowchart showing the operation of the control device of the linear compressor drive device described in FIG. 6;

[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, 47 Subtractor 33 Position control Unit 35 speed control unit 37 current control unit 38, 38 'phase control unit 41, 42 zero point detection unit 43 phase difference detection unit 44 frequency control unit 45, 46 peak value detection unit 48 gain control unit 51, 52 peak point detection unit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F04B 49/06 341 F04B 35/04 G05B 13/02 H02P 7/00 101

Claims (3)

(57) [Claims] 1. A driving device for a linear compressor which generates a compressed gas by reciprocating a piston in a cylinder by a linear motor, wherein the power source is capable of controlling an output current for driving the linear motor, according to a sine function. Position instructing means for instructing the position of the piston in the cylinder, position detecting means for detecting the position of the piston in the cylinder, a position instructed by the position instructing means and detected by the position detecting means Speed command means for calculating a command value of the piston speed by multiplying the difference from the position by a first gain constant, and commanding the piston speed based on the calculated value; speed for detecting the piston speed Detecting means, a speed commanded by the speed command means and a speed detected by the speed detecting means; Current command means for calculating a command value of the output current of the power supply by multiplying a difference between the output power and the second gain constant by a second gain constant, and commanding an output current of the power supply based on the calculated value. Current detection means for detecting, current control means for controlling the output current of the power supply so that the current detected by the current detection means matches the current commanded by the current command means, detected by the speed detection means Phase difference detection means for detecting a phase difference between the speed of the piston and the output current of the power supply commanded by the current command means, and a peak value of the position of the piston in the cylinder commanded by the position command means. A peak value difference detecting means for detecting a difference from a peak value of the position detected by the position detecting means, a position detected by the phase difference detecting means. Frequency adjusting means for adjusting the frequency of the sine function used in the position command means so as to eliminate the difference, and used in the speed command means so as to eliminate the peak value difference detected by the peak value difference detecting means. A driving device for a linear compressor, comprising: a gain adjusting means for adjusting at least one of a first gain constant and a second gain constant used in the current command means. 2. The phase difference detecting means detects a zero cross point of the speed of the piston detected by the speed detecting means and a zero cross point of an output current of the power supply commanded by the current command means. The driving device for a linear compressor according to claim 1, wherein the phase difference is detected based on a detection result. 3. The phase difference detecting means detects a peak point of the speed of the piston detected by the speed detecting means and a peak point of an output current of the power supply commanded by the current commanding means. The driving device for a linear compressor according to claim 1, wherein the phase difference is detected based on a detection result.