Linear refrigerator piston online control system and linear refrigerator

Abstract

The invention relates to an on-line control system for a piston of a linear refrigerator, and the system comprises an excitation signal generation unit which generates an initial magnetic field, and the initial magnetic field changes when a compression piston of the linear refrigerator moves, so as to generate an excitation signal; the excitation signal processing unit is used for obtaining the average value of the center positions of the compression piston in the N motion periods according to the excitation signals; the piston offset calculation unit is used for obtaining the offset of the current center position of the compression piston relative to the initial center position according to the center position average value; and the piston motion control unit is used for calculating direct-current voltage enabling the current center position of the compression piston to return to the initial center position according to the offset, and applying the direct-current voltage to a coil winding of the linear refrigerator. According to the method, the piston position information of the linear compressor can be obtained in real time, the compression piston is reset to the initial position according to the offset, and the piston is prevented from colliding with the cylinder.

Description

Technical Field

[0001] The invention relates to the technical field of refrigerators, and in particular to an online control system of a linear refrigerator piston and a linear refrigerator. Background Art

[0002] As a pressure wave generator, the linear compressor is the core component of linear low-temperature refrigerators such as Stirling refrigerators and pulse tube refrigerators. Unlike traditional crank-connecting rod piston compressors, linear compressors use a free piston structure. During the actual operation of the refrigerator, due to piston wear and other reasons, the piston of the linear compressor will be offset (that is, the difference between the average piston displacement and the initial piston position, also known as "piston offset"). If the piston offset is too large, the compressor rotor assembly will contact the limiter and hit the cylinder, causing the refrigerator power consumption to increase or even structural fracture failure. Therefore, how to accurately control the piston offset of the linear compressor to avoid hitting the cylinder is an urgent problem to be solved. Summary of the invention

[0003] The object of the present invention is to provide an online control system for a linear refrigerator piston and a linear refrigerator, which can obtain the piston position information of a linear compressor in real time and restore the compression piston to its initial position according to the offset to avoid the piston hitting the cylinder.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] An online control system for a linear refrigerator piston is provided, comprising:

[0006] An excitation signal generating unit, which generates an initial magnetic field, and the initial magnetic field changes when the compression piston of the linear refrigerator moves to generate an excitation signal;

[0007] an excitation signal processing unit, connected to the excitation signal generating unit, and configured to obtain an average value of the center position of the compression piston within N movement cycles according to the excitation signal;

[0008] a piston offset calculation unit connected to the excitation signal processing unit and configured to obtain an offset of a current center position of the compression piston relative to an initial center position according to the center position average value;

[0009] And, a piston motion control unit, which is connected to the piston offset calculation unit, is used to calculate a DC voltage that restores the current center position of the compression piston to the initial center position according to the offset, and apply the DC voltage to the coil winding of the linear refrigerator.

[0010] Preferably, the piston motion control unit comprises:

[0011] a DC voltage calculation unit, used for calculating, according to the offset, a DC voltage required to restore the current center position of the compression piston to the initial center position;

[0012] and a DC current transmission unit connected to the DC voltage calculation unit, for transmitting a DC current corresponding to the DC voltage to the coil winding of the linear refrigerator after modulating the current.

[0013] Preferably, the excitation signal generating unit is a wound coil.

[0014] Preferably, the excitation signal is a voltage signal.

[0015] Preferably, the offset=average value of the center position of the compression piston in N movement cycles−initial center position of the compression piston.

[0016] Preferably, the DC voltage = (R×Ks×ΔX) / Ke, wherein Ke = B×L, representing the thrust coefficient of the linear compressor; B, L, and R are respectively the magnetic induction intensity at the location of the excitation signal generating unit, the circumference of a single turn of the coil winding, and the resistance of the coil winding; ΔX is the offset of the current center position of the compression piston relative to the initial center position; and Ks is the elastic coefficient of the spring that provides restoring force for the compression piston.

[0017] Preferably, the excitation signal processing unit obtains the average value of the center position of the compression piston in N movement cycles according to the excitation signal, comprising the following steps:

[0018] The excitation signal processing unit obtains the real-time displacement of the compression piston in each movement cycle according to formula (1):

[0019] U (t) =NBLV (t) =2πfNBLX (t) (1)

[0020] Among them, U (t) V is the real-time voltage generated at time t when the compression piston 7 moves in each movement cycle; (t) is the moving speed of the compression piston 7 at time t when it moves in each movement cycle; N is the number of turns of the coil; B is the magnetic induction intensity at the location of the excitation signal generating unit 13; L is the circumference of a single turn of the coil; f is the moving frequency of the compression piston 7; X (t) is the real-time displacement of the compression piston 7 at time t when it moves in each movement cycle;

[0021] According to the real-time displacement of the compression piston at different moments in each movement cycle, the current center position of the compression piston at the end of the movement cycle is obtained;

[0022] When the compression piston moves in N movement cycles, the current center position at the end of each movement cycle is averaged and used as the average center position of the compression piston in the N movement cycles.

[0023] Preferably, the online control system further comprises:

[0024] A temperature signal processing unit connected to the piston motion control unit;

[0025] and a temperature sensor, which is disposed at the cold end of the expander of the linear refrigerator and connected to the temperature signal processing unit, and is used to obtain the cold end temperature and transmit it to the temperature signal processing unit;

[0026] The temperature signal processing unit generates a corresponding voltage control signal according to the cold end temperature, and the piston motion control unit controls the AC voltage applied to the coil winding of the linear refrigerator according to the voltage control signal.

[0027] Preferably, the online control system further comprises:

[0028] A power connection port is connected to one or more of the piston displacement calculation unit, the piston motion control unit, the temperature signal processing unit and an external power supply.

[0029] On the other hand, a linear refrigerator is also provided, which includes the above-mentioned online control system.

[0030] In summary, the present invention has the following beneficial effects compared with the prior art:

[0031] The present invention can obtain the piston position information of the linear compressor in real time, and generate a DC voltage based on the offset so that the compression piston overcomes the spring force to return to the initial position, and apply it to the coil winding so that the piston position is always within a safe displacement range to avoid the piston hitting the cylinder. At the same time, the AC voltage of the coil winding can be adjusted by the cold end temperature to achieve rapid adjustment of the refrigeration power. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a structural schematic diagram of the online control system of the linear refrigerator piston in the present invention. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0034] Example 1

[0035] like Figure 1 As shown, this embodiment provides an online control system for a linear refrigerator piston, wherein the linear refrigerator includes one or more of a Stirling refrigerator and a pulse tube refrigerator. On this basis, the linear refrigerator includes:

[0036] A linear compressor, an expander 1 and a connecting pipe 2, wherein two ends of the connecting pipe 1 are connected to the inside of the linear compressor and the expander 1 respectively.

[0037] Specifically, the linear compressor includes:

[0038] The outer shell 3 is a cylindrical structure as a whole;

[0039] The cylinder seat 4 is connected to the housing 3 and the two are coaxially arranged. At the same time, after the cylinder seat 4 and the housing 3 are connected, a closed cavity S is formed inside them;

[0040] The mover assembly and the stator assembly are both arranged in the cavity S and are coaxially arranged with the cylinder seat 9 .

[0041] Furthermore, the mover assembly comprises:

[0042] Movable skeleton 5;

[0043] A spring 6 connected to the mover frame 5; in this embodiment, the spring 6 is a mechanical spring, including a leaf spring or a column spring, etc.;

[0044] A compression piston 7, which is connected to the spring 6 and the mover frame 5, and the end of which extends into the cylinder seat 4 and is in clearance fit with the cylinder seat 4;

[0045] An inner magnetic yoke 8 connected to the outer wall surface of the cylinder base 4 by welding or bonding;

[0046] and a mover magnetic member 9 (such as magnetic steel, etc.), which is connected to the mover frame 5 by welding or bonding;

[0047] In this embodiment, the mover frame 5, spring 6, compression piston 7, inner yoke 8, and mover magnetic part 9 are all coaxially arranged with the cylinder base 4, and the compression piston 7, inner yoke 8, and mover magnetic part 9 are arranged in sequence from inside to outside along the radial direction.

[0048] The stator assembly comprises:

[0049] The stator frame 10 is sleeved on the periphery of the mover assembly and is coaxially connected to the spring 6 through fasteners and the like, and is connected to the inner wall surface of the cylinder seat 4 by bonding, welding, etc.;

[0050] An outer yoke 11, which is connected to the stator frame 5 and has winding grooves;

[0051] and a coil winding 12 mounted in the winding slot;

[0052] The stator frame 10 , the outer yoke 11 , and the coil winding 12 are all coaxially arranged with the cylinder base 4 , and the stator frame 10 , the outer yoke 11 , and the coil winding 12 are all located at the periphery of the mover magnetic component 9 .

[0053] The working principle of the above linear refrigerator is as follows:

[0054] When alternating current is passed through the coil winding 12, the compression piston 7 of the stator assembly is driven to perform reciprocating linear motion through the magnetic field effect to generate periodic pressure waves, so that the working fluid gas periodically enters and exits the expander 1 through the connecting pipe 2, and reaches the expansion chamber at the cold end through the cold storage material such as the metal wire mesh filled in the cold storage device of the expander 1, so as to perform periodic expansion and heat absorption, reduce the temperature and generate cooling capacity.

[0055] On this basis, the online control system of the linear refrigerator piston includes:

[0056] An excitation signal generating unit 13 is disposed close to the movable magnetic member 9 and generates an initial magnetic field. When the compression piston 7 and the movable magnetic member 9 move linearly in sync, the initial magnetic field changes to generate an excitation signal, and the excitation signal generating unit 13 outputs the excitation signal;

[0057] an excitation signal processing unit 14, which is connected to the excitation signal generating unit 13, and is used to receive the excitation signal, and obtain the average value of the center position of the compression piston 7 in N movement cycles according to the excitation signal, that is, the average value of the current center positions of all compression pistons 7 at the end of each movement cycle in the N movement cycles, wherein N is a positive integer greater than or equal to 2; the center position is the position of the geometric center of the compression piston 7;

[0058] A piston offset calculation unit 15, which is connected to the excitation signal processing unit 14, is used to receive the average value of the center position of the compression piston 7 in N movement cycles, and obtain the offset ΔX of the current center position of the compression piston 7 relative to the initial center position of the compression piston 7 at the end of the N movement cycles according to the average value of the center position. Specifically, the offset ΔX=the average value of the center position of the compression piston in N movement cycles-the initial center position of the compression piston. The initial center position of the compression piston 7 can be obtained according to the parameters of the compression piston 7 when it leaves the factory;

[0059] And, a piston motion control unit 16, which is connected to the piston offset calculation unit 15, is used to calculate the DC voltage that restores the current center position of the compression piston 7 to the initial center position at the end of N motion cycles based on the offset ΔX, and transmits a DC current corresponding to the DC voltage to the coil winding 12 to apply the DC voltage to the coil winding 12.

[0060] Specifically, the piston motion control unit 16 includes:

[0061] The DC voltage calculation unit 161 is used to calculate the DC voltage that makes the current center position of the compression piston 7 return to the initial center position at the end of N movement cycles according to the offset ΔX; specifically, in this embodiment, the DC voltage calculation unit 161 obtains the DC voltage U according to U=(R×Ks×ΔX) / Ke, and the specific derivation process is as follows: if the offset of the compression piston 7 is ΔX, the elastic force F1 generated by the deformation of the spring 6 is F1=Ks×ΔX, wherein Ks is the elastic coefficient of the spring 6. If the spring 6 is to be restored to the initial position, it is necessary to energize the coil winding 12 to energize the elastic coefficient of the spring 6. The spring 6 exerts an axial electromagnetic force F2 which is opposite to the elastic force F1 and of the same magnitude, and F2=(Ke×U) / R, wherein Ke=B×L, which is used to represent the thrust that the linear compressor can generate under a current of 1A, i.e., the thrust coefficient, i.e.; B, L, U, and R are respectively the magnetic induction intensity at the location of the excitation signal generating unit 13, the circumference of a single coil of the coil winding 12, the DC voltage that makes the compression piston 7 return to the initial position, and the resistance of the coil winding 12, and B, L, and R are all known values. Since F1=F2, Ks×ΔX=(Ke×U) / R, and finally U=(R×Ks×ΔX) / Ke is obtained;

[0062] The DC current transmission unit 162 is connected to the DC voltage calculation unit 161 and is used to transmit a DC current corresponding to the DC voltage U to the coil winding 12 through the power supply cable 17 after modulating the current.

[0063] Therefore, the online control system in this embodiment can obtain the piston position information (i.e., offset) of the linear compressor in real time, and generate a DC voltage based on the offset to enable the compression piston to overcome the spring force and return to the initial position, and apply it to the coil winding so that the piston position is always within the safe displacement range to avoid the piston hitting the cylinder.

[0064] Embodiment 2:

[0065] The difference between this embodiment and embodiment 1 is that the excitation signal generating unit 13 is a coil wound by enameled wire, and the coil is connected to the axial end surface of the outer magnetic yoke 11 by bonding or the like. Correspondingly, the excitation signal is a voltage signal. On this basis, the excitation signal processing unit 14 obtains the average value of the center position of the compression piston 7 in N movement cycles according to the excitation signal, including the following steps:

[0066] The excitation signal processing unit 14 obtains the real-time displacement of the compression piston 7 in each movement cycle according to formula (1):

[0067] U (t) =NBLV (t) =2πfNBLX (t) (1)

[0068] Among them, U (t) V is the real-time voltage generated at time t when the compression piston 7 moves in each movement cycle; (t) is the moving speed of the compression piston 7 at time t when it moves in each movement cycle; N is the number of turns of the coil; B is the magnetic induction intensity at the location of the excitation signal generating unit 13; L is the circumference of a single turn of the coil; f is the moving frequency of the compression piston 7; X (t) is the real-time displacement of the compression piston 7 at time t when it moves in each movement cycle;

[0069] The current center position of the compression piston 7 at the end of the movement cycle is obtained according to the real-time displacement at different moments when the compression piston 7 moves in each movement cycle; for example, at moments t1, t3, t5...tn (n is an odd number) in the same cycle, the positive real-time displacements of the compression spring 7 are x1, x3, x5...xn respectively, and at moments t2, t4, t6...t(n+1) (n+1 is an even number), the negative real-time displacements of the compression spring 7 are x2, x4, x6...x(n+1) respectively. All real-time displacements, i.e., x1, x2, x3...x(n+1), are averaged to obtain the current center position of the compression piston 7 at the end of the movement cycle, wherein the "positive displacement" and "negative displacement" refer to the displacement of the compression piston 7 relative to the zero position, and the zero position may be the initial center position of the compression piston 7;

[0070] When the compression piston 7 moves in N movement cycles, the current center position at the end of each movement cycle is averaged, and the average value is the average value of the center position of the compression piston 7 in the N movement cycles.

[0071] Embodiment 3:

[0072] The difference between this embodiment and embodiment 1 or 2 is that the online control system further includes:

[0073] A temperature signal processing unit 18 connected to the piston motion control unit 16;

[0074] A temperature sensor 19, which is disposed at the cold end of the expander 1 and connected to the temperature signal processing unit 18 via a cable 20, and is used to obtain the cold end temperature in real time and transmit it to the temperature signal processing unit 18;

[0075] and a power connection port 21, which is connected to one or more of the piston offset calculation unit 15, the piston motion control unit 16, the temperature signal processing unit 18 and an external power source, and is used to supply power to one or more of the piston offset calculation unit 15, the piston motion control unit 16, and the temperature signal processing unit 18;

[0076] The temperature signal processing unit 18 is used to process the cold end temperature to generate a corresponding voltage control signal and send it to the piston motion control unit 16. The piston motion control unit 16 is used to control the AC voltage applied to the coil winding 12 according to the voltage control signal, thereby adjusting the displacement amplitude of the compression piston 7, and further realizing the adjustment of the refrigeration power of the refrigerator (the larger the displacement amplitude of the compression piston 7, the greater the refrigeration power of the refrigerator, and vice versa).

[0077] Embodiment 4:

[0078] This embodiment provides a linear refrigerator, which includes the online control system described in any one of Embodiments 1-3.

[0079] In summary, the present invention has a simple structural design and is easy to implement. On the one hand, it can obtain the piston position information (i.e., offset) of the linear compressor in real time, and generate a DC voltage based on the offset to enable the compression piston to overcome the spring force and return to the initial position, and apply it to the coil winding so that the piston position is always within a safe displacement range to avoid the piston hitting the cylinder. On the other hand, the AC voltage of the coil winding can be adjusted by the cold end temperature to achieve rapid adjustment of the refrigeration power.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An online control system for a linear refrigerator piston, characterized in that: include: An excitation signal generating unit, which generates an initial magnetic field, and the initial magnetic field changes when the compression piston of the linear refrigerator moves to generate an excitation signal; an excitation signal processing unit, connected to the excitation signal generating unit, and configured to obtain an average value of the center position of the compression piston within N movement cycles according to the excitation signal; a piston offset calculation unit connected to the excitation signal processing unit and configured to obtain an offset of a current center position of the compression piston relative to an initial center position according to the center position average value; And, a piston motion control unit, which is connected to the piston offset calculation unit, is used to calculate a DC voltage that restores the current center position of the compression piston to the initial center position according to the offset, and apply the DC voltage to the coil winding of the linear refrigerator.

2. The online control system according to claim 1, characterized in that: The piston motion control unit comprises: a DC voltage calculation unit, used for calculating, according to the offset, a DC voltage required to restore the current center position of the compression piston to the initial center position; and a DC current transmission unit connected to the DC voltage calculation unit, for transmitting a DC current corresponding to the DC voltage to the coil winding of the linear refrigerator after modulating the current.

3. The online control system according to claim 1, characterized in that: The excitation signal generating unit is a wound coil.

4. The online control system according to claim 1, characterized in that: The excitation signal is a voltage signal.

5. The online control system according to claim 1, characterized in that: The offset amount=the average value of the center position of the compression piston in N movement cycles−the initial center position of the compression piston.

6. The online control system according to claim 1, characterized in that: The DC voltage = (R×Ks×ΔX) / Ke, where Ke = B×L, representing the thrust coefficient of the linear compressor; B, L, and R are respectively the magnetic induction intensity at the location of the excitation signal generating unit, the circumference of a single turn of the coil winding, and the resistance of the coil winding; ΔX is the offset of the current center position of the compression piston relative to the initial center position; and Ks is the elastic coefficient of the spring that provides a restoring force for the compression piston.

7. The online control system according to claim 1, characterized in that: The excitation signal processing unit obtains the average value of the center position of the compression piston in N movement cycles according to the excitation signal, including the following steps: The excitation signal processing unit obtains the real-time displacement of the compression piston in each movement cycle according to formula (1): And (t) =NBLV (t) =2πfNBLX (t) (1) Among them, U (t) V is the real-time voltage generated at time t when the compression piston 7 moves in each movement cycle; (t) is the moving speed of the compression piston 7 at time t when it moves in each movement cycle; N is the number of turns of the coil; B is the magnetic induction intensity at the location of the excitation signal generating unit 13; L is the circumference of a single turn of the coil; f is the moving frequency of the compression piston 7; X (t) is the real-time displacement of the compression piston 7 at time t when it moves in each movement cycle; According to the real-time displacement of the compression piston at different moments in each movement cycle, the current center position of the compression piston at the end of the movement cycle is obtained; When the compression piston moves in N movement cycles, the current center position at the end of each movement cycle is averaged and used as the average center position of the compression piston in the N movement cycles.

8. The online control system according to claim 1, characterized in that: The online control system also includes: A temperature signal processing unit connected to the piston motion control unit; and a temperature sensor, which is disposed at the cold end of the expander of the linear refrigerator and connected to the temperature signal processing unit, and is used to obtain the cold end temperature and transmit it to the temperature signal processing unit; The temperature signal processing unit generates a corresponding voltage control signal according to the cold end temperature, and the piston motion control unit controls the AC voltage applied to the coil winding of the linear refrigerator according to the voltage control signal.

9. The online control system according to claim 8, characterized in that: The online control system also includes: A power connection port is connected to one or more of the piston displacement calculation unit, the piston motion control unit, the temperature signal processing unit and an external power supply.

10. A linear refrigerator, characterized in that: The invention comprises the online control system as described in any one of claims 1 to 9.

Images