Online control system of linear refrigerator piston and linear refrigerator

Abstract

The present application relates to a kind of linear refrigeration machine piston's on-line control system, it includes: excitation signal generation unit, it generates initial magnetic field, and the initial magnetic field changes when linear refrigeration machine's compression piston movement, to generate excitation signal;Excitation signal processing unit is used to obtain the average value of the center position of compression piston in N movement cycles according to excitation signal;Piston offset calculation unit is used to obtain the offset amount of the current center position of compression piston relative to initial center position according to the average value of the center position;And, piston movement control unit is used to calculate the direct current voltage that makes the current center position of the compression piston return to initial center position according to offset amount, and the direct current voltage is applied on the coil winding of the linear refrigeration machine.The present application can obtain the piston position information of linear compressor in real time, and makes the compression piston return to initial position according to the offset amount, avoid generating piston cylinder collision.

Description

TECHNICAL FIELD

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

[0002] Linear compressor as a pressure wave generator is the core component of linear cryogenic refrigerator such as Stirling refrigerator and pulse tube refrigerator. Different from traditional crank-connecting rod type piston compressor, linear compressor adopts free piston structure. In the actual working process of the refrigerator, due to piston wear and other reasons, the piston of the linear compressor will be offset (i.e. the difference between the average value of piston displacement and the initial position of the piston, i.e. "piston offset"), and the piston offset is too large, which will cause the contact between the compressor moving assembly and the stopper and the cylinder collision, resulting in increased power consumption of the refrigerator or even structural fracture failure. Therefore, how to accurately control the piston offset of the linear compressor to avoid cylinder collision is an urgent problem to be solved. SUMMARY

[0003] The present application aims to provide an online control system of a linear refrigerator piston and a linear refrigerator, which can obtain the piston position information of the linear compressor in real time, and make the compression piston return to the initial position according to the offset, to avoid the occurrence of piston cylinder collision.

[0004] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0005] Provided is an online control system of a linear refrigerator piston, comprising:

[0006] An excitation signal generating unit 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 is connected to the excitation signal generating unit, and is used to obtain the average value of the center position of the compression piston in N movement cycles according to the excitation signal;

[0008] A piston offset calculation unit is connected to the excitation signal processing unit, and is used to obtain the offset of the current center position of the compression piston relative to the initial center position according to the average value of the center position;

[0009] And a piston movement control unit is connected to the piston offset calculation unit, and is used to calculate the direct current voltage that makes the current center position of the compression piston return to the initial center position according to the offset, and to apply the direct current voltage on the coil winding of the linear refrigerator.

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

[0011] a direct current voltage calculation unit for calculating a direct current voltage for returning the current center position of the compression piston to the initial center position according to the offset;

[0012] and a direct current current delivery unit connected to the direct current voltage calculation unit for delivering a direct current current corresponding to the direct current voltage to the coil winding of the linear compressor after modulating the current.

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

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

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

[0016] Preferably, the direct current voltage = (R x Ks x ΔX) / Ke, wherein Ke = B x L, indicating the thrust coefficient of the linear compressor; B, L, and R are the magnetic induction intensity at the position of the excitation signal generation unit, the coil circumference of the coil winding, and the resistance of the coil winding, respectively; 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 providing the return 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 motion cycles according to the excitation signal, including the following steps:

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

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

[0020] wherein U (t) is the real-time voltage generated at time t when the compression piston 7 moves in each motion cycle; V (t) is the moving speed at time t when the compression piston 7 moves in each motion cycle; N is the number of turns of the coil; B is the magnetic induction intensity at the position of the excitation signal generation unit 13; L is the coil circumference; f is the moving frequency of the compression piston 7; X (t) is the real-time displacement at time t when the compression piston 7 moves in each motion cycle;

[0021] Obtaining the current center position of the compression piston at the end of each movement cycle based on the real-time displacement of the compression piston at different moments during the movement of the compression piston in each movement cycle;

[0022] When the compression piston moves in N motion cycles, the current center position at the end of each motion cycle is averaged and used as the average center position of the compression piston in the N motion 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 provided at the cold end of the expander of the linear refrigerator and connected to the temperature signal processing unit, for acquiring the cold end temperature and transmitting the temperature 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 offset 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 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 to enable the compression piston to overcome the spring force and return to the initial position, and apply it to the coil winding to ensure 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 according to the cold end temperature to achieve rapid adjustment of the cooling 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 both ends of the connecting pipe 1 are connected to the interior 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 base 4 is connected to the housing 3 and the two are coaxially arranged. At the same time, after the cylinder base 4 and the housing 3 are connected, a closed cavity S is formed therein;

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

[0041] Furthermore, the mover assembly includes:

[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;

[0044] A compression piston 7 is connected to the spring 6 and the mover frame 5, and an end portion thereof 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 of the cylinder base 4 by welding or bonding;

[0046] and a mover magnetic member 9 (such as a 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 magnetic yoke 8, and mover magnetic part 9 are all coaxially arranged with the cylinder base 4, and the compression piston 7, inner magnetic yoke 8, and mover magnetic part 9 are arranged in sequence from the inside to the outside along the radial direction.

[0048] The stator assembly comprises:

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

[0050] an outer magnetic yoke 11 connected to the stator frame 10 and having winding slots;

[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 outside the mover magnetic component 9 .

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

[0054] When alternating current is supplied to 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, causing the working fluid gas to periodically enter and exit the expander 1 through the connecting pipe 2, and reach the expansion chamber at the cold end through the cold storage material such as the metal wire mesh filled in the cold storage tank of the expander 1, so as to perform periodic expansion and absorb heat, 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, which is disposed near 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, connected to the excitation signal generating unit 13, for receiving the excitation signal and obtaining, based on the excitation signal, an average value of the center position of the compression piston 7 within N motion cycles, that is, an average value of the current center positions of all compression pistons 7 at the end of each motion cycle within the N motion 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 connected to the excitation signal processing unit 14, configured to receive an average value of the center position of the compression piston 7 during N movement cycles, and obtain, based on the average value of the center position, an 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. Specifically, the offset ΔX = the average value of the center position of the compression piston during the N movement cycles - the initial center position of the compression piston. The initial center position of the compression piston 7 can be obtained based on 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 causes the current center position of the compression piston 7 to return to the initial center position at the end of N motion cycles based on the offset ΔX, and transmit 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 required to restore the current center position of the compression piston 7 to the initial center position at the end of N movement cycles based on the offset ΔX. Specifically, in this embodiment, the DC voltage calculation unit 161 obtains the DC voltage U based on U=(R×Ks×ΔX) / Ke. 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, where Ks is the elastic coefficient of the spring 6. If the spring 6 is to be restored to its initial position, it is necessary to energize the coil winding 12 to energize the spring. The spring 6 exerts an axial electromagnetic force F2 in the opposite direction to the elastic force F1 and of the same magnitude, and F2 = (Ke × U) / R, where Ke = B × L, which represents the thrust that the linear compressor can generate under a current of 1 A, i.e., the thrust coefficient. 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 turn of the coil winding 12, the DC voltage required to return the compression piston 7 to its initial position, and the resistance of the coil winding 12. B, L, and R are all known values. Since F1 = F2, Ks × ΔX = (Ke × U) / R, and finally U = (R × Ks × ΔX) / Ke.

[0062] The DC current transmission unit 162 is connected to the DC voltage calculation unit 161 and is configured 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] Example 2:

[0065] The only 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 other means. 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 within 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 during 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] According to the real-time displacement amount of the compression piston 7 at different time points during each movement cycle, the current center position of the compression piston 7 at the end of the movement cycle is obtained; for example, at time points t1, t3, t5...tn (n is an odd number) in the same cycle, the positive real-time displacement amounts of the compression piston 7 are x1, x3, x5...xn respectively, and at time points t2, t4, t6...t(n+1) (n+1 is an even number), the negative real-time displacement amounts of the compression piston 7 are x2, x4, x6...x(n+1) respectively, and the average value of all real-time displacement amounts, i.e. x1, x2, x3...x(n+1), is obtained, which is 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 point position, and the zero point position can be the initial center position of the compression piston 7.

[0070] The current center positions of the compression piston 7 at the end of each movement cycle during N movement cycles are averaged, and the average value is the center position average value of the compression piston 7 during N movement cycles.

[0071] Embodiment 3:

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

[0073] a temperature signal processing unit 18 connected to the piston movement control unit 16;

[0074] a temperature sensor 19 arranged at the cold end of the expander 1 and connected to the temperature signal processing unit 18 through a cable 20, which 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 connected to one or more of the piston offset calculation unit 15, the piston movement control unit 16, the temperature signal processing unit 18 and an external power supply, which is used to supply power to one or more of the piston offset calculation unit 15, the piston movement control unit 16, the temperature signal processing unit 18 and the external power supply;

[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 movement control unit 16, and the piston movement control unit 16 is used to control the alternating voltage applied to the coil winding 12 according to the voltage control signal, so as to adjust the displacement amplitude of the compression piston 7 and further adjust the refrigeration power of the refrigerator (the greater 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 also be adjusted according to the cold end temperature to achieve rapid adjustment of the cooling 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 principles of the present invention should be included in the scope of protection 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, for obtaining an offset of the current center position of the compression piston relative to the initial center position based on 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 based on 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, configured to calculate, based on the offset, a DC voltage required to return the current center position of the compression piston to an 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 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, respectively; 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 providing the 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 moves in each movement cycle; (t) is the speed of the compression piston at time t during 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 movement frequency of the compression piston; X (t) is the real-time displacement of the compression piston at time t when it moves in each motion cycle; Obtaining the current center position of the compression piston at the end of each movement cycle based on the real-time displacement of the compression piston at different moments during the movement of the compression piston in each movement cycle; When the compression piston moves in N motion cycles, the current center position at the end of each motion cycle is averaged and used as the average center position of the compression piston in the N motion cycles.

8. The online control system according to claim 1, characterized in that: The online control system further comprises: a temperature signal processing unit connected to the piston motion control unit; and a temperature sensor, which is provided at the cold end of the expander of the linear refrigerator and connected to the temperature signal processing unit, for acquiring the cold end temperature and transmitting the temperature 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 further comprises: A power connection port is connected to one or more of the piston offset 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 online control system comprises the one described in any one of claims 1 to 9.

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