CN112413919B

CN112413919B - Low-temperature refrigerator

Info

Publication number: CN112413919B
Application number: CN202011236257.9A
Authority: CN
Inventors: 王哲; 胡子珩; 章彬; 汪桢子; 汪伟; 李奥; 李艳锋
Original assignee: Shenzhen Power Supply Bureau Co Ltd
Current assignee: Shenzhen Power Supply Bureau Co Ltd
Priority date: 2020-12-21
Filing date: 2020-12-21
Publication date: 2022-06-07
Anticipated expiration: 2040-12-21
Also published as: CN112413919A

Abstract

The invention discloses a low-temperature refrigerator which comprises a cylinder (9) and a cover body (2) connected to the cylinder (9), wherein a pushing piston (10) is installed in the cylinder (9), a connecting rod (4) is installed in the cover body (2) and connected with the pushing piston (10), the connecting rod (4) drives the pushing piston (10) to reciprocate up and down, the speed of the connecting rod (4) moving from a top dead center to a bottom dead center is the same as the speed of the connecting rod (4) moving from the bottom dead center to the top dead center, and the time from the top dead center or the bottom dead center to a balance position is different from the time from the balance position to the bottom dead center or the top dead center. The low/high pressure valve of the invention shortens the time of opening in advance when the pushing piston reaches the lower/upper dead point, so that the gas capable of generating refrigeration can undergo more sufficient expansion and compression processes in the cylinder, the cold cavity and the pushing piston inside, thereby improving the refrigeration capacity and the refrigeration efficiency.

Description

Low-temperature refrigerator

Technical Field

The invention relates to the technical field of low-temperature refrigerators, in particular to a low-temperature refrigerator.

Background

As a cryogenic refrigerator having a cryogenic temperature, a refrigerator having a moving piston, such as a Gifford Mcmahon (GM) cycle refrigerator or a stirling cycle refrigerator, is generally known.

In the GM refrigerator, a push piston is reciprocable in a cylinder, and a low temperature end in the cylinder forms an expansion space. In addition, a large amount of heat exchange materials are filled in the pushing piston, the gas is cooled by the heat exchange materials and is expanded and refrigerated at the low-temperature end, and the expansion space is communicated with the room-temperature space of the pushing piston by the gas flow.

The reciprocating motion of the pushing piston is converted into axial linear motion by a crank-connecting rod mechanism at the room temperature end. In the traditional GM refrigerator structure, a connecting rod is connected with a piston and driven by a driving component to do up-and-down reciprocating sinusoidal motion. In order to prevent the connecting rod from deflecting, the upper end and the lower end of the connecting rod are provided with guide mechanisms. In the cryogenic refrigerator, the switching of high-pressure gas and low-pressure gas is closely linked with the movement of the pushing piston, and the appropriate switching of the high-pressure gas and the low-pressure gas is set according to the movement state of the piston, so that the refrigerating efficiency of the refrigerator can be greatly improved.

When a valve of a traditional refrigerator is opened, high-pressure refrigerating gas is filled into a cylinder or gas is exhausted from the cylinder and returns to a compressor through the valve, a time process is needed, so that the valve is required to be opened in advance before a piston is pushed to move to a bottom dead center or a top dead center, the pressure in the cylinder reaches a set high pressure or low pressure, and the refrigerating capacity of the refrigerator is lost when the valve is lifted and opened.

Disclosure of Invention

The technical problem to be solved by the present invention is to provide a cryogenic refrigerator to effectively improve the refrigerating capacity.

In order to solve the technical problem, the invention provides a low-temperature refrigerator, which comprises a cylinder and a cover body connected to the cylinder, wherein a pushing piston is arranged in the cylinder, a connecting rod is arranged in the cover body and is connected with the pushing piston, the connecting rod drives the pushing piston to reciprocate up and down, the speed of the connecting rod moving from a top dead center to a bottom dead center is the same as the speed of the connecting rod moving from the bottom dead center to the top dead center at the same displacement position, and the time from the top dead center or the bottom dead center to a balance position is different from the time from the balance position to the bottom dead center or the top dead center.

Further, the time elapsed for the link to move from the top dead center to the equilibrium position is longer than the time elapsed for the link to move from the equilibrium position to the bottom dead center.

Further, the time elapsed for the link to move from the bottom dead center to the equilibrium position is longer than the time elapsed for the link to move from the equilibrium position to the top dead center.

Further, the connecting rod comprises a sliding groove, and the shape of the sliding groove is 180 degrees symmetrical relative to the central position of the connecting rod.

Furthermore, the mechanism for driving the pushing piston to reciprocate up and down further comprises a cam assembly and a driving sleeve, wherein the driving sleeve is annular and is placed in the chute, and the outer diameter of the driving sleeve is tangent to the upper edge and the lower edge of the chute.

Further, the cam assembly comprises a cam and a cam handle, the cam is installed on a motor spindle, the cam handle is installed on the eccentric position of the cam, and the size of an inner hole is matched with the inner diameter of the driving sleeve.

The embodiment of the invention has the beneficial effects that: the time of the low/high pressure valve opening in advance when the pushing piston reaches the lower/upper dead point is shortened, so that the gas capable of generating refrigeration can undergo more sufficient expansion and compression processes in the cylinder, the cold cavity and the pushing piston inside, and the refrigeration capacity and the refrigeration efficiency are improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a cryocooler according to an embodiment of the present invention.

Fig. 2 is a schematic diagram of a driving structure of a cryocooler according to an embodiment of the present invention.

Fig. 3 is a schematic view of a driving structure of a conventional cryocooler.

Fig. 4 is a schematic diagram of the movement of the drive mechanism of the embodiment of the present invention.

FIG. 5 is a graph showing the relationship between the pressure (P) and the volume (V) in the cold chamber of the refrigerator, in which (1) represents a P-V diagram corresponding to a conventional structure, and (2) is a P-V diagram of an embodiment of the present invention.

Fig. 6 is a diagram illustrating a movement process of a link of a cryocooler according to an embodiment of the present invention.

Fig. 7 is a graph showing the change of the position of the moving piston in the direction Z1-Z2 according to the rotation angle of the cryocooler according to the embodiment of the present invention.

Detailed Description

The following description of the embodiments refers to the accompanying drawings, which are included to illustrate specific embodiments in which the invention may be practiced. The terms of direction and position of the present invention, such as "up", "down", "front", "back", "left", "right", "inside", "outside", "top", "bottom", "side", etc., refer to the direction and position of the attached drawings. Accordingly, the use of directional and positional terms is intended to illustrate and understand the present invention and is not intended to limit the scope of the present invention.

A low-temperature refrigerating machine comprises a cylinder 9 and a cover body 2 connected to the cylinder 9, a pushing piston 10 is installed in the cylinder 9, a connecting rod 4 is installed in the cover body 2 and connected with the pushing piston 10, the connecting rod 4 drives the pushing piston 10 to reciprocate up and down, the speed of the connecting rod 4 moving from a top dead center to a bottom dead center is the same as the speed of the connecting rod 4 moving from the bottom dead center to the top dead center, and the time of the connecting rod 4 moving from the top dead center or the bottom dead center to a balance position is different from the time of the connecting rod 4 moving from the balance position to the bottom dead center or the top dead center.

Specifically, as shown in fig. 1, a pushing piston 10 is accommodated in a cylinder 9 and is movable in the vertical direction. The upper end of pushing piston 10 is coaxially connected to connecting rod 4. When the driving sleeve 3 moves along the circular track 6 around the central axis O, the driving sleeve drives the connecting rod 4 to reciprocate up and down (Z1-Z2 direction in fig. 1).

The cylinder 9 is installed with the cover body 2, the connecting rod 4 extends into the cover body 2, the radial direction (vertical to the direction Z1-Z2) is limited by the guide sleeves 5a and 5b, the connecting rod cannot move, and only the connecting rod can move along the directions Z1-Z2.

The compressor 1 generates a high-pressure refrigerant gas by compressing a refrigerant gas (helium gas). The high-pressure refrigerant gas PH is supplied to the high-pressure valve 12a through the passage 1a, and is supplied into the cylinder 9 through the gas passage 7. The airflow enters the hot cavity 8, enters the pushing piston 10 through the channel 10a, exchanges heat with the heat exchange material 10c, enters the cold cavity 11 through the channel 10b, the volume of the cold cavity 11 is increased, and the gas expands for refrigeration.

On the other hand, when the high-pressure valve 12a is closed and the low-pressure valve 12b is opened, the refrigerant gas is returned to the compressor 1 through the reverse path to the above-described path at the time of supply, and is changed to the low-pressure gas flow PL.

Referring to fig. 2, the mechanism for driving the pushing piston 10 to reciprocate up and down includes a cam assembly 14, a connecting rod 4 and a driving sleeve 3. The upper rod 43 and the lower rod 44 of the connecting rod 4 are coaxially connected to the outer frames of the middle sliding

chutes

41 and 42. The driving sleeve 3 is circular and is placed in the

sliding grooves

41 and 42, and the outer diameter of the driving sleeve is just tangent to the

upper edges

41a, 41b, 42a and 42b of the

sliding grooves

41 and 42.

Cam assembly 14 includes a cam 14a and a cam shaft 14b, cam 14a is mounted on a motor spindle (not shown), and when the motor is activated, cam 14a will rotate along central axis O. The cam shank 14b is arranged on the eccentric position of the cam 14a, the size of an inner hole is equivalent to the inner diameter of the driving sleeve 3, and the cam shank 14b penetrates through the inner hole of the driving sleeve 3 during installation. When the cam 14a rotates, the eccentric cam shaft 14b will move along the track 6 in fig. 1 in a circular manner, and will drive the driving sleeve 3 to move along the same track.

When the driving sleeve 3 rotates along the central axis O at a constant speed, the projection of the trajectory 6 in the direction Z1-Z2 shows a vertical reciprocating motion, which is a standard sinusoidal motion, and fig. 4H shows the relative position of the pushing piston 10 corresponding to the vertical reciprocating motion.

As shown in fig. 3, the frame of the inner chute 41 'of the conventional connecting rod 4 is a standard rectangle, and the upper/lower edges 41 a', 41b 'are axially perpendicular to Z1-Z2, so that when the driving sleeve 3 is tangent to the side line of the chute 41', the tangent direction is always parallel to Z1-Z2, and thus the connecting rod 4 also exhibits a sinusoidal motion mode under the driving of the driving sleeve 3.

Because the high-pressure valve 12a is completely opened, the gas in the cylinder 9 is completely changed from low pressure to high pressure, and a certain time is needed to complete the inflation process; the low pressure valve 12b is fully opened, the gas in the cylinder 9 is completely changed from high pressure to low pressure, and a certain time is required for completing the charging and discharging process.

Therefore, in the design process of the embodiment of the invention: when the cold chamber 11 is at its maximum volume (displacement piston 10 at top dead center, corresponding to positions b and c in fig. 5) and changes towards its minimum volume (displacement piston 10 towards bottom dead center, corresponding to positions a and d in fig. 5), the cold chamber volume V and the gas pressure P change along the c → d curve, and before the displacement piston 10 reaches bottom dead center, the valve 12a must be opened (at point f) to advance the high-pressure charging of the cylinder, so that the change of the cold chamber 11 volume V and the gas pressure P can only change along the f → a curve, to the minimum volume and the maximum pressure, but not along d → a curve. The advanced opening time t1 corresponding to f → a is θ 1/ω, and θ 1 is the angle that the cam 14a rotates when the height of the link 4 (cold chamber 11) corresponding to f moves to the bottom dead center (the volume of the cold chamber 11 is minimum) in fig. 5(1), i.e., the corresponding angle θ 1 on the right side in fig. 4.

Similarly, when the pushing piston 10 moves from the bottom dead center (point a in fig. 5 (1)) to the top dead center (point b in fig. 5 (1)), the high pressure valve 12a closes and the low pressure valve 12b opens earlier, and the opening point is point e, and the variation relationship between the volume V of the cold chamber 11 and the gas pressure P can only vary along the e → c curve, to the maximum volume and the minimum pressure, but not along the b → c curve. The advanced opening time t2 corresponding to e → c is θ 2, ω, θ 2 is the height of the link 4 (cold chamber 11) corresponding to point e in fig. 5(1), and when the height moves to the top dead center (the volume of the cold chamber 11 is maximum), the angle that the cam 14a rotates, i.e. the corresponding angle θ 2 on the left side shown in fig. 4, is shown in fig. 4.

The area enclosed by the volume V of the cold chamber 11 and the change of the internal gas pressure P in one cycle represents the refrigerating capacity of the refrigerator, the conventional refrigerator must refrigerate according to the quadrilateral area enclosed by the point a → e → c → f → a shown in fig. 5, and two triangular areas, namely the area afd and the area ebc, are refrigerating capacity losses of the refrigerator relative to the abcd rectangular area.

In the embodiment of the present invention, as shown in fig. 2, the

sliding slots

41 and 42 in the connecting rod 4 are not rectangular, the upper and

lower side lines

41a, 41b, 42a and 42b are not perpendicular to the axial direction of Z1 — Z2, and the 4 side lines are parallel to each other, and have 180 ° symmetry with respect to the center O of the connecting rod 4.

The advantage of the embodiment of the invention according to fig. 5(2), 6 and 7 is that the sliding piston 10 moves in the same displacement position from the top dead center to the bottom dead center in the same manner as from the bottom dead center to the top dead center. The time for moving the push piston 10 from the top dead center to the bottom dead center is equal to the time for moving from the bottom dead center to the top dead center, as shown in fig. 7, the dotted line is the conventional movement trace, the solid line is the movement trace of the push piston 10 of the present invention, the change from the rotation angle of the cam 14a is from 0 ° to 180 °, and the change from 180 ° to 360 ° for two half cycles is that the push piston 10 is changed from the top dead center to the bottom dead center and then moved to the top dead center.

However, as shown in fig. 7, in the conventional structure in which the pushing piston 10 moves from the top dead center to the equilibrium position and the equilibrium position to the bottom dead center, the cams 14a each undergo a rotation angle of 90 °, which indicates that the two process times are the same; moving from top dead center to the equilibrium position and vice versa, the cams 14a also experience 90 ° of rotation, as do the times experienced by both processes.

In the embodiment of the present invention, as shown in fig. 7, the cam 14a experiences a rotation angle greater than 90 ° when moving from the top dead center to the equilibrium position, and a rotation angle less than 90 ° when moving from the equilibrium position to the bottom dead center, which means that the time elapsed in the former stage is longer than the time elapsed in the latter stage.

Moving from bottom dead center to equilibrium position, cam 14a experiences an angle of rotation greater than 90 ° and less than 90 ° from equilibrium position to top dead center, which is apparent from the fact that the time elapsed in the preceding phase is also greater than the time elapsed in the following phase.

As further described with reference to (1) to (6) of fig. 6, when the link 4 moves close to the bottom dead center, the high-pressure valve 12a is opened in advance by an advance angle θ 1, and continues to move downward as shown in (1) and is positioned as shown in (2); after the lowest point is reached, the pushing piston 10 starts to move upwards, and due to the structural characteristics of the present invention, as can be seen from fig. 2 to fig. 3, the pushing piston 10 hardly moves upwards, the volume of the cold chamber 11 is still at a minimum, and the rotation angle corresponding to the residence time is α 1, which satisfies the following formula: θ 1+ α 1 ═ θ 1', corresponding to the angles in fig. 7. Thus, θ 1< θ 1', and the pushing piston 10 does not rise in the time corresponding to α 1. This also means that in fig. 5(2), the position of the high pressure valve 12a is changed from point f to point f ', and the piston 10 is pushed to the bottom dead center corresponding to point a': the elapsed time f ' → a ' corresponds to the rotation angle θ 1, and the elapsed time a ' → a corresponds to the rotation angle α 1.

Similarly, when the pushing piston 10 moves to approach the top dead center, the low pressure valve 12b is opened in advance, the advance angle is θ 2, as shown in (4), the pushing piston continues to move upward, and the position is as shown in (5), when the pushing piston 10 starts to move downward after rotating to the highest point, because of the structural characteristics of the invention, as can be seen from (5) to (6), the pushing piston 10 hardly moves downward, the volume of the cold chamber 11 is still in the maximum state, and the rotation angle corresponding to the residence time is α 2, which satisfies the following formula: θ 2+ α 2 ═ θ 2', corresponding to the angles in fig. 7. Thus, θ 2< θ 2', and the pusher piston 10 does not descend in the time corresponding to α 2. This also means that the open position of the low pressure valve 12b in fig. 5(2) changes from point e to point e ', moving the piston 10 to the top dead center corresponding to point c': the time elapsed e ' → c ' corresponds to the rotation angle θ 2, and the time elapsed c ' → c corresponds to the rotation angle α 2.

In this way, compared with the area of the quadrangle enclosed by the original a → e → c → f → a → f and the area of the quadrangle enclosed by e → e' → c → e correspond to the newly increased cooling capacity, so that the cooling efficiency of the refrigerator is improved.

As can be seen from the above description, the embodiments of the present invention have the following beneficial effects:

while the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. The low-temperature refrigerating machine is characterized by comprising a cylinder (9) and a cover body (2) connected to the cylinder (9), a pushing piston (10) is installed in the cylinder (9), a connecting rod (4) is installed in the cover body (2) and connected with the pushing piston (10), the connecting rod (4) drives the pushing piston (10) to reciprocate up and down, the speed of the connecting rod (4) moving from a top dead center to a bottom dead center is the same as the speed of the connecting rod (4) moving from the bottom dead center to the top dead center, the time spent by the connecting rod (4) moving from the top dead center to a balance position is longer than the time spent by the connecting rod moving from the balance position to the bottom dead center, and the time spent by the connecting rod (4) moving from the bottom dead center to the balance position is longer than the time spent by the connecting rod moving from the balance position to the top dead center.

2. The cryocooler according to claim 1, characterized in that the connecting rod (4) comprises a sliding slot (41), the shape of the sliding slot (41) being 180 ° symmetrical with respect to the central position of the connecting rod (4).

3. The cryogenic refrigerator according to claim 2, wherein the mechanism for driving the pushing piston (10) to reciprocate up and down further comprises a cam assembly (14) and a driving sleeve (3), the driving sleeve (3) is annular and is placed in the chute (41), and the outer diameter of the driving sleeve is tangent to the upper edge and the lower edge of the chute (41).

4. The cryocooler according to claim 3, characterized in that the cam module (14) comprises a cam (14a) and a cam shank (14b), the cam (14a) being mounted on the motor spindle, the cam shank (14b) being mounted eccentrically on the cam (14a) and having an inner bore which is dimensioned to fit the inner diameter of the drive sleeve (3).