Exhaust valve assembly of carbon dioxide heat pump compressor and using method of exhaust valve assembly

Abstract

The invention provides an exhaust valve assembly of a carbon dioxide heat pump compressor and a using method thereof.The exhaust valve assembly comprises a valve plate, an exhaust valve plate and a lift limiter, the valve plate is provided with an exhaust hole and a buffer cavity, the exhaust hole is covered with the head of the exhaust valve plate, the lift limiter is fixed to the upper portion of the exhaust valve plate, and the buffer cavity is arranged in the valve plate; the buffer cavity is located on the lower side of the exhaust valve plate. According to the exhaust valve assembly, the impact between the exhaust valve plate and the lift limiter and between the exhaust valve plate and the valve plate can be reduced, the bending stress of the root of the exhaust valve plate can be reduced, stress distribution of the exhaust valve is comprehensively improved, the exhaust valve assembly adapts to severe working conditions of the carbon dioxide compressor, and the service life of the exhaust valve assembly is prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of semi-hermetic refrigeration reciprocating compressors, and in particular to an exhaust valve assembly of a carbon dioxide heat pump compressor and a use method thereof. Background Art

[0002] Reciprocating compressors are widely used in CO2 heat pump systems due to their good sealing performance. The gas valve is a key component in the reciprocating compressor. Improving the economy and reliability of the gas valve is of great significance to improving the overall performance and extending the service life of the CO2 heat pump compressor.

[0003] The reciprocating compressor forms a closed volume by closing the air valve. The crankshaft rotation drives the connecting rod to swing and the piston to reciprocate, so as to reduce the basic volume and increase the gas pressure in the volume. When the pressure reaches the exhaust pressure, the air valve opens and the gas is discharged until the pressure in the cavity is lower than the exhaust pressure and the air valve closes. Therefore, the air valve plays an important role in the entire working cycle. During the operation of the compressor, the air valve will open and close continuously, and will collide with the valve plate and the lift limiter continuously, generating a large impact stress. Moreover, the valve plate relies on its own deformation to realize the opening and closing of the air valve, and there will be different degrees of vibration when it is opened. Therefore, the valve plate must also withstand the constantly changing bending stress. The working conditions of the air valve are harsh and it is very easy to cause damage. Especially for the carbon dioxide heat pump compressor, the intake and exhaust pressure is high, the working pressure difference is large, and the air valve is more easily damaged. In addition, the quality of the air valve design also affects the intake and exhaust resistance loss, exhaust reflux and other unfavorable factors, which have a great impact on the performance of the compressor. Therefore, it is of great significance to propose a valve suitable for carbon dioxide compressors to solve the problem of easy damage of the air valve and improve the efficiency of the whole machine.

[0004] When the exhaust valve is opened, the entire exhaust valve will be blocked by the lift limiter. By adjusting the shape of the lift limiter, the movement of the exhaust valve can be controlled, thereby reducing the bending stress and impact stress of the valve plate. However, there is currently little research on the specific improvement of the lift limiter shape and the valve plate design that matches it. Summary of the invention

[0005] The purpose of the present invention is to provide an exhaust valve assembly of a carbon dioxide heat pump compressor and a method of using the same, to control the movement process of the valve plate, to reduce the vibration intensity of the valve plate, to reduce the impact stress generated when the valve plate collides with the lift limiter, to reduce the bending stress when the gas valve is opened and the impact stress between the exhaust valve plate and the valve seat when the valve is closed, to adapt to the working conditions of high pressure and large pressure difference in the carbon dioxide heat pump compressor, to extend the service life of the exhaust valve in the compressor, to reduce the energy consumption of the whole machine, and to improve the overall efficiency.

[0006] According to one object of the present invention, the present invention provides an exhaust valve assembly of a carbon dioxide heat pump compressor, comprising a valve plate, an exhaust valve sheet and a lift limiter, wherein the valve plate is provided with an exhaust hole and a buffer cavity, the head of the exhaust valve sheet covers the exhaust hole, the lift limiter is fixed above the exhaust valve sheet, and the buffer cavity is located at the lower side of the exhaust valve sheet.

[0007] Furthermore, the exhaust valve plate includes a valve plate fixing portion, a valve plate root, a valve plate connecting portion and a valve plate head portion, the arc radius of the valve plate head portion is smaller than the arc radius of the valve plate fixing portion, and the arc of the valve plate connecting portion is connected to the arc of the valve plate head portion and the arc of the valve plate fixing portion.

[0008] Furthermore, the buffer cavity is a waist-shaped buffer cavity, and the waist-shaped buffer cavity is arranged perpendicular to the length direction of the exhaust valve sheet.

[0009] Furthermore, the length of the waist-shaped buffer cavity is 1.5 to 2 times the width of the exhaust valve sheet, and the depth of the waist-shaped buffer cavity is 0.8 to 1.2 times the thickness of the exhaust valve sheet.

[0010] Furthermore, the length of the straight portion of the waist-shaped buffer cavity is greater than the width of the exhaust valve sheet.

[0011] Furthermore, the arc radius of the valve plate head is 1 mm larger than the radius of the exhaust hole.

[0012] Furthermore, the length of the exhaust valve plate is 36 to 40 times the width of the exhaust valve plate.

[0013] Furthermore, the lift limiter comprises a limiter fixing portion, a limiter root portion, a limiter connecting portion and a limiter head portion, and a limiter mounting hole is provided on the limiter fixing portion.

[0014] Furthermore, the slopes of the tangent lines at various locations between the curve at the root of the limiter and the curve at the head of the limiter are less than or equal to the slopes of the tangent lines at various locations of the curve at the connecting portion of the limiter.

[0015] According to another object of the present invention, the present invention provides a method for using the exhaust valve assembly of the carbon dioxide heat pump compressor, comprising the following steps:

[0016] S1, when the exhaust valve plate falls back, the buffer cavity on the valve plate below the exhaust valve plate forms an air cushion. When the valve plate collides with the valve plate, the gas in the buffer cavity is compressed and the pressure increases, which generates a force on the exhaust valve plate in the opposite direction to the closing direction of the exhaust valve plate, thereby reducing the impact speed of the exhaust valve plate and reducing the impact stress; at the same time, the gas flows away from both sides of the buffer cavity, which reduces the impact while not affecting the timely closing of the exhaust valve plate, thereby reducing the loss caused by exhaust backflow;

[0017] S2, when the exhaust valve plate opens, the exhaust valve plate first contacts with the root of the lift limiter. When it is about to be fully opened and the exhaust valve plate fits with the lift limiter, the head of the exhaust valve plate will collide with the lift limiter with a larger area, reducing the impact stress.

[0018] The exhaust valve assembly of the technical solution of the present invention can reduce the impact between the exhaust valve plate and the lift limiter and the valve plate, can reduce the bending stress at the root of the exhaust valve plate, and comprehensively improve the stress distribution of the exhaust valve to adapt to the harsh working conditions of the carbon dioxide compressor and extend the service life of the exhaust valve assembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 It is a structural schematic diagram of an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the structure of a valve plate according to an embodiment of the present invention;

[0022] Figure 3 This is a schematic diagram of the structure of the exhaust hole and the buffer cavity according to an embodiment of the present invention;

[0023] Figure 4 It is a schematic diagram of the structure of the exhaust valve sheet according to an embodiment of the present invention;

[0024] Figure 5 Schematic diagram of the structure of a lift limiter according to an embodiment of the present invention;

[0025] In the figure: 1-valve plate, 2-valve bolt;

[0026] 3-lift limiter, 31-limiter fixing part, 32-limiter root, 33-limiter connecting part, 34-limiter head;

[0027] 4-exhaust valve plate, 41-valve plate fixing part, 42-valve plate root, 43-valve plate connecting part, 44-valve plate head, 45-valve plate mounting hole, 46-notch;

[0028] 5-exhaust hole, 6-waist-shaped buffer cavity, 7-air valve mounting screw hole, 8-air inlet hole, 9-valve plate mounting hole, 10-total air inlet, 11-total exhaust port, 12-boss, 13-groove. DETAILED DESCRIPTION

[0029] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0031] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined. In addition, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] Example 1

[0033] For the carbon dioxide heat pump system, it mainly includes four major parts, namely the compressor, condenser, throttle valve and evaporator. The compressor compresses carbon dioxide to increase the pressure and discharges high-temperature and high-pressure gas. The gas then enters the condenser and exchanges heat with the outside world to dissipate heat. The heat pump uses this part of heat. Carbon dioxide dissipates heat in the condenser and condenses into liquid. After coming out, it passes through the throttle valve, and the pressure and temperature are reduced. When entering the evaporator, it absorbs heat from the external environment, evaporates into gas, and then enters the compressor to complete a cycle. The above-mentioned system is only the most basic process. In the actual system, there will be a variety of auxiliary devices and system changes, improvements and optimizations, but the actual principles are the same.

[0034] In the above system, the compressor is the core of the whole system, providing power for the whole cycle and is the main moving part. The compressor mainly determines which working conditions the system can be applied to. The compressor is the part that produces the main energy consumption in the system. Improving the performance and efficiency of the compressor is of great significance to reducing the energy consumption of the whole system.

[0035] The critical temperature of carbon dioxide is low and the critical pressure is high. When the carbon dioxide heat pump system uses a transcritical carbon dioxide cycle, the heating efficiency will be greatly improved, but the system pressure will be very high, especially the compressor needs to adapt to a high pressure and large pressure difference working condition, which has many technical difficulties. The gas valve is the most important key component in the compressor.

[0036] Commercial carbon dioxide heat pump systems mostly use reciprocating compressors. For reciprocating compressors, the exhaust valve assembly controls the on and off of exhaust. The crankshaft drives the connecting rod, which in turn causes the piston to reciprocate between the top and bottom dead centers of the cylinder. When the piston moves from the bottom dead center to the top dead center, the gas is compressed and the pressure increases. When the pressure is greater than the exhaust pressure, the exhaust valve opens and the compressed high-temperature and high-pressure gas is discharged from the cylinder. When the pressure in the cylinder is lower than the exhaust pressure, the exhaust valve closes and the gas no longer flows out.

[0037] The above process is completed once in each revolution of the compressor. The exhaust valve plate will continuously deform and bear alternating bending stress, which is prone to fatigue damage. In addition, the exhaust valve plate will continuously collide with the lift limiter and the valve plate, bearing impact stress. When the exhaust valve is in the closed state, the exhaust valve plate will be concave toward the exhaust hole due to the pressure difference between the upper and lower surfaces of the valve plate, which will also cause greater stress. It can be seen that the working environment of the gas valve is very harsh and it is very easy to be damaged. Moreover, in the carbon dioxide compressor, the high pressure and large pressure difference make the exhaust valve more susceptible to damage.

[0038] Based on this, the present invention proposes an exhaust valve assembly for a carbon dioxide heat pump reciprocating compressor to solve the problem that the exhaust valve of such compressor is easily damaged, reduce the maximum stress of the exhaust valve during the entire working process, weaken the vibration of the exhaust plate, and extend the service life of the exhaust valve assembly.

[0039] like Figure 1-Figure 5 As shown, an exhaust valve assembly of a carbon dioxide heat pump compressor includes a valve plate 1, a lift limiter 3 and an exhaust valve plate 4, the lift limiter 3 is arranged on the exhaust valve plate 4, and the valve bolt 2 penetrates the lift limiter 3 and the exhaust valve plate 4 to fix the lift limiter 3 and the exhaust valve plate 4 on the valve plate 1.

[0040] like Figure 3As shown, the valve plate 1 is provided with an exhaust hole 5 and a waist-shaped buffer cavity 6. The waist-shaped buffer cavity 6 is located on one side of the exhaust hole 5. A boss 12 and a groove 13 are provided on the outer side of the exhaust hole 5. The valve plate 1 is also provided with an air valve mounting screw hole 7, an air inlet hole 8, a valve plate mounting hole 9, a total air inlet port 10 and a total exhaust port 11.

[0041] like Figure 4 As shown, the exhaust valve plate 4 includes a valve plate fixing portion 41, a valve plate root portion 42, a valve plate connecting portion 43 and a valve plate head portion 44, and a valve plate mounting hole 45 is provided on the valve plate fixing portion 41;

[0042] like Figure 5 As shown, the lift limiter 3 includes a limiter fixing portion 31, a limiter root portion 32, a limiter connecting portion 33 and a limiter head portion 34. A limiter mounting hole is provided on the limiter fixing portion 31. The valve bolt 2 passes through the mounting hole on the limiter fixing portion 31 and the mounting hole 45 on the valve plate fixing portion 41 and is fixed to the valve plate 1.

[0043] The valve plate head 44 of the exhaust valve plate 4 covers the exhaust hole 5 on the valve plate 1, and the limiter head 34 of the lift limiter 3 is located directly above the valve plate head 44. When the air valve is opened, the exhaust valve plate 4 is deformed and fits the lift limiter 3, and the limiter head 34 of the lift limiter 3 collides with the exhaust valve plate 4.

[0044] When the gas pressure in the cylinder is greater than the exhaust pressure, the exhaust valve opens and exhaust occurs. At this time, the gas will flow out from the exhaust hole 5 on the valve plate 1. Under the impact of the airflow and the pressure difference between the upper and lower surfaces, the valve head 44 of the exhaust valve plate 4 moves upward, thereby causing the valve connecting part 43 and the valve root 42 to deform and lift upward. Then the exhaust valve plate 4 collides with the lift limiter 3. After vibrating several times, the exhaust valve plate 4 fits with the lift limiter 3 or continues to vibrate slightly. When the cylinder pressure drops below the exhaust pressure, the exhaust valve plate 4 falls back, the deformation is restored, the exhaust valve plate 4 collides with the valve plate 1, and the exhaust valve plate 4 covers the exhaust hole 5 to block the gas flow.

[0045] In this embodiment, the valve plate head 44 of the exhaust valve plate 4 covers the exhaust hole 5 on the valve plate 1, and the lift limiter 3 is located above the exhaust valve plate 4 to block the movement of the exhaust valve plate 4. The shape of the lift limiter 3 is a combination of multiple curves.

[0046] like Figure 2As shown, in this embodiment, the waist-shaped buffer cavity 6 on the valve plate 1 is on the lower side of the valve plate connection portion 43 of the exhaust valve plate 4, and the position of the waist-shaped buffer cavity 6 is perpendicular to the length direction of the exhaust valve plate 4. In this way, when the exhaust is completed, the exhaust valve plate 4 falls back to the valve plate 1. In the waist-shaped buffer cavity 6 just below the valve plate connection portion 43 of the exhaust valve plate 4, because the exhaust valve plate 4 moves toward the waist-shaped buffer cavity 6, a part of the gas does not have time to flow out, resulting in a certain degree of compression. This part of the gas generates a certain airflow thrust on the exhaust valve plate 4, reducing the impact speed between the exhaust valve plate 4 and the valve plate 1, thereby reducing the impact stress and improving the reliability of the exhaust valve assembly. At the same time, the waist-shaped buffer cavity 6 is a waist-shaped hole structure, and its position is perpendicular to the length direction of the exhaust valve plate. In this way, the gas in the waist-shaped buffer cavity 6 can mainly flow out from the semicircular on both sides of the waist-shaped buffer cavity, and while providing a certain thrust to the exhaust valve plate 4, it flows away in time without affecting the timely closing of the exhaust valve plate 4. Moreover, the gas will flow out to both sides of the exhaust valve plate 4 in the width direction and will not flow to the exhaust hole 5, thus reducing the exhaust gas backflow and improving the compressor efficiency.

[0047] In this embodiment, the length of the waist-shaped buffer cavity 6 is 1.5 to 2 times the width of the exhaust valve sheet 4, and the depth is 0.8 to 1.2 times the thickness of the exhaust valve sheet 4. In this way, reasonable size selection can ensure that the waist-shaped buffer cavity 6 can play an effective role. The length of the waist-shaped buffer cavity 6 is based on the width of the exhaust valve sheet 4. While ensuring that the length of the waist-shaped buffer cavity 6 is greater than the width of the exhaust valve sheet 4 and the gas can flow out, the length cannot be too long to avoid insufficient airflow thrust. The depth of the waist-shaped buffer cavity 6 is based on the thickness of the exhaust valve sheet 4, because the thickness determines the rigidity of the exhaust valve sheet 4. The greater the thickness, the greater the rigidity. When the exhaust valve sheet 4 falls back, the elastic force generated by itself will increase the impact speed. Therefore, the depth is based on the thickness at this time. If the depth is increased in time, more gas is compressed in the waist-shaped buffer cavity 6, which effectively increases the airflow thrust and weakens the impact.

[0048] In this embodiment, the length of the straight portion of the waist-shaped buffer cavity 6 is slightly greater than the width of the exhaust valve plate 4. In this way, the exhaust valve plate 4 will not block the semicircles on both sides of the waist-shaped buffer cavity 6, so that the airflow can flow out relatively smoothly without affecting the timely closing of the exhaust valve.

[0049] In this embodiment, if Figure 4 As shown, the valve plate fixing portion 41 of the exhaust valve plate 4, the joint portion of the valve plate connecting portion 43 and the valve plate root 42, and the valve plate head portion 44 are all composed of arc structures. In this way, the shape of the exhaust valve plate 4 is entirely composed of arcs, and the size transition is gentle. Since the exhaust valve plate 4 will continuously deform and generate bending stress, the use of all arcs with gentle transitions can effectively avoid stress concentration and reduce stress.

[0050] In this embodiment, the arc radius of the valve plate head 44 of the exhaust valve plate is smaller than the arc radius of the valve plate fixing portion 41, and the arcs at the valve plate root 42 and the valve plate connecting portion 43 are respectively connected to the arcs of the valve plate head 44 and the valve plate fixing portion 41, and the arc connections are tangent to each other. In this way, the arc radius of the valve plate fixing portion 41 is larger, and the valve plate root 42 is connected to the valve plate fixing portion 41, so the width of the valve plate root 42 is larger. Since the exhaust valve plate 4 is similar to a cantilever beam, the bending stress will be the largest at the valve plate root 42. Increasing the width of the valve plate root 42 can effectively reduce the stress here. At the arc connection of the entire exhaust valve plate 4, the arcs are tangent to each other, which can ensure smooth transitions at various locations of the exhaust valve plate, avoid defects, and reduce stress concentration.

[0051] In this embodiment, the arc radius of the valve plate head 44 of the exhaust valve plate 4 is 1 mm larger than the radius of the exhaust hole 5 on the valve plate 1. In this way, the exhaust valve plate 4 will seal the edge of the exhaust hole 5 by more than 1 mm. The size is set to 1 mm, which can ensure the sealing effect and prevent leakage from the exhaust hole, while also ensuring that the exhaust valve plate 4 is not too large and occupies too much installation area.

[0052] In this embodiment, the length of the exhaust valve plate 4 is 36 to 40 times the width of the exhaust valve plate 4. In this way, the length is selected based on the width of the exhaust valve plate 4 to ensure that the exhaust valve plate 4 has a suitable rigidity. Moreover, the length is much greater than the width, which is also to increase the length of the exhaust valve plate 4 as much as possible, so that under a certain lift, the average deformation of the exhaust valve plate 4 is smaller, reducing the bending stress.

[0053] In this embodiment, the above-mentioned “lift” refers to the distance between the center of the exhaust hole 5 and the center of the valve head 44 of the exhaust valve plate 4 on the surface where the exhaust valve plate 4 contacts the valve plate 1 when the exhaust valve plate 4 is fully opened.

[0054] In this embodiment, if Figure 4 As shown, a semicircular notch 46 is provided on one side of the valve plate fixing portion 41 of the exhaust valve plate 4. In this way, the front and back sides of the exhaust valve plate 4 can be marked. Since the exhaust hole 5 needs to be sealed on the side of the exhaust valve plate 4 that contacts the valve plate 1, the surface roughness of this side is required to be less than Ra0.2, which is a very high requirement. Other sides do not need it, so only this side is processed to save costs. The semicircular notch 46 is used to mark the surface that needs fine processing, which is convenient for distinguishing when installing the exhaust valve plate 4. Moreover, the notch 46 is located in the valve plate fixing portion 41, where no stress will be generated, so adding the notch 46 will not cause stress concentration.

[0055] In this embodiment, if Figure 5As shown, the profile of the lift limiter 3 is composed of a straight line and three curved lines. The limiter fixing portion 31 is a straight line structure, which flattens the exhaust valve plate 4 and prevents it from deforming; the limiter root 32, the limiter connecting portion 33 and the limiter head 34 each have a corresponding curved line, thereby controlling the deformation displacement of the exhaust valve plate 4 at various locations, and then controlling the deformation law of the exhaust valve plate 4, thereby reducing the bending stress and vibration degree of the exhaust valve plate 4.

[0056] In this embodiment, if Figure 5 As shown, the tangent slopes of the curves of the limiter root 32 and the limiter head 34 of the lift limiter 3 are less than or equal to the tangent slopes of the curves of the limiter connection 33. The tangent slopes of the limiter root 32 of the lift limiter 3 are small in order to reduce the deformation degree of the valve root 42 of the exhaust valve plate 4 and reduce the stress of the valve root 42. The tangent slopes of the limiter head 34 are small because the movement distance of the valve head 44 of the exhaust valve plate 4 is the largest and the collision is the most intense. The small tangent slope can make the valve head 44 of the exhaust valve plate 4 contact with the lift limiter 3 with a larger area when colliding, thereby reducing the impact stress. The tangent between each section of the curve can ensure that the lift limiter is subjected to reasonable force and avoid stress concentration. At the same time, the deformation of the exhaust valve plate 4 can also be smooth.

[0057] In this embodiment, the exhaust valve assembly is used for a semi-closed reciprocating heat pump compressor. This type of compressor is connected by bolts and sealed with sealing gaskets, and can be disassembled for maintenance. The motor and the crankcase are in a housing to avoid leakage at the shaft seal. The exhaust valve assembly of the present invention is used for this type of compressor. The semi-closed reciprocating heat pump compressor is used in a transcritical carbon dioxide circulation system. The efficiency of this cycle is higher, but the pressure is high and the pressure difference is large. The present invention can adapt to such high pressure and large pressure difference conditions and can be used in compressors in transcritical carbon dioxide circulation systems.

[0058] When the exhaust valve plate falls back, the waist-shaped buffer cavity on the valve plate below the exhaust valve plate connection portion can form an air cushion. When the valve plate collides with the valve plate, the gas in the buffer cavity is compressed to a certain extent, the pressure increases, and a force opposite to the closing direction of the valve plate is generated on the valve plate, thereby reducing the impact speed of the exhaust valve plate and reducing the impact stress. At the same time, the waist-shaped shape can make the gas flow away from both sides of the buffer cavity, while reducing the impact, it does not affect the timely closing of the exhaust valve, and reduces the loss caused by exhaust backflow.

[0059] When the air valve is opened, due to the different curvatures of the lift limiter profile, the curvature of the curve at the connection is greater than the root and the head. The exhaust valve plate will first contact the root of the lift limiter. When it is about to be fully opened and the exhaust valve plate is in contact with the lift limiter, the head of the exhaust valve plate will collide with the lift limiter with a larger area, reducing the impact stress.

[0060] When the air valve opens, the root of the exhaust valve plate first fits against the lift limiter, the free movement length of the exhaust valve plate is reduced, and the valve plate stiffness is increased, so that the elastic force of the exhaust valve plate itself is increased, thereby slowing down the collision between the valve plate and the lift limiter.

[0061] Since the arc radius of the fixed part of the exhaust valve plate is large and the arc of the head is small, the two are connected by an arc with a larger radius, which avoids the stress concentration caused by the small arc at the connection between the connecting part, the head and the fixed part. The larger arc of the fixed part makes the root of the valve plate wider, and the curvature and height of the lift limiter at the root are smaller, so the bending stress at the root can be greatly reduced.

[0062] The head of the exhaust valve plate is far away from the fixed part, has the largest movement displacement, and is most prone to violent vibration. The tangent slope of the curve between the root of the lift limiter and the head is relatively small, so the head of the exhaust valve plate will fit better with the lift limiter, thereby reducing the amplitude of vibration.

[0063] The arc radius of the exhaust valve plate head is 1mm larger than the radius of the exhaust hole. Reasonable size selection ensures that the exhaust valve plate will not be too large and will not occupy the limited installation area while ensuring that the leakage from the exhaust valve is very small when the exhaust valve is closed.

[0064] The exhaust valve assembly of the present invention can reduce the collision between the exhaust valve plate and the lift limiter and the valve plate, can reduce the bending stress at the root of the exhaust valve plate, and comprehensively improve the stress distribution of the exhaust valve to adapt to the harsh working conditions of the carbon dioxide compressor and extend the service life of the exhaust valve assembly.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An exhaust valve assembly for a carbon dioxide heat pump compressor, characterized in that: It includes a valve plate, an exhaust valve sheet and a lift limiter. The valve plate is provided with an exhaust hole and a buffer cavity. The head of the exhaust valve sheet covers the exhaust hole. The lift limiter is fixed above the exhaust valve sheet. The buffer cavity is located at the lower side of the exhaust valve sheet.

2. The exhaust valve assembly of the carbon dioxide heat pump compressor according to claim 1, characterized in that: The exhaust valve plate includes a valve plate fixing part, a valve plate root, a valve plate connecting part and a valve plate head part. The arc radius of the valve plate head part is smaller than the arc radius of the valve plate fixing part. The arc of the valve plate connecting part is connected to the arcs of the valve plate head part and the valve plate fixing part.

3. The exhaust valve assembly of the carbon dioxide heat pump compressor according to claim 1, characterized in that: The buffer cavity is a waist-shaped buffer cavity, and the waist-shaped buffer cavity is arranged perpendicular to the length direction of the exhaust valve sheet.

4. The exhaust valve assembly of the carbon dioxide heat pump compressor according to claim 3, characterized in that: The length of the waist-shaped buffer cavity is 1.5 to 2 times the width of the exhaust valve sheet, and the depth of the waist-shaped buffer cavity is 0.8 to 1.2 times the thickness of the exhaust valve sheet.

5. The exhaust valve assembly of the carbon dioxide heat pump compressor according to claim 4, characterized in that: The length of the straight portion of the waist-shaped buffer cavity is greater than the width of the exhaust valve sheet.

6. The exhaust valve assembly of the carbon dioxide heat pump compressor according to claim 2, characterized in that: The arc radius of the valve plate head is 1 mm larger than the radius of the exhaust hole.

7. The exhaust valve assembly of the carbon dioxide heat pump compressor according to claim 1, characterized in that: The length of the exhaust valve sheet is 36 to 40 times the width of the exhaust valve sheet.

8. The exhaust valve assembly of the carbon dioxide heat pump compressor according to claim 1, characterized in that: The lift limiter comprises a limiter fixing part, a limiter root part, a limiter connecting part and a limiter head part, and a limiter mounting hole is provided on the limiter fixing part.

9. The exhaust valve assembly of the carbon dioxide heat pump compressor according to claim 8, characterized in that: The slopes of the tangent lines at various locations of the curve at the root of the limiter and the curve at the head of the limiter are less than or equal to the slopes of the tangent lines at various locations of the curve at the connecting portion of the limiter.

10. The method for using the exhaust valve assembly of the carbon dioxide heat pump compressor according to claim 1, characterized in that: The steps include: S1, when the exhaust valve plate falls back, the buffer cavity on the valve plate below the exhaust valve plate forms an air cushion. When the valve plate collides with the valve plate, the gas in the buffer cavity is compressed, the pressure increases, and a force opposite to the closing direction of the exhaust valve plate is generated on the exhaust valve plate, thereby reducing the impact speed of the exhaust valve plate and reducing the impact stress; at the same time, the gas flows away from both sides of the buffer cavity, while reducing the impact, it does not affect the timely closing of the exhaust valve plate, and reduces the loss caused by exhaust backflow; S2, when the exhaust valve plate opens, the exhaust valve plate first contacts with the root of the lift limiter. When it is about to be fully opened and the exhaust valve plate fits with the lift limiter, the head of the exhaust valve plate will collide with the lift limiter with a larger area, reducing the impact stress.

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