Reciprocating compressor with non-self-actuating suction valve

Abstract

A reciprocating compressor (1') comprising a suction valve (110'), a discharge valve (120') and a working chamber (251'), wherein the suction valve (110') is configured to provide fluid communication between a suction passage (40') and the working chamber (251'), the discharge valve (120') is configured to provide fluid communication between the working chamber (251') and a discharge passage (50'), the suction valve (110') comprising at least one non-self-actuated valve, and the discharge valve (120') comprising at least one self-actuated check valve.

Description

Detailed Description of the Invention

[0001] [Technical field] The present invention relates to a gas compressor and its suction and discharge valve systems.

[0002] [Background technology] Compressors are utilized in various machines such as heat pumps. Many heat pumps have a gas / vapor compressor as a core component. More specifically, in the case of vapor compression cycles, which are often used in residential heat pumps, refrigerators, air conditioning systems in automobiles, and industrial heat pumps, the compressor is the central component. The main advantage of using heat pumps over traditional boiler or furnace systems is that heat pumps generate several times the heat required to run them, making them more energy efficient and often more economical to operate. Furthermore, if heat pumps can effectively replace fossil fuel heat sources, they can significantly reduce climate gas emissions. As the reduction of climate gas emissions becomes more and more important, so too does the need for new and more advanced heat pump technologies that can cover new and additional applications, especially within various industries, and the need for new and better compressor configurations.

[0003] There are two main types of compressors used in heat pumps: flow-type machines (often implemented as centrifugal compressors) and positive displacement machines, which are based on several geometric principles and can use a very wide variety of devices, such as screw compressors, scroll compressors, vane-type compressors and reciprocating / piston compressors, each of which has its own advantages and disadvantages, but will not be described in more detail here.

[0004] Common to all types of compressors is that they operate with a working fluid, also commonly referred to as a refrigerant, or simply a gas. In some examples, the working fluid may be a condensable gas. In some examples, the working fluid never changes phase, and therefore the working fluid operates exclusively in a gas phase. Throughout this disclosure, when referring to a working fluid, any working fluid in any phase state is intended, some of which include, but are not limited to, liquid, gas, and supercritical.

[0005] In the examples described herein, the compressors are of the piston type (also commonly referred to as reciprocating compressors), however, it should be noted that the present disclosure is not limited to only piston type compressors and may be equally applicable and useful to other types of compressors.

[0006] The performance of a heat pump compressor, more specifically a gas / vapor compressor, is primarily a result of three characteristics: 1. Mechanical efficiency, 2. Volumetric efficiency, and 3. Isentropic efficiency.

[0007] Mechanical efficiency is primarily a result of internal mechanical friction, or rather the lack of it. Volumetric efficiency is primarily a result of the internal so-called dead volume (also called the clearance volume in the compressor's working chamber, which is the minimum internal volume achievable in the cylinder of the compressor's working chamber during compression). Finally, isentropic efficiency is primarily a result of the effectiveness of the gas exchange processes, including the intake and exhaust processes.

[0008] There are other factors that affect the above mentioned properties such as heat leakage / undesirable heat exchange through internal surfaces such as cylinder walls, which affect isentropic efficiency, gas leakage through sealing elements etc., which affect isentropic and volumetric efficiency.

[0009] In the following, a reciprocating compressor with a conventional crankshaft is disclosed to more simply explain the operation principle. Basically, the operation of the compressor is simple and consists of four main processes (or steps) that are performed periodically. In the case of a piston-type compressor, these processes, namely, "1. suction process, 2. compression process, 3. discharge process, 4. re-expansion process", are performed once per crankshaft revolution.

[0010] The intake and discharge processes comprise a gas exchange process during which the working fluid, usually in gas / vapor form, is either drawn into the cylinder or discharged from the cylinder. Again, this is assuming a piston compressor, but the exact same process occurs in all other positive displacement machines. In general, in piston compressors, the gas exchange process is managed by the intake and discharge valves: during the intake process, the intake valve controls the inflow of fresh uncompressed gas into the cylinder, and during the discharge process, the discharge valve controls the outflow of compressed gas.

[0011] A compressor may have one or more cylinders, each with a corresponding set of suction and discharge valves, each also consisting of multiple valves, most often acting in parallel. In conventional compressor designs, the suction / discharge valves are usually in the form of so-called reed valves, and form a simple, yet efficient, key building block for many compressor applications.

[0012] A reed valve basically comprises at least a valve plate or valve port with a reed element (also called a reed valve blade) and a retainer (sometimes called a stop plate). The reed element is usually in the form of a sheet metal, sometimes made of a spring material, and is responsible for the actual opening and closing of the valve by covering or uncovering a port opening, slot or the like in the valve plate or valve port. Sometimes a separate spring element is provided, which is always made to push, exerting a force on the reed element in the closing direction, to assist in the closing of the valve and to prevent flow through the valve when it should be closed. The retainer can also be a piece of relatively stiff sheet metal, usually curved, shaped to "roll" the reed element against its curved surface, to guide the reed element by limiting its movement and to prevent damage caused by excessive bending during operation. In other cases, the retainer is in the form of a retainer plate, often fixed at a certain distance from the reed element, with the spring element between them. Although the main function is the same, their design can be varied. The basic characteristic of a reed valve is that it is passively operating, meaning that it opens and closes only due to a pressure difference (or lack thereof) across the reed element in the opening direction.

[0013] Reed valves are small and lightweight, generally simple in design, and easy and affordable to manufacture. However, reed valves have some drawbacks in some applications. It is difficult to design a reed valve that has an effective flow range like other types of valves, and it is difficult to design a compressor with very low dead volume, especially when the suction valve is of the reed type. As a result, compressors with reed valves usually have a larger dead volume and a smaller effective flow range than necessary. This in turn leads to reduced volumetric and isentropic efficiency.

[0014] Additionally, and as mentioned above, in order for a reed valve to close properly during operation, the reed valve is typically provided with a spring force in the closing direction, either by making the reed element itself out of a spring material or by providing a separate spring element that presses against the reed element.

[0015] Furthermore, reed valves often suffer from what is called valve flutter under certain circumstances, during which the reed elements are subjected to excessive stresses that can lead to damaging fatigue or other types of deformation, or in the worst case, catastrophic failure. This usually occurs over a certain frequency range, which in the case of compressors means a certain speed range due to cyclic operation. To overcome this, stiffer springs or thicker reed materials are sometimes used, which leads to increased resistance to fluid flow, further resulting in flow losses and a corresponding decrease in the isentropic efficiency of the compressor.

[0016] Modern refrigeration and heat pump systems often use modern synthetic working fluids of the so-called fourth generation. These generally contain hydrofluoroolefins (HFOs) and hydrochlorofluoroolefins (HCFOs). One difference between these and other fluids is that they tend to be denser for the conditions typically present in refrigeration and heat pump systems. Particularly for industrial heat pumps in the high temperature category, the relevant modern working fluids have a density during operation that is typically between 30 and 100 kg / m 3 or even higher under the relevant operating conditions. This is significantly higher than other fluids, meaning that valve performance becomes more critical in maximizing efficiency and performance. In particular, due to the higher density, pressure drops in valves, ports, pipes, etc. within the heat pump system are typically higher, leading to increased losses, so any increase in valve performance will result in a significant performance gain.

[0017] Poppet valves are extremely common and used in a wide variety of applications (e.g., combustion engines), have a long history, are widely proven and accepted in industry, and are widely available and manufactured at low cost around the world.

[0018] Poppet valves are typically actively controlled by mechanical means such as a camshaft, cam follower, push rod, or rocker arm, so they can be actively opened without the significant pressure drop that can occur with reed valves, and their opening and closing timing can be completely independent of the pressure differential across the valve, providing useful flexibility in controlling the compressor's gas exchange process.

[0019] Furthermore, poppet valves generally have very good flow characteristics, mainly due to their geometry offering little resistance to flow, even for dense fluids. Poppet valves are used in many different applications, from heavily loaded diesel engines to hydraulic circuits, and there is a vast amount of empirical knowledge about their mechanics, limitations, and overall performance. Poppet valve flow characteristics, as well as other properties such as durability, have been widely documented over the years.

[0020] GB 2416196A discloses a valve control system for a reciprocating gas compressor having at least one suction valve between the gas supply and the compressor cylinder. The suction valve opens and closes automatically in response to pressure in the cylinder, but has a locking assembly which holds the valve in an open position for a selected time after opening, in sync with the compressor piston stroke. This allows gas to enter and leave the compressor through the suction valve during the cycle in which the valve is open, thereby removing heat with the gas, thereby allowing the cylinder chamber to cool. The valve may be a disc or reed valve, and the locking assembly may be electromagnetic or pneumatic. The compressor may have a regenerative heat exchanger mounted within the compressor cylinder to allow heat to be transferred from the cylinder.

[0021] US 2019 / 003604(A1) discloses a valve assembly including: a valve seat plate having a top surface and a bottom surface; a plurality of first valve modules disposed at a first height relative to the valve seat plate such that a first seating surface of each of the plurality of first valve modules is substantially coplanar with a first plane that is substantially parallel to at least one of the top surface and the bottom surface of the valve seat plate; and at least one second valve module disposed at a second height relative to the valve seat plate such that a second seating surface of the at least one second valve module is substantially coplanar with a second plane that is substantially parallel to the first plane, the second plane being offset from the first plane by a first distance.

[0022] US Patent No. 4,370,103(A) discloses a piston pump mechanism for use in positive pressure and vacuum pumping systems for pumping various gases such as air, freon, and natural gas. The pump mechanism implements an intake and discharge valve system that substantially eliminates unpurged or unswept gas volume in the pump cylinder during each reciprocating stroke of the pump piston. The pump mechanism also implements a control spool that floats in the pump head and has a sealed flexible interconnection with the discharge valve that allows the discharge valve to seek optimal seating engagement around the entire circumference of the cylinder. The valve control spool may be pressure balanced or controllably unbalanced as desired for the action of the discharge valve. The spool also provides a gas intake to an intake valve that may be incorporated within the discharge valve.

[0023] WO 2006 / 115348 discloses an intake and exhaust valve for a cylinder-type air compressor. The intake valve includes a valve body having a plurality of intake ports, a movable shaft elastically mounted on the valve body to open and close the intake ports, a packing elastically supporting the outer surface of the valve head of the movable shaft when the movable shaft moves up and down to reduce banging noise, and an elastic support element elastically supporting the lower end of a stopper. The exhaust valve includes a plurality of exhaust ports defined in the valve body so as to be arranged in a circumferential direction around the movable shaft around the intake ports, and a ring-shaped movable opening and closing element elastically supported to open and close the plurality of exhaust ports.

[0024] GB 2396667A discloses a reciprocating gas compressor which is described as operating according to a long-term cycle of 4, 6 or more strokes, where the first two strokes are sequential suction and compression strokes using low pressure gas as the working fluid and compressing it to high pressure gas, and the remaining strokes are pairs of sequential charge and full discharge strokes using more of the low pressure gas as the heat transfer fluid to transfer heat from inside the gas compressor to outside. The gas compressor also includes a regenerative heat exchanger which absorbs heat from the compressed gas and releases it to the heat transfer fluid.

[0025] US 2003 / 030226 A1 relates to the use of elastomers in the sealing elements of a reciprocating gas compressor valve to increase the reliability of the hermetic seal within the reciprocating gas compressor valve and to extend the useful life of the reciprocating gas compressor valve. The elastomeric material is used as a coating layer on the sealing elements of the reciprocating gas compressor valve or as the entire sealing element. The elastomeric material acts as a cushion to reduce wear on the sealing elements, provides a superior hermetic seal, and is more resistant to entrained dust and liquids in the air stream, thereby extending the operational life of the reciprocating gas compressor valve.

[0026] China Patent No. 111022293 relates to a transcritical reciprocating piston compressor that takes CO2 as the refrigerant.

[0027] At least one object of the present invention is to obviate or at least mitigate one or more disadvantages associated with the prior art.

[0028] [Summary of the invention] According to a first aspect of the present invention, there is provided a reciprocating compressor comprising a suction valve, a discharge valve and a working chamber, the suction valve configured to provide fluid communication between a suction passage and the working chamber, the discharge valve configured to provide fluid communication between the working chamber and the discharge passage, the suction valve comprising at least one non-self-actuated valve, and the discharge valve comprising at least one self-actuated check valve.

[0029] Embodiments of the present invention may be advantageous in that they combine some of the best features of non-self-actuating and self-actuating valves to create an improved compressor, particularly when the compressor is in the form of a heat pump or refrigeration compressor.

[0030] The embodiments of the present invention are based on the inventor's efforts in recognizing that the greatest performance disadvantage is often found during the intake process of the compressor. During this process, the direction of fluid flow is toward the working chamber, and the pressure difference during compression is in the direction of the intake valve closing, so a poppet valve is considered to be an alternative to a reed valve. However, for the discharge process, the poppet valve is not as suitable, since the pressure direction is opposite to the valve closing direction, and therefore, a better solution is pursued in various embodiments by the inventor to provide an effective poppet discharge valve that can manage the pressure difference even when closed.

[0031] Furthermore, the inventors have determined that the need for higher valve performance is generally less critical for the discharge process than for the suction process, because, among other reasons, in a reciprocating compressor, the discharge process occurs when the piston approaches top dead center (TDC), a time when the volumetric flow rate is lower due to the deceleration of the piston(s) and therefore the reduction in instantaneous piston velocity, which determines the volumetric fluid flow rate and velocity from the discharge port. Thus, an embodiment using a poppet valve or equivalent for the suction valve system and a reed valve or equivalent for the discharge valve system can provide a good compromise with improved overall performance.

[0032] The self-actuating check valve may comprise, for example, one or more of a reed valve, a plate valve, a self-actuating poppet valve, and a self-actuating ball check valve.

[0033] The non-self-actuated valves may be, for example, one or more of a poppet valve, a rotary valve, a piston valve, a slide valve, and a spool valve. The non-self-actuated valves may be one or more of a mechanically controlled, a pneumatically controlled, an electrically controlled, and a hydraulically controlled.

[0034] The reciprocating compressor may further comprise a compressor block having at least one cylinder with a piston arranged for reciprocating movement therein, and at least one cylinder head, and the intake valve may be disposed within the cylinder head.

[0035] The intake valve may be located on a central longitudinal axis of the at least one cylinder.

[0036] At least one cylinder head may include a valve plate.

[0037] The at least one cylinder may comprise a first cylinder in which a first piston is arranged to reciprocate therein, and a second cylinder in which a second piston is arranged to reciprocate therein, and the at least one cylinder head may comprise a first cylinder head and a second cylinder head, the first cylinder head configured to connect with the first cylinder, and the second cylinder head configured to connect with the second cylinder.

[0038] The first and second cylinders may be disposed at approximately 90 degrees relative to one another to form a V-shaped configuration.

[0039] The at least one discharge valve may be a plurality of self-actuating check valves.

[0040] The discharge valve may be disposed concentrically with the inlet valve. The plurality of self-actuating check valves may each be concentric with the inlet valve. The inlet valve may be disposed such that a central axis of the inlet valve is shared with a central axis of the at least one cylinder.

[0041] This allows for maximizing the available valve area while providing a practical shape. It is noted that reed valves are typically limited in size due to the need to be flexible while simultaneously reducing mass. Thus, in a reed valve based valve system, multiple reed valves may be used in parallel. The reed valves may also be conveniently configured in parallel. The valves may also be conveniently designed with a shape that allows for placement in a circular pattern corresponding to the circular shape of the compressor cylinder, thereby allowing for maximum utilization of the flow area.

[0042] The discharge valve may be arranged such that a central axis of the discharge valve is shared with a central axis of at least one cylinder.

[0043] The piston may be provided with at least one protrusion and the cylinder head may be provided with at least one cylinder head recess, and the at least one protrusion and the at least one cylinder head recess may be aligned such that during use the protrusion displaces at least a portion of the volume of the cylinder head recess.

[0044] At least a portion of the volume of the cylinder head recess may be at least 50%, or at least 60%, or at least 70% of the volume of the recess, or may be the majority of the volume of the cylinder head recess.

[0045] The at least one protrusion may be a plurality of protrusions and the at least one cylinder head recess may be a plurality of cylinder head recesses.

[0046] The piston may be provided with at least one piston recess shaped and configured to receive a non-self-actuating valve in use.

[0047] The piston recess may be configured such that during use the non-self-actuating valve displaces at least 50%, or at least 60%, or at least 70%, or the majority of the volume of the piston recess.

[0048] This provides the additional benefit of further optimizing the volumetric efficiency of the compressor, which is not possible when using only passive reed-based valve systems, since suction valves using reed valves, which require having a backstop or stop plate, cannot replace this portion of the dead volume, since the dead volume created by the backstop / stop plate is hidden "back" away from the piston and cannot be replaced.

[0049] The intake passage may comprise a first portion formed in the compressor block and a second portion formed in at least one cylinder head, the first and second portions being arranged to be connected at a connection to form a fluid flow path between the first and second portions for delivering the working fluid to the working chamber during use. Since the intake passage always experiences the lowest temperature compared to the discharge passage, the intake passage can be designed to be part of the casting of the compressor block, thus eliminating additional pipes, seals and flanges, and also providing the freedom to shape this part of the intake passage to suit the needs. Thus, a combination of good flow characteristics and reduced part count, including seals prone to leaks, can be avoided.

[0050] The first portion of the inlet passage may include a fluid inlet passage adjacent the connection when the first and second portions are connected in use, the fluid inlet passage configured to direct fluid at an angle of 20 degrees to 80 degrees relative to a normal to the central axis of the cylinder, the angle may be about 45 degrees.

[0051] An improved flow path is achieved through careful design of the fluid inlet passage, which is hydrodynamically optimized and promotes tighter turns within the fluid flow path, reducing pressure drop.

[0052] The first part may comprise a buffer vessel having a volume significantly larger than the volume of the working chamber such that, in use, when working fluid is pumped from the buffer vessel to fill the working chamber, there is no significant pressure drop within the buffer vessel.

[0053] The working chamber may be a first working chamber, the suction passage may be a first suction passage, and the compressor may further include a second working chamber and a second suction passage, and the first and second suction passages may merge to form a merged suction passage having an inlet through which the compressor receives working fluid.

[0054] This is generally advantageous as it reduces the number of parts in the compressor and, importantly, reduces the number of sealing surfaces.

[0055] The inlet may comprise a manifold.

[0056] According to a second aspect of the present invention, there is provided a heat pump comprising the reciprocating compressor according to the first aspect of the present invention.

[0057] The heat pump may be a high temperature heat pump capable of providing an output temperature, during use, of greater than 55 degrees Celsius, greater than 80 degrees Celsius, greater than 90 degrees Celsius, greater than 100 degrees Celsius, greater than 110 degrees Celsius, greater than 120 degrees Celsius, greater than 130 degrees Celsius, greater than 140 degrees Celsius, greater than 150 degrees Celsius, greater than 160 degrees Celsius, greater than 170 degrees Celsius, greater than 180 degrees Celsius, greater than 190 degrees Celsius, greater than 200 degrees Celsius, greater than 210 degrees Celsius, greater than 220 degrees Celsius, greater than 230 degrees Celsius, greater than 240 degrees Celsius, or greater than 250 degrees Celsius.

[0058] According to a third aspect of the present invention there is provided the use of a reciprocating compressor according to the first aspect of the present invention in a heat pump.

[0059] According to a fourth aspect of the present invention, there is provided a method of operating the reciprocating compressor according to the first aspect of the present invention, comprising the steps of drawing working fluid into a working chamber via at least one non-self-actuated valve and discharging the working fluid from the working chamber via at least one self-actuated check valve.

[0060] According to a fifth aspect of the present invention, there is provided a reciprocating compressor comprising an inlet valve, a discharge valve and a working chamber, the inlet valve being configured to provide fluid communication between an inlet passage and the working chamber, the discharge valve being configured to provide fluid communication between the working chamber and the discharge passage, the compressor further comprising a compressor block having at least one cylinder with a piston arranged for reciprocating movement therein, and at least one cylinder head, the inlet valve being arranged in the cylinder head, the inlet passage comprising a first portion formed in the compressor block and a second portion formed in the at least one cylinder head, the first and second portions being arranged to connect at a connection to form a fluid flow path between the first and second portions for delivering working fluid to the working chamber in use. The inlet valve may comprise at least one non-self-actuating valve and the discharge valve may comprise at least one self-actuating check valve. The reciprocating compressor of the fifth aspect of the present invention may have any one or more other features as described in relation to the reciprocating compressor of the first aspect of the present invention.

[0061] According to a sixth aspect of the present invention, there is provided a method of using the reciprocating compressor according to the sixth aspect of the present invention.

[0062] According to a seventh aspect of the present invention, there is provided a reciprocating compressor comprising a working chamber and a buffer tank, the buffer tank having a volume significantly larger than that of the working chamber such that there is no significant pressure drop in the buffer tank when working fluid is drawn from the buffer tank and charged into the working chamber during use. The reciprocating compressor may comprise a suction valve, a discharge valve and a working chamber, the suction valve configured to provide fluid communication between the suction passage and the working chamber, and the discharge valve configured to provide fluid communication between the working chamber and the discharge passage. The suction valve may comprise at least one non-self-actuating valve and the discharge valve may comprise at least one self-actuating check valve. The reciprocating compressor may have any one or more other features as described in relation to the reciprocating compressor of the first aspect of the present invention.

[0063] According to an eighth aspect of the present invention, there is provided a method of operating the reciprocating compressor according to the seventh aspect of the present invention, comprising the step of drawing working fluid from a buffer tank into a working chamber. [Brief description of the drawings]

[0064] Prior art and embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Figure 1] FIG. 1 shows a standard prior art compressor. [Diagram 2] FIG. 2 shows an improved compressor. [Diagram 3] FIG. 3 shows the improved compressor of FIG. 2 with an improved alternative suction path. [Figure 4] FIG. 4 shows the improved compressor of FIG. 2 having an alternative suction path. [Diagram 5] FIG. 5 shows a detailed cross-sectional view of a piston compressor. [Figure 6] FIG. 6 shows a detailed cross-sectional view of the piston compressor of FIG. [Figure 7] FIG. 7 shows a detailed bottom view of the cylinder head of FIG. [Figure 8]FIG. 8 shows a partial cross-sectional view of the discharge valve of the piston compressor shown in FIG. [Figure 9] FIG. 9 shows an optional lubricant return system for the compressor shown in FIG. [Figure 10a] FIG. 10a shows a first example of a self-actuating valve. [Figure 10b] FIG. 10b shows a first example of a self-actuating valve. [Figure 11a] FIG. 11a shows a second example of a self-actuating valve. [Figure 11b] FIG. 11b shows a second example of a self-actuating valve. [Figure 12a] FIG. 12a shows a third example of a self-actuating valve. [Figure 12b] FIG. 12b shows a third example of a self-actuating valve. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0065] [Detailed Description of the Invention] 1 shows a prior art piston compressor configuration 1 utilizing a condensable working fluid. The compressor 1 comprises a compressor block 20 having a cylinder 250 within which a reciprocating piston 240 is disposed, and a cylinder head 10 having an intake passage 40 and a discharge passage 50. The cylinder 250, cylinder head 10 and piston 240 define a working chamber 251 for compressing a compressible working fluid therein. Selection of a suitable compressible working fluid is well known in the prior art.

[0066] The inflow of the working fluid is controlled and allowed to flow from the intake passage 40 through the intake valve 110 into the working chamber 251, and the outflow of the working fluid is controlled and allowed to flow from the working chamber 251 through the two discharge valves 120 to the discharge passage 50. As is clear from FIG. 1, the intake passage 40 is arranged to draw the working fluid into the working chamber 251. The intake passage 40 has a substantially vertical and substantially linear configuration. It will be understood by those skilled in the art that the intake passage 40 connects to other piping and / or manifolds to which the working fluid is supplied. Although the example described here has one intake valve 110 and two discharge valves 120, any number of intake valves 110 and discharge valves 120 operating in parallel may be found in other prior art examples.

[0067] The valves 110, 120 shown in FIG. 1 are of the reed type and have at least a reed valve blade 121 and a reed valve retainer plate 122, also called a stop plate. The reed blade 121 controls the valve opening through a valve opening 143, also called a valve port or valve slot, in the cylinder head 10, and thereby controls the fluid communication through the valve opening 143. Reed valves function in such a way that they are actuated by the pressure difference on both sides of them, and as such are "passively controlled", meaning that they do not require any actuating element for opening or closing. Opening and closing is performed simply as a function of the pressure difference on both sides of the reed blade 121, and in this way the valve can have a simple structure, but also has the disadvantages mentioned above. That is, the valve is closed by the reed blade 121 pressing against the valve slot 143, closing the slot, due to the pressure difference on both sides of the reed blade 121 in this direction. Reed valves therefore also function as check valves, since they only open in one direction.

[0068] FIG. 2 shows an example of an improved compressor 1'. Similar to the prior art compressor 1 described with reference to FIG. 1, the compressor 1' is a piston-type compressor that utilizes a condensable working fluid. The compressor 1' comprises a compressor block 20' having a cylinder 250' with a reciprocating piston 240' disposed therein, and a cylinder head 10' having an intake passage 40' and a discharge passage 50'. The cylinder 250', the cylinder head 10', and the piston 240' define a working chamber 251' that compresses the working fluid therein.

[0069] The inflow of working fluid is controlled and allowed to flow from the inlet passage 40' through the inlet valve 110' into the working chamber 251', and the outflow of working fluid is controlled and allowed to flow from the working chamber 251' through the outlet valve 120' to the outlet passage 50'. As is clear from FIG. 2, the inlet passage 40' is arranged to draw working fluid into the working chamber 251' with the inlet passage 40' in a generally vertical and generally linear configuration. Those skilled in the art will appreciate that the inlet passage 40' connects to other piping to which the working fluid is supplied. Although the example described here has one inlet valve 110' and two outlet valves 120' for one cylinder 250', in other examples where multiple cylinders 250' are provided, any number of inlet and outlet valves operating in parallel may be found. Similarly, although the example described herein shows one intake valve 110' and two exhaust valves 120', in other examples there may be any number of intake valves 110' and / or any number of exhaust valves 120' for each cylinder 250'.

[0070] The suction valve 110' in the example shown in Figure 2 is a poppet valve, while the discharge valve 120 is a reed valve, as in the prior art compressor 1 shown in Figure 1. Given the same overall dimensions of the compressor 1', such as the cylinder bore, the shape of the poppet-type suction valve 110' allows for a larger effective opening area than would be possible using a reed valve. Additionally, the poppet-type suction valve 110' can be actively controlled using a mechanical actuator, as described in more detail below with reference to the following figures.

[0071] 2, it can be seen that in the example described herein, the inlet valve 110' is centrally disposed with respect to the working chamber 251' and the cylinder 250', i.e., the inlet valve 110' lies on the central axis 252' of the cylinder 250'. It can also be seen that the discharge valve 120' is disposed circumferentially around the inlet valve 110', i.e., the discharge valve 120' surrounds the inlet valve 110', the inlet valve 110' and the discharge valve 120' share a central axis with the central axis 252' of the cylinder 250', and the inlet valve 110' and the discharge valve 120' together use substantially the entire area of ​​the top of the working chamber 251'. The inlet valve 110' and the discharge valve 120' are concentrically disposed as shown in FIG. 2. In some alternative examples, the inlet valve 110' and the discharge valve 120' may be concentrically disposed but not share a central axis 252' with the cylinder 240'.

[0072] 3, an alternative compressor 1'' is shown having an intake passage 40'' configured to provide an intake fluid flow path 41'' therethrough, in use. The intake fluid flow path 41'' is significantly different to the fluid flow path of compressor 1' (not shown). The intake fluid flow path 41'' is formed by the connection of compressor block 20'' and cylinder head 10'' at connection 42''. The intake passage 40'' is partly within cylinder head 10'' and partly within compressor block 20''. The intake passage 40'' is within compressor block 20'' and comprises a common manifold 43'' through which working fluid from auxiliary piping first enters intake passage 40'', a buffer tank 44'' and a fluid inlet passage 45'' connecting buffer tank 44'' to working chamber 251''. With further reference to the cross-sectional view shown in FIG. 3, compressor 1'' has a front portion towards the viewer of FIG. 3, a rear portion towards the viewer, and a top portion where intake passage 40'' and discharge passage 50'' connect to further piping.

[0073] When the working fluid enters the common manifold 43'' of the intake passage 40'' at the rear of the compressor 1'', it travels towards the front of the compressor 1'', towards the viewer in FIG. 3, and travels downwards to the buffer tank 44''. From the buffer tank 44'', the working fluid is sent upwards to the top of the compressor 1'' through the connection 42'', and through the fluid inlet passage 45'' to the working chamber 251''. In the example described here, the working fluid travels across the compressor 1'', and then through an angle 46'' in the buffer tank 44'', and then upwards to the top of the compressor 1''. In the example described here, the angle 46'' is 90 degrees. That is, the fluid travels across the compressor 1'', perpendicular to the central axis 252'' of the cylinder along a horizontal axis 47'', as can be seen in FIG. 3, then travels parallel to the central axis 252'', along a vertical axis 48'', and then turns into the working chamber 251'' through the intake valve 110''.

[0074] In another exemplary compressor (not shown) with multiple cylinders 250'', one common manifold 43'' may be provided that receives the working fluid from the auxiliary piping. In this regard, each cylinder 250'' may be arranged to receive the working fluid from the common manifold 43'', dividing the working fluid between the common manifold 43'' and each buffer tank 44''. This not only reduces the number of external connections that would otherwise be required (e.g., one for the intake passage 40'' of each cylinder head 10'', but also significantly reduces the number of seals / gaskets required, since the connections 42'' are sealed with the same seals that would be required anyway at the interface between the cylinder head 10'' and the compressor block 20'', as will be described in more detail below.

[0075] 3, it can be seen that in the example described herein, the inlet valve 110'' is centrally disposed with respect to the working chamber 251'' and the cylinder 250'', i.e., the inlet valve 110'' is on the central axis 252'' of the cylinder 250''. It can also be seen that the discharge valve 120'' is circumferentially disposed about the inlet valve 110'', i.e., the discharge valve 120'' surrounds the inlet valve 110'' and shares a central axis with the central axis 252'' of the cylinder 250'', and the inlet valve 110'' and the discharge valve 120'' together use substantially the entire area of ​​the top of the working chamber 251''.

[0076] 4, another alternative compressor 1''' is shown having an intake passage 40''' configured to provide an intake fluid flow path 41''' therethrough, in use. Similar to compressor 1'' of FIG. 3, the intake fluid flow path 41''' is formed by the connection of compressor block 20''' and cylinder head 10''' at connection 42'''. The intake passage 40''' is partially within cylinder head 10''' and partially within compressor block 20'''. The intake passage 40''' is within compressor block 20''' and includes a common manifold 43''' through which working fluid from the auxiliary piping initially enters intake passage 40''', a buffer vessel 44''' and a fluid inlet passage 45''' connecting buffer vessel 44''' to working chamber 251'''. With further reference to the cross-sectional view shown in FIG. 4, compressor 1''' has a front portion facing toward the person viewing FIG. 4, a rear portion facing away from the viewer, and a top portion where suction passage 40''' and discharge passage 50''' connect to further piping.

[0077] As the working fluid enters the common manifold 43''' of the intake passage 40''' at the rear of the compressor 1'''', it travels towards the front of the compressor 1''' towards the viewer in FIG. 4 and travels downwards to the buffer vessel 44''''. From the buffer vessel 44''', the working fluid is sent upwards through the connection 42'''' towards the top of the compressor 1''' and through the fluid inlet passage 45'''' into the working chamber 251''''. In the example described here, the working fluid travels across the compressor 1'''' and then upwards towards the top of the compressor 1'''' through an angle 46'''' in the buffer vessel 44''''. In the example described here, the angle 46'''' is 45 degrees. That is, the fluid travels across the compressor 1'''' along a horizontal axis 47'''' at a right angle to the central axis 252'''' of the cylinder 240'''' as shown in FIG. 4 and then travels diagonally to the central axis 252'''' of the cylinder 240''''. In other examples, angle 46''' may be provided with a different acuteness. For example, angle 46''' may be 30 degrees, or 40 degrees, or between 40 and 50 degrees, or 60 degrees.

[0078] Reducing the angle 46''' that the working fluid must turn within the buffer tank 44''' may result in a smoother path that the fluid flow paths 41''' take as they pass through the compressor 1''', resulting in improved performance of the compressor 1''' by reducing the pressure drop as the working fluid flows from the common manifold 43''' to the fluid inlet passage 45'''.

[0079] In some examples, the cylinder head 10''' may include a valve plate (not shown in FIG. 4) at the top of the working chamber 251''' configured to provide seating and sealing for the intake valve 110''' and the discharge valve 120'''.

[0080] Figure 5 shows a detailed cross-sectional view of the alternative compressor 1'''', Figure 6 shows a detailed cross-sectional view of the valve system of compressor 1'''', Figure 7 shows a detailed bottom view of the cylinder head of compressor 1'''', and Figure 8 shows a detailed view of the discharge valve of compressor 1''''.

[0081] Referring first to FIG. 5, the compressor 1'''' comprises first and second cylinder heads 10A, 10B, a compressor block 20'''', a lubricant sump 30'''', a crankshaft 210'''' having a counterweight 220'''' for reducing vibration, and first and second connecting rods 211A, 211B connected between the crankshaft 210'''' and first and second pistons 240A, 240B disposed within first and second cylinders 250A, 250B to define first and second working chambers 251A, 251B. The compressor 1'''' further comprises first and second intake passages 40A, 40B configured to supply working fluid to the working chambers 251A, 251B during use. Compressor 1'''' is designed with a so-called "V" configuration, where first and second cylinders 250A, 250B are angularly separated by approximately 90°. Preferably, a V-configured compressor, such as the example described herein, may include an even number of cylinders 250A, 250B, although it may be envisioned that in some examples compressor 1'''' may be configured with an odd number of cylinders 250A, 250B.

[0082] Typically, the working fluid is preheated, evaporated, and superheated in one or more heat exchangers (not shown) before entering compressor 1'''', typically through a pipe, manifold, or network of pipes (not shown). The working fluid enters compressor 1'''' through a single common manifold 43'''', thereby providing a single entry point for the working fluid into compressor 1''''. In the example described here, as in the example above, common manifold 43'''' is located at the rear of compressor 1''''. It will be appreciated that in other examples the front and rear of compressor 1'''' may be reversed, and indeed in some examples common manifold 43'''' may be centrally located on the compressor rather than at the front or rear.

[0083] 5, after the working fluid enters the common manifold 43'''', it splits and travels from the common manifold 43'''' towards the front of the compressor 1'''', in two separate streams of working fluid (not shown) traveling in a downward direction, with a first working fluid stream traveling to a first buffer tank 44A and a second working fluid stream traveling to a second buffer tank 44B. For simplicity, the following description will only relate to the first fluid stream. However, it will be understood that the same description applies mutatis mutandis to the second fluid stream.

[0084] The first fluid flow proceeds from the first buffer vessel 44A through the first connection 42A upward towards the top of the compressor 1'''', via the first fluid inlet passage 45A into the first working chamber 251A. Briefly, in the example described here, the working fluid proceeds across the compressor 1'''', and then upward through the first buffer vessel 44A towards the top of the compressor 1'''''.

[0085] As the first piston 240A moves away from the cylinder head 10A and expands the volume of the working chamber 251A, suction causes working fluid to flow into the first working chamber 251A through the first intake valve 110A, which in the example described herein is a poppet valve.

[0086] The rotational movement of the crankshaft 210'''' causes a translatory movement of the first piston 240A inside the first cylinder 250A, periodically "moving" the piston 240A down to a bottom dead center (BDC) position where the suction process stops. The compressor 1'''' then starts compressing the working fluid in the first working chamber 251A until the working fluid reaches a pressure that exceeds the pressure in the discharge passage 50A, after which the discharge process begins when the first discharge valve 120A, which in the example described here is a reed valve, opens due to the pressure differential across the reed blades as described above.

[0087] The same steps are performed for the second piston 240B in the second cylinder 250B, as described above. The first outlet passage 50A may continue to a manifold, pipe, or the like, where a fluid connection may be made to the second outlet passage 50B to allow the working fluid flows to be combined, and the combined flows may be further directed to one or more heat exchangers (not shown), where the working fluid is cooled, typically from a superheated state, condensed, and optionally subcooled. In other examples, one or more of these processes may be applied, or other processes may be applied to the discharged working fluid.

[0088] The first and second intake valves 110A, 110B are actuated by conventional valve actuation mechanisms, the design and selection of which are well within the skill of those in the art.

[0089] The first intake passage 40A is partially within the first cylinder head 10A and partially within the compressor block 20'''', and the two portions of the first intake passage 40A are connected by a first connection portion 42A.

[0090] In the example described herein, the working fluid in the first fluid stream travels across compressor 1'''' and upwardly to the top of compressor 1''''.

[0091] While the working fluid paths have only been described above with reference to the first buffer vessel 44A, it will be appreciated that the second buffer vessel 44B may also be configured similarly to that described for the first buffer vessel 44A. It will also be appreciated that in examples having more cylinders, for example 16 cylinders, some or all of the buffer vessels may be as described above for the first buffer vessel 44A.

[0092] 5, the first buffer tank 44A has a large volume compared to the common manifold 43'''' and piping leading to the first buffer tank 44A. As can be seen from FIG. 5, the first buffer tank 44A is located directly adjacent to the first working chamber 251A with only the necessary fluid inlet passage 45A connecting the first buffer tank 44A and the first working chamber 251A. This allows the first buffer tank 44A to maintain a sufficient volume of working fluid, thereby preventing a large pressure drop when the working fluid is drawn into the first working chamber 251A. Such a large pressure drop could occur if the relatively narrow piping between the common manifold 43'''' and the first buffer tank 44A extended directly to the working chamber 251A without entering a larger volume area. In this regard, the first buffer tank 44A is sufficiently large in volume relative to the first working chamber 251A such that when a volume of working fluid equal to the volume of the first working chamber 251A when the first piston is at the bottom dead center position, i.e., the entire volume of the first working chamber 251A, is withdrawn from the first buffer tank 44A, there is no significant pressure drop in the fluid therein. In this regard, the first working chamber 251A always has available to it a sufficiently pressurized fluid. Furthermore, the first buffer tank 44A can be continuously "topped off" by continuously supplying working fluid from the common manifold 43'''' to the first buffer tank 44A, rather than the first working chamber 251A drawing fluid from the entire intake passage 40A, which would result in a pressure drop. Reducing or eliminating the significant pressure drop improves the performance of the compressor 1''''.

[0093] 5, once compressor 1'''' is assembled and ready for operation, for example in a heat pump system, there are several internal volumes 60'''' within compressor 1'''' that are pressurized due to the properties of the working fluid being used. Therefore, compressor 1'''' needs to be sealed against the atmosphere. To still provide practical access to the critical internal volumes 60'''' of compressor 1'''', compressor 1'''' is provided with pressure reinforcement covers 101A, 101B, 201A, 201B that are strong enough to withstand the internal pressures of internal volumes 60'''' of compressor 1'''' when pressurized, while still providing practical access during assembly, maintenance, or other relevant reasons.

[0094] The lubricant reservoir 30'''' is equipped with a number of lubricant heaters 301'''' embedded in the main block 300'''' of the lubricant reservoir 30''''. These heaters 301'''' can be operated by a standard control system (not shown) when required.

[0095] FIG. 6 shows a detailed view of the intake and exhaust of the first working chamber 251A and the associated components mentioned above.

[0096] FIG. 7 shows a detailed cross-sectional view of the first cylinder head 10A of compressor 1'''', where the first cylinder head 10A contacts the compressor block 20''''. It can be seen that the first inlet valve 110A is surrounded by the first outlet valve 120A. The first outlet valve 120A comprises a first valve plate 140A having a plurality of first outlet valve slots 142A and corresponding first outlet valve bridges 143A between the slots 142A. In the example described here, the plurality of first outlet valve slots 142A are arranged concentrically, but it will be understood that other arrangements are possible.

[0097] The first discharge valve slot 142A provides fluid communication between the first working chamber 251A (shown in FIGS. 5 and 6) and the first discharge passage 50A. In some examples (not shown), the first valve plate 140A may be omitted and its function may be replaced by a cylinder head main block (not shown), as will be appreciated by those skilled in the art.

[0098] The cross-sectional view of FIG. 7 also shows the first connection portion 42A and the first discharge passage 50A.

[0099] FIG. 8 shows a detailed view of the first discharge valve 120A. The first discharge valve 120A includes a first reed valve blade 121A that presses against a first valve slot 142A of a first valve plate 140A to close the first discharge valve 120A. A separate first reed valve spring 123A presses against a first valve retainer plate 122A on the opposite side of the first reed valve blade 121A, thereby providing a closing force to the first reed valve blade 121A. In another example, the spring force provided by the first reed valve spring 123A may be provided by forming the first reed valve blade 121A from a spring material and arranging the first reed valve blade 121A to automatically close the discharge valve 120A by its own inherent spring force (such an arrangement is shown in FIGS. 1-4). However, in the preferred embodiment shown in Figures 5-8, a separate first reed valve spring 123A is used, so that the first reed valve blade 121A can be made of a non-spring material.

[0100] In the present invention, as can be seen from Fig. 8, the first valve plate 140A is provided with a first recess 141A. In order to reduce the contribution of the first reed valve slot 142A to the dead volume, the first recess 141A extends to the area including the first reed valve slot 142A. The first recess 141A is formed by machining away this area which does not require the full thickness of the first valve plate 140A, so that material can be machined away without compromising the required stiffness.

[0101] Volumetric efficiency is a key performance factor of any compressor and is closely related to the dead volume of the compressor cylinder. Dead volume is the combination of non-displaceable (by the piston) volume caused by two main factors: first, the clearance volume required to ensure that the piston does not collide with the cylinder head, valve plate or valves due to manufacturing tolerances, valve movement, gasket thickness variations, etc., and second, the negative volume required as part of ports, slots, etc., which require a certain material thickness to accommodate them.

[0102] Referring again to FIG. 6, the first piston 240A includes a first piston crown 241A including a first crown recess 242A and a first crown protrusion 243A. The first crown recess 242A is provided such that the intake valve 110A enters the first crown recess 242A to replace a majority of its volume when the first piston 240A is near top dead center (TDC) during operation. Although the first crown protrusion 243A is found on both sides of the first crown recess 242A, it will be readily appreciated that the first crown protrusion 243A is annular on the first piston 240A. The first crown protrusion 243A is aligned with the first recess 141A such that the first crown protrusion 243A enters the first recess 141A to replace a majority of its volume when the first piston 240A is near top dead center (TDC) during operation. By providing the first crown protrusion 243A and the first crown recess 242A, the dead volume is reduced, thereby improving the volumetric efficiency.

[0103] Referring now to FIG. 9, compressor 1'''' is again shown, but this time with an optional lubricant return system 400 comprising an inlet 401'''' fluidly connected to the underside of first buffer tank 44A. Inlet 401'''' communicates lubricant to tank 402'''', where it is temporarily stored during use. Tank 402'''' comprises a valve 403'''' selectively openable to transfer lubricant from tank 402'''' to lubricant tank 30''''. Valve 403'''' may be configured with a timer such that valve 403'''' opens to return lubricant to lubricant tank 30'''', for example every 20, 30, 40 seconds. As an alternative or in addition to a timer, valve 403'''' may be configured to be selectively opened by a user of the system, or automatically opened when a certain amount of lubricant has collected in tank 402''''. Although shown in FIG. 9 in connection with only the first buffer vessel 44A, it will be understood that only one, all, or some of the buffer vessels may be provided with a lubricant return system 400''''. For example, if 16 cylinders are used, 16 lubricant return systems 400'''' may be provided. In some examples with multiple buffer vessels, the lubricant from each buffer vessel may be conveyed and collected in a tank before being returned to the lubricant vessel 30''''. In some examples, a valve (not shown) may be provided at the inlet 401'''' to selectively control the supply of lubricant to the tank 402''''. In other examples, the tank 402'''' may not be present.

[0104] In any of the above examples, the intake passages 40', 40'', 40''', 40A, 40B and / or the discharge passages 50', 50'', 50''', 50A, 50B may be formed during casting of the cylinder heads 10', 10'', 10''', 10A, 10B and compressor blocks 20', 20'', 20''', 20'''', respectively.

[0105] The compressor described herein allows a lower pressure drop to be maintained across the suction valve during operation, thereby maintaining greater compressor efficiency when utilizing more demanding working fluids, especially those with higher densities.

[0106] Poppet and reed valves are described in this disclosure. It will be understood that the reed valves may be replaced by any one or more self-actuating check valves, and the poppet valves may be replaced by any one or more non-self-actuating valves. By way of non-limiting example only, known arrangements of self-actuating check valves are briefly described with reference to Figs. 10a through 12b. Referring initially to Figs. 10a, 10b, there is shown a first self-actuating check valve 500 configured to move from a closed position shown in Fig. 10a to an open position shown in Fig. 10b. The self-actuating check valve 500 comprises a valve plate 510 and first and second reed elements 521, 522 biased to close first and second holes 531, 532, respectively, in the valve plate 510 in the absence of sufficient pressure in the direction of arrow A. The self-actuating check valve 500 further comprises first and second curved stop plates 541, 542 configured to inhibit movement of the first and second reed elements 521, 522 when the reed elements 521, 522 move to the open position.

[0107] As another non-limiting example, another self-actuating check valve 600 in the form of a plate valve is provided, configured to move from a closed position shown in Fig. 11a to an open position shown in Fig. 11b. The self-actuating check valve 600 comprises a valve plate 610 and first, second and third biased closure elements 621, 622, 623 biased to close first, second and third holes 631, 632, 633 of the valve plate 610, respectively, in the absence of sufficient pressure in the direction of arrow A. The self-actuating check valve 600 further comprises first, second and third stop plates 641, 642, 643 configured to block the movement of the biased closure elements 621, 622, 623 when the first, second and third biased closure elements 621, 622, 623 move to the open position shown in Fig. 11b. The actual biasing means used are not shown, but it will be understood that the biasing can be performed in a myriad of ways.

[0108] As another non-limiting example, another self-actuating check valve 700 is provided that is configured to move from a closed position shown in Figure 12a to an open position shown in Figure 12b. The self-actuating check valve 700 includes a valve plate 710 and first, second and third spring biased poppet elements 721, 722, 723 that are biased to close first, second and third holes 731, 732, 733, respectively, in the valve plate 710 in the absence of sufficient pressure in the direction of arrow A.

[0109] As noted above, reed and poppet valves are referenced throughout this disclosure. However, it will be appreciated that the reed valve or valves may be replaced with any self-actuating check valve or valves, and the poppet valve or valves may be replaced with any non-self-actuating valve or valves. The self-actuating valve may be any of the non-limiting examples shown in Figures 10-12, or any other self-actuating valve.

[0110] It will also be recognized that "self-actuating" is intended to have its standard meaning within the art, i.e., a self-actuating valve opens and closes passively, i.e., in response to fluid pressure within a system, rather than being actuated by an external electrical or mechanical source provided for that purpose. Similarly, "non-self-actuating" is also intended to have its standard meaning within the art, i.e., a valve is actively actuated, rather than opening and closing in response to fluid pressure within a system.

[0111] As of this writing, the term "high temperature heat pump" will be understood to generally refer to a heat pump capable of providing an output temperature above 55 degrees Celsius. Those skilled in the art will recognize that the definition of "high temperature" in this context may change over time, and that it is foreseeable that in the future, due to advances in technology, "high temperature" may be used to refer to heat pumps having output temperatures, for example, above 80 degrees Celsius, or even higher.

[0112] In the above description, there are some features of the described examples that are well known to those skilled in the art, but which have been omitted or at least not described in detail for the sake of brevity. Furthermore, while the preferred examples comprise heat pump compressors, and more specifically heat pump compressors that utilize condensable gases, the invention is not so limited and may equally relate to other applications requiring a compressor, such as air compressors, natural gas compressors, CO2 compressors, etc.

[0113] It will be appreciated that multiple non-self-actuating valves may together form an "intake valve," i.e., there need not be one single non-self-actuating valve element that forms the entire intake valve. Similarly, multiple self-actuating check valves may together form an "exhaust valve," i.e., there need not be one single self-actuating check valve element that forms the entire exhaust valve.

[0114] For example, as shown in the example described with reference to Figure 2, there are two self-actuating check valve discharge elements forming the discharge valve. It will be appreciated that in some examples (not shown) there may likewise be two, three, four or more non-self-actuating intake valve elements forming the intake valve.

Claims

1. A reciprocating compressor (1', 1'', 1''', 1''"), comprising: an intake valve (110', 110'', 110''', 110A, 110B); A discharge valve (120', 120'', 120''', 120A); and an operating chamber (251', 251'', 251''', 251A, 251B), a reciprocating compressor (1', 1'', 1''', 1''"), wherein the suction valve (110', 110'', 110''', 110A, 110B) is configured to provide fluid communication between the suction passage (40', 40'', 40''', 40A, 40B) and the working chamber (251', 251'', 251''', 251A, 251B), and the discharge valve (120', 120'', 120''', 120A) is configured to provide fluid communication between the working chamber (251', 251'', 251''', 251A, 251B) and the discharge passage (50', 50'', 50''', 50A, 50B), the suction valve (110', 110", 110'", 110A, 110B) comprises at least one non-self-actuating valve, and the discharge valve (120', 120", 120'", 120A) comprises at least one self-actuating check valve.

2. 2. The reciprocating compressor (1', 1'', 1''', 1'''') of claim 1, wherein the self-actuated check valve comprises one or more of a reed valve, a plate valve, a self-actuated poppet valve, and a self-actuated ball check valve.

3. 10. The reciprocating compressor (1', 1'', 1''', 1'''') of any one of the preceding claims, wherein the non-self-actuating valves are one or more of poppet valves, rotary valves, piston valves, slide valves, and spool valves.

4. 10. The reciprocating compressor (1', 1'', 1''', 1'''') according to any one of the preceding claims, wherein the non-self-actuated valves are one or more of mechanically controlled, pneumatically controlled, electrically controlled, and hydraulically controlled.

5. a compressor block (20', 20", 20''', 20"") having at least one cylinder (250', 250", 250A, 250B) with a piston (240', 240", 240'", 240A, 240B) disposed for reciprocating movement therein; At least one cylinder head (10', 10'', 10''', 10A, 10B), The reciprocating compressor (1', 1'', 1''', 1'''') according to any one of the preceding claims, wherein the suction valve (110', 110'', 110''', 110A, 110B) is disposed in the cylinder head (10', 10'', 10''', 10A, 10B).

6. 6. The reciprocating compressor (1', 1'', 1''', 1'''') of claim 5, wherein the suction valve (110', 110'', 110''', 110A, 110B) is located on a central longitudinal axis (252', 252'', 252''') of the at least one cylinder (250', 250'', 250A, 250B).

7. The reciprocating compressor (1', 1'', 1''', 1'''') according to claim 5 or 6, wherein the at least one cylinder head (10', 10'', 10''', 10A, 10B) comprises a valve plate.

8. The at least one cylinder (250A, 250B) comprises a first cylinder (250A) in which a first piston (240A) is arranged to reciprocate therein, and a second cylinder (250B) in which a second piston (240B) is arranged to reciprocate therein; The at least one cylinder head (10A, 10B) comprises a first cylinder head (10A) and a second cylinder head (10B); 8. The reciprocating compressor (1"") according to any one of claims 5 to 7, wherein the first cylinder head (10A) is configured to connect with the first cylinder (250A) and the second cylinder head (10B) is configured to connect with the second cylinder (250B).

9. 9. The reciprocating compressor (1"") of claim 8, wherein the first cylinder (250A) and the second cylinder (250B) are disposed at approximately 90 degrees relative to each other to form a V-shaped configuration.

10. The reciprocating compressor (1', 1'', 1''', 1'''') of any one of the preceding claims, wherein the at least one discharge valve (120', 120'', 120''', 120A) is a plurality of self-actuated check valves.

11. The reciprocating compressor (1', 1'', 1''', 1'''') of any one of the preceding claims, wherein the discharge valve (120', 120'', 120''', 120A) is arranged concentrically with the suction valve (110', 110'', 110''', 110A, 110B).

12. The reciprocating compressor (1', 1'', 1''', 1'''') of claim 10, wherein the plurality of self-actuating check valves are each concentric with the suction valve (110', 110'', 110''', 110A, 110B).

13. The reciprocating compressor (1', 1'', 1''', 1'''') according to any one of claims 5 to 9 or, when dependent from claim 5, according to any one of claims 10 to 12, wherein the suction valves (110', 110'', 110''', 110A, 110B) and / or discharge valves (120', 120'', 120''', 120A) are arranged such that their central axis is shared with the central axis (252', 252'', 252''') of the at least one cylinder (250', 250'', 250A, 250B).

14. 13. The reciprocating compressor (1"") according to any one of claims 5 to 9, or, when dependent on claim 5, any one of claims 10 to 12, wherein the piston (240A) is provided with at least one protrusion (243A) and the cylinder head is provided with at least one cylinder head recess (141A), the at least one protrusion (243A) and the at least one cylinder head recess (141A) being aligned such that, in use, the protrusion (243A) displaces at least a part of a volume of the cylinder head recess (141A).

15. 15. The reciprocating compressor (1"") of claim 14, wherein the at least a portion of the volume of the cylinder head recess (141A) is at least 50%, or at least 60%, or at least 70% of the volume of the recess, or is a majority of the volume of the cylinder head recess (141A).

16. The reciprocating compressor (1"") according to claim 14 or 15, wherein the at least one protrusion (342A) is a plurality of protrusions and the at least one cylinder head recess (141A) is a plurality of cylinder head recesses.

17. 17. The reciprocating compressor (1"") according to any one of claims 5 to 9, or, when dependent on claim 5, any one of claims 10 to 16, wherein the piston (240) is provided with at least one piston recess (242A) that is shaped and configured to receive a non-self-actuating valve in use.

18. 18. The reciprocating compressor (1"") of claim 17, wherein the piston recess (242A) is configured such that, during use, the non-self-actuated valve displaces at least 50%, or at least 60%, or at least 70%, or a majority of the volume of the piston recess (242A).

19. The suction passage (40A) is a first portion formed in said compressor block (20''''); a second portion formed in the at least one cylinder head (10A), 19. The reciprocating compressor (1"") according to any one of claims 5 to 9, or according to any one of claims 10 to 18 when dependent on claim 5, wherein the first and second parts are configured to be connected at a connection (42A) to form a fluid flow path between the first and second parts for delivering working fluid to the working chamber (251A) in use.

20. 20. The reciprocating compressor (1"") of claim 19, wherein the first portion of the suction passage (40A) comprises a fluid inlet passage adjacent the connection portion (42A) when the first and second portions are connected in use, the fluid inlet passage configured to direct fluid at an angle of 20 degrees to 80 degrees relative to a normal on a cylinder central axis (252A).

21. 21. The reciprocating compressor (1'''') of claim 20, wherein the angle is about 45 degrees.

22. The reciprocating compressor (1"") according to any one of claims 19 to 21, wherein the first portion comprises a buffer tank (44A).

23. 23. The reciprocating compressor (1') according to claim 22, wherein the buffer tank (44A) has a volume significantly larger than a volume of the working chamber (251A) such that there is no significant pressure drop in the buffer tank (44A) when working fluid is pumped out of the buffer tank (44A) to fill the working chamber (251A) during use.

24. The working chamber (251A) is a first working chamber (251A), and the suction passage (40A) is a first suction passage (40A), The compressor (1', 1'', 1''', 1'''') further comprises a second working chamber (251B) and a second suction passage (40B); 13. The reciprocating compressor (1', 1'', 1''', 1'''') of any one of the preceding claims, wherein the first inlet passage (40A) and the second inlet passage (40B) join to form a joined inlet passage (43'''') having an inlet for receiving a working fluid from the compressor.

25. The reciprocating compressor (1', 1'', 1''', 1'''') of claim 24, wherein the inlet comprises a manifold.

26. A heat pump comprising a reciprocating compressor (1', 1'', 1''', 1'''') according to any one of claims 1 to 25.

27. 27. The heat pump of claim 26, wherein the heat pump is a high temperature heat pump capable of providing an output temperature, during use, of greater than 55 degrees Celsius, greater than 80 degrees Celsius, greater than 90 degrees Celsius, greater than 100 degrees Celsius, greater than 110 degrees Celsius, greater than 120 degrees Celsius, greater than 130 degrees Celsius, greater than 140 degrees Celsius, greater than 150 degrees Celsius, greater than 160 degrees Celsius, greater than 170 degrees Celsius, greater than 180 degrees Celsius, greater than 190 degrees Celsius, greater than 200 degrees Celsius, greater than 210 degrees Celsius, greater than 220 degrees Celsius, greater than 230 degrees Celsius, greater than 240 degrees Celsius, or greater than 250 degrees Celsius.

28. Use of a reciprocating compressor (1', 1'', 1''', 1'''') according to any one of claims 1 to 25 in a heat pump.

29. A method of operating a reciprocating compressor (1', 1'', 1''', 1'''') according to claim 1, comprising the steps of: a step a) of drawing a working fluid into the working chamber (251', 251'', 251''', 251A, 251B) through the at least one non-self-actuating valve; and b) discharging the working fluid from said working chamber (251', 251'', 251''', 251A, 251B) via said at least one self-actuating check valve.

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