Variable compressor

Abstract

A compressor (10) is proposed that comprises a compressor cylinder (12), a compressor piston (14), an inlet valve (16), an outlet valve (18), and an actuator (202). The compressor cylinder (12) and the compressor piston (14) jointly form a compression chamber (20) arranged to compress gas when operating the compressor (10). The inlet valve (16) is a check valve arranged to allow gas to enter the compression chamber (20), and the outlet valve (18) is a check valve arranged to allow gas to exit the compression chamber (20). The actuator (202) is connected to the inlet valve (16) and arranged to selectively force the inlet valve (16) to be open.

Description

TECHNICAL FIELD

[0001] The proposed technology generally relates to the field of compressors, and specifically to compressors powered by reciprocating engines.BACKGROUND

[0002] It is known to power compressors using reciprocating engines. The power is typically supplied to the compressor via a cycling clutch by which the compressor is operated intermittently to regulate the pressurization. It is also known to vary the pressurization using variable-displacement compressors.SUMMARY

[0003] An object of the proposed technology is to provide a compressor that can quickly adjust the output pressure. It is a specific object to provide a variable output pressure at a continuous operation of the compressor, preferably at a low power loss. It is a further object of the proposed technology to provide a compressor that can supply a wide range of output pressures. It is a specific object to provide a reciprocating compressor that is compact in the direction of reciprocation.

[0004] In a first aspect of the proposed technology, a compressor comprises: a compressor cylinder, a compressor piston, an inlet valve, and an outlet valve. The compressor cylinder and the compressor piston jointly form a compression chamber arranged to compress gas, or air, when operating the compressor. The inlet valve is a check valve arranged to allow gas to enter, or to allow an inflow of gas into, the compression chamber, and the outlet valve is a check valve arranged to allow gas to exit, or to allow an outflow of gas from, the compression chamber. Worded differently, the compressor is a reciprocating compressor, or a piston compressor. The compressor further comprises: an actuator. The actuator is connected, or operationally coupled, to the inlet valve and arranged to selectively force the inlet valve to be open. Worded differently, the actuator is connected to the inlet valve and arranged to force the inlet valve to be open when activated. It is understood that this may be to allow gas to exit the compression chamber via the inlet valve, or to allow a backflow of gas from the compression chamber via the inlet valve. This in turns allows for regulating the volume of the gas that is compressed, and in extension the resulting pressure.

[0005] In a second aspect of the proposed technology, a compressor-engine assembly comprises: a compressor, and an engine. The compressor is arranged to be powered, or driven, by the reciprocating engine. It is understood that the compressor may be a compressor according to the first aspect of the proposed technology. The engine may be a reciprocating engine, or piston engine. It is understood that the reciprocating engine is an internal combustion engine. For example, the engine may have pneumatically powered, or operated, engine valves, and the compressor, or the outlet of the compressor, may be coupled, or fluidly connected, to the engine valves to supply the engine valves with pressurized gas, or air.

[0006] In a third aspect of the proposed technology, a vehicle comprises: a compressor-engine assembly according to the second aspect of the proposed technology. For example, the vehicle may be a car, truck, airplane, or boat.

[0007] In a fourth aspect of the proposed technology, a method is provided for controlling a compressor. The compressor comprises: a compressor cylinder, a compressor piston, an inlet valve, and an outlet valve. The compressor cylinder and the compressor piston jointly form a compression chamber arranged to compress gas, or air, when operating the compressor. The inlet valve is a check valve arranged to allow gas to enter, or to allow an inflow of gas into, the compression chamber, and the outlet valve is a check valve arranged to allow gas to exit, or to allow an outflow of gas from, the compression chamber. The method may comprise: selectively forcing the inlet valve to be open. It is understood that this may be to allow gas to exit the compression chamber via the inlet valve, or to allow a backflow of gas from the compression chamber via the inlet valve.

[0008] It is understood that the compressor is a positive displacement and reciprocating compressor. The compressor may be a non-variable displacement compressor, or fixed displacement compressor. It is understood that that the compressor may be an air compressor. The compressor may be a single acting compressor. The compressor may be a single stage compressor. The compressor may be a single cylinder compressor. This means that the compressor cylinder is the only cylinder of the compressor, and that the compressor piston is the only piston of the compressor.

[0009] It is understood that the compressor piston may have a bottom dead center and a top dead center. The bottom dead center is the bottommost position of the compressor piston relative to the compressor cylinder, or to the compressor crankshaft described below. The top dead center is the topmost position of the compressor piston relative to the compressor cylinder, or to the compressor crankshaft described below. It is further understood that the compressor piston may have a stroke length. The stroke length is the distance the compressor piston travels in a full stroke, or between the bottom dead center and the top dead center. It is understood that the compressor piston can perform a compression stroke within the compressor cylinder corresponding to a change in position of the compressor piston from the bottom dead center to the top dead center. It is further understood that the compressor piston can perform an intake stroke within the compressor cylinder corresponding to a change in position of the compressor piston from the top dead center to the bottom dead center.

[0010] It is specified that the compressor cylinder and the compressor piston jointly form a compression chamber. It is understood that the compression chamber has a volume that changes when the compressor is operated. It is understood that the volume of the compression chamber is the largest at the bottom dead center and the smallest at the top dead center. The compression chamber has a swept volume, which is the change in the volume of the compression chamber at a transition from the bottom dead center to the top dead center. The compression chamber has a clearance volume i the top dead center of the compressor piston.

[0011] It is understood that a valve can be open or closed, and that passage through the valve is allowed when the valve is open and prevented when the valve is closed. A check valve is understood as a valve that normally allows passage of a fluid, such as gas, in only one direction. These valves are also called non-return valves or one-way valves.

[0012] It is understood that the inlet valve is fluidly connected to the compression chamber. It is specified that the inlet valve is a check valve arranged to allow gas to enter the compression chamber. It is further understood that the inlet valve may be arranged to open and allow gas to enter the compressor cylinder at a transition of the compressor piston from the top dead center to the bottom dead center, at an increase of the volume of the compression chamber, or at lower pressure in the compressor cylinder, or compression chamber, than outside of the inlet valve. It is further understood that the inlet valve may be arranged to close and prevent gas to exit the compressor cylinder at a transition from the bottom dead center to the top dead center, at a decrease of the volume of the compression chamber, or at higher pressure in the compressor cylinder, or compression chamber, than outside of the inlet valve.

[0013] It is understood that the outlet valve is fluidly connected to the compression chamber. It is specified that the outlet valve is a check valve arranged to allow gas to exit the compression chamber. It is further understood that the outlet valve may be arranged to open and allow gas to exit the compressor cylinder at a transition of the compressor piston from the bottom dead center to the top dead center, at a decrease of the volume of the compression chamber, or at a higher pressure in the compressor cylinder, or compression chamber, than outside outlet valve. It is further understood that the outlet valve may be arranged to close and prevent gas to enter the compressor cylinder at a transition from the top dead center to the bottom dead center, at an increase of the volume of the compression chamber, or at a lower pressure in the compressor cylinder, or compression chamber, than outside outlet valve.

[0014] The compressor may comprise a control unit that is connected to the actuator. It is understood that the control unit is arranged to control the operation, or function, of the actuator. The compressor, or the control unit, may be arranged to operate the actuator in one or more modes of operation. It is specified that the inlet valve is a check valve arranged to allow gas to enter the compression chamber. It is further specified that the actuator is arranged to selectively force the inlet valve to be open.

[0015] The compressor, or the control unit, may be arranged to operate, or selectively operate, the actuator to force the inlet valve to be open at the bottom dead center of the compressor piston. Worded differently, the compressor, or the control unit, may be arranged to operate, or selectively operate, the actuator to force the inlet valve to be open at the start of a compression stroke. This may be a first mode of operation. The proposed method may comprise: forcing the inlet valve to be open at the bottom dead center of the compressor piston.

[0016] The compressor, or the control unit, may be arranged to operate, or selectively operate, the actuator to force the inlet valve to be open at a change in position of the compressor piston from the bottom dead center towards the top dead center. Worded differently, the compressor, or the control unit, may be arranged to operate, or selectively operate, the actuator to force the inlet valve to be open over, or during, an initial stage of a compression stroke. This may be a second mode of operation. The proposed method may comprise: forcing the inlet valve to be open at a change in position of the compressor piston from the bottom dead center towards the top dead center.

[0017] The compressor, or the control unit, may be arranged to operate, or selectively operate, the actuator to force the inlet valve to be open at a complete transition of the compressor piston from the bottom dead center to the top dead center. Worded differently, the compressor, or the control unit, may be arranged to operate, or selectively operate, the actuator to force the inlet valve to be open during a complete compression stroke. This may be a third mode of operation. The proposed method may comprise: forcing the inlet valve to be open at a complete transition from the bottom dead center to the top dead center, or forcing the inlet valve to be open during a complete compression stroke. The operation described here allows for a backflow of gas from the compression chamber that empties the compression chamber, and no air is compressed. Effectively, this allows the compressor to idle with the compressor piston reciprocating. The power loss will be less compared with interrupting the flow of the compressed gas.

[0018] The compressor, or the control unit, may be arranged to operate, or selectively operate, the actuator to force the inlet valve to be open at a change in position of the compressor piston from the bottom dead center to an intermediate position, or selected intermediate position, between the bottom dead center and the top dead center. It is understood that the compressor, or the control unit, may further be arranged to operate, or selectively operate, the actuator to allow the inlet valve to be closed at a change in position of the compressor piston from the intermediate position to the top dead center. This may be a fourth mode of operation. The proposed method may comprise: forcing the inlet valve to be open at a change in position of the compressor piston from the bottom dead center to an intermediate position between the bottom dead center and the top dead center. The method may further comprise: allowing the inlet valve to be closed at a change in position of the compressor piston from the intermediate position to the top dead center. The operations described here allows for a backflow of gas from the compression chamber until the compressor piston reaches the intermediate position. This means that only a part of the swept volume is compressed, which reduces the generated pressure.

[0019] Worded differently, the compressor piston may have an intermediate position between the bottom dead center and the top dead center. It is understood that the intermediate position may be selected or predetermined. The compressor, or control unit, may be arranged to operate the actuator to transition from forcing the inlet to be open to allowing the inlet valve to be closed at the intermediate position. More specifically, the compressor, or the control unit, may be arranged to operate, or selectively operate, the actuator to force the inlet valve to be open at a transition from the bottom dead center to the intermediate position. It is understood that this is in a compression stroke of the compressor piston. It is understood that the compressor, or the control unit, may be arranged to operate, or selectively operate, the actuator to allow the inlet valve to be closed at a transition from the intermediate position to the top dead center. The compressor, or the control unit, may be arranged to operate, or selectively operate, the actuator at different intermediate position. The proposed method may comprise: forcing the inlet valve to be open at a transition from the bottom dead center to the intermediate position. It is understood that the method may further comprise: allowing the inlet valve to be closed at a transition from the intermediate position to the top dead center.

[0020] The compressor, or the control unit, may be arranged to operate, or selectively operate, the actuator to allow the inlet valve to be closed at a complete transition from the bottom dead center to the top dead center. Worded differently, the compressor, or the control unit, may be arranged to operate, or selectively operate, the actuator to allow the inlet valve to be closed during a complete compression stroke. This may be a fifth mode of operation. The proposed method may comprise: allowing the inlet valve to be closed at a complete transition from the bottom dead center to the top dead center, or allowing the inlet valve to be closed during a complete compression stroke. The operation described here allows for the compression of the full swept volume, which maximizes the generated pressure. This essentially corresponds to the function without an actuator present.

[0021] The compressor, or the control unit, may be arranged to dynamically determine, or select, between the different modes of operation described above, or to or to dynamically determine, or select, how to operate the actuator. More specifically, the compressor, or control unit, may be configured to receive a control signal and to determine, or select, a mode of operation based on the control signal, or to determine, or select, how to operate the actuator based on the control signal. The compressor, or the control unit, may be arranged to dynamically determine, or select, the intermediate position. Additionally or alternatively, the compressor, or control unit, may be arranged to receive a control signal and to determine, or select, the intermediate position depending on the control signal.

[0022] The compressor cylinder is understood as a structure of the compressor. The compressor cylinder may have a cylinder head. It is understood that the cylinder head contributes to enclose the compression chamber. It is further understood that that the compressor piston moves towards the cylinder head at a transition from the bottom dead center to the top dead center, and that the compressor piston moves away from the cylinder head at a transition from the top dead center to the bottom dead center.

[0023] The inlet valve may be located at the cylinder head. Similarly, the outlet valve may be located at the cylinder head. The cylinder head may have a top-cylinder face that faces the compressor piston. The top-cylinder face may outline, or define, a planar geometry. Worded differently, the top-cylinder face may be planar, or flat. It is understood that the compressor cylinder, or the cylinder bore, has a compressor-cylinder axis. It is further understood that the compressor piston is arranged to reciprocate along the compressor-cylinder axis. It is understood that the compressor cylinder head may form part of the inlet valve and / or the outlet valve, or vice versa.

[0024] It is understood that the compressor piston is arranged to reciprocate within the compressor cylinder when operating the compressor. The compressor piston may have a piston seal arranged to prevent gas from passing between the compressor piston and the compressor cylinder. It is understood that the compressor cylinder has a cylinder bore and that the compressor piston conforms to the cylinder bore. For example, the cylinder bore may have a circular cross-section.

[0025] The compressor cylinder, or the cylinder bore of the compressor cylinder, may have a cylinder diameter. It is understood that the cylinder diameter is perpendicular, or transverse, to the compressor-cylinder axis described above. The cylinder diameter may be more than two times, three times, or four times greater than the stroke length of the compressor piston. In other words, the compressor piston may be a short-stroke piston.

[0026] The compressor may have an inlet and an outlet, the inlet is arranged to receive gas, or air, to the compressor, and the outlet is arranged to expel compressed gas, or air, from the compressor. The compressor may have, or form, an inlet conduit, or inlet duct, arranged to lead gas, or air, from the inlet to the inlet valve. The compressor may have, or form, an outlet conduit, or outlet duct, arranged to lead gas, or air, from the outlet valve to the outlet.

[0027] The compressor may have a compressor housing. It is understood that the compressor cylinder and / or the cylinder head may be connected to, or form part of, the compressor housing. Worded differently, the compressor housing may form the compressor cylinder and / or the cylinder head. The compressor housing may form the inlet and / or the outlet. The compressor housing may form the inlet conduit and / or the outlet conduit.

[0028] It is understood that the compressor may comprise a compressor crankshaft that is operationally connected to the compressor piston and arranged to reciprocate the compressor piston at a rotation of the compressor crankshaft. The compressor may comprise a compressor connecting rod, wherein the compressor connecting rod is rotationally connected to the compressor crankshaft and pivotally connected to the compressor piston. It is further understood that the compressor crankshaft and compressor connecting rod are arranged to convert a rotation of the compressor crankshaft to a reciprocating linear motion of the compressor piston inside the compressor cylinder. For example, the compressor crankshaft may have a crank pin, the compressor may comprise a rod bearing centered on the crank pin, and the compressor connecting rod may be connected to the crank pin via the rod bearing. For example, the rod bearing may be a rolling-element bearing. It is understood that the compressor crankshaft may be arranged to rotate around a compressor crankshaft axis. It is further understood that the crank pin is spaced apart from the compressor crankshaft axis. The compressor may comprise a piston pin that pivotally connects the compressor connecting rod to the compressor piston.

[0029] The compressor housing may form a compressor crankcase, wherein the compressor connecting rod is connected to the compressor crankshaft inside the compressor crankcase. It is specified above that the compressor housing may have an inlet conduit arranged to lead gas from the inlet to the inlet valve. The compressor crankcase may form part of the inlet conduit. Worded differently, the compressor crankcase may be fluidly connected to the inlet conduit, or to the inlet and the inlet valve. This allows for the compressor piston to form a partial vacuum in the inlet conduit during a compression stroke, which contributes to fill the inlet conduit with gas, or air, via the inlet.

[0030] The compressor may comprise an oil squirter, or nozzle, arranged to expel an oil into the inlet conduit, or into the compressor crankcase. The oil squirter may be arranged to expel the oil towards the compressor crankshaft and the compressor connecting rod. It is understood that the oil may be intended to lubricate and / or cool the compressor. It is specified that the oil may be expelled into the inlet conduit, which means that it will mix with gas, or air, that reaches the inlet valve, compression chamber, and outlet valve and lubricate and cool these parts.

[0031] It is specified that the compressor comprises an inlet valve. Worded differently, it may comprise a suction valve or intake valve. It is understood that the inlet valve can be open or closed, and that gas can pass through the inlet valve when open and gas is prevented from passing through the inlet valve when closed. The inlet valve may be normally closed. Worded differently, the inlet valve may biased itself to be closed. For example, the inlet valve may comprise a spring arrangement that biases the inlet valve to be closed. It is understood that the inlet valve has an inside and an outside relative to the compressor cylinder, or relative to the compression chamber. The inside is in fluid communication with the compression chamber when the inlet valve is open and closed. The outside is in fluid communication with the compression chamber when the inlet valve is open and not in fluid communication with the compression chamber when the inlet valve is closed. Worded differently, the inside is exposed to the compression chamber and the outside is exposed to the inlet conduit. The inlet valve may extend through the cylinder head. More specifically, the inlet valve may be arranged to lead gas, or air, through the cylinder head.

[0032] The inlet valve may be a poppet valve. The poppet valve may comprise a stem, or shaft, a head, or plug, and a valve seat, wherein the stem is connected, or attached, to the head, the head and stem can move relative to the valve seat, and the head is arranged to cooperate with the valve seat. It is understood that the head may be arranged to cooperate with the valve seat to allow or prevent passage of gas through the poppet valve. It is understood that the poppet valve, or more specifically the head of the poppet valve, is arranged to bias the head towards, or against the valve seat, or to bias the poppet valve to be closed, at a higher pressure in the compressor cylinder than in the inlet conduit, or at a higher pressure on the inside of the poppet valve than on the outside of the poppet valve. It is further understood that the poppet valve is arranged to bias the head away from the valve seat, or to bias the poppet valve to be open, at a lower pressure in the compressor cylinder than in the inlet conduit, or at a lower pressure on the inside of the poppet valve than on the outside poppet valve. It is understood that the head contacts the valve seat and prevents gas from passing from the compression chamber between the head and the valve seat when the poppet valve is closed. It is further understood that the poppet valve forms a gap between the head and the valve seat that allows gas to pass into the compression chamber when the poppet valve is open. The valve seat may form part of the cylinder head. Worded differently, the cylinder head may form the valve seat.

[0033] It is understood that the stem can move relative to the valve seat. The poppet valve may further comprise a valve guide arranged to cooperate with the valve stem and guide the stem and head relative to the valve seat. It is understood that the stem is elongated. It is further understood that the head can be disc shaped and arranged perpendicular, or transversely, to the stem. The stem may have a tip at one end and may be connected to the head at the other end.

[0034] The actuator may be connected to the stem. Worded, differently, the actuator may be arranged to operate the poppet valve via the stem. More specifically, the actuator may be connected to the tip of the stem.

[0035] It is specified that the inlet valve may be normally closed, and that the inlet valve may comprise a spring arrangement that biases the inlet valve to be closed. The poppet valve, or the spring arrangement, may comprise a spring retainer and a coil spring. The spring retainer is attached to the stem, for example at the tip of the stem. The coil spring may be centered on the stem. The coil spring may be arranged to bias the spring retainer relative to the compressor cylinder, or the cylinder head. It is understood that the coil spring biases the poppet valve to be closed.

[0036] The poppet valve may comprise a valve body that forms the valve seat. The valve body may further form the valve guide. The coil spring may be arranged to bias the spring retainer relative to the valve body. The valve body may be attached to the compressor cylinder, or to the cylinder head. In extension, this means that the coil spring is arranged to bias the spring retainer relative to the compressor cylinder, or the cylinder head.

[0037] The head of the poppet valve may have an inner face that faces the compressor piston. The inner face may outline, or define, a planar geometry. Worded differently, the inner face may be planar, or flat. This contributes to reduce the clearance volume. It is specified that the top-cylinder face of the cylinder head may outline a planar geometry. The inner face and the top-cylinder face may be co-planar when the poppet valve is closed. More specifically, the valve body may position the inner face of the head of the poppet valve and the inner side of the cylinder head in co-planar relationship when the poppet valve is closed. It is understood that the head of the poppet valve may move towards the compressor piston, or into the compression chamber, at a transition of the inlet valve from closed to open.

[0038] It is specified that the compressor comprises an outlet valve. Worded differently, it may comprise a discharge valve, exhaust valve, or delivery valve. It is understood that the outlet valve can be open or closed, and that gas can pass through the outlet valve when open and gas is prevented from passing through the outlet valve when closed. The outlet valve may be normally closed. Worded differently, the outlet valve may be biased to be closed. For example, the outlet valve may comprise a spring arrangement that biases the outlet valve to be closed. It is understood that the outlet valve has an inside and an outside relative to the compressor cylinder, or relative to the compression chamber. The inside is in fluid communication with the compression chamber when the outlet valve is open and closed. The outside is in fluid communication with the compression chamber when the outlet valve is open and not in fluid communication with the compression chamber when the outlet valve is closed. Worded differently, the inside is exposed to the compression chamber and the outside is exposed to the outlet conduit.

[0039] The outlet valve may be a plate valve. The plate valve may be located at the cylinder head. The plate valve may comprise a valve plate or movable part, a guard or stop, and a valve seat, wherein the valve plate is located between the guard and the valve seat. It is understood that the valve plate is arranged to cooperate with the valve seat to allow or prevent passage of gas through the plate valve. It is understood that the valve plate may be located between the guard and the cylinder head. The guard is arranged to retain the valve plate relative to the valve seat. The guard or stop may be a guard plate or stop plate. A plate is understood as a structure that is flat and has an overall planar shape. The guard or guard plate may be attached to, or fixed relative to, the cylinder head.

[0040] The valve plate may be perpendicular to, or transverse to, the compressor-cylinder axis, or parallel with, or aligned with, the planar geometry outlined by the top-cylinder face. The cylinder head may be located between the valve plate and the compression chamber. It is understood that the plate valve is arranged to bias the valve plate towards, or against the valve seat, or to bias the plate valve to be closed, at a lower pressure in the compressor cylinder than outside plate valve. It is further understood that the plate valve is arranged to bias the valve plate away from the valve seat, or to bias the plate valve to be open, at a higher pressure in the compressor cylinder than outside plate valve.

[0041] It is understood that the valve plate contacts the valve seat and prevents gas from passing from the compression chamber between the valve plate and the valve seat when the plate valve is closed. It is further understood that the valve plate is spaced apart from the valve seat and allows gas to exit the compression chamber between the head and the valve seat when the plate valve is open. The valve seat may form part of the cylinder head. Worded differently, the cylinder head may form the valve seat. For example, the valve plate may be of polyether ether ketone, polyamide, glass- or carbon-fiber reinforced plastics, or steel.

[0042] The valve plate may comprise a plurality of guide holes and the plate valve has a plurality of guide pins, wherein each guide hole is a through hole and each guide pin extends through a guide hole, and the guide holes and the guide pins are arranged to cooperate and guide the valve plate at a transition of the plate valve between open and closed. Each guide pin may be connected to the cylinder head and the guard, or guard plate. The guide holes and guide pins may be arranged to prevent, or limit, a movement of the valve plate in a direction parallel, or aligned, with the valve plate, or perpendicular to the compressor cylinder axis.

[0043] The valve plate may be biased against, contact, or be flush with, the guard, or guard plate, when the plate valve is fully open. It is specified that the outlet valve may be normally closed. The plate valve, or the spring arrangement, may comprise a plurality of coil springs that are spaced apart relative to one another. Each coils spring may be centered on a guide pin. The coil springs may be arranged to bias the valve plate relative to, or away from, the guard, or guard plate, or to bias the valve plate relative to, or towards, the valve seat, or the cylinder head. It is understood that the coil springs bias the plate valve to be closed. The coil springs may be conical springs. This contributes to a more compact plate valve.

[0044] It is specified that the valve plate may be biased against, contact, or be flush with, the guard, or guard plate, when the plate valve is fully open. The guard, or guard plate, may have a plurality of countersinks, or recesses, wherein each countersink is located at a coil spring and arranged to receive the complete coil spring when the plate valve is fully open, or at a biasing, or contact, between the valve plate and the guard, or guard plate. This contributes to a more compact plate valve. It is understood that the abovementioned guide pins may be connected to the guard, or guard plate, within the countersinks.

[0045] The cylinder head may form, or have, a plurality of cylinder-head apertures, and the outlet valve, or more specifically the plate valve, may be fluidly connected to the compression chamber via the plurality of cylinder-head apertures. It is understood that the cylinder-head apertures are arranged to allow gas to exit the compression chamber via the cylinder-head apertures. The cylinder-head apertures may form part of the compression chamber. For example, they may partly form the clearance volume.

[0046] The valve seat may comprise a plurality of annular ridges, wherein each cylinder-head aperture is encircled, or enfolded, by one of the annular ridges. It is understood that the annular ridges may extend from the cylinder head towards the valve plate. Each annular ridge may be located at the cylinder-head aperture it encircles. Each annular ridge may outline a shape corresponding to, or congruent with, the shape of the cylinder-head aperture it encircles. The annular ridges may form part of the cylinder head. Worded differently, the cylinder head may form the annular ridges, or the annular ridges may be attached to the cylinder head. The valve plate may be biased against the annular ridges when the plate valve is closed, or at a lower pressure in the compressor cylinder than in the outlet conduit, or at a lower pressure on the inside of the plate valve than on the outside of the plate valve. The annular ridges contribute to a faster opening of the plate valve. It is understood that the valve plate covers the cylinder head apertures when the plate valve is closed. The cylinder-head apertures may be elongated. Additionally, the cylinder-head apertures may be straight. This is advantageous in combination with the protrusions described below. It is understood that the cylinder-head apertures are elongated in a direction perpendicular, or transverse, to the compressor-cylinder axis, or parallel, or aligned, with the planar geometry outlined by the top-cylinder face.

[0047] The cylinder-head apertures may be divided into a first group and a second group, the cylinder-head apertures in the first group are aligned, or parallel, the cylinder-head apertures in the second group are aligned, or parallel, and the cylinder-head apertures in the first group are inclined, or at an angle, relative to the cylinder-head apertures in the second group. The first group of cylinder-head apertures and the second group of cylinder-head apertures may be mirror symmetric relative to a symmetry axis that passes through and is perpendicular to the compressor-cylinder axis.

[0048] The inlet valve may be located between, or positioned directly between, one or more cylinder-head apertures of the first group and one or more cylinder-head apertures of the second group. It is specified above that the inlet valve may be a poppet valve, and that the poppet valve may comprise a valve seat. The valve seat of the poppet valve may be located between, or positioned directly between, one or more cylinder-head apertures of the first group and one or more cylinder-head apertures of the second group. The valve seat may be centered on the abovementioned symmetry axis.

[0049] The valve plate may form, or have, a plurality of valve-plate apertures. The valve-plate apertures are arranged to allow gas to pass through the valve plate when the plate valve is open. It is understood that valve plate has an inner side that faces the cylinder head, or valve seat, and an outer side that faces away from the cylinder head, or the valve seat, and that the valve-plate apertures extend from the inner side to the outer side. The valve-plate apertures and the cylinder-head apertures may be non-overlapping when the plate valve is closed. The valve-plate apertures may be located between the cylinder-head apertures. More specifically, each valve-plate aperture may at least in part be located between two neighboring cylinder-head apertures. The valve-plate apertures may be elongated. Additionally, the valve-plate apertures may be straight.

[0050] The guard, or guard plate may form, or have, a plurality of guard apertures. The guard apertures are arranged to allow gas to pass through the guard, or guard plate, when the plate valve is open. It is understood that guard, or guard plate, has an inner side that faces the valve plate and an outer side that faces away from the valve plate, and that the guard apertures extend from the inner side to the outer side. The guard apertures may overlap the valve-plate apertures when the plate valve is open. It is understood that each guard aperture may overlap a single valve-plate aperture. The guard aperture may have a shape that conforms to the single valve-plate aperture. This means that the guard apertures may be elongated and straight.

[0051] It is specified that the compressor cylinder head may have a top-cylinder face that faces the compressor piston. The compressor piston may have a top-piston face that faces the cylinder head, or more specifically the top-cylinder face. The top-piston face may be located at the top-cylinder face at the top dead center of the compressor piston. It is specified that the top-cylinder face may outline a planar geometry. Similarly, the top-piston face may outline a planar geometry that conforms to the planar geometry of the top-cylinder face. It is specified that the cylinder head may form a plurality of cylinder-head apertures. Additionally or alternatively to the planar geometry, the top-piston face may outline a non-planar geometry that conforms to the cylinder-head apertures at the top dead center of the compressor piston.

[0052] The compressor piston, or the top-piston face, may have, or form, a plurality of protrusions, wherein the protrusions extend into the cylinder-head apertures at the top dead center of the compressor piston. The protrusions may have a clearance to the cylinder head, or cylinder-head apertures, at the top dead center of the compressor piston. The protrusions may define the abovementioned non-planar geometry. This contributes to reduce the clearance volume. Worded differently, each protrusion may mate, or at least partly fill, a cylinder-head aperture. The protrusion may have a shape that conforms to the shape of the single cylinder-head aperture. For example, it is specified that cylinder-head apertures may be elongated and straight, and the protrusions may be elongated and straight. Worded differently, the protrusions may be ridges. It is understood that the protrusions protrude in a direction parallel with, or aligned with, the compressor-cylinder axis, or perpendicular to, or transverse to, the planar geometry outlined by the top-piston face.

[0053] It is specified that the cylinder-head apertures may be divided into a first group and a second group. The protrusions may be divided into the corresponding groups, and the protrusions in the first group are aligned, or parallel, the protrusions in the second group are aligned, or parallel, and the protrusions in the first group are inclined, or at an angle, relative to the protrusions in the second group.

[0054] The cylinder-head apertures may have a height along the compressor-cylinder axis, and the protrusions may have a height along the compressor-cylinder axis that is greater than the height of the cylinder-head apertures. It is specified that the outlet valve may be a plate valve that comprises a valve plate and a valve seat. The protrusions may be located at the abovementioned valve plate at the top dead center of the compressor piston. The protrusions may have a clearance to the valve plate at the top dead center of the compressor piston. Alternatively, the protrusions may contact the valve plate at the top dead center of the compressor piston. Worded differently, the protrusions may extend through the cylinder-head apertures, or more specifically through the complete cylinder-head apertures, at the top dead center of the compressor piston, or extend from the valve seat, or ridges, towards the valve plate at the top dead center of the compressor piston. The protrusions may bias the valve plate away from the valve seat at a transition from the bottom dead center to the top dead center of the compressor piston. Worded differently, the protrusions may bias the valve plate away from the valve seat at, or in, the top dead center of the compressor piston, or the protrusions may be arranged to contact valve plate and transition the plate valve from closed to open at the top dead center of the compressor piston. More generally, the protrusion may be arranged to cooperate with and open the outlet valve at the top dead center of the compressor piston. This allows for a stronger spring arrangement in the outlet valve and a higher pressure to be achieved before the outlet valve opens. It also allows for a backflow through the outlet valve. It is understood that that the protrusions may be spaced apart from the cylinder-head apertures at the bottom dead center of the compressor piston and that the protrusions enters the cylinder-head apertures in a transition from the bottom dead center to the top dead center of the compressor piston.

[0055] It is specified that the actuator is arranged to selectively open the inlet valve when closed to allow gas to exit the compressor cylinder. It is understood that the gas exit is via the inlet valve. It is further understood that the actuator is operationally coupled to the inlet valve.

[0056] The actuator may be a linear actuator. Alternatively, the actuator may be a linear motor. The actuator may be an electro-mechanical actuator. The actuator may be a moving-magnet actuator or a voice-coil actuator.

[0057] The actuator may be a single-acting actuator that can produce a force, or displacement in a single direction. It is specified above that the inlet valve may be a poppet valve. The single direction may be aligned with, or parallel with, the stem of the poppet valve. The actuator may be connected to the stem. The actuator may be arranged to push the stem and the head of the poppet valve towards, or into, compressions chamber or cylinder bore, or towards the compressor piston. It is understood that this is when the actuator is activated. Worded differently, the single direction may be towards the compressor piston. This is advantageous in combination with the poppet valve comprising a coil spring, as described above.

[0058] Alternatively, the actuator may be a double-acting actuator that can produce a first force, or first displacement, in a first direction, and a second force, or second displacement, in an opposite second direction. It is specified above that the inlet valve may be a poppet valve. The first direction and the second direction may be aligned with, or parallel with, the stem of the poppet valve. The actuator may be connected to the stem. The actuator may be arranged to push the stem and the head of the poppet valve towards the compressor piston and to pull the stem and the head of the poppet valve away from the compressor piston. Worded differently, the first direction may be towards the compressor piston and the second direction may be away from the compressor piston. This is advantageous in combination with the poppet valve comprising no coil spring.

[0059] The compressor may comprise an actuator housing, wherein the actuator housing is of metal and the actuator is located in the actuator housing. The actuator and the actuator housing may be arranged to transfer heat generated in the actuator to the actuator housing. Worded differently the actuator housing may be arranged as a heat sink for the actuator. This is advantageous in combination with an actuator that generates heat when operated, such as an electro-mechanical actuator. For example, the compressor may comprise a thermal paste or thermal pad that thermally connects the actuator and the actuator housing. Alternatively, the actuator may contact the actuator housing directly. It is understood that the actuator housing may form part of the compressor housing.

[0060] It is specified that the compressor comprises an inlet valve. It is understood that the compressor can have several inlet valves. Worded differently, the compressor may comprise a plurality of inlet valves. It is specified that the compressor may comprise an actuator. It is understood that the compressor may have several actuators. Worded differently, the compressor may comprise a plurality of actuators. Each of the inlet valves may be arranged as and comprise any of the features of the inlet valve described above, and each of the inlet actuators may be arranged as and comprise any of the features of the actuator described above. For example, each the inlet valves may be a check valve, and each of the actuators may be connected to one of the inlet valves and arranged to selectively force the inlet valve to be open.

[0061] It is specified that the compressor may comprise a control unit. The control unit may be connected to each of the actuators. The control unit may be arranged to control the operation, or function, of the actuators independently from one another. Worded differently, the control unit may be arranged to individually control the operation, or function, of respective actuator.

[0062] Different modes of operation are described above. It is understood that the compressor, or control unit, may be arranged to simultaneously operate each of the actuators in one or more of the different modes of operation. The compressor, or the control unit, may be arranged to selectively operate the actuators in the same mode of operation. The compressor, or the control unit, may be arranged to selectively operate the actuators in different modes of operation. For example, one inlet valve may be operated in the third mode of operation to the other inlet valves being operated in the fourth or fifth mode. This means that gas, or air, will leak through the inlet valve operated in the third mode of operation during the compression, which may result in a lower pressure of the compressed air that exits via the outlet valve.

[0063] The inlet valves, or all inlet valves, may be selectively operated in the fourth mode of operation. The compressor, or control unit, may be arranged to operate the actuator to transition from forcing the inlet to be open to allowing the inlet valve to be closed at different intermediate positions for the inlet valves. It is understood that this is in a transition from the bottom dead center to the top dead center, or in a single, or the same, compression stroke.

[0064] For example, the compressor may comprise three inlet valves. The inlet valves may be poppet valves, as described above. The inlet valves may be arranged in a triangular pattern. It is understood that the compressor cylinder has a cylinder wall that outlines a cylindrical geometry. The cylindrical geometry is centered on the abovementioned compressor-cylinder axis. It is specified that the inlet valve may extend through the cylinder head. Two of the inlet valves may be located at the cylinder wall, or at one side of the compressor cylinder, or cylinder bore. The outlet valve may be located at the opposite side of the compressor cylinder, or cylinder bore. The remaining inlet valve may be located at the compressor-cylinder axis. The outlet valve may be located on three sides of the remaining inlet.

[0065] The compressor may comprise a compressor pulley, compressor sprocket, or compressor gear, wherein the compressor pulley, sprocket, or gear is connected to the compressor crankshaft. The compressor pulley, sprocket, or gear may be connected directly to the compressor crankshaft. The compressor pulley, sprocket, or gear may be fixed to the compressor crankshaft. This means that there is no clutch arrangement between the compressor pulley, sprocket, or gear and the compressor crankshaft. It is understood that the compressor pulley may be configured to cooperate with a belt for rotating the compressor crankshaft, that the compressor sprocket may be configured to cooperate with a roller chain for rotating the compressor crankshaft, and that that the compressor gear may be configured to cooperate with another gear for rotating the compressor crankshaft.

[0066] It is specified above that the compressor may have a compressor housing. It is understood that the compressor crankshaft may be rotationally supported relative to the compressor housing. For example, the compressor housing may comprise a compressor-crankshaft bearing, such as a rolling-element bearing, that rotationally connects the compressor crankshaft to the compressor housing.BRIEF DESCRIPTION OF THE DRAWINGS

[0067] A more complete understanding of the abovementioned and other features and advantages of the proposed technology will be apparent from the following detailed description of preferred embodiments of the proposed technology in conjunction with the appended drawings, wherein: Figs. 1a to 1c are external views of an embodiment of a compressor with Fig. 1a showing a perspective view and Figs. 1b and 1c showing side views of the compressor. Figs. 2a to 2c are cross-sectional views of the compressor with Fig. 2a centered on the compressor crankshaft and parallel with the compressor cylinder, Fig. 2b centered on the compressor cylinder and parallel with the compressor crankshaft, and Fig. 2c centered on the compressor cylinder and perpendicular to the compressor crankshaft. Fig. 3 is a cross-sectional view of the compressor at the actuators and parallel with the compressor crankshaft. Figs. 4a and 4b are a perspective view respective a cross-sectional view of an inlet valve of the compressor. Fig. 5 is a perspective view of the cylinder head of the compressor cylinder of the compressor. Fig. 6 is a perspective view of the valve plate of the outlet valve of the compressor. Figs. 7a and 7b are perspective views of the guard of the outlet valve of the compressor. Figs. 8a to 8c are cross-sectional views of the compressor parallel with the compressor crankshaft at the outlet valve of the compressor. Figs. 9a and 9b are cross-sectional views of the compressor parallel with the compressor crankshaft between the compressor piston and the cylinder head, with Fig. 9a being in a direction from the compressor crankshaft and Fig. 9b being in a direction compressor towards the crankshaft. DETAILED DESCRIPTION OF THE DRAWINGS

[0068] An embodiment of a reciprocating and positive displacement compressor 10 is shown in Figs. 1a to 1c and Figs. 2a to 2c. The compressor 10 is a single acting and single stage compressor. The compressor 10 has a single compressor cylinder 12, a single compressor piston 14, three inlet valves 16, and an outlet valve 18. The three inlet valves 16 can be seen in Fig. 9a. In alternative embodiments, the number of inlet valves 16 can be different. The compressor cylinder 12 and the compressor piston 14 jointly form a compression chamber 20 that can compress gas when the compressor 10 is operated.

[0069] The compressor cylinder 12 has a cylinder head 22, see for example Figs. 2a to 2c, 5, and 9a,that contributes to enclose the compression chamber 20. The inlet valves 16 and the outlet valve 18 are located at the cylinder head 22. The cylinder head 22 has a top-cylinder face 24 that faces the compressor piston 14 and outline a planar geometry.

[0070] The compressor piston 14 is arranged to reciprocate within the compressor cylinder 12 when the compressor 10 is operated. The compressor cylinder 12 has a cylinder bore 26 with a circular cross-section and the compressor piston 14 conforms to the cylinder bore 26. The compressor piston 14 has a piston seal 28 arranged to prevent gas from passing between the compressor piston 14 and the compressor cylinder 12. The cylinder bore 26 of the compressor cylinder 12 has a compressor-cylinder axis 30 along which the compressor piston 14 can reciprocate.

[0071] The compressor piston 14 has a bottom dead center and a top dead center. The compressor piston 14 moves towards the cylinder head 22 at a transition of the compressor piston 14 from the bottom dead center to the top dead center, and away from the cylinder head 22 at a transition of the compressor piston 14 from the top dead center to the bottom dead center. It further has a stroke length between the bottom dead center and the top dead center. It can perform a compression stroke corresponding to a change in position from the bottom dead center to the top dead center. It can further perform an intake stroke corresponding to a change in position from the top dead center to the bottom dead center. The volume of the compression chamber 20 changes when the compressor 10 is operated, and the volume of the compression chamber 20 is the largest at the bottom dead center of the compressor piston 14 and the smallest at the top dead center of the compressor piston 14. The compression chamber 20 has a swept volume corresponding to the change in the volume of the compression chamber 20 at a transition of the compressor piston 14 from the bottom dead center to the top dead center. It further has a clearance volume at the top dead center of the compressor piston 14.

[0072] The compressor 10 has a compressor housing 32 and the compressor cylinder 12 and the cylinder head 22 form part of the compressor housing 32. The compressor housing 32 forms an inlet 34 and an outlet 36 of the compressor 10 by which the compressor 10 can receive respectively expel gas, see Figs. 1a and 2a to 2c. The compressor housing 32 also forms an inlet conduit 38 that can lead gas from the inlet 34 to the inlet valve 16 and an outlet conduit 40 that can lead gas from the outlet valve 18 to the outlet 36.

[0073] The compressor 10 has a compressor crankshaft 42 that is operationally connected to the compressor piston 14 and can reciprocate the compressor piston 14. A compressor connecting rod 44 is rotationally connected to the compressor crankshaft 42 and pivotally connected to the compressor piston 14. The compressor crankshaft 42 has a crank pin 46 and the compressor connecting rod 44 is connected to the crank pin 46 via a rod bearing 48. The compressor connecting rod 44 is connected to the compressor piston 14 via a piston pin 50.

[0074] The compressor 10 has a compressor pulley 52 that is fixed to the compressor crankshaft 42 and can cooperate with a belt for rotating the compressor crankshaft 42 and powering the compressor 10. In an alternative embodiment, the compressor 10 has a compressor sprocket or compressor gear instead of the compressor pulley 52 that can cooperate with a roller chain respective another gear. The compressor housing 32 has compressor-crankshaft bearings 54 in the form of rolling-element bearings that rotationally connects the compressor crankshaft 42 to the compressor housing 32. This way, the compressor crankshaft 42 can rotate around a compressor crankshaft axis 106. The compressor housing 32 has an opening 108 centered on the compressor crankshaft axis 106 located on the opposite side of the housing 32 relative to the compressor pulley 52 and through which the compressor crankshaft 42 can be accessed, for example to drive an external component. The opening 108 is covered with a removable lid 110.

[0075] The compressor housing 32 forms a compressor crankcase 56 within which the compressor connecting rod 44 is connected to the compressor crankshaft 42. The compressor crankcase 56 is fluidly connected to the inlet conduit 38, which means that the compressor piston 14 can form a partial vacuum in the inlet conduit 38 during a compression stroke. The compressor 10 has an oil squirter 58 that can expel an oil into the inlet conduit 38 towards the compressor crankshaft 42 and the compressor connecting rod 44 for lubricating and cooling the compressor 10.

[0076] The three inlet valves 16 are check valves that individually can allow gas to enter the compression chamber 20. Each inlet valve 16 is fluidly connected to the compression chamber 20. Each inlet valve 16 has an inside that is exposed to the compression chamber 20 and an outside that is exposed to the inlet conduit 38. The inlet valves 16 extend through the cylinder head 22, see Figs. 2a and 2c, and they are arranged to lead gas through the cylinder head 22.

[0077] Each inlet valve 16 is a poppet valve 16, see Fig. 4b. The poppet valve 16 has a head 60, a stem 62, and a valve body 66. The valve body 66 forms a valve seat 64 and a valve guide 68. The stem 62 is attached to the head 60, the head 60 and stem 62 can move relative to the valve seat 64, and the head 60 can cooperate with the valve seat 64 to allow or prevent passage of gas through the poppet valve 16. The poppet valve 16 will bias the head 60 against the valve seat 64 at a higher pressure in the compressor cylinder 12 than outside poppet valve 16 and to bias the head 60 away from the valve seat 64 at a lower pressure in the compressor cylinder 12 than outside poppet valve 16, at which the head 60 is spaced apart from the valve seat 64 and gas can pass into the compression chamber 20 between the head 60 and the valve seat 64. The elongated stem 62 is connected to the disc-shaped head 60 and the valve guide 68 cooperates with the valve stem 62 and can guide the stem 62 and head 60 relative to the valve seat 64. The stem 62 has a tip at one end and is connected to the head 60 at the other end. This way, the inlet valves 16 are arranged to open and allow gas to enter the compressor cylinder 12 at a transition of the compressor piston 14 from the top dead center to the bottom dead center, at which the pressure is lower in the compressor cylinder 12 than outside of the inlet valve 16. They are further arranged to close and prevent gas to exit the compressor cylinder 12 at a transition from the bottom dead center to the top dead center, at which the pressure in the compressor cylinder 12 is higher than outside of the inlet valve 16.

[0078] Each inlet valve 16 has a spring arrangement 70 that biases the inlet valve 16 to be closed. It is composed of a spring retainer 72 and a coil spring 74. The spring retainer 72 is attached to the stem 62 at the tip of the stem 62. The coil spring 74 biases the spring retainer 72 relative to the valve body 66. The valve body 66 is attached to the cylinder head 22, which in extension means that the coil spring 74 biases the spring retainer 72 relative to the cylinder head 22.

[0079] The head 60 of the poppet valve 16 has a flat inner face 76 that faces the compressor piston 14 and outlines a planar geometry that is co-planar with the top-cylinder face 24 when the poppet valve 16 is closed, as shown in Figs 2a and 2c.

[0080] The outlet valve 18 is a check valve that is arranged to allow gas to exit the compression chamber 20. The outlet valve 18 is fluidly connected to the compression chamber 20. The outlet valve 18 has an inside that is exposed to the compression chamber 20 and an outside that is exposed to the outlet conduit 40.

[0081] The outlet valve 18 is a plate valve 18, see Figs. 5, 6, 7a, 7b, and 8a to 8c. The plate valve 18 is be located at the cylinder head 22 and the cylinder head 22 forms part of the plate valve 18. The plate valve 18 has a movable valve plate 78, a guard 80, and a valve seat 82. The valve seat 82 is formed by the cylinder head 22 and the guard 80 is a plate that is attached to the cylinder head 22. The valve plate 78 is located between the valve seat 82 and the guard 80, and the guard 80 retains the valve plate 78 relative to the valve seat 82. The valve plate 78 can cooperate with the valve seat 82 to allow or prevent passage of gas through the plate valve 18. The cylinder head 22 is located between the valve plate 78 and the compression chamber 20. The plate valve 18 is arranged to bias the valve plate 78 against the valve seat 82 formed by the cylinder head 22 at a lower pressure in the compressor cylinder 12 than outside plate valve 18, this way preventing gas from entering the compression chamber 20 via the plate valve 18. The plate valve 18 is arranged to bias the valve plate 78 away from the valve seat 82 formed by the cylinder head 22, at a higher pressure in the compressor cylinder 12 than outside plate valve 18, this way allowing gas to exit the compression chamber 20 via the plate valve 18.

[0082] The valve plate 78 has a plurality of guide holes 84, and the plate valve 18 has a plurality of guide pins 86 that are connected to the cylinder head 22 and the guard 80 and extends through the guide holes 84. The guide holes 84 and the guide pins 86 cooperate to guide the valve plate 78 at a transition of the plate valve 18 between open and closed and to prevent a movement of the valve plate 78 in a direction parallel the valve plate 78.

[0083] The plate valve 18 has a plurality of coil springs 88 that are spaced apart relative to one another with each coil spring 88 centered on a guide pin 86. The coil springs 88 biases the valve plate 78 away from the guard 80 to close the plate valve 18. When the valve is fully open, the valve plate 78 contacts and is flush with the guard 80. The guard 80 has a plurality of countersinks 90, and each countersink 90 is located at a coil spring 88 and arranged to receive the complete coil spring 88 when the plate valve 18 is fully open.

[0084] The cylinder head 22 forms elongated and straight cylinder-head apertures 92 that form part of the compression chamber 20 and by which the plate valve 18 is fluidly connected to the compression chamber 20. The valve seat 82 has annular ridges 94 that each is located at, encircles, and has a shape congruent with one of the cylinder-head apertures 92. The valve plate 78 is biased against the annular ridges 94 and covers the cylinder head 22 apertures when the plate valve 18 is closed.

[0085] The cylinder-head apertures 92 are divided into a first group and a second group. The cylinder-head apertures 92 in each group extend in parallel, and the cylinder-head apertures 92 in the first group are inclined relative to the cylinder-head apertures 92 in the second group. The first group of cylinder-head apertures 92 and the second group of cylinder-head apertures 92 are mirror symmetric relative to a symmetry axis 96 that passes through and is perpendicular to the compressor-cylinder axis 30, see Fig. 9a. One of the inlet valves 16 is located on the symmetry axis 96 with its valve seat 64 between some of the cylinder-head apertures 92 of the first group and some of the cylinder-head apertures 92 of the second group.

[0086] The valve plate 78 forms elongated and straight valve-plate apertures 98 that are non-overlapping with the cylinder-head apertures 92 and allow gas to pass through the valve plate 78 when the plate valve 18 is open. The valve-plate apertures 98 are partly or fully located between neighboring cylinder-head apertures 92 when the plate valve 18 is closed, as shown in Figs. 8a and 8b.

[0087] The guard 80 forms elongated and straight guard apertures 100 that each overlap a valve-plate aperture 98 and allow gas to pass through the guard 80 when the plate valve 18 is open. Each guard aperture 100 has a shape that conforms to the shape pf the single valve-plate aperture 98 it overlaps, as shown in Fig 8c.

[0088] As described here, the outlet valve 18 is arranged to open allow gas to exit the compressor cylinder 12 at a transition of the compressor piston 14 from the bottom dead center to the top dead center, at which the pressure in the compressor cylinder 12 is higher than outside outlet valve 18. It is further arranged to close and prevent gas to enter the compressor cylinder 12 at a transition from the top dead center to the bottom dead center, at which the pressure in the compressor cylinder 12 is lower than outside outlet valve 18.

[0089] The compressor piston 14 has a top-piston face 102 that faces the top-cylinder face 24 of the cylinder head 22, see Figs. 2a to 2c, 9a, and 9b. The top-piston face 102 is located at the top-cylinder face 24 at the top dead center of the compressor piston 14. The top-piston face 102 outlines a planar geometry that conforms to the planar geometry of the top-cylinder face 24 with the compressor piston 14 at the top dead center. The compressor cylinder 12 forms protrusions 104 in the top-piston face 102 that extend into and partly fills the cylinder-head apertures 92 at the top dead center of the compressor piston 14. The protrusions 104 are elongated and straight and have a shape that conforms to the shape of the cylinder-head apertures 92. This way, the top-piston face 102 also outlines a non-planar geometry that conforms to the cylinder-head apertures 92.

[0090] The protrusions 104 are located at and has a clearance to the valve plate 78 at the top dead center of the compressor piston 14. In an alternative embodiment, the protrusions 104 enters the cylinder-head apertures 92, contacts the valve plate 78, and bias the valve plate 78 away from the valve seat 82 at the top dead center of the compressor piston 14.

[0091] The compressor 10 has three actuators 106 that are separately connected to the inlet valves 16 such that each inlet valve 16 can be controlled by a single actuator 202, see Fig. 3. Each actuator 202 is arranged to selectively force the inlet valve 16 to be open when activated to allow a backflow of gas from the compression chamber 20 via the inlet valve 16.

[0092] The actuators 106 are connected to the tips of the stems 62 of the poppet valves 16. The actuators 106 are linear electro-mechanical actuator 202 in the form of moving-magnet actuators 106. In an alternative embodiment the actuators 106 are voice-coil actuators 106. Each actuator 202 is a single-acting actuators 106 that can produce a force in a single direction aligned with the stems 62 of the poppet valves 16. The actuator 202 can push the stem 62 and the head 60 of the poppet valve 16 towards the compressor piston 14. In an alternative embodiment, the actuators 106 are double-acting actuators 106 that can produce a first force in a first direction and a second force in an opposite second direction, with the first direction and the second direction aligned with the stems 62 of the poppet valves 16. This way, the actuator 202 is arranged to push the stem 62 and the head 60 of the poppet valve 16 towards the compressor piston 14 and to pull the stem 62 and the head 60 of the poppet valve 16 away from the compressor piston 14.

[0093] The compressor 10 has an actuator housing 204 that forms part of the compressor housing 32, see Figs. 2a to 2c and 3. The actuator housing 204 is of metal and the actuators 106 are located within the actuator housing 204. Thermal paste thermally connects the actuators 106 and the actuator housing 204. This way, the actuators 106 and the actuator housing 204 are arranged to transfer heat generated in the actuator 202 to the actuator housing 204, and the actuator housing 204 can function as a heat sink for the actuators 106.

[0094] The compressor 10 has a control unit 206 that is connected to each actuator 202 that can control the operation of the actuators 202. The control unit 206 can simultaneously operate the actuators 202 in the same or different modes of operation.

[0095] In a first mode of operation of an actuator 202, the control unit 206 selectively operates the actuator 202 to force the inlet valve 16 to be open at the bottom dead center of the compressor cylinder 12, which means that the actuator 202 forces the inlet valve 16 to be open at the start of a compression stroke. This corresponds to an operation step of forcing the inlet valve 16 to be open at the bottom dead center of the compressor piston 14.

[0096] In a second mode of operation of an actuator 202, the control unit 206 selectively operates the actuator 202 to force the inlet valve 16 to be open at a change in position of the compressor piston 14 from the bottom dead center towards the top dead center, which means that the actuator 202 forces the inlet valve 16 to be open over an initial stage of a compression stroke. This corresponds to an operation step of forcing the inlet valve 16 to be open at a change in position of the compressor piston 14 from the bottom dead center towards the top dead center.

[0097] In a third mode of operation of an actuator 202, the control unit 206 selectively operates the actuator 202 to force the inlet valve 16 to be open at a complete transition from the bottom dead center to the top dead center, which means that the actuator 202 forces the inlet valve 16 to be open during a complete compression stroke. This corresponds to an operation step of forcing the inlet valve 16 to be open at a complete transition from the bottom dead center to the top dead center.

[0098] In a fourth mode of operation of an actuator 202, the control unit 206 selectively operates the actuator 202 to force the inlet valve 16 to be open at a change in position of the compressor piston 14 from the bottom dead center to a selected intermediate position between the bottom dead center and the top dead center, and to selectively operate the actuator 202 to allow the inlet valve 16 to be closed at a change in position of the compressor piston 14 from the intermediate position to the top dead center. This corresponds to the operation steps of forcing the inlet valve 16 to be open at a change in position of the compressor piston 14 from the bottom dead center to an intermediate position between the bottom dead center and the top dead center, and allowing the inlet valve 16 to be closed at a change in position of the compressor piston 14 from the intermediate position to the top dead center. The control unit 206 is arranged to selectively operate the actuator 202 at different intermediate position.

[0099] In a fifth mode of operation of an actuator 202, the control unit 206 selectively operates the actuator 202 to allow the inlet valve 16 to be closed at a complete transition from the bottom dead center to the top dead center, which means that the actuator 202 allows the inlet valve 16 to be closed during a complete compression stroke. This corresponds to an operation step of allowing the inlet valve 16 to be closed at a complete transition from the bottom dead center to the top dead center.

[0100] The control unit 206 is configured to receive a control signal and to select a mode of operation depending on the control signal. The control unit 206 is also configured to select the intermediate position in the fourth mode of operation depending on the control signal.ITEM LIST

[0101] 10 compressor 12 compressor cylinder 14 compressor piston 16 inlet valve or poppet valve 18 outlet valve or plate valve 20 compression chamber 22 cylinder head 24 top-cylinder face 26 cylinder bore 28 piston seal 30 compressor-cylinder axis 32 compressor housing 34 inlet 36 outlet 38 inlet conduit 40 outlet conduit 42 compressor crankshaft 44 compressor connecting rod 46 crank pin 48 rod bearing 50 piston pin 52 compressor pulley 54 compressor-crankshaft bearing 56 compressor crankcase 58 oil squirter 60 head of poppet valve 62 stem of poppet valve 64 valve seat of poppet valve 66 valve body of poppet valve 68 valve guide of poppet valve 70 spring arrangement of poppet valve 72 spring retainer of poppet valve 74 coil spring of poppet valve 76 inner face 78 valve plate 80 guard 82 valve seat 84 guide holes 86 guide pins (88 coil springs) 90 countersink 92 cylinder-head aperture 94 annular ridge 96 symmetry axis 98 valve-plate aperture 100 guard apertures 102 top-piston face 104 protrusion 106 compressor crankshaft axis 108 opening 110 lid 202 actuator 204 actuator housing 206 control unit

Claims

1. A compressor (10) that comprises: - a compressor cylinder (12), - a compressor piston (14), - an inlet valve (16), and - an outlet valve (18), - an actuator (202), wherein the compressor cylinder (12) and the compressor piston (14) jointly form a compression chamber (20) arranged to compress gas, or air, when operating the compressor (10), the inlet valve (16) is a check valve arranged to allow gas to enter the compression chamber (20), the outlet valve (18) is a check valve arranged to allow gas to exit, or to allow an outflow of gas from, the compression chamber (20), and the actuator (202) is connected to the inlet valve (16) and arranged to selectively force the inlet valve (16) to be open.

2. The compressor (10) according to claim 1, wherein the compressor (10) is arranged to selectively operate the actuator (202) to force the inlet valve (16) to be open at the bottom dead center of the compressor piston (14).

3. The compressor (10) according to claim 1 or 2, wherein the compressor (10) is arranged to selectively operate the actuator (202) to force the inlet valve (16) to be open at a change in position of the compressor piston (14) from the bottom dead center towards the top dead center.

4. The compressor (10) according to any one of the claims 1 to 3, wherein the compressor (10) is arranged to selectively operate the actuator (202) to force the inlet valve (16) to be open at a complete transition of the compressor piston (14) from the bottom dead center to the top dead center.

5. The compressor (10) according to any one of the claims 1 to 4, wherein the compressor (10) is arranged to selectively operate the actuator (202) to force the inlet valve (16) to be open at a change in position of the compressor piston (14) from the bottom dead center to a selected intermediate position between the bottom dead center and the top dead center.

6. The compressor (10) according to any one of the claims 1 to 5, wherein the compressor (10) is arranged to selectively operate the actuator (202) to allow the inlet valve (16) to be closed at a complete transition from the bottom dead center to the top dead center.

7. The compressor (10) according to any one of the claims 1 to 6, wherein the compressor (10) comprises a control unit that is connected to the actuator (202) and arranged to control the operation of the actuator (202), and the control unit is arranged to receive a control signal and to determine how to operate the actuator (202) based on the control signal.

8. The compressor (10) according to any one of the claims 1 to 7, wherein the inlet valve (16) is normally closed.

9. The compressor (10) according to any one of the claims 1 to 8, wherein the inlet valve (16) is a poppet valve (16) that comprise a stem (62), a head (60), and a valve seat (64), wherein the stem (62) is connected to the head (60), the head (60) and stem (62) can move relative to the valve seat (64), the head (60) is arranged to cooperate with the valve seat (64), the actuator (202) is an electro-mechanical linear actuator, the actuator (202) is connected to the stem (62), and the actuator (202) is arranged to push the stem (62) and the head (60) of the poppet valve (16) towards the compressor piston (14) when activated.

10. The compressor (10) according to any one of the claims 1 to 9, wherein the outlet valve (18) is normally closed.

11. The compressor (10) according to any one of the claims 1 to 10, wherein the compressor cylinder (12) has a cylinder head (22), the cylinder head (22) forms a plurality of cylinder-head apertures (92), and the outlet valve (18) is fluidly connected to the compression chamber (20) via the cylinder-head apertures (92).

12. The compressor (10) according to claim 11, wherein outlet valve (18) is a plate valve that comprises a valve plate (78), a guard (80), and a valve seat (82), the valve plate (78) is located between the guard (80) and the valve seat (82), the guard (80) is arranged to retain the valve plate (78) relative to the valve seat (82), the valve seat (82) comprises a plurality of annular ridges (94) that form part of the cylinder head (22), and each cylinder-head aperture (92) is encircled by one of the annular ridges (94).

13. The compressor (10) according to claim 11 or 12, wherein the cylinder-head apertures (92) are elongated and straight, the cylinder-head apertures (92) are divided into a first group and a second group, the cylinder-head apertures (92) in the first group are aligned, the cylinder-head apertures (92) in the second group are aligned, and the cylinder-head apertures (92) in the first group are inclined relative to the cylinder-head apertures (92) in the second group.

14. The compressor (10) according to any one of the claims 11 to 13, wherein the compressor piston (14) has a bottom dead center and a top dead center, the compressor piston (14) has a plurality of protrusions (104), and the protrusions (104) extend into the cylinder-head apertures (92) at the top dead center of the compressor piston (14).

15. The compressor (10) according to claim 14, wherein the protrusions (104) extend through the cylinder-head apertures (92) at the top dead center of the compressor piston (14).

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