Reciprocating piston compressor and method for operating a reciprocating piston compressor

Abstract

The invention relates to a reciprocating piston compressor comprising: - a cylinder (103), - a piston (105) which is arranged in a linearly movable manner within the cylinder, - an oil circuit (107) for building up an oil film in a gap (109) between an inner wall (111) of the cylinder and the piston, - a piezo-driven oil pump (113), which can be actuated separately from the piston, for conveying oil from an oil sump (115) into the oil circuit, - wherein the oil pump has a further cylinder (117) in which a piezo actuator (119) is arranged as a further piston, - wherein the further cylinder has a compression chamber (121) which is fluidically connected to the oil sump and to the oil circuit, - a controller (123) which is designed to actuate the piezo actuator by applying an electrical voltage to the piezo actuator in such a way that, when an electrical voltage is applied to the piezo actuator, the piezo actuator changes its size in order to change a compression volume of the compression chamber in order to convey oil from the oil sump into the oil circuit, - wherein the controller is designed to actuate the piezo actuator independently of the piston. The invention relates to a method for operating a reciprocating piston compressor, to a computer program and to a machine-readable storage medium.

Description

[0001] R. 412013

[0002] Description

[0003] title

[0004] Reciprocating compressor and method for operating a reciprocating compressor

[0005] State of the art

[0006] For the lubrication and sealing of reciprocating compressors, an oil film in the gap between the piston and cylinder is necessary. Various oil pump principles are used to create the oil circuit. In these systems, the oil pump is driven by the movement of the entire compressor. The delivery rate is therefore directly linked to the movement of the compressor. In the event of a leak in the oil circuit, it is only refilled after the compressor starts. The formation of the oil film in the relevant gap therefore occurs with a time delay.

[0007] Patent US 8,070,460 B2 discloses a reciprocating pump.

[0008] Disclosure of the invention

[0009] The object underlying the invention is to provide a concept that enables an oil supply to a reciprocating compressor that is independent of compressor movement.

[0010] This problem is solved by means of the respective subject matter of the independent claims. Advantageous embodiments of the invention are the subject matter of dependent claims.

[0011] Following a first aspect, a reciprocating compressor is provided, comprising: one cylinder, R. 412013

[0012] - 2 - a piston arranged to be linearly movable within the cylinder, an oil circuit for building up an oil film in a gap between an inner wall of the cylinder and the piston, a piezo-driven oil pump separately controllable from the piston for pumping oil from an oil sump into the oil circuit, wherein the oil pump has a further cylinder in which a piezo actuator is arranged as a further piston, wherein the further cylinder has a compression chamber which is fluidically connected to the oil sump and to the oil circuit, a control device which is configured to control the piezo actuator by applying an electrical voltage to the piezo actuator such that when an electrical voltage is applied to the piezo actuator it changes its size in order to change a compression volume of the compression chamber in order to pump oil from the oil sump into the oil circuit, wherein the control device is configured,to control the piezo actuator independently of the piston.

[0013] Following a second aspect, a procedure for operating a reciprocating compressor according to the first aspect is provided, comprising the following steps:

[0014] The control device controls the piezo actuator by applying an electrical voltage to the piezo actuator in such a way that the electrical voltage applied to the piezo actuator changes its size in order to change a compression volume of the compression chamber in order to pump oil from the oil sump into the oil circuit.

[0015] According to a third aspect, a computer program is provided, comprising commands which, when the computer program is executed by the control unit of the reciprocating compressor according to the first aspect, cause it to execute a procedure according to the second aspect.

[0016] According to a fourth aspect, a machine-readable storage medium is provided on which the computer program is stored according to the third aspect. R. 412013

[0017] - 3 -

[0018] The invention is based on the understanding that the above problem is solved by providing the reciprocating compressor with a piezoelectric-driven oil pump that can be controlled independently of the piston. This piezoelectric-driven oil pump can draw oil from an oil sump into the oil circuit, thereby building up an oil film in the gap between the inner wall of the cylinder and the piston. Because this piezoelectric-driven oil pump can be controlled independently of the piston, the oil film in the gap between the inner wall of the cylinder and the piston can be built up independently of any movement of the reciprocating compressor, and in particular, any movement of the piston. Thus, for example, it is advantageously possible to build up the oil film even before the piston moves linearly within the cylinder.In other words, this makes it advantageously possible to start the oil supply even before the compressor starts, in order to build up the oil film.

[0019] This advantageously avoids a dry start. Furthermore, because the oil supply is independent of compressor movement, a demand-based oil delivery rate can be advantageously achieved.

[0020] The concept described here is based on an independently controlled piezoelectric actuator that generates a pumping effect by changing the volume in the compression chamber. The independent electrical control advantageously decouples the oil delivery from the operating state of the overall compressor.

[0021] In one embodiment of the piston compressor, the compression chamber is fluidically connected to the oil sump and the oil circuit via check valves such that each check valve allows only one flow direction: from the oil sump to the compression chamber and from the compression chamber to the oil circuit. R. 412013

[0022] - 4 -

[0023] This results, for example, in the technical advantage that the oil can be efficiently pumped from the oil sump through the compression chamber into the oil circuit.

[0024] According to this embodiment, the compression chamber is fluidically connected to the oil sump via a first check valve in such a way that the first check valve only allows one flow direction from the oil sump into the compression chamber, wherein the compression chamber is fluidly connected to the oil circuit via a second check valve in such a way that the second check valve only allows one flow direction from the compression chamber into the oil circuit.

[0025] In one embodiment of the reciprocating compressor, the piezo actuator is fixed on a first side and, with a second side opposite the first side, defines the compression space.

[0026] This results, for example, in the technical advantage that the compression volume can be efficiently changed by changing the size of the piezo actuator.

[0027] The size of the piezoelectric actuator refers specifically to its length. Therefore, a change in size, as described, includes a change in length.

[0028] In one embodiment of the reciprocating compressor, the control unit is designed to control the piezo actuator independently of the operating state of the reciprocating compressor.

[0029] This results, for example, in the technical advantage that the oil film can be built up independently of the operating condition of the reciprocating compressor.

[0030] In one embodiment of the method, the piezo actuator is controlled by the control unit independently of the operating state of the reciprocating compressor. R. 412013

[0031] - 5 -

[0032] This results, for example, in the technical advantage that the oil film can be built up independently of the operating condition of the reciprocating compressor.

[0033] The process characteristics are derived analogously from the characteristics of the reciprocating compressor, and vice versa. Statements made in connection with the process apply analogously to the reciprocating compressor, and vice versa.

[0034] The method is, for example, a computer-implemented method.

[0035] The control unit is, for example, programmed to execute the computer program.

[0036] The invention is explained in more detail below with reference to preferred embodiments. These include:

[0037] Fig. 1 shows a reciprocating compressor,

[0038] Fig. 2 shows a flowchart of a method for operating a reciprocating compressor and

[0039] Fig. 3 shows a machine-readable storage medium.

[0040] Fig. 1 shows a reciprocating piston compressor 101 in a schematic representation.

[0041] The reciprocating compressor 101 comprises a cylinder 103 and a piston 105, which is arranged to be linearly movable within the cylinder 103.

[0042] For clarity, cylinder 103 and piston 105 are shown in a truncated view. R. 412013

[0043] - 6 -

[0044] The reciprocating compressor 101 includes an oil circuit 107 for building up an oil film in a gap 109 between an inner wall 111 of the cylinder 103 and the piston 105.

[0045] Furthermore, the reciprocating compressor 101 includes a piezo-driven oil pump 113, which can be controlled separately from the piston 105, for pumping oil from an oil sump 115 into the oil circuit 107.

[0046] The oil pump 113 has a further cylinder 117 in which a piezo actuator 119 is arranged as a further piston.

[0047] The further cylinder 117 has a compression chamber 121, which is fluidly connected to the oil sump 115 and to the oil circuit 107.

[0048] The reciprocating compressor 101 includes a control unit 123, which is configured to control the piezoelectric actuator 119 by applying an electrical voltage to the piezoelectric actuator 119 such that, when an electrical voltage is applied to the piezoelectric actuator 119, it changes its size to change the compression volume of the compression chamber 121 in order to pump oil from the oil sump 115 into the oil circuit 107 to build up the oil film in the gap 109. The control unit 123 is configured to control the piezoelectric actuator 119 independently of the piston 105.

[0049] The reciprocating compressor 101 includes a voltage source 125 that provides the electrical voltage. The control unit 123 is configured to control the voltage source 125 such that it provides the required electrical voltage.

[0050] By applying an electrical voltage to the piezoelectric actuator 119, it changes its size, in particular its length, so that this change in size, in particular change in length, increases or decreases the compression volume of the compression chamber 121 accordingly, thus creating a pumping effect to transfer oil from the oil sump 115 into the oil circuit 107. R. 412013

[0051] - 7 -

[0052] Fig. 1 schematically shows a piezo actuator 119 enlarged by applying a corresponding electrical voltage, which is symbolically represented by dashed lines with the reference numeral 127.

[0053] The compression chamber 121 is connected to the oil sump 115 via a first check valve 129 such that the first check valve only allows flow from the oil sump 115 into the compression chamber 121. This flow direction is indicated by a first arrow with the reference numeral 131.

[0054] The compression chamber 121 is connected to the oil circuit 107 via a second check valve 133 such that the second check valve 133 only allows flow from the compression chamber 121 into the oil circuit 107. This flow direction is indicated by a second arrow with the reference numeral 135.

[0055] The oil circuit 107 includes a supply line 137, which leads from the compression chamber 121 to the gap 109. The oil circuit 107 includes a return line 139, which leads from the gap 109 back to the oil sump 115.

[0056] Oil is thus pumped by the oil pump 113 from the oil sump 115 via the supply line 137 to the gap 109 in order to build up an oil film in the gap 109. Oil is then pumped back to the oil sump 115 via the return line 139.

[0057] The piezo actuator 119 is fixed at a first side 141. The piezo actuator 119, together with a second side 143 opposite the first side 141, defines the compression chamber 121. Both sides 141 and 143 are end faces of the piezo actuator 119.

[0058] Fig. 2 shows a flowchart of a method for operating a reciprocating compressor according to the first aspect, comprising the following steps:

[0059] Controlling 201 of the piezo actuator by the control unit by applying 203 an electrical voltage to the piezo actuator such that the electrical voltage applied to the piezo actuator changes its size to achieve a value of R. 412013

[0060] - 8 -

[0061] To change the compression volume of the compression chamber in order to pump oil from the oil sump into the oil circuit.

[0062] Fig. 3 shows a machine-readable storage medium 301 on which a computer program 303 is stored. The computer program 303 comprises instructions which, when executed by the control unit of the reciprocating compressor according to the first aspect, cause it to execute a procedure according to the second aspect.

Claims

R. 412013 - 9 - Claims 1. Reciprocating compressor (101) comprising: a cylinder (103), a piston (105) arranged to move linearly within the cylinder (103), an oil circuit (107) for building up an oil film in a gap (109) between an inner wall (111) of the cylinder (103) and the piston (105), a piezo-driven oil pump (113) separately controllable from the piston (105) for pumping oil from an oil sump (115) into the oil circuit (107), wherein the oil pump (113) has a further cylinder (117) in which a piezo actuator (119) is arranged as a further piston (105), wherein the further cylinder (117) has a compression chamber (121) which is fluidly connected to the oil sump (115) and to the oil circuit (107), a control device (123) which is set up to control the piezo actuator (119) by applying an electrical voltage to the piezo actuator (119) in such a way that when an electrical voltage is applied to the piezo actuator (119) it changes its size,to change the compression volume of the compression chamber (121) in order to pump oil from the oil sump (115) into the oil circuit (107), wherein the control device (123) is configured to actuate the piezo actuator (119) independently of the piston (105).

2. Reciprocating compressor (101) according to claim 1, wherein the compression chamber (121) is fluidically connected to the oil sump (115) and to the oil circuit (107) via a check valve (129, 133) in such a way that the corresponding check valve (129, 133) only allows one flow direction from the oil sump (115) into the compression chamber (121) and from the compression chamber (121) into the oil circuit (107).

3. Reciprocating piston compressor (101) according to claim 1 or 2, wherein the piezo actuator (119) is fixedly fixed to a first side (141) and connected to one of the first sides R. 412013 - 10 - (141) opposite second side (143) limits the compression space (121).

4. Reciprocating piston compressor (101) according to one of the preceding claims, wherein the control device (123) is configured to control the piezo actuator (119) independently of an operating state of the reciprocating piston compressor (101).

5. Method for operating a reciprocating compressor (101) according to any of the preceding claims, comprising the following steps: Control (201) of the piezo actuator (119) by the control device (123) by applying (203) an electrical voltage to the piezo actuator (119) such that the electrical voltage applied to the piezo actuator (119) changes its size in order to change a compression volume of the compression chamber (121) in order to pump oil from the oil sump (115) into the oil circuit (107).

6. Method according to claim 5 with respect to the reciprocating compressor (101) referred back to claim 4, wherein the piezo actuator (119) is controlled by the control device (123) independently of an operating state of the reciprocating compressor (101).

7. Computer program (303) comprising commands which, when the computer program (303) is executed by the control device (123) of the reciprocating compressor (101) according to one of claims 1 to 4, cause it to execute a method according to claim 5 or claim 6.

8. Machine-readable storage medium (301) on which the computer program (303) according to claim 7 is stored.

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