Compressor assembly, air supply system, vehicle

Abstract

A compressor for a commercial vehicle comprises: a plurality of cylinders, wherein each cylinder accommodates a reciprocating piston, wherein the reciprocating piston is driven by a crankshaft, and a plurality of cooling means, arranged at a cylinder head region of the cylinder, wherein one specific cooling means is assigned to one cylinder respectively. The compressor assembly comprises a sensor network, wherein the sensor network comprises a plurality of temperature sensitive switches, wherein each temperature sensitive switch is assigned to a cylinder.

Claims

1. A compressor assembly for a commercial vehicle, comprising: a plurality of cylinders, wherein each cylinder accommodates a reciprocating piston, wherein the reciprocating piston is operatively coupled to a crankshaft, and a plurality of cooling means arranged at a cylinder head region of the cylinder, wherein one specific cooling means is assigned to one cylinder, respectively, wherein the compressor assembly comprises: a sensor network comprising a plurality of temperature sensitive switches, wherein: each temperature sensitive switch is assigned to a cylinder, and each temperature sensitive switch comprises a first electric terminal and a second electric terminal and is adapted to switch from a closed position to an open position in which an electric connection between the first electric terminal and the second electric terminal is interrupted when a switch temperature at the temperature sensitive switch is reached or exceeded, and the sensor network is adapted to provide an overheat signal when at least one temperature sensitive switch is in the open position.

2. A compressor assembly according to claim 1, wherein the sensor network further comprises a first temperature sensing device configured to determine a motor temperature at an electric motor of the compressor assembly and/or a second temperature sensing device, configured to determine a power electronics temperature at a power electronics unit of the compressor assembly.

3. A compressor assembly according to claim 1, wherein the compressor assembly comprises an electric motor, adapted to drive the crankshaft.

4. A compressor assembly according to claim 1, wherein the temperature sensitive switch is a bimetallic switch.

5. A compressor assembly according to claim 1, wherein the switch temperature is defined to be in a range from 140 C. to 260 C.

6. A compressor assembly according to claim 1, wherein the temperature sensitive switch is arranged in the cylinder head region or between the cylinder head region and the cooling means.

7. A compressor assembly according to claim 1, wherein the temperature sensitive switches of the sensor network are electrically connected in series, and the sensor network is configured to provide the overheat signal if a measurement voltage and/or a measurement current is not present at a measurement terminal.

8. A compressor assembly according to claim 1, wherein the temperature sensitive switches of the sensor network are electrically connected in parallel, each temperature sensitive switch is arranged in a parallel branch of the sensor network, a measurement terminal is arranged in one of the parallel branches, and the sensor network is configured to provide the overheat signal if a measurement current at the measurement terminal changes.

9. A compressor assembly according to claim 8, wherein at least two parallel branches comprise a resistor with a resistance, wherein a first resistance of a first resistor in a first parallel branch differs from a second resistance of a second resistor in a second parallel branch.

10. A compressor assembly according to claim 7, wherein the overheat signal is representative for the measurement current at the measurement terminal of the temperature sensitive switch where the switch temperature is exceeded.

11. A compressor assembly according to claim 1, wherein the sensor network comprises a signal processing unit, adapted to provide the overheat signal in dependence of the measurement voltage and/or a measurement current, wherein preferably the signal processing unit is connected to an electronic control unit of the commercial vehicle.

12. An air supply system for a commercial vehicle, comprising a compressor assembly according to claim 1.

13. A commercial vehicle, comprising: at least one pneumatic consumer, and a compressor assembly according to claim 1.

14. A commercial vehicle according to claim 13, comprising an electronic control unit connected to the sensor network, in particular to a signal processing unit, adapted to receive an overheat signal and to provide an alarm indication via an alarm indication device, preferably to display an alarm message, in dependence of the overheat signal.

Description

(1) Further advantages, features and details of the invention result from the following description of the preferred embodiments as well as from the drawings, which show in:

(2) FIG. 1A an illustration of a temperature sensitive switch in the form of a bimetallic switch in a closed position for an compressor assembly according to the first aspect of the invention,

(3) FIG. 1B an illustration of a temperature sensitive switch in the form of a bimetallic switch in an open position for an compressor assembly according to the first aspect of the invention,

(4) FIG. 2A a schematic illustration of a first preferred embodiment of a compressor assembly with a first sensor network,

(5) FIG. 2B a schematic illustration of a second preferred embodiment of a compressor assembly with a second sensor network,

(6) FIGS. 3A, 3B a front view and a side view of a compressor assembly according to the first aspect of the invention, which preferably can be configured as the first or the second preferred embodiment of the compressor assembly,

(7) FIG. 4 A schematic illustration of a vehicle according to the third aspect of the invention, comprising an air supply system according to the second aspect of the invention.

(8) FIG. 1A shows an illustration of a temperature sensitive switch 110 in a closed position 110A. The temperature sensitive switch 110 comprises a contact bridge 115, adapted to electrically connect a first electric terminal 112 with a second electric terminal 114. The contact bridge 115 comprises a first material layer 116 with a first temperature coefficient TC1, and a second material layer 118 with a second temperature coefficient TC2. The first material layer 116 is attached to the second material layer 118, preferably by means of an adhesive or a welded connection, or by means of other bonding techniques such as rolling. The first material layer 116 and/or the second material layer 118 are preferably made of metallic materials. The contact bridge 115 is adapted to open and close an electric connection between the first electric terminal 112 and the second electric terminal 114 at a contact point K in dependence of a switch temperature TS. In the closed position 110A, the contact bridge 115 is in contact with a contact foundation 119, establishing an electric connection between the first electric terminal 112 and the second electric terminal 114. In other words, the contact point K is the point of contact between the contact bridge 115 and the contact foundation 119.

(9) FIG. 1B shows the temperature sensitive switch 110 shown in FIG. 1A, but in an open position 110B. The open position 110B is established when a temperature T at the temperature sensitive switch 110, in particular at the contact bridge 115, reaches or exceeds the switch temperature TS, in particular due to a heat flow H. In particular, the heat flow H is emitted by a piston and/or cylinder of a compressor assembly not shown here. The heat flow H tends to increase when a cooling means (not shown in FIG. 1A and FIG. 1B), assigned to the same cylinder as the temperature sensitive switch 110, is not operating. The contact bridge 115 is adapted to lift from the contact foundation 118 in an opening movement MO. The contact bridge 115 is configured to perform the opening movement MO, since the second temperature coefficient TC2 is greater than the first temperature coefficient TC1, resulting in a bending of the contact bridge 150 in a direction that is substantially perpendicular to the contact bridge 115. A greater temperature coefficient TC means a greater expansion when subjected to heat. The greater the difference between the first temperature coefficient TC1 and the second temperature coefficient TC2, the greater the amplitude of the opening movement MO. Preferably, the switch temperature TS is in the range from 140 C. to 260 C., more preferably from 180 C. to 220 C., even more preferably 200 C.

(10) The temperature sensitive switch 110 is in the form of a bimetallic switch 111. In other embodiments, the temperature sensitive switch 110 can be of another configuration, for example comprising other materials than metallic materials.

(11) FIG. 2A shows a schematic illustration of a first preferred embodiment of a compressor assembly 100. The compressor assembly 100 comprises a first sensor network 200 with a plurality of four temperature sensitive switches 110, namely a first temperature sensitive switch 110.1, a second temperature sensitive switch 110.2, a third temperature sensitive switch 110.3 and a fourth temperature sensitive switch 110.4. Each temperature sensitive switch 110 shown here is configured as a bimetallic switch 111.

(12) The temperature sensitive switches 110.1, 110.2, 110.3, 110.4 are connected in series by means of a serial electric circuit 246. This means, that a first electric terminal 112.1 of the first temperature sensitive switch 110.1 is connected to a first source terminal 242 of an electric source 240. A second electric terminal 114.1 of the first temperature sensitive switch 110.1 is connected to a first electric terminal 112.2 of the second temperature sensitive switch 110.2. A second electric terminal 114.2 of the second temperature sensitive switch 110.2 is connected to a first electric terminal 112.3 of the third temperature sensitive switch 110.3. A second electric terminal 114.3 of the third temperature sensitive switch 110.3 is connected to a first electric terminal 112.4 of the fourth temperature sensitive switch 110.4. A second electric terminal 114.4 of the fourth temperature sensitive switch 110.4 is connected to a second source terminal 244 of the electric source 240. Optionally, a fifth temperature sensitive switch 110.5 and/or a sixth temperature sensitive switch 110.6, or more temperature sensitive switches 110, can be additionally integrated, as indicated here.

(13) The electric source 240 is adapted to provide a measurement voltage UM and/or a measurement current IM between the first source terminal 242 and the second source terminal 244. The first temperature sensitive switch 110.1 is assigned to a first cylinder 140.1 of the compressor assembly 200. Preferably, the first temperature sensitive switch 110.1 is located at or near the first cylinder 140.1, such as here between a first cylinder head region 142.1 of the first cylinder 140.1 and a first cooling means 160.1 (not shown here) assigned to the first cylinder 140.1. When a first temperature T1 reaches or exceeds the switch temperature TS, the first temperature sensitive switch 110.1 switches from a closed position 110A to an open position 1101B, such as described in FIG. 1A and FIG. 1B.

(14) The above description referring to the first temperature sensitive switch 110.1 and the first cylinder 140.1 applies in an analog manner with corresponding numbering to the second, third and fourth temperature sensitive switch 110.2, 110.3, 110.4 as well as the second, third and fourth cylinder 140.2, 140.3, 140.4, respectively.

(15) The sensor network 100 further comprises a signal processing unit 210, adapted to provide an overheat signal SO in dependence of the measurement voltage UM and/or the measurement current IM. In the embodiment shown here, the signal processing unit 210 is connected to the serial electric circuit 246 by means of a measurement terminal 230 and is adapted to detect the measurement current IM. The measurement terminal 230 is connected in series between the first source terminal 242 and the first electric terminal 112.1 of the first temperature sensitive switch 110.1.

(16) The signal processing unit 210 is adapted to provide the overheat signal SO if no measurement current IM is detected. This is the case, if at least one of the temperature sensitive switches 110.1, 110.2, 110.3, 110.4 is in an open position 110B, because the corresponding temperature T1, T2, T3, T4 has reached or exceeded the switch temperature TS, and consequently the serial electric circuit 246 is interrupted.

(17) FIG. 2B shows a second preferred embodiment of a further compressor assembly 100, comprising a further sensor network 200 with a parallel arrangement of temperature sensitive switches 110. Each temperature sensitive switch 110 is arranged in a parallel branch 180. In the embodiment shown, the sensor network 200 comprises a plurality of four temperature sensitive switches 110, namely a first temperature sensitive switch 110.1, second temperature sensitive switch 110.2, a third temperature sensitive switch 110.3 and a fourth temperature sensitive switch 110.4, each arranged in a corresponding first to fourth parallel branch 180.1, 180.2, 180.3, 180.4. The parallel branches 180.1, 180.2, 180.3, 180.4 together form a parallel electric circuit 248. Optionally, the further sensor network 200 can comprise further parallel branches 180, such as a fifth parallel branch 180.5 with a fifth temperature sensitive switch 110.5 and a fifth resistor 170.5, and/or a sixth parallel branch 180.6 with a sixth temperature sensitive switch 110.6 and a sixth resistor 170.6.

(18) Due to the layout with parallel branches 180.1, 180.2, 180.3, 180.4, the sensor network 200 of the embodiment shown advantageously provides the function of a current divider. When one of the temperature sensitive switches 110.1, 110.2, 110.3, 110.4 is in an open position 110B, and the measurement current IM1, IM2, IM3, IM4 in the corresponding parallel branch 180.1, 180.2, 180.3, 180.4 is interrupted, the measurement current IM1, IM2, IM3, IM4 in all other, non-interrupted parallel branches 180.1, 180.2, 180.3, 180.4 will change, enabling the identification of the parallel branch 180.1, 180.2, 180.3, 180.4 where the measurement current IM is interrupted. Accordingly, the corresponding parallel branch 180.1, 180.2, 180.3, 180.4, where the temperature sensitive switch 110 is in its open position 110R, can be identified by detecting one of the measurement currents IM1, IM2, IM3, IM4.

(19) In the shown embodiment, each parallel branch 180.1, 180.2, 180.3, 180.4 comprises a corresponding electric resistor 170.1, 170.2, 170.3, 170.4 each with a corresponding resistance value R1, R2, R3, R4, wherein each resistance value R1, R2, R3, R4 is different from the other resistance values R1, R2, R3, R4 in terms of its Ohmic value. For example, the resistance values R1, R2, R3, R4 can have the relation R1<R2<R3<R4.

(20) The first measurement current IM1 in the corresponding first parallel branch 180.1 can be determined as follows:

(21) $\mathrm{IM}1=\mathrm{IT}*\frac{R1}{R1+R2+R3+R4}$

(22) When the first temperature sensitive switch 110.1 switches to its open position 110R, the first measurement current IM1 will be zero, as the first parallel branch 180.1 is interrupted. If one of the other temperature sensitive switches 110.2, 110.3, 110.4 switches to its open position 110B, the corresponding other measurement current IM2, IM3, IM4 will be zero. For example, if the fourth temperature sensitive switch 110.4 switches to its open position 110B, the fourth parallel branch 180.4 will be interrupted and the fourth resistor 170.4 with its fourth resistance value R4 will be rendered ineffective. In such case, the first measurement current would be determined as follows:

(23) $\mathrm{IM}{1}^{}=\mathrm{IT}*\frac{R1}{R1+R2+R3}$

(24) Hence, the further measurement current IM1 is greater than the measurement current IM1 above, since the total current IT is distributed on fewer parallel branches 180.1, 180.2, 180.3. Because of the individual, different resistance values R1, R2, R3, R4, it can be detected for each cylinder 140.1, 140.2, 140.3, 140.4 individually, whether the corresponding temperature sensitive switch 110.1, 110.2, 110.3, 110.4 has switched to its open position 110B. In the embodiment shown in FIG. 2B, the signal processing unit 210 is connected to the parallel electric circuit 248 via a measurement terminal 230 electrically connected to the fourth parallel branch 180.4. Consequently, the fourth measurement current IM4 determined by the signal processing unit 210 will be zero when the fourth temperature sensitive switch 110.4 is in its open position 110B.

(25) When the first temperature sensitive switch 110.1 is in its open position 110B, the fourth measurement current IM4 will be as follows:

(26) $\mathrm{IM}{4}^{}=\mathrm{IT}*\frac{R4}{R2+R3+R4}$

(27) When the second temperature sensitive switch 110.2 is in its open position 110B, the fourth measurement current IM4 will be as follows:

(28) $\mathrm{IM}{4}^{}=\mathrm{IT}*\frac{R4}{R1+R3+R4}$

(29) When the third temperature sensitive switch 110.3 is in its open position 110B, the fourth measurement current IM4 will be as follows:

(30) $\mathrm{IM}{4}^{}=\mathrm{IT}*\frac{R4}{R1+R2+R4}$

(31) Hence, it can be individually determined for each cylinder 140.1, 140.2, 140.3, 140.4, whether the corresponding temperature T1, T2, T3, T4 has reached or exceeded the switch temperature TS, and a first to fourth overheat signal SO1, SO2, SO3, SO4 can be output accordingly.

(32) Even more, also if a combination of several temperature sensitive switches 110.1, 110.2, 110.3given that they are arranged in parallel branches 180.1, 180.2, 180.3 not comprising the measurement terminal 230switch to the open position 110B, such combination can be determined by an individual value of the fourth measurement current IM4.

(33) In other embodiments, the measurement terminal 230 can be connected to any other parallel branch 180.1, 180.2, 180.3 of the sensor network 200.

(34) In optional embodiments, the sensor network 200 or the further sensor network 200 can comprise further temperature sensitive switches 110, in particular a fifth temperature sensitive switch 110.5 and/or a sixth temperature sensitive switch 110.6, as further described in the context of FIG. 3A and FIG. 3B.

(35) FIG. 3A shows a preferred embodiment of a compressor assembly 200 in the form of a reciprocating compressor 202, comprising an amount of four cylinders 140.1, 140.2, 140.3, 140.4 in a front view, with the first cylinder 140.1 and the second cylinder 140.2 visible. The first cylinder 140.1 and the fourth cylinder 140.4 are arranged in a first V-shaped configuration V1. In an analog manner, the second cylinder 140.2 and the third cylinder 140.3 are also arranged in a second V-shaped configuration V2, as also visible in the side view of FIG. 3B. The compressor assembly 200 is driven by an electric motor 250, which is located symmetrically in between the first V-shaped configuration V1 and the second V-shaped configuration V2. In FIG. 3B, a third reciprocating piston 150.3 assigned to the third cylinder 140.3, as well as the crankshaft 154 are visible in an exemplary cut out view.

(36) A cooling means 160 in the form of a fan 162 is assigned to each cylinder 140. Consequently, a first cooling means 160.1 in the form of a first fan 162.1 is assigned to the first cylinder 140.1. The first cooling means 160.1 is arranged on a first cylinder head region 142.1 of the first cylinder 140.1. The first temperature sensitive switch 110.1 comprises a first electric terminal 112.1 and a second electric terminal 140.1. The first temperature sensitive switch 110.1 is arranged at the first cylinder head region 142.1, in between the first cylinder head region 142.1 and the first cooling means 160.1.

(37) The first temperatures sensitive switch 110.1 is adapted to switch to an open position 110B when a first temperature T1 reaches or exceeds a switch temperature TS, as described in FIG. 1A and FIG. 1B. This is particularly the case when the first cooling means 160.1 stops operating or is operating in an abnormal operating mode, in particular with reduced efficiency.

(38) The above description referring to the first temperature sensitive switch 110.1 and the first cylinder 140.1 applies in an analog manner to the second, third and fourth temperature sensitive switch 110.2, 110.3, 110.4 as well as the second, third and fourth cylinder 140.2, 140.3, 140.4, respectively.

(39) In particular, the compressor assembly 100 shown in FIG. 3A and FIG. 3B can comprise a sensor network 200 as shown in FIG. 2A or alternatively, a sensor network 200 as shown in FIG. 2B. In particular, the according sensor network 200, 200 can be achieved by the corresponding wiring of each first electric terminal 112 and each second electric terminal 114 of the temperature sensitive switches 110.

(40) The compressor assembly 200 can optionally comprise a first temperature sensing device 122, configured to determine a motor temperature TM at the electric motor 250. Preferably, the first temperature sensing device 122 can be in the form of a fifth temperature sensitive switch 110.5, adapted to switch into an open position 110B when a further switch temperature TS2 is reached or exceeded. Depending on the architecture of the sensor network 200, 200, the fifth temperature sensitive switch 110.5 can be arranged in series with the other temperature sensitive switches 110 in a serial electrical circuit 246, or in a fifth parallel branch 180.5 in a parallel electrical circuit 248.

(41) The compressor assembly 200 can optionally comprise a second temperature sensing device 124, configured to determine a power electronics temperature TP at a power electronics unit 260. In particular, the power electronics unit 260 can be in the form of or comprise an inverter 262, as shown in FIG. 3B. Preferably, the second temperature sensing device 124 can be in the form of a sixth temperature sensitive switch 110.6, adapted to switching to an open position 110 be when an even further switch temperature TS3 is reached or exceeded. Depending on the architecture of the sensor network 200, 200, the sixth temperature sensitive switch 110.6 can be arranged in series with the other temperature sensitive switches 110 in a serial electrical circuit 246, or in a sixth parallel branch 180.6 in a parallel electrical circuit 248.

(42) FIG. 4 shows a schematic view of a vehicle 1000 comprising a compressor assembly 100 according to the concept of the invention. The vehicle 1000 can be a conventional combustion vehicle 1001 with a drive means 1100 in the form of a combustion engine 1101. In other embodiments, the vehicle 1000 can be an electric vehicle 1002, with drive means 1100 in the form of one or more electric drive motors 1102. In again other embodiments, the vehicle 1000 can be a hybrid vehicle 1004, with a drive means 1100 combining a combustion engine 1101 and one or more electric drive motors 1102. The drive means 1100 is adapted to provide a drive motion MD for propelling the vehicle 1000.

(43) The vehicle 1000 further comprises an electric energy source 1200, in particular a vehicle battery 1202 such as a traction battery 1204 and/or a system supply battery 1206. In other embodiments, the electric energy source 1200 can alternatively or additionally comprise a fuel cell 1208. The electric energy source 1200 is adapted to provide electric energy E to the one or more electric drive motors 1102 and/or the electric motor 250 of the compressor assembly 200. Independent of the mode of propulsion, the vehicle 1000 can be a commercial vehicle 1012 or a passenger vehicle 1014.

(44) The depicted vehicle 1000 exemplarily comprises two axles 530, a front axle 532 and a rear axle 534. Wheels 540 are attached to the front axle 532 as well as to the rear axle 534. In other embodiments, the drivetrain can be different, such as an individual electric motor 1102 assigned to each axle 530 or wheel 540. In other embodiments, the number of axles 530 and wheels 540 can vary.

(45) The vehicle 1000 comprises an air supply system 800 with a compressor assembly 100. The main components of the compressor assembly 100 are shown schematically, with a rotational axis AR of the crankshaft 154 indicated. The orientation of the rotational axis AR and thus, the modular compressor assembly 100, can vary depending on the available space and installation position in the vehicle 1000, and is hereas an examplesubstantially parallel to the vehicle 1000.

(46) The air supply system comprises at least one pneumatic consumer 810, such as a pneumatic brake system 812 and/or an air suspension system 814 and/or a sensor cleaning system 816.

(47) The signal processing unit 210 of the sensor network 100 is configured to communicate with an electronic control unit 700 of the vehicle 1000, in order to provide an overheat signal SO to the electronic control unit 700. In particular, the signal processing unit 210 is connected to the electronic control unit 700 by means of a signal line 740.

(48) The electronic control unit 700 is again configured to provide an alarm indication 722 in dependence of the overheat signal SO. The vehicle 1000 can comprise an alarm indication device 720, adapted to output the alarm indication 722. The alarm indication device 720 is preferably adapted to output an alarm message 724 and for this purpose can comprise a display screen. In other embodiments, the alarm indication device 720 can comprise other indication devices, such as a lightbulb, an audio speaker or the like output means for indicating a visual and/or aural alarm indication 722.

LIST OF REFERENCE SIGNS (PART OF THE DESCRIPTION)

(49) 100 compressor assembly 100 further compressor assembly 110 temperature sensitive switch 110.1 first temperature sensitive switch 110.2 second temperature sensitive switch 110.3 third temperature sensitive switch 110.4 fourth temperature sensitive switch 110.5 fifth temperature sensitive switch 110.6 sixth temperature sensitive switch 110A closed position of the temperature sensitive switch 110B open position of the temperature sensitive switch 111 bimetallic switch 112 first electric terminal 112.1 first electric terminal of the first temperature sensitive switch 112.2 first electric terminal of the second temperature sensitive switch 112.3 first electric terminal of the third temperature sensitive switch 112.4 first electric terminal of the fourth temperature sensitive switch 114 second electric terminal 114.1 second electric terminal of the first temperature sensitive switch 114.2 second electric terminal of the second temperature sensitive switch 114.3 second electric terminal of the third temperature sensitive switch 114.4 second electric terminal of the fourth temperature sensitive switch 115 contact bridge 116 first material layer 118 second material layer 119 contact foundation 122 first temperature sensing device 124 second temperature sensing device 140 cylinder 140.1 first cylinder 140.2 second cylinder 140.3 third cylinder 140.4 fourth cylinder 142.1 first cylinder head region 150 contact bridge 150.3 third reciprocating piston 154 crankshaft 160 cooling means 160.1 first cooling means 162 fan 162.1 first fan 170.1 first electric resistor 170.2 second electric resistor 170.3 third electric resistor 170.4 fourth electric resistor 180 parallel branch 180.1 first parallel branch 180.2 second parallel branch 180.3 third parallel branch 180.4 fourth parallel branch 180.5 fifth parallel branch 180.6 sixth parallel branch 200 sensor network 200 further sensor network 202 reciprocating compressor 210 signal processing unit 230 measurement terminal 240 electric source 242 first source terminal 244 second source terminal 246 serial electric circuit 248 parallel electric circuit 250 electric motor 260 power electronics unit 262 inverter 530 axle 532 front axle 534 rear axle 540 wheel 700 electronic control unit 720 alarm indication device 722 alarm indication 724 alarm message 740 signal line 800 air supply system 810 pneumatic consumer 812 pneumatic brake system 814 air suspension system 816 sensor cleaning system 1000 vehicle 1001 combustion vehicle 1002 electric vehicle 1004 hybrid vehicle 1012 commercial vehicle 1014 passenger vehicle 1100 drive means 1101 combustion engine 1102 electric drive motor 1200 electric energy source 1202 vehicle battery 1204 traction battery 1206 system supply battery 1208 fuel cell AR rotational axis E electric energy H heat flow IM measurement current IT total current K contact point MD drive motion MO opening movement SO overheat signal T temperature TC greater temperature coefficient TM motor temperature TP power electronics temperature TS switch temperature TS2 further switch temperature TS3 even further switch temperature UM measurement voltage V1 first V-shaped configuration of cylinders V2 second V-shaped configuration of cylinders