Linear motor with heat dissipating capabilities and heat reducing considerations

A linear motor is disclosed, the linear motor comprising a longitudinal coil assembly comprising coil units arranged in a cascading manner and a magnet track spaced from the coil assembly, and adapted to move along a path which traces a periphery of the coil assembly. The linear motor further comprises sensors, each sensor being associated with a subset of the coil units, and adapted to send a first sensor signal in response to detecting the magnet track. The linear motor further comprises a control unit, wherein the control unit is configured to receive the first sensor signal, identify the sensor which sent the first sensor signal, and power up the subset of the coil units associated with the sensor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage of International Application No. PCT/SG2018/050550, filed on Oct. 31, 2018, which claims priority to SG 10201709114V, filed on Nov. 6, 2017, the contents of each of which is hereby incorporated by reference in their entirety.

FIELD OF THE INVENTION

The following discloses a linear motor, and more particularly a linear motor with heat dissipating capabilities and heat reducing considerations.

BACKGROUND

When current is supplied to a linear motor, a linear trust is produced which results in either the motion of the magnet track or the coil assembly, which cause heat to be generated. To address the overheating, U.S. Pat. No. 6,528,907 B2 teaches a linear motor having thermo-electric semiconductor cooling modules to dissipate heat from the stator element.

However, this solution is inefficient as it requires the continuous powering of the thermoelectric semiconductor cooling modules along the length of the stator element. This inefficiency is compounded when the length of the motor coil is long. Furthermore, this solution is ineffective when the heat generation is in specific areas.

The present invention therefore seeks to provide a linear motor with the capability to selectively cool portions of its coil assembly. Furthermore, another object of the invention is to selectively power up portions of the coil assembly, with the aim of reducing the overall heat being generated by the linear motor. Other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background of the disclosure.

SUMMARY OF INVENTION

According to a first aspect of the invention, a linear motor is disclosed, the linear motor comprising a longitudinal coil assembly comprising a plurality of coil units arranged in a cascading manner and a magnet track spaced from the coil assembly, and adapted to move along a path which traces a periphery of the coil assembly. The linear motor further comprises a plurality of sensors, each sensor in the plurality of sensors being associated with a subset of the plurality of coil units, and adapted to send a first sensor signal in response to detecting the magnet track. The linear motor further comprises a control unit, wherein the control unit is configured to receive the first sensor signal, identify the sensor in the plurality of sensors, the sensor having sent the first sensor signal, and power up the subset of the coil units associated with the sensor.

Preferably, the linear motor further comprises a plurality of thermo-electric cooling units and wherein each sensor in the plurality of sensors are further associated with a subset of the plurality of thermo-electric cooling units, and wherein the control unit is further configured to identify another sensor in the plurality of sensors, the another sensor having sent the first sensor signal, and activate the subset of the plurality of thermo-electric cooling units associated with the another sensor.

Preferably, the subset of the plurality of thermo-electric cooling units associated with the another sensor are positioned adjacent to, and are adapted to cool the subset of the plurality of coil units associated with the sensor.

Preferably, the subset of the plurality of coil units associated with the sensor comprises a “U” coil winding, a “V” coil winding and a “W” coil winding, and wherein the subset of the plurality of thermo-electric cooling units associated with the another sensor are adapted to cool the “U” coil winding, the “V” coil winding, and the “W” coil winding.

Preferably, each sensor in the plurality of sensors is further adapted to send a second sensor signal in response to not detecting the magnet track, and wherein the control unit is further configured to receive the second sensor signal from the sensor and depower the subset of the plurality of coil units associated with the sensor.

Preferably, the control unit is further configured to receive the second sensor signal from the another sensor and deactivate the subset of the plurality of thermo-electric cooling units associated with the another sensor.

Preferably, the sensor and the another sensor are the same sensor.

Preferably, the plurality of sensors comprises hall sensors adapted to detect a magnetic field of the magnet track or optical sensors adapted to detect a position of the magnet track.

Preferably, the linear motor further comprises a coil assembly cap and wherein the plurality of thermo-electric cooling units are embedded in the coil assembly cap.

Preferably, the linear motor further comprises a heat sink positioned adjacent to the plurality of thermo-electric cooling units

Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been depicted to scale. For example, the dimensions of some of the elements in the block diagrams or steps in the flowcharts may be exaggerated in respect to other elements to help improve understanding of the present embodiment.

DETAILED DESCRIPTION

In embodiments, a linear motor is described, the linear motor comprising a longitudinal coil assembly. The coil assembly comprises coil units arranged in a cascading manner. The linear motor also comprises a magnet track spaced from the coil assembly, and adapted to move along a path which traces the periphery of the coil assembly. The linear motor also comprises sensors such as hall sensors, which can be positioned and spaced along the length of the linear motor. Each sensor is associated with a subset (one or more but not all) of the coil units. Each sensor is adapted to send or output a first sensor signal in response to detecting the magnet track.

The linear motor also comprises a control unit, the control unit configured to receive the first sensor signal (the signal that indicates that the magnet track has been detected), identify the sensor (amongst the plurality of sensors) which sent the first sensor signal, and power up the subset of the coil units associated with that sensor. The control unit can store the association between the sensors and their associated subset of coil units. This association can be based on the proximity from one another i.e. the sensor is positioned near or close to its associated subset of coil units.

In operation, a particular sensor detects the magnet track as it commutes along its path. The particular sensor sends the first sensor signal to the control unit. In response, the control unit powers up only the coil units associated with the particular sensor. The coil units associated with the particular sensor would typically be near or proximate to the particular sensor which therefore follows that only the coil units near or proximate to the current position of the magnet track will be powered up. These associated coil units can be the coil units which are “ahead” of the magnet track along its path. Therefore, the coil units are selectively powered up, and relative to the current position of the magnet track as it moves along its path. This is advantageous as the coil units which are not near to the current position of the magnet track will not be powered up which helps to mitigate the overall heat generation of the linear motor.

Furthermore, due to the selective nature of powering up the coil units, not all of the coil units are powered up together at any one time. Instead, only a subset of the coil units are powered up at any one time which again helps to reduce the overall heat generation of the linear motor.

In embodiments, the linear motor can further comprise thermo-electric cooling units. The thermo-electric cooling units are for cooling or removing heat from the coil units. Each sensor can be further associated with a subset (one or more but not all) of the thermo-electric cooling units. The control unit can be configured to receive the first sensor signal (the signal that indicates that the magnet track has been detected), identify the sensor (amongst the plurality of sensors) which sent the first sensor signal, and activate the subset of thermo-electric cooling units associated with that sensor. The control unit can store the association between the sensors and their associated subset of thermo-electric cooling units. This association can be based on the proximity from one another i.e. the sensor is positioned near or close to its associated subset of thermo-electric cooling units.

In operation, a particular sensor detects the magnet track as it commutes along its path. The particular sensor sends the first sensor signal to the control unit. In response, the control unit activates only the thermo-electric cooling units associated with the particular sensor. The thermo-electric cooling units associated with the particular sensor would typically be near or proximate to the particular sensor which therefore follows that only the thermo-electric cooling units near or proximate to the current position of the magnet track will be activated. These associated thermo-electric cooling units can be the thermo-electric cooling units which are “ahead” of the magnet track along its path. Therefore, the thermo-electric cooling units are selectively activated, and relative to the current position of the magnet track as it moves along its path. This is advantageous as the thermo-electric cooling units which are not near to the current position of the magnet track will not be activated which helps to mitigate the overall heat generation of the linear motor.

Furthermore, due to the selective nature of activating the thermo-electric cooling units, not all of the thermo-electric cooling units are activated together at any one time. Instead, only a subset of the thermo-electric cooling units are activated at any one time which again helps to reduce the overall heat generation of the linear motor.

Even further still, the subset of the thermo-electric cooling units that have been activated can be proximate to the subset of coil units that have been powered up. Therefore, the subset of the thermo-electric cooling units that have been activated can cool the subset of the coil units that have been powered up. This results in a synergistic effect in that portions of the coil assembly are “selectively powered-up” and “selectively cooled”.

In embodiments, the sensors can be further adapted to send a second sensor signal in response to not detecting the magnet track. The control unit can be further configured to receive the second sensor signal (the signal that indicates that the magnet track can no longer be detected), identify the sensor which sent the second sensor signal, and depower the subset of the coil units associated with that sensor. Therefore, the associated coil units, which will typically be a distance from or not proximate to the current position of the magnet track will be depowered. These associated coil units can be the coil units which are “behind” the magnet track as the magnet track moves along its path. Therefore, the coil units are depowered relative to the sensors no longer detecting the magnet track.

In embodiments, the control unit can be further configured to receive the second sensor signal (the signal that indicates that the magnet track can no longer be detected), identify the sensor which sent the second sensor signal, and deactivate the subset of the thermo-electric cooling units associated with that sensor. Therefore, the associated thermo-electric cooling units, which will typically be a distance from or not proximate to the magnet track will be deactivated. These associated thermo-electric cooling units can be the thermo-electric cooling units which are “behind” the magnet track as the magnet track moves along its path. Therefore, the thermo-electric cooling units are deactivated relative to the sensors no longer detecting the magnet track.

In embodiments, a linear motor having the capability to selectively power-up and selectively cool portions of its coil assembly has been described. The efficiency of the linear motor is increased as the energy used at any one time is only for a subset of the coil units and for a subset of the thermo-electric cooling units. As such, embodiments of the inventions can achieve localized power-up or target cooling of the coil assembly, and can allow for a higher input current than its rating without causing the coil assembly to over-heat.

FIG. 1shows a perspective view of a linear motor in accordance with certain embodiments. Linear motor100can have magnet track101and coil assembly102. Magnet track101can be configured to follow a path or a trajectory. The path or trajectory of magnet track101can follow or trace a periphery or an edge of coil assembly102. When moving along the trajectory, magnet track101can be in close proximity to coil assembly102, but does not directly contact coil assembly102.

Coil assembly102can be made up of a plurality of coil units103. Coil units103can be concatenated in a cascading arrangement as shown inFIG. 1. Each coil unit103can be formed by winding multiple turns of conducting wire into coil windings, and connecting each of the poly phase in either WYE or DELTA arrangement. For example, coil unit103can have a “U” coil winding, a “V” coil winding and a “W” coil winding. The coil windings can be encapsulated in a thermally conductive and yet highly electrically resistive medium or epoxy. Each coil unit103can be in a “powered” or “depowered” mode.

Linear motor100can also comprise a plurality of thermo-electric cooling units104. Thermo-electric cooling units104can be arranged in an array as depicted inFIG. 1. Thermo-electric cooling units104can be adapted to cool coil units103. An exemplary thermo-electric cooling unit104is illustrated inFIG. 2. Thermo-electric cooling unit104can comprise multiple pairs of N semiconductor elements201and P semiconductor elements202, each N-P pair forming a thermocouple. The N semiconductor elements201and P semiconductor elements202can be held between two temperature resistant ceramic substrates203, and can be electrically connected to lead-out conductors204,205. Ceramic substrates203can serve to hold the overall structure together and also insulate the N semiconductor elements201and P semiconductor elements202from one another. Lead-out conductors204,205can be connected to power source206. The N semiconductor elements201can be doped such that it has an excess of electrons and the P semiconductor elements202can be doped to have a deficiency of electrons. To activate the thermo-electric cooling unit104, power from power source206is supplied through lead-out conductors204,205, and the electrons move heat energy from one ceramic substrate203(which experiences heat removal) to the other ceramic substrate203(which experiences heat dissipation).

Thermo-electric cooling units104can be located adjacent (in contact or in close proximity) to coil units103(for example, seeFIG. 1). There can be a thermo-electric cooling unit104designated for, and to cool each coil unit103. Alternatively, there can be a thermo-electric cooling unit104designated for each coil winding in coil unit103. For example, as illustrated inFIG. 3, coil unit103has “U” coil winding301, “V” coil winding302and “W” coil winding303, and each coil winding has a thermo-electric cooling unit104designated to it.

Thermo-electric cooling units104can be in an “activated” or a “de-activated” mode. When power is supplied to lead-out conductors204,205, thermo-electric cooling units104are activated, and begin actively removing heat from coil unit103(i.e. cool coil unit103). When power is removed from lead-out conductors204,205, thermo-electric cooling units104switch to the deactivated mode.

In embodiments, linear motor100can also comprise coil assembly cap105. Referring toFIG. 3, coil assembly cap105can be placed intermediate between coil units103and thermo-electric cooling units104. Coil assembly cap105can be affixed to the base of coil units103. Coil assembly cap105can serve as a conductive medium whereby heat from coil units103can be conducted out to thermo-electric cooling units104. Coil assembly cap105can also serve as a mounting medium for attaching external mechanical parts, whereby attachment to coil assembly cap105can be via tap holes304.

In embodiments, linear motor100can also comprise heat sink305. Referring toFIG. 3, heat sink305can be located adjacent (in contact or in close proximity) to thermo-electric cooling units104such that heat flows from thermo-electric cooling units104to heat sink305.

Linear motor100can also comprise a plurality of sensors106(seeFIG. 1). Each sensor in the plurality of sensors106can be adapted to detect magnet track101at some point as it moves along its path or trajectory. Each sensor106can be adapted to send sensor signals in response to detecting and no longer detecting magnet track101. For example, if a sensor106detects magnet track101, the sensor106can send a first sensor signal (DETECT), and if the sensor106does not detect magnet track101, the sensor106can send a second sensor signal (NO_DETECT). The plurality of sensors106can be positioned and spaced along the length of linear motor100. The plurality of sensors106(such as hall sensors) can also be positioned and spaced along coil assembly cap105(for example, seeFIG. 1). Non-exhaustive examples of sensors106can be hall sensors, optical sensors, infra-red sensors and the like.

In embodiments, each sensor in the plurality of sensors106can be associated with one or more coil units103. This association can be attributed to the close proximity between the sensor106and the one or more coil units103. For example, a sensor106can be associated with three coil units103as the physical location of the coil units103are near or proximate to the physical location of the sensor106. In embodiments, multiple sensors106can also be associated with a single coil unit103. This association can be attributed to the close proximity between the sensors106and the single coil unit103. For example, two sensors106can be associated with a single coil unit103as the physical location of the two sensors106are near or proximate to the physical location of the single coil unit103. The association between the plurality of sensors106and coil units103can be stored in an association table.

In embodiments, each sensor in the plurality of sensors106can be associated with one or more thermo-electric cooling units104. This association can be attributed to the close proximity between the sensor106and the one or more thermo-electric cooling units104. For example, a sensor106can be associated with three thermo-electric cooling units104as the physical location of the three thermo-electric cooling units104are near or proximate to the physical location of the sensor106. In embodiments, multiple sensors106can also be associated with a single thermo-electric cooling unit104. This association can be attributed to the close proximity between the sensors106and the single thermo-electric cooling unit104. For example, two sensors106can be associated with a single thermo-electric cooling unit104as the physical location of the two sensors106are near to or proximate the physical location of the single thermo-electric cooling unit104. The association between the plurality of sensors106and thermo-electric cooling units104can be stored in the association table.

In embodiments, linear motor100can comprise a control unit. The control unit can be adapted to receive the sensor signals sent from the sensors106. The control unit can be adapted to identify the sensor106which sent the sensor signal. If the identified sensor106has sent a first sensor signal (DETECT), the control unit can be configured to power-up the coil unit(s)103associated with the identified sensor106and/or activate the thermo-electric cooling unit(s)104associated with the identified sensor106.

If the identified sensor106has sent a second sensor signal (NO_DETECT), the control unit can be configured to depower the coil unit(s)103associated with the identified sensor106and/or deactivate the thermo-electric cooling unit(s)104associated with the identified sensor106.

In embodiments, the control unit can comprise switching control means for powering/depowering the coil unit(s)103associated with the identified sensor106, and activating/deactivating the thermo-electric cooling unit(s)104associated with the identified sensor106. In embodiments, the control unit can be configured to reference the association table to ascertain the coil unit(s)103and the thermo-electric cooling unit(s)104associated with the identified sensor106.

Referring toFIG. 4a, sensors401,402,403of plurality of sensors106are operationally connected to control unit410. Sensors401,402,403can be positioned and spaced along the length of linear motor100. Sensors401,402,403are adapted to send sensor signals to control unit410. Control unit410is adapted to identify which sensor401,402,403sent the sensor signal. Control unit410references association table411to ascertain which of the coil units420,421,422is/are associated with the identified sensor (401,402,403). Control unit410can use switching control means412to selectively power-up coil units420,421,422, which will draw power from power source206. Control unit410can also use switching control means412to selectively depower coil units420,421,422, wherein coil units420,421,422stop drawing power from power source206.

Referring toFIG. 4b, in a similar fashion to what had been described forFIG. 4a, control unit410references association table411to ascertain which of the thermo-electric cooling units (TECs)430,431,432is/are associated with the identified sensor (401,402,403). Control unit410can use switching control means412to selectively activate TECS430,431,432, which will draw power from power source206. Control unit410can also use switching control means412to selectively deactivate TECS430,431,432, wherein TECS430,431,432stop drawing power from power source206.

FIG. 5depicts a flowchart which outlines a method for selectively powering-up portions of a coil assembly of a linear motor, in accordance with certain embodiments. In step501, sensor401detects magnet track101commuting along its trajectory, and sends the first sensor signal (DETECT) to control unit410.

In step502, control unit410identifies that sensor401has sent the first sensor signal (DETECT). In step503, control unit410references association table411and ascertains that coil unit420is associated with sensor401. In step504, control unit410uses switching control means412to power-up coil unit420.

In step505, as magnet track101commutes further along its trajectory, sensor401no longer detects magnet track101and sends the second sensor signal (NO_DETECT) to control unit410.

In step506, control unit410identifies that sensor401has sent the second sensor signal (NO_DETECT). In step507, control unit410references association table411and ascertains that coil unit420is associated with sensor401. In step508, control unit410uses switching control means412to depower coil unit420. Although a single sensor401to a single coil unit420ratio has been described inFIG. 5, it will be obvious to a skilled person that variations are possible, and a single sensor401can be associated with multiple coil units or that multiple sensors can be associated with a single coil unit420.

FIG. 6depicts a flowchart which outlines a method for selectively cooling portions of a coil assembly of a linear motor, in accordance with certain embodiments. In step601, sensor401detects magnet track101commuting along its trajectory, and sends the first sensor signal (DETECT) to control unit410.

In step602, control unit410identifies that sensor401has sent the first sensor signal (DETECT). In step603, control unit410references association table411and ascertains that thermo-electric cooling unit (TEC)430is associated with sensor401. In step604, control unit410uses switching control means412to activate TEC430.

In step605, as magnet track101commutes further along its trajectory, sensor401no longer detects magnet track101and sends the second sensor signal (NO_DETECT) to control unit410.

In step606, control unit410identifies that sensor401has sent the second sensor signal (NO_DETECT). In step607, control unit410references association table411and ascertains that TEC430is associated with sensor401. In step608, control unit410uses switching control means412to deactivate TEC430. Although a single sensor401to a single TEC430ratio has been described inFIG. 6, it will be obvious to a skilled person that variations are possible, and a single sensor401can be associated with multiple TECs or that multiple sensors can be associated with a single TEC430.

FIG. 7depicts a flowchart which outlines a method for selectively powering-up and selectively cooling portions of a coil assembly of a linear motor, in accordance with certain embodiments. In step701, sensor401detects magnet track101commuting along its trajectory, and sends the first sensor signal (DETECT) to control unit410.

In step702, control unit410identifies that sensor401has sent the first sensor signal (DETECT). In step703, control unit410references association table411and ascertains that coil unit420and thermo-electric cooling unit (TEC)430are associated with sensor401. In step704, control unit410uses switching control means412to power-up coil unit420and activate TEC430.

In step705, as magnet track101commutes further along its trajectory, sensor401no longer detects magnet track101and sends the second sensor signal (NO_DETECT) to control unit410.

In step706, control unit410identifies that sensor401has sent the second sensor signal (NO_DETECT). In step707, control unit410references association table411and ascertains that coil unit420and TEC430are associated with sensor401. In step708, control unit410uses switching control means412to depower coil unit420and deactivate TEC430.

FIG. 8show the time step illustration as magnet track101commutes along its trajectory and proximate to an array of coil units103(coil assembly102), in accordance with certain embodiments. Each coil unit103is sectioned into its 3 coil windings301,302,303. An array of thermo-electric cooling units104are adjacent to the array of coil units103. Each coil winding301,302,303has a dedicated thermo-electric cooling unit104. Coil units103are powered-up/depowered and thermo-electric cooling units104are activated/deactivated in accordance with the disclosed embodiments.

As shown inFIG. 8, as magnet track101commutes along its trajectory, three coil units103are powered-up (depicted as shaded), and nine thermo-electric cooling units104are activated (depicted as shaded) to cool the respective three coil units103, in accordance with the disclosed embodiments.

FIG. 9shows an illustrative example of the positioning of optical sensors901on linear motor100, in accordance with certain embodiments.

FIG. 10shows magnet track101side by side with coil unit103. Magnet track101can comprise two longitudinal ferromagnetic plates1001,1002, linked by a shorter base plate1003. Magnet track101can have a U-shaped cross-section. Each ferromagnetic plate1001,1002can have an array of periodic alternating permanent magnets1004,1005. Ferromagnetic plates1001,1002and base plate1003can also have mounting holes1006.

Unless specifically stated otherwise, and as apparent from the following, it will be appreciated that throughout the present specification, discussions utilizing terms such as “processing”, “transferring”, “loading”, “storing”, “executing” “scanning”, “calculating”, “determining”, “replacing”, “generating”, “initializing”, “outputting”, or the like, refer to the action and processes of a computer system, or similar electronic device, that manipulates and transforms data represented as physical quantities within the computer system into other data similarly represented as physical quantities within the computer system or other information storage, transmission or display devices.

In the application, unless specified otherwise, the terms “comprising”, “comprise”, and grammatical variants thereof, intended to represent “open” or “inclusive” language such that they include recited elements but also permit inclusion of additional, non-explicitly recited elements.

It will be apparent that various other modifications and adaptations of the application will be apparent to the person skilled in the art after reading the foregoing disclosure without departing from the spirit and scope of the application and it is intended that all such modifications and adaptations come within the scope of the appended claims.