STATOR COOLING ASSEMBLY FOR A LINEAR MOTOR

A stator cooling assembly for a linear motor includes a stator and a modular cooling arrangement. The modular cooling arrangement comprises: a U-shaped fluid cooling pipe having first and second linear segments extending along first and second opposite longitudinal sides of the stator; an inlet and outlet port connected to a free end of the first and second linear segments, respectively, for circulating a cooling fluid; a central cooling arrangement comprising primary cooling units mounted into recesses of the stator; and connecting members connecting the central cooling arrangement to the fluid cooling pipe. Each primary cooling unit comprises a heat pipe having first and second portions extending along a recess of the stator and along a portion of the fluid cooling pipe, respectively. The connecting members connect the second portion of the heat pipe of each primary cooling unit to corresponding portions of the fluid cooling pipe.

CROSS REFERENCE TO RELATED APPLICATION

This application claims benefit to European Patent Application No. EP 22156490.9, filed on Feb. 14, 2022, which is hereby incorporated by reference herein.

FIELD

The present invention relates to a stator cooling assembly for a linear motor, comprising a stator and a modular cooling arrangement mounted on the stator for heat dissipation. The invention also relates to a linear motor comprising the stator cooling assembly.

BACKGROUND

Conventional approaches to dissipate heat on electric motors rely on the thermal conductivity of motor components to transport heat. However, generally motor components need to provide high electrical resistance for safety and operating reasons. High electrical resistance typically comes with high thermal resistance, thus traditional cooling strategies are limited by this factor.

Liquid-cooled stators for linear motors are well-known in the art and many solutions have been proposed.

EP1354392B1, for example, discloses a cooled stator for a linear motor, comprising a stator having a magnetic laminated core and a cooling arrangement mounted on the stator. The cooling arrangement is made of a first and a second corrugated metal hose for flowing a cooling medium along the longitudinal direction of the stator. The first corrugate metal hose is arranged to form a serpentine flow path mainly in bores of the laminated core while the second corrugated metal hose is arranged on top of the first corrugate metal hose to form a serpentine flow path in the slots of the stator.

The cooling arrangement of EP1354392B1 has several disadvantages. This cooling arrangement is not modular and designing and producing a cooling arrangement specific to a particular motor length may be tedious, time consuming and therefore costly since every motor with a different length needs a specific corrugated hose shape. Significant pressure drop may also occur due to the significant length and multiple turns of the cooling arrangement. This cooling arrangement has also a negative impact on the motor performance as electrically conductive cooling hose are inserted in the slots of the stator where strong magnetic fields are present.

U.S. Pat. No. 7,309,931B2 discloses an electric linear motor comprising a heat-generating motor part, and a modular cooling arrangement. The cooling arrangement has a meandering configuration and is secured to the motor part for removal of heat. The cooling arrangement comprises separate straight cooling pipes, and separate deflections for attachment and interconnection of the straight cooling pipes. The deflection includes two separate elbows made of plastic and a coupling section for connecting the elbows to one another, with one of the elbows made in one piece with the coupling section.

This cooling arrangement is modular at the cost of additional complexity and at the risk of cooling fluid leakage at the joints between segments.

DE19604643B4 discloses a linear motor comprising a cooling arrangement including pipes press-fitted into slots located at the back of the lamination stack of the magnetic core, thus avoiding degrading the motor performance. Placing the cooling arrangement at the back of the lamination stack has however the drawback to significantly reduce the cooling capacity of the cooling arrangement.

SUMMARY

In an embodiment, the present invention provides a stator cooling assembly for a linear motor. The stator cooling assembly includes a stator and a modular cooling arrangement mounted on the stator. The modular cooling arrangement comprises: a U-shaped fluid cooling pipe having a first linear segment extending along a first longitudinal side of the stator and a second linear segment extending along a second longitudinal side of the stator, opposite the first longitudinal side; an inlet and an outlet port connected to a free end of the first and second linear segments, respectively, of the U-shaped fluid cooling pipe for circulating a cooling fluid along the first and second longitudinal sides of the stator; a central cooling arrangement comprising primary cooling units mounted into respective recesses of the stator extending across the stator from the first to the second longitudinal side; and connecting members connecting the central cooling arrangement to the U-shaped fluid cooling pipe. Each of the primary cooling units comprises at least one heat pipe having a first portion extending along the respective recess of the stator, and a second portion extending along a portion of the U-shaped fluid cooling pipe. The connecting members connect the second portion of the at least one heat pipe of each of the primary cooling units to corresponding portions of the U-shaped fluid cooling pipe

DETAILED DESCRIPTION

An aim of embodiments of the present invention is to provide a stator cooling assembly for a linear motor, comprising a modular cooling arrangement which overcomes the above limitations.

More particularly, an aim of embodiments of the present invention is to provide a stator cooling assembly for a linear motor, comprising a modular cooling arrangement that is easy to manufacture and cost effective.

Another aim of embodiments of the present invention is to provide a stator cooling assembly for a linear motor, comprising a modular cooling arrangement that produces insignificant pressure drop occurring along the cooling arrangement.

A further aim of embodiments of the present invention is to provide a stator cooling assembly for a linear motor, comprising a modular cooling arrangement presenting a lower risk of leakage.

These aims are achieved by a stator cooling assembly for a linear motor according to an embodiment of the present invention, comprising a stator and a modular cooling arrangement mounted on the stator. The modular cooling arrangement comprises:a U-shaped fluid cooling pipe comprising a first linear segment extending along a first longitudinal side of the stator and a second linear segment extending along a second longitudinal side of the stator, opposite the first longitudinal side,an inlet and an outlet port connected to a free end of the first and second linear segments respectively of the fluid cooling pipe for circulating a cooling fluid along both longitudinal sides of the stator,a central cooling arrangement comprising primary cooling units mounted into respective recesses of the stator extending across said stator from the first to the second longitudinal side, andconnecting members connecting the central cooling arrangement to the U-shaped fluid cooling pipe.

Each primary cooling unit comprises at least one heat pipe having a first portion extending along the corresponding recess of the stator, and a second portion extending along a portion of the U-shaped fluid cooling pipe. The connecting members connect the second portion of the at least one heat pipe of each primary cooling unit to the corresponding portions of the U-shaped fluid cooling pipe.

In an embodiment, the at least one heat pipe of each primary cooling unit of the central cooling arrangement is L-shaped.

In an embodiment, each primary cooling unit comprises a first and a second L-shaped heat pipe comprising each the first and second portions. The first portion of the first and second L-shaped heat pipes of each primary cooling unit extends along the recess. The second portion of the first and second L-shaped heat pipes of each primary cooling unit extends along a portion of respectively the first and second linear segments of the U-shaped fluid cooling pipe.

In an embodiment, each connecting member comprises two pipe receiving portions parallel to each other. One receiving portion receives a portion of either the first and second linear segments of the U-shaped fluid cooling pipe. The other receiving portion receives the second portion of either the first and second L-shaped heat pipes of the corresponding primary cooling unit. The pipe receiving portions are for example in the form of grooves extending across the connecting member or in the form of through-holes extending through said connecting member.

In an embodiment, each primary cooling unit comprises a primary insert having a first and a second pipe receiving portion, for example a first and a second groove, parallel to each other and receiving respective first portions of the first and second L-shaped heat pipes.

In an embodiment, the modular cooling arrangement further comprises two secondary cooling units arranged into recesses of the stator extending along both sides of the central cooling arrangement. Each secondary unit comprises a single L-shaped heat pipe having a first and a second portion extending respectively along the recess and along a portion of respective first and second linear segments.

In an embodiment, each secondary cooling unit comprises a secondary insert having a single pipe receiving portion, for example a groove, receiving the first portion of the single L-shaped heat pipe.

In an embodiment, the primary and secondary inserts of respective primary and secondary cooling units are press-fitted into the corresponding recesses of the stator.

In an embodiment, the primary and secondary inserts and the connecting members are made of metal having a thermal conductivity coefficient exceeding 200 W m−1K−1at 20° C. and 1 bar, such as aluminum or copper.

In an embodiment, the second portion of the first L-shaped heat pipe of each primary cooling unit extends along the first linear segment of the U-shape fluid cooling pipe in a first direction. The second portion of the second L-shaped heat pipe of each primary unit extends along the second linear segment of the U-shape fluid cooling pipe in a second direction opposite the first direction.

In an embodiment, the cross-section of the L-shaped heat pipes is smaller than the cross-section of the U-shaped fluid cooling pipe.

In an embodiment, the U-shaped fluid cooling pipe further comprises a third linear segment between the first and second linear segments. The third linear segment extends along a lateral side of the stator.

Another embodiment of the invention provides a primary part of a linear motor, comprising the stator cooling assembly as described above and a housing arranged to encapsulate the stator cooling assembly.

In an embodiment, spacers are mounted on mounting portions of the stator such that a top side of each spacer is in contact against a bottom side of the housing which is opposite the housing top side to keep the bottom side away from the modular cooling arrangement to avoid excessive heating of the housing.

In an embodiment, the first and second linear segments of the U-shaped fluid cooling pipe are mounted against two opposite longitudinal sides of the housing by means of the cooling members which are fixed to the opposite longitudinal sides of the housing to cool down the housing.

Another embodiment of the invention a linear motor comprising the primary part as described above.

With reference toFIGS.1to4, the primary part80of a linear motor comprises a housing70encapsulating a stator cooling assembly10. The stator cooling assembly10comprises a stator12and a modular cooling arrangement20mounted on the stator. The modular cooling arrangement20comprises a U-shaped fluid cooling pipe22provided with a first and a second port24,26mounted on free ends of the U-shaped fluid cooling pipe22for circulating a cooling fluid around a central part of the stator. In this respect, the fluid cooling pipe22comprises a first linear segment23arranged along a first longitudinal side of the stator, a second linear segment25arranged along a second longitudinal side of the stator, opposite to the first longitudinal side and a third linear segment28arranged along a lateral side of the stator.

Referring toFIG.5, the modular cooling arrangement20further comprises a central cooling arrangement40mounted on a top side of the stator12, as shown inFIGS.1and2, and surrounded by the fluid cooling pipe22.

The central cooling arrangement40comprises primary cooling units42mounted into recesses14of the stator12between mounting portions16of the stator as shown inFIG.1. The recesses14extend from the first to the second longitudinal side of the stator. In an embodiment, each primary cooling unit42comprises a primary insert50adapted to be press-fitted into the respective recesses14of the stator as well as a first and a second L-shaped heat pipe44a,44bmounted in the primary insert (FIG.6). To this end, each primary insert50comprises pipe receiving portions52a,52bfor example in the form of parallel grooves, as per the modular cooling arrangement of the illustrated embodiment, extending along the insert50, or in the form of parallel through-holes extending through the insert according to a non-illustrated variant.

With reference toFIG.3, the first and second L-shaped heat pipes44a,44bof each primary cooling unit comprise each a first portion46and a second portion48. The first portion46of the first and second heat pipes44a,44bextends along respectively the first and second grooves52a,52bof the insert50. The second portion48of the first and second heat pipes44a,44bextend along a portion of respectively the first and second linear segments23,25of the U-shaped fluid cooling pipe20.

In a preferred embodiment, the second portion48of the first L-shaped heat pipe44aof each primary cooling unit42extends along the first linear segments23in a first direction whereas the second portion48of the second L-shaped heat pipe44bof each primary unit42extends along the second linear segment25in a second direction opposite the first direction.

With reference toFIG.5, the modular cooling arrangement20further comprises two secondary cooling units54mounted into recesses14of the stator12(FIG.1) extending along both sides of the central cooling arrangement40. In an embodiment, each secondary unit54comprises a secondary insert60with a pipe receiving portion62and a single L-shaped heat pipe56. The width of the secondary insert60is approximately half the width of the primary inserts50. The secondary insert60is press-fitted into the corresponding recess14of similar width. The single heat pipe56comprises a first portion57extending along the pipe receiving portion62, for example along a groove, and a second portion58along a portion of respective first and second segments23,25of the fluid cooling pipe22as shown inFIG.3.

The modular cooling arrangement20further comprises connecting members30connecting the heat pipes to the fluid cooling pipe22. More particularly, the connecting member30comprises two pipe receiving portions32a,32bin the form, for example, of parallel grooves. One receiving portion32aof each connecting member30receives a portion of either the first and second linear segments23,25of the fluid cooling pipe22. The other receiving portion32bof each connecting member30receives the second portion48of either the first and second L-shaped heat pipes44a,44bof the corresponding primary cooling unit42or the second portion58of the L-shaped heat pipe56of the corresponding secondary unit54.

The primary and secondary inserts50,60as well as the connecting members30are made of metal having a high thermal conductivity coefficient, preferably exceeding 200 W m−1K−1at 20° C. and 1 bar, such as aluminum or copper to maximize heat transfer.

The heat pipes of the primary and secondary cooling units42,54comprise each a working fluid which turns into vapour by absorbing heat from the primary and secondary inserts50,60which are heated by the stator when in operation. The vapour then travels from the first to the second portion of the heat pipes, whereupon the working fluid in a gaseous state is cooled down by the fluid cooling pipe22, thereby condensing the working fluid back into a liquid and releasing the latent heat. The liquid then returns from the second to the first portion of the heat pipes through capillary action to cool down the stator and to repeat a cooling cycle.

In another non illustrated embodiment, the first portion of the L-shaped heat pipes of the primary and secondary cooling units are directly fitted into the respective recesses of the stator to avoid one thermal interface.

In the embodiment ofFIG.1, a top side of the housing70comprises though-holes72. During manufacturing, the housing70is fixed to the stator cooling assembly10by means of screws fitted into the through-holes72and screwed into the mounting portions16of the stator located between the stator recesses14. The bottom side of the housing top side is therefore in direct contact with the modular cooling arrangement20. After motor potting operation, these screws are removed and the housing70is thus glued onto the stator cooling assembly10. During operation, the housing top side, which is a customer interface, is therefore heated. Excessive heating may be however an issue for certain customer applications.

The embodiment illustrated inFIG.7solve the above issue. Spacers64are mounted on the mounting portions16of the stator12such that a top side of each spacer is in contact against a bottom side of the housing70which is opposite the housing top side so as to keep the bottom side away from the modular cooling arrangement to avoid excessive heating of the housing during operation.

Advantageously, the first and second linear segments23,25of the U-shaped fluid cooling pipe22are mounted against two opposite longitudinal sides of the housing70by means of the connecting members30which are fixed to the opposite longitudinal sides so as to cool down the housing.

To this end, each connecting member30is designed to have a supporting part34supporting the corresponding portions of the L-shaped heat pipes44a,44band of the U-shaped fluid cooling pipe22, and a fixing part36fixed to respective longitudinal sides of the housing by means of screws38.

Various modifications and variations to the described embodiments of the invention will be apparent to those skilled in the art without departing from the scope of the invention as defined in the appended claims. For example, each primary cooling unit may have just one heat pipe to provide a more cost-effective modular cooling arrangement at the expense of a decrease in cooling efficiency.

REFERENCE LIST