Patent Description:
In the electric power steering system, the electronic control unit can be connected with an electric motor for supplying power to the electric motor from a power source such as a battery. The electric power steering system can assist in a handling operation, typically a steering, of a transportation equipment by a driver. The transportation equipment can be an automobile.

The electric power steering system may further comprise a torque sensor, a steering shaft, a handle, typically a steering wheel, and the power source. In the following, a typical arrangement and operation of the electric power steering apparatus in an automobile will be described.

The torque sensor may be mounted on the steering shaft. Upon rotating the steering shaft by operating the handle, the torque sensor detects a torque being applied to the steering shaft by the operation of the handle. Upon detection of the torque by means of the torque sensor, a torque signal is output from the torque sensor to the electronic control unit. The electronic control unit then drives the electric motor based at least on the torque signal. Optionally, the control device may include further data such as vehicle speed in addition to the torque signal for controlling the driving of the electric motor.

The electronic control unit drives the electric motor by supplying a driving current from the power source, such as the battery of the automobile, to the electric motor. A driving force generated from the electric motor is then transmitted to the wheels directly or via a gearbox depending on the configuration in the automobile. As a result, the electric power steering apparatus changes a steering angle of the wheels by amplifying the torque of the steering shaft by means of the electric motor. This enables the driver to operate the handle with less force.

The electronic control unit comprises a power board electrically connected with the electric motor. The power to the electric motor is transmitted via this power board. Thereby, the power board generates heat during operation of the electronic control unit. To prevent overheating and damage of the electronic control unit, a heat sink may be provided inside of the electronic control unit and arranged in thermal contact with a housing of the electric power steering system or electric motor.

<CIT> describes a power unit for an electric steering system. The power unit comprises a motor housing for a motor, a heat sink and control electronics for the motor attached to the heat sink.

<CIT> discloses the preamble of the independent claim and describes a motor apparatus including an electric motor having a rotation shaft and two control circuit boards. The motor apparatus further comprises a connector equipped with two connection terminals. A first of the two connection terminals electrically connects the connector to the first control circuit board. The second of the two connection terminals electrically connects the connector to the second control circuit boards.

It is an object of the present invention to improve the electronic control unit for an electric power steering system and an electric power steering system known from the state of the art, in particular to provide an electronic control unit for an electric power steering system and an electric power steering system having improved assembly characteristics, in particular a compact, low-cost and easy-to-assemble design.

This problem is solved by the claims. Therefore, this object is solved by an electronic control unit according to independent claim <NUM> and an electric power steering system according to dependent claim <NUM>.

Further details of the invention unfold from the dependent claims <NUM> to <NUM> as well as the description and the drawings. Thereby, the features and details described in connection with the electronic control unit of the invention apply in connection with the electric power steering system and the other way around, so that regarding the disclosure of the individual aspects of the invention it is or can be referred to one another.

According to a first aspect of the invention, the problem is solved by an electronic control unit for an electric power steering system, the electric power steering system comprising a housing and an electric motor, the electronic control unit being configured to be arranged inside the housing and to be electrically connected to the electric motor, whereby the electronic control unit comprises a first power board having a first electric motor connector for electric connection with the electric motor, a second power board having a second electric motor connector for electric connection with the electric motor, and whereby a connector plate of the electronic control unit is electrically connected by means of at least one plug connector of the connector plate to the first power board via at least one first power connector and to the second power board via at least one second power connector, wherein the at least one first power connector is shorter than the at least one second power connector.

By means of providing different lengths of the first power connector and the second power connector, improved assembly characteristics, in particular a compact, low-cost and easy-to-assemble design, of the electronic control unit are achieved. That is, the first power board and the second power board may be arranged at different distances from the connector plate. Further, the first power board and the second power board may be arranged parallel to one another.

In particular, the first power connector may have a first length corresponding to a distance of the first power board from the connector plate and the second power connector may have a second length corresponding to a distance of the second power board from the connector plate, whereby the first length is smaller than the second length.

The first power board and the second power board may in particular be provided as printed circuit boards. The two power boards may comprise electronic components such as coils and capacitors for enabling the power board to transmit power from a power source to the electric motor.

The electric motor may in particular be arranged inside the housing. The housing may in particular be an electric motor housing, i.e. the housing of the electric motor. The housing may in particular have a tubular shape. The housing may further in particular have a circular or elliptical cross section. Also, the housing may be made from a heat-conducting material. The heat-conducting material may in particular be or comprise a metal such as aluminum, magnesium, copper or similar.

In particular, the two power boards may be separately from one another connected to the connector plate and thereby to the power source. The connector plate may be made from plastic, for example. The connector plate may be formed as a cap for sealing the housing at an end thereof. The connector plate may be provided with a sealing for sealing the inside of the housing against the outside. The sealing may be made from a silicone rubber. The connector plate may comprise one, two, three or more connectors, in particular plug connectors. At or inside of the plug connectors, the connector plate may be provided with electrical contacts. The electrical contacts may be made from a copper alloy, for example, to provide great electrical conductivity. One or multiple of the plug connectors may be provided for contacting the control board of the transportation equipment with the logic board. Thereby, the torque sensor, other sensors and/or other electronic control units may be connected to the logic board. The plug connectors may be connected by means of power connectors to the power boards.

It is possible, that the connector plate is connected to the first power board via two first power connectors and to the second power board via two second power connectors, wherein both first power connectors are shorter than both second power connectors.

Further, it is possible, that the at least one first power connector and/or the at least one second power connector are provided as metal strips. In particular, the metal strips may be provided as metal sheets. Aluminum, copper, alloys of the aforementioned or other metal having high electrical conductivity may be used for the metal strips. The at least one first power connector and the at least one second power connector may have flat and/or rectangular shape. The metal strips may be bent along their length such that they are positioned in the electronic control unit according to the defined geometry of other parts of the electronic control unit such as the power boards and the logic board.

It is further possible, that the at least one second power connector has at least <NUM> %, in particular at least <NUM> % and further in particular at least <NUM> %, of the length of the first power connector. Thereby, a large heat sink, i.e. having a large thickness, may be arranged in between the two power boards for providing good heat dissipation characteristics.

It is possible, that each of the first power board and the second power board is provided with three phases of electricity to supply three-phase electric power to the electric motor. Thereby, both power boards are able to provide the electric motor with three-phase electric power independent from one another. Further, it is possible, that the first power board and the second power board are arranged to supply three-phase electric power to the electric motor upon failure of the other one of the first power board and the second power board. For this purpose, a logic board of the electronic control may be arranged to detect failure of one of the two power boards and instruct the functioning power board to drive the electric motor. Further, it is possible, that the first power board and the second power board are arranged as redundant power boards to supply six phases of electricity to the electric motor. For this purpose, the electric motor may be a six-phase electric motor. Thereby, a better and more reliable power transmission to the electric motor may be achieved. In particular, if one power board of the two power boards fails, the other one may still be operated to provide the electric motor with electricity. Thus, the electric motor can be separately driven by the driving current supplied separately by any one or both of the two power boards. Thereby, it can be ensured that the electronic control unit can safely provide the electric motor with electricity even when one of the two power boards fail. This provides for a redundant and failure unsusceptible design of the electronic control unit and the electric power steering system.

Further, it is possible, that the logic board is sandwiched in between the first power board and the connector plate. The logic board may in particular be provided as a printed circuit board. The logic board does not have to be attached to a heat sink of the electronic control unit. In particular, the logic board may not be attached to the heat sink. The logic board in operation of the electronic control unit generates less heat than the two power boards and thus it may be prioritized that the two power boards that are generating more heat in operation of the electronic control unit are attached to the heat sink.

Thereby, it is possible that the logic board is logically connected to at least one of the at least one plug connector of the connector plate by means of at least one signal connector. Thereby, the connector plate is logically connected to the logic board separate from its power connection with the power boards.

It is also possible, that the first power board comprises at least one first power board recess through which the at least one second power connector extends to the second power board. Thereby, the first power connector may be easily guided through the first power board and to the second power board.

According to the invention the electronic control unit comprises a heat sink, the heat sink being sandwiched in between the first power board and the second power board. The first power board may be provided on one side of the heat sink and the second power board may be provided on another side of the heat sink. The first power board and the second power board may be directly attached with their circuit board and electronic components to the heat sink. A thermal interface material may be provided between the first power board and the heat sink and the second power board and the heat sink to thermally attached the respective parts with each other for better thermal conductivity.

Both power boards may be attached to the heat sink. In particular, both power boards may be fitted onto the heat sink. Both power boards may be surround by a heat sink edge of the heat sink. The heat sink edge of the heat sink may comprise a groove arranged for crimping the housing into the groove and thereby at least securing, and possibly thermally connecting, the heat sink with the housing. When crimping the housing into the groove of the heat sink, a particularly tight fitting of the heat sink inside of the housing is achieved and the thermal conductivity from the heat sink to the housing is improved. Further, the overall contact surface of the heat sink with the housing and thereby the overall thermal conductivity from the heat sink to the housing is even further improved. Also, providing the heat sink with the groove may be performed at relatively low cost when manufacturing the heat sink and the crimping of the housing into the groove is a relatively simple, fast and cost-effective way of securing the heat sink and in particular in the entire electronic control unit with the housing of the electric power steering system. The crimping may be performed by squeezing the housing at its outer side into the groove. Thereby, the housing is deformed plastically and contacted with the heat sink at its groove. The groove may have a rectangular, U-type or V-type shape, for example. Also, it is possible to provide more than just one groove for crimping it with the housing in the heat sink. For example, the heat sink edge of the heat sink may comprise at least two grooves for crimping the housing into the at least two grooves.

The heat sink may be configured as an at least partially circular heat plate. In particular, the heat sink may be at least a half or fully circular heat plate. The heat sink edge of the heat sink may have or circumscribe the circular form of the heat plate. The heat sink may be a flat plate in the sense that its thickness is less than its diameter or radius. The heat sink may comprise several heat conduction surfaces arranged in contact with electronic components of the power boards. Thermal interface material may be provided in between the electronic components and the heat conduction surfaces. Thereby, heat generated by the electronic components may be conducted to the heat sink very effectively. The several heat conduction surfaces may be arranged at different heights along a thickness of the heat sink to accommodate electronic components of different height. Thereby, the design freedom of the at least one power board with regard to its specific electronic components, such as their size and geometry, may be maintained while still enabling a high thermal conductivity of the power boards to the heat sink. In other words, the heat sink may be adapted in its form and geometry to the at least one power board and not the other way around.

It is also possible, that the heat sink comprises heat sink through holes and the first power board is secured to the heat sink by means of bolts passing through the heat sink through holes and being fastened in domes extending from the connector plate. This enables a simple yet reliable and detachable connection of the power boards with the heat sink and further with the connector plate.

Alternatively, or additionally, it is possible, that the heat sink comprises heat sink holes and the second power board is secured to the heat sink by means of bolts being fastened in the heat sink holes. Thereby, a simple yet reliable and detachable connection between the second power board with the heat sink is provided.

In particular, the first power board may be attached by means of the heat sink through holes and domes in the connector plate and the second power board may be attached by means of the holes in the heat sink. This provides for particularly good serviceability, because the second power board may be exchanged without demounting the first power board from the heat sink and further improves the reliability of the secure connection.

According to the invention the heat sink comprises heat sink recesses for the at least one second power connector, the at least one second power connector extending from the connector plate through the heat sink recesses inside of the heat sink to the second power board. The at least one second power connector may be used for transferring current from the connector plate, which may be connected to the power source, to the second power board. The heat sink recesses allow for simple yet cost-effective design of the heat sink and the at least one second power connector. The heat sink recesses may be designed as flat slots.

It is also possible, that the heat sink comprises a heat sink cutout, in particular extending from a heat sink edge to an inside of the heat sink, a second logic connector extending from a logic board of the electronic control unit through the heat sink cutout to the second power board. The heat sink cutout may have a partially circular and/or partially flat shape. The heat sink cutout allows for simple yet cost-effective design of the heat sink and the second logic connector.

Thereby, it is possible, that the first electric motor connector from the second power board extends through the heat sink cutout for connection with the electric motor of the electric power steering system. Thereby, the number of cutouts or recesses may be reduced and the electronic control unit may have a compact design. By means of the first electric motor connector, driving current from the first power board may be transmitted along the electronic control unit, passing by the heat sink, to the electric motor.

Further it is possible, that the heat sink comprises heat sink projections projecting from the heat sink beyond the first power board and the second power board and being arranged to rest on an inner rim inside of the housing of the electric power steering system. By means of the heat sink projections, when installing the electronic control unit in the housing, the end position of the electronic control unit in the housing may be easily detected. The end position is achieved when the projections rest on the inner rim inside the housing and the electronic control unit cannot be pushed into the housing any further without using excessive force to bend or damage the projections. Thereby, a defined position at which the housing is crimped into the groove is provided and the crimping can be performed at that defined position every time when joining the heat sink with the housing facilitating the manufacture.

According to a second aspect of the invention, the problem raised in the introduction of this description is solved by an electric power steering system comprising the electronic control unit according to the first aspect of the invention, whereby the electric motor of the electric power steering system is electrically connected to the first power board by means of the first electric motor connector and to the second power board by means of the second electric motor connector.

When the heat sink comprises projections projecting from the heat sink beyond the at least one power board, the projections may rest on an inner rim inside of the housing of the electric power steering system. Thereby, a defined position of the electronic control unit in the housing and a stable connection therewith is achieved.

The electric power steering system may further comprise a torque sensor, a steering shaft, a handle, in particular a steering wheel, and a power source. The electric power steering system may further have the arrangement and be arranged for operation of in an automobile as described in the introductory part of this description.

Further advantages, features and details of the invention unfold from the following description, in which by reference to drawings of the following Figures an embodiment of the present invention is described in detail. Thereby, the features from the claims as well as the features mentioned in the description can be essential for the invention as taken alone or in an arbitrary combination.

<FIG> shows an exploded illustration of an electronic control unit <NUM> according to an embodiment of the invention from a bottom side perspective view. According to this bottom side perspective view, bottom sides of the parts of the electronic control unit <NUM> are visibly illustrated.

<FIG> shows the same electronic control unit <NUM> of <FIG> with the difference that it is from a top side perspective view. According to this top side perspective view, top sides of the parts of the electronic control unit <NUM> are visibly illustrated.

As can be taken from <FIG> and <FIG>, the electronic control unit <NUM> comprises two power boards <NUM>, <NUM>, namely a first power board <NUM> and a second power board <NUM>. The power boards <NUM>, <NUM> may also be referred to as power-stages. The two power boards <NUM>, <NUM> are arranged so as to supply an electric motor (not shown) of an electric power steering system <NUM> (see <FIG> and <FIG>) with driving current. For this purpose, the first power board <NUM> is connected to a first electric motor connector <NUM> electrically connectable with the electric motor. Further, for this purpose, the second power board <NUM> is connected to a second electric motor connector <NUM> electrically connectable with the electric motor.

Further, the electronic control unit <NUM> comprises a connector plate <NUM>. The connector plate <NUM> comprises multiple, in this particular embodiment three, plug connectors <NUM>, <NUM>, <NUM>. In this particular embodiment, the first plug connector <NUM> and the second plug connector <NUM> are provided with electric contacts (not shown) inside thereof. The electric contacts may be made from a copper alloy, for example, to allow for good electric conductivity. These electric contacts are arranged as first and second signal connectors <NUM>, <NUM>. The signal connectors <NUM>, <NUM> extend from the plug connectors <NUM>, <NUM> on a top side of the connector plate <NUM> to a bottom side of the connector plate <NUM>.

The electronic control unit <NUM> also comprises a logic board <NUM>. The logic board <NUM> is arranged so as to control the two power boards <NUM>, <NUM> or, in other words, the operation of the electronic control unit <NUM> or, in further other words, the transmission of driving current to the electric motor. For this purpose, the signal connectors <NUM>, <NUM> are connected with the logic board <NUM>. Further, the logic board <NUM> is connected via a first logic connector <NUM> to the first power board <NUM>. Also, the logic board <NUM> is connected via a second logic connector <NUM> to the second power board <NUM>.

Signal plugs (not shown) may be attached to the plug connectors <NUM>, <NUM> for supplying signals from a sensor, such as a torque sensor, or other units, such as a further electronic control unit from a transportation equipment (not shown), such as an automobile, to the logic board <NUM>. By means of the signals, such as a torque detected by the torque sensor or a travelling speed of the transportation equipment, the logic board <NUM> may control the driving current via the two power boards <NUM>, <NUM>.

The connector plate <NUM> further comprises a third plug connector <NUM>. This third plug connector <NUM> comprises inside further electric contacts. These electric contacts are provided as first power connectors <NUM>, <NUM> and second power connectors <NUM>, <NUM>. The second power connectors <NUM>, <NUM> are longer than the first power connectors <NUM>, <NUM> such that they may accordingly connect with their respective power boards <NUM>, <NUM> at their respective distance from the connector plate <NUM>. In this embodiment, the first power connectors <NUM>, <NUM> and the second power connectors <NUM>, <NUM> are provided as metal strips.

A power plug (not shown) may be connected to the third plug connector <NUM> to provide power to the first power connectors <NUM>, <NUM> and second power connectors <NUM>, <NUM>. The power plug may be attached to a power source such as a battery (not shown) of the transportation equipment. The power source is arranged as a three-phase electric power source. The connector plate <NUM> may also be referred to as a power and logic connector plate as it provides power and logic or signal processing connections to the respective boards <NUM>, <NUM>, <NUM> of the electronic control unit <NUM>.

The first power connectors <NUM>, <NUM> are connected to the second power board <NUM> and the second power connectors <NUM>, <NUM> are connected to the first power board <NUM>. Thereby, the first power board <NUM> is provided with a three-phase electric current and the second power board <NUM> is provided with a three-phase electric current. The electronic control unit <NUM> is thereby provided with six phases and the electric motor may be provided as a six-phases electric motor. When one of the two power boards <NUM>, <NUM> fails due to an error, the other one can ensure safe and reliable operation of the electric motor by transmitting driving current to it. Thereby, it is prevented that an error in one of the power boards <NUM>, <NUM> leads to undesirable loss of the steering function and possibly in an accident and damage of the driver and passengers of the transportation equipment.

As can further be taken from <FIG> and <FIG>, a heat sink <NUM> is arranged in between the first power board <NUM> and the second power board <NUM>. The heat sink <NUM> is thus sandwiched in between the two power boards <NUM>, <NUM>. The heat sink <NUM> in this embodiment is provided as a die-cast aluminum. The heat sink <NUM> allows for the heat generated in the two power boards <NUM>, <NUM> to be dissipated away. For this purpose, the heat sink <NUM> is connected to a housing <NUM> of the electric power steering system <NUM>, which will be explained later in more detail.

Also, the connector plate <NUM> comprises a venting opening <NUM> and a venting element (not shown) for closing the venting opening <NUM>. When the electronic control unit <NUM> is inserted into the housing <NUM>, which also will be explained in more detail letter, the venting element provides for pressure compensation of the inside of the housing <NUM> with the environment. Further, the connector plate <NUM> comprises a sealing <NUM>. The sealing <NUM> is made from a silicone rubber in this particular embodiment. The sealing <NUM> seals the electronic control unit <NUM> inside the housing <NUM> against the environment when it is inserted into the housing <NUM>.

<FIG> shows the logic board <NUM>, first power board <NUM> and second power board <NUM> in more detail in an exploded view. The logic board <NUM> comprises first electronic components <NUM>, of which the first electronic components <NUM>, <NUM>, <NUM> are exemplary denominated. Further, the first power board <NUM> comprises second electronic components <NUM>, of which the second electronic components <NUM>, <NUM>, <NUM> are exemplary denominated. Moreover, the second power board <NUM> comprises third electronic components <NUM>, of which the third electronic components <NUM>, <NUM>, <NUM> are exemplary denominated.

The first electronic components <NUM> may be coils, capacitors, at least one computing unit, such as a processor, and other electronic components for enabling calculation operations based on received signals and logic communication of the logic board <NUM> with the two power boards <NUM>, <NUM>. The second and third electronic components <NUM>, <NUM> may be coils, capacitors and other electronic components for enabling the respective power board <NUM>, <NUM> to transmit power from a power source to the electric motor as will be explained further later.

The logic board <NUM>, the first power board <NUM> and the second power board <NUM> are shown in an orientation with their respective top sides and bottom sides such as they are arranged within the electronic control unit <NUM>. Thus, the largest of the second electronic components <NUM>, <NUM>, <NUM> on a bottom side of the first power board <NUM> show towards the largest of the third electronic components <NUM>, <NUM>, <NUM> of the second power board <NUM>. These large electronic components <NUM>, <NUM> generate a lot of heat and by virtue of this arrangement a heat sink <NUM> may receive the second and third electronic components <NUM>, <NUM> to allow for good heat conductivity characteristics so as to remove the heat from the two power boards <NUM>, <NUM> via the heat sink <NUM> and housing <NUM> effectively.

Further, the first power board <NUM> comprises first power board recesses <NUM>, <NUM> for guiding the second power connectors <NUM>, <NUM> therethrough. Also, the first power board <NUM> comprises power board through holes <NUM>, <NUM>, <NUM> for guiding bolts <NUM> therethrough for fastening the heat sink <NUM> to the connector plate <NUM>. These features will be explained later in more detail.

<FIG> shows an assembly of the logic board <NUM> with the connector plate <NUM>. The first and second signal connectors <NUM>, <NUM> are connected to the logic board <NUM>. In particular, the first and second signal connectors <NUM>, <NUM> comprise multiple pins being attached to corresponding pin receiving holes in the logic board <NUM>.

The logic board <NUM> comprises two logic connectors <NUM>, <NUM> connected thereto and having the purpose of enabling communication and control of the two power boards <NUM>, <NUM> by means of the logic board <NUM>. Therefore, each of the two logic connectors <NUM>, <NUM>, namely the first logic connector <NUM> and the second logic connector <NUM>, comprises multiple electrical connector pins (not denominated). The electrical connector pins of the first logic connector <NUM> are relatively shorter than the electrical connector pins of the second logic connector <NUM>. The reason for this is that the first logic connector <NUM> connects the logic board <NUM> with the first power board <NUM>, whereby the distance between the logic board <NUM> and the first power board <NUM> in an assembled state of the electronic control unit <NUM> is relatively short. However, the distance between the logic board <NUM> and the second power board <NUM>, which are connected by means of the second logic connector <NUM>, is relatively longer because the first power board <NUM> and the heat sink <NUM> are arranged in between as can be seen in the assembled state of the electronic control unit <NUM> from <FIG>, for example.

The electrical connector pins are inserted into corresponding connector pin holes (not denominated) inside the logic board <NUM>. The connector pin holes for the respective electrical connector pins are arranged at two opposite ends of the logic board <NUM>. Thereby, the first logic connector <NUM> and the second logic connector <NUM> are arranged at the two opposite ends of the logic board <NUM>. Further, the logic board <NUM> comprises connection pin holes (not denominated) for corresponding first connection pins (not denominated) of the first logic connector <NUM> and connection pin holes for corresponding second connection pins (not denominated) of the second logic connector <NUM>. By means of the connection pins the two logic connectors <NUM>, <NUM> are securely fastened in the logic board <NUM>.

The electrical connector pins are arranged in logic connector housings <NUM>, <NUM> of the logic first logic connector <NUM> and the second logic connector <NUM>. In this particular embodiment, the second logic connector housing <NUM> consists of two separate parts. This design may be chosen due to the long extension of the its electrical connector pins. The first part of the second logic connector housing <NUM> comprises the connection pins for corresponding connection pin holes of the logic board <NUM> and the second part of the second logic connector housing <NUM> comprises connection pins for securing them in corresponding connection pin holes of the second power board <NUM>. Moreover, the first logic connector housing <NUM> comprises connection pins for securing them in corresponding connection pin holes of the first power board <NUM>.

As may be taken from this Figure, the logic board <NUM> comprises cutouts at its edge for domes <NUM>, <NUM>, <NUM> projecting from the connector plate <NUM> towards and beyond the logic board <NUM>. These domes <NUM>, <NUM> enable fastening of the heat sink <NUM> with the connector plate <NUM> and thereby sandwiching the logic board <NUM> and the first power board <NUM> in between these as will be explained later. The domes <NUM>, <NUM> may be provided with molded holes inside. The molded holes may be pre-threaded for bolts <NUM> or threaded by means of self-tapping bolts or screws <NUM>.

The first power connectors <NUM>, <NUM> are extending from the connector plate <NUM> through a cutout (not denominated) at the edge of the logic board <NUM> towards the first power board <NUM>. Further, the second power connectors <NUM>, <NUM> extend from the connector plate <NUM> next to logic board <NUM> and the first power connectors <NUM>, <NUM> towards the second power board <NUM>.

<FIG> shows an assembly of the first power board <NUM> with the logic board <NUM> and the connector plate <NUM>.

A first electric motor connector <NUM> comprises three first electric phase pins <NUM>, <NUM>, <NUM> for electric connection with the electric motor of the electric power steering system <NUM>. The three first electric phase pins <NUM>, <NUM>, <NUM> are received in a first electric motor connector housing <NUM>. The first electric motor connector housing <NUM> comprises connection pins (not denominated) for connection with corresponding connection pin holes (not denominated) in the first power board <NUM>. Further, the three first electric phase pins <NUM>, <NUM>, <NUM> comprise at ends opposite of the ends for connecting with corresponding electric motor pins (not shown) of the electric motor several first power board connection pins (not shown) for electrically connecting these with the first power board <NUM>.

The first logic connector <NUM> is connected with the first power board <NUM>. Further, the second power connectors <NUM>, <NUM> are guided through the first power board recesses <NUM>, <NUM> of the first power board <NUM>.

The first electric motor connector <NUM> is arranged next to the second logic connector <NUM> such that they may extend together along a heat sink cutout <NUM> as shown in the heat sink <NUM> of <FIG>. The first electronic components <NUM> of the first power board <NUM> extend towards the heat sink <NUM> to be arranged on the top side of the first power board <NUM>.

<FIG> shows the heat sink <NUM> in more detail and from its bottom side. A heat sink edge <NUM> of the heat sink <NUM> circumscribes the heat sink <NUM>. The heat sink <NUM>, in particular the heat sink edge <NUM>, comprises the groove <NUM> for crimping the housing <NUM> of the electric power steering system <NUM> into the groove <NUM>. Thereby, the housing <NUM> is mechanically secured to the heat sink <NUM> and ultimately to the electronic control unit <NUM>. Further, the heat sink <NUM> is thermally connected to the housing <NUM> such that the heat generated by the two power boards <NUM>, <NUM> may be dissipated via the heat sink <NUM> along the housing <NUM> having a much larger surface area for dissipation. Also, the surface area of the housing <NUM> may be in thermal connection with the environment such that the housing <NUM> is cooled or, in other words, may exchange heat with the environment.

The groove <NUM> is a circumferential groove <NUM> such that it is arranged around the circumference of the heat sink edge <NUM>. The heat sink edge <NUM> further comprises two circumferential outer surfaces <NUM>, <NUM>, in between which the circumferential groove <NUM> is provided. The two circumferential outer surfaces <NUM>, <NUM> of the heat sink edge <NUM> are configured to contact an inner surface <NUM> of the housing <NUM> as may be taken from Figure <NUM>. For this purpose, the outer diameter of the circumferential outer surfaces <NUM>, <NUM> equals or substantially equals the inner diameter of the inner surface <NUM> of the housing <NUM>.

The structure of the heat sink <NUM> will in the following be further explained with reference to <FIG> and <FIG>, <FIG> showing a process of assembling the heat sink <NUM> with the first power board <NUM> assembled with the logic board <NUM> and the connector plate <NUM> and <FIG> showing the assembly according to the process of <FIG> and <FIG> show a top side of the heat sink <NUM> whereas <FIG> shows a bottom side of the heat sink <NUM>.

The heat sink <NUM> is configured as a circular heat plate, whereby the heat sink <NUM> comprises a heat sink cutout <NUM>. The heat sink cutout <NUM> extends from the heat sink edge <NUM> to an inside of the heat sink <NUM>. The second logic connector <NUM> and the first electric motor connector <NUM> extend through the heat sink cutout <NUM> in the assembled state where the heat sink <NUM> is attached to the first power board <NUM> as can be seen in <FIG>.

Further, the heat sink <NUM> comprises several heat conduction surfaces <NUM> on its bottom side and on its top side for attaching them to the first power board <NUM> and the second power board <NUM>, in particular the first electronic components <NUM> and the second electronic components <NUM>, by means of a thermal interface material (not shown). The heat conduction surfaces <NUM>, <NUM> on the bottom side and the heat conduction surface <NUM> on the top side are exemplary denominated in the <FIG> and <FIG>. In the assembled state of <FIG>, the first electronic components <NUM> of the first power board <NUM> are in direct contact via the thermal interface material with the heat conduction surfaces <NUM>, <NUM> on the bottom side of the heat sink <NUM>. The heat conduction surfaces <NUM>, <NUM> of the bottom side are arranged at different heights along a thickness of the heat sink <NUM> and thereby can accommodate or attach to first electronic components <NUM> of different size or height. The same can be applied to the top side such that heat conduction surfaces <NUM> of the top side of the heat sink <NUM> may be arranged at different heights along the thickness of the heat sink <NUM>. Thereby, the first electronic components <NUM> are effectively transferring heat to the heat sink <NUM>.

Moreover, the heat sink <NUM> comprises heat sink through holes <NUM>, <NUM>, <NUM> as can be seen in <FIG> from the bottom side and in <FIG> from the top side. The first power board <NUM> is secured by means of bolts <NUM> passing through the heat sink through holes <NUM> and being fastened in the domes <NUM>, <NUM> of the connector plate <NUM>. The bolts <NUM> further pass through the power board through holes <NUM>, <NUM>, <NUM> of the first power board <NUM> as shown in Figure.

Also, the heat sink <NUM> comprises heat sink recesses <NUM> for guiding the second power connectors <NUM>, <NUM> of the connector plate <NUM> therethrough. This enables for the second power connectors <NUM>, <NUM> to be connected to the second power board <NUM> when the heat sink <NUM> is attached to the first power board <NUM>.

Moreover, the heat sink <NUM> comprises heat sink projections <NUM>, <NUM>, <NUM> projecting from the heat sink <NUM> beyond the two power boards <NUM>, <NUM> in the assembled state of the electronic control unit <NUM> as can be seen in <FIG>. These heat sink projections <NUM>, <NUM>, <NUM> may be arranged resting on an inner rim <NUM> inside of the housing <NUM> of the electric power steering system <NUM>.

The heat sink <NUM> also comprises heat sink holes <NUM>, <NUM>, <NUM> on its top side. The second power board <NUM> may be fastened to the heat sink <NUM> by means of bolts <NUM> in the heat sink holes <NUM>, <NUM>, <NUM>. The heat sink holes <NUM>, <NUM>, <NUM> may be pre-threaded or threaded by means of self-tapping bolts or screws <NUM>.

<FIG> shows the electronic control unit <NUM> in the assembled state. The second power board <NUM> with the second electronic components <NUM> on the bottom side are attached the to the heat conduction surfaces <NUM> of the top side of the heat sink <NUM>. The second electric motor connector <NUM> comprises three second electric phase pins <NUM>, <NUM>, <NUM> arranged in a second electric motor connector housing <NUM>. The second electric motor connector housing <NUM> comprises further connection pins for connection with sixth connection pin holes in the second power board <NUM>.

Further, the three second electric phase pins <NUM>, <NUM>, <NUM> comprise at ends opposite of the ends for connecting with corresponding electric motor pins (not shown) of the electric motor several second power board connection pins for electrically connecting these with the second power board <NUM>. Further, the second electric motor connector housing <NUM> comprises second electric motor connector housing through holes for guiding bolts <NUM> therethrough for connection of the second power board <NUM> to the heat sink holes <NUM>, <NUM> of the heat sink <NUM> by means of the second electric motor connector housing <NUM>.

Further bolts <NUM> are guided through corresponding through holes in the second power board <NUM> for connection to the heat sink holes <NUM>, <NUM> of the heat sink <NUM>. Here, the second power board <NUM> is attached to the top side of the heat sink <NUM> with its bottom side. The second power board <NUM> also comprises second power board recesses <NUM>, <NUM>, <NUM> through with the first electric phase pins <NUM>, <NUM>, <NUM> of the first electric motor connector <NUM> are guided.

All bolts <NUM> are fastened such that the second power board <NUM> is fastened to the heat sink <NUM> and the heat sink <NUM> is fastened to the connector plate <NUM>. The heat sink <NUM> is thereby sandwiched in between the first power board <NUM> and the second power board <NUM>. The logic board <NUM> is sandwiched in between the first power board <NUM> and the heat sink <NUM>. The electric phase pins <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> extend out of the second power board <NUM> and in particular beyond the heat sink projections <NUM>, <NUM>, <NUM> such that they may be connected with the electric motor pins of the electric motor. The venting element may be inserted into the venting opening <NUM> after inserting the electronic control unit <NUM> into the housing <NUM>.

<FIG> shows the process of inserting the electronic control unit <NUM> into the housing <NUM> of the electric power steering system <NUM>. The heat sink projections <NUM>, <NUM>, <NUM> act as guides during this process.

<FIG> shows a cross section through a part of the electric power steering system <NUM> having the housing <NUM>. Therein, the housing <NUM> is not yet crimped into the groove <NUM> of the heat sink <NUM>. However, the operation of crimping is indicated by an arrow referenced with the direction of force F of the crimping operation. Thereby, the housing <NUM> is plastically deformed and extends into the groove <NUM> of the heat sink <NUM>. The heat sink <NUM> and the housing <NUM> thereby become attached to one another and thermally coupled.

Further, the circumferential outer surfaces <NUM>, <NUM> of the heat sink <NUM> are attached to the inner surface <NUM> of the housing <NUM> for thermal coupling and allowing the heat sink <NUM> to dissipate heat generated by the two power boards <NUM>, <NUM> attached to the heat sink <NUM> through the housing <NUM> into the environment. Also, the heat sink projections <NUM>, <NUM>, <NUM> may be arranged to rest on the inner rim <NUM> inside of the housing <NUM>.

Claim 1:
Electronic control unit (<NUM>) for an electric power steering system (<NUM>), the electric power steering system (<NUM>) comprising a housing (<NUM>) and an electric motor, the electronic control unit (<NUM>) being configured to be arranged inside the housing (<NUM>) and to be electrically connected to the electric motor, whereby the electronic control unit (<NUM>) comprises a first power board (<NUM>) having a first electric motor connector (<NUM>) for electric connection with the electric motor, a second power board (<NUM>) having a second electric motor connector (<NUM>) for electric connection with the electric motor, and whereby a connector plate (<NUM>) of the electronic control unit (<NUM>) is electrically connected by means of at least one plug connector (<NUM>) of the connector plate (<NUM>) to the first power board (<NUM>) via at least one first power connector (<NUM>) and to the second power board (<NUM>) via at least one second power connector (<NUM>), wherein the at least one first power connector (<NUM>) is shorter than the at least one second power connector (<NUM>),
whereby the electronic control unit (<NUM>) comprises a heat sink (<NUM>), the heat sink (<NUM>) being sandwiched in between the first power board (<NUM>) and the second power board (<NUM>), and
characterised in that
the heat sink (<NUM>) comprises at least one heat sink recess (<NUM>) for the at least one second power connector (<NUM>) of the electronic control unit (<NUM>), the at least one second power connector (<NUM>) extending from the connector plate (<NUM>) through the at least one heat sink recess (<NUM>) inside of the heat sink (<NUM>) to the second power board (<NUM>).