A power cut off mechanism

Abstract

The present subject matter relates to a rotary assembly (100) that includes a rotary machine, a power converter, a housing (102) in which the rotary machine and power converter is disposed. The power converter is in electric interface with the rotary machine and forms a electronic circuit, the electric interface being achieved by an interconnection of a bus bar in the power converter and terminals of a stator in the rotary machine. The rotary assembly (100) further includes an interface cover (104) that closes an interface opening, formed in the housing (102), the interface opening exposing the electric interface. The rotary assembly (100) further includes a power cut off mechanism (106a; 106b) that includes a cover side device (106a) mounted on the interface cover (104), and a housing side device (106b) mounted on the housing (102). The housing side device (106b) is mounted on the housing (102) in a manner that a threshold distance (dx) is maintained between the cover side device (106a) and the housing side device (106b). The threshold distance (dx) defines a predefined distance between the cover side device (106a) and the housing side device (106b) for prompting closure of the electronic circuit.

Description

Title of the Invention: A POWER CUT OFF MECHANISMFIELD OF INVENTION

[0001] The present subject matter generally relates to a power cut off mechanism in a rotary assembly, and in particular relates to a power cut of mechanism, provided on the housing of a rotary assembly, that ensures safe opening and / or closing of a electronic circuit, accommodated in the housing, for servicing.BACKGROUND

[0002] Conventionally, an integrated motor system (or rotary assembly) includes a motor and an inverter electrically connected to the motor, and a housing in which the motor and inverter are housed. During operation, alternating current (AC) in the inverter is transmitted to the motor windings through an interface. The interface between the motor and inverter is achieved by interconnecting an inverter bus bar of the inverter and terminals from the motor. The interface is accessible for service through an interface opening in the housing that exposes said interface between the motor and the inverter. An interface cover is used to close the interface opening in the housing. In high voltage motor applications, such openings in the housing may pose safety concerns for a person accessing the interface for service or repairs. For instance, in applications where the rotor assembly operates as traction for an electric motor vehicle, high voltage current may electrocute the person accessing the interface. Therefore, for safety, a power cut off mechanism is used. In a known manner, a power cut off switch is installed on the interface cover that is configured to stop current flow when the interface cover is opened during service.

[0003] Conventionally, the power cut off switch includes a male connector (typically with electrically conductive pins, or “pins”) that connectto a female connector installed on the housing. Therefore, when the interface cover closes the interface opening, the male connector is connected to the female connected and a electronic circuit of the rotor assembly is closed. When the interface cover is opened, the male connector and the female connector are disconnected from each other, thereby opening the electronic circuit of rotor assembly and preventing the risk of service personnel from getting electrocuted.

[0004] The above-described configuration of the conventional configuration of the power cut off switch, i.e. , the male connector and the female connector is however challenging to assemble. Specifically, mechanical alignment of the male connector to the female connector at the time of assembling the interface cover to the housing is challenging, as they have to be precisely aligned. A misalignment at the time of assembly may cause pins in the male connector to bend, or break, and be operationally unfit. Therefore, such a misalignment leads to costs for replacement of parts and wastage of time. Moreover, a damage to either one or both connectors means that electronic circuit is either left open or closed. For instance, in one scenario, a damage to either one or both the connectors may leave the electronic circuit closed, even upon removing the interface cover. In said scenario, safety of the service personnel is at risk. In another scenario, the damage to either one or both the connectors may leave the electronic circuit open, even upon attachment of the interface cover to the housing, making the rotary assembly inoperable.

[0005] Therefore, the technical problem to be solved by the present subject matter is how to provide a power cut off mechanism to open and close a electronic circuit of a rotary assembly for safe handling and servicing whilst ensuring the structural integrity of the power cut-off mechanism is maintained.SUMMARY OF THE INVENTION

[0006] The present subject matter seeks to solve the above- mentioned technical problem of power cut off mechanism in a conventional rotary assembly. The present subject matter relates to a rotary assembly comprising: a rotary machine comprising a stator and a rotor rotatable on an interaction with the stator; a power converter in electric interface with the rotary machine and forming a electronic circuit, the electric interface achieved by an interconnection of a bus bar in the power converter and terminals of the stator) in the rotary machine; a housing in which the rotary machine and the power converter is disposed, the housing comprising an interface opening that exposes the electric interface; an interface cover attached to the housing and closing said interface opening; a power cut-off mechanism comprising a cover side device mounted on the interface cover, and a housing side device mounted on the housing, wherein a threshold distance is maintained between the cover side device and the housing side device, the threshold distance defining a predefined distance between the cover side device and the housing side device for prompting closure of the electronic circuit.

[0007] The power cut off mechanism does not require any direct mechanical interactions, and therefore, is not susceptible to structural damages. Moreover, the opening and closing of the electronic circuit by virtue of separation and attachment respectively of the interface cover provides for an automated way of ensuring safety for a service personnel to access the electric interface. Further, the power cut of mechanism allows for real time control based on whether the interface cover is attached or removed from the housing. The threshold distance is maintained between the cover side device and the housing side device when the interface cover is attached to the housing. This threshold distance is indicative that the interface cover is attached to the housing. If in the scenario the interface cover is separated, a distance between the cover side device and thehousing side device exceeds the threshold distance, and the electronic circuit is opened.

[0008] According to yet an example of the present subject matter, the housing comprises: a first portion for housing the rotary machine, a second portion for housing the power converter, and a third portion for accommodating the electric interface between the rotary machine and the power converter. The third portion, also known as ‘terminal box’, accommodate phase cables, amongst other internal components, that interconnect the stator in the rotary machine and the bus bar in the power converter. The interface opening is formed specifically on the third portion of the housing, and the interface cover is adapted to cover said third portion. The interface cover may facilitate a hermetic sealing of the interface opening when attached.

[0009] According to an aspect of the present subject matter, the housing side device is mounted in the third portion where the electric interface is accommodated and is exposed by the interface opening when the interface cover is separated from the housing.

[0010] According to an aspect of the present subject matter, the cover side device is mounted on an inner surface side of the interface cover.

[0011] According to an aspect of the present subject matter, the cover side device is facing the housing side device when the interface cover is attached to the housing.

[0012] According to an example of the present subject matter, the housing side device is a sensor and the cover side device is a target detectable by the sensor when the interface cover is attached to the housing. Accordingly, if the threshold distance is reached, the electronic circuit is closed and the rotary assembly may operate.

[0013] According to an example of the present subject matter, the sensor is a proximity sensor and the target is a metal target, the proximity sensor being adapted to detect the threshold distance. The proximity sensor may be a capacitive proximity sensor, inductive proximity sensor, photoelectric sensor, magnetic proximity sensor, or ultrasonic proximity sensor. Based on the types of proximity sensors aforementioned, a suitable target, metallic or non-metallic, is selected.

[0014] According to an example of the present subject matter, the housing comprises a transmission portion in which a gear system is disposed, the gear system being coupled to a rotor shaft of the rotary machine. The aforementioned configuration of the rotary housing with the rotary machine, power converter and gear system included in a single housing is referred to as ‘eAxle’. Such an eAxle may provide traction to an at least partially electric motor vehicle by a coupling between the gear system and an axle.

[0015] The present subject matter also relates to a method for controlling an electronic circuit of a rotary assembly configured in the manner described above, the method comprising: detecting a distance between the cover side device and housing side device; closing the electronic circuit in response to the distance being equal to the threshold distance between the cover side device and the housing side device, said threshold distance indicating attachment of the interface cover to the housing; and opening the electronic circuit when the distance between the cover side device and the housing side device exceeds the threshold distance. In an example, the housing side device is the sensor and the cover side device is the target. Alternatively, the cover side device is the sensor and the housing side device is the target. For both the aforementioned examples, the sensor continuously monitors the proximity of the target. When the target is at a distance equal to or less than the threshold distance dx from the sensor, the sensor sends a signal to acontrol unit, prompting the closure of the electronic circuit. When the target is at a distance more than the threshold distance dx from the sensor, the sensor sends a signal to the control unit, prompting the opening of the electronic circuit. Accordingly, an automated safe switch on and switch off of the electronic circuit is achieved by virtue of the housing side device and cover side device of the power cut off mechanism. Moreover, the power cut of mechanism allows for real time control based on whether the interface cover is attached or removed from the housing. A direct mechanical interaction or contact is not established between the housing side device and the cover side device during operation, thereby ensuring no structural damages occur.BRIEF DESCRIPTION OF DRAWINGS

[0016] The features, aspects, and advantages of the present invention will be better understood with regard to the following description and accompanying figures. The description refers to the annexed drawings, wherein:

[0017] FIG. 1 illustrates a schematic view of a rotary assembly, particularly a schematic view of a housing of the rotary assembly and an interface cover of the rotary assembly, configured in accordance with the present subject matter;

[0018] FIG. 2 illustrates a rotary electrical machine, depicting a region 114, configured in accordance with the present subject matter;

[0019] FIG. 3 illustrates a perspective zoomed in view of the region 114 of the rotary machine, depicted in FIG. 2, configured in accordance with the present subject matter; and

[0020] FIG. 4 is a schematic view of the rotary assembly for providing traction to an axle of a motor vehicle, configured in accordance with an example of the present subject matter.

[0021] The figures are not necessarily to scale, and the size of some parts may be exaggerated to more clearly illustrate the example shown. Moreover, the drawings provide examples and / or examples consistent with the description, however, the description is not limited to the examples and / or examples provide in the drawings.DETAILED DESCRIPTION

[0022] In the description that follows, reference is made to accompanying drawings, which form part thereof, and in which is shown by way of illustration specific implementations in which the invention maybe practiced. These implementations are described in sufficient detail to enable that skilling in the art to practice the invention, and it is to be understood that the implementations may be combined, or that other implementations may be utilized, and that structural and logical changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims and their equivalents.

[0023] FIG. 1 illustrates a schematic view of a rotary assembly 100, configured in accordance with the present subject matter. FIG. 2 illustrates a perspective view of the rotary assembly 100, configured in accordance with the present subject matter. FIG. 3 illustrates a zoomed in view of FIG. 2, particularly illustrating a region 114 of the rotary assembly 100 configured in accordance with the present subject matter.

[0024] The present subject matter relates to a rotary assembly 100 that includes a rotary machine 110, a power converter 112 in electric interface with the rotary machine 110, a housing 102 in which the rotary machine 110 and the power converter 112 are housed, an interface cover 104 to close an interface opening 122 formed on the housing 102, and a power cut off mechanism 106a, 106b. The rotary machine 110 includes astator 118 and a rotor rotatable on an interaction with the stator 118. A electronic circuit is formed by virtue of the electric interface between the power converter 112 and the rotary machine 110. The electric interface is achieved by an interconnection of a bus bar 116 in the power converter 112 and terminals of the stator 118 in the rotary machine 110. The power cut off mechanism 106a, 106b includes a cover side device 106a and a housing side device 106b. The cover side device 106a is mounted on the interface cover 104; and the housing side device 106b is mounted on the housing 102. The cover side device 106a and the housing side device 106b are configured to interact with each other to close the electronic circuit when the interface cover 104 is attached to the housing 102. Further, when the interface cover 104 is separated from the housing 102, the interaction between the cover side device 106a and the housing side device 106b is configured to open the electronic circuit.

[0025] According to the present subject matter, the rotary machine 110 operates to convert electrical energy into mechanical energy, or vice versa. The power converter 112 converts direct current (DC) to alternating current (AC), or vice versa. Therefore, the power converter 112, may function as a rectifier bridge in generator mode and / or as an inverter in a motor mode of the rotary machine 110. The housing 102 houses both the rotary machine 110 and the power converter 112. Detaching the interface cover 104 reveals the interface opening 122 in a region 114 (a zoomed in perspective of which is shown in FIG.3) where the interconnection between the bus bar 116 of the power converter 112 and the terminals of the stator 118 is accessible. The interface cover 104 protects internal components, particularly the electric interface, from external damage. It is therefore desirable that the interface cover 104 hermetically seals the interface opening 122 where the electric interface is exposed. The interface cover 104 is fixed to the housing 102 by means on fasteners (not shown).

[0026] In the assembled condition, where the interface cover 104 is attached to the housing 102, the housing side device 106b detects the presence of the cover side device 106a in close proximity, and accordingly facilitates the electronic circuit to be closed. A direct mechanical contact between the housing side device 106b and the cover side device 106a is established in the assembled condition. Moreover, in the assembled condition, a threshold distance dx is maintained between the cover side device 106a and the housing side device 106b. In a scenario where servicing is required at the electric interface, the fasteners are removed, and the interface cover 104 is detached. Accordingly, the cover side device 106a is moved further away from the housing side device 106b. Further, the increased distance of the cover side device 106b from the housing side device 106b is detected by the housing side device 106b, and the power cut-off mechanism 106a, 106b facilitates the close the electronic circuit. Therefore, in the disassembled condition, where the interface cover 104 is separated from the housing 102, current flow within the electronic circuit is cut off and the rotary assembly 100 does not operate. The personnel therefore accesses the electric interface without fear of electrocution.

[0027] In the example shown in FIGs. 2 and 3, the housing 102 is formed of more than one portion. A first portion for housing the rotary machine 110, a second portion for housing the power converter 112, and a third portion (commonly known as “terminal box”) for housing the electric interface. The third portion is what is shown in FIG. 2 and 3 to be the region 114 where the interface opening 122 is formed. FIG. 3 focuses on the region 114 and more particularly the interface opening 122 that exposes internal components. One such internal component that is exposed is the phase cables 120 that interconnect terminals from the stator 118 (particularly, terminals from end windings 117 of the stator 118) and the bus bar 116 in the power converter 112. The housing side device 106b may be one amongst one such internal components that is exposed uponseparating and removing the interface cover 104. In other words, the housing side device 106b is disposed in the third portion of the housing 102, and is directed to face the cover side device 106a when the interface cover 104 is attached to the housing 102.

[0028] According to the present subject matter, the housing side device 106b is mounted within the third portion, that is, in the housing 102 where the interface opening 122 is formed. The cover side device 106b is mounted on an inner surface side 108 of the interface cover 104. During the assembly of the interface cover 104 to the housing 102, the interface cover 104 is moved in an assembly direction 108, shown in FIG. 1 , and attached in a manner that the cover side device 106a and the housing side device 106b are aligned along a direction parallel to the assembly direction 108. The assembly direction 108 is a direction parallel to a rotational axis 124 of the rotor, the rotational axis 124 being directed into the FIG.2 as shown.

[0029] According to an example of the present subject matter, the housing side device 106b is a sensor and the cover side device 106a is a target. The target is detectable by the sensor when the interface cover 104 is attached to the housing 102. In an alternate example, the cover side device 106a is a sensor and the housing side device 106b is a target detectable by the sensor when the interface cover 104 is attached to the housing 102. The two aforementioned examples, the sensor and the target are configured to be aligned in parallel to the assembly direction 108 once the interface cover 104 is attached to the housing 102. Moreover, the sensor and the target are configured to be facing each other in the assembled condition. In the assembled condition, a threshold distance dx is maintained between the target and the sensor. That is, no direct mechanical contact is establish between the sensor and the target. This threshold distance dx of the target from the sensor is monitored by the sensor and accordingly the electronic circuit is opened or closed. In boththe examples aforementioned, the sensor continuously monitors the proximity of the target. When the target is at a distance equal to or less than the threshold distance dx from the sensor, the sensor sends a signal to a control unit (not shown), prompting the closure of the electronic circuit. In the scenario where the interface cover 104 is separated from the housing 102, the threshold distance dx is increased, therefore indicating that the interface cover 104 is separated. A signal indicating the separation of the interface cover 104 facilitates the electronic circuit to be instantly opened. In the scenario where the interface cover 104 is assembled, or attached, to the housing 102, the distance between the cover side device 106a and the housing side device 106b exceeds the threshold distance dx; and accordingly the signal indicative of the attachment of the interface cover 104 facilitates the electronic circuit to be instantly closed. Accordingly an automated safe switch on and switch off of the electronic circuit is achieved by virtue of the power cut off mechanism 106a, 106b.

[0030] According to an example of the present subject matter, the sensor is a proximity sensor adapted to detect the threshold distance dx. Accordingly, a suitable target may be chosen. Further, the proximity sensor may be any one of the following types - capacitive proximity sensor, inductive proximity sensor, photoelectric sensor, magnetic proximity sensor, or ultrasonic proximity sensor. Preferably, the proximity sensor is an inductive proximity sensor and accordingly the target is a metal target. Therefore, in the example where the housing side device 106b is a sensor and the cover side device is a target 106a, the sensor may be an inductive sensor and the target may be a metal target. The working principle of inductive proximity sensors is generally known, and therefore not elaborated in the present description. Accordingly, once the interface cover 104 is attached to the housing 102, the inductive sensor (provided in the housing 102, in the region 114) detects the threshold distance dx of themetal target (provided on the inner surface side 108 of the interface cover 104) and closes the electronic circuit of the rotary assembly 100.

[0031] According to an example of the present subject matter, the housing 102, of the rotary assembly 100, further includes a transmission portion where a gear system 126 is disposed. Such a rotary assembly 100 of the aforementioned type that includes the rotary machine 110, power converter 112, and gear system 126 in a single housing 102 is commonly known as an ‘eAxle”. The gear system 126 of the rotary assembly 100 (configured in the ‘eAxle’ type) is coupled to the rotary machine 110. The coupling is achieved by coupling a rotor shaft (not shown) in the rotor of the rotary machine 110 and a gear in the gear system 126. Further, as shown in FIG. 2, the gear system 126 is arranged between the rotary machine 110 and the power converter 112, the power converter 112 being arranged and / or aligned in a tangential direction to the rotational axis 124 of the rotary machine 110. The third portion of the housing 102 is provided at the region 114 dedicated to accommodate the electric interface between the rotary machine 110 and the power converter 112.

[0032] FIG. 4 illustrates a schematic view of the rotary assembly 100 of the eAxle type, an example of which is also shown in FIG. 3. A power source 400, such as a battery, provides DC current to the power converter 112. The power converter 112, functioning as inverter in the motor mode and rectifier in the generator mode, provides power to the rotary machine 110. For example, in the motor mode, the power converter 112 provides AC to the rotary machine 110. The AC is provided to the stator 118 of the rotary machine 110 by an electric interface 402, i.e., the phase cables 120, shown in the region 114 where the third portion (terminal box) of the housing 102 is provided. The rotor shaft of the rotary machine 110 is coupled to the gear system 126 for a torque transfer there-between. Further, the gear system is couple to an Axle 404 of a motor vehicle (the motor vehicle being of at least partially electric), thereby providing tractionto the motor vehicle. The aforementioned normal operation of the rotary assembly 100 is ensured if the electronic circuit is closed. The electronic circuit is closed only if the power cut off mechanism 106a, 106b indicates that the interface cover 104 is attached to the housing 102.

[0033] In the scenario where a service is required, particularly, if a service at the electric interface is required, the interface cover 104 is removed to reveal the interface opening 122 as shown in FIG. 2 and 3. The power cut off mechanism 106a, 106b, in said scenario, detects that the distance between the sensor and the target exceeds the threshold distance dx; and accordingly closes the electronic circuit of the rotary assembly 100, thereby allowing a service personnel to access the electric interface 402 for repairs without exposure to safety issues, such as electrocution.

[0034] FIG. 5 illustrates a flowchart depicting a method 500 for controlling an electronic circuit of a rotary assembly 100 configured in accordance with the present subject matter. According to the present subject matter, the method 500 includes a step of detecting 502 a distance between the cover side device 106a and the housing side device 106b. In the example where the housing side device 106b is the sensor and the cover side device 106a is the target, the sensor is continuously monitoring the proximity of the target. In an alternate example, cover side device 106a is the sensor and the housing side device 106b is the target, and the sensor is continuously monitoring the proximity of the target from the sensor.

[0035] Further, the method 500 includes a step of closing 504 the electronic circuit in response to the distance being equal to the threshold distance dx between the cover side device 106a and the housing side device 106b. The threshold distance dx indicates an attachment of the interference cover 104 to the housing 102. The method 500 further includes a step of opening 506 the electronic circuit when the distance between the cover side device 106a and the housing side device 106b exceed thethreshold distance dx. In the scenario where the target is at a distance that equals or is less than the threshold distance dx from the sensor, the sensor sends a signal to the control unit which prompts the closure of the electronic circuit. The closure of the electronic circuit is achieved without any direct mechanical contact between the sensor and the target.

[0036] The method 500 further includes a step of opening 506 the electronic circuit when the distance between the cover side device 106a and the housing side device exceeds the threshold distance dx. Therefore, in the scenario where the target is at a distance that more than the threshold distance dx from the sensor, the sensor sends a signal to the control unit which prompts the opening of the electronic circuit. The opening of the electronic circuit is achieved without any direct mechanical contact between the sensor and the target.

[0037] Various modifications of the disclosed embodiments, as well as alternate embodiments of the subject matter, will become apparent to persons skilled in the art upon reference to the description of the subject matter. It is therefore contemplated that such modifications can be made without departing from the scope of the present subject matter is defined.

Claims

CLAIMS:

1. Rotary assembly (100) comprising: a rotary machine (110) comprising a stator (118) and a rotor rotatable on an interaction with the stator (118); a power converter (112) in electric interface with the rotary machine (110) and forming an electronic circuit, the electric interface achieved by an interconnection of a bus bar (116) in the power converter (112) and terminals of the stator (118) in the rotary machine (110); a housing (102) in which the rotary machine (110) and the power converter (112) is disposed, the housing (102) comprising an interface opening (122) that exposes the electric interface (402); an interface cover (104) attached to the housing (102) and closing said interface opening (122); a power cut-off mechanism (106a; 106b) comprising a cover side device (106a) mounted on the interface cover (104), and a housing side device (106b) mounted on the housing (102), wherein a threshold distance (dx) is maintained between the cover side device (106a) and the housing side device (106b), the threshold distance (dx) defining a predefined distance between the cover side device (106a) and the housing side device (106b) for prompting closure of the electronic circuit.

2. Rotary assembly (100) as claimed in claim 1 , wherein the housing (102) comprises: a first portion for housing the rotary machine (110), a second portion for housing the power converter (112), and a third portion for accommodating the electric interface (402) between the rotary machine (110) and the power converter (112).

3. Rotary assembly (100) as claimed in claim 2, wherein the housing side device (106a) is mounted in the third portion where the electric interface (402) is accommodated and is exposed by the interfaceopening (122) when the interface cover (104) is separated from the housing (102).

4. Rotary assembly (100) as claimed in any one of the preceding claims, wherein the cover side device (106a) is mounted on an inner surface side 108 of the interface cover (104).

5. Rotary assembly (100) as claimed in any one of the preceding claims, wherein the cover side device (106a) is facing the housing side device (106b) when the interface cover (104) is attached to the housing (102).

6. Rotary assembly (100) as claimed in any one of the preceding claims, wherein the housing side device (106b) is a sensor and the cover side device (106a) is a target detectable by the sensor when the interface cover (104) is attached to the housing (102).

7. Rotary assembly (100) as claimed in any one of claims 1 to 5, wherein the cover side device (106a) is a sensor and the housing side device (106b) is a target detectable by the sensor when the interface cover (104) is attached to the housing (102).

8. Rotary assembly (100) as claimed in any one of the preceding claims, wherein the sensor is a proximity sensor and the target is a metal target, the proximity sensor being adapted to detect the threshold distance (dx).

9. Rotary assembly (100) as claimed in any one of the preceding claims, wherein the housing (102) comprises a transmission portion in which a gear system (126) is disposed, the gear system (126) being coupled to a rotor shaft of the rotary machine (110).

10. Method (500) for controlling an electronic circuit of a rotary assembly (100) configured in accordance with any one of the preceding claims, the method (500) comprising: detecting a distance between the cover side device (106a) and housing side device (106b); closing the electronic circuit in response to the distance being equal to the threshold distance (dx) between the cover side device (106a) and the housing side device (106b), said threshold distance (dx) indicating attachment of the interface cover (104) to the housing (102); and opening the electronic circuit when the distance between the cover side device (106a) and the housing side device (106b) exceeds the threshold distance (dx).

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