Electric machine with passive valve

Abstract

The present invention relates to an electric machine comprising: a stator; a rotor rotatably supported about a central axis of rotation (16); a shaft (1) to which the rotor is fastened and which has a first axial bore (2), a passive valve (4) being arranged in the first axial bore (2) of the shaft (1) for temperature-dependent flow regulation of the coolant, wherein the passive valve (4) has a valve body (5), a valve piston (6) which is axially displaceable in the valve body (5) and has a second axial bore (7), and an axially displaceable valve cover (8) which is fixedly connected to the valve piston (6); an inflow element (3) which extends into the second axial bore (7) of the shaft (1) in such a way that coolant can flow from the inflow element (3) into the second axial bore (7), a first valve spring (9) being arranged between the valve body (5) and the valve piston (6), said first valve spring pressing the valve piston (6) and thus the valve cover (8) into a first position, namely a closed position of the passive valve (4), and a second valve spring (9) pressing the valve cover (8) into a second position, namely a closed position of the passive valve (4), a second valve spring (10) is arranged between the valve body (5) and the valve cover (8), said second valve spring being made of a shape memory alloy and being designed in such a way that said second valve spring expands when a limit temperature is exceeded and presses the valve cover (8) in order to press the valve piston (6) into a second position, i.e. An open position of the passive valve (4).

Description

Technical Field

[0001] The invention relates to an electric machine comprising a rotor fastened to a shaft, wherein the shaft has a first axial bore, wherein a passive valve is arranged in the first axial bore of the shaft, which passive valve releases a coolant flow into the rotor as a function of a limit temperature, ie in a temperature-dependent manner. Background Art

[0002] Electric machines of the aforementioned type serve to convert electrical energy into mechanical energy and vice versa and are frequently used in the field of motor vehicle technology as motors and / or generators.

[0003] An electric machine comprises a stationary stator and a movable rotor, wherein the rotor, in the most common embodiment of an electric machine, is rotatably mounted in an annular stator.

[0004] The electric motor generates heat due to dielectric losses during its operation, which on the one hand causes a decrease in the efficiency of the electric motor and on the other hand negatively affects the reliable operation of the electric motor during its service life. Therefore, a cooling device is usually provided in a drive device having an electric motor, which cools the components of the electric motor to be cooled.

[0005] Conventional cooling systems for electric machines use circulating gaseous or liquid coolants. The coolant circulates, for example, in the housing of the electric machine or in a rotor shaft designed as a hollow shaft, on which the rotor of the electric machine is arranged. The coolant absorbs heat due to its heat capacity and transports it away. Summary of the invention

[0006] The object of the invention is to provide an electric machine which is characterized by load-point-dependent cooling of the rotor.

[0007] This need is met by the subject matter of the invention according to independent claim 1. Advantageous embodiments of the invention are described in the dependent claims.

[0008] According to the invention, an electric machine comprises a stator, a rotor which is supported about a central rotation axis, a shaft on which the rotor is fastened and which has a first axial bore, and an inflow element.

[0009] According to the invention, a passive valve is arranged in the first axial bore of the shaft, which passive valve releases the coolant flow into the shaft as a function of the shaft temperature.

[0010] According to the invention, the passive valve comprises a valve body, a valve piston which is axially displaceable in the valve body and a valve cover which is fixedly connected to the valve piston and is axially displaceable, the valve piston having a second axial hole.

[0011] In this context, the directional specification "axial" describes a direction along or parallel to the central rotational axis of the rotor.

[0012] In this context, the directional specification "radial" describes the direction normal to the central rotation axis of the rotor.

[0013] The inflow element extends into the second axial bore such that coolant can flow from the inflow element into the second axial bore.

[0014] According to the invention, a first valve spring is arranged between the valve body and the valve piston, which presses the valve piston and thus the valve cover into a first position, ie the closed position of the passive valve.

[0015] Furthermore, according to the invention, a second valve spring is arranged between the valve body and the closure cap, which second valve spring is made of a shape memory alloy. Shape memory alloys are understood to be special metal alloys which can exist in two different crystal structures depending on the temperature. The shape change is based on a temperature-dependent lattice transformation. In this case, the structural transformation is independent of the speed of the temperature change.

[0016] The fact that the second valve spring consists of a shape memory alloy means that the second valve spring undergoes a change in length, ie a stroke, when a limiting temperature is exceeded, so that the valve cover and thus the valve piston are pressed into the second position, ie the open position of the passive valve.

[0017] The second valve spring thus represents an actuator for actuating the passive valve.

[0018] In a preferred embodiment of the invention, the passive valve has a bypass channel through which a coolant can flow and which fluidically connects a chamber, in which the second valve spring is arranged, to the second axial bore. The chamber separates the second, heat-sensitive valve spring from the main coolant flow. The chamber filled with a coolant, for example oil, ensures a constant and uniform heat transfer from the shaft to the second, heat-sensitive valve spring at all operating points of the motor.

[0019] In a preferred embodiment of the present invention, the valve piston has at least one radial hole, and the second axial hole can be connected to the environmental fluid of the shaft via the radial hole, wherein the valve body includes a sealing area, and in the open position of the passive valve, the radial hole abuts against the sealing area to seal the axial hole towards the environment of the shaft.

[0020] The valve body further preferably comprises a valve seat and a sealing area, wherein the sealing area of ​​the valve cover bears against the valve seat in the closed position of the passive valve.

[0021] The passive valve is preferably arranged in the region of a shaft input of the shaft, preferably in the region of the shaft input of the shaft in which an output toothing is formed on the outer circumference of the shaft.

[0022] Particularly preferably, the valve body is formed from a material having a lower thermal conductivity than the thermal conductivity of the fluid present in the chamber.

[0023] The valve body can be produced from a polymer material, ie, for example, plastic. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention is described below by way of example with reference to the accompanying drawings.

[0025] Figure 1 A detail view of the shaft is shown with the passive valve in the closed position.

[0026] Figure 2 A detail view of the shaft is shown with the passive valve in the open position. DETAILED DESCRIPTION

[0027] Figure 1 and Figure 2 In each case a detailed view of a shaft 1 of an electric machine according to the invention is shown.

[0028] The electric machine comprises a stator (not shown) and a rotor (not shown). The stator is fastened in a housing (not shown) and the rotor is supported in the stator so as to be rotatable about a central axis of rotation 16. The rotor is fastened to the shaft 1 in a rotationally fixed and axially fixed manner.

[0029] The shaft 1 has a first axial bore 2. A passive valve 4 is arranged in the first axial bore 2 of the shaft 1 for temperature-dependent control of the coolant flow.

[0030] In this context, the directional specification “axial” describes a direction along or parallel to the central rotational axis 16 of the rotor.

[0031] In this context, the directional specification “radial” describes a direction normal to the central rotation axis 16 of the rotor.

[0032] The passive valve 4 is arranged in the region of a shaft input 17 of the shaft 1 , ie in the region of the shaft input 17 of the shaft 1 where an output toothing 18 is formed on the outer circumference of the shaft 1 .

[0033] The passive valve 4 has a valve body 5 , a valve piston 6 which is axially displaceable in the valve body 5 , and an axially displaceable valve cover 8 which is fixedly connected to the valve piston 6 .

[0034] The valve body 5 is made of a material with poor thermal conductivity.

[0035] The valve piston 6 has a second axial bore 7 and a plurality of radial bores 19 in the region of a first end 20 of the valve piston 6. The radial bores 19 connect the second axial bore 7 to the surrounding fluid of the shaft 1. A valve cover 8 is arranged in the region of the second end 21 of the valve piston 6.

[0036] The inflow element 3 of the electric motor extends in the region of the first end 20 of the valve piston 6 into the second axial bore 7 , so that coolant can flow from the inflow element 3 into the second axial bore 7 .

[0037] A first valve spring 9 is arranged between the valve body 5 and the valve piston 6. The first valve spring 9 presses the valve piston 6 and thus the valve cover 8 into the first position, i.e. the closed position of the passive valve 4, against the spring force of the second valve spring 10. Therefore, the first valve spring 9 acts as a closing spring.

[0038] A second valve spring 10 is provided between the valve body 5 and the closing cover 8. The second valve spring 10 is made of a shape memory alloy (FGL; English: SMA " s hape m emory a lloy”) is implemented and constructed so that the second valve spring expands when the limit temperature is exceeded and presses the valve cover and thus the valve piston into the second position, i.e. the open position of the passive valve. The thermosensitive second valve spring 10 is a helical compression spring, so that the desired temperature-dependent length change and subsequently the required stroke at the valve piston 6 can be achieved via the helical compression spring.

[0039] The first valve spring 9 has a spring force which is greater than the spring force of the second valve spring 10 as long as the temperature of the second valve spring 10 is below the limit temperature. For its part, the passive valve 4 is in the closed position ( Figure 1 ). If the limiting temperature is reached or exceeded, the second valve spring 10 undergoes a change in length in the axial direction (the second valve spring expands). The spring force of the second valve spring 10 is selected so that it exceeds the spring force of the first valve spring 9 in the operating condition. For its part, the passive valve 4 is in the open position ( Figure 2 ).

[0040] The second valve spring 10 is arranged in a chamber 12 formed by the components "shaft 1", "valve body 5" and "valve cover 8". The chamber 12 is fluidically connected to the second axial bore 7 in the valve piston 6 via a bypass channel 11. The chamber 12 is filled with coolant via a hole arranged in the bypass channel 11, i.e. parallel to the main flow path shown by the second axial bore 7. A limited, continuous fluid exchange between the chamber 12 and the cooling system is achieved via a defined leakage path. The circulation of the coolant volume in the chamber 12 achieved thereby ensures a reliable bidirectional functioning of the passive valve 4.

[0041] The valve body 5 has a valve seat 13, against which the sealing area 15 of the valve cover 8 abuts in the closed position of the passive valve 4, whereby the second axial bore 7 of the valve piston 6 is sealed toward the first axial bore 2 of the shaft 1 ( Figure 1In the open position of the passive valve 4, the sealing area 15 of the valve cover 8 is lifted from the valve seat 13 and releases the coolant flow from the second axial bore 7 towards the first axial bore 2 ( Figure 2 ).

[0042] Furthermore, the valve body 5 has a sealing region 14 which, in the open position of the passive valve 4, seals the radial bore 19 in the region of the first end 20 of the valve piston 6 towards the environment of the shaft 1 and releases a coolant flow through the second axial bore 7 towards the first axial bore 2 ( Figure 2 In the closed position of the passive valve 4, the radial bore 19 of the valve piston 6 does not rest against the sealing area 14 of the valve body 5, but rather a coolant path is opened from the second axial bore 7 via the radial bore 19 to the environment of the shaft 1 ( Figure 1 ). Thus, an additional proportional directional valve function can be provided by the radial bore 19 formed at the first end 20 of the valve piston 6. As a result, coolant can be supplied to additional cooling or lubricating points in the environment of the shaft 1, so that, for example, the cooling of rolling bearings and gears, such as the driven gear 18, of the shaft 1 can be controlled in a temperature-dependent manner. Furthermore, any dynamic pressure can be built up via the additional coolant path, and pressure acting in the closed position of the passive valve 4 can be avoided.

[0043] Reference numerals list

[0044] 1 axis

[0045] 2 First axial hole

[0046] 3 Inflow element

[0047] 4 Passive valve

[0048] 5 Valve body

[0049] 6-valve piston

[0050] 7 Second axial hole

[0051] 8 Valve cover

[0052] 9 First valve spring

[0053] 10 Second valve spring

[0054] 11 Bypass channel

[0055] 12 Chamber

[0056] 13 Valve seat

[0057] 14 Sealing area of ​​valve body

[0058] 15 Sealing area of ​​the bonnet

[0059] 16 Central rotation axis

[0060] 17-axis input

[0061] 18 Driven gear

[0062] 19 Radial holes

[0063] 20 First end portion (of valve piston)

[0064] 21 Second end portion (of valve piston)

Claims

1. A motor, comprising: -stator, a rotor mounted rotatably about a central axis of rotation (16), - a shaft (1) on which the rotor is fastened and which has a first axial hole (2), A passive valve (4) is arranged in the first axial hole (2) of the shaft (1) for regulating the flow rate of the coolant in a temperature-dependent manner, wherein the passive valve (4) comprises a valve body (5), a valve piston (6) which can be axially displaced in the valve body (5), and a valve cover (8) which is fixedly connected to the valve piston (6) and can be axially displaced, and the valve piston has a second axial hole (7). an inflow element (3) extending into the second axial bore (7) so that coolant can flow from the inflow element (3) into the second axial bore (7), A first valve spring (9) is arranged between the valve body (5) and the valve piston (6), and the first valve spring presses the valve piston (6) and thereby the valve cover (8) into a first position, i.e., a closed position of the passive valve (4); and a second valve spring (10) is arranged between the valve body (5) and the valve cover (8), and the second valve spring is made of a shape memory alloy and is configured so that the second valve spring expands and presses the valve cover (8) and thereby the valve piston (6) into a second position, i.e., an open position of the passive valve (4) when a limit temperature is exceeded.

2. The motor according to claim 1, It is characterized in that The passive valve (4) has a bypass channel (11) which fluidically connects a chamber (12) with the second axial bore (7), wherein the second valve spring (10) is arranged in the chamber (12).

3. The electric machine according to claim 1 or 2, It is characterized in that The valve piston has at least one radial hole (19) via which the second axial hole (7) can be connected to the ambient fluid of the shaft (1), wherein the valve body (5) comprises a sealing area (14) against which the radial hole (19) abuts in the open position of the passive valve (4).

4. An electric machine according to claim 1, 2 or 3, It is characterized in that The valve body (5) comprises a valve seat (13) against which a sealing area (15) of the valve cover (8) bears in the closed position of the passive valve (4).

5. An electric machine according to any one of the preceding claims, It is characterized in that The passive valve (4) is arranged in the region of a shaft input (17) of the shaft (1).

6. The motor according to claim 5, It is characterized in that In the region of a shaft input (17) of the shaft (1), an output toothing (18) is formed on the outer circumference of the shaft (1).

7. The electric machine according to any one of claims 2 to 6, It is characterized in that The valve body (5) is formed from a material having a thermal conductivity lower than that of the fluid present in the chamber (12).

8. The electric machine according to claim 7, It is characterized in that The valve body (5) is made of polymer material.

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