Spur gear, its manufacturing method, and brushless motor

Abstract

The present invention relates to a spur gear (1) for a transmission mechanism (35) of a brushless electric motor (10), having: a toothing section (32); a receiving bore (38) which is constructed in the toothing section (32) for receiving a rotor shaft (30); a signal transmitter section (34) which is torsionally rigidly connected to the toothing section (32) and which has a plurality of magnetic field generating regions (48), said regions being constructed for cooperating with a magnetic field sensitive sensor element (5), in particular a Hall element, in order to detect the rotational angular position of the spur gear (1) when it rotates about a rotational axis (20).

Description

Field of the Invention

[0001] The present invention relates to a spur gear for a transmission mechanism of a brushless motor, wherein the brushless motor is in particular a component of a brake booster in a vehicle. Furthermore, the present invention relates to a brushless motor with a spur gear according to the invention and a method for manufacturing a spur gear according to the invention. Background Art

[0002] It is already known from the prior art that an electric motor is a component of a brake booster, wherein the rotational movement of the output shaft of the electric motor is decelerated by a transmission mechanism in order to generate a lifting movement of a rod, which in turn acts at least indirectly on the braking device of the vehicle.

[0003] When the electric motor is configured as a brushless motor, in order to manipulate or energize the individual wire windings (Drahtwicklung) of the stator of the brushless motor, it is important to know the rotational angular position of the rotating rotor relative to the stator arranged in a position-fixed manner. For this purpose, it is already known that a spur gear connected to the rotor shaft as the output shaft is on the one hand configured for force transmission or as a component of a transmission mechanism and on the other hand the rotational angular position of the spur gear connected torsion-proof to the rotor shaft of the motor is detected by arranging regions generating a magnetic field or magnetic elements on the spur gear. For this purpose, Hall elements are usually used as components of Hall sensors, which detect these regions or magnetic elements based on the change in the magnetic field when the regions or magnetic elements generating the magnetic field move past and can thus determine the rotational angular position of the rotor. Summary of the Invention

[0004] The spur gear according to the invention for a transmission mechanism of a brushless motor has the advantage that it well meets the functional requirements in terms of forming regions generating a magnetic field and the functional requirements of the toothing section (Verzahnungsabschnitt) for force transmission, and at the same time enables a particularly simple and cost-effective manufacturing from a manufacturing technology perspective.

[0005] For this purpose, it is basically stipulated according to the invention that both the toothing section and the signal transmitter section on the spur gear having regions generating a magnetic field are configured as a common or integral sintered component, wherein different materials are used for the respective sections according to the different requirements of the toothing section and the signal transmitter section of the spur gear. These materials can, for example, have particularly low wear or high hardness for the toothing section, while for the signal transmitter section it is stipulated that the material is selected such that the material for generating the regions generating a magnetic field can be magnetized particularly simply and well.

[0006] Advantageous improvements of the spur gear according to the invention for a drive mechanism of a brushless motor include, but are not limited to: the signal transmitter section has a wall section radially surrounding the receiving bore, and the magnetic field generating area is arranged in the area of this wall section; the magnetic field generating area (48) is arranged around the rotational axis of the receiving bore with a preferably uniform angular pitch and extends along the longitudinal direction of the wall section or parallel to the rotational axis; the signal transmitter section is configured in a can shape and has an annular or disk-shaped section that connects the toothed section to the wall section of the signal transmitter section, so that a receiving space for accommodating a support mechanism for the rotor shaft is constructed radially inside the wall section; the toothed section extends into the annular or disk-shaped section of the signal transmitter section when viewed in the direction of the rotational axis of the receiving bore and is connected to the signal transmitter section, in particular form-fittingly, in the connection area, and the teeth of the toothed section are axially arranged outside the signal transmitter section or the receiving space; the toothed section has radial teeth, and the radial extension range of the teeth is completely arranged inside the wall section radially.

[0007] In order to achieve a particularly accurate or precise detection of the rotational angular position of the rotor or a high resolution in consideration of a stator with multiple wire windings, it is stipulated in an advantageous structural design of the spur gear that the signal transmitter section has a wall section arranged radially around the longitudinal axis of the receiving bore of the spur gear, and the magnetic field generating area is arranged in the area of this wall section. Thereby, a relatively large radial spacing is achieved between the receiving bore or the rotational axis of the rotor shaft of the brushless motor or the spur gear and the magnetic field generating area on the spur gear, and this spacing allows multiple magnetic field generating areas, especially those with alternating polarities, to be arranged with a spacing formed in the circumferential direction between the magnetic field generating areas.

[0008] Advantageously, in the structural improvement of the last proposed suggestion, the magnetic field generating area is arranged around the receiving bore of the spur gear with a preferably uniform angular pitch and extends in the longitudinal direction of the radially surrounding wall section of the spur gear.

[0009] In another preferred structural design of the spur gear that enables the accommodation of a support mechanism (Lagereinrichtung) for the rotor shaft, it is proposed that the signal transmitter section is configured in a can shape and has an annular or disk-shaped section that connects the toothed section to the wall section of the signal transmitter section, so that a receiving area for accommodating a support mechanism for the rotor shaft is constructed inside the radially surrounding wall section of the spur gear.

[0010] An improvement of the last proposed suggestion lies in that the toothing section extends in the direction of the accommodation bore into the annular or disk-shaped section of the signal transmitter section and is connected to the signal transmitter section in the connection area there, wherein the toothing of the toothing section is arranged outside the accommodation area.

[0011] The invention also includes a brushless motor, especially a brushless motor as part of a brake booster, which has a spur gear according to the invention as described so far.

[0012] Furthermore, the invention also includes a method for manufacturing a spur gear for a transmission mechanism of a brushless motor, especially a spur gear according to the invention, wherein the spur gear has a toothing section and a signal transmitter section with a plurality of magnetic field generating regions. The method according to the invention is characterized in that the toothing section and the signal transmitter section are manufactured as an integral or monolithic sintered component using different materials.

[0013] In an improvement of the manufacturing method according to the invention, it is stipulated that the toothing section and the signal transmitter section are manufactured at least almost simultaneously in time. Thereby, especially less production time can be achieved and thus high efficiency of the die for manufacturing the spur gear can be achieved.

[0014] Regarding the magnetization of the magnetic field generating regions in the signal transmitter section of the spur gear, there are different feasible solutions. In the first variant, it is stipulated that the magnetic field generating regions of the signal transmitter section are generated by magnetization of the material of the sintered material in the die during the manufacture of the spur gear. Here, at least a part of the time period for producing the sintered component can be advantageously used for the magnetization at the same time.

[0015] In an alternative design, it can also be stipulated that the magnetic field generating regions of the signal transmitter section are generated by magnetization of the material of the sintered material outside the die after the manufacture of the spur gear. This design minimizes the time for producing the spur gear in the die and furthermore may have the advantage that the magnetization can be carried out more simply or effectively by means arranged outside the die. Description of the Drawings

[0016] Other advantages, features and details of the invention result from the following description of the preferred embodiments and with the aid of the drawings.

[0017] Figure 1 In the schematic diagram, a brake booster for a motor vehicle with a brushless motor is shown;

[0018] Figure 2 A longitudinal section in the area of the brushless motor of the brake booster according to Figure 1 is shown;

[0019] Figure 3 shows a longitudinal section of a spur gear as used in an electric motor according to Figure 2 ; and

[0020] Figure 4 shows a cross-section in the region of the signal transmitter section of the spur gear to illustrate the arrangement of the regions generating the magnetic field. Detailed Description

[0021] Identical or functionally identical elements are labeled with the same reference numerals in the figures.

[0022] In Figure 1 the brake force amplifier 100 is shown highly schematically as part of a braking device in a vehicle. The brake force amplifier 100 has an adjusting element in the form of a rod 102 which can move in the direction of the longitudinal axis 104 of the rod 102 and which is at least indirectly used to generate a braking force on the vehicle wheels.

[0023] The brake force amplifier 100 has a brake force amplifier housing 106 to which the motor housing 12 of the electric motor 10, which can especially be seen in Figure 2 , is flange-connected. The electric motor 10 is constructed as a brushless electric motor 10 and, corresponding to the illustration in Figure 2 , has a stator 14 arranged in the motor housing 12, which stator has, for example, ten copper wire windings 18 arranged at a uniform angular pitch around the longitudinal axis 16 of the stator 14. The stator 14 interacts in a known manner with a rotor 22 which is supported in a rotatable manner about a rotational axis 20, wherein the rotational axis 20 extends coaxially with the longitudinal axis 16. On the outer circumference of the rotor 22, permanent magnet elements 24 are likewise arranged at a uniform angular pitch around the rotational axis 20 in a known manner. By successively energizing the individual copper wire windings 18 of the stator 14 in time, the rotor 22 is set into rotation. Here, the rotor 22 has, for example, a rotor shaft 30 arranged in two axially spaced-apart bearing mechanisms 26, 28. The rotor shaft 30 is connected torsionally rigid to the spur gear 1. In Figure 3 the spur gear 1 shown separately has a toothing section 32 and a signal transmitter section 34.

[0024] The spur gear 1 is only schematically shown in detail in Figure 1 as part of a transmission 35, in particular a planetary gear transmission, which serves to reduce the rotational speed of the electric motor 10 and at the same time increase its torque. In addition, the electric motor 10 is at least used to indirectly drive the rod 102.

[0025] As can especially be seen with the aid of Figure 3As can be seen, the toothing section 32 has a toothing 36 outside the signal transmitter section 34, which cooperates with a gear of a transmission mechanism not shown, for example a planet gear of a planetary gear transmission. Thus, the spur gear 1 forms the sun gear in the planetary gear transmission. The toothing section 32 is basically configured in a sleeve shape and has a receiving bore 38 that extends concentrically with the rotational axis 20. A rotor shaft 30 (not shown) is received in the receiving bore 38, wherein an anti-torsion connection is preferably constructed between the spur gear 1 or the toothing section 32 and the rotor shaft 30 by means of a press fit.

[0026] The signal transmitter section 34 is basically configured in a can shape and has an annular or disk-shaped section 40 that extends perpendicular to the rotational axis 20, to which a radially circumferential wall section 42 is connected. A receiving space 44 is constructed radially within the wall section 42, which is especially used for receiving the Figure 2 support mechanism 26 visible in.

[0027] The spur gear 1 is configured as a sintered component or manufactured by a sintering process, wherein different materials or different metal powders are used for the materials A and B of the toothing section 32 and the signal transmitter section 34. The toothing section 32 projects axially, that is to say when viewed in the direction of the rotational axis 20, up to the height of the disk-shaped section 40 of the signal transmitter section 34 and is integrally or monolithically connected to the disk-shaped section 40 in the connection area 46 there.

[0028] The material of the toothing section 32 consists of material A (for example a sintered steel containing copper, nickel and molybdenum), which is especially distinguished by a particularly high wear resistance and / or hardness in view of the output or force transmission function of the spur gear 1 as part of the transmission mechanism 35. In contrast, the material B of the can-shaped signal transmitter section 34 consists especially of a material that can be magnetized well, for example strontium hard ferrite or cobalt hard ferrite. This results in that the signal transmitter section 34, as can be seen especially clearly when viewed around the rotational axis 20 in the circumferential direction, has for example ten magnetic field generating regions 48, which are preferably arranged around the rotational axis 20 with the same angular spacing. The magnetic field generating regions 48 are formed by magnetization of ferromagnetic particles of the material B for the signal transmitter section 34. The magnetic field generating regions 48 cooperate with sensor elements 50, which are especially part of a Hall sensor, visible only in Figure 4 and Figure 2 and 4 Thereby, the rotational angular position of the rotor 20 can be deduced in a manner known per se when the rotor 20 rotates, so as to thereby timely or angularly control or energize the copper wire windings of the stator 14.

[0029] The region 48 generating the magnetic field is constructed or arranged in the region of the wall section 42 and extends along the longitudinal direction of the wall section 42, that is, extends parallel to the rotation axis 20. However, the magnetization direction is preferably oriented radially, so that the north and south poles alternate on the circumference. The sensor element 50 is then arranged, in particular, radially opposite to the circumference of the signal transmitter section 34.

[0030] The production of the spur gear 1 in the sintering process is completed by a common die (not shown) by preferably introducing at least almost simultaneously or, however, successively in time the materials for the toothing section 32 and the signal transmitter section 34 and then pressing the materials under high pressure and heat, as is known per se. Here, the magnetic field generating region 48 can be formed either by magnetization within the die region or, however, either after removing the formed spur gear 1 in a separate mechanism.

[0031] The spur gear 1 described so far can be changed or modified in a variety of ways without departing from the inventive concept.

Claims

1. A spur gear (1) for a transmission (35) of a brushless electric motor (10), comprising: a toothing section (32); a receiving bore (38) formed in the toothing section (32) for receiving a rotor shaft (30); a signal transmitter section (34) connected to the toothing section (32) in a rotationally fixed manner, the signal transmitter section having a plurality of magnetic field-generating regions (48) designed to cooperate with a magnetic field-sensitive sensor element (50) in order to detect the rotational angular position of the spur gear (1) when the spur gear (1) rotates about an axis of rotation (20), wherein: The spur gear (1) is designed as a sintered component, wherein the materials (A, B) of the sintered material for the toothing section (32) and for the signal transmitter section (34) are different, and wherein the region (48) generating the magnetic field extends parallel to the axis of rotation (20) of the receiving bore (38) and the magnetization direction is oriented radially so that north and south poles alternate on the circumference.

2. The spur gear according to claim 1, characterized in that The signal transmitter section (34) has a wall section (42) arranged radially around the receiving bore (38), and the magnetic field generating region (48) is arranged in the region of the wall section (42).

3. The spur gear according to claim 2, characterized in that The magnetic field generating region (48) is arranged around the rotation axis (20) of the receiving bore (38) and extends in the longitudinal direction of the wall section (42) or parallel to the rotation axis (20).

4. The spur gear according to claim 2 or 3, characterized in that: The signal transmitter section (34) is pot-shaped and has an annular or disk-shaped section (40) which connects the toothing section (32) to a wall section (42) of the signal transmitter section (34), so that a receiving space (44) for receiving a bearing (26) for the rotor shaft (30) is formed radially inside the wall section (42).

5. The spur gear according to claim 4, characterized in that The toothing section (32), viewed in the direction of the rotation axis (20) of the receiving bore (38), extends into an annular or disk-shaped section (40) of the signal transmitter section (34) and is connected there to the signal transmitter section (34) in a connecting region (46), and the toothing (36) of the toothing section (32) is arranged axially outside the signal transmitter section (34) or the receiving space (44).

6. The spur gear according to claim 2 or 3, characterized in that: The toothing section (32) has radial teeth, the radial extent of which is arranged completely radially within the wall section (42).

7. The spur gear according to claim 1, characterized in that The magnetic field-sensitive sensor element (50) is a Hall element.

8. The spur gear according to claim 3, characterized in that The magnetic field generating regions (48) are arranged at uniform angular intervals around the rotation axis (20) of the receiving bore (38).

9. The spur gear according to claim 5, characterized in that The toothing section (32) is connected to the signal transmitter section (34) in a positive-locking manner in the connecting region (46).

10. A brushless electric motor (10) having a spur gear (1) configured according to any one of claims 1 to 9.

11. A method for producing a spur gear (1) for a transmission mechanism (35) of a brushless electric motor, wherein: A spur gear (1) comprises a toothing section (32) and a signal transmitter section (34) having a plurality of magnetic field generating regions (48), characterized in that the toothing section (32) and the signal transmitter section (34) are manufactured as a one-piece sintered component using different materials (A, B) for the toothing section (32) and the signal transmitter section (34), wherein the magnetic field generating regions (48) extend parallel to the axis of rotation (20) of the receiving bore (38) and are oriented radially in the magnetization direction so that north and south poles alternate on the circumference.

12. The method according to claim 11, characterized in that The toothing section (32) and the signal transmitter section (34) are produced at least approximately simultaneously.

13. The method according to claim 11 or 12, characterized in that The magnetic field-generating region (48) of the signal transmitter section (34) is produced during the production of the spur gear (1) in a mold for producing the spur gear (1) by magnetizing the material (B) of the spur gear.

14. The method according to claim 11 or 12, characterized in that The magnetic field-generating region (4) of the signal transmitter section (34) is produced after the spur gear (1) is produced outside a mold for producing the spur gear (1) by magnetizing the material (B) of the spur gear.

15. The method according to claim 11, characterized in that The spur gear (1) is constructed according to any one of claims 1 to 9.

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