Actuator for a parking lock system of a vehicle gearbox

Abstract

The present invention relates to an actuator (10) for a parking lock system of a vehicle gearbox, the actuator (10) comprising an electric motor (1) that has a housing (2) in which a stator (3) and a rotor (4) are housed, the rotor (4) being connected to a rotary shaft (5), the shaft (5) being rotatably guided by at least two guide elements (6, 7), the actuator (10) further comprising a mechanism with a wheel (21) and a worm (20) that is located on the motor shaft (5). At least two rings (8, 9) are mounted on the motor shaft (5) in such a way that, under the effect of an axial force (F1, F2) generated by the wheel (21) on the worm (20), at least one of the rings (8, 9) comes into contact with the housing (2) or with at least one of the guide elements (6, 7) in order to generate a friction torque, whereby the actuator (10) is placed in a situation of over-center locking.

Description

Description Title of the invention: Actuator for a parking lock system of a vehicle transmission [1] The invention relates to an actuator for a parking lock system of a vehicle gearbox, in particular a motor vehicle equipped with an automatic gearbox, for example a hybrid vehicle. The invention also applies to a parking lock system of a reducer associated with an electric vehicle motor. The gearbox or reducer will more generally be called a transmission box. This locking system is better known by its English term "park-lock" or "parking lock". [2] Such an actuator allows the transmission box to be locked in parking by means of an actuating element, for example a lever engaging with a toothing of the transmission box. [3] Actuators of this type are known and are conventionally designed with a gear system of toothed wheel and worm gear to transmit the rotational motion of an electric motor to a torque output element of the actuator linked to the actuating element. [4] It is necessary to provide self-locking of the gear wheel and worm gear system when the electric motor is not supplied with electrical energy to prevent unwanted movement of the actuating element when unwanted torque is applied to it. [5] The classic geometry of the teeth of the gear wheel and worm gear system does not always allow sufficient self-locking to be achieved. Indeed, to obtain sufficient self-locking of the gear wheel and worm gear system, it is necessary that the angle of attack of the worm screw is low, but this design generates a lot of friction which leads to premature wear of the system and oversizing of the electric motor. In addition, the self-locking of the gear wheel and worm gear system is very sensitive to external parameters such as shocks, vibrations, surface roughness, grease, etc. [6] One of the objectives of the invention is therefore to provide an actuator for a parking lock system of a vehicle transmission which reliably prevents any unwanted movement of the actuating element when an unwanted torque is applied thereto. [7] Thus the invention proposes an actuator for a parking locking system of a vehicle transmission box, said actuator comprises an electric motor having a casing in which a stator and a rotor are housed, said rotor being linked in rotation to a rotary shaft, said shaft being guided in rotation by at least two guide elements, said actuator further comprises a mechanism with a wheel and a worm screw located on the motor shaft, at least two rings are mounted on the motor shaft so that under the effect of an axial force generated by the wheel on the worm screw at least one of the rings comes into abutment against the casing or against at least one of the guide elements in order to generate a friction torque thus making the actuator in a buttressing situation. [8] Conventionally, the casing of the electric motor is coupled to a cover closing the internal volume of the casing. In the present invention, the term casing is to be considered in the broad sense as being the combination of the casing and the cover. [9] Generally, at least one of the rings abuts against an element fixed relative to the stator of the electric motor. The casing and the guide elements are fixed relative to the stator of the electric motor.

[0010] The combination of the friction of the ring against the casing or against the guide element and the friction of the wheel and worm mechanism thus creates a self-locking of the actuator. The actuator in an over-bracing situation means that, regardless of the torque applied to the wheel associated with the worm, the electric motor will not rotate. In other words, the mechanical forces associated with the friction of the ring against the casing or against the guide element and the mechanical forces associated with the friction of the wheel and worm mechanism remain within their friction cone.

[0011] Thus, the primary function of the rings is to generate a friction torque as explained previously but also have the secondary function of axially wedging the shaft of the electric motor.

[0012] According to the invention, when no axial force is generated by the wheel on the worm screw, there is axial play between the rings and the casing or the guide elements, this play is for example between 0.1 and 0.3 mm.

[0013] According to the invention, the rings are made of metal, in particular steel. The rings are tightly fitted onto the shaft and / or welded onto the shaft, in particular by laser welding. The shaft is also made of metal, in particular steel.

[0014] According to the invention, the guide elements are rolling bearings or bearings, in particular sintered bearings. The guide elements are mounted tightly in the casing. More specifically, the guide elements are mounted tightly in the casing and in the cover.

[0015] According to an additional characteristic of the invention, the carcass has a front face on the side facing the worm screw and a rear face opposite the front face, the first element for guiding the rotation of the shaft is located at the front face of the carcass and the second element for guiding the rotation of the shaft is located at the rear face of the carcass.

[0016] According to a first embodiment of the invention, the first ring is located axially between the first rotational guide element of the shaft and the worm screw and the second ring is located axially between the rotor and the first rotational guide element of the shaft. According to this configuration, one ring is inside the electric motor and the other ring is at least partly outside.

[0017] According to a second embodiment of the invention, the first ring is located axially between the rotor and the second element for guiding the rotation of the shaft and the second ring is located at the end of the shaft opposite the worm screw. According to this configuration, one ring is inside the electric motor and the other ring is at least partly outside.

[0018] According to a third embodiment of the invention, the first ring is located axially between the rotor and the first element for guiding the rotation of the shaft and the second ring is located axially between the rotor and the second rotational guide element of the shaft. In this configuration, both rings are inside the electric motor.

[0019] According to a fourth embodiment of the invention, the first ring is located axially between the first rotational guide element of the shaft and the worm screw and the second ring is located axially at the end of the shaft opposite the worm screw. According to this configuration, the two rings are at least partly outside the electric motor.

[0020] Other characteristics and advantages of the invention will emerge from the following reading of detailed examples of embodiments, with reference to the appended figures:

[0021] [Figure 1] represents an example of an actuator for a parking lock system of a vehicle transmission to which the invention can be applied;

[0022] [Figure 2] represents a first embodiment of the invention;

[0023] [Figure 3] represents a second embodiment of the invention;

[0024] [Figure 4] represents a third embodiment of the invention;

[0025] [Figure 5] represents a fourth embodiment of the invention.

[0026] It should be noted that the figures disclose the invention in sufficient detail for its implementation, said figures helping to better define the invention if necessary. The invention should not, however, be limited to the embodiments disclosed in the description.

[0027] Referring to [Figure 3], there is illustrated an actuator 10 for a parking lock system of a vehicle transmission. The actuator 10 mainly comprises a housing 11, an electric drive motor 1, a gear power transmission system 20, 21 and a torque output element 22 adapted to be connected to an actuating element. The housing 11 is adapted to be fixed to a vehicle transmission.

[0028] The electric motor 1 is a brushed direct current motor with a casing 2 in which a stator 3 and a rotor 4 are housed. The rotor 4 is connected in rotation to a rotating shaft 5 and this shaft 5 is guided in rotation by two guide elements 6, 7.

[0029] The gear power transmission system 20, 21 reduces the speed and increases the torque of the electric motor 1. The gear power transmission system is a gear wheel 21 and worm screw 5 system. The worm screw 20 is located on an output shaft 5 of the electric motor 1.

[0030] The torque output element 22 is made in the form of a shaft, one end of which has the shape of a male or female star-shaped socket in which the actuating element (not shown) of a locking system is capable of engaging. The locking system makes it possible to lock or unlock a toothing of the transmission box (not shown) by an actuating lever or latch (not shown). The torque output element 22 comprises a toothed sector meshing with the gear power transmission system 21. Under certain conditions, when an external torque is applied to the actuating element, this torque is transmitted into the actuator 1 from the torque output element 22, which generates an axial force F1, F2 from the wheel 21 onto the worm screw 20. For optimal use of the actuator, this axial force F1, F2 must create a self-locking of the actuator.

[0031] The invention is illustrated in connection with the following figures representing four embodiments. These four embodiments have in common two rings 8, 9, also called friction rings, which are mounted on the motor shaft 5 in such a way that under the effect of an axial force F1, F2 generated by the wheel 21 on the worm screw 20 at least one of the rings 8, 9 comes into abutment against the casing 2 or against at least one of the guide elements 6, 7 in order to generate a friction torque. For example, the friction torque under an axial load of 75N must be between 10 and 30 Nmm to ensure self-locking.

[0032] When no axial force F1, F2 is generated by the wheel 21 on the worm screw 20, there is axial play between the rings 8, 9 and the casing 2 or the guide elements 6, 7. This play is for example between 0.1 and 0.3 mm.

[0033] The rings 8, 9 are made of metal, in particular steel. The rings 8, 9 are tightly fitted onto the shaft 5. More precisely, the rings 8, 9 are welded onto shaft 5, in particular by laser welding. Shaft 5 is also made of steel.

[0034] The casing 2 of the electric motor 1 has a front face 2a on the side facing the worm screw 20 and a rear face 2b opposite the front face 2a. The first element 6 for guiding the shaft 5 in rotation is located at the front face 2a of the casing 2 and the second element 7 for guiding the shaft 5 in rotation is located at the rear face 2b of the casing 2. The guide elements 6, 7 are bearings, in particular sintered bearings.

[0035] In the first embodiment illustrated in [Figure 2] the first ring 8 is located axially between the first element 6 for guiding the rotation of the shaft 5 and the worm 20 and the second ring 9 is located axially between the rotor 4 and the first element 6 for guiding the rotation of the shaft 5.

[0036] When a force F1 is generated by the wheel 21 on the screw 20 the first ring 8 comes into abutment against the first guide element 6 or against the front face 2a of the motor 1, i.e. the front face of the casing 2.

[0037] When a force F2 is generated by the wheel 21 on the screw 20 the second ring 9 comes into abutment against the first guide element 6.

[0038] In the second embodiment illustrated in [Figure 3] the first ring 8 is located axially between the rotor 4 and the second guide element 7 in rotation of the shaft 5 and the second ring 9 is located at the end of the shaft 5 opposite the worm screw 20.

[0039] When a force F1 is generated by the wheel 21 on the screw 20 the first ring 8 comes into abutment against the second guide element 7.

[0040] When a force F2 is generated by the wheel 21 on the screw 20 the second ring 9 comes into abutment against the second guide element 7 or against the rear face 2b of the motor 1, i.e. the rear face of the casing 2.

[0041] In the third embodiment illustrated in [Figure 4] the first ring 8 is located axially between the rotor 4 and the first element 6 for guiding the rotation of the shaft 5 and the second ring 9 is located axially between the rotor 4 and the second element 7 for guiding the rotation of the shaft 5.

[0042] When a force F1 is generated by the wheel 21 on the screw 20, the second ring 9 comes into abutment against the second guide element 7.

[0043] When a force F2 is generated by the wheel 21 on the screw 20, the first ring 8 comes into abutment against the first guide element 6. In both cases, the combination of the abutment with the rotation of the shaft 5 generates a friction torque and creates a self-locking of the actuator.

[0044] In the fourth embodiment illustrated in [Figure 5] the first ring 8 is located axially between the first guide element 6 for rotation of the shaft 5 and the worm screw 20 and the second ring 9 is located axially at the end of the shaft 5 opposite the worm screw 20.

[0045] When a force F1 is generated by the wheel 21 on the screw 20 the first ring 8 comes into abutment against the first guide element 6 or against the front face 2a of the motor 1, i.e. the front face of the casing 2.

[0046] When a force F2 is generated by the wheel 21 on the screw 20 the second ring 9 comes into abutment against the second guide element 7 or against the rear face 2b of the motor 1, i.e. the rear face of the casing 2.

[0047] In all the cases mentioned above, the combination of the stop with the rotation of the shaft 5 generates a friction torque and creates a self-locking of the actuator.

[0048] Although the invention has been described in connection with several particular embodiments, it is obvious that it is in no way limited thereto and that it includes all technical equivalents of the means described.

[0049] In the claims, reference symbols in parentheses are not to be construed as a limitation of the claim.

Claims

Claims

1. Actuator (10) for a parking lock system of a vehicle transmission, said actuator (10) comprises an electric motor (1) having a casing (2) in which a stator (3) and a rotor (4) are housed, said rotor (4) being rotationally connected to a rotary shaft (5), said shaft (5) being rotationally guided by at least two guide elements (6, 7), said actuator (10) further comprises a mechanism with a wheel (21) and a worm screw (20) located on the motor shaft (5), characterized in that at least two rings (8, 9) are mounted on the motor shaft (5) so that under the effect of an axial force (F1, F2) generated by the wheel (21) on the worm screw (20) at least one of the rings (8, 9) abuts against the casing (2) or against at least one of the guide elements (6, 7) in order to generate a friction torque thus making the actuator (10) in a buttressing situation.

2. Actuator (10) according to claim 1, characterized in that when no axial force (F1, F2) is generated by the wheel (21) on the worm screw (20), there is an axial clearance between the rings (8, 9) and the carcass (2) or the guide elements (6, 7), for example between 0.1 and 0.3 mm.

3. Actuator (10) according to claim 1 or 2, characterized in that the rings (8, 9) are made of metal, in particular steel.

4. Actuator (10) according to one of the preceding claims, characterized in that the rings (8, 9) are tightly fitted onto the shaft (5) and / or welded onto the shaft (5), in particular by laser welding.

5. Actuator (1) according to one of the preceding claims, characterized in that the guide elements (6, 7) are rolling bearings or bearings, in particular sintered bearings.

6. Actuator (1) according to one of the preceding claims, characterized in that the carcass (2) has a front face (2a) on the side facing the worm screw (20) and a rear face (2b) opposite the front face (2a), the first guide element (6) in rotation of the shaft (5) is located at the front face (2a) of the carcass (2) and the second guide element (7) for rotation of the shaft (5) is located at the rear face (2b) of the carcass (2).

7. Actuator (1) according to claim 6, characterized in that the first ring (8) is located axially between the first guide element (6) in rotation of the shaft (5) and the worm screw (20) and the second ring (9) is located axially between the rotor (4) and the first guide element (6) in rotation of the shaft (5).

8. Actuator (1) according to claim 6, characterized in that the first ring (8) is located axially between the rotor (4) and the second guide element (7) in rotation of the shaft (5) and the second ring (9) is located at the end of the shaft (5) opposite the worm screw (20).

9. Actuator (1) according to claim 6, characterized in that the first ring (8) is located axially between the rotor (4) and the first guide element (6) in rotation of the shaft (5) and the second ring (9) is located axially between the rotor (4) and the second guide element (7) in rotation of the shaft (5).

10. Actuator (1) according to claim 6, characterized in that the first ring (8) is located axially between the first guide element (6) in rotation of the shaft (5) and the worm screw (20) and the second ring (9) is located axially at the end of the shaft (5) opposite the worm screw (20).

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