Actuator for a vehicle transmission parking lock system
The actuator design with metal rings and guide elements addresses the self-locking issues of conventional worm gear systems, ensuring reliable operation and reduced wear by generating friction torque and axial stabilization.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- VALEO SYSTEMES DE CONTROLE MOTEUR SAS
- Filing Date
- 2022-11-16
- Publication Date
- 2026-05-15
AI Technical Summary
Conventional worm gear systems in vehicle transmission actuators fail to provide sufficient self-locking, leading to undesired movement under external torque, and are prone to wear and sensitivity to external factors like shocks and vibrations.
An actuator design incorporating metal rings press-fitted or welded onto the shaft, which generate friction torque and axial stabilization, combined with guide elements to create a self-locking mechanism, ensuring the actuator remains stationary despite external torque.
The actuator achieves reliable self-locking and axial stabilization, preventing unwanted movement and reducing wear, even under varying conditions.
Smart Images
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Abstract
Description
Title of the invention: Actuator for a vehicle transmission parking lock system
[0001] The invention relates to an actuator for a parking lock system for a vehicle gearbox, particularly a motor vehicle equipped with an automatic transmission, for example, a hybrid vehicle. The invention also applies to a parking lock system for a reduction gear associated with an electric vehicle motor. The gearbox or reduction gear will more generally be referred to as a transmission. This locking system is better known by its English term "park lock."
[0002] Such an actuator allows the transmission box to be locked in parking position by means of an actuation element, for example a lever engaging with a gear of the transmission box.
[0003] Actuators of this type are known and are classically designed with a gear system of toothed wheel and worm gear to transmit the rotational movement of an electric motor to a torque output element of the actuator linked to the actuation element.
[0004] It is necessary to provide a self-locking of the gear system of toothed wheel and worm gear when the electric motor is not supplied with electrical energy to prevent an undesired movement of the actuating element when an undesired torque is applied to it.
[0005] The conventional geometry of the teeth in a worm gear system does not always allow for sufficient self-locking. Indeed, to achieve sufficient self-locking of the worm gear system, the worm's angle of attack must be small, but this design generates a lot of friction, leading to premature wear of the system and oversizing of the electric motor. Furthermore, the self-locking of the worm gear system is very sensitive to external parameters such as shocks, vibrations, surface roughness, grease, etc.
[0006] One of the objectives of the invention is therefore to provide an actuator for a parking lock system of a vehicle transmission that reliably prevents any unwanted movement of the actuating element when an unwanted torque is applied to it.
[0007] Thus, the invention proposes an actuator for a parking lock system for a vehicle transmission, said actuator comprising an electric motor having a housing in which a stator and a rotor are housed, said rotor being linked to a rotating shaft, said shaft being guided in rotation by at least two guide elements, said actuator further includes a mechanism with a wheel and a worm gear 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 gear at least one of the rings comes to rest against the frame or against at least one of the guide elements in order to generate a frictional torque thus making the actuator in a buttressed position.
[0008] Conventionally, the casing of the electric motor is coupled to a cover that closes the internal volume of the casing. In the present invention, the term casing is to be understood in a broad sense as the combination of the casing and the cover.
[0009] Generally, at least one of the rings abuts against an element fixed relative to the stator of the electric motor. The housing and the guide elements are fixed relative to the stator of the electric motor.
[0010] The combination of friction between the ring and the housing or guide element, and the friction of the worm gear mechanism, creates a self-locking of the actuator. The actuator being in this locked state means that, regardless of the torque applied to the worm gear, the electric motor will not rotate. In other words, the mechanical forces associated with the friction of the ring against the housing or guide element and the mechanical forces associated with the friction of the worm gear mechanism remain within their respective friction cones.
[0011] Thus, the primary function of the rings is to generate a friction torque as explained previously, but they also have the secondary function of axially stabilizing the shaft of the electric motor.
[0012] According to the invention, when no axial force is generated by the wheel on the worm gear, there is axial play between the rings and the frame 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 press-fitted onto the shaft and / or welded to 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 bearings or bushings, in particular sintered bushings. The guide elements are press-fitted into the housing. More precisely, the guide elements are press-fitted into the housing and into the cover.
[0015] According to an additional feature of the invention, the housing has a front face on the side facing the worm gear 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 housing and the second element for guiding the rotation of the shaft is located at the 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 gear, and the second ring is located axially between the rotor and the first rotational guide element of the shaft. In this configuration, one ring is inside the electric motor and the other ring is at least partially outside.
[0017] According to a second embodiment of the invention, the first ring is located axially between the rotor and the second rotational guide element of the shaft, and the second ring is located at the end of the shaft opposite the worm gear. In this configuration, one ring is inside the electric motor and the other ring is at least partially outside.
[0018] According to a third embodiment of the invention, the first ring is located axially between the rotor and the first rotational guide element 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 gear, and the second ring is located axially at the end of the shaft opposite the worm gear. In this configuration, both rings are at least partially outside the electric motor.
[0020] Other features and advantages of the invention will become apparent from the following detailed examples of embodiments, with reference to the attached figures:
[0021] [Fig.1] represents an example of an actuator for a parking lock system of a vehicle transmission box to which the invention can be applied;
[0022] [Fig.2] represents a first embodiment of the invention;
[0023] [Fig.3] represents a second embodiment of the invention;
[0024] [Fig.4] represents a third embodiment of the invention;
[0025] [Fig.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, and that the figures help to further define the invention if necessary. However, the invention should not be limited to the embodiments disclosed in the description.
[0027] With reference to [Fig. 1], an actuator 10 for a parking lock system of a vehicle transmission is illustrated. The actuator 10 mainly comprises a housing 11, an electric drive motor 1, a gear power transmission system 20, 21, and an output element of Couple 22 is suitable for connection to an actuation element. Housing 11 is suitable for attachment to a vehicle transmission.
[0028] The electric motor 1 is a brushed DC motor with a frame 2 in which a stator 3 and a rotor 4 are housed. The rotor 4 is rotationally linked 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 21 and worm gear 5 system. The worm gear 20 is located on an output shaft 5 of the electric motor 1.
[0030] The torque output element 22 is in the form of a shaft, one end of which has a male or female star-shaped socket into which the actuating element (not shown) of a locking system can be engaged. The locking system allows a gear of the transmission (not shown) to be locked or unlocked by means of an actuating lever or latch (not shown). The torque output element 22 includes a toothed sector that meshes with the gear power transmission system 21. Under certain conditions, when an external torque is applied to the actuating element, this torque is transmitted to the actuator 1 from the torque output element 22, which generates an axial force Fl, F2 from the wheel 21 on the worm gear 20. For optimal operation of the actuator, this axial force Fl, F2 must cause the actuator to self-lock.
[0031] The invention is illustrated with reference to 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 drive shaft 5 such that, under the effect of an axial force Fl, F2 generated by the wheel 21 on the worm gear 20, at least one of the rings 8, 9 comes to rest against the housing 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 75 N must be between 10 and 30 Nmm to ensure self-locking.
[0032] When no axial force Fl, F2 is generated by the wheel 21 on the worm gear 20, there is an axial play between the rings 8, 9 and the frame 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 press-fitted onto the shaft 5. More precisely, the rings 8, 9 are welded to the shaft 5, in particular by laser welding. The shaft 5 is also made of steel.
[0034] The housing 2 of the electric motor 1 has a front face 2a on the side facing the worm gear 20 and a rear face 2b opposite the front face 2a. The first rotational guide element 6 of the shaft 5 is located at the front face 2a of the housing 2 and the second rotational guide element 7 of the shaft 5 is located at the rear face 2b of the frame 2. The guiding elements 6, 7 are bearings, in particular sintered bearings.
[0035] In the first embodiment illustrated in [Fig.2] the first ring 8 is located axially between the first rotating guide element 6 of the shaft 5 and the worm gear 20 and the second ring 9 is located axially between the rotor 4 and the first rotating guide element 6 of the shaft 5.
[0036] When a force Fl is generated by the wheel 21 on the screw 20 the first ring 8 comes to rest against the first guide element 6 or against the front face 2a of the motor 1, that is to say 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 to rest against the first guide element 6.
[0038] In the second embodiment illustrated in [Fig.3] the first ring 8 is located axially between the rotor 4 and the second rotating guide element 7 of the shaft 5 and the second ring 9 is located at the end of the shaft 5 opposite the worm gear 20.
[0039] When a force Fl is generated by the wheel 21 on the screw 20 the first ring 8 comes to rest 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 to rest against the second guide element 7 or against the rear face 2b of the motor 1, that is to say the rear face of the casing 2.
[0041] In the third embodiment illustrated in [Fig.4] the first ring 8 is located axially between the rotor 4 and the first rotating guide element 6 of the shaft 5 and the second ring 9 is located axially between the rotor 4 and the second rotating guide element 7 of the shaft 5.
[0042] When a force Fl is generated by the wheel 21 on the screw 20 the second ring 9 comes to rest 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 to a stop against the first guide element 6. In both cases, the combination of the stop 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 [Fig.5] the first ring 8 is located axially between the first rotating guide element 6 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 Fl is generated by the wheel 21 on the screw 20 the first ring 8 comes to rest against the first guide element 6 or against the front face 2a of the motor 1, that is to say 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 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 quite evident that it is by no means limited to them and that it includes all the technical equivalents of the means described.
[0049] In the claims, the reference symbols in parentheses should not be interpreted as a limitation of the claim.
Claims
Demands
1. Actuator (10) for a parking locking system of a vehicle transmission, said actuator (10) comprising an electric motor (1) having a housing (2) in which a stator (3) and a rotor (4) are housed, said rotor (4) being connected to a rotating shaft (5), said shaft (5) being guided in rotation by at least two guide elements (6, 7), said actuator (10) further comprising a mechanism with a wheel (21) and a worm gear (20) located on the motor shaft (5), characterized in that at least two rings (8, 9) are mounted on the motor shaft (5) such that under the effect of an axial force (F1, F2) generated by the wheel (21) on the worm gear (20) at least one of the rings (8, 9) comes to rest against the housing (2) or against at least one of the guide elements (6, 7) in order to generate a frictional torque thus making the actuator (10) in a jammed state.
2. Actuator (10) according to claim 1, characterized in that when no axial force (Fl, F2) is generated by the wheel (21) on the worm gear (20), there is axial play between the rings (8, 9) and the frame (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 any one of the preceding claims, characterized in that the rings (8, 9) are press-fitted onto the shaft (5) and / or welded onto the shaft (5), in particular by laser welding.
5. Actuator (1) according to any one of the preceding claims, characterized in that the guiding elements (6, 7) are bearings or bushings, in particular sintered bushings.
6. Actuator (1) according to any one of the preceding claims, characterized in that the frame (2) has a front face (2a) on the side facing the worm gear (20) and a rear face (2b) opposite the front face (2a), the first rotational guide element (6) of the shaft (5) is located at the front face (2a) of the frame (2) and the second rotational guide element (7) of the shaft (5) is located at the rear face (2b) of the frame (2).
7. Actuator (1) according to claim 6, characterized in that the first ring (8) is located axially between the first rotating guide element (6) of the shaft (5) and the worm gear (20) and the second ring (9) is located axially between the rotor (4) and the first rotating guide element (6) 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 rotating guide element (7) of the shaft (5) and the second ring (9) is located at the end of the shaft (5) opposite the worm gear (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 rotating guide element (6) of the shaft (5) and the second ring (9) is located axially between the rotor (4) and the second rotating guide element (7) of the shaft (5).
10. Actuator (1) according to claim 6, characterized in that the first ring (8) is located axially between the first rotating guide element (6) of the shaft (5) and the worm gear (20) and the second ring (9) is located axially at the end of the shaft (5) opposite the worm gear (20).