Linear drive apparatus

A linear drive apparatus including: a housing. Located inside the housing are an electric motor, a transmission gear, which meshes with an output gear on an output shaft of the electric motor, a gear shaft, and a linear motion assembly. The transmission gear is mounted on the gear shaft, the linear motion assembly is mounted to cooperate with the transmission gear, and converts rotational motion of the transmission gear to linear motion. An axis of the linear motion assembly is arranged in the same plane as an axis of the electric motor output shaft and an axis of the gear shaft. The linear drive apparatus has the advantages of a compact structure, small volume, light weight, and good heat dissipation.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a U.S. national stage of application No. PCT/EP2017/056694, filed on Mar. 21, 2017. Priority is claimed on Chinese Application No. CN201620221955.4, filed Mar. 22, 2016, the content of which is incorporated here by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present device relates to a motor vehicle component product, in particular to a linear drive apparatus for use in a motor vehicle driving force assembly.

2. Description of the Prior Art

In the motor vehicle industry, to increase the air intake efficiency and reduce the emission of pollutants, it is often necessary to use a valve apparatus capable of precisely controlling intake and exhaust in the driving force assembly system, e.g. an apparatus such as an exhaust gas recirculation control valve used in an engine's exhaust gas recirculation system. The majority of such valve apparatuses are linear drive apparatuses, which use an electric motor as a source of driving force, and then convert a rotational output of the electric motor to linear motion of a linear motion assembly (e.g. a valve rod).

In linear drive apparatuses currently on the market, the electric motor, transmission gears and valve rod are in most cases arranged in both transverse and longitudinal directions, and the transmission gears are not of a weight-saving design; the result is that the overall volume and weight of the linear drive apparatus is relatively large.

SUMMARY OF THE INVENTION

An object of the present device is to provide a linear drive apparatus, which solves the problems affecting existing linear drive apparatuses, namely that their structure is not compact, have a large volume, a heavy weight, and poor heat dissipation. The linear drive apparatus provided by the present device comprises: a housing and, located inside the housing: an electric motor; a transmission gear meshed with an output gear on an output shaft of the electric motor, the transmission gear being mounted on a gear shaft located inside the housing; and a linear motion assembly, which is fitted to the transmission gear and converts rotational motion of the transmission gear to linear motion; wherein an axis of the linear motion assembly is arranged in the same plane as an axis of the electric motor output shaft and an axis of the gear shaft. Furthermore, the transmission gear is a cam gear.

According to one aspect of the invention, the cam gear comprises a cam gear part and a cam groove part; the cam gear part meshes with the output gear of the electric motor.

According to one aspect of the invention, the cam gear part has a weight-saving hole.

According to one aspect of the invention, the cam groove part has a groove inner wall close to a central axis of the cam gear and a groove outer wall remote from the central axis of the cam gear.

According to one aspect of the invention, one end of the cam groove part is an open groove, while the other end is a closed groove. Furthermore, the linear motion assembly comprises an adjusting rod, a connecting rod structure, a bearing, a magnet assembly and a sensor; the connecting rod structure is mounted on the adjusting rod; the bearing, the magnet assembly and the sensor are all mounted on the connecting rod structure; and the bearing is located in the cam groove part, so as to convert rotational motion of the cam gear to linear motion of the linear motion assembly. Furthermore, an axis of the adjusting rod is arranged in the same plane as the axis of the electric motor output shaft and the axis of the gear shaft. Furthermore, an axis of the bearing is arranged in the same plane as the axis of the adjusting rod, the axis of the electric motor output shaft, and the axis of the gear shaft.

According to one aspect of the invention, the axis of the bearing is arranged in the same plane as the axis of the linear motion assembly, the axis of the electric motor output shaft, and the axis of the gear shaft.

According to one aspect of the invention, the sensor is a non-contact sensor. Furthermore, the linear drive apparatus also comprises a cooling water path, which surrounds the linear motion assembly.

According to one aspect of the invention, the cooling water path is located in the housing. Furthermore, the linear drive apparatus also comprises a limiting pin disposed inside the housing; the transmission gear will abut the limiting pin upon rotation to a certain angle, thereby realizing mechanical stoppage. Furthermore, the linear drive apparatus also comprises: a return spring mounted on the gear shaft, the return spring being used for return of the transmission gear; an end cover fitted to the housing, and an adjusting head fixed to one end of the linear motion assembly.

Compared with the prior art, the linear drive apparatus provided by the present device has the advantages of a compact structure, small volume, light weight, and good heat dissipation. Description of the accompanying drawings The accompanying drawings, which form part of this application, are intended to furnish further understanding of the present device.

PARTICULAR EMBODIMENTS

The linear drive apparatus of the present device is described below by with reference to the accompanying drawings.FIG. 1is an exploded schematic view of the linear drive apparatus of the present device.FIG. 2is a three-dimensional perspective drawing of the linear drive apparatus shown inFIG. 1after assembly (excluding the end cover). As shown inFIGS. 1 and 2, the linear drive apparatus comprises the following structure: a housing1; and, located inside the housing1: an electric motor2, a transmission gear3, which meshes with an output gear on an output shaft of the electric motor2, and a gear shaft4and a linear motion assembly5; the transmission gear3is mounted on the gear shaft4, the linear motion assembly5is mounted to cooperate with the transmission gear3, and converts rotational motion of the transmission gear3to linear motion to reduce the overall width of the linear drive apparatus, be conducive to the center of gravity layout and increase the conversion efficiency of linear motion. The following special design is implemented in this embodiment: the axis of the linear motion assembly5is arranged in the same plane as the axis of the output shaft of the electric motor2and the axis of the gear shaft4.

Preferably, to better realize transmission and reduce the weight of the linear drive apparatus, the transmission gear3may be designed as a cam gear, specifically as shown inFIG. 6. The cam gear comprises a cam gear part31and a cam groove part32; the cam gear part31meshes with the output gear of the electric motor to realize rotational motion and perform torque transfer, and the cam gear part31also has one or more holes33; in this embodiment, there are two weight-saving holes. The cam groove part32also has a groove inner wall34proximate to a central axis of the cam gear and a groove outer wall35remote from the central axis of the cam gear. Moreover, one end of the cam groove part32is an open groove, while the other end is a closed groove.

Preferably, as shown inFIGS. 1 to 5, in order to cooperate with the transmission gear3(cam gear3) described above and convert rotational motion of the gear to linear motion, the linear drive apparatus in this embodiment also comprises an adjusting rod51, a connecting rod structure52, a bearing53, a magnet assembly54, and a sensor55. The connecting rod structure52is mounted on the adjusting rod51, the bearing53, the magnet assembly54and the sensor55are all mounted on the connecting rod structure52, and the bearing53is located in a groove of the cam groove part32, so as to convert rotational motion of the cam gear3to linear motion of the linear motion assembly5. Specifically, when the cam gear3moves in one of the directions (e.g. when the linear drive apparatus executes a valve opening motion), the linear motion assembly5is in contact with the groove inner wall34, and moves downward under the action of the groove inner wall34; conversely, when the cam gear3moves in the opposite direction (e.g. when the linear drive apparatus executes a valve closing motion), the linear motion assembly5is in contact with the groove outer wall35, and moves upward under the action of the groove outer wall35. Preferably, a cam curve of the cam groove part32is divided into three sections: a lead-in section, a motion section, and a lifting section (not marked with numerical labels in the figures). The lead-in section is the open groove mentioned previously, the design objective thereof being to enable the bearing53to slide smoothly into the cam groove part32. Such an open cam groove design facilitates assembly of components, and enables the linear motion assembly to slide in through an opening.

Preferably, the axis of the adjusting rod51is arranged in the same plane as the axis of the output shaft of the electric motor2and the axis of the gear shaft4. More preferably, the axis of the bearing53is arranged in the same plane as the axis of the adjusting rod51, the axis of the output shaft of the electric motor2, and the axis of the gear shaft4, as the longitudinal arrangement shown by the figure direction, or the axis of the bearing53is arranged in the same plane as the axis of the linear motion assembly5, the axis of the output shaft of the electric motor2, and the axis of the gear shaft4. Such a design has the following advantages:

1) three or four components sharing a common plane can effectively reduce the transverse dimension of the linear motion apparatus (valve body), to meet special requirements of a customer regarding dimension;

2) four components sharing a common plane facilitates arrangement of the center of gravity of the linear motion apparatus, thereby increasing the performance stability thereof under vibrating conditions; and

3) with the central axes of the gear shaft4, bearing53and linear motion assembly5sharing a common plane, the efficiency of conversion of rotational motion to linear motion can also be increased effectively.

Preferably, the sensor55is a non-contact sensor, e.g. may be a magnetoresistive sensor, an inductive sensor or a Hall sensor, and has the following operating principles: when a drive transmission system drives a change in position of the linear motion assembly5, the position of an inductive element (such as a magnet assembly54, inductive pointer, etc.) connected to the linear motion assembly5also changes accordingly; at this time, the sensor55can sense a change in the magnetic field of the inductive element, and convert this into a change in a voltage signal, which is outputted to an engine control unit or an electronic control unit; then, by comparing differences between an actual voltage signal and a target voltage signal, the engine control unit or electronic control unit continuously adjusts an instruction until the linear drive apparatus reaches a target position. Preferably, as shown inFIGS. 1 to 4andFIG. 7, the linear drive apparatus also comprises a cooling water path6, which surrounds the linear motion assembly5. Specifically, the water path described in this embodiment is an integral water path located in the housing1, as shown inFIG. 7; the letter A indicates a water inlet, the letter B indicates a water outlet, and the black arrows mark the water flow directions. The arrangement of the cooling system has the following characteristics: 1) the water path is arranged between exhaust gas and the transmission system, so can effective reduce the amount of heat transferred from exhaust gas to the transmission system part, and in turn reduce the effect of exhaust gas temperature on the performance and lifespan of the linear drive apparatus, 2) the water path is arranged all around the linear motion assembly5, so on the one hand the volume of the linear drive apparatus can be reduced, and on the other hand the area of contact with exhaust gas can be increased so as to ensure the cooling effect.

Preferably, as shown inFIGS. 1 to 3, the linear drive apparatus also comprises a limiting pin7disposed in the housing1. The transmission gear3comes into striking contact with the limiting pin7upon rotation to a certain angle, thereby realizing mechanical stoppage of motion through a stroke.

Preferably, as shown inFIGS. 1 to 5, the linear drive apparatus also comprises a return spring8mounted on the gear shaft, the return spring8being used for return of the transmission gear3, an end cover9fitted to the housing1, and an adjusting head56fixed to one end of the linear motion assembly5. When mounted (with the linear drive apparatus in a closed state), the return spring8is in a preloaded state, so that it can be ensured that in case of a power cut, the linear drive apparatus can return to an initial position (closed state), and when the linear drive apparatus is in an operational state, the return spring8will be further preloaded, thereby ensuring that it has a sufficient return force in case of no power. In summary, the operating modes of the linear drive apparatus in this embodiment are roughly as follows:

1) When the linear drive apparatus is energized, the output gear of the electric motor2rotates clockwise, driving the cam gear3(transmission gear3) to rotate anticlockwise. The rotation of the cam groove part32of the cam gear3drives the bearing53to move downwards along the cam groove part32, in turn pushing the linear motion assembly5to move downwards. In this way, a valve of the linear drive apparatus is opened, and exhaust gas enters through a valve opening.
2) When the supply of power to the linear drive apparatus is cut, since the return spring8is preloaded at the time of mounting, the preload of the return spring8is transferred to the gear shaft4through a spring bush, the gear shaft4rotates clockwise, driving the cam gear3to rotate clockwise, and under the action of the cam groove outer wall35the bearing53is driven to move upwards along the cam groove part32, in turn pulling the linear motion assembly5to move upwards until the valve closes.

During the process of opening and closing of the valve mentioned above, the position of the magnet assembly54mounted on the linear motion assembly5is an input signal of the sensor55; after receiving the signal, the sensor55learns the extent to which the valve is opened, and transmits this to the engine control unit; the engine control unit then controls the on/off switching of a power supply, thereby realizing control of opening/closing of the valve.

Although the present device has been disclosed above by means of preferred embodiments, it is by no means limited to this. Various changes and amendments made by any person skilled in the art within the spirit and scope of the present device shall be included in the scope of protection thereof. Thus, the scope of protection of the present device should be regarded as the scope defined by the claims.