WO2017049469A1

WO2017049469A1 - Independent suspension employing horizontal suspension strut for vehicle wheel individually driven by electric motor

Info

Publication number: WO2017049469A1
Application number: PCT/CN2015/090324
Authority: WO
Inventors: Benedikt MANSBART; Takashi Shigematsu
Original assignee: Robert Bosch Gmbh
Priority date: 2015-09-23
Filing date: 2015-09-23
Publication date: 2017-03-30

Abstract

An independent suspension for attaching a non-steerable vehicle wheel individually driven by an electric motor to a vehicle frame is disclosed. The independent suspension comprises a first link, a second link and a suspension strut. The first link is pivotably mounted to the vehicle frame and pivotably connected to a middle point of the second link. The second link is pivotably connected to a rim of the vehicle wheel and pivotably connected to the suspension strut. The suspension strut is horizontally orientated and connected to the vehicle frame. The first link, the second link and the suspension strut are configured to allow the vehicle wheel to move up and down substantially in a vertical direction of the vehicle, under a spring-like damping action from the suspension strut.

Description

Independent Suspension Employing Horizontal Suspension Strut for Vehicle Wheel Individually Driven by Electric Motor

Technical Field

The invention relates to an independent suspension for a vehicle wheel individually driven by an electric motor.

Background Art

In an electric vehicle, one or more wheels may each be individually driven by an electric motor disposed in the wheel or by an electric motor disposed outside but close to the wheel. A close-to-wheel motor offer advantages with respect to an in-wheel motor in some aspects like a lower unsprung mass, design freedom for the electric motor and a higher possible transmission ratio of a gearbox. On the other hand, a close-to-wheel motor needs a larger installation space and is more difficult to be incorporated into a single module.

US2013228994A1 discloses a single wheel suspension system for a driven, non-steerable wheel. The driven wheel is equipped with a close-to-wheel motor, and a two-stage gearbox located within a space enclosed by a wheel rim. The gearbox has a two-part housing, allowing the gearbox to perform a scissor-like movement to compensate the vertical springing movement of the wheel which is defined by an arrangement of suspension links. The gearbox and the suspension system are both located within the rim. A torsional spring and a torsional damper are located between the two parts of the housing of the gearbox as well as between the gearbox and the electric motor.

The concept in US2013228994A1 offers a compact packaging by including a two-stage gearbox into suspension links that are able to perform a scissor movement during the springing movement of the wheel. The arrangement of the suspension links requires a torsional spring/damper to be included between the parts of the gearbox housing and the electrical motor. However, such a torsional spring/damper is not commonly used in current vehicle suspensions. This renders the system complex and requires special technology to manufacture. Further, the springing movement of the wheel is limited due to small axial offset between the wheel and the electric motor, so it is difficult to apply the system in vehicles that need a high ground clearance.

Summary of the Invention

An object of the invention is to provide an improved configuration for such an independent suspension for a vehicle wheel individually driven by an electric motor.

According to one aspect of the invention, there provides an independent suspension for attaching a non-steerable vehicle wheel individually driven by an electric motor to a vehicle frame, the independent suspension comprising:

a first link, a second link and a suspension strut；

the first link having a first end pivotably mounted to the vehicle frame at a first connecting point and a second opposite end pivotably connected to the second link at a second connecting point；

the second link having a first end pivotably connected to a rim of the vehicle wheel at a third connecting point and a second opposite end pivotably connected to a first end of the suspension strut at a fourth connecting point；

the suspension strut being orientated to telescope substantially horizontally in a longitudinal direction of the vehicle, and having a second end, which is opposite to its first end, connected to the vehicle frame； and

the first link, the second link and the suspension strut being configured to allow the vehicle wheel to move up and down substantially in a vertical direction of the vehicle, under a spring-like damping action from the suspension strut.

According to a possible embodiment of the invention, the second connecting point is the middle point of the second link； and the first connecting point and the fourth connecting point being disposed substantially at the same level in the vertical direction.

According to a possible embodiment of the invention, in the projection onto a vertical plane defined by the longitudinal direction and the vertical direction, the third connecting point is substantially directly below the first connecting point.

According to a possible embodiment of the invention, in the projection onto the vertical plane defined by the longitudinal direction and the vertical direction, the first link have a length that substantially equals to half of the length of the second link.

According to a possible embodiment of the invention, the suspension strut is arranged at a level higher than the fourth connecting point, and an offset member is fixed to the suspension strut and extends downwards to be pivotable connected with the second link at the fourth connecting point.

According to a possible embodiment of the invention, the pivot axes at the first to fourth connecting points all extend substantially in a transverse direction of the vehicle. Alternatively, the pivot axes at the third and fourth connecting points extend substantially in the transverse direction while the pivot axes at the first and second connecting points are slightly oblique from the transverse direction.

According to a possible embodiment of the invention, the independent suspension further comprises a power transmission for transmitting the output power of the electric motor to the vehicle wheel, wherein the power transmission comprises a speed reducing mechanism having at least two stages disposed in a two-part type gear housing which comprises a first housing part accommodating the first stage of the speed reducing mechanism and a second housing part accommodating the second stage of the speed reducing mechanism, the first housing part defining the first link and the second housing part defining the second link.

According to a possible embodiment of the invention, the first stage of the speed reducing mechanism comprises a first gearwheel and a second gearwheel meshed therewith, and the second stage of the speed reducing mechanism comprises a third gearwheel and a fourth gearwheel meshed therewith, the first gearwheel being mounted to a motor shaft of the electric motor, with the central axis of the motor shaft defining the first connecting point, the second gearwheel and the third gearwheel being mounted on an intermediate shaft, with the central axis of the intermediate shaft defining the second connecting point, and the fourth gearwheel being mounted to an output shaft which is connected with the rim, with the central axis of the output shaft defining the third connecting point.

According to a possible embodiment of the invention, the electric motor is fixedly mounted to the vehicle frame, and the second housing part comprises an intermediate member fixed thereto, which extends to the fourth connecting point to form the second end of the second link.

According to a possible embodiment of the invention, the suspension strut has a standard configuration as commonly used in vehicle suspensions. For example, the suspension strut may have a double wishbone or a McPherson strut configuration.

According to a possible embodiment of the invention, the independent suspension is arranged in at least two layers in the transverse direction, including at least one layer disposed in the space enclosed by the wheel rim and at least another layer disposed outside the wheel rim.

According to a possible embodiment of the invention, the second housing part, with the second stage of the speed reducing mechanism accommodated therein, is located in a first layer in the space enclosed by the wheel rim, and the first housing part, with the first stage of the speed reducing mechanism accommodated therein, is located in a second layer outside the wheel rim.

According to a possible embodiment of the invention, the suspension strut is disposed in the second layer, substantially directly above the first housing part.

According to a possible embodiment of the invention, mechanical stops are provided on the first housing part and/or the suspension strut and/or the vehicle frame to define upper and lower movement limitations of the vehicle wheel.

This invention provides an improved arrangement of the suspension links that makes it possible to employ a suspension strut commonly used within current vehicle suspension systems, which simplifies the structure of the independent suspension and eliminates the requirement of special manufacturing technology. Further, the independent suspension realizes an axial distance between the wheel and the electric motor and therefore increases the ground clearance, so the independent suspension can be used in vehicles having a high chassis.

Brief Description of the Drawings

Figure 1 is a schematic sketch of a suspension mechanism of an independent suspension according to the invention, projected onto a vertical plane in X-Z direction.

Figure 2 is a schematic sketch of a power transmission integrated into the independent suspension according to the invention, projected onto the vertical plane in X-Z direction.

Figure 3 is a schematic plan view showing a possible layout of the independent suspension integrated with the power transmission as shown in Figure 2.

Detailed Description of Preferred Embodiments

Now some preferred embodiments of the invention will be described with reference to the drawings.

The invention relates to an independent suspension of an electric vehicle, the independent suspension being a suspension system which attaches a non-steerable vehicle wheel driven by an electric motor to the vehicle chassis or vehicle frame while allows the wheel to move vertically independently.

In general, the independent suspension of the invention mainly comprises a suspension mechanism. For describing this mechanism, some directions are defined here first: X direction refers to a longitudinal direction or front-back direction of the vehicle, Y direction refers to a transverse direction or right-left direction of the vehicle, and Z direction refers to a vertical direction or top-bottom direction of the vehicle. Figure 1 shows the kinematic configuration of the suspension mechanism in a vertical X-Z plane.

As shown in Figure 1, the suspension mechanism mainly comprises a first link 1, a second link 2 and a slider 3. The first link 1 is mounted at one end to the vehicle frame at point M and coupled at the other end to the second link 2 at point A which is the middle point of the second link 2. The slider 3 is coupled to one end of the second link 2 at point B and is slidable horizontally in X direction with respect to the vehicle frame. The second link 2 is pivotably mounted at the other end of it to a vehicle wheel 4 at point W.

The first and

second links

1 and 2 may each have a rotational degree-of-freedom at points M, A, W and B, with their pivot axes all extending substantially in Y direction. The pivot axes at points M and A may alternatively be slightly oblique with respect to Y direction. The slider 3 has a translational degree-of-freedom in X direction. Each of the

links

1 and 2 is moveable substantially in the X-Z plane.

In the projected on the vertical plane in X-Z direction, points M and B are disposed substantially at the same level in Z direction, and point W is substantially directly below point M. Points W, A and B are substantially collinear. The distance L_MA between points M and A is half of distance L_WB between points W and B, that is to say, the distance L_MA between points M and A equals to the distance L_WA between points W and A and the distance L_AB between points A and B. In this way, an imaginary line connecting points M and B and an imaginary line connecting points M and W forms a right angle at point M. This ensures that point W and thus the wheel 4 are moveable vertically in Z direction. Upper and lower movement limitations of the wheel 4 can be provided by mechanical stops.

It is appreciated that the above configuration and dimensions can provide the wheel 4 with a straight vertical movement； however, the scope of the invention also covers the condition in which a substantially straight vertical movement is provided to the wheel 4, that is to say, the vertical movement path of the wheel 4 may includes a small component in X direction.

The slider 3 is configured to have a damper function to provide damping action to the vertical movement of the wheel 4. Under this damping action, the wheel 4 move up and down springingly when the wheel 4 runs on an uneven ground surface.

According to the invention, as schematically shown in Figure 2, a power transmission for transmitting the driving power of an electric motor 6 to the wheel 4 is integrated into the independent suspension. The electric motor 6 is fixedly mounted to the vehicle frame, outside and independent of the wheel 4, that is to say, not integrated into the wheel 4. The electric motor 6 here can be referred to as a close-to-wheel motor.

Specifically, the power transmission mainly comprises a gear-type speed reducing mechanism having at least two stages, the first stage comprising a first gearwheel 7 and a second gearwheel 8 meshed therewith to provide a first speed reducing ratio, and the second stage comprising a third gearwheel 9 and a fourth gearwheel 10 meshed therewith to provide a second speed reducing ratio. The fourth gearwheel 10 is connected with a rim 4a of the wheel 4.

The slider 3 with damper function is embodied in the form of a suspension strut 11. The suspension strut 11 is horizontally disposed in X direction and coupled between the second link 2 and the vehicle frame to be able to telescope therebetween. The suspension strut 11, which is preferably linear, has a strut segment 11a coupled to the second link 2 at point B and being able to move with respect to the remaining portion of the suspension strut 11 in X direction.

In accordance with a possible embodiment, the suspension strut 11 is arranged substantially directly above the first stage of the speed reducing mechanism for effectively using available space. In this case, in order to avoid interference between the suspension strut 11 and the first stage of the speed reducing mechanism, a vertical offset member 12 is used. The offset member 12 has an upper end fixed to the strut segment 11a, for example, fixed to the tip end of the strut segment 11a, and a lower end pivotable coupled with the second link 2 at point B. By means of this offset member 12, the central axis of the suspension strut 11 is offset vertically from the horizontal moving path of point B. It is appreciated that the suspension strut 11 may alternatively be disposed at other locations, and thus the connection between the suspension strut 11 and the second link 2 can be designed according to the concrete positional relation therebetween.

For the suspension shown in Figure 2, the first and

second links

1 and 2 can be embodied in the form of the gear housing of the speed reducing mechanism. As shown in Figure 3, the gear housing is formed as a two-part gear housing, including a first housing part 13 accommodating the first gearwheel 7 and the second gearwheel 8 and a second housing part 14 accommodating the third gearwheel 9 and the fourth gearwheel 10.

The first gearwheel 7 is mounted to a motor shaft 6a of the electric motor 6 which extends substantially in Y direction (or slightly oblique from Y direction) into the first housing part 13. The second gearwheel 8 is directly connected with the third gearwheel 9 by being mounted on a common intermediate shaft 15 which extends substantially in Y direction (or slightly oblique from Y direction) into both the first and

second housing parts

13 and 14. The fourth gearwheel 10 is mounted on an output shaft 16 which extends substantially in Y direction from the second housing part 14 and is connected with the rim 4a of the wheel.

The first housing part 13 is pivotable around the motor shaft 6a, the second housing part 14 is pivotable around the output shaft 16, and the first and

second housing parts

13 and 14 are pivotable with respect to each other around the intermediate shaft 15.

In this manner, the first housing part 13 forms the first link 1 of the suspension mechanism, the second housing part 14 forms the second link 2 of the suspension mechanism, and thus point A lies on the axis of the intermediate shaft 15, i.e., the rotational axis of the second gearwheel 8 and the third gearwheel 9. As a result, the first and

second housing parts

13 and 14 are able to move with respect to each other in a scissor-like manner. Further, the first housing part 13 is pivotably carried by the motor shaft 6a of the electric motor 6, so point M lies on the central axis of the motor 6, i.e., the rotational axis of the first gearwheel 7, and the second housing part 14 is pivotably carried by the output shaft 16, so point W lies on the axis of the output shaft 16, i.e., the rotational axis of the fourth gearwheel 10.

As described above, the second housing part 14 which forms the second link 2 shall be connected with the suspension strut 11 at point B, possibly by the help of the offset member 12. In the case that the second housing part 14 is formed to have a size and dimension only for accommodating the second stage of the speed reducing mechanism, an intermediate member 17 is used here, the intermediate member 17 having one end fixed to the second housing part 14 and the other end extended to point B and forming pivotable connection with the suspension strut 11, possibly via the offset member 12. The intermediate member 17 may have any suitable shape and structure, rather than the illustrated one, in accordance with design requirement.

The independent suspension is arranged in at least two layers in Y direction, including at least one layer disposed in the space enclosed by the wheel rim 4a and at least another layer disposed outside the wheel rim 4a. The second housing part 14 which forms the second link 2, together with the third gearwheel 9 and the fourth gearwheel 10 accommodated therein, is located as a first layer in the space enclosed by the wheel rim 4a, while the first housing part 13 which forms the first link 1, together with the first gearwheel 7 and a second gearwheel 8 accommodated therein, is located as a second layer outside the wheel rim 4a. The suspension strut 11 may be arranged in the second layer, above the first housing part 13, or be arranged in any other layer outside the wheel rim 4a. The electric motor 6 is disposed further away from the wheel rim 4a.

By arranging the first housing part 13 and the suspension strut 11 outside the wheel rim 4a, free movements or actions of them are guaranteed, which enlarges the whole suspension mechanism, and thus the wheel 4 may have an increased vertical movement range, so the independent suspension can be used in vehicles requiring a large ground clearance.

Mechanical stops may be provided, for example, on the first housing part 13 and/or the suspension strut 11 and/or the vehicle frame, to define the upper and lower movement limitations of the wheel 4 and to avoid collision between the first housing part 13 and the suspension strut 11.

Further, since only the second housing part 14 is located in the space enclosed by the wheel rim 4a, there is room outside the wheel rim 4a for disposing the suspension strut 11, so the suspension strut 11 may have increased design flexibility.

The suspension strut 11 may be a spring type, a hydraulic type, a spring-hydraulic combination type or any other type of suspension strut that is commonly used in vehicle industry. For example, the suspension strut 11 may have a configuration like that used in a double wishbone suspension or in a McPherson strut suspension, or have any other standard configuration as commonly used in vehicle suspensions.

Compared with the prior art in which torsional springs/dampers are used, the arrangement of the suspension of the invention simplifies the construction, as the suspension strut does not need to be based on a torsional movement to be integrated into the gearbox, but can be linear. This makes it possible to use a commonly used suspension strut, which results in simple structure and reduced cost of the suspension.

Further, room for the suspension strut is gained due to the layered arrangement of the suspension. In addition, as the suspension strut is located outside the wheel rim, possibly directly above the first gear housing part, the suspension of the invention is easy to manufacture, and the suspension strut is convenient to remove for maintenance.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. The attached claims and their equivalents are intended to cover all the modifications, substitutions and changes as would fall within the scope and spirit of the invention.

Claims

An independent suspension for attaching a non-steerable vehicle wheel (4) individually driven by an electric motor (6) to a vehicle frame, the independent suspension comprising:

a first link (1) , a second link (2) and a suspension strut (11) ；

the first link (1) having a first end pivotably mounted to the vehicle frame at a first connecting point (M) and a second opposite end pivotably connected to the second link (2) at a second connecting point (A) ；

the second link (2) having a first end pivotably connected to a rim (4a) of the vehicle wheel (4) at a third connecting point (W) and a second opposite end pivotably connected to a first end of the suspension strut (11) at a fourth connecting point (B) ；

the suspension strut (11) being orientated to telescope substantially horizontally in a longitudinal direction of the vehicle, and having a second end, which is opposite to its first end, connected to the vehicle frame； and

the first link (1) , the second link (2) and the suspension strut (11) being configured to allow the vehicle wheel (4) to move up and down substantially in a vertical direction of the vehicle, under a spring-like damping action from the suspension strut (11) .
The independent suspension of claim 1, wherein the second connecting point (A) is the middle point of the second link (2) ； and

the first connecting point (M) and the fourth connecting point (B) being disposed substantially at the same level in the vertical direction.
The independent suspension of claim 1 or 2, wherein in the projection onto a vertical plane defined by the longitudinal direction and the vertical direction, the third connecting point (W) is substantially directly below the first connecting point (M) .
The independent suspension of claim 3, wherein in the projection onto the vertical plane defined by the longitudinal direction and the vertical direction, the first link (1) have a length that substantially equals to half of the length of the second link (2) .
The independent suspension of any one of claims 1 to 4, wherein the suspension strut (11) is arranged at a level higher than the fourth connecting point (B) , and an offset member (12) is fixed to the suspension strut (11) and extends downwards to be pivotable connected with the second link (2) at the fourth connecting point (B) .
The independent suspension of any one of claims 1 to 5, wherein the pivot axes at the first to fourth connecting points (M, A, W, B) all extend substantially in a transverse direction of the vehicle； or

the pivot axes at the third and fourth connecting points (W, B) extend substantially in the transverse direction while the pivot axes at the first and second connecting points (M, A) are slightly oblique from the transverse direction.
The independent suspension of any one of claims 1 to 6, further comprising a power transmission for transmitting the output power of the electric motor (6) to the vehicle wheel (4) , wherein the power transmission comprises a speed reducing mechanism having at least two stages disposed in a two-part type gear housing which comprises a first housing part (13) accommodating the first stage of the speed reducing mechanism and a second housing part (14) accommodating the second stage of the speed reducing mechanism, the first housing part (13) defining the first link (1) and the second housing part (14) defining the second link (2) .
The independent suspension of claim 7, wherein the first stage of the speed reducing mechanism comprises a first gearwheel (7) and a second gearwheel (8) meshed therewith, and the second stage of the speed reducing mechanism comprises a third gearwheel (9) and a fourth gearwheel (10) meshed therewith, the first gearwheel (7) being mounted to a motor shaft (6a) of the electric motor (6) , with the central axis of the motor shaft (6a) defining the first connecting point (M) , the second gearwheel (8) and the third gearwheel (9) being mounted on an intermediate shaft (15) , with the central axis of the intermediate shaft (15) defining the second connecting point (A) , and the fourth gearwheel (10) being mounted to an output shaft (16) which is connected with the rim (4a) , with the central axis of the output shaft (16) defining the third connecting point (W) .
The independent suspension of claim 7 or 8, wherein the electric motor (6) is fixedly mounted to the vehicle frame, and the second housing part (14) comprises an intermediate member (17) fixed thereto, which extends to the fourth connecting point (B) to form the second end of the second link (2) .
The independent suspension of any one of claims 1 to 9, wherein the suspension strut (5) has a standard configuration as commonly used in vehicle suspensions.
The independent suspension of claim 10, wherein the suspension strut (5) has a double wishbone or a McPherson strut configuration.
The independent suspension of any one of claims 7 to 11, wherein the independent suspension is arranged in at least two layers in the transverse direction, including at least one layer disposed in the space enclosed by the wheel rim (4a) and at least another layer disposed outside the wheel rim (4a) .
The independent suspension of claim 12, wherein the second housing part (14) , with the second stage of the speed reducing mechanism accommodated therein, is located in a first layer in the space enclosed by the wheel rim (4a) , and the first housing part (13) , with the first stage of the speed reducing mechanism accommodated therein, is located in a second layer outside the wheel rim (4a) .
The independent suspension of claim 13, wherein the suspension strut is disposed in the second layer, substantially directly above the first housing part (13) .
The independent suspension of claim 14, wherein mechanical stops are provided on the first housing part (13) and/or the suspension strut (11) and/or the vehicle frame to define upper and lower movement limitations of the vehicle wheel (4) .