WO2017049468A1

WO2017049468A1 - Independent suspension employing vertical suspension strut for vehicle wheel individually driven by electric motor

Info

Publication number: WO2017049468A1
Application number: PCT/CN2015/090322
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 comprises first to third links (1, 2, 3) forming a four-bar linkage with the vehicle frame, the four-bar linkage being configured to allow an end of the second link (2) which is connected to the wheel (4) to move in a substantially straight path in a vertical direction, and a suspension strut (5) extending vertically and connected between the second link (2) and the vehicle frame.

Description

Independent Suspension Employing Vertical 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.

Summary of the Invention

An object of the invention is to provide an improved solution for integrating the power transmission of a close-to-wheel electric motor into a suspension for a non-steerable single wheel.

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:

first to third links each having a first end and a second opposite end；

the first end of the first link being mounted to the vehicle frame at a first connecting point, and the second end of the first link being connected to the second link at a second connecting point between the first and second ends of the second link；

the first end of the third link being mounted to the vehicle frame at a third connecting point, and the second end of the third link being connected to the first end of the second link at a fourth connecting point；

the first to fourth connecting points each defining a pivot axis, the first to third links being pivotable about corresponding pivot axes, and the first to third links and the vehicle frame forming a four-bar linkage which is configured to allow the second end of the second link to move in a substantially straight path in a vertical direction of the vehicle；

the second end of the second link being pivotably connected to a rim of the vehicle wheel at a fifth connecting point； and

a suspension strut extending substantially vertically and having a lower end connected with the second link at or near the fifth connecting point and an upper end connected to a corresponding portion of the vehicle frame.

According to a possible embodiment of the invention, in the projection onto a vertical plane defined by a longitudinal direction of the vehicle and the vertical direction, the third connecting point is substantially directly above the first connecting point, and the first connecting point and the fifth connecting point are disposed at longitudinally opposite sides of the second connecting point.

According to a possible embodiment of the invention, the four-bar linkage is configured to be a crank-rocker mechanism in which the third link is a crank and the first link is a rocker.

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 length of the first link is about half that of the second link, and the second connecting point is at or near the middle point of the second link.

According to a possible embodiment of the invention, in a neutral position of the vehicle wheel, the third link is substantially vertical in the projection onto the vertical plane defined by the longitudinal direction and the vertical direction, with the pivot axis at the fourth connecting point being substantially directly above the pivot axis at the third connecting point.

According to a possible embodiment of the invention, the pivot axes at the first to fifth connecting points all extend substantially in a transverse direction of the vehicle. Alternatively, the pivot axes at the third, fourth and fifth connecting points may extend substantially in the transverse direction while the pivot axes at the first and second connecting points may be 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, and 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 being coincided with the pivot axis at 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 being coincided with the pivot axis at 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 being coincided with the pivot axis at the fifth 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 is connected at the fourth connecting point with the second, upper end of the third link, the first, lower end of the third link being connected at the third connecting point with a fixing element which is fixed relative to the vehicle frame. Preferably, the fixing element comprises a fixing ring which is fixed around the electric motor.

According to a possible embodiment of the invention, the lower end of the suspension strut is connected to the second housing part or the intermediate member or both.

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 has 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 the space enclosed by the wheel rim, and the first housing part, with the first stage of the speed reducing mechanism accommodated therein, and the suspension strut are located outside the wheel rim.

According to a possible embodiment of the invention, the pivot axes at the second connecting point and the fifth connecting point are within or extend through the space enclosed by the wheel rim, and the pivot axes at the first connecting point, the third connecting point and the fourth connecting point extend outside the space enclosed by the wheel rim.

According to the invention, the power transmission of a close-to-wheel electric motor is integrated into a suspension for a non-steerable single wheel by means of suspension links with a suspension strut that is commonly used in current vehicle suspension systems, which decreases the required installation space and the cost of the whole suspension, simplifies the structure of the suspension, and eliminates the requirement of special manufacturing technology.

Further, according to the layout of the suspension mechanism and the multiple layer configuration of the invention, the axis of the electric motor is separated by a larger distance from the axis of the wheel compared with that of US2013228994A1, which allows a larger vertical straight movement of the wheel, so the independent suspension can be used in vehicles having a high chassis.

Brief Description of the Drawings

Figures 1 to 3 are schematic sketches of a suspension mechanism of an independent suspension according to the invention, projected onto a vertical plane in X-Z direction. Figure 4 is a schematic plan view of the independent suspension integrated with a power transmission according to the invention.

Figures 5 and 6 are schematic perspective views of the independent suspension integrated with the power transmission as shown in Figure 4, taken in different directions.

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. Figures 1-3 show the kinematic configuration of the suspension mechanism in a vertical X-Z plane.

As shown in Figures 1-3, the suspension mechanism mainly comprises a first link 1, a second link 2 and a third link 3, the first link 1 being coupled at one end to a portion of the second link 2 at point A and mounted at the other end to the vehicle frame at point M, and the third link 3 being coupled at one end to one end of the second link 2 at point B and mounted at the other end to the vehicle frame at point C.

The second link 2 is pivotably mounted at the other end of it to a vehicle wheel 4 at point W, with points B and W being located at longitudinally opposite sides of point A. These links may each have a rotational degree-of-freedom at points M, A, B, W and C, 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. Each of the

links

1, 2 and 3 is moveable substantially in the X-Z plane, and the

links

1, 2 and 3 and the vehicle frame form a four-bar linkage.

In Figures 1-3, points B, A and W are shown as collinear, but it is not necessarily always so, and point A may alternatively be offset from an imaginary line connecting points B and W.

Points M and W are arranged at opposite sides of point A in the longitudinal or X direction. Point C is arranged at the same side in X direction with point M, and is higher than point M.

The lengths of the

links

1, 2 and 3 and the positions of points A, C and M are determined so that, in a neutral position of the wheel 4 as shown in Figure 1, point B is substantially directly above point C, that is to say, the third link 3 is substantially vertical； point A is lower than point B, and points M and W are lower than point A.

The lengths of the

links

1, 2 and 3 and the positions of points A, C and M are also determined so that, in the neutral position of the wheel 4 as shown in Figure 1, the wheel 4 or point W is moveable up and down along a substantially straight path. Here “substantially straight” means that the wheel 4 has a movement component in X direction much smaller than a movement component in Z direction in a range about neutral position of the wheel 4.

Figure 2 shows the suspension mechanism in a completely expended state in which the wheel 4 is in its lowest position. When the wheel 4 moves downwards to the lowest position from the neutral position, the third link 3 rotates about point C in an anticlockwise direction and the first link 1 also rotates about point M in an anticlockwise direction. At the lowest position of the wheel 4, the third link 3 is nearly horizontal, or has been rotated about 90 degrees in the anticlockwise direction from its original vertical position； the first link 1 now may also be nearly horizontal, although it is not necessarily always so.

Figure 3 shows the suspension mechanism in a completely compressed state in which the wheel 4 is in its highest position. When the wheel 4 moves upwards to the highest position from the neutral position, the third link 3 rotates about point C in a clockwise direction and the first link 1 also rotates about point M in a clockwise direction. At the highest position of the wheel 4, the third link 3 is nearly horizontal, or has been rotated about 90 degrees in the clockwise direction from its original vertical position； the first link 1 now may also be nearly horizontal, although it is not necessarily always so.

The wheel 4 is moveable vertically between its lowest and highest positions, and the lowest and highest positions may be defined either by additional mechanical stops or by the four-bar linkage itself. Preferably, the length of the second link 2 is much smaller than either one of the length of the first link 1, the distance between points A and B and the distance between points C and M, so that the four-bar linkage forms a crank-rocker mechanism, wherein the third link 3 is a crank while the first link 1 is a rocker.

The ratios of the lengths of the

links

1, 2 and 3 determine how straight the movement of the wheel 4 is, whereas the location of the mounting points M and C determine the direction of the movement. Preferably, point A is the middle point of the second link 2, and the length of the first link 1 is about half that of the second link 2, so a wanted straight movement of the wheel 4, which is substantially parallel to an imaginary line connecting points M and C, is obtained.

A vertical suspension strut (not shown in Figures 1-3) , as will be described, is connected between the second link 2 and the vehicle frame for damping the vertical movement of the wheel 4, so the vertical up-down movement of the wheel 4 is straight springing movement.

As a possible embodiment of the invention as schematically shown in Figures 4-6, a power transmission for transmitting the driving power of an electric motor 6 to the wheel 4 is integrated into the independent suspension of the invention.

The electric motor 6 is 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 disposed in a gear housing, 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 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) , the electric motor 6 being fixedly mounted to the vehicle frame. The second gearwheel 8 is directly connected with the third gearwheel 9 by being mounted on a common intermediate shaft 11 which extends substantially in Y direction (or slightly oblique from Y direction) . The fourth gearwheel 10 is mounted on an output shaft 12 which extends substantially in Y direction and is connected with a rim 4a of the wheel.

The gear housing is formed as a two-part gear housing, the first housing part accommodating the first gearwheel 7 and the second gearwheel 8 while the second housing part accommodating the third gearwheel 9 and the fourth gearwheel 10. The first housing part is pivotable around the motor shaft 6a, the second housing part is pivotable around the output shaft 12, and the first and second housing parts being pivotable with respect to each other around the intermediate shaft 11.

The first housing part forms the first link 1 of the suspension mechanism, the second housing part forms the second link 2 of the suspension mechanism, and thus point A lies on the axis of the intermediate shaft 11, i.e. , the rotational axis of the second gearwheel 8 and the third gearwheel 9. The first and second housing parts are able to move with respect to each other in a scissor-like manner. Further, the first housing part 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 is pivotably carried by the output shaft 12, so point W lies on the axis of the output shaft 12, i.e. , the rotational axis of the fourth gearwheel 10.

The third link 3 is in the form of a short bar which is disposed above the central axis of the electric motor 6 and extends substantially in the vertical Z direction. The third link 3 is pivotably connected at its lower end to a fixing element which is fixed relative to the vehicle frame, for example, a fixing ring 3a which is fixed around the electric motor 6, and pivotably connected at its upper end to an intermediate member 2a which is fixed to the second housing part. The intermediate member 2a may be regarded as a portion or an extension of the second housing part. Note the intermediate member 2a may have any suitable shape and structure, rather than the illustrated one, in accordance with design requirement.

By means of the intermediate member 2a, the second housing part is pivotable with respect to the upper end of the third link 3, so point B lies on the pivot axis between the intermediate member 2a and the third link 3. Point C lies on the pivot axis between the third link 3 and the motor 6. Point C is directly above the central axis of the electric motor 6 and point B is directly above point C.

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. For example, the second housing part 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 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 intermediate member 2a may be located outside the wheel rim 4a as a third layer. The electric motor 6 is disposed further away from the wheel rim 4a.

The intermediate member 2a which forms a portion of the second housing part extends outside the wheel rim 4a so that the second link 2 is extended in length. Thus, only the pivot axes at points A and W are within or extend through the space enclosed by the wheel rim 4a, and the pivot axes at the points M, C and B do not extend through the space enclosed by the wheel rim 4a. This 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 having a high chassis.

A suspension strut 5, which is preferably linear, is coupled between the second housing part and the vehicle frame for providing springing and damping action to the independent suspension. Since only the second housing part is located in the space enclosed by the wheel rim 4a, there is room outside the wheel rim 4a for disposing the suspension strut 5, so the suspension strut 5 may have increased design flexibility. The suspension strut 5 may be arranged in either the second layer or another layer (such as the third layer) outside the wheel rim 4a.

The suspension strut 5 extends substantially vertically in Z direction, having a lower end connected at a point near the output shaft 12, that is, at or near point W, to either or both of the second housing part and the intermediate member 2a and an upper end connected to a portion of the vehicle frame. The suspension strut 5 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 5 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, having a similar upper damping segment with a mounting point that is situated above the turning axis of the wheel. The suspension strut 5 also has a strut segment connected to the second housing part of the gearbox housing at or near point W, as described above. It is appreciated that the integrated independent suspension as illustrated in Figures 4-6 can perform the scissor-like actions as described above with reference to Figures 1-3.

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. Further, room for the suspension strut is gained, as the arrangement of the suspension of the invention features an electric motor with a turning axis that is separated by a distance from the wheel’s axis, while maintaining a straight springing movement.

As the suspension strut is located directly above the wheel’s axis, the suspension of the invention furthermore can easily replace existing double wishbone suspensions or McPherson strut suspensions, as they feature similar mounting points.

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:

first to third links (1, 2, 3) each having a first end and a second opposite end；

the first end of the first link (1) being mounted to the vehicle frame at a first connecting point (M) , and the second end of the first link (1) being connected to the second link (2) at a second connecting point (A) between the first and second ends of the second link (2) ；

the first end of the third link (3) being mounted to the vehicle frame at a third connecting point (C) , and the second end of the third link (3) being connected to the first end of the second link (2) at a fourth connecting point (B) ；

the first to fourth connecting points (M, A, C, B) each defining a pivot axis, the first to third links (1, 2, 3) being pivotable about corresponding pivot axes, and the first to third links (1, 2, 3) and the vehicle frame forming a four-bar linkage which is configured to allow the second end of the second link (2) to move in a substantially straight path in a vertical direction of the vehicle；

the second end of the second link (2) being pivotably connected to a rim (4a) of the vehicle wheel (4) at a fifth connecting point (W) ； and

a suspension strut (5) extending substantially vertically and having a lower end connected with the second link (2) at or near the fifth connecting point (W) and an upper end connected to a corresponding portion of the vehicle frame.
The independent suspension of claim 1, wherein in the projection onto a vertical plane defined by a longitudinal direction of the vehicle and the vertical direction, the third connecting point (C) is substantially directly above the first connecting point (M) , and the first connecting point (M) and the fifth connecting point (W) are disposed at longitudinally opposite sides of the second connecting point (A) .
The independent suspension of claim 2, wherein the four-bar linkage is configured to be a crank-rocker mechanism in which the third link (3) is a crank and the first link (1) is a rocker.
The independent suspension of claim 2 or 3, wherein in the projection onto the vertical plane defined by the longitudinal direction and the vertical direction, the length of the first link (1) is about half that of the second link (2) , and the second connecting point (A) is at or near the middle point of the second link (2) .
The independent suspension of claim 3 or 4, wherein in a neutral position of the vehicle wheel (4) , the third link (3) is substantially vertical in the projection onto the vertical plane defined by the longitudinal direction and the vertical direction, with the pivot axis at the fourth connecting point (B) being substantially directly above the pivot axis at the third connecting point (C) .
The independent suspension of any one of claims 1 to 5, wherein the pivot axes at the first to fifth connecting points (M, A, C, B, W) all extend substantially in a transverse direction of the vehicle； or

the pivot axes at the third, fourth and fifth connecting points (C, B, W) 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 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 (1) and the second housing part 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) being coincided with the pivot axis at the first connecting point (M), the second gearwheel (8) and the third gearwheel (9) being mounted on an intermediate shaft (11) , with the central axis of the intermediate shaft (11) being coincided with the pivot axis at the second connecting point (A) , and the fourth gearwheel (10) being mounted to an output shaft (12) which is connected with the rim (4a) , with the central axis of the output shaft (12) being coincided with the pivot axis at the fifth 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 comprises an intermediate member (2a) fixed thereto, which is connected at the fourth connecting point (B) with the second, upper end of the third link (3) , the first, lower end of the third link (3) being connected at the third connecting point (C) with a fixing element which is fixed relative to the vehicle frame.
The independent suspension of claim 9, wherein the fixing element comprises a fixing ring (3a) which is fixed around the electric motor (6) .
The independent suspension of claim 9 or 10, wherein the lower end of the suspension strut (5) is connected to the second housing part or the intermediate member (2a) or both.
The independent suspension of any one of claims 1 to 11, wherein the suspension strut (5) has a standard configuration as commonly used in vehicle suspensions.
The independent suspension of claim 12, wherein the suspension strut (5) has a double wishbone or a McPherson strut configuration.
The independent suspension of any one of claims 7 to 13, 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 14, wherein the second housing part, with the second stage of the speed reducing mechanism accommodated therein, is located in the space enclosed by the wheel rim (4a) , and the first housing part, with the first stage of the speed reducing mechanism accommodated therein, and the suspension strut are located outside the wheel rim (4a) .
The independent suspension of claim 14 or 15, wherein the pivot axes at the second connecting point (A) and the fifth connecting point (W) are within or extend through the space enclosed by the wheel rim (4a) , and the pivot axes at the first connecting point (M) , the third connecting point (C) and the fourth connecting point (B) extend outside the space enclosed by the wheel rim (4a) .