METHOD FOR REDUCING A VIBRATION OF A VEHICLE BODY OF AN ELECTRIC VEHICLE BY MEANS OF THE ELECTRIC MOTOR OF SAID VEHICLE

Abstract

A method uses the electric motor (4) of an electric vehicle to reduce vibration of the vehicle body (1). The electric motor (4) is supported on the vehicle body (1) or on the subframe (2) of the electric vehicle. The method includes determining a vibration of a subframe (2) or of the vehicle body (1) in the area of force introduction sites where electric motor (4) is supported. The method proceeds by determining a torque required to be generated by the electric motor (4) to introduce a force into the subframe (2) or into the body (1) for counteracting the force caused by the determined oscillation acting on the subframe (2) or the vehicle body (1) and adjusting at least one driving signal of the electric motor (4) such that the required torque is generated based on the change in the drive torque of the electric motor (4).

Claims

1. A method for reducing a vibration of a vehicle body (1) of an electric vehicle by using an electric motor (4) of the vehicle, the electric motor (4) being supported on the vehicle body (1) or on a subframe (2) of the electric vehicle, the method comprising: determining a vibration of the subframe (2) or the vehicle body (1) in an area of force introduction sites to the subframe (2) or the vehicle body (1); determining a torque required to be generated by the electric motor (4) to introduce a force into the subframe (2) or into the body (1) to counteract the force caused by the determined vibration acting on the subframe (2) or the vehicle body (1); adjusting at least one driving signal of the electric motor (4) such that the torque required to counteract the force caused by the determined vibration is generated by the electric motor (4).

2. The method of claim 1, wherein determining the vibration comprises sensing vibration frequencies in a range of 30 Hz to 40 Hz.

3. The method of claim 1, wherein the vibration is determined by at least two sensors.

4. The method of claim 3, wherein the at least two sensors are accelerometers.

5. The method of claim 3, wherein the at least two sensors are arranged on the subframe (2) or the vehicle body (1) at plural positions spaced apart along a longitudinal axis of the electric vehicle.

6. The method of claim 3, wherein the at least two sensors are arranged at bearing points of the subframe (2) on the vehicle body (1).

7. The method of claim 3, wherein the at least two sensors are at maximum distance of 30 cm from bearing points of the subframe (2) on the vehicle body (1).

8. The method of claim 3, wherein determining the vibration further comprises subtracting from one another the vibration signals output by the at least two sensors.

9. The method of claim 1, wherein the vibration is determined by at least four sensors, where equal numbers of sensors are arranged on a right side and on a left side of the electric vehicle relative to a longitudinal axis running centrally through the electric vehicle.

10. The method of claim 9, wherein determining the vibration comprises averaging the signals determined on the right side and on the left side of the vehicle corresponding to one another in terms of their position relative to the longitudinal axis of the vehicle.

11. An electric vehicle comprising: a vehicle body (1) and a subframe (2); an electric motor (4) supported on the subframe (2) or on the vehicle body (1); sensors arranged on at least one of the subframe (2) or on the vehicle body (1) in an area of force introduction sites via the subframe (2), the sensors being configured for determining a vibration of the subframe (2) or the vehicle body (1) in the area of the force introduction sites; a control circuit connected to the sensors and to a control unit of the electric motor (4), the control unit being configured to determine a torque required to be generated by the electric motor (4) to introduce a force into the subframe (2) or into the body (1) to counteract the force caused by the determined vibration acting on the subframe (2) or the vehicle body (1), and adjusting at least one driving signal of the electric motor (4) such that the torque required to counteract the force caused by the determined vibration is generated by the electric motor (4).

12. The electric vehicle of claim 11, wherein the sensors are configured for sensing vibration frequencies in a range of 30 Hz to 40 Hz.

13. The electric vehicle of claim 11, wherein the sensors are accelerometers.

14. The electric vehicle of claim 13, wherein the sensors are arranged on the subframe (2) or the vehicle body (1) at plural positions spaced apart along a longitudinal axis of the electric vehicle.

15. The electric vehicle of claim 13, wherein the at least two sensors are arranged at bearing points of the subframe (2) on the vehicle body (1).

16. The electric vehicle of claim 13, wherein the at least two sensors are at maximum distance of 30 cm from bearing points of the subframe (2) on the vehicle body (1).

17. The electric vehicle of claim 13, wherein the sensors comprise at least four sensors with equal numbers of sensors are arranged on a right side and on a left side of the electric vehicle relative to a longitudinal axis running centrally through the electric vehicle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 is a schematic representation of a rear of the vehicle with a subframe and an electric motor supported thereon.

[0026] FIG. 2 is a schematic illustration of a rear of the vehicle with a subframe and an electric motor supported on the vehicle body.

DETAILED DESCRIPTION

[0027] FIG. 1 is a schematic illustration of a rear portion of a vehicle body 1 having a subframe 2 and an electric motor 4 supported thereon. A wheel suspension 3 is supported on the subframe 2. The subframe 2 itself is in turn supported at the rear of the vehicle body 1. The black lines, not explicitly marked with reference numerals, represent connecting elements between the respective units specified.

[0028] While traveling, vibrations are stimulated via the roadway by movement of the tires or the wheel 8 and the axle that is supported on the subframe 2. The oscillations are transferred to the subframe 2 at the first axle bearing point 51 and the second axle bearing point 52. Since a total torque is transferred to the subframe 2, the force acting at the first axle bearing point 51 is opposite to the force acting at the second axle bearing point 52. Both forces (and further forces mentioned below) are represented by corresponding force arrows. Generally, i.e., without application of the method according to the invention, these forces transfer from the subframe 2 to the vehicle body at the first subframe bearing point 61 and the second subframe bearing point 62.

[0029] However, as part of the method of the invention, vibration of the subframe 2 is determined or detected. A required torque of the electric motor 4 then is determined to introduce a force into the subframe 2, which at least partially counteracts the force caused by the determined vibration and acting on the subframe 2. FIG. 1 represents this compensatory force in the form of the two oppositely directed force arrows that are transferred to the subframe 2 at the first engine bearing point 71 and the second engine bearing point 72. The compensatory force is generated by adjusting at least one driving signal of the electric motor 2 such that the required moment is generated from the change in the drive torque of the electric motor 4 to produce the two forces acting at the first and second engine bearing points 71, 72. These forces are opposed to the forces acting on the subframe at the first and second axle bearing points 51, 52 and are large enough to minimize the oscillation behavior of the subframe 2 or to completely suppress those forces in the optimal case. As a result, the subframe 2 does not transfer forces to the vehicle body 1 at the first and second subframe bearing points 61, 62.

[0030] To determine the forces or vibrations, corresponding sensors, e.g. accelerometers, can be arranged at all bearing points shown in FIG. 1. A control circuit is configured to perform the method of the invention and is connected to the sensors and to a control unit of the electric motor 4. In the context of the invention, a “control unit” can, for example, be a machine or an electronic circuit or a powerful computer. A control unit can be a central processing unit (CPU), a microprocessor or a microcontroller, for example an application-specific integrated circuit or a digital signal processor, possibly in combination with a storage unit for storing program commands, etc. A control unit also can be a virtualized processor, a virtual machine or a soft CPU and may be a programmable processor that is equipped with configuration steps for carrying out the method according to the invention or is configured with configuration steps so that the programmable processor realizes features according to the method, the control circuit, the sensors, or of other aspects and/or partial aspects of the invention. Furthermore, the system may have highly parallel computing units.

[0031] FIG. 2 shows a scenario slightly modified compared to FIG. 2, in which the electric motor 4 is mounted not on the subframe 2, but directly on the vehicle body 1. Otherwise, the remaining structure corresponds to the structure shown in FIG. 1, so the same reference signs are used for the same elements without describing them again.

[0032] In a vehicle designed in this way, an introduction of forces from the vehicle body 2 to the vehicle body inevitably takes place at the first and second subframe bearing points 61, 62, thereby causing the vehicle body 1 to vibrate. To minimize the effects of the induction of force of the subframe 2 on the vehicle body 1, drive torque change (required torque) creates compensatory forces at the first and second engine bearing points 71, 72. Compared to the vehicle body illustrated in FIG. 1, these forces then are located on the vehicle body 1 and not on the subframe 2.

[0033] In the two scenarios shown in FIGS. 1 and 2, compensatory forces are generated by the targeted generation of a torque in addition to the currently applied regular drive torque, which counteract the forces acting on the subframe 2 (FIG. 1) or the forces introduced by the subframe 2 on the vehicle body 1 (FIG. 2). As a result, the vibration of the vehicle body 2, at least in a predetermined target frequency range, and thus ultimately the airborne sound created in the passenger compartment, is minimized.