GB2410803A

GB2410803A - Improvement for balancing a vehicle wheel

Info

Publication number: GB2410803A
Application number: GB0402507A
Authority: GB
Inventors: Philip Alexander Barber; Steven Allan Miller; Nicholas Winston Fussey
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2004-02-05
Filing date: 2004-02-05
Publication date: 2005-08-10
Also published as: GB0402507D0

Abstract

A motor vehicle having a body 3 which is carried by suspension units 4 and wheels 1 and includes a device for calculating the angular position and mass of a correction weight while the vehicle is in motion. This device includes for each wheel a vertical accelerometer 10 for determining the vertical acceleration of the body 3; a sensor 5 that reads a mark on a rotating wheel 6 which is associated to the wheel 1 for determining the speed and the angular position of the wheel 1 and an Electronic Control Unit 8 to calculate with the phase correlation of the vertical acceleration output signal and the angular position of the wheel the mass and location of weight to correct the imbalance. The device further includes a means 8 for memorising the said mass and location of the correction weight and a screen display 15 integrated to the instrument panel of the vehicle for displaying to a user the said mass and location of the correction weight by a direct readout. Thus, the imbalance is directly measured on the vehicle.

Description

24 1 0803 - 1 Improvement for balancing a vehicle wheel The present

invention relates to a method for measuring the amount of imbalance of a wheel of a motor vehicle and for calculating the angular position and mass of a correction weight.

Conventionally, the balancing of vehicle wheel assemblies is most often accomplished by removing the lyre/wheel assemblies from the vehicle and mounting each of the lyre/wheel assemblies on an off-car-balancer. The off-car balancer rotates the lyre/wheel assembly, measures the imbalance forces and displays the amount and location of a weight to add to the wheel to bring the lyre/wheel assembly into a balanced condition.

Whlist this compensates for the out of balance of the wheel, no account is made of any eccentric rotation of a wheel once it is installed on the vehicle.

It is an object of the present invention to provide an improvement in the determination of the imbalance of a wheel of a motor vehicle.

According to a first aspect of the invention there is provided a motor vehicle having a body which is carried by suspension units and wheels, wherein in the proximity of each wheel is arranged means for determining the vertical acceleration of the body; means for determining speed and an angular position of the wheel; an Electronic Control Unit adapted to calculate as a function of the vertical acceleration, a wheel speed and the angular position of the wheel, a mass and location of a correction weight to correct a wheel imbalance; means for memorising the said mass and location of the correction weight and a means for displaying to a user the said mass and location of the correction weight.

An advantage of this invention over the conventional method is that measurements are made while the vehicle is in motion taking into account wheel speed, road conditions and tyre temperature.

In one embodiment the said means for determining the speed and the angular position of the wheel comprise a sensor that detects a marker on a rotating wheel which is associated with the wheel.

Alternatively, the said marker can be can be a broad line or a broad tooth that are detected by an optical sensor.

Preferably, the said means for determining the speed and the angular position of the wheel are fitted as part of a known anti-lock braking system (ABS) and the said means for determining the vertical acceleration of the body is a vertical accelerometer which is fitted as part of a known adaptive ride control system (ADRC).

The said means for displaying to a user the said mass and location of the correction weight is preferably a clock face display integrated into the instrument panel.

According to a second aspect of the invention there is provided a method for detecting imbalance of a vehicle wheel onboard a motor vehicle, the method comprising the steps of determining while the vehicle is in motion, the vertical acceleration of the vehicle body, the speed and the angular position of a wheel of the vehicle, calculating the phase angle of the out of balance moment and a balance solution, correcting the phase angle of an out of balance moment by using a look up table dependent on the wheel speed from which the phase angle of the out of balance was calculated in order to take into account the dynamics of a suspension unit of the said wheel, and memorising the phase angle of the out of balance moment and the balance solution.

According to a third aspect of the invention there is provided a device for detecting imbalance of a vehicle wheel onboard a motor vehicle, the device comprising means for determining while the vehicle is in motion, the vertical acceleration of the vehicle body, the speed and the angular position of a wheel of the vehicle, means for calculating the phase angle of an out of balance moment and a balance solution, correcting the phase angle of - 3 the out of balance moment by using a look up table dependent on the wheel speed from which the phase angle of the out of balance was calculated in order to take into account the dynamics of a suspension unit of the said wheel, memory for memorising the phase angle of the out of balance moment and the balance solution and means for displaying to a user the said phase angle of the out of balance moment and the balance solution.

The invention will now be described by way of example with reference to the accompanying drawings of which: Fig.1 is a diagrammatic view of a wheel assembly of a motor vehicle provided with a device for measuring an imbalance of a wheel according to an embodiment of the present invention, and Fig.2 illustrates schematically the device of Fig. 1.

Referring to figure 1, a wheel assembly of a vehicle has front wheels 1 (only one shown) carried on a front axle 2 and rear wheels carried on a rear axle (not shown), each wheel comprising a hub 19 and a rim 14. The vehicle has a body 3, which is carried on a chassis, the vehicle weight being resiliently supported by front suspension units 4 and rear suspension units.

The wheel assembly further includes a rotational sensor system 5,6 fitted as part of a known anti-lock braking system (ABS). This rotational sensor system includes a sensor 5 that reads scan marks on a rotating wheel 6, and provides a sensor output signal on a line 7 which is a signal representative of the speed of rotation and of the angular position of the wheel 1. The sensor output signal is input to an electronic control unit (ECU) 8, which also receives a vertical acceleration output signal 9 of the vehicle body from a vertical accelerometer 10, in this example, fitted as part of a known an adaptive ride control system (ADRC).

Figure 2 summarizes the method of operation of the calculated angular position and mass of the correction weight. First, the vertical acceleration output signal 9 and a wheel speed and a angular position of the wheel output signal 7 are transmitted to the ECU 8, which then calculates a balance solution 21, i.e. a correction weight to correct the wheel imbalance and a phase angle of the out-of-balance moment 20. This phase angle output 20 is compared with a look-up table 13 dependent on the wheel speed to deduce a real phase angle of the out of balance 20'. The balance solution 21 and the real phase of the out of balance 20' are stored into a memory 18. From this, the data 21, 20' stored in the memory can be displayed on a display screen 15.

In the following description will be described a means for detecting imbalance in relation to one wheel. It will be appreciated that the same means can be arranged in the same manner for any other wheel.

In operation, the sensor 5 scans the scan marks on the rotating wheel 6. These scan marks are teeth 11 that are scanned, i.e. read, by a Hall effect sensor. A synchronization mark is a portion 12 where a tooth is missing. When scanning a scan mark which is a tooth gap, the sensor 5 skips a pulse. The data read by the sensor 5 are input to the Electronic Control Unit 8, that determines the relative angular position of the wheel.

While the vehicle is in motion the ECU 8 calculates separately for each wheel in accordance with known techniques, i.e. by the phase correlation between the wheel position and the vertical acceleration of the vehicle body, the phase angle of the out of balance moment 20 and the balance solution 21 based on the measured vertical acceleration and wheel speed.

Once the phase angle of the out of balance moment is calculated, the Electronic Control Unit corrects this phase angle by using the look up table 13 dependent on the - 5 wheel speed from which the phase angle of the out balance was calculated in order to take into account the dynamics of the suspension units of the wheel.

The electronic Control Unit calculates also the balance solution, which sets forth the precise mass 17 and location of weights 16 that have to be applied to the rim wheel 14 for optimum wheel balancing. This balance solution of each wheel is transferred to the memory 18, which is accessible to the user of the vehicle via an onboard display screen integrated into the instrument panel of the vehicle, such as the display screen of a satellite navigation system.

Thus the balance solution can be displayed to a technician or the user of the vehicle who may then actually implement the balance solution by applying the weights to the rim wheel 14. The information of the onboard display is only accessible when the vehicle is stopped in order to allow the ECU 8 to bring up to date the accurate angular position of the imbalance for each wheel with the stopped position of the vehicle.

It will be appreciated that a switch, for instance on the instrument panel, allows the user to select the wheel that he wants to see the state of balance.

The angular position of the imbalance is preferably displayed in the form of a clock face display 1 5showing, with respect to the vertical of the stationary car, the position of the balance weight 16 to be fitted and the value 17 of the weight 16. This clock face display permits a direct readout of the angular position of the imbalanced wheel and the user can then know directly the value and exact position of the compensation mass, i.e. a self adhesive weight, that he has to adhere to the wheel to bring it back into balance. - 6

Claims

1. A motor vehicle having a body which is carried by suspension units and wheels, wherein in the proximity of each wheel is arranged means for determining the vertical acceleration of the body; means for determining speed and an angular position of the wheel; an Electronic Control Unit adapted to calculate as a function of the vertical acceleration wheelspeed and the angular position of the wheel; a mass and location of a correction weight to correct a wheel imbalance; means for memorising the said mass and location of the correction weight and a means for displaying to a user the said mass and location of the correction weight.

2. A motor vehicle according to claim 1 wherein the said means for determining the speed and the angular position of the wheel comprise a sensor that detects a marker on a rotating wheel which is associated with the wheel.

3. A motor vehicle according to claim 2 wherein the said means for determining the speed and the angular position of the wheel are fitted as part of an Automatic Braking System.

4. A motor vehicle according to any preceding claim wherein the said means for determining the vertical acceleration of the body is a vertical accelerometer which is fitted as part of an Adaptive Ride Control system.

5. A motor vehicle according to any preceding claim wherein the said means for displaying to a user the said mass and location of the correction weight is a clock face display integrated into the instrument panel.

6. A method for detecting imbalance of a vehicle wheel onboard a motor vehicle, the method comprising the steps of determining while the vehicle is in motion, the vertical acceleration of the vehicle body, the speed and the angular position of a wheel of the vehicle, calculating the phase angle of an out of balance moment and a balance solution, correcting the phase angle of the out of balance moment by using a look up table dependent on the wheel speed from which the phase angle of the out of balance was calculated in order to take into account the dynamics of a suspension unit of the said wheel, and memorising the phase angle of the out of balance and the balance solution.

8. A device for detecting imbalance of a vehicle wheel onboard a motor vehicle, the device comprising means for determining while the vehicle is in motion, the vertical acceleration of the vehicle body, the speed and the angular position of a wheel of the vehicle, means for calculating the phase angle of an out of balance moment and a balance solution, correcting the phase angle of the out of balance moment by using a look up table dependent on the wheel speed from which the phase angle of the out of balance was calculated in order to take into account the dynamics of a suspension unit of the said wheel, memory for memorising the phase angle of the out of balance moment and the balance solution and means for displaying to a user the said phase angle of the out of balance moment and the balance solution.

7. A motor vehicle having a device for measuring an unbalanced wheel, the device being substantially as described herein with reference to the accompanying drawings.