WO2002012851A1

WO2002012851A1 - A machine for motor vehicle wheel balancing provided with laser pointing device

Info

Publication number: WO2002012851A1
Application number: PCT/IT2001/000426
Authority: WO
Inventors: Liviano Petrolati
Original assignee: Mondolfo Ferro-S.P.A.
Priority date: 2000-08-04
Filing date: 2001-08-01
Publication date: 2002-02-14
Also published as: ITAN20000032A0; AU2001282507A1; IT1316739B1; ITAN20000032A1

Abstract

The present invention relates to a machine used to balance motor vehicle wheels, provided with a laser pointing device used both during the acquisition of data on the wheel to be balanced and during the search of the application points for the compensation weights on the rim.

Description

A machine for motor vehicle wheel balancing provided with laser pointing device.

The present invention relates to a machine used to balance motor vehicle wheels, provided with a laser pointing device that displays the correction planes chosen by the operator with a luminous sign during the acquisition of the geometrical data of the rim and displays the application points of the compensation weights on the rim with a luminous sign during the search for the correction planes.

In order to understand the advantages offered by the present invention it is necessary to describe the techniques that are currently used to balance motor vehicle wheels. This operation is carried out with special balancing machines that make use of normally piezoelectric transducers to detect the constraining reactions caused along the wheel rotation axis by the centrifugal force acting on the wheel when the wheel is not balanced.

With reference to the letters and numbers shown in fig. 1 , the motor balancing process of vehicle wheels includes the following operating stages: a - acquisition of the distances (L1 and L2) of the correction planes (P1 and

P2) chosen by the operator with respect to a reference plane (P0) of the balancing machine; b - acquisition of the internal diameters (d1 and d2) of the circumferences formed by the intersection of the correction planes (P1 and P2) with the internal surface of the rim; c - first launch of the wheel with simultaneous determination of the compensation weights and their angular positions using the electronic detection and data calculation devices of the machine; d - operator's intervention to apply the compensation weights in the correction planes (P1 and P2) on the rim; e - second control launch. It must be noted that the distances (L1 and L2) and diameters (d1 and d2) are normally acquired with a tracer arm that is manually moved by the operator until it touches the internal surface of the rim in the correction planes chosen by the operator. Moreover, it must be said that during the stage (d) the operator must:

I - identify the two correction planes;

II- identify the angular positions of the application points of the compensation weights in the two correction planes based on the indications given by the machine; III - apply the compensation weights.

This stage is very critical, especially as regards the first operation, when the operator must identify the correction planes that he has previously selected with the tracer arm visually, only relying on his memory.

The positive result of the balancing process mostly depends on the accurate identification of the correction planes by the operator for the application of the compensation weights, while their masses and angular positions are calculated and indicated by the electronic devices of the machine.

In view of the above, the manufacturers of balancing machines provide them with an automatic or semiautomatic device to ensure the accurate identification of the correction planes, so that the positive result of the balancing process no longer depends on the operator's personal skills.

In this perspective the same applicant developed and registered a balancing machine in Italy, which is provided with a laser pointing device (patent application AN98A000047 registered on 14/09/1998) that allows for the automatic, accurate and immediate identification and visualisation of the application points of the compensation weights.

This special machine - of which the machine according to the present invention represents an improved version - is schematically illustrated in fig. 2.

With reference to this figure, the machine (1) includes a sliding tracer arm (2) of known type for the acquisition of data (L1 , L2, d1 , d2) of the correction planes (P1 and P2), as well as an electronic device of known type used to calculate the value and angular position of the compensation weights to be applied on the correction planes chosen by the operator.

The machine (1) also includes a laser source (3) mounted at the end of a support arm (4), sliding in parallel direction to the tracer arm (2) along a parallel direction to the X-X rotation axis of the wheel (R).

The luminous source (3) is directed in such a way that the projection of the luminous ray (5) occurs along a direction (Y-Y) orthogonal to the translation axis (Z-Z) of the support arm (4). Using the machine (1) described above and illustrated in fig. 2, the balancing process of the wheel (R) includes the following operating stages:

- manual movement of the tracer arm (2) by the operator, who, after selecting the correction planes (P1 and P2) visually, places the oscillating end (2a) of the tracer arm (2) against the internal wall of the rim in order to simultaneously and automatically detect the data (L1 , L2, d1 , d2);

- backward movement of the tracer arm (2) to its idle position;

- launch of the wheel with simultaneous identification of the compensation weights and their angular positions by means of the electronic device;

- automatic search of the application points of the compensation weights by means of the laser pointing device;

- application of the compensation weights on the points indicated by the projection of the luminous ray (5) on the rim.

More precisely, during the automatic search, the support arm (4) automatically moves forward by means of an actuator, whose stroke is directly related to the stroke of the tracer arm (4), so that the projection of the luminous ray (5) exactly indicates the correction plane on the wheel rim, after detecting its distance (L1 or L2).

If, for example, the same reference plane (PO) is used to measure the strokes of the tracer arm (2) and support arm (4), the actuator will translate the support arm (4) with a stroke exactly equal to the stroke of the (2) tracer arm during the acquisition of data.

While using this balancing machine, we noted that, during the acquisition of data, the operator cannot exactly control the correction plane to be selected with the oscillating end (2a), since he cannot see the contact point between the end (2a) of the tracer arm (2) and the internal wall of the rim. This is because the end (2a) is inserted inside the rim and lifted by the operator until it engages with the rim surface in the top of its upper semicircle; during this stage the operator's head is located above the wheel (R) and therefore the operator cannot see the internal profile of the upper semicircle of the rim, exactly where the end (2a) touches during the automatic acquisition of the data (L1 , L2, d1 , d2).

Vice versa, the operator can see most of the lower semicircle of the rim and examine the rim profile in order to select the correction planes conveniently, although he has no means to check whether the end (2a) is placed against the upper semicircle of the rim in a point that perfectly lays on the same correction plane chosen on the lower semicircle.

In view of the above, the balancing machine has been improved using the laser pointing device during the acquisition of data (L1 , L2, d1 , d2) in order to provide the operator with a visual sign on the lower circumference of the rim, exactly indicating the correction plane detected by the tracer arm. To do this, the reference plane (PO) is used to measure the strokes of the tracer arm (2) and support arm (4) and move the tracer arm (2) and support arm (4) during the detection of the data, so that the projection of the luminous ray (5) indicates the correction plane chosen by the operator and detected by the tracer arm on the lower semicircle of the rim.

Claims

1) A machine used to balance motor vehicle wheels, provided with a laser pointing device, of the type comprising:

- a sliding tracer arm (2) of known type for the acquisition of the data (L1 , L2, d1 , d2) of the two correction planes (P1 and P2); - an electronic device of known type used to calculate the value and angular position of the compensation weights to be applied on the correction planes chosen by the operator;

- a laser source (3) mounted at the end of a support arm (4), sliding in parallel direction to the tracer arm (2), along a parallel direction to the X-X rotation axis of the wheel (R), it being provided that the luminous source (3) is directed in such a way that the projection of the luminous ray (5) falls on the lower semicircle of the rim according to a (Y-Y) direction orthogonal to the translation axis (Z-Z) of the support arm (4), a machine characterised by the fact that the same reference plane (PO) is used to measure the strokes of the tracer arm (2) and support arm (4) and that the tracer arm (2) and support arm (4) are simultaneously moved during the detection of the data (L1 , L2, d1 , d2), so that the projection of the luminous ray (5) indicates the correction plane chosen by the operator and detected by the tracer arm on the lower semicircle of the rim.