MXPA98004614A - A method and apparatus to test plains - Google Patents

Abstract

In the tire examination method, before and after an alteration in tire pressure, an interferogram of the rim surface is produced, using coherent radiation, and the interferogram becomes a 2ô module image, which its part is processed to obtain an image in gray value, and in which case, from a comparison of the images in gray value, the information with respect to any defects present in the rim is obtained. To test a tire, the wheel, which carries this tire to be tested, is mounted on a wheel balancing machine. A test head configured on the wheel balancing machine moves towards the rim, to be at a predetermined test distance from it, to produce the interferogram. In a first test segment of the rim, the test is performed to determine the defects. The wheel is increasingly rotated by the wheel balancing machine by an amount equal to the size of a test segment, and the last mentioned steps are repeated, until the entire tire has been examined. The tire testing apparatus has a wheel balancing machine (2), on which the wheel mounting the tire to be tested can be mounted, a setting element (18 and 20) for a test head (16) , with which the test head is to be advanced to produce the interferogram towards the rim (11), as far as a predetermined test distance from the rim, and a control element for the wheel balancing machine (2). ) in order to rotate the wheel increasingly by an amount corresponding to a test segment, when the test segment of the previous test segment is concluded

Description

A METHOD AND APPARATUS FOR TESTING TIRES The invention relates to a method for testing tires, wherein, before and after an alteration in tire pressure, a respective interferogram of the rim surface is produced using coherent radiation, and the interferogram becomes an image. module 2tt, which in turn is processed to obtain an image in gray value, and in which case, from the images in gray value, information is obtained with respect to any defects present in the rim and in addition to an apparatus for the realization of the method. German Patent Publication Number 4231578 Al discloses a method for determining the structural strength of the rims, wherein the rim is illuminated with coherent light, the diffusely reflected radiation back from the rim is divided into a two-way interferometer beams, in two beam parts, in the double beam interferometer one of the two beam parts is tilted relative to the other beam part as a tear operation, in the beam double interferometer one of the two beam parts phase is changed in steps, the radiation is reflected diffusely by the object being tested, and it is divided into two beam parts, and then joined again and returned through the components, presenting an image of the surface of the the rim with a large opening to an electronic image sensor system, and the signals produced by the image sensor system are digitized and further processed to give an image of module 2 tr, and the 2tr module image is confirmed with an output gray value image. In accordance with German Patent Publication No. 195 02 073 A1, the aforementioned method is further developed to the extent that the image is partially differentiated in output gray value, a second image in gray value identical to the output gray value image, and it moves geometrically in the direction of tearing in relation to the gray output value image, and is altered by a gray value that is constant over the entire image area, and the second image in gray value manipulated in this way is subtracted from the image in output gray value, and in this way an image in resulting gray value is produced, from which any defects in the rim can be seen. When it is borne in mind that the structural damage to the tires, and more particularly to the carcass that includes the band, can damage the safety of the vehicle, and it will be seen that it is desirable to perform tire tests at regular intervals. An object of the invention is to create a tire test method and apparatus, which allows to examine the tires as part of the service operations for the wheels of a vehicle from time to time. For this purpose, in the method according to the invention for examination on a rim, the wheel mounting the rim to be tested, is mounted on a motor-driven machine; a test head is moved to produce the interferograms towards the rim, to stay at a predetermined distance from it, the test is performed to determine defects on a first test segment of the rim, the motor of the Rolling wheels to rotate the wheel increasingly by an amount equal to the size of a test segment, and repeat the last two mentioned steps until the entire tire has been tested. The costs of the test head depend substantially on the area that can be covered in a single measurement step. Accordingly, the expense due to the test head can be substantially reduced to the extent that measurement is provided by segments of the rim, wherein a plurality of rim test segments are placed in a field of view of the tire. Test head one after the other. You could think about turning the wheel increasingly by hand. This would certainly minimize the costs of adapting the wheel balancing machine for this particular purpose. Another alternative would be to use a separate small electric motor to rotate the arrow of the wheel balancing machine by appropriate amounts corresponding to the size of the test segment. This would add substantial hardware costs, including the motor and its control. In accordance with the invention, the motor of the wheel balancing machine is not only used to rotate the wheel during the balancing procedure, but also to rotate the wheel increasingly during the tire testing procedure. The problem with this solution is that the motor of the wheel balancing machine is usually designed as a strong motor to provide sufficient speed to a wheel, to perform the balancing procedure. In the balancing procedure, the wheel is driven to a particular maximum speed, then the engine is stopped, and the wheel is allowed to slow down, or is slowed down by a braking action. The motor control required for this procedure is not adequate to rotate the wheel on the wheel balancing machine at a slow speed, and less to control the rotation increasingly. Accordingly, a suitable motor control method and apparatus is needed, in order to adapt the wheel balancing machine of the state of the art to the present purpose. In other words, in the combination of the known tire tester of German Patent Application No. 42 31 578 A1, and a state-of-the-art wheel balancing machine in a single machine, certain changes and provisions have to be made to make this combination possible. In spite of the specialized motor control required for the machine, a combination machine is provided in the present application, which has distinct advantages over the state of the art with respect to cost and operation. In the case of a further convenient embodiment of the invention, the drive motor of the roller assembly is operated by a computer by means of a frequency converter, and more especially, the increasing rotation of the wheel is measured, and a input signal corresponding to the computer. This ensures that the wheel can be reliably rotated in an increasing manner exactly by the required amount, without unnecessarily increasing the structural complexity. In accordance with a further convenient development of the method, the size data necessary for the additional rotation of the wheel, such as the size of the tire to the computer, are supplied or obtained from a computer table. If the size data is saved in the form of a table, it is possible that this table is continuously supplemented by manual entries, so that there is the advantage that the adjustment of the apparatus for the test is made continuously simpler. A further convenient development of the method of the invention is characterized in that the test head moves in the X and Y directions, in order to put it in the test position for wheels of different sizes. By means of this simple movement scheme, the test head can be placed in the correct test position easily and without other elements. A further convenient development of the method according to the invention is characterized in that, during the approach movement of the test head, its distance from the rim is monitored, and an indication is displayed, when the test head has reached its intended position, and then the test head is stopped. This means that a safe, fast, and accurate adjustment of the test head relative to the rim is possible. A further convenient development of the method according to the invention is characterized in that the tire pressure is reduced for each test step, and after the test has been completed, it is returned to the nominal pressure. Following this method, you can change the pressure of the tire during a whole test cycle, where the test sectors are measured one after the other, with a minimum loss of time, as the pressure change begins. from a first test step to a second test step, from the final pressure present at the end of the first test step. Additionally, after each pressure change, the tire has to rest for a certain period of time, so that the test results are not influenced by the continuous movements due to the change in pressure. Therefore, the time consumed for these recovery time periods is minimized if the number of pressure changes made during a test cycle is minimized. The number of recovery time periods would be increased if the tire pressure were brought up to the nominal pressure after each test step of the rim with respect to a particular section of the rim. The tire test apparatus of the invention comprises an air pressure element for altering the pressure of the tire, a test head, and a computer, which before and after an alteration in the air pressure procedure, using coherent radiation, a respective interferogram is made of the surface of the rim, and the interferogram is converted into an image of module 2tr, which in turn is processed to give an image in gray value, and where, based on a comparison of the images in gray value information is obtained with respect to any defects in the rim, and the apparatus is characterized by a wheel balancing machine on which the wheel can be mounted with the rim to be tested on the same, by means of a positioning element for the test head, with which the test head is to be moved to a predetermined distance from the rim to produce the interferograms, and by means of a n control element for the wheel balancing machine, in order to rotate the wheel increasingly by an amount corresponding to a test segment, when the test of the previous test segment is concluded. A convenient embodiment of the tire testing apparatus of the invention is characterized in that the motor of the wheel balancing machine is operated by means of a frequency converter, which is adapted to be controlled by a computer. This is the most reliable way to control the motor of the wheel balancing machine, in such a way that it increasingly moves the wheel at a low speed during the tire test procedure. A convenient embodiment of the apparatus for testing tires of the invention is characterized in that a synchronizer is connected to the arrow of the wheel balancing machine, this synchronizer detecting the increasing rotation of the arrow, and supplying a corresponding signal to the computer, which switches the motor pulse to off, when the wheel has been rotated incrementally through an additional test segment. By using this configuration, a feedback related to the increasing movement of the wheel can be produced, and can be used to accurately control the increasing movement of the wheel on the balancing machine. A convenient embodiment of the apparatus for testing tires of the invention is characterized in that the computer comprises a memory, wherein a table with size data is provided, as is necessary for the increasing rotation of a wheel, in a manner dependent on the size of the wheel. the wheel. Computer memory ensures that as little expert knowledge as possible is needed to run the machine. A convenient embodiment of the tire testing apparatus of the invention is characterized in that the positioning element has a slider X to move the test head in parallel with the axis of the arrow, and a slider Y to move the test head perpendicularly to the axis. of the arrow, and because the sliders and the test head are integrated into a housing of the wheel balancing machine. This embodiment of the invention has the advantage that the volume of the machine is minimized, and the test head is somewhat protected inside the housing of the wheel balancing machine, which is an important advantage in view of the harsh environment present in the automotive service shops where these machines are used. A convenient embodiment of the tire testing apparatus of the invention is characterized in that the slider X and the slider Y can be moved by motors under the control of a computer. In this way, the placement of the test head is automated, and this can be done automatically without a particular knowledge or ability of the person operating the machine. A convenient embodiment of the apparatus for testing rims of the invention is characterized in that the positioning element comprises two pivoting arms, which are provided on the wheel balancing machine, or in that the positioning element comprises a strut on the test head. Preferably, the positioning element, or, respectively, the tie rod, can be stopped when the test head has reached the test position. These modalities are mechanical elements to support the test head and adjust the distance between the rim and the test head, and as mechanical elements, they are more reliable and simple to operate.

A convenient embodiment of the tire test apparatus of the invention is characterized by a device that establishes the distance, to establish the distance between the test sleeve and rim. Preferably, the distance-setting device comprises two obliquely-established diodes on the end of the test head, the beams of these diodes intersecting at the test distance. This distance-setting device allows to adjust the distance without touching the wire by means of an optical element. The distance setter device can be easily operated. A convenient embodiment of the tire testing apparatus of the invention is characterized in that the distance-setting device comprises a mechanical sensor on the test head, whose sensor, upon reaching the test distance, contacts the rim. This is a mechanical version of the distance-setting device that is simple and adapts to a harsh environment. A convenient embodiment of the tire test apparatus of the invention is characterized in that the distance-setting device comprises an ultrasonic range-matching element. This distance-setting device is another device that does not need to touch the rim, which is also convenient if the accessible surface has some profile. A convenient embodiment of the tire test apparatus of the invention is characterized by a valve that can be established both with respect to the size of its opening, as well as with respect to the opening time. This valve enables rapid and automatic setting of tire pressure under the control of a computer, which only controls the size of the valve opening and the opening time of the valve. This also has the advantage of minimizing the time needed to perform a complete test cycle. A convenient embodiment of the tire testing apparatus of the invention is characterized by a central control element for controlling the air pressure in the rim, the pressure in the rim having to be reduced for each step of testing by one stage, and having to return to nominal pressure at the conclusion of a test. As already mentioned above, this minimizes the time needed to complete a complete test process cycle. A convenient embodiment of the tire testing apparatus of the invention is characterized by a central computing element for controlling the functions of the tire testing apparatus, preferably integrating the computing element of the wheel balancing machine. By combining the computing element of the test apparatus with the element of the balancing machine, some savings can be made with respect to the hardware required, which reduces costs and improves reliability. A further convenient development of the apparatus of the invention is characterized by a monitor for displaying the results of the measurement, and which also serves to display the information during the rolling of the wheel. This is another system that shares the hardware to reduce costs. The embodiments of the invention will now be described with reference to the accompanying drawings.

Figure 1 shows diagrammatically, a plan view, of a tire testing apparatus according to a first embodiment of the invention, using a wheel balancing machine. Figure 2 shows a diagrammatic lateral elevation of an apparatus for testing tires according to a second embodiment of the invention, using a wheel balancing machine. Figure 3 is a view of the front of the test head. Figure 4 is a diagrammatic plan view of part of a further embodiment of the tire testing apparatus of the invention. Referring now to Figure 1, a first embodiment of the tire testing machine of the invention will be described. Figure 1 shows a wheel balancing machine 2 comprising a keyboard 4 and a monitor 6, they are configured on a housing 8. A wheel 10 is mounted with a rim 11 by means of an instantaneous holding element 14 on an arrow 12 of the wheel balancing machine 2, the fastening element engaging with the metal part 13 (FIG. 2) of the wheel 10. A test head 16 is mounted by means of two parallel links or arms 18 and 20 on the housing 8 of the wheel balancing machine 2. The arm 20 has one end pivotally mounted on a clamp 22 of the housing 8. A connection 24 connects the arm 20 with the arm 18, and the arm 18 is connected by means of a connection with the test head 16. Accordingly, it is possible for the test head 16 to pivot from a position (not shown) where it is withdrawn on the housing 8 into a test position (Figure 1), where it is possible for the side wall of the rim 11 to be in the test position. A handle 28 is provided on the test head 16, and has a push-button switch (not shown), by which the positioning element (parallel guides or arms 18 and 20) can be stopped when the test head 16 has reached the test position. Figure 2 shows a second embodiment of the invention in a lateral elevation, the parts having equivalents to those of Figure 1 having the same reference numerals. To support the test head 16, a strut 30 is provided, with which the test head 16 can be stopped at the same level as the arrow of the wheel balancing machine. When the test head 16 is located in the test position, the stay 30 can be stopped in this position, in order to ensure that the test head 16 remains in the test position. The test head 16 can be directed to its position with the help of a handle 32. The stopping effect can be caused by using a push-button switch (not shown), which is provided on the handle 32. A cable serves to supply the test head with electrical power, and to supply the signals to the central computing unit. In the housing 8 (Figures 1 and 2), there is further a control element (not shown), which comprises the controller for an air pressure element, which comprises a pressure hose 40 and a valve 42, which can Mount on the rim inlet valve. The valve 42 can be controlled or set both with respect to its opening (discharge flow rate), and also with respect to its opening and closing, such that the alteration in tire pressure can be varied by adjusting the opening of the valve, as well as adjusting the time during which the valve is open. The test head 16 is illustrated at the end in Figure 3, and the laser diodes 44 will be seen to scan or detect the interferograms. In addition, two diodes 46 and 48 are provided, which serve to adjust the test distance between the test head 16 and the side wall of the rim 11. For this purpose, the two laser diodes 46 and 68 are to be adjusted obliquely. in the visible range where they make their laser beams at an angle to each other, and intersect at the point corresponding to the test distance between the test head and the side surface of the rim 11. When the head is moved test 16 towards the rim 11, will be at the test distance, when the two laser beams form a single point on the side wall of the rim 11. Furthermore, the figure shows diagrammatically a target 45 of a camera, which takes photographs of the tire that is being tested. The speed of rotation of the motor (not shown) of the wheel balancing machine is controlled by means of a controlled frequency converter (not illustrated), by means of the central computing unit, which has a relatively low constant value. A synchronizer on arrow 12 responds to the rotation speed of the arrow, and produces an output signal corresponding to the pitch or the amount by which the tire has been rotated. On the computer, the output signal from the synchronizers is used to deactivate the pulse motor when the rim has increasingly rotated by an amount corresponding to the size of a test segment. In the case of the embodiment illustrated in Figure 3, a test segment is equal to 1/8 of the total periphery of the rim, so that the rim should be rotated seven additional steps or increments in order to verify the rim completely. The conductors for compressed air, for the supply of electric power to the test head, and for a data line leading to the computer unit, are connected to the control element and the test head. In addition, the motor for driving the arrow of the wheel balancing machine and the synchronizers on the arrow of the wheel balancing machine are connected to the computing unit, the connecting lines and the computer unit not being illustrated with the purpose of make the most direct drawing. In Figure 4, a further embodiment of the tire testing apparatus will be seen, the parts equivalent to those of Figures 1 to 3 having the same reference numerals.

In Figure 4, an XY setter element is illustrated, with a slider X 50 and a slider Y 52, and a test head 54 is illustrated. Slider X 50 serves to adjust the distance between the test head 54 and the surface side of the rim 11. In the illustrated embodiment, the X direction of the slider X 50 is parallel to the arrow 12, and the Y direction of the Y slider 52 is perpendicular to the arrow 12. The X 50 slider and the slider 52 they are slidably supported by linear bearings that have arrow guides. The slider X 50 and the slider Y 52 are respectively provided with stop elements (not shown), which make it possible to stop the sliders in a test position, wherein the test head 54 is located in the position for the verification operation of the rim.

In the case of the embodiment according to Figure 4, the adjustment of the distance between the test head 54 and the side wall of the rim 11 is performed using a sensor 60, which the upper part of the test head 54, it can be moved out as far as a position corresponding to the test distance or tolerance. When the test head 54 has been placed with the sliders 50 and 52 in the test position, the sensor 60 will engage with the inner wall of the rim 11. Following this, the test head is stopped, and retracted the sensor 60. In this embodiment of the invention, we have the advantage that the sliders 50 and 52 are driven by motors (not shown) under the control of the computer. In this case, it is possible that an output signal is supplied by the sensor 60 to the computer, when the test position is reached. In all embodiments of the invention, a central computer element is provided for controlling the functions of the tire test apparatus, this computer element being integrated into the computer of the wheel balancing machine, so that here too it is reduced the complexity of the hardware. In addition, the monitor is used to indicate the readings of the measurement, both for wheel balancing and for tire testing, to the extent that the information relevant to the two test methods is displayed on the same monitor. The way to operate the tire testing device is as follows. First the wheel is mounted, which leads to the rim to be examined, on a wheel balancing machine, the arrow of the wheel balancing machine being able to be driven at different speeds of rotation under the control of a computer, both for the rolling of the wheel as well as for the rim test. The next step is to move a test head to the rim, to stay at a test distance previously determined from it, to produce the interferograms and stop at that position. After mounting the rim on the wheel balancing machine, the air pressure valve is connected to the rim. Before carrying out the first test sequence, the specific data for the wheel and, respectively, the size data for the increasing rotation of the arrow of the wheel balancing machine, such as the rotation duration a A constant speed of rotation, which depend on the dimensions of the rim, to the computer as an input, or, respectively, are searched in a Table. Then the tire is examined on a first rim segment of the rim, using the aforementioned method. After the first test segment has been tested, the wheel is further rotated by the arrow of the wheel balancing machine by a pitch equal to the size of a test segment, with the arrow of the wheel balancing machine being controlled by a computer, and in a way dependent on the output signals of a synchronizer on the arrow of the wheel balancing machine. When the next wheel test segment has been placed in position, the test head is activated in order to test or examine the next test segment. Subsequently, test sequences and additional incremental steps of rotation are performed, until the entire tire has been tested. For each test sequence, as already mentioned, between a first series of interferograms and a second series of interferograms, the pressure is reduced, this being also controlled by computer. The reduction in pressure, therefore, occurs in two stages, reducing the pressure from a nominal pressure by one step in each test sequence. Once the test has been completed, the air pressure in the rim is then returned to the nominal pressure, also using the valve and the control element connected with it. The invention is not limited to the work modalities described. Therefore, for example, the adjustment of the distance between the test head and the side surface of the rim can be made using an ultrasonic range finder, and not optically (Figure 1) or mechanically (Figure 4). It should be understood that the foregoing description is intended as illustrative and not restrictive. The experts in this field will be able to see many modalities when reviewing the previous description. Those skilled in the art will recognize an equivalent or alternative method of tire testing, and a combination of a tire testing machine with a tire rolling machine. Accordingly, the scope of the invention should be determined not with reference to the foregoing description, but instead, should be determined with reference to the appended claims, together with the total scope of equivalence to which these claims are entitled. .

Claims (24)

1. A method for testing tires, where, before and after an alteration in tire pressure, a respective interferogram of the rim surface is produced, using coherent radiation, and the interferogram becomes a 2tr module image, which in turn is processed to obtain an image in gray value, and in which case, from a comparison of the images in gray value, the information is obtained with respect to any defects present in the rim, characterized in that: (a) to test a tire, a wheel is mounted to carry this tire to be tested, on a motor-driven wheel-balancing machine, (b) a test head configured on the wheel-rolling machine moves to the tire, to be at a test distance previously determined from it, to produce the interferograms, (c) in a first test segment, the tire is examined to determine the defects c) the motor of the wheel balancing machine is driven to rotate the wheel increasingly by an amount equal to the size of a test segment, and (e) and steps (c) and (d) are repeated , until the entire tire has been examined.

2. The method as claimed in claim 1, characterized in that, the drive motor of the wheel balancing machine is operated by the computer by means of a controlled frequency converter.

3. The method as claimed in claim 2, characterized in that, the additional increasing rotation of the motor is detected, and an input signal corresponding to the computer is fed.

4. The method as claimed in claim 3, characterized in that, the size data, such as the size of the rim, are communicated for an additional increasing rotation of the wheel, to the computer, or are searched in a table. Computer.

5. The method as claimed in claim 1, characterized in that, the test head moves in the directions X, and Y, in order to put it in the position for rims of different sizes.

The method as claimed in claim 1, characterized in that, when the test head is moved towards the rim, the distance of the test head from the rim is monitored, and a signal is displayed when the test head a reached the test position, and because then the test head stops.

The method as claimed in claim 1, characterized in that, the tire pressure is reduced for each test step, and after the test has been completed it is returned to the nominal pressure.

8. A tire testing apparatus for carrying out the method as claimed in claim 1, which comprises an air pressure element for altering the pressure of the tire, a test head, and a computer, which before and after an alteration in air pressure, using coherent radiation, produce a respective interferogram of the rim surface, and convert the interferogram into a 2tr module image, which in turn is processed to produce an image in gray value , and wherein, based on a comparison of the images in gray value, the information is obtained with respect to any defects in the rim, and the apparatus is characterized by a motor-driven wheel balancing machine (2), on which the ruda can be mounted with the rim that is going to be tested on it, by means of a setting element (18, 20, 50 and 52) for the test head (16 and 54), with which it is going to move the test head to a previously determined distance from the rim (1), to produce the interferograms, and by means of a control element for the motor of the wheel balancing machine (2), in order to rotate the wheel increasingly by an amount corresponding to a test segment, when the test of the previous test segment is concluded.

9. The apparatus as claimed in claim 8, characterized in that the motor of the wheel balancing machine (2) is operated by means of a frequency converter, which is adapted to be controlled by a computer.

The apparatus as claimed in claim 9, characterized in that a synchronizer is connected to the arrow of the wheel balancing machine, this synchronizer detecting the increasing rotation of the arrow, and supplying a corresponding signal to the computer that deactivates the Motor boost, when the wheel has been rotated incrementally through an additional test segment.

The apparatus as claimed in claim 10, characterized in that the computer comprises a memory, wherein a table is provided which comprises size data, as necessary for the increasing rotation of a wheel in a manner dependent on the size of the the wheel.

The apparatus as claimed in claim 8, characterized in that the positioning element has a slider X (50) for moving the test head (54) parallel to the axis of the arrow (12) and a Y slider (52) for moving the test head (54) perpendicularly to the axis of the arrow (12), and because the sliders and the test head are integrated in a housing of the wheel balancing machine.

The apparatus as claimed in claim 12, characterized in that the slider X (50) and the slider Y (52) can be moved by motors under the control of a computer.

The apparatus as claimed in claim 8, characterized in that the positioning element comprises two pivoting arms (18 and 20), which are provided on the wheel balancing machine.

15. The apparatus as claimed in claim 8, characterized in that the positioning element comprises a strut (30) on the test head (16).

16. The apparatus as claimed in any of claims 12 to 15, characterized in that the positioning element (18 and 20), or, respectively, the brace (30) can be stopped, when the test head (16) has reached the test position.

The apparatus as claimed in claim 8, characterized in that the distance adjustment device, for adjusting the distance between the test head (16 and 54) and the rim.

The apparatus as claimed in claim 17, characterized in that the distance adjustment device comprises two obliquely established diodes (44 and 46) on the end of the test head (16), the beams intersecting from these diodes to the test distance.

The apparatus as claimed in claim 17, characterized in that the distance adjustment device comprises a mechanical sensor (60) on the test head (54), whose sensor, upon reaching the test distance, makes contact with rim.

20. The apparatus as claimed in claim 17, characterized in that the distance adjustment device comprises a finding element of the ultrasonic range.

21. The apparatus as claimed in claim 8, characterized by a valve (42) that can be adjusted both with respect to the size of its opening, and also with respect to the opening time.

22. The apparatus as claimed in claim 21, characterized by a central control element for control of the air pressure in the rim, the pressure in the rim having to be reduced for each test step by one stage, and having to return to nominal pressure at the conclusion of a test.

23. The apparatus as claimed in claim 8, characterized by a central computing element for controlling the functions of the tire testing apparatus, preferably integrating the computing element with the computing element of the wheel balancing machine.

24. The apparatus as claimed in any of claims 8 to 23, characterized by a monitor for displaying the results of the measurement, and which also serves to display the information during the rolling of the wheel. SUMMARY In the tire examination method, before and after an alteration in tire pressure, an interferogram of the rim surface is produced, using coherent radiation, and the interferogram becomes a 2tr module image, which its part is processed to obtain an image in gray value, and in which case, from a comparison of the images in gray value, the information with respect to any defects present in the rim is obtained. To test a tire, the wheel, which carries this tire to test, is mounted on a rocking machine. A test head configured on the wheel balancing machine moves towards the rim, to be at a predetermined test distance from it, to produce the interferogram. In a first test segment of the rim, the test is performed to determine the defects. The wheel is increasingly rotated by the wheel balancing machine by an amount equal to the size of a test segment, and the last mentioned steps are repeated, until the entire tire has been examined. The tire testing apparatus has a wheel balancing machine (2), on which the wheel mounting the tire to be tested can be mounted, a setting element (18 and 20) for a test head (16) , with which the test head is to be advanced to produce the interferograms towards the rim (11), as far as a previously determined test distance from the rim, and a control element for the wheel balancing machine (2). ) in order to rotate the wheel increasingly by an amount corresponding to a test segment, when the test of the previous test segment is concluded.