Air pressure measuring device of a tire test stand

Abstract

Air pressure measuring device of a tire test stand with a mounting flange (1) for attachment to a vehicle wheel having a pneumatic tire to be tested, characterized in that a bearing bore (2) is formed in the mounting flange (1) in which a measuring spindle (9) is axially displaceable from a home position via a central position to an end position against the force of a first spring (21), wherein the measuring spindle (9) has an axial passage (14) which has an outwardly opening connection (15) at a first end region of the measuring spindle (9) facing away from the pneumatic tire and is closed off from the interior of the pneumatic tire in the home position, wherein a first valve (13) can be opened by the movement of the measuring spindle (9) to its central position, through which the interior of the pneumatic tire can be connected via the passage (14) and the outwardly opening connection (15) to a pressure measuring sensor.The measuring spindle (9) can be connected to the measuring port (22), and the movement of the measuring spindle (9) from the central position to the end position opens a second valve (10) through which the inside of the pneumatic tire is connected to the environment via an outlet (24) formed in the receiving flange (1).

Description

The invention relates to an air pressure measuring device of a tire test stand having a receiving flange for attachment to a vehicle wheel having a pneumatic tire to be tested.Such tire test stands, in particular production test stands, are used, among other things, to perform acoustic, vibration, torque and function tests on the rotationally driven test object. In many tests, forces as occur between the tire and the roadway must be simulated. In order to be able to apply these forces to the tire, the tire must be filled with air. The filling with air and measurement of the air pressure take place via a valve or an air pressure sensor in the vicinity of the test spindle of the tire test stand.In production test stands for commercial vehicle tires, in particular of up to 1500 mm and a tread width of up to 600 mm, these dimensions lead to considerable influences on the cycle time of the tests both during filling and also during emptying of the tire with air, as a result of the high volumes of air required at the same time. The distance between the air pressure sensor system and the pneumatic tire to be tested leads to inertias in the measuring system during the filling and emptying of the pneumatic tire with air and thus to higher cycle times.In this context, DE 10 2011 113 622 A1 discloses a wheel test stand for testing a wheel under driving conditions. The wheel test stand comprises a bearing device for rotatably supporting the wheel and a rotary feedthrough which is passed through the bearing device and is mechanically assigned to the pneumatic tire of the wheel. The wheel test stand is configured such that the rotary feedthrough has a fluid path which is connected or connectable to an air chamber of the pneumatic tire of the wheel and a compressed air source, respectively.It is therefore an object of the invention to provide an air pressure measuring device of a tire test stand of the type mentioned at the beginning which enables air pressure measurements in short cycle times and avoids imbalance of the vehicle wheels during the test.This object is achieved according to the invention in that a bearing bore is formed directly or indirectly in the receiving flange, in which bearing bore a measuring spindle is mounted axially displaceably counter to a force of a first spring from a basic position via a central position into an end position, wherein the measuring spindle has an axial passage which has a connection opening outwards at a first end region of the measuring spindle facing away from the pneumatic tire and is shut off from the interior of the pneumatic tire in the basic position, wherein a first valve can be opened by the movement of the measuring spindle into its central position, by means of which valve the interior of the pneumatic tire can be connected via the passage and the connection opening outwards to a measuring connection having a pressure measuring sensor and which can be connected to the measuring spindle, and in that a second valve can be opened by the movement of the measuring spindle from the central position into the end position, by which the interior of the pneumatic tire is connected to the atmosphere via an outlet formed in the receiving flange.Due to the embodiment according to the invention, the pressure measurement sensor is located close to the pneumatic tire during the measurement, so that no adverse influence on the cycle time takes place. During the test run, however, the measurement connection with the pressure measurement sensor is decoupled from the vehicle wheel and therefore cannot lead to an imbalance of the vehicle wheel to be tested. This is particularly important when the tire test stand is a production test stand for heavy-volume commercial vehicle tires.A displacement of the measuring spindle can take place by means of the measuring connection, in particular in an automatic manner, by means of a coupling device, so that both the measuring process and the venting process can take place quickly and the required cycle time is thus reduced.The first valve and the second valve may be poppet valves.In a simple embodiment, the measuring spindle has a first flange-like widening at its end facing the interior of the pneumatic tire, which widening, in the basic position of the measuring spindle, is in contact with a second annular sealing region and, in the central position, is lifted from the second annular sealing region, connecting the interior of the pneumatic tire to the passage of the measuring spindle.If, furthermore, a tube-like closure part is guided on the measuring spindle such that it can be displaced between a closure position and an open position, said closure part having, at its end facing the interior of the pneumatic tire, a second flange-like widening which, in the basic position and the central position of the measuring spindle, bears against a first annular sealing region and, in the end position of the measuring spindle, connects the interior of the pneumatic tire to the outlet formed in the receiving flange, the air pressure measuring device is of rotationally symmetrical construction and can therefore not lead to imbalance of the vehicle wheels during the test.A component-saving small structural size is furthermore achieved if the second annular sealing region is formed on the closure part.The axial passage of the measuring spindle can be closed at its end facing the pneumatic tire and can have one or more radial outlets on the side of the first flange-like widening facing away from the pneumatic tire.In order that the second seat valve remains securely closed when the first seat valve is opened, the closure part can be loaded into its closure position by the force of a second spring supported on the measuring spindle, wherein the force of the second spring is less than the force of the first spring.In a simple embodiment, for the movement of the closure part by the measuring spindle, the measuring spindle can have a stop, by means of which the closure part can be acted upon movably from its closure position into its open position during the movement of the measuring spindle from the central position into the end position.The stop can be a radially protruding flange arranged coaxially on the measuring spindle.A compact construction of the air pressure measuring device is achieved if the first spring is a helical compression spring supported at its one end on the receiving flange and acts on the flange at its other end.An exemplary embodiment of the invention is illustrated in the drawing and is described in more detail below. The following are shown: FIG. 1 is a perspective view of an air pressure measuring device of a tire test stand FIG. 2 shows a cross section of the air pressure measuring device in the basic position FIG. 3 shows a cross section of the air pressure measuring device according to FIG. 1 in a middle position FIG. 4 shows a cross section of the air pressure measuring device according to FIG. 1 in an end position.The illustrated air pressure measurement device of a production test stand for pneumatic vehicle tires of commercial vehicles has a not-illustrated receiving flange 1 to which a vehicle wheel of a pneumatic tire to be tested is attached and one side 26 of which is open to an interior of the pneumatic tire.The receiving flange 1 has a bearing bore 2 which runs axially through from this one side to the opposite, outwardly open side of the receiving flange 1 and into which a first plain bearing bush 3 is fixedly inserted.A tubular closure part 4 is displaceably guided in the first plain bearing bush 3, which closure part is sealed with respect to the wall of the bearing bore 2 by a first sealing ring 17 and has a first flange-like widening 5 at its end facing the interior of the pneumatic tire.In the basic position of the air pressure measuring device shown in FIG. 2, the radially outer circumferential region of the first flange-like widening 5 axially abuts a first annular sealing region 6 of the receiving flange 1, with which it forms a second seat valve 10.In this closed position of the closure part 4, its outwardly directed end region 7 protrudes out of the bearing bore 2.In the through bore 18 of the tube-like closure part 4 a second bearing bush 8 is fixedly arranged, in which a measuring spindle 9 is displaceably mounted, which in all its positions projects with its outwardly directed end region from the closure part 4. The measuring spindle 9 is sealed with respect to the through bore 18 by a second sealing ring 19.At its end directed toward the interior of the pneumatic tire, the measuring spindle 9 has a second flange-like widening 11. In the basic position of the air pressure measuring device shown in FIG. 2, the radially outer circumferential region of the second flange-like widening 11 axially abuts a second annular sealing region 12 of the closure part 4, with which it forms a first seat valve 13.A coaxial passage 14 is formed in the measuring spindle 9, which has a connection 15 opening out to the outside at the end region of the measuring spindle 9 facing away from the pneumatic tire.At the end portion facing the pneumatic tire, the coaxial passage 14 is closed. Radial outlets 16 of the passage 14 open radially outwards on the side of the second flange-like widening 11 facing the closure part 4.At its end facing away from the pneumatic tire, the measuring spindle 9 has a flange 20 which forms a stop and extends radially outwards and which is located at an axial distance from the closure part 4 in the basic position of the air pressure measuring device shown in FIG. 2. A prestressed first compression spring 21 supported on the receiving flange 1 applies force to the flange 20 away from the closure part 4.A tube-like measuring connection 22 can be placed on the end of the measuring spindle 9 facing away from the pneumatic tire and its interior 23 can be connected to the connection 15.A pressure measurement sensor, not shown, is arranged in the measurement connection 22.In the basic position shown in FIG. 2, the air pressure measuring device is attached to a vehicle wheel by means of the receiving flange 1 even without a measuring connection 22. Both the first seat valve 13 and the second seat valve 10 are in their closed position. In this initial position, the pneumatic tire is filled with air via a valve, not shown, in order to be subjected to various tests later. For this purpose, the air pressure present in the pneumatic tire must first be measured.For this purpose, the measurement connection 22 containing the pressure measurement sensor is placed on the measurement spindle 9 and, counter to the force of the first compression spring 21, the measurement spindle 9 is displaced by means of the measurement connection 22 into the central position of the air pressure measurement device illustrated in FIG. 3 until the flange 20 bears against the end face of the closure part 4 which is remote from the pneumatic tire. At this time, the second seat valve 10 is opened so that the inside of the pneumatic tire is connected to the internal space 23 of the measurement port 22 via the radial outlets 16, the coaxial passage 14, and the port 15, and thus the pressure of the pneumatic tire is applied to and measured by the pressure measurement sensor.In order that the closure part 4 is not moved along and the second seat valve 10 is opened during the movement of the measuring spindle 9, the closure part 4 is acted upon into its closure position by the force of a second spring 25 supported on the measuring spindle 9, wherein the force of the second spring 25 is less than the force of the first compression spring 21.After this measuring process, the pneumatic tire must be depressurized again rapidly.For this purpose, the measuring spindle 9 is displaced further in the direction of the pneumatic tire by means of the measuring connection 22 into the end position of the air pressure measuring device shown in FIG. 4.The flange 20 comes to rest against the side of the receiving flange 1 facing away from the pneumatic tire and opens the second seat valve 10, so that the interior of the pneumatic tire is connected via the passage of the opened second seat valve 10 to an outlet 24 formed in the receiving flange 1 and leading into the environment, via which outlet the pneumatic tire is vented.Reference numerals denote reference numerals1 Receiving flange 2 Bearing bore 3 First plain bearing bush 4 Closure part 5 First flange-like widening 6 First annular sealing region 7 End region 8 Second bearing bush 9 Measuring spindle 10 Second seat valve 11 Second flange-like widening 12 Second annular sealing region 13 First seat valve 14 Passage 15 Connection 16 Radial outlets 17 First sealing ring 18 Passage bore 19 Second sealing ring 20 Flange 21 First compression spring 22 Measuring connection 23 Interior space 24 Outlet 25 Second spring 26 Side

Claims

Air pressure measuring device of a tire test stand having a receiving flange (1) for attachment to a vehicle wheel having a pneumatic tire to be tested, characterized in that a bearing bore (2) is formed in the receiving flange (1), in which bearing bore a measuring spindle (9) is mounted axially displaceably from a basic position via a central position into an end position counter to a force of a first spring (21), wherein the measuring spindle (9) has an axial passage (14) which has a connection (15) opening outwards at a first end region of the measuring spindle (9) facing away from the pneumatic tire and is shut off from the interior of the pneumatic tire in the basic position, wherein a first valve (13) can be opened by the movement of the measuring spindle (9) into its central position, through which the interior of the pneumatic tire can be connected via the passage (14) and the connection (15) opening out to a measurement connection (22) having a pressure measurement sensor and connectable to the measurement spindle (9), and that, as a result of the movement of the measurement spindle (9) from the central position into the end position, a second valve (10) can be opened, through which the interior of the pneumatic tire is connected to the environment via an outlet (24) formed in the receiving flange (1).Air pressure measuring device according to claim 1, characterised in that the first valve and the second valve are seat valves (13, 10).Air pressure measuring device according to Claim 2, characterized in that the measuring spindle (9) has, at its end facing the interior of the pneumatic tyre, a first flange-like widening (5) which, in the basic position of the measuring spindle (9), is in contact with a second annular sealing region (12) and, in the central position, the interior of the pneumatic tyre is lifted from the second annular sealing region (12), connecting the passage (14) of the measuring spindle (9).Air pressure measuring device according to Claim 3, characterized in that a tube-like closure part (4) is guided on the measuring spindle (9) such that it can be displaced between a closure position and an open position, said closure part having, at its end facing the interior of the pneumatic tyre, a second flange-like widening (11) which, in the basic position and the central position of the measuring spindle (9), is in contact with a first annular sealing region (6) and, in the end position of the measuring spindle (9), connects the interior of the pneumatic tyre to the outlet (24) formed in the receiving flange (1).Air pressure measuring device according to claim 4, characterised in that the second annular sealing region (12) is formed on the closure part (4).Air pressure measuring device according to Claim 5, characterized in that the axial passage (14) of the measuring spindle (9) is closed at its end facing the pneumatic tyre and has one or more radial outlets (16) on the side of the first flange-like widening (5) facing away from the pneumatic tyre.Air pressure measuring device according to one of Claims 4 to 6, characterized in that the closure part (4) is acted upon in its closure position by the force of a second spring (25) supported on the measuring spindle (9), wherein the force of the second spring (25) is less than the force of the first spring (21).Air pressure measuring device according to one of the preceding claims, characterized in that the measuring spindle (9) has a stop (20), by means of which the closure part (4) can be acted upon during the movement of the measuring spindle (9) from the central position into the end position from its closure position into its open position.Air pressure measuring device according to claim 8, characterised in that the stop is a radially protruding flange (20) arranged coaxially on the measuring spindle (9).Air pressure measuring device according to one of the preceding claims, characterized in that the first spring (21) is a helical compression spring (21) supported at its one end on the receiving flange (1) and acting at its other end on the flange (20).

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