RU2279649C1 - Method of determining load applied to railway wheel by brake block - Google Patents

Abstract

FIELD: railway transport.

SUBSTANCE: method comprises setting the sensitive members on the surface of the wheel, generating ultrasonic wave in the wheel, and recoding time of propagation of the ultrasonic wave as a function of the value of the load applied to the sensitive member in the absence of the brake block, recording time of propagation of ultrasonic wave in the presence of brake block and applying load to the block, and determining braking load of the block applied to the wheel from the dependence obtained.

EFFECT: reduced labor consumption.

2 cl, 2 dwg

Description

The invention relates to railway transport, in particular to methods for determining the forces of pressing brake pads on the wheels of railway cars.

A known method for determining and checking the forces of pressing brake pads on the wheels of railway cars, which consists in first determining for a new parking brake or taking (accepting) a known value of the gear ratio of the lever parking brake and the gear ratio of the worm gear of the parking brake of a railway car, and then calculate the force of pressing the brake pads on the wheel from the action of the parking brake, taking into account the large number of parameters and dimensional characteristics of the kinematics iCal chains [1].

However, this method has low accuracy, since the determination of the real force of pressing the brake pads on the wheel is carried out purely by calculation and does not take into account all the parameters of the linkage.

As a prototype of the claimed technical solution, the method for determining the static force of pressing the brake pads on the wheel is selected, which consists in simulating the effect of the brake pads on the wheel using a measuring device placed instead of the pads between the surface of the wheel and the brake shoe and containing strain gauges as a sensitive element [ 2]. When a force equal to the pressing force of a real brake shoe is applied to the measuring device, a thin metal plate in contact with the wheel is deformed. This deformation is recorded by a bridge circuit, in the shoulders of which are strain gauges that convert the resulting deformations into an electrical signal proportional to the pressing force acting on the measuring device.

The disadvantage of this method is the high complexity in the process of determining the pressing forces of a large number of blocks, for example, a set of blocks of a passenger or freight car, due to the need to dismantle each block in the process of determining its pressing force.

The technical result that can be obtained by using the invention is to reduce the complexity of determining the force of pressing the brake pads on a railway wheel.

The specified technical result is achieved by the fact that in the method for determining the force of pressing the brake pads on a railway wheel, in which a sensitive element is placed on the wheel surface and deformed by mechanical forces, an ultrasonic wave is introduced into the sensitive element, and the calibration dependence t ₁ = f (H ) the propagation time t _{1 of the} ultrasonic wave from the value applied to the sensitive element of the pressing force N in the absence of a brake pad, record the propagation time t ₂ ultra sound wave when placing the brake pads on the sensing element and applying the pressing force to the shoe, and determine the effective pressing force according to the dependence t ₁ = f (N) and the value of t ₂ . In this case, oblique input of the ultrasonic wave into the sensing element is carried out, and its frequency is chosen to exceed 5 MHz.

The invention is illustrated by drawings. Figure 1 schematically shows a device by which the inventive method is implemented; figure 2 illustrates the propagation of ultrasonic (ultrasound) waves in a sensitive element.

A device for implementing the proposed method includes a sensing element - an acoustic plate 1 with known linear dimensions - length L and thickness d, a piezoelectric transducer (acting as a transmitter and receiver of ultrasonic waves) 2, combined with an inclined prism and located on the unloaded end of the plate 1, an ultrasonic generator waves 3 and the computing unit 4. The plate 1 is made of a material with low acoustic impedance, for example steel, with a thickness of 2-3 mm. To reduce the heterogeneity of the transitions "plate - block" and "plate - wheel" between the plate 1 - on the one hand, and the block 5 and the wheel 6 - on the other hand, are insulators 7, made, for example, in the form of a rubber membrane. The device can be mounted either with a magnet on a wheel or with a spring on a block.

The measurement of the clamping force of the brake pads 5 to the surface of the railway wheel 6 is as follows.

The first step is calibration. The plate 1 is placed on the surface of the wheel 6 and, in the absence of the brake pad 5, is loaded with a varying (for example, stepwise with a certain step) load, the range of change of which corresponds to the actual range of the pressing force of the pad 5 to the wheel 6 under operating conditions. By means of a piezoelectric transducer 2, an inclined introduction of ultrasonic vibrations into the plate 1 is carried out. The frequency of ultrasonic vibrations F is chosen to be greater than 5 MHz, since at a lower frequency most of the energy of the ultrasonic wave is not reflected from the deformed upper layers of the crystal lattice of plate 1 and leaves plate 1 through its side surfaces.

The nature of the propagation of ultrasonic waves in the material of the acoustic plate 1 is shown in figure 2.

The value of h determines the stroke length of the wave front in one period

The number of reflections n of the ultrasonic wave is

In practice, to measure the pressing force of the pad, L is chosen equal to ≈130 mm, d≈1 mm, α = 30 degrees, then h = 1,155 mm, n = 225. When the plate 1 is deformed, for example, equal to 5 μm, the deceleration of the frontal velocity of the ultrasonic wave corresponds to the path traveled by the ultrasonic wave - 5n = 1.125 mm. This value may well be solvable by a typical piezoelectric transducer, which confirms the possibility of practical implementation of the proposed method.

The measurement of the pressing force is based on the fact that the application of a force H to the plate 1, oriented perpendicular to its lateral surfaces, leads to the deformation of the crystal lattice of the upper layers of the plate 1 and the formation of an additional interface between the stressed and unstressed regions of the plate 1, from which rereflection occurs Ultrasound waves. As a result, the frontal velocity of the ultrasonic wave is increasing. Removing the calibration dependence consists in measuring the arrival time of the reflected ultrasonic wave t ₁ from the magnitude of the force H.

After removing the calibration dependence t ₁ = f (H), the brake shoe 5 is installed on the plate 1 and the arrival time t _{2 of the} reflected ultrasound wave is determined under the conditions of a real pressing force. Then, from the measured value of t ₂ and the calibration dependence t ₁ = f (N), the effective pressing force is determined.

Thus, in comparison with the prototype method, the claimed method is characterized by significantly less laboriousness, since the dismantling of the shoe during the general test of the entire set of brake shoes is carried out only once - at the calibration stage.

LITERATURE

1. RF patent No. 2097240, cl. B 61 H 13/34, 1997

2. US patent No. 5038605, NKI 73/129, 1991 (prototype).

Claims (3)

1. The method of determining the force of pressing the brake pads on a railway wheel, in which a sensitive element is placed on the wheel surface and deformed by mechanical forces, characterized in that an ultrasonic wave is introduced into the sensitive element, and the calibration dependence t ₁ = f (H) of time is removed the propagation of the ultrasonic wave t ₁ from the magnitude of the pressing force N applied to the sensor element in the absence of a brake pad, the propagation time t _{2 of the} ultrasonic wave is recorded when placing t brake pads on the sensing element and the application of the pressing force to the shoe and determine the effective pressing force according to the dependence of t ₁ = f (H) and the value of t ₂ . 2. The method for determining the force of pressing the brake pads on a railway wheel according to claim 1, characterized in that the inclined input of the ultrasonic wave into the sensing element is carried out. 3. The method for determining the force pressing the brake pads on a railway wheel according to claim 1, characterized in that an ultrasonic wave with a frequency of more than 5 MHz is introduced into the sensor element.

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