JP2014029265A - Speed measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a speed measurement device with improvement in measurement accuracy, the device that is incorporated in a transport machine such as railway and uses a Doppler effect of electromagnetic waves.SOLUTION: A speed measurement device includes: a speed detection part, incorporated in a transportation machine, for measuring a speed with a stationary article as reference by emitting an electromagnetic wave toward the stationary article, receiving the electromagnetic wave reflected thereby and measuring a difference in frequency between the emitted and reflected waves; a chassis for internally accommodating the speed detection part; and a transparent window, disposed in the chassis, for letting the electromagnetic wave emitted and received to transmit. Further, the chassis has an inclined surface that has an angle of between 90 degrees and 180 degrees, both ends exclusive, relative to the transparent window or an extended plane thereof and is in a direction positive to a speed to be measured by the speed measurement part.

Description

  The present invention calculates a velocity by radiating an electromagnetic wave such as a millimeter wave band or a quasi-millimeter wave band toward the ground and measuring a frequency change amount of a reflected wave for the purpose of contactlessly measuring a ground speed of a transport device The present invention relates to a speed measuring device.

  As a method for detecting a ground speed in a transportation device such as an automobile or a railway vehicle, a method of obtaining a speed by measuring the number of rotations of a wheel is generally used. However, it is known that this method cannot measure the ground speed when the wheel slips, and a measurement error occurs when the wheel diameter changes due to tire air loss or wheel scraping.

  On the other hand, there is also known a speed measuring device that radiates a continuous wave of millimeter waves to the ground, receives a reflected wave thereof, measures a frequency change amount of the reflected wave, and calculates a ground speed. For example, a technique such as Patent Document 1 is known. Since this method is a non-contact type, the ground speed can be measured even when slipping, and it is not affected by changes in the wheel diameter.

JP 2006-184144 A

  However, in the technique described in Patent Document 1, when a pollutant or water adheres to the radiation surface or reception surface of the electromagnetic wave, the electromagnetic wave is scattered and absorbed on the attachment surface. Measurement performance may be degraded. In particular, in railways, iron powder may be generated by scraping wheels or rails. However, iron powder scatters electromagnetic waves greatly, and thus, there is a high possibility that speed measurement performance will be deteriorated if it adheres.

  An object of the present invention is to provide a speed measuring device with high measurement accuracy in a speed measuring device that mainly uses the Doppler effect of electromagnetic waves mounted on transportation equipment such as railways.

  In order to achieve the above object, a speed measuring device of the present invention is mounted on a transportation device, radiates an electromagnetic wave toward a fixed object, receives an electromagnetic wave reflected from the fixed object, receives the radiated wave and the A speed detection unit that measures a speed based on the fixed object by measuring a frequency difference of reflected waves, a housing that houses the speed detection unit, and a speed detection unit that is provided in the housing And a transmission window that transmits the electromagnetic wave that is radiated and received, wherein the casing is inclined at an angle that is greater than 90 degrees and less than 180 degrees with the transmission window or an extended surface of the transmission window. The surface is in the positive direction of the speed measured by the speed detector.

  According to the present invention, it is possible to provide a speed measuring device with high measurement accuracy.

An example of a speed measuring device according to the present invention Example of installing a speed measurement device on a railway vehicle Example of configuration of speed measurement unit Another example of the speed measuring device according to the present invention Another example of the speed measuring device according to the present invention Another example of the speed measuring device according to the present invention Another example of the speed measuring device according to the present invention

  Hereinafter, the configuration of the speed measuring device will be described with reference to FIGS. 1 to 3. In this embodiment, a speed measuring device using an electromagnetic wave of 77 GHz band is taken as an example, but an electromagnetic wave type speed measuring device using other frequencies including an optical type can be implemented with the same configuration.

  FIG. 1 is a diagram illustrating an example of the configuration of the speed measurement device 300. The speed measuring device 300 is mainly composed of a speed measuring unit 1, a fixed base 2 for fixing the speed measuring unit 1 to the casing of the speed measuring device 300, an inclined surface 303 and an inclined surface 303A for deflecting the air flow direction, and a speed measuring unit. 1 is formed of a transmission window 304 that transmits an electromagnetic wave radiated from 1 and reflected and returned from an electromagnetic wave reflection surface.

  For example, as shown in FIG. 2, the speed measuring device 300 is installed on the bottom surface S of a railway vehicle C, radiates an electromagnetic wave M in an oblique direction with respect to the ground G, and a frequency change amount 01. It is the structure which measures speed and calculates speed.

  An example of the configuration of the speed measuring unit 1 of the speed measuring apparatus 300 is shown in FIG. The speed measurement unit 1 mainly includes a MMIC (Monolithic Microwave Integrated Circuit) 11, an antenna 139, a lens 12, and an arithmetic circuit 13. Among these, the MMIC 11 mainly includes a transmitter 134, a transmission amplifier 110, an isolator 119, a reception amplifier 113, and a mixer 112. An antenna 139 is connected to the isolator 119.

  The operation of the speed measuring unit 1 will be described below. The high frequency signal in the 77 GHz band generated by the oscillator 134 is amplified by the transmission amplifier 110, then propagated to the antenna 139 through the isolator 119, and is radiated as an electromagnetic wave from the antenna 139 to the space. The emitted electromagnetic wave is converged by the lens 12 and incident on the ground. The millimeter wave is reflected on the ground, and the frequency of the reflected wave is changed by the Doppler effect in proportion to the speed with the ground. The electromagnetic wave reflected from the ground enters the antenna 139 through the lens 12. A signal received by the antenna 139 is propagated to the receiving amplifier 113 by the isolator 119. This signal is amplified by the receiving amplifier 113 and mixed with the high frequency signal output from the transmitter 134 by the mixer 112 to generate an IF (Intermediate Frequency) signal, which is input to the arithmetic circuit 13. The frequency of this IF signal is the absolute value of the frequency change due to the Doppler effect. The operation of the arithmetic circuit 13 is to convert the IF signal into a digital signal mainly by an AD converter, obtain the frequency of the IF signal by FFT (Fast Fourier Transform) processing, and convert it to the speed v. The speed v is θ, where θ is the angle formed between the incident direction of the millimeter wave and the reverse direction of the speed.

It is expressed by the relational expression. Here, c is the speed of light, f ₀ is the frequency of the signal output from the oscillator, and f _d is the amount of frequency change due to the Doppler effect.

  Here, returning to FIG. 1, when the vehicle C travels, an air flow W <b> 1 is generated around the speed measuring device 300 in the direction opposite to the traveling direction V of the vehicle C. The air flow W1 flowing into the speed measuring device 300 from the traveling direction is deflected in the direction W2 by the inclined surface 303, and the air flows in the horizontal portion 305 in the horizontal direction W3. On the other hand, the fouling substance P that rides on the air flow W1 and moves toward the speed measuring device 300 is gradually changed in the direction of the ground G by the air flow W2, but depending on the speed of the air flow W2 and the weight of the fouling substance P, It may collide with the inclined surface 303 due to the inertia of the fouling substance P. Regardless of whether or not they collide, the pollutant P passes through the front surface of the inclined surface 303 on the air flow W2. After passing, due to the inertia effect, the fouling substance P does not go to the horizontal part 305 but goes to the ground G direction.

  Due to this effect, it is possible to adopt a configuration in which the pollutant P that prevents the propagation of electromagnetic waves does not easily reach the transmission window 304, and it is possible to provide a speed measurement device with high measurement accuracy by preventing a decrease in speed measurement performance due to adhesion of the pollutant. . In addition, this makes it possible to reduce the number of maintenance operations such as removal of pollutants due to fouling of the transmission window 304.

  In general, railway vehicles have two traveling directions, ie, an ascending and descending direction. Therefore, by providing an inclined surface 303 and an inclined surface 303A in both directions of the horizontal portion 305, the vehicle is opposite to the traveling direction V in FIG. Even if C progresses, it is possible to obtain the same effect.

  In addition to the pollutant, the same effect can be obtained with water such as rain water. The transmission window 304 may be subjected to a water-repellent coating process for the purpose of splashing rainwater or the like that affects the transmission characteristics of electromagnetic waves.

  Further, FIG. 4 shows the configuration of the speed measuring device 310 that enhances the effect of preventing fouling substances and water from adhering to the transmission window 304. In this configuration, a wind direction control plate 312 is added to the speed measurement device 300 shown in FIG. As a more preferable configuration, the area of the opening 311 of the speed measuring device 310 is made larger than the area of the opening 314 beside the horizontal part 305 in order to increase the speed of the air flow W1 as shown in FIG. Thus, it is possible to increase the speed of the air flow W2 and increase the speed at which the pollutant P jumps out of the opening 314. In the case of a railroad, since there are two traveling directions, that is, ascending and descending, the wind direction control plate 312A is similarly installed so as to be able to cope with traveling in the direction opposite to the traveling direction V shown in FIG.

  FIG. 5 shows the configuration of the speed measuring device 330 that enhances the effect that the pollutant P and water hardly adhere to the transmission window 304. This structure has a structure having arc shapes 335 and 335A on both sides of the horizontal portion 305 with respect to the speed measuring device 310 shown in FIG. When the traveling direction is an arrow direction indicated by V, air flows from the opening 311 to generate an air flow W1 opposite to the traveling direction V, and the inclined surface 303 deflects the direction to W2. If the fouling substance P is taken in from the opening 311, the fouling substance P is blown from the opening 314 toward the ground by the air flow W <b> 2. In addition, at the tip 337 of the inclined surface 303, the air flow W <b> 2 sucks out air inside the arc shape 335, and the air flow WR <b> 3 is generated along the arc shape 335. When the air flow WR3 is generated, an air flow WR2 is generated in the traveling direction on the surface of the transmission window 304, and the air flow WR1 is generated inside the arc shape 335A by the air flow WR2. Further, a part of the air flow W3 flowing out from the opening 314 flows into the arc shape 335A. As a result, vortices due to air flows W3, WR1, WR2, and WR3 are generated in front of the transmission window 304. Since the air vortex is in a state in which the pollutant P is small, the pollutant P is difficult to reach the transmission window 304.

  Furthermore, it is good also as a structure of the speed measurement apparatus 340 shown in FIG. 6 as another example of the speed measurement apparatus 330 shown in FIG. In this configuration, the central angle of the arc shapes 345 and 345A is 90 ° or more, and the angle formed between the arc and the horizontal portion 305 is 180 ° or less. Since the tip portion 348A formed by the arc shape 345A and the horizontal portion 305 is inferior, even if a fouling material enters the arc shape 345A, the air flow WR1 generated in the arc shape 345A gives centrifugal force to the pollutant. The fouling substance is unlikely to reach the transmission window 304 from the tip 348A.

  Moreover, it is good also as a structure which provides the convex structure 355 in the corner | angular part formed with the vertical wall 353 and the horizontal part 305 like the structure of the speed measurement apparatus 350 shown in FIG. When the traveling direction is the arrow direction indicated by V, if the pollutant P that collides with the vertical wall 353 does not adhere to the vertical wall 353 due to the air flow W1 opposite to the traveling direction V, the air flow W2 Get on the ground. When the fouling substance adheres to the vertical wall 353, the fouling substance P falls along the vertical wall 353 in the ground direction, and the fouling substance P is blown off by the air flow at the tip of the convex structure 355. A wind direction control plate 352 may be added to enhance this effect. The horizontal portion 305 including the transmission window 304 is structured so as to enter the inside, so that the pollutant P is difficult to reach the transmission window 304. In order to cope with the case where the traveling direction V is reverse, a vertical wall 353A, a convex structure 355A, and a wind direction control plate 352A are added. In the configuration of FIG. 7, the vertical walls 353 and 353 </ b> A are not necessarily perpendicular to the horizontal portion 305.

  The embodiment described above can be used not only in the railway field but also in various transportation equipment fields including elevators, construction machines, and agricultural equipment.

DESCRIPTION OF SYMBOLS 1 Speed measuring part 300,310,330,340,350 Speed measuring device 303,303A Inclined surface 304 Transmission window 305 Horizontal part 312,312A, 322,322A, 352 Wind direction control board

Claims (10)

Mounted on a transport device, radiates an electromagnetic wave in the direction of a fixed object, receives an electromagnetic wave reflected from the fixed object, and measures the frequency difference between the radiated wave and the reflected wave as a reference. A speed detector that measures the speed to be transmitted; a housing that houses the speed detector; and a transmission window that is provided in the housing and transmits the electromagnetic waves that are radiated and received from the speed detector. In the speed measurement device,
The casing has an inclined surface whose angle formed by the transmission window or an extended surface of the transmission window is greater than 90 degrees and less than 180 degrees in a positive direction of a speed measured by the speed detection unit. Measuring device. The speed measuring device according to claim 1,
The speed measurement device according to claim 1, wherein the casing has the inclined surface in both a forward direction and a reverse direction of a speed measured by the speed detection unit. The speed measuring device according to claim 1,
A plate is arranged at a position facing the inclined surface,
A speed measuring device, wherein a space is formed by the inclined surface and the plate. The speed measuring device according to claim 3,
The speed measurement device according to claim 1, wherein an opening on the front end side of the casing of the space is larger than an opening on the transmission window side of the casing. In the speed measuring device according to any one of claims 1 to 4,
A speed measuring device having an arc shape between the transmission window or an extended surface of the transmission window and the inclined surface. The speed measuring device according to claim 5,
An angle formed by the transmissive window or an extended surface of the transmissive window and the circular arc shape is 180 degrees or less. The speed measuring device according to claim 1,
A speed measurement device, wherein a wall structure is provided perpendicularly to an extension surface of the transmission window on a side formed by the transmission window or an extension surface of the transmission window and the inclined surface. The speed measuring device according to claim 7,
The speed measurement device according to claim 1, wherein the casing is provided with the inclined surface and the wall structure in both a forward direction and a reverse direction of a speed measured by the speed detection unit. The speed measuring device according to claim 7,
A plate is arranged at a position facing the inclined surface,
A speed measuring device, wherein a space is formed by the inclined surface and the plate. The speed measurement device according to claim 9, wherein
The speed measurement device according to claim 1, wherein an opening of the space on the front end side of the housing is larger than an opening of the housing on the side closer to the transmission window.