JPS62288592A - Ultrasonic range finder - Google Patents

Abstract

PURPOSE:To accurately measure a distance regardless of the variation in the speed of an ultrasonic wave due to temp., by providing a measuring side end part opened toward a measuring direction, a transmitter side end part provided with an ultrasonic transmitter and a receiver side end part provided with an ultrasonic receiver. CONSTITUTION:The ultrasonic wave guide 2 of an ultrasonic range finder 1 is mounted to the under surface of the trank lid A of a car and two measuring side end parts 2a, 2b thereof are opened toward the rear of the car. By making the distance from the transmitter side end part 2c of the ultrasonic wave guide 2 to the first measuring side end part 2a equal to that from the transmitter side end part 2c to a receiver side end part 2d, a time when an ultrasonic pulse is emitted from the first measuring side end part 2a toward the rear of the car coincides with a time when the ultrasonic pulse passing through the ultrasonic wave guide 2 is received by an ultrasonic receiver 4. By this constitution, when the pipeline transmitting time from the emitting time to the receiving time is measured, the ultrasonic wave propagation speed (v) at that time is obtained accurately and, therefore, a distance can be measured always accurately.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention Field of Industrial Application The present invention relates to an ultrasonic distance measuring device, and more specifically,
The present invention relates to an ultrasonic distance measuring device that can accurately measure distance without being influenced by temperature, etc.

BACKGROUND ART Conventionally, as a device for detecting the presence or absence of an object and its distance using ultrasonic waves, there has been known a device disclosed in, for example, Japanese Patent Laid-Open No. 57-84377.

This device is used to detect objects behind a car. It emits ultrasonic waves to the rear of the car, receives the reflected waves that are reflected by the object, and detects the waves from the time of emission to the time of reception. The time required is measured, and the presence or absence of an object and the distance are determined based on the time required.

That is, when the time required from the time of emission to the time of reception is τ, and the speed of the ultrasonic wave is V, the distance ilL to the object is L
It can be determined by = r v /2.

Therefore, the maximum distance required to be detected is Lo
When τ. - Time τ calculated by L6/v. If the reflected wave is not received in a shorter time, the distance WA
It can be determined that there is no object within L. And τ. If a reflected wave is received within the required time, the distance to the object can be found by dividing the required time by V.

Problems with the Prior Art In this type of device, it is necessary to know the ultrasonic velocity V, but the ultrasonic velocity V is a variable value; for example, if the temperature rises by 1°C, the ultrasonic velocity V becomes 0°. 6m/s faster.

Therefore, in order to perform accurate distance measurement, a means for detecting and calibrating the variation in the ultrasonic velocity V is required.

However, in the past, there was no simple means to perform such calibration, so it was often omitted (especially when installed in a car), and as a result, there was a problem in that only a low level of detection could be performed.

OBJECT OF THE INVENTION The object of the present invention is to provide an ultrasonic distance measuring device that can accurately measure distance regardless of variations in the speed of ultrasonic waves due to temperature, etc., and that can be particularly suitably mounted on a car. It is about providing.

Structure of the Invention The ultrasonic distance measuring device of the present invention has a measurement side end portion that opens toward the measurement direction, a transmitter side end portion that is provided with an ultrasonic transmitter, and a receiver side end portion that is provided with an ultrasonic receiver. The ultrasonic pulse emitted by the ultrasonic transmitter is received by the ultrasonic receiver through the ultrasonic waveguide, and the passage time from the time of emission to the time of reception is measured. 1. The timekeeping means 1, the ultrasonic pulse emitted by the ultrasonic transmitter and emitted from the measurement side end is reflected by an object and returns, and the reflected wave pulse is received by the ultrasonic receiver, and a second timer for measuring the time required for reflection until reception, and
Equipped with calculation means for obtaining the ultrasonic propagation velocity from the ultrasonic waveguide distance from the ultrasonic transmitter to the ultrasonic receiver and the conduit transmission time, and calculating the distance to the object from this and the required reflection time. The structural feature is that the

Function The ultrasonic distance measuring device of the present invention uses an ultrasonic waveguide to guide and receive ultrasonic pulses emitted by an ultrasonic transmitter to an ultrasonic receiver.

The distance from the ultrasonic transmitter to the ultrasonic receiver is determined by the length of the ultrasonic waveguide, so if you measure the pipe travel time from the time of emission to the time of reception, you can determine the ultrasonic propagation velocity at that time. V can be obtained accurately.

Since the measurement of the velocity V of the ultrasonic waves can be performed integrally with the measurement of the distance to the object, it is simpler than measuring the distance to the object separately, and is more accurate because there is no time lag.

EXAMPLES Hereinafter, the present invention will be explained in more detail based on examples shown in the drawings. Here, FIG. 1 is a perspective view of the rear of an automobile equipped with an ultrasonic distance measuring device according to an embodiment of the present invention, FIG. 2 is a block diagram of an embodiment of the ultrasonic distance measuring device according to the present invention, and FIG. 4 is a time chart of each signal in the block diagram shown in FIG. 2, and FIG. 5 is a schematic diagram of main parts of another embodiment of the present invention. It is a diagram. Note that the present invention is not limited to the embodiments shown in the figures.

In Fig. 1, on the bottom surface of the trunk lid A of the automobile,
An ultrasonic waveguide 2 of an ultrasonic distance measuring device 1 according to an embodiment of the present invention is attached, and its two measurement side ends 2. and 2
b opens toward the rear of the automatic tonne.

As shown in FIG. 2, the first measurement side end 2□ of the ultrasonic waveguide 2 is one end of a relatively long straight tube part, and the ultrasonic transmitter 3 is attached to the other end 2c. It is provided. Also, the second
The measurement side end 2b is one end of a relatively short straight pipe section, and the other end 2a is provided with an ultrasonic receiver 4.

The two straight pipe portions are connected to each other at locations close to the measurement side ends 2m and 2b.

The fundamental wave generation circuit 5 has an ultrasonic frequency (for example, 40kl).
(z), the pulse generation circuit 6 generates a pulse signal P at a predetermined timing, and the ultrasonic oscillation signal pulsed by the gate circuit 7 is amplified by the amplifier 8 to generate the ultrasonic wave. added to the transmitter 3, the ultrasonic transmitter 3
emits ultrasonic pulses.

The emitted ultrasonic pulse passes through the ultrasonic waveguide 2 and is emitted from the first measurement side end 2□ to the rear of the automobile. The waves also pass through the ultrasonic waveguide 2 and are received by the ultrasonic receiver 4 .

If the distance from the transmitter side end 2c of the ultrasonic waveguide 2 to the first measurement side end 21 is equal to the distance from the transmitter side end 2c to the receiver side end 2J, etc. , the time when the ultrasonic pulse was emitted from the first measurement side end 28 toward the rear of the automobile, and the time when the ultrasonic pulse passed through the inside of the ultrasonic waveguide 2 and was received by the ultrasonic receiver 4. The time of the day matches.

The output signal of the ultrasonic receiver 4 is amplified by the amplifier 9, only the necessary frequency band is selected by the filter IO, and the output signal is sent to the shaping circuit 1.
1, the waveform is shaped into a received pulse signal P.

A pulse signal P output from the pulse generating circuit 6.

is the first R-S flip-flop 12 and the second R-S flip-flop 12
-S Serves as the manual setting force S for the flip-flop 13 and also serves as a trigger input for the one-shot circuit 14.

On the other hand, the received pulse signal P becomes the human reset power R of the first RS flip-flop 12 and becomes the reset human power R of the second RS flip-flop 13 via the AND gate 15 .

The one-shot circuit 14 outputs a pulse signal for a predetermined period of time after receiving the pulse signal P, and sends a mask signal M to the AND gate 15 via the inverter 16.

Therefore, the function of the AND gate 15 is to not pass the received pulse signal Pr for a predetermined period of time after the pulse signal P is output (while the mask signal M is being output), and only after that, the received pulse signal Pr is passed as the reset manual power R of the second R-S flip-flop 13.

The first timer circuit 17 measures the time during which the output Q of the first R-S flip-flop 12 is set.

The second timer circuit 18 measures the time during which the output Q2 of the second RS flip-flop 13 is clocked.

The arithmetic circuit 20 receives the clock output T1 of the first timer circuit 17.
The following calculation is performed based on the time measurement output T2 of the second timer circuit 18 and the length l stored in advance. however,
l is the length of the ultrasonic waveguide 2 from the transmitter end 2e to the receiver end 2J.

L=fT2/2T,...■This is the third
As will be explained below with reference to FIG. 4 and FIG. 4, it represents the distance from the vehicle to object 0.

That is, as shown in FIG. 3, the transmitter side end 2. of the ultrasonic waveguide 2. from the first measurement side end 2. Let the distance to the object O be l, and let the distance from the measurement side end 2k to the object O be L. The distance of the conduit from the transmitter side end 2° of the ultrasonic waveguide 2 to the receiver side end 2a is as described above.
c to the first measurement side end 2. is equal to l.

As shown in FIG. 4, the pulse generation circuit 6 generates a pulse signal P
, the ultrasonic transmitter 3 emits an ultrasonic pulse at that timing, and the outputs Q and Q of the R-S flip-flops 12 and 13 are output.

is set. Further, the one shift circuit 14 and the inverter 16 output a mask signal M.

The ultrasonic pulses emitted from the ultrasonic transmitter 3 are emitted to the rear of the automobile from the first measurement side end 21, and
The waves pass through the duct of the ultrasonic waveguide 2 and are received by the ultrasonic receiver 4 . Therefore, among the received pulse signals P, a first pulse signal a shown in FIG. 4 is generated.

The first R-S flip-flop 12 is reset by this pulse signal a, so its output Q1 becomes a reset state, and the first timer circuit 17 measures the time T. This time TI is the distance j! of the ultrasonic waveguide 2.
11 is the transmission time for the ultrasonic wave to travel. Further, the time at which the pulse signal a is generated is the time at which the ultrasonic pulse is emitted from the automobile.

The pulse signal a is input to the gate circuit 15, but since the mask signal M is generated at this time, it is blocked from passing.
The second RS flip-flop 13 is not reset.

The ultrasonic pulse emitted from the first measurement side opening 2m is
The reflected pulse hits the object 0 behind the car, returns to the car, and enters the ultrasonic waveguide 2 from the second measuring end 2b.
and is received by the ultrasonic receiver 4. As a result, a pulse signal shown in FIG. 4 of the received pulse signal P is generated.

Although the pulse signal S is input to the first R-S flip-flop 12, it has no effect since it has already been reset. However, when input to the gate circuit 15,
At this time, since the mask signal M is gone, it passes through the gate circuit 15 and is passed through the gate circuit 13 of the second R-S flip-flop.
This will require human power R to reset. Therefore, the output Q2 of the second RS flip-flop 13 is in a reset state.

The second timer circuit 18 measures the time T2 during this period. This time T2 is the time required from the time when the ultrasonic pulse is emitted by the ultrasonic transmitter 3 to the time when the reflected pulse reflected by the object is received by the ultrasonic receiver 4.

Now, when the speed of the ultrasonic pulse is V, the following equation holds true.

v = 17 T l...■v=
<1 + 2 L) /T2'''■ However, the distance from the second measurement side end 2t to the receiver side end 2- is ignored.

If you eliminate V using the above formula 00 and solve for L, L, = 1 (T2 /TI -1) /2...
■It becomes. Here, assuming that T2/T is sufficiently larger than l, the formula 0 becomes L=IT2/2Tl...■', which is equivalent to the formula 0 above.

Therefore, it will be understood that the distance from the car to the object 0 is calculated by the arithmetic circuit 20.

It should be noted that Equation 0 (or Equation 07) includes Equation 0, and in that sense it can be said that the ultrasonic propagation velocity V is obtained indirectly. Therefore, even if the ultrasonic velocity V fluctuates due to temperature fluctuations,
The distance NL can always be accurately calculated based on the speed V at that time.

The distance calculated by the arithmetic circuit 20 is displayed on the display 21.

FIG. 5 shows the main parts of an ultrasonic distance measuring device according to another embodiment of the present invention. The shape is different from that of the waveguide 2.

Effects of the Invention According to the present invention, a measurement side end portion opening toward the measurement direction, a transmitter side end portion provided with an ultrasonic transmitter, and a receiver side end portion provided with an ultrasonic receiver are provided. an ultrasonic waveguide having an ultrasonic transmitter; Timing means: The ultrasonic pulse emitted by the ultrasonic transmitter and emitted from the measurement side end is reflected by an object and returns to the ultrasonic receiver. a second timer for measuring the time it takes for the reflection to reach the ultrasonic wave; An ultrasonic distance measuring device is provided which is characterized by being equipped with a calculation means for calculating the distance to an object from the required time, and the following effects can be obtained thereby.

■ Accurate distance measurements can always be made without being affected by changes in ultrasonic speed due to temperature changes, etc.

■ It can be conveniently installed in a car by using the trunk room of the car.

(2) If the shape of the ultrasonic waveguide 2 is appropriate, the time (start point) at which an ultrasonic pulse is emitted to an object can be accurately determined.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the rear of an automobile equipped with an ultrasonic distance measuring device according to an embodiment of the present invention, FIG. 2 is a block diagram of an embodiment of the ultrasonic distance measuring device according to the present invention, and FIG. A schematic cross-sectional plan view showing the positional relationship between the device and the object, Figure 4 is the second
The time chart of each signal in the block diagram shown in the figure,
FIG. 5 is a schematic diagram of main parts of another embodiment of the present invention. (Explanation of symbols) 1.1'...Ultrasonic distance measuring device 2.2'...Ultrasonic waveguide 2□, 2b, 2@', 26'...Measurement side end portion 2c, 2
c'...Transmitter side end 2a, 2a'...Receiver side end 3...Ultrasonic transmitter 4...Ultrasonic receiver 12.13...R-S flip-flop 14 ...Wanshikosoto circuit 15...And gate 17.18...Timer circuit 20...Arithmetic circuit 21...Display circuit i...
・Ultrasonic waveguide distance L from the ultrasonic transmitter to the ultrasonic receiver...distance T to the object,...pipe transmission time T,...required time for reflection.

Claims (1)

[Claims] 1. (a) A measurement side end portion opening toward the measurement direction, a transmitter side end portion provided with an ultrasonic transmitter, and a receiver side end portion provided with an ultrasonic receiver. (b) The ultrasonic pulse emitted by the ultrasonic transmitter is received by the ultrasonic receiver through the ultrasonic waveguide, and the pipe transmission time from the time of emission to the time of reception is (c) a first timekeeping means for measuring; (c) an ultrasonic receiver receives a reflected wave pulse in which the ultrasonic pulse emitted by the ultrasonic transmitter and emitted from the measurement side end is reflected by an object; A second timing means for measuring the time required for reflection from the time of emission or from the time of emission to the time of reception, and obtaining the ultrasonic propagation velocity from the acoustic waveguide pipe distance and the pipe transmission time, and from that and the time required for reflection. An ultrasonic distance measuring device characterized by comprising a calculation means for calculating a distance to an object. 2. Pipe distance from the ultrasonic transmitter to the ultrasonic receiver,
The ultrasonic distance measuring device according to claim 1, wherein the duct distances from the ultrasonic transmitter to the opening that emits the ultrasonic pulses are equal. 3. Claim 1 attached to the rear trunk lid of a car and used for detecting objects behind the car
The ultrasonic distance measuring device according to item 1 or 2.