JPH06289128A - Ultrasonic type distance detecting device - Google Patents

Abstract

PURPOSE:To improve measuring accuracy by correcting a difference resulting from atmospheric temperature in a receiving sensitivity level in the case where a distance measurement such as the detection of ground height is carried out through an ultrasonic sensor. CONSTITUTION:Atmosphenic temperature is detected by a temperature sensor 12, and a conditional expression based on a temperature scope is discriminated by CPU 10, and when an ultrasonic wave which is emitted from the transmitter 7a of an ultrasonic sensor 7 and reflected on a detected article is received by a receiver 7b, amplification circuits 14 to 17 having a different amplification degree are selected so as to change the receiving sensitivity level of the receiver 7b to adjust an input signal from the receiver 7b for outputting it to CPU 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can detect the ground height of a pre-mowing treatment device in a combine, the ground height of a tilling work machine pulled by a tractor, and the ground height of a work vehicle of a construction machine. Therefore, the ultrasonic waves emitted from the transmitter mounted on these traveling aircraft are reflected by the object to be detected, and the receiver receives the reflected wave, and the control unit measures the distance to the object to be detected. The present invention relates to an ultrasonic distance detecting device for doing so.

[0002]

2. Description of the Related Art As a cutting height detecting device in a combine, which has been widely used in the past, a mechanical sensor having a contact portion that comes into contact with the ground is damaged by a foreign matter of the root of a grain stem hitting the contact portion. There was a drawback that it was easy to do. On the other hand, recently, as disclosed in JP-A-58-142279, a non-contact type ultrasonic sensor is often used.

[0003]

By the way, in the ultrasonic sensor, as shown by the solid line in FIG. 6, the reception sensitivity level of the received wave by the receiver is extremely low in the low temperature region and the high temperature region,
It tends to be high at room temperature near 20 ° C. Therefore, if you set the sensitivity adjustment of the ultrasonic sensor to the normal temperature range,
Since work vehicles are often used in an environment where the temperature changes drastically due to the climate such as early morning or evening, or winter or summer, it is necessary to use an ultrasonic sensor to detect objects such as the height to the ground. There are problems that the distance cannot be detected and the detection accuracy fluctuates significantly.

It is an object of the present invention to compensate for this difference in the receiving sensitivity level due to temperature so that distance detection can always be performed with high accuracy regardless of changes in climate or the like. .

[0005]

In order to achieve the above object, the present invention receives a reflected wave, which is a reflected wave obtained by reflecting an ultrasonic wave emitted from a transmitter mounted on a traveling machine body of a work vehicle on an object to be detected. Then, in the ultrasonic distance detecting device for measuring the distance from the received signal to the detected object in the control unit, the received signal from the receiver is input to the control unit via the reception amplification circuit. On the other hand, the control unit is configured to input a detection signal from a temperature sensor, and is controlled to change the amplification degree of the reception amplification circuit according to the detection signal from the temperature sensor. is there.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described. FIG. 1 is a side view of the combine, FIG. 2 is a front view thereof, and the hydraulic pressure shown in FIG. The cutting pretreatment device 2 is mounted via a cylinder 9 so as to be movable up and down. The cutting pretreatment device 2 has a grain culm raising device 3 in which the lower end is inclined forward and the upper end is inclined rearward, and a portion in front of the lower end. It comprises a grass body 4, a cutting blade 5 at the lower rear of the grain culm raising device 3, and a grain culm transporting device 6.

The ultrasonic sensor 7 in the ultrasonic distance detecting device of this embodiment is arranged on a bracket (not shown) provided on the back side of the grain culm raising device 3, and as shown in FIG. The ultrasonic sensor 7 is arranged so that the transmitting portion (horn portion) of the transmitter 7a and the receiving portion of the receiver 7b face the ground 8. FIG. 3 shows a first embodiment of the ultrasonic detecting device of the present invention and its control unit, and reference numeral 10 is a central processing unit (C) as a control unit in the ultrasonic distance detecting device.
A read-only memory (RO) that stores data such as a control program (not shown) and conditional expressions (described later).
M), a readable / writable memory (RAM) for temporarily storing various detected values, data, and the like, an interface, a bus, and the like.

A drive pulse P1 output from the CPU 10 (see FIG.
The driving circuit 11 is actuated according to the reference), and the oscillator 7a outputs the oscillation wave P2 in the duty section W2 at predetermined time intervals W1. The receiver 7b receives the received wave P3 which is the transmitted wave P2 from the transmitter 7a reflected on the ground 8. From the start of the emission of the transmitted wave P2, a constant level H
The time difference W3 until the above received wave P3 is received is measured. At this time, it is possible to accurately measure the distance from the ultrasonic sensor 7 to the ground by correcting the fact that it is at the constant level (reception sensitivity level) by the temperature compensation circuit described later.

The relationship between the measured time difference W3 and the distance is previously stored in the ROM as a look-up table such as a relational expression by an experiment, and the CPU 10
The distance L is calculated from the measured value W3 and the look-up table. In the embodiment, the vertical distance between the lower end surface of the mowing pretreatment device 2 and the ground 8 or the vertical distance from the mowing blade 5 to the ground 8 is the distance required for control. The CPU 10 outputs a predetermined up-and-down command signal to the drive circuit 19 according to the calculated distance, operates the electromagnetic solenoid of the hydraulic pressure switching valve 20 according to the output from the drive circuit 19, and performs the pre-mowing process. The hydraulic cylinder 9 for raising and lowering the device 2 is operated.

Next, the temperature correction control will be described. Reference numeral 12 shown in FIG. 3 is a temperature sensor for detecting the temperature of the ultrasonic sensor 7 and / or the atmosphere in the vicinity of the object to be detected. Use a temperature sensor such as. The input signal from the temperature sensor 12 is sent to the central processing unit CP via a predetermined detection circuit 13 (including an amplification circuit).
It is input to U10 as a detection signal.

Reference numerals 14, 15, 16 and 17 shown in FIG. 3 denote reception amplifier circuits, and input signals from the receiver 7b are inputted to respective amplifier circuits 14 to 17 via an amplification degree switching circuit 18.
To the CPU 10 via the amplification degree (actually, the reduction of the amplification degree) in each amplifier circuit. In CPU10,
A temperature range is discriminated (discrimination of the following conditional expression) by the detection signal T from the temperature sensor 12, and a command signal is issued to the amplification degree switching circuit 18 according to the conditional expression to determine which of the amplifier circuits 14, Specify whether to use 15, 16, 17 (selection)
Will be done.

The temperature correction is performed as shown in FIG. That is, the reception sensitivity level of the receiver 7b before correction is as shown by the solid line X1, has an upward slope toward the normal temperature range (temperatures t2 to t3) around 20 ° C. from the temperature t0, and then toward the high temperature range t5. Since the curve becomes an upward convex curve having a downward slope, and the reception sensitivity level is significantly different, this is corrected so as to be averaged.

For example, when the measured temperature T is t0 or lower and t5 or higher (T≤t0, t5≤T), the reference amplifier circuit 1 is used.
Use 4 The reception sensitivity level of the receiver 7b based on the amplification degree of the reference circuit 14 is used as a reference, and this is set to 0 dB (decibel). When the measured temperature T is conditional expression 1, that is, in the range of t0 <T ≦ t1 and the range of t4 ≦ T <t5, the amplifier circuit 15 that lowers the reception sensitivity level by 2 dB is selected. Further, in the case of the conditional expression 2, that is, when the measured temperature T is in the range of t1 <T ≦ t2 and the range of t3 ≦ T <t4, the amplifier circuit 16 that lowers the reception sensitivity level by 4 dB is selected. Furthermore, in the case of conditional expression 3, that is,
When the measurement temperature T is in the range of t2 <T <t3, the amplifier circuit 17 that lowers the reception sensitivity level by 6 dB is selected. By doing so, the receiving sensitivity level in each of the amplifier circuits 14 to 17 becomes like the broken line X2 in FIG. 6, and the difference between the maximum and the minimum receiving sensitivity level in the temperature range t0 to t5 is X3. Especially it will be shortened. This control is shown in the flowchart of FIG.

FIG. 5 is a functional block diagram of another embodiment of the temperature correction control circuit. An input signal from the temperature sensor 12 is sent to the central processing unit CPU 10 via a predetermined detection circuit 13 (including an amplification circuit). It is inputted as a detection signal, the temperature range is discriminated in the same manner as in the above-mentioned embodiment, and the CP
In U10, the amplification degree switching circuit 18 controls to switch the amplification degree (amplifier gain) in one amplification circuit 21 according to the determination of the temperature range (determination of the conditional expression).

[0015]

As described above, according to the present invention, the reflected wave obtained by reflecting the ultrasonic wave emitted from the transmitter mounted on the traveling machine body of the work vehicle on the object to be detected is received. In an ultrasonic distance detection device for receiving and measuring the distance from the received signal to the object to be detected in the control unit, the reception signal from the receiver is input to the control unit via a reception amplification circuit. On the other hand, the control unit is configured to input a detection signal from a temperature sensor, and is controlled to change the amplification degree of the reception amplification circuit according to the detection signal from the temperature sensor. Therefore, even if the reception sensitivity level at the receiver in the ultrasonic distance detecting device greatly varies depending on temperature,
By adjusting the amplification degree in the reception amplification circuit, it is possible to control so that the fluctuation of the reception sensitivity level can be reduced over a wide temperature range, and it is possible to accurately perform distance measurement in a work vehicle regardless of the season or time zone. To play.

[Brief description of drawings]

FIG. 1 is a side view of a combine.

FIG. 2 is a front view of the combine.

FIG. 3 is a functional block diagram of control means.

FIG. 4 is a time chart of a transmitted wave and a received wave of the ultrasonic sensor.

FIG. 5 is a functional block diagram of another embodiment of the control means.

FIG. 6 is an explanatory diagram of reception sensitivity levels.

FIG. 7 is a control flowchart.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Traveling machine 2 Pre-cutting device 3 Grain sprouting device 4 Weeding body 5 Cutting blade 7 Ultrasonic sensor 7a Transmitter 7b Receiver 9 Hydraulic cylinder 10 CPU 12 Temperature sensor 13 Detection circuit 14-17, 21 Amplification circuit 20 Hydraulic switching valve

Claims (1)

[Claims] 1. A receiver receives a reflected wave obtained by reflecting an ultrasonic wave emitted from a transmitter mounted on a traveling body of a work vehicle by a detection object, and from the received signal to the detection object in a control unit. In the ultrasonic distance detecting apparatus for measuring the distance of, while the reception signal from the receiver is configured to be input to the control unit via a reception amplification circuit, the control unit is provided with a temperature sensor from An ultrasonic distance detecting device, which is configured to input a detection signal, and is controlled so as to change the amplification degree of the reception amplification circuit according to the detection signal from the temperature sensor.