JPS644601B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention includes a transmitter that transmits ultrasonic pulses;
The present invention relates to a ground level detection device for a working section equipped with a receiver that receives the reflected ultrasonic waves, and for example, relates to a ground level detection device for a reaping device that is movably supported on a combine harvester.

A ground level detection device that uses ultrasonic waves emits ultrasonic pulses from a transmitter toward the ground, and a receiver receives the reflected waves from the transmitted ultrasonic pulses that hit the ground and convert them into electrical signals. , the distance to the ground is measured by measuring the time delay from the time an ultrasonic pulse is transmitted until it is received.

A problem with the prior art is the so-called direct wave wrap-around phenomenon, in which the ultrasonic pulses received from the transmitter are directly received by the receiver. This point will be explained. In order to determine the point in time when the receiver receives the reflected ultrasound, it is determined whether the detection signal of the reflected ultrasound output from the receiver is equal to or higher than a set level. The intensity of the reflected ultrasonic wave is strong when the object to be detected is close and weak when it is far away, so the level of the detection signal output from the receiver changes depending on the distance of the object to be detected. There is a restriction that the measurable distance cannot be increased unless a threshold value for determining the reception point of reflected ultrasound waves is set low. Although the amount of the direct wave that goes around is very small compared to the total energy emitted from the transmitter, it cannot be ignored compared to the normal reflected signal voltage because the threshold value is set low for the above-mentioned reason. It was hot. For this reason, in the past, the transmitter and receiver had to be separated to prevent interference, making it difficult to miniaturize a ground level detection device that uses ultrasonic pulses.

In addition, as a practical problem when using a ground level detection device that uses ultrasonic pulses, in addition to the above-mentioned direct waves going around, there is also a problem in the frame where the transmitter and receiver are attached, as well as various parts around it. There is a problem of sensing unwanted reflected waves.
This point will be explained by taking as an example a case in which the present invention is incorporated and used as a ground level detection device for a reaping device that is supported in a combine harvester as a reaping machine so as to be able to rise and fall freely. Generally, in a combine harvester, a ground level detection device is provided at the front end of the reaping device to prevent the front end of the reaping device from plunging into the ground.
In order to protect the detection device, it is installed behind the weeding tool installed at the tip of the reaping device. More specifically, the lower part of the tip of the weeding tool is attached to a support frame in terms of support strength, and
In order to maintain sufficient ground level detection accuracy, the detection device should be installed as high as possible from the ground, so in reality, the ground level detection device is installed above the support frame on the back of the weeding implement. has been established. Therefore, when incorporating a ground level detection device using ultrasonic pulses into a reaping device,
The support frame is located between the detection device and the ground, and there is a problem in that the receiver receives the reflected wave from the support frame before receiving the reflected wave from the ground, causing a malfunction.

The present invention prevents malfunctions caused by direct waves,
The object of the present invention is to provide a ground level detection device for a working section that prevents malfunctions due to reception of unnecessary reflected waves.

A feature of the technical means of the present invention is that the transmission cycle of the ultrasonic pulse from the transmitter is set to be longer than the time interval from when the ultrasonic pulse is transmitted until it is reflected on the detection target ground and received. In addition, a threshold adjusting means is provided on the receiver side for changing the sensing level so as to decrease it as time elapses from the time when the transmitter transmits the ultrasonic wave.

Next, the effects of the present invention will be explained. The above-mentioned wrap-around of direct waves is a problem that occurs when the transmitter and receiver are placed close to each other, and because of the close proximity, the short-circuit path of the ultrasonic waves is also short, so the direct wave is detected immediately after the ultrasonic pulse is emitted. Additionally, since the distance between the detection device and various components is constant, unnecessary reflected waves from various components near the detection device are always detected after a certain period of time after transmitting the ultrasonic pulse. The delay time is shorter than the reflected wave from the ground. That is, when an ultrasonic pulse is transmitted, a direct wave is first received, then an unnecessary reflected wave is detected after a predetermined delay time, and then a reflected wave from the ground, which is the farthest point, is received. The present invention focuses on this point, and sets the threshold high immediately after transmitting an ultrasonic pulse, and reduces the detection level as time passes while excluding direct waves and unnecessary reflected waves. This ensures that weak reflected waves from the ground are received as legitimate reflected waves. Therefore, even if the transmitter and receiver are placed close to each other, the device may receive direct waves from the transmitter, causing malfunctions, or receiving unnecessary reflected waves from objects near the ground level detection device. This can prevent malfunctions. As a result, it is possible to reduce the size of the ground level detection device, and when it is incorporated into equipment that utilizes it, it is possible to obtain superior effects such as ease of selection of its installation position.

Next, embodiments of the present invention will be described based on the drawings.

FIG. 1 is a side view of a reaping device 1 at the front of a combine as a reaping and harvesting machine, and the reaping device 1 has a pulling device 2, a cutting blade 3, a conveying device 4, and a weeding tool 5. ... is arranged at the front of the lower part of the lifting device 2. The weeding tools 5 have their lower tip portions fixed to the tip portions of support frames 6 connected to the body frame of the reaping device 1. and,
Transmitter 7 and receiver 8 configured integrally or separately
The ultrasonic sensor 9 consisting of...
It is fixed behind one of the (the one closest to the already cut side) and arranged above the support frame 6 thereof.

FIG. 2 is a block diagram of the control device. 10 is a pulse generator that generates pulses at regular time intervals, the output of which is input to the ultrasonic transmitter 7 to transmit ultrasonic waves at regular time intervals;
The signal is input to a control calculation unit 11 and a threshold value adjusting means 12 that generates a threshold value of the sensing level. Therefore, the ultrasonic transmitter 7 is activated by the input of the timing pulse and emits ultrasonic waves toward the ground for a certain period of time, while the threshold value adjusting means 12 is activated as time passes, as will be described in detail later. generates a potential that drops as the voltage increases.

The ultrasonic waves emitted from the transmitter 7 are reflected by the ground, the support frame 6 of the weed trimmer 5, and other parts of the reaping device 1, and enter the receiver 8 as reflected waves. Therefore, the receiver 8 generates a potential corresponding to the sound pressure of the received ultrasonic wave. However, this potential signal is input to a comparator 13 which uses the output of the threshold adjusting means 12 as a reference potential, and is compared there with the reference potential. If the output potential of the receiver is higher than the threshold, the comparator 13 detects The signal is sent to the control calculation section 11. Then, so that only the reflected wave from the ground is emitted as the output of the comparator 13,
A temporal pattern of the output potential of the threshold value adjusting means 12 is set.

The control calculation unit 11 measures the time difference between the input of the timing pulse from the pulse generator 10 and the input of the detection signal from the comparator 13, and adjusts the height of the reaping device 1 from the ground based on this time difference. Detect the The detected height is compared with the set height to generate a signal for adjusting the height of the reaping device 1 above the ground.

This signal then operates the solenoid of the electromagnetic valve 15 provided in the hydraulic system of the hydraulic cylinder 14 that moves the reaping device 1 up and down.

Furthermore, this control device includes the support frame 6.
If the reflected wave is abnormally strong, a means is provided to detect this and turn on the alarm lamp 20. That is, 17 is a one-shot circuit which outputs a high level potential for a certain period of time according to the output pulse of the pulse generator 10, and opens the gate 18 during that period. This predetermined period of time is from when the transmitter 7 emits ultrasonic waves to when the support frame 6
The time required for the reflected wave to enter the receiver 8 is slightly longer than the time required for the reflected wave to enter the receiver 8, and this time is determined theoretically from the distance between the ultrasonic sensor 9 and the support frame 6.

According to this configuration, if a large amount of mud or the like adheres to the support frame 6, the reflected wave becomes abnormally strong, and the detection signal of this reflected wave is transmitted to the comparator 1.
3, this detection signal passes through the AND gate 18 and sets the flip-flop 19, and the output from the flip-flop 19 lights up the alarm lamp 20. On the other hand, the reflected wave from the ground lags behind the reflected wave from the frame, and the gate 18 is closed during that time, so the flip-flop 19 is not set. Incidentally, this flip-flop 19 is configured to be reset by a start signal from a control device or a separately provided switch.

FIG. 3 is a timing chart. a is a timing pulse, and b is an ultrasonic wave transmitted by the transmitter 7. c is a received wave by the receiver 8, and input signals c-1, c-2, and c-3 are a direct wave from the transmitter 7, a reflected wave from the support frame 6, and a reflected wave from the support frame 6, respectively. This is a reflected wave from the ground. Then, when d is the output of the threshold adjusting means 12 and the output of the receiver 8 exceeds this threshold, a detection signal is generated from the comparator 13 only at that time. e indicates the output of the one-shot circuit 17.

As shown in FIG. 2, the threshold value adjusting means 12 includes a capacitor C, a resistor R, and a diode D.
It consists of Since it is normally set so that only c-3 exceeds the threshold, normally only the detection signal of the reflected wave c-3 from the ground is sent to the control calculation section.

Incidentally, although reference numerals are written in the claims section for convenient comparison with the drawings, the present invention is not limited to the structure shown in the accompanying drawings.

[Brief explanation of the drawing]

The drawings illustrate an embodiment of the invention; FIG. 1 is a partially cutaway side view of the front part of the combine, FIG. 2 is a block diagram of the control device, and FIG. 3 is a timing chart. 7... Transmitter, 8... Receiver, 12... Threshold adjustment means.

Claims (1)

[Claims] 1. A ground level detection device for a working section comprising a transmitter 7 that transmits ultrasonic pulses and a receiver 8 that receives the reflected ultrasound waves, wherein the transmission period of the ultrasonic pulses from the transmitter 7 is Set it longer than the time interval from when the ultrasonic pulse is transmitted until it is reflected on the detection target ground and received.
A ground level detection device for a working section, which is provided with a threshold adjusting means 12 on the side of the receiver 8 so as to change the sensing level to become smaller as time elapses from the time when the transmitter 7 emits ultrasonic waves. .