JPS58142275A - Ultrasonic object detector - Google Patents

Abstract

PURPOSE:To achieve a small size with reduction in leak waves penetrating into a receiving duct from a transmitting duct by mounting a pair of elements for transmitting and receiving ultrasonic waves on a transmitting duct and a receiving duct which are arranged at such an angle that the center axes thereof expand in the radiating direction of ultrasonic waves. CONSTITUTION:A pair of a transmitting element 2 and a receiving element 3 are provided on a transmitting duct 5 and a receiving duct 6 arranged in a shape of L with an inclined surface 4. The transmitting duct 5 and the receiving duct 6 are fixed in a case 1 at a duct space l and at such an angle theta between the center axis 10 and the center axis 11 thereof that they expand in the radiating direction of ultrasonic waves of the transmitting duct 5. An ultrasonic wave transmitted from the transmitting element 2 is bent to an object to the opening of the transmitting duct 5 in such a radiating distribution of ultrasonic waves as indicated by the transmitting directivity 7. A part of the radiated ultrasonic wave is reflected on a detecting member 9, penetrates into the receiving duct 6 in such a receiving sensitivity distribution of ultrasonic wave as defined by the receiving directivity 8 and reaches the receiving element 3. Thus, the ultrasonic wave can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention detects objects located at nine distant locations using ultrasonic signals, and relates to an ultrasonic object detection device that integrates a transmitting element and a receiving element.

In a conventional object detection device, ultrasonic waves are transmitted from a pair into a case tube, as shown in the plan view in Fig. 1, the front view in Fig. 2, and the side cross-sectional view (A-A section in Fig. 2) in Fig. 5. An ultrasonic transmitting element 2 and an ultrasonic receiving element 5 for receiving the reflected ultrasonic waves are provided at the bottom surface 4 with an inclination, and are provided at the recessed upper part of the L-shaped duct 5 and the duct 6, and further Duct distance between duct 5 and duct 6 fl+f duct 5
The distance was selected such that the ultrasonic radiation distribution of the duct 6, that is, the transmission directivity 7, and the reception sensitivity distribution of the duct 6, that is, the reception directivity 8, did not overlap greatly. In addition, the central axes 10' and H' of the directivity 7.8 of the ducts 5 and 6 toward the sensing object 9 side, or the transmission and reception directions, are in the same direction and parallel to each other. The location was fixed. Therefore, for downsizing, the duct interval between duct 5 and duct 6 is 1/, x'ft.
If they are placed close to each other, the number of overlapping parts 12 between the transmission directivity 7 and the reception directivity 8 will increase, resulting in an ultrasonic signal that directly enters the duct 6 from the duct 5 without being reflected by the detection object 9 located at the detection distance L1, that is, ( (This is generally called a leakage wave) This leakage wave increases, and this
This had the disadvantage that it affected the reflected waves from the object, making it impossible to detect objects and making it impossible to measure distances. For this reason, it is necessary to separate the ducts 111 in order to reduce leakage waves, and the case iris naturally becomes large, which has the disadvantage of limiting miniaturization.

Also, the central axes fo' and if' of the directivity 7 and 8 of transmitting and receiving
The purpose of the present invention is to overcome the above-mentioned drawbacks and to design and manufacture a case that reduces the size of the case while minimizing leakage waves. An object of the present invention is to provide an easy-to-use ultrasonic object detection device.

The gist of the present invention is that a pair of elements for transmitting and receiving ultrasonic waves is attached to both ducts, and that the central axes of the transmitting duct and the receiving duct are angled so as to spread out relative to the ultrasonic radiation direction. .

The device is compact and designed to greatly reduce the leakage waves that enter the receiving duct from the transmitting duct.

This makes manufacturing easier.

Next, an embodiment of the present invention will be explained using 4th WJ to 8th WJ. No. Figure, Figure 5 1...1. Figure 6.

is a case, a transmitting element that emits 2Fi ultrasonic waves, 5 a receiving element that receives reflected ultrasonic waves, 4 an inclined surface of an L-shaped duct, 5 a transmitting duct, 6 a receiving duct, and 7 a transmitting duct. Ultrasonic radiation distribution of the duct 5, that is, transmission directivity,
8Fi reception ultrasonic reception sensitivity distribution of duct 6, i.e. reception directivity, 9 is the detection object, IQ is the central axis of duct 5,
11 is the center axis of the duct 6, and the duct spacing between the transmitting duct 5 and the receiving duct 6 is ft.
, *detection distance to the known object 9, θ is the angle between the central axis 10 of the duct 5 and the central axis 11 of the duct 6.

That is, a pair of transmitting element 2 and receiving element 5 are provided in the recessed upper part of the L-shaped transmitting duct 5 and receiving duct 6 having an inclined II+ surface 4.

The transmitting duct 5 and the receiving duct have a distance l, and an angle θ between the force λ and its central axis 1o and its central axis 11.
It has an angle such that it spreads out along the ultrasonic radiation direction of the transmission duct 5, and is fixed in the case 1 with a radius. To detect an object, the ultrasonic wave is transmitted from the transmitting element 2, bent by the inclined surface 4 toward the opening of the transmitting duct 5, and radiated toward the object. The ultrasonic radiation distribution becomes as shown in the transmission directivity 7 of I. A part of the ultrasonic waves irradiated to the object 1 is reflected by the sensing object 9. The reflected ultrasonic wave enters the receiving duct 6 having an ultrasonic receiving sensitivity distribution as shown in the receiving directivity 8 in Fig. 4, reaches the receiving element 6 via the inclined surface 4t-, and detects the ultrasonic wave. . The distance to the sensing object 9 is measured based on the propagation speed of the ultrasonic wave, and the ultrasonic wave is modulated with pulses of a certain period and transmitted, and the sensing object 9 is measured at a certain distance away.
The modulated pulse that is reflected back is received and the delay time is measured.

Displaying Distance・Here, the positional relationship between the transmitting duct 5 and the receiving duct 6 is selected to satisfy the following conditions.

That is, the transmitting directivity 7 of the transmitting duct 5 in FIG. 4 indicates an ultrasonic radiation distribution with a constant intensity, and similarly, the receiving directivity 8 of the receiving duct 6 indicates an ultrasonic receiving sensitivity distribution with a constant intensity. It shows. Therefore, if the ultrasonic intensity differs, the transmission directivity 7 and the reception directivity 8 will exhibit different distributions,
Naturally, there is also a small amount of ultrasonic radiation from the transmitting duct 5 toward the receiving duct 6. In addition, in Fig. 4h, the detection distance to the detection object 9 and the duct interval 2 are depicted as not being much different, but in reality, the duct interval β is extremely small compared to the detection distance. For example, L is 2. ODO
There is a large difference between ~3,000wm and 20~50w1. Therefore, from transmitting duct 5 to receiving duct 6
Even if the ultrasonic signal component that does not reflect to the sensing object 9 and directly enters the receiving duct 6, that is, the leakage wave is small, the ultrasonic signal component reflected by the sensing object 9 that is received by the receiving duct 6 This leakage wave must be kept below a certain value because it easily affects the sound wave signal and may prevent distance measurement. It also needs to be easy to design and construct. For this reason, as a means of facilitating design and manufacturing without reducing the object detection ability or increasing the size of the case, and keeping the leakage waves below a certain value, it is necessary to The opposing positions of the central axes 11 are set at an angle θ, which means that the central axes of the transmitting directivity 7 and the receiving directivity 8 are substantially aligned with the central axis fQ of both ducts 5 and 6. This was done with a focus on the fact that they match.
The results shown in FIGS. 7 and 8 were obtained for nine fixed-shaped sending and receiving ducts subjected to experiments. According to Figure 7,
When the angle θ=09, that is, when the central axis 10 of the duct 5 and the central axis 11 of the duct 6 are parallel to the ultrasonic radiation direction, the leakage voltage is the standard at θ=10°. It will be about half of the value.

At θ=20°, it decreases to one-fifth. On the other hand, in Fig. 8, when the angle θ=0° is used as a reference, θ=1
When θ is 0°, there is no significant difference from θ=0°, and even when θ=20″, there is no significant decrease in object detection ability. However, when the angle θ
If is set too large, the leakage voltage becomes extremely small (Fig. 7), but at the same time the object detection ability decreases significantly (Fig. 8). Therefore, the value of angle θ is 06 or more and 506 by taking into account the two dimensions, object detection ability, leakage voltage, etc.
It is selected as appropriate within the following range.

Note that even if the above conditions are taken into account, the value of the angle θ is at most 90° or less due to the nature of ultrasonic waves.

As described above, according to the present invention, 1. This reduces leakage voltage without increasing the duct spacing.

It is possible to provide an ultrasonic object detection device that is small in size, has high detection ability, and is easy to design and manufacture, especially since an angle is formed between the center axes of both ducts.

[Brief explanation of drawings]

1, 7 and 5 are a plan view and a side view of a conventional ultrasonic object detection device, and a sectional view taken along line A-A in FIG. FIG. 4 is an open plan view, front view, and QB-B sectional view of an embodiment of the invention, FIG. 7 is a characteristic diagram showing the relationship between the angle and leakage voltage, and FIG. 8 is the angle and object detection ability. FIG. 2... Transmission element. 6...Receiving element. 5...Duct. 6...Duct. 7...Transmission directivity. 8... Reception directivity. 9...Detected object. 10... Central axis of duct 5. 11... Central axis of duct 6. 2...Duct spacing. θ...Angle. L...Detection distance. Applicant: Hitachi Thermal Appliances Co., Ltd. Figure 1

Claims (1)

[Claims] In an ultrasonic object detection device that integrates a transmitting element and a receiving element, an ultrasonic transmitting element (2) and an ultrasonic receiving element (
3] to each of the ducts) (5) and C6), and the central axis (112) of each of those ducts (112) #
(11) at an angle (
An ultrasonic object detection device characterized by having θ].