JPH07318647A - Ultrasonic ground vehicle speed sensor and ultrasonic oscillator - Google Patents

Abstract

PURPOSE:To enhance the detection accuracy of an ultrasonic ground vehicle speed sensor and the transmission performance of an ultrasonic transmitter by reducing the adverse effect of side lobe on the detection accuracy. CONSTITUTION:An ultrasonic transmitter 30 transmits an ultrasonic wave of predetermined frequency toward a pavement and receives a reflected wave in order to determine a vehicle speed based on a Doppler frequency. the ultrasonic transmitter 30 comprises an oscillator 34 oscillating at a predetermined frequency, an acoustic matching unit 36 bonded to the oscillator in order to transmit the oscillation thereof into the air, and a casing 42 bonded to the acoustic matching unit around the oscillator and supporting the acoustic matching unit. Rigidity of the acoustic matching unit 36 is set lower on the pavement side with respect to the oscillator than on the opposite side through a groove 46, for example.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle speed sensor used in a vehicle such as an automobile, and more particularly to an ultrasonic ground vehicle speed sensor and an ultrasonic transmitter.

[0002]

2. Description of the Related Art As one of vehicle speed sensors for detecting a vehicle speed of a vehicle such as an automobile, a pulsed ultrasonic wave having a predetermined frequency is generated by an ultrasonic wave generator as described in, for example, Japanese Patent Laid-Open No. 4-328482. Send diagonally downward to the road surface,
An ultrasonic vehicle speed sensor configured to receive the reflected wave from the road surface by a receiver and obtain the ground vehicle speed from the magnitude of the difference between the Doppler frequency, that is, the difference between the transmission frequency and the reception frequency caused by the Doppler effect, is more conventional than before. Are known.

According to such an ultrasonic type vehicle speed sensor, ultrasonic waves are transmitted to the road surface and reflected waves from the road surface are received, and the Doppler frequency increases in proportion to the relative speed of the vehicle to the traveling path. Since the vehicle speed is detected by means of, for example, the speed between the wheels and the road surface, as compared to the case of a general vehicle speed sensor that detects the vehicle speed by electromagnetically or optically detecting the rotation speed of the gear of the transmission. Even when slippage occurs in the vehicle, the ground vehicle speed of the vehicle can be accurately detected.

[0004]

However, for example, as shown in FIG. 14, in the ultrasonic wave 102 transmitted by the ultrasonic wave transmitter 100 in the ultrasonic type ground vehicle speed sensor,
In addition to the main lobe 106 that propagates substantially in alignment with the axis 104 of the ultrasonic transmitter, a plurality of side lobes 108 that propagate in a direction inclined with respect to the axis 104 are included, and the sound pressure level of the side lobes is Although lower than that of the main lobe, the side lobe is also reflected by the road surface 110 and received by the receiver of the vehicle speed sensor depending on the mounting position and mounting angle of the vehicle speed sensor. Has a problem that the ground vehicle speed may not be accurately detected.

The present invention has been made in view of the above-described problems in the conventional ultrasonic type ground vehicle speed sensor and the ultrasonic wave transmitter thereof, and the main problem of the present invention is that the side lobe is the vehicle speed sensor. Focusing on the adverse effect on the vehicle speed detection accuracy, the side lobe is prevented from being reflected by the road surface or the sound pressure level of the side lobe is reduced to reduce the adverse effect of the side lobe on the vehicle speed detection accuracy. It is to improve the vehicle speed detection accuracy of the ultrasonic ground vehicle speed sensor and the transmission performance of the ultrasonic transmitter.

[0006]

According to the present invention, the main problem as described above is to transmit an ultrasonic wave of a predetermined frequency to a road surface by an ultrasonic wave transmitter and receive a reflected wave from the road surface to receive the Doppler wave. In an ultrasonic ground vehicle speed sensor for determining a vehicle speed from a frequency, a baffle plate which is arranged below the ultrasonic transmitter and prevents side lobes of ultrasonic waves transmitted by the ultrasonic transmitter from colliding with a road surface. An ultrasonic ground vehicle speed sensor characterized in that it has a member (construction of claim 1), an ultrasonic wave transmitter transmits an ultrasonic wave of a predetermined frequency to a road surface, and receives a reflected wave from the road surface. In an ultrasonic type ground vehicle speed sensor for obtaining a vehicle speed from a Doppler frequency, the ultrasonic transmitter transmits a vibration of the vibrating body that is vibrated at a predetermined frequency and the vibrating body to the air. Acoustic matching body, before A casing joined to and supporting the acoustic matching body around the vibrating body is provided, and the rigidity of the acoustic matching body at a portion on the road surface side with respect to the vibrating body is higher than that at a portion on the other side. Is set to a low value, the ultrasonic type ground vehicle speed sensor (configuration of claim 2), a vibrating body vibrating at a predetermined frequency, and vibration of the vibrating body joined to the vibrating body to the air. In an ultrasonic transmitter having an acoustic matching body for transmitting and a casing joined to and supporting the acoustic matching body around the vibrating body, in an area on a specific side of the vibrating body. This is achieved by an ultrasonic transmitter (configuration according to claim 3) characterized in that the rigidity of the acoustic matching body is set to be lower than that of the portion on the other side.

[0007]

According to the above-mentioned structure of the present invention, the baffle plate member for preventing the side lobes of the ultrasonic waves transmitted from the ultrasonic transmitter from colliding with the road surface is arranged below the ultrasonic transmitter. Therefore, the side lobes transmitted by the ultrasonic transmitter collide with the road surface and the reflected waves are reliably prevented from being received by the receiver, so the side lobes with a relatively high sound pressure level are transmitted by the transmitter. Even in such a case, the side lobe can surely be prevented from adversely affecting the vehicle speed detection accuracy of the vehicle speed sensor.

Further, according to the result of an experimental study conducted by the inventor of the present application, a vibration body such as a piezoelectric element in which an ultrasonic oscillator vibrates at a predetermined frequency, and vibration of the vibration body joined to the vibration body Rigidity of the acoustic matching body at a site on a specific side with respect to the vibrating body in the case where the acoustic matching body transmitting to the vibrating body and the casing joined to and supporting the acoustic matching body around the vibrating body are provided. Is set lower than the parts on the other side, the sound pressure of the side lobe on the specific side is different because the vibration characteristics of the acoustic matching body on the part on the specific side are different from those of the other parts. It was confirmed that the sound pressure level of the main lobe increased as the level decreased.

According to the above-mentioned structure of the second aspect, the rigidity of the acoustic matching body at the portion on the road surface side with respect to the vibrating body is set lower than that at the portion on the other side. The sound pressure level of the side lobe transmitted toward the road surface is reduced and the sound pressure level of the main lobe is increased,
Even if the side lobe is reflected by the road surface, its sound pressure level becomes much lower than the level of the reflected wave of the main lobe, which substantially eliminates the adverse effect of the side lobe on the detection accuracy of the vehicle speed sensor.

Further, according to the third aspect of the invention, the rigidity of the acoustic matching body at a site on a specific side of the vibrating body is set lower than that at the site on the other side. The sound pressure level of the side lobe transmitted toward a more specific side is reduced and the sound pressure level of the main lobe is increased, which improves the ultrasonic transmission performance of the ultrasonic transmitter. Therefore, when an ultrasonic wave transmitter is used as an ultrasonic wave transmitter for an ultrasonic ground speed sensor and a specific side is aligned with the road surface side, even if the side lobe is reflected by the road surface, the sound pressure level of the side lobe is reflected by the main lobe. Much lower than the wave level, which substantially eliminates the adverse effects of sidelobes on the detection accuracy of the vehicle speed sensor.

[0011]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

1 to 3 are a plan view, a front view and a side view, respectively, showing a first embodiment of an ultrasonic type ground speed sensor according to the present invention as viewed from above, rear and side of a vehicle. FIG. 4 is an enlarged side view showing the first embodiment shown in FIGS. 1 to 3.

In these figures, reference numeral 10 denotes the body of the ground vehicle speed sensor, that is, the ultrasonic transmitter and receiver.
Reference numeral 2 denotes a baffle plate member. Ground speed sensor body 1
Although not shown in detail in the drawing, 0 is fixed to the lower surface of the vehicle body 16 near the rear end of the vehicle 14 by a mounting bracket. The axis 18 of the main body 10 extends so as to be inclined rearward of the vehicle with respect to the vertical direction, whereby the ultrasonic transmitter of the ground vehicle speed sensor is provided with an ultrasonic wave 22 (main wave) having a predetermined frequency with respect to the road surface 20 along the axis 18. The receiver receives the reflected wave 24 from the road surface, the Doppler frequency is calculated by an arithmetic control unit (not shown), and the vehicle speed is obtained from the Doppler frequency.

On the other hand, the baffle member 12 is arranged below the transmitting and receiving surface 10A of the body 10 of the ground vehicle speed sensor, and is attached to the lower surface of the vehicle body 16 in front of the body 10 of the ground vehicle speed sensor. It is supported by. The baffle plate member 12 in this embodiment has a rectangular plate shape inclined toward the rear of the vehicle at an angle of substantially 45 ° with respect to the road surface 20, and its upper surface is made of an ultrasonic wave such as glass or aluminum alloy. It is made of a material that has excellent reflection performance, is lightweight, and is not easily scratched by flying stones.

The baffle member 12 prevents the side lobe from colliding with the road surface by surely reflecting the side lobe 28 transmitted substantially vertically downward from the ultrasonic transmitter to the rear of the vehicle. As shown in FIG. 1, the main body 10 of the ground speed sensor when viewed from above the vehicle.
Has a dimension in the front-back direction and in the lateral direction larger than that of the transmitting and receiving surface 10A. The pair of left and right arm portions of the mounting stay 26 are spaced apart from each other in the lateral direction of the vehicle by a dimension substantially equal to the entire width of the baffle plate member 12 so that the side lobes do not reflect specularly to the receiver. There is.

FIGS. 5 and 6 are a side view (A) and a plan view (B) showing a second and a third embodiments of the ultrasonic type ground vehicle speed sensor according to the present invention, respectively. 5 and 6, parts corresponding to the parts shown in FIG. 4 are denoted by the same reference numerals as those given in FIG.

In the second embodiment shown in FIG. 5, the baffle member 12 radially reflects the side lobes 28 emitted substantially vertically downward from the ultrasonic transmitter in a substantially horizontal direction. To prevent the side lobes from colliding with the road surface by making the bus bar substantially 45 ° with respect to the road surface 20.
It has a substantially conical shape that inclines at an angle of .alpha., And the upper surface of the baffle plate member is made of a material such as an aluminum alloy that has excellent ultrasonic wave reflection performance, is lightweight, and is not easily damaged by flying stones.

Further, in the third embodiment shown in FIG. 6, the baffle plate member 12 extends substantially horizontally, and the transmission and reception of the main body 10 of the ground speed sensor when viewed from above the vehicle. It has front-rear and lateral dimensions that are larger than the surface 10A. The upper surface of the baffle plate member is made of an ultrasonic absorbing material such as polyethylene foam material or filled urethane foam material,
The surface of the ultrasonic absorbing material is rough, so that the baffle member absorbs the side lobe transmitted substantially vertically downward from the ultrasonic transmitter, thereby preventing the side lobe from colliding with the road surface. It is supposed to do.

Thus, according to the above-mentioned first to third embodiments, the side lobes 28 emitted by the ultrasonic transmitter of the main body 10 collide with the road surface 20 and the reflected wave 2 by the road surface 2 is generated.
4 is surely blocked by the baffle plate member 12 from being received by the receiver, and the side lobes are not reflected toward the receiver by the baffle plate member, so that the transmitter causes the sound pressure level to be relatively high. Even when a high side lobe is transmitted, it is possible to reliably prevent the vehicle speed detection accuracy of the vehicle speed sensor from being adversely affected by the side lobe.

Particularly according to the first embodiment, the baffle plate member 1
2 is disposed in front of the main lobe 22 and the propagation path of the reflected wave 24, and is substantially 45 with respect to the road surface 20.
Since it has a plate shape that is inclined toward the rear of the vehicle at an angle of °, it captures the splash that is wound up by the wheels when running in the rain, etc., so that the propagation path of the main lobe 22 and the reflected wave 24 can be captured. It is also possible to effectively prevent a decrease in vehicle speed measurement accuracy due to the splash entering at a high density.

Further, according to the third embodiment, the side lobes are absorbed by the baffle member instead of being reflected, so that the reflected side lobes adversely affect the ultrasonic devices of other vehicles. Can be reliably prevented. Since the ultrasonic waves are relatively easily attenuated, the side lobes reflected by the baffle plate hinder the normal operation of the ultrasonic devices of other vehicles in the first and second embodiments. There is no adverse effect on.

Further, in the above-mentioned first to third embodiments, the ultrasonic transmitter tilts rearward of the vehicle and transmits the ultrasonic wave downward, but the ultrasonic wave forwards the vehicle. The baffle plate member 12 may be inclined and transmitted downward, and in that case, the baffle plate member 12 is supported by a mounting stay 26 fixed to the vehicle body at the rear of the vehicle with respect to the ultrasonic transmitter, particularly in the first embodiment. Is provided in a state of being inclined toward the front of the vehicle.

The ultrasonic transmitters in the first to third embodiments may have any known or publicly known structure, but in the structures of the fourth to eighth embodiments described below. According to this, since the sound pressure level of the side lobe in the direction toward the road surface is lower than that of the conventional structure, the ultrasonic transmitters of the first to third embodiments have the fourth to eighth embodiments. Preferably, an ultrasonic transmitter of

FIGS. 7 to 9 are front views (A) and longitudinal sectional views (B) showing the ultrasonic transmitters of the fourth to sixth embodiments of the ultrasonic ground vehicle speed sensor according to the present invention, respectively. FIG. 9 is an explanatory diagram showing a sound pressure distribution of ultrasonic waves transmitted by the ultrasonic transmitter of the fourth embodiment, in comparison with a case of a conventional ultrasonic transmitter. In these drawings, parts corresponding to each other are designated by the same reference numerals, and the lower side of the axis of the vehicle speed sensor is the road surface side.

In the fourth embodiment shown in FIG. 7, the ultrasonic transmitter 30 includes a substantially disk-shaped vibrating body 34 aligned with its axis 32 and joined to each other. Also has a substantially disk-shaped acoustic matching member 36 having a large diameter. The vibrating body 34 is made of a material such as a piezoelectric element, and when a pulsed control voltage is applied via a pair of lead wires 38 and 40, it vibrates substantially along the axis 32 at a predetermined frequency. There is. The acoustic matching body 36 is made of a material having excellent vibration characteristics, such as an epoxy resin in which minute hollow glass spheres are dispersed, and transmits the vibration of the vibration body to the air.

On the inner surface 36A of the acoustic matching body 36, one end of a substantially cylindrical casing 42 is provided around the vibrating body at a position spaced radially outward from the vibrating body by an adhesive such as an epoxy resin adhesive. It is joined. The casing 42 is made of a metal such as an aluminum alloy, and is used as the acoustic matching body 3.
6 has an outer diameter substantially the same as the diameter of 6, and the other end is closed by a disc-shaped lid member 44 made of an ultrasonic absorbing material. The axis 3 is formed on the outer surface 36B of the acoustic matching body 36.
2, a groove 46 having a V-shaped cross section is provided which is aligned with the inner wall surface of the casing 42 on the lower side with respect to 2, and extends in an arc shape over an angle range of substantially 90 °. 36, the rigidity of the portion on the road surface side with respect to the vibrating body 34 is reduced as compared to the other portions.

Further, in the fifth embodiment shown in FIG. 8, the outer edge of the outer surface 36B of the acoustic matching member 36 extends over an angle range of substantially 90 ° below the axis 32. A chamfer 48 that is inclined at 45 ° with respect to the outer surface 36B is provided, and in the sixth embodiment shown in FIG. 9, the outer edge of the outer surface 36B of the acoustic matching body 36 is aligned with the axis 32. On the lower side, there is provided a step portion 50 extending over an angle range of substantially 90 °, whereby the acoustic matching body 36 of these embodiments is provided on the road surface side with respect to the vibrating body 34. Rigidity is reduced compared to other parts.

Thus, according to these embodiments, the rigidity of the acoustic matching body 36 at the portion on the road surface side with respect to the vibrating body 34 is set to be lower than that at the other portions, and therefore, for example, the fourth embodiment. As shown in FIG. 10, the main lobe 22 transmitted from the acoustic matching body 36 along the axis 32.
The sound pressure level of the side lobe 28 is reduced and the sound pressure level of the side lobe 28 is reduced. As a result, the ultrasonic wave transmission performance of the ultrasonic wave transmitter is improved. This is much lower than the level of the reflected wave of the lobe, and the vehicle speed sensor can detect the ground vehicle speed more accurately than before.

In the illustrated fourth to sixth embodiments,
The groove 46, the chamfered portion 48, and the stepped portion 50 are provided around the axis 32 over an angle range of substantially 90 °. The angle range in which these are provided depends on the situation in which the ultrasonic transmitter is used. For example, it may be an arbitrary angle range of 10 to 90 °. Also, in the illustrated fourth to sixth embodiments,
In the acoustic matching body 36, the rigidity of the portion on the road surface side with respect to the vibrating body 34 is reduced as compared with the other portions due to the groove 46 having a specific cross-sectional shape, but with respect to the vibrating body 34 of the acoustic matching body 36. As long as the rigidity of the part on a specific side can be set lower than that of the other part, the means, that is, the groove 46, the chamfered part 4 is used.
8. The cross-sectional shape of the step portion 50 may be any shape,
Further, the groove, the chamfered portion, and the stepped portion may be provided in any combination.

11 and 12 are a front view (A) and a longitudinal sectional view (B) showing the seventh and eighth embodiments of the ultrasonic type ground vehicle speed sensor according to the present invention, and FIG. 13 is the seventh embodiment. It is explanatory drawing which shows the sound pressure distribution in an example compared with the case of the conventional ultrasonic type ground vehicle speed sensor. In these figures, the parts corresponding to the parts shown in FIGS. 7 and 11 are denoted by the same reference numerals as those given in these figures.

In the seventh embodiment shown in FIG. 11,
Although the acoustic matching body 36 does not have the groove 46 or the like, one end of the casing 42 is provided with a cutout portion 52 that extends over an angle range of substantially 90 ° on the lower side with respect to the axis 32. In this region, the casing is not joined to the acoustic matching body, so that the acoustic matching body 36 has a supporting rigidity by the casing in a portion on the road surface side with respect to the vibrating body 34 as compared with other portions. Have been reduced.

Also in the eighth embodiment shown in FIG. 12, the acoustic matching member 36 does not have the groove 46 and the like, and one end of the casing 42 is located below the axis 32. The cutout portion 52 extending substantially over an angle range of 90 ° is provided, but the cutout portion 52 is filled with an ultrasonic wave absorbing material 54 such as rubber or resin, and in this region, The casing is joined to the acoustic matching body via the ultrasonic absorbing material 54, whereby the acoustic matching body 36 has a supporting rigidity by the casing in a portion on the road surface side with respect to the vibrating body 34 as compared with other portions. Have been reduced.

Thus, according to these embodiments, the acoustic matching body 36 is set to have a lower supporting rigidity in the portion on the road surface side with respect to the vibrating body 34 than in the other portions, and therefore, for example, the seventh embodiment. As shown in FIG. 13 for the embodiment of
As in the case of the fourth to sixth embodiments, the sound pressure level of the main lobe 22 transmitted along the axis 32 from the acoustic matching body 36 is increased and the sound pressure level of the side lobe 28 is reduced, which results in The ultrasonic wave transmission performance of the ultrasonic wave transmitter is improved, and even if the side lobe is reflected by the road surface, the sound pressure level is much lower than the level of the reflected wave of the main lobe. Vehicle speed detection accuracy is improved.

In particular, according to the eighth embodiment, since the inside of the ultrasonic transmitter 30 is maintained in a completely sealed state as in the fourth to sixth embodiments, the seventh embodiment is as follows. As compared with the above case, it is possible to effectively reduce the possibility that the vehicle speed sensor may malfunction due to the intrusion of dust or muddy water into the ultrasonic transmitter.

In the illustrated seventh and eighth embodiments,
The cutout portion 52 or the ultrasonic wave absorbing material 54 is provided around the axis 32 over an angular range of substantially 90 °, but the angular range in which these are provided depends on the situation in which the ultrasonic transmitter is used. For example, it may be an arbitrary angle range of 10 to 90 °. Further, the structure of the seventh or eighth embodiment and any one of the above-mentioned fourth to sixth embodiments may be combined.

Further, in the seventh and eighth embodiments, the notch 52 is provided at one end of the casing 42,
The notch may be provided on the inner surface 36A of the acoustic matching body 36, and setting the supporting rigidity of the acoustic matching body 36 on the road surface side with respect to the vibrating body 34 to be low is a predetermined area on this side. May be achieved by not applying an adhesive between the acoustic matching body and one end of the casing.

Although the present invention has been described above in detail with reference to specific embodiments, the present invention is not limited to these embodiments, and various other embodiments within the scope of the present invention. It will be apparent to those skilled in the art that

For example, in each of the above embodiments, the ultrasonic transmitter and the receiver are functionally independent from each other, but in at least the first to third embodiments, the body of the vehicle speed sensor is The ultrasound transmitter may be configured to also perform the function of a receiver.

[0039]

As is apparent from the above description, according to the structure of the first aspect of the present invention, the side lobe transmitted by the ultrasonic transmitter collides with the road surface and the reflected wave is received by the receiver. Since the baffle plate member prevents the side lobe with a relatively high sound pressure level from being transmitted by the transmitter, the side lobe may adversely affect the vehicle speed detection accuracy of the vehicle speed sensor. This is surely prevented, and thereby the vehicle speed detection accuracy of the vehicle speed sensor can be improved.

According to the second aspect of the invention, the sound pressure level of the side lobe transmitted from the acoustic matching member toward the road surface is reduced and the sound pressure level of the main lobe is increased, so that the side lobe is caused by the road surface. Even if reflected, the sound pressure level becomes much lower than the level of the reflected wave of the main lobe, so the adverse effect of the side lobe on the detection accuracy of the vehicle speed sensor is virtually eliminated, and the vehicle speed detection accuracy of the vehicle speed sensor is improved. Can be improved.

According to the third aspect of the invention, the sound pressure level of the side lobe transmitted toward the specific side from the acoustic matching body is reduced and the sound pressure level of the main lobe is increased. Since the ultrasonic wave transmission performance of the ultrasonic wave transmitter is improved by the ultrasonic wave transmitter, it is used as an ultrasonic wave oscillator for an ultrasonic ground vehicle speed sensor, and when a specific side is fitted to the side of the road surface, a side lobe is detected. Even if the vehicle is reflected by the road surface, its sound pressure level becomes much lower than the level of the reflected wave of the main lobe, and therefore the adverse effect of the side lobe on the detection accuracy of the vehicle speed sensor is substantially eliminated, and the vehicle speed of the vehicle speed sensor is thereby eliminated. The detection accuracy can be improved.

[Brief description of drawings]

FIG. 1 is a front view showing a first embodiment of an ultrasonic ground vehicle speed sensor according to the present invention as viewed from the rear of a vehicle.

FIG. 2 is a front view showing the first embodiment as viewed from the rear of the vehicle.

FIG. 3 is a side view showing the first embodiment as viewed from the side of the vehicle.

FIG. 4 is an enlarged side view showing the first embodiment shown in FIGS. 1 to 3.

FIG. 5 is a side view (A) and a plan view (B) showing a second embodiment of an ultrasonic ground vehicle speed sensor according to the present invention.

FIG. 6 is a side view (A) and a plan view (B) showing a third embodiment of an ultrasonic ground vehicle speed sensor according to the present invention.

FIG. 7 is a front view (A) and a longitudinal sectional view (B) showing an ultrasonic transmitter of a fourth embodiment of an ultrasonic ground vehicle speed sensor according to the present invention.

FIG. 8 is a front view (A) and a vertical sectional view (B) showing an ultrasonic transmitter of a fifth embodiment of an ultrasonic ground vehicle speed sensor according to the present invention.

FIG. 9 is a front view (A) and a longitudinal sectional view (B) showing an ultrasonic transmitter of a sixth embodiment of an ultrasonic vehicle-to-ground vehicle speed sensor according to the present invention.

FIG. 10 is an explanatory diagram showing the sound pressure distribution of ultrasonic waves transmitted by the ultrasonic transmitter of the fourth embodiment, in comparison with the case of a conventional ultrasonic transmitter.

FIG. 11 is a front view (A) and a vertical sectional view (B) showing an ultrasonic transmitter of a seventh embodiment of an ultrasonic ground vehicle speed sensor according to the present invention.

FIG. 12 is a front view (A) and a vertical sectional view (B) showing an ultrasonic transmitter of an eighth embodiment of an ultrasonic ground vehicle speed sensor according to the present invention.

FIG. 13 is an explanatory diagram showing the sound pressure distribution of ultrasonic waves transmitted by the ultrasonic transmitter of the seventh embodiment, in comparison with the case of a conventional ultrasonic transmitter.

FIG. 14 is an explanatory diagram showing main lobes and side lobes of ultrasonic waves transmitted by a conventional ultrasonic transmitter.

[Explanation of symbols]

 10 ... Main body of ground speed sensor 12 ... Baffle plate member 20 ... Road surface 22 ... Ultrasonic wave (main lobe) 24 ... Reflected wave from road surface 30 ... Ultrasonic transmitter 34 ... Vibrating body 36 ... Acoustic matching body 42 ... Casing 46 ... Groove 48 ... Chamfer 50 ... Step 52 ... Notch

Claims (3)

[Claims] 1. An ultrasonic-type vehicle-to-ground speed sensor which transmits an ultrasonic wave of a predetermined frequency to a road surface by an ultrasonic wave transmitter and receives a reflected wave from the road surface to obtain a vehicle speed from a Doppler frequency. An ultrasonic ground vehicle speed sensor having a baffle member arranged below the transmitter to prevent side lobes of ultrasonic waves transmitted from the ultrasonic transmitter from colliding with a road surface. 2. An ultrasonic type vehicle-to-ground speed sensor which transmits an ultrasonic wave of a predetermined frequency to a road surface by an ultrasonic wave transmitter and receives a reflected wave from the road surface to obtain a vehicle speed from a Doppler frequency. The oscillator includes a vibrating body that vibrates at a predetermined frequency, an acoustic matching body that is joined to the vibrating body and transmits the vibration of the vibrating body to the air, and is joined to the acoustic matching body around the vibrating body. And a casing for supporting
An ultrasonic vehicle-to-ground speed sensor, characterized in that the rigidity of the acoustic matching body at a portion on the road surface side of the vibrating body is set to be lower than that at a portion on the other side. 3. A vibrating body that vibrates at a predetermined frequency, an acoustic matching body that is joined to the vibrating body and transmits the vibration of the vibrating body to the air, and is joined to the acoustic matching body around the vibrating body. In the ultrasonic transmitter having a casing that supports the acoustic matching body, the rigidity of the acoustic matching body at a site on a specific side with respect to the vibrating body is set to be lower than that at a site on the other side. An ultrasonic transmitter characterized by being present.