JPH0440223B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a hovercraft that can be used as a practical hovercraft or a toy.

It is often difficult to move and transport objects on cleared roads during search and rescue operations at distress sites during disasters, and for forestry operations in forest areas. It is also often performed on soft ground, wetlands, or on water. In such an environment, normal vehicles cannot drive, so it is necessary to move and work through the air. Many of these tasks do not require flying high into the air, just slightly above the ground.

Furthermore, smaller vehicles are often more suitable for such environments. For example, if we use a helicopter to perform work in a forest area,
Descending from the air to the ground is difficult because of the obstacles of tree branches and leaves. It is possible to fly through the forest while avoiding trees, but the rotor diameter is large and difficult. Therefore, the dimensions of the aircraft body including the rotor (or propeller) must be small.

[Prior Art] Helicopters are often used for the above purposes, but hovercrafts are another possible vehicle. Therefore, problems with hovercraft and helicopters will be clarified, and the effects of the present invention will be clarified.

A conventional hovercraft supports its own weight by maintaining an air cushion (static pressure) with a pressure higher than atmospheric pressure between the aircraft body and the ground surface. Using the terms related to the present invention, it is called a static pressure hovercraft. belong to In principle, it is difficult to float at a high altitude because in order to maintain a high pressure, the amount of air flowing out from the pressure chamber must be small.

However, the propulsion efficiency (support load per power) is better than other aircraft, and when the propulsion efficiency is constant,
The levitation height is proportional to the size of the aircraft. Current large hovercraft have a maximum flying height of about 1 m, and since the ground is uneven in the above application, it is even more difficult for small hydrostatic hovercraft to float. In other words, it is practically unusable on rough terrain.

Next, although a helicopter is a vehicle suitable for the above-mentioned purpose, its large rotor diameter poses an obstacle. Furthermore,
When flying a helicopter close to the ground, it is extremely difficult to maneuver due to the complex aerodynamic effects of the terrain. These characteristics of helicopters are due to the fact that they are not intended to fly close to the ground. That is, if the air density is ρ, the thrust is T, and the rotor radius is R, the propulsion efficiency η when hovering at an altitude where there is no influence from the ground is η=R√2 according to momentum theory. Therefore, when a predetermined thrust is obtained, R
The propulsion efficiency improves as the value increases. Therefore, it is best to slowly rotate a large rotor; for example, even in an unmanned helicopter with a payload of 9.5 kg, the rotor diameter is 1.6 m, and in a 10-seater helicopter, the rotor diameter reaches 9 m. Also, since the rotational speed of the rotor is slow, in the case of a piston engine, the rotational speed is reduced to one-tenth to one-twentieth.
A speed reduction mechanism with more than one stage is required, and its weight cannot be ignored at 50 kg even for a small aircraft.

[Problems to be Solved by the Invention] As described above, it is difficult for conventional hydrostatic hovercrafts and helicopters to operate in narrow places on uneven ground.

This invention was made in view of the above-mentioned circumstances, and is a vehicle that is small and lightweight, can fly at a relatively high altitude near the ground, and can adapt to complex terrain even though it is difficult to fly high in the air. is necessary,
The present invention addresses this need.

[Means for Solving the Problems] The present invention is similar to a helicopter in that thrust is obtained by rotating a propeller around a substantially vertical axis, but changes in aerodynamic characteristics due to the ground (hereinafter referred to as ground effect) and engine characteristics With this in mind, the aim is to achieve greater terrain adaptability by making it smaller and lighter, making it possible to attach multiple propellers.

[Operation] The propeller rotates around a nearly vertical axis to obtain thrust and float.

[Example] Hereinafter, details of the present invention will be explained with reference to drawings showing an example.

In FIGS. 1 and 2, 100 is a hydrodynamic hovercraft. Reference numeral 1 denotes a bumper, which has an annular shape around the center of gravity of the aircraft and encloses the propeller.
0 to prevent the propeller 5 from coming into contact with obstacles. 2 is a frame, which corresponds to the aircraft body. 3 is a power source such as a battery mounted on the frame 2. As shown in Figure 1, frame 2
has an intersection at the center of gravity of the aircraft. The intersection is not an open ceiling in the vertical direction, but forms a part closed to the airflow that blocks the vertical airflow.
The wake of the propeller 5 bounces off the ground and generates an upward airflow, and this closed part functions to block the upward airflow and convert it into lift (thrust). The power source 3 is fixed to this closed part. 4 is a rotating device attached below the frame 2, 5 is a propeller having blade elements with a large blade width ratio (chord length/diameter), and in order to obtain terrain adaptability, the shape is shaped with the apex at the propeller installation position. Four of them are attached at positions whose centers are parallel to and coincide with the center of gravity. Reference numeral 6 denotes a deflection plate for adjusting the position and direction by receiving the airflow from the propeller, and is attached to the frame 2. 7 is the rotation axis of the deflection plate. 8 is an arrow indicating the rotation direction of the propeller,
9 is the ground. The fuselage has a structure that does not obstruct the airflow of the propeller. 10 is a power device that drives the rotating device 4.

However, although the power source 3 is located at the center of the fuselage in the figure, it may not be located at the center of the fuselage as long as the center of gravity of the aircraft coincides with the center of the thrust generated by the propeller. For example, if the power source 3 is a fuel tank of an engine, it may be around the fuselage.

Further, the rotational direction of the propeller 5 does not necessarily have to be the direction shown in the figure, as long as the moments around the vertical axis can be balanced by the control mechanism. Further, although the case where there are four propellers 5 is shown, any number may be used.

Further, the position of the power device 10 (engine, motor, etc.) may be the position of the rotating device 4, or may be the center of the aircraft body. When the power device 10 is placed in the position of the rotating device 4, the rotating device 4 can also be considered as a speed reduction mechanism, and
When the propeller 5 is directly connected to the power plant 10, the power plant 10 also functions as a rotating device. When one power unit 10 is placed at the center of the aircraft body, the rotating device 4 is driven via a belt or the like.

Further, the deflection plate 6 may be installed at a position where the flow velocity of the air flow of the propeller 5 is large, and does not necessarily need to be installed at the position shown in the figure. For example, it may be directly below the propeller 5. However, in this case, the flying height must be greater than the height of the deflection plate 7. In short, the deflection plate 7 serves to generate a horizontal force by inserting it into the air stream. Also, a plurality of deflection plates may be used. However, in order to generate horizontal force on the aircraft body, other attitude control mechanisms may be used in addition to the deflection plate. As such an attitude control mechanism, the technique described in Japanese Patent Publication No. 3-24384 (Patent Application No. 175671 of 1982) can be used.

The basic feature of the present invention is to use a structure that does not impede the air flow of the propeller installed below the fuselage and having a large propeller blade width ratio.

The effects of the present invention will be explained in detail below.

When one propeller rotates near the ground,
It is known that the lift-to-drag ratio (lift/drag) increases. That is, the airflow tube expands rapidly as it approaches the ground, as shown in FIG. In FIG. 3, 11 is a streamline, and 12 is a rotating surface of the propeller 5. Under the condition that the flow rate is constant, if the cross-sectional area of the flow tube increases, the vertical component of the flow velocity decreases. That is, propeller 5
The flow velocity induced by the rotation of is smaller than in the case where there is no ground.

Figure 4 shows the effect of induced velocity on the lift and drag of the wing elements. However, frictional resistance due to air viscosity is not shown. For a blade element located r from the center of rotation, there is a component of horizontal flow velocity rω due to the rotation of the propeller. However, ω is the rotational angular velocity. Furthermore, since there is a component of the induced velocity u, the effective pitch angle for the blade element is obtained by subtracting the angle β formed by u and rω from the attachment pitch angle α of the blade element. It is known that as the effective pitch angle (α-β) increases within a range that does not stall, both lift and drag force increase. Further, when there is an induced speed u, the lift force is inclined with respect to the rotation axis Z as shown by the arrow L, and its horizontal component becomes the induced resistance D and the Z component becomes the thrust force T. Therefore, if u is small, the induced resistance D will decrease and the thrust will increase.

Therefore, overall, if the induced speed u is small, both thrust and drag will increase due to an increase in the effective pitch angle (α-β), but the increase in drag will be smaller by the amount of decrease in induced resistance. . In summary, as the propeller approaches the ground, its effectiveness increases, but so does its lift-drag ratio.

The reason why a rotor with a large diameter is used in a helicopter is that, according to blade theory, the induced speed is generated by the blade tip vortex, so the larger the propeller diameter, the smaller the induced speed. Therefore, the induced speed becomes small near the ground due to the influence of the ground, so even if the propeller diameter is made smaller, the lift-drag ratio will not decrease. In reality, the induced speed does not become 0, so the larger the propeller diameter, the greater the lift-drag ratio.However, by making the propeller diameter smaller, the lift-drag ratio decreases compared to when there is no ground. It will be less. Let S be the area of the wing element at radius r, and let v be the speed.
(=rω), the thrust force T and the drag force D generated by the blade element are expressed by the following equations.

T=(1/2)ρv ² C _T S D=(1/2)ρv ² C _D S However, C _T and C _D are coefficients of thrust and drag, which are determined by the blade shape and pitch angle. The power P required to rotate the blade element is determined by the following equation.

P=vD In this case, the propulsion efficiency η is η=T/P=(C _T /C _D )(1/v) =(C _T /C _D )(1/rω). According to the above discussion, if there is no change in C _T and _CD due to the size of the propeller diameter due to the influence of the ground, the propulsion efficiency η is a function of only v. Therefore, for the propeller shown by the solid line in Figure 5, the radius is reduced by a times, the chord length is increased by 1/a times, and the rotational speed is reduced by 1/
If the speed is increased by a times, the propulsion efficiency remains constant. From the above, a propeller with a large blade width ratio can be used near the ground. Additionally, the propeller should be mounted below the fuselage so as to be close to the ground to create a ground effect, and the fuselage structure should be such that it does not hinder the spread of airflow.

As shown in FIG. 6, the engine characteristics are such that the output reaches its maximum at a certain rotation speed. The rotation speed at maximum output is
It is quite fast at 2000RPM to 20000RPM. Therefore, by rotating a propeller with a small diameter at high speed, there is no need for large decelerations like in a helicopter, and when using a relatively small engine with a maximum output speed, the propeller can be connected directly to the engine. It also becomes possible.

It was idealized that the propulsion efficiency would be constant even with a propeller whose diameter is small due to the ground effect, but in reality it is necessary to maintain a floating height above a certain level, and the induced speed will not become 0 but if the diameter becomes small. Since the propulsion efficiency deteriorates, the reduction in diameter should be kept within an acceptable range in the design. Furthermore, since the chord length is limited by the propeller diameter, there is also a limit to the reduction of the propeller diameter. In reality, the blade width ratio of propeller blades is 0.1~
It is desirable to set it to 0.5.

In addition, by taking advantage of the fact that the guidance and air flow speed increase due to a reduction in the propeller diameter, it is possible to insert a deflection plate to generate a force perpendicular to the plate and use that force to finely adjust the position and direction. . On the other hand, when the propeller diameter is large, the force acting on the deflection plate is so weak that it does not serve the purpose of adjusting the position or direction.

As a result of the hydrodynamic hovercraft of this invention being able to attach multiple propellers, it is possible to attach multiple propellers to provide ground adaptability even to complex terrain, and to adapt to ground effects that vary depending on the terrain. Ground adaptability can be further improved by controlling the thrust of the propellers individually.

A model (body diameter: 30 cm) having a structure similar to that shown in Figures 1 and 2 was fabricated. Number of propellers 4 propeller blade width ratio 0.5, total weight of the aircraft
It floated using Ni-Cd batteries (60g) as a 20Kg power source and motors (20g each) as a power unit. The propeller is directly connected to the motor. Also, it naturally floats when a model engine is used.

[Effects of the Invention] In this way, the hydrodynamic hovercraft of the present invention utilizes airflow from the propeller, uses a propeller with a large blade width ratio, and effectively utilizes the ground effect. It is lightweight, compact, and highly adaptable to terrain, so it can operate on complex terrain such as rough terrain and in narrow spaces.

What is particularly important is that according to the present invention, it is possible to obtain a levitator using a propeller with a small diameter, which was conventionally considered to be disadvantageous based on common sense.

[Brief explanation of the drawing]

Fig. 1 is an explanatory plan view of the hydrodynamic hovercraft of the present invention, Fig. 2 is an explanatory side view of the hydrodynamic hovercraft of the invention, and Fig. 3 is an explanatory diagram showing airflow when the propeller is rotated near the ground. , Figure 4 is an explanatory diagram showing the influence of induced speed on the lift and drag of the blade elements, Figure 5 is an explanatory diagram showing the radial length and circumferential length of the propeller, and Figure 6 is an explanatory diagram showing the engine output and rotation. It is a graph showing the relationship between numbers. DESCRIPTION OF SYMBOLS 1... Bumper, 2... Frame, 3... Power source, 4... Rotating device, 5... Propeller, 6... Deflection plate, 7... Rotation axis of deflection plate, 8... Arrow, 9...
...Ground, 10...Power unit, 11...Streamline, 12
...The rotating surface of the propeller, 100...Dynamic pressure type hovercraft.

Claims (1)

[Claims] 1. The aircraft has a fuselage on a vertical line passing through the center of gravity of the aircraft and has a closed part perpendicular to said vertical line that blocks airflow, and has four or more propellers having blade elements with a blade width ratio of greater than 0.1. At a position where the center of a polygon perpendicular to the vertical line with the mounting position as the apex is on the vertical line, the rotating surface is oriented below the aircraft body in the vertical line direction so that the sum of normal forces is generated in the upward direction of the vertical line. a bumper attached to the fuselage at a position that encloses the propeller, and a deflection plate with a variable deflection angle is attached below the vertical direction on the side of the fuselage; 1. A dynamic pressure type hovercraft, characterized in that it is configured to generate dynamic pressure without restricting the airflow ejected around the body as the body rotates.