JPH0418591B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an Atskermann-Giant mechanism that is a steering mechanism for a vehicle that changes the direction of travel using steering wheels. The term "vehicle" as used herein refers to a vehicle with opposite steering wheels on its body, such as a vehicle with front two-wheel steering such as a general automobile, a vehicle with rear two-wheel steering such as a forklift truck, and a self-propelled cart with front and rear wheel steering. Refers to any vehicle that changes its direction of travel by steering its steering wheels. [Prior Art] As is well known, when turning a vehicle as described above, it is necessary to create different steering angles for the left and right steering wheels so that the turning centers of the left and right steering wheels coincide. This will be explained with reference to FIG. 1 for a rear two-wheel steered vehicle such as a forklift truck. Front wheels 2 and 3 of the vehicle body 1 are fixed wheels (non-steered wheels), and rear wheels 4 and 5 are steered wheels. Figure 1 shows a case where the vehicle body is moving forward and making a right turn. In order for the turning centers of the steering wheels 4 and 5 to coincide, the extension line of each axle must pass through the turning center 6. No. In order to satisfy this condition, the relationship expressed by the following equation (1) must always be maintained between the steering angles θ _R and θ _L of the steered wheels 4 and 5. 1/tanθ _L −1/tanθ _R =K/L (1) Here, K is the distance between the king pins of the steered wheels, and L is the wheel base. The mechanism for realizing the relationship of equation (1) regarding the steering angles θ _R and θ _L is the Atskerman-Giant mechanism. In the past, various Atsukerman-Jandt mechanisms have been proposed and put into practical use, but industrial vehicles such as forklift trucks and self-propelled carts with front and rear wheel steering are required to turn in narrow passages, and general automobiles, etc. In addition, the steering angles of the left and right steering wheels must satisfy the relationship shown in equation (1). When such a large steering angle is required, the approximate mechanisms that have been used in the past are:
There is something like the one shown in Figure 2. In the figure, 1
2 is a drag link that transmits rotational driving force from a steering wheel (not shown); 11 is a bell crank that rotates around point A by transmitting the rotational driving force of the drag link 12; 9 and 10 are steering wheels 4; This is a link mechanism consisting of a link, one end of which is rotatably supported by the knuckle arms 7 and 8 attached to the vehicle, and the other end of which is rotatably supported by the bell crank 11. FIG. 2a shows the straight-ahead state, and FIG. Each state is shown below. As estimated from Figure 2b, this mechanism has a limit to its operation, and the maximum steering angle that can be generated is about 90° at the inner wheel, and as the steering angle increases, the left and right It is well known from experience that the relationship between steering angles deviates significantly from the relationship expressed by equation (1). Therefore, several mechanisms have been proposed to overcome the limitations of the link mechanism described above. As shown in Figure 3, these mechanisms create a large steering angle in which the center of the turn reaches the center of the axle of the fixed wheels (non-steering wheels), making it possible to perform so-called ``turning on the spot.'' be. Specifically, the left and right rotation angle generated by the link mechanism shown in Figure 2 and other trapezoidal link mechanisms used in automobiles, etc. is increased by a transmission mechanism such as a gear or chain, and the increased rotation angle is The state shown in FIG. 3 is achieved by adjusting the steering angle. [Problems to be Solved by the Invention] However, the above-mentioned system focuses on increasing the maximum steering angle, and the relationship between the left and right steering angles shown by equation (1) is as follows. It is only approximately maintained. In addition, in this method, by adding a speed increasing mechanism to the link mechanism, it is necessary to significantly increase the number of parts that make up the entire mechanism, and in order to best approximate equation (1), For each car body with a different wheelbase and kingpin distance, it is necessary to determine the link ratio and speed increase ratio through trial and error each time, making the actual design extremely time-consuming. There are problems such as. On the other hand, the left and right steering angles are approximated to the relationship in equation (1) using a transmission mechanism such as a gear whose transmission ratio changes stepwise according to the rotation angle, or a transmission mechanism using an eccentric gear. A method has also been proposed to obtain a large steering angle that allows for ``turning on the spot'' while maintaining the same level of stability. However, while this type of system is simple in principle, it requires a complicated mechanism when actually manufactured, and there are parts that can be used in common for car bodies with different wheelbases and distances between king pins. In addition, in any of the conventional methods, it is difficult to calculate the approximate Atsukerman
As long as it is a jet mechanism, a considerable amount of effort is required in designing it to achieve better approximation. The present invention has been devised in view of such problems, and its purpose is completely different from all conventional approximate Atskermann-Giant mechanisms, and its purpose is to "turn on the spot" from a straight-ahead state without using any approximate method. The object of the present invention is to provide a steering mechanism that satisfies the Atskermann-Giant geometry up to the ``state.'' [Example] The present invention proposes two inventions in order to solve the above-mentioned problems, and the first invention (the invention described in claim 1) will be explained first. 4 and 5 are explanatory diagrams of the basic structure and operation showing the principle of the first invention. 1st
The second invention is composed of two links each on the left and right, and 13 and 14 are L-shaped links with a length ratio of b/a=K/2L. The rotation center positions P _R and P _L are respectively
Rotate while moving along the Y _R and Y _L axes at a distance of 2b. This is called a steering angle input link. still,
K is the distance between the king pins of the steering wheels, and L is the wheel base. Further, 15 and 16 have one end slidably connected to the tips Q _R and Q _L of the steering angle input links 13 and 14, respectively, and the other end thereof on the Y _R and Y _L axes, This link is rotatably supported around the midpoints O _R and O _L of the distance 2b, and is called a steering angle output link. The steering angle input links 13 and 14 are
If you follow the diagram from a to e in Fig. 5 and look at its operation, it is clear that the respective nodes P _R and P _L are Y _R ,
Performs rotational motion while moving along the Y _{and L} axes. The rotation angle is 180° from a to e in Figure 5.

Rotate left and right synchronously [±90° with c as the neutral point]. Here, in the state shown in Fig. 5d, the steering input angle θ, that is, Y _R , the angle formed by the Y _L axis, _{R R} , _{L L} , and the steering output angle ψ _R , ψ _L, that is, the Y _R axis and _{R R} As is clear from FIG. 6, the relationship between the angle formed by the Y _L axis and _{the L L} axis can be modified as follows. tanψ _R = asinθ/(acosθ−bsinθ) …(2) tanψ _L = asinθ/(acosθ+bsinθ) …(3) 1/tanψ _R = (acosθ−bsinθ)/asinθ =1/tanθ−b/a…… (4) 1/tanψ _L = (acosθ+bsinθ)/asinθ = 1/tanθ+b/a ...(5) Furthermore, taking the difference between equations (4) and (5), 1/tanψ _L -1/tanψ _R = 2b/a=K/L
...(6) Therefore, this is an equation in which Q _R and Q _L in conditional equation (1) of the Atskerman-Giant mechanism are rewritten as ψ _R and ψ _L. The relationship in equation (6) above holds true in all the states from a to e in Figure 5, and the link mechanism according to this method completely satisfies the conditions of the Atsukerman-Giant mechanism, while also allowing the link mechanism to move more easily than straight ahead. This makes it possible to generate a steering angle that leads to "field turning."
Incidentally, although a detailed explanation will be omitted, as shown in FIG. 7, the steering input angle θ is the steering angle when the steering wheel is assumed to be centered between the left and right king pins. The above is the basic explanation of the first invention.
In configuring the actual link mechanism, guides orthogonal to X _R , Y _R and X _L , Y _L are provided, and points P _R and P _L are connected to the steering handle (see Fig. 5). There is a method of moving it along the Y _R and Y _L axes according to the rotation of (not shown). (There are various driving methods for this, such as a method using a link mechanism and a method using a hydraulic cylinder.) However, here, a means for driving the link mechanism of the present invention by a rotational movement according to the rotation of the steering wheel is used. show. FIG. 8 is an explanatory diagram of the means. As can be seen by comparing with Fig. 6, drive link 1 is shown here.
7, 18 are O _R , one end is _{R R} with O _L as the rotation center
The intermediate points _SR and _LL of are added so as to be connected to the intermediate point _SL of _L. Drive link 17,1
The length of 8 is b/2. When the drive links 17 and 18 connected in this way rotate by a predetermined steering angle θ, the input links 13 and 14 guided by the X _R , _XL , Y _R , and Y _L axes also rotate by the angle θ. ,and,
The nodes P _R and _PL move on Y _R and Y _L so that each O _R P _R = O _L P _L = bsinθ. By rotating the drive links 17 and 18 in this manner, the steering mechanism according to the first invention can be constructed. FIG. 9 is a schematic diagram of an embodiment of the steering mechanism according to the first invention. Steering angle input link 13,
Each of the 14 nodes P _R , R _R , P _L and R _L is guided by guides 21 , 22 , 23 and 24 via cam followers and the like. Steering output link 15, 16
are connected to steering angle input links 13 and 14 via sliding bearings at points Q _R and Q _L , respectively. Further, the rotation of the steering angle output links 15 and 16 about O _R and O _L is directly transmitted to the wheels 25 and 26, and can generate a steering angle. In this example, the drive links 17, 1 shown in FIG.
8, there are sprocket wheels 19 and 20 here, and the steering input link 1 is connected at a point eccentric by b/2 from their centers O _R and O _L.
It is rotatably connected to the S _R and S _L points of 3 and 14. These sprocket wheels 19, 20 are driven by another sprocket wheel 27 via chains 28, 29. With the above configuration, if the rotation of the steering handle (not shown) is transmitted to the sprocket wheel 27 directly or via a hydraulic motor or the like, the sprocket wheels 19, 20 will rotate and the left and right link mechanisms can be operated. Next, the principle of the second invention (invention according to claim 2) will be explained with reference to FIGS. 10 and 11. The second invention provides a first link 30 corresponding to the steering angle input links 13 and 14 in the embodiment of the first invention, and a steering angle output link 1.
It is constituted by second links 31 corresponding to Nos. 5 and 16. The first link 30 is an L-shaped link with a ratio of d/c=K/L, and is synchronized with the steering angle of the steered wheels 26, and its rotation center position is on the Y axis according to the rotation angle. and rotates while moving a distance of 2d. The second link 31 has one end slidably connected to the tip Q of the first link, and the other end pivots on the Y axis and around the midpoint O of the distance 2d. It is freely supported and can rotate according to the rotation of the first link 30. Note that K is the distance between the king pins of the steered wheels, and L is the wheel base. Now, as shown in FIG. 11, the first link 30
Letting the rotation angle of ψ ₁ be ψ 1 and the rotation angle of the second link 31 be ψ ₂ , the relationship between ψ ₁ and ψ ₂ is expressed by the following equation (7). (ccosψ ₁ −dsinψ ₁ ) tanψ ₂ = csinψ ₁ ...(7) From equation (7), tanψ ₂ = csinψ ₁ / (ccosψ ₁ − dsinψ ₁ ), which is further transformed to 1/tanψ ₂ = 1/tanψ ₁ -d/c 1/tanψ ₁ =1/tanψ ₂ =d/c=K/L
...(8) becomes. Equation (8) is an equation in which the steering angles θ _L and θ _R in conditional equation (1) of the Atsukerman-Giant mechanism are replaced with ψ ₁ and ψ ₂ , and it is clear that ψ ₁ and ψ ₂ are equivalent to the left and right steering angles. It can be seen that it can be used as a corner. That is, in the second invention, by rotating the first link 30 by the same angle as the steering angle of either the left or right wheel, the steering angle of the remaining one wheel can be obtained from the second link 31. become. FIG. 12 is a schematic diagram of an embodiment thereof, in which, unlike the first embodiment of the invention (FIG. 9), the left sprocket wheel 20 is rotated via the sprocket wheels 27, 34 and the chain 29.
The rotation angle directly corresponds to the steering angle of the left wheel 26. On the other hand, the right sprocket wheel 19
Similarly to the second invention, rotating the first link 30,
In response to the rotation of this first link 30, the second link 3
1 can rotate and steer the right wheel 25. [Effect of the invention] As explained above, the Atsukerman-Giant mechanism according to the first and second inventions is a link mechanism with a simple structure, but it is capable of large-scale steering from straight-ahead movement to "turning on the spot." generates a corner,
Moreover, the relationship between the left and right steering angles can theoretically satisfy the conditions of the Atskermann-Giant mechanism. Therefore, it can be said that the Ackermann-Giant mechanism according to the present invention is very suitable as a steering mechanism for industrial vehicles and the like that are required to turn with a small turning radius. Furthermore, in all conventional approximate Atsukerman-Giant mechanisms, in order to determine the link dimensions for better approximation, a very time-consuming process such as trial and error drawing was required; With the Atsukerman-Giant mechanism according to the invention, as long as the wheelbase of the vehicle body and the distance between the king pins are determined, the length of the link can be determined according to the ratio thereof, and there is no need for confirmation by drawing.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the relationship between the steering angles of the left and right steered wheels, Fig. 2 is a schematic diagram of the conventional Atskermann-Giant mechanism, and Fig. 3 shows the steering state in the case of so-called "on-spot turning". Explanatory diagrams, FIGS. 4 and 5 are explanatory diagrams of the fundamental structure and operation of the first invention, and FIG. 6 is an explanatory diagram showing the relationship of link angles in the embodiment of the first invention. , 7th
The figure shows the rotation angle θ of the steering angle input link and the rotation angle ψ _R of the steering angle output link in the first embodiment.
8 and 9 are explanatory and schematic diagrams showing the actual driving means of the embodiment of the first invention, and FIGS. 10 and 11 are diagrams showing the relationship between the vehicle body and _ψ
11 and 12 are schematic diagrams of an embodiment of the second invention. 1...Vehicle body, 2...Right non-steered wheel, 3...Left non-steered wheel, 4...Right steered wheel, 5...Left steered wheel, 6...
Turning center point, 13... Steering angle input link (right side), 14... Steering angle input link (left side), 15
... Steering angle output link (right side), 16 ... Steering angle output link (left side), 17 ... Drive link (right side), 18 ... Drive link (left side), 19 ...
Sprocket wheel (right), 20... Sprocket wheel (left), 21... Y-axis guide (right),
22...Y-axis guide (left), 23...X-axis guide (right), 24...X-axis guide (left), 25...Wheel,
27... Drive sprocket wheel, 28... Chain (right), 29... Chain (left), 30...
1st link, 31...2nd link.

Claims (1)

[Scope of Claims] 1. A steering angle input link whose rotation center position is on a predetermined straight line and rotates while moving a predetermined distance according to the rotation angle; The other end is rotatably supported on the predetermined straight line and about the midpoint of a predetermined distance in response to rotation of the steering angle input link. It is composed of a steering angle output link that steers the steered wheels of the vehicle body while rotating, and the length a of the steering angle input link is such that the predetermined distance is 2b, and the distance between the king pins of the steered wheels is K.
A steering mechanism characterized in that it is constructed with a length ratio of b/a=K/2L, where L is the wheelbase and L is the wheelbase. 2. A first link that rotates in synchronization with the steering angle of either the left or right steering wheel, and whose center of rotation rotates on a predetermined straight line and moves a predetermined distance according to the rotation angle; It is slidably connected to the tip of the first link, and the other end is rotatably supported on the predetermined straight line and around the midpoint of a predetermined distance, so that the first link rotates. and a second link that steers the remaining steered wheel while rotating accordingly, and the length c of the first link is defined by the predetermined distance being 2d, the distance between the king pins of the steered wheels being K, and the wheel base. A steering mechanism characterized in that it is constructed with a length ratio of d/c=K/L, where L is d/c=K/L.