GB2311355A - Vehicle suspension arrangement - Google Patents

Abstract

A wheel for supporting a magnetic levitation vehicle 40 at low speeds (or an aircraft wheel) is mounted on a pivoted arm 20, and raised and lowered by cylinder assembly 50, and supported by an arrangement of four springs 70 around the cylinder. The arrangement is damped by a cylinder coaxial with the cylinder 50.

Description

A LEG SYSTEM AND METHOD OF POSITIONING SPRINGS ON A CYLINDER The present invention concerns leg systems provided with wheel elevation functions. In particular, it concerns an effective technique ideal for use in such applications as magnetic levitation carriages where space restrictions are severe. Further, this invention also concerns a technique of positioning springs around the outer periphery of a cylinder in order to support the load which bears in the axial direction of that cylinder. In the cylinder an oil damper or actuator, etc., are included.

When springs are positioned around the outer periphery of a cylinder the space required for mounting the springs is generally limited. This is based on the concept of downsizing the equipment that has been made up of these components. However, depending on the equipment, the cause lies in the fact that the actual space required for installing the components directly related to it, such as the springs and spring seatings, is in itself limited from the start by the relationship of other components and mechanisms. Consider, for example, a leg system for a magnetic levitation vehicle. For instance, taking the type of magnetic levitation vehicle which works on the electromagnetic induction principle, this vehicle runs by levitation at high speed. However, at low speed it runs on wheels because a high levitation force cannot be obtained. The leg system enables both forms of running, i.e.

by levitation and on wheels, to be realised. In a leg system of this kind, a cylinder undertakes the function of raising and lowering the wheel. However, in addition to the raising and lowering function, the leg system must have a shock-absorbing function to improve the quality of the ride. Normally, the shock-absorbing function is fulfilled by a damper or, as discussed here, by springs (in other words, a spring mechanism).

In a leg system of this kind, the space for positioning such types of mechanism, or required to install them, is extremely restricted. The reason is that these mechanisms must inevitably be mounted on the bottom of the bogie, and that is an area where there is mutual interference with the room taken up by the propulsion mechanism, etc., of a magnetic levitation vehicle (the superconductive magnets which generate the propulsive or levitating force, or the cooling system for the superconductive magnets). Accordingly, because of the limitations on installation space, attempts are being made, for instance by means of the technology demonstrated under Patent Publications Heisei 4 (1992) -261305 and Heisei 5 (1993)-131921, to position a single coil spring on the outer periphery of an oil damper formed of a cylinder, and coaxial with that cylinder. By that method it is possible to make effective use of the dead space on the inside of the spring, and to increase the effects of space saving.

However, in the case of a magnetic levitation vehicle, even if the bogie is supported at several places, by, say, supporting it with four legs, one each at left and right, front and rear, the vehicle load exceeds several tens of kN, so the wire diameter of each coil spring becomes thicker, and it becomes impossible to obtain a sufficient spring length (height) owing to the previously described limitations on space. For this reason it is difficult to secure the required relaxation of the springs, and consequently, there was one more obstacle to a further improvement in ride comfort.

According to a first aspect of the present invention, there is provided a leg system as claimed in claim 1.

It is thus possible to provide a technology which enables, within the constraints on installation space, a further improvement to be made in the effects of shockabsorption by using springs.

In particular, it is possible to provide a leg system which has outstanding ride comfort characteristics while requiring only a compact space for installation.

It is also possible to provide a technique of positioning springs around the outer periphery of a cylinder which can co-exist with an oil damper.

Preferably, springs are positioned around the outer periphery of Cylinder in order to support the load in the axial direction of Cylinder. Each of the multiple Spring Units is spaced around the axial centre of Cylinder in such a way as to obtain with them a spring constant which exactly counterbalances that support. When this is done, the load supported by Cylinder is dispersed and borne on each of the Spring Units, so that both the wire diameter and spring length of each spring decrease in comparison with the case of the single spring, thereby enabling a reduction to be made in the installation space required for Springs.

Preferably, a second Cylinder Member is installed on the outer periphery of Cylinder Main Body of Cylinder, and coaxial to it, Oil Chambers and are partitioned between the Cylinder Main Body and the Second Cylinder Member. The Oil Chambers are utilised to form a Damper. The Damper absorbs the shock of any variation in the load bearing in an axial direction on Cylinder. By means of this construction, the component parts of Damper are contained within the axial length of the Cylinder Main Body, so that in spite of its being a cylinder complete with damper, the axial length of Cylinder is the same as the length of the Cylinder itself. This configuration creates, in conjunction with the effect of a reduction in length stemming from the multiplication of the number of springs, the advantage of reducing the axial length of Cylinder. Furthermore, by positioning the springs and Damper around Cylinder, the arrangement has the advantage that the number of points of installation on the bogie are relatively few.

As regards the multiple Spring Units, it is both possible to space them at equal intervals on the outer periphery of Cylinder, but otherwise to adopt all kinds of positioning such that they will be centrally symmetrical around the axial centre of Cylinder. For instance, it is possible to position Spring Units around the axial centre both in central symmetry around the axial centre and in left-right symmetry to the plane containing the axial line which passes through the axial centre. Also, even within such a centre- and left-right symmetrical placing, several Spring Units may be located to left and right, preferably two each side; and further, the space occupied by the two Spring Units each side (i.e. the left-hand and right-hand groups of Spring Units) and Cylinder can be shortened in length in a direction parallel to the plane which includes the said axial line, compared with the direction perpendicular to that plane. It can then be effectively applied even in cases where the allowable installation space is particularly limited in one direction, as in a rectangular cross-section.

Preferably, the springs positioned around the outer periphery of Cylinder are compression springs. Advantageously, the springs are coil springs, but it is possible to use disc springs instead of Coil Springs. The disc springs are employed by stacking several springs one above the other in series.

It is preferable to obtain linearly superior damping characteristics by pre-loading these compression springs.

Also, the multiple Spring Units (if coil springs, each separate Coil Spring, or, if disc springs, disc spring units consisting of several disc springs stacked in layers), are all given identical spring constants in order to make the support around the axial centre uniform. In addition, although coil springs are the most suitable, compared to disc springs, coil springs have a tendency to become slightly longer in the axial direction, so it is preferable to use for the coil springs those springs which can be reduced as far as possible in length, for example, those of a rectangular coil section and shorter in length along the axial direction compared with the length perpendicular to it.

The effectiveness of this invention can be particularly demonstrated by its application to a leg system for a magnetic levitation vehicle or for an aircraft. In a preferred configuration of a leg system based on this invention, the Cylinder has the Damper mounted on the outer periphery of Cylinder Main Body in addition to the mechanism of Springs. Thus it is possible to construct an 'L'-shaped Leg system, which has the Cylinder, including Damper and Springs, and Trailing Arm, which connects Axle of the Wheel and the Bogie, coupled together in an 'L' configuration. This 'L'shaped Leg system is most suitable from its space-saving aspect, in that the axial length of wheel elevating Cylinder is short, and also has the advantage of having few - only two points of attachment to Bogie.

The present invention will further be described by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side-view of a leg system constituting an embodiment of this invention; Figure 2 is a frontal view of the leg system shown in Figure 1; Figure 3 is a sectional view of the elevating cylinder in the leg raised state, and shows the cross-section along the line 3 - 3 in Figure 4; Figure 4 is a sectional view of the elevating cylinder in the leg lowered state, and shows the cross-section along the line 4 -4 in Figure 6; Figure 5 is a sectional view along the line 5 - 5 in Figure 3; and Figure 6 is a view of the elevating cylinder of Figure 4 seen from the axial direction.

Figures 1 and 2 illustrate the overall construction of 'L'-shaped Leg System 10. "'L'-shaped" is a term applied to the configuration of the support formed by a Trailing Arm 20 which extends almost horizontally, and Assembly 30 of a wheel elevating Cylinder 50. The Trailing Arm 20 is an arm which connects an Axle 22 and a Bogie 24, one end 20a of the arm 20 being supported on one end of Axle 22 so that rotation is possible, and the other end 20b being supported by a Lower Bracket 23 and Pin 25 so that rotation is possible. The points of attachment of 'L'-shaped Leg system 10 to the Bogie 24 are at two places (at the end of Trailing Arm 20 and the end of Cylinder Assembly 30).

Located about Axle 22 is a Wheel 40 for use when a vehicle incorporating the present invention is running on wheels. Wheel 40 consists of Tyre 42 (e.g. nitrogen gasfilled) and a metal wheel disc, which supports Tyre 42, on its inner periphery. The metal wheel disc is integrally provided with an externally-mounted Auxiliary Wheel 44 to cope with tyre punctures. Also, to the side of Wheel 40 is located a Vertical Arm 46 which extends in a vertical direction. Its purpose is to support Guide Wheel 47. Further, on the inside of Wheel 40 is also located Wheel Disc Brake Gear 48.

A lower end 30d of Cylinder Assembly 30 is connected to the Axle 22 via the Trailing Arm 20, and its upper end 30u is connected to the Bogie 24 via an Upper Bracket 33. Thus the rocking motion of Trailing Arm 20 about its pivotal support point on Lower Bracket 23 in response to the elongation or contraction of Cylinder Assembly 30 makes it possible to raise or lower the Wheel 40 on the Axle 22. In Figures 1 and 2, the condition where Wheel 40 is lowered (running on wheels) is represented by the continuous lines, and the condition where Wheel 40 is raised (running by magnetic levitation) by the broken lines.

The installation space for 'L'-shaped Leg System 10, as has been stated above, is fairly restricted, since the propulsion mechanism, etc., of the magnetic levitation vehicle takes up a great deal of room. In Figures 1 and 2, the outside envelope indicated by the broken lines is the installation space allowed for Leg System 10, and that installation space is greatly restricted particularly by the height from Track Surface G to the bottom of Bogie 24 and the widthways distance of Bogie 24. From the point of view of this installation space, it is necessary to reduce the axial length of Cylinder Assembly 30. Cylinder Assembly 30 has as its main element wheel elevating Cylinder 50, which is a hydraulic actuator, and integral with Cylinder 50 are a number of ancillary or auxiliary mechanisms. Cylinder 50 which forms the main component will be explained in detail later. In order to make that explanation more intelligible, here we will make clear what kind of mechanisms, and how, Cylinder Assembly 30 incorporates around the outer periphery of Cylinder 50.

Cylinder 50 itself includes a Cylinder Main Body 52 and a Piston Rod 54 which is on the same axis as Cylinder Main Body 52. At the head end of Cylinder Main Body 52 is located Adjusting Screw Mechanism 60, the purpose of which is to adjust the axial length of Cylinder Assembly 30. Then, in Leg System 10, Springs (Spring Mechanism) 70, which contains the compression springs, and Damper 80, which includes the oil chambers, are positioned in the section around the outer periphery of Cylinder Main Body 52.

Figures 3 and 4 illustrate one example of a cylinder which employs coil springs. They are both cross-section structural drawings of Cylinder 50, Diagram 3 showing Piston Rod 54 in extended state (with leg lowered, for running on wheels), and Diagram 4 showing Piston Rod 54 in retracted state (with leg raised, for magnetic levitation running). The Cylinder Main Body 52 of Cylinder 50 extends from 52r at the rod end to 52h at the head end, and its internal diameter is uniform. On Cylinder Main Body 52 are respectively located an Outward Flange 522 on the outer periphery at rod end 52r, and Screw Cap 524 on the end section at head end 52h. One end of Rod End Housing 53 abuts against one side of Outward Flange 522, and also Rod Bearing 55 is screwed into the opening at the other end of Rod Housing 53. Rod Bearing 55 guides the Piston Rod 54 in its axial stroke, and moreover prevents the ingress of foreign bodies into Cylinder 50 by means of a Dust Seal 55s.

The interior of Piston Rod 54 is hollow, and at its centre is a Coupling 58 which connects Rod End Member 57 with Piston 56. Rod End Member 57 is itself screwed into a Press Fit Cap 59 on the Piston Rod side, and is retained by means of Nut 57n. This Retaining Nut 57n, as can be understood from Figure 4, also supports Dock 12d, the purpose of which is to operate leg-up detecting Switch 12. On Rod End Member 57, in addition to First Support 510, which is attached by a pin to Axle 22, Leg-Lower Port 572 is located. This Port 572 passes into the interior of Cylinder Main Body 52 via Coupling 58.

At the head end of a Piston Rod 54, Piston Rod 56 is integrated with Rod 54. Piston 56 is of a slightly larger diameter than Rod 54, and bears a Piston Ring 56s on its outer periphery.

This Piston Ring 56s, by virtue of its sealing action, divides the inside of Cylinder Main Body 52 into a rod end side First Control Chamber 91, and a head end side Second Control Chamber 92. Leg-Up Port 532 arranged in Rod End Housing 53 communicates with First Control Chamber 91. When fluid pressure (for example, oil pressure) is supplied to First Control Chamber 91 via Port 532, Leg System 10 retracts Piston Rod 54 of Cylinder 50 into Cylinder Main Body 52 and assumes the leg-raised state shown in Figure 4. On the other hand, when oil pressure is supplied to Second Control Chamber 92 via Leg-Lower Port 572 situated in part of Rod End Member 57, Leg System 10 extends Piston Rod 54 and assumes the leg-lowered state shown in Figure 3. When in the leg-lowered state, a Lock Mechanism 200 on the inner periphery of Piston 56 locks Piston Rod 54 against Cylinder Main Body 52. For this Lock Mechanism 200 a two-stage type of mechanical lock is ideal.

In the leg system of this invention, Damper 80 , the purpose of which is to improve ride comfort, and Spring Mechanism 70 are arranged around the outer periphery of Cylinder Main Body 52 of wheel elevating Cylinder 50 and integrally with it. Moreover, Leg System 10 illustrated in the drawings uses some components of Damper 80 and some components of Spring Mechanism 70 in common, so the overall number of component parts has been comparatively reduced.

On the outer periphery of Cylinder Main Body 52, a Second Cylinder Member 150 is installed co-axially, ad optionally concentrically, with Cylinder Main Body 52. This Second Cylinder Member 150 is both the member which divides the oil chambers of Damper 80, and forms the spring seating for one end of Spring Mechanism 70. In Spring Mechanism 70, coil springs are used as the spring units, and in particular a number (here, four Coil Springs 750) are positioned around Cylinder Main Body 52. Due to Coil Springs 750 being divided into several separate parts, it is not only possible to reduce the axial length of the springs, but also to reduce space particularly in the transverse direction along the axis of Axle 22 by locating each separate Coil Spring 750 from the point of view of space in an inclined position circumferentially (for instance, instead of equally spacing the four Coil Springs circumferentially, grouping them into two pairs).

Each Coil Spring 750 as a spring unit is supported between a First Spring Seating 710 at the rod end side and a Second Spring Seating at the head end side. In Leg System 10, the Second Cylinder Member 150 functions as Second Spring Seating. The First Spring Seating 710 on its inner periphery abuts on Outward Flange 522 of Cylinder Main Body 52 and in the case of Member 150 functioning as Second Spring Seating, Seal Mounting 152 which protrudes into its inner periphery abuts on the end face of Screw Cap 524, so it is possible to maintain the state of compression which has given a pre-loading to each individual Coil Spring 750. On the inner periphery of each Coil Spring 750 its own Spring Guide 760 is located. Each Spring Guide 760 consists of First Spring Guide 761 which is supported by First Spring Seating 710, and Second Spring Guide 762 which is supported by Second Spring Seating. First and Second Spring Guides 761 and 762 fit into each other and vary the axial length of Spring Guide 760 as a whole. The Centre Holes 761h and 762h arranged in Spring Guides 761 and 762 are air vents for the purpose of expelling or intaking the air inside when Spring Guides 760 elongate or retract. Such a type of Spring Guide 760 of course guides Coil Springs 750 smoothly, but in addition, if by any chance the situation should arise that a Coil Spring 750 breaks, it also performs the function of a safety guarantee in preventing the broken spring from flying off.

The Rod end side First Spring Seating 710 is integral with Cylinder Main Body 52, and they never move relatively to each other even when there is a distortion in a Coil Spring 750. However, Member 150 acting as Second Spring Seating, although positionally controlled in relation to the head end by means of Screw Cap 524, does move in an axial direction relative to Cylinder Main Body 52 in response to the compressive distortion of Coil Springs 750. On the outer periphery near to the central section of Cylinder Main Body 52, Ring Mounting 526 is situated. Ring Mounting 526 is the part to which Seal Ring 526s and Guide Ring 526g are attached, and in combination with Guide Ring 524g mounted on the outer periphery of Screw Cap 524 guides the movement of Second Cylinder Member 150. Here, owing to the fact that Seal Ring 524s, Seal Ring 152s and Seal Ring 526s are located on the inner periphery of Screw Cap 524, Seal Mounting 152 and Ring Mounting 526 respectively, the two oil chambers, i.e. First Oil Chamber 810 and Second Oil Chamber 820, are separated on either side adjacent to the axial direction of Seal Mounting 152.

From the orientation of Leg System 10, First Oil Chamber 810 is the lower chamber, and Second Oil Chamber 820 is the upper chamber. The reason that the material thickness of the section from Ring Mounting 526 of Cylinder Main Body 52 to the extremity of the head end is greater than the thickness of the section at the rod end side is in order to cope with the pressure generated in Control Chambers 91 and 92. Second Oil Chamber 820 communicates with Oil Reservoir 160 via Passage 153 inside Member 150 acting as Spring Seating.

Similarly to Oil Reservoir 160, the equipment installed on the outer periphery of Second Cylinder Member 150 is a Proportional Valve 180. The purpose of Proportional Valve 180 is to ensure the linearity of the damper characteristics and to improve ride comfort even more. This Proportional Valve 180 is located at 900 about the axial centre from Oil Reservoir 160 (see Diagram 6 in particular).

Next, we concentrate on the head end section of Cylinder Main Body 52. In this head end section is located Adjusting Screw Mechanism 60, the purpose of which is to regulate the axial length (i.e. the height) of Cylinder Assembly 30. This height is the length between First Support 510 at the rod end side and Second Support 520 at the head end side. Now the actual mechanism for adjusting it can be located at any suitable point from First Support 510 to Second Support 520. For preference, it is better to locate it on the head end section, as in Adjusting Screw Mechanism 60. This is because adjustment can be carried out from within Bogie 24.

Adjusting Screw Mechanism 60 consists of Head End Housing 62 which is integral with Second Cylinder Member 150, Height Adjusting Nut 64, which is screwed onto the outer periphery of Housing 62, Head End Member 66, which is supported through a stepped section on Height Adjusting Nut 64, and Nut 68, which is screwed onto the outer periphery of Head End Member 66 and also functions to retain Adjusting Nut 64.

Therefore, by turning Adjusting Nut 64, the axial position of Head End Member 66, i.e. the position of Second Support 520, may be adjusted.

Claims (12)

1. A leg system comprises a trailing arm of which one end is connected to an axle which supports a wheel, while the other end is installed on the bogie side; an elevator cylinder which is connected to the trailing arm and performs the raising and lowering of the wheel; and springs for the purpose of supporting the load between wheel and bogie; in which multiple spring units are spaced about the axial centre of the cylinder in such a way as to obtain a spring constant which substantially counterbalances the said support.

2. A leg system as claimed in Claim 1, in which the positioning of each of the aforementioned spring units is in central symmetry around the axial centre of the said cylinder.

3. A leg system as claimed in claim 2, in which the spring units are positioned in left - right symmetry with respect to a plane that includes the axial line that passes through the axial centre of the cylinder.

4. A leg system as claimed in claim 3, in which the space occupied by the spring units in left - right symmetry and the cylinder has a length in a direction parallel to the axial line shorter than its length perpendicular to the plane which includes the axial line.

5. A leg system as claimed in any one of the preceding claims, in which the spring units consist of the same type of coil springs with identical spring constants.

6. A leg system as claimed in any one of claims 1 to 4, in which the said spring units are disc spring units consisting of multiple disc springs arrayed in series, and each disc spring has an identical spring constant.

7. A leg system as claimed in Claim 5, further including a guide member within the inner periphery of each coil spring, which guides the expanding and contracting coil springs.

8. A leg system as stated in Claim 5 or Claim 7, in which the sectional profile of the coil of each of the said coil springs is rectangular, and its length along the axial direction is shorter than its length in the direction perpendicular to the axial line.

9. A method of positioning springs a the cylinder, which, when the springs are positioned around the outer periphery of that cylinder in order to support the load which bears in the axial direction of the cylinder, reduces the installation space required for the said springs by spacing each of the multiple spring units around the axial centre of the said cylinder in such a way as to obtain with those multiple ! spring units a spring constant which just counterbalances the said support.

10. A method of positioning the springs as claimed in Claim 9, in which a second cylinder member is coaxial to the cylinder main body on the outer periphery of the said cylinder main body; and in which oil chambers between the outer periphery of the cylinder main body and the second cylinder member construct a damper against the said load; and in which each spring unit is outside the damper.

11. A method of positioning the springs as claimed in Claim 9 or Claim 10, in which each of the said spring units is centrally symmetrical around the axial centre of the said cylinder, and moreover in left-right symmetry with respect to the plane that contains the axial line which passes through the axial centre.

12. A method of positioning the springs as claimed in Claim 11, in which the springs on the outer periphery of the said cylinder are provided with multiple spring units to left and right respectively, and further, when regarding the space occupied by the left and right groups of springs and the cylinder, compared to its length in the direction perpendicular to the plane which includes the said axial line, its length in the direction parallel to that plane is the shorter.