JPS60201130A - Construction of leaf spring - Google Patents

Abstract

PURPOSE:To set a leaf spring to a suitable spring constant, by using a shape- memory alloy for a tightening band in the leaf spring, which suspends a car body, and adjusting the tightening force of the tightening band to be changed in accordance with a road surface condition. CONSTITUTION:A plurality of tightening bands 2 hold plural sheets of leaf springs 1, and this tightening band 2 is fastened by a tightening bolt 3 made of shape-memory alloy. The leaf spring connecting an electric circuit to a member of shape-memory alloy constituting a part of the tightening band 2, is constituted so as to heat the member of shape-memory alloy and adjust tightening force of the tightening band 2 in accordance with a road surface condition.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a structure of a leaf spring for suspending a vehicle body. In particular, the present invention relates to a leaf spring structure in which the spring constant can be changed by sensing road surface conditions and changing the tightening force of a shape memory alloy tightening band.

[Description of prior art]

A vehicle suspension system supports the weight of the vehicle body, buffers vertical vibration of the wheels due to uneven road surfaces, prevents vibrations from being transmitted to the vehicle body, protects the vehicle body, passengers, cargo, etc.
There is a need for a basic function that suppresses irregular wheel vibrations and stabilizes driving.

Suspension springs and dampers are used to satisfy these functions, but among these suspension springs, leaf springs store less elastic energy per unit volume than coil springs or torsion bars. As a structural member of a suspension mechanism, it still has a wide range of uses because of its great advantages such as the simple structure of the mounting part.

The load-deflection characteristics of leaf springs are the most common conventional springs, which show a straight line and the spring constant is always constant, and parent-child leaf springs, which are two leaf springs stacked one on top of the other, where the load is applied to the car body. The spring constant changes only when increases to a certain constant value. Furthermore, in the case of a progressive spring in which multiple auxiliary springs are attached to the lower side of the leaf spring, the spring constant changes over a certain value as the load increases, similar to the above-mentioned parent-child leaf spring, but the spring constant changes in the vicinity of the point of change. Only the curve changes to a parabolic shape.

Therefore, the spring constant is completely constant, or even if it changes, it only changes due to an increase in the weight applied to the vehicle, and it does not change due to changes in driving conditions or road surface conditions, making it possible to obtain the optimal spring constant at the time of driving. Leaf springs still don't exist.

The inventor of the present invention focused on the fact that if the tightening force of the tightening band of a leaf spring can be changed, an optimal spring constant can be obtained that immediately responds to the running condition of the vehicle and the road surface condition. We have completed the present invention which applies memory alloys.

[Purpose of the invention]

The present invention automatically buffers vertical vibrations according to vehicle running conditions or road surface conditions, protects the vehicle body, passengers, cargo, etc.
Furthermore, it is an object of the present invention to provide a leaf spring structure that can suppress irregular vibrations of the wheels and stabilize running.

[Features of the invention]

The present invention provides a leaf spring structure including a leaf spring and a tightening band for tightening the leaf springs, wherein at least a part of the tightening band is made of a shape memory alloy. It is characterized by comprising electric circuit means for applying a heating current.

Furthermore, by having means for detecting that the vibration of the vehicle body exceeds a predetermined darkness value, and having means for automatically heating the shape memory alloy when the means has a detection output, the spring of the leaf spring can be heated. The constant can be changed depending on driving conditions or road surface conditions.

The above vehicle body vibration shall be the amount of information based on any one or a combination of one or more of the following: vertical vibration acceleration, vibration velocity, vibration displacement, lateral acceleration of the vehicle body, steering angle, and vehicle speed. I can do it.

The shape memory alloy used in the present invention memorizes a certain shape in a certain temperature range, and no matter what shape it takes in a temperature range other than that temperature range, it retains its shape when returned to the original temperature range. It is an alloy that exhibits a reversible shape memory effect that allows it to return to its original shape and memorize its shape on both the high temperature and low temperature sides when subjected to special treatments such as plastic working or heat treatment.

[Explanation based on examples]

Next, the structure of an embodiment of the present invention will be explained in detail based on the drawings.

FIG. 1 is a front view of a leaf spring according to the first embodiment of the present invention.
FIG. 2 is a block diagram of the leaf spring control according to the first embodiment of the present invention, and FIG. 3 is a block diagram of the leaf spring control according to the second embodiment of the present invention.

As shown in FIG. 1, the leaf spring according to the first embodiment of the present invention has a plurality of leaf springs 1 stacked on top of each other, the leaf springs 1 are held by a plurality of tightening bands 2, and the tightening hands 2 are It is tightened by a tightening port 3 made of shape memory alloy.

This tightening bolt 3 is electrically insulated from the tightening band 2, and a resistor 4, a battery 5 serving as a power source, and a relay G for opening and closing the current of this battery 5 are connected in a series circuit.

Also, a microcomputer 7 takes in the vibration acceleration of the vehicle as a signal, compares it with a dark value, and instructs the relay 6 to open/close according to the value, and an integration circuit connected to the microcomputer 7 to integrate the vibration acceleration. 8 and a vibration acceleration detector 9 that detects vibration acceleration.

The operation of the first embodiment of the present invention configured as described above will be explained. The tightening bolt 3 made of a shape memory alloy memorizes a length that will provide a tightening force with a spring constant determined based on vehicle body vibration when the road surface condition is good and riding comfort in a normal temperature range. In addition, in high temperature ranges, the length of the leaf spring 1 is determined by increasing the tightening force to obtain the spring constant determined based on the vibration and riding comfort when driving on rough roads.
The length is set to be shorter than that at room temperature to increase the friction between the plates and the spring constant.

If the road surface condition is good, the vibration acceleration signal detected from the vibration acceleration detector 9 is integrated at a predetermined time constant, for example every several tens of seconds, in the integration circuit 8 and input to the microcomputer 7. Since the vibration acceleration is lower than the predetermined value of the vibration acceleration, the computer 7 does not issue a command to close the relay 6, so no current flows, and in order to maintain the normal temperature range, the relay 6 is made of shape memory alloy. There is no change in the tightening bolt 3, and the spring constant of the leaf spring 1 remains unchanged.

When the vehicle enters a rough road, the signal from the vibration acceleration detector 9 is sent to the microcomputer 7 via the integrating circuit 8, and it is compared and determined that the vibration acceleration is equal to or higher than the dark value. This sends an electric signal to the relay 6, which closes and current flows from the battery 5, heating the shape memory alloy tightening bolt 3 to a high temperature. The tightening bolt 3 changes to the memorized length in the high temperature range, and tightening the tightening band 2 increases the friction between the plates of the leaf spring 1 and increases the spring constant.

While the vehicle is running, the above-mentioned components are always in operation, and the road surface condition can be constantly detected to maintain the spring constant of the leaf spring l at an optimum value.

In the above example, the resistor 4 is wrapped around the tightening bolt 3, etc.
It can be arranged near the tightening bolt 3 and have a structure that utilizes the heat generated by the resistor 4.

Next, a second embodiment of the present invention shown in FIG. 3 will be described. In this second embodiment, a plurality of leaf springs 1 are tightened with a seamless tightening band 12 made of a shape memory alloy, and this tightening band 12 can be used in the same way as in the first embodiment in the normal temperature range, depending on the road surface condition. The inner dimensions that provide the required spring constant when the vehicle is good are stored, and the inner dimensions that provide the required spring constant on rough roads in the high temperature range are stored, in this case, the inner dimensions that are smaller than in the normal temperature range are stored.

The other configuration and operation are as explained in the first embodiment.
Similarly, the vibration acceleration detector 9 constantly detects the condition of the road surface, and the leaf spring 1 can be constantly controlled to increase or decrease the friction between the plates to maintain an optimum spring constant.

Next, a third embodiment of the present invention shown in FIG. 4 will be explained. This structure has a structure in which a leaf spring l is tightened by a shape memory alloy tightening bolt 3 using a plate-shaped tightening fitting 2'. be. Its operation is similar to that of the first embodiment shown in FIG. 2 above.

〔Effect of the invention〕

As described above, according to the present invention, a shape memory alloy is used for the tightening bolt for the tightening band that holds the leaf spring, or for the tightening band itself, and by means of heating the shape memory alloy. The tightening force of the tightening bolt or the tightening band can be changed in accordance with vehicle vibrations that change depending on road surface conditions. Along with this, the leaf spring's friction between the plates is controlled and the spring constant is changed to buffer vertical vibrations depending on the road surface conditions, protect the vehicle body, passengers, cargo, etc., and suppress irregular vibrations of the wheels. It has excellent effects such as being able to stabilize driving.

[Brief explanation of drawings]

FIG. 1 is a front view of a leaf spring according to a first embodiment of the present invention. FIG. 2 is a block diagram of leaf spring control according to the first embodiment of the present invention. FIG. 3 is a configuration diagram of leaf spring control according to a second embodiment of the present invention. FIG. 4 is a configuration diagram of leaf spring control according to a third embodiment of the present invention. 1... Leaf spring, 2. 12... Tightening (= J band, 3... Tightening bolt, 4... Heating resistor, 5...
...Battery, 6...Relay, 7...Microcomputer, 8...Integrator circuit, 9...Vibration acceleration detector. Patent applicant Hino Motors Co., Ltd. Agent Patent attorney Nao Ide Takashi 1 Invitation 2 (21

Claims (3)

[Claims] (1) In a leaf spring structure including a leaf spring and a tightening band that overlaps and tightens the leaf spring, at least a portion of the tightening hand is made of a shape memory alloy, and the shape memory alloy is heated. A structure of a leaf spring characterized by having an electric circuit means (JM) for applying electric current. (2) The electric circuit means includes a means for detecting that the vibration of the vehicle body exceeds a predetermined dark value, and a means for automatically applying a current to heat the shape memory alloy when this means has a detection output. A leaf spring structure according to claim (1). (3) Vehicle body vibration is the amount of information based on any one or a combination of one or more of the following: vertical vibration acceleration, vibration velocity, vibration displacement, lateral acceleration of the vehicle body, steering angle, and vehicle speed. A leaf spring structure according to claim (2).