WO2003044472A1

WO2003044472A1 - Device and method for measuring axle road

Info

Publication number: WO2003044472A1
Application number: PCT/SE2002/001909
Authority: WO
Inventors: Andreas Lundmark
Original assignee: Volvo Lastvagnar Ab
Priority date: 2001-11-23
Filing date: 2002-10-21
Publication date: 2003-05-30
Also published as: AU2002339820A1; SE0103928L; EP1451539A1; SE520499C2

Abstract

The invention relates to a load sensor for a leaf-spring-mounted axle on a motor vehicle, comprising a bracket intended to be fixed on the spring shackle of the leaf spring and a sensor which is connected to the bracket via a link arm, where the sensor detects the rotation of said spring shackle.

Description

TITLE : Device and method for measuring axle load

TECHNICAL FIELD

The present invention relates to a device for measuring axle load on a vehicle with leaf-spring suspension according to the preamble of patent claim 1, and a method for measuring axle load on a vehicle with leaf- spring suspension according to the preamble of patent claim 5.

BACKGROUND

A truck has to comply with many different legal requirements and regulations. These requirements often vary from country to country and/or from market to market. One example of such a requirement is the maximum permitted axle load. In this connection, it is important for the driver to ensure that the axle load never exceeds valid limits on any of the axles of the vehicle. These limits can vary depending on inter alia the type of road. The simplest and safest way of complying with valid rules is for the vehicle to be equipped with sensors which measure the load on each axle. When the vehicle is equipped with air suspension, the axle load is calculated by means of the pressure in the air bellows. For leaf-spring-mounted axles, the axle load has to be measured in a different way. Many vehicle manufacturers provide systems which measure the axle load on leaf-spring-mounted axles as optional equipment .

On the one hand, there are simple systems where a switch which is preset for a given axle load gives a signal when the set axle load is exceeded. The disadvantage of such systems is that it is possible to use them only for a preset axle load. An example of a similar system is described in US5376760. There are also more advanced systems which measure the axle load for each axle with a sensor. These systems provide a continuous signal which represents the current axle load for each axle . A common method of measuring the axle load is to measure the distance between the axle and the chassis. The distance between the axle and the chassis is normally measured with a sensor which is fixed in the chassis and is connected to the axle via a lever. A change in position of the axle is detected by the sensor, and this signal is then used in order to calculate the axle load. Such a system is described in, for example, JP08304154. This solution can function well when there is space for its installation but does not function when, for example, the axle load is also to be measured on the front axle of the vehicle. There is no room to install such a solution on the front axle of the vehicle, because engine, gearbox, the steering of the vehicle etc. are in the way.

DISCLOSURE OF THE INVENTION

The object of the invention is therefore to produce a device for measuring axle load on a vehicle with leaf- spring suspension which can be mounted in a space- saving and simple manner and also a method for measuring axle load on a vehicle with leaf-spring suspension in as simple and reliable a manner as possible .

The solution according to the invention for achieving this object is described in the characterizing part of patent claim 1 with regard to the device and by the features of patent claim 5 with regard to the method. The other patent claims contain advantageous embodiments and developments of the device according to the invention (claims 2 to 4) and the method according to the invention (claims 6 and 7) . With an axle load detector for a leaf-spring-mounted axle on a motor vehicle, comprising a bracket intended to be fixed on the spring shackle of a leaf spring and a sensor which is connected to the bracket via a link 5 arm, the object of the invention is achieved by virtue of the fact that the sensor detects the rotation of said spring shackle.

The method according to the invention achieves the L0 object by detecting the rotation of the spring shackle of a leaf spring.

By means of this first embodiment of the axle load detector according to the invention, the axle load can L5 be obtained by measuring the rotation of the spring shackle of a leaf spring. The advantage of this is that the axle load can be obtained by measuring at one end of the leaf spring instead of measuring on the axle or in the center of the leaf spring. This leads to the

20 axle load detector according to the invention being usable where a conventional measuring device cannot be mounted owing to lack of space .

In an advantageous first development of the axle load 25 detector according to the invention, the axle load detector comprises a potentiometer. The advantage of this is that the conversion to axle load can be effected with discrete components.

0 In an advantageous second development of the axle load detector according to the invention, the axle load detector comprises an optical pulse generator. The advantage of this is that the conversion to axle load can be effected digitally in a simple manner. 5

In an advantageous third development of- the axle load detector according to the invention, the axle load detector comprises a mechanical ratio. The advantage of this is that the entire active range of the sensor can be utilized.

In an advantageous design of the method according to the invention, the rotation of the spring shackle of a leaf spring is detected. The advantage of this method is that it is possible to obtain the axle load by measuring at one end of the leaf spring instead of measuring on the axle or in the center of the leaf spring.

In an advantageous first development of the method according to the invention, the detection of the rotation of the spring shackle is carried out with a bracket connected to a sensor. The advantage of this is that the length of the bracket can be adapted so that the entire measuring range of the sensor can be utilized.

BRIEF DESCRIPTION OF FIGURES

The invention will be described in greater detail below with reference to illustrative embodiments shown in the accompanying drawings, in which

FIG. 1 shows an advantageous embodiment of an axle load detector according to the invention.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The illustrative embodiments of the invention described below with developments are to be regarded only as examples and are in no way to be limiting of the scope of protection of the patent claims.

Fig. 1 shows an axle load detector 1 according to the invention. It comprises a bracket 2 which is mounted on a spring shackle 7. The axle load detector 1 also comprises a sensor 5 which is mounted on a frame 9 by means of a mounting angle 6. The sensor 5 is provided with a sensor arm 4 which is connected to the bracket 2 via a link arm 3.

The front end of the leaf spring 8 is suspended from the frame 9 by means of a spring mounting and a spring bolt (not shown) . This spring mounting allows the front end to rotate around the spring bolt. The rear end of the leaf spring 8 is attached to a spring shackle 7. The spring shackle 7 is an articulated mounting which connects the rear end of the leaf spring 8 to the frame. The spring shackle 7 is on the one hand attached in an articulated manner to the leaf spring 8 by a spring bolt, and on the other hand attached in an articulated manner by a spring bolt to a spring mounting 10 mounted on the frame. When the leaf spring 8 changes deflection, for example under increased load, the distance between the two attachment points of the leaf spring will change. As the front end is rigidly attached, this change in distance will lead to the spring shackle 7 carrying out a rotary movement. This rotary movement is proportional to the load, that is to say the axle load can be calculated from this rotation.

The rotary movement carried out by the spring shackle 7, and thus the bracket 2 as well, when the leaf spring changes deflection, for example under increased load, is transmitted to the sensor 5 via the sensor arm 4 and the link arm 3. The output signal of the sensor 5 is thus changed. This change is detected by, for example, a control unit which can indicate the current axle value on a display, for example in the instrument.

The mechanical ratio between the rotation of the spring shackle 7 and the rotation of the sensor 5 is determined by the length of the bracket 2 together with the length of the sensor arm 4. When the distance from the point of rotation of the bracket 2 to the attachment of the link arm 3 is the same as the distance from the point of rotation of the sensor arm 4 to the attachment of the link arm 3, the angular movement detected by the sensor 5 will be the same as the rotation of the spring shackle 7.

A sensor often has a greater detection angle than the angle through which the spring shackle can rotate. It is therefore advantageous to make the distance from the point of rotation of the bracket 2 to the attachment of the link arm 3 greater than the distance from the point of rotation of the sensor arm 4 to the attachment of the link arm 3. In this way, a mechanical ratio is obtained, so that the active range of the sensor can be utilized as effectively as possible. This increases the resolution and the accuracy in measurement. For example, a spring shackle rotation of 40 degrees can be transformed into a sensor detection of 150 degrees in this way.

In this example, the sensor 5 is a potentiometer. The sensor 5 can also be of a different type. It may be suitable to use, for example, an optical pulse generator. It is also possible to use capacitive or magnetic sensors.

The sensor 5 is connected to a unit which converts the signal of the sensor into a value which corresponds to the current axle load, for example a load-indicating unit or a control unit. This unit can either be a freestanding unit, for example a load-indicating unit which only calculates and indicates axle load, or it can be integrated into an existing control unit. Advantageously, the unit is positioned in the cab, but it is possible to position it anywhere on the vehicle. It is also possible to integrate a conversion function into the sensor so that the output signal of the sensor is directly proportional to the axle load.

The conversion to axle load can take place in a discrete analog manner, a digital analog manner, or completely digitally. In the case of discrete analog conversion, the signal-processing is carried out with discrete components. In the case of digital analog conversion, the analog signal is converted to a digital signal which is signal-processed with a processor. In the case of completely digital conversion, when the sensor is, for example, a pulse generator, the signal- processing is carried out with a processor without the signal having to be converted first. The conversion method is selected depending on inter alia which sensor is used and the characteristic of the output signal. The signal-processing carried out by the conversion function can include inter alia compensating for the linearity of the signal, compensating for external temperature, low-pass filtering the signal etc.

The current axle value can be indicated on a display, for example in the instrument. If the current axle value exceeds a predefined value, for example a maximum permitted axle load, the control unit can also give an alarm that a non-permitted state is present. This function can be used when the vehicle is being loaded, for example . When the permitted load for an axle is exceeded, a signal is given, and the loading can be stopped, or the load can be redistributed so that maximum use is made of the loading capacity.

This function can also be used while underway. This may apply for, for example, a truck with what is known as a pusher axle. When the pusher axle is lifted, the load and thus the pressure on the other axles is increased. If the load on, for example, the front axle thus becomes too great, the unit warns that this is the case. The driver must then lower the pusher axle again. If the driver has lifted the pusher axle so as to increase the load on the driving axle in order, for example, to be able to get away in slippery road conditions, he can lower the pusher axle again as soon this is possible. It is also possible to save information about the load on an axle . The maximum measured axle load can be saved, for example, or the time for which the axle load exceeded a predefined load can be saved. This information may be important for service or for detecting overloading.

In a first illustrative embodiment of the method according to the invention for measuring the axle load for a leaf-spring-mounted axle, the method comprises the step of detecting the rotation of the spring shackle of a leaf spring. The rotation of the spring shackle is advantageously detected with a bracket which is mounted on the spring shackle. The bracket transmits the rotation of the spring shackle to a sensor via a link arm. The rotation of the spring shackle is proportional to the load acting on the axle, that is to say the axle load. The output signal of the sensor is signal-processed in a suitable manner so that a value which corresponds to the axle load is obtained. This axle load value can be indicated on a display.

The invention is not to be regarded as being limited to the illustrative embodiments described above, but a number of further variants and modifications are conceivable within the scope of the following patent claims. For example, the method according to the invention can also be used for measuring axle load on trackbound vehicles which are leaf-spring-mounted.

Claims

PATENT CLAIMS

1. An axle load detector (1) for a leaf-spring- mounted axle on a motor vehicle, comprising a bracket (2) intended to be fixed on the spring shackle (7) of a leaf spring and a sensor (5) which is connected to the bracket (2) via a link arm (3) , characterized in that the sensor (5) detects the rotation of said spring shackle (7) .

2. The axle load detector as claimed in claim 1, characterized in that the bracket (2) is mounted to a leaf spring (8) which supports the front axle of the vehicle .

3. The axle load detector as claimed in claim 1 or 2, characterized in that the distance from the point of rotation of the bracket (2) to the attachment of the link arm (3) is greater than the distance from the point of rotation of the sensor arm (4) to the attachment of the link arm (3) .

4. The axle load detector as claimed in any one of claims 1 to 3 , characterized in that the sensor (5) is a potentiometer or an optical pulse generator.

5. A method for measuring the axle load for a leaf- spring-mounted axle on a motor vehicle with a spring shackle, comprising the step of detecting the rotation of the spring shackle of the leaf spring by measuring with a sensor the rotation of the spring shackle around a spring mounting attached to the frame of the vehicle.

6. The method as claimed in claim 5, characterized in that the detection of the rotation of the spring shackle is carried out with a bracket connected to the sensor.

7. The method as claimed in claim 5 or 6, characterized in that the method also comprises the step of converting the output signal of the sensor to a value which corresponds to the axle load.