Live load measuring device and live load measuring method

Abstract

To improve the accuracy of measuring the live load of a vehicle comprising a chassis frame.SOLUTION: A live load measuring device 10 measures the live load of a vehicle 1 comprising a chassis frame 2 having left and right side members 21 to which a rear wheel axle is connected via a leaf spring, and the live load measuring device 10 comprises: a strain gauge that is attached to a side face of each of the side members 21 and measures the strain on the side face; and an on-vehicle instrument 200 that calculates the live load of the vehicle 1 on the basis of measured values from the strain gauges.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a live load measuring device and a live load measuring method. [Background technology]

[0002] A known live load measuring device has a strain gauge attached to an axle shaft via a base plate (see, for example, Patent Document 1). In the live load measuring device described in Patent Document 1, the strain gauge detects the strain of the axle shaft caused by the live load and outputs a detection signal. The detection signal output from the strain gauge is amplified by an amplifier and calculated by a controller to calculate the live load of the vehicle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-71437 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the live load measuring device described in Patent Document 1, a temperature difference occurs between the axle shaft and the base plate due to heat generated by the brakes and differential gears, which causes a difference in the amount of thermal expansion between the axle shaft and the base plate, generating stress in the base plate and causing distortion in the base plate.

[0005] In addition, in the case of a vehicle with dual tires, if one side of the dual tires is lifted off the ground due to an uneven road surface, the point of force of the load acting on the axle shaft from the road surface changes. This changes the magnitude of the bending moment acting on the axle shaft, causing a change in the distortion of the axle shaft.

[0006] If the distortion of the base plate or axle shaft changes due to factors other than the magnitude of the vehicle's load, the influence of these distortions will affect the measurement accuracy of the load, and measures will be required.

[0007] In view of the above circumstances, an object of the present invention is to provide a live load measuring device and a live load measuring method that can improve the measurement accuracy of the live load of a vehicle equipped with a chassis frame. [Means for solving the problem]

[0008] The load measuring device of the present invention is a load measuring device that measures the load of a vehicle having a chassis frame with left and right side members to which the axles are connected via springs, and is equipped with a strain measuring unit that is attached to the side of the side member and measures the distortion of the side, and a load calculation unit that calculates the load of the vehicle based on the measurement value of the strain measuring unit.

[0009] The live load measurement method of the present invention is a live load measurement method for measuring the live load of a vehicle having a chassis frame with left and right side members to which axles are connected via springs, in which a strain measuring unit is attached to the side of the side member to measure the strain of the side, and the live load of the vehicle is calculated based on the measurement value of the strain measuring unit. Effect of the Invention

[0010] According to the present invention, it is possible to improve the measurement accuracy of the load of a vehicle having a chassis frame. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing the configuration of a live load measuring device according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a graph showing a stress strain curve. [Diagram 3] FIG. 3 is a perspective view of the vehicle for explaining the mounting position of the load sensor shown in FIG. [Figure 4]FIG. 4 is a diagram showing a sensor base provided in the load sensor shown in FIGS. [Diagram 5] FIG. 5 is a diagram showing the results of a stress analysis of a side member. [Figure 6] FIG. 6 shows the results of a stress analysis of the side member depending on the condition of the road surface under the rear wheels. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present invention will be described below along with preferred embodiments. Note that the present invention is not limited to the embodiments shown below, and the embodiments shown below can be modified as appropriate within the scope of the present invention. In addition, in the embodiments shown below, some configurations are omitted from illustration and description, but for the details of the omitted technologies, publicly known or well-known technologies are applied as appropriate within the scope of no contradiction with the contents described below.

[0013] Fig. 1 is a diagram showing the configuration of a live load measuring device 10 according to one embodiment of the present invention. As shown in this figure, the live load measuring device 10 according to this embodiment is mounted on a vehicle 1 such as a truck or a lorry in which the live load of a loading platform 7 acts on a chassis frame 2. The chassis frame 2 includes left and right side members 21 and a plurality of cross members 22 (see Fig. 3) that connect the left and right side members 21.

[0014] The live load measuring device 10 includes a plurality of load sensors 100 and an in-vehicle device 200. The number of the load sensors 100 installed is twice the number of axles of the vehicle 1. In this embodiment, since the vehicle 1 has two axles, four load sensors 100 are provided, two load sensors 100 are attached to the left side member 21, and two load sensors 100 are attached to the right side member 21. Each load sensor 100 detects the amount of distortion of the side member 21 as a voltage and transmits a voltage signal to the in-vehicle device 200.

[0015] The vehicle-mounted device 200 is a display device that displays the live load of the vehicle 1, and has a live load calculation function that calculates the live load of the vehicle 1 based on the voltage signals transmitted from each load sensor 100, and a display function that displays the calculated live load of the vehicle 1. The vehicle-mounted device 200 stores load / voltage conversion information such as tables, formulas, maps, etc. for converting the voltage values ​​transmitted from each load sensor 100 into loads. The vehicle-mounted device 200 also calculates the live load of the vehicle 1 by adding up the calculated loads for each load sensor 100.

[0016] 2 is a graph showing a stress-strain curve. As shown in this graph, the stress-strain curve has a linear region where the strain increases linearly with increasing stress up to the yield point. According to the relationship between stress and strain in this linear region, the weight / voltage conversion information is generated, which shows the relationship between the measured value of the load (stress) of each load sensor 100 and the strain (load sensor output) of each load sensor 100.

[0017] Fig. 3 is a perspective view of the vehicle 1 for explaining the mounting position of the load sensor 100 shown in Fig. 1. As shown in this figure, the load sensor 100 is mounted near the front wheel axle 3 of the left side member 21, near the rear wheel axle 4 of the left side member 21, near the front wheel axle 3 of the right side member 21, and near the rear wheel axle 4 of the right side member 21. The rear wheels 5 are dual tires.

[0018] Here, the two load sensors 100 near the rear wheel axle 4 are attached to an area below the cargo bed 7 on the side surface 21A of the side member 21, i.e., the side surface 21A of the side member 21 in the area where the cargo bed 7 is mounted. The two load sensors 100 near the rear wheel axle 4 are attached to areas near support points on the side surface 21A of the side member 21 where the ends of the leaf springs 6 are supported. In particular, the two load sensors 100 near the rear wheel axle 4 are attached between two support points on the side surface 21A of the side member 21 where both ends of the main leaf spring 62 (see FIG. 5) are supported.

[0019] Fig. 4 is a diagram showing the sensor base 101 included in the load sensor 100 shown in Fig. 1 and Fig. 3. As shown in this figure, the load sensor 100 includes the sensor base 101, a case (not shown), and an amplifier. The sensor base 101 and the amplifier are housed in the case.

[0020] The sensor base 101 includes a strain gauge 101A and a base plate 101B. The strain gauge 101A is fixed to the base plate 101B, and detects the amount of strain of the base plate 101B as a voltage and outputs it to the amplifier. The voltage output from the strain gauge 101A is amplified by the amplifier and transmitted to the vehicle-mounted device 200.

[0021] The base plate 101B is a plate material whose longitudinal direction is the vertical direction of the vehicle, and is made of the same material as the side members 21. Note that it is not essential that the base plate 101B be made of the same material as the side members 21, but it is desirable that there is no or only a small difference in the linear expansion coefficient between the base plate 101B and the side members 21.

[0022] The longitudinal center portion of the base plate 101B is formed flat, and the strain gauge 101A is attached to the longitudinal center portion by adhesion or the like. Both longitudinal ends of the base plate 101B are bent toward the side member 21 with respect to the longitudinal center portion, and are fixed to the side surface 21A of the side member 21 by any fixing method such as welding or adhesion. The base plate 101B is fixed to the side surface 21A of the side member 21 so as to extend in the vehicle up-down direction (a direction perpendicular to the longitudinal direction of the side surface 21A of the side member 21).

[0023] Here, the side member 21 is a frame having a C-shaped (U-shaped) cross section made of C-shaped steel, lip groove steel, etc. Therefore, the load of the vehicle 1 acts on the side member 21 in the vertical direction of the vehicle, and a stress corresponding to the applied load in the vertical direction of the vehicle is generated on the side surface 21A of the side member 21.

[0024] Also, while the stress of the axle shaft (rear wheel axle 4) changes due to the heat generated by the brakes and differential gear, the stress of the side member 21 does not change due to the heat generated. Also, while the stress of the axle shaft changes due to the change in moment caused by the condition of the road surface below the dual rear wheels 5, the stress of the side member 21 does not change due to the change in moment.

[0025] Therefore, in the live load measuring device 10 of this embodiment, a strain gauge 101A is attached to the side surface 21A of the side member 21 via a base plate 101B, the amount of strain of the side surface 21A of the side member 21 is detected as a voltage, and the live load of the vehicle 1 is calculated by the on-board device 200 based on the detected voltage.

[0026] Here, the load in the vertical direction of the vehicle is not evenly applied to the side member 21, but a larger load is applied near the support point to which the leaf spring 6 is fixed on the side member 21. Therefore, as described later, a larger stress is generated near the support point of the leaf spring 6 on the side member 21, and the difference in stress due to the difference in live load also becomes larger.

[0027] Therefore, in the live load measuring device 10 of this embodiment, from the viewpoint of detecting the stress of the side member 21 at a position where the difference in stress due to the difference in live load is greater and improving the measurement accuracy of the live load, the load sensor 100 on the rear wheel axle 4 side is attached near the support point of the leaf spring 6 on the side member 21.

[0028] Fig. 5 is a diagram showing the results of a stress analysis of the side member 21. In the stress analysis shown in this figure, a CAE (Computer Aided Engineering) analysis was performed on the area surrounded by a dashed line in the side member 21 of the vehicle 1 shown in Fig. 3. This area includes the support points that support the rear wheel axle 4 on the side surface 21A of the side member 21 via the leaf spring 6.

[0029] As shown in Fig. 5, it was confirmed that the stress is maximum near the support points of the leaf spring 6 on the side member 21. In particular, in this analysis, it was confirmed that the stress is maximum at the two support points where both ends of the auxiliary leaf spring 61 are attached. Therefore, from the viewpoint of detecting the stress of the side member 21 at a position where the difference in stress due to the difference in live load is larger and improving the measurement accuracy of the live load, it is desirable to dispose the load sensor 100 near the support points where both ends of the auxiliary leaf spring 61 are attached (for example, between the two support points where both ends of the main leaf spring 62 are attached).

[0030] Fig. 6 is a diagram showing the results of a stress analysis of the side member 21 depending on the condition of the road surface under the rear wheel 5. In the stress analysis shown in this figure, a CAE analysis was performed on the area of ​​the side member 21 surrounded by a dashed line in Fig. 5. This area includes the support points of the auxiliary leaf spring 61 and the main leaf spring 62 on the vehicle rear side.

[0031] The first column from the left in Fig. 6 shows the stress analysis results of the side member 21 when the live load is 0t. The second column from the left in Fig. 6 shows the stress analysis results of the side member 21 when the live load is 1t. The third column from the left in Fig. 6 shows the stress analysis results of the side member 21 when the live load is 2t. Furthermore, the rightmost column in Fig. 6 shows the stress analysis results of the side member 21 when the live load is 3t.

[0032] The upper part of Fig. 6 shows the results of a stress analysis of the side member 21 in a situation where the road surface underneath the dual rear wheels 5 is flat. The middle part of Fig. 6 shows the results of a stress analysis of the side member 21 in a situation where a plate is placed underneath the outer tire of the rear wheels 5. The lower part of Fig. 6 shows the results of a stress analysis of the side member 21 in a situation where a plate is placed underneath the inner tire of the rear wheels 5.

[0033] Comparing the stress distributions in each row and each stage in Figure 6, it was confirmed that there was a significant increase in stress in response to an increase in the load. Also, comparing the stress distributions in each row and each stage in Figure 6, it was confirmed that the condition of the road surface under the rear wheel 5, which is a dual tire, had little effect on the change in stress.

[0034] As described above, the live load measuring device 10 according to this embodiment includes the strain gauge 101A attached to the side surface 21A of the side member 21 to measure the strain of the side surface 21A, and the on-board device 200 to calculate the live load of the vehicle 1 based on the measurement value of the strain gauge 101A. Here, the side surface 21A of the side member 21 has a sufficiently large difference in stress due to the difference in live load, and compared to the axle shaft, the change in stress due to the influence of the road surface condition under the rear wheels 5, which are dual tires, and heat generation of the brakes and differential gears is suppressed. Therefore, according to the live load measuring device 10 according to this embodiment, the strain gauge 101A used for calculating the live load of the vehicle 1 is attached to the side surface 21A of the side member 21, so that the measurement accuracy of the live load of the vehicle 1 can be improved.

[0035] In particular, in the live load measuring device 10 according to this embodiment, the strain gauge 101A is attached to an area below the loading platform 7 on the side surface 21A of the side member 21. Here, the area below the loading platform 7 on the side surface 21A of the side member 21 is subject to significant distortion due to the live load acting in the vehicle up-down direction. Therefore, the measurement accuracy of the live load of the vehicle 1 can be improved more effectively.

[0036] Moreover, in the live load measuring device 10 according to this embodiment, the strain gauge 101A is attached near the support point where the leaf spring 6 is supported on the side surface 21A of the side member 21. Here, the difference in stress due to the difference in live load is particularly noticeable in the area under the cargo bed 7 near the support point where the leaf spring 6 is supported on the side surface 21A of the side member 21. This makes it possible to more effectively improve the measurement accuracy of the live load of the vehicle 1.

[0037] The present invention has been described above based on the above embodiment, but the present invention is not limited to the above embodiment, and modifications may be made to the above embodiment without departing from the spirit of the present invention, and publicly known or well-known technologies may be combined as appropriate.

[0038] For example, in the live load measuring device 10 of the above embodiment, the load sensors 100, the number of which is twice the number of axles, are all attached to the side surface 21A of the side member 21, but it is sufficient to attach at least the load sensors 100 in the vicinity of the rear wheel axles 4 to the side surface 21A of the side member 21. Furthermore, in the case where there are two rear wheel axles 4, four load sensors 100 are attached to the side surface 21A of the side member 21, and so on. The number and attachment positions of the load sensors 100 may be appropriately set according to the specifications of the vehicle 1.

[0039] In the live load measuring device 10 of the above embodiment, the load sensor 100 is attached between two support points on the side surface 21A of the side member 21 where both ends of the main leaf spring 62 are supported. However, although the attachment position of the load sensor 100 is preferably a position where a difference in stress due to a difference in live load becomes noticeable, there are no particular restrictions on the attachment position as long as it is within the range below the cargo bed 7 on the side surface 21A of the side member 21.

[0040] Furthermore, in the live load measuring device 10 of the above embodiment, the spring that connects the rear wheel axle 4 to the side surface 21A of the side member 21 is the leaf spring 6, but the spring may be another type of spring such as an air spring. [Explanation of symbols]

[0041] 1: Vehicle 2: Chassis frame 4: Rear wheel axle (axle) 6: Leaf spring 7: Cargo platform 10: Load measuring device 21: Side member 21A: Side 101A: Strain gauge (strain measurement part) 200: On-board unit (load calculation section)

Claims

1. A live load measuring device for measuring a live load of a vehicle having a chassis frame having left and right side members to which axles are connected via springs, comprising: A strain measuring unit attached to a side surface of the side member and configured to measure strain on the side surface; a load calculation unit that calculates a load of the vehicle based on the measurement value of the strain measurement unit; A load measuring device comprising:

2. 2. The load measuring device according to claim 1, wherein the strain measuring section is disposed in an area below a loading platform on a side surface of the side member.

3. 3. The live load measuring device according to claim 2, wherein the strain measuring portion is disposed in the vicinity of a support point at which the spring is supported on a side surface of the side member.

4. A method for measuring a live load of a vehicle having a chassis frame with left and right side members to which axles are connected via springs, comprising the steps of: A strain measuring unit is attached to a side surface of the side member to measure the strain of the side surface; Calculating the load of the vehicle based on the measurement value of the strain measuring unit How to measure live load.

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