Load measurement device

Abstract

To improve the measurement accuracy of a load.SOLUTION: A load measurement device includes: a first calculation unit that performs linear correction on an output signal of a load sensor 21 according to the temperature measured by a temperature sensor 22 by using a temperature correction coefficient m; a second calculation unit that performs variation correction on the corrected output signal of the load sensor after the linear correction during vehicle stop according to the temperature variation over a specified elapsed time by using a temperature variation correction coefficient a; a third calculation unit that calculates a load on the basis of the corrected output signal of the load sensor after variation correction; and a fourth calculation unit that compares a reference value for setting the temperature variation correction coefficient with a physical quantity related to the output signal of the load sensor during vehicle stop, sets a temperature variation correction coefficient a1 at the time of non-precipitation when an axle shaft S thermally expands as a temperature variation correction coefficient if the variation in the physical quantity is equal to or greater than the reference value, and sets a temperature variation correction coefficient a2 at the time of precipitation when the axle shaft thermally contracts as a temperature variation correction coefficient if the variation in the physical quantity is smaller than the reference value.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] The load measuring device is mounted on a vehicle and measures the load of a load when the vehicle is stopped to load or unload. In a vehicle, the axle shaft of each wheel expands and contracts depending on the load, and the amount of distortion changes. For this reason, as a load measuring device, for example, a load sensor of a distortion measuring type is installed on the upper part of the axle shaft of each wheel, and the load is calculated based on the output of the load sensor when the vehicle is stopped. This type of load measuring device is disclosed, for example, in the following Patent Documents 1 and 2. Here, in the load sensor, the output characteristics change depending on the temperature rise of the load sensor itself due to the current flow and the surrounding temperature environment, so that output fluctuation (so-called temperature drift) occurs. In addition, the axle shaft expands and contracts due to the temperature change of the axle shaft itself. Therefore, the output of the load sensor includes the amount of distortion depending on the temperature change of the axle shaft. The load measuring devices of Patent Documents 1 and 2 detect the temperature difference between the load sensor and its installation location, and correct the output of the load sensor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-132871 A [Patent Document 2] Japanese Patent Application Publication No. 11-160140 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when a vehicle stops, cooling by the wind while the vehicle is running is no longer performed. Therefore, when it is not raining, such as when it is sunny or cloudy, the temperature of the axle shaft increases and the axle shaft thermally expands when the vehicle is stopped. On the other hand, when it is raining, rainwater and the like adheres to the lower and side parts of the axle shaft, and the rainwater and the like removes heat from the lower and side parts of the axle shaft as heat of vaporization. Therefore, when it is raining, the temperature of the upper part of the axle shaft increases when the vehicle is stopped, while the lower and side parts of the axle shaft are cooled, causing the axle shaft to thermally contract. Conventional load measuring devices cannot respond to such changes in the expansion and contraction characteristics of the axle shaft due to differences in weather, and there is room for improvement in improving the measurement accuracy of the load.

[0005] SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide a load capacity measuring device capable of improving the measurement accuracy of the load capacity. [Means for solving the problem]

[0006] The present invention includes a distortion measuring load sensor that is installed on top of the axle shaft of each wheel of a vehicle and outputs an output signal of a physical quantity corresponding to the distortion of the axle shaft, a temperature sensor for each of the load sensors that measures the temperature at the installation location of the load sensor, a first calculation unit that uses a temperature correction coefficient that represents the ratio of the amount of fluctuation in the output signal of the load sensor to the amount of temperature change from a reference temperature when the vehicle is stopped and unloaded to linearly correct the output signal of the load sensor in accordance with the measured temperature of the temperature sensor, thereby compensating for the influence of temperature drift contained in the output signal, and a second calculation unit that uses a temperature change correction coefficient that represents the ratio of the amount of fluctuation in the corrected output signal of the load sensor after linear correction to the amount of temperature change over a specified elapsed time when the vehicle is stopped and unloaded to linearly correct the output signal of the load sensor after linear correction when the vehicle is stopped. The vehicle speed control system is characterized by comprising a second calculation unit that corrects the amount of change in a corrected output signal in accordance with the amount of temperature change over a specified elapsed time, thereby compensating for a response delay of distortion to temperature changes in the axle shaft when the vehicle is stopped; a third calculation unit that calculates the load capacity of the vehicle based on the corrected output signal of the load sensor after the amount of change correction; and a fourth calculation unit that compares a reference value for setting the temperature change correction coefficient with a physical quantity related to the output signal of the load sensor when the vehicle is stopped, and if the amount of change in the physical quantity is equal to or greater than the reference value, sets the temperature change correction coefficient to the temperature change correction coefficient when it is not raining when the axle shaft is thermally expanding, and if the amount of change in the physical quantity is smaller than the reference value, sets the temperature change correction coefficient to the temperature change correction coefficient when it is raining when the axle shaft is thermally contracting. Effect of the Invention

[0007] The load weight measuring device according to the present invention cancels output fluctuations (temperature drift) caused by temperature changes in the load sensor. This load weight measuring device switches the temperature change correction coefficient between a non-precipitation temperature change correction coefficient when it is not raining and a precipitation temperature change correction coefficient when it is raining. This load weight measuring device uses the output of the load sensor compensated for the effects of such temperature drift and a temperature change correction coefficient according to the weather to calculate the load weight taking into account the expansion and contraction characteristics of the axle shaft, which differ depending on the weather. Therefore, the load weight measuring device according to the present invention can improve the measurement accuracy of the load weight. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram showing a load measuring device according to an embodiment. [Diagram 2] FIG. 2 is a diagram showing an example of a vehicle to which the load measuring device of the embodiment is applied, as viewed from the side of the vehicle. [Diagram 3] FIG. 3 is a view of an example of a vehicle to which the load measuring device of the embodiment is applied, as viewed from the rear of the vehicle. [Figure 4] FIG. 4 is a view showing an example of a vehicle to which the load measuring device of the embodiment is applied, as viewed from below the vehicle. [Diagram 5] FIG. 5 is a diagram for explaining the transition of the temperature measurement result of the temperature sensor with the elapsed time after the vehicle is stopped when it is not raining. [Figure 6] FIG. 6 is a diagram for explaining the transition of the physical quantity related to the output signal of the load sensor with respect to the elapsed time after the vehicle has stopped when it is not raining. [Figure 7] FIG. 7 is a diagram illustrating the transition of the temperature measurement result of the temperature sensor versus the elapsed time after the vehicle stopped in the first precipitation situation. [Figure 8] FIG. 8 is a diagram illustrating the transition of the physical quantity related to the output signal of the load sensor versus the elapsed time after the vehicle has stopped in a first precipitation situation. [Figure 9] FIG. 9 is a diagram illustrating the transition of the temperature measurement result of the temperature sensor versus the elapsed time after the vehicle is stopped in the second precipitation situation. [Figure 10] FIG. 10 is a diagram illustrating the transition of the physical quantity related to the output signal of the load sensor versus the elapsed time after the vehicle has stopped in the second precipitation situation. [Figure 11] FIG. 11 is a flowchart illustrating the calculation process of the load measuring device according to the embodiment. [Figure 12] FIG. 12 is a flowchart illustrating the correction coefficient setting process. [Figure 13] FIG. 13 is a flowchart illustrating the load amount calculation process. [Figure 14]FIG. 14 is a flowchart illustrating the luggage compartment state determination process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a load measuring device according to the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the embodiment.

[0010] [Embodiment] One embodiment of a load measuring device according to the present invention will be described with reference to FIGS. 1 to 14. FIG.

[0011] 1, reference numeral 1 denotes a load weight measuring device of this embodiment. This load weight measuring device 1 is mounted on a vehicle AM ​​and is used when measuring the load weight of a load when the vehicle is stopped.

[0012] The load measuring device 1 includes an electronic control device 10, a sensor unit 20, a vehicle information input unit 31, a control instruction input unit 32, a display device 33, and an external storage device 34 (FIG. 1).

[0013] The electronic control device 10 includes a control unit 11, a first input / output interface unit 12, a second input / output interface unit 13, a display unit 14, an alarm output unit 15, and a memory unit 16 (FIG. 1). The electronic control device 10 also includes a power supply unit 17, and supplies power from a power supply BT such as a secondary battery in the vehicle to the sensor unit 20 and the like via the power supply unit 17 (FIG. 1).

[0014] The control unit 11 is responsible for the calculation process when measuring the load amount.

[0015] The control unit 11 operates when the vehicle is stopped and the ignition is off, based on the vehicle information obtained from the vehicle information input unit 31 via the first input / output interface unit 12 and the control instruction signal from the control instruction input unit 32 via the first input / output interface unit 12. The vehicle information input unit 31 transmits a vehicle speed signal and an ignition off signal from the vehicle side to the control unit 11. The control instruction input unit 32 is, for example, a measurement start button and a measurement end button installed in the vehicle cabin. The control unit 11 receives the ignition off signal and also receives a measurement start signal accompanying the pressing of the measurement start button by an operator, and starts measuring the load weight. The control unit 11 then ends the measurement of the load weight based on the measurement end signal received when the measurement end button is pressed by the operator.

[0016] The control unit 11 calculates the load amount based on the load information and temperature information obtained from the sensor unit 20 via the second input / output interface unit 13.

[0017] The sensor unit 20 is installed on the upper part of the axle shaft S of the vehicle AM ​​(FIGS. 2 to 4). In this load measuring device 1, one sensor unit 20 is provided for each of the axle shafts S1, S2, S3, and S4 of the wheels W1, W2, W3, and W4 of the vehicle AM ​​(sensor units 20A, 20B, 20C, and 20D).

[0018] The sensor unit 20 includes a load sensor 21, a temperature sensor 22, an input / output interface unit 23, an MCU (Micro Controller Unit) 24, an ASIC (Application Specific Integrated Circuit) 25, and a power supply circuit 26 (FIG. 1).

[0019] The axle shafts S1, S2, S3, and S4 of the wheels W1, W2, W3, and W4 are in an initial state when there is no load, and are distorted when a load is placed on the wheels. Therefore, as described above, each axle shaft S1, S2, S3, and S4 expands and contracts according to the load, and the amount of distortion changes. For this reason, the load sensor 21 is a distortion measurement type that outputs an output signal of a physical quantity (for example, a frequency in Hz) according to the amount of distortion of the axle shaft S.

[0020] Here, the load sensor 21 generates an output fluctuation (so-called temperature drift) according to the temperature change. In addition, the load measuring device 1 measures the load when the vehicle is stopped. Therefore, the temperature environment around the load sensor 21 tends to rise when the vehicle is stopped because cooling by the traveling wind is no longer performed. For example, heat from the braking device B is transmitted to each of the axle shafts S1, S2, S3, and S4. Heat from the differential device DF is also transmitted to the axle shafts S3 and S4 of the rear wheels W3 and W4. When the axle shafts S1, S2, S3, and S4 are traveling, the influence of the heat transfer is offset by cooling by the traveling wind, but when the vehicle is stopped, the temperature rises due to the influence of the heat transfer. The temperature sensor 22 is provided to correct the output fluctuation (temperature drift) according to the temperature change and the output fluctuation according to the distortion amount accompanying the temperature change of the axle shafts S1, S2, S3, and S4 with respect to the output of the load sensor 21. Therefore, the temperature sensor 22 measures the temperature at the location where the load sensor 21 is installed.

[0021] The load amount measuring device 1 includes a first calculation unit that uses a temperature correction coefficient m to linearly correct the output signal F of the load sensor 21 in accordance with the measured temperature of the temperature sensor 22, thereby compensating for the effect of temperature drift contained in the output signal F. Here, this first calculation unit is provided in the control unit 11 of the electronic control device 10. The temperature correction coefficient m represents the ratio of the amount of fluctuation in the output signal F of the load sensor 21 to the amount of temperature change ΔT1 from a reference temperature (e.g., 25 degrees) when the vehicle is stopped and has no load.

[0022] The first calculation unit obtains the difference between the measured temperature obtained from the output signal of the temperature sensor 22 and the reference temperature (the temperature change amount ΔT1 from the reference temperature), and calculates the corrected output signal F1 of the load sensor 21 after linear correction using the following equation 1 based on the output signal F of the load sensor 21, the temperature change amount ΔT1 from the reference temperature, and the temperature correction coefficient m. F1 = F + m * ΔT1 (1)

[0023] The load measuring device 1 includes a second calculation unit that uses a temperature change correction coefficient a to correct the amount of change in the corrected output signal F1 of the load sensor 21 after linear correction when the vehicle is stopped in accordance with the amount of temperature change ΔTt over a specified elapsed time, thereby compensating for the response delay of the distortion to the temperature change in the axle shaft S when the vehicle is stopped. This second calculation unit is provided in the control unit 11 of the electronic control device 10. The temperature change correction coefficient a represents the ratio of the amount of change in the corrected output signal F1 of the load sensor 21 after linear correction to the amount of temperature change ΔTt over a specified elapsed time when the vehicle is stopped and without a load. The specified elapsed time is, for example, the output period of the output signals of the sensor unit 20 (the output signal of the load sensor 21 and the output signal of the temperature sensor 22).

[0024] The second calculation unit calculates a corrected output signal F2 of the load sensor 21 after the change amount correction based on the corrected output signal F1 of the load sensor 21 after the linear correction, the temperature change amount ΔTt over a specified elapsed time, and the temperature change correction coefficient a using the following equation 2. F2 = F1 + a * ΔTt (2)

[0025] The load weight measuring device 1 includes a third calculation unit that calculates the load weight of the vehicle AM ​​based on the corrected output signal F2 of the load sensor 21 after the change amount correction. This third calculation unit is provided in the control unit 11 of the electronic control device 10. The load weight calculation process may be performed using a well-known technique in this technical field.

[0026] The load measuring device 1 has a fourth calculation unit which sets the temperature change correction coefficient a to the temperature change correction coefficient a by comparing the first reference physical quantity AH0 with the correction output signal F1 immediately before the start of measurement, and sets the temperature change correction coefficient a to the temperature change correction coefficient a1 when the axle shaft S is thermally expanding (i.e., when it is not raining) (hereinafter referred to as the "temperature change correction coefficient when it is not raining") a1 when the axle shaft S is thermally contracting (i.e., when it is raining) (hereinafter referred to as the "temperature change correction coefficient when it is raining") a2 when the axle shaft S is thermally contracting (i.e., when it is raining) if the change in the physical quantity is smaller than the reference value. This fourth calculation unit is provided in the control unit 11 of the electronic control device 10.

[0027] As described above, when it is not raining, such as when it is sunny or cloudy, the temperature of the axle shaft S rises and thermally expands when the vehicle is stopped. Therefore, the temperature change correction coefficient a1 when it is not raining is set to the ratio of the amount of change in the corrected output signal F1 of the load sensor 21 after linear correction related to the axle shaft S with a tendency to thermally expand to the amount of temperature change ΔTt over a specified elapsed time when the vehicle is stopped when it is not raining and there is no load. Also, when it is raining, rainwater, etc. adheres to the lower part and sides of the axle shaft S, and the rainwater, etc. removes heat from the lower part and sides of the axle shaft S as heat of vaporization, so that the temperature of the upper part of the axle shaft S rises when the vehicle is stopped, while the lower part and sides of the axle shaft S are cooled, causing the axle shaft S to thermally contract. Therefore, the temperature change correction coefficient a2 during precipitation is the ratio of the amount of fluctuation in the corrected output signal F1 of the load sensor 21 after linear correction related to the axle shaft S, which has a tendency to thermally contract, to the amount of temperature change ΔTt over a specified elapsed time when the vehicle is stopped during rain and has no cargo.

[0028] Here, the temperature change correction coefficient a2 during precipitation is subdivided according to the precipitation condition. In this example, the temperature change correction coefficient a2 during precipitation is set to the first temperature change correction coefficient a2a during the first precipitation condition, and the temperature change correction coefficient a2 during precipitation is set to the second temperature change correction coefficient a2b during the second precipitation condition. The first precipitation condition is a condition in which the amount of water scooped up on the road surface during driving is less than that in the second precipitation condition. For example, the first precipitation condition is a normal rainfall condition in which the amount of precipitation is equal to or less than the reference precipitation amount. The second precipitation condition is a heavy rainfall condition in which the amount of precipitation is greater than the reference precipitation amount.

[0029] The fourth calculation unit compares a reference physical quantity during precipitation for setting the temperature change correction coefficient a2 with a physical quantity related to the output signal of the load sensor 21 when the vehicle is stopped, and if the physical quantity is greater than the reference physical quantity during precipitation, sets the temperature change correction coefficient a2 during precipitation to a first temperature change correction coefficient a2a, and if the physical quantity is equal to or less than the reference physical quantity, sets the temperature change correction coefficient a2 during precipitation to a second temperature change correction coefficient a2b. The second temperature change correction coefficient a2b has a ratio of the amount of change in the corrected output signal F1 of the load sensor 21 after linear correction to the amount of temperature change ΔTt over a specified elapsed time that is greater than the first temperature change correction coefficient a2b.

[0030] FIG. 5 shows the transition of the time elapsed after the vehicle is stopped and the temperature measurement result of the temperature sensor 22 when it is not raining. FIG. 6 shows the transition of the time elapsed after the vehicle is stopped and the physical quantity related to the output signal of the load sensor 21 when it is not raining. FIG. 7 shows the transition of the time elapsed after the vehicle is stopped and the temperature measurement result of the temperature sensor 22 in a first precipitation condition. FIG. 8 shows the transition of the time elapsed after the vehicle is stopped and the physical quantity related to the output signal of the load sensor 21 in the first precipitation condition. FIG. 9 shows the transition of the time elapsed after the vehicle is stopped and the temperature measurement result of the temperature sensor 22 in a second precipitation condition. FIG. 10 shows the transition of the time elapsed after the vehicle is stopped and the physical quantity related to the output signal of the load sensor 21 in the second precipitation condition.

[0031] An example of the calculation process in the load measuring device 1 will be described below with reference to the flowcharts of FIGS.

[0032] The output signals of the sensor unit 20 (the output signal of the load sensor 21 and the output signal of the temperature sensor 22) are repeatedly input to the control unit 11 of the electronic control device 10 at specified elapsed time intervals until an ignition off signal of the vehicle AM ​​is input (steps ST1, ST2).

[0033] When the control unit 11 detects the input of an ignition-off signal in step ST2 after the vehicle has stopped, the control unit 11 calculates a corrected output signal F1 based on the output signal F of the load sensor 21, the temperature change amount ΔT1 from the reference temperature, and the temperature correction coefficient m (step ST3). The control unit 11 sets the corrected output signal F1 calculated in step 3 to a first reference value (here, the first reference physical amount AH0) for setting the temperature change correction coefficient a (step ST4).

[0034] The control unit 11 acquires the output signals of the sensor unit 20 (the output signal of the load sensor 21 and the output signal of the temperature sensor 22), and calculates a corrected output signal F1 based on the output signal F of the load sensor 21, the temperature change ΔT1 from the reference temperature, and the temperature correction coefficient m (step ST5). After that, the control unit 11 proceeds to a correction coefficient setting process of step ST6 (flowchart in FIG. 12).

[0035] When the fourth calculation unit of the control unit 11 starts the correction coefficient setting process, it compares the corrected output signal F1 calculated in step ST5 with the first reference physical quantity AH0 set in step ST4 (step ST11).

[0036] If the correction output signal F1 is equal to or greater than the first reference physical quantity AH0 in step ST11, there is a possibility that the axle shaft S will thermally expand and become significantly distorted when it is not raining. In this case, the fourth calculation unit of the control unit 11 sets the temperature change correction coefficient a to the non-precipitation temperature change correction coefficient a1 (step ST12), and ends this correction coefficient setting process.

[0037] On the other hand, if the correction output signal F1 is smaller than the first reference physical quantity AH0 in step ST11, it may be that the axle shaft S is thermally contracted during precipitation and is not distorted as much as during thermal expansion. In this case, the fourth calculation unit of the control unit 11 sets the temperature change correction coefficient a to the precipitation temperature change correction coefficient a2.

[0038] As described above, here, the temperature change correction coefficient during precipitation a2 is subdivided according to the precipitation state. When the corrected output signal F1 is smaller than the first reference physical quantity AH0 in step ST11, the fourth calculation unit of the control unit 11 sets a second reference value (here, the second reference physical quantity BH0) as a reference physical quantity during precipitation for setting the temperature change correction coefficient during precipitation a2, and compares the corrected output signal F1 used in step ST11 with the second reference physical quantity BH0 (step ST13). For example, the second reference physical quantity BH0 is obtained by subtracting a specified value (here, "3") from the first reference physical quantity AH0.

[0039] If the correction output signal F1 is greater than the second reference physical quantity BH0 in step ST13, there is a possibility that the precipitation condition is a first precipitation condition in which the distortion of the axle shaft S is large among various precipitation conditions. In this case, the fourth calculation unit of the control unit 11 sets the precipitation temperature change correction coefficient a2 (temperature change correction coefficient a) to the first precipitation temperature change correction coefficient a2a (step ST14), and ends this correction coefficient setting process.

[0040] On the other hand, if the correction output signal F1 is equal to or less than the second reference physical quantity BH0 in step ST13, there is a possibility that the precipitation condition is a second precipitation condition in which the distortion of the axle shaft S is small among various precipitation conditions. In this case, the fourth calculation unit of the control unit 11 sets the precipitation temperature change correction coefficient a2 (temperature change correction coefficient a) to the second precipitation temperature change correction coefficient a2b (step ST15), and ends this correction coefficient setting process.

[0041] After completing this correction coefficient setting process, the control unit 11 judges whether or not a measurement start signal has been input (step ST7). The control unit 11 repeats steps ST5 and ST6 until a measurement start signal is input, and when it detects input of a measurement start signal in response to pressing of the measurement start button of the control instruction input unit 32, it proceeds to a load amount calculation process (flowchart in FIG. 13) in step ST8.

[0042] The control unit 11 sets a third reference value (here, a third reference physical quantity CH0) for calculating the load amount (step ST21). For the third reference physical quantity CH0, the latest corrected output signal F1 calculated in step ST5 is set.

[0043] The control unit 11 acquires the output signals of the sensor unit 20 (the output signal of the load sensor 21 and the output signal of the temperature sensor 22), and calculates a corrected output signal F1 based on the output signal F of the load sensor 21, the temperature change ΔT1 from the reference temperature, and the temperature correction coefficient m (step ST22). Thereafter, the control unit 11 proceeds to a luggage compartment state determination process in step ST23 (flowchart in FIG. 14).

[0044] The control unit 11 judges whether or not the operation is only loading (step ST31). For example, if the control instruction input unit 32 has a loading instruction button that instructs only loading in addition to the measurement start button, the control unit 11 judges whether or not the operation is only loading based on whether or not a signal accompanying the pressing of the loading instruction button is received. Also, for example, if the control instruction input unit 32 has an unloading instruction button that instructs only unloading, the control unit 11 judges that the operation is not only loading based on the reception of a signal accompanying the pressing of the unloading instruction button. Also, for example, if the control instruction input unit 32 has an unloading instruction button that instructs both loading and unloading, the control unit 11 judges that the operation is not only loading based on the reception of a signal accompanying the pressing of the unloading instruction button. Also, for example, if the control instruction input unit 32 has a loading instruction button that instructs both loading and unloading, the control unit 11 judges that the operation is not only loading based on the reception of a signal accompanying the pressing of the unloading instruction button. Also, for example, if the control unit 11 does not receive any of the loading instruction button, the unloading instruction button, and the signal accompanying the pressing of the unloading instruction button, the control unit 11 judges that the operation is not only loading.

[0045] When it is determined in step ST31 that only loading is performed, the control unit 11 compares the corrected output signal F1 calculated in step ST22 with the third reference physical quantity CH0 set in step ST21 (step ST32).

[0046] If the corrected output signal F1 is equal to or greater than the third reference physical quantity CH0 in step ST32, the control unit 11 terminates the cargo compartment state determination process since there is a possibility that distortion of the axle shaft S due to loading has occurred, which is consistent with the determination result of step ST31.

[0047] Furthermore, if the correction output signal F1 is smaller than the third reference physical quantity CH0 in step ST32, there is a possibility that distortion of the axle shaft S due to unloading has occurred, which is inconsistent with the judgment result of step ST31. Therefore, the control unit 11 proceeds to the correction coefficient setting process of step ST33 (flowchart in FIG. 12), reviews the temperature change correction coefficient a, and ends this cargo space state judgment process.

[0048] Furthermore, when the control unit 11 determines in step ST31 that the operation is not only loading, it determines whether or not the operation is only unloading (step ST34). For example, the control unit 11 determines whether or not the operation is only unloading based on whether or not a signal accompanying the pressing of an unloading instruction button is received. Also, for example, the control unit 11 determines that the operation is not only unloading but both loading and unloading based on the reception of a signal accompanying the pressing of an unloading instruction button.

[0049] When it is determined in step ST34 that only unloading is to be performed, the control unit 11 compares the corrected output signal F1 calculated in step ST22 with the third reference physical quantity CH0 set in step ST21 (step ST35).

[0050] If the correction output signal F1 is equal to or greater than the third reference physical quantity CH0 in step ST35, there is a possibility that distortion of the axle shaft S due to loading has occurred, which is inconsistent with the judgment result of step ST34. Therefore, the control unit 11 proceeds to the correction coefficient setting process of step ST33 (flowchart in FIG. 12), reviews the temperature change correction coefficient a, and ends this cargo space state judgment process.

[0051] Furthermore, if the corrected output signal F1 is smaller than the third reference physical quantity CH0 in step ST35, the control unit 11 determines that distortion of the axle shaft S due to unloading may have occurred, which is consistent with the determination result of step ST34, and therefore ends the cargo space state determination process.

[0052] Moreover, when the control unit 11 determines in step ST34 that not only unloading is taking place, there is a possibility that both loading and unloading are taking place, and therefore ends this luggage compartment state determination process.

[0053] After completing this luggage compartment state determination process, the control unit 11 calculates the load amount (step ST24). This calculation process is performed using a well-known technique (for example, the technique disclosed in Japanese Patent Application Laid-Open No. 2008-064593).

[0054] For example, in this step ST24, the first calculation unit of the control unit 11 linearly corrects the output signal F of the load sensor 21 in accordance with the measured temperature of the temperature sensor using the temperature correction coefficient m based on the above equation 1, thereby compensating for the effect of temperature drift contained in the output signal F.

[0055] Next, the second calculation unit of the control unit corrects the amount of change in the corrected output signal F1 of the load sensor 21 after linear correction according to the amount of temperature change ΔTt over a specified elapsed time based on the temperature change correction coefficient a set in the correction coefficient setting process based on the above equation 2, thereby compensating for the response delay of the distortion in the axle shaft S to the temperature change when the vehicle is stopped.

[0056] Then, the third calculation section of the control section 11 calculates the vehicle load based on the corrected output signal F2 of the load sensor 21 after the change amount has been corrected.

[0057] The control unit 11 judges whether or not a measurement end signal is input (step ST25). The control unit repeats steps ST22, ST23, and ST24 until a measurement end signal is input, and when the control unit detects input of the measurement end signal in response to pressing of the measurement end button of the control instruction input unit 32, etc., it finally fixes the measurement result to the payload calculated in step ST24 (step ST26).

[0058] For example, in the electronic control device 10, the control unit 11 passes the calculation processing result (loading amount information, etc.) to the display unit 14, and the display unit 14 displays the calculation processing result on a display device 33 such as a monitor in the vehicle cabin. Also, in the electronic control device 10, when the control unit 11 detects warning information such as overloading, the warning output unit 15 displays the warning information on the display device 33 in the vehicle cabin. Also, the control unit 11 records the calculation processing result in an external storage device 34 in the vehicle cabin.

[0059] As described above, the load amount measuring device 1 of this embodiment cancels the output variation (temperature drift) in response to the temperature change in the load sensor 21. The load amount measuring device 1 of this embodiment switches the temperature change correction coefficient a between a non-precipitation temperature change correction coefficient a1 when it is not raining and a precipitation temperature change correction coefficient a2 when it is raining. This load amount measuring device 1 uses the output of the load sensor 21 compensated for the effect of such temperature drift and the temperature change correction coefficient a according to the weather to calculate the load amount taking into account the expansion and contraction characteristics of the axle shaft S that differ depending on the weather. Furthermore, this load amount measuring device 1 switches the precipitation temperature change correction coefficient a2 between a first precipitation temperature change correction coefficient a2a and a second precipitation temperature change correction coefficient a2b depending on the amount of precipitation. This load amount measuring device 1 uses the output of the load sensor 21 compensated for the effect of such temperature drift and the temperature change correction coefficient a according to the weather to calculate the load amount taking into account the expansion and contraction characteristics of the axle shaft S that differ depending on the weather. Therefore, the load amount measuring device 1 of this embodiment can improve the measurement accuracy of the load amount.

[0060] Furthermore, during the period from the start to the end of measurement, the load amount measuring device 1 of this embodiment monitors the instruction form of loading, unloading, etc., in the previous cargo compartment state determination process, and the actual loading and unloading form in the cargo compartment based on the output of the load sensor 21. If there is a discrepancy between the instruction form and the actual loading and unloading form, this load amount measuring device 1 performs the correction coefficient setting process again to optimize the temperature change correction coefficient a. Therefore, the load amount measuring device 1 of this embodiment can improve the measurement accuracy of the load amount in this respect as well.

[0061] Here, the control unit 11 may store the output signals of the sensor unit 20 (the output signal of the load sensor 21 and the output signal of the temperature sensor 22) in the memory unit 16 in a chronological order when the load is calculated. The control unit 11 may then calculate a temperature change correction coefficient a based on the accumulated data of the output signals of the sensor unit 20, and replace the temperature change correction coefficient a with a highly accurate temperature change correction coefficient a that matches the actual conditions of the vehicle AM. For example, in the braking device B, the amount of heat generated changes due to wear or replacement of the facing material. In the differential device DF, the amount of heat generated changes due to deterioration of the lubricating oil. The load amount measuring device 1 of this embodiment can obtain a highly accurate measurement result of the load amount that also corresponds to the change in the amount of heat generated by timely replacing the temperature change correction coefficient a with a highly accurate one that matches the actual conditions of the vehicle AM. [Explanation of symbols]

[0062] 1. Load measuring device 10 Electronic control device 11 Control section 20, 20A, 20B, 20C, 20D Sensor unit 21 Load sensor 22 Temperature Sensor a1 Temperature change correction coefficient during non-precipitation a2 Precipitation temperature change correction coefficient a2a First precipitation temperature change correction coefficient a2b Second precipitation temperature change correction coefficient AM train m Temperature correction factor S, S1, S2, S3, S4 axle shaft Wheels W1, W2, W3, W4

Claims

1. A strain measuring load sensor is installed on an upper portion of an axle shaft of each wheel of a vehicle and outputs an output signal of a physical quantity corresponding to the amount of strain of the axle shaft; a temperature sensor for each of the load sensors that measures a temperature at a location where the load sensor is installed; a first calculation unit that uses a temperature correction coefficient that represents a ratio of a fluctuation amount of the output signal of the load sensor to a temperature change amount from a reference temperature when the vehicle is stopped and has no load, and linearly corrects the output signal of the load sensor in accordance with the temperature measured by the temperature sensor, thereby compensating for an effect of temperature drift contained in the output signal; a second calculation unit that uses a temperature change correction coefficient representing a ratio of a change amount of the linearly corrected corrected output signal of the load sensor to a temperature change amount over a specified elapsed time when the vehicle is stopped and unloaded, and corrects a change amount of the linearly corrected corrected output signal of the load sensor while the vehicle is stopped in accordance with the temperature change amount over the specified elapsed time, thereby compensating for a response delay of distortion to a temperature change in the axle shaft while the vehicle is stopped; a third calculation unit that calculates a load of the vehicle based on a corrected output signal of the load sensor after the change amount is corrected; a fourth calculation unit that compares a reference value for setting the temperature change correction coefficient with a physical quantity related to the output signal of the load sensor when the vehicle is stopped, and if the physical quantity is equal to or greater than the reference value, sets the temperature change correction coefficient to a temperature change correction coefficient when it is not raining when the axle shaft is thermally expanding, and if the physical quantity is smaller than the reference value, sets the temperature change correction coefficient to a temperature change correction coefficient when it is raining when the axle shaft is thermally contracting; A load measuring device comprising:

2. the non-precipitation temperature change correction coefficient is a ratio of a change in the corrected output signal of the load sensor after linear correction of the thermal expansion tendency of the axle shaft to a change in temperature over the specified elapsed time when the vehicle is stopped in a non-precipitation state and has no load, The load measuring device according to claim 1, wherein the temperature change correction coefficient during precipitation is a ratio of the amount of fluctuation in the corrected output signal of the load sensor after linear correction related to the axle shaft having a tendency to thermal contraction to the amount of temperature change over the specified elapsed time when the vehicle is stopped during precipitation and has no load.

3. the fourth calculation unit compares a reference physical quantity during precipitation for setting the temperature change correction coefficient during precipitation with a physical quantity related to the output signal of the load sensor while the vehicle is stopped, and if the physical quantity is greater than the reference physical quantity during precipitation, sets the temperature change correction coefficient during precipitation to a first temperature change correction coefficient during precipitation, and if the physical quantity is equal to or smaller than the reference physical quantity, sets the temperature change correction coefficient during precipitation to a second temperature change correction coefficient during precipitation; The load measuring device according to claim 1 or 2, characterized in that the second precipitation temperature change correction coefficient is a ratio of the amount of fluctuation in the corrected output signal of the load sensor after linear correction to the amount of temperature change over the specified elapsed time that is greater than the first precipitation temperature change correction coefficient.

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