AU2016334863A1

AU2016334863A1 - Load weight measuring device for concrete mixer vehicle

Info

Publication number: AU2016334863A1
Application number: AU2016334863A
Authority: AU
Inventors: Syunji Harada; Takeshi NIIJIMA; Yoshimitsu Takahashi; Yoshihiko TOMITAKA
Original assignee: KYB Corp
Current assignee: KYB Corp
Priority date: 2015-10-09
Filing date: 2016-10-07
Publication date: 2018-05-17
Also published as: JP6326394B2; WO2017061613A1; JP2017072556A

Abstract

This load weight measuring device 100, 200 is provided with: load cells 71, 72 disposed in a rear drum receiving part 50 that supports the rear of a mixer drum 10 at the rear of a vehicle body 2 to measure the load on the mixer drum 10; and a computation unit 110 that calculates the weight of the load on the basis of measured values of the load cells 71, 72 and at least one of a vehicle body state quantity indicating the state of the vehicle body 2 and a drum state quantity indicating the state of the mixer drum 10.

Description

DESCRIPTION

LOAD AMOUNT WEIGHING APPARATUS FOR MIXER TRUCK

TECHNICAL FIELD [0001] The present invention relates to a load amount weighing apparatus for mixer truck.

BACKGROUND ART [0002] JP9-193134A describes a load amount weighing apparatus for mixer truck including a load cell installed on a front drum receiving part and a load cell installed on each of a pair of left and right rear drum receiving parts. JP9-193134A discloses, as a method of calculating a load amount of mixer truck, a method of adding detection values of load cells together and a method of estimation from a sharing ratio of loads acting on the front drum receiving part and the rear drum receiving part and the detection value of the load cell installed on the front drum receiving part.

SUMMARY OF INVENTION [0003] The load cell in general detects a load in a predetermined direction. That is, in the load amount weighing apparatus for mixer truck described in JP9-193134A, when a vehicle body is inclined, the load cells detects a load not in a vertical direction but in a direction perpendicular to a vehicle body. As described above, if the vehicle body is tilted, there Is a concern that weighing accuracy of the load amount might be lowered since the load direction detected by each of the load cells is not a vertical direction any more.

[0004] Moreover, in the load amount weighing apparatus for mixer truck described in JP9-193134A, the sharing ratio for loads acting on the front drum

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- 2 receiving part and the rear drum receiving part are assumed to be constant. However, the load sharing ratio changes in accordance with a distribution state of load in a drum, and the distribution state of the loads is changed by inclination of the vehicle body, a rotation speed of the drum, viscosity of loads and the like. That is, if the sharing ratio of the loads is made assumed constant, the weighing accuracy of the load amount can be lowered.

[0005] The present invention has an object to improve weighing accuracy of the load amount on the mixer truck.

[0006] According to one aspect of the present invention, a load amount weighing apparatus for mixer truck configured to weigh a load amount of a load in a drum rotatably mounted on a vehicle body is provided. The load amount weighing apparatus includes: a rear load detector provided on a rear drum receiving part supporting a rear of the drum on a rear of the vehicle body, the rear load detector being configured to detect a load of the drum; and a calculation part configured to calculate a load amount of the load on the basis of the detection value of the rear load detector and at least either one of a vehicle-body state quantity or a drum state quantity, the vehicle-body state quantity indicating a state of the vehicle body, the drum state quantity indicating a state of the drum.

BRIEF DESCRIPTION OF DRAWINGS [0007] Fig. 1 is a side view of a mixer truck including a load amount weighing apparatus according to a first embodiment of the present invention. Fig. 2 is a sectional view of the mixer truck along II-II line in Fig. 1.

Fig. 3 is a sectional view of a guide roller along III-ΠΙ line in Fig. 2.

Fig. 4 is a block diagram of the load amount weighing apparatus

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- 3 according to the first embodiment of the present invention.

Fig. 5 is a circuit diagram of a load cell of the load amount weighing apparatus according to the first embodiment of the present invention.

Fig. 6 is a view for explaining a balance of forces acting on a mixer drum of the mixer truck.

Fig. 7 is a graph indicating correlation between a calculated weight and an actual weight changing in accordance with inclination angles of the vehicle body.

Fig. 8 is a graph indicating correlation between a calculated weight and an actual weight changing in accordance with a rotation number of the mixer drum.

Fig. 9 is a graph indicating correlation between a calculated weight and an actual weight changing in accordance with a slump value.

Fig. 10 is a flowchart showing a calculation procedure of a weight measurement mode by the load amount weighing apparatus according to the first embodiment of the present invention.

Fig. 11 is a view for explaining movement of center of gravity of the load when the mixer drum is rotated.

Fig. 12 is a graph indicating correlation between a load difference and a slump value per unit volume.

Fig. 13 is a flowchart showing a calculation procedure of a slump value estimation mode by the load amount weighing apparatus according to the first embodiment of the present invention.

Fig. 14 is a flowchart showing a calculation procedure of a vehicle-body overturning determination mode by the load amount weighing apparatus according to the first embodiment of the present invention.

Fig. 15 is a block diagram of a load amount weighing apparatus according

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- 4 to a second embodiment of the present invention.

Fig. 16 is an enlarged view showing a front drum receiving part of a mixer truck including the load amount weighing apparatus according to the second embodiment of the present invention in an enlarged manner.

Fig. 17 is a sectional view of the front drum receiving part along XVII-XVII line in Fig. 16.

DESCRIPTION OF EMBODIMENTS [0008] A load amount weighing apparatus for mixer truck according to embodiments of the present invention will be described below by referring to the attached drawings.

[0009] <First embodiment

First, a mixer truck 1 on which a load amount weighing apparatus 100 is provided will be described by referring to Figs. 1 to 3. The mixer truck 1 illustrated in Fig. 1 is a vehicle for transporting ready-mixed concrete (hereinafter referred to as “fresh concrete”) input into a mixer drum 10 in a concrete plant. The mixer truck 1 transports aggregates such as gravel and sand other than the fresh concrete but the case of loading the fresh concrete as a load will be described in the following.

[0010] The mixer truck 1 includes the mixer drum 10 for loading the fresh concrete, a driving device 20 for rotatably driving the mixer drum 10, a hopper 30 for supplying the fresh concrete to the mixer drum 10, and a chute 40 for guiding the fresh concrete discharged from the mixer drum 10 to a predetermined position.

[0011 ] The mixer drum 10 is a cylindrical member having a rear end formed

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- 5 as an opening end and is rotatably mounted on a frame 2 a of a vehicle body 2. [0012] A driving shaft 10a extending along a rotation axis Cl of the mixer drum 10 is provided on a front end of the mixer drum 10, and an annular roller ring 10b is provided on a rear-part outer periphery of the mixer drum 10. The driving shaft 10a of the mixer drum 10 is connected to a hydraulic motor (not shown) provided in the driving device 20 arranged on a front side of the frame 2a through a gear box (not shown). The mixer drum 10 is constituted to rotate forward or backward by the hydraulic motor.

[0013] The rear side of the mixer drum 10 is supported from below by a rear drum receiving part 50 arranged on a rear of the frame 2a through the roller ring 10b. The front side of the mixer drum 10 is supported from below by a front drum receiving part 60 arranged on a front of the frame 2 a through the driving device 20. The mixer drum 10 is arranged on the frame 2a in a front down attitude in which the rear part is lifted higher than the front part.

[0014] The mixer drum 10 supported as above is rotated around an X’ axis in an X’ - Y’ coordinate system rotated around an origin O only by a predetermined angle (elevation angle Θ) with respect to an X - Y coordinate system assuming that a horizontal direction in a vehicle -body longitudinal direction is an X axis, a vertical direction is a Y axis, and a virtual support point of the front drum receiving part 60 is the origin O in Fig. 1. That is, the rotation axis C1 of the mixer drum 10 matches the X’ axis. If the vehicle body 2 is horizontal in the longitudinal direction, the elevation angle Θ becomes the predetermined rotation axis angle θ 1, On the other hand, if the vehicle body 2 is inclined in the longitudinal direction, the elevation angle Θ becomes a size obtained by adding or subtracting an inclination angle a with respect to the rotation axis angle θ 1.

[0015] A drum blade, not shown, is disposed spirally along a drum inner

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- 6 wall surface in the mixer drum 10. The fresh concrete loaded in the mixer drum 10 is agitated or the like by the drum blade rotated with the mixer drum 10.

[0016] When the mixer drum 10 is rotated forward, the drum blade moves the fresh concrete In the mixer drum 10 forward while agitating it. On the other hand, if the mixer drum 10 is rotated backward, the drum blade moves the fresh concrete to the rear while agitating it. By rotating the mixer drum 10 backward as above, the fresh concrete can be discharged from the opening end of the mixer drum 10. The fresh concrete discharged from the mixer drum 10 is guided to a predetermined position through the chute 40 provided capable of turning on a lower rear part of the mixer truck 1.

[0017] When the fresh concrete is to be input into the mixer drum 10 through the hopper 30 provided on the upper rear part of the mixer truck 1, the mixer drum 10 is rotated forward at a speed higher than that in agitating so as to rapidly move the input fresh concrete to the front.

[0018] Subsequently, a structure of the rear drum receiving part 50 will be described by referring to Figs. 2 and 3. Fig. 2 is a sectional view along II II line in Fig. 1 and illustrates a structure inside the mixer drum 10 and below the rear drum receiving part 50 in an omitted manner. Fig. 3 is a sectional view along III-III line in Fig. 2.

[0019] As illustrated in Fig. 2, on the rear drum receiving part 50, a first guide roller 51 supporting a right side of the mixer drum 10 when seen from a rear side of the vehicle body 2 and a second guide roller 52 supporting a left side of the mixer drum 10 are provided, respectively. Pin type load cells 71 and 72 are incorporated in the guide rollers 51 and 52, respectively. A structure of the first guide roller 51 will be described by referring to Fig. 3. [0020] The first guide roller 51 has an annular roller 54 in contact with the

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- 7 roller ring 10b, a pin type first load cell 71 rotatably supporting the roller 54, and a pair of support frames 55 in which an insertion hole 55a through which the first load cell 71 is inserted without contact is formed.

[0021] As described above, the pin supporting the roller 54 is constituted by a pin type first load cell 71. The first load cell 71 is an elastic body formed having a columnar shape, its both end parts 71b are fixed by fixing members 56 fixed to the support frames 55, and a center part 71a is pressed and fixed to an inner ring of a roller bearing 57 provided between that and the roller 54. [0022] Distortion generating parts 71c generating distortion by a load acting on the first load cell 71 are provided between the center part 71a and the both end parts 71b, respectively. A distortion gauge, not shown, is mounted on the distortion generating part 71c, and resistance of the distortion gauge is changed in accordance with a distortion amount in the distortion generating part 71c, whereby an electric signal in propart with the load is output from the first load cell 71.

[0023] The first guide roller 51 is disposed so that a shaft core C2 of the first load cell 71 and the rotation axis Cl of the mixer drum 10 are in parallel with the mixer drum 10. Thus, on the first load cell 71, the load in the Y’ axis direction acts as indicated by a bold arrow in Fig. 3. That is, the first load cell 71 detects a load of the mixer drum 10 in the Y’ axis direction perpendicular to the rotation axis Cl (X’ axis) of the mixer drum 10, not the load in the vertical direction of the mixer drum 10.

[0024] The second guide roller 52 has a structure similar to that of the first guide roller 51, and the pin type second load cell 72 is incorporated in a pin supporting the roller 54. The second load cell 72 detects the load of the mixer drum 10 in the Y’ axis direction perpendicular to the rotation axis Cl of the mixer drum 10 similarly to the first load cell 71.

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- 8 [0025] Subsequently, the load amount weighing apparatus 100 for weighing the load amount of the fresh concrete loaded in the mixer drum 10 will be described by referring mainly to Figs. 4 and 5. Fig. 4 is a block diagram illustrating an outline constitution of the load amount weighing apparatus 100. Fig. 5 is a circuit diagram of the load cells 71 and 72.

[0026] The load amount weighing apparatus 100 includes a pair of the load cells 71 and 72 as rear load detectors provided on the rear drum receiving part 50 supporting the rear of the mixer drum 10 and detecting a load of the mixer drum 10 in the Y’ axis direction perpendicular to the rotation axis Cl of the mixer drum 10, a calculation part 110 for calculating a load amount of the fresh concrete on the basis of detection values of the pair of load cells 71 and 72 and at least either one of a vehicle-body state quantity indicating a state of the mixer truck 1 or a drum state quantity indicating a state of the mixer drum 10, and a display part 120 displaying a calculation result and the like of the calculation part 110.

[0027] The calculation part 110 has a memory, not shown, storing a program for calculating a load amount or the like, a map, a calculation formulas and the like, a CPU, not shown, for calculating a load amount or the like in accordance with the program, and an input/output interface, not shown, into which detection values of the various sensors and the load cells are input and outputting the calculation results and the like to the display part 120. Moreover, the calculation part 110 has a determination part 111 for comparing a threshold value determined in advance with the calculation result.

[0028] Into the calculation part 110, a detection value of an inclination sensor 131 for detecting an inclination angle in the longitudinal direction with respect to a horizontal surface of the mixer truck 1 and a detection value of a

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- 9 mixer drum sensor 132 for detecting a rotation speed and a rotation position of the mixer drum 10 are input. Moreover, into the calculation part 110, information such as density or a slump value of the fresh concrete Input by an operator through an input part 133 and measurement values from other devices such as a slump measuring device, for example, connected through the input/output interface are input. The inclination sensor 131 is disposed on the frame 2a, and the mixer drum sensor 132 (not shown) is provided in the driving device 20.

[0029] The display part 120 displays results calculated in the calculation part 110 such as a weight and a slump value of the fresh concrete, risk of overturning of the vehicle body 2 and the like. Moreover, if the displayed contents contain a risk, the display part 120 notifies the operator of the contents by changing a display color or emitting an alarm sound. As described above, the display part 120 also has an alarm function in addition to simple display of the calculation results.

[0030] The calculation part 110, the display part 120, and the input part 133 are disposed in a cabin of a vehicle as one calculation display part 150 as illustrated in Fig. 1. Particularly the input part 133 may be integrated with the display part 120 by providing a touch panel or the like on the display part 120.

[0031] The load cells 71 and 72 are the pin type first load cell 71 and second load cell 72 incorporated as pins supporting the roller 54 as described above. The first load cell 71 and the second load cell 72 are connected to the calculation part 110 disposed in the cabin through a load cell connection box 145 disposed on the frame 2a illustrated in Fig. 1. In the load cell connection box 145, a circuit switching part 140 having a circuit for synthesizing an output of the first load cell 71 and an output of the second load cell 72 is

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- 10 provided as illustrated in Fig. 5. Into the calculation part 110, an output value of the first load cell 71 and the second load cell 72 synthesized in the circuit switching part 140 is input.

[0032] The circuit switching part 140 has a change-over switch 141 capable of switching between a first position and a second position and when the change-over switch 141 is at the first position, a first connection state (state shown in Fig. 5) where an output of the load first load cell 71 and an output of the second load cell 72 are connected with the same polarity is brought about, while when the change-over switch 141 is at the second position, a second connection state where the output of the first load cell 71 and the output of the second load cell 72 are connected with different polarity is brought about.

[0033] Specifically, when the change-over switch 141 is at the first position, a positive pole of the first load cell 71 is connected to a positive pole of the second load cell 72, and a negative pole of the first load cell 71 is connected to a negative pole of the second load cell 72, respectively, and a value obtained by adding the output of the first load cell 71 and the output of the second load cell 72 is output to the calculation part 110.

[0034] On the other hand, when the change-over switch 141 is at the second position, the positive pole of the first load cell 71 is connected to the negative pole of the second load cell 72, and the negative pole of the first load cell 71 is connected to the positive pole of the second load cell 72, respectively, and a difference between the output of the first load cell 71 and the output of the second load cell 72 is output to the calculation part 110. Switching of the change-over switch 141 is controlled by the calculation part 110.

[0035] Subsequently, a method of weighing the load amount of the fresh concrete in the mixer drum 10 by the load amount weighing apparatus 100

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- 11 will be described.

[0036]

Fig. 6 illustrates a balance of a force acting on the mixer drum 10 when the vehicle body 2 is horizontal. When the mixer drum 10 is supported by the rear drum receiving part 50 and the front drum receiving part 60, by assuming that a support force of the rear drum receiving part 50 is Wl, and a support force of the front drum receiving part 60 is W2, a weight W of the mixer drum 10 is expressed by W = Wl + W2 by the balance of a force in the Y axis direction. On the other hand, concerning the Y’ axis direction perpendicular to the rotation axis Cl (X’ axis) of the mixer drum 10, WcosO = WlcosO + W2cos0. [0037] Here, the load cells 71 and 72 for detecting the load in the rear drum receiving part 50 are mounted so as to detect the load in the Y’ axis direction as described above. Therefore, a value obtained by adding the output values of the pair of load cells 71 and 72 together corresponds to WlcosO.

[0038] Moreover, if the vehicle body 2 is inclined in the longitudinal direction with respect to the horizontal surface, the elevation angle Θ has a size obtained by adding or subtracting the inclination angle a with respect to the rotation axis angle Θ1. Thus, the value obtained by adding the output values of the load cells 71 and 72 becomes Wlcos (01 ± a). The inclination angle a is detected by the inclination sensor 131, and since the rotation axis angle 01 is a value set in advance, the support force Wl of the rear drum receiving part 50 is calculated easily. Therefore, by calculating the sharing ratio between the support force Wl of the rear drum receiving part 50 and the support force W2 of the front drum receiving part 60, the weight W of the mixer drum 10 can be calculated on the basis of the support force Wl of the rear drum receiving part 50 and the sharing ratio.

[0039] However, the sharing ratio between the support force Wl of the rear

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- 12 drum receiving part 50 and the support force W2 of the front drum receiving part 60 is not constant but changes in accordance with a distribution state of the fresh concrete in the mixer drum 10, that is, a position of center of gravity of the fresh concrete. Thus, in this embodiment, by correcting the calculated weight W of the of the mixer drum 10 on the basis of at least either one of the drum state quantity indicating the state of the mixer drum 10 or the vehicle-body state quantity indicating the state of the vehicle body 2 which influence a change in the position of center of gravity of the fresh concrete, more accurate weight W of the mixer drum 10 is calculated.

[0040] Specifically, an input amount of the fresh concrete in the mixer drum 10, a rotation number of the mixer drum 10, and a slump value (viscosity) of the fresh concrete in the mixer drum 10 are used as the drum state quantity, and the inclination angle a of the vehicle body 2 is used as the vehicle-body state quantity.

[0041] First, an influence of the input amount of the fresh concrete in the mixer drum 10 on the position of center of gravity of the fresh concrete will be described.

[0042] If the fresh concrete is input into the mixer drum 10 in a state where the vehicle body 2 is horizontal and the mixer drum 10 is stopped, as the input amount increases, the position of center of gravity of the fresh concrete moves from the front to the rear. That is, as the input amount of the fresh concrete increases, the position of center of gravity of the fresh concrete gets closer to the rear drum receiving part 50. Thus, assuming that the sharing ratio is constant, by calculating the weight W of the mixer drum 10 from the load detected by the rear drum receiving part 50, an error is generated with respect to an actual weight.

[0043] In this case, a calculated weight Weal calculated from the load

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- 13 detected by the rear drum receiving part 50 assuming that the sharing ratio is constant and an actual weight Wr have a relationship indicated by a solid line in a graph In Fig. 7. For example, as Indicated by a dotted line, the actual weight Wr is larger than the calculated weight Weal calculated when the input amount is small. This is because, if the input amount is small, the position of center of gravity of the fresh concrete is separated from the rear drum receiving part 50, and a ratio of the load acting on the rear drum receiving part 50 to the entire load becomes smaller.

[0044] Thus, by creating a conversion formula or a map on the basis of correlation between the calculated weight Weal and the actual weight Wr and by correcting the calculated weight Weal on the basis of this conversion formula or the like, a correction weight Wcor of the mixer drum 10 compensating the influence of the Input amount of the fresh concrete on the position of center of gravity of the fresh concrete can be calculated. The conversion formula or the map is stored in the memory of the calculation part 110 and is used when the correction weight Wcor of the mixer drum 10 is calculated.

[0045] Subsequently, an influence of the inclination angle of the vehicle body 2 on the position of center of gravity of the fresh concrete will be described.

[0046] When the vehicle is stopped on an inclined land, since Inclination of the mixer drum 10 is also changed, the fresh concrete with fluidity loaded in the mixer drum 10 has its position of center of gravity moved In accordance with the inclination angle a of the vehicle. In a front down state where the front of the vehicle body 2 is lower than the rear, for example, the position of center of gravity of the fresh concrete moves to the front as compared with the case where the vehicle body 2 is horizontal, while in a rear down state where

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- 14 the rear of the vehicle body 2 is lower than the front, the position of center of gravity of the fresh concrete moves to the rear as compared with the case where the vehicle body 2 is horizontal. As described above, when the position of center of gravity of the fresh concrete is changed, the sharing ratio is also changed, and thus, if the weight W of the mixer drum 10 is calculated by assuming that the sharing ratio is constant from the load detected by the rear drum receiving part 50, an error is generated with respect to the actual weight

Wr.

[0047] In this case, the calculated weight Weal calculated from the load detected by the rear drum receiving part 50 by assuming that the sharing ratio is constant, the inclination angle of the vehicle body 2 and the actual weight Wr have a relationship indicated by a broken line and a one-dot chain line in a graph in Fig. 7. The broken line indicates the case where the vehicle body 2 is front down, while the one-dot chain line indicates the case where the vehicle body 2 is rear down. In the graph in Fig. 7, a solid line indicates a case where the vehicle body 2 is not inclined but in the horizontal state.

[0048] As indicated in the graph in Fig. 7, the calculated weight Weal is calculated smaller than the actual weight Wr in the case where the vehicle body 2 is front down (broken line) as compared with the case where the vehicle body 2 is rear down (one-dot chain line), for example. That is because, when the vehicle body 2 is front down, the position of center of gravity of the fresh concrete is separated from the rear drum receiving part 50, and the ratio of the load acting on the rear drum receiving part 50 to the entire load becomes smaller. The more the vehicle body 2 is inclined front down, the smaller the inclination of the graph becomes, while the more the vehicle body 2 is inclined rear down, the larger the inclination of the graph becomes.

[0049] Thus, by creating a conversion formula or a map on the basis of

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- 15 correlation among the calculated weight Weal, the inclination angle a of the vehicle body 2, and the actual weight Wr and by correcting the calculated weight Weal on the basis of this conversion formula or the like, the correction weight Wcor of the mixer drum 10 compensating the influence of the inclination angle a of the vehicle body 2 on the position of center of gravity of the fresh concrete can be calculated. The conversion formula or the map is stored in the memory of the calculation part 110 and is used when the correction weight Wcor of the mixer drum 10 is calculated. The inclination angle a of the vehicle body 2 is detected by the aforementioned inclination sensor 131.

[0050] Subsequently, an influence of the rotation number of the mixer drum 10 on the position of center of gravity of the fresh concrete will be described. The rotation number of the mixer drum 10 is a rotation number per unit time and means a so-called rotation speed.

[0051] The fresh concrete in the mixer drum 10 during agitation rotation is pressed to the front of the mixer drum 10 by the spiral drum blade provided in the mixer drum 10. Thus, a surface of the fresh concrete is inclined rear down as indicated by a broken line in Fig. 6, for example. The higher the rotation number of the mixer drum 10 is, that is, the higher the rotation speed is, the larger this inclination of the surface of the fresh concrete becomes, and the larger the inclination is, the more forward the position of center of gravity of the fresh concrete is moved.

[0052] In this case, the relationship among the calculated weight Weal calculated from the load detected by the rear drum receiving part 50 by assuming that the sharing ratio is constant, the rotation number of the mixer drum 10, and the actual weight Wr is changed in accordance with the rotation number of the mixer drum 10 as illustrated in a graph in Fig. 8. In the graph

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- 16 in Fig. 8, a solid line indicates a case where the mixer drum 10 is not rotated, a broken line indicates a case where the mixer drum 10 is rotated at a low speed, and a one-dot chain line indicates a case where the mixer drum 10 is rotated at a speed higher than that indicated by the broken line.

[0053] As indicated by a dotted line, the calculated weight Weal is calculated smaller than the actual weight Wr in the case where the mixer drum 10 is rotated at a high speed (one-dot chain line) as compared with the case where the mixer drum 10 is rotated at a low speed (broken line). That is because, when the mixer drum 10 is rotated at a high speed, the position of center of gravity of the fresh concrete is separated from the rear drum receiving part 50, and the ratio of the load acting on the rear drum receiving part 50 to the entire load becomes smaller.

[0054] Thus, by creating a conversion formula or a map on the basis of correlation among the calculated weight Weal, the rotation number of the mixer drum 10, and the actual weight Wr and by correcting the calculated weight Weal on the basis of this conversion formula or the like, the correction weight Wcor of the mixer drum 10 compensating the influence of the rotation number of the mixer drum 10 on the position of center of gravity of the fresh concrete can be calculated. The conversion formula or the map is stored in the memory of the calculation part 110 and is used when the correction weight Wcor of the mixer drum 10 is calculated. The rotation number of the mixer drum 10 is detected by the aforementioned mixer drum sensor 132.

[0055] Subsequently, an influence of the slump value of the fresh concrete in the mixer drum 10 on the position of center of gravity of the fresh concrete will be described.

[0056] As described above, the fresh concrete in the rotating mixer drum 10 is pressed to the front of the mixer drum 10 by the spiral drum blade provided

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- 17 in the mixer drum 10, and the surface of the fresh concrete is inclined rear down. The inclination of the surface of the fresh concrete is correlated with the slump value (viscosity) of the fresh concrete, and the smaller the slump value is, that is, the larger the viscosity is, the larger the inclination becomes. And the larger the inclination of the surface of the fresh concrete is, the more forward the position of center of gravity of the fresh concrete is moved.

[0057] In this case, the relationship among the calculated weight Weal calculated from the load detected by the rear drum receiving part 50 by assuming that the sharing ratio is constant, the slump value of the fresh concrete, and the actual weight Wr is changed in accordance with the slump value of the fresh concrete as illustrated in a graph in Fig. 9. In the graph in Fig. 9, a broken line indicates a case where the mixer drum 10 is rotated with a predetermined rotation number, and the slump value is large (viscosity is low), and a one-dot chain line indicates a case where the mixer drum 10 is rotated with the same rotation number as in the case of the broken line, and the slump value is small (viscosity is high).

[0058] As indicated by a dotted line, the calculated weight Weal is calculated smaller than the actual weight Wr in the ease where the slump value is small and viscosity is high (one-dot chain line) as compared with the case where the slump value is large and viscosity is low (broken line). That is because, when the viscosity is large, the position of center of gravity of the fresh concrete is separated from the rear drum receiving part 50, and the ratio of the load acting on the rear drum receiving part 50 to the entire load becomes smaller.

[0059] Thus, by creating a conversion formula or a map on the basis of correlation among the calculated weight Weal, the slump value, and the actual weight Wr and by correcting the calculated weight Weal on the basis of this

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- 18 conversion formula or the like, the correction weight Wcor of the mixer drum 10 compensating the influence of the slump value on the position of center of gravity of the fresh concrete can be calculated. The conversion formula or the map is stored in the memory of the calculation part 110 and is used when the correction weight Wcor of the mixer drum 10 is calculated. The slump value may be input by the operator through the input part 133 or may be input from a slump measuring device connected through the input/output interface, or a value estimated by a slump value estimation mode which will be described later may be used.

[0060] Subsequently, a weight measurement mode of the fresh concrete in the mixer drum 10 performed in the load amount weighing apparatus 100 will be described by referring to a flowchart in Fig. 10.

[0061] When start of the weight measurement mode is instructed by the operator through the input part 133, the weight measurement of the fresh concrete is started in the calculation part 110.

[0062] First, at Step S101, the change-over switch 141 is switched to the first position by an instruction from the calculation part 110 so that the first connection state where the output of the first load cell 71 and the output of the second load cell 72 are connected with the same polarity is brought about. As a result, an added value of a detection value of the first load cell 71 and a detection value of the second load cell 72 is input into the calculation part 110. [0063] Subsequently, at Step SI02, type discrimination of the weight measurement mode is carried out. Here, which of a measurement-in-rotation mode in which a weight is measured in a state where the mixer drum 10 is rotated and a measurement-in-stop mode in which weight is measured in a state where the mixer drum 10 is stopped is selected by the operator is discriminated.

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- 19 [0064] If the measurement-in-stop mode is selected, the routine proceeds to Step S103, and the weight measurement is started in the state where the mixer drum 10 is stopped. On the other hand, if the measurement-in-rotation mode is selected, the routine proceeds to Step S104, and the weight measurement is started in the state where the mixer drum 10 is rotated.

[0065] In the measurement-in-stop mode, the mixer drum 10 is stopped at a predetermined position set in advance at Step S105. Since the drum blade is disposed spirally in the mixer drum 10, there is a concern that the load of the drum blade acting on the first load cell 71 and the second load cell 72 is fluctuated depending on the stop position. Thus, the mixer drum 10 is stopped at a position where the load of the drum blade acting on the first load cell 71 and the second load cell 72 becomes uniform.

[0066] When the stop of the mixer drum 10 at the predetermined position is confirmed by the mixer drum sensor 132, the routine proceeds to Step S107. [0067] On the other hand, in the measurement-in-rotation mode, the mixer drum 10 is rotated with a measurement rotation number set in advance at Step S106. If the rotation number is fluctuated, the distribution state of the fresh concrete is not made stable, and the position of center of gravity is changed. Thus, the rotation number of the mixer drum 10 is set to a certain rotation number. When the rotation of the mixer drum 10 with the predetermined rotation number is confirmed by the mixer drum sensor 132, the routine proceeds to Step S107. The rotation number of the mixer drum 10 is not limited to the measurement rotation number but may be an arbitrary rotation number.

[0068] At Step S107, the added value of the detection value of the first load cell 71 and the detection value of the second load cell 72, and the detection

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- 20 value of the inclination sensor 131 are obtained in the calculation part 110. As described above, the added value is a value corresponding to Wlcos(0±a). [0069] Subsequently, at Step S108, the calculated weight Weal of the mixer drum 10 is calculated on the basis of the obtained detection values of the load cells 71 and 72 and the detection value of the inclination sensor 131. Here, the sharing ratio between the support force W1 of the rear drum receiving part 50 and the support force W2 of the front drum receiving part 60 is assumed to be a predetermined value.

[0070] Subsequently, at Step SI09, a parameter influencing the sharing ratio, that is, a parameter influencing the position of center of gravity of the fresh concrete is obtained as a correction parameter. Specifically, the inclination angle a detected by the inclination sensor 131, the rotation number of the mixer drum 10 detected by the mixer drum sensor 132, and the slump value of the fresh concrete input by the operator are read in. In the measurement-in-stop mode, the rotation number of the mixer drum 10 is not read in, but since the surface of the fresh concrete is maintained in the state inclined rear down in accordance with the slump value even after the rotation is stopped, the slump value Is read in. Moreover, in the measurement-in-rotation mode, if the rotation number of the mixer drum 10 is set to the measurement rotation number set in advance, the reading of the rotation number of the mixer drum 10 is not necessary.

[0071] At Step SI 10, the calculated weight Weal of the mixer drum 10 is corrected on the basis of the read-in correction parameters (inclination angle a, the rotation number of the mixer drum 10, the slump value of the fresh concrete). As described above, there is correlation illustrated in Figs. 7 to 9 between the calculated weight Weal and the actual weight Wr. In the calculation part 110, the calculated weight Weal is corrected by the conversion

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- 21 formula or the like created on the basis of these correlations, and the correction weight Wcor is calculated. If the rotation number of the mixer drum 10 in the measurement-in-rotation mode is the same as the rotation number when correlation by the viscosity illustrated in Fig. 9 is measured, the correlation by the rotation number of the mixer drum 10 illustrated in Fig. 8 does not have to be incorporated in the correction.

[0072] In the correction, a correction amount by the slump value of the fresh concrete or the correction amount by the rotation number of the mixer drum 10 may be used together with the correction by the inclination angle a by converting it to the correction amount by the inclination angle a. Specifically, if the inclination angle a is 2° and the slump value is 15 cm, if the correction by the slump value corresponds to the correction when the inclination angle a is 3°, for example, the same result is obtained by correcting the calculated weight Weal by setting the inclination angle a at 5° (= 2° + 3°).

[0073] Subsequently, at Step Sill, an average value of the correction weights Wcor is calculated. As described above, the drum blade is disposed spirally in the mixer drum 10. Thus, the distribution state of the fresh concrete in the mixer drum 10 is changed by the drum blade, but when the mixer drum 10 makes one round, the drum blade returns to the same position. Thus, the distribution state of the fresh concrete in the mixer drum 10 becomes substantially the same state each time the mixer drum 10 makes one round. Therefore, by averaging the correction weights Wcor over the one round of tire mixer drum 10, more accurate weight can be calculated. In the measurement-in-stop mode, averaging does not have to be carried out.

[0074] Specifically, the correction weight Wcor is calculated a predetermined number of times (60 times, for example) during one round of the mixer drum 10, and an average value thereof is calculated each time the

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- 22 mixer drum 10 makes one round. The averaging may be averaging of not the correction weights Wcor but the calculated weights Weal, and in this case, the aforementioned correction is made to the averaged calculated weight Weal. [0075] At Step SI 12, the correction weight Wcor averaged at Step Sill is output from the calculation part 110 to the display part 120 and is displayed on the display part 120. The displayed weight may be the weight of the entire mixer drum 10 including the fresh concrete or may be the weight of only the fresh concrete (only the load) obtained by subtracting the weight of the mixer drum 10 as a single body. Moreover, if density of the fresh concrete is input by the operator through the input part 133, a volume V of the fresh concrete can be also displayed. Moreover, if the proper load amount of the fresh concrete is set by the operator through the input part 133, if the weight of the fresh concrete is not within a predetermined range such as a case where the weight of the fresh concrete exceeds the predetermined load amount or a case where it falls under the predetermined load amount, attention can be drawn from the operator by changing a display color of the weight displayed on the display part 120 to yellow or red or by emitting an alarm sound.

[0076] As described above, according to the load amount weighing apparatus 100, the accurate weight W and volume V of the mixer drum 10 can be weighed and displayed to the operator.

[0077] In the load amount weighing apparatus 100 with the aforementioned constitution, estimation of the slump value (viscosity) of the fresh concrete and determination of risk of overturning of the vehicle body 2 are carried out.

[0078] A method of estimating the slump value in the load amount weighing apparatus 100 will be described by referring to Fig. 11. Fig. 11 illustrates a state of movement of the center of gravity of the fresh concrete

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- 23 when the mixer drum 10 is rotated in a direction indicated by a dotted arrow in a sectional view along II-II line in Fig. 1.

[0079] When the fresh concrete which is the load is agitated in the mixer drum 10, the surface of ihe fresh concrete is inclined from the horizontal state indicated by the broken line to the left-and-right direction of the vehicle body 2 as indicated by the solid line, and the position of center of gravity G is also moved with that. The larger the viscosity of the fresh concrete is, the larger the inclination of the surface of the fresh concrete becomes, and a movement amount of center of gravity G also becomes larger with that. Moreover, by means of the movement of the position of center of gravity G, a difference is generated between the value detected by the first load cell 71 and the value detected by the second load cell 72. If the position of center of gravity G of the fresh concrete is moved closer to the first load cell 71 as illustrated in Fig. 11, for example, the value detected by the first load cell 71 becomes larger than the value detected by the second load cell 72.

[0080] Moreover, the movement amount of center of gravity G is changed by the volume of the fresh concrete in the mixer drum 10, and even if the slump value of the fresh concrete is the same, the larger the volume is, the larger the movement amount of the center of gravity G becomes. That is, there is correlation among the position of center of gravity G, the volume, and the slump value of the fresh concrete, and the slump value of the fresh concrete can be estimated from the position of center of gravity G and the volume of the fresh concrete.

[0081] Thus, in the load amount weighing apparatus 100, the slump value of the fresh concrete is estimated on the basis of a load difference AWl between the load cells 71 and 72 changed by the movement of the position of center of gravity G of the fresh concrete in the left-and-right direction of the vehicle body

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- 24 2 and the volume V converted from the weight calculated in the weight measuring mode. The load difference per unit volume (AW1/V) obtained by dividing the load difference AW1 by the volume V and the slump value of the fresh concrete have the relationship as illustrated in a graph In Fig. 12. For example, even if the load difference AWl is the same, the larger the volume V Is the smaller the inclination of the surface of the fresh concrete becomes and thus, the slump value of the fresh concrete is large. That is, viscosity is estimated to be low.

[0082] By creating a conversion formula or a map on the basis of correlation between the load difference per unit volume (AW1/V) and the slump value of the fresh concrete illustrated in Fig. 12, the slump value of the fresh concrete can be estimated from the load difference per unit volume (AW1/V) on the basis of this conversion formula or the like. The conversion formula or a map is stored in the memory of the calculation part 110 and is used when the slump value of the fresh concrete is estimated. The slump value of the fresh concrete may be estimated on the basis of a relationship among the volume V, the load difference AWl, and the slump value of the fresh concrete made into a three-dimensional map instead of the correlation among the load difference per unit volume (AW1/V) and the slump value of the fresh concrete.

[0083] Moreover, in the load amount weighing apparatus 100, an actually measured slump value using a slump cone is recorded in the memoiy together with the estimated slump value, and the map or conversion formula used for the estimation is sequentially updated so that a difference between the actually measured slump value and the estimated slump value becomes small. Since a driving pressure of the hydraulic motor for driving the mixer drum 10 is also changed depending on the position of center of gravity of the fresh

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- 25 concrete, the slump value of the fresh concrete may be estimated on the basis of the driving pressure of tire hydraulic motor instead of the load difference AWl.

[0084] Subsequently, a slump value estimating mode carried out in the load amount weighing apparatus 100 will be described by referring to a flowchart in Fig. 13.

[0085] When start of the slump value estimating mode is instructed by the operator through the input part 133, the estimation of the slump value is started in the calculation part 110.

[0086] First, at Step S201, it is determined whether the weight of the fresh concrete has been measured or not. If the weight of the fresh concrete has not been measured yet, the routing proceeds to Step S202, and the weight measuring mode is started. If the weight of the fresh concrete has been already measured, the routine proceeds to Step S203, and the change-over switch 141 is switched to the second position by an instruction from the calculation part 110 so that a second connection state where the output of the first load cell 71 and the output of the second load cell 72 are connected with different polarity is brought about. As a result, the load difference AWl which is a difference between the detection value of the first load cell 71 and the detection value of the second load cell 72 is input into the calculation part 110. [0087] Subsequently, at Step S204, the mixer drum 10 is rotated with the measurement rotation number set in advance. If the rotation number is fluctuated, the distribution state of the fresh concrete is not made stable, and the position of center of gravity is changed. Thus, the rotation number of the mixer drum 10 is set to a certain measurement rotation number. When the rotation of the mixer drum 10 with the predetermined rotation number is confirmed by the mixer drum sensor 132, the routine proceeds to Step S205.

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- 26 [0088] At Step S205, the load difference AWl which is a difference between the detection value of the first load cell 71 and the detection value of the second load cell 72 is obtained in the calculation part 110.

[0089] Subsequently, at Step S206, the load difference per unit volume (AWl/V) is calculated from the obtained load difference AWl and the volume V of the fresh concrete, and the slump value is estimated on the basis of the correlation between the load difference per unit volume (AWl/V) stored in the memory and the slump value of the fresh concrete.

[0090] At Step S207, an average value of the estimated slump values is calculated. As described above, the drum blade is disposed spirally in the mixer drum 10. The distribution state of the fresh concrete in the mixer drum 10 is changed by the drum blade, but when the mixer drum 10 makes one round, the drum blade returns to the same position and thus, the distribution state of the fresh concrete in the mixer drum 10 becomes substantially the same state each time the mixer drum 10 makes one round. Therefore, by averaging the estimated slump values over the one round of the mixer drum 10, more accurate slump value can be calculated. In the averaging, not the estimated slump value but the load difference AW1 may be averaged. In this case, the slump value is estimated on the basis of the averaged load difference AWl and the volume V.

[0091] At Step S208, the slump value averaged at Step S207 is output from the calculation part 110 to the display part 120 and is displayed on the display part 120. If the actually measured slump value using the slump cone is input, it may be also displayed together with the estimated slump value.

[0092] Subsequently, at Step S209, the estimated slump value is stored in the memory. Then, at Step S210, the estimated slump value stored in the memory is compared with the actually measured slump value in the

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- 27 calculation part 110, and the conversion formula or map used for the estimation is updated so that a difference between the estimated slump value and the actually measured slump value is made small.

[0093] As described above, according to the load amount weighing apparatus 100, the slump value of the fresh concrete can be estimated and displayed to the operator. The estimated slump value may be used in the weight measuring mode.

[0094] Subsequently, a method of determining a risk of overturning of the vehicle body 2 in the load amount weighing apparatus 100 will be described by referring to Fig. 11.

[0095] In the mixer truck 1, the mixer drum 10 is rotated during traveling in order to agitate the fresh concrete. Thus, as illustrated in Fig. 11, the center of gravity of the fresh concrete is moved to the left-and-right direction of the vehicle body 2, and a state where the fresh concrete is biased to one side is easily brought about. If the vehicle turns around a curve in such a state where the fresh concrete is biased as above, the fresh concrete is further biased by a centrifugal force, and probability of overturning of the vehicle increases.

[0096] Moreover, in a case where a total weight of the fresh concrete is small and a case where it is large, even if the weight difference of the fresh concrete in the left-and-right direction of the vehicle body 2 is the same, the inclination of the surface of the fresh concrete is smaller in the case of the larger total weight and thus, the probability of overturning of the vehicle is low. That is, it is difficult to determine whether the vehicle body 2 could be overturned or not only from the weight difference in the fresh concrete in the left-and-right direction of the vehicle body 2 which means a biased state of the fresh concrete, and the total weight of the fresh concrete also needs to be

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- 28 considered in order to determine the probability of overturning of the vehicle body 2 more accurately.

[0097] Thus, in the load amount weighing apparatus 100, probability of overturning of the vehicle body 2 is determined on the basis of the load difference AWl between the load cells 71 and 72 changed by a bias of the fresh concrete caused by the movement of the position of center of gravity of the fresh concrete in the left-and-right direction of the vehicle body 2 and the centrifugal force and the weight W of the fresh concrete calculated by the weight measuring mode.

[0098] Specifically, the load difference per unit weight (AWl /W) obtained by dividing the load difference AWl by the weight W is compared with a predetermined threshold value in the determination part 111, and when the load difference per unit weight (AWl/W) exceeds the predetermined threshold value, it is determined that the vehicle body 2 is likely to overturn. In determination of the overturning of the vehicle body 2, a ratio of the load difference per unit weight (AWl /W) to the threshold value may be displayed as the risk degree instead of determination of presence of probability.

[0099] Subsequently, an overturning determination mode carried out in the load amount weighing apparatus 100 will be described by referring to a flowchart in Fig. 14.

[0100] When start of the vehicle-body overturning determination mode is instructed by the operator through the input part 133, determination of probability of overturning of the vehicle body 2 is started in the calculation part 110.

[0101] First, at Step S301, it is determined whether the weight of the fresh concrete has been measured or not. If the weight of the fresh concrete has not been measured yet, the routine proceeds to Step S302, and the weight

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- 29 measuring mode is started. If tire weight of the fresh concrete has been already measured, the routine proceeds to Step S303, and the change-over switch 141 is switched to the second position by an instruction from the calculation part 110 so that the second connection state where the output of the first load cell 71 and the output of the second load cell 72 are connected with different polarity is brought about. As a result, the load difference AWl which is a difference between the detection value of the first load cell 71 and the detection value of the second load cell 72 is input into the calculation part 110.

[0102] Subsequently, at Step S304, the load difference AWl which is a difference between the detection value of the first load cell 71 and the detection value of the second load cell 72 is obtained in the calculation part 110, and at Step S305, the load difference per unit weight (AWl/W) is calculated from the obtained load difference AWl and the weight W of the mixer drum 10.

[0103] Subsequently, at Step S306, a risk degree D which is a ratio of the load difference per unit weight (AWl/W) to the threshold value stored in the memory is calculated in the determination part 111. The threshold value is set to such a value that the vehicle body 2 is likely to overturn if the load difference per unit weight (AWl/W) exceeds this threshold value. That is, if the risk degree D is 1 or more, it means that the vehicle body 2 is likely to overturn.

[0104] At Step S307, smoothing processing of the calculated risk degree D is carried out. Since the risk degree D is required to be a real-time value, it is processed at a relatively high speed, and noises are removed.

[0105] At the subsequent Step S308, the smoothened risk degree D is output from the calculation part 110 to the display part 120 and is displayed on the display part 120. The display color of the risk degree D is changed in

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- 30 accordance with intensity of the risk degree D and is displayed in green when it is 0.8 or less, in yellow when it is 0.8 to 1.0 or less, and in red when it is larger than 1.0, for example, on the display part 120.

[0106] At Step S309, it is determined whether the risk degree D is larger than 1 or not in the determination part 111. If the risk degree D exceeds 1, it is extremely likely that the vehicle body 2 overturns and thus, at Step S310, an alarm is output from the determination part 111 to the display part 120, and the risk of overturning is notified to the operator by an alarm sound or flashing of a lamp or the like on the display part 120. On the other hand, if the risk degree D is 1 or less, the determination is finished.

[0107] As described above, according to the load amount weighing apparatus 100, the risk of overturning of the vehicle body 2 can be determined, and the risk degree D can be displayed to the operator. Moreover, if the risk is high, an alarm can be output.

[0108] According to the aforementioned first embodiment, the following effects are exerted.

[0109] In the load amount weighing apparatus 100, the load cells 71 and 72 are disposed so that the load of the mixer drum 10 working in the direction perpendicular to the rotation axis C1 of the mixer drum 10 is detected. Thus, even if the vehicle body 2 is inclined, the weight of the mixer drum 10 in the vertical direction can be calculated easily on the basis of the inclination angle a of the vehicle body 2. As a result, weighing accuracy of the load amount of the mixer truck 1 can be improved.

[0110] Moreover, in the load amount weighing apparatus 100, the load amount of the mixer truck 1 is weighed by the pair of load cells 71 and 72 disposed on the rear drum receiving part 50. Since the load amount can be weighed by the load cells 71 and 72, fewer than before as described above, a

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- 31 manufacturing cost of the load amount weighing apparatus 100 can be reduced.

[0111] Moreover, in the load amount weighing apparatus 100, the calculated weight Weal calculated from the detection values of the load cells 71 and 72 is corrected on the basis of the volume of the fresh concrete in the mixer drum 10, the rotation number of the mixer drum 10, the slump value of the fresh concrete in the mixer drum 10, and the inclination angle a of the vehicle body 2 causing a change in the position of center of gravity of the fresh concrete. As described above, since the influences of the changes of the position of center of gravity of the fresh concrete are compensated for, the weighing accuracy of the load amount of the mixer truck 1 can be improved. [0112] Moreover, the load cells 71 and 72 of the load amount weighing apparatus 100 are incorporated in pin parts supporting the rollers 54 of the guide rollers 51 and 52. As described above, since the load cells 71 and 72 are incorporated instead of members having been conventionally provided, they can be incorporated easily without drastically changing the structure of the vehicle. Moreover, since the load cells 71 and 72 are incorporated in the pin parts supporting the rollers 54 of the guide rollers 51 and 52, a vehicle height does not have to be changed or the weight of the vehicle body 2 is scarcely increased.

[0113] Moreover, in the load amount weighing apparatus 100, the slump value of the fresh concrete input into the mixer drum 10 can be estimated by using the difference in the detection values between the load cells 71 and 72, and the risk of overturning when the vehicle turns around a curve can be determined.

[0114] Moreover, in the load amount weighing apparatus 100, the volume of the fresh concrete loaded in the mixer drum 10 can be also displayed. In

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- 32 general, in a casting work of concrete such as a civil engineering or construction work, fresh concrete is ordered by the part of volume. Thus, by using an apparatus capable of displaying a remaining amount of the fresh concrete in the mixer drum 10 changing in accordance with input and discharge of the fresh concrete by the part of volume as in the load amount weighing apparatus 100, the amount of the fresh concrete can be managed properly in accordance with the detected remaining amount of the fresh concrete.

[0115] Moreover, since it becomes possible to check the remaining amount of the fresh concrete in the mixer drum 10 immediately after the fresh concrete is discharged at a work site, determination on whether the mixer truck should go to another work site or it should go for replenishment of the fresh concrete can be made appropriately.

[0116] <Second embodiment

Subsequently, a load amount weighing apparatus 200 according to a second embodiment of the present invention will be described by referring to Figs. 15 to 17. In the following, differences from the first embodiment will be mainly described, and the same reference numerals are given to the constitutions similar to those in the first embodiment, and explanation will be omitted.

[0117] As illustrated in Fig. 15, the basic constitution of the load amount weighing apparatus 200 is similar to the load amount weighing apparatus 100 according to the first embodiment. The load amount weighing apparatus 200 is different from the load amount weighing apparatus 100 in a point that a third load cell 73 and a fourth load cell 74 provided in the front drum receiving part 60 are included.

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- 33 [0118] A structure of the front drum receiving part 60 on which the third load cell 73 and the fourth load cell 74 are provided will be described by referring to Figs. 16 and 17. Fig. 16 is an enlarged view illustrating the front drum receiving part 60 in an enlarged manner. Fig. 17 is a sectional view along XVII-XVII line in Fig. 16. In Fig. 16, the section of the driving device 20 is illustrated in an omitted manner.

[0119] The third load cell 73 and the fourth load cell 74 are flat-plate type load cells disposed between a base 61 provided on the frame 2a of the vehicle body 2 and the driving device 20.

[0120] As illustrated in Fig. 16, a center part 73a of the third load cell 73 is connected to the driving device 20 through a pressing member 62, and both end parts 73b are connected to the base 61 through leg parts 63. A distortion generating part 73c generating distortion by a load acting on the third load cell 73 is provided between the center part 73a and the both end parts 73b, respectively. A distortion gauge, not shown, is mounted on the distortion generating part 73c, and an electric signal in propart with the load by change of resistance of the distortion gauge in accordance with a distortion amount in the distortion generating part 73c is output from the third load cell 73. The fourth load cell 74 also has the similar constitution and is connected to the driving device 20 and the base 61.

[0121] The third load cell 73 and the fourth load cell 74 are disposed so that their longitudinal directions are in parallel with the rotation axis Cl of the mixer drum 10, Moreover, the third load cell 73 and the fourth load cell 74 are disposed symmetrically by sandwiching the rotation axis Cl of the mixer drum 10 between them in the left-and-right direction of the vehicle body 2. Thus, the third load cell 73 and the fourth load cell 74 detect not a load of the mixer drum 10 in the vertical direction but a load of the mixer drum 10 in the

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- 34 Y’ axis direction perpendicular to the rotation axis Cl (X’ axis) of the mixer drum 10 as indicated by a bold arrow in Fig. 16.

[0122) The third load cell 73 and the fourth load cell 74 are connected to the calculation part 110 through the load cell connection box 145 disposed on the frame 2a similarly to the first load cell 71 and the second load cell 72. In the circuit switching part 140 provided in the load cell connection box 145, the output of the third load cell 73 and the output of the fourth load cell 74 are connected with the same polarity. That is, an added value of a detection value of the third load cell 73 and a detection value of the fourth load cell 74 is Input into the calculation part 110 as a load in the Y’ axis direction acting on the front drum receiving part 60.

[0123] To the calculation part 110, the display part 120, the input part 133, the inclination sensor 131, and the mixer drum sensor 132 are connected as illustrated in Fig. 15 other than each of the load cells 71 to 74 similarly to the aforementioned first embodiment.

[0124] Subsequently, a method of weighing the weight of the fresh concrete in the mixer drum 10 by the load amount weighing apparatus 200 with the aforementioned constitution will be described.

[0125] As described in the aforementioned first embodiment, when the mixer drum 10 is supported by the rear drum receiving part 50 and the front drum receiving part 60 as illustrated in Fig. 6, by assuming that the support force of the rear drum receiving part 50 is W1 and the support force of the front drum receiving part 60 is W2, the weight W of the mixer drum 10 becomes W = W1 + W2 by the balance of the force in the Y axis direction. On the other hand, concerning the Y’ axis direction perpendicular to the rotation axis C1 (X’ axis) of the mixer drum 10, WcosO = WlcosO + W2cos0.

[0126] Here, similarly to the aforementioned first embodiment, the load

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- 35 cells 71 and 72 for detecting the load in the rear drum receiving part 50 are mounted so as to detect the load in the Y’ axis direction. Therefore, a value obtained by adding the output values of the pair of load cells 71 and 72 together corresponds to WlcosO. Moreover, in the load amount weighing apparatus 200, the load cells 73 and 74 for detecting the load on the front drum receiving part 60 are mounted so as to detect the load in the Y’ axis direction. Therefore, a value obtained by adding the output values of the load cells 73 and 74 together corresponds to W2cos0.

[0127] If the vehicle body 2 is inclined in the longitudinal direction with respect to the horizontal surface, the elevation angle Θ has a size obtained by adding or subtracting the inclination angle a with respect to the rotation axis angle 01. Thus, the output values of the load cells 71 and 72 become Wlcos (01±a), and the output values of the load cells 73 and 74 become W2cos (01±a). Here, the inclination angle a is detected by the inclination sensor 131, and the rotation axis angle 01 is a value set in advance and thus, cos (01±a), WI and W2 are easily calculated. Therefore, by adding the support force WI of the rear drum receiving part 50 and the support force W2 of the front drum receiving part 60 together, the weight W of the mixer drum 10 is calculated, and by subtracting the weight of the mixer drum 10 in the state without a load from this weight W, the weight of the fresh concrete can be easily calculated. Moreover, if the density of the fresh concrete has been input by the operator, the volume V of the fresh concrete can be also displayed.

[0128] Moreover, since the load amount weighing apparatus 200 includes the load cells 71 and 72 for detecting the load on the rear drum receiving part 50, the slump value estimating mode and the vehicle-body overturning determination mode can be executed similarly to the aforementioned first embodiment.

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- 36 [0129] According to the aforementioned second embodiment, the following effects are exerted.

[0130] In the load amount weighing apparatus 200, the weight W of the mixer drum 10 is calculated on the basis of the detection values of the load cells 71 and 72 for detecting the load on the rear drum receiving part 50, the detection values of the load cells 73 and 74 for detecting the load on the front drum receiving part 60, and the detection value of the inclination sensor 131. As described above, the weight W of the mixer drum 10 can be calculated in the load amount weighing apparatus 200 without considering the distribution state of the fresh concrete in the mixer drum 10, that is, the sharing ratio changing in accordance with the position of center of gravity of the fresh concrete. As a result, in calculating the weight W of the mixer drum 10, since the influence of movement of the position of center of gravity of the fresh concrete is not applied, weighing accuracy of the load amount of the mixer truck 1 can be improved.

[0131] The constitution, actions, and effects of the embodiments of the present invention constituted as above will be collectively described.

[0132] The load amount weighing apparatus 100, 200 includes the load cells 71 and 72 provided on the rear drum receiving part 50 supporting the rear of the mixer drum 10 on the rear of the vehicle body 2 and detecting the load of the mixer drum 10 and the calculation part 110 for calculating the load amount of the load on the basis of the detection values of the load cells 71 and 72 and at least either one of the vehicle-body state quantity indicating the state of the vehicle body 2 or the drum state quantity indicating the state of the mixer drum 10.

[0133] In this constitution, the load amount of the load is calculated on the basis of the detection values of the load cells 71 and 72 and at least either one

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- 37 of the vehicle-body state quantity indicating the state of the vehicle body 2 or the drum state quantity indicating the state of the mixer drum 10. As described above, the load amount of the load is calculated by considering not only the detection values of the load cells 71 and 72 but also the vehicle-body state quantity indicating the vehicle body 2 and the drum state quantity indicating the state of the mixer drum 10 influencing the distribution state of the load in the mixer drum 10. As a result, the weighing accuracy of the load amount of the mixer truck can be improved. Moreover, by displaying the volume as the load amount, the amount of the fresh concrete can be managed properly.

[0134] Moreover, the rear drum receiving part 50 has the roller 54 supporting the mixer drum 10 in contact while rotating and the pin provided by inserting the roller 54 and rotatably supporting the roller 54, and the load cells 71 and 72 detect the load of the mixer drum 10 acting on the pin through the roller 54.

[0135] In this constitution, the load cells 71 and 72 are incorporated in the pin parts supporting the rollers 54 of the guide rollers 51 and 52. As described above, since the load cells 71 and 72 are incorporated instead of members having been conventionally provided, they can be incorporated easily without drastically changing the structure of the vehicle. Moreover, since the load cells 71 and 72 are incorporated in the pin parts supporting the rollers 54 of the guide rollers 51 and 52, a vehicle height is not changed or the weight of the vehicle body 2 is scarcely increased. Moreover, the load of the mixer drum 10 in the direction perpendicular to the rotation axis Cl of the mixer drum 10 acts on the roller 54 and the pins. Since the load cells 71 and 72 are to measure the load in the perpendicular direction with accuracy in general, the load of the mixer drum 10 on which the load is mounted can be measured with

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- 38 accuracy by the load cells 71 and 72 incorporated in the pin parts.

[0136] Moreover, the rollers 54 are provided in a pair, the load cells 71 and 72 have the first load cell 71 and the second load cell 72 provided on the pins inserted into the rollers 54, respectively, the vehicle-body state quantity is an inclination amount of the vehicle body 2 in the longitudinal direction, the drum state quantity is at least one of the rotation number of the mixer drum 10 and the viscosity of the load in the mixer drum 10, the calculation part 110 calculates the weight of the load from the sum of the detection value of the first load cell 71 and the detection value of the second load cell 72 and calculates the load amount of the load by correcting the calculated weight of the load on the basis of at least either one of the vehicle- body state quantity or the drum state quantity.

[0137] In this constitution, the calculated weight Weal calculated from the detection values of the first load cell 71 and the second load cell 72 is corrected on the basis of the inclination angle of the vehicle body 2, the rotation number of the mixer drum 10, and the slump value of the fresh concrete in the mixer drum 10 causing the change in the position of center of gravity of the fresh concrete. As described above, since the influence of the change in the position of center of gravity of the fresh concrete is compensated for, the weighing accuracy of the load amount of the mixer truck 1 can be improved. [0138] Moreover, the weight amount weighing apparatus 100, 200 further includes the determination part 111 for determining the risk of overturning of the vehicle body 2 and the display part 120 for displaying the determination result of the determination part 111 and the calculation result of the calculation part 110, and the determination part 111 determines the risk of overturning of the vehicle body 2 on the basis of the difference between the detection value of the first load cell 71 and the detection value of the second

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- 39 load cell 72, while the display part 120 displays the risk of overturning of the vehicle body 2 determined in the determination part 111.

[0139] In this constitution, the risk of overturning when the vehicle turns around a curve can be determined by using the difference in the detection values between the load cells 71 and 72 and the risk of overturning can be notified to the operator through the display part 120. Moreover, the weight W of the mixer drum 10 and the slump value calculated in the calculation part 110 can be notified to the operator through the display part 120.

[0140] Moreover, the load amount weighing apparatus 200 is provided on the front drum receiving part 60 supporting the front of the mixer drum 10 in the front of the vehicle body 2 and further includes the load cells 73 and 74 for detecting the load of the mixer drum 10, and the calculation part 110 calculates the load amount of the load on the basis of the vehicle-body state quantity, the detection values of the load cells 73 and 74, and the detection values of the load cells 71 and 72.

[0141] In this constitution, the weight W of the mixer drum 10 is calculated on the basis of the detection values of the load cells 71 and 72 detecting the load on the rear drum receiving part 50, the detection values of the load cells 73 and 74 detecting the load on the front drum receiving part 60, and the detection value of the inclination sensor 131. As described above, in the load amount weighing apparatus 200, since the weight of the mixer drum 10 is detected on the front drum receiving part 60 and the rear drum receiving part 50, the weight W of the mixer drum 10 can be calculated without considering the distribution state of the fresh concrete in the mixer drum 10, that is, the sharing ratio changing in accordance with the position of center of gravity of ihe fresh concrete. As a result, in calculating the weight W of the mixer drum 10, since the influence of movement of the position of center of gravity of the

GS11976/16G-P1066-PCT

- 40 fresh concrete is not applied, weighing accuracy of the load amount of the mixer truck 1 can be improved.

[0142] Moreover, the load cells 71 and 72 provided on the rear drum receiving part 50 and the load cells 73 and 74 provided on the front drum receiving part 60 detect the load of the mixer drum 10 in the direction perpendicular to the rotation axis Cl of the mixer drum 10.

[0143] According to this constitution, the load cells 71 to 74 are disposed so as to detect the load ofthe mixer drum 10 in the direction perpendicular to the rotation axis C1 of the mixer drum 10 or in other words, so as to detect the load of the mixer drum 10 in the same direction. Thus, even if the vehicle body 2 is inclined, for example, the weight of the mixer drum 10 in the vertical direction can be easily calculated on the basis of the inclination angle a of the vehicle body 2 and the rotation axis angle 01 of the mixer drum 10. As a result, the weighing accuracy of the load amount of the mixer truck can be improved. Moreover, by displaying the volume as the load amount, the amount of the fresh concrete can be managed properly.

[0144] Embodiments of the present invention were described above, but the above embodiments are merely examples of applications of the present invention, and the technical scope of the present invention is not limited to the specific constitutions of the above embodiments.

[0145] Whether the added value of the output of the first load cell 71 and the output of the second load cell 72 is input or the difference is input into the calculation part 110 is switched by the change-over switch 141 of the circuit switching part 140, for example. Instead of this, it may be so configured that the both outputs of the first load cell 71 and the second load cell 72 are input into the calculation part 110, and they are added or the difference thereof is calculated in the calculation part 110.

GS11976/16G-P1066-PCT

- 41 [0146] This application claims priority based on Japanese Patent Application No. 2015-201376 filed with tire Japan Patent Office on October 9, 2015, the entire contents of which are incorporated into this specification by reference.

GS11976/16G-P1066-PCT

Claims

1. A load amount weighing apparatus for mixer truck configured to weigh a load amount of a load in a drum rotatably mounted on a vehicle body, comprising:

a rear load detector provided on a rear drum receiving part supporting a rear of the drum on a rear of the vehicle body, the rear load detector being configured to detect a load of the drum; and a calculation part configured to calculate a load amount of the load on the basis of the detection value of the rear load detector and at least either one of a vehicle-body state quantity or a drum state quantity, the vehicle-body state quantity indicating a state of the vehicle body, the drum state quantity indicating a state of the drum.

2. The load amount weighing apparatus for mixer truck according to claim 1, wherein the rear drum receiving part has a roller configured to support the drum in contact while rotating and a pin provided by inserting the roller, the pin being configured to rotatably support the roller; and the rear load detector is configured to detect the load of the drum acting on the pin through the roller.

3. The load amount weighing apparatus for mixer truck according to claim 2, wherein the rollers are provided in a pair;

GS11976/16G-P1066-PCT

- 43 the rear load detector has a first rear load detector and a second rear load detector provided on the pins inserted into the rollers, respectively;

the vehicle-body state quantity is an inclination amount of the vehicle body in a longitudinal direction;

the drum state quantity is at least one of a rotation number of the drum and viscosity of the load in the drum; and the calculation part calculates the load amount of the load by calculating a weight of the load from a sum of a detection value of the first rear load detector and a detection value of the second rear load detector and by correcting the calculated weight of the load on the basis of at least either one of the vehicle-body state quantity or the drum state quantity.

4. The load amount weighing apparatus for mixer truck according to claim 2 or 3, further comprising:

a determination part configured to determine a risk of overturning of the vehicle body; and a display part configured to display a determination result of the determination part and a calculation result of the calculation part, wherein the determination part is configured to determine the risk of overturning of the vehicle body on the basis of a difference between the detection value of the first rear load detector and the detection value of the second rear load detector; and the display part is configured to display the risk of overturning of the vehicle body determined in the determination part.

5. The load amount weighing apparatus for mixer truck according to

GS11976/16G-P1066-PCT

- 44 any one of claims 1 to 4, further comprising:

a front load detector provided on a front drum receiving part supporting a front of the drum on a front of the vehicle body, the front load detector being configured to detect the load of the drum, wherein the calculation part is configured to calculate the load amount of the load on the basis of the vehicle-body state quantity, the detection value of the front load detector, and the detection value of the rear load detector.

6. The load amount weighing apparatus for mixer truck according to claim 5, wherein the front load detector and the rear load detector are configured to detect the load of the drum in a direction perpendicular to a rotation axis of the drum.

1/14

10 ^10B

150

X’

131 2a

145 50

FIG. 1

2/14

FIG. 2

3/14

10b ϊ

56 55a

71c

71b

71c

C2

FIG. 3

100

4/14

111 133

FIG. 4

140(145)

141

FIG. 5

5/14

FIG. 6

6/14

CALCULATED WEIGHT Wcal

ACTUAL WEIGHT Wr (WEIGHT Wcor AFTER CORRECTION)

FIG. 7

CALCULATED WEIGHT Wcal (WEIGHT Wcor AFTER CORRECTION)

FIG. 8

7/14

CALCULATED WEIGHT Wcal

SLUMP VALUE LARGE

SLUMP VALUE SMALL

-=-►

ACTUAL WEIGHT Wr (WEIGHT Wcor AFTER CORRECTION)

FIG. 9

8/14

START

WEIGHT MEASURING MODE

S101

SWITCH CHANGE-OVER SWITCH 141 TO FIRST POSITION

S102

DISCRIMINATE MEASURING MODE

S103

MEASUREMENT-IN-STOP

MODE

S104

MEASUREMENT-IN-ROTATION

MODE

S105

No

DRUM AT PREDETERMINED

S106

POST'

ION?

ROTATE AT

PREDETERMINED SPEED

Yes

S107

OBTAIN SENSOR OUTPUT VALUE

S108

CALCULATE CALCULATED WEIGHT Wcal FROM SENSOR OUTPUT VALUE

S109

END

J

FIG. 10

9/14

FIG. 11

10/14

LOAD DIFFERENCE PER UNIT VOLUME (AW1/V)

SLUMP VALUE OF FRESH CONCRETE

FIG. 12

11/14

START

SLUMP VALUE ESTIMATING MODE

S201

WEIGHT HAS BEEN MEASURED?

Yes

S203

SWITCH CHANGE-OVER SWITCH 141 TO SECOND POSITION

S204

ROTATE AT PREDETERMINED SPEED

S205

OBTAIN LOAD CELL LOAD DIFFERENCE

S206

ESTIMATE SLUMP VALUE BY CONVERSION FORMULA S207 r AVERAGING PROCESSING 1 S208 r SLUMP DISPLAY VALUE | /OUTPUT |

S209

STORE ESTIMATED SLUMP VALUE | IN MEMORY | S210 r UPDATE CONVERS ESTIMATED SLU ACTUALLY MEA SION FORMULA BY JMP VALUE AND lSURED SLUMP

FIG. 13

12/14

START

VEHICLE-BODY OVERTURNING DETERMINATION MODE

S301

WEIGHT HAS BEEN MEASURED?

Yes

S302

No

WEIGHT MEASURING MODE

S303

SWITCH CHANGE-OVER SWITCH 141 TO SECOND POSITION

S304±

OBTAIN LOAD CELL LOAD DIFFERENCE

S308

DISPLAY/OUTPUT OVERTURNING RISK DEGREE D

S309

RISK DEGREE D > 1?

No

S310

Yes

OUTPUT ALARM

END

FIG. 14

13/14

200

111 133

FIG. 15

14/14

FIG. 16

FIG. 17