Wheel loader

Abstract

To provide a wheel loader which allows for acquiring load weight even when the position of a load loaded on the wheel loader moves within a bucket, and easily making correct weight measurement of the load during wheel loader operation.SOLUTION: A wheel loader provided herein is configured to record and hold front frame-equivalent weight, and measure weight of a load in a bucket in response to a change in load position using a bucket cylinder pressure sensor.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a wheel loader that measures load weight for production volume management and the like. [Background technology]

[0002] Wheel loaders are machines that run on wheels, are four-wheel drive, and have pivot steering, as well as derivatives thereof, and are fitted with work equipment such as a bucket for scooping up soil and sand at the front of the vehicle (also called the body or frame) on which the wheels are mounted. With a wheel loader, the height and angle of the bucket, as well as the direction and speed of the vehicle, are controlled by an operator in the driver's seat, and the wheel loader performs excavation work by scooping up soil above the ground surface with the bucket, transportation work by moving the scooped up soil and sand, and loading work by discharging the scooped up soil and sand into the bed of a dump truck.

[0003] The work of a wheel loader involves transporting and loading earth and sand, and the progress of the work is managed by the weight of the earth and sand that has been transported or loaded. In order to measure the weight of earth and sand during transportation or loading, Patent Documents 1 and 2 disclose a method of measuring the weight of earth and sand in the work machine (bucket) during work, in which the weight of earth and sand in the work machine (bucket) is converted into load using the pressure inside a cylinder. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-078348 [Patent Document 2] Japanese Patent Application Publication No. 2020-002698 Summary of the Invention [Problem to be solved by the invention]

[0005] The method described in Patent Document 1 is based on an example in which only a lift cylinder supports the lift arm from the front frame. Wheel loaders have a structure in which the lift arm is supported by both a lift cylinder and a bucket cylinder, and because the support structure differs from that described in Patent Document 1, the calculation formula described in Patent Document 1 cannot be applied. Therefore, Patent Document 2 creates a map of lift cylinder pressure sensor values ​​for each displacement of the bucket-supporting cylinder under multiple loading conditions (e.g., no load and constant load), and references this map during measurement to calculate the load from the lift cylinder pressure. However, particularly during loading operations, the position of the soil inside the bucket changes, and the manner in which this changes varies depending on the characteristics of the soil being loaded and the operator's lever operation. When this occurs, if the distance between the bucket's rotation support pin and the load center changes, the load on the lift cylinder also changes, resulting in an inaccurate measurement of the weight of the soil in the work machine (bucket).

[0006] In view of this situation, the present invention has an object to provide a wheel loader that can acquire the load weight even if the position of the load moves within the bucket, without the need to take the time and effort of creating a complicated map, and that can easily and correctly measure the weight of the load during wheel loader operation. [Means for solving the problem]

[0007] In order to achieve the above object, the wheel loader of the present invention includes a vehicle body, a bucket, a lift arm that is supported on the vehicle body so as to be rotatable in the vertical direction and that supports the bucket so as to be rotatable in the vertical direction, a lift cylinder for rotating the lift arm in the vertical direction to raise and lower the bucket, a bucket cylinder for rotating the bucket in the vertical direction to tilt the bucket, a bell crank that is rotatably connected to the lift arm and is interposed between the bucket cylinder and the bucket, and that transmits the bucket cylinder force of the bucket cylinder to the bucket, a lift arm position sensor that measures the relative position of the lift arm and the vehicle body, a bell crank position sensor that measures the relative position of the bell crank and the lift arm, and a bell crank position sensor that measures the relative position of the lift cylinder. a lift cylinder pressure sensor that detects a lift cylinder force acting on the bucket cylinder, a bucket cylinder pressure sensor that detects a bucket cylinder force acting on the bucket cylinder, and a controller, wherein the controller holds a front frame equivalent weight that corresponds to the total weight of the bucket, the lift arm, and the bell crank when the bucket is in an empty state, and calculates the load in the bucket using the relative position between the lift arm and the vehicle body measured by the lift arm position sensor, the relative position between the bell crank and the lift arm measured by the bell crank position sensor, the lift cylinder force detected by the lift cylinder pressure sensor, the bucket cylinder force detected by the bucket cylinder pressure sensor, and the front frame equivalent weight. The lift arm is structured to be supported by a pin so as to be rotatable in the vertical direction relative to the vehicle body, and the controller calculates the front frame equivalent weight by performing a process in which the greater the force applied in the vertical direction at the pin support portion between the lift arm and the vehicle body, the greater the total weight of the bucket, the lift arm, and the bell crank when the bucket is empty, based on the relative position between the lift arm and the vehicle body measured by the lift arm position sensor. do. [Effects of the Invention]

[0008] According to the present invention, the load weight can be obtained even if the position of the load moves within the bucket without the need to take the time to create a complicated map, making it possible to easily and correctly measure the weight of the load during wheel loader operation and facilitating adjustment of the load amount to suit the loading target during wheel loader excavation and loading operations.

[0009] Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is an external side view of a wheel loader according to a first embodiment. [Figure 2] 1 is an external perspective view of a wheel loader according to a first embodiment. [Figure 3] FIG. 1 is a system configuration diagram of a wheel loader according to a first embodiment. [Figure 4] 1 is a system configuration diagram of a load measurement system for a wheel loader in a first embodiment. [Figure 5] FIG. 3 is an explanatory diagram of a load measurement process in the first embodiment. [Figure 6] FIG. 10 is a diagram for supplementing the process of converting the total weight of the front members into the equivalent weight W0 of the front frame. [Figure 7] An explanatory diagram of the calculation process for attitude coefficients (b, c, d, e, f, L) (related to bucket cylinder). [Figure 8] An explanatory diagram of the calculation process for attitude coefficients (b, c, d, e, f, L) (related to lift cylinders). [Figure 9] 4 is a flowchart of a load measurement process in the first embodiment. [Figure 10] FIG. 10 is a system configuration diagram of a load measurement system for a wheel loader in a second embodiment. [Figure 11] 10 is a flowchart of a load measurement process in the second embodiment. [Figure 12] FIG. 10 is a system configuration diagram of a load measurement system for a wheel loader in a third embodiment. [Figure 13] 11 is a flowchart of a load measurement process in the third embodiment. [Figure 14] FIG. 10 is a system configuration diagram of a load measurement system for a wheel loader in a fourth embodiment. [Figure 15] 10 is a flowchart of a load measurement process in the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the description of the drawings, the same elements are given the same reference numerals, and duplicate explanations will be omitted. In the following description, the directions and positions of up / down, left / right, and front / rear are based on the normal use state of the wheel loader, i.e., the state when the wheels are in contact with the ground.

[0012] [Example 1] First, a first embodiment for carrying out the present invention will be described.

[0013] The wheel loader to which the present invention is directed is a machine that runs on wheels, has a four-wheel drive system, and has pivot steering, as well as machines derived therefrom.

[0014] External views of the wheel loader are shown in Fig. 1 and Fig. 2.

[0015] The wheel loader 50 has a working machine section 2 at the front of a vehicle section 1 (also called a vehicle body or frame), and is equipped with a bucket 3 for scooping up earth and sand.

[0016] The wheel loader 50 is a machine in which an operator in a driver's seat 4B installed on the vehicle controls the height and angle of the bucket 3, as well as the direction and speed at which the wheeled vehicle travels, and performs excavation work to scoop up soil and sand from the ground surface with the bucket 3, transportation work to move the scooped up soil and sand, and loading work to dump the scooped up soil and sand onto the bed of a dump truck.

[0017] The vehicle section 1 has a structure in which a front frame 6 having a work machine section 2 and front wheels 5 and a rear frame 8 having rear wheels 7, an engine compartment 4A, and a driver's seat 4B are connected so as to be able to bend by a center pin 9, and the bending angle can be changed by left and right hydraulic cylinders (also called steer cylinders) 10. An engine 4 is mounted in the engine compartment 4A.

[0018] The wheel loader 50 performs steering while traveling by changing the angle (bending angle) of the front frame 6 relative to the rear frame 8 by extending and retracting the left and right hydraulic cylinders 10.

[0019] The work machine section 2 is made up of a bucket 3 and a lift arm 11 for supporting the bucket 3.

[0020] The lift arms 11 are configured as a pair, left and right, and are connected to (the front end of) the front frame 6 so that they can rotate (tilt) up and down around fulcrums 21 spaced apart in the left-right (width) direction. A lift cylinder 12 is connected (interposed) to (the front end of) the front frame 6 and (the middle part of) the lift arm 11 so that the load of the lift arm 11 can be supported by the front frame 6 and the angle (height) of the lift arm 11 relative to the front frame 6 can be changed. Attached to the lift cylinder 12 are a pressure sensor 12b (Fig. 4) that measures the internal pressure on the bottom side of the lift cylinder 12, and a pressure sensor 12r (Fig. 4) that measures the internal pressure on the rod side of the lift cylinder 12. These pressure sensors 12b and 12r may be attached anywhere in the piping where the same pressure is present.

[0021] The bucket 3 is connected to (the front end of) the lift arm 11 so as to be rotatable (tiltable) in the vertical direction about a fulcrum 13. A bucket cylinder 16 is connected to (the front end of) the front frame 6 via a push rod 14 and a bell crank 15 so as to vary the angle (tilt) of the bucket 3 relative to the lift arm 11. The bucket cylinder 16 is connected to (the front end of) the front frame 6 at a fulcrum 17 (at a position different from the fulcrum of the lift cylinder 12 on the front frame 6 side). The bell crank 15 is connected to (the tip of) the bucket cylinder 16 so as to be rotatable about a fulcrum 22. The push rod 14 is connected to (the tip of) the bell crank 15 so as to be rotatable about a fulcrum 24. The bell crank 15 is also connected to (the middle part of) the lift arm 11 so as to be rotatable about a connection point 25. The bucket 3 is connected to (the tip of) the push rod 14 so as to be rotatable about a fulcrum 23. The push rod 14, bell crank 15, and bucket cylinder 16 are disposed midway between the pair of left and right lift arms 11. The bucket cylinder 16 is fitted with a pressure sensor 16b (FIG. 4) that measures the internal pressure on the bottom side of the bucket cylinder 16, and a pressure sensor 16r (FIG. 4) that measures the internal pressure on the rod side of the bucket cylinder 16. These pressure sensors 16b and 16r may be fitted at any location within the piping where the pressure is the same.

[0022] The height of the bucket 3 can be changed by extending and retracting the lift cylinder 12, and the angle (tilt) of the bucket 3 can be changed by extending and retracting the bucket cylinder 16. In other words, the extension and retraction of the lift cylinder 12 causes the lift arm 11 to rotate vertically, raising and lowering the bucket 3. In addition, the bell crank 15 and the push rod 14 are interposed between the bucket cylinder 16 and the bucket 3, and the bucket cylinder force (extension and retraction force) of the bucket cylinder 16 is transmitted to the bucket 3 via the bell crank 15 and the push rod 14. Therefore, the extension and retraction of the bucket cylinder 16 causes the bucket 3 to rotate vertically via the bell crank 15 and the push rod 14, causing the bucket 3 to tilt (crowd or dump).

[0023] A lift arm angle sensor 19, which detects the angle the lift arm 11 makes with respect to the front frame 6 (in other words, the relative position of the lift arm 11 with respect to the front frame 6), is attached to a fulcrum 21, and a bell crank angle sensor 20, which detects the angle the bell crank 15 makes with respect to the lift arm 11 (in other words, the relative position of the bell crank 15 with respect to the lift arm 11), is attached to a connection point 25, and these sensors can obtain the results of extension and contraction of the lift cylinder 12 and the bucket cylinder 16. In other words, the lift arm angle sensor 19 and the bell crank angle sensor 20 measure the relative position (relative angle) between the lift arm 11 and the front frame 6 and the relative position (relative angle) between the bell crank 15 and the lift arm 11, and these two angle sensors can measure the relative position (relative angle) of the bucket 3 with respect to the front frame 6.

[0024] The system configuration of the wheel loader 50 will be described with reference to FIG.

[0025] An output shaft 100 of the engine 4 is directly connected to a torque converter 101, a hydraulic pump 102, and a brake pump 103. The rotation speed of the engine 4 is controlled by an electrical signal 105 from an engine controller 104, which in turn indicates the rotation speed of the engine 4 based on the amount of depression of an accelerator pedal 106.

[0026] The output shaft of the torque converter 101 is connected to a drive shaft 108 via a transmission 107 to drive the front and rear wheels. The driving force transmitted from the torque converter 101 to the transmission 107 increases as the rotation speed of the output shaft 100 of the engine 4 increases relative to the output rotation speed of the torque converter 101, and the driving force output by the torque converter 101 increases by increasing the rotation speed of the engine 4 by the amount of depression of the accelerator pedal 106.

[0027] The transmission 107 cuts off the connection between the output of the torque converter 101 and the drive shaft 108 to reduce the driving force of the front and rear wheels, or reverses the direction of rotation to change the direction of the driving force of the front and rear wheels, using an electrical signal 110 from the transmission controller 109.

[0028] An electrical signal 110 from the transmission controller 109 is output to cut off the connection when the depression amount of the brake pedal 112 is equal to or greater than a certain amount.

[0029] A vehicle speed sensor (not shown) that measures the rotation speed of the drive shaft 108 is attached to the transmission 107.

[0030] The hydraulic pump 102 outputs a constant flow rate of pressurized oil for each rotation of the output shaft 100 of the engine 4. The pressurized oil output from the hydraulic pump 102 is supplied to the lift cylinder 12 and the bucket cylinder 16, which serve as hydraulic actuators, via a bucket control hydraulic circuit 113, and causes the lift cylinder 12 and the bucket cylinder 16 to extend and retract.

[0031] The amount of pressurized oil output from the hydraulic pump 102 increases as the rotation speed of the output shaft 100 of the engine 4 increases, so when the rotation speed of the engine 4 is increased by depressing the accelerator pedal 106, the extension / retraction speed of the lift cylinder 12 and the bucket cylinder 16 (and thus the operating speed of the lift arm 11 or bucket 3) increases.

[0032] The bucket control hydraulic circuit 113, when operated by the operator using the lift lever 114, cuts off the connection between the output of the hydraulic pump 102 and the lift cylinder 12 to stop the operation of the lift arm 11, or reverses the extension / retraction direction to switch the up / down movement of the lift arm 11.

[0033] When the operator operates a bucket lever 115, the bucket control hydraulic circuit 113 cuts off the connection between the output of the hydraulic pump 102 and the bucket cylinder 16 to stop the operation of the bucket 3, or reverses the extension / retraction direction to switch the forward / backward operation of the angle (tilt) of the bucket 3.

[0034] The pressure oil output from the hydraulic pump 102 is connected to the left and right steering cylinders 10 as hydraulic actuators via a steering control hydraulic circuit 116, and causes the left and right steering cylinders 10 to extend and retract.

[0035] When the operator turns the steering wheel 117 to the right, the steering control hydraulic circuit 116 outputs a steering angle signal 116S and simultaneously connects the pressure oil output from the hydraulic pump 102 in the direction that retracts the right steering cylinder 10R and the direction that extends the left steering cylinder 10L, thereby turning the vehicle body to the right.When the operator turns the steering wheel 117 to the left, the steering control hydraulic circuit 116 outputs a steering angle signal 116S and simultaneously connects the pressure oil output from the hydraulic pump 102 in the direction that extends the right steering cylinder 10R and the direction that retracts the left steering cylinder 10L, thereby turning the vehicle body to the left.

[0036] The pressure oil output from the brake pump 103 is stored in an accumulator 118, and the pressure oil stored in the accumulator 118 is passed through a brake control hydraulic circuit 119 to control the braking force of the four wheels.

[0037] The brake control hydraulic circuit 119 adjusts the control pressure (braking force) according to the amount of depression of the brake pedal 112 by the operator.

[0038] This system configuration includes a controller 120 that measures the weight (load) of a load, such as soil and sand, in the bucket 3. The controller 120 includes, for example, a central processing unit (CPU), a read-only memory (ROM), and a random access memory (RAM). The controller 120 implements each of the functional blocks described below by having the CPU read and execute program code stored in the ROM. The RAM is used as a work area when the CPU executes the program. However, the specific configuration of the controller 120 is not limited thereto, and the controller 120 may be implemented by hardware such as an application-specific integrated circuit (ASIC) or a field-programmable gate array (FPGA). In this embodiment, the controller 120 measures the load weight using information from a lift arm angle sensor 19, a bell crank angle sensor 20, and the like, in response to operation of the lift lever 114 by the operator, and outputs the measurement result to a monitor 123 (details will be described later).

[0039] The system configuration of the load measurement system for the wheel loader 50 will be described with reference to FIG.

[0040] The load measurement system of this embodiment is composed of lift arm angle sensor 19, bell crank angle sensor 20, lift cylinder bottom side pressure sensor 12b, lift cylinder rod side pressure sensor 12r, bucket cylinder bottom side pressure sensor 16b, bucket cylinder rod side pressure sensor 16r, controller 120, and monitor 123, all of which are connected to each other by electrical wiring that exchanges electrified information.

[0041] The controller 120 calculates the load weight using information from these connected sensors, and outputs the calculated load weight to the monitor 123.

[0042] The controller 120 has, as functional blocks for executing the calculation process (load measurement process), a bucket cylinder differential force calculation unit 201, a lift cylinder differential force calculation unit 202, an attitude coefficient calculation unit 203, a front frame total weight calculation unit 204, a front frame equivalent weight holding unit 205, and a front frame weight subtraction unit 206.

[0043] The calculation process performed by the controller 120 to measure the load will be explained using Figure 5. Figure 5 is a schematic redrawing of the configuration shown in Figures 1 and 2. Of these, the lift cylinder 12 and bucket cylinder 16 are extendable, while the rest are rigid bodies that do not extend or contract, and each is rotatably connected by a pin. The bottom diagram in Figure 5 shows the dimensions used in the weight calculation process. The vertical distances to the pins on which the generated force acts as shown are defined as a, b, c, d, e, f, and L.

[0044] a is the vertical distance from the force acting on the entire front frame weight W_all, including the load in the bucket 3, due to the gravitational acceleration to the pin (fulcrum 13) between the lift arm 11 and the bucket 3.

[0045] b is the vertical distance from the force acting on the push rod 14 to the pin (fulcrum 13) between the lift arm 11 and the bucket 3.

[0046] c is the vertical distance from the force acting on the push rod 14 to the pin (connection point 25) between the lift arm 11 and the bell crank 15.

[0047] d is the vertical distance from the force Fb acting on the bucket cylinder 16 to the pin (connection point 25) between the lift arm 11 and the bell crank 15.

[0048] e is the vertical distance from the force Fb acting on the bucket cylinder 16 to the pin (fulcrum 21) between the lift arm 11 and the front frame 6.

[0049] f is the vertical distance from the force Fc acting on the lift cylinder 12 to the pin (fulcrum 21) between the lift arm 11 and the front frame 6.

[0050] L is the vertical distance from the pin (fulcrum 13) between the lift arm 11 and the bucket 3 to the pin (fulcrum 21) between the lift arm 11 and the front frame 6.

[0051] Equation 1 is obtained from the balance of moments around the pin support between the front frame 6 and the lift arm 11. Note that g is the gravitational acceleration, which is approximately 9.8 [m / s^2]. (Number 1) W_all g×(L+a)=Fc×f+Fb×e...Formula 1

[0052] Similarly, Equation 2 is obtained from the balance of moments around the connecting pin between the bell crank 15 and the lift arm 11 and the balance of moments around the connecting pin between the lift arm 11 and the bucket 3. (Number 2) Fb=W_all g×(a / b)×(c / d)...Equation 2

[0053] By eliminating a from equations 1 and 2 and solving for W_all, we obtain equation 3. (Number 3) W_all=(Fcf+Fb(e-db / c)) / (L×g)...Equation 3

[0054] 4 calculates the force (bucket cylinder force) Fb acting on the bucket cylinder 16. The lift cylinder differential force calculation unit 202 calculates the force (lift cylinder force) Fc acting on the lift cylinder 12.

[0055] Here, the bucket cylinder force Fb calculated by bucket cylinder differential force calculation unit 201 is found by the value of bucket cylinder bottom side pressure sensor 16b × bucket cylinder bottom side pressure receiving area − value of bucket cylinder rod side pressure sensor 16r × bucket cylinder rod side pressure receiving area.

[0056] The lift cylinder force Fc calculated by the lift cylinder differential force calculation unit 202 is calculated by multiplying the value of the lift cylinder bottom side pressure sensor 12b by the lift cylinder bottom side pressure-receiving area minus the value of the lift cylinder rod side pressure sensor 12r by the lift cylinder rod side pressure-receiving area. As shown in the perspective view of Figure 2, if there are two lift cylinders 12, Fc is doubled.

[0057] 4 calculates the attitude coefficients b, c, d, e, f, and L required to calculate the above-mentioned front frame total weight W_all. Here, the attitude coefficients b, c, d, e, f, and L calculated by the attitude coefficient calculation unit 203 are found based on the value of the lift arm angle sensor 19 and the value of the bell crank angle sensor 20.

[0058] The front frame total weight calculation unit 204 can use Equation 3 to calculate the front frame total weight W_all, including the load inside the bucket 3, from the values ​​of Fc, Fb, b, c, d, e, f, L, and g.

[0059] The front frame weight subtraction unit 206 can calculate the load weight W using the front frame total weight W_all and the front frame equivalent weight W0 using Equation 4. The front frame equivalent weight W0 is a value stored in the front frame equivalent weight holding unit 205 and input from the front frame equivalent weight holding unit 205. (Number 4) W = W_all - W0 Equation 4

[0060] The front frame equivalent weight W0 is the total weight of, for example, the bell crank 15, lift arm 11, push rod 14, bucket 3, the rod portion of the lift cylinder 12, and the rod portion of the bucket cylinder 16. In other words, the front frame equivalent weight W0 is the sum of the bucket cylinder force Fb and the lift cylinder force Fc that are applied when there is no load in the bucket 3 (empty load). The front frame equivalent weight W0 is the sum of these forces minus friction generated inside the cylinder and the force generated at the pin support portion between the lift arm 11 and the front frame 6, and is affected by the attitude of the bucket 3. Therefore, the angle of the lift cylinder 12 or the bucket cylinder 16 may be used to convert this total weight to the front frame equivalent weight W0. Figure 6 provides a supplementary explanation of the process for converting the total weight of the front members to the front frame equivalent weight W0. As shown in the upper diagram of Figure 6, when the lift arm 11 is horizontal and the bucket 3 is in a position far from the front frame 6 (in other words, before the lift arm 11 is raised and before the bucket 3 is raised), the force generated at the pin support part between the lift arm 11 and the front frame 6 is small. As shown in the lower diagram of Figure 6, when the lift arm 11 is vertical and the bucket 3 is in a high position (in other words, after the lift arm 11 has been raised and the bucket 3 has been raised), the force generated at the pin support part between the lift arm 11 and the front frame 6 is large. Therefore, it is good to find the front frame equivalent weight W0 from the total front frame weight according to the value of the lift arm angle sensor 19. Simply put, for example, using ∠JAI shown in Figure 8 (J is the direction of gravity relative to A), the value W0 called up from the front frame equivalent weight holder 205 can be calculated using Equation 5. (Number 5) W0 = total weight of front frame × sin∠JAI Formula 5

[0061] Using this equation 5, it is possible to calculate from the value of the lift arm angle sensor 19 that the greater the force that the weight of the lift arm 11 applies in the vertical direction at the pin support portion between the lift arm 11 and the front frame 6, the smaller (decreasing) the front frame equivalent weight W0 becomes. In other words, the greater the force (corresponding to Sin∠JAI) that is applied in the vertical direction at the pin support portion between the lift arm 11 and the front frame 6, based on the relative position (relative angle) between the lift arm 11 and the front frame 6 measured by the lift arm angle sensor 19, relative to the total front frame weight (the sum of the weights of the bucket 3 and the like when the bucket 3 is empty), the greater the decrease in the front frame equivalent weight W0 can be calculated.

[0062] If a more accurate value is required, the force acting on the pin support portion between the lift arm 11 and the front frame 6 can be calculated using Equation 6, since it can be found from the balance of forces in the vertical direction. (Number 6) Force acting on the pin support between the lift arm and the front frame = W0g - vertical component of Fb - vertical component of Fc...Equation 6

[0063] Since the front frame equivalent weight W0 is a value assuming an empty load, the force acting on the pin support portion between the lift arm 11 and the front frame 6 can be calculated using known weights and dimensions, and the force acting on the pin support portion between the lift arm 11 and the front frame 6 for each value of lift arm angle and bell crank angle can be calculated using Equation 6. Therefore, if the result is taken as a function h, it can be calculated using Equation 7, for example. (Number 7) W0 = total weight of front frame - h (lift angle, bell crank angle) / g Equation 7

[0064] Here, we have explained a method of making corrections using the force generated at the pin support portion between the lift arm 11 and the front frame 6, but it is also possible to take into account the magnitude of the friction force acting on the cylinder using a calculated or experimentally recorded value (see Figure 6).

[0065] The calculation process for the attitude coefficients b, c, d, e, f, and L required to calculate the total weight of the front frame will be explained using Figures 7 and 8. Figures 7 and 8 are diagrams in which the rigid body parts and pins are extracted from the structure beyond the front frame 6, with the pin supports assigned the symbols A, B, C, D, G, H, I, K, and M.

[0066] These attitude coefficients b, c, d, e, f, and L are calculated by the attitude coefficient calculation unit 203 shown in FIG. 4, as described above. Using the values ​​from the lift arm angle sensor 19 and the bell crank angle sensor 20 and the dimensions of each component, the attitude coefficients b, c, d, e, f, and L can be calculated. For example, e can be calculated from the relationship between ABCD. The length of AD is calculated using the cosine law of △ACD, ∠DAC is calculated using the cosine law of △DAC, ∠DAB is calculated as the sum of ∠DAC and ∠CAB, BD is calculated using the cosine law of △DAB, ∠ADB is calculated using the cosine law of △DAB, and e can be calculated as AD × sin∠ADB (see FIG. 7). Similarly, b, c, d, f, and L can be calculated using the relationships between the pin, rigid body, and angle sensor. In this way, if the dimensions and relative angles of each component are known, the posture coefficients b, c, d, e, f, and L can be calculated. Therefore, it is advisable to make it possible to change the settings of the dimensions and relative angles of each component when, for example, changing attachments.

[0067] As described above, an example has been described in which the attitude coefficient is determined from the values ​​of the lift arm angle sensor 19 and the bell crank angle sensor 20. However, the sensors required to calculate the attitude coefficient (in other words, to detect the attitude) are not limited to these two angle sensors. Instead, the lengths of the two variable cylinders may be detected by sensors. For example, wire displacement meters with fixed ends attached to the rod and bottom sides of the cylinder may be attached to obtain the cylinder length. As another alternative, an IMU (inertial measurement unit) may be attached to measure the angle. For example, if an IMU is attached to the front frame 6 and the lift arm 11, a value equivalent to that of a lift angle sensor can be obtained from the relative change in the direction of gravity.

[0068] FIG. 9 shows a flowchart of the load measurement process.

[0069] As shown in Fig. 9, the controller 120 performs the following processing in order: lift cylinder differential force calculation S101, bucket cylinder differential force calculation S102, attitude coefficient calculation S103, front frame total weight calculation S104, front frame equivalent weight subtraction S105, and display on monitor 123 S106, and then ends the processing. Each of the processing steps S101, S102, S103, S104, S105, and S106 is performed by the respective function blocks 202, 201, 203, 204, and 206 shown in Fig. 4.

[0070] (Effects of Example 1) The configuration and method described above makes it possible to obtain the load weight even if the load position moves within the bucket, without the need to go to the trouble of creating a complicated map, making it possible to easily and correctly measure the weight of the load when using a wheel loader, and has the effect of making it easier to adjust the load amount to suit the object being loaded when using a wheel loader for excavation and loading.

[0071] [Example 2] Regarding a second embodiment of the present invention, which is different from the first embodiment, additions and changes from the first embodiment will be described. The system configuration in the second embodiment will be described using the system configuration in FIG. 10 instead of the system configuration in FIG. 4 used in the first embodiment. The flowchart in the second embodiment will be described using the flowchart in FIG. 11 instead of the system configuration in FIG. 9 used in the first embodiment. Compared to FIG. 4, FIG. 10 adds an empty load determination unit 207 between the attitude coefficient calculation unit 203 and the front frame equivalent weight holding unit 205. Compared to FIG. 9, FIG. 11 adds an empty load determination step S107 at the beginning of the processing and a front frame equivalent weight holding step S108 in the latter half of the processing.

[0072] The empty load determination S107 is a process for determining whether there is any weight inside the bucket 3 (i.e., whether the bucket 3 is in an empty state) during operation. For example, the values ​​of the lift arm angle sensor 19 and the bell crank angle sensor 20 are used to calculate the inclination angle of the bottom of the bucket 3 relative to the ground. If the angle is such that no earth or sand remains inside the bucket 3, the bucket 3 is determined to be empty. Specifically, the determination is made based on whether the inclination angle of the bottom of the bucket 3 relative to the ground is greater than a predetermined threshold. The threshold is set to, for example, 45°, a value sufficiently greater than the angle of repose of the earth or sand expected to be excavated. Furthermore, the empty load determination can be made based on whether the lift arm angle has subsequently increased (in other words, after the lift cylinder 12 has extended) and whether the bell crank angle has subsequently increased (in other words, after the bucket cylinder 16 has extended). This allows the front frame total weight (front frame equivalent weight W0) to be correctly calculated under the same extension history state when the lift cylinder 12 and the bucket cylinder 16 have hysteresis. For example, during excavation work, the lift cylinder 12 and bucket cylinder 16 are both extended, so the total front frame weight (front frame equivalent weight W0) can be correctly calculated. The total front frame weight (front frame equivalent weight W0) may be stored for each combination of when the lift cylinder 12 and bucket cylinder 16 are extended and when they are retracted, and may be called up according to the cylinder state. This empty load determination S107 is performed by the empty load determination unit 207 shown in Figure 10.

[0073] In front frame equivalent weight holding (empty load update) S108, the front frame equivalent weight W0 is updated and held by processing it using equation 8 so that the loaded weight calculated in S105 becomes 0. This front frame equivalent weight holding (empty load update) S108 is performed by the front frame equivalent weight holding unit 205 shown in FIG. (Number 8) W0=W0+W...Formula 8

[0074] By doing so, the loaded weight calculated in S105 becomes 0, and at the same time, it becomes possible to calculate the difference thereafter when a load is loaded. That is, in this embodiment, when the relative position (relative angle) between the lift arm 11 and the front frame 6 measured by the lift arm angle sensor 19 and the relative position (relative angle) between the bell crank 15 and the lift arm 11 measured by the bell crank angle sensor 20 are within a predetermined range (an angle at which no load will remain inside the bucket 3), the front frame equivalent weight W0 is updated and held so that the calculated result of the load inside the bucket 3 becomes 0. Furthermore, the conditions for updating the front frame equivalent weight W0 include at least one of after the lift arm angle has increased or after the bell crank angle has increased.

[0075] When the conversion of Equation 5 is used, Equation 9 should be used instead of Equation 8. (Number 9) W0=(W0+W)×arcsin∠JAI...Equation 9

[0076] (Effects of Example 2) With the configuration and method described above, the second embodiment has the advantage that the load inside the bucket 3 can be calculated correctly even if the weight of the bucket 3 changes due to deterioration over time, for example.

[0077] [Example 3] Regarding a third embodiment of the present invention, which is different from the first embodiment, additions and changes from the first embodiment will be described. The system configuration in the third embodiment will be described using the system configuration in FIG. 12 instead of the system configuration in FIG. 4 used in the first embodiment. The flowchart in the third embodiment will be described using the flowchart in FIG. 13 instead of the flowchart in FIG. 9 used in the first embodiment. Compared to FIG. 4, FIG. 12 adds a calculable attitude determination unit 301, an empty load map call unit 302, a load measurement unit 303, and a loaded weight correction unit 304. Compared to FIG. 9, FIG. 13 adds S110 to S119 in the latter half of the processing.

[0078] In steps S110 to S111, the load in the bucket 3 is measured by a known method.

[0079] In S110, the calculable attitude determination unit 301 determines whether lift-up is being performed with the bucket 3 tilted backward, and if the determination is affirmative, the process proceeds to S111. Specifically, using the value of the attitude coefficient calculation unit 203, it is determined that the length of the bucket cylinder 16 is close to its maximum and that the length of the lift cylinder 12 is in the process of changing from a long state to a short state.

[0080] In S111, the empty-load map calling unit 302 calls up the empty-load lift cylinder force from the empty-load map using the value of the lift arm angle sensor 19, and the load measuring unit 303 measures the measured load value W_in inside the bucket 3. Here, the empty-load map held by the empty-load map calling unit 302 is a table of lift arm angles (more specifically, the lift arm angle when the lift cylinder 12 is extended in an empty state) and empty-load lift cylinder forces. The empty-load lift cylinder forces (21 in total) are recorded for each possible lift arm angle, for example, in 1-degree increments, in the range of lift arm angles (∠JAI) from 60° to 80°, i.e., the range of 30° to 10° from the ground horizontal (21 values ​​in total). The empty-load lift cylinder force is the lift cylinder force measured when there is no soil or sand in the bucket 3. In S111, the load measurement unit 303 calculates the difference between the lift cylinder force at the lift arm angle and the unladen lift cylinder force retrieved from the unladen map using the lift arm angle, and divides this difference by the distance between the lift hinge pin (A) and the load center (L in Figure 8, i.e., AI sin∠JAI) and the gravitational acceleration G. The calculated results (21 values ​​in total) for the lengths of the lift cylinder 12 from long to short are averaged to obtain the load measurement value W_in.

[0081] The difference between the lift cylinder force at the above-mentioned lift arm angle and the unladen lift cylinder force retrieved from the unladen map using the lift arm angle is the moment due to the cargo load around point A. Dividing this difference by L and G gives the load. The number of values ​​(21) is just an example, and it is also possible to measure the load at only one specific angle, for example.

[0082] In S112, the tilt-side correction coefficient (also called tilt-side correction gain) Kt is calculated and recorded (stored). Equation 10 is used for the calculation. Here, W_in in Equation 10 is the load measurement value calculated in S111 using the known method described above, W is the loaded weight W calculated in S105, and K is recorded as the tilt-side correction coefficient Kt. (Number 10) K=W_in / W Equation 10

[0083] After the tilt-side correction coefficient Kt is recorded in S112, or if it is determined in S110 that lift-up is not being performed with the bucket 3 tilted backward, the process proceeds to S113.

[0084] In S113, it is determined whether the first dump operation has started since the load measurement value W_in was recorded, and if the determination is affirmative, the process proceeds to S114. The start of the dump operation is determined, for example, when the value of the bell crank angle sensor 20 decreases by a predetermined angle (for example, 1 degree) or more, which indicates that the bucket cylinder 16 is retracted due to the dump operation.

[0085] In S114, K calculated by Equation 10 is recorded as a dump truck side correction coefficient (also called dump truck side correction gain) Kd.

[0086] If it is determined in S114 that the first dump operation has started after the dump side correction coefficient Kd has been recorded or after the load measurement value W_in has been recorded in S113, the process proceeds to S115.

[0087] In S115, it is determined whether or not soil is being dumped after the dump truck side correction coefficient Kd is recorded, and if it is, the process proceeds to S116. On the other hand, if soil is not being dumped, the process proceeds to S117. Whether or not soil is being dumped may be determined by counting the time from when the dump truck side correction coefficient Kd described above is recorded until all soil is dumped. The determination of whether or not soil is being dumped may be made by, for example, calculating the tilt angle of the bucket 3 using the values ​​of the lift arm angle sensor 19 and the bell crank angle sensor 20, and determining whether the angle is such that no soil remains inside the bucket 3.

[0088] In S116, it is determined whether the most recent operation history is on the dump operation side, and if so, the process proceeds to S119. The most recent operation history is on the dump operation side when a dump operation input is being performed by the operator, or when a dump operation input is no longer being performed but a tilt operation input is not being performed. On the other hand, if a tilt operation input is being performed by the operator, the process proceeds to S117. For example, if the most recent change in the value of the bell crank angle sensor 20 is equal to or greater than a predetermined angle (for example, 1 degree), it is on the dump operation side if it is on the increase side, i.e., when the bucket cylinder 16 is extended, it is on the tilt operation side.

[0089] In S119, corrected loaded weight W' is calculated using dump truck side correction coefficient Kd for K in equation 11. That is, when the bell crank angle decreases for the first time after the value of lift-up load measuring unit 303 is determined, dump truck side correction coefficient Kd is calculated and stored from the value of lift-up load measuring unit 303 and the calculation result of the load inside bucket 3, and dump truck side correction coefficient Kd is used when calculating the load inside bucket 3 until the bell crank angle becomes equal to or less than a predetermined threshold value (an angle at which no load remains inside bucket 3). (Number 11) W'=K*W…Equation 11

[0090] In S117, it is determined whether or not the tilt-side correction coefficient Kt is recorded.

[0091] In S118, that is, to summarize S115 to S117, if the tilt side correction coefficient Kt is recorded and the time period from when the dump side correction coefficient Kd was recorded until full soil discharge has occurred or if the tilt side correction coefficient Kt is present after a tilt side operation has been performed, the tilt side correction coefficient Kt is used for K in equation 11 to calculate the corrected loaded weight W'. In other words, when the value of the load measuring unit 303 due to lift-up is determined, the tilt side correction coefficient Kt is calculated and stored from the value of the load measuring unit 303 due to lift-up and the calculation result of the load inside the bucket 3, and the tilt side correction coefficient Kt is used to calculate the load inside the bucket 3 from when the bell crank angle becomes equal to or less than a predetermined threshold value (an angle at which no load remains inside the bucket 3) until the value of the load measuring unit 303 due to lift-up is determined again.

[0092] The above-mentioned processes of S112 to S119 are performed by the loaded weight correcting unit 304 shown in FIG.

[0093] By doing so, the load inside the bucket 3 can be calculated taking into consideration the influence of hysteresis due to the direction of extension and contraction of the cylinder, as described above.

[0094] (Effects of Example 3) With the configuration and method described above, this third embodiment has the advantage of being able to improve the accuracy of obtaining the load weight during tilting or dumping by the amount of hysteresis included in the hydraulic sensor, and being able to calculate the load inside the bucket 3 taking into account the influence of hysteresis due to the extension and retraction direction of the cylinder, as described above.

[0095] [Example 4] Regarding a fourth embodiment of the present invention, which is different from the third embodiment, additions and changes from the third embodiment will be described below. The system configuration in the fourth embodiment will be described using the system configuration in FIG. 14 instead of the system configuration in FIG. 12 used in the third embodiment. The flowchart in the fourth embodiment will be described using the flowchart in FIG. 15 instead of the flowchart in FIG. 13 used in the third embodiment. Compared to FIG. 12, FIG. 14 has an acceleration sensor 401 and an excavation start determination unit 402 added. Compared to FIG. 13, S116 has been removed and S201 and S202 have been added.

[0096] In S201, a known method is used to determine whether excavation has started. In S201, if the excavation start determination unit 402 has not determined that excavation has started, the process proceeds to S119. On the other hand, if the excavation start determination unit 402 has determined that excavation has started, the process proceeds to S117. The excavation start determination is made when the orientation, acceleration, and lift cylinder force of the bucket 3 all indicate an excavation start state. The orientation of the bucket 3 is determined using the value of the attitude coefficient calculation unit 203, and the bucket 3 is determined to be in an excavation state when the angle of the bottom of the bucket 3 is within a predetermined angle (e.g., ±10 degrees) from the horizontal and facing forward. The acceleration is determined using the value of the acceleration sensor 401, and the direction of travel is positive, and the acceleration is determined to be less than a predetermined value (e.g., -3 m / s^2). This reflects the fact that when the bucket 3 comes into contact with soil, it receives a reaction force, causing the vehicle body to suddenly decelerate. The lift cylinder force is determined to be in an excavation state when the value of the lift cylinder differential force calculation unit 202 is used, and the lift cylinder force is determined to be greater than, for example, 1.3 times the value when there is no soil in the bucket 3. This also reflects the fact that when bucket 3 comes into contact with soil and sand, it receives a reaction force and rises.

[0097] Furthermore, there is a risk of misjudgment for the angle of the bucket 3 depending on the position at the end of work, there is a risk of misjudgment for the lift cylinder force when soil remains in the bucket 3 or due to the gravitational effect of an uneven road surface, and there is a risk of misjudgment for the vehicle speed when braking or going up a steep slope. Therefore, since there is a high risk of misjudgment when judging any one of these conditions, the start of excavation is judged using the three conditions as an AND condition.

[0098] Then, S119 is followed by S202, in which the loaded weight correction unit 304 processes the corrected loaded weight W' calculated using the dump truck side correction coefficient Kd so that it monotonically decreases from the value at the start of soil discharge. That is, for example, the initial value of the maximum output value is set to W_in, and when the output value W' of S119 is smaller than the maximum value, the output value W' is output and simultaneously continued to be updated as the maximum value, so that when the output value W' of S119 becomes a value higher than the maximum value, the maximum value is output instead. As a result, the corrected loaded weight W' output to S106 monotonically decreases from the start of soil discharge.

[0099] In this way, by limiting the calculation result of the load inside the bucket 3 using the dump side correction coefficient Kd when an excavation start determination has not been made to a monotonically decreasing value, it is possible to prevent the calculated result, the corrected load weight W', from changing unnecessarily due to the influence of hysteresis, for example, during tilt operation.

[0100] (Effects of Example 4) With the above-described configuration and method, the fourth embodiment has the advantage of being able to prevent unnecessary changes in the calculation result (corrected loaded weight W') due to the influence of hysteresis, for example, during tilt operation.

[0101] [Summary of Examples 1 to 4] As described above, the wheel loader 50 of the first embodiment comprises a vehicle body (front frame 6, rear frame 8), a bucket 3, a lift arm 11 that is supported by the vehicle body so as to be rotatable in the vertical direction and that supports the bucket 3 so as to be rotatable in the vertical direction (so that it can be dumped or crumpled), a lift cylinder 12 for rotating the lift arm 11 in the vertical direction to raise and lower the bucket 3, a bucket cylinder 16 for rotating the bucket 3 in the vertical direction to tilt the bucket 3, and a bucket cylinder 16 that is rotatably connected to the lift arm 11 and is interposed between the bucket cylinder 16 and the bucket 3. a bell crank 15 that transmits the bucket cylinder force (extension / contraction force) to the bucket 3, a lift arm position sensor (lift arm angle sensor 19) that measures the relative position (relative angle) between the lift arm 11 and the vehicle body, a bell crank position sensor (bell crank angle sensor 20) that measures the relative position (relative angle) between the bell crank 15 and the lift arm 11, lift cylinder pressure sensors (12b, 12r) that detect the lift cylinder force acting on the lift cylinder 12, bucket cylinder pressure sensors (16b, 16r) that detect the bucket cylinder force acting on the bucket cylinder 16, and a controller 120. The controller 120 holds a front frame equivalent weight corresponding to the total weight of the bucket 3, the lift arm 11, and the bell crank 15 when the bucket 3 is in an empty state, and calculates the load (loaded weight) in the bucket 3 using the relative position (relative angle) between the lift arm 11 and the vehicle body measured by the lift arm position sensor (lift arm angle sensor 19), the relative position (relative angle) between the bell crank 15 and the lift arm 11 measured by the bell crank position sensor (bell crank angle sensor 20), the lift cylinder force detected by the lift cylinder pressure sensors (12b, 12r), the bucket cylinder force detected by the bucket cylinder pressure sensors (16b, 16r), and the front frame equivalent weight.

[0102] This (specifically, by providing a bucket cylinder pressure sensor that detects the bucket cylinder force acting on the bucket cylinder 16) makes it possible to obtain the load weight even if the position of the load moves within the bucket, without the need to go to the trouble of creating a complicated map, making it possible to easily and correctly measure the weight of the load when the wheel loader is operating, and making it easier to adjust the load amount to suit the object being loaded when the wheel loader is excavating and loading.

[0103] Furthermore, in the wheel loader 50 of the first embodiment, the lift arm 11 is structured to be pin-supported relative to the vehicle body so as to be rotatable in the vertical direction, and the controller 120 calculates the front frame equivalent weight by performing processing such that the greater the force (equivalent to Sin∠JAI) applied in the vertical direction at the pin support portion between the lift arm 11 and the vehicle body, the greater the decrease in this weight (total front frame weight) based on the relative posture (relative angle) between the lift arm 11 and the vehicle body measured by the lift arm posture sensor (lift arm angle sensor 19).

[0104] This makes it possible to maintain the accuracy of obtaining the load weight even in a structure in which the lift arm 11 is rotatably supported by a pin.

[0105] Furthermore, in the wheel loader 50 of the second embodiment, when at least one of the relative position (relative angle) between the lift arm 11 and the vehicle body measured by the lift arm position sensor (lift arm angle sensor 19) or the relative position (relative angle) between the bell crank 15 and the lift arm 11 measured by the bell crank position sensor (bell crank angle sensor 20) is within a predetermined range (an angle at which no load remains inside the bucket 3), the controller 120 updates the front frame equivalent weight so that the calculation result of the load inside the bucket 3 becomes zero.

[0106] This allows the load inside the bucket 3 to be calculated correctly, for example, even if the weight of the bucket 3 changes due to deterioration over time (even if the weight of the bucket 3 changes due to rust, etc.).

[0107] Furthermore, in the wheel loader 50 of this second embodiment, the conditions for updating the front frame equivalent weight include at least one of the following: after the lift arm angle, which is the relative angle between the lift arm 11 and the vehicle body, has increased; or after the bell crank angle, which is the relative angle between the bell crank 15 and the lift arm 11, has increased.

[0108] This makes it possible to improve the accuracy of obtaining the loaded weight by the amount of hysteresis included in the hydraulic sensor when updating the empty load weight, and to correctly calculate the load inside the bucket 3.

[0109] Furthermore, in the wheel loader 50 of this third embodiment, the controller 120 holds an empty load map that indicates the relationship between the lift cylinder force and the relative position between the lift arm 11 and the vehicle body when the lift cylinder 12 is extended with no load weight in the bucket 3 (when the bucket 3 is lifted up with the bucket 3 tilted backward), and has a lift-up load measurement unit 303 that measures the load weight in the bucket 3 by referring to the relative position between the lift arm 11 and the vehicle body, the lift cylinder force, and the empty load map value when the lift cylinder 12 is extended with a load weight in the bucket 3 (when the bucket 3 is lifted up with the bucket 3 tilted backward).

[0110] Then, when the value of load measuring unit 303 due to lift-up is determined, the controller 120 calculates and stores a tilt-side correction gain (tilt-side correction coefficient) from the value of load measuring unit 303 due to lift-up and the calculation result of the load inside the bucket 3, and uses the tilt-side correction gain (tilt-side correction coefficient) when calculating the load inside the bucket 3 until the value of load measuring unit 303 due to lift-up is determined again (after the bell crank angle becomes equal to or less than a predetermined threshold value (an angle at which no load remains inside the bucket 3)).

[0111] Furthermore, when the bell crank angle, which is the relative angle between the bell crank 15 and the lift arm 11, decreases after the value of the load measuring unit 303 due to lift-up has been determined, the controller 120 calculates and stores a dump truck side correction gain (dump truck side correction coefficient) from the value of the load measuring unit 303 due to lift-up and the calculation result of the load inside the bucket, and uses the dump truck side correction gain (dump truck side correction coefficient) when calculating the load inside the bucket 3 (until the bell crank angle becomes equal to or less than a predetermined threshold value (an angle at which no load remains inside the bucket 3)).

[0112] This allows the accuracy of obtaining the load weight during tilting or dumping to be improved by the amount of hysteresis contained in the hydraulic sensor, and the load inside the bucket 3 can be calculated taking into account the influence of hysteresis due to the extension and retraction direction of the cylinder mentioned above.

[0113] Furthermore, in the wheel loader 50 of this fourth embodiment, the controller 120 has an excavation start determination unit 402 that determines the start of excavation, and limits the calculation result of the load in the bucket 3 using the dump truck side correction gain (dump truck side correction coefficient) in a state where the excavation start determination has not been made to a monotonically decreasing value.

[0114] This makes it possible to prevent the calculation result (corrected loaded weight W') from changing unnecessarily due to the influence of hysteresis, for example, during a tilt operation.

[0115] In the wheel loader 50 of the above embodiment, the controller 120 has a structure in which the bucket 3 is supported by a rotatable pin relative to the lift arm 11, has push rods 14 supported by rotatable pins relative to the bell crank 15 and the bucket 3, and holds the distance between the pin (fulcrum 13) about which the bucket 3 rotates relative to the lift arm 11 and the pin (fulcrum 23) about which the bucket 3 rotates relative to the push rod 14 as a variable, and calculates the load inside the bucket 3 using this variable.

[0116] This allows the accuracy of obtaining the loaded weight to be maintained even when the bucket 3 as an attachment is replaced.

[0117] It should be noted that the present invention is not limited to the above-described embodiment, and includes various modifications. For example, the above-described embodiment has been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to an embodiment having all of the described configurations.

[0118] Furthermore, the above-described configurations, functions, processing units, processing means, etc. may be partially or entirely implemented in hardware, for example, by designing them as integrated circuits. The above-described configurations, functions, etc. may also be implemented in software, with a processor interpreting and executing a program that implements each function. Information such as the programs, tables, and files that implement each function can be stored in a memory, a storage device such as a hard disk or SSD (Solid State Drive), or a recording medium such as an IC card, SD card, or DVD.

[0119] In addition, the control lines and information lines shown are those that are considered necessary for the explanation, and do not necessarily show all the control lines and information lines in the product. In reality, it can be assumed that almost all components are interconnected. [Explanation of symbols]

[0120] 1 Vehicle Department 2 Work equipment section 3 buckets 4 Engine 4A Engine Room 4B Driver's seat 5 front wheels 6 Front Frame 7 rear wheels 8 Rear frame 9 Center Pin 10 Hydraulic cylinder (steer cylinder or steering cylinder) 11 Lift arm 12 Lift cylinder 12b Lift cylinder bottom pressure sensor 12r Lift cylinder rod side pressure sensor 14 Push rod 15 Bell crank 16 Bucket cylinder 16b Bucket cylinder bottom pressure sensor 16r Bucket cylinder rod side pressure sensor 19 Lift arm angle sensor (lift arm position sensor) 20 Bell crank angle sensor (bell crank position sensor) 50 Wheel Loader 120 Controller 123 monitor

Claims

1. A vehicle body, Bucket and a lift arm that is supported on the vehicle body so as to be rotatable in the vertical direction and that supports the bucket so as to be rotatable in the vertical direction; a lift cylinder for vertically rotating the lift arm to raise and lower the bucket; a bucket cylinder for tilting the bucket by rotating the bucket in a vertical direction; a bell crank rotatably connected to the lift arm and interposed between the bucket cylinder and the bucket, the bell crank transmitting a bucket cylinder force of the bucket cylinder to the bucket; a lift arm position sensor that measures the relative position between the lift arm and the vehicle body; a bell crank position sensor that measures the relative position between the bell crank and the lift arm; a lift cylinder pressure sensor for detecting a lift cylinder force acting on the lift cylinder; a bucket cylinder pressure sensor that detects a bucket cylinder force acting on the bucket cylinder; a controller; The controller a front frame equivalent weight corresponding to the total weight of the bucket, the lift arm, and the bell crank when the bucket is unloaded; a relative position between the lift arm and the vehicle body measured by the lift arm position sensor; a relative position between the bell crank and the lift arm measured by the bell crank position sensor; the lift cylinder force detected by the lift cylinder pressure sensor; the bucket cylinder force detected by the bucket cylinder pressure sensor; The load in the bucket is calculated using the front frame equivalent weight, The lift arm has a structure supported by a pin so as to be rotatable in the vertical direction relative to the vehicle body, the controller calculates the front frame equivalent weight by performing processing such that the greater the force applied in the vertical direction at the pin support portion between the lift arm and the vehicle body, the greater the total weight of the bucket, the lift arm, and the bell crank when the bucket is empty, is reduced based on the relative position of the lift arm and the vehicle body measured by the lift arm position sensor.

2. A vehicle body, Bucket and a lift arm that is supported on the vehicle body so as to be rotatable in the vertical direction and that supports the bucket so as to be rotatable in the vertical direction; a lift cylinder for vertically rotating the lift arm to raise and lower the bucket; a bucket cylinder for tilting the bucket by rotating the bucket in a vertical direction; a bell crank rotatably connected to the lift arm and interposed between the bucket cylinder and the bucket, the bell crank transmitting a bucket cylinder force of the bucket cylinder to the bucket; a lift arm position sensor that measures the relative position between the lift arm and the vehicle body; a bell crank position sensor that measures the relative position between the bell crank and the lift arm; a lift cylinder pressure sensor for detecting a lift cylinder force acting on the lift cylinder; a bucket cylinder pressure sensor that detects a bucket cylinder force acting on the bucket cylinder; a controller; The controller a front frame equivalent weight corresponding to the total weight of the bucket, the lift arm, and the bell crank when the bucket is unloaded; a relative position between the lift arm and the vehicle body measured by the lift arm position sensor; a relative position between the bell crank and the lift arm measured by the bell crank position sensor; the lift cylinder force detected by the lift cylinder pressure sensor; the bucket cylinder force detected by the bucket cylinder pressure sensor; The load in the bucket is calculated using the front frame equivalent weight, the controller updates the front frame equivalent weight so that the calculated load in the bucket becomes zero when at least one of the relative position between the lift arm and the vehicle body measured by the lift arm position sensor and the relative position between the bell crank and the lift arm measured by the bell crank position sensor is within a predetermined range.

3. A vehicle body, Bucket and a lift arm that is supported on the vehicle body so as to be rotatable in the vertical direction and that supports the bucket so as to be rotatable in the vertical direction; a lift cylinder for vertically rotating the lift arm to raise and lower the bucket; a bucket cylinder for tilting the bucket by rotating the bucket in a vertical direction; a bell crank rotatably connected to the lift arm and interposed between the bucket cylinder and the bucket, the bell crank transmitting a bucket cylinder force of the bucket cylinder to the bucket; a lift arm position sensor that measures the relative position between the lift arm and the vehicle body; a bell crank position sensor that measures the relative position between the bell crank and the lift arm; a lift cylinder pressure sensor for detecting a lift cylinder force acting on the lift cylinder; a bucket cylinder pressure sensor that detects a bucket cylinder force acting on the bucket cylinder; a controller; The controller a front frame equivalent weight corresponding to the total weight of the bucket, the lift arm, and the bell crank when the bucket is unloaded; a relative position between the lift arm and the vehicle body measured by the lift arm position sensor; a relative position between the bell crank and the lift arm measured by the bell crank position sensor; the lift cylinder force detected by the lift cylinder pressure sensor; the bucket cylinder force detected by the bucket cylinder pressure sensor; The load in the bucket is calculated using the front frame equivalent weight, the controller updates the front frame equivalent weight so that a calculation result of the load in the bucket becomes zero when at least one of the relative position between the lift arm and the vehicle body measured by the lift arm position sensor or the relative position between the bell crank and the lift arm measured by the bell crank position sensor is within a predetermined range; a wheel loader characterized in that the condition for updating the front frame equivalent weight includes at least one of the following: after a lift arm angle, which is the relative angle between the lift arm and the vehicle body, has increased; or after a bell crank angle, which is the relative angle between the bell crank and the lift arm, has increased.

4. A vehicle body, Bucket and a lift arm that is supported on the vehicle body so as to be rotatable in the vertical direction and that supports the bucket so as to be rotatable in the vertical direction; a lift cylinder for vertically rotating the lift arm to raise and lower the bucket; a bucket cylinder for tilting the bucket by rotating the bucket in a vertical direction; a bell crank rotatably connected to the lift arm and interposed between the bucket cylinder and the bucket, the bell crank transmitting a bucket cylinder force of the bucket cylinder to the bucket; a lift arm position sensor that measures the relative position between the lift arm and the vehicle body; a bell crank position sensor that measures the relative position between the bell crank and the lift arm; a lift cylinder pressure sensor for detecting a lift cylinder force acting on the lift cylinder; a bucket cylinder pressure sensor that detects a bucket cylinder force acting on the bucket cylinder; a controller; The controller a front frame equivalent weight corresponding to the total weight of the bucket, the lift arm, and the bell crank when the bucket is unloaded; a relative position between the lift arm and the vehicle body measured by the lift arm position sensor; a relative position between the bell crank and the lift arm measured by the bell crank position sensor; the lift cylinder force detected by the lift cylinder pressure sensor; the bucket cylinder force detected by the bucket cylinder pressure sensor; The load in the bucket is calculated using the front frame equivalent weight, The controller an empty load map is stored which shows the relationship between the relative position of the lift arm and the vehicle body and the lift cylinder force when the lift cylinder is extended with no load weight in the bucket; a lift-up load measuring unit that measures the load weight in the bucket by referring to the relative position between the lift arm and the vehicle body, the lift cylinder force, and the value of the empty load map when the lift cylinder is extended with a load weight in the bucket; When the value of the load measuring unit due to the lift-up is determined, a tilt-side correction gain is calculated from the value of the load measuring unit due to the lift-up and the calculation result of the load inside the bucket, and is stored; a wheel loader, wherein the tilt-side correction gain is used when calculating the load in the bucket until the value of the load measuring unit due to lift-up is determined again.

5. A vehicle body, Bucket and a lift arm that is supported on the vehicle body so as to be rotatable in the vertical direction and that supports the bucket so as to be rotatable in the vertical direction; a lift cylinder for vertically rotating the lift arm to raise and lower the bucket; a bucket cylinder for tilting the bucket by rotating the bucket in a vertical direction; a bell crank rotatably connected to the lift arm and interposed between the bucket cylinder and the bucket, the bell crank transmitting a bucket cylinder force of the bucket cylinder to the bucket; a lift arm position sensor that measures the relative position between the lift arm and the vehicle body; a bell crank position sensor that measures the relative position between the bell crank and the lift arm; a lift cylinder pressure sensor for detecting a lift cylinder force acting on the lift cylinder; a bucket cylinder pressure sensor that detects a bucket cylinder force acting on the bucket cylinder; a controller; The controller a front frame equivalent weight corresponding to the total weight of the bucket, the lift arm, and the bell crank when the bucket is unloaded; a relative position between the lift arm and the vehicle body measured by the lift arm position sensor; a relative position between the bell crank and the lift arm measured by the bell crank position sensor; the lift cylinder force detected by the lift cylinder pressure sensor; the bucket cylinder force detected by the bucket cylinder pressure sensor; The load in the bucket is calculated using the front frame equivalent weight, The controller an empty load map is stored which shows the relationship between the relative position of the lift arm and the vehicle body and the lift cylinder force when the lift cylinder is extended with no load weight in the bucket; a lift-up load measuring unit that measures the load weight in the bucket by referring to the relative position between the lift arm and the vehicle body, the lift cylinder force, and the value of the empty load map when the lift cylinder is extended with a load weight in the bucket; when a bell crank angle, which is a relative angle between the bell crank and the lift arm, decreases after the value of the load measuring unit due to lift-up is determined, a dump truck side correction gain is calculated and held from the value of the load measuring unit due to lift-up and a calculation result of the load inside the bucket; A wheel loader characterized in that the dump side correction gain is used when calculating the load in the bucket.

6. A vehicle body, Bucket and a lift arm that is supported on the vehicle body so as to be rotatable in the vertical direction and that supports the bucket so as to be rotatable in the vertical direction; a lift cylinder for vertically rotating the lift arm to raise and lower the bucket; a bucket cylinder for tilting the bucket by rotating the bucket in a vertical direction; a bell crank rotatably connected to the lift arm and interposed between the bucket cylinder and the bucket, the bell crank transmitting a bucket cylinder force of the bucket cylinder to the bucket; a lift arm position sensor that measures the relative position between the lift arm and the vehicle body; a bell crank position sensor that measures the relative position between the bell crank and the lift arm; a lift cylinder pressure sensor for detecting a lift cylinder force acting on the lift cylinder; a bucket cylinder pressure sensor that detects a bucket cylinder force acting on the bucket cylinder; a controller; The controller a front frame equivalent weight corresponding to the total weight of the bucket, the lift arm, and the bell crank when the bucket is unloaded; a relative position between the lift arm and the vehicle body measured by the lift arm position sensor; a relative position between the bell crank and the lift arm measured by the bell crank position sensor; the lift cylinder force detected by the lift cylinder pressure sensor; the bucket cylinder force detected by the bucket cylinder pressure sensor; The load in the bucket is calculated using the front frame equivalent weight, The controller an empty load map is stored which shows the relationship between the relative position of the lift arm and the vehicle body and the lift cylinder force when the lift cylinder is extended with no load weight in the bucket; a lift-up load measuring unit that measures the load weight in the bucket by referring to the relative position between the lift arm and the vehicle body, the lift cylinder force, and the value of the empty load map when the lift cylinder is extended with a load weight in the bucket; when a bell crank angle, which is a relative angle between the bell crank and the lift arm, decreases after the value of the load measuring unit due to lift-up is determined, a dump truck side correction gain is calculated and held from the value of the load measuring unit due to lift-up and a calculation result of the load inside the bucket; The dump truck side correction gain is used when calculating the load inside the bucket, the controller has an excavation start determination unit that determines when excavation starts, and limits a calculation result of the load in the bucket using the dump truck side correction gain when the excavation start determination has not been made to a monotonically decreasing value.

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