Work vehicle

Abstract

To provide a work vehicle capable of properly adjusting a balance between a vehicle speed limit and a stop position of the work vehicle while reducing operation load of an operator during a loading work.SOLUTION: A wheel loader 1 provided with a work device 2 comprises: a motion state detecting device detecting a motion state of the work device 2; and a loading target sensor 32 detecting a distance L to a loading target where a cargo in the work device 2 is loaded and a height H of the loading target. A controller 5 determines whether or not a vehicle body travel ahead and the work device 2 moves in an upper direction on bases of a travel state of the vehicle body and a motion state of the work device 2, calculates vehicle speed limit Qup1 on bases of the distance L from the vehicle body to the loading target and the height of the loading target when determining the vehicle travels ahead and the work device 2 moves in the upper direction, and control a travel driving device 100A to limit vehicle speed on a basis of the calculated limit Qup1.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to a work vehicle equipped with a work implement. [Background technology]

[0002] Work vehicles such as wheel loaders perform loading operations by moving the work implement upward while traveling forward to load the load stored in the work implement into a loading destination such as a dump truck or hopper. During this loading operation, the operator must simultaneously operate the vehicle and the work implement, which is a complex operation that requires skill. Therefore, in recent years, work vehicles equipped with functions that reduce the operational burden on the operator during loading operations and enable the vehicle to approach the loading destination efficiently have been introduced.

[0003] For example, Patent Document 1 discloses a wheel loader equipped with a controller that determines whether specific conditions for upward movement of the lift arm during forward travel are met based on the travel state and the discharge pressure of a cargo-handling hydraulic pump, and if the specific conditions are met, limits the vehicle speed by controlling the displacement of the travel hydraulic pump or the displacement of the travel hydraulic motor in accordance with an increase in the discharge pressure of the cargo-handling hydraulic pump or an increase in the input torque of the cargo-handling hydraulic pump.In this wheel loader, the controller limits the vehicle speed during loading operations, thereby adjusting the travel distance to the loading destination and reducing the burden on the operator when operating the vehicle. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6683883 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the wheel loader described in Patent Document 1 limits the vehicle speed based on sensor information related to the lift arm raising operation, thereby shortening the distance to the loading destination, and because the vehicle speed limit is a predetermined value that is arbitrarily set in advance, it does not adjust the balance between the vehicle speed limit and the stopping position of the working equipment moving upward. In order to adjust the balance between the vehicle speed limit and the stopping position of the working equipment during operation to an appropriate level, the operator needs to change the setting of the vehicle speed limit each time, which increases the operator's workload.

[0006] Therefore, an object of the present invention is to provide a work vehicle that is capable of appropriately adjusting the balance between vehicle speed restrictions and the stopping position of the working equipment during loading operations while reducing the operating burden on the operator. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a work vehicle including a vehicle body, a working device attached to the vehicle body so as to be rotatable in a vertical direction, a traveling drive device that causes the vehicle body to travel, a traveling condition detection device that detects the traveling condition of the vehicle body, and a controller that controls the operation of the working device and the traveling drive device, and further includes an operation condition detection device that detects the operating condition of the working device, and a loading destination detection device that detects the distance to a loading destination where a load in the working device is to be loaded and the height of the loading destination, wherein the controller determines whether the vehicle body is traveling forward and the working device is operating in an upward direction based on the traveling condition of the vehicle body detected by the traveling condition detection device and the operating state of the working device detected by the operation condition detection device, and when it is determined that the vehicle body is traveling forward and the working device is operating in an upward direction, calculates a vehicle speed limit based on the distance from the vehicle body to the loading destination and the height of the loading destination detected by the loading destination detection device, and controls the traveling drive device based on the calculated limit [Effects of the Invention]

[0008] According to the present invention, it is possible to appropriately adjust the balance between the vehicle speed limit and the stopping position of the working implement during loading operations while reducing the operational burden on the operator. Problems, configurations, and effects other than those described above will become clear from the description of the following embodiments. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is an external side view showing an example of the configuration of a wheel loader according to an embodiment of the present invention. [Figure 2] FIG. 1 is an explanatory diagram illustrating V-shape loading by a wheel loader. [Figure 3] FIG. 1 is an explanatory diagram illustrating loading work by a wheel loader. [Figure 4] 1 is a system configuration diagram showing an example of the configuration of a drive system of a wheel loader. [Figure 5] FIG. 2 is a functional block diagram showing functions of a controller. [Figure 6] 10 is a graph showing the relationship between the discharge pressure of the cargo handling hydraulic pump and the increase in the minimum displacement of the HST motor. [Figure 7] 10 is a graph showing the relationship between running load pressure and minimum displacement of an HST motor. [Figure 8] 10 is a graph showing the relationship between the vehicle speed and tractive force of a wheel loader. [Figure 9] 10 is a flowchart showing the flow of processing executed by a controller. DETAILED DESCRIPTION OF THE INVENTION

[0010] In the following, a wheel loader that performs loading and unloading work will be described as an example of one aspect of a work vehicle according to an embodiment of the present invention.

[0011] <Overall configuration of wheel loader 1> First, the overall configuration of a wheel loader 1 according to an embodiment of the present invention will be described with reference to FIG.

[0012] FIG. 1 is an external side view showing an example of the configuration of a wheel loader 1 according to an embodiment of the present invention.

[0013] The wheel loader 1 is an articulated work vehicle that is steered by bending the vehicle body near the center, with a front frame 1A forming the front part of the vehicle body and a rear frame 1B forming the rear part of the vehicle body connected by a center joint 10 so that the front frame 1A can rotate freely in the left-right direction relative to the rear frame 1B. In the following explanation, within the left-right direction of the vehicle body, the direction to the left relative to the forward direction is referred to as the "left direction," and the direction to the right relative to the forward direction is referred to as the "right direction."

[0014] The vehicle body is provided with four wheels 11, two of which are front wheels 11A and are provided on both the left and right sides of the front frame 1A, and the remaining two are rear wheels 11B and are provided on both the left and right sides of the rear frame 1B. Of the four wheels 11, only the front wheel 11A and the rear wheel 11B, which are provided on the left side, are shown in Fig. 1.

[0015] A hydraulically driven working device 2 is attached to the front of the front frame 1A to perform loading and unloading operations, such as digging up work objects such as soil and minerals and loading the excavated work objects into a loading destination such as a dump truck or hopper.

[0016] The working device 2 has a lift arm 21 attached to the front frame 1A so as to be rotatable in the vertical direction, two lift arm cylinders 22L, 22R (see FIG. 4) as hydraulic cylinders that drive the lift arm 21, a bucket 23 attached to the tip of the lift arm 21 so as to be rotatable in the vertical direction, a bucket cylinder 24 that serves as a hydraulic cylinder that drives the bucket 23, and a bell crank 25 rotatably connected to the lift arm 21 and that forms a link mechanism between the bucket 23 and the bucket cylinder 24.

[0017] The two lift arm cylinders 22L, 22R are arranged side by side at a predetermined distance in the left-right direction of the vehicle body, and in FIG. 1, only the lift arm cylinder 22L arranged on the left side is shown by a dashed line.

[0018] The lift arm 21 rotates up and down relative to the front frame 1A as two lift arm cylinders 22L, 22R extend and retract.

[0019] A lift arm angle sensor 31 that detects the angle of the lift arm 21 (hereinafter referred to as "lift arm angle") is attached to the base end of the lift arm 21 (the attachment portion to the front frame 1A). This lift arm angle sensor 31 is one form of a posture detection device that detects the posture of the working implement 2 (the height of the lift arm 21 when the ground contact surface of the vehicle body is used as the reference).

[0020] Bucket 23 rotates vertically relative to lift arm 21 as bucket cylinder 24 expands and contracts. This allows bucket 23 to scoop up and discharge (dig and dump) work objects such as earth and sand or minerals.

[0021] The bucket 23 can be replaced with various attachments, such as a blade, and the wheel loader 1 can perform various tasks such as snow removal and earth-pulling in addition to loading and unloading operations using the bucket 23.

[0022] The lift arm 21 and the bucket 23 are each operated by operating a cargo handling operation lever 120 (see FIG. 4) provided in the operator's cab 12. In this embodiment, the lift arm 21 and the bucket 23 can be operated by a single cargo handling operation lever 120, but this is not limiting, and for example, an operation lever for operating the lift arm 21 and an operation lever for operating the bucket 23 may be provided separately.

[0023] The rear frame 1B is provided with a cab 12 in which the operator sits, a machine room 13 that houses various devices required for driving the wheel loader 1, and a counterweight 14 that maintains balance with the work implement 2 to prevent the vehicle body from tilting. On the rear frame 1B, the cab 12 is located at the front, the counterweight 14 at the rear, and the machine room 13 between the cab 12 and the counterweight 14.

[0024] In this embodiment, a loading destination sensor 32 serving as a loading destination detection device that detects the distance L to the loading destination (for example, a dump truck or a hopper) where the load in the bucket 23 is to be loaded and the height H of the loading destination is provided at the front end portion of the ceiling of the cab 12. The loading destination sensor 32 uses, for example, an imaging device such as millimeter-wave radar, LIDAR (Light Detection and Ranging), or a stereo camera, and detects the distance L to the loading destination in front of the wheel loader 1 and the height H of the loading destination.

[0025] <About cargo handling operations> Next, the cargo handling operation performed by the wheel loader 1 will be described with reference to FIGS.

[0026] Fig. 2 is an explanatory diagram illustrating V-shape loading by the wheel loader 1. Fig. 3 is an explanatory diagram illustrating loading work by the wheel loader 1.

[0027] The wheel loader 1 performs loading and unloading work by using the work implement 2 to excavate work objects such as earth and sand or minerals and load them into a loading destination such as a dump truck or hopper. In other words, the loading and unloading work is divided into an excavation work to excavate the work object, and a loading work to load the work object (load) into a loading destination.

[0028] 2, first, the wheel loader 1 moves forward toward the mound of natural ground α, which is the work target, as indicated by arrow X1, and performs excavation work by plungeing the bucket 23 into the mound of natural ground α to scoop up earth, sand, minerals, etc. Once the excavation work is completed, the wheel loader 1 moves back to its original location as indicated by arrow X2.

[0029] In the subsequent loading operation, the wheel loader 1 moves forward, as indicated by arrow Y1, towards the dump truck β onto which the load in the bucket 23 is to be loaded, and stops in front of the dump truck β. At this time, the wheel loader 1 operates the working implement 2 in an upward direction while traveling forward. Note that in Figure 2, the wheel loader 1 stopped in front of the dump truck β is shown by a dashed line.

[0030] As shown in Fig. 3, in loading work, first, the operator fully depresses the accelerator pedal (full accelerator) and raises the lift arm 21 (the state shown on the right side in Fig. 3). Next, the operator, while keeping the accelerator pedal in the full accelerator state, further raises the lift arm 21 (the state shown in the center in Fig. 3). Then, the operator activates the brakes to stop the truck in front of the dump truck β, dumps the bucket 23, and loads the load (earth, sand, minerals, etc.) in the bucket 23 into the dump truck β.

[0031] When the loading operation is completed, the wheel loader 1 retreats to its original location, as shown by the arrow Y2 in Figure 2. This method of the wheel loader 1 traveling back and forth in a V shape between the mound of ground α and the dump truck β to perform excavation and loading operations is called "V-shape loading."

[0032] <Wheel loader 1 drive system> Next, the drive system of the wheel loader 1 will be described with reference to FIG.

[0033] FIG. 4 is a system configuration diagram showing an example of the configuration of the drive system of the wheel loader 1.

[0034] The travel drive device 100A that causes the body of the wheel loader 1 to travel is of the HST type and is configured to include an HST pump 41 as a travel hydraulic pump driven by the engine 40, an HST charge pump 41A that supplies pressure oil for controlling the HST pump 41, and an HST motor 42 as a travel hydraulic motor connected in a closed circuit to the HST pump 41. Each device, such as the HST pump 41 and the HST motor 42, is controlled by a controller 5.

[0035] The HST pump 41 is a variable displacement hydraulic pump of a swash plate type or a bent axis type, in which the displacement volume is controlled according to the tilt angle. The tilt angle is adjusted by a pump regulator 410 in accordance with a command signal output from the controller 5.

[0036] The HST motor 42 is a variable displacement hydraulic motor of a swash plate type or an inclined axis type whose displacement is controlled according to the tilt angle, and transmits the driving force of the engine 40 to the wheels (front wheels 11A and rear wheels 11B). As in the case of the HST pump 41, the tilt angle is adjusted by a motor regulator 420 in accordance with a command signal output from the controller 5.

[0037] In the HST traveling drive system, first, when the operator depresses the accelerator pedal 61 provided in the cab 12, the engine 40 rotates, and the driving force of the engine 40 drives the HST pump 41. Then, the HST motor 42 rotates due to the pressure oil discharged from the HST pump 41, and the output torque from the HST motor 42 is transmitted to the front wheels 11A and rear wheels 11B via the axles 15, causing the wheel loader 1 to travel.

[0038] Specifically, when the operator depresses accelerator pedal 61, the depression amount of accelerator pedal 61 detected by depression amount sensor 610 provided on accelerator pedal 61 is input to controller 5, and a command signal relating to a target engine rotation speed is output from controller 5 to engine 40. The rotation speed of engine 40 is controlled in accordance with this target engine rotation speed.

[0039] The target engine rotation speed increases as the depression amount of the accelerator pedal 61 increases. When the target engine rotation speed increases, the discharge flow rate of the HST pump 41 increases, and the flow rate of pressure oil flowing from the HST pump 41 to the HST motor 42 increases. This increases the rotation speed of the HST motor 42, and the vehicle speed increases.

[0040] In this way, in an HST type traveling drive system, the vehicle speed is adjusted (changed) by continuously increasing or decreasing the discharge flow rate of the HST pump 41, enabling smooth starts and less shock-inducing stops for the wheel loader 1. Note that it is not necessarily necessary to control the vehicle speed by adjusting the discharge flow rate on the HST pump 41 side, and the vehicle speed may also be controlled by adjusting the displacement volume on the HST motor 42 side.

[0041] The travel direction of the wheel loader 1, i.e., selection of forward or reverse, is made by a forward / reverse selector switch 62 provided in the operator's cab 12. When the operator switches the forward / reverse selector switch 62 to the forward position, a switch signal indicating forward travel is output to the controller 5, and the controller 5 outputs a command signal to the transmission to engage the forward clutch of the transmission. When the transmission receives the command signal related to forward travel output from the controller 5, the forward clutch is engaged and the travel direction of the vehicle body is switched to forward travel. A similar mechanism is used to switch the vehicle body to reverse travel.

[0042] The operator's cab 12 is also provided with a speed step switch 63 that can set the maximum vehicle speed to one of four speed steps. With this speed step switch 63, the maximum vehicle speed increases in the order of speed step 1, speed step 2, speed step 3, and speed step 4. For example, the operator selects speed step 1, which provides the lowest maximum vehicle speed, for excavation work, and speed step 2, which provides a maximum vehicle speed (for example, 9 to 15 km / h) that is higher than the maximum vehicle speed of speed step 1, for loading work.

[0043] The depression amount sensor 610, forward / reverse switch 62, and speed step switch 63 are one aspect of a driving condition detection device that detects the driving condition of the vehicle body. Note that the determination of the driving condition of the vehicle body does not necessarily have to be based on the depression amount of the accelerator pedal 61, the forward / reverse switching state, and the selected speed step, and may be made comprehensively based on, for example, each piece of data detected by a plurality of other driving condition detection devices mounted on the vehicle body.

[0044] The work drive device 100B that drives the work implement 2 is hydraulically driven and includes a cargo handling hydraulic pump 43, a lift arm directional control valve 44 provided between the cargo handling hydraulic pump 43 and the two lift arm cylinders 22L, 22R, a bucket directional control valve 45 provided between the cargo handling hydraulic pump 43 and the bucket cylinder 24, a first lift arm electromagnetic control valve 44L and a second lift arm electromagnetic control valve 44R that control the lift arm directional control valve 44, and a first bucket electromagnetic control valve 45L and a second bucket electromagnetic control valve 45R that control the bucket directional control valve 45.

[0045] The cargo handling hydraulic pump 43 is driven by the engine 40, and pumps up hydraulic oil stored in a hydraulic oil tank 430 and supplies it to each of the two lift arm cylinders 22L, 22R and the bucket cylinder 24. Note that although the cargo handling hydraulic pump 43 is shown in Figure 4 as a variable displacement hydraulic pump, it does not necessarily have to be a variable displacement type and may be a fixed displacement type.

[0046] A discharge pressure sensor 43A is provided on the discharge side of the cargo handling hydraulic pump 43 to detect the discharge pressure Pa of the cargo handling hydraulic pump 43. The discharge pressure Pa of the cargo handling hydraulic pump 43 detected by the discharge pressure sensor 43A is output to the controller 5.

[0047] The discharge pressure sensor 43A and the cargo handling operation lever 120 are one aspect of an operation state detection device that detects the operation state of the working device 2. Note that the determination of the operation state of the working device 2 does not necessarily have to be based on the discharge pressure Pa of the cargo handling hydraulic pump 43 and the operation signal output from the cargo handling operation lever 120, and may be based on, for example, the lift arm angle detected by the lift arm angle sensor 31 described above.

[0048] The lift arm direction control valve 44 controls the flow (direction and flow rate) of hydraulic oil discharged from the cargo handling hydraulic pump 43 and guided to each of the two lift arm cylinders 22L, 22R.

[0049] The first lift arm electromagnetic control valve 44L and the second lift arm electromagnetic control valve 44R each control the lift arm directional control valve 44 based on a command signal output from the controller 5.

[0050] For example, when an operator operates the cargo handling operation lever 120 to perform a lifting operation of the lift arm 21, a lifting operation signal is output from the cargo handling operation lever 120 to the controller 5. When the controller 5 acquires the lifting operation signal output from the cargo handling operation lever 120, it outputs a lifting operation command signal to each of the first lift arm electromagnetic control valve 44L and the second lift arm electromagnetic control valve 44R to lift the lift arm 21.

[0051] The first lift arm electromagnetic control valve 44L and the second lift arm electromagnetic control valve 44R each control the operation of the spool of the lift arm directional control valve 44 based on the lifting operation command signal output from the controller 5 so as to connect the cargo handling hydraulic pump 43 to the bottom chambers of the two lift arm cylinders 22L, 22R.

[0052] As a result, the hydraulic oil discharged from the cargo handling hydraulic pump 43 flows into the bottom chambers of the two lift arm cylinders 22L, 22R, and each rod 220 extends, causing the lift arm 21 to rotate upward relative to the front frame 1A.

[0053] Furthermore, when the operator operates the cargo handling operation lever 120 to lower the lift arms 21, a lowering operation signal is output from the cargo handling operation lever 120 to the controller 5. When the controller 5 acquires the lowering operation signal output from the cargo handling operation lever 120, it outputs a lowering operation command signal to each of the first lift arm electromagnetic control valve 44L and the second lift arm electromagnetic control valve 44R to lower the lift arms 21.

[0054] The first lift arm electromagnetic control valve 44L and the second lift arm electromagnetic control valve 44R each control the operation of the spool of the lift arm directional control valve 44 based on a lowering operation command signal output from the controller 5 so as to connect the cargo handling hydraulic pump 43 to each rod chamber of the two lift arm cylinders 22L, 22R.

[0055] As a result, the hydraulic oil discharged from the cargo handling hydraulic pump 43 flows into the rod chambers of the two lift arm cylinders 22L, 22R, causing the rods 220 to contract and the lift arms 21 to rotate downward relative to the front frame 1A.

[0056] The bucket direction control valve 45 controls the flow (direction and flow rate) of hydraulic oil discharged from the cargo handling hydraulic pump 43 and guided to the bucket cylinder 24 .

[0057] The first bucket electromagnetic control valve 45L and the second bucket electromagnetic control valve 45R each control the bucket directional control valve 45 based on a command signal output from the controller 5.

[0058] For example, when the operator operates the cargo handling operation lever 120 to tilt (tilt backward) the bucket 23, a tilt operation signal is output from the cargo handling operation lever 120 to the controller 5. When the controller 5 acquires the tilt operation signal from the cargo handling operation lever 120, it outputs a rearward tilt operation command signal to each of the first bucket electromagnetic control valve 45L and the second bucket electromagnetic control valve 45R to tilt the bucket 23 backward.

[0059] Then, based on a rearward tilt operation command signal output from controller 5, first bucket electromagnetic control valve 45L and second bucket electromagnetic control valve 45R each control the operation of the spool of bucket directional control valve 45 so as to connect cargo handling hydraulic pump 43 and the bottom chamber of bucket cylinder 24.

[0060] As a result, the hydraulic oil discharged from the cargo handling hydraulic pump 43 flows into the bottom chamber of the bucket cylinder 24, the rod 240 extends, and the bucket 23 rotates upward relative to the lift arm 21 and tilts backward (towards the vehicle body).

[0061] Furthermore, when the operator operates cargo handling operation lever 120 to perform a dump operation (forward tilt operation) of bucket 23, a dump operation signal is output from cargo handling operation lever 120 to controller 5. Upon receiving the dump operation signal output from cargo handling operation lever 120, controller 5 outputs a forward tilt operation command signal to each of first bucket electromagnetic control valve 45L and second bucket electromagnetic control valve 45R to tilt bucket 23 forward.

[0062] Then, based on the forward tilting operation command signal output from controller 5, first bucket electromagnetic control valve 45L and second bucket electromagnetic control valve 45R each control the operation of the spool of bucket directional control valve 45 so as to connect cargo handling hydraulic pump 43 and the rod chamber of bucket cylinder 24.

[0063] As a result, the hydraulic oil discharged from the cargo handling hydraulic pump 43 flows into the rod chamber of the bucket cylinder 24, causing the rod 240 to contract and the bucket 23 to rotate downward relative to the lift arm 21 and tilt forward (towards the front of the vehicle body).

[0064] (Controller 5 configuration) Next, the configuration of the controller 5 will be described with reference to FIGS.

[0065] Fig. 5 is a functional block diagram showing the functions of the controller 5. Fig. 6 is a graph showing the relationship between the discharge pressure Pa of the cargo handling hydraulic pump 43 and the increase Qup in the minimum displacement of the HST motor 42. Fig. 7 is a graph showing the relationship between the traveling load pressure and the minimum displacement Qmin of the HST motor 42. Fig. 8 is a graph showing the relationship between the vehicle speed and tractive force of the wheel loader 1.

[0066] The controller 5 is configured by interconnecting a CPU, RAM, ROM, HDD, input I / F, and output I / F via a bus. Various operating devices, such as the forward / reverse switch 62, speed stage switch 63, and cargo handling operation lever 120, as well as various sensors, such as the lift arm angle sensor 31, loading destination sensor 32, discharge pressure sensor 43A, and depression amount sensor 610, are connected to the input I / F, and the motor regulator 420, first lift arm electromagnetic control valve 44L, and second lift arm electromagnetic control valve 44R are connected to the output I / F.

[0067] In such a hardware configuration, the CPU reads out a control program (software) stored on a recording medium such as a ROM, HDD, or optical disk, expands it on RAM, and executes the expanded control program, whereby the control program and hardware work together to realize the functions of the controller 5.

[0068] In this embodiment, the configuration of the controller 5 is described as a combination of software and hardware, but this is not limiting, and the controller 5 may also be configured using an integrated circuit that realizes the functions of a control program executed on the wheel loader 1 side.

[0069] The controller 5 includes a data acquisition unit 51 , a state determination unit 52 , a restriction amount calculation unit 53 , a height threshold selection unit 54 , a stop position determination unit 55 , a command signal output unit 56 , and a memory unit 57 .

[0070] The data acquisition unit 51 acquires the switching signal output from the forward / reverse switch 62, the speed stage signal output from the speed stage switch 63, the operation signal output from the cargo handling operation lever 120, the depression amount of the accelerator pedal 61 detected by the depression amount sensor 610, the lift arm angle detected by the lift arm angle sensor 31, the discharge pressure Pa of the cargo handling hydraulic pump 43 detected by the discharge pressure sensor 43A, and the loading destination data detected by the loading destination sensor 32.

[0071] Here, the "loading destination data" is data related to the dump truck, hopper, or the like that will be the loading destination, and includes, for example, the distance L from the vehicle body (wheel loader 1) to the loading destination and the height H of the loading destination relative to the ground on which the vehicle body is in contact. Note that the distance L from the vehicle body to the loading destination and the height H of the loading destination do not necessarily need to be included in the loading destination data, and may be calculated by the controller 5 based on, for example, the position of the loading destination detected by the loading destination sensor 32.

[0072] The state determination unit 52 determines whether or not the vehicle body is traveling forward based on the switching signal, speed step signal, and depression amount of the accelerator pedal 61 acquired by the data acquisition unit 51. Specifically, the state determination unit 52 determines that the wheel loader 1 is traveling forward for loading work when the switching signal is a signal indicating forward movement, the speed step signal is a signal indicating two speed steps, and the depression amount of the accelerator pedal 61 is a value indicating full acceleration.

[0073] The state determination unit 52 can determine whether or not the wheel loader 1 is traveling forward for loading work by using the speed gear signal acquired by the data acquisition unit 51 to determine the traveling state, but it is not always necessary to use the speed gear signal to determine the traveling state; it is sufficient to determine the traveling state using at least the switching signal and the amount of depression of the accelerator pedal 61.

[0074] Furthermore, the state determination unit 52 determines whether the lift arms 21 (working devices 2) are operating in the upward direction based on the operation signal acquired by the data acquisition unit 51 and the discharge pressure Pa of the cargo handling hydraulic pump 43. Specifically, the state determination unit 52 determines that the lift arms 21 are performing a lifting operation related to loading work when the operation signal is a lifting operation signal and the discharge pressure Pa is equal to or greater than the first pressure threshold value P1 (Pa≧P1).

[0075] Here, the "first pressure threshold P1" is a value corresponding to the discharge pressure of the cargo handling hydraulic pump 43 when the lift arm 21 starts the operation of lifting the loaded bucket 23 upward.

[0076] Furthermore, the state determination unit 52 determines the magnitude relationship between the discharge pressure Pa of the cargo handling hydraulic pump 43 acquired by the data acquisition unit 51 and each of the first pressure threshold P1, the second pressure threshold P2, and the third pressure threshold P3.

[0077] The "second pressure threshold P2" is a value corresponding to the discharge pressure of the cargo handling hydraulic pump 43 when the lift arm 21 is in a horizontal position. The "third pressure threshold P3" is a value corresponding to the discharge pressure of the cargo handling hydraulic pump 43 when the lift arm 21 is fully raised, i.e., the relief pressure.

[0078] That is, the first to third pressure threshold values ​​P1, P2, and P3 are all values ​​related to the pressure (discharge pressure of the cargo handling hydraulic pump 43) required for the lift arm 21 to lift the loaded bucket 23. These first to third pressure threshold values ​​P1, P2, and P3 are stored in the memory unit 57.

[0079] When the state determination unit 52 determines that the vehicle body is moving forward and the working device 2 is operating upward, the limit calculation unit 53 calculates the speed limit of the vehicle speed. In the present embodiment, the limit calculation unit 53 calculates, as the speed limit of the vehicle speed, a limit value Qup1 (>0) related to an increase in the minimum retraction volume of the HST motor 42.

[0080] The limit calculation unit 53 first calculates a ratio Ra between the distance L from the vehicle body to the loading destination and the height H of the loading destination acquired by the data acquisition unit 51. Subsequently, the limit calculation unit 53 calculates a predetermined limit value Qup1 based on the calculated ratio Ra.

[0081] Then, as shown in FIG. 6, when the state determination unit 52 determines that the discharge pressure Pa is equal to or greater than the first pressure threshold value P1 and less than the second pressure threshold value P2 (P1≦Pa<P2), the limit calculation unit 53 calculates the minimum retraction volume Qmin of the HST motor 42 such that the increase Qup in the minimum retraction volume of the HST motor 42 increases up to a predetermined limit value Qup1 as the discharge pressure Pa of the cargo handling hydraulic pump 43 increases. In this case, the vehicle speed of the wheel loader 1 is restricted (decelerated) so that the restriction width (deceleration width) gradually increases.

[0082] Further, when the state determination unit 52 determines that the discharge pressure Pa is equal to or greater than the second pressure threshold value P2 and less than the third pressure threshold value P3 (P2≦Pa<P3), the limit calculation unit 53 calculates the minimum retraction volume Qmin of the HST motor 42 such that the increase Qup in the minimum retraction volume of the HST motor 42 is maintained at a predetermined limit value Qup1 regardless of the increase in the discharge pressure Pa. In this case, the vehicle speed of the wheel loader 1 is restricted (decelerated) with a constant restriction width (deceleration width).

[0083] Here, as shown in FIG. 7, by increasing the minimum displacement Qmin of the HST motor 42 from Qmin1 to Qmin2 (i.e., by increasing it by Qup) (Qmin1 → Qmin2, Qmin2 > Qmin1), the vehicle speed of the wheel loader 1 is limited (decelerated) from Smax1 to Smax2 (Smax1 → Smax2, Smax2 <Smax1)。

[0084] When the state determination unit 52 determines that the vehicle body is traveling forward and the working device 2 is operating in an upward direction, the height threshold selection unit 54 selects the height threshold Hth that is closest to the loading destination height H acquired by the data acquisition unit 51 from among the multiple height thresholds stored in the memory unit 57. The multiple height thresholds are values ​​set as the loading destination heights corresponding to the multiple stopping positions of the working device 2, respectively.

[0085] The stop position determination unit 55 determines the height Hs (hereinafter referred to as the "stop position height Hs") at the stop position (i.e., the position where the bucket 23 dumps) of the lift arm 21 (work device 2) moving upward, based on the height threshold Hth selected by the height threshold selection unit 54 and the current height Ha of the lift arm 21 (work device 2).

[0086] The "current height Ha of the lift arm 21" can be obtained by calculating the height of the hinge pin of the bucket 23 (the height from the contact surface of the vehicle body to the hinge pin of the bucket 23) based on the lift arm angle acquired by the data acquisition unit 51.

[0087] Command signal output unit 56 outputs a command signal to motor regulator 420 in accordance with the minimum displacement volume Qmin of HST motor 42 calculated by restriction amount calculation unit 53.

[0088] Also, when the current height Ha of the lift arm 21 is lower than the stop position height Hs (Ha < Hs), the command signal output unit 56 outputs an upward movement command signal to each of the electromagnetic control valve 44L for the first lift arm and the electromagnetic control valve 44R for the second lift arm until the height of the lift arm 21 reaches the stop position height Hs.

[0089] On the other hand, when the current height Ha of the lift arm 21 is equal to or higher than the stop position height Hs (Ha ≥ Hs), since the height of the lift arm 21 has reached the stop position height Hs, that is, since the bucket 23 can be dumped, the command signal output unit 56 outputs a stop command signal to stop the upward movement to each of the electromagnetic control valve 44L for the first lift arm and the electromagnetic control valve 44R for the second lift arm.

[0090] (Processing executed by the controller 5) Next, the flow of the process executed by the controller 5 will be described with reference to FIG. 9.

[0091] FIG. 9 is a flowchart showing the flow of the process executed by the controller 5.

[0092] In the controller 5, first, the data acquisition unit 51 acquires the switching signal output from the forward / reverse switching switch 62, the speed step signal output from the speed step switch 63, the operation signal output from the handling operation lever 120, the depression amount of the accelerator pedal 61 detected by the depression amount sensor 610, and the discharge pressure Pa of the handling oil pressure pump 43 detected by the discharge pressure sensor 43A (step S501).

[0093] Next, the state determination unit 52 determines whether the wheel loader 1 is traveling forward based on the switching signal, the speed step signal, and the depression amount of the accelerator pedal 61 acquired in step S501, and determines whether the working device 2 is operating upward based on the operation signal and the discharge pressure Pa acquired in step S501 (step S502).

[0094] In step S502, when it is determined that the wheel loader 1 is moving forward and the working device 2 is operating upward (step S502 / YES), the data acquisition unit 51 acquires the loading destination data detected by the loading destination sensor 32 (specifically, the distance L from the vehicle body to the loading destination and the height H of the loading destination) (step S503).

[0095] Next, in the present embodiment, the limit quantity calculation unit 53 calculates the ratio Ra between the distance L from the vehicle body to the loading destination and the height H of the loading destination acquired in step S503 (step S504), and calculates a predetermined limit value Qup1 based on the calculated ratio Ra (step S505).

[0096] Next, the state determination unit 52 determines whether or not the discharge pressure Pa of the cargo handling hydraulic pump 43 acquired in step S501 is equal to or greater than the first pressure threshold value P1 and less than the second pressure threshold value P2 (step S506).

[0097] In step S506, when it is determined that the discharge pressure Pa is equal to or greater than the first pressure threshold value P1 and less than the second pressure threshold value P2 (P1≦P<P2) (step S506 / YES), the limit quantity calculation unit 53 calculates the minimum retraction volume Qmin of the HST motor 42 so that the increase amount Qup of the minimum retraction volume increases to the predetermined limit value Qup1 as the discharge pressure Pa increases (step S507).

[0098] Then, the command signal output unit 56 outputs a command signal according to the minimum retraction volume Qmin of the HST motor 42 calculated in step S507 to the motor regulator 420 (step S508), and returns to step S501.

[0099] On the other hand, if it is determined in step S506 that the discharge pressure Pa is not greater than the first pressure threshold P1 and less than the second pressure threshold P2 (Pa < P1 or Pa ≥ P2) (step S506 / NO), the state determination unit 52 determines whether the discharge pressure Pa is greater than or equal to the second pressure threshold P2 and less than the third pressure threshold P3 (step S509).

[0100] If it is determined in step S509 that the discharge pressure Pa is greater than or equal to the second pressure threshold P2 and less than the third pressure threshold P3 (P2 ≤ Pa < P3) (step S509 / YES), the limit quantity calculation unit 53 calculates the minimum retraction volume Qmin of the HST motor 42 so that the increase amount Qup of the minimum retraction volume is maintained at a predetermined limit value Qup1 regardless of the increase in the discharge pressure Pa (step S510).

[0101] Then, the command signal output unit 56 outputs a command signal corresponding to the minimum retraction volume Qmin of the HST motor 42 calculated in step S510 to the motor regulator 420 (step S508), and returns to step S501.

[0102] Also, in this embodiment, after the process of step S503, the controller 5 proceeds to step S511 in parallel with the process of step S504, and the height threshold selection unit 54 selects the height threshold Hth closest to the height H of the loading destination obtained in step S503 from among a plurality of height thresholds stored in the storage unit 57.

[0103] Next, the data acquisition unit 51 acquires the lift arm angle detected by the lift arm angle sensor 31, and the stop position determination unit 55 calculates the current height Ha of the lift arm 21 based on the lift arm angle (step S512).

[0104] Subsequently, the stop position determination unit 55 determines the stop position height Hs of the lift arm 21 that is operating upward based on the selected height threshold value Hth in step S511 and the current height Ha of the lift arm 21 calculated in step S512 (step S513).

[0105] Then, when the current height Ha of the lift arm 21 is lower than the stop position height Hs (Ha < Hs) (step S514 / YES), the command signal output unit 56 outputs an upward movement command signal to each of the electromagnetic control valve 44L for the first lift arm and the electromagnetic control valve 44R for the second lift arm (step S515), and returns to step S512.

[0106] On the other hand, when the current height Ha of the lift arm 21 is equal to or higher than the stop position height Hs (Ha ≥ Hs) (step S514 / NO), the command signal output unit 56 outputs a stop command signal to each of the electromagnetic control valve 44L for the first lift arm and the electromagnetic control valve 44R for the second lift arm (step S516), and the processing in the controller 5 ends.

[0107] Also, in step S502, when it is determined that the wheel loader 1 is moving forward and the working device 2 is not operating upward (step S502 / NO), the processing in the controller 5 ends.

[0108] In this way, when the controller 5 determines that the wheel loader 1 is moving forward and the working device 2 is operating upward, that is, during the loading operation, by limiting the vehicle speed within the speed limit based on the distance L from the vehicle body to the loading destination and the height H of the loading destination, it is possible to appropriately adjust the balance between the vehicle speed limit and the stop position of the working device 2 in operation while reducing the operator's operation burden during the loading operation.

[0109] Furthermore, in this embodiment, the controller 5 determines the stopping position of the working device 2 operating in the upward direction based on the height threshold Hth that is closest to the height H of the loading destination and the current posture of the working device 2 (height of the lift arm 21), thereby making it possible to more accurately adjust the balance between the vehicle speed limit and the stopping position of the working device 2 during operation.

[0110] The above describes an embodiment of the present invention. However, the present invention is not limited to the above embodiment and includes various other modifications. For example, the above embodiment has been described in detail to clearly explain the present invention, and is not necessarily limited to having all of the described configurations. Furthermore, it is possible to replace part of the configuration of the above embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of the above embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of the above embodiment with other configurations.

[0111] For example, in the above embodiment, a wheel loader 1 was used as an example of one type of work vehicle, but this is not limiting and other work vehicles equipped with a work implement 2 may also be used.

[0112] Furthermore, in the above embodiment, an HST type has been described as an example of one aspect of the traveling drive device 100A of the wheel loader 1, but this is not limiting and, for example, a torque converter type may also be used. [Explanation of symbols]

[0113] 1: Wheel loader (work vehicle) 1A: Front frame (body) 1B: Rear frame (body) 2: Work equipment 5: Controller 31: Lift arm angle sensor (posture detection device) 32: Loading destination sensor (loading destination detection device) 43A: Discharge pressure sensor (operating state detection device) 62: Forward / reverse switch (driving condition detection device) 63: Speed ​​switch (driving condition detection device) 100A: Travel drive unit 100B: Work drive device 120: Load handling operation lever (operation status detection device) 610: Pedal amount sensor (driving state detection device) H: Height of loading destination Hs: Stop position height Hth: Height threshold L: Distance from the vehicle to the loading point Qup1: Limit value (limit amount) Ra: ratio

Claims

1. The car body and a working device attached to the vehicle body so as to be rotatable in the vertical direction; a travel drive device that causes the vehicle body to travel; a running state detection device for detecting the running state of the vehicle body; a controller that controls the operation of the working device and the traveling drive device; In a work vehicle equipped with an operating state detection device that detects an operating state of the working device; a loading destination detection device that detects the distance to a loading destination where a load is to be loaded in the working device and the height of the loading destination; and The controller determining whether the vehicle body is traveling forward and the working device is operating upward based on the traveling state of the vehicle body detected by the traveling state detection device and the operating state of the working device detected by the operating state detection device; When it is determined that the vehicle body is traveling forward and the working device is operating in an upward direction, a vehicle speed limit amount is calculated based on the distance from the vehicle body to the loading destination and the height of the loading destination detected by the loading destination detection device, The travel drive device is controlled based on the calculated limit amount to limit the vehicle speed. A work vehicle characterized by:

2. The work vehicle according to claim 1, The controller calculating a ratio between a distance from the vehicle body detected by the loading destination detection device to a height of the loading destination; The limit amount is calculated based on the calculated ratio. A work vehicle characterized by:

3. The work vehicle according to claim 1, a working drive device that drives the working device; an attitude detection device that detects the attitude of the working device; and The controller includes: a plurality of height thresholds set as the height of the loading destination corresponding to each of a plurality of stopping positions of the work device are stored; The controller selecting a height threshold value that is closest to the height of the loading destination detected by the loading destination detection device from among the plurality of height threshold values; determining a stop position of the working device during an upward movement based on the selected height threshold and the attitude of the working device detected by the attitude detection device; An upward movement command signal is output to the working drive device until the height of the working device reaches the determined height of the stopping position of the working device. A work vehicle characterized by:

Images