Control device for a wheel loader

Abstract

The present invention aims to provide a control device of a wheel loader capable of achieving a reduction in the operation time required for a digging operation, thereby improving the productivity of the digging operation. The control device (120) is a control device of a wheel loader (1) that advances a vehicle body (2) by rotation of wheels (5f, 5r) to cause a bucket (3) to protrude to an object, thereby digging the object. The vehicle body (2) is advanced in a state in which the bucket (3) protrudes to the object, and when the rotation speed of the wheels (5f, 5r) exceeds a predetermined threshold value (BS), the control device (120) brakes the wheels (5f, 5r).

Description

Technical Field

[0001] This invention relates to a control device for wheel loaders. Background Technology

[0002] A wheel loader is a type of work machinery and its derivatives that are driven by four wheels and steered with a center-hinged mechanism. A bucket and other working devices are attached to the front of the wheel loader to scoop up objects such as sand and soil. The control system of the wheel loader controls the height and angle of the bucket, as well as the speed and direction of the vehicle, according to the operation of the operator in the cab. Thus, wheel loaders can perform digging operations using the bucket, moving objects loaded in the bucket to the bed of a dump truck, and loading operations such as transferring objects from the bucket to the bed of a dump truck.

[0003] In excavation operations, the process begins with the bucket being moved to a position approximately parallel to the ground. The vehicle accelerates forward by operating the accelerator pedal, causing the bucket to scoop up the target object. During this scooping action, after the bucket scoops up the target object, the vehicle moves forward by adjusting the wheel rotation using the accelerator pedal. Simultaneously, during the scooping action, the bucket is lifted upwards by operating the lifting lever, and rotated (tilted) in the loading direction by operating the bucket control lever. As a result, the target object is stored inside the bucket, and the bucket is in a loaded state.

[0004] To simplify the series of operations in this excavation work, Patent Document 1 discloses the following automatic excavation technology: lifting the bucket and rotating it in the loading direction while in full acceleration. Furthermore, Patent Document 2, using Patent Document 1 as prior art, discloses the following technology: when the wheel loader approaches the excavation start position, the engine speed is increased and the tilt rate of the travel hydraulic motor is reduced, thereby reducing the vehicle speed and suppressing the impact at the start of the excavation operation (when the bucket plunges towards the object). Additionally, Patent Document 3, using Patent Document 2 as prior art, discloses the following technology: without reducing the tilt rate of the travel hydraulic motor, the speed level of the transmission is shifted to the low-speed side, thereby suppressing the impact at the start of the excavation operation and expanding the types of machines that can be applied.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 62-185928

[0008] Patent Document 2: Japanese Patent Application Publication No. 2008-133657

[0009] Patent Document 3: US Patent No. 10041229 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] However, the technologies disclosed in Patent Documents 2 and 3 reduce the vehicle speed before the digging operation begins in order to suppress the impact at the start of the digging operation. Therefore, the technologies disclosed in Patent Documents 2 and 3 may increase the operation time required for digging and reduce the productivity of the digging operation. Furthermore, the technology disclosed in Patent Document 1 completely fails to consider shortening the operation time required for digging, leaving room for improvement.

[0012] In view of the above, the object of the present invention is to provide a control device for a wheel loader that can reduce the operation time required for digging operations, thereby improving the productivity of digging operations.

[0013] Methods for solving problems

[0014] To address the aforementioned issues, the present invention provides a control device for a wheel loader, wherein the wheel loader advances its vehicle body by rotating its wheels, causing the bucket to penetrate into an object, thereby excavating the object. The control device is characterized in that, while the vehicle body is advancing with the bucket penetrating the object, the control device brakes the wheels when the rotational speed of the wheels exceeds a predetermined threshold.

[0015] Invention Effects

[0016] According to the present invention, a control device for a wheel loader can be provided, which can reduce the operation time required for digging operations, thereby improving the productivity of digging operations. Attached Figure Description

[0017] Figure 1 (a) is a side view showing the appearance of the wheel loader. Figure 1 (b) is Figure 1 The three-dimensional diagram of (a).

[0018] Figure 2 yes Figure 1 The system diagram of the wheel loader shown in (a) is as follows.

[0019] Figure 3 This is a block diagram illustrating the functional structure of the control device in Implementation Method 1.

[0020] Figure 4 It means by Figure 3 The flowchart shows the processing performed by the control device.

[0021] Figure 5 This is a block diagram illustrating the functional structure of the control device in Embodiment 2.

[0022] Figure 6 This is a block diagram illustrating the functional structure of the control device in Embodiment 3.

[0023] Figure 7 This is a block diagram illustrating the functional structure of the control device in Embodiment 4. Detailed Implementation

[0024] Hereinafter, embodiments of the present invention will be described using the accompanying drawings. Structures marked with the same symbols in each embodiment have the same function in each embodiment unless specifically mentioned otherwise, and their descriptions are omitted.

[0025] [Implementation Method 1]

[0026] use Figures 1-4 The control device 120 of the wheel loader 1 in Embodiment 1 will be described.

[0027] Figure 1 (a) is a side view showing the appearance of the wheel loader 1. Figure 1 (b) is Figure 1 The three-dimensional diagram of (a).

[0028] The wheel loader 1 is a working machine and derivative machine that travels on four-wheel drive wheels 5f and 5r and is steered with a center-folding steering mechanism. A working device 4, such as a bucket 3, for scooping up objects like sand or soil, is connected to the front of the wheel loader 1's body 2. The control device 120 of the wheel loader 1 controls the height and angle of the bucket 3 (i.e., the posture of the bucket 3), as well as the speed and direction of the body 2, according to the operation of the operator in the cab 7. Thus, the wheel loader 1 can perform digging operations using the bucket 3, transport operations moving objects loaded in the bucket 3 to the dump truck's cargo box, and loading operations transferring objects from the bucket 3 to the dump truck's cargo box.

[0029] The vehicle body 2 includes: a front frame 6, which has a working device 4 and front wheels 5f; and a rear frame 8, which has rear wheels 5r, a cab 7, and an engine 100. The front frame 6 and the rear frame 8 are connected by a center pin 9, which can be bent to the left and right. The bending angle can be changed by steering cylinders 10L and 10R located on the left and right sides of the center pin 9. During driving, the steering cylinders 10L and 10R are extended or retracted to change the angle (bending angle) of the front frame 6 relative to the rear frame 8, thereby steering the vehicle body 2.

[0030] The working device 4 includes: a lifting arm 11, which is connected to the front frame 6 and is rotatable; and a bucket 3, which is connected to the lifting arm 11 and is rotatable.

[0031] The lifting boom 11 is connected to the lifting cylinder 12. The lifting cylinder 12 is connected to the front frame 6 so that the load of the bucket 3 connected to the lifting boom 11 can be supported by the front frame 6. The lifting cylinder 12 performs lifting by rotating the lifting boom 11 upward to raise the height of the bucket 3 and lowering by rotating the lifting boom 11 downward to lower the height of the bucket 3. A lifting cylinder pressure sensor 12b is installed on the lifting cylinder 12 to measure the pressure in the bottom chamber of the lifting cylinder 12. The installation position of the lifting cylinder pressure sensor 12b is not particularly limited as long as it can measure the same pressure as the pressure in the bottom chamber of the lifting cylinder 12.

[0032] The bucket 3 is connected to the boom 11 in a manner that allows rotation at a pivot point 13. The pivot point 13 is connected to the bucket cylinder 16 via a push rod 14 and a boom crank 15, allowing the angle of the bucket 3 relative to the boom 11 to be changed. The bucket cylinder 16 is connected to the front frame 6 at a pivot point 17. The height of the bucket 3 can be changed by extending or retracting the boom cylinder 12. The angle of the bucket 3 can be changed by extending or retracting the bucket cylinder 16. A boom crank angle sensor 19a and a boom angle sensor 19b are mounted on the working device 4 to calculate the height and angle of the bucket 3 (i.e., the posture of the bucket 3) based on known dimensions.

[0033] Figure 2 yes Figure 1 The system diagram of the wheel loader 1 shown in (a) is as follows.

[0034] The output shaft 100a of the engine 100, which serves as the power source for wheels 5f and 5r, is directly connected to the torque converter 101, the hydraulic pump 102, and the brake pump 103. The speed of the engine 100 is controlled by an electrical signal 105s from the engine controller 104. The engine controller 104 controls the speed of the engine 100 based on the amount of pressure applied to the accelerator pedal 106 or an electrical signal 106s from the control device 120.

[0035] The output shaft of torque converter 101 is connected to drive shaft 108 via transmission 107, driving wheels 5f and 5r. Torque converter 101 is configured such that the higher the engine speed of 100 relative to the output speed of torque converter 101, the greater the power transmitted to transmission 107. A greater depressor of accelerator pedal 106 increases the engine speed of 100, thereby increasing the power output from torque converter 101.

[0036] The transmission 107, based on the electrical signal 110s from the transmission controller 109, disconnects the connection between the output shaft of the torque converter 101 and the drive shaft 108, or reverses the rotation direction of the drive shaft 108. The transmission 107, together with the torque converter 101 and the drive shaft 108, transmits power from the engine 100 to the wheels 5f and 5r. When the connection between the output shaft of the torque converter 101 and the drive shaft 108 is disconnected, the transmission of power from the engine 100 to the wheels 5f and 5r is interrupted, and the driving force of the wheels 5f and 5r decreases. If the rotation direction of the drive shaft 108 is reversed, the direction of the driving force of the wheels 5f and 5r is reversed, and the rotation direction of the wheels 5f and 5r is reversed. The transmission controller 109 outputs an electrical signal 110s to disconnect the connection between the output shaft of the torque converter 101 and the drive shaft 108 when the brake pedal 112 is depressed to a certain degree, or based on the electrical signal 107s from the control device 120. A vehicle speed sensor 21 is installed in the transmission 107. The vehicle speed sensor 21 measures the rotational speed of the wheels 5f and 5r based on the rotational speed of the drive shaft 108. The vehicle speed sensor 21 calculates the amount of movement of the vehicle body 2 per unit time based on the rotational speed of the wheels 5f and 5r and the dimensions of the wheels 5f and 5r, thereby enabling the measurement of the vehicle speed of the vehicle body 2.

[0037] Hydraulic pump 102 sprays a certain amount of pressurized oil per revolution of the output shaft 100a of engine 100. The pressurized oil sprayed from hydraulic pump 102 is supplied to lifting cylinder 12 and bucket cylinder 16 respectively via bucket drive hydraulic circuit 113. Lifting cylinder 12 and bucket cylinder 16 extend and retract due to the pressurized oil from bucket drive hydraulic circuit 113. The more the engine speed of 100 increases, the more pressurized oil is sprayed from hydraulic pump 102. Therefore, when the accelerator pedal 106 is pressed more, increasing the engine speed of 100, the extension and retraction speed of lifting cylinder 12 and bucket cylinder 16 increases.

[0038] The bucket drive hydraulic circuit 113, based on the operator's operation of the lifting lever 114 or the electrical signal 113s from the control device 120, blocks the supply of pressurized oil from the hydraulic pump 102 to the lifting cylinder 12, or reverses the extension / retraction direction of the lifting cylinder 12. When the supply of pressurized oil from the hydraulic pump 102 to the lifting cylinder 12 is blocked, the rotation of the lifting arm 11 stops. If the extension / retraction direction of the lifting cylinder 12 is reversed, the rotation direction of the lifting arm 11 switches to upward or downward.

[0039] The bucket drive hydraulic circuit 113, based on the operator's operation of the bucket operating lever 115 or the electrical signal 113s from the control device 120, blocks the supply of pressurized oil from the hydraulic pump 102 to the bucket cylinder 16, or reverses the extension / retraction direction of the bucket cylinder 16. When the supply of pressurized oil from the hydraulic pump 102 to the bucket cylinder 16 is blocked, the rotation of the bucket 3 stops. If the extension / retraction direction of the bucket cylinder 16 is reversed, the bucket 3 switches to the dumping or crowding rotation direction.

[0040] Pressurized oil injected from hydraulic pump 102 is supplied to steering cylinders 10L and 10R via steering drive hydraulic circuit 116. Steering cylinders 10L and 10R extend and retract by the pressurized oil from steering drive hydraulic circuit 116.

[0041] The steering drive hydraulic circuit 116 extends and retracts the steering cylinders 10L and 10R according to the operator's operation of the steering wheel 117. For example, when the steering wheel 117 is turned to the right, the steering drive hydraulic circuit 116 supplies pressurized oil injected from the hydraulic pump 102, causing the right steering cylinder 10R to retract and the left steering cylinder 10L to extend. This allows steering of the vehicle body 2 in a rightward turn. Similarly, when the steering wheel 117 is turned to the left, the steering drive hydraulic circuit 116 supplies pressurized oil injected from the hydraulic pump 102, causing the right steering cylinder 10R to extend and the left steering cylinder 10L to retract. This allows steering of the vehicle body 2 in a leftward turn.

[0042] The pressurized oil ejected from the brake pump 103 is stored in the accumulator 103a. The pressurized oil stored in the accumulator 103a is supplied to the brake 118, which is a braking device for braking wheels 5f and 5r, via the brake drive hydraulic circuit 119.

[0043] The brake drive hydraulic circuit 119 controls the braking pressure applied to the wheels 5f and 5r based on the amount of pressure applied to the brake pedal 112 by the operator or the electrical signal 118s from the control device 120. If the braking pressure applied to the wheels 5f and 5r increases, the braking force on the wheels 5f and 5r increases, thus reducing the rotational speed of the wheels 5f and 5r and reducing the vehicle speed of the vehicle body 2.

[0044] Figure 3 This is a block diagram illustrating the functional structure of the control device 120 in Embodiment 1.

[0045] In excavation operations, the wheel loader 1 moves from a digging posture where the bucket 3 is roughly parallel to the ground to a position near the ground, then performs a driving action that moves the vehicle body 2 forward so that the bucket 3 can penetrate into the object, and then performs an excavation action that uses the bucket 3 to lift the object.

[0046] The control device 120 performs the following automatic digging process: controlling the movement of the vehicle body 2 and the posture of the bucket 3 to automatically perform the digging action in the digging operation. The digging action performed by the automatic digging process of this embodiment is as follows: while moving the vehicle body 2 forward, the bucket 3 is lifted; after the brakes 118 are driven in a manner that prevents the wheels 5f and 5r from spinning (i.e., after braking the wheels 5f and 5r), the bucket 3 is rotated in the loading direction to put the bucket 3 into a loaded state; when the bucket 3 reaches a predetermined height, the lifting stops.

[0047] Furthermore, the control device 120 can also perform automatic driving processing as follows: controlling the movement of the vehicle body 2 and the posture of the bucket 3 to automatically perform driving actions during excavation operations. The driving actions performed by the automatic driving processing in this embodiment are as follows: moving the bucket 3 to a digging posture approximately parallel to the ground, maintaining the vehicle body 2 at a speed above a predetermined speed to propel the vehicle body 2 forward and bring the bucket 3 into contact with the target object. The predetermined speed is, for example, 2 km / h. Therefore, the control device 120 does not decelerate the vehicle body 2 before the bucket 3 enters the target object, thus shortening the time required for driving actions during excavation operations.

[0048] For automated excavation, control unit 120 acquires the rotational speeds of wheels 5f and 5r (and the vehicle speed of body 2) measured by vehicle speed sensor 21. Control unit 120 acquires the angle of boom crank 15 measured by boom crank angle sensor 19a. Control unit 120 acquires the angle of boom 11 measured by boom angle sensor 19b. Control unit 120 acquires the pressure (bottom chamber pressure) of boom cylinder 12 measured by boom cylinder pressure sensor 12b. Furthermore, based on this acquired information, control unit 120 outputs an electrical signal 118s representing a control command for brake drive hydraulic circuit 119, and an electrical signal 113s representing a control command for bucket drive hydraulic circuit 113.

[0049] The control device 120 includes: a posture calculation unit 121, an automatic excavation processing unit 122, a braking drive command unit 125, a lifting drive command unit 126, and a bucket drive command unit 127.

[0050] The posture calculation unit 121 calculates the claw tip angle and height of the bucket 3 based on the angles of the double boom crank 15 and the lifting boom 11 measured by the double boom crank angle sensor 19a and the lifting boom angle sensor 19b, respectively. The claw tip angle of the bucket 3 is the angle between the bottom surface of the bucket 3 and the ground.

[0051] The automatic excavation processing unit 122 performs necessary processing when automatic excavation processing begins. The automatic excavation processing unit 122 has an effectiveness determination unit 123 for determining whether automatic excavation processing is effective and an start determination unit 124 for determining whether automatic excavation processing should begin.

[0052] The validity determination unit 123 determines whether the automatic digging process is valid based on the rotational speeds of the wheels 5f and 5r measured by the vehicle speed sensor 21 and the calculation results of the posture calculation unit 121. Valid automatic digging is envisioned as a state where, while the wheel loader 1 remains in its current state, the bucket 3 thrusts into the target object and automatic digging begins, and digging action is performed appropriately. The start determination unit 124 determines whether to start the automatic digging process based on the determination result of the validity determination unit 123, the calculation result of the posture calculation unit 121, and the pressure of the lifting cylinder 12 measured by the lifting cylinder pressure sensor 12b.

[0053] The automatic excavation processing unit 122 can generate an automatic excavation operation plan when the start determination unit 124 determines that automatic excavation operation has started. Alternatively, the automatic excavation processing unit 122 can also read a pre-generated and stored automatic excavation operation plan. The operation plan may be, for example, a shift of target values ​​for the rotational speeds of the wheels 5f and 5r (and the vehicle speed of the body 2), the angle (claw tip angle) of the bucket 3, and the height. The shift of the target values ​​for the angle and height of the bucket 3 is the target movement trajectory of the bucket 3. The automatic excavation processing unit 122 can output the operation plan to the brake drive command unit 125, the lifting drive command unit 126, and the bucket drive command unit 127.

[0054] The brake drive command unit 125 calculates the braking pressure to be applied to the wheels 5f and 5r based on the rotational speeds of the wheels 5f and 5r measured by the vehicle speed sensor 21 and the output from the automatic digging processing unit 122, and generates a control command for the brake pressure control solenoid valve 119a. The brake drive command unit 125 generates an electrical signal 118s representing the generated control command and outputs it to the brake pressure control solenoid valve 119a of the brake drive hydraulic circuit 119.

[0055] The lifting drive command unit 126 calculates the extension and retraction amount of the lifting cylinder 12 based on the output from the automatic digging processing unit 122, and generates a control command for the bucket drive hydraulic circuit 113. The lifting drive command unit 126 generates an electrical signal 113s representing the generated control command and outputs it to the bucket drive hydraulic circuit 113.

[0056] The bucket drive command unit 127 calculates the extension and retraction amount of the bucket cylinder 16 based on the output from the automatic digging processing unit 122, and generates a control command for the bucket drive hydraulic circuit 113. The bucket drive command unit 127 generates an electrical signal 113s representing the generated control command and outputs it to the bucket drive hydraulic circuit 113.

[0057] Figure 4 It means by Figure 3 A flowchart of the processing performed by the control device 120 shown.

[0058] In step S101, the control device 120 uses the validity determination unit 123 to determine whether the automatic digging process is valid. If the validity determination unit 123 determines that the automatic digging process is valid, the control device 120 proceeds to step S102. If the validity determination unit 123 does not determine that the automatic digging process is valid, the control device 120 repeats step S101, for example, every second, until the automatic digging process is determined to be valid.

[0059] The valid determination unit 123 determines that the automatic digging process is valid when the bucket 3 is in a digging posture converged within a specified range and the vehicle body 2 is moving forward. A digging posture where the bucket 3 is converged within a specified range means that the bucket 3 is approximately parallel to the ground (claw tip angle within 10°) and the height of the bucket 3 is near the ground. Moving forward of the vehicle body 2 can mean that the vehicle body 2's speed is above a specified speed. The specified speed is, for example, 2 km / h.

[0060] In step S102, the control device 120 uses the automatic digging processing unit 122 to perform a preparatory action for automatic digging processing on the wheel loader 1 before the start determination unit 124 determines whether to start automatic digging processing in step S103.

[0061] The preparatory action for automatic digging is, for example, supplying pressurized oil to the side of the lifting arm 11 that rotates upward in the bottom chamber or boom chamber of the lifting cylinder 12, within the range where the lifting cylinder 12 is not actually extended or retracted. As a result, the control device 120 can move the position of the electromagnetic proportional valve included in the bucket drive hydraulic circuit 113 from the neutral position towards the side that rotates the lifting arm 11 upward, before the start determination unit 124 determines whether to start automatic digging. The control device 120 can shorten the response time of the lifting cylinder 12 from when the start determination unit 124 determines that automatic digging has started until the lifting cylinder 12 actually extends or retracts. Therefore, the control device 120 can immediately begin lifting the bucket 3 during automatic digging, thus shortening the time required for digging operations.

[0062] In addition, the preparatory actions for automatic excavation can be, for example, by notifying the operator or surrounding workers in advance of the start of automatic excavation through the sound of a buzzer installed on the wheel loader 1, the illumination of lights, or the display on a monitor. Therefore, the control device 120 will not suddenly start automatic excavation for the operator or surrounding workers, thus mitigating their psychological impact.

[0063] In step S103, the control device 120 uses the start determination unit 124 to determine whether to start automatic digging. When the start determination unit 124 determines that automatic digging has started, the control device 120 starts automatic digging and proceeds to step S104. When the start determination unit 124 does not determine that automatic digging has started, the control device 120 repeats step S103, for example, every second, until it determines that automatic digging has started.

[0064] When the automatic digging process is determined to be effective by the validity determination unit 123, and the pressure of the lifting cylinder 12, which is in a digging posture and lifting the bucket 3, changes to exceed a predetermined pressure, the start determination unit 124 determines that the automatic digging process has started. The determination criterion for whether the bucket 3 is in a digging posture can also be the same as in step S101. The predetermined pressure used as the determination criterion for the pressure of the lifting cylinder 12 is a value greater than the pressure of the lifting cylinder 12 when the bucket 3 is moving forward in an unloaded state, or it can be a value less than the pressure of the lifting cylinder 12 that increases due to the impact from the object when the bucket 3 plunges into the object. The reason why the lower limit of the predetermined pressure used as the determination criterion for the pressure of the lifting cylinder 12 is set as the pressure of the lifting cylinder 12 when the bucket 3 is moving forward in an unloaded state is because it has been determined in step S101 that the bucket 3 is moving forward in a digging posture. That is, when the bucket 3 is moving forward in a digging posture, the bucket 3 moves forward in a posture that is approximately parallel to the ground, so even if the bucket 3 is loaded, a lot of object will spill out of the bucket 3. When the bucket 3 is moving forward in a digging posture, it is generally not considered that the bucket 3 is maintaining a loaded state. Therefore, it is reasonable to set the lower limit of the specified pressure, which is the criterion for determining the pressure of the lifting cylinder 12, as the pressure of the lifting cylinder 12 when the bucket 3 is moving forward in an unloaded state.

[0065] When the start determination unit 124 determines that automatic digging processing has begun, the control device 120 initiates automatic digging processing. Specifically, as part of the automatic digging process, the control device 120 begins lifting the bucket 3 as it plunges into the target object while advancing the vehicle body 2. At this time, the control device 120 rotates the wheels 5f and 5r so that even if the bucket 3 plunges into the target object and receives a reaction force, the vehicle body 2 continues to advance. The rotational speed of the wheels 5f and 5r can be maintained at or above the threshold BE (described later) by the control device 120. For detailed control related to the lifting of the bucket 3, the technology disclosed in Patent Document 1 can be applied, for example.

[0066] In addition, to prevent malfunctions in initiating automatic digging processing while the wheel loader 1 is stationary, the control device 120 may return to step S101 again if the vehicle speed 2 falls below a predetermined speed (e.g., 2 km / h) in step S103. Then, the control device 120 may repeat step S101, for example, every second, until the automatic digging processing is determined to be effective.

[0067] In step S104, the control device 120 determines whether the rotational speed of wheels 5f and 5r exceeds the threshold BS. If the rotational speed of wheels 5f and 5r exceeds the threshold BS, the control device 120 proceeds to step S105. If the rotational speed of wheels 5f and 5r is below the threshold BS, the control device 120 rotates the bucket 3 in the loading direction to put the bucket 3 into a loading state, and stops lifting when the bucket 3 reaches the specified height. After that, the control device 120 terminates. Figure 4 The processing is shown.

[0068] The threshold BS is a predetermined threshold to prevent the wheels 5f and 5r from spinning freely. The threshold BS represents the rotational speed of the wheels 5f and 5r such that even if the bucket 3 is to penetrate the object and the vehicle body 2 is to move forward, the wheels 5f and 5r will not spin freely. The threshold BS can be a criterion for determining whether to activate the brake 118 to prevent the wheels 5f and 5r from spinning freely. The threshold BS is a value larger than the threshold BE described later. When converted to the vehicle body 2's speed, the threshold BS can be, for example, 6 km / h. The threshold BS is a value set through experiments based on the shape and hardness (penetration ease) of the object being excavated, the slipperiness of the ground, etc. The threshold BS can be adjusted according to the working environment of the wheel loader 1. For example, when the ground on which the vehicle body 2 travels is a slippery snow surface, the threshold BS is adjusted to a smaller value than usual. For example, when the object is light, such as sawdust, easily penetrated, and has little impact on the bucket 3, the threshold BS is adjusted to a larger value than usual. Alternatively, the control device 120 can replace the rotational speeds of the wheels 5f and 5r, using the vehicle speed of the body 2 and a threshold BS based on that speed to determine whether to start anti-idling processing.

[0069] In step S105, the control device 120 begins to drive the brake 118 to prevent the wheels 5f and 5r from spinning freely. In this embodiment, the control device 120 outputs an electrical signal 118s to the brake pressure control solenoid valve 119a, indicating a control command to apply a predetermined braking pressure to the wheels 5f and 5r. As a result, the rotation amount of the wheels 5f and 5r decreases, and the rotation speed of the wheels 5f and 5r decelerates. That is, by performing steps S104 and S105, the control device 120 moves the vehicle body 2 forward while the bucket 3 is thrust into the object, and when the rotation speed of the wheels 5f and 5r exceeds the threshold BS, it drives the brake 118 in a manner that prevents the wheels 5f and 5r from spinning freely, thereby braking the wheels 5f and 5r.

[0070] The prescribed braking pressure applied to the wheels 5f and 5r can also be a braking pressure that suppresses the rotation of the wheels 5f and 5r within the range where the deceleration of the wheels 5f and 5r relative to the vehicle body 2 is not freewheeling due to the reaction force of the bucket 3 on the object.

[0071] The specified braking pressure can be pre-calculated based on the specifications of the wheel loader 1 or experimental calculations. For example, the deceleration A of the vehicle body 2 caused by the reaction force from the object is -4 m / s². 2 The maximum braking pressure corresponding to the maximum depressor displacement of brake pedal 112 is 5 MPa, and the deceleration B of wheels 5f and 5r when the maximum braking pressure is applied is -6 m / s². 2 When wheels 5f and 5r are spinning freely, the deceleration C of wheels 5f and 5r relative to the ground is -3 m / s². 2 In this case, to prevent wheels 5f and 5r from spinning freely relative to the deceleration A of the vehicle body 2 caused by the reaction force from the object, it is sufficient that 1 / 6 of the deceleration B of wheels 5f and 5r when the maximum braking pressure is applied is greater than the deceleration C of wheels 5f and 5r relative to the ground when spinning freely. Therefore, in this case, the specified braking pressure can be calculated as 5 / 6 MPa, which is equivalent to 1 / 6 of the maximum braking pressure of 5 MPa. Furthermore, to ensure that wheels 5f and 5r have a margin to prevent spinning freely due to errors, the specified braking pressure can be calculated as 1 MPa, which is equivalent to 1 / 5 of the maximum braking pressure of 5 MPa.

[0072] Furthermore, the deceleration A of the vehicle body 2 caused by the reaction force from the object, the deceleration B of the wheels 5f and 5r when the maximum braking pressure is applied, and the deceleration C of the wheels 5f and 5r relative to the ground when idling can be calculated in advance according to the specifications or experiments of the wheel loader 1. Alternatively, the acceleration of the wheels 5f and 5r relative to the ground when idling can be set to a negative number to calculate the deceleration C of the wheels 5f and 5r relative to the ground when idling.

[0073] When the rotation of wheels 5f and 5r significantly exceeds their movement relative to the ground, wheels 5f and 5r spin freely. Therefore, the above calculation method at the specified braking pressure aims to reduce the rotation of wheels 5f and 5r by actuating the brake 118. Simultaneously, the above calculation method at the specified braking pressure aims to prevent the rotation of wheels 5f and 5r from becoming too small due to the actuation of the brake 118, ensuring that wheels 5f and 5r receive propulsion from the ground. The propulsion received by wheels 5f and 5r from the ground increases proportionally to the difference between their rotation and their movement relative to the ground. However, when this difference is too large, wheels 5f and 5r spin freely, and the propulsion received from the ground decreases sharply.

[0074] The amount of movement of wheels 5f and 5r relative to the ground can be calculated based on the speed of the vehicle body 2 before the bucket 3 penetrates the object and the deceleration A of the vehicle body 2 caused by the reaction force from the object. The amount of rotation of wheels 5f and 5r can be calculated based on the rotational speed of wheels 5f and 5r measured by the vehicle speed sensor 21.

[0075] In the example above, the deceleration B (i.e., -6 m / s) of the wheels 5f and 5r when the maximum braking pressure is applied. 2 4 / 6 of ) (i.e. -4m / s) 2 When decelerating, the difference between the rotational amount of wheels 5f and 5r and the displacement of wheels 5f and 5r relative to the ground is zero. In this case, wheels 5f and 5r cannot obtain propulsive force from the ground, so it is unsuitable. Furthermore, when the maximum braking pressure is applied, the deceleration B of wheels 5f and 5r is 0 / 6 (i.e., 0 m / s²). 2 During deceleration, the difference between the rotation of wheels 5f and 5r and the movement of wheels 5f and 5r relative to the ground remains at -4 m / s². 2 The corresponding values ​​remain unchanged, but are less than the deceleration C of the wheel relative to the ground during idling (i.e., -3 m / s²). 2 The corresponding value. In this case, wheels 5f and 5r spin freely, so it is not suitable. The deceleration B of wheels 5f and 5r when maximum braking pressure is applied is 1 / 6 (i.e., -1 m / s²). 2During deceleration, the difference between the rotation of wheels 5f and 5r and the movement of wheels 5f and 5r relative to the ground is near the limit value within the range where wheels 5f and 5r do not idle. If the rotation of wheels 5f and 5r is suppressed near the limit value within the range where wheels 5f and 5r do not idle, the propulsive force received by wheels 5f and 5r from the ground increases. As a result, the control device 120 can make the bucket 3 penetrate to a deeper position (the inner position of the object) of the object. By extracting the bucket 3 and rotating it in the loading direction, the control device 120 can store a large amount of object inside the bucket 3, maximizing the loading capacity of the bucket 3 in a single digging operation. Therefore, the control device 120 can minimize the number of digging operations during the digging process.

[0076] In step S106, the control device 120 determines whether the rotational speed of wheels 5f and 5r is below the threshold BE. If the rotational speed of wheels 5f and 5r is below the threshold BE, the control device 120 proceeds to step S107. If the rotational speed of wheels 5f and 5r exceeds the threshold BE, step S106 can be repeated, for example, every 0.1 seconds until the rotational speed of wheels 5f and 5r is below the threshold BE. The threshold BE represents the rotational speed of wheels 5f and 5r such that even if the bucket 3 plunges into the object and receives a reaction force, the vehicle body 2 will still move forward. The threshold BE can be a criterion for determining whether to end the anti-idling process.

[0077] The threshold BE, for example, when converted to vehicle speed, can be a value 3 km / h lower than the threshold BS. Therefore, the control device 120 can apply a predetermined braking pressure to wheels 5f and 5r during the period when the vehicle speed decelerates by 3 km / h. By changing this threshold BE, the control device 120 can indirectly change the duration for which the predetermined braking pressure is applied to wheels 5f and 5r. Alternatively, the control device 120 can use the vehicle speed of the vehicle body 2 and the threshold BE based on that speed, instead of the rotational speed of wheels 5f and 5r, to determine whether to terminate the anti-spinning process.

[0078] In step S107, the control device 120 terminates the anti-slip processing initiated in step S105. When the anti-slip processing terminates, the brake 118 stops actuating. That is, by performing steps S106 and S107, the control device 120 maintains the rotational speed of wheels 5f and 5r at or above the threshold BE, so that the vehicle body 2 continues to move forward even when the bucket 3 is thrust into the object. After the anti-slip processing is completed, the control device 120 rotates the bucket 3 in the loading direction to load the bucket 3, and stops lifting when the bucket 3 reaches a predetermined height. Then, the control device 120 terminates... Figure 4 The processing is shown.

[0079] As described above, the control device 120 of Embodiment 1 is a control device for a wheel loader 1 that uses the rotation of wheels 5f and 5r to move the vehicle body 2 forward, thereby causing the bucket 3 to penetrate into the target object and excavate the target object. The control device 120 of Embodiment 1 moves the vehicle body 2 forward while the bucket 3 is in the position of penetrating the target object, and brakes the wheels 5f and 5r when their rotational speed exceeds a predetermined threshold BS.

[0080] Therefore, even when the bucket 3 thrusts into the object, the control device 120 of Embodiment 1 can provide propulsion from the ground without causing the wheels 5f and 5r to spin freely, thus propelling the vehicle body 2 forward. By lifting the bucket 3 and rotating it in the loading direction, the control device 120 of Embodiment 1 can maximize the loading capacity of the bucket 3 in a single digging operation. Therefore, the control device 120 of Embodiment 1 can minimize the number of digging operations. Thus, the control device 120 of Embodiment 1 can reduce the operation time required for digging operations and improve the productivity of digging operations.

[0081] Furthermore, the control device 120 of Embodiment 1 automatically performs the digging operation of the wheel loader 1 by controlling the movement of the vehicle body 2 and the posture of the bucket 3. The digging operation performed by the automatic digging process is as follows: while moving the vehicle body 2 forward, the bucket 3 that has entered the object is lifted; after braking the wheels 5f and 5r, the bucket 3 is rotated in the loading direction to put the bucket 3 into a loading state; and the lifting stops when the bucket 3 reaches a predetermined height.

[0082] Therefore, the control device 120 of Embodiment 1 can enable the wheel loader 1 to perform digging operations without relying on the operator's operation, thus preventing the time required for a single digging operation from becoming excessive due to the operator's skill. Furthermore, the control device 120 of Embodiment 1 can reliably ensure the loading capacity of the bucket 3 during a single digging operation. Therefore, the control device 120 of Embodiment 1 can shorten the time required for a full digging operation. Thus, the control device 120 of Embodiment 1 can further reduce the operating time required for digging operations, thereby further improving the productivity of digging operations.

[0083] Furthermore, the control device 120 of Embodiment 1 includes an effectiveness determination unit 123 for determining whether automatic digging processing is effective and a start determination unit 124 for determining whether automatic digging processing should begin. When the bucket 3 is in a digging posture converging within a predetermined range and the vehicle body 2 is moving forward, the effectiveness determination unit 123 determines that automatic digging processing is effective. When the effectiveness determination unit 123 determines that automatic digging processing is effective, the bucket 3 is in a digging posture, and the pressure of the lifting cylinder 12 that is lifting exceeds a predetermined pressure, the start determination unit 124 determines that automatic digging processing should begin.

[0084] Therefore, the control device 120 of Embodiment 1 can automatically begin digging after the bucket 3 reliably penetrates the object, thereby enabling the wheel loader 1 to perform digging operations appropriately. That is, the control device 120 of Embodiment 1 can prevent malfunctions such as the wheel loader 1 failing to perform digging operations properly because automatic digging begins before the bucket 3 penetrates the object. The control device 120 of Embodiment 1 can prevent the time required for digging operations from becoming excessive due to such malfunctions. Therefore, the control device 120 of Embodiment 1 can reliably reduce the operation time required for digging operations, thereby reliably improving the productivity of digging operations.

[0085] Furthermore, when the effective determination unit 123 determines that the automatic excavation process is effective, the control device 120 of Embodiment 1 performs a preparatory action for the automatic excavation process of the wheel loader 1 before the start determination unit 124 determines whether to start the automatic excavation process.

[0086] Therefore, the control device 120 of Embodiment 1 can shorten the response time of the lifting cylinder 12 from the time the start determination unit 124 determines that automatic digging processing has begun until the lifting cylinder 12 actually extends or retracts. Therefore, the control device 120 of Embodiment 1 can immediately begin lifting the bucket 3 during automatic digging processing, thus shortening the time required for digging actions in digging operations. Therefore, the control device 120 of Embodiment 1 can further reduce the operating time required for digging operations, thereby further improving the productivity of digging operations.

[0087] Furthermore, in Embodiment 1, the control device 120 maintains the vehicle speed of the vehicle body 2 at a predetermined speed or higher before the bucket 3 plunges into the target object, thereby propelling the vehicle body 2 forward.

[0088] Therefore, the control device 120 of Embodiment 1 does not decelerate the vehicle speed of the body 2 before the bucket 3 plunges into the object, thus shortening the time required for travel during excavation operations. Therefore, the control device 120 of Embodiment 1 can further reduce the operation time required for excavation operations, thereby further improving the productivity of excavation operations.

[0089] [Implementation Method 2]

[0090] use Figure 5 The control device 120 of the wheel loader 1 in Embodiment 2 will be described. Regarding the control device 120 in Embodiment 2, which has the same structure and operation as in Embodiment 1, the description is omitted.

[0091] Figure 5 This is a block diagram showing the functional structure of the control device 120 in Embodiment 2.

[0092] In Embodiment 1, the control device 120 uses the pressure of the lifting cylinder 12 as one of the criteria for determining whether the start determination unit 124 has started automatic digging. In Embodiment 2, the control device 120 may use the relative distance between the bucket 3 and the object as one of the criteria for determining whether the start determination unit 124 has started automatic digging.

[0093] like Figure 5 As shown, the wheel loader 1 of Embodiment 2 includes: a GNSS receiver 22 for receiving position information of the vehicle body 2, and a communication unit 23 for obtaining position information of an object through communication with an external device. The start determination unit 124 of Embodiment 2... Figure 4 In step S103, a different process is performed compared to Embodiment 1. That is, the start determination unit 124 of Embodiment 2 calculates the position information of the bucket 3 based on the position information of the vehicle body 2, and calculates the relative distance between the bucket 3 and the object based on the position information of the bucket 3 and the position information of the object. Furthermore, the start determination unit 124 of Embodiment 2 determines to start automatic digging processing when the effective determination unit 123 determines that automatic digging processing is effective, the bucket 3 is in a digging posture, and the relative distance between the bucket 3 and the object is less than a predetermined distance.

[0094] The specified distance could be, for example, 1 meter. If the specified distance is set to 1 meter, the threshold BS is converted to vehicle speed and set to 6 km / h, and the vehicle speed of the body 2 is set to 6 km / h or higher, then the bucket 3 will penetrate the target object in approximately 0.5 seconds or less, and automatic digging processing will begin while anti-idling processing will also begin. If the time from the start of anti-idling processing to the actual application of braking force to the wheels 5f and 5r is approximately 0.5 seconds, then the braking force is applied to the wheels 5f and 5r after the bucket 3 penetrates the target object. Therefore, even in such a case, the impact on the digging action performed by automatic digging processing is very small. Therefore, it is effective for the start determination unit 124 of Embodiment 2 to use the relative distance between the bucket 3 and the target object being less than the specified distance as one of the criteria for starting automatic digging processing.

[0095] The control device 120 of Embodiment 2, like that of Embodiment 1, is capable of providing propulsion from the ground to the vehicle body 2 without causing the wheels 5f and 5r to spin freely. Therefore, the control device 120 of Embodiment 2 can reduce the operation time required for excavation operations, thereby improving the productivity of excavation operations.

[0096] Furthermore, in Embodiment 2, the wheel loader 1 can replace the communication unit 23, which obtains the location information of the object through communication with an external device, and instead has a terminal device capable of inputting the location information of the object. The start determination unit 124 in Embodiment 2 can also obtain the location information of the object from the terminal device.

[0097] [Implementation Method 3]

[0098] use Figure 6 The control device 120 of the wheel loader 1 in Embodiment 3 will be described. In the control device 120 of Embodiment 3, the structure and operation are the same as those in Embodiment 1, and therefore the description is omitted.

[0099] Figure 6 This is a block diagram illustrating the functional structure of the control device 120 in Embodiment 3.

[0100] In Embodiment 1, the control device 120 uses a drive brake 118 to brake wheels 5f and 5r, serving as a deceleration unit to prevent the rotational speed of wheels 5f and 5r during idling. In Embodiment 3, the control device 120, in addition to braking wheels 5f and 5r, also uses a method to reduce the output of the power source of wheels 5f and 5r, serving as a deceleration unit to prevent the rotational speed of wheels 5f and 5r during idling. Reducing the output of the power source of wheels 5f and 5r can, for example, be achieved by reducing the rotational speed of engine 100.

[0101] like Figure 6 As shown, the control device 120 in Embodiment 3 further includes an engine command unit 128. Based on the output from the automatic digging processing unit 122, the engine command unit 128 calculates the reduction amount (correction amount) of the engine speed 100 and generates a control command for the engine controller 104. The engine command unit 128 generates an electrical signal 106s representing the generated control command and outputs it to the engine controller 104.

[0102] The control device 120 in embodiment 3 Figure 4 In step S105, a different process is performed compared to Embodiment 1. That is, in addition to outputting an electrical signal 118s indicating a control command related to the aforementioned brake pressure to the brake pressure control solenoid valve 119a, the control device 120 in Embodiment 3 also outputs an electrical signal 106s indicating a control command to reduce the speed of the engine 100 to the engine controller 104. This control command to reduce the speed of the engine 100 may, for example, be a corrective control command that reduces the speed of the engine 100 by 300 revolutions per minute compared to normal.

[0103] Thus, when the rotational speed of wheels 5f and 5r exceeds the threshold BS, the control device 120 of embodiment 3 brakes wheels 5f and 5r and reduces the output of the power source of wheels 5f and 5r.

[0104] Therefore, compared with Embodiment 1, the control device 120 of Embodiment 3 can efficiently suppress the rotational speed of wheels 5f and 5r during the anti-idling process, thus further preventing the wheels 5f and 5r from spinning. Therefore, compared with Embodiment 1, the control device 120 of Embodiment 3 can further reduce the operation time required for excavation operations, thereby further improving the productivity of excavation operations.

[0105] [Implementation Method 4]

[0106] use Figure 7 The control device 120 of the wheel loader 1 in Embodiment 4 will be described. In the control device 120 of Embodiment 4, the structure and operation are the same as in Embodiment 1, so the description is omitted.

[0107] Figure 7 This is a block diagram illustrating the functional structure of the control device 120 in Embodiment 4.

[0108] In addition to braking wheels 5f and 5r, the control device 120 of embodiment 4 can also block the transmission of power from the power source of wheels 5f and 5r to wheels 5f and 5r, serving as a deceleration unit to prevent the rotational speed of wheels 5f and 5r during idling. Blocking the transmission of power from the power source of wheels 5f and 5r to wheels 5f and 5r can, for example, block the transmission of power from the power source of wheels 5f and 5r, i.e., the engine 100, to wheels 5f and 5r. Specifically, blocking the transmission of power from the power source of wheels 5f and 5r to wheels 5f and 5r can be achieved by blocking the connection between the output shaft of the torque converter 101 and the drive shaft 108 in the transmission 107.

[0109] like Figure 7 As shown, the control device 120 in Embodiment 4 further includes a transmission command unit 129. The transmission command unit 129 generates a control command to disconnect the output shaft of the torque converter 101 from the drive shaft 108 based on the output from the automatic excavation processing unit 122. The transmission command unit 129 generates an electrical signal 107s representing the generated control command and outputs it to the transmission controller 109.

[0110] The control device 120 in embodiment 4 Figure 4 In step S105, a different process is performed compared to Embodiment 1. That is, the control device 120 in Embodiment 4 not only outputs an electrical signal 118s to the brake pressure control solenoid valve 119a, indicating a control command related to the aforementioned brake pressure, but also outputs an electrical signal 107s to the transmission controller 109, indicating a control command to block the connection between the output shaft of the torque converter 101 and the drive shaft 108. This is equivalent to the transmission 107 shifting into neutral, blocking the transmission of power from the engine 100 to the wheels 5f and 5r.

[0111] Thus, when the rotational speed of wheels 5f and 5r exceeds the threshold BS, the control device 120 of embodiment 4 brakes wheels 5f and 5r and blocks the transmission of power from the power source of wheels 5f and 5r to wheels 5f and 5r.

[0112] Therefore, compared with Embodiment 1, the control device 120 of Embodiment 4 can efficiently suppress the rotational speed of wheels 5f and 5r during the anti-idling process, thus further preventing the wheels 5f and 5r from spinning. Therefore, compared with Embodiment 1, the control device 120 of Embodiment 4 can further reduce the operation time required for excavation operations, thereby further improving the productivity of excavation operations.

[0113] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the above-described embodiments. Various modifications can be made without departing from the spirit of the present invention as set forth in the claims. The present invention can add the structure of one embodiment to the structure of another embodiment, replace the structure of one embodiment with another embodiment, or delete a part of the structure of one embodiment.

[0114] Symbol Explanation

[0115] 1…Wheel loader, 2…Body, 3…Bucket, 5f…Front wheel, 5r…Rear wheel, 12…Lifting cylinder, 100…Engine, 107…Transmission, 118…Brake (braking device), 120…Control device, 123…Valid determination unit, 124…Start determination unit, BS…Threshold.

Claims

1. A control device for a wheel loader, wherein, The wheel loader advances its body by rotating its wheels, causing the bucket to thrust into the object, thereby excavating the object. Its characteristic is that... While the vehicle body is advancing with the bucket thrust into the object, when the rotational speed of the wheels exceeds a predetermined threshold, the control device brakes the wheels in such a way that the difference between the amount of wheel rotation calculated based on the wheel rotational speed and the amount of wheel movement relative to the ground is near a limit value within the range where the wheels do not spin freely. The amount of wheel movement relative to the ground is calculated based on the vehicle body's speed before the bucket thrusts into the object and the vehicle body's deceleration caused by the reaction force from the object.

2. The control device for a wheel loader according to claim 1, characterized in that, The control device performs the following automatic digging process: controlling the movement of the vehicle body and the posture of the bucket to automatically perform the digging action of the wheel loader. The digging action performed by the automatic digging process is as follows: while moving the vehicle forward, the bucket that has entered the object is lifted; after braking the wheels, the bucket is rotated in the loading direction to put the bucket into a loading state; and the lifting is stopped when the bucket reaches a predetermined height.

3. The control device for a wheel loader according to claim 2, characterized in that, The control device includes: a validity determination unit that determines whether the automatic digging process is valid; and a start determination unit that determines whether to start the automatic digging process. When the bucket is in a digging posture that converges within a specified range and the vehicle body is moving forward, the validity determination unit determines that the automatic digging process is valid. When the effective determination unit determines that the automatic digging process is effective, the bucket is in the digging posture, and the pressure of the lifting cylinder that performs the lifting changes to exceed the specified pressure, the start determination unit determines that the automatic digging process is started.

4. The control device for a wheel loader according to claim 2, characterized in that, The control device includes: a validity determination unit that determines whether the automatic digging process is valid; and a start determination unit that determines whether to start the automatic digging process. When the bucket is in a digging posture that converges within a specified range and the vehicle body is moving forward, the validity determination unit determines that the automatic digging process is valid. When the effective determination unit determines that the automatic excavation process is effective, the bucket is in the excavation posture, and the relative distance between the bucket and the object is less than a predetermined distance, the start determination unit determines that the automatic excavation process is to begin.

5. The control device for a wheel loader according to claim 3 or 4, characterized in that, When the effective determination unit determines that the automatic excavation process is effective, before the start determination unit determines whether to start the automatic excavation process, the control device causes the wheel loader to perform the preparation action for the automatic excavation process.

6. The control device for a wheel loader according to claim 1, characterized in that, Before the bucket penetrates the object, the control device maintains the vehicle speed at or above a predetermined speed to propel the vehicle forward.

7. The control device for a wheel loader according to claim 1, characterized in that, When the rotational speed of the wheel exceeds the threshold, the control device brakes the wheel and reduces the output of the wheel's power source.

8. The control device for a wheel loader according to claim 1, characterized in that, When the rotational speed of the wheel exceeds the threshold, the control device brakes the wheel and blocks the power transmission from the power source of the wheel to the wheel.

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