JP2019173916A - Work vehicle - Google Patents

Abstract

To suppress deterioration in workability by determining a working scene on the basis of an operation amount of an accelerator pedal and a brake operation amount in a work vehicle such as a wheel loader, protect a drive force transmission device, and improve fuel economy.SOLUTION: A vehicle body controller (61) determines a working scene that a travel device (49) and a work machine (8) perform on the basis of an operation amount of an accelerator pedal (31) and an operation amount of a brake pedal (32). When the working scene is determined to be a working scene in which an increase in the number of rotations of an engine is desired, a lock-up clutch (46) is switched to a disconnection state even when a hydraulic actuator provided to the work machine (8) is not operated, and the number of rotations of the engine is increased. When the working scene is determined to be a working scene in which a large load is applied to a travel driving system from the engine (41) to the travel device (49), the lock-up clutch (46) is also switched to the disconnection state.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a work vehicle such as a wheel loader.

  In a work vehicle such as a wheel loader, a traveling device and a hydraulic pump are driven by a driving force from an engine. The driving force from the engine is transmitted to the traveling device via the torque converter device, so that the vehicle travels. Further, when the hydraulic pump is driven, hydraulic oil is supplied from the hydraulic pump to the work machine. Thereby, the work machine is driven.

  A torque converter device having a torque converter and a lock-up clutch is known. By connecting the lockup clutch, the input shaft and the output shaft of the torque converter are directly connected, and the driving force is transmitted without loss. Switching between the locked state and the disconnected state of the lockup clutch is automatically performed by the control unit. The control unit switches the lockup clutch between the non-connected state and the connected state according to the traveling state of the vehicle. Patent Document 1 discloses a configuration in which when a vehicle speed reaches a predetermined switching speed, the lockup clutch is switched from a non-connected state to a connected state. In Patent Document 2, in a work vehicle such as a wheel loader, a state in which the load on the work implement increases by detecting the operation amount of the operation lever that operates the work implement is determined. A configuration is disclosed in which the lock-up is released when operated as described above.

JP 2011-103258 A JP 2011-169347 A

  In the configuration disclosed in Patent Document 2, the timing at which the lockup is released may not be suitable depending on the way the operator operates. For example, during work such as raising the work implement while approaching the dump truck, adjusting the vehicle speed with the brake pedal, operating the accelerator pedal to increase the engine speed, and increasing the work implement raise speed However, the lockup is not released until the operating lever is operated to the threshold operating amount, so if the operating lever is operated after the accelerator pedal operation, the work implement is raised. The engine rotation speed that is appropriate for the operation (loading operation) cannot be obtained and the workability is lowered.

  Also, during excavation, when the lockup is connected and the work implement rushes into the earth and sand, an excessive load is applied to the driving force transmission device from the engine to the traveling device due to the driving force of the engine and the reaction force from the earth and sand. However, if the lockup is connected to a low speed to improve fuel efficiency, it cannot be avoided under vehicle speed conditions. In addition, when the increase in the load on the work implement is detected and the lockup is released, the load on the driving force transmission device is not detected, so that it is possible to avoid an engine stall or a failure of the traveling device. Can not.

  An object of the present invention is to determine a work scene based on an accelerator pedal operation amount and a brake operation amount in a work vehicle such as a wheel loader to suppress deterioration of workability, protect a driving force transmission device, and improve fuel efficiency. There is to make it.

  In order to achieve the above object, a typical working vehicle according to the present invention is supplied with an engine whose number of rotations is increased or decreased by depression of an accelerator pedal, a hydraulic pump driven by the engine, and hydraulic oil from the hydraulic pump. A hydraulic actuator that operates, a traveling device that transmits power output from the engine via a torque converter, a braking device that applies a braking force to the traveling device by depressing a brake pedal, and an output shaft of the torque converter; In a work vehicle comprising: a lockup device that switches between connecting and disconnecting an input shaft; and a control device that controls connection and disconnection of the output shaft of the lockup device and the input shaft. The accelerator pedal and the brake are connected with the output shaft and the input shaft of the torque converter being connected. Determining the release conditions on the basis of the state of depression of Kipedaru, and controls the lockup device to release the connection between the output shaft and the input shaft of the torque converter based on said release condition.

  According to the present invention, the release condition for releasing the connection state (lock-up) between the input shaft and the output shaft of the torque converter is determined based on the depression operation state of the accelerator pedal and the depression operation state of the brake pedal. When loading into a dump truck where the accelerator pedal and brake pedal are operated at the same time, regardless of the operation of the control lever, the lockup is released to improve the engine speed and reduce workability. Can be suppressed. In addition, when excavation work is performed by depressing only the accelerator pedal without depressing the brake pedal, an excessive load is applied to the driving force transmission device device by releasing the lockup by detecting an increase in the load on the driving force transmission device. The device can be protected. Other problems, configurations, and effects will become apparent from the description of the embodiments described below.

1 is an external view of a wheel loader as a work vehicle according to a first embodiment. 1 is a system configuration diagram of a wheel loader as a work vehicle according to a first embodiment. It is a typical lineblock diagram of the torque converter device concerning a 1st embodiment. It is a functional block diagram of the vehicle body controller which concerns on 1st Embodiment. It is a format block diagram of ROM which concerns on 1st Embodiment. It is a table | surface figure which shows the list of the work scenes which can be recognized from the accelerator operation state of the wheel loader which concerns on 1st Embodiment, and a brake operation state. It is a table | surface figure which shows the list of the releasing conditions of the lockup clutch suitable for the work scene of the wheel loader which concerns on 1st Embodiment. It is a flowchart which shows the lockup clutch cancellation | release determination processing procedure of the wheel loader which concerns on 1st Embodiment. It is a figure which shows the connection state of the various signals with respect to the vehicle body controller and transmission controller of the wheel loader which concern on 2nd Embodiment. It is a table | surface figure which shows the list of the work scenes which can be recognized from the inclination state of the wheel loader which concerns on 2nd Embodiment, an accelerator operation state, and a brake operation state. It is a table | surface figure which shows the list | wrist of the release conditions of the lockup clutch suitable for the work scene of the wheel loader which concerns on 2nd Embodiment. It is a flowchart which shows the lockup clutch cancellation | release determination processing procedure of the wheel loader which concerns on 1st Embodiment.

  Hereinafter, the wheel loader of the present invention will be described for each embodiment.

[First Embodiment]
FIG. 1 is an external view of a wheel loader as a work vehicle according to the first embodiment, and FIG. 2 is a system configuration diagram of the wheel loader according to the first embodiment. In the wheel loader 1 according to the first embodiment, the control device performs switching control of the lockup clutch based on the detection signal of the accelerator operation amount detection device, the detection signal of the brake operation amount detection device, and the traveling state of the vehicle. It is characterized by.

  As shown in FIG. 1, the wheel loader 1 according to the first embodiment is connected to a rear frame 3 having a cab 2 and a front side of the rear frame 3 (advancing side of the wheel loader 1) via a connection pin 4. The front frame 5, the rear frame 3 and the rear wheels 6 and 7 provided on the front frame 5, and the work machine 8 attached to the front portion of the front frame 5 are mainly configured. A braking device 9 such as a brake disk is incorporated in the rear wheel 6 and the front wheel 7. In the present specification, the rear frame 3 and the front frame 5 may be collectively referred to as “vehicle body”.

  The work machine 8 includes a lift arm 11 having one end connected to the front frame 5 via a connection pin 10, a bucket 13 connected to the tip of the lift arm 11 via a connection pin 12, and connection pins 14, 15. Both ends of the lift arm cylinder 16 are connected to the front frame 5 and the lift arm 11, a bell crank 18 is swingably connected to the lift arm 11 via a connecting pin 17, and one end is a bell crank. 18, a link member 19 having the other end connected to the bucket 13, and a bucket cylinder 22 having both ends connected to the front frame 5 and the bell crank 18 via connection pins 20 and 21. In the present specification, the lift arm cylinder 16 and the bucket cylinder 22 may be collectively referred to as “hydraulic actuator”. In this example, only one lift arm 11, connecting pins 12, 14, 15, and lift arm cylinder 16 are provided, but in an actual machine, these members are arranged on the left and right sides of the bucket 13. Provided in pairs.

  The cab 2 is provided with an accelerator pedal 31 that increases and decreases the engine speed and a brake pedal 32 that brakes the wheel loader 1, and an operator who enters the cab 2 controls each of the pedals 31 and 32. By operating, the wheel loader 1 can be accelerated, decelerated and stopped.

  Further, in the cab 2, a forward / reverse switching operation member 33 such as a forward / reverse switching switch for switching the traveling direction of the wheel loader 1 to forward or reverse, and the speed stage during forward or reverse travel are set to a first speed, a second speed, A shift switching operation member 34 such as a shift switch for switching to the third speed or the fourth speed is provided, and an operator who gets into the cab 2 operates the switching operation members 33 and 34 to thereby change the wheel loader. 1 forward / reverse switching and speed stage selection can be performed.

  Furthermore, a steering device (not shown) is provided in the cab 2, and the operator who has entered the cab 2 operates the steering device while moving the wheel loader 1 forward or backward, thereby steering the wheel loader 1. The vehicle can be steered in a direction corresponding to the operation direction of the apparatus. When the steering device is operated, the front frame 5 is bent with respect to the rear frame 3 around the connecting pin 4, and the wheel loader 1 can be steered.

  Further, in the cab 2, a lift arm operation member 35 such as a lift arm operation lever that extends and contracts the lift arm cylinder 16, and a bucket operation member 36 such as a bucket operation lever that extends and contracts the bucket cylinder 22, , And an operator who has entered the cab 2 operates the operation members 35 and 36 so that the lift arm 11 can be raised or lowered and the bucket 13 can be tilted upward or downward. It has become. That is, when the lift arm cylinder 16 is extended, the lift arm 11 and the bucket 13 are raised, and when the lift arm cylinder 16 is contracted, the lift arm 11 and the bucket 13 are lowered. Further, when the bucket cylinder 22 is extended, the bucket 13 tilts upward, and when the bucket cylinder 22 contracts, the bucket 13 tilts downward.

  The operator performs excavation, traveling, running on the wheel loader 1 by performing a forward / backward operation or braking operation of the wheel loader 1, an upward operation or downward operation of the lift arm 11, and an upward tilt operation or downward tilt operation of the bucket 13. Various operations such as loading can be performed.

  As shown in FIG. 2, the wheel loader 1 according to the first embodiment includes an engine 41 that is a power source, a torque converter device 43 and a transmission 44 that transmit the driving force of the engine 41 to the propeller shaft 42, and the propeller shaft. And an accelerator shaft 45 that transmits the rotation of 42 to the rear wheel 6 and the front wheel 7. In the engine 41, the vehicle body controller 61 calculates a target engine speed corresponding to the amount of operation of the accelerator pedal 31 and transmits it to the engine controller 62, and the engine speed is controlled based on the target speed signal from the engine controller 62. The The transmission 44 and the lockup clutch 46 are switched by a switching signal from the transmission controller 63. In the present specification, the transmission 44, the propeller shaft 42, the accelerator shaft 45, the rear wheel 6 and the front wheel 7 are collectively referred to as a “traveling device 49”.

  FIG. 3 is a schematic configuration diagram of the torque converter device according to the first embodiment. As shown in FIG. 3, the torque converter device 43 of this example includes a lockup clutch 46 and a torque converter 47. In the figure, reference numeral 43 a denotes an input shaft of the torque converter 47, 43 b denotes an output shaft, the input shaft 43 a is connected to the output shaft of the engine 41, and the output shaft 43 b is connected to the transmission 44. The lock-up clutch 46 of this example is a hydraulically operated clutch, and the output shaft 43b and the input shaft 43a of the torque converter 47 are switched by a switching signal from the transmission controller 63 via the lock-up clutch proportional valve 48. It is configured to be able to switch to a connected state to be connected or a released state to release the connection between the output shaft 43b of the torque converter 47 and the input shaft 43a.

  When the lockup clutch 46 is in the disengaged state, the driving force of the engine 41 is transmitted to the traveling device 49 via the torque converter 47. On the other hand, when the lockup clutch 46 is in the connected state, the input shaft 43 a and the output shaft 43 b of the torque converter 47 are directly connected, and the driving force of the engine 41 is transmitted to the traveling device 49 via the lockup clutch 46. The

  Further, the wheel loader 1 according to the embodiment includes a hydraulic pump 51 that is driven by the driving force of the engine 41 and discharges hydraulic oil, as shown in FIG. The lift arm cylinder 16 and the bucket cylinder 22 expand or contract in response to the supply of hydraulic oil from the hydraulic pump 51. That is, a work machine control valve 52 is provided between the discharge port of the hydraulic pump 51 and the lift arm cylinder 16 and between the discharge port of the hydraulic pump 51 and the bucket cylinder 22. An operation signal corresponding to the operation amount and the operation direction of the lift arm operation member 35 and an operation signal corresponding to the operation amount and the operation direction of the bucket operation member 36 are input to the signal input unit 52. Accordingly, the lift arm cylinder 16 extends or contracts by a stroke corresponding to the operation direction and the operation amount of the lift arm operation member 35. Similarly, the bucket cylinder 22 extends or contracts by a stroke corresponding to the operation direction and the operation amount of the bucket operation member 36.

  The hydraulic pump 51 of this example is a variable displacement hydraulic pump and includes a pump regulator 53. The pump regulator 53 controls the displacement of the hydraulic pump 51 in accordance with a command signal output from the vehicle body controller 61.

  The vehicle body controller 61 is a control device that controls the entire driving of the wheel loader 1. As shown in FIG. 2, the detection signal a of the accelerator operation amount detection device 64 that detects the operation amount of the accelerator pedal 31, and the operation of the brake pedal 32. The detection signal b of the brake operation amount detection device 65 for detecting the amount, the operation signal c of the forward / reverse switching operation member 33, the operation signal d of the shift switching operation member 34, the torque converter output rotation sensor 67 provided in the torque converter device 43. Detection signal f, a detection signal g from a vehicle speed sensor 68 provided in the transmission 44, and lockup operation information k. The vehicle body controller 61 receives an engine output torque signal h and an engine speed signal i output from the engine controller 62.

  On the other hand, the transmission controller 63 outputs a lockup clutch switching signal j for the proportional valve 48 for the lockup clutch, and the vehicle body controller 61 outputs a tilt angle control signal for the pump regulator 53 and a target engine speed for the engine controller 62. A signal m, a transmission switching signal n for the transmission controller 63, and a switching signal l for the lockup clutch proportional valve 48 are output.

  In FIG. 2, the vehicle body controller 61 and the transmission controller 63 are described separately, but the vehicle body controller 61 and the transmission controller 63 may be configured integrally.

  FIG. 4 is a functional block diagram of the vehicle body controller according to the first embodiment. As shown in FIG. 4, the vehicle body controller 61 of this example includes a ROM (Read Only Memory) 72, a RAM (Random Access Memory) 73, a CPU (Central Processing Unit) 74, and a signal connected to each other via a bus 71. The computer includes a hardware resource such as an input unit 75 and a signal output unit 76. The engine controller 62 and the transmission controller 63 are also computers having the same hardware configuration.

  The ROM 72 is a non-volatile semiconductor memory that can retain programs and data even when the power is turned off. The ROM 72 includes an SD memory card, a micro SD memory card, a USB (Universal Serial Bus) memory, and the like.

  FIG. 5 is a format block diagram of the ROM according to the first embodiment. As shown in FIG. 5, the ROM 72 includes an OS (Operating System) storage unit 81 that is basic software, a drive control program storage unit 82 that operates on the OS and controls the wheel loader 1, and an accelerator. A storage unit 83 for an accelerator threshold Acc_th serving as a reference for determining whether the pedal 31 has been operated, and a storage unit 84 for a brake threshold Brk_th serving as a reference for determining whether the brake pedal 32 has been operated. And a storage unit 85 for a torque threshold value Trq_th, which serves as a reference for controlling the release of the lock-up clutch 46. The drive control program storage unit 82 is also provided with a switching control program storage unit 86 that performs switching control of the lockup clutch 46. A method for setting the accelerator threshold Acc_th, the brake threshold Brk_th, and the torque threshold Trq_th will be described later.

  The RAM 73 is a volatile semiconductor memory that temporarily stores programs and data.

  The CPU 74 reads out the program, the threshold value, and other data from the ROM 72, develops it on the RAM 73, and executes the drive control program for the wheel loader 1 including the switching control program for the lockup clutch 46. Thereby, the CPU 74 functions as a control device that realizes appropriate switching control of the lockup clutch 46 in accordance with the operating state (working scene) of the wheel loader 1.

  Hereinafter, a method for setting the accelerator threshold Acc_th, the brake threshold Brk_th, and the torque threshold Trq_th will be described.

  The accelerator threshold Acc_th serves as a criterion for determining whether or not the accelerator pedal 31 has been operated, and is set to an amount of depression of the accelerator pedal 31 that is accelerated when the wheel loader 1 starts running from a stopped state. The brake threshold value Brk_th is a criterion for determining whether or not the brake pedal 32 has been operated. The brake threshold value Brk_th is set to a depression amount of the brake pedal 32 such that the wheel loader 1 can be decelerated by the braking force generated by the braking device 9. Is done.

  On the other hand, the torque threshold value Trq_th is a reference when the lock-up clutch 46 is instructed to be released, and the torque threshold value Trq_th depends on the engine stall caused by the load acting on the engine and the load acting on the torque converter device 43 and the traveling device 49 The generated torque value is set so that no failure occurs. The torque threshold value Trq_th is set to an appropriate value for each work scene such as loading and excavation according to the operation of the accelerator pedal 31 and the brake pedal 32 of the wheel loader 1, but is expressed as Trq_th in the description of this embodiment. . The generated torque is an added value of the output torque of the engine 41 and the inertia torque accompanying the rotation generated in the input shaft 43a of the torque converter 47. The output torque of the engine 41 can be obtained from the engine controller 62. The inertia torque is calculated from the inertia of the input shaft 43a of the torque converter 47 and the deceleration of the input shaft 43a or the output shaft 43b of the torque converter 47, and is a specification value of the wheel loader 1. The deceleration of the input shaft 43a or the output shaft 43b of the torque converter 47 can also be calculated from the deceleration of the output shaft of the transmission 44 and the gear ratio of the selected speed stage.

  The vehicle body controller 61 recognizes the work scene of the wheel loader 1 from the operation state of the accelerator pedal 31 and the operation state of the brake pedal 32, and instructs to release the lockup clutch 46 based on the torque threshold value Trq_th corresponding to the recognized work scene. Execute.

  FIG. 6 is a table showing a list of work scenes that can be recognized from the accelerator operation state and the brake operation state of the wheel loader according to the first embodiment, and FIG. 7 is a lock-up according to the work scene of the wheel loader according to the first embodiment. FIG. 6 is a table showing a list of clutch release conditions.

  As shown in FIG. 6, when both the accelerator pedal 31 and the brake pedal 32 are stepped on, the vehicle body controller 61 determines that it is a loading work scene and connects the lockup clutch 46 as shown in FIG. A signal for switching from the state to the disconnected state is output to the transmission controller 63. As a result, the lock-up clutch 46 is in a disengaged state, and the hydraulic actuator provided in the work implement 8 is not operated in a loading work scene where the engine speed is to be increased while adjusting the vehicle speed with the brake pedal 32. Even in this case, since the rotational speed of the engine 41 can be quickly increased to the required engine rotational speed, the loading operation can be performed smoothly.

  Further, as shown in FIG. 6, when the accelerator pedal 31 is depressed and the brake pedal 32 is not depressed, the vehicle body controller 61 determines that it is an excavation work scene or an uphill traveling scene, and as shown in FIG. When it is determined that the generated torque calculated based on the output torque of the engine 41 and the inertia torque generated on the input shaft 43a of the torque converter 47 exceeds the torque threshold value Trq_th, the lockup clutch 46 is released from the connected state. A signal for switching to the state is output to the transmission controller 63. As a result, the lock-up clutch 46 is in a disconnected state, and the lock-up can be released before the load on the driving force transmission device that occurs during the excavation work scene increases, thus avoiding engine stall or failure of the traveling device. be able to.

  Further, as shown in FIG. 6, when the accelerator pedal 31 is not depressed and the brake pedal 32 is depressed, the vehicle body controller 61 determines that it is a brake operation scene for deceleration, as shown in FIG. When it is determined that the inertia torque calculated based on the deceleration of the input shaft 43a or the output shaft 43b of the torque converter 47 exceeds the torque threshold value Trq_th, the lockup clutch 46 is switched from the connected state to the disconnected state. A signal for switching is output to the transmission controller 63. As a result, the lock-up clutch 46 is in a disengaged state, and it is possible to prevent an excessive load from acting on the traveling drive system from the engine 41 to the traveling device 49 when the brake is suddenly applied, and the wheel loader 1 is damaged. Can be prevented.

  On the other hand, as shown in FIG. 6, when both the accelerator pedal 31 and the brake pedal 32 are not depressed, the vehicle body controller 61 determines that it is a flat ground deceleration scene, and as shown in FIG. As a release condition, the lock-up clutch 46 is maintained in the connected state without giving an instruction to release the lock-up clutch 46, and the wheel loader 1 is driven at the vehicle speed at that time. Thereby, the fuel consumption of the wheel loader 1 can be improved.

  Hereinafter, the lock-up clutch release determination processing procedure of the wheel loader according to the first embodiment will be described with reference to FIG. FIG. 8 is a flowchart illustrating a lockup clutch release determination processing procedure of the wheel loader according to the first embodiment. The lockup clutch release determination process shown in FIG. 8 is executed in accordance with a lockup clutch 46 switching control program stored in the ROM 72 of the vehicle body controller 61.

  When the release determination process of the lockup clutch 46 is started, the vehicle body controller 61 determines whether or not the lockup clutch 46 is in a connected state (step S1), and the depression amount of the accelerator pedal 31 sets the accelerator threshold Acc_th. It is determined in this order (step S2) whether the brake pedal 32 has been exceeded (step S2) and whether the amount of depression of the brake pedal 32 exceeds the brake threshold value Brk_th (step S3). Whether or not the lock-up clutch 46 is in a connected state is determined based on a signal from the transmission controller 63.

  In step S1, it is determined that the lock-up clutch 46 is in a connected state (Yes). In step S2, it is determined that the amount of depression of the accelerator pedal 31 exceeds the accelerator threshold Acc_th (Yes). In step S3, the brake pedal 32 is If it is determined that the amount of depression exceeds the brake threshold value Brk_th (Yes), the procedure proceeds to step S4 to determine that the lockup release operation is a loading operation, and the lockup clutch 46 is switched to the disengaged state in step S5. (Lock-up release).

  In step S3, when it is determined that the amount of depression of the brake pedal 32 does not exceed the brake threshold value Brk_th (No), the process proceeds to step S6, and the lockup release operation is determined to be excavation work or uphill travel. Next, the process proceeds to step S7, where the generated torque is calculated, and it is determined whether the generated torque exceeds the torque threshold value Trq_th (step S8). If it is determined in step S8 that the generated torque exceeds the torque threshold value Trq_th (Yes), the process proceeds to step S9, the lockup clutch 46 is switched to the disengaged state, and the process ends. If it is determined in step S8 that the generated torque does not exceed the torque threshold value Trq_th (No), the processing is terminated as it is.

  If it is determined in step S2 that the amount of depression of the accelerator pedal 31 does not exceed the accelerator threshold Acc_th (No), the process proceeds to step S10 and whether or not the amount of depression of the brake pedal 32 exceeds the brake threshold Brk_th. Make a decision. If it is determined in step S10 that the amount of depression of the brake pedal 32 exceeds the brake threshold value Brk_th (Yes), the process proceeds to step S11 and the lockup release operation is determined to be a brake operation. Next, the process proceeds to step S12, where inertia torque is calculated, and it is determined whether or not the inertia torque exceeds the torque threshold value Trq_th (step S13). If it is determined in step S13 that the inertia torque exceeds the torque threshold value Trq_th (Yes), the process proceeds to step S14, the lockup clutch 46 is switched to the disengaged state, and the process ends. If it is determined in step S10 that the amount of depression of the brake pedal 32 does not exceed the brake threshold value Brk_th (No), and if it is determined in step S13 that the inertia torque does not exceed the torque threshold value Trq_th (No), the processing is performed as it is. Exit.

  In the wheel loader 1 according to the first embodiment, the vehicle body controller 61 determines a work scene based on the depression amount of the accelerator pedal 31 and the depression amount of the brake pedal 32, and the determined work scene is an operation for which the engine speed is to be increased. If it is determined that it is a scene, the speed of the engine 41 can be quickly increased to the engine speed required for the work regardless of the operation state of the hydraulic actuator, so that the loading operation can be performed smoothly. . Even when it is determined that the determined work scene is a work scene where a large load acts on the travel drive system from the engine 41 to the travel device 49, the lockup clutch 46 is switched from the connected state to the disconnected state. It is possible to reliably prevent engine stalls and damage to the drive system. Further, when it is determined that it is not a work scene where it is desired to increase the engine speed and when it is determined that the work drive system does not apply a large load, the lockup clutch 46 is maintained in the connected state. The fuel consumption of the wheel loader 1 can be improved.

  This point will be described in more detail. In the conventional technology, the threshold value of the operation amount by the operation lever is a condition for increasing the load on the work machine when the work machine is raised and operated while approaching the dump truck. Therefore, the travel ratio in the locked-up state is reduced by the amount until the lock-up is released from the stage before the brake operation and the brake operation is started. Further, if a vehicle speed threshold value for releasing the lockup is set so that a large load does not act on the driving force transmission device, it is necessary to increase the value, and the ratio of low-speed traveling in the locked-up state is reduced. On the other hand, if the configuration of the present invention is adopted, the ratio of traveling in the locked-up state can be increased, so that fuel consumption can be improved.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS. The second embodiment of the present invention is characterized in that the work scene of the wheel loader 1 is determined based on the depression amount of the accelerator pedal 31, the depression amount of the brake pedal 32, and the inclination of the wheel loader 1.

  FIG. 9 is a diagram illustrating a connection state of various signals to the vehicle body controller and the transmission controller of the wheel loader according to the second embodiment. As shown in FIG. 9, in the wheel loader 1 according to the second embodiment, the detection signal of the tilt angle sensor 69 is input to the vehicle body controller 61. The inclination angle sensor 69 is installed at an appropriate position on the vehicle body of the wheel loader 1. Since others are the same as those of the wheel loader 1 according to the first embodiment, the corresponding parts are denoted by the same reference numerals and description thereof is omitted.

  FIG. 10 is a table showing a list of work scenes that can be recognized from the tilt state, accelerator operation state, and brake operation state of the wheel loader according to the second embodiment, and FIG. 11 is a work scene of the wheel loader according to the second embodiment. It is a table | surface figure which shows the list of the release conditions of the lockup clutch suitable for.

  When it is determined from the detection signal of the tilt angle sensor 69 that the wheel loader 1 is in a flat or downhill state, as shown in FIG. 10, when both the accelerator pedal 31 and the brake pedal 32 are depressed, The controller 61 determines that it is a loading operation scene, and outputs a signal for switching the lockup clutch 46 from the connected state to the disconnected state to the transmission controller 63 as shown in FIG. As a result, the lock-up clutch 46 is in a disconnected state, and the speed of the engine 41 can be quickly increased to the engine speed required for the work, so that the work can be performed smoothly.

  Further, when it is determined from the detection signal of the inclination angle sensor 69 that the wheel loader 1 is in a flat or downhill state, as shown in FIG. 10, the accelerator pedal 31 is stepped on and the brake pedal 32 is not stepped on. In this case, the vehicle body controller 61 determines that it is an excavation work scene, and the generated torque calculated based on the output torque of the engine 41 and the inertia torque generated on the input shaft 43a of the torque converter 47 as shown in FIG. When it is determined that Trq_th is exceeded, a signal for switching the lockup clutch 46 from the connected state to the disconnected state is output to the transmission controller 63. As a result, the lock-up clutch 46 is in a disconnected state, and the lock-up can be released before the load on the driving force transmission device that occurs during the excavation work scene increases, thus avoiding engine stall or failure of the traveling device. be able to.

  Further, when it is determined from the detection signal of the tilt angle sensor 69 that the wheel loader 1 is in a flat or downhill state, the accelerator pedal 31 is not depressed and the brake pedal 32 is depressed as shown in FIG. When the vehicle body controller 61 determines that it is a brake operation scene, the inertia torque calculated based on the deceleration of the vehicle body exceeds the torque threshold value Trq_th, as shown in FIG. A signal for switching the lockup clutch 46 from the connected state to the disconnected state is output to the transmission controller 63. As a result, the lock-up clutch 46 is in a disengaged state, and it is possible to prevent an excessive load from acting on the traveling drive system from the engine 41 to the traveling device 49 when the brake is suddenly applied, and the wheel loader 1 is damaged. Can be prevented.

  In addition, when it is determined from the detection signal of the tilt angle sensor 69 that the wheel loader 1 is in a flat or downhill state, as shown in FIG. 10, neither the accelerator pedal 31 nor the brake pedal 32 is depressed. In this case, the vehicle body controller 61 determines that the scene is a flat ground deceleration scene, and as shown in FIG. 11, the lockup clutch 46 is maintained in the connected state with only the vehicle speed as a release condition, and the wheel loader 1 is driven at the vehicle speed at that time. Let Thereby, the fuel consumption improvement of the wheel loader 1 is achieved.

  On the other hand, when it is determined from the detection signal of the tilt angle sensor 69 that the wheel loader 1 is in the uphill state, as shown in FIG. 10, both the accelerator pedal 31 and the brake pedal 32 are depressed. The vehicle body controller 61 determines that it is a loading work scene while traveling uphill, and outputs a signal for switching the lockup clutch 46 from the connected state to the disconnected state to the transmission controller 63 as shown in FIG. As a result, the lock-up clutch 46 is in a disengaged state, and the hydraulic oil necessary for performing the loading operation while traveling uphill can be discharged from the hydraulic pump 51, and the wheel loader 1 is prevented from popping out. The workability of the loader 1 is improved.

  Further, when it is determined from the detection signal of the tilt angle sensor 69 that the wheel loader 1 is in an uphill state, as shown in FIG. 10, when the accelerator pedal 31 is depressed and the brake pedal 32 is not depressed, The controller 61 determines that the vehicle is going uphill, and the generated torque calculated based on the output torque of the engine 41 and the inertia torque generated on the input shaft 43a of the torque converter 47 becomes the torque threshold value Trq_th as shown in FIG. When it is determined that it has exceeded, a signal for switching the lockup clutch 46 from the connected state to the disconnected state is output to the transmission controller 63. As a result, the lock-up clutch 46 is in a disengaged state, and the lock-up can be released before the load on the driving force transmission device that occurs during uphill travel increases, thus avoiding engine stalls and failure of the travel device. be able to.

  Further, when it is determined from the detection signal of the tilt angle sensor 69 that the wheel loader 1 is in an uphill state, as shown in FIG. 10, the accelerator pedal 31 is not depressed and the brake pedal 32 is depressed. The vehicle body controller 61 determines that it is a brake operation scene, and the inertia torque calculated based on the deceleration of the input shaft 43a or the output shaft 43b of the torque converter 47 exceeds the torque threshold Trq_th as shown in FIG. When it is determined that the lockup clutch 46 is present, a signal for switching the lockup clutch 46 from the connected state to the disconnected state is output to the transmission controller 63. As a result, the lock-up clutch 46 is in a disengaged state, and it is possible to prevent an excessive load from acting on the traveling drive system from the engine 41 to the traveling device 49 when the brake is suddenly applied, and the wheel loader 1 is damaged. Can be prevented.

  In addition, when it is determined from the detection signal of the tilt angle sensor 69 that the wheel loader 1 is in an uphill state, as shown in FIG. 10, when both the accelerator pedal 31 and the brake pedal 32 are not depressed, The controller 61 determines that the scene is a flat ground deceleration scene, and as shown in FIG. 11, the lockup clutch 46 is maintained in the connected state with only the vehicle speed as a release condition, and the wheel loader 1 is driven only at the vehicle speed at that time. Thereby, the fuel consumption improvement of the wheel loader 1 is achieved.

  Hereinafter, the lockup clutch release determination processing procedure of the wheel loader according to the second embodiment will be described with reference to FIG. FIG. 12 is a flowchart illustrating a lockup clutch release determination processing procedure of the wheel loader according to the second embodiment. The lockup clutch release determination process shown in FIG. 12 is executed in accordance with the lockup clutch 46 switching control program stored in the ROM 72 of the vehicle body controller 61.

  When the release determination process of the lockup clutch 46 is started, the vehicle body controller 61 determines whether or not the lockup clutch 46 is in a connected state (step S101). In step S101, the lockup clutch 46 is in a connected state. If it is determined that the wheel loader 1 is present (Yes), the process proceeds to step S102 to determine whether or not the wheel loader 1 is in an uphill state from the detection signal of the tilt angle sensor 69. If it is determined in step S102 that the wheel loader 1 is not in the uphill state (No), the processes of steps S103 to S115 are executed.

  The processing in steps S103 to S106 is processing when the lock-up release work is determined as loading work, and is the same as the processing in steps S2 to S5 shown in FIG. Description is omitted. Moreover, the process of procedure S104 and procedure S107-procedure S110 is a process when it is determined that the lock-up release work is excavation work, and is the same as the process of procedure S3 and procedure S6-procedure S9 shown in FIG. Therefore, the description is omitted to avoid duplication. Furthermore, the process of step S103 and step S111 to step S115 is a process when the lock-up release work is determined to be a brake operation, and is the same as the process of step S2 and step S10 to step S14 shown in FIG. Therefore, the description is omitted to avoid duplication.

  In step S101, it is determined that the lockup clutch 46 is in a connected state (Yes), in step S102, it is determined that the wheel loader 1 is in an uphill state (Yes), and in step S116, the amount of depression of the accelerator pedal 31 is determined by the accelerator threshold Acc_th. If it is determined that the amount of depression of the brake pedal 32 exceeds the brake threshold value Brk_th (Yes) in step S107, the process proceeds to step S118 and the lockup release operation is performed on an uphill road. The lock-up clutch 46 is switched to the disengaged state in step S119.

  If it is determined in step S117 that the amount of depression of the brake pedal 32 does not exceed the brake threshold value Brk_th (No), the process proceeds to step S120, and the lockup release operation is determined to be traveling uphill. Next, the process proceeds to step S121 to calculate the generated torque, and it is determined whether or not the generated torque exceeds the torque threshold value Trq_th (step S122). If it is determined in step S122 that the generated torque exceeds the torque threshold value Trq_th (Yes), the process proceeds to step S123, the lockup clutch 46 is switched to the disengaged state, and the process ends. If it is determined in step S122 that the generated torque does not exceed the torque threshold value Trq_th (No), the process ends.

  If it is determined in step S116 that the amount of depression of the accelerator pedal 31 does not exceed the accelerator threshold Acc_th (No), the process proceeds to step S124 and whether or not the amount of depression of the brake pedal 32 exceeds the brake threshold Brk_th. Make a decision. If it is determined in step S124 that the amount of depression of the brake pedal 32 exceeds the brake threshold value Brk_th (Yes), the process proceeds to step S125, and the lockup release operation is determined as the brake operation. Next, the process proceeds to step S126, where inertia torque is calculated, and it is determined whether the inertia torque exceeds the torque threshold value Trq_th (procedure S127). If it is determined in step S127 that the inertia torque exceeds the torque threshold value Trq_th (Yes), the process proceeds to step S128, the lockup clutch 46 is switched to the disengaged state, and the process ends. If it is determined in step S124 that the amount of depression of the brake pedal 32 does not exceed the brake threshold Brk_th (No), and if it is determined in step S127 that the inertia torque does not exceed the torque threshold Trq_th (No), the processing is performed as it is. Exit.

  The wheel loader 1 according to the second embodiment has the same effects as the wheel loader 1 according to the first embodiment, and further includes a tilt angle sensor 69 in the vehicle body of the wheel loader 1, and is based on a detection signal of the tilt angle sensor 69. Since the vehicle body controller 61 determines whether the traveling state of the wheel loader 1 is a flat ground (downhill) traveling or an uphill traveling, the engine speed, the vehicle speed, etc., as in the wheel loader 1 according to the first embodiment. Therefore, it is not necessary for the vehicle body controller 61 to calculate the traveling state of the wheel loader 1, and the burden on the vehicle body controller 61 can be reduced.

  It should be noted that the scope of the present invention is not limited to the description of the above-described embodiment, but includes those in which the above-described embodiment is appropriately changed, added, or deleted without changing the gist of the present invention. For example, in the first and second embodiments, the wheel loader 1 has been described as an example of a work vehicle. However, the present invention can also be applied to other work vehicles such as a dump truck.

DESCRIPTION OF SYMBOLS 1 Wheel loader 8 Working machine 31 Accelerator pedal 32 Brake pedal 41 Engine 43 Torque converter device 44 Transmission 46 Lockup clutch 49 Traveling device 51 Hydraulic pump 61 Car body controller 64 Accelerator operation amount detection device 65 Brake operation amount detection device 69 Tilt angle sensor 72 ROM
83 Acceleration threshold value storage unit 84 Brake threshold value storage unit 85 Torque threshold value storage unit

Claims (5)

An engine whose number of rotations increases or decreases when the accelerator pedal is depressed;
A hydraulic pump driven by the engine;
A hydraulic actuator that is supplied with hydraulic oil from the hydraulic pump and operates;
A traveling device in which power output from the engine is transmitted via a torque converter;
A braking device that applies a braking force to the traveling device by depressing a brake pedal;
A lockup device that switches between connecting and disconnecting the output shaft and the input shaft of the torque converter;
In a work vehicle including a control device that controls connection and disconnection of the output shaft and the input shaft of the lockup device according to a traveling state of a vehicle body,
The control device determines a release condition based on a depression state of the accelerator pedal and the brake pedal in a state where the output shaft and the input shaft of the torque converter are connected, and based on the release condition, the torque converter A work vehicle that controls the lock-up device to release the connection between the output shaft and the input shaft. The work vehicle according to claim 1,
The control device includes the output shaft of the torque converter as a release condition when the accelerator pedal and the brake pedal are depressed in a state where the output shaft and the input shaft of the torque converter are connected. A work vehicle, wherein the lockup device is controlled to release the connection with the input shaft. The work vehicle according to claim 1,
The control device reduces the input shaft of the torque converter when the accelerator pedal is not depressed and the brake pedal is depressed while the output shaft and the input shaft of the torque converter are connected. The work vehicle, wherein the lockup device is controlled so as to release the connection between the output shaft and the input shaft of the torque converter with the release condition that an inertia torque based on speed exceeds a predetermined threshold. . The work vehicle according to claim 1,
When the accelerator pedal is depressed and the brake pedal is not depressed in a state where the output shaft and the input shaft of the torque converter are connected, the control device outputs the engine output torque and the torque. The connection between the output shaft and the input shaft of the torque converter is released with the release condition that the generated torque calculated from the inertia torque based on the deceleration of the input shaft of the converter exceeds a predetermined threshold. A work vehicle characterized by controlling a lock-up device. The work vehicle according to claim 1,
The vehicle body includes an inclination angle sensor,
The control device includes a flat ground or a downhill state and an uphill state detected by the inclination angle sensor in a state where the output shaft and the input shaft of the torque converter are coupled, and the accelerator pedal and the brake pedal. A work vehicle that determines the release condition based on a stepped-on state and controls the lockup device to release the connection between the output shaft and the input shaft of the torque converter based on the release condition.

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