JP2022148140A - wheel loader - Google Patents

Abstract

To provide a wheel loader in which sediment or the like hardly comes down from a bucket.SOLUTION: A wheel loader (1) comprises: a vehicle body (6,8); a bucket (3); a lift arm (11) holding the bucket; a lift arm cylinder (12) driving the lift arm; an engine (100); control devices (104, 121); an angle sensor (18) detecting an angle of the lift arm; an accumulator (124) connected with a hydraulic chamber (12b) of the lift arm cylinder in which pressure oil can flow into/out between the hydraulic chamber and itself; and a pressure sensor (205) detecting a pressure of the accumulator. The control device reduces the rotation number of the engine based on the pressure of the accumulator when the angle of the lift arm satisfies a deceleration control condition reducing the rotation number of the engine.SELECTED DRAWING: Figure 10

Description

The present invention relates to wheel loaders with buckets.

As a background art of this technical field, for example, in Patent Document 1, when a switch is operated for the purpose of absorbing pressure fluctuations in the bottom chamber of the boom cylinder, the controller controls the ride control valve between the accumulator and the bottom chamber of the boom cylinder. A wheel loader is described that is configured to send a signal into communication with the .

JP 2007-186942 A

The condition of the road surface on which the wheel loader travels varies depending on the work place, and there are rough roads with continuous steps on the road surface. If there are continuous bumps on the road surface, the accumulator cannot sufficiently absorb pressure fluctuations in the bottom chamber of the lift arm cylinder (boom cylinder), and as a result, there is a possibility that earth and sand in the bucket will spill out due to vibration. In Patent Document 1, the configuration is limited to absorbing the vibration by the accumulator, and when the wheel loader runs on a rough road with continuous steps, the vibration may be amplified and the vibration may not be absorbed. . If it runs in a state where it cannot absorb the vibration, the earth and sand that need to be moved will spill out of the bucket.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a wheel loader that does not require adjustment of the vehicle speed even when traveling on a rough road, and prevents dirt and the like from spilling out of the bucket.

In order to achieve the above object, a representative aspect of the present invention is a vehicle body to which front wheels and rear wheels are attached, a bucket provided in the front part of the vehicle body, a lift arm holding the bucket, and the lift A wheel loader comprising a lift arm cylinder that drives an arm, an engine that is a drive source of the vehicle body, and a control device that controls the rotation speed of the engine, an angle sensor that detects the angle of the lift arm; An accumulator that is connected to the hydraulic chamber of the lift arm cylinder and allows pressure oil to flow in and out of the hydraulic chamber; and a pressure sensor that detects the pressure of the accumulator. When the angle of the lift arm detected by the sensor satisfies a deceleration control condition for decelerating the rotation speed of the engine, the rotation speed of the engine is reduced based on the pressure of the accumulator detected by the pressure sensor. Characterized by deceleration.

ADVANTAGE OF THE INVENTION According to this invention, the wheel loader which is hard to spill earth and sand etc. from a bucket can be provided. Moreover, according to the present invention, it is not necessary to adjust the vehicle speed even when traveling on a rough road. Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

It is a side view of a wheel loader concerning an embodiment of the present invention. 1 is a perspective view of a wheel loader according to an embodiment of the invention; FIG. It is a figure which shows the drive system structure of a wheel loader. It is a figure which shows the system configuration|structure of a driving|running|working vibration suppression hydraulic circuit. FIG. 5 is a diagram showing pressure fluctuations in the bottom chamber of the lift arm cylinder and changes in the cylinder length of the lift arm cylinder when the wheel loader has climbed over a step; FIG. 10 is a diagram showing pressure fluctuations in the bottom chamber of the lift arm cylinder when the wheel loader runs over successive steps at the same vehicle speed; FIG. 10 is a diagram showing a comparison of pressure fluctuations in the bottom chamber of the lift arm cylinder when the wheel loader runs over a step at different vehicle speeds; FIG. 10 is a diagram showing pressure fluctuations in the bottom chamber of the lift arm cylinder when the wheel loader first climbs over a step and then decelerates to get over the next step; 3 is a block diagram schematically showing the hardware configuration of a main controller; FIG. It is a block diagram showing an electrical configuration of the wheel loader. 3 is a functional block diagram of a main controller; FIG. 4 is a flow chart showing a processing procedure of a deceleration control determination unit; 4 is a flowchart showing a processing procedure of a deceleration gain calculator; 4 is a map diagram showing the relationship between reference pressure and deceleration gain; FIG. FIG. 4 is a diagram showing changes in reference pressure over time; 4 is a flow chart showing a processing procedure of a command rotation speed calculation unit; FIG. 4 is a map diagram showing the relationship between the depression amount of the accelerator pedal and the required engine speed;

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of the wheel loader which concerns on this invention is described, referring drawings.

FIG. 1A is a side view of a wheel loader according to an embodiment of the invention, FIG. 1B is a perspective view of the wheel loader according to an embodiment of the invention.

As shown in FIGS. 1A and 1B, the wheel loader 1 includes a front frame (vehicle body) 6 having a lift arm 11, a bucket 3, a pair of front wheels 5, etc., a driver's cab 4, an engine compartment 20, a pair of rear wheels 7, etc. and a rear frame (vehicle body) 8 having a An engine 100 is mounted in the engine room 20 and a counterweight 21 is attached to the rear of the rear frame 8 . The front frame 6 and the rear frame 8 are rotatably connected to each other by a center pin 9 , and the front frame 6 is bent left and right with respect to the rear frame 8 by expansion and contraction of the steering cylinder 10 . In the following description, the front wheels 5 and the rear wheels 7 may be collectively referred to as "wheels 5 and 7".

A pair of lift arm cylinders 12 are driven to rotate the lift arm 11 vertically (elevate), and a bucket cylinder 16 is driven to rotate the bucket 3 vertically (cloud or dump). A link mechanism including a bell crank 15 and a push rod 14 is interposed between the bucket cylinder 16 and the bucket 3, and the bucket cylinder 16 rotates the bucket 3 via this link mechanism. The work machine 2 is composed of the lift arm 11, the bucket 3, the pair of lift arm cylinders 12, the bucket cylinder 16, the bell crank 15, the push rod 14, and the like.

A lift arm angle sensor (angle sensor) 18 is attached to the connecting portion between the lift arm 11 and the front frame 6 , and the rotation angle of the lift arm 11 is detected by the lift arm angle sensor 18 . A bucket angle sensor 19 for detecting the angle of the bucket 3 with respect to the lift arm 11 is attached to a predetermined position of the bell crank 15 .

The operator's cab 4 mounted on the front part of the rear frame 8 includes a driver's seat where the operator sits, a steering wheel 117 for controlling the steering angle of the wheel loader 1, a key switch for starting and stopping the wheel loader 1, and information for the operator. , a main controller (control device) 121 for controlling the overall operation of the wheel loader 1, and the like.

Note that FIG. 1A shows the posture of the wheel loader 1 during transportation work. During transportation work, the lift arm 11 is lifted up to such a height that the bucket 3 does not obstruct the operator's field of vision in front, so that the bucket 3 scooping up earth and sand does not come into contact with the ground during traveling.

FIG. 2 is a diagram showing the drive system configuration of the wheel loader 1. As shown in FIG. As shown in FIG. 2, an output shaft 100a of the engine 100 is directly connected to a torque converter 101, a hydraulic pump 102, and a brake pump 103. The engine controller 104 outputs the electric signal 105 based on the rotation speed command 127 from the main controller 121 . The main controller 121 outputs a rotational speed command 127 based on the depression amount of the accelerator pedal 106 .

The output shaft of torque converter 101 is connected to drive shaft 108 via transmission 107, and the driving force of engine 100 is transmitted to wheels 5 and 7 via torque converter 101, transmission 107, and drive shaft 108. . As a result, the wheels 5, 7 rotate.

Torque converter 101 is a fluid clutch made up of an impeller, a turbine, and a stator. The driving force transmitted from the torque converter 101 to the transmission 107 increases as the rotation speed of the output shaft 100a of the engine 100 increases with respect to the output rotation speed of the torque converter 101. By increasing the rotation speed of the torque converter 101, the driving force output by the torque converter 101 is increased. When there is no difference between the output rotation speed of the torque converter 101 and the rotation speed of the output shaft 100a of the engine 100, the driving force output by the torque converter 101 is zero.

When the vehicle is traveling on flat ground where the running resistance acting on the wheels 5 and 7 is constant, if the rotation speed of the output shaft 100a of the engine 100 is constant, the running speed is also constant. The wheel loader 1 accelerates when the rotation speed of the output shaft 100a of the engine 100 is increased, and decelerates when the rotation speed of the output shaft 100a of the engine 100 is decreased.

The transmission 107 cuts off the connection between the output of the torque converter 101 and the drive shaft 108 in response to an electric signal 110 from the transmission controller 109 to reduce the driving force of the wheels 5 and 7, or reverses the direction of rotation to change the direction of the driving force. change it.

Specifically, the transmission 107 controls the combination of a plurality of gears so as to achieve a gear ratio corresponding to, for example, one of the 1st to 4th gear stages in forward or reverse travel. As a result, the torque, rotation speed, and rotation direction of the output shaft of torque converter 101 are transmitted to wheels 5 and 7 in accordance with the set speed stage.

The electric signal 110 of the transmission controller 109 is output so as to cut off the connection when the operator's forward/backward movement instruction switch 111 is in neutral and when the amount of depression of the brake pedal 112 exceeds a certain level.

A vehicle speed sensor (not shown) for measuring the rotation speed of the drive shaft 108 is attached to the transmission 107, and the transmission controller 109 measures the vehicle speed of the wheel loader 1 based on the vehicle speed sensor. The vehicle speed of the wheel loader 1 may be measured by directly detecting the rotation speeds of the wheels 5 and 7 instead of the vehicle speed sensor.

The hydraulic pump 102 outputs a constant flow of pressurized oil each time the output shaft 100a of the engine 100 rotates once. In this embodiment, the hydraulic pump 102 is a swash plate type or oblique shaft type variable displacement hydraulic pump whose displacement volume is controlled according to the tilt angle. good.

The pressure oil output from the hydraulic pump 102 is supplied to the lift arm cylinder 12 and the bucket cylinder 16 via the working machine control hydraulic circuit 113 to extend and retract the lift arm cylinder 12 and the bucket cylinder 16 .

The amount of pressurized oil output from the hydraulic pump 102 increases as the rotational speed of the output shaft 100a of the engine 100 increases. The telescopic speed of the bucket cylinder 16 increases.

The work machine control hydraulic circuit 113 cuts off the connection between the output of the hydraulic pump 102 and the lift arm cylinder 12 by operating the lift lever 114 by the operator, stops the operation of the lift arm 11, reverses the expansion/contraction direction, For example, the vertical movement of the arm 11 is switched.

The work machine control hydraulic circuit 113 cuts off the connection between the output of the hydraulic pump 102 and the bucket cylinder 16 by operating the bucket lever 115 by the operator to stop the operation of the bucket 3, reverse the expansion/contraction direction, and For example, switching the operation in the forward and backward direction of the angle.

The pressure oil output from the hydraulic pump 102 is connected to the left and right steering cylinders 10 via the steering control hydraulic circuit 116 to extend and retract the left and right steering cylinders 10 .

When the operator rotates the steering wheel 117 to the right, the steering control hydraulic circuit 116 connects pressure oil output from the hydraulic pump 102 in the direction in which the right steering cylinder 10R contracts and in the direction in which the left steering cylinder 10L extends. When the wheel loader 1 is turned to the right and the operator turns the steering wheel 117 to the left, the pressure oil output from the hydraulic pump 102 is connected in the direction in which the right steering cylinder 10R extends and in the direction in which the left steering cylinder 10L contracts. Then, the wheel loader 1 is turned left.

The pressure oil output from the brake pump 103 is accumulated in the accumulator 118 , and the pressure oil accumulated in the accumulator 118 controls the braking force of the wheels 5 and 7 via the brake control hydraulic circuit 119 .

The brake control hydraulic circuit 119 adjusts the control pressure according to the amount of depression of the brake pedal 112 by the operator.

FIG. 3 is a diagram showing the system configuration of the running vibration suppressing hydraulic circuit 123 shown in FIG. As shown in FIG. 3 , the control valve solenoid valve 201 is driven by an excitation signal (electrical signal) 305 from the main controller 121 . In the energized state, the control valve solenoid valve 201 is switched to the position 201 a to apply the pressure of the pilot hydraulic pressure source 202 to the switching valve 203 . Then, the switching valve 203 is switched to the communicating position 203a. On the other hand, in the non-excitation state, the control valve solenoid valve 201 switches to the position 201b, and the switching valve 203 switches to the non-communication position 203b.

When the switching valve 203 is at the communication position 203a, the bottom chamber (hydraulic chamber) 12b of the lift arm cylinder 12 and the accumulator 124 communicate with each other, and pressurized oil flows between them. Also, the rod chamber 12 c of the lift arm cylinder 12 and the tank 204 communicate with each other, and the pressure oil in the rod chamber 12 c is introduced to the tank 204 . On the other hand, when the switching valve 203 is at the non-communication position 203b, the communication between the accumulator 124 and the bottom chamber 12b of the lift arm cylinder 12 is cut off, and the communication between the rod chamber 12c of the lift arm cylinder 12 and the tank 204 is cut off. .

An accumulator pressure sensor 205 measures the pressure of the accumulator 124 and outputs a pressure signal 206 to the main controller 121 .

The main controller 121 outputs an excitation signal 305 to the control valve electromagnetic valve 201 when the travel vibration suppression control changeover switch 126 is ON, the detection value of the lift arm angle sensor 18 is a predetermined value, and the vehicle speed is above a certain speed. In other cases, excitation is not performed (details will be described later).

Although not shown, the main controller 121, the engine controller 104, and the transmission controller 109 are all connected via a communication network.

FIG. 4 is a diagram showing pressure fluctuations in the bottom chamber 12b of the lift arm cylinder 12 and changes in the cylinder length of the lift arm cylinder 12 when the wheel loader 1 climbs over a step. In FIG. 4, the upper part shows the pressure in the bottom chamber 12b of the lift arm cylinder 12, and the lower part shows the change in the cylinder length of the lift arm cylinder 12. As shown in FIG.

When the switching valve 203 is in the communication position 203a, the accumulator 124 and the bottom chamber 12b of the lift arm cylinder 12 are communicated with each other, so that the pressure fluctuation of the accumulator 124 is equal to the pressure fluctuation of the bottom chamber 12b of the lift arm cylinder 12. is equal to Therefore, the accumulator pressure detected by the accumulator pressure sensor 205 can be regarded as the pressure P of the bottom chamber 12 b of the lift arm cylinder 12 .

When the front wheel 5 of the wheel loader 1 runs over a step, the pressure P in the bottom chamber 12b of the lift arm cylinder 12 rises as shown in section 1a. Since the accumulator 124 absorbs the increase in the pressure P in the bottom chamber 12b of the lift arm cylinder 12, the cylinder length L of the lift arm cylinder 12 is reduced.

In section 1b, the pressure oil accumulated in the accumulator 124 is led to the bottom chamber 12b of the lift arm cylinder 12, so the cylinder length L of the lift arm cylinder 12 is extended.

When the front wheel 5 of the wheel loader 1 rides over the step and lands, the pressure P in the bottom chamber 12b of the lift arm cylinder 12 rises as shown in section 1c. Since the accumulator 124 absorbs the increase in the pressure P in the bottom chamber 12b of the lift arm cylinder 12, the cylinder length L of the lift arm cylinder 12 is reduced. After that, while the cylinder length L of the lift arm cylinder 12 expands and contracts, the fluctuation of the pressure P of the accumulator 124 attenuates.

In this way, the accumulator 124 absorbs the pressure fluctuations generated in the bottom chamber 12b of the lift arm cylinder 12, so that the impact acting on the bucket 3 connected to the tip of the lift arm 11 is reduced, and the earth and sand, etc. are removed from the bucket 3. It is suppressed that it spills from.

Next, a case where steps are continuous will be described. FIG. 5 is a diagram showing pressure fluctuations in the bottom chamber 12b of the lift arm cylinder 12 when the wheel loader 1 rides over continuous steps at the same vehicle speed. In FIG. 5, sections 1a to 1c show the state in which the front wheel 5 of the wheel loader 1 has climbed over the first step, and are the same as sections 1a to 1c in FIG.

Section 2a is a state in which the front wheels 5 have run over the second step after the front wheels 5 have run over the first step and before the pressure fluctuations in the bottom chamber 12b of the lift arm cylinder 12 have stopped attenuating.

As shown in FIG. 5, in section 2a, the pressure fluctuation in the bottom chamber 12b of the lift arm cylinder 12 is amplified, and the impact on the bucket 3 is also amplified, so that dirt and the like fall from the bucket 3. As shown in FIG.

FIG. 6 is a diagram showing a comparison of pressure fluctuations in the bottom chamber 12b of the lift arm cylinder 12 when the wheel loader 1 runs over a step at different vehicle speeds. In FIG. 6, sections 1a to 1c show the state in which the front wheel 5 runs over a step at the same vehicle speed as in FIG. As shown in sections 3a to 3c of FIG. 6, by suppressing the vehicle speed of the wheel loader 1, the ground impact on the front wheels 5 is weakened, so pressure fluctuations in the bottom chamber 12b of the lift arm cylinder 12 are reduced.

FIG. 7 is a diagram showing pressure fluctuations in the bottom chamber 12b of the lift arm cylinder 12 when the wheel loader 1 first climbs over a step and then decelerates to get over the next step. In section 4a of FIG. 7, although the pressure fluctuation in the bottom chamber 12b of the lift arm cylinder 12 is amplified, since the second step is overcome at low speed, the pressure of the lift arm cylinder 12 is lower than that of the section 2a of FIG. Pressure fluctuations in the bottom chamber 12b are suppressed. As a result, the impact on the bucket 3 is also weakened, and it is possible to prevent earth and sand from spilling out of the bucket 3. - 特許庁

In this way, in order to prevent earth and sand from spilling out of the bucket 3 when the wheel loader 1 climbs over a series of steps, it is important to suppress amplification of pressure fluctuations in the bottom chamber 12b of the lift arm cylinder 12. Become.

FIG. 8 is a block diagram schematically showing the hardware configuration of the main controller 121. As shown in FIG. As shown in FIG. 8, the main controller 121 includes a CPU (Central Processing Unit) 121A that performs various calculations for controlling the overall motion of the vehicle body, and a ROM (Read Only) that stores programs for executing calculations by the CPU 121A. Memory) 121B and other storage devices, a RAM (Random Access Memory) 121C that serves as a work area when the CPU 121A executes a program, and an input/output interface 121D that inputs and outputs various information and signals to and from an external device. It consists of hardware including

In such a hardware configuration, the program stored in the ROM 121B is read out to the RAM 121C and operated according to the control of the CPU 121A so that the program (software) and the hardware work together to achieve the functions of the main controller 121, which will be described later. A function block that realizes is configured.

The engine controller 104 and transmission controller 109 also have the same configuration as the main controller 121 .

FIG. 9 is a block diagram showing the electrical configuration of the wheel loader 1. As shown in FIG. As shown in FIG. 9, the main controller 121 receives vehicle speed information 301 from the transmission controller 109, ON information 302 of the travel vibration suppression control changeover switch 126, angle information 303 of the lift arm angle sensor 18, and an accumulator pressure sensor 205. A pressure signal 206 and a depression amount 304 of the accelerator pedal 106 are input.

FIG. 10 is a functional block diagram of the main controller 121. As shown in FIG. As shown in FIG. 10 , the travel vibration suppression determination unit 401 determines whether the vehicle travels based on vehicle speed information 301 of the wheel loader 1 , ON information 302 of the travel vibration suppression control switch 126 , and angle information 303 of the lift arm 11 . An excitation signal 305 is set to excite the control valve solenoid valve 201 of the vibration suppression hydraulic circuit 123 .

Specifically, when the wheel loader 1 is traveling at a predetermined speed, the travel vibration suppression control switch 126 is ON, and the lift arm 11 is within a predetermined angle range (that is, when the bucket 3 is on the ground). ), the traveling vibration suppression determination unit 401 sets the excitation signal 305 . Here, the “transportation posture” is a posture in which the bucket 3 is held at a position slightly higher than the ground by the lift arm 11 with earth and sand etc. contained in the bucket 3. For example, the posture shown in FIG. 1A. is the transportation posture in this embodiment.

In this embodiment, based on the vehicle speed information 301 of the wheel loader 1, the ON information 302 of the travel vibration suppression control switch 126, and the angle information 303 of the lift arm 11, the control valve of the travel vibration suppression hydraulic circuit 123 is controlled. Although the excitation signal 305 is set to excite the solenoid valve 201 , the excitation signal 305 should be output based on at least the angle information 303 of the lift arm 11 . In situations where the vehicle speed is low, such as during dump loading or excavation work, the operation of the travel vibration suppression control may cause the vehicle to become unstable, which may interfere with dump loading or excavation work. be. Therefore, the travel vibration suppression determination unit 401 constantly monitors the vehicle speed information 301, and when the vehicle speed is equal to or lower than a predetermined vehicle speed corresponding to dump loading work, excavation work, or the like, the engine rotation speed is adjusted to cancel the travel vibration suppression control. It is preferable not to execute this control for automatically decelerating .

A deceleration control determination unit 402 sets a deceleration control determination signal 403 and a differential pressure 404 to be described later based on the excitation signal 305 and the pressure signal 206 of the accumulator 124 .

FIG. 11 is a flow chart showing the processing procedure of the deceleration control determination unit 402. As shown in FIG. Note that the processing shown in FIG. 11 is repeatedly performed every predetermined time (for example, 10 milliseconds).

As shown in FIG. 11, when the excitation signal 305 is OFF in S101, that is, when the control valve solenoid valve 201 is de-excited (S101/No), the deceleration control determination unit 402 determines the pressure of the accumulator 124 as the reference pressure. The value (detected pressure) of the signal 206 is set (S108), the differential pressure 404 is set to 0 (S109), and the deceleration control determination signal 403 (deceleration control) is set to OFF (S110). In other words, engine speed deceleration control is not performed (vehicle speed is not decelerated).

On the other hand, when the excitation signal 305 is ON in S101, the deceleration control determination unit 402 sets the differential pressure 404 to a value obtained by subtracting the reference pressure (previous value) from the value of the pressure signal 206 (detected pressure) (S102), If the differential pressure 404 is greater than the set pressure in S103 (S103/Yes), the timer is set to 0 (S104), and the deceleration control determination signal 403 is set to ON (S105). In other words, engine speed deceleration control is performed (vehicle speed is decelerated).

Here, S103 is a process for determining whether or not there is a possibility that dirt or the like will spill from the bucket 3. In other words, it is determined whether or not to perform control to reduce the engine speed. This process is for That is, according to the determination in S103, if there is a possibility that dirt or the like will fall from the bucket 3, the engine speed is reduced; otherwise, the engine speed is not reduced. Therefore, the set value in S103 is determined based on the pressure difference (differential pressure) of the bottom chamber 12b of the lift arm cylinder 12, which can be regarded as the earth and sand etc. drowning from the bucket 3 when the wheel loader 1 climbs over the step. .

If the differential pressure 404 is equal to or less than the set value in S103 (S103/No), the deceleration control determination unit 402 sets a value obtained by adding 1 to the timer (previous value) in the timer (S106), and the timer is less than the set time. In the case of (S107/Yes), the deceleration control determination signal 403 is set to ON (S105). In other words, engine speed deceleration control is performed (vehicle speed is decelerated).

On the other hand, if the timer is equal to or longer than the set time (S107/No), the deceleration control determination unit 402 sets the deceleration control determination signal 403 to OFF (S110). In other words, engine speed deceleration control is not performed (vehicle speed is not decelerated).

Here, the reason why the set time is provided in S107 is that the wheel loader 1 may hunt if the deceleration control is immediately turned OFF (S110) when the differential pressure 404 is equal to or less than the set pressure in S103. That is, hunting of the wheel loader 1 is prevented by performing the processing of S106 and S107.

Further, if the set time is set too long, the vehicle speed will be decelerated, and work efficiency may be deteriorated. Therefore, in this embodiment, the time (for example, 1 second) from when the front wheels 5 run over the step (specific position) until the rear wheels 7 run over the step is set as the set time. That is, the set time is determined based on the vehicle speed and the wheelbase (the distance between the front wheels 5 and the rear wheels 7).

Next, the deceleration gain calculator 405 in FIG. 10 sets the deceleration gain 406 based on the inputs of the deceleration control determination signal 403 and the differential pressure 404 .

FIG. 12 is a flow chart showing the processing procedure of the deceleration gain calculator 405. As shown in FIG. Note that the processing shown in FIG. 12 is repeatedly performed every predetermined time (for example, 10 milliseconds).

As shown in FIG. 12, when the deceleration control determination signal 403 is OFF (S201/No), the deceleration gain calculator 405 sets the reference pressure to 0 (S206) and sets the deceleration gain 406 to 1 (S207). ). That is, the vehicle speed is set according to the depression amount 304 of the accelerator pedal 106 .

In S201, if the deceleration control determination signal 403 is ON (S201/Yes), the deceleration gain calculator 405 compares the differential pressure 404 with the reference pressure (previous value) (S202). If the pressure is equal to or lower than the reference pressure (previous value) (S202/No), the reference pressure (previous value) is set (S205), and deceleration obtained by referring to the map (FIG. 13) is applied to the deceleration gain 406. A gain (map value) is set (S204).

FIG. 13 is a map diagram showing the relationship between the reference pressure and the deceleration gain. As shown in FIG. 13, the ROM 121B stores map data having characteristics such that the deceleration gain decreases as the reference pressure increases. As a result, the larger the differential pressure 404 becomes, the smaller the deceleration gain becomes, thereby decelerating the engine speed. For example, when the reference pressure is Pr1, the deceleration gain calculator 405 acquires the deceleration gain G1 (0<G1<1) corresponding to the reference pressure Pr1 from the map data shown in FIG.

On the other hand, in S202 of FIG. 12, if the differential pressure 404 is greater than the reference pressure (previous value) (S202/Yes), the deceleration gain calculator 405 sets the differential pressure 404 to the reference pressure (S203), and the deceleration gain A deceleration gain (map value) obtained by referring to the map (FIG. 13) is set in 406 (S204).

Thus, in this embodiment, when the differential pressure 404 is greater than the reference pressure (previous value), the reference pressure is set to the differential pressure (S203), so the deceleration gain (-) increases. On the other hand, when the differential pressure 404 is equal to or less than the previous reference pressure, the reference pressure is set to the reference pressure (previous value) (S205), so the previous deceleration gain is maintained.

This will be described in detail with reference to FIG. FIG. 14 is a diagram showing changes in reference pressure over time. As shown in FIG. 14, the reference pressure rises to Pr1 at time t1 when deceleration control is turned ON, and gradually rises from time t1 to time t2 as time elapses. The deceleration gain increases (the engine speed decelerates) as the reference pressure increases. When the differential pressure 404 becomes equal to or lower than the reference pressure (previous value) at time t2, the differential pressure 404 (one-dot chain line) decreases, but the reference pressure is maintained at the previous value Pr2. Therefore, the deceleration gain corresponding to the previous value Pr2 is maintained. Then, at time t3 when the deceleration control is turned off, the reference pressure becomes zero. In this manner, the deceleration gain gradually increases from time t1 to time t2, and becomes a constant deceleration gain (constant engine speed) from time t2 to time t3.

A command rotation speed calculation unit 407 shown in FIG. 10 sets a rotation speed command 127 based on inputs of a deceleration gain 406 and a depression amount 304 of the accelerator pedal 106 .

FIG. 15 is a flow chart showing the processing procedure of command rotation speed calculation unit 407 . Note that the processing shown in FIG. 15 is repeatedly performed every predetermined time (for example, 10 milliseconds). As shown in FIG. 15, the command rotation speed calculation unit 407 sets the required engine rotation speed (map value) obtained by referring to the map shown in FIG. 14 as the required engine rotation speed (S301).

FIG. 16 is a map showing the relationship between the depression amount 304 of the accelerator pedal 106 and the required engine speed (rpm). As shown in FIG. 16, the ROM 121B stores map data showing the characteristic that the required engine speed increases as the depression amount 304 increases. As a result, the more the accelerator pedal 106 is depressed, the more the vehicle speed increases. For example, when the depression amount 304 is V1, the command rotation speed calculation unit 407 acquires the required engine rotation speed N1 corresponding to the depression amount V1 from the map data shown in FIG.

Next, the command rotation speed calculation unit 407 sets the target engine rotation speed to a value obtained by multiplying the required engine rotation speed by the deceleration gain (406) (S302). The command rotation speed calculation unit 407 compares the engine target rotation speed with a preset minimum engine rotation speed (S303). , the minimum engine speed is set in the speed command 127 (S305), and if the target engine speed is greater than the minimum engine speed in S303 (S303/Yes), the target engine speed is set in the speed command 127. set. Here, the minimum engine speed is, for example, the engine speed during idling.

As described above, according to this embodiment, the main controller 121 controls the engine 100 based on the pressure signal 206 of the accumulator 124 when the angle information 303 of the lift arm 11 satisfies the deceleration control condition of the engine 100 . Since the rotation speed of the bucket 3 is reduced, the vehicle speed can be suppressed when the wheel loader 1 rides over a continuous step, so that earth and sand can be prevented from falling from the bucket 3. - 特許庁More specifically, as the vehicle speed is reduced, pressure fluctuations in the bottom chamber 12b of the lift arm cylinder 12 are suppressed, so the posture of the bucket 3 is stabilized. As a result, dirt and the like are less likely to spill out of the bucket 3 .

Further, after the differential pressure of the accumulator 124 becomes equal to or less than the set pressure (S103/No), when the set time elapses (S107/NO), the deceleration control of the engine 100 is terminated (S110). 1 hunting is prevented. Here, since the set time is set in advance based on the vehicle speed of the wheel loader 1 and the distance between the front wheels 5 and the rear wheels 7, it takes time for the front wheels 5 to climb over the bump and for the rear wheels 7 to climb over the bump. During this period, the deceleration control of the engine 100 can be reliably performed.

In addition, since the engine speed is reduced as the differential pressure 404 of the accumulator 124 increases (see FIG. 13), the spillage of earth and sand from the bucket 3 is further prevented.

Further, when the differential pressure 404 of the accumulator 124 acquired this time is larger than the differential pressure acquired last time, the engine speed is decelerated as the differential pressure 404 becomes larger, and the differential pressure 404 acquired this time is less than or equal to the differential pressure 404 acquired last time. In the case of , the engine speed corresponding to the differential pressure 404 obtained last time is maintained (see FIG. 14), so that dirt and the like are further prevented from falling from the bucket 3 .

As described above, according to the present embodiment, when the earth and sand are scooped into the bucket 3 and transported, the earth and sand from the bucket 3 do not need to be finely adjusted by the operator even when traveling on a road surface with continuous steps. etc. can be prevented from spilling. Therefore, the operation of the transportation work is facilitated, and the working efficiency of an inexperienced operator is improved.

In addition, the present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the gist of the present invention. subject of the present invention. Although the above embodiments show preferred examples, those skilled in the art can realize various alternatives, modifications, variations or improvements from the contents disclosed in this specification, These are included in the technical scope described in the appended claims.

For example, if the present invention is applied to an unmanned wheel loader that carries out transportation work remotely without an operator on board, when the wheel loader runs on a running road surface with continuous unevenness, earth and sand in the bucket will spill out. can be prevented. That is, the present invention is also suitable for an unmanned wheel loader.

In the above-described embodiment, the driving force of the engine 100 is transmitted to the wheels 5 and 7 via the torque converter 101 and the transmission 107, but the present invention employs a so-called HST (Hydro Static Transmission) type It can also be applied to wheel loaders.

1 wheel loader 2 working machine 3 bucket 5 front wheel 6 front frame (vehicle body)
7 rear wheel 8 rear frame (body)
11 lift arm 12 lift arm cylinder 12b bottom chamber (hydraulic chamber)
16 bucket cylinder 18 lift arm angle sensor (angle sensor)
100 engine 101 torque converter 104 engine controller (control device)
107 transmission 109 transmission controller 121 main controller (control device)
124 Accumulator 126 Running vibration suppression control switch 205 Accumulator pressure sensor (pressure sensor)

Claims (5)

A vehicle body to which front and rear wheels are attached, a bucket provided in the front part of the vehicle body, a lift arm holding the bucket, a lift arm cylinder for driving the lift arm, and a drive source for the vehicle body. A wheel loader equipped with an engine and a control device for controlling the rotation speed of the engine,
an angle sensor that detects the angle of the lift arm;
an accumulator connected to the hydraulic chamber of the lift arm cylinder and capable of flowing pressure oil into and out of the hydraulic chamber;
and a pressure sensor that detects the pressure of the accumulator,
The control device is
When the angle of the lift arm detected by the angle sensor satisfies the deceleration control condition for decelerating the rotation speed of the engine, the rotation of the engine is based on the pressure of the accumulator detected by the pressure sensor. A wheel loader characterized by decelerating numbers. In the wheel loader according to claim 1,
The control device is
calculating the differential pressure between the previous pressure of the accumulator detected by the pressure sensor and the current pressure of the accumulator detected by the pressure sensor;
When the differential pressure exceeds a set pressure, deceleration of the engine speed is started, and when the differential pressure becomes equal to or less than the set pressure and a set time elapses, the deceleration of the engine speed is finished. A wheel loader characterized by: In the wheel loader according to claim 2,
A wheel loader, wherein the set time is predetermined based on a vehicle speed of the wheel loader and a distance between the front wheels and the rear wheels. In the wheel loader according to claim 1,
The control device is
A differential pressure between the previous accumulator pressure detected by the pressure sensor and the current accumulator pressure detected by the pressure sensor is calculated. A wheel loader characterized by slowing down the In the wheel loader according to claim 4,
The control device is
When the differential pressure acquired this time is greater than the differential pressure acquired last time, the rotational speed of the engine is reduced as the differential pressure increases, and when the differential pressure acquired this time is less than or equal to the differential pressure acquired last time. maintains the rotational speed of the engine corresponding to the previously obtained differential pressure.

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