JP7824906B2 - Work machinery - Google Patents

Description

The present invention relates to a work machine with excellent driving and steering performance.

In a known work machine, such as a hydraulic excavator, stable travel steering is ensured by arranging left and right travel control valves with meter-in throttles and left and right pressure compensation valves in left and right travel hydraulic supply lines into which oil flows from a single hydraulic pump. (See Patent Document 1.)

In recent years, there has been a demand for reduced manufacturing costs for hydraulic excavators, and there is also a demand for simplified configurations for the control valves that control each actuator to reduce manufacturing costs.

Japanese Patent Application Laid-Open No. 2006-336731

It is conceivable to remove the pressure compensation valves from the left and right travel hydraulic supply oil lines in order to reduce manufacturing costs, but when the work machine is made to make gentle turns by simultaneously driving the left and right travel motors at different speeds, the load on the outer travel motor, which should be faster, increases, causing oil to flow into the inner travel motor, which should be under a lower load, reducing the speed difference between the left and right travel motors and causing the work machine to be unable to turn sufficiently.

In order to solve the above problem, stable driving and steering performance can be ensured by supplying oil from two independent pumps to the left and right driving hydraulic supply oil lines, but this is not a simple configuration and manufacturing costs cannot be reduced.

The present invention was developed in consideration of the problems with the prior art described above, and its objective is to provide a work machine that can ensure stable driving and steering performance using a control valve with a simple configuration.

In order to solve the above-mentioned problems, the present invention provides a work machine comprising a pair of left and right travel motors through which hydraulic oil discharged from a hydraulic pump flows, a pair of directional control valves that control the flow rate of the hydraulic oil flowing to the pair of left and right travel motors by increasing or decreasing the opening area of the spool, and a pair of control levers that are tilted forward or backward to increase or decrease the opening area of the spool of the directional control valve in the corresponding direction based on the amount of operation, and the work machine is equipped with a control device that executes a first control that reduces the amount of increase in the opening area of the spool based on the amount of operation of one of the pair of control levers with a smaller amount of operation when the pair of control levers are tilted in the same direction by different amounts of operation.

The present invention provides a work machine that can ensure stable driving and steering performance using a control valve with a simple configuration.

1 is a perspective view of a hydraulic excavator according to an embodiment of the present invention. 1 is a schematic diagram of a control system for a hydraulic excavator according to an embodiment of the present invention. FIG. 2 is a flowchart of a control flow for a hydraulic excavator according to an embodiment of the present invention. FIG. 10 is a schematic diagram of a control system for a hydraulic excavator according to another embodiment of the present invention. FIG. 10 is a flowchart of a control flow for a hydraulic excavator according to another embodiment of the present invention.

Hereinafter, a hydraulic excavator 100 will be described in detail as a representative example of a work machine according to the present invention, with reference to Figure 1. Note that the direction in which the work device 400 is arranged on the upper rotating body 300 is referred to as the front, and the opposite direction is referred to as the rear.

The hydraulic excavator 100 is composed of a self-propelled lower traveling body 200, an upper rotating body 300 rotatably supported on the lower traveling body 200, a working device 400 supported in front of the upper rotating body 300 so that it can rotate up and down, and a control system 500.

The working device 400 is composed of a swing post 410 supported at the tip of the upper rotating body 300 so as to rotate horizontally, a boom 420 supported on the swing post 410 so as to be rotatable up and down, an arm 430 attached to the tip of the boom 420 so as to be rotatable up and down, a bucket 450 attached to the tip of the arm 430 so as to be rotatable up and down, a swing cylinder (not shown) installed below the upper rotating body 300 and which rotates the swing post 410 horizontally, a boom cylinder 460 installed in front of and below the boom 420 and which moves the boom 420, an arm cylinder 470 installed above the boom 420 and which moves the arm 430, and a bucket cylinder 480 installed in front of the arm 430 and which moves the bucket 450 via a bucket link 440.

The lower traveling body 200 has a center frame 210 and side frames 211a, 211b that are paired symmetrically and extend in the fore-and-aft direction. A drive wheel 212a driven by a left traveling motor 516a is mounted at the rear end of the left side frame 211a, and multiple idler wheels 213a are arranged facing forward. Tracks 214a are wound around the drive wheel 212a and idler wheels 213a. A drive wheel 212b (not shown) driven by a right traveling motor 516b is mounted at the rear end of the right side frame 211b, and multiple idler wheels 213b (not shown) are arranged facing forward. Tracks 214b are wound around the drive wheel 212b and idler wheels 213b. An earth removal device 220 is attached to the front of the center frame 210.

The upper rotating body 300 is composed of a counterweight 310 installed at the rear end, a body frame 320 extending forward from the counterweight 310, a driver's seat 330 located between the counterweight 310 and a swing post 410 installed at the tip of the body frame 320, and an engine room 340 located below a seat 331 located behind the driver's seat 330.

The driver's seat 330 is formed from an operating device 332, a seat 331, and a floor material 333 that extends forward from the front wall of the engine room 340 below the seat 331 and is formed above the aircraft frame 320.

The engine room 340 is equipped with several pieces of equipment, including an engine (not shown), a variable displacement pump 511 that is driven by the engine and pumps hydraulic oil to several actuators that move the hydraulic excavator 100, such as the boom cylinder 460 and arm cylinder 470, a control valve 514 that is located below the floor material 333 and controls the several actuators, and a pilot pump 512 that generates a control signal pressure (pilot pressure) input to the control valve 514 and a primary pressure of the pilot pressure that is input to a regulator 511a that controls the flow rate of the variable displacement pump 511.

The operating device 332 can operate each actuator via the control device 520 by outputting the operating direction and amount as an electrical signal.

The operating device 332 is arranged in a row on the left and right in front of the driver's seat 330 and consists of a left travel lever 332a and a right travel lever 332b that protrude from the floor material 333, and a left operating lever 332c and a right operating lever 332d that are erected in console boxes located on the left and right of the seat 331 and are used to operate or rotate the work machine 400.

By tilting the operating lever forward or backward, the left travel lever 332a and the right travel lever 332b rotate the left travel motor 516a and the right travel motor 516b so that the lower traveling body 200 moves in the direction where the soil removal device 220 is installed, or in the opposite direction.

Next, the control system 500 for the hydraulic excavator 100 will be described using Figure 2.

The control system 500 consists of a hydraulic circuit 510, a control device 520, and an operating device 332.

The hydraulic circuit 510 is shown with a solid line representing the high-pressure hydraulic oil piping extending from the variable displacement pump 511, and a dotted line representing the low-pressure hydraulic oil (pilot pressure) piping extending from the pilot pump 512.

Hydraulic circuit 510 consists of a center bypass flow path 513 extending from variable displacement pump 511 and a control valve 514 consisting of a directional control valve that controls each actuator connected to the oil passage extending from center bypass flow path 513.Hydraulic circuit 510 is a so-called closed center circuit in which no flow path connecting center bypass flow path 513 to tank 515 is formed regardless of the sliding position of the spool of the directional control valve, but is not limited to this.

The control valve 514 consists of a directional control valve 514a that controls the left travel motor 516a, a directional control valve 514b that controls the right travel motor 516b, and multiple other directional control valves that respectively control multiple other actuators; the multiple other actuators and multiple other directional control valves are not shown in the hydraulic circuit 510.

Reduced pilot pressure is input from electromagnetic proportional valves 517a1 and 517a2 to pilot pressure input ports 514a1 and 514a2 of directional control valve 514a in accordance with the direction and amount of operation (tilt amount) of left travel lever 332a, causing the spool of directional control valve 514a to slide, and oil according to the opening amount of the corresponding spool flows to left travel motor 516a.

When the left travel lever 332a is tilted forward and operated, pilot pressure is input to the input port 514a1, causing the left travel motor 516a to rotate forward.

When the left travel lever 332a is tilted rearward and operated, pilot pressure is input to the solenoid proportional valve 514a2, causing the left travel motor 516a to rotate rearward.

Reduced pilot pressure is input from electromagnetic proportional valves 518b1 and 518b2 to pilot pressure input ports 514b1 and 514b2 of directional control valve 514b in accordance with the direction and amount of operation of right travel lever 332b, causing the spool of directional control valve 514b to slide, and oil according to the opening amount of the corresponding spool flows to right travel motor 516b.

When the right travel lever 332b is tilted forward, pilot pressure is input to the input port 514b1, causing the left travel motor 516b to rotate forward.

When the right travel lever 332b is tilted rearward, pilot pressure is input to the input port 514b2, causing the left travel motor 516b to rotate rearward.

The variable displacement pump 511, which supplies oil to the hydraulic circuit 510, controls the flow rate of hydraulic oil by inputting the pilot pressure reduced by the electromagnetic proportional valve 517c to the regulator 511a in accordance with the amount of operation of the operating device 332.

In other words, as the amount of operation of the operating device 332 decreases, the flow rate of the variable displacement pump 511 decreases, and as the amount of operation of the operating device 332 increases, the flow rate of the variable displacement pump 511 increases.

The control device 520 is an ECU (electronic control unit) and is composed of a signal input section consisting of an input buffer that converts the signal level of digital input signals and an AD converter that converts analog input signals into digital form, a calculation section 521 consisting of a microcomputer that calculates control variables from various input signals, and a signal output section consisting of an output driver that converts the output signal of the microcomputer into a drive signal that drives the actuator.

The signal input to the signal input section of the control device 520 is represented by a dashed line with an arrow pointing towards the control device 520, and is a signal detected from the operating device 332.

The signal output from the signal output unit of the control device 520 is output to the electromagnetic proportional valves 517a1, 517a2, 517b1, 517b2, and 517c.

The calculation unit 521 is composed of a pump flow rate calculation unit 522, a spool opening area calculation unit 523, and a driving operation amount correction calculation unit 524.

The pump flow rate calculation unit 522 calculates the oil flow rate required of the variable displacement pump 511 from the operation amount of the operating device 332 input to the signal input unit of the control device 520.

The oil flow rate required for the variable displacement pump 511 is calculated based on the amount of operation of the left travel lever 332a, right travel lever 332b, left operating lever 332c, and right operating lever 332d, etc.

The signal output unit controls the solenoid proportional valve 51 based on the calculation result of the pump required flow rate calculation unit 522.
7c.

The spool opening area calculation unit 523 calculates the opening amount of the spool of the directional control valve of the corresponding control valve 514 from the operation amount of the operating device 332 input to the signal input unit of the control device 520.

When the left travel lever 332a is tilted forward, a signal corresponding to the amount of operation is input to the signal input section of the control device 520, and the spool opening area calculation section 523 calculates the opening amount of the spool of the directional control valve 514a, which rotates the left travel motor 516a forward in accordance with the amount of operation.

The signal output unit outputs a signal to the electromagnetic proportional valve 517a1 based on the calculation results of the spool opening area calculation unit 523, causing the spool of the directional control valve 514a to slide. The left traveling motor 516a, into which oil flows according to the amount of spool opening, rotates forward, and the hydraulic excavator 100 swings to the right.

When the left travel lever 332a and the right travel lever 332b are simultaneously tilted forward by the same amount, a signal corresponding to that amount of operation is input to the signal input section of the control device 520.

The spool opening area calculation unit 523 calculates the opening amount of the spool of the directional control valve 514a, which rotates the left travel motor 516a forward in accordance with the amount of operation, and the opening amount of the spool of the directional control valve 514b, which rotates the right travel motor 516b forward in accordance with the amount of operation. Here, the opening amounts of the two spools calculated by the spool opening area calculation unit 523 are the same because the amount of operation is the same.

The signal output unit outputs the same amount of signal to the solenoid proportional valves 517a1 and 517b1 based on the calculation results of the spool opening area calculation unit 523.

The spools of directional control valves 514a and 514b slide the same amount, and the same amount of oil flows to left travel motor 516a and right travel motor 516b according to the opening amount of these spools. Travel motor 516a and right travel motor 516b rotate forward at the same speed, and the hydraulic excavator 100 moves straight ahead.

When the left travel lever 332a and right travel lever 332b are simultaneously tilted forward and operated, with the left travel lever 332a tilted more than the right travel lever 332b, the travel operation amount correction calculation unit 524 calculates a correction operation amount to make the operation amount of the right travel lever 332b, which has a smaller operation amount, even smaller.

The correction operation amount is calculated by subtracting the operation amount of the right travel lever 332b from the operation amount of the left travel lever 332a.

Here, if the operation amount when the travel lever is tilted forward to its maximum stroke is set to 100%, and the neutral position is set to 0%, if the difference between the operation amount of the left travel lever 332a and the operation amount of the right travel lever 332b is greater than 50%, the operation amount correction calculation unit 524 does not calculate the correction operation amount, and the spool opening area calculation unit 523 calculates the spool opening amount of the directional control valve 514b based on the operation amount of the right travel lever 332b, and the signal output unit outputs a signal to the solenoid proportional valve 517b1 based on the results of these calculations.

Furthermore, the method for calculating the correction operation amount is not limited to the above embodiment, and for example, the operation amount of the right travel lever 332b may be calculated by subtracting a value determined by a map from the value obtained by subtracting the operation amount of the right travel lever 332b from the operation amount of the left travel lever 332a.

The spool opening area calculation unit 523 calculates the spool opening amount of the directional control valve 514a, which rotates the left travel motor 516a in the forward direction according to the operation amount, and the spool opening amount of the directional control valve 514b, which rotates the right travel motor 516b in the forward direction according to the corrected tilt amount. In other words, the spool opening amount of the directional control valve 514b is calculated as a spool opening amount that is smaller than the spool opening amount calculated using the operation amount before correction.

The signal output unit outputs a signal to the electromagnetic proportional valve 517a1 and the electromagnetic proportional valve 517b1 based on the calculation results of the spool opening area calculation unit 523.

The spools of directional control valves 514a and 514b slide, and oil flows to left travel motor 516a and travel motor 516b according to the opening amount of these spools. Travel motor 516a rotates at a faster speed than right travel motor 516b, and the hydraulic excavator 100 performs a gentle turn to the right.

The right travel motor 516b receives an amount of oil based on a correction amount that reduces the amount of operation of the right travel lever 332b, which has a smaller operation amount. Therefore, even if, during a turn, an increase in the load on the outer left travel motor 516a causes some of the oil that should flow to the left travel motor 516a to flow to the right travel motor 516b, the difference in the amount of oil flowing to the left travel motor 516a and the right travel motor 516b can be maintained, and the speed difference between the left travel motor 516a and the right travel motor 516b can be maintained.

In addition, the variable displacement pump 511 can increase its discharge volume based on the amount of operation of the left travel lever 332a and the right travel lever 332b, making it possible to increase the speed difference between the left travel motor 516a and the right travel motor 516b.

With these configurations, stable driving and steering performance can be ensured using a control valve with a simple configuration.

Next, the control flow will be explained using Figure 3. Figure 3 is a flowchart related to the control method.

Initiate driving by simultaneously tilting the left and right travel levers 332a and 332b in one direction from the neutral position. (S1)

When the control device 520 determines that the difference in the tilt amount between the left travel lever 332a and the right travel lever 332b is 50% or less, where the maximum stroke is 100% and the neutral position is 0% (S2: YES), the control device 520 executes a first control to control the speed of the travel motor (the opening of the spool of the corresponding directional control valve) corresponding to the smaller travel lever, based on the amount of operation of either the left travel lever 332a or the right travel lever 332b, minus the difference in the amount of operation. The speed of the other travel motor (the opening of the spool of the other directional control valve) is controlled based on the amount of operation of the other travel lever. (S3)

If the difference in the amount of operation of the left travel lever 332a and the right travel lever 332b does not meet the specific condition (S2: NO), the control device 520 executes steady-state control, which controls the speed of the corresponding travel motor (the opening amount of the spool of the corresponding directional control valve) according to the amount of operation of the left travel lever 332a and the right travel lever 332b. (S6)

When the difference in the amount of operation of the travel lever 332a and the right travel lever 332b no longer meets the specified condition (S4), the first control is stopped (S5) and steady-state control is then executed (S6).

The control device 500 repeatedly executes the processes of steps S1 to S6 above. The flowchart shown in Figure 3 is merely an example, and processes may be added or omitted as appropriate, and the order of processes may be changed as appropriate.

Next, we will explain another embodiment of the present invention using Figure 4.

The other embodiment of Figure 4 has the same effect as the embodiment of Figure 2, so only the differences from the embodiment of Figure 2 will be explained.

The calculation unit 521 of the other embodiment in Figure 4 includes a pump flow rate correction calculation unit 525 in addition to the pump flow rate calculation unit 522, spool opening area calculation unit 523, and traveling operation amount correction calculation unit 524 of the other embodiment in Figure 2.

The pump flow rate correction calculation unit 525 calculates the correction operation amount for correcting the operation amount of the operating device 332, which is the reference value of the oil flow rate required for the variable displacement pump 511, from the difference between the operation amounts of the left travel lever 332a and the right travel lever 332b.

The correction operation amount is calculated by multiplying the difference in operation amount between the left travel lever 332a and the right travel lever 332b by a coefficient, but it may also be calculated from a map set for the difference in operation amount.

The pump flow rate correction calculation unit 525 calculates the oil flow rate required of the variable displacement pump 511 from the value obtained by adding the correction operation amount to the operation amount of the left travel lever 332a, right travel lever 332b, left operation lever 332c, right operation lever 332d, etc.

With these configurations, the speed difference between the left travel motor 516a and the right travel motor 516b can be increased, ensuring stable travel and steering performance with a control valve of simple configuration.

Next, the control flow for another embodiment will be explained using Figure 5. Figure 5 is a flowchart relating to the control method for another embodiment.

Initiate driving by simultaneously tilting the left and right travel levers 332a and 332b in one direction from the neutral position. (S6)

If the control device 520 determines that the difference in the amount of operation of the left travel lever 332a and the right travel lever 332b meets a specific condition (S7: YES), the control device 520 executes the first control and the second control, which increases the discharge flow rate of the variable displacement pump 511 based on the difference in the amount of operation of the left travel lever 332a and the right travel lever 332b. The speed of the other travel motor (the opening of the spool of the other directional control valve) is also controlled based on the amount of operation of the other travel lever. (S8)

If the difference in the amount of operation of the left travel lever 332a and the right travel lever 332b does not meet the specific condition (S9: NO), the control device 520 executes steady-state control, which controls the speed of the corresponding travel motor (the opening amount of the spool of the corresponding directional control valve) according to the amount of operation of the left travel lever 332a and the right travel lever 332b. (S11)

When the difference in the amount of operation of the travel lever 332a and the right travel lever 332b no longer meets the specified condition (S9), the first control and second control are stopped (S10) and steady-state control is then executed (S11).

The control device 500 repeatedly executes the processes of steps S6 to S11 described above. The flowchart shown in Figure 3 is merely an example, and processes may be added or omitted as appropriate, and the order of processes may be changed as appropriate.

The work machines according to the present embodiment and other embodiments described above can be specified as follows:

<Appendix 1> A work machine equipped with a pair of left and right travel motors through which hydraulic oil discharged from a hydraulic pump flows, a pair of directional control valves that control the flow rate of the hydraulic oil flowing to the pair of left and right travel motors by increasing or decreasing the opening area of the spool, and a pair of control levers that are tilted forward or backward to increase or decrease the opening area of the spool of the directional control valve in the corresponding direction based on the amount of operation, wherein the work machine is equipped with a control device that executes a first control that reduces the amount of increase in the opening area of the spool based on the amount of operation of one of the pair of control levers with a smaller amount of operation when the pair of control levers are tilted in the same direction but by different amounts of operation.

<Appendix 2> A work machine as described in Appendix 1, wherein the first control reduces the amount of increase in the opening area of the spool based on the amount of operation of one of the control levers, based on the difference between the amounts of operation of the pair of control levers.

<Appendix 3> A work machine as described in Appendix 1 or Appendix 2, wherein the first control is executed when the difference in the operation amount of the pair of operating levers is equal to or less than a specified value.

<Appendix 4> A work machine described in any one of Appendices 1 to 3, wherein the control device controls the flow rate of hydraulic oil discharged from the hydraulic pump based on the amount of operation of the pair of operating levers.

<Appendix 5> A work machine described in any one of Appendices 1 to 4, wherein the control device executes second control to increase the flow rate of hydraulic oil discharged from the hydraulic pump based on the difference between the amounts of operation of the pair of operating levers.

As a further modification, instead of a closed center circuit, the hydraulic circuit 510 may be an open center circuit in which the center bypass flow path communicates with the tank 515.

When the hydraulic circuit 510 is an open center circuit, the discharge flow rate of the variable displacement pump 511 is controlled by positive control or negative control in accordance with the amount of operation of the operating device.

The other embodiments, modifications, or various configurations described in the embodiments described above can be combined as appropriate.

Although the above description has been given using a hydraulic excavator as an example of a work machine, the work machine is not limited to a hydraulic excavator and may be other work machines such as a wheel loader or a compact track loader.

The above describes an embodiment of the present invention, but the scope of the present invention is not limited to this, and can be expanded or modified without departing from the spirit of the invention.

The present invention relates to a work machine and has industrial applicability.

100 Hydraulic excavator (work machine) 332a Left travel lever (operation lever) 332b Right travel lever (operation lever) 511 Variable displacement pump (hydraulic pump) 514a Directional switching valve 514b Directional switching valve 516a Left travel motor (travel motor) 516b Right travel motor (travel motor) 520 Control device

Claims (5)

A work machine equipped with a pair of left and right travel motors through which hydraulic oil discharged from a hydraulic pump flows, a pair of directional control valves that control the flow rate of the hydraulic oil flowing to the pair of left and right travel motors by increasing or decreasing the opening area of the spool, and a pair of control levers that are tilted forward or backward to increase or decrease the opening area of the spool of the directional control valve in the corresponding direction based on the amount of operation; and a control device that executes a first control that reduces the amount of increase in the opening area of the spool based on the amount of operation of one of the pair of control levers with a smaller amount of operation when the pair of control levers are tilted in the same direction but by different amounts of operation. A work machine according to claim 1, wherein the first control reduces the increase in the opening area of the spool based on the operation amount of one of the control levers based on the difference between the operation amounts of the pair of control levers. A work machine according to claim 2, wherein the first control is executed when the difference in the operation amount of the pair of operating levers is less than or equal to a specified value. A work machine as described in claim 3, wherein the control device controls the flow rate of hydraulic oil discharged from the hydraulic pump based on the amount of operation of the pair of operating levers. 5. The work machine according to claim 1, wherein the control device executes second control to increase the flow rate of hydraulic oil discharged from the hydraulic pump based on a difference between the amounts of operation of the pair of operation levers.