JP2015218537A - Construction machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a construction machine capable of properly traveling, regardless of the size of a travel load, even when executing combined operation including travel operation.SOLUTION: A shovel 1 comprises a travel rectilinear valve 11R, pressure sensors S3 and S4 for detecting a travel load and a controller 54 for controlling the travel rectilinear valve 11R. The travel rectilinear valve 11R comprises a first valve position 11R1 capable of supplying a hydraulic fluid discharged by a travel rectilinear valve hydraulic pump 10L to a left side travel hydraulic motor 42L and capable of supplying the hydraulic fluid discharged by a hydraulic pump 10R to a right side travel hydraulic motor 42R and a second valve position 11R2 capable of supplying the hydraulic fluid discharged by a hydraulic pump 10L to the left side travel hydraulic motor 42L and the right side travel hydraulic motor 42R. A controller 54 changes a switching speed between the valve positions of the travel rectilinear valve 11R in response to the size of the travel load when executing combined operation including travel operation.

Description

  The present invention relates to a construction machine provided with a straight traveling valve.

  Travel having a straight travel position that is a valve position that separates a travel system circuit composed of left and right travel control valves and a work machine system circuit composed of a work machine control valve when the work machine system actuator is operated during travel A construction machine having a straight valve is known (see Patent Document 1).

  In the traveling straight valve, when the two circuits are separated, the first main pump is communicated only with the left and right traveling control valves, and the second main pump is communicated with the work machine control valve. In addition, when the work implement actuator is slightly manipulated during running, this travel straight travel valve is located between the normal valve position and the straight travel position, and the travel system circuit and work implement system circuit are connected. Rather than completely separating, both the first main pump and the second main pump are communicated with the traveling system circuit and the work machine system circuit, respectively. This is to prevent a sudden decrease in the flow rate supplied to the traveling hydraulic motor and a shock during traveling.

JP 2012-36951 A

  However, the straight travel valve described above is used when the work machine actuator is finely operated during traveling, and when the traveling load pressure, which is the pressure of hydraulic oil flowing into the traveling hydraulic motor, is high, The hydraulic motor may not be driven properly. When the work machine load pressure, which is the pressure of the working oil flowing into the work machine system actuator, is lower than the traveling load pressure, most of the hydraulic oil discharged from each of the first main pump and the second main pump is on the low pressure side work machine system. This is because it flows into the actuator.

  In view of the above, it is desirable to provide a construction machine that can travel appropriately regardless of the travel load even when a complex operation including a travel operation is performed.

  In the construction machine according to the embodiment of the present invention, the hydraulic oil discharged from the first hydraulic pump can be supplied to the first traveling hydraulic motor and the first hydraulic actuator, and the hydraulic oil discharged from the second hydraulic pump is the first. A first valve position that can be supplied to the second traveling hydraulic motor and the second hydraulic actuator; hydraulic oil discharged from the first hydraulic pump can be supplied to the second traveling hydraulic motor; and the second hydraulic pressure A traveling straight valve having a second valve position that allows hydraulic oil discharged from the pump to be supplied to the first hydraulic actuator, a traveling load detector that detects a traveling load, and a control device that controls the traveling straight valve; The control device changes the switching speed between the valve positions of the straight travel valve according to the magnitude of the travel load when a composite operation including a travel operation is performed.

  By the above-described means, a construction machine that can travel appropriately regardless of the travel load even when a complex operation including a travel operation is performed is provided.

It is a side view which shows the structural example of the shovel which concerns on the Example of this invention. It is a circuit diagram which shows the structural example of the hydraulic system mounted in the shovel of FIG. It is a detailed view of a traveling straight valve. It is a figure which shows the state of the hydraulic system in case driving | running | working operation is performed independently. It is a figure which shows the state of a hydraulic system when combined operation of driving | running | working operation and arm closing operation is performed. It is a flowchart which shows an example of a stroke speed adjustment process. It is a figure which shows the relationship of various parameters in case the compound operation of driving | running | working operation and arm closing operation is performed. It is a figure which shows the typical situation which increases the switching speed of a driving | running | working straight travel valve.

  FIG. 1 is a side view showing a configuration example of a construction machine according to an embodiment of the present invention. In FIG. 1, an excavator 1 as a construction machine has an upper swing body 3 mounted on a crawler-type lower traveling body 2 via a swing mechanism so as to be rotatable around the X axis.

  Further, the upper swing body 3 includes a drilling attachment in the front center portion. The excavation attachment includes a boom 4, an arm 5, and a bucket 6, and includes a boom cylinder 7, an arm cylinder 8, and a bucket cylinder 9 as hydraulic actuators.

  FIG. 2 is a circuit diagram showing a configuration example of a hydraulic system mounted on the shovel of FIG. In FIG. 2, the high-pressure hydraulic line is indicated by a solid line, the pilot line is indicated by a broken line, and the electric signal line is indicated by a dotted line.

  The hydraulic pumps 10L and 10R are variable displacement pumps that are driven by a drive source such as an engine or an electric motor. In the present embodiment, the hydraulic pump 10L circulates the hydraulic oil to the hydraulic oil tank 22 through the center bypass conduit 30L that communicates with the control valves 11L to 15L. The hydraulic pump 10L can supply hydraulic oil to the control valves 11L to 15L through a parallel pipe 31L extending in parallel with the center bypass pipe 30L. Similarly, the hydraulic pump 10R circulates the hydraulic oil to the hydraulic oil tank 22 through the center bypass pipe line 30R that communicates with the control valves 11R to 15R. The hydraulic pump 10R can supply hydraulic oil to the control valves 11R to 15R through a parallel pipe line 31R extending in parallel with the center bypass pipe line 30R. Hereinafter, the hydraulic pump 10L and the hydraulic pump 10R may be collectively referred to as the “hydraulic pump 10”. The same applies to the other components configured by a pair of left and right.

  The control valve 11L switches the flow of hydraulic oil so as to supply hydraulic oil discharged from the hydraulic pump 10L to the hydraulic hydraulic motor 42L for left side traveling as a hydraulic actuator when the left side traveling lever 26L as an operating device is operated. It is a spool valve.

  The control valve 11R is a spool valve as a traveling straight valve. In the present embodiment, the travel straight valve 11R is a 4-port 2-position spool valve, and has a first valve position 11R1 and a second valve position 11R2. The straight travel valve 11R includes a pilot port 11Rp and a spring 11Rs that generates a force that opposes the force generated by the pilot pressure received at the pilot port 11Rp. The details of the straight travel valve 11R will be described later.

  The control valve 12L is a spool valve that switches the flow of hydraulic oil to supply hydraulic oil discharged from the hydraulic pump 10 to an optional hydraulic actuator (not shown).

  The control valve 12R switches the flow of hydraulic oil to supply the hydraulic oil discharged from the hydraulic pump 10 to the hydraulic motor 42R for right driving as a hydraulic actuator when the right driving lever 26R as the operating device is operated. It is a spool valve.

  The control valve 13L is hydraulic oil for supplying hydraulic oil discharged from the hydraulic pump 10 to the hydraulic hydraulic motor 44 for rotation as a hydraulic actuator when a swing operation lever (not shown) as an operation device is operated. It is a spool valve that switches the flow of the.

  The control valve 13R is a spool valve that switches the flow of hydraulic oil to supply hydraulic oil discharged from the hydraulic pump 10 to the bucket cylinder 9 when a bucket operating lever (not shown) as an operating device is operated. It is.

  The control valves 14 </ b> L and 14 </ b> R switch the flow of hydraulic oil to supply the hydraulic oil discharged from the hydraulic pump 10 to the boom cylinder 7 when a boom operation lever (not shown) as an operation device is operated. It is a spool valve. The control valve 14L additionally supplies hydraulic oil to the boom cylinder 7 when the boom operation lever is operated in the boom raising direction with a predetermined lever operation amount or more.

  The control valves 15L and 15R are spool valves that switch the flow of hydraulic oil to supply the hydraulic oil discharged from the hydraulic pump 10 to the arm cylinder 8 when the arm operation lever 26A as an operation device is operated. The control valve 15R additionally supplies hydraulic oil to the arm cylinder 8 when the arm operation lever 26A is operated with a predetermined lever operation amount or more.

  The center bypass pipes 30L and 30R are respectively provided with negative control throttles 20L and 20R between the control valves 15L and 15R located on the most downstream side and the hydraulic oil tank 22. Hereinafter, the negative control is abbreviated as “negative control”. The negative control throttles 20L and 20R generate a negative control pressure upstream of the negative control throttles 20L and 20R by restricting the flow of hydraulic oil discharged from the hydraulic pumps 10L and 10R.

  The pressure sensors S1 and S2 detect the negative control pressure generated upstream of the negative control throttles 20L and 20R, and output the detected value to the controller 54 as an electrical negative control pressure signal.

  The pressure sensors S3 and S4 are an example of a traveling load pressure detection unit, detect the discharge pressures of the hydraulic pumps 10L and 10R, and output the detected values to the controller 54 as electrical discharge pressure signals.

  The pressure sensors S5, S6, and S7 detect the pilot pressure generated by the left traveling lever 26L, the right traveling lever 26R, and the arm operation lever 26A, and output the detected values to the controller 54 as electrical pilot pressure signals. . Although illustration is omitted, the pilot pressure generated by the turning operation lever, boom operation lever, bucket operation lever, etc. is similarly detected by the corresponding pressure sensor, and each pressure sensor outputs the detected value to the electric pilot. It outputs to the controller 54 as a pressure signal.

  The controller 54 is a functional element that controls the hydraulic system, and is, for example, a computer including a CPU, RAM, ROM, NVRAM, and the like. In the present embodiment, the controller 54 is the operation content (for example, presence / absence of lever operation, lever operation direction, lever operation amount, etc.) of various operation devices based on the output of the operation content detection unit such as the pressure sensors S5 to S7. ) Is detected electrically. Note that the operation content detection unit may be configured by a sensor other than the pressure sensor, such as an inclination sensor that detects the inclination of various operation levers.

  Then, the controller 54 causes the CPU to execute programs corresponding to various functional elements that operate the electromagnetic valve 55 and the like according to the operation contents of the various operation devices.

  The electromagnetic valve 55 is a valve that operates according to a command output from the controller 54. In the present embodiment, the electromagnetic valve 55 is an electromagnetic pressure reducing valve that adjusts the traveling straight pilot pressure acting on the pilot port 11Rp of the traveling straight valve 11R according to the current command output by the controller 54. In this embodiment, the electromagnetic valve 55 adjusts the traveling straight pilot pressure using the hydraulic fluid discharged from the control pump 52 that is a fixed displacement pump.

  The pump regulators 40L and 40R are mechanisms for controlling the discharge amounts of the hydraulic pumps 10L and 10R. In the present embodiment, the pump regulators 40L and 40R control the discharge amounts of the hydraulic pumps 10L and 10R according to a command generated by the controller 54.

  For example, when none of the hydraulic actuators in the excavator 1 is operated, the hydraulic oil discharged from the hydraulic pumps 10L and 10R passes through the center bypass pipelines 30L and 30R to the negative control throttles 20L and 20R, and the negative control throttle 20L. , Increase negative control pressure generated upstream of 20R. In this case, the pump regulators 40L and 40R reduce the discharge amounts of the hydraulic pumps 10L and 10R according to a command generated by the controller 54 based on the negative control pressure signal. As a result, pressure loss (pumping loss) when hydraulic oil discharged from the hydraulic pumps 10L and 10R passes through the center bypass pipes 30L and 30R is suppressed.

  On the other hand, when any hydraulic actuator is operated, the hydraulic oil discharged from the hydraulic pumps 10L and 10R flows into the hydraulic actuator via a control valve corresponding to the hydraulic actuator. Therefore, the amount reaching the negative control throttles 20L and 20R decreases or disappears, and the negative control pressure generated upstream of the negative control throttles 20L and 20R decreases. In this case, the pump regulators 40L, 40R increase the discharge amount of the hydraulic pumps 10L, 10R, circulate sufficient hydraulic oil to each hydraulic actuator, and ensure the driving of each actuator.

  Further, when the discharge pressures of the hydraulic pumps 10L and 10R exceed a predetermined value determined according to the discharge amount, the pump regulators 40L and 40R cause the hydraulic pump 10L to respond to a command generated by the controller 54 based on the discharge pressure signal. The discharge amount of 10R is reduced. This is to prevent the absorption horsepower of the hydraulic pumps 10L and 10R from exceeding the output horsepower of the engine as the drive source.

  The pump regulators 40L and 40R use the negative control pressure upstream of the negative control throttles 20L and 20R, the discharge pressure of the hydraulic pump 10L, and the discharge pressure of the hydraulic pump 10R to hydraulically control the discharge amounts of the hydraulic pumps 10L and 10R. You may control to.

  Next, with reference to FIG. 3, the details of the straight travel valve 11R will be described. FIG. 3 is a detailed view of the straight travel valve 11R. Specifically, FIG. 3A is an enlarged view of the traveling straight valve 11R in the hydraulic system of FIG. FIG. 3B is a diagram showing the relationship between the traveling straight pilot pressure acting on the pilot port 11Rp of the traveling rectilinear valve 11R and the stroke of the traveling rectilinear valve 11R. FIG. 3C is a diagram showing the relationship between the opening areas of the four flow paths F1 to F4 in the travel straight valve 11R and the stroke of the travel straight valve 11R.

  As shown in FIG. 3A, the straight travel valve 11R is a 4-port 2-position spool valve, and has a first valve position 11R1 and a second valve position 11R2. Specifically, the first valve position 11R1 has a flow path F1 that communicates the hydraulic pump 10L and the parallel pipe line 31L, and a flow path F2 that communicates the hydraulic pump 10R and the control valve 12R. The second valve position 11R2 includes a flow path F3 that communicates the hydraulic pump 10R and the parallel pipe line 31L, and a flow path F4 that communicates the hydraulic pump 10L and the control valve 12R.

  The straight travel valve 11R includes a pilot port 11Rp and a spring 11Rs that generates a spring force that opposes the pilot force generated by the straight travel pilot pressure received at the pilot port 11Rp. Specifically, when the straight traveling pilot pressure increases and the pilot force exceeds the spring force, the straight traveling valve 11R moves (strokes) from the first valve position 11R1 to the second valve position 11R2. Further, the spring 11Rs is compressed and the spring force increases as the second valve position 11R2 moves, and the travel straight valve 11R stops its movement (stroke) when the pilot force and the spring force are balanced. Further, when the traveling straight pilot pressure decreases and the pilot force falls below the spring force, the traveling straight valve 11R moves (strokes) toward the first valve position 11R1. Further, as the movement (stroke) toward the first valve position 11R1 is increased, the spring 11Rs is expanded and the spring force is reduced. When the pilot force and the spring force are balanced, the traveling straight valve 11R stops the movement (stroke). .

  FIG. 3B is a diagram showing the above-described relationship, and the fact that the stroke amount of the travel straight valve 11R is the minimum stroke amount Kmin corresponds to the state in which the travel straight valve 11R is at the first valve position 11R1. The maximum stroke amount Kmax corresponds to the state in which the traveling straight valve 11R is in the second valve position 11R2. In this embodiment, the minimum stroke amount Kmin is zero [mm]. Further, when the travel straight travel pilot pressure acting on the pilot port 11Rp is the minimum travel straight travel pilot pressure PVmin, the travel straight travel valve 11R is in the first valve position 11R1, and when the travel straight travel pilot pressure PVmax is the maximum travel travel straight valve 11R, Indicates that the valve is in the two-valve position 11R2.

  FIG. 3C shows that the respective opening areas of the flow paths F1 to F4 change according to the change in the stroke amount of the straight travel valve 11R. Specifically, the flow path F1 and the flow path F2 are opened and the flow path F3 and the flow path F4 are closed when the travel straight valve 11R has the minimum stroke amount Kmin. Further, it indicates that the flow path F3 opens when the stroke amount of the travel straight valve 11R reaches the value K1, and the flow path F3 opens when the value reaches the value K2. In addition, the flow path F1 is closed when the stroke amount of the traveling straight valve 11R reaches the value K3, and the flow path F2 is closed when the stroke amount reaches the value K4.

  With this configuration, the controller 54 travels so that hydraulic oil is exclusively supplied from the hydraulic pump 10L to both the left traveling hydraulic motor 42L and the right traveling hydraulic motor 42R in order to improve the straight traveling performance of the lower traveling body 2. The rectilinear valve 11R can be switched to the second valve position 11R2. Specifically, when the left traveling hydraulic motor 42L, the right traveling hydraulic motor 42R and any other hydraulic actuator are operated simultaneously, that is, when a combined operation of the traveling operation and the upper object operation is performed. The controller 54 outputs a current command to the electromagnetic valve 55. Then, the controller 54 sets the traveling straight valve 11R to the second valve position 11R2, and the hydraulic oil discharged from the hydraulic pump 10L is supplied to both the left traveling hydraulic motor 42L and the right traveling hydraulic motor 42R. It should not be supplied to the hydraulic actuator. Note that the controller 54 does not output a current command to the solenoid valve 55 when the traveling operation is not performed or when the traveling operation is performed alone. Therefore, the traveling straight valve 11R is in the first valve position 11R1, and the hydraulic oil discharged from the hydraulic pump 10L is not allowed to flow into the right traveling hydraulic motor 42R, but the hydraulic oil discharged from the hydraulic pump 10R is discharged to the right traveling hydraulic motor. 42R.

  The “traveling operation” means a simultaneous operation of the left traveling hydraulic motor 42L and the right traveling hydraulic motor 42R. Further, in this embodiment, “traveling operation” means a case where the left traveling lever 26L and the right traveling lever 26R are simultaneously operated at full lever. The “full lever operation” means a lever operation performed with a predetermined operation amount or more, and the predetermined operation amount is, for example, an operation amount of 80% or more. The operation amount 100% corresponds to the operation amount when the operation lever is tilted to the maximum, and the operation amount 0% corresponds to the operation amount when the operation lever is neutral (when the operation lever is not operated). To do. The “upper object operation” means an operation of a hydraulic actuator other than the left traveling hydraulic motor 42L and the right traveling hydraulic motor 42R. Further, the “other hydraulic actuator” at this time is referred to as an upper actuator, the load pressure of the upper actuator is referred to as an upper load pressure, and the load pressure of the traveling hydraulic motor 42 is referred to as a traveling load pressure.

  4 and 5 are circuit diagrams of the hydraulic system corresponding to FIG. FIG. 4 shows the state of the hydraulic system when the traveling operation is performed alone. The thick solid line in FIG. 4 represents the flow of hydraulic oil flowing into the traveling hydraulic motor 42. FIG. 5 shows the state of the hydraulic system when a combined operation of a traveling operation and an arm closing operation is performed. 5 represents the flow of hydraulic oil flowing into the traveling hydraulic motor 42, and the thick dotted line represents the flow of hydraulic oil flowing into the arm cylinder 8.

  Further, as shown in FIG. 3C, the traveling straight valve 11R has a stroke amount not less than the value K2 and less than the value K3, that is, an intermediate position between the first valve position 11R1 and the second valve position 11R2. When in the valve position, all of the flow paths F1-F4 are at least partially opened. The straight travel valve 11R communicates the hydraulic pump 10L and the hydraulic pump 10R with the control valve 12R and the parallel pipe line 31L. Therefore, when the traveling straight valve 11R is in the intermediate valve position when the traveling operation and the upper object operation are performed, the hydraulic oil discharged from the hydraulic pump 10L and the hydraulic pump 10R has a low load pressure. It flows to the place. Therefore, when the upper load pressure is lower than the traveling load pressure, most of the hydraulic oil discharged from the hydraulic pump 10L and the hydraulic pump 10R flows into the upper actuator. As a result, sufficient hydraulic oil cannot be supplied to the traveling hydraulic motor 42, and the excavator may be decelerated or stopped.

  Therefore, the controller 54 controls the travel straight valve 11R according to the magnitude of the travel load so that sufficient hydraulic oil is supplied to the travel hydraulic motor 42 even when the travel load pressure is larger than the upper load pressure. The switching speed between the first valve position 11R1 and the second valve position 11R2 is changed.

  FIG. 6 is a flowchart showing an example of processing (hereinafter referred to as “stroke speed adjustment processing”) in which the controller 54 changes the stroke speed, which is the switching speed between the valve positions of the travel straight valve 11R, according to the magnitude of the travel load. is there. In the present embodiment, the controller 54 repeatedly executes this stroke speed adjustment process at a predetermined control period during the excavator operation.

  First, the controller 54 determines whether or not the excavator is traveling (step ST1). In this embodiment, the controller 54 determines whether or not the excavator is traveling based on the pilot pressures of the left traveling lever 26L and the right traveling lever 26R detected by the pressure sensors S5 and S6. The controller 54 may determine whether or not the excavator is traveling based on other detection values such as the rotational speeds of the left traveling hydraulic motor 42L and the right traveling hydraulic motor 42R. The controller 54 may determine that the vehicle is traveling only when both the left traveling lever 26L and the right traveling lever 26R are fully levered in the same direction.

  When it is determined that the excavator is not traveling (NO in step ST1), the controller 54 sets the traveling rectilinear valve 11R to the first valve position 11R1 (step ST2).

  On the other hand, if it is determined that the excavator is traveling (YES in step ST1), the controller 54 determines whether or not a combined operation of the traveling operation and the upper article operation has been performed (step ST3). Specifically, the controller 54 determines whether or not an upper operation has been performed based on the pilot pressure of the upper actuator operating lever detected by the pressure sensor. In the present embodiment, the controller 54 determines whether or not the arm operation has been performed based on the arm pilot pressure of the arm operation lever detected by the pressure sensor S7.

  If it is determined that the combined operation of the traveling operation and the upper article operation has not been performed (NO in step ST3), the controller 54 sets the traveling straight valve 11R to the first valve position 11R1 (step ST2).

  On the other hand, when it is determined that the combined operation of the traveling operation and the upper article operation has been performed (YES in step ST3), the controller 54 determines whether or not the traveling load pressure is less than the predetermined value TH1 (step ST4). . In this embodiment, the controller 54 determines that the traveling load pressure has a predetermined value TH1 based on at least one of the discharge pressure of the hydraulic pump 10L detected by the pressure sensor S3 and the discharge pressure of the hydraulic pump 10R detected by the pressure sensor S4. It is judged whether it is less than. The controller 54 uses a pressure sensor (not shown) to indicate the load pressure of the left traveling hydraulic motor 42L (the pressure of the hydraulic oil at the supply side port of the left traveling hydraulic motor 42L) or the load pressure of the right traveling hydraulic motor 42R. It may be detected directly, and it may be determined whether or not the traveling load pressure is less than a predetermined value TH1 based on the detected value. Further, the controller 54 determines the travel load pressure based on at least one of the discharge pressure of the hydraulic pump 10L, the discharge pressure of the hydraulic pump 10R, the load pressure of the left travel hydraulic motor 42L, and the load pressure of the right travel hydraulic motor 42R. It may be determined whether or not is less than a predetermined value TH1.

When it is determined that the traveling load pressure is less than the predetermined value TH1 (YES in step ST4), the controller 54 moves (strokes) the traveling straight valve 11R at a low load stroke speed (step ST5). Specifically, the controller 54 outputs a current command to the electromagnetic valve 55 to increase the traveling straight pilot pressure acting on the pilot port 11Rp of the traveling straight valve 11R. In this case, the controller 54 exerts a straight traveling pilot pressure multiplied by the predetermined low load fixed pressure gain G _L to quality goods pilot pressure from the control lever for quality goods actuator to the pilot port 11Rp. The predetermined low load fixed pressure gain _GL is, for example, a value obtained by dividing the maximum traveling straight traveling pilot pressure PVmax applicable to the pilot port 11Rp by the maximum upper pilot pressure PAmax that can be generated by the upper actuator operating lever. . The low load stroke speed is the stroke speed of the straight travel valve 11R determined by the straight travel pilot pressure derived as described above.

  When it is determined that the traveling load pressure is equal to or higher than the predetermined value TH1 (YES in step ST4), the controller 54 determines whether the traveling load pressure is equal to or higher than the predetermined value TH2 (> TH1) (step ST6). ).

When it is determined that the traveling load pressure is equal to or greater than the predetermined value TH2 (YES in step ST6), the controller 54 moves (strokes) the traveling straight valve 11R at a high load stroke speed (step ST7). Specifically, the controller 54 outputs a current command to the electromagnetic valve 55 and travels straight to a pressure value higher than the travel straight travel pilot pressure when the travel straight travel valve 11R is moved (stroked) at a low load stroke speed. Increase pressure. In this case, the controller 54 exerts a straight traveling pilot pressure multiplied by the predetermined high load fixed pressure gain G _H to quality goods pilot pressure to the pilot port 11Rp. The predetermined high load fixed pressure gain _GH is, for example, a value obtained by dividing the maximum traveling straight pilot pressure PVmax by a predetermined upper pilot pressure PA1. The predetermined upper pilot pressure PA1 is lower than the maximum upper pilot pressure PAmax. Further, the stroke speed at the time of high load increases as the predetermined upper pilot pressure PA1 decreases. The high load stroke speed is the stroke speed of the straight travel valve 11R determined by the straight travel pilot pressure derived as described above.

When it is determined that the traveling load pressure is less than the predetermined value TH2 (NO in step ST6), the controller 54 moves the traveling straight valve 11R at a medium load stroke speed (step ST8). Specifically, the controller 54 outputs a current command to the electromagnetic valve 55, travels at a stroke speed higher than the travel straight travel pilot pressure when the travel travel straight valve 11R is moved at a low load stroke speed, and at a high load stroke speed. The traveling rectilinear pilot pressure is increased to a pressure value lower than the traveling rectilinear pilot pressure when moving the rectilinear valve 11R. In this case, the controller 54 applies a traveling straight traveling pilot pressure obtained by multiplying the upper pilot pressure by a predetermined variable pressure gain to the pilot port 11Rp. The predetermined variable pressure gain is, for example, a value derived from the current traveling load pressure, and is larger than the low load fixed pressure gain _{GL and} smaller than the high load fixed pressure gain _GH . In this embodiment, the predetermined variable pressure gain, running load pressure from the low-load fixed pressure gain G _L when the travel load pressure is a predetermined value TH1 is to high load fixed pressure gain G _H when the predetermined value TH2 Increases in proportion to the traveling load pressure. The stroke speed at medium load is the stroke speed of the straight travel valve 11R determined by the straight travel pilot pressure derived as described above.

  Next, with reference to FIG. 7, the relationship between various parameters when a combined operation of a traveling operation and an arm closing operation is performed will be described. Specifically, FIG. 7A shows the relationship between the traveling straight advance pilot pressure and the arm pilot pressure as the upper pilot pressure, and FIG. 7B shows the stroke amount of the traveling straight valve 11R and the arm pilot pressure. Show the relationship. FIG. 7C shows the relationship between the pressure gain and the travel load pressure, and FIG. 7D shows the arm pilot pressure and the travel load necessary for setting the stroke amount of the travel straight valve 11R to the maximum stroke amount Kmax. The relationship with pressure is shown. The broken line in FIG. 7 shows the transition when the running load pressure is low (less than TH1), the alternate long and short dash line shows the transition when the medium load (TH1 or more and less than TH2), and the solid line shows the high load (TH2 or more). The transition at the time is shown.

As shown in FIG. 7A, the straight traveling pilot pressure is derived as a value obtained by multiplying the arm pilot pressure by a low load fixed pressure gain _GL when the load is low (see the broken line). Then, when the arm pilot pressure is the minimum arm pilot pressure PAmin, it becomes the minimum traveling straight pilot pressure PVmin, increases as the arm pilot pressure increases, and when the arm pilot pressure is the maximum arm pilot pressure PAmax, the maximum traveling rectilinear pilot pressure PVmax. It becomes. Further, in the case of a high load, the traveling straight pilot pressure is derived as a value obtained by multiplying the arm pilot pressure by a high pressure fixed pressure gain _GH (see a solid line). When the arm pilot pressure is the minimum arm pilot pressure PAmin, the minimum traveling straight pilot pressure PVmin is obtained. The arm traveling pressure increases as the arm pilot pressure increases, and when the arm pilot pressure is equal to or greater than a predetermined pressure value PA1, the maximum traveling straight pilot pressure is reached. PVmax. In addition, the straight traveling pilot pressure is derived as a value obtained by multiplying the arm pilot pressure by a predetermined variable pressure gain in the case of a medium load (refer to a one-dot chain line). When the arm pilot pressure is the minimum arm pilot pressure PAmin, the pilot travel pressure PVmin becomes the minimum travel straight travel pilot pressure PVmin. The arm pilot pressure increases as the arm pilot pressure increases, and the arm pilot pressure is determined according to the travel load pressure. When PA1 <PA2 <PAmax) or more, the maximum traveling straight pilot pressure PVmax is obtained. 7A indicates that the variable pressure gain, which is the slope of the transition indicated by the alternate long and short dash line, changes according to the traveling load pressure.

  Further, as shown in FIG. 7B, the stroke amount of the straight travel valve 11R shows the same tendency as the straight travel pilot pressure in relation to the arm pilot pressure. Specifically, in the case of a low load, when the arm pilot pressure is the minimum arm pilot pressure PAmin, the minimum stroke amount is Kmin, and increases as the arm pilot pressure increases, and when the arm pilot pressure is the maximum arm pilot pressure PAmax. The maximum stroke amount is Kmax. In the case of a high load, the minimum stroke amount Kmin is obtained when the arm pilot pressure is the minimum arm pilot pressure PAmin, increases as the arm pilot pressure increases, and the maximum stroke when the arm pilot pressure is equal to or higher than the predetermined pressure value PA1. The amount is Kmax. Further, in the case of a medium load, when the arm pilot pressure is the minimum arm pilot pressure PAmin, the minimum stroke amount Kmin is obtained. The arm pilot pressure increases as the arm pilot pressure increases, and the arm pilot pressure is determined according to the traveling load pressure. When the pressure is greater than or equal to PA2 (PA1 <PA2 <PAmax), the maximum stroke amount Kmax is obtained. In addition, the bidirectional arrow of FIG. 7 (B) represents that the inclination of the transition shown by the alternate long and short dash line changes according to the traveling load pressure, as in FIG. 7 (A).

Further, as shown in FIG. 7C, the pressure gain is constant at the low load fixed pressure gain _GL when the load is low, that is, when the traveling load pressure is less than TH1. In the present embodiment, the low load fixed pressure gain _GL is a value obtained by dividing the maximum traveling straight pilot pressure PVmax by the maximum arm pilot pressure PAmax. The pressure gain in the case of high load, i.e. the travel load pressure becomes constant at high load fixed pressure gain G _H when more than TH2. In the present embodiment, the high load fixed pressure gain _GH is a value obtained by dividing the maximum traveling straight traveling pilot pressure PVmax by a predetermined arm pilot pressure PA1. The pressure gain in the case of medium load, i.e. when the traveling load pressure is lower than TH1 or TH2, as travel load pressure increases, increases from low load fixed pressure gain G _L to high load fixed pressure gain G _H To do.

  Further, as shown in FIG. 7 (D), an arm required for setting the stroke amount of the traveling straight valve 11R to the maximum stroke amount Kmax, that is, for setting the traveling straight valve 11R to the second valve position 11R2. The pilot pressure (hereinafter referred to as “arm pilot pressure during maximum stroke”) is set to the maximum arm pilot pressure PAmax when the load is low, that is, when the traveling load pressure is less than TH1. On the other hand, when the load is high, that is, when the traveling load pressure is equal to or higher than TH2, the arm pilot pressure during the maximum stroke is set to a predetermined arm pilot pressure PA1 that is less than the maximum arm pilot pressure PAmax. In the case of a medium load, that is, when the traveling load pressure is greater than or equal to TH1 and less than TH2, the maximum stroke arm pilot pressure decreases from the maximum arm pilot pressure PAmax to a predetermined arm pilot pressure PA1 as the traveling load pressure increases. . Therefore, the relationship in FIG. 7D indicates that the traveling straight valve 11R becomes the second valve position 11R2 when the operation amount of the arm operation lever 26A is smaller as the traveling load pressure is higher.

  FIG. 8 is a diagram illustrating a typical situation in which the controller 54 increases the switching speed of the straight travel valve 11R. Specifically, FIG. 8 shows that when the excavator 1 tries to climb the slope with the propulsive force (running force) by the lower traveling body 2, the tip of the excavation attachment is applied on the slope to obtain the force for lifting the excavator 1. Indicates the situation. In this situation, since the traveling load pressure is higher than the upper load pressure, most of the hydraulic oil discharged from the hydraulic pump 10L and the hydraulic pump 10R flows into the upper actuator when the switching speed of the straight travel valve 11R is slow. End up. When most of the hydraulic fluid flows into the upper actuator, the rotation of the traveling hydraulic motor 42 is decelerated or stopped, and the traveling force is significantly reduced. As a result, the movement of the excavation attachment prevents the movement of the excavator 1 trying to climb the slope. However, the controller 54 increases the switching speed of the traveling straight valve 11R from the first valve position 11R1 to the second valve position 11R2 as the traveling load pressure increases. Therefore, the controller 54 prevents most of the hydraulic oil discharged from each of the hydraulic pump 10L and the hydraulic pump 10R from flowing into the upper actuator. Specifically, the controller 54 sets the traveling straight valve 11R to the second valve position 11R2 earlier, and the hydraulic oil discharged by the hydraulic pump 10L is used for the left traveling hydraulic motor even when the excavation attachment is moved. 42L and the right traveling hydraulic motor 42R are supplied. As a result, even when the excavation attachment is moved, the traveling hydraulic motor 42 is rotated at a desired speed to prevent the traveling force from being remarkably reduced, and the excavator 1 that tries to climb the slope is appropriately moved. Can continue.

  With the above configuration, the controller 54 can change the switching speed between the valve positions of the traveling straight valve 11R according to the magnitude of the traveling load. Therefore, even when a combined operation including a traveling operation is performed, the excavator can be appropriately traveled regardless of the travel load.

  For example, the controller 54 controls the electromagnetic valve 55 that can adjust the pilot pressure acting on the pilot port 11Rp of the traveling straight valve 11R to change the switching speed between the valve positions of the traveling straight valve 11R. Therefore, the controller 54 can adjust the straight traveling pilot pressure with a simple configuration.

  For example, when the traveling load pressure is equal to or greater than the predetermined value TH1, the controller 54 increases the switching speed between the valve positions of the traveling straight valve 11R as the traveling load increases. Specifically, the controller 54 controls the pilot pressure that acts on the straight travel valve 11R according to the magnitude of the operation of the upper actuator when a combined operation including the driving operation and the operation of the upper actuator is performed. The magnitude is determined, and the ratio of the magnitude of the straight traveling pilot pressure to the magnitude of the operation of the upper actuator is changed according to the magnitude of the running load. For example, the controller 54 determines the magnitude of the straight traveling pilot pressure according to the upper pilot pressure, and the pressure gain that is the ratio of the straight traveling pilot pressure to the upper pilot pressure according to the magnitude of the traveling load. To change. Therefore, the controller 54 prevents most of the hydraulic fluid discharged from the hydraulic pump 10L and the hydraulic pump 10R from flowing into the upper actuator even when the straight traveling valve 11R is in the intermediate valve position. it can. Further, in order to gradually increase the switching speed between the valve positions of the traveling straight valve 11R in accordance with an increase in the traveling load pressure, the occurrence of a shock due to a sudden decrease in the flow rate of the hydraulic oil supplied to the traveling hydraulic motor 42 is prevented. Can be prevented.

  In addition, the magnitude of the traveling load is, for example, at least one of the discharge pressure of the hydraulic pump 10L, the discharge pressure of the hydraulic pump 10R, the load pressure of the left traveling hydraulic motor 42L, and the load pressure of the right traveling hydraulic motor 42R. Detected based on one. Therefore, the controller 54 can grasp the traveling load of the shovel easily and accurately.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. Is possible.

  For example, in the above-described embodiment, the straight travel valve 11R is a pilot pressure driven hydraulic spool valve, but may be a solenoid valve. In the case of an electromagnetic valve, for example, the controller 54 adjusts the switching speed of the electromagnetic traveling straight valve by changing the magnitude of the current command for the electromagnetic traveling straight valve in accordance with the magnitude of the traveling load.

In the above-described embodiment, when the traveling load pressure is medium load, the predetermined variable pressure gain is the traveling load pressure between the low load fixed pressure gain _GL and the high load fixed pressure gain _GH. Increase proportionally. However, the present invention is not limited to this configuration. For example, the predetermined variable pressure gain may increase nonlinearly from the low load fixed pressure gain _GL to the high load fixed pressure gain _GH .

  DESCRIPTION OF SYMBOLS 1 ... Excavator 2 ... Lower traveling body 3 ... Upper turning body 4 ... Boom 5 ... Arm 6 ... Bucket 7 ... Boom cylinder 8 ... Arm cylinder 9 ... Bucket cylinder 10L, 10R ... Hydraulic pump 11L, 11R, 12L, 12R, 13L, 13R, 14L, 14R, 15L, 15R ... Control valve 20L, 20R ... Negacon throttle 22 ... Hydraulic oil tank 26A・ ・ ・ Arm operation lever 26L ・ ・ ・ Left travel lever 26R ・ ・ ・ Right travel lever 30L, 30R ・ ・ ・ Center bypass pipe 31L, 31R ・ ・ ・ Bypass pipe 40L, 40R ・ ・ ・ Pump regulator 42L, 42R ... Travel hydraulic motor 44 ... Turning hydraulic motor 52 ... Control pump 54 ... Control La 55 ... electromagnetic valve F1~F4 ··· flow path S1~S7 ··· pressure sensor

Claims (5)

The hydraulic oil discharged from the first hydraulic pump can be supplied to the first traveling hydraulic motor and the first hydraulic actuator, and the hydraulic oil discharged from the second hydraulic pump can be supplied to the second traveling hydraulic motor and the second hydraulic actuator. The first valve position to be supplied, the hydraulic oil discharged from the first hydraulic pump can be supplied to the second traveling hydraulic motor, and the hydraulic oil discharged from the second hydraulic pump is supplied to the first hydraulic pressure. A travel straight valve having a second valve position enabling supply to the actuator;
A travel load detector for detecting the travel load;
A control device for controlling the straight travel valve,
The control device changes the switching speed between the valve positions of the travel straight valve according to the magnitude of the travel load when a composite operation including a travel operation is performed.
Construction machinery. The control device controls an electromagnetic valve capable of adjusting a pilot pressure acting on the straight travel valve to change a switching speed between valve positions of the straight travel valve;
The construction machine according to claim 1. When the travel load is a predetermined value or more, the control device increases the switching speed between the valve positions of the travel straight valve as the travel load increases.
The construction machine according to claim 1 or 2. The travel load detection unit includes a discharge pressure of the first hydraulic pump, a discharge pressure of the second hydraulic pump, a load pressure of the first travel hydraulic motor, and a load pressure of the second travel hydraulic motor. Detecting a driving load based on at least one;
The construction machine according to any one of claims 1 to 3. The control device sets the size of the operation of the first hydraulic actuator or the second hydraulic actuator when a combined operation including a traveling operation and an operation of the first hydraulic actuator or the second hydraulic actuator is performed. In response, the magnitude of the pilot pressure acting on the straight travel valve is determined, and the ratio of the pilot pressure to the magnitude of the operation is changed according to the magnitude of the running load.
The construction machine according to any one of claims 1 to 4.

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