JP2020076221A - Construction machine - Google Patents

Abstract

To provide a construction machine capable of suppressing a reduction in the speed of a work machine at the time of the selection of a crane mode to set an engine speed to be lower.SOLUTION: The construction machine includes a travel motor and a work machine actuator using a variable displacement pump 51 as a hydraulic power source, a revolving motor 44 using a fixed displacement pump 52 as a hydraulic power source, a pump regulator 51a for controlling the discharge flow amount of the variable displacement pump 51, a solenoid proportional valve 51c for generating a pressure signal to be input to the pump regulator 51a, a controller 70 for transmitting a control command to be input to the solenoid proportional valve 51c, and a pressure sensor 51h for converting a negative control pressure generated at the upstream of negative control throttles 51f, 51g into an electric signal to be output to a controller 70. When the crane mode is selected, the controller 70 reduces the target speed of an engine 42 and increases the discharge flow amount of the variable displacement pump 51.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a construction machine.

  In Patent Document 1 below, in a hydraulic excavator that can be switched between a shovel specification and a crane specification, and the discharge amount of a hydraulic pump is controlled by negative control, when a turning operation is detected in a state where the specification is switched to a crane specification, the pump tilts. A technique is disclosed in which a discharge amount of a hydraulic pump is changed to a small flow rate by introducing a pressure oil larger than a negative control pressure into a hydraulic cylinder for changing a turning angle.

  In the following Patent Document 2, in the backhoe configured to be able to switch between the excavation work mode and the crane mode, when the crane mode is selected, the maximum rotation speed for the crane mode is set lower than the normal maximum rotation speed. A technique for automatically setting the engine speed is disclosed.

JP, 2003-293400, A JP 2002-294760 A

  In Patent Document 1, since the flow rate of the pressure oil of the swing motor, the working machine, and the traveling motor is controlled by the variable displacement pump, when the crane is used, the working machine is also required if the pump flow rate is reduced to reduce the swing speed. As a result, the speed is reduced and the workability is deteriorated.

  In addition, when the technology of Patent Document 2 is applied to a construction machine including a fixed displacement pump that supplies pressure oil to a swing motor and a split flow type hydraulic pump that supplies pressure oil to a working machine or a traveling motor, the engine speed is Since the flow rate of the fixed displacement pump decreases with the decrease of the rotation speed, the turning speed can be decreased, but the speed of the working machine is also decreased, which deteriorates the workability.

  Therefore, in view of the above problems, it is an object of the present invention to provide a construction machine capable of suppressing a reduction in the speed of a working machine when selecting a crane mode in which the engine speed is set to a low speed.

The construction machine according to the present invention is a construction machine capable of switching between an excavation mode in which a bucket is provided at the tip of a working machine and a crane mode in which a hook is provided at the tip of the working machine. ,
A mode selection device capable of selecting the crane mode,
A prime mover, a variable displacement pump and a fixed displacement pump driven by the prime mover, a traveling motor and a work machine actuator that use the variable displacement pump as a hydraulic source, and a swing motor that uses the fixed displacement pump as a hydraulic source. When,
A center bypass flow passage that communicates from the variable displacement pump to the oil tank through the directional switching valve when the directional switching valve that controls the flow rate and the direction of the pressure oil from the variable displacement pump is neutral, and the center. A negative control throttle arranged at the most downstream of the bypass flow path,
A pump regulator that controls the discharge flow rate of the variable displacement pump, a pressure signal generation device that generates a pressure signal that is input to the pump regulator, and a controller that issues a control command that is input to the pressure signal generation device, An electric signal generation device for converting a negative control pressure generated upstream of the negative control throttle into an electric signal and outputting the electric signal to the controller,
The controller has a target rotation speed setting unit that sets a target rotation speed of the prime mover, and a control command generation unit that multiplies the electric signal by a gain to generate the control command,
When the crane mode is selected by the mode selection device, the target rotation speed setting unit changes the target rotation speed from the first target rotation speed to the second target rotation speed lower than the first target rotation speed, The control command generation unit changes the gain so that the control command becomes a command for increasing the discharge flow rate of the variable displacement pump.

  According to the present invention, when the crane mode is selected, the target rotation speed of the prime mover is reduced to reduce the discharge flow rate of the fixed displacement pump, so that the speed of the swing motor using the fixed displacement pump as a hydraulic source is reduced. descend. When the target rotation speed of the prime mover is reduced, the discharge flow rate of the variable displacement pump also decreases, and the speed of the work machine actuator that uses the variable displacement pump as a hydraulic source also tries to decrease. It is possible to suppress a decrease in the speed of the work machine actuator by suppressing the decrease in the discharge flow rate of the variable displacement pump by changing the gain for the purpose of mechanical control.

It is a side view which shows the hydraulic excavator which concerns on this embodiment. It is a figure which shows the hydraulic circuit of the hydraulic shovel which concerns on this embodiment.

  Embodiments of the present invention will be described below with reference to the drawings.

[Structure of hydraulic excavator]
First, a schematic structure of a hydraulic excavator 1 as an example of a construction machine will be described with reference to FIG.

  The lower traveling body 2 is driven by receiving power from the engine 42 to drive the hydraulic excavator 1. The lower traveling body 2 includes a pair of left and right crawlers 21 and 21 and a pair of left and right traveling motors 22 and 22 (the right traveling motor 22 is not shown in FIG. 1). The left and right traveling motors 22, 22, which are hydraulic motors, respectively drive the left and right crawlers 21, 21 to enable the hydraulic excavator 1 to move forward and backward. Further, the lower traveling body 2 is provided with a blade 23 and a blade cylinder 24 which is a hydraulic actuator for rotating the blade 23 in the vertical direction.

  The work machine 3 receives power from the engine 42 and is driven to perform an excavation work such as earth and sand. The work machine 3 includes a boom 31, an arm 32, and a bucket 33, and drives them independently to enable excavation work. The boom 31, the arm 32, and the bucket 33 each correspond to a working unit, and the hydraulic excavator 1 has a plurality of working units.

  The boom 31 has its base end supported by the front of the upper swing body 4 and is rotated by a boom cylinder 31a that is movable in an extendable and contractible manner. The arm 32 has a base end supported by the tip of the boom 31 and is rotated by an arm cylinder 32a that is movable in a telescopic manner. The bucket 33 has its base end supported by the tip of the arm 32, and is rotated by a bucket cylinder 33a that is movable in an expandable and contractible manner. The boom cylinder 31a, the arm cylinder 32a, and the bucket cylinder 33a correspond to hydraulic actuators that drive the working unit.

  The bucket 33 is a container-like member that is provided at the tip of the work machine 3 and has a claw for performing excavation work. The bucket 33 is rotatably attached to the tip of the arm 32 via a pin 34. Further, the bucket 33 is connected to the bucket cylinder 33a via a link mechanism 35.

  A hook 36 for crane work is attached to the tip of the arm 32. The hook 36 is a hook-shaped member that performs crane work, and is rotatably provided on the link mechanism 35. The hook 36 is rotatably supported with the shaft of the link mechanism 35 as a fulcrum of rotation, and is arranged between a deployed state in which it is projected from the bucket 33 shown in FIG. 1 and a stored state in which the bucket 33 is stored. You can change the posture.

  The hydraulic excavator 1 can be switched between an excavation mode in which the hook 36 is stored and the excavation work is performed by the bucket 33, and a crane mode in which the hook 36 is deployed and the crane work is performed by the hook 36. The excavation mode and the crane mode are selected by the operator using a mode selection device (not shown).

  The upper revolving structure 4 is configured to be revolvable with respect to the lower traveling structure 2 via a revolving bearing (not shown). The upper revolving unit 4 is provided with a control unit 41, an engine 42, a revolving base 43, a revolving motor 44, and the like. The upper revolving structure 4 revolves through a revolving bearing by the driving force of a revolving motor 44 which is a hydraulic motor. The upper swing body 4 is provided with a plurality of hydraulic pumps (not shown in FIG. 1) driven by the engine 42. These hydraulic pumps supply pressure oil to the traveling motors 22, 22, the swing motor 44, the boom cylinder 31a, the arm cylinder 32a, the bucket cylinder 33a, and the like.

  A pilot seat 411 is arranged in the pilot section 41. A pair of work operation levers 412 and 412 are arranged on the left and right of the cockpit 411, and a pair of travel levers 413 and 413 are arranged on the front side. The operator sits on the cockpit 411 and operates the work operation levers 412, 412, the travel levers 413, 413, etc. to control the engine 42, each hydraulic motor, each hydraulic actuator, etc. to travel, turn, Can perform work, etc.

[Structure of hydraulic circuit]
The hydraulic circuit 5 of the hydraulic excavator 1 will be described with reference to FIG. The hydraulic circuit 5 includes a first traveling motor 22a, a second traveling motor 22b (either the left traveling motor 22 or the right traveling motor 22), a first working machine actuator 30a, a second working machine actuator 30b, and a third working machine. Machine actuator 30c (boom cylinder 31a, arm cylinder 32a, bucket cylinder 33a), attachment motor 30d for hydraulic work attachment (hydraulic hammer, etc.), swing motor 44, variable displacement pump 51, fixed displacement pump 52, a pilot pump 53, and a controller 70.

  The variable displacement pump 51 and the fixed displacement pump 52 are driven by the engine 42 and are hydraulic actuators (first traveling motor 22a, second traveling motor 22b, first working machine actuator 30a, second working machine actuator 30b, The pressure oil supplied to the third working machine actuator 30c, the attachment motor 30d, and the turning motor 44) is discharged. The variable displacement pump 51 applies pressure oil to the first traveling motor 22a, the second traveling motor 22b, the first working machine actuator 30a, the second working machine actuator 30b, the third working machine actuator 30c, and the attachment motor 30d. Supply and drive. The fixed displacement pump 52 supplies pressure oil to the turning motor 44 to drive it.

  The variable displacement pump 51 can control the discharge flow rate of the pressure oil by changing the inclination angle of the movable swash plate 51b by driving the pump regulator 51a. The pump regulator 51a is driven by the pressure (pilot pressure) of the pilot oil discharged from the pilot pump 53.

  An electromagnetic proportional valve 51c (corresponding to a pressure signal generation device) is provided in an oil passage 53a between the pump regulator 51a and the pilot pump 53. The solenoid proportional valve 51c generates a pressure signal (pilot signal pressure) input to the pump regulator 51a. The solenoid proportional valve 51c can adjust the pilot signal pressure according to a control command from the controller 70.

  The variable displacement pump 51 is a so-called split flow type hydraulic pump including a first discharge port P1 and a second discharge port P2. The pressure oil discharged from the first discharge port P1 is supplied to the first traveling direction switching valve 55e and the attachment direction switching valve 55d, which will be described later, via the first center bypass oil passage 51d, and the second discharging port P2. The discharged pressure oil passes through the second center bypass oil passage 51e, and the first working machine directional switching valve 55a, the second working machine directional switching valve 55b, the third working machine directional switching valve 55c, and It is supplied to the second traveling direction switching valve 55f.

  A first negative control throttle 51f is provided on the most downstream side of the first center bypass oil passage 51d. The first negative control throttle 51f restricts the flow of the pressure oil flowing through the first center bypass oil passage 51d to generate the first negative control pressure upstream of the first negative control throttle 51f. Similarly, a second negative control throttle 51g is provided on the most downstream side of the second center bypass oil passage 51e. The second negative control throttle 51g restricts the flow of the pressure oil flowing through the second center bypass oil passage 51e to generate the second negative control pressure upstream of the second negative control throttle 51g.

  The pressure sensor 51h (corresponding to an electric signal generation device) detects the low-pressure side negative control pressure of the first negative control pressure and the second negative control pressure, converts the detected value into an electrical signal, and controls it as an electrical negative control pressure. Output to 70.

  The pressure oil discharged from the fixed displacement pump 52 is supplied to the turning direction switching valve 55g described later via the third center bypass oil passage 52a.

  The hydraulic actuators (first working machine actuator 30a, second working machine actuator 30b, third working machine actuator 30c, attachment motor 30d, first traveling motor 22a, second traveling motor 22b, turning motor 44) include: Corresponding directional switching valves 55 are provided, and the directional switching valve 55 is a pilot type directional switching valve capable of switching the direction and volume of the pressure oil to be pressure-fed from the variable displacement pump 51 and the fixed displacement pump 52 to the hydraulic actuator. Is. The direction switching valve 55 can be switched to a plurality of positions by sliding the spool. When the pilot signal pressure is not applied to any of the two pilot ports of the direction switching valve 55, the direction switching valve 55 is held at the neutral position by the biasing force of the spring. When the direction switching valve 55 is in the neutral position, the pressure oil is not supplied to the corresponding hydraulic actuator and passes through the first center bypass oil passage 51d, the second center bypass oil passage 51e, and the third center bypass oil passage 52a. Flows to the oil tank. On the other hand, when the pilot signal pressure is applied to any pilot port of the direction switching valve 55, the direction switching valve 55 is switched from the neutral position to another position, and the pressure oil is supplied to the corresponding hydraulic actuator. ..

  In the present embodiment, the first working machine directional switching valve 55a corresponding to the first working machine actuator 30a, the second working machine directional switching valve 55b corresponding to the second working machine actuator 30b, and the third working machine actuator 30c. Corresponding to the third working machine direction switching valve 55c, the attachment motor 30d corresponding to the attachment direction switching valve 55d, the first traveling motor 22a corresponding to the first traveling direction switching valve 55e, the second traveling motor A second traveling direction switching valve 55f corresponding to 22b and a turning direction switching valve 55g corresponding to the turning motor 44 are provided. These directional control valves are collectively called control valves.

  The pilot pump 53 mainly discharges pilot oil as a command input to the direction switching valve 55. However, in FIG. 2, the oil passage from the pilot pump 53 to the direction switching valve 55 is not shown. The pilot pump 53 is driven by the engine 42 and discharges pressure oil to generate pilot signal pressure in the oil passage.

  The controller 70 sends a control command to the solenoid proportional valve 51c. The operation of the solenoid proportional valve 51c is controlled by the controller 70, and the pilot signal pressure for the pump regulator 51a can be adjusted according to the magnitude of the applied control current value. That is, the control command is, for example, a control current value.

  The controller 70 includes a control command generator 71. The control command generation unit 71 multiplies the electric signal input from the pressure sensor 51h by a gain to generate a control command. By adjusting the magnitude of the gain and adjusting the control command, the pilot signal pressure applied to the pump regulator 51a can be adjusted. In the present embodiment, the electromagnetic proportional valve 51c reduces the flow rate of the pilot pressure oil supplied to the pump regulator 51a by increasing the magnitude of the gain and increasing the control command (the pilot applied to the pump regulator 51a. Reduce the signal pressure). At this time, the pump regulator 51a increases the discharge flow rate of the variable displacement pump 51.

  The controller 70 also includes a target rotation speed setting unit 72 that sets a target rotation speed of the engine 42. The controller 70 controls the rotation speed of the engine 42 so as to reach the target rotation speed set by the target rotation speed setting unit 72.

  A mode selection switch 81 (corresponding to a mode selection device) is electrically connected to the controller 70. The mode selection switch 81 is for the operator to select the crane mode. The mode selection switch 81 sends a crane mode command to the controller 70 when the crane mode is selected by the operator.

  When the crane mode is not selected by the mode selection switch 81, that is, in the excavation mode, the controller 70 sets the target rotation speed of the engine 42 to the first target rotation speed instructed by the operator or the like, and the pressure sensor The gain by which the electric signal input from 51h is multiplied is set to the first gain defined in advance. On the other hand, in the controller 70, when the crane mode is selected by the mode selection switch 81, the target rotation speed setting unit 72 changes the target rotation speed from the first target rotation speed to the second target rotation speed lower than the first target rotation speed. The control command generation unit 71 is configured to change the gain so that the control command becomes a command to increase the discharge flow rate of the variable displacement pump 51. In the present embodiment, the control command generator 71 is configured to change the gain from the first gain to the second gain higher than the first gain.

  According to the hydraulic excavator 1 of the present embodiment, when the crane mode is selected, the fixed displacement pump 52 is hydraulically operated by lowering the target rotation speed of the engine 42 and decreasing the discharge flow rate of the fixed displacement pump 52. The speed of the swing motor 44 serving as the source decreases. When the target rotation speed of the engine 42 is reduced, the discharge flow rate of the variable displacement pump 51 is also reduced, and the speed of the working machine actuator that uses the variable displacement pump 51 as a hydraulic power source is also reduced. By suppressing the decrease in the discharge flow rate of the variable displacement pump 51 by increasing the gain for electrically controlling the discharge flow rate, it is possible to suppress the decrease in the speed of the working machine actuator. Therefore, when selecting the crane mode in which the engine speed is set to a low speed, it is possible to suppress a decrease in the speed of the work machine.

[Other Embodiments]
A mode adjusting device (not shown) may be electrically connected to the controller 70. The mode adjustment device is a device capable of adjusting the amount of change in gain changed by the control command generator 71. By adjusting the magnitude of the second gain, the operator can arbitrarily adjust the speed of the work implement actuator.

  Although the embodiments of the present invention have been described above with reference to the drawings, it should be considered that the specific configurations are not limited to these embodiments. The scope of the present invention is shown not only by the above description of the embodiments but also by the claims, and further includes meanings equivalent to the claims and all modifications within the scope.

DESCRIPTION OF SYMBOLS 1 hydraulic excavator 2 lower traveling body 3 working machine 4 upper revolving body 5 hydraulic circuit 22a first traveling motor 22b second traveling motor 30a first working machine actuator 30b second working machine actuator 30c third working machine actuator 30d for attachment Motor 36 Hook 42 Engine 44 Swing Motor 51 Variable Displacement Pump 51a Pump Regulator 51c Electromagnetic Proportional Valve 51d First Center Bypass Oil Path 51e Second Center Bypass Oil Path 51h Pressure Sensor 52 Fixed Displacement Pump 53 Pilot Pump 55 Directional Change Valve 70 Controller 71 Control command generation unit 72 Target rotation speed setting unit 81 Mode selection switch

Claims (2)

In a construction machine capable of switching between an excavation mode for performing excavation work with a bucket provided at the tip of the working machine and a crane mode for performing crane work with a hook provided at the tip of the working machine,
A mode selection device capable of selecting the crane mode,
A prime mover, a variable displacement pump and a fixed displacement pump driven by the prime mover, a traveling motor and a work machine actuator that use the variable displacement pump as a hydraulic source, and a swing motor that uses the fixed displacement pump as a hydraulic source. When,
A center bypass flow passage that communicates from the variable displacement pump to the oil tank through the directional switching valve when the directional switching valve that controls the flow rate and the direction of the pressure oil from the variable displacement pump is neutral, and the center. A negative control throttle arranged at the most downstream of the bypass flow path,
A pump regulator that controls the discharge flow rate of the variable displacement pump, a pressure signal generation device that generates a pressure signal that is input to the pump regulator, and a controller that issues a control command that is input to the pressure signal generation device, An electric signal generation device for converting a negative control pressure generated upstream of the negative control throttle into an electric signal and outputting the electric signal to the controller,
The controller has a target rotation speed setting unit that sets a target rotation speed of the prime mover, and a control command generation unit that multiplies the electric signal by a gain to generate the control command,
When the crane mode is selected by the mode selection device, the target rotation speed setting unit changes the target rotation speed from the first target rotation speed to the second target rotation speed lower than the first target rotation speed, The construction machine, wherein the control command generation unit changes the gain so that the control command becomes a command for increasing a discharge flow rate of the variable displacement pump. The construction machine according to claim 1, further comprising a mode adjustment device capable of adjusting a change amount of the gain changed by the control command generation unit.

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