JP2006194321A - Hydraulic drive mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic drive mechanism having inexpensive system construction, wherein signal pressure in a road sensing system is used for selecting the operation or cancellation of automatic idling function. <P>SOLUTION: A signal pressure (maximum load pressure) valve device 52 in a signal line 37 is switched to apply pressure lower than the set pressure of a pilot relief valve 42 to a pressure sensor 53. A pressure value is set to be further lower than a set value for a main relief valve. As a result, the pressure proofing performance and the detecting performance of the pressure sensor 53 are both kept lower than in the case of directly detecting the maximum load pressure. The valve device 52 has a first pressure receiving portion 52a and a second pressure receiving portion 52c so that pressure on the upstream side of an oil cooler 38 and a return filter 39 is guided in opposition to the signal pressure in the signal line 37 to cancel the influences of pressure drop due to the oil cooler 38 and the return filter 39. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hydraulic drive apparatus for a construction machine such as a hydraulic excavator, and more particularly to a hydraulic drive apparatus having a load sensing system and an engine auto-idle function.

  A hydraulic drive device for a construction machine such as a hydraulic excavator has a load sensing system and an auto-idle function of an engine, for example, as disclosed in Japanese Patent Laid-Open No. 9-209409.

  According to this prior art, in the load sensing system, the highest load pressure, which is the highest pressure among the load pressures of a plurality of actuators, is detected and led to the regulator of the hydraulic pump as a signal pressure. The displacement of the hydraulic pump is controlled so as to be higher than the signal pressure (maximum load pressure) by a predetermined value.

  The auto idle function uses the fact that the signal pressure of the load sensing system becomes the tank pressure when all the directional control valves are in the neutral position. When the signal pressure becomes the tank pressure, the engine speed is reduced. ing.

JP-A-9-209409

  In the prior art, in the auto idle function, the maximum load pressure of the load sensing system is directly detected by a pressure sensor. For this reason, the pressure sensor requires pressure resistance performance of the set rated pressure value (main relief pressure) of the main circuit, and the pressure sensor must be expensive.

  In addition, when the operation lever is neutral (when the directional control valve is neutral) when the auto idle function is activated, the signal pressure (maximum load pressure) is the tank return pressure of the main return line. In the vicinity of the tank of the main return pipe, hydraulic equipment that causes pressure loss such as an oil cooler and a return filter is installed. For this reason, the signal pressure (maximum load pressure) when the control lever neutral is released (when the directional control valve neutral is released) is affected by the pressure loss, and becomes higher at low temperatures than at normal temperature. Therefore, when setting the threshold value for canceling the auto idle function, it is necessary to set the threshold value to a high value so that the valve device is reliably switched by the signal pressure at the low temperature.

  However, considering the increase in pressure loss at low temperatures, if the auto-idle function release threshold is set to a high value, the auto-idle function release timing at room temperature will be the operation timing that the operator intended (the operating lever was It is assumed that the timing is later than the timing, and the operator feels uncomfortable.

  SUMMARY OF THE INVENTION A first object of the present invention is to provide a hydraulic drive device capable of switching the operation and release of an auto idle function using the signal pressure in a load sensing system and having an inexpensive system configuration. It is.

  The second object of the present invention is to switch the operation and release of the auto-idle function using the signal pressure in the load sensing system, and cancel the influence of pressure loss on the signal pressure. In any case, when the neutral of the direction control valve is released, the auto-idle function is quickly released, and a hydraulic drive device that enables a smooth starting operation is provided.

  In order to solve the above problems, the present invention employs the following configuration.

  That is, the present invention provides a variable displacement hydraulic pump, an engine that drives the hydraulic pump, a plurality of actuators that are driven by the oil discharged from the hydraulic pump, and the hydraulic pump that supplies the plurality of actuators. A plurality of directional control valves for controlling the flow of pressure oil, a first detection means for detecting a highest load pressure, which is the highest pressure among the load pressures of the plurality of actuators, as a signal pressure, and a discharge pressure of the hydraulic pump A load sensing control regulator that controls the displacement of the hydraulic pump so that the pressure is higher than the signal pressure, and the engine idle speed is activated when the plurality of directional control valves are all in the neutral position. A pilot pressure generator for generating a pilot pressure in a hydraulic drive device comprising an auto idle means for lowering A circuit, a valve device that is operated by the signal pressure and switches the pressure on the output side to the pilot pressure and a pressure lower than the pilot pressure, second detection means for detecting the pressure on the output side of the valve device, And control means for switching the operation and release of the auto-idle function based on a change in pressure detected by the two detecting means.

  With this configuration, when the valve device is switched by the signal pressure and the pressure on the output side of the valve device changes and the detection pressure of the first detection means changes, the operation and release of the auto idle function are switched. When all the directional control valves are neutral and the signal pressure decreases, the auto idle function is activated to lower the engine speed, and when any directional control valve is neutral, the auto idle function It is possible to increase the engine speed by canceling. That is, the load sensing system can switch the operation and release of the auto idle function using the signal pressure.

  Further, the second detection means does not directly detect the signal pressure, but detects the pilot pressure that is the pressure on the output side of the valve device or a pressure lower than that, so both the pressure resistance performance and detection performance of the second detection means are The signal pressure (maximum load pressure) can be kept lower than when directly detected, the second detection means (pressure sensor) can be made inexpensive, and an inexpensive system configuration is possible.

  In the hydraulic drive device according to the present invention, the first detection unit is configured to communicate with a main return line when the plurality of directional control valves are all in a neutral position, and the main return line is The valve device includes an oil cooler and a return filter, and the valve device includes a first pressure receiving portion to which the signal pressure is guided, an urging unit provided facing the direction in which the signal pressure acts, and the urging unit. The oil cooler of the main return pipe and a second pressure receiving portion to which the pressure upstream of the return filter is guided, the signal pressure, the oil cooler of the main return pipe, and the return filter When the pressure difference from the upstream pressure becomes lower than the set value of the biasing means, the output pressure is switched from the pilot pressure to the low pressure.

  In this way, the valve device is provided with the first pressure receiving portion and the second pressure receiving portion, and the upstream side of the oil cooler and the return filter is guided opposite to the signal pressure, thereby canceling the influence of the pressure loss due to the oil cooler and the return filter. As a result, in both cases of normal temperature and low temperature, when neutralization of the directional control valve is canceled, the auto-idle function is quickly released, the engine speed increases, and a smooth start-up operation becomes possible.

  According to the present invention, operation and cancellation of the auto idle function can be switched using the signal pressure in the load sensing system, and an inexpensive system configuration is possible.

  Further, according to the present invention, the influence of pressure loss on the signal pressure is canceled, and the auto-idle function is quickly released when the neutral of the directional control valve is released at both normal temperature and low temperature, and smooth start-up operation is performed. Is possible.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a view showing a hydraulic drive apparatus according to an embodiment of the present invention.

  In FIG. 1, the hydraulic drive apparatus according to the present embodiment includes an engine 1, a variable displacement hydraulic pump 2 and a fixed displacement pilot pump 3 driven by the engine, and pressure oil discharged from the hydraulic pump 2. The plurality of actuators 5a, 5b, 5c, 5c, 5e driven by the cylinder and the plurality of closed center type directional control valves 7a for controlling the flow of pressure oil supplied from the hydraulic pump 2 to the plurality of actuators 5a to 5e, respectively. , 7b, 7c, 7d, 7e, a plurality of pressure compensating valves 12, 13, 14, 15, 16 that respectively control the differential pressure across the plurality of directional control valves 7a-7e, and the directional control valves 7a-7e and the pressure Load check valves 17a to 17e, which are arranged between the compensation valves 12 to 16 and prevent the backflow of pressure oil, and the discharge pressure of the hydraulic pump 2 has a plurality of actuators 5 A pump regulator 18 for load sensing control for controlling the tilting (displacement volume) of the hydraulic pump 2 to be higher by a predetermined value than the maximum load pressure of ˜5e, and a pump regulator 19 for limiting the absorption torque of the hydraulic pump 2 I have.

  The construction machine according to the present embodiment is, for example, a hydraulic excavator, the actuators 5a to 5d are, for example, a boom cylinder, an arm cylinder, a bucket cylinder, and a blade cylinder of the hydraulic excavator, and the actuator 5e is, for example, a swing motor of the hydraulic excavator.

  Although not shown, operation lever means for outputting an operation command signal is provided for each of the actuators 5a to 5e, and the plurality of directional control valves 7a to 7e are switched by the operation command signal.

  The direction control valves 7a to 7e also serve as flow rate control valves and incorporate meter-in throttles. The directional control valves 7a to 7e include self-load pressure detection lines 20 to 24, and the maximum load pressure among the load pressures detected by the detection lines 20 to 24 is the signal lines 25 to 29, the shuttle valves 30 to 33, and It is detected via the signal lines 34 to 36 and led to the signal line 37 as a signal pressure.

  When the direction control valves 7a to 7e are in the non-neutral position (operating position), the return oil from the actuators 5a to 5e is returned from the tank ports 8a to 8e of the direction control valves 7a to 7e to the respective return oil passages 9a to 9e. It is returned to the tank 11 through the main return line 10. An oil cooler 38 and a return filter 39 are provided in front of the tank 11 in the main return pipe 10. The detection lines 20 to 24 of the direction control valves 7a to 7e communicate with the tank ports 8a to 8e when the direction control valves 7a to 7e are in the neutral position, so that all the direction control valves 7a to 7e are in the neutral position. The signal pressure of the signal line 37 is configured to be the pressure upstream of the oil cooler 38 and the return filter 39 of the main return line 10.

  The pump regulator 18 for load sensing control is connected to a swash plate 2 a that is a variable capacity member of the hydraulic pump 2, and adjusts the tilt angle thereof, and the hydraulic chamber 40 a of the servo piston 40 and the pilot pump 3. A load sensing control valve (hereinafter referred to as an LS control valve) 41 for switching and controlling the connection between the discharge oil passage 3b and the tank 11 is provided. The discharge oil passage 3 b is provided with a pilot relief valve 42, and the pressure of the discharge oil passage 3 b is maintained at the set pressure of the pilot relief valve 42. The set pressure of the pilot relief valve 42 (pilot pressure of the discharge oil passage 3b) is, for example, about 40 kg / cm 2.

  The discharge pressure of the hydraulic pump 2 and the signal pressure of the signal line 37 (maximum load pressure) act on the LS control valve 41 as control pressures. When the pump discharge pressure becomes higher than the total pressure of the signal pressure (maximum load pressure) and the set value of the spring 41a (target LS differential pressure), the hydraulic chamber 40a of the servo piston 40 is connected to the discharge oil passage 3b of the pilot pump 3. Then, by guiding the pressure of the discharge oil passage 3b to the hydraulic chamber 40a, the piston 40b is moved to the left in the figure by overcoming the force of the spring 40c, and the inclination of the swash plate 2a is reduced to reduce the discharge flow rate of the hydraulic pump 2. cut back. On the contrary, when the pump discharge pressure becomes lower than the total pressure of the signal pressure (maximum load pressure) and the set value (target LS differential pressure) of the spring 41a, the hydraulic chamber 40a of the servo piston 40 is connected to the tank 11, and the hydraulic pressure is increased. By depressurizing the chamber 40a, the piston 40b is moved rightward in the figure by the force of the spring 40c, and the tilt of the swash plate 2a is increased to increase the discharge flow rate of the hydraulic pump 2. By such operation of the LS control valve, the pump discharge pressure becomes higher than the maximum load pressure by the set value of the spring 41a (target LS differential pressure), that is, the differential pressure between the discharge pressure of the hydraulic pump 2 and the maximum load pressure. Is maintained at the target LS differential pressure, the tilt (displacement volume) of the hydraulic pump 2 is controlled.

  The pump regulator 19 for limiting the absorption torque inputs the discharge pressure of the hydraulic pump 2 and controls the tilt of the swash plate 2a of the hydraulic pump 2 so that the absorption torque of the hydraulic pump 2 does not exceed the limit value.

  The pressure compensation valves 12 to 16 are respectively provided with a pair of pressure receiving portions 12a, 12b, 13a, 13b, 14a, 14b, 15a, 15b, 16a, 16b and another pair of pressure receiving portions 12c, 12d, 13c, 13d. , 14c, 14d, 15c, 15d, 16c, and 16d, and the pressure receiving portions 12a, 12c, 13a, 13c, 14a, 14c, 15a, 15c, 16a, and 16c are the sides that operate the pressure compensating valves in the closing direction. The pressure receiving portions 12b, 12d, 13b, 13d, 14b, 14d, 15b, 15d, 16b, and 16d are provided on the side that operates each pressure compensating valve in the opening direction.

  The pressure receiving portions 12a and 12b of the pressure compensating valve 12 are led to the upstream pressure and the downstream pressure (negative pressurization of the traveling motor 2 detected by the detection line 20) of the meter-in throttle portion of the direction control valve 7a. The pressure receiving parts 12c and 12d are supplied with the maximum load pressure derived from the signal line 37 and the discharge pressure of the hydraulic pump 2, and the pressure compensation valve 12 is supplied with the discharge pressure and maximum load of the hydraulic pump 2 guided to the pressure receiving parts 12c and 12d. The differential pressure between the upstream side and the downstream side of the meter-in throttle part of the directional control valve 7a guided to the pressure receiving parts 12a and 12b is controlled using the differential pressure from the pressure as the target compensation differential pressure (the differential pressure across the meter-in throttle part). To do. The same applies to the pressure compensation valves 13 to 16.

  The target compensation differential pressures of the pressure compensation valves 12 to 16 are all the same value of the differential pressure between the discharge pressure of the hydraulic pump 2 and the maximum load pressure, and the differential pressure between the discharge pressure of the hydraulic pump 2 and the maximum load pressure is Thus, the pump regulator 18 is controlled so as to maintain the target LS differential pressure. Thus, the same value of the differential pressure between the discharge pressure of the hydraulic pump 2 controlled by the pump regulator 18 and the maximum load pressure is set as the target compensation differential pressure of the pressure compensation valves 12-16, and the differential pressure across the directional control valves 7a-7e. The pressure oil discharged from the hydraulic pump 2 can be divided by the ratio of the opening areas of the direction control valves 7a to 7e regardless of the magnitude of the load pressure. In addition, when the discharge flow rate of the hydraulic pump 2 reaches a saturation state where the required flow rate is less than the required flow rate, the differential pressure between the discharge pressure of the hydraulic pump 2 and the maximum load pressure decreases according to the ratio of insufficient supply. The pressure oil discharged from the hydraulic pump 2 can be divided by the ratio of the opening areas of the control valves 7a to 7e.

  The hydraulic drive device according to the present embodiment further includes a throttle dial 51, a valve device 52, a pressure sensor 53, and a controller 54 as an engine control system provided with an auto idle means, and the engine 1 has an electronic governor 55. Is provided.

  The throttle dial 51 is operated by an operator to set a target rotational speed of the engine 1, and the operation signal is input to the controller 54. The valve device 52 is operated by the signal pressure of the signal line 37 (maximum load pressure), and the pressure on the output side is switched between the pressure of the discharge oil passage 3b of the pilot pump 3 (pilot pressure) and a pressure lower than this pressure, A first pressure receiving portion 52a connected to the signal line 37 to which the signal pressure is guided, a spring 52b which is an urging means provided facing the direction in which the signal pressure acts, and provided on the same side as the spring 52b And connected to the upstream side of the oil cooler 38 and the return filter 39 of the main return pipe line 10 through the oil path 56, and the pressure of the relevant part of the main return pipe line 10 (the upstream side of the oil cooler 38 and the return filter 39. And a second pressure receiving portion 52c through which pressure is guided. The input port of the valve device 52 is connected to the discharge oil passage 3 a of the pilot pump 3, and the output port is connected to the pressure sensor 53. The pressure sensor 53 detects the pressure at the output port of the valve device 52.

  When the differential pressure between the signal pressure of the signal line 37 and the pressure of the oil passage 56 (the pressure on the upstream side of the oil cooler 38 and the return filter 39 of the main return pipe 10) is higher than the set value of the spring 52b, the valve device 52 is When the differential pressure is lower than the set value of the spring 52b, the valve device 52 is switched from the illustrated position. When the valve device 52 is in the illustrated position, the discharge oil passage 3b is connected to the output port, and when the valve device 52 is switched from the illustrated position, the output port is connected to the tank 11. As a result, the valve device 52 has a differential pressure between the signal pressure of the signal line 37 and the pressure of the oil passage 56 (the pressure on the upstream side of the oil cooler 38 and the return filter 39 of the main return pipe 10) from the set value of the spring 52b. When the pressure becomes lower, the pressure of the output port is switched from the pressure of the discharge oil passage 3a (pilot pressure) to the pressure of the tank 11 (constant pressure), and the pressure detected by the pressure sensor 53 is switched from the pilot pressure to the tank pressure.

  Instead of the spring 52b, other urging means such as a pressure receiving portion to which a predetermined pressure is guided may be provided.

  The controller 54 inputs an operation signal of the throttle dial 51 and a detection signal of the pressure sensor 53, performs a predetermined calculation process, and outputs a target rotational speed signal to the electronic governor 55. Further, the controller 54 realizes an auto idle function for lowering the rotational speed of the engine 1 based on a change in pressure detected by the pressure sensor 53 (described later).

  FIG. 2 is a characteristic diagram showing the function of the valve device 52. The first quadrant in FIG. 1 is a differential pressure (hereinafter referred to as a corrected signal pressure) between the signal pressure of the signal line 37 (maximum load pressure) and the pressure of the oil passage 56 (pressure upstream of the oil cooler 38 and the return filter 39). And the spool stroke of the valve device 52 (corresponding to the displacement of the spring 52b), and the second quadrant shows the relationship between the spool stroke of the valve device 52 and the spool opening area on the input port side (pilot oil pressure side). The third quadrant shows the relationship between the spool opening area on the input port side (pilot oil pressure side) of the valve device 52 and the pressure on the output port side (pressure sensor side), and the fourth quadrant shows the correction signal pressure and the valve device 52. The relationship with the pressure on the output port side (pressure sensor side) is shown.

  In the first quadrant of FIG. 2, the spool stroke of the valve device 52 (corresponding to the displacement of the spring 52b) decreases from Smax to 0 as the correction signal pressure decreases. In the second quadrant, when the spool stroke of the valve device 52 is greater than the vicinity of Sa, the spool opening area on the input port side (pilot oil pressure side) is the maximum Amax, and the spool stroke of the valve device 52 decreases to the vicinity of Sa or less. The spool opening area on the input port side (pilot oil pressure side) is 0 (closed). In the third quadrant, when the spool opening area on the input port side (pilot oil pressure side) of the valve device 52 is the maximum Amax, the pressure on the output port side (pressure sensor side) is the pressure of the discharge oil passage 3a (pilot pressure). When the spool opening area on the input port side (pilot oil pressure side) of the valve device 52 is equal to or less than Aa corresponding to Sa, the pressure on the output port side (pressure sensor side) becomes the pressure (low pressure) of the tank 11. . In the fourth quadrant, when the corrected signal pressure is higher than Pca corresponding to Sa, the pressure on the output port side (pressure sensor side) is the pressure of the discharge oil passage 3a (pilot pressure), and when the corrected signal pressure becomes Sa or lower. The pressure on the output port side (pressure sensor side) becomes the pressure (low pressure) of the tank 11.

  Thus, the pressure control characteristic of the valve device 52 changes in a binary manner depending on the spring 52b and the spool opening characteristic.

  FIG. 3 is a functional block diagram showing the processing contents of the controller 54. The controller 54 has functions of a target rotation speed setting unit 54a, an auto idle rotation speed setting unit 54b, an auto idle determination unit 54c, and a target rotation speed switching unit 54d.

  The target rotational speed setting unit 54a inputs an operation signal from the throttle dial 51, and sets the target rotational speed of the engine 1 corresponding to the operation signal. The rotation speed set by the target rotation speed setting unit 54a includes an idle rotation speed, a maximum rotation speed, and an intermediate rotation speed. The intermediate rotation speed is variably changed from the idle rotation speed to the maximum rotation speed. Increase.

  The auto idle speed setting unit 54b sets a target speed for auto idle control, and the idle speed is stored as the target speed for auto idle control.

  The auto idle determination unit 54c receives a detection signal from the pressure sensor 53, determines whether or not auto idle control is necessary, and switches the target rotational speed switching unit 54d from the illustrated position when it is determined that auto idle control is necessary. When the detected pressure of the pressure sensor 53 (pressure on the output port side of the valve device 52) is the pressure of the discharge oil passage 3a (pilot pressure), an OFF determination signal is output, and the detected pressure is the pressure of the tank 11 When the pressure is low, an ON determination signal is output.

  When the determination signal of the auto idle determination unit is OFF, the target rotation number switching unit 54d holds the position shown in the figure, selects the target rotation number set by the target rotation number setting unit 54a, and determines the determination signal of the auto idle determination unit. When is turned ON, the position is switched from the illustrated position, and the target rotational speed (idle rotational speed) set in the auto idle rotational speed setting unit 54b is selected.

  The target rotational speed selected by the target rotational speed switching unit 54d is output to the electronic governor 55 as a target rotational speed signal. The electronic governor 55 controls the fuel injection amount based on the target rotational speed signal so that the rotational speed of the engine 1 becomes the target rotational speed.

  The determination signal of the auto idle determination unit is switched from OFF to ON, and the target rotation number selected by the target rotation number switching unit 54d is set from the target rotation number set by the target rotation number setting unit 54a to the auto idle rotation number setting. When switching to the target rotational speed (idle rotational speed) of the automatic idle control set in the unit 54b (when the automatic idle function operates), the target rotational speed (idle rotational speed) of the automatic idle control is immediately output. Instead, it may be output with a delay of a certain time (for example, 4 to 5 seconds). As a result, when the operator operates the control lever means in a short time after the operator returns the control lever means to the neutral state and the work is continued, the engine speed is prevented from decreasing and unnecessary engine speed reduction is prevented. it can.

  4 shows a differential pressure between the signal pressure of the signal line 37 and the pressure of the oil passage 56 (the pressure on the upstream side of the oil cooler 38 and the return filter 39 of the main return pipe 10), that is, the corrected signal pressure and the auto idle control. It is operation | movement explanatory drawing which shows these relationships. The horizontal axis represents the corrected signal pressure, and the vertical axis represents the target rotational speed of the engine 1.

  When the correction signal pressure is higher than the set pressure (threshold value) of the spring 52b, the controller 54 selects the target rotational speed set by the target rotational speed setting unit 54a, so the auto idle function is canceled and the engine The number of revolutions of 1 is controlled to be the number of revolutions according to the setting of the throttle dial 51.

  When the correction signal pressure becomes lower than the set pressure (threshold value) of the spring 52b, the controller 54 selects the target engine speed (idle engine speed) set in the auto idle engine speed setting unit 54b. Is operated, and the rotational speed of the engine 1 is reduced to the idle rotational speed.

  In the above, the discharge oil passage 3a of the pilot pump 3 and the pilot relief valve 42 constitute a pilot pressure generating circuit that generates a pilot pressure, and the pilot pressure generating circuit, the valve device 52, the pressure sensor 53, and the controller 54 are plural. When all the directional control valves 7a to 7e are in the neutral position, an auto idle means is configured to operate the auto idle function and reduce the rotational speed of the engine 1.

  In addition, the auto idle speed setting unit 54 b, the auto idle determination unit 54 c, and the target rotation number switching unit 54 d of the controller 54 are controlled to switch the operation and release of the Oidle function based on the change in pressure detected by the pressure sensor 53. Configure the means.

  FIG. 5 is a view showing an appearance of a hydraulic excavator on which the hydraulic drive device is mounted. The hydraulic excavator includes a lower traveling body 100, an upper swing body 101, and a front work machine 102. The lower traveling body 100 has left and right crawler traveling devices 103a and 103b, and is driven by left and right traveling motors 104a and 104b. A blade 105 is provided at the front of the lower traveling body and is moved up and down by a blade cylinder 5d (see FIG. 1). The upper turning body 101 is driven to turn about the axis O on the lower traveling body 100 by a turning motor 5e (see FIG. 1). The front work machine 102 can move up and down at the front part of the upper swing body 101. The front work machine 102 has an articulated structure having a boom 110, an arm 111, and a bucket 112. The boom 110, the arm 111, and the bucket 112 are respectively connected to a boom cylinder 5a, an arm cylinder 5b, and a bucket cylinder 5c (see FIG. 1) with an axis O. Is driven to rotate in a plane including In FIG. 1, illustration of the left and right traveling motors 103a and 103b is omitted.

  Next, the operation of the present embodiment configured as described above will be described.

  During driving of an arbitrary actuator (for example, the actuator 5a) performed by operating an arbitrary direction control valve (for example, the direction control valve 7a), the signal pressure of the signal line 37 (maximum load pressure) and the pressure of the oil passage 56 (oil cooler) 38 and the upstream pressure of the return filter 39), that is, the correction signal pressure is higher than the set pressure (threshold value) of the spring 52b, so that the auto idle function is canceled as shown in FIG. The engine 1 is controlled to have a rotational speed corresponding to the setting of the throttle dial 51.

  From the above state, when the operation lever means is returned to the neutral position and the direction control valve (for example, the direction control valve 7a) is returned to the neutral position, the pressure oil is supplied from the hydraulic pump 2 to the actuator (for example, the actuator 5a). The actuator stops and the drive of the actuator stops. At the same time, since the detection line (for example, the detection line 20) of the direction control valve (for example, the direction control valve 7a) communicates with the tank port (for example, the tank port 8a), the signal pressure of the signal line 37 also decreases. The signal pressure of the signal line 37 is guided to the pressure receiving portion 52a of the valve device 52, and the differential pressure (the pressure upstream of the oil cooler 38 and the return filter 39) between the signal pressure of the signal line 37 and the pressure of the oil passage 56 ( When the correction signal pressure) is lower than the set pressure (10 Kg / cm 2) of the spring 52b, the auto-idle function operates as shown in FIG. 4, and the engine 1 is controlled to become the idling speed. That is, the engine speed automatically decreases from the set speed of the throttle dial 51 to the idle speed.

  Thereafter, by operating any operating lever means with the intention of resuming the work and switching the corresponding one of the direction control valves 7a to 7e (for example, the direction control valve 7a) from the neutral position, the corresponding actuator ( For example, pressure oil is supplied to the actuator 5a) and the actuator is driven. At the same time, the load pressure of the corresponding actuator (for example, the actuator 5a) is detected in the detection line (for example, the detection line 20) of the direction control valve (for example, the direction control valve 7a), and the signal pressure of the signal line 37 increases. The signal pressure of the signal line 37 is guided to the pressure receiving portion 52a of the valve device 52, and the pressure difference between the signal pressure of the signal line 37 and the pressure of the oil passage 56 (pressure upstream of the oil cooler 38 and the return filter 39) ( When the correction signal pressure) becomes higher than the set pressure (10 Kg / cm 2) of the spring 52b, the auto idle function is canceled as shown in FIG. 4, and the engine 1 is set at the target speed set by the target speed setting unit 54a. It is controlled to become. That is, the engine speed automatically increases from the idle speed to the speed corresponding to the setting of the throttle dial 51.

  Further, in the present embodiment, the valve device 52 is not switched only by the signal pressure of the signal line 37, but the signal pressure of the signal line 37 and the pressure of the oil passage 56 (the pressure on the upstream side of the oil cooler 38 and the return filter 39). The valve device 52 is switched by the differential pressure (corrected signal pressure) with respect to the above), and the following effects can be obtained.

  First, a comparative example will be described. FIG. 6 is an operation explanatory view similar to FIG. 4 in the case where the valve device 52 does not have the second pressure receiving portion 52c and the valve device 52 is switched only by the signal pressure of the signal line 37 as a comparative example. The horizontal axis is the signal pressure of the signal line 37, and the vertical axis is the target rotational speed of the engine 1.

  The pressure loss due to the oil cooler 38 and the return filter 39 varies depending on the temperature of the hydraulic oil. In other words, when the viscous resistance of the hydraulic oil is low at normal temperature, the pressure loss due to the oil cooler 38 and the return filter 39 is as small as ΔPLOSSL in FIG. 6 (for example, 2 Kg / cm 2), and at low temperatures. When the viscosity resistance of the hydraulic oil is high, the pressure loss due to the oil cooler 38 and the return filter 39 increases to ΔPLOSSH in FIG. 6 (for example, 12 kg / cm 2). For this reason, the signal pressure (maximum load pressure) at the time of neutralization of the control lever (at the time of neutralization of the directional control valve) is affected by the pressure loss, and becomes higher at low temperature than at normal temperature. Therefore, when setting the threshold value for canceling the auto idle function (set pressure of the spring of the valve device), set the threshold value to a high value so that the valve device can be switched reliably with the signal pressure at low temperature. There is a need.

  For example, the threshold value that is not affected by pressure loss due to the oil cooler 38 and the return filter 39 when the auto idle function is canceled (the chain line A in FIG. 6) is set to 10 kg / cm 2 as in the present embodiment, and the pressure loss at room temperature is set to 2 kg / cm 2. When the pressure loss at low temperature is 12 kg / cm 2, the signal pressure at the time of releasing the operation lever neutral at normal temperature is 2 kg / cm 2 +10 kg / cm 2 = 12 kg / cm 2 (dotted line B in FIG. 6), whereas at low temperature The signal pressure at the time of releasing the control lever neutral at is 12 kg / cm 2 +10 kg / cm 2 = 22 kg / cm 2 (dotted line C in FIG. 6). Therefore, the threshold value for canceling the auto idle function (the set pressure of the spring of the valve device) needs to be set to a high value of 22 kg / cm 2 (dotted line C in FIG. 6) or more.

  However, if the threshold value for canceling the auto idle function is set to a high value in consideration of the low temperature, the signal pressure when the auto idle function is canceled is as low as 12 kg / cm 2 (dotted line B in FIG. 6) at room temperature. It takes time for the pressure to rise to the threshold value of 22 kg / cm 2, and it is assumed that the auto-idle function release timing at room temperature is delayed from the operation timing intended by the operator (the timing when the operating lever means is operated). The operator feels uncomfortable and there is a concern that the startup operation is not smooth.

  In contrast, in the present embodiment, the pressure on the upstream side of the oil cooler 38 and the return filter 39 is guided to the pressure receiving portion 52c so as to face the pressure receiving portion 52a to which the signal pressure of the valve device 52 is guided, and the oil cooler 38 and The valve device 52 is canceled by the differential pressure (corrected signal pressure) between the signal pressure of the signal line 37 and the pressure of the oil passage 56 (pressure upstream of the oil cooler 38 and the return filter 39). Is switched. As a result, when the auto idle function is canceled, when the correction pressure becomes higher than the set pressure in both the normal temperature and the low temperature (the signal pressure is the pressure loss + the set pressure of the spring 52b (in the above numerical example, the normal pressure is 12 kg / 4) When the temperature is low, the auto idle function is released as shown in FIG. 4, and when the operation is resumed, the neutral of the operating lever means is released so that the auto idle function can be quickly activated. The engine speed is released and the engine is started smoothly.

  As described above, according to the present embodiment, it is possible to switch between the operation and the release of the auto idle function using the control pressure of the load sensing system in the hydraulic drive device including the load sensing system.

  Further, the pressure sensor 53 does not directly detect the signal pressure of the signal line 37 but detects the pilot pressure which is the pressure on the output side of the valve device 52 or a pressure (tank pressure) lower than the pilot pressure. The pressure resistance performance and detection performance of the sensor can be kept low compared to the case of directly detecting the signal pressure (maximum load pressure), the pressure sensor 53 can be made inexpensive, and an inexpensive system configuration can be realized. .

  Further, the valve device 52 is provided with a first pressure receiving portion 52a and a second pressure receiving portion 52c, and opposes the signal pressure of the signal line 37 to guide the pressure on the upstream side of the oil cooler 38 and the return filter 39. Since the influence of the pressure loss due to the return filter 39 is canceled, the auto idle function is immediately released and the engine speed increases when the neutrality of the direction control valves 7a to 7e is canceled at both normal temperature and low temperature. Thus, a smooth start-up operation is possible.

It is a circuit diagram showing a hydraulic drive device of a construction machine according to an embodiment of the present invention. It is a characteristic view which shows the function of a valve apparatus. It is a functional block diagram which shows the processing content of a controller. It is operation | movement explanatory drawing which shows the relationship between correction signal pressure and auto idle control. It is a figure which shows the external appearance of the hydraulic shovel in which the hydraulic drive unit shown in FIG. 1 is mounted. It is operation | movement explanatory drawing which shows the relationship between the pressure of the signal line of a comparative example, and auto idle control.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Hydraulic pump 3 Pilot pumps 5a-5e Actuators 7a-7e Direction control valve 10 Main return line 11 Tank 12-16 Pressure compensation valve 18 Pump regulator 19 for load sensing control Pump regulators 20-24 for limiting absorption torque Detection lines 25 to 29 Signal lines 30 to 33 Shuttle valves 34 to 36 Signal lines 37 Signal lines 38 Oil cooler 39 Return filter 40 Servo piston 41 LS control valve 51 Throttle dial 52 Valve device 52a First pressure receiving portion 52b Spring 52c Second pressure receiving 53 Pressure sensor 54 Controller 55 Electronic governor 56 Oil passage

Claims (2)

A variable displacement hydraulic pump, an engine for driving the hydraulic pump, a plurality of actuators driven by oil discharged from the hydraulic pump, and a flow of pressure oil supplied from the hydraulic pump to the plurality of actuators are controlled. A plurality of directional control valves, a first detection means for detecting a highest load pressure, which is the highest pressure among the load pressures of the plurality of actuators, as a signal pressure, and a discharge pressure of the hydraulic pump being higher than the signal pressure A load sensing control regulator that controls the displacement of the hydraulic pump so as to increase, and an auto idle means that operates an auto idle function to reduce the engine speed when all of the plurality of directional control valves are in a neutral position; In a hydraulic drive comprising:
A pilot pressure generating circuit for generating the pilot pressure;
A valve device that operates by the signal pressure and switches the pressure on the output side to the pilot pressure and a pressure lower than the pilot pressure;
Second detection means for detecting pressure on the output side of the valve device;
A hydraulic drive apparatus comprising: control means for switching between operation and release of the auto idle function based on a change in pressure detected by the second detection means. The hydraulic drive device according to claim 2, wherein
The first detection means is configured to communicate with a main return line when all of the plurality of directional control valves are in a neutral position;
The main return line includes an oil cooler and a return filter,
The valve device is provided with a first pressure receiving portion to which the signal pressure is guided, an urging means provided in a direction opposite to the direction in which the signal pressure acts, and provided on the same side as the urging means, and the main return A difference between the signal pressure and the pressure on the upstream side of the oil cooler on the main return line and the return filter; and a second pressure receiving portion to which the pressure on the upstream side of the return line is guided. The hydraulic drive apparatus according to claim 1, wherein when the pressure becomes lower than a set value of the urging means, the pressure on the output side is switched from the pilot pressure to the low pressure.

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