JP4077789B2 - Hydraulic drive device and hydraulic drive method for work machine - Google Patents

Description

[0001]
Technical field
The present invention includes an engine having a fuel injection control device provided in a work machine such as a hydraulic excavator and capable of controlling a governor region to an isochronous characteristic or an inverse droop characteristic, and a variable displacement hydraulic pump driven by the engine. The present invention relates to a hydraulic drive device and a hydraulic drive method for a working machine provided.
[0002]
Background art
2. Description of the Related Art Conventionally, there is a hydraulic drive device for a working machine including a mechanical governor type engine as disclosed in, for example, Japanese Patent Laid-Open No. 7-83084.
[0003]
Conventional technologies having this type of mechanical governor engine generally include a variable displacement hydraulic pump driven by the engine and a push of the hydraulic pump. Noke A regulator that controls the volume, a plurality of hydraulic actuators that are driven by pressure oil discharged from the hydraulic pump, a pressure detector that detects the discharge pressure of the hydraulic pump and outputs a discharge pressure signal, and an output from the pressure detector Input the discharge pressure signal and press the hydraulic pump to the regulator. Noke And a controller for outputting a control signal for controlling the volume.
[0004]
In the prior art having this mechanical governor type engine, the engine output characteristic is the engine output in the governor region where the mechanical governor is controlled. torque It has a droop characteristic in which the engine speed increases as (engine load) decreases. Such droop characteristics are caused by the inertia of the flywheel included in the mechanical governor.
[0005]
Therefore, when the work implement is a hydraulic excavator, for example, during the unloading operation after loading and discharging the earth and sand in the bucket, the discharge pressure of the hydraulic pump becomes lower, the engine load becomes lighter and the engine speed increases. The discharge flow rate of the hydraulic pump increases, the flow rate supplied to the hydraulic actuator increases, and a relatively fast hydraulic actuator speed can be obtained. As a result, the work speed in the unloading operation is increased, and the work efficiency can be improved.
[0006]
Further, unlike the conventional conventional governor type engine, for example, JP-A-10-89111 and JP-A-10-159599, a fuel injection control device capable of controlling the governor region to an isochronous characteristic or an inverse droop characteristic. There has also been proposed a hydraulic drive device for a working machine equipped with an engine having an engine (hereinafter, referred to as an engine that performs isochronous control or reverse droop control as appropriate). The engine control isochronous characteristic is a characteristic that keeps the engine speed constant in the governor region regardless of the lightness of the engine load, that is, regardless of the decrease in the engine output torque. The reverse droop characteristic is the engine output torque ( The engine speed decreases as the engine load decreases.
[0007]
In such a prior art, the influence by the inertia of a flywheel like a mechanical governor can be excluded, and low fuel consumption and low noise can be realized as compared with a work machine including an engine having a mechanical governor.
[0008]
Disclosure of the invention
As described above, a working machine equipped with an engine that performs isochronous control or reverse droop control has the advantage of realizing low fuel consumption and low noise, but the engine speed does not increase even when the engine is lightly loaded. , May cause work problems. For example, as described above, when the work machine is a hydraulic excavator, even when an unloading operation is performed and the engine load is light, the discharge speed of the hydraulic pump does not increase because the engine speed does not increase. The flow rate supplied to the hydraulic actuator cannot be increased, and improvement in work efficiency cannot be expected.
[0009]
In addition, when working with a work machine equipped with an engine that performs isochronous control or reverse droop control, an operator accustomed to the operation of a work machine equipped with a mechanical governor-type engine, although the engine load is light. Since the speed of the hydraulic actuator does not increase unlike a working machine with a mechanical governor type engine, the operation feeling may be uncomfortable.
[0010]
It is an object of the present invention to provide a hydraulic drive apparatus having an engine having a fuel injection control device capable of controlling at least a part of a governor region to either an isochronous characteristic or a reverse droop characteristic. An object of the present invention is to provide a hydraulic drive device and a hydraulic drive method for a working machine capable of increasing the discharge flow rate of a hydraulic pump as the weight is reduced.
[0011]
(1) In order to achieve the above object, the present invention provides a fuel injection control device capable of controlling at least a part of a governor region to any one of isochronous characteristics, reverse droop characteristics, and characteristics combining isochronous characteristics and reverse droop characteristics. In a hydraulic drive device for a working machine, comprising: a variable displacement hydraulic pump driven by the engine; and a plurality of hydraulic actuators driven by pressure oil discharged from the hydraulic pump. Pump absorption torque control means for controlling the displacement volume of the hydraulic pump so that the displacement volume of the hydraulic pump does not exceed a value determined by a preset pump absorption torque curve when the discharge pressure exceeds the first predetermined pressure; and the hydraulic pump When the discharge pressure of the hydraulic pump is below the first predetermined pressure, the discharge pressure of the hydraulic pump is Shall and a flow rate correction control means for controlling so that the displacement volume of the hydraulic pump increases as lower from the predetermined pressure.
[0012]
In the present invention configured as described above, when the engine load during work is a heavy load and the discharge pressure of the hydraulic pump is higher than the first predetermined pressure, the engine output by the pump absorption torque control (pump absorption horsepower control). Effective use of horsepower becomes possible. Further, for example, when the engine load shifts from a heavy load to a light load during work, and the discharge pressure of the hydraulic pump becomes equal to or lower than the second predetermined pressure, the flow rate correction control means pushes the hydraulic pump according to the decrease in the pump discharge pressure. Noke The volume is controlled to increase, so that the discharge flow rate of the hydraulic pump can be increased even if the engine speed does not increase due to isochronous characteristics or reverse droop characteristics in the governor region, and the hydraulic actuator speed can be increased at light engine loads. The speed can be increased.
[0013]
(2) In order to achieve the above object, according to the present invention, at least a part of the governor region is controlled to any one of isochronous characteristics, reverse droop characteristics, and characteristics combining isochronous characteristics and reverse droop characteristics. In a hydraulic drive device for a working machine, comprising: an engine having a control device; a variable displacement hydraulic pump driven by the engine; and a plurality of hydraulic actuators driven by pressure oil discharged from the hydraulic pump. A regulator for controlling the displacement of the pump, a pressure detector for detecting the discharge pressure of the hydraulic pump, and when the discharge pressure of the hydraulic pump detected by the pressure detector exceeds a first predetermined pressure, Make sure that the displacement does not exceed the value determined by the preset pump absorption torque curve. When the discharge pressure of the hydraulic pump is below the first predetermined pressure and the discharge pressure of the hydraulic pump is lower than the second predetermined pressure, the displacement volume of the hydraulic pump is increased. Flow rate correction control means for controlling the regulator so as to increase is provided.
[0014]
Also in the present invention configured as described above, as described in (1) above, effective use of engine output horsepower by pump absorption torque control (pump absorption horsepower control) and increase control of pump discharge flow rate at light engine load The hydraulic actuator speed can be increased when the engine is lightly loaded.
[0015]
(3) In the above (1) or (2), preferably, the second predetermined pressure coincides with the first predetermined pressure.
[0016]
As a result, when the discharge pressure of the hydraulic pump becomes equal to or lower than the first predetermined pressure, the flow rate correction control means immediately functions, and the displacement volume of the hydraulic pump can be increased.
[0017]
(4) Further, in the above (1) or (2), further provided is a control release means for invalidating the increase control of the hydraulic pump push-off volume by the flow rate correction control means.
[0018]
Thereby, the control by the flow rate correction control means can be canceled as necessary, and the flow rate control according to the work content becomes possible.
[0019]
(5) In the above (4), preferably, the fuel injection control device is capable of controlling at least a part of the governor region to an isochronous characteristic, and the control release means includes a travel mode switch, a suspended load mode switch. , Including at least one of leveling mode switches.
[0020]
As a result, in an operation or work that does not require increase control of the discharge flow rate of the hydraulic pump, such as travel operation, suspended load work, and leveling work, the hydraulic actuator speed is made equal regardless of increase or decrease in engine load, Suspended load work and leveling work can be carried out.
[0021]
(6) In the above (1) or (2), preferably, the flow rate correction control means increases the discharge flow rate of the hydraulic pump as the discharge pressure of the hydraulic pump becomes lower than the second predetermined pressure. The displacement of the hydraulic pump is controlled.
[0022]
As a result, as described in (1) above, the discharge flow rate of the hydraulic pump can be increased even if the engine speed does not increase due to isochronous characteristics or reverse droop characteristics in the governor region.
[0023]
(7) Further, in the above (1) or (2), the fuel injection control device is capable of controlling at least a part of the governor region to have an inverse droop characteristic, and the flow rate correction control means includes the hydraulic pump A first means for controlling the displacement of the hydraulic pump so that the discharge flow rate of the hydraulic pump increases as the discharge pressure of the hydraulic pump decreases from the second predetermined pressure, and the discharge pressure of the hydraulic pump from the second predetermined pressure. There is a second means for controlling the displacement of the hydraulic pump so that the discharge flow rate of the hydraulic pump is kept constant when the pressure becomes low, and a selection means for selecting one of the first means and the second means.
[0024]
Thus, regardless of the characteristics of the governor region, the discharge flow rate of the hydraulic pump is controlled to increase when the first means is selected, and the discharge flow rate of the hydraulic pump is kept constant when the second means is selected. The flow rate is controlled according to the work content.
[0025]
(8) In the above (7), preferably, the flow rate correction control means further includes a third means for invalidating the increase control of the displacement volume of the hydraulic pump, and the selection means includes the first correction means. One of the first means, the second means, and the third means is selected.
[0026]
Thereby, when the third means is selected, the increase control of the displacement volume of the hydraulic pump becomes invalid, and the flow rate control according to the work content becomes possible.
[0027]
(9) In the above (1) or (2), preferably, the pump absorption torque control means calculates a target displacement for pump absorption torque control from a discharge pressure of the hydraulic pump and a pump absorption torque curve. And a means for holding the target displacement volume at a constant value when the discharge pressure of the hydraulic pump is equal to or lower than the first predetermined pressure, and the flow rate correction control means has a discharge pressure of the hydraulic pump Means for calculating a displacement correction value that increases as the pressure decreases from the second predetermined pressure, and means for calculating a corrected second displacement by adding the displacement correction value to the target displacement volume, The displacement of the hydraulic pump is controlled by the corrected target displacement.
[0028]
As a result, the pump absorption torque control means and the flow rate correction control means can be computerized.
[0029]
(10) In the above (1) or (2), preferably, the pump absorption torque control means is a means for limiting a maximum displacement volume of the hydraulic pump to a value determined by the pump absorption torque curve or less. The flow rate correction control means is a means for controlling the maximum displacement of the hydraulic pump to increase as the discharge pressure of the hydraulic pump becomes lower than a second predetermined pressure.
[0030]
As described in (1) above, this enables effective use of engine output horsepower by pump absorption torque control (pump absorption horsepower control) and increase control of the pump discharge flow rate when the engine is lightly loaded. When the required flow rate of the actuator is small, the displacement of the hydraulic pump is controlled accordingly, and a desired actuator speed can be obtained.
[0031]
(11) Further, in the above (1) or (2), the pump absorption torque control means further includes first calculation means for calculating a first target displacement according to the required flow rates of the plurality of hydraulic actuators. A second target displacement for pump absorption torque control is calculated from the discharge pressure of the hydraulic pump and a pump absorption torque curve, and the target displacement is calculated when the discharge pressure of the hydraulic pump is below the first predetermined pressure. Second calculation means for holding the volume at a constant value, and the flow rate correction control means calculates a displacement correction value that increases as the discharge pressure of the hydraulic pump decreases from the second predetermined pressure; Means for calculating the corrected second target displacement by adding the displacement correction value to the second target displacement, and correcting the first target displacement. Select a target displacement volume for controlling a smaller one of the second target displacement volume which is the vignetting volume the correction, controls the displacement volume of the hydraulic pump.
[0032]
Accordingly, when the first target displacement volume corresponding to the required flow rates of the plurality of hydraulic actuators is larger than the corrected second target displacement volume, the corrected second target displacement volume becomes the control target displacement volume. The displacement of the hydraulic pump is limited to the corrected second target displacement, and as described in (1) above, effective use of engine output horsepower by pump absorption torque control (pump absorption horsepower control) and when the engine is lightly loaded The pump discharge flow rate can be increased. On the other hand, when the first target displacement is smaller than the corrected second target displacement, the first target displacement is the control target displacement, so that the displacement of the hydraulic pump is based on the first target displacement. It is controlled according to the required flow rate, and a desired actuator speed can be obtained.
[0033]
(12) In order to achieve the above object, according to the present invention, at least a part of the governor region is controlled to any one of isochronous characteristics, reverse droop characteristics, and characteristics combining isochronous characteristics and reverse droop characteristics. In the hydraulic drive method of a working machine comprising: an engine having a control device; a variable displacement hydraulic pump driven by the engine; and a plurality of hydraulic actuators driven by pressure oil discharged from the hydraulic pump. When the pump discharge pressure exceeds the first predetermined pressure, the displacement of the hydraulic pump is controlled so that the displacement of the hydraulic pump does not exceed a value determined by a preset pump absorption torque curve. When the pressure is below the first predetermined pressure, whether the discharge pressure of the hydraulic pump is the second predetermined pressure Be controlled so that the displacement volume of the hydraulic pump increases as lower Rumo Let's say.
[0034]
As described in (1) above, this enables effective use of engine output horsepower by pump absorption torque control (pump absorption horsepower control) and increase control of pump discharge flow at light engine load. The hydraulic actuator speed can be increased.
[0035]
(13) In the above (12), preferably, when the discharge pressure of the hydraulic pump is equal to or lower than the first predetermined pressure, the displacement of the hydraulic pump increases as the discharge pressure of the hydraulic pump becomes lower than the second predetermined pressure. Either the control to increase or the control to keep the displacement of the hydraulic pump constant can be selected.
[0036]
Thereby, the increase control of the displacement volume can be canceled as necessary, and the flow rate control according to the work content becomes possible.
[0037]
(14) In the above (12), preferably, when the discharge pressure of the hydraulic pump is equal to or lower than the first predetermined pressure, the discharge pressure of the hydraulic pump decreases as the discharge pressure of the hydraulic pump decreases from the second predetermined pressure. The displacement of the hydraulic pump is controlled so that the discharge flow rate increases.
[0038]
As a result, as described in (1) above, the discharge flow rate of the hydraulic pump can be increased even if the engine speed does not increase due to isochronous characteristics or reverse droop characteristics in the governor region.
[0039]
(15) In the above (12), preferably, the fuel injection control device is capable of controlling at least a part of the governor region to a reverse droop characteristic, and a discharge pressure of the hydraulic pump is set to the first predetermined value. When the pressure is lower than the pressure, control to increase the displacement of the hydraulic pump so that the discharge flow rate of the hydraulic pump increases as the discharge pressure of the hydraulic pump becomes lower than the second predetermined pressure, and the discharge of the hydraulic pump One of the controls for increasing the displacement of the hydraulic pump can be selected so that the discharge flow rate of the hydraulic pump is kept constant as the pressure becomes lower than the second predetermined pressure.
[0040]
As a result, regardless of the characteristics of the governor region, the flow rate control according to the work content becomes possible.
[0041]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0042]
FIG. 1 is a diagram showing an entire system including a hydraulic circuit of a hydraulic drive device for a working machine according to an embodiment of the present invention.
[0043]
The hydraulic drive apparatus according to the present embodiment is provided in a working machine, for example, a hydraulic excavator. As shown in FIG. 1, the engine 1, the electronic governor 12 constituting the fuel injection control apparatus of the engine 1, and the engine A controller 13 is provided. The electronic governor 12 and the engine controller 13 are capable of controlling the governor region to isochronous characteristics, that is, performing the isochronous control for maintaining the engine 1 at the rated speed regardless of the increase or decrease of the engine load in the governor region. The electronic governor 12 is controlled by the engine controller 13 and injects fuel into the engine 1. This type of fuel injection control device is known from, for example, Japanese Patent Laid-Open No. 10-159599.
[0044]
Further, as shown in FIG. 1, the hydraulic drive apparatus according to the present embodiment includes, for example, a swash plate type variable displacement hydraulic pump 2 driven by an engine 1 and a displacement volume (swash plate) of the hydraulic pump 2. And a plurality of hydraulic actuators such as a hydraulic cylinder 3 driven by pressure oil discharged from the hydraulic pump 2, a hydraulic motor 4 and hydraulic cylinders 5 and 6, and these hydraulic actuators. An operation lever device 50 for generating pilot pressure for switching the direction control valves 7 to 10, the main relief valve 11, and the direction control valves 7 to 10 for controlling the flow of the supplied pressure oil (1). Only), a pressure detector 14 that detects the discharge pressure of the hydraulic pump 2 and outputs a discharge pressure signal P, and detects the tilt angle (displacement volume) of the swash plate of the hydraulic pump 2 The tilt angle detector 15 that outputs the angle signal θ, the mode selection switch 17 that can output the control unlocking signal F, and the pilot pressure from the operation lever device 50,. A signal control valve 53 having a combination of shuttle valves to be output, a pressure detector 55 for detecting a pilot pressure output from the signal control valve 53 and outputting a pilot pressure signal D, and a discharge output from the pressure detector 14 The pressure signal P, the tilt angle signal θ output from the tilt angle detector 15, the control release signal F output from the mode selection switch 17, and the pilot pressure signal D output from the pressure detector 55 are input. The regulator 16 is provided with a work machine controller 18 that outputs a control current signal R for controlling the displacement volume.
[0045]
FIG. 2 shows an external appearance of a hydraulic excavator in which the hydraulic drive device according to the present embodiment is mounted.
[0046]
The hydraulic excavator includes a lower traveling body 102, an upper swing body 103, and a front work machine 104. The upper swing body 103 is turnably mounted on the upper part of the lower travel body 102. It is attached to the front part so that it can move up and down. The upper swing body 103 is provided with an engine room 105 and an operator cab 106. The front work machine 104 has an articulated structure having a boom 108, an arm 109, and a bucket 110. The lower traveling body 102, the upper swing body 103, and the front work machine 104 have left and right traveling motors 111 (only one shown), a swing motor 112, a boom cylinder 113, an arm cylinder 114, and a bucket cylinder 115 as actuators. The traveling body 102 travels by the rotation of the left and right traveling motors 111, the upper swing body 103 rotates by the rotation of the swing motor 112, and the boom 108 of the front work machine 104 rotates vertically by the expansion and contraction of the boom cylinder 113, Ah 1 09 is vertically rotated by the expansion and contraction of the arm cylinder 114, and the bucket 110 is vertically rotated by the expansion and contraction of the bucket cylinder 115.
[0047]
The hydraulic cylinders 3, 5 and 6 and the hydraulic motor 4 shown in FIG. 1 represent the above-described actuators. For example, the hydraulic cylinders 3, 5 and 6 are a boom cylinder 113, an arm cylinder 114, and a bucket cylinder 115. The motor 4 is a turning motor 112.
[0048]
Further, the operation lever devices 50,... And the mode selection switch 17 are disposed in the cab 106, and the engine 1 and the hydraulic pump 2 are disposed in the engine room 105. Hydraulic equipment and electronic equipment such as the direction control valves 7 to 10, the engine controller 13, and the work machine controller 18 are installed at appropriate positions of the upper swing body 103.
[0049]
FIG. 3 shows a relationship between the rotational speed N of the engine 1 and the output torque Te by a fuel injection control device (using the electronic governor 12 and the engine controller 13) that performs isochronous control.
[0050]
As shown in FIG. 3, the output torque characteristic of the engine 1 is divided into a governor area 33 characteristic (isochronous characteristic) represented by a straight line 32 and an entire load area characteristic represented by a curve 30. The governor region 33 is an output region when the governor opening is 100% or less, and the full load region is an output region where the governor opening is 100%. In the figure, a broken line 31 indicates a characteristic (droop characteristic) in a governor region of a conventional mechanical governor type engine for comparison. Since the mechanical governor has a structure in which the fuel injection amount is adjusted by balancing the flywheel and the spring, the governor region of the mechanical governor type engine, as indicated by the broken line 31, decreases the engine output torque (engine load) Te. It has a droop characteristic in which the engine speed N increases. On the other hand, in the engine 1 according to the present embodiment, as indicated by the straight line 32, the isochronous control in which the engine speed N is kept constant at the rated speed N0 by the electronic governor 12 regardless of the decrease in the engine output torque Te in the governor region. It has isochronous characteristics to implement. By this isochronous control, it is possible to realize low fuel consumption and low noise compared to a working machine having a mechanical governor type engine.
[0051]
FIG. 4 shows details of the regulator 16. The regulator 16 controls the tilt angle of the hydraulic pump 2 to match the target pump tilt angle indicated by the control current signal R based on the control current signal R output from the work machine controller 18. 60, a servo valve 61, and a servo piston 62. The electromagnetic proportional pressure reducing valve 60 receives the control current signal R from the work machine controller 18 and outputs a control pressure proportional to the control current signal R, and the servo valve 61 is operated by the control pressure to position the servo piston 62. The servo piston 62 drives the swash plate 2a of the hydraulic pump 2 and controls its tilt angle.
[0052]
The discharge pressure of the hydraulic pump 2 is guided to the input port of the servo valve 61 via the check valve 63 and always acts on the small diameter chamber 62 a of the servo piston 62 via the passage 54. The discharge pressure of the pilot pump 66 is guided to the input port of the electromagnetic proportional pressure reducing valve 60, and the electromagnetic proportional pressure reducing valve 60 is actuated to reduce the pressure to the control pressure. This control pressure acts on the pilot piston 61 a of the servo valve 61 through the passage 67. When the discharge pressure of the hydraulic pump 2 is lower than the discharge pressure of the pilot pump 66, the discharge pressure of the pilot pump 66 is guided to the input port of the servo valve 61 through the check valve 69 as a servo assist pressure.
[0053]
FIG. 5 shows the relationship between the control current signal R applied to the electromagnetic proportional pressure reducing valve 60 and the tilt angle of the swash plate 2a of the hydraulic pump 2 (hereinafter simply referred to as simply the tilt angle of the hydraulic pump 2 or the pump tilt). Show.
[0054]
When the control current signal R is equal to or less than R1, the electromagnetic proportional pressure reducing valve 60 does not operate, and the control pressure from the electromagnetic proportional pressure reducing valve 60 is zero. Therefore, the spool 61b of the servo valve 61 is pushed leftward by the spring 61c, and the discharge pressure of the hydraulic pump 2 (or the discharge pressure of the pilot pump 66) passes through the check valve 63, the sleeve 61d, the spool 61b, and the servo piston 62. Acting on the large-diameter chamber 62b. The small diameter chamber 62a of the servo piston 62 also passes through the passage 54. hydraulic Although the discharge pressure of the pump 2 is acting, the servo piston 62 moves to the right in the figure due to the area difference.
[0055]
When the servo piston 62 moves to the right in the figure, the feedback lever 71 rotates counterclockwise in the figure with the pin 72 as a fulcrum. Since the tip of the feedback lever 71 is connected to the sleeve 61d by the pin 73, the sleeve 61d moves in the left direction in the figure. The servo piston 62 is moved until the notch in the opening of the sleeve 61d and the spool 61b is closed. 62 Stops.
[0056]
By these operations, the tilt angle of the hydraulic pump 2 becomes the minimum position, and the discharge flow rate of the hydraulic pump 2 becomes the minimum.
[0057]
When the control current signal R becomes larger than R1 and the electromagnetic proportional pressure reducing valve 60 is operated, the control pressure corresponding to the operation amount of the electromagnetic proportional pressure reducing valve 60 acts on the pilot piston 61a of the servo valve 61 through the passage 67, and the spool 61b is moved rightward in the drawing to a position where it balances with the force of the spring 61c. When the spool 61b moves, the large-diameter chamber 62b of the servo piston 62 is connected to the tank 75 via a passage inside the spool 61b. Since the discharge pressure of the hydraulic pump 2 (or the discharge pressure of the pilot pump 66) is constantly acting on the small diameter chamber 62a of the servo piston 62 through the passage 54, the servo piston 62 moves to the left in the figure, and the large diameter chamber 62b. Is returned to the tank 75.
[0058]
When the servo piston 62 moves to the left in the figure, the feedback lever 71 rotates clockwise with the pin 72 as a fulcrum, and the sleeve 61d of the servo valve 61 moves to the right in the figure. The servo piston 62 is moved until the notch in the opening of the sleeve 61d and the spool 61b is closed. 62 Stops.
[0059]
By these operations, the tilt angle of the hydraulic pump 2 increases, and the discharge flow rate of the hydraulic pump 2 increases. Further, the increase amount of the discharge flow rate of the hydraulic pump 2 is proportional to the increase amount of the control pressure, that is, the increase amount of the control current signal R.
[0060]
When the control current signal R decreases and the control pressure from the electromagnetic proportional pressure reducing valve 60 decreases, the spool 61b of the servo valve 61 is returned to the left in the drawing to the position where it balances with the force of the spring 61c, and the discharge pressure of the hydraulic pump 2 (or (Discharge pressure of pilot pump 66) is servo valve 61 The servo piston 62 acts on the large diameter chamber 62b of the servo piston 62 through the sleeve 61d and the spool 61b. 62 Moves to the right in the figure.
[0061]
When the servo piston 62 moves to the right in the figure, the feedback lever 71 rotates counterclockwise in the figure with the pin 72 as a fulcrum, and the sleeve 61d of the servo valve 61 moves to the left in the figure. The servo piston 62 is moved until the notch in the opening of the sleeve 61d and the spool 61b is closed. 62 Stops.
[0062]
By these operations, the tilt angle of the pump 2 is reduced, and the discharge flow rate of the hydraulic pump 2 is reduced. The decrease amount of the discharge flow rate of the hydraulic pump 2 is proportional to the decrease amount of the control pressure, that is, the decrease amount of the control current signal R.
[0063]
FIG. 6 is a functional block diagram showing details of the mode selection switch 17 and the calculation function of the work machine controller 18.
[0064]
The mode selection switch 17 includes, for example, a travel mode switch 17a, a hanging mode switch 17b, and a leveling mode switch 17c, and outputs a control release signal F when any of these switches 17a to 17c is operated by an operator.
[0065]
The work machine controller 18 includes a first target pump tilt angle calculation unit 81, a second target pump tilt angle calculation unit 82, a tilt angle correction value calculation unit 83, a switching unit 84, an addition unit 85, Each function includes a minimum value selector 86, a subtractor 87, and a control current calculator 88.
[0066]
The first target pump tilt angle calculation unit 81 inputs the pilot pressure signal D from the pressure detector 55, refers to the table stored in the memory, and corresponds to the pilot pressure indicated by the signal D at that time The first target tilt θD of the hydraulic pump 2 to be calculated is calculated. This first target tilt θD is a positive control target tilt according to the lever operation amount (required flow rate) of the operation lever device 50 (see FIG. 1), and the pilot pressure increases in the memory table. Accordingly, the relationship between the two is set so that the first target tilt θD also increases.
[0067]
The second target pump tilt angle calculation unit 82 inputs the discharge pressure signal P of the hydraulic pump 2 from the pressure detector 14 and refers to the table stored in the memory, and the signal P at that time indicates The second target tilt θT of the hydraulic pump 2 corresponding to the pump discharge pressure (hereinafter, for convenience, denoted by the same symbol P as the signal) is calculated. This second target tilt θT is a limit value for performing torque control of the hydraulic pump 2, and the memory table shows the pump discharge pressure P based on the pump absorption torque curve as shown in FIG. A relationship with the second target tilt θT (limit value) of the hydraulic pump 2 is set.
[0068]
In FIG. 7, reference numeral 20 denotes a pump absorption torque curve, which is set so as to coincide with the curve 21 of the output torque Te (see FIG. 3) at a predetermined rotation speed (for example, rated rotation speed N0) of the engine 1. In a range where the pump discharge pressure P is P1 or more, the second target pump tilt θT changes along the pump absorption torque curve 20, and the second target pump tilt θT decreases as the pump discharge pressure P increases.
[0069]
When the pump discharge pressure P is P1, the second target pump tilt θT is the first maximum tilt θmax1, and when the discharge pressure P is lower than P1, the second target pump tilt θT is 1 The maximum tilt θmax1 is maintained. This first maximum tilt θmax1 is a design specification of a hydraulic excavator, for example, the aforementioned swing motor 112, boom cylinder 113, arm cylinder 114, bucket cylinder 115 (hydraulic cylinder 3, 5 , 6 and the hydraulic motor 4) are determined by design specifications such as the operating speed. That is, the first maximum inclination θmax1 is set so that the pump discharge flow rate obtained thereby gives the desired operating speed of the actuators.
[0070]
Pmin is the minimum discharge pressure of the hydraulic pump 2, and Pmax is the maximum discharge pressure of the hydraulic pump 2. The maximum discharge pressure Pmax corresponds to the set pressure of the main relief valve 11 (see FIG. 1).
[0071]
A range 23 between the minimum discharge pressure Pmin and the pressure P1 is a region corresponding to the governor region 33 described above.
[0072]
The absorption torque of the hydraulic pump 2 is represented by the product of the discharge pressure of the hydraulic pump 2 and the displacement (tilt angle) of the hydraulic pump 2. Therefore, calculating the second target tilt θT corresponding to the pump discharge pressure P from the pump absorption torque curve 20 and controlling the tilt angle of the hydraulic pump 2 so as to be the second target pump tilt θT is as follows. Controlling the tilt of the hydraulic pump 2 so that the product of the discharge pressure P and the second target pump tilt θT (absorption torque of the hydraulic pump 2) is maintained at the pump absorption torque (constant value) represented by the curve 20 Means.
[0073]
The tilt angle correction value calculation unit 83 inputs the discharge pressure signal P of the hydraulic pump 2 from the pressure detector 14, refers to the table stored in the memory, and discharges the pump indicated by the signal P at that time. A correction value S of the second target tilt θT of the hydraulic pump 2 corresponding to the pressure (hereinafter, similarly denoted by the same symbol P as the signal) is calculated. This correction value S is such that even if the engine speed in the governor region 33 (FIG. 3) is constant by isochronous control, the tilt angle of the hydraulic pump 2 is increased and the discharge flow rate is increased as the engine load is reduced. This is for correcting the tilt angle of the hydraulic pump 2, and in the memory table, as shown in FIG. 8, when the pump discharge pressure P is P1 or more, the correction value S = 0, and the discharge pressure P When is smaller than P1, the relationship between the discharge pressure P and the correction value S is set so that the correction value S increases linearly proportionally as the discharge pressure P decreases.
[0074]
The switching unit 84 opens when the control release signal F is output from the mode selection switch 17 and invalidates the correction value S of the target pump tilt.
[0075]
The adder 85 adds the target pump tilt correction value S calculated by the tilt angle correction value calculator 83 to the second target tilt θT of the hydraulic pump 2 calculated by the second target pump tilt angle calculator 82. And the corrected second target tilt θT is calculated.
[0076]
FIG. 9 shows the relationship between the discharge pressure P corrected by the adding unit 85 and the second target tilt θT.
[0077]
By adding the correction value S to the second target tilt θT, the characteristic line 19 shown in FIG. 7 is corrected like the characteristic line 22 and corrected as the pump discharge pressure P decreases from P1 to Pmin. The second target tilt θT increases linearly from the first maximum tilt θmax1 to the second maximum tilt θmax2 (= first maximum tilt θmax1 + Smax). The second maximum tilt θmax2 is set, for example, corresponding to the maximum tilt (pump performance limit) on the structure of the hydraulic pump 2.
[0078]
The minimum value selecting unit 86 selects the smaller one of the first target tilt θD of the hydraulic pump 2 calculated by the first target pump tilt angle calculating unit 81 and the second target tilt θT corrected by the adding unit 85. The target tilt θc for controlling the hydraulic pump 2 is used. Thus, when the first target tilt θD of the hydraulic pump 2 calculated by the first target pump tilt angle calculating unit 81 is larger than the corrected second target tilt θT, the corrected second target tilt θT is The target pump tilt θc for control is output as the control target pump tilt θc, and the control target pump tilt θc is limited to the corrected second target tilt θT or less.
[0079]
The subtraction unit 87 calculates a deviation Δθ between the control target pump tilt θc and the tilt angle signal θ output from the tilt angle detector 15, and the control current calculation unit 88 calculates the deviation by, for example, integral control calculation. The control current signal R is calculated from Δθ. Thus, the tilt angle signal θ is controlled to coincide with the control target pump tilt θc.
[0080]
The operation of the present embodiment configured as described above is as follows.
[0081]
First, the case where none of the switches 17a to 17c of the mode selection switch 17 is operated and the release signal F is not output, that is, the case where the switching unit 84 of the work machine controller 18 is closed will be described. .
[0082]
When the engine 1 is started to drive the hydraulic pump 2 and any one of the operation lever devices 50,... Is operated, the pressure oil discharged from the hydraulic pump 2 passes through the corresponding ones of the direction control valves 7-10. The cylinder is supplied to the cylinders 3, 5, 6, or the hydraulic motor 4, and the front working machine 104 of the excavator shown in FIG. 2, for example, is driven to perform excavation work of earth and sand.
[0083]
In the work machine controller 18, the first target pump tilt angle calculator 81 calculates the first target tilt θD of the hydraulic pump 2 corresponding to the pilot pressure signal D output from the pressure detector 55, and the second target pump tilt angle calculator 81 calculates the second target tilt θD. The pump tilt angle calculator 82 calculates the second target tilt θT of the hydraulic pump 2 corresponding to the discharge pressure signal P of the hydraulic pump 2 output from the pressure detector 14, and the tilt angle correction value calculator 83. , The correction value S of the target tilt of the hydraulic pump 2 corresponding to the discharge pressure signal P of the hydraulic pump 2 output from the pressure detector 14 is calculated.
[0084]
At this time, if the lever operation amount of the operation lever device is small and θD <θc (= θT), the minimum value selection unit 86 calculates the first of the hydraulic pump 2 calculated by the first target pump tilt angle calculation unit 81. The target tilt θD is selected as the control target tilt θc, and the control current signal R for making the tilt angle signal θ coincide with the target tilt θc is calculated by the subtractor 87 and the control current calculator 88. A control current signal R is output to the electromagnetic proportional pressure reducing valve 60 of the regulator 16. As a result, the tilt angle of the hydraulic pump 2 is controlled to coincide with the target tilt θc (= θD) for control, and the hydraulic pump 2 has the product of the target tilt θc and the rotational speed N of the engine 1 at that time. Discharges a proportional flow rate. This discharge flow rate is a flow rate corresponding to the lever operation amount of the operation lever device, and this discharge flow rate is supplied to the corresponding one of the hydraulic cylinders 3, 5, 6 or the hydraulic motor 4, and the actuator operates the operation lever device. It is driven at a speed according to the amount.
[0085]
On the other hand, for example, when the operating lever of the operating lever device is fully operated and θD> θc (= θT), the minimum value selecting unit 86 calculates the second target pump tilt angle calculating unit 82 of the hydraulic pump 2. Two target tilt θT is selected as the target tilt θc for control, and a control current signal R calculated from the target tilt θc and the tilt angle signal θ is output to the electromagnetic proportional pressure reducing valve 60 of the regulator 16. .
[0086]
At this time, for example, when heavy excavation or the like is performed and the pump discharge pressure indicated by the signal P output from the pressure detector 14 is P2 higher than P1 shown in FIG. The value S = 0 is calculated, and the second target pump tilt angle calculator 82 calculates the second target tilt θT = θ2, and the θ2 becomes the corrected second target tilt θT as it is. For this reason, the tilt angle of the hydraulic pump 2 is limited to θ2, and the discharge flow rate of the hydraulic pump 2 is also limited to the following flow rate Q1.
[0087]
Q1 = a ・ θ2 ・ N
(A is a constant)
As a result of limiting the discharge flow rate of the hydraulic pump 2 in this way, the horsepower consumption of the hydraulic pump 2 expressed by the product of the discharge flow rate of the hydraulic pump 2 and the discharge pressure is also limited. As a result, overload of the engine 1 can be prevented, and the output horsepower of the engine 1 can be effectively utilized within a range in which engine stall does not occur.
[0088]
Control of the tilt angle of the hydraulic pump 2 based on the pump absorption torque curve 20 is called pump absorption torque control, and control of the discharge flow rate of the hydraulic pump 2 is called pump absorption horsepower control.
[0089]
From the state as described above, for example, when earth and sand are discarded from the bucket 110 and an unloading operation is performed, the discharge pressure P of the hydraulic pump 2 decreases from P2. When the pump discharge pressure P is reduced to P3 smaller than P1, for example, the tilt angle correction value calculation unit 83 calculates the correction value S = S1, and the second target pump tilt angle calculation unit 82 calculates the second target tilt θT. = Θmax1 is calculated, and the value obtained by adding the correction value S1 to θmax1 is the corrected second target tilt θT. Therefore, the tilt angle of the hydraulic pump 2 is controlled to be θmax1 + S1, and the discharge flow rate of the hydraulic pump 2 is also controlled to be the following flow rate Q3.
[0090]
Q3 = a · (θmax1 + S1) · N
That is, the tilt angle of the hydraulic pump 2 increases by the correction value S1 compared to the first maximum tilt θmax1 that is the tilt angle when the discharge pressure of the hydraulic pump 2 is at P1, and accordingly the hydraulic pressure is increased. The discharge flow rate of the pump 2 also increases.
[0091]
Here, the correction value S is set so as to increase linearly as the discharge pressure P becomes lower than P1, and the corrected second target tilt θT is the pump discharge pressure as indicated by the characteristic line 22. As P decreases from P1, it linearly increases from the first maximum tilt θmax1 to the second maximum tilt θmax2 (= first maximum tilt θmax1 + Smax). For this reason, even if the rotational speed of the engine 1 is constant in the range 23 corresponding to the governor region 33 (FIG. 3) by isochronous control, the discharge flow rate of the hydraulic pump 2 is controlled to increase as the engine load becomes lighter. Accordingly, the operating speed of the hydraulic actuators such as the hydraulic cylinders 3, 5, 6 and the hydraulic motor 4 can be increased. The characteristic indicated by the characteristic line 22 apparently substantially coincides with the droop characteristic line 31 in the mechanical governor shown in FIG.
[0092]
10A and 10B show the relationship between the pump discharge pressure P and the pump tilt θ and the relationship between the pump discharge pressure and the pump discharge flow rate according to the prior art having a mechanical governor engine that controls the governor region to the droop characteristic.
[0093]
In the prior art that does not include the tilt angle correction value calculation unit 83, the switching unit 84, and the addition unit 85 shown in FIG. 6 in the calculation function of the work machine controller, Pmin and P1 corresponding to the governor region 33 (FIG. 3) In the range 23 between them, the pump tilt θ is constant as shown by the straight line 25. On the other hand, in the governor region 33 of the mechanical governor type engine, as shown by a broken line 31 in FIG. Engine output torque (Engine load) A droop characteristic in which the engine speed N increases as Te decreases is obtained. For this reason, in the range 23 between Pmin and P1, the engine speed N increases as the pump discharge pressure P decreases from P1, so that even if the pump tilt θ is constant, the pump discharge due to the increase in the engine speed N. The flow rate Q increases as indicated by the broken line 26. As a result, the flow rate supplied to the hydraulic actuator is increased, the working speed in the unloading operation is increased, and the working efficiency can be improved.
[0094]
FIG. 11A and FIG. 11B show the relationship between the pump discharge pressure P and the pump tilt θ and the relationship between the pump discharge pressure and the pump discharge flow rate according to the present embodiment, the conventional technology having an engine that controls the governor region to isochronous characteristics. Show.
[0095]
In the governor region 33 of the engine that controls the governor region to isochronous characteristics, the engine speed N is constant at the rated speed N0 regardless of the decrease in the engine output torque Te as shown by the straight line 32 in FIG. For this reason, in the range 23 between Pmin and P1 corresponding to the governor region 33, when the pump tilt θ is constant as shown by the one-dot chain line 27, the pump discharge flow rate Q is also represented by the one-dot chain line 28 in FIG. It is constant as shown. On the other hand, in this embodiment, in the range 23 between Pmin and P1 corresponding to the governor region 33, the pump tilt θ changes like a straight line 35 corresponding to the characteristic line 22 in FIG. The discharge flow rate Q changes as shown by a straight line 36 as the pump tilt θ increases. That is, even if the engine speed N is constant, the pump discharge flow rate Q increases linearly as the pump discharge pressure P decreases from P1. As a result, as in the prior art shown in FIGS. 10A and 10B, the flow rate supplied to the hydraulic actuator increases, the work speed in the unloading operation increases, and the work efficiency can be improved.
[0096]
Further, as described above, there are a traveling operation, a suspended load operation, and a leveling operation as operations or operations that do not require the increase control of the discharge flow rate of the hydraulic pump 2 at the time of light engine load. When performing such an operation or work, the operator operates the corresponding one of the switches 17a to 17c of the mode selection switch 17. As a result, the control release signal F is output from the mode selection switch 17 to the work machine controller 18, the switching unit 84 is opened, and the target pump tilt correction value S is invalidated. As a result, the increase control of the discharge flow rate of the hydraulic pump 2 by the correction value S of the turning angle correction value calculation unit 83 is not performed.
[0097]
Note that, for example, the travel mode switch 17 a of the mode selection switch 17 described above may be configured to operate when a signal from a detection unit that detects operation of the travel operation lever is input to the work machine controller 18. The same applies to the other mode switches 17b and 17c.
[0098]
According to this embodiment configured as described above, the pump discharge flow rate Q can be gradually increased as the engine load becomes lighter even in the governor region 33 in the engine 1 to which the isochronous control is applied. That is, the pump discharge flow rate can be increased substantially equivalent to the flow rate increase due to the droop characteristic in the mechanical governor. As a result, the hydraulic actuator speed when the engine is lightly loaded can be increased, and the work efficiency during light loads such as empty work can be improved. Further, it is possible to give a good operation feeling to an operator who is used to operating a working machine equipped with a mechanical governor engine.
[0099]
When traveling operation, suspended load work, and leveling work are performed, the correction value S by the turning angle correction value calculation unit 83 is invalidated, and isochronous control is performed according to the isochronous characteristic line 32 shown in FIG. Regardless of the engine load, the discharge flow rate of the hydraulic pump 2 is constant, and the hydraulic actuator speed can be made constant regardless of the increase or decrease of the engine load, so that it is possible to carry out good traveling operation, hanging load work, and leveling work.
[0100]
A second embodiment of the present invention will be described with reference to FIGS. In the present embodiment, the present invention is applied to a hydraulic drive device including an engine having a fuel injection control device capable of controlling a governor region to have an inverse droop characteristic.
[0101]
The overall configuration of the hydraulic drive apparatus according to this embodiment is substantially the same as that of the first embodiment shown in FIG. 1 except for the following points.
[0102]
In the present embodiment, the fuel injection control device including the electronic governor 12 and the engine controller 13 shown in FIG. 1 is capable of controlling the governor region to the reverse droop characteristic, whereby the engine 1 is engine-controlled in the governor region. Control is performed such that the rotational speed of the engine 1 decreases as the output torque Te (engine load) decreases.
[0103]
FIG. 12 shows the relationship between the rotational speed N of the engine 1 controlled by the reverse droop characteristic and the output torque Te. In FIG. 12, the governor region 33 has a reverse droop characteristic in which the engine speed N decreases as the engine output torque Te (engine load) decreases, as indicated by a straight line 34. Due to this reverse droop characteristic, the engine speed at light load can be further reduced and further fuel efficiency and noise can be realized as compared with the droop characteristic and isochronous characteristic.
[0104]
FIG. 13 is a functional block diagram showing the calculation function of the work machine controller 18 according to the present embodiment.
[0105]
The work machine controller 18 includes a first target pump tilt angle calculation unit 81, a second target pump tilt angle calculation unit 82, a first tilt angle correction value calculation unit 83A, and a second tilt angle correction value calculation. The unit 83B, the 0 setting unit 83C, the switching unit 84A, the addition unit 85, the minimum value selection unit 86, the subtraction unit 87, and the control current calculation unit 88 are provided.
[0106]
The first and second tilt angle correction value calculation units 83A and 83B each input the discharge pressure signal P of the hydraulic pump 2 from the pressure detector 14, and refer to the table stored in the memory, A correction value S for the second target tilt θT of the hydraulic pump 2 is calculated.
[0107]
Even if the engine speed in the governor region 33 decreases due to the reverse droop characteristic, the first tilt angle correction value calculation unit 83A allows the hydraulic pump 2 to increase the discharge flow rate of the hydraulic pump 2 as the engine load decreases. As shown in FIG. 14, in the memory table, the correction value Sa = 0 when the pump discharge pressure P is equal to or higher than P1, and the discharge pressure P is smaller than P1, as shown in FIG. Then, the relationship between the discharge pressure P and the correction value Sa is set so that the correction value Sa increases linearly as the discharge pressure P decreases.
[0108]
Further, the second tilt angle correction value calculation unit 83B is configured so that the discharge flow rate of the hydraulic pump 2 is constant regardless of the engine load even if the engine speed in the governor region 33 decreases due to the reverse droop characteristic. As shown in FIG. 14, in the memory table, when the pump discharge pressure P is equal to or higher than P1, the correction value Sb = 0 and the discharge pressure P is P1. As the discharge pressure P decreases, the discharge pressure P and the discharge pressure P become linearly proportional as the discharge pressure P decreases at a rate smaller than the correction value Sa calculated by the first tilt angle correction value calculation unit 83A. A relationship with the correction value Sb is set.
[0109]
The 0 setting unit 83C outputs 0 as the correction value S.
[0110]
The mode selection switch 17A is a dial type and has first, second, and third switching positions.
[0111]
The switching unit 84A selects the correction value Sa calculated by the first tilt angle correction value calculation unit 83A as illustrated when the mode selection switch 17A is in the first position illustrated, and the mode selection switch 17A is the second When switched to the position, the correction value Sb calculated by the second tilt angle correction value calculation unit 83B is selected, and when the mode selection switch 17A is switched to the third position, the correction value S ( = 0) and output as correction values S, respectively.
[0112]
In the adding unit 85, as in the first embodiment, the second target tilt θT of the hydraulic pump 2 calculated by the second target pump tilt angle calculating unit 82 and the correction value S selected by the switching unit 84A are added. Then, the corrected second target tilt θT is calculated.
[0113]
FIG. 15 shows the relationship between the pump discharge pressure P corrected by the adding unit 85 and the second target tilt θT.
[0114]
A range corresponding to the governor region 33 when the correction value Sa calculated by the first tilt angle correction value calculation unit 83A is selected in the switching unit 84A. 23 The characteristic line 19 is corrected like the characteristic line 40, and as the pump discharge pressure P decreases from P1 to Pmin, the corrected second target tilt θT is changed from the first maximum tilt θmax1 to the fourth maximum tilt θmax4. It increases linearly up to (= first maximum tilt θmax1 + Samax). The fourth maximum tilt θmax4 is set corresponding to, for example, the maximum tilt (pump performance limit) on the structure of the hydraulic pump 2.
[0115]
A range corresponding to the governor region 33 when the correction value Sb calculated by the second tilt angle correction value calculation unit 83B is selected in the switching unit 84A. 23 The characteristic line 19 is corrected like the characteristic line 41, and the corrected second target tilt θT is changed from the first maximum tilt θmax1 to the third maximum tilt θmax3 as the pump discharge pressure P decreases from P1 to Pmin. It increases linearly up to (= first maximum tilt θmax1 + Sbmax).
[0116]
A range corresponding to the governor region 33 when the correction value S = 0 of the 0 setting unit 83C is selected in the switching unit 84A. 23 The characteristic line 19 is not corrected, and the second target tilt θT calculated by the second target pump tilt angle calculator 82 is output as it is.
[0117]
The characteristic indicated by the characteristic line 40 is substantially identical to the droop characteristic line 31 of the mechanical governor shown in FIG. 12, and the characteristic indicated by the characteristic line 41 is substantially the same as the characteristic line 32 of isochronous control shown in FIG. Match.
[0118]
The operation of the present embodiment configured as described above is performed except that the engine 1 is controlled to the reverse droop characteristic and the discharge flow rate increase control of the hydraulic pump 2 is performed by either the correction value Sa or the correction value Sb. This is substantially the same as the first embodiment.
[0119]
That is, for example, when the operation lever of the operation lever device is fully operated during work such as heavy excavation, and θD> θc (= θT) and P> P1, the mode changeover switch 17A is switched to the first position, and the first tilt When the correction value Sa calculated by the rotation angle correction value calculation unit 83A is selected, increase control (increase control of discharge flow rate) of the tilt angle of the hydraulic pump 2 is performed by the characteristic line 40 shown in FIG. The changeover switch 17A is switched to the second position, and the second tilt angle correction value calculation unit 83B When the correction value Sb calculated in step S1 is selected, the tilt angle of the hydraulic pump 2 is controlled to increase (discharge flow rate hold control) using the characteristic line 41 shown in FIG.
[0120]
FIG. 16A and FIG. 16B show the relationship between the pump discharge pressure P and the pump tilt θ and the relationship between the pump discharge pressure and the pump discharge flow rate according to the prior art having an engine that controls the governor region to the reverse droop characteristic.
[0121]
As described above, when the calculation function of the work machine controller does not include the tilt angle correction value calculation unit 83, the switching unit 84, and the addition unit 85 illustrated in FIG. 6, Pmin and P1 corresponding to the governor region 33 In the range 23 between them, the pump tilt θ is constant as shown by the straight line 25. On the other hand, in the reverse droop characteristic, as shown by the straight line 34 in FIG. 12, the engine speed N decreases as the engine output torque (engine load) Te decreases. For this reason, in the range 23 between Pmin and P1, the engine speed N decreases as the pump discharge pressure P decreases from P1, so that even if the pump tilt θ is constant, the pump discharge due to the decrease in the engine speed N. The flow rate Q decreases as shown by the broken line 44. As a result, the flow rate supplied to the hydraulic actuator is reduced, and there is a problem that the working speed in the unloading operation is further slower than in the case of isochronous control.
[0122]
17A and 17B show the relationship between the pump discharge pressure P and the pump tilt θ according to the present embodiment and the relationship between the pump discharge pressure and the pump discharge flow rate.
[0123]
In the present embodiment, when the correction value Sa calculated by the first tilt angle correction value calculation unit 83A is selected and the characteristic line 19 shown in FIG. 15 is corrected to the characteristic line 40, it corresponds to the governor region 33. In the range 23 between Pmin and P1, the pump tilt θ changes as a straight line 45 corresponding to the characteristic line 40 in FIG. 15, and the pump discharge flow rate Q is indicated by a straight line 46 as the pump tilt θ increases. To change. That is, even if the engine speed N decreases due to the reverse droop characteristic, the pump discharge flow rate Q increases linearly as the pump discharge pressure P decreases from P1. As a result, as in the prior art shown in FIGS. 10A and 10B, the flow rate supplied to the hydraulic actuator increases, the work speed in the unloading operation increases, and the work efficiency can be improved.
[0124]
When the correction value Sb calculated by the second tilt angle correction value calculation unit 83B is selected and the characteristic line 19 shown in FIG. 15 is corrected to the characteristic line 41, Pmin and P1 corresponding to the governor region 33 are displayed. In the range 23, the pump tilt θ changes like a straight line 47 corresponding to the characteristic line 41 of FIG. 15, and the pump discharge flow rate Q becomes as shown by a straight line 48 as the pump tilt θ increases. That is, even if the engine speed N decreases due to the reverse droop characteristic, the decrease in the pump discharge flow rate Q is canceled by the increase in the pump tilt, and the pump discharge flow rate Q is controlled to be kept constant. As a result, in an operation or operation that does not require an increase control of the discharge flow rate of the hydraulic pump 2 such as a traveling operation, a suspended load operation, or a leveling operation, the hydraulic actuator speed is set to a constant speed regardless of the increase or decrease in the engine load. It is possible to carry out suspended load work and leveling work.
[0125]
When the correction value S = 0 of the 0 setting unit 83C is selected and the characteristic line 19 shown in FIG. 15 is not corrected, the pump tilt θ is shown in FIG. 15 in the range 23 between Pmin and P1 corresponding to the governor region 33. Corresponding to the characteristic line 19, the pump discharge flow rate Q becomes constant as shown by the straight line 50 due to a decrease in the engine speed N due to the reverse droop characteristic, as in FIG. 16B. . Thereby, fuel consumption can be further improved.
[0126]
According to the present embodiment configured as described above, the same effect as that of the first embodiment can be obtained in the hydraulic drive apparatus including the engine controlled to the reverse droop characteristic. That is, by switching the mode changeover switch 17A to the first position and selecting the correction value Sa calculated by the first tilt angle correction value calculation unit 83A, the pump is reduced as the engine load becomes light even in the governor region 33. The discharge flow rate Q can be gradually increased, and the pump discharge flow rate can be increased substantially equivalent to the increase in flow rate due to the droop characteristic in the mechanical governor. As a result, the hydraulic actuator speed when the engine is lightly loaded can be increased, and the work efficiency during light loads such as empty work can be improved. In addition, it is possible to give a good operation feeling to an operator who is used to operating a working machine equipped with the mechanical governor type engine 1.
[0127]
When traveling operation, suspended load work, and leveling work are performed, the mode changeover switch 17A is switched to the second position, and the correction value Sb calculated by the second tilt angle correction value calculation unit 83B is selected. Regardless of the engine load, the discharge flow rate of the hydraulic pump 2 is constant, and the hydraulic actuator speed can be made constant regardless of the increase or decrease of the engine load, so that it is possible to carry out good traveling operation, hanging load work, and leveling work.
[0128]
In addition, according to the present embodiment, since the hydraulic pump 2 is driven using the engine controlled to the reverse droop characteristic, at a light load as compared with the first embodiment using the engine controlled to the isochronous characteristic. The engine speed of the engine can be further reduced to realize further low fuel consumption and low noise.
[0129]
In order to give the highest priority to fuel efficiency during light excavation, the discharge flow rate of the hydraulic pump 2 is reduced by switching the mode selector switch 17A to the third position and selecting the set value S = 0 in the 0 setting section 83C. Furthermore, fuel consumption can be improved.
[0130]
A third embodiment of the present invention will be described with reference to FIGS.
[0131]
In the above embodiment, the present invention is applied to the hydraulic drive device including an engine that controls the governor region to the isochronous characteristic or the reverse droop characteristic, but the characteristic of the governor region is not limited thereto. In the present embodiment, as an example, the present invention is applied to an engine equipped with an engine in which the governor region is controlled to a characteristic combining isochronous characteristics and reverse droop characteristics.
[0132]
FIG. 18 shows the relationship between the engine speed N and the output torque Te controlled to a characteristic that combines the isochronous characteristic and the reverse droop characteristic. In FIG. 18, in the governor region 33, as shown by a straight line 90a, an isochronous characteristic that keeps the engine speed N at a constant value of the rated speed N0 regardless of a decrease in the engine output torque Te (engine load) and a straight line 90b. In addition, a characteristic 90 is combined with an inverse droop characteristic in which the engine speed N decreases as the engine output torque Te decreases. Due to this characteristic 90, the engine speed is kept constant by the isochronous characteristic at medium load, the actuator speed is ensured to some extent and the noise and fuel consumption are improved, and the engine is further improved by the reverse droop characteristic at light load smaller than that. Noise and fuel efficiency can be improved.
[0133]
FIG. 19 is a diagram showing the characteristics of the pump tilt correction value S in the tilt angle correction value calculation unit 83 (see FIG. 6) when the engine has such a characteristic 90. The characteristic of the pump tilt correction value S is set to a broken line corresponding to the characteristics of the straight line 90a and the straight line 90b shown in FIG.
[0134]
FIG. 20 is a characteristic diagram similar to FIG. 9 when the correction value S of the tilt angle correction value calculation unit 83 has the characteristics shown in FIG. By adding the correction value S to the second target tilt θT, the characteristic line 19 is corrected to a broken line characteristic similar to the broken line of the correction value S like the characteristic line 91. Thus, in an operation where the tilt angle of the hydraulic pump 2 is limited to the second target tilt θT, such as heavy excavation, the pump tilt θ in the range 23 between Pmin and P1 corresponding to the governor region 33 is As shown by the characteristic line 91, the discharge flow rate of the hydraulic pump changes as shown by the straight line 36 in FIG. 11B, and the increase control of the pump discharge flow rate as in the first embodiment can be performed.
[0135]
In the above embodiment, the pump discharge flow rate that substantially matches the droop characteristic in the mechanical governor is used as the characteristic of the correction value S that increases the pump discharge flow rate at the time of engine light load when the pump discharge pressure P is P1 or less. Although what can perform increase control was set, this invention is not restricted to setting to such a discharge flow volume characteristic. For example, the slope of the characteristic line of the pump tilt correction value S shown in FIG. 8 may be increased to increase the pump discharge flow rate more than the increase of the pump discharge flow rate due to the droop characteristic, and vice versa. Also good. Further, even when the governor region characteristic is not a combination of the isochronous characteristic and the reverse droop characteristic, the characteristic line of the pump tilt correction value S shown in FIG. 8 may be a broken line. Further, the characteristic line of the pump tilt correction value S may be a curve instead of a straight line.
[0136]
Further, in the above-described embodiment, the pump discharge pressure with the correction value S set to 0 is matched with P1 that is the control start pressure by the pump absorption torque curve 20, but a lower pressure may be used.
[0137]
In the above embodiment, one characteristic corresponding to the droop characteristic is set as the characteristic of the correction value S that increases the pump discharge flow rate at the time of engine light load when the pump discharge pressure P becomes P1 or less. One or a plurality of characteristics may be set, and the operator may select one of them by switching the mode selection switch. Alternatively, the mode selection switch may be a dial type that continuously changes the output so that the characteristic of the correction value S can be continuously changed. As a result, the work implement can have a plurality of operation performances while maintaining the effects of low fuel consumption and low noise, which are the merits of isochronous characteristics or reverse droop characteristics, and the operator can select the operation speed desired by the operator.
[0138]
Further, in the above embodiment, the actuator portion of the fuel injection control device that can be controlled to the isochronous characteristic or the reverse droop characteristic is the electronic governor 12, but the present invention is not limited to this, and the injection is performed regardless of the engine speed. A common rail fuel injection control device or a unit injector fuel injection control device capable of controlling the amount may be provided.
[0139]
In the above embodiment, the tilt angle of the hydraulic pump 2 is controlled according to the required flow rate, the absorption torque control (absorption horsepower control) of the hydraulic pump 2, and the tilt of the hydraulic pump at light load, which is a feature of the present invention. The calculation of the command value for the angle increase control is all performed by the work machine controller 18, and the tilt angle of the hydraulic pump is controlled by sending a control current signal to the regulator 16, but some of them (for example, according to the required flow rate) Control of the tilt angle of the hydraulic pump 2 and absorption torque control (absorption horsepower control) of the hydraulic pump 2 may be performed hydraulically by a regulator. Further, in the above embodiment, the tilt angle of the hydraulic pump 2 is detected by the tilt angle detector 15 and controlled by the feedback loop so that the tilt angle matches the target tilt angle. The tilt angle of the hydraulic pump may be controlled in an open loop without providing the vessel 15.
[0140]
Industrial applicability
According to the present invention, in a hydraulic drive apparatus having an engine capable of controlling at least a part of a governor region to any one of isochronous characteristics, reverse droop characteristics, and characteristics combining isochronous characteristics and reverse droop characteristics, However, the discharge flow rate of the hydraulic pump can be increased as the engine load becomes lighter, and the hydraulic actuator speed when the engine is lightly loaded can be increased in the same way as with a mechanical governor engine. The work efficiency can be improved.
[0141]
Further, it is possible to give a good operation feeling to an operator who is used to operating a working machine equipped with a mechanical governor engine.
[0142]
Further, according to the present invention, control is performed so that the discharge flow rate of the hydraulic pump is selectively constant, the hydraulic actuator speed is made constant regardless of the increase or decrease of the engine load, and the operation or work desired by the operator is carried out satisfactorily. Can be made.
[Brief description of the drawings]
FIG. 1 is a diagram showing an entire system including a hydraulic circuit of a hydraulic drive device for a working machine according to a first embodiment of the present invention.
FIG. 2 is a diagram showing an external appearance of a hydraulic excavator in which a hydraulic drive device according to the present embodiment is mounted.
FIG. 3 is a characteristic diagram showing the relationship between the rotational speed and output torque of an engine having an electronic governor that performs isochronous control.
FIG. 4 is a diagram showing details of the structure of the regulator.
FIG. 5 is a diagram showing a relationship between a control current signal given to an electromagnetic proportional pressure reducing valve of a regulator and a tilt angle of a hydraulic pump.
FIG. 6 is a functional block diagram showing a calculation function of the work machine controller.
FIG. 7 is a diagram showing a relationship between a pump discharge pressure used in a second target tilt angle calculation unit of the work machine controller and a second target tilt.
FIG. 8 is a diagram showing a relationship between a pump discharge pressure and a pump tilt angle correction value used in a tilt angle correction value calculation unit of the work machine controller.
FIG. 9 is a diagram showing a relationship between pump discharge pressure corrected by an adding unit and second target pump tilting.
FIG. 10A is a diagram showing the relationship between the pump discharge pressure P and the pump tilt θ according to the prior art having a mechanical governor engine that controls the governor region to the droop characteristic, and FIG. It is a figure which shows the relationship between the pump discharge pressure by and pump discharge flow rate.
FIG. 11A is a diagram showing the relationship between the pump discharge pressure P and the pump tilt θ according to the present embodiment and the prior art having an engine that controls the governor region to isochronous characteristics, and FIG. It is a figure which shows the relationship between the pump discharge pressure and pump discharge flow volume by a prior art and this Embodiment.
FIG. 12 is a characteristic diagram showing a relationship between an engine speed and an output torque of an engine having an electronic governor that performs control of the reverse droop characteristic according to the second embodiment of the present invention.
FIG. 13 is a functional block diagram showing a calculation function of the work machine controller according to the second embodiment.
FIG. 14 is a diagram illustrating a relationship between a pump discharge pressure and a pump tilt angle correction value used in a tilt angle correction value calculation unit of the work machine controller.
FIG. 15 is a diagram illustrating a relationship between a discharge pressure signal corrected by an adding unit and a second target tilt.
FIG. 16A is a diagram showing the relationship between pump discharge pressure P and pump tilt θ according to the prior art having an engine that controls the governor region to reverse droop characteristics, and FIG. 16B is a pump according to the prior art. It is a figure which shows the relationship between discharge pressure and pump discharge flow rate.
FIG. 17A is a diagram showing a relationship between pump discharge pressure P and pump tilt θ according to the second embodiment, and FIG. 17B is a diagram showing pump discharge pressure and pump discharge according to the second embodiment. It is a figure which shows the relationship with a flow volume.
FIG. 18 is a characteristic diagram showing a relationship between an engine speed and an output torque of an engine having an electronic governor that performs control combining the isochronous characteristic and the reverse droop characteristic according to the third embodiment of the present invention.
FIG. 19 is a diagram showing a relationship between a pump discharge pressure and a pump tilt angle correction value used in a tilt angle correction value calculation unit of the work machine controller.
FIG. 20 is a diagram illustrating a relationship between a discharge pressure signal corrected by an adding unit and a second target tilt.

Claims (15)

An engine (1) having a fuel injection control device (12, 13) capable of controlling at least a part of a governor region to any one of isochronous characteristics, reverse droop characteristics, and characteristics combining isochronous characteristics and reverse droop characteristics;
A variable displacement hydraulic pump (2) driven by this engine;
In a hydraulic drive device for a working machine comprising a plurality of hydraulic actuators (3-6) driven by pressure oil discharged from the hydraulic pump,
When the discharge pressure of the hydraulic pump (2) exceeds the first predetermined pressure (P1), the displacement volume of the hydraulic pump does not exceed the value determined by the pump absorption torque curve (20) set in advance. Pump absorption torque control means (82) for controlling
When the discharge pressure of the hydraulic pump is lower than the first predetermined pressure (P1), the flow rate correction is controlled so that the displacement of the hydraulic pump increases as the discharge pressure of the hydraulic pump becomes lower than the second predetermined pressure (P1). A hydraulic drive device for a working machine comprising control means (83, 85; 17A, 83A, 83B, 84A, 85). An engine (1) having a fuel injection control device (12, 13) capable of controlling at least a part of a governor region to any one of isochronous characteristics, reverse droop characteristics, and characteristics combining isochronous characteristics and reverse droop characteristics;
A variable displacement hydraulic pump (2) driven by this engine;
In a hydraulic drive device for a working machine comprising a plurality of hydraulic actuators (3-6) driven by pressure oil discharged from the hydraulic pump,
A regulator (16) for controlling the displacement of the hydraulic pump (2);
A pressure detector (14) for detecting the discharge pressure of the hydraulic pump;
When the discharge pressure of the hydraulic pump detected by the pressure detector exceeds the first predetermined pressure (P1), the displacement of the hydraulic pump does not exceed the value determined by the preset pump absorption torque curve (20). Pump absorption torque control means (82) for controlling the regulator (16);
When the discharge pressure of the hydraulic pump is equal to or lower than the first predetermined pressure (P1), the regulator (so that the displacement volume of the hydraulic pump increases as the discharge pressure of the hydraulic pump decreases from the second predetermined pressure (P1)). A hydraulic drive device for a working machine, comprising flow rate correction control means (83, 85; 17A, 83A, 83B, 84A, 85) for controlling 16). In the hydraulic drive device of the working machine according to claim 1 or 2,
The hydraulic drive device for a working machine, wherein the second predetermined pressure (P1) coincides with the first predetermined pressure (P1). In the hydraulic drive device of the working machine according to claim 1 or 2,
Control release means (17, 84; 17A, 83C) for disabling the increase control of the hydraulic pump displacement volume by the flow rate correction control means (83, 85; 17A, 83A, 83B, 84A, 85) is further provided. A hydraulic drive device for a working machine. The hydraulic drive device for a working machine according to claim 4,
The fuel injection control device (12, 13) is capable of controlling at least part of the governor region to isochronous characteristics,
The hydraulic drive device for a working machine, wherein the control release means (17, 84) includes at least one of a travel mode switch (17a), a suspended load mode switch (17b), and a leveling mode switch (17c). In the hydraulic drive device of the working machine according to claim 1 or 2,
The flow rate correction control means (83, 85; 17A, 83A, 84A, 85) increases the discharge flow rate of the hydraulic pump as the discharge pressure of the hydraulic pump (2) becomes lower than the second predetermined pressure (P1). A hydraulic drive device for a working machine, wherein the displacement of the hydraulic pump is controlled so as to perform the operation. In the hydraulic drive device of the working machine according to claim 1 or 2,
The fuel injection control device (12, 13) is capable of controlling at least a part of the governor region to a reverse droop characteristic,
The flow rate correction control means (17A, 83A, 83B, 84A, 85) is arranged so that the discharge flow rate of the hydraulic pump increases as the discharge pressure of the hydraulic pump (2) becomes lower than the second predetermined pressure (P1). The first means (83A, 85) for controlling the displacement of the hydraulic pump, and the discharge flow rate of the hydraulic pump is kept constant when the discharge pressure of the hydraulic pump becomes lower than the second predetermined pressure (P1). And a second means (83B, 85) for controlling the displacement of the hydraulic pump, and a selection means (17A, 84A) for selecting one of the first means and the second means. Machine hydraulic drive. The hydraulic drive device for a working machine according to claim 7,
The flow rate correction control means (17A, 83A, 83B, 84A, 85) further includes a third means (83C) for invalidating the increase control of the displacement volume of the hydraulic pump (2). The means (17A, 84A) selects any one of the first means, the second means, and the third means. In the hydraulic drive device of the working machine according to claim 1 or 2,
The pump absorption torque control means (82) calculates a target displacement (θT) for pump absorption torque control from the discharge pressure of the hydraulic pump (2) and a pump absorption torque curve, and discharges the hydraulic pump. Means (82) for holding the target displacement at a constant value (θmax1) when the pressure is equal to or lower than the first predetermined pressure (P1);
The flow rate correction control means (83, 85; 17A, 83A, 83B, 84A, 85) is a displacement correction value (S) that increases as the discharge pressure of the hydraulic pump decreases from the second predetermined pressure (P1). And a means for calculating a corrected second displacement volume (θT) by adding the displacement displacement correction value to the target displacement volume and adding the displacement displacement correction value to the target displacement volume. A hydraulic drive device for a working machine, wherein a displacement volume of the hydraulic pump is controlled by a displacement volume. In the hydraulic drive device of the working machine according to claim 1 or 2,
The pump absorption torque control means (82) is a means for limiting the maximum displacement volume of the hydraulic pump (2) to a value determined by the pump absorption torque curve (20) or less,
The flow rate correction control means (83, 85; 17A, 83A, 83B, 84A, 85) is arranged so that the maximum displacement volume of the hydraulic pump increases as the discharge pressure of the hydraulic pump becomes lower than the second predetermined pressure. A hydraulic drive device for a working machine, characterized by being a means for controlling. In the hydraulic drive device of the working machine according to claim 1 or 2,
A first calculating means (81) for calculating a first target displacement volume (θD) corresponding to the required flow rates of the plurality of hydraulic actuators (3-6);
The pump absorption torque control means (82) calculates a second target displacement volume (θT) for pump absorption torque control from the discharge pressure of the hydraulic pump (2) and the pump absorption torque curve (20), and Second calculating means (82) for holding the target displacement at a constant value (θmax1) when the discharge pressure of the hydraulic pump is equal to or lower than the first predetermined pressure (P1);
The flow rate correction control means (83, 85; 17A, 83A, 83B, 84A, 85) is a displacement correction value (S) that increases as the discharge pressure of the hydraulic pump decreases from the second predetermined pressure (P1). Means ( 83 ; 83A, 83B), and means (85) for calculating a corrected second target displacement volume (θT) by adding the displacement correction value to the second target displacement volume. ,
A hydraulic drive device for a working machine, wherein a smaller one of the first target displacement and the corrected second target displacement is selected as a target displacement for control, and the displacement of the hydraulic pump is controlled. . An engine (1) having a fuel injection control device (12, 13) capable of controlling at least a part of a governor region to any one of isochronous characteristics, reverse droop characteristics, and characteristics combining isochronous characteristics and reverse droop characteristics;
A variable displacement hydraulic pump (2) driven by this engine;
In a hydraulic drive method for a working machine including a plurality of hydraulic actuators (3-6) driven by pressure oil discharged from the hydraulic pump,
When the discharge pressure of the hydraulic pump (2) exceeds the first predetermined pressure (P1), the displacement of the hydraulic pump should not exceed the value determined by the preset pump absorption torque curve (20). Control the displacement volume,
When the discharge pressure of the hydraulic pump is equal to or lower than the first predetermined pressure (P1), control is performed so that the displacement of the hydraulic pump increases as the discharge pressure of the hydraulic pump becomes lower than the second predetermined pressure (P1). A hydraulic drive method for a working machine characterized by the above. In the hydraulic drive method of the working machine according to claim 12,
When the discharge pressure of the hydraulic pump is equal to or lower than the first predetermined pressure (P1), control for increasing the displacement of the hydraulic pump as the discharge pressure of the hydraulic pump becomes lower than the second predetermined pressure (P1); A hydraulic drive method for a working machine, wherein either one of control for keeping a displacement volume of a pump constant can be selected. In the hydraulic drive method of the working machine according to claim 12,
When the discharge pressure of the hydraulic pump is equal to or lower than the first predetermined pressure (P1), the hydraulic pump is configured such that the discharge flow rate of the hydraulic pump increases as the discharge pressure of the hydraulic pump decreases from the second predetermined pressure (P1). A hydraulic drive method for a working machine, characterized by controlling a displacement volume of the working machine. In the hydraulic drive method of the working machine according to claim 12,
The fuel injection control device (12, 13) is capable of controlling at least a part of the governor region to a reverse droop characteristic,
When the discharge pressure of the hydraulic pump is equal to or lower than the first predetermined pressure (P1), the discharge flow rate of the hydraulic pump decreases as the discharge pressure of the hydraulic pump (2) becomes lower than the second predetermined pressure (P1). The control for increasing the displacement of the hydraulic pump to increase, and the hydraulic pump so that the discharge flow rate of the hydraulic pump is kept constant as the discharge pressure of the hydraulic pump becomes lower than the second predetermined pressure (P1). A hydraulic drive method for a working machine, wherein either one of the controls for increasing the displacement volume of the work machine can be selected.

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