JPH03271534A - Prime mover control device for construction machine - Google Patents

Abstract

PURPOSE:To eliminate necessity for providing a detector in each operating means so as to simplify a structure by controlling a rotational speed of a prime mover to a low value of the preset speed or less, when a differential pressure between a delivery pressure of an oil hydraulic pump and its maximum load pressure is increased to a predetermined value or more. CONSTITUTION:Pipe lines 4A, 4B are branched from a delivery pipe line 4 of a variable displacement oil hydraulic pump 2 driven by a prime mover 1, and a work cylinder device 7 is connected to the pipe line 4A through pipe lines 8A, 8B. The pipe line 4 is connected to a running oil hydraulic motor 5 through a pair of pipe lines 6A, 6B, and control valves 9, 10 for work and running are provided on the way of the pipe line 4 or the like. The prime mover 1 is provided with a governor 27 for controlling its rotational speed, and this governor 27 is driven by an electric motor 28 controlled by a controller 30 connected to a fuel lever 26, differential pressure sensor 25 and a turn angle sensor 29 or the like. When a differential pressure between a delivery pressure and a maximum load pressure is increased to a predetermined value or more higher than a target differential pressure, a rotational speed of the prime mover is controlled to a low value of preset rotational speed or less.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is a construction machine prime mover control device that is installed in a construction machine such as a wheeled hydraulic excavator and is suitable for use in controlling the rotational speed of the prime mover. Regarding.

[Prior Art] Generally, a motor is driven by a prime mover, a rotation speed setting means for setting the rotation speed of the prime mover, a variable displacement hydraulic pump driven by the prime mover, and pressure oil discharged from the hydraulic pump. a plurality of hydraulic actuators, a plurality of control valves provided in the middle of each pipe connecting each of the hydraulic actuators and a hydraulic pump, and controlling the flow rate of pressure oil supplied to and discharged from each of the hydraulic actuators; A plurality of operation levers for operating the multi-control valve from the outside, a plurality of lever detectors provided on each of the operation levers and individually detecting the amount of tilting operation of each of the operation levers, and a plurality of lever detectors for individually detecting the tilting operation amount of each of the operation levers; control for controlling the rotational speed of the prime mover to a low rotational speed lower than the rotational speed set by the rotational speed setting means after a predetermined delay time when it is determined that all the operating levers are in the neutral position based on the signal; A prime mover control device for a construction machine comprising means is known, for example, from Japanese Patent Publication No. 60-38561.

In this type of prime mover control device, when each operating lever is returned to the neutral position and all hydraulic actuators are stopped, the prime mover's rotational speed set by the rotational speed setting means is automatically changed to a low speed. By lowering the engine speed, for example to the idle speed, the fuel consumption (hereinafter referred to as fuel consumption) of the prime mover can be significantly reduced.

[Problems to be Solved by the Invention] By the way, in the above-mentioned conventional technology, whether or not each hydraulic actuator driven by pressure oil from a hydraulic pump is stopped is determined based on the operating state of each operating lever. Therefore, it is necessary to provide a lever detector for each operating lever, which increases the number of parts, complicates the structure, and increases costs. Furthermore, the control means for controlling the rotational speed of the prime mover must be configured to constantly monitor signals from each lever detector, resulting in a problem of poor control processing efficiency.

Furthermore, since the rotation speed of the prime mover is controlled based on the signals from all lever detectors, even if any of the lever detectors fails, the prime mover cannot be automatically controlled to a low rotation speed. , there is a problem that reliability cannot be improved. In addition, the lever detector must be set appropriately for each operating lever, and if the play (dead zone) angle of each operating lever differs depending on the applicable hydraulic actuator, each lever detector must be set appropriately. The problem is that it is extremely difficult.

The present invention has been made in view of the problems of the prior art described above.The present invention eliminates the need to provide a detector for each operating means such as an operating lever, simplifies the structure, and automatically moves the prime mover to a low speed. The object of the present invention is to provide a prime mover control device for construction machinery that can control the rotation speed and improve reliability.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention includes a prime mover,
a rotation speed setting means for setting the rotation speed of the prime mover; a variable displacement hydraulic pump driven by the prime mover; a plurality of hydraulic actuators driven by pressure oil discharged from the hydraulic pump; and each hydraulic pressure. a plurality of control valves that are provided in the middle of each pipe connecting the actuator and the hydraulic pump and control the flow rate of pressure oil supplied to and discharged from each of the hydraulic actuators according to the amount of operation of the operating means; and the hydraulic pump. a discharge capacity variable means for controlling the discharge capacity of the hydraulic pump so that the discharge pressure is higher than the maximum load pressure of the load pressure of each hydraulic actuator by a predetermined target differential pressure; unloading means for returning pressurized oil from the hydraulic pump to the tank when the differential pressure between the load pressure and the target differential pressure is higher than a set value; and a differential pressure between the discharge pressure and the maximum load pressure. differential pressure detection means for detecting the
When the differential pressure detected by the detection means exceeds a predetermined value higher than the target differential pressure, the rotational speed of the prime mover is controlled to a low rotational speed equal to or lower than the rotational speed set by the rotational speed setting means. A configuration consisting of rotation speed control means is adopted.

Preferably, the rotational speed control means controls the rotational speed of the prime mover to a low rotational speed after a predetermined delay time has elapsed after the differential pressure becomes equal to or higher than the predetermined value.

The invention further includes a tilting amount detection means for detecting a tilting amount of the hydraulic pump, and the rotation speed control means detects when the differential pressure becomes equal to or higher than the predetermined value and the tilted amount becomes equal to or less than the predetermined amount.
The rotational speed of the prime mover may be controlled to a low rotational speed. In this case, the rotational speed control means lowers the rotational speed of the prime mover to a low rotational speed after a predetermined delay time has elapsed after the differential pressure is equal to or greater than the predetermined value and the tilting amount becomes less than or equal to the predetermined amount. It is preferable to have a configuration in which the control is performed.

The hydraulic pump further includes a discharge pressure detection means for detecting the discharge pressure of the hydraulic pump, and the rotation speed control means is configured such that the differential pressure is equal to or higher than the predetermined value, the tilting amount is equal to or lower than the predetermined amount, and the discharge pressure is equal to or higher than the predetermined value. The configuration may be such that the rotational speed of the prime mover is controlled to a low rotational speed in the following cases. And in this case,
The rotation speed control means controls the rotation speed of the prime mover after a predetermined delay time has elapsed after the differential pressure becomes equal to or greater than the predetermined value, the tilt amount is equal to or less than the predetermined amount, and the discharge pressure becomes equal to or less than the predetermined pressure. It is preferable to adopt a configuration in which the rotational speed is controlled to a low speed.

[Effect]

With the above configuration, it is possible to detect the differential pressure between the discharge pressure of the hydraulic pump and the maximum load pressure of each hydraulic actuator, and determine whether all the hydraulic actuators are in a stopped state, for example, based on this detection signal. Further, by providing a predetermined delay time, it is possible to prevent malfunctions when all the hydraulic actuators accidentally stop during work. Furthermore, by adding the tilting amount determination and the discharge pressure determination of the hydraulic pump, it becomes possible to more effectively prevent malfunctions such as those caused when the operating means is slightly operated.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 11, taking as an example a control circuit for a wheeled hydraulic excavator as a prime mover control device for construction machinery.

1 to 4 show a first embodiment of the present invention.

In the figure, 1 is a prime mover configured by a diesel engine or the like, and 2 is a variable displacement hydraulic pump driven by the prime mover 1. The hydraulic pump 2 has a variable capacity section 2A, The oil is discharged as high pressure oil (hereinafter referred to as pressure oil) into the pipe 4 and pipes 4A and 4B branched from the pipe 4. 5 is a pair of pipes 6A and 6B
Hydraulic pump via 2. A traveling hydraulic motor as a hydraulic actuator connected to a tank 3 is shown, and the hydraulic motor 5 constitutes a traveling snowmaking machine together with front and rear wheels (none of which are shown), and uses pressure oil from a hydraulic pump 2. The vehicle is made to run by rotating the front and rear wheels when the fuel is being supplied or discharged.

7 is a hydraulic pump 2.7 via pipes 4, 4A and pipes 8A, 8B. A cylinder device as a working hydraulic actuator connected to the tank 3 is shown, and the cylinder device 7 constitutes a boom cylinder for operating a boom, for example, among working devices constituted by a boom, an arm, a bucket, etc., and the cylinder device 7 is a hydraulic pump. By supplying and discharging the pressure oil from 2 into the oil chambers 7A and 7B, the rod 7C is extended and contracted from the tube 7D.

Reference numeral 9.10 indicates a control valve for work and travel provided in the middle of the pipe 4, etc., and the control valves 9 and 10 are switched from the neutral position (a) to the left and right switching positions (b).

(c), the pressure oil from the hydraulic pump 2 is transferred from the pipe 4 to the pipe 6A, 8A or 6B.

Hydraulic motor 5. The cylinder device 7 is operated. Here, the control valve 9 has five buttons 3 operated by an operating lever 9A serving as an operating means.
The control valve 10 is comprised of a 5-position, 3-position hydraulic pilot type directional switching valve. The control valve 10 is operated by a hydraulic pilot section 10.
A.

By supplying a pilot pressure, which will be described later, to 10B, the neutral position (a) can be switched to the switching positions (b) and (c). Note that the control valve 9 may also be a hydraulic pilot type directional switching valve.

Reference numeral 11 indicates a pilot pump driven by the prime mover 1 together with the hydraulic pump 2, and 12 indicates a pressure reducing valve type pilot valve. The rotational speed of the hydraulic motor 5 (traveling speed of the work vehicle) is controlled by controlling the pilot pressure to be reduced in accordance with the operating amount and adjusting the stroke amount of the control valve 10. Reference numeral 13 indicates a forward/reverse switching valve constituting the operating means for forward/reverse movement, and the switching valve 13 is switched from a neutral position (N) to a forward position (F) and a reverse position (R) by an operating lever 13A. At (N), the vehicle is stopped, and at forward position (F) and reverse position (R), the vehicle is moved forward or backward. 14 is aperture 14A
This figure shows a slow return valve as a speed regulating valve.

15 is a counterbalance valve provided in the middle of the pipes 6A and 6B, and 16A and 16B are a pair of overbalance valves located between the counterbalance valve 15 and the hydraulic morph 5 and provided between the pipes 6A and 6B. The overload relief valves 16A and 16B constitute a brake valve together with the counterbalance valve 15, and when the control valve 1o returns to the neutral position (A), braking pressure is generated in the pipes 6A and 6B. is generated, and the hydraulic motor 5 is gradually stopped. 17 is a counter balance valve 15 and a control valve 10
Conduit 6A is located between.

It shows a center joint as a rotary joint provided in the middle of 6B etc.

18 is a servo cylinder in which the tip of a rod 18A is connected to the variable capacity section 2A in order to variably set the discharge capacity of the hydraulic pump 2; 19 is a capacity control valve which together with the servo cylinder 18 constitutes a variable discharge capacity means; The capacity control valve 19
is composed of a 3-bot, 2-position hydraulic pilot type switching valve, which connects pilot pipe 19A to pipes 4, 4B, and 4C.
The switching positions are switched to the switching positions a and b based on the discharge pressure of the hydraulic pump 2 guided through the hydraulic pump 2, the maximum load pressure from the pilot pipe 19B, and the set pressure of the spring 19C.

Here, the spring 19C of the capacity control valve 19 sets the target differential pressure for load sensing to, for example, about 15 kg/am'', and normally switches the capacity control valve 19 to the switching position a. In addition, the pilot pipe line 19B guides the load pressure acting on the hydraulic motor 5 and the cylinder device 7 from the outside via the pipe lines 2OA and 20B downstream of the control valves 9 and 10, and the pilot pipe line 19B guides the load pressure acting on the hydraulic motor 5 and the cylinder device 7 from the outside through the pipe lines 2OA and 20B on the downstream side of the control valves 9 and 10. The maximum load pressure is selected by the shuttle valve 21 as a high pressure selection valve, and this maximum load pressure is applied to the capacity control valve 19 as a pilot pressure.
The discharge pressure of the hydraulic pump 2 from 9A is transferred to the pilot pipe 19.
Target differential pressure compared to the maximum load pressure from B, e.g. 15
kg/cm" or more, the switch is switched from the switching position a to the switching position side, and the hydraulic pump 2 is
By applying the discharge pressure from the servo cylinder 18 to the servo cylinder 18, the servo cylinder 18 drives the variable capacity section 2A to the small tilt side, thereby reducing the discharge amount (displaced volume) per rotation of the hydraulic pump 2. let Further, when the discharge pressure becomes smaller than the target differential pressure compared to the maximum load pressure, the capacity control valve 19 is switched to the switching position a side, and the capacity variable part 2A is moved to the large tilt side by the servo cylinder. 18 to increase the displacement of the hydraulic pump 2. As a result, the discharge capacity of the hydraulic pump 2 is controlled so that the discharge pressure is higher than the maximum load pressure by the target differential pressure. Ru.

23 indicates an unloading valve constituting the unloading means;
The unload valve 23 is set at a pressure difference between the discharge pressure of the hydraulic pump 2 guided through the pilot pipes 23A and 23B and the maximum load pressure, which is higher than the target pressure difference, for example, at a set value of 21 kg/ When the pressure exceeds approximately Cm'', the pressure oil discharged from the hydraulic pump 2 into the pipe line 4 is returned to the tank 3, and the hydraulic pump 2 is operated in an unloading operation.

Reference numerals 24A and 24B indicate pressure compensation valves located between the hydraulic pump 2 and the control valve 9.10 and provided in the middle of the pipes 4 and 4A, and the volume compensation valve 24A.

24B independently compensates the operations of the hydraulic motor 5 and the cylinder device 7, and causes the hydraulic pump 2 to supply pressure higher than the respective load pressures by a predetermined pressure to these.

Reference numeral 25 indicates a differential pressure sensor as differential pressure detection means disposed between the pipe line 4B and the pilot pipe line 19B, and the differential pressure sensor 25 is connected to the hydraulic pump 2 guided through the pipe lines 4 and 4B.
The differential pressure ΔP between the discharge pressure and the maximum load pressure from the pilot pipe line 19B is detected, and the detection signal is output to a controller 30, which will be described later. Reference numeral 26 indicates a fuel lever as a rotation speed setting means for setting the rotation speed of the prime mover 1. The fuel lever 26 is tilted by the driver, and a setting signal Nl corresponding to the amount of tilting operation is generated (see FIG. 3). )
is output to the controller 30.

Reference numeral 27 indicates a governor that is attached to the prime mover 1 and controls the rotation speed of the prime mover 1, and the governor 27 is connected to the governor lever 27A.
The rotational speed of the prime mover 1 (engine rotational speed N) is increased or decreased in accordance with the rotation angle of the governor lever 27A. 28 indicates an electric motor that constitutes a rotation speed control mechanism that controls the rotation speed of the prime mover 1 together with the governor 27;
The electric motor 28 is composed of a stepping motor or the like, and is configured to rotate a governor lever 27A using a drive lever 28A to control the rotational speed of the prime mover 1 based on a target rotational speed Nro, which will be described later.

29 is connected to the drive lever 28A of the electric motor 28,
The rotation angle sensor 29 detects the rotation angle of the drive lever 28A as the rotation angle of the governor lever 27A, and the rotation angle sensor 29 detects the rotation speed of the prime mover 1 based on the rotation angle of the governor lever 27A. By outputting the detected rotational speed value Nrp to the controller 30, servo control of the rotational speed is performed as described later.
0 indicates a controller as a rotation speed control means configured by a microcomputer or the like, the input side of the controller 30 is connected to the fuel lever 26, the differential pressure sensor 25, the rotation angle sensor 29, etc., and the output side is an electric motor. It is connected to the motor 28 and the like. Then, the controller 3
0 stores programs shown in FIGS. 2 and 4 in its memory circuit, and performs rotation speed control processing of the prime mover 1 including servo control processing. Further, in the memory circuit of the controller 30, a target rotational speed map shown in FIG. 3 and a predetermined value ΔP0 of about 21 kg/cm'', etc., which is higher than the target differential pressure, are stored in a memory area 30A. .

The control circuit for the wheeled hydraulic excavator according to this embodiment has the above-mentioned configuration.Next, the rotational speed control process of the prime mover 1 by the controller 30 will be explained with reference to FIGS. 2 to 4.

First, when the processing operation is started by starting the prime mover l, in step 1, the differential pressure ΔP from the differential pressure sensor 25 is read, and the setting signal N1 from the fuel lever 26 is read, and in step 2, as shown in FIG. The target rotation speed Net based on the setting signal N1 is read from the target rotation speed map. next,
Proceeding to step 3, it is determined whether the differential pressure ΔP between the discharge pressure from the hydraulic pump 1 and the maximum load pressure is equal to or higher than a predetermined value of 620, for example about 21 kg/am'', and rYE
When it is determined that the differential pressure ΔP is, for example, 21 kg/Cm'' or more than the set value set by the unload valve 23, and the hydraulic pump 2 is in unload operation, the process moves to step 4 and the target rotation speed of the prime mover 1 is set. NrO at low rotation speed,
For example, the idle rotation speed is set to N0 as shown in FIG.

As a result, the target rotational speed Nro of the prime mover l is independent of the target rotational speed Nrj set by the fuel lever 26.
For example, idle speed N. is set, and servo control processing, which will be described later, is performed in step 5. Further, when it is determined that rNOJ is determined in step 3, the differential pressure ΔP is lower than the predetermined value ΔP0, and the displacement is controlled so that, for example, the discharge pressure of the hydraulic pump 2 is higher than the maximum load pressure by a target differential pressure of about 15 kg/cm2. Since the displacement variable portion 2A is tilted and driven by the valve 19 via the servo cylinder 18 and the discharge displacement of the hydraulic pump 2 is controlled by load sensing, the process moves to step 6 and the target rotation speed Nrt is set by the fuel lever 26. is set as the target rotation speed NrO of the prime mover 1, and in step 5
Then, the servo control process shown in FIG. 4 is performed.

That is, in the servo control process, in step 11, the target rotation speed N. is read out, and in step 12, the detected rotational speed value Nrp is read. In step 13, the rotational speed difference n is calculated as n = N rP - N ro - (1). In step 14, the absolute value of the rotational speed difference n is calculated. It is determined whether or not lnl is greater than or equal to a predetermined hysteresis value, and when it is determined that rNOJ, the detected rotational speed value Nrp is equal to the target rotational speed N.
ro, so in step 15 a command signal is output to stop the electric motor 28 and hold the drive lever 28A at that rotation angle.

Furthermore, when it is determined that rYEsJ is present in step 14,
Proceeding to step 16, it is determined whether or not the rotational speed difference n is a positive value, and when it is determined that the rotational speed difference n is a positive value, the rotational speed detection value N
Since rp is a value smaller than the target rotational speed Nt0, the step knob 17 outputs a forward rotation command signal to the electric motor 28, and sets the detected rotational speed NrP as the actual rotational speed to the target rotational speed Nro control to bring it close to . and,
When the step knob 16 determines rYESJ, the process moves to step 18 to reverse the electric motor 28 (a reverse command signal is output, and the rotation speed of the prime mover 1 is set to the target rotation speed N).
Control based on ro.

Thus, according to this embodiment, when the differential pressure ΔP between the discharge pressure of the hydraulic pump 2 and the maximum load pressure exceeds the predetermined value 620 of about 21 kg/cm'', the target rotation speed N ro of the prime mover 1 is increased. is reduced to the idle rotation speed N regardless of the target rotation speed Nrj set by the fuel lever 26. Therefore, all the hydraulic actuators such as the hydraulic motor 5 and the cylinder device 7 are substantially stopped, and the hydraulic pump 2 is reduced to the idle rotation speed N. When the motor 1 is unloaded, the motor 1 can be controlled to auto-idle.Therefore, as described in the prior art, there is no need to provide individual detectors for the operation lever, -9A, travel pedal 12A, etc. In addition to being able to simplify the structure, auto-idling control can be performed based only on the signal from the differential pressure sensor 25, and various effects are achieved, such as significantly improving the fuel efficiency and reliability of the prime mover 1.

Next, FIG. 5 shows a second embodiment of the present invention. In this embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and their explanations will be omitted. The feature of this embodiment is that the program shown in FIG. 5 is stored in the memory circuit of the controller 30, and the rotational speed control process of the prime mover 1 is performed. 'Also, in the storage circuit of the controller 3o, a target rotation speed map shown in FIG. 3 is stored in the storage area 30A, a set value 00 corresponding to a predetermined delay time in addition to a predetermined value ΔP0 higher than the target differential pressure, etc. Stored.

Here, the controller 30 performs the processing from steps 21 to 23 in the same manner as steps 1 to 3 in FIG. The counter C is incremented, and when the determination is "NO", the counter C is reset to zero in step 28. Then, in step 25, the count value of the counter C exceeds the set value 00, and rY E S
When it is determined as J, the predetermined delay time has elapsed, so the process moves to steps 26 and 27, and step 4 in FIG.
．． The same process as in step 5 is performed, and when the determination in step 25 is "NO", the process moves to step 29 and the same process as in step 6 in FIG. 2 is performed.

Thus, even in this embodiment configured in this way, the first
In this embodiment, the counter C is activated when the differential pressure ΔP exceeds a predetermined value of 620, and after a predetermined delay time has elapsed, the motor 1 is activated. Since the target rotation speed Nro is lowered to the idle rotation speed N0, the hydraulic motor 5. It is possible to prevent malfunctions in the event that all hydraulic actuators such as the cylinder device 7 stop accidentally (-temporarily), and by controlling the prime mover 1 based on the target rotation speed Net, the operability of the control lever 9A etc. is improved. can.

Next, FIGS. 6 and 7 show a third embodiment of the present invention. In this embodiment, the same components as in the first embodiment are given the same reference numerals, and their explanations will be omitted. Assuming,
The feature of this embodiment is that the discharge amount (displacement volume) per revolution of the hydraulic pump 2 is detected (and the hydraulic pump 2 is provided with a tilting amount detecting means for detecting the tilting amount θ of the variable capacity section 2A. A rotation sensor 31 is attached, and signals from the tilt sensor 31 and the differential pressure sensor 25 are output to a controller 32 as rotation speed control means.

The controller 32 stores a program shown in FIG. 7 in a memory circuit, and performs a rotational speed control process of the prime mover 1. In addition, the memory circuit of the controller 32 has a target rotational speed map shown in FIG. A predetermined amount such as 00 corresponding to is stored.

Here, as shown in FIG. 7, the controller 32 reads the differential pressure ΔP, the setting signal N1, and the tilting amount θ in step 31, and in step 32, 33 reads step 2 in FIG.
3, and in step 34, the capacitance variable part 2A
The amount of tilting θ is the predetermined amount θ. It is determined whether or not the following is true, and when it is determined that both are rYESJ in steps 33 and 34, the same process as step 4.5 shown in FIG. 2 is performed in steps 35 and 36, and NO”
When it is determined that this is the case, the same process as step 6 in FIG. 2 is performed in step 37.

(Thus, in this embodiment configured in this way, it is possible to obtain almost the same effects as in the first embodiment, but in particular, in this embodiment, the differential pressure ΔP is equal to or higher than the predetermined value of 620. , and when the tilting amount θ is less than or equal to the predetermined amount θ, the target rotation speed Nr6 of the prime mover 1 is reduced to the idle rotation speed N0, so that the differential pressure ΔP temporarily decreases to the predetermined value 6.
Even when the tilt amount θ is 20 or more, it is possible to more accurately determine whether or not to perform auto idle control based on the tilt amount θ.
When the differential pressure ΔP does not decrease due to slight operation of the operation lever 9A or the travel pebble 12A, malfunction can be prevented, and the reliability of auto-idling control can be further improved.

In the third embodiment, it has been described that the predetermined amount θ0 corresponds to the tilt amount close to the minimum of the variable capacity section 2A, but instead of this, the storage area 3 of the controller 32
A value corresponding to the minimum tilt amount of the capacity variable portion 2A may be stored in 2A, and it may be determined in the process of step 34 whether the tilt amount θ has reached the minimum tilt amount.

Next, FIG. 8 shows a fourth embodiment of the present invention. In this embodiment, the same components as in the third embodiment are given the same reference numerals, and their explanations will be omitted. The feature of this embodiment is that the program shown in FIG. 8 is stored in the memory circuit of the controller 32, and the rotational speed control process of the prime mover 1 is performed. In addition, the memory circuit of the controller 32 has a target rotation speed map shown in FIG. 3 in a memory area 32A, a predetermined value ΔP0 higher than the target differential pressure, a predetermined amount θ0, and settings corresponding to a predetermined delay time. A value such as 00 is stored.

Here, the controller 32 performs steps 41 to 44 in the same manner as steps 31 to 34 in FIG.
5, the counter C as a delay timer is incremented by "1", and when the determination is "NO", the counter C is reset to zero in step 49. Then, in step 46, the count value of counter C becomes the set value 00 or more, and "YES" is selected.
When it is determined as J, the predetermined delay time has elapsed, so the process moves to steps 47 and 48, and step 4 in FIG.
．． The process similar to step 5 is performed, and when it is determined in step 46 that it is rNOJ, the process moves to step 50 and the process similar to step 6 in FIG. 2 is performed.

Thus, in this embodiment configured in this manner, it is possible to obtain substantially the same effects as in the third embodiment, but especially in this embodiment, the tilting amount θ is the predetermined amount θ. Since the counter C is activated when the target rotation speed Nr0 of the prime mover 1 is lowered to the idle rotation speed N0 after a predetermined delay time has elapsed, the hydraulic motor 5. By controlling the prime mover 1 based on the target rotation speed Nr1, it is possible to more effectively prevent operations in the event that all hydraulic actuators such as the cylinder device 7 stop accidentally (-temporarily), and by controlling the prime mover 1 based on the target rotation speed Nr1, the operating lever 9A, etc. This will definitely improve the operability of the system.

Next, FIG. 9 and FIG. 10 show a fifth embodiment of the present invention. In this embodiment, the same components as in the third embodiment are given the same reference numerals, and their explanations will be omitted. The feature of this embodiment is that the discharge pressure P of the hydraulic pump 2 is detected (a pressure sensor 41 as a discharge pressure detection means is provided in the middle of the pipe line 4, and a signal from the pressure sensor 41 is detected). The configuration is such that the signals from the differential pressure sensor 25 and the tilt sensor 31 are output to the controller 42 as rotation speed control means.

The controller 42 stores a program shown in FIG. 10 in a memory circuit, and performs rotational speed control processing of the prime mover 1. In addition, the memory circuit of the controller 42 has a target rotational speed map shown in FIG. For example, a predetermined pressure Po that approximately corresponds to the set value of the unload valve 23 (for example, about 21 kg/cm'') is stored.

Here, the controller 42 reads the discharge pressure P of the hydraulic pump 2 in addition to the differential pressure ΔP, the tilting amount θ, and the setting signal N1 in step 51, as shown in FIG.
In steps 54 to 54, the same processes as steps 32 to 34 in FIG.
When it is determined that the SJ is SJ, the same process as steps 4 and 5 in FIG.
4 or 55, the same process as step 6 in FIG. 2 is performed.

Thus, in this embodiment configured in this way, it is possible to obtain almost the same effects as in the third embodiment, but in particular, in this embodiment, when the differential pressure ΔP is the predetermined value 620 or more,
The tilting amount θ is a predetermined amount θ. and when the discharge pressure P becomes less than the predetermined pressure P0, the target rotation speed N of the prime mover l
Since ra is lowered to the idle speed No. and automatic idle control is performed, for example, the fuel lever 26 is fully operated to increase the rotation speed of the prime mover 1, and the operation lever 9A, travel pedal 12A, etc. are fully operated. Even if the unload valve 23 is temporarily opened in a state where Idle control malfunctions can be more accurately prevented and reliability improved.

Next, FIG. 11 shows a sixth embodiment of the present invention. In this embodiment, the same components as in the fifth embodiment are given the same reference numerals, and their explanations will be omitted. The feature of this embodiment is that the program shown in FIG. 11 is stored in the memory circuit of the controller 42 to perform the rotation speed control process of the prime mover 1. In addition to the target rotational speed map shown in FIG. 3, a predetermined value ΔPo higher than the target differential pressure, a predetermined amount θ, and a predetermined pressure P0, the storage area 42A stores a set value 00 corresponding to a predetermined delay time, etc. has been done.

Here, the controller 42 performs steps 61 to 65 in the same manner as steps 51 to 55 in FIG.
When it is determined that rYESJ is determined in step 65, the process moves to step 66 and the counter C as a delay timer is incremented by "1", and when it is determined that rNOJ is determined, step 70
The counter C is reset to zero. And step 67
When the count value of counter C becomes more than the set value 00, rYES
When it is determined as J, the predetermined delay time has elapsed, so the process moves to steps 68 and 69 and steps 4 in FIG.
, 5 is performed, and when it is determined in step 67 that it is rNOJ, the process moves to step 71 and the same process as step 6 in FIG. 2 is performed.

Thus, in this embodiment configured in this way, it is possible to obtain substantially the same effects as in the fifth embodiment, but in particular, in this embodiment, auto-idling control is performed after a predetermined delay time has elapsed. , malfunctions can be more effectively prevented, and the operability of the operating lever 9A and the like can be greatly improved.

In each of the above embodiments, the case where the fuel lever 26 is used as the rotation speed setting means of the prime mover 1 has been explained as an example, but instead of this, a signal corresponding to the amount of depression of the travel pedal 12A is set to 30, (32, 42), thereby configuring the rotation speed setting means (the hydraulic actuator is not limited to the hydraulic motor 5. The present invention can also be applied to a case where a hydraulic motor or the like is included and these are driven by a single hydraulic pump 2 or a plurality of hydraulic pumps 2.

Further, in each of the embodiments described above, the control circuit of a wheeled hydraulic excavator has been described as an example, but the present invention is not limited to this, and can be applied to, for example, a tracked hydraulic excavator.

It can also be applied to control devices for prime movers mounted on various construction machines such as hydraulic cranes.

〔Effect of the invention〕

As detailed above, according to the present invention, in a hydraulic circuit using a load sensing system, when the differential pressure between the discharge pressure of the hydraulic pump and the maximum load pressure exceeds a predetermined value, the rotation speed of the prime mover is set. Since the rotational speed is controlled to a low speed below the rotational speed, there is no need to provide a detector for each operating means as in the prior art, the structure can be simplified, and the reliability of rotational speed control can be improved. In addition, by providing a delay time or adding load to the tilting amount determination and discharge pressure determination, various effects can be achieved, such as being able to reliably prevent malfunctions and further improving reliability.

[Brief explanation of drawings]

Figures 1 to 4 show the first embodiment of the present invention, with Figure 1 being a control circuit diagram, Figure 2 being a flowchart showing the rotational speed control process of the prime mover, and Figure 3 being the memory area of the controller. FIG. 4 is a flowchart showing the servo control process, FIG. 5 is a flowchart similar to FIG. 2 showing the second embodiment, and FIGS. 6 and 7 are 6 is a control circuit diagram, FIG. 7 is a flowchart showing the rotation speed control process of the prime mover, and FIG. 8 is a seventh embodiment showing the fourth embodiment.
9 and 10 show the fifth embodiment, FIG. 9 is a control circuit diagram, FIG. 10 is a flowchart showing the rotational speed control process of the prime mover, and FIG. 10 is a flowchart similar to FIG. 10 showing an embodiment of the present invention. 1... Prime mover, 2... Hydraulic pump, 2A... Variable capacity part, 3... Tank, 4.4A, 4B, 4C, 6A
. 6B, 8A, 8B...Pipe line, 5...Hydraulic motor, 7
...Cylinder device, 9.10...Control valve, 9A...
・Operation lever 11...pilot pump, 12...
・Pilot valve, 12A...Travel pedal, 18...
Servo cylinder, 19... Capacity control valve, 23... Unload valve, 24A, 24B... Pressure compensation valve, 25.
... Differential pressure sensor (differential pressure detection means), 26 ... Fuel lever (rotation speed setting means), 27 ... Governor, 28 ...
electric motor. 29...Rotation angle sensor, 30, 32.42...Controller (rotation speed control means), 31...Tilt sensor (
41...Pressure sensor (discharge pressure detection means), ΔP...Differential pressure, θ...Tilt amount, P...Discharge pressure.

Claims (6)

[Claims] (1) A prime mover, a rotation speed setting means for setting the rotation speed of the prime mover, a variable displacement hydraulic pump driven by the prime mover, and a plurality of hydraulic pumps driven by pressure oil discharged from the hydraulic pump. A plurality of controls are provided in the middle of each pipe connecting the actuator and each of the hydraulic actuators and the hydraulic pump, and that control the flow rate of pressure oil supplied to and discharged from each of the hydraulic actuators according to the operating amount of the operating means. a valve, and a discharge capacity variable means for controlling the discharge capacity of the hydraulic pump so that the discharge pressure of the hydraulic pump is higher than the maximum load pressure of the load pressures of each of the hydraulic actuators by a predetermined target differential pressure. , unloading means for returning pressure oil from the hydraulic pump to the tank when the differential pressure between the discharge pressure and the maximum load pressure exceeds a set value higher than the target differential pressure; differential pressure detection means for detecting a pressure difference between the load pressure and the load pressure; and when the differential pressure detected by the detection means exceeds a predetermined value higher than the target differential pressure, the rotation speed of the prime mover is set to the rotation speed. A prime mover control device for construction machinery, comprising a rotation speed control means for controlling the rotation speed to a low rotation speed lower than a rotation speed set by the rotation speed. (2) Claim (1) wherein the rotational speed control means is configured to control the rotational speed of the prime mover to a low rotational speed after a predetermined delay time has elapsed after the differential pressure has exceeded the predetermined value. A prime mover control device for the construction machine described above. (3) A tilt amount detection means for detecting a tilt amount of the hydraulic pump is provided, and the rotation speed control means is configured to detect when the differential pressure is equal to or greater than the predetermined value and the tilt amount is less than or equal to the predetermined amount. ,
A prime mover control device for a construction machine according to claim 1, wherein the prime mover control device is configured to control the rotational speed of the prime mover to a low rotational speed. (4) The rotation speed control means has a differential pressure equal to or higher than the predetermined value;
The prime mover control for construction machinery according to claim (3), wherein the rotation speed of the prime mover is controlled to a low rotation speed after a predetermined delay time has elapsed after the tilting amount becomes equal to or less than a predetermined amount. Device. (5) Discharge pressure detection means for detecting the discharge pressure of the hydraulic pump, and the rotation speed control means is configured such that the differential pressure is equal to or greater than the predetermined value, the tilting amount is equal to or less than the predetermined amount, and the discharge pressure is The prime mover control device for construction machinery according to claim 3, wherein the prime mover control device is configured to control the rotation speed of the prime mover to a low rotation speed when the pressure is below a predetermined pressure. (6) The rotational speed control means is configured to control the rotation speed of the prime mover after a predetermined delay time has elapsed since the differential pressure becomes equal to or greater than the predetermined value, the tilt amount is equal to or less than the predetermined amount, and the discharge pressure becomes equal to or less than the predetermined pressure. A prime mover control device for a construction machine according to claim 5, which is configured to control the rotational speed to a low rotational speed.