JPH0968169A - Hydraulic drive for construction machinery - Google Patents

Abstract

(57) [PROBLEMS] To provide a hydraulic drive system for a construction machine capable of reducing pump absorption torque and rapidly increasing engine speed when returning from an idle state. SOLUTION: At the time of returning from the idling state, the operating means 9 is operated while the auto idle switch 11 is ON, the pilot switch 12 is turned ON, and the target rotation speed N ₁ in the auto idle control unit 1a becomes a large rotation speed N ₁₁ . Since the engine speed is restored, the target speed N ₂ of the throttle control unit 1b is selected by the minimum value selection unit 1c, and the engine 2 speed is returned to normal. Then, the tilt angle switching signal S ₃ is turned off, the target tilt angle θ ₂ is set by the normal table in the horsepower control unit 5b, and the minimum value selection unit 5c sets the minimum of θ ₂ and θ ₁ of the positive control unit 5a. A value is selected, and the target tilt angle returns to the normal horsepower control / positive control control setting. At this time, the tilt angle switching signal is turned OFF after the elapse of a predetermined time T _u from the time of recovery, so that the pump tilt angle is set to the normal value after the engine speed becomes sufficiently high and becomes equal to the normal target speed N _2. To the target tilt angle of.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic drive system for a construction machine, for example, which determines a rotational speed of an engine based on a target value from a throttle lever. The present invention relates to a hydraulic drive system for a construction machine that reduces fuel consumption, noise, and vibration by switching the values.

[0002]

2. Description of the Related Art A conventional hydraulic drive system for a construction machine of this type will be described with reference to FIGS. FIG. 9 shows a hydraulic circuit diagram of the entire hydraulic drive system. In FIG. 9, the hydraulic drive system is a so-called electronically controlled engine 102, a rotation speed control device 103 provided in the engine 102 to control the rotation speed of the engine 102, and a variable displacement type drive driven by the engine 102. The hydraulic pump 104, the tilt angle setting device 105 that determines the tilt angle of the variable displacement hydraulic pump 104, and the capacity of the hydraulic pump 104 so that the value determined by the tilt angle setting device 105 becomes ( A regulator 115 for adjusting the tilt angle) and an actuator 1 driven by the pressure oil sent from the hydraulic pump 104.
06, a load 107 operated by driving the actuator 106, and a pilot type directional control valve 108 for controlling the direction and flow rate of the pressure oil discharged from the hydraulic pump 104.
The operation means 109 for controlling the switching direction of the direction switching valve 108 and the rotation angle sending device for transmitting the hydraulic pump tilt angle switching signal to the tilt angle setting device 105 and sending the engine speed command value to the rotation speed control device 103. The number setting device 101, an engine speed operating means for operating the engine speed, for example, the throttle lever 113, and a restriction state for limiting the engine speed to the idling speed and a normal state without this restriction are switched. A switching means, for example, an auto idle switch 111 and a pilot switch 112, and a shuttle valve 110 for selecting the maximum pilot pressure for operating the directional control valve 108 and guiding it to the pilot switch 112 are provided.

FIG. 10 is a block diagram showing details of control functions of the tilt angle setting device 105 and the rotation speed setting device 101. 10, the tilt angle setting device 105 includes a positive control unit 105a to which the maximum pilot pressure signal from the operating means 9 is introduced, and a horsepower control unit 105b to which the self-discharge pressure signal of the hydraulic pump 4 is introduced. Is equipped with.
The positive control unit 105a calculates a target tilt angle that is a target flow rate substantially proportional to the maximum pilot pressure P ₁ based on a table as shown in the figure, and the horsepower control unit 105b makes a hydraulic pump 104 based on the table as shown. A target tilt angle that provides a target flow rate that is substantially inversely proportional to the discharge pressure P ₂ is calculated. At this time, the table of the horsepower control unit 105b is switched by a tilting angle switching signal described later, and the solid line in the figure indicates that the tilting angle switching signal is off.
The broken line corresponds to when the tilt angle switching signal is on. That is, the absorption torque of the hydraulic pump is reduced when the tilt angle switching signal is ON. The smaller one of these two target tilt angles is the minimum value selection unit 105.
It is selected in c and is output to the regulator 115 as a final tilt angle command value.

On the other hand, the rotation speed setting device 101 includes an auto idle control section 101a to which a signal from an auto idle switch 111 and a signal from a pilot switch 112 are input, and a throttle to which a throttle signal V from a throttle lever 113 is input. And a control unit 101b.

FIG. 11 is a diagram showing details of control in the auto idle control unit 101a. In FIG. 11, when the signal S ₁ from the auto idle switch 111 is on and the signal S ₂ from the pilot switch 112 is off, the auto idle control unit 101a delays the engine by a predetermined time T _e , and The target rotation speed N ₂ is reduced to a predetermined idling rotation speed. And this time the tilting Tsunokiri signal S ₃ cuttings on simultaneously Kawari switch to their respective positions where the target flow rate of the power control unit 105b of the tilt angle setting device 105 is shown by a broken line in FIG. As a result, the absorption torque of the hydraulic pump 104 is reduced, and the engine 10
Since the load of 2 becomes lighter, it prevents the engine speed from dropping more than necessary during auto idle. Then, when the pilot switch 112 is turned on again, the tilt angle switching signal S ₃ immediately returns to off, and the engine target speed N ₁
The original speed is immediately restored.

Returning to FIG. 10, the throttle control unit 101b
Calculates an engine target speed N ₂ which is approximately proportional to the throttle signal V from the throttle lever 113 based on a table as shown. Then, the smaller one of the engine target rotation speeds N ₁ and N ₂ is selected by the minimum value selection unit 101c, and is output to the rotation speed control device 103 as a final engine rotation speed command value.

[0007]

However, the above-mentioned conventional structure has the following problems. That is, when the pilot switch 112 is turned on again from the idle state, the engine target speed N ₁ is immediately returned to the original value in the auto idle control unit 101a as described above. However, even if this N ₁ is selected by the minimum value selection unit 101c and is output to the rotation speed control device 103 as an engine rotation speed command value, the actual engine rotation speed at this time takes a long time to respond and immediately Do not follow. On the other hand, by the tilt angle switching signal, the target tilt angle according to the target flow rate Q ₂ (shown by the broken line) in the horsepower control unit 105b is selected by the minimum value selecting unit 105c, and the tilt angle command value is selected. When the output is output to the regulator 115 as, the response of the tilt angle of the hydraulic pump 104 is relatively quick and quickly returns to the original value.

That is, the pilot switch 112 is used when returning from the idle state to the normal state.
Immediately after turning off from on, only the tilt angle of the hydraulic pump 104 may increase while the engine speed is not sufficiently high. This allows
There is a possibility that the absorption torque of the hydraulic pump 104 becomes large, the rotation speed of the engine 102 becomes difficult to increase, the amount of black smoke in the exhaust increases, the amount of fuel consumption increases, or noise and vibration increase.

An object of the present invention is to provide a hydraulic drive system for a construction machine capable of reducing the absorption torque of the hydraulic pump and rapidly increasing the engine speed when returning from an idle state to a normal state. is there.

[0010]

In order to achieve the above object, according to the present invention, an engine, a variable displacement hydraulic pump driven by the engine, and pressure oil discharged from the hydraulic pump are used. An actuator to be driven, a direction switching valve for controlling the flow of pressure oil supplied from the hydraulic pump to the actuator, a switching valve operating means for controlling a stroke amount of the direction switching valve, and an engine speed idling. A switching means for switching between a limited state in which the rotation speed is limited and a normal state in which this limitation is not performed, and a first target speed for calculating the first target rotation speed of the engine when the switching means is switched to the normal state.
Target rotation speed calculation means and second target rotation speed calculation for calculating a second target rotation speed that is a value smaller than the first target rotation speed when the switching means is switched to the restricted state. An engine speed setting means having means, an engine control means for controlling the engine speed according to the first and second target speeds set by the engine speed setting means, and the switching means. Target displacement volume calculating means for calculating a first target displacement volume of the hydraulic pump for limiting the input torque of the hydraulic pump to the output torque of the engine or less when the normal pressure is switched to the normal state, and A second target displacement that is smaller than the first target displacement in the low discharge pressure region of the hydraulic pump when the switching unit is switched to the restricted state. Displacement volume setting means having a second target displacement volume calculation means for calculating and displacement volume of the hydraulic pump is controlled according to the first and second target displacement volumes set by the displacement volume setting means. In a hydraulic drive system for a construction machine having a pump control means, the displacement volume setting means, when the switching means is switched from a limited state to a normal state, after a predetermined time delay from the time of switching,
There is provided a hydraulic drive system for a construction machine, characterized in that the second target displacement volume setting state is changed to a first target displacement volume setting state.

Preferably, in the hydraulic drive system for the construction machine, the switching means switches the operating speed detecting means for detecting the operating status / non-operating status of the switching valve operating means and the engine speed to the idling speed. When the auto idle switch is ON and the operation state detecting means detects the non-operation state of the switching valve operating means, the engine speed is set to the idling speed. The engine speed is limited to the number of revolutions, when the auto idle switch is OFF, and when the auto idle switch is ON and the operation state of the switching valve operation means is detected by the operation state detection means. There is provided a hydraulic drive system for a construction machine, which is characterized in that the above limitation is lifted.

Further, preferably, in the hydraulic drive system for the construction machine, a rotation speed operation means for operating the rotation speed of the engine, and a rotation speed operation amount detection means for detecting an operation amount of the rotation speed operation means. And a third target rotation speed calculation means for calculating a third target rotation speed of the engine according to the operation amount detected by the rotation speed operation amount detection means. And a minimum target rotation speed selection means for selecting the minimum one of the first to third target rotation speeds and outputting it to the engine control means. A drive is provided.

Further preferably, the hydraulic drive system for the construction machine further comprises a switching valve operation amount detecting means for detecting an operation amount of the switching valve operating means, and the displacement volume setting means is the switching valve. Third target displacement volume calculating means for calculating a third target displacement volume of the hydraulic pump according to the operation amount detected by the operation amount detecting means,
A hydraulic drive system for a construction machine, further comprising: minimum displacement volume selecting means for selecting the smallest one of the first to third target displacement volumes and outputting it to the pump control means. To be done.

That is, in such a structure, when the operator does not work for a relatively long period of time, the switching means is switched to the restriction state for restricting the engine to the idling speed. That is, for example, the auto idle switch for turning the engine speed to the idling speed can be turned on without operating the switching valve operating means. At this time, since the non-operating state of the switching valve operating means for controlling the stroke amount of the directional switching valve is detected by the operating state detecting means, the second target rotational speed calculating means provided in the engine rotational speed setting means. Then, a relatively small second target rotation speed corresponding to the idling rotation speed is calculated. Then, the engine control means controls the engine speed in accordance with the second target engine speed, whereby the engine speed follows this and drops to the idling speed. At this time, at the same time, the second target displacement volume calculating means provided in the displacement volume setting means calculates a second target displacement volume which is a relatively small value in the low discharge pressure region, and the pump control means operates the second target displacement volume. The displacement of the hydraulic pump is controlled according to the target displacement of the hydraulic pump, and the displacement of the hydraulic pump follows this and becomes small.

When the operator restarts the work from this state, the switching means is switched from the restricted state to the normal state. That is, for example, if the switching valve operating means is operated to stroke the direction switching valve to supply pressure oil to the actuator, the operating state of the switching valve operating means at this time is detected by the operating state detecting means, so that the engine rotation speed is reduced. The first target rotation speed calculation means provided in the number setting means calculates a first target rotation speed that is higher than the second target rotation speed. The operator may turn off the auto idle switch.
The same applies to this case. Then, the engine control means controls the engine speed in accordance with the first target engine speed, and the engine speed follows this and returns from the idling engine speed to the normal engine speed. On the other hand, at this time, the first target displacement volume calculating means provided in the displacement volume setting means calculates the first target displacement volume for limiting the input torque of the hydraulic pump to the output torque of the engine or less, and the pump control means. Then, the displacement of the hydraulic pump is controlled according to the first target displacement,
The capacity of the hydraulic pump follows this and returns from a small capacity to a normal capacity. At the time of such a return, the displacement volume setting means shifts from the state of setting the second target displacement volume to the state of setting the first target displacement volume. Here, in general, the response of the actual engine speed in the control by the engine control means is relatively slow, and it takes a longer time for following the response of the actual pump displacement in the control by the pump control means. In the configuration of the present invention, in response to this difference in response time, the target displacement setting means changes the switching means from the limited state to the normal state, and at the same time the second target displacement set state is changed to the first target. Instead of shifting to the setting state of the displacement, the control unit shifts to the setting state of the first target displacement after a lapse of a predetermined time after the switching unit is switched from the limited state to the normal state. Therefore, the displacement of the hydraulic pump can be increased to the first target displacement after the engine speed becomes sufficiently large and becomes substantially equal to the first target displacement.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the present invention.
This will be described with reference to FIG. FIG. 1 shows a hydraulic circuit diagram of the hydraulic drive system for the construction machine according to the present embodiment.

In FIG. 1, the hydraulic drive system is a so-called electronically controlled engine 2, a rotation speed control device 23 provided in the engine 2 for controlling the rotation speed of the engine 2, and a variable drive system driven by the engine 2. A displacement type hydraulic pump 4 and an auxiliary pump 17 for generating pilot pressure,
A so-called electronic regulator 24 that adjusts the capacity (tilt angle) of the hydraulic pump 4, an actuator 6 that is driven by the pressure oil sent from the hydraulic pump 4, a load 7 that is driven by the drive of the actuator 6, and a hydraulic pump. No. 4, a pilot type directional control valve 8 for controlling the direction and flow rate of the pressure oil discharged, operating means 9 for controlling the switching direction of the directional control valve 8, and a rotational speed of the engine 2. Rotation speed operation means, for example, the throttle lever 13
And a switching means, such as an auto idle switch 11 and a pilot switch 12, for switching between a limited state in which the engine speed is limited to the idling speed and a normal state in which the engine speed is not limited, and a pilot pressure for operating the directional control valve 8. The shuttle valve 10 that selects the largest one and guides it to the pilot switch 12, the discharge pressure sensor 25 that detects the discharge pressure of the hydraulic pump 4 and outputs a corresponding detection signal to the controller 29, and the maximum of the shuttle valve 10 The controller 2 detects the pilot pressure and outputs the corresponding detection signal.
9, and an operation pressure sensor 26 for outputting to 9.

A block diagram showing the details of the control function of the controller 29 is shown in FIG. In FIG. 2, the controller 29 calculates a target displacement (target tilt angle) of the hydraulic pump 4 and outputs the tilt angle setting unit 5 to the regulator 24, and a target rotation speed of the engine 2 to calculate a rotation speed control device. 23, and a rotation speed setting unit 1 for outputting to 23.
The tilt angle setting unit 5 includes a positive control unit 5a to which the maximum pilot pressure signal from the operating means 9 is introduced and a horsepower control unit 5b to which a self-discharge pressure signal of the hydraulic pump 4 is introduced.
And The positive control unit 5a calculates a target tilt angle θ ₁ that is a target flow rate Q ₁ almost proportional to the maximum pilot pressure P ₁ based on the table shown in the figure, and the horsepower control unit 5b uses the table shown in the figure. Then, a target tilt angle θ ₂ is calculated which is a target flow rate Q ₂ that is substantially inversely proportional to the discharge pressure P ₂ of the hydraulic pump 4. At this time, the horsepower control unit 5b
The table is switched by a tilting angle switching signal, which will be described later. The solid line in the figure corresponds to when the tilting angle switching signal is off, and the broken line corresponds to when the tilting angle switching signal is on. That is, when the tilt angle switching signal is ON, the absorption torque of the hydraulic pump is switched to be small. Then, the smaller one of these two target tilt angles θ ₁ and θ ₂ is selected by the minimum value selection unit 5c and is output to the regulator 24 as a final tilt angle command value.

On the other hand, the rotation speed setting section 1 includes an auto idle control section 1a to which a signal from the auto idle switch 11 and a signal from the pilot switch 12 are input, and a throttle control to which a throttle signal from the throttle lever 13 is input. And a section 1b.

FIG. 3 is a diagram showing details of control in the auto idle control section 1a. In FIG. 3, when the signal S ₁ from the auto idle switch 11 is turned on and the signal S ₂ from the pilot switch 12 is turned off, the auto idle control unit 1a delays the engine target speed by a predetermined time T _e. N ₁ is reduced to a predetermined idling speed N ₁₀ . This is because when the operator is operating the auto idle switch 11 while the operator is operating, and the operating lever is moved in the opposite direction across the neutral position, the operation amount becomes zero for a short moment and the pilot switch 12 transitions. OFF
This is to prevent malfunction in such a case. At this time, the tilt angle switching signal S
_{3 is} also turned on after a delay of a predetermined time T _d (T _d <T _e ), and the target flow rate of the horsepower control unit 5b of the tilt angle setting unit 5 is indicated by the broken line in FIG. 2 as described above. Switch to. As a result, the absorption torque of the hydraulic pump 4 is reduced and the load on the engine 2 is reduced, so that it is possible to prevent the engine speed from dropping more than necessary during auto idle. Then, when the pilot switch 12 is turned on again, the target engine speed N ₁ is immediately returned to the original speed, while the tilt angle switching signal S ₃ is turned off after the elapse of the predetermined time T _u. Has become.

Returning to FIG. 2, the throttle control unit 1b operates the throttle lever 13 based on a table as shown.
A target engine speed N ₂ that is approximately proportional to the throttle signal V from is calculated. Then, the engine target speed N ₁ ,
The smaller one of N ₂ is selected by the minimum value selection unit 1c, and the engine speed control device 23 is set as the final engine speed command value.
Is output to

The operation and action of this embodiment will be described below. In the above configuration, the automatic idle switch 11 is turned on, and when the operator does not work for a relatively long period of time, the operating means 9 is set to the neutral position. At this time, the pilot switch 12 connected via the shuttle valve 10 is turned off by the non-operating state of the operating means 9. As a result, the target idle speed N ₁ is set to a relatively low idling speed N ₁₀ by the auto idle control unit 1a provided in the rotary speed setting unit 1 of the controller 29. Also in this case the throttle control unit 1b, on the basis of the table shown in FIG. 2, the target rotational speed N ₂ is but is set to a rotational speed corresponding to the throttle signal V, these N _10, N ₂ at minimum value selector 1c The smaller one is selected as the command value that is the final target rotation speed, and the rotation speed of the engine 2 is controlled by the rotation speed control device 23 accordingly. Therefore, even if the throttle lever 13 is set to a relatively high rotation speed, the rotation speed of the engine 2 decreases until it reaches the idling rotation speed N ₁₀ . On the other hand, at this time, the horsepower control unit 5 of the displacement volume setting unit 5 from the automatic idle control unit 1a
The tilt angle switching signal S ₃ output to b is turned on. The horsepower control unit 5b, accordingly, instead of the solid line of the table shown in FIG. 2, using dashed lines in the table as a relatively small value in the low discharge pressure zone, corresponding to the discharge pressure P ₂ at that time target Set the tilt angle θ ₂ . At this time, the positive control unit 5a
2, the target tilt angle θ ₁ is based on the table shown in FIG. 2 and the target flow rate Q corresponding to the pilot pressure signal P ₁ = 0.
_The target tilt angle θ ₁₀ is set to ₁₀ and the smaller one of these θ ₂ and θ ₁₀ is selected as the command value which is the final target tilt angle by the minimum value selection unit 5c. Accordingly, the tilt angle of the hydraulic pump 4 is controlled by the regulator 24. Therefore, even if θ ₁₀ is set to a relatively high tilt angle, the tilt angle of the hydraulic pump 4 is a predetermined small tilt angle based on the characteristic line indicated by the broken line in the table of the horsepower control unit 5b. Fall to.

When the operator resumes work from such an idling state, for example, the operating means 9 is operated to stroke the direction switching valve 8 and supply pressure oil to the actuator 6. Then, the maximum pilot pressure at this time is introduced via the shuttle valve 10, and the pilot switch 12 is turned on. As a result, the target rotation speed N ₁ set by the auto idle control unit 1a returns from the idling rotation speed N ₁₀ to a relatively large rotation speed N ₁₁ . Instead of the operator operating the operating means 9, the auto idle switch 11 may be turned off. The same applies to this case. As a result, the target value N ₂ from the throttle control unit 1b is always selected as the command value in the minimum value selection unit 1c, and the throttle signal V is supplied to the rotation speed control device 23.
The engine speed of the engine 2 is controlled in accordance with the target engine speed N ₂ corresponding to. Then, the rotation speed of the engine 2 follows this and returns from the idling rotation speed to the normal rotation speed. On the other hand, at this time, the tilt angle switching signal S ₃ output from the auto idle 1a to the horsepower control unit 5b is OF
It becomes F. In response to this, the horsepower control unit 5b again uses the broken line table to the solid line table shown in FIG.
According to the discharge pressure P ₂ at that time, the target tilt angle θ ₂ is set so as to limit the input torque of the hydraulic pump 4 to the output torque of the engine 2 or less. At this time, also in the positive control unit 5a, the target tilt angle θ ₁ is set so that the target flow rate Q ₁ corresponding to the pilot pressure signal P ₁ is set based on the table shown in FIG. The smaller of θ ₂ and θ ₁ is selected as the command value that is the final target tilt angle. That is, the setting of the pump target tilt angle is
The restriction of the idling state is released, and the normal horsepower control and positive control control settings are restored. Then, the tilt angle of the hydraulic pump 4 is controlled by the regulator 24 according to this command value, and the displacement of the hydraulic pump 4 follows this and returns from the small displacement to the normal displacement.

Here, as described above, at the time of returning from the idling state to the normal state, the horsepower control section 5b.
Is to shift from a state in which a relatively small tilt angle is set in the low discharge pressure region shown by a broken line in the table in FIG. 2 to a state in which a normal tilt angle is set as shown by a solid line. Become. Here, in general, the response of the actual rotation speed of the engine 2 when controlled by the rotation speed control device 23 is relatively slow, and is lower than the response of the actual displacement of the hydraulic pump 4 when controlled by the regulator 24. , It takes a long time to follow up. In the hydraulic drive system of the present embodiment, the tilt angle switching signal for switching the table of the horsepower control unit 5b corresponding to this difference in response time is returned by the operator from the restricted state to the normal state (operating the operating means 9). Or turn off the auto idle switch 11)
At the same time, it does not return from ON to OFF, but it turns OFF after a predetermined time T _u has elapsed from the time of restoration (see FIG. 3). Therefore, after the rotation speed of the engine 2 becomes sufficiently large and becomes substantially equal to the target rotation speed N ₂ in the normal state,
The tilt angle of the hydraulic pump 4 can be increased to the target tilt angle at the normal time. Therefore, as in the conventional case in which the tilt angle switching signal is turned OFF and the tilt angle is increased at the same time when the normal state is restored, the tilt angle of the hydraulic pump 4 is changed before the rotational speed of the engine 2 is sufficiently increased. It is possible to quickly increase the rotation speed of the engine 2 without increasing the absorption torque first, that is, in a state where the absorption torque of the hydraulic pump 4 is small. Therefore, it is possible to prevent an increase in black smoke in the exhaust gas of the engine 2 and an increase in fuel consumption, noise, and vibration.

In the first embodiment, the tilting angle control section 5 of the controller 29 includes the horsepower control section 5b.
Although the horsepower control performed in 1. and the positive control performed in the positive control control unit 5a are combined, the present invention is not limited to this, and negative control may be performed instead of positive control. Also in this case, the same effect is obtained.

A second embodiment of the present invention will be described with reference to FIGS. The present embodiment is an embodiment in which a hydraulic regulator is used. Members equivalent to those in the first embodiment are denoted by the same reference numerals. FIG. 4 shows a hydraulic circuit diagram of the hydraulic drive system for the construction machine according to the present embodiment. In FIG. 4, the main points of this embodiment different from the first embodiment are as follows.
That is, a so-called hydraulic tilt angle control device 205 having the functions of the electronic regulator 24 and the tilt angle setting unit 5 in the controller 29 is provided. That is, although the tilt angle control device 205 has a known configuration and the details are not shown, the pressure oil from the pilot pump 17 is introduced through the electromagnetic proportional valve 219 and the shuttle valve 1 is also provided.
The maximum operating pressure and the discharge pressure of the hydraulic pump 4 are guided via 0, and thereby the positive control control section 5a and the horsepower control section 5b provided in the tilt angle setting section 5 of the first embodiment shown in FIG. , And the function of the minimum value selection unit 5c. Further, accordingly, the discharge pressure sensor 25 and the operation pressure sensor 26 are omitted. Further, the control content of the controller 228 is slightly different from that of the controller 29 of the first embodiment in a form corresponding to this. A block diagram showing this detail is shown in FIG. In FIG. 5, the controller 2
The control function of 28 is similar to the function of the rotation speed setting unit 1 of the controller 29 of the first embodiment shown in FIG. That is, the controller 228 includes an auto idle control section 1a and a throttle control section 1b. The auto idle control section 1a controls the signal S ₁ from the pilot switch 12 when the signal S ₁ from the auto idle switch 11 is on. _{When 2} is turned off, a predetermined time T _e
After that, the engine target speed N ₁ is lowered to a predetermined idling speed. Further, at this time, the tilt angle switching drive signal S ₄ corresponding to the tilt angle switching signal is output to the solenoid proportional valve 219, but this drive signal S ₄ remains for a predetermined time T _d (where T _d <T _e ), The solenoid proportional valve 219 converts the hydraulic pressure signal into a hydraulic signal, and the hydraulic pressure signal is transmitted to the tilt angle control device 205. On the other hand, the throttle control unit 1b
Is calculated based on a table as shown in the drawing, the engine target speed N ₂ which is approximately proportional to the throttle signal V from the throttle lever 13, and the smaller one of N ₁ and N ₂ is selected by the minimum value selection unit 1c. The final engine speed command value is output to the speed control device 23.

Other configurations and operations are almost the same as those of the first embodiment. Also according to this embodiment, the same effect as that of the first embodiment can be obtained.

A third embodiment of the present invention will be described with reference to FIG. The present embodiment is an embodiment in the case of adjusting the engine speed using a stepping motor provided outside the engine. Members equivalent to those of the first and second embodiments are denoted by the same reference numerals. FIG. 6 shows a hydraulic circuit diagram of the hydraulic drive system for the construction machine according to the present embodiment. In FIG. 6, the main difference between the present embodiment and the second embodiment is that the engine 302 is not of a so-called electronic control type, and the governor lever 320 provided inside the engine 302 is connected to the outside of the engine 302 via a cable 314. The rotation speed is controlled by driving the stepping motor 322 and displacing it at a predetermined angle, and the controller 327 controls the rotation speed accordingly.
Is to be input to the stepping motor 322.

Other configurations and operations are almost the same as those of the second embodiment. Also according to this embodiment, the same effects as those of the first and second embodiments can be obtained.

A fourth embodiment of the present invention will be described with reference to FIG. The present embodiment is an embodiment in which the engine speed is adjusted by a manual lever. Members equivalent to those in the first to third embodiments are denoted by the same reference numerals. FIG. 7 shows a hydraulic circuit diagram of the hydraulic drive system for the construction machine according to the present embodiment. In FIG. 7, the main difference of the present embodiment from the third embodiment is that in the engine 402, a governor drive link 421 is connected to a governor lever 320 via a spring 416.
1 is connected to a throttle lever 413 via a cable 314, and a hydraulic cylinder 415 provided for driving the governor lever 320 is connected to the auxiliary pump 17.
Solenoid proportional valve 41 for controlling and supplying pressure oil from the
8 is provided.

In addition, in accordance with this, the controller 40
The control contents of 1 are different. A diagram showing this detail is shown in FIG.
Shown in In FIG. 8, the control function of the controller 401 is similar to the function of the auto idle control unit 1a of the first embodiment shown in FIG. That is,
When the signal S ₂ from the pilot switch 12 is turned off while the signal S ₁ from the auto idle switch 11 is on, the controller 401 delays the engine target speed N ₁ by a predetermined idling speed by delaying by a predetermined time T _e. The target rotation speed instructing drive signal S ₅ is output to the solenoid proportional valve 418 so as to reduce the number. Further, at this time, the tilt angle switching drive signal S ₄ output to the solenoid proportional valve 219 is switched to the ON state with a delay of a predetermined time T _d (where T _d <T _e ), and the solenoid proportional valve 219 operates hydraulic pressure. It is converted into a signal and transmitted to the tilt angle control device 205.

Here, the selection and setting of the target rotation speed in the engine 402 is as follows. That is, in the throttle lever 413, the governor lever 320, and the governor driving link 421, the direction A in the drawing is the direction of increasing the engine speed, and the direction B is the direction of decreasing the engine speed. The rotational speed of the engine 2 is finally determined by the displacement angle of the governor lever 320. The governor lever 320 is connected to the hydraulic cylinder 415 side, the spring 416, the governor drive link 421, the cable 3
Since both can be driven from the throttle lever 413 side via 14, it is important how each target rotation speed instruction is selected.

(1) When the target rotation speed of the throttle lever 413 is smaller than the target rotation speed of the hydraulic cylinder 415, that is, in this case, the throttle cylinder is more extended than the force that displaces the governor lever 320 in the direction A in the figure. Since the force of displacement in the A direction by the lever 413 is larger, the governor lever 3 can be operated only by the latter force.
20 is largely displaced in the A direction together with the governor drive link 421, and the engine 402 is connected to the throttle lever 413.
Is the target rotation speed. (2) When the target rotation speed of the hydraulic cylinder 415 <the target rotation speed of the throttle lever 413 In other words, in this case, the hydraulic cylinder 415 extends more than the force that pulls the throttle lever 413 to displace the governor lever 320 in the direction A in the figure. Since the force for displacing in the A direction is larger, the governor lever 320 moves the governor drive link 421 while bending the spring 416.
It is displaced in the A direction by a larger amount. Therefore, the engine 402 has the target rotation speed of the hydraulic cylinder 415.

From the above (1) and (2), the engine 4 is eventually
The number of revolutions of 02 is, of the target number of revolutions of the hydraulic cylinder 415 and the target number of revolutions of the throttle lever 413,
Since it is adjusted to be smaller, it can be seen that the function of the minimum value selection unit 1c shown in FIG. 5 of the second embodiment is fulfilled. Other configurations and operations are almost the same as those in the third embodiment. Also according to this embodiment, the same effects as those of the first to third embodiments are obtained.

[0035]

According to the present invention, in the target displacement setting means, the switching means is switched from the limited state to the normal state, and at the same time, the second target displacement setting state is changed to the first target displacement setting state. Instead of shifting to (1), after a lapse of a predetermined time from the time when the switching means is switched from the restricted state to the normal state, it shifts to the first target displacement setting state. Therefore, the displacement of the hydraulic pump can be increased to the first target displacement after the engine speed becomes sufficiently large and becomes substantially equal to the first target displacement. Therefore, as in the conventional case in which the displacement means is switched to the normal state and the displacement volume setting means is shifted to the first target displacement volume setting state at the same time, the pump displacement volume is increased before the engine speed is sufficiently increased. It is possible to increase the engine speed in a state where the absorption torque of the hydraulic pump is small without increasing first and then increasing the absorption torque. Therefore, it is possible to prevent the engine speed from increasing, and to prevent an increase in black smoke in the exhaust gas and an increase in fuel consumption, noise, and vibration.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram of a hydraulic drive system for a construction machine according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing details of a control function of the controller shown in FIG.

FIG. 3 is a diagram showing details of control in an auto idle control section shown in FIG.

FIG. 4 is a hydraulic circuit diagram of a hydraulic drive system for a construction machine according to a second embodiment of the present invention.

5 is a block diagram showing details of a control function of the controller shown in FIG. 4. FIG.

FIG. 6 is a hydraulic circuit diagram of a hydraulic drive system for a construction machine according to a third embodiment of the present invention.

FIG. 7 is a hydraulic circuit diagram of a hydraulic drive system for a construction machine according to a fourth embodiment of the present invention.

FIG. 8 is a diagram showing details of control functions of the controller shown in FIG. 4;

FIG. 9 is a hydraulic circuit diagram of a hydraulic drive system for a construction machine according to a conventional technique.

10 is a block diagram showing details of control functions of the tilt angle setting device and the rotation speed setting device shown in FIG.

11 is a diagram showing control details in the auto idle control unit shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 rotational speed setting part (engine rotational speed setting means) 2 engine 4 hydraulic pump 5 tilt angle setting part (displacement volume setting means) 6 actuator 7 load 8 directional switching valve 9 operating means 10 shuttle valve 11 auto idle switch (switching means) ) 12 pilot switch (switching means) 13 throttle lever (rotation speed operation means) 17 auxiliary pump 23 rotation speed control device (engine control means) 24 regulator (pump control means) 25 discharge pressure sensor 26 operation pressure sensor 29 controller 205 tilting Angle control device 219 Electromagnetic proportional valve 228 Controller 302 Engine 314 Cable 320 Governor lever 322 Stepping motor 327 Controller 401 Controller 402 Engine 413 Throttle lever 415 Hydraulic cylinder 416 Sp Ring 418 Electromagnetic proportional valve 421 Governor drive link

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location F15B 11/00 F15B 11/00 F

Claims (4)

[Claims] 1. An engine, a variable displacement hydraulic pump driven by the engine, an actuator driven by pressure oil discharged from the hydraulic pump, and a pressure oil supplied from the hydraulic pump to the actuator. A directional control valve for controlling the flow, a directional control valve operating means for controlling the stroke amount of the directional control valve, a restriction state for limiting the engine speed to an idling speed, and a normal state for not performing this restriction. The switching means for performing, the first target rotation speed calculation means for calculating the first target rotation speed of the engine when the switching means is switched to the normal state, and the switching means are switched to the restricted state. When the second target rotation speed is smaller than the first target rotation speed, the second target rotation speed calculation means for calculating the second target rotation speed is provided. The engine rotation speed setting means, the engine control means for controlling the engine rotation speed according to the first and second target rotation speeds set by the engine rotation speed setting means, and the switching means are in the normal state. A first target displacement calculation means for calculating a first target displacement of the hydraulic pump that limits the input torque of the hydraulic pump to a value equal to or less than the output torque of the engine when switched, and the switching means are limited. A second target displacement volume calculating means for calculating a second target displacement volume which is smaller than the first target displacement volume in the low discharge pressure region of the hydraulic pump when being switched to the state is provided. Displacement volume setting means and displacement of the hydraulic pump according to the first and second target displacement volumes set by the displacement volume setting means. In a hydraulic drive system for a construction machine having a pump control means for controlling the product, the displacement volume setting means, when the switching means is switched from a restriction state to a normal state, a predetermined time delay from the switching time. The hydraulic drive system for a construction machine, characterized in that after passing through, the second target displacement setting state is shifted to the first target displacement setting state. 2. The hydraulic drive system for a construction machine according to claim 1, wherein the switching means detects an operating state / non-operating state of the switching valve operating means, and an engine speed idling rotation. The number of revolutions of the engine when the auto idle switch is ON and the operation state detecting means detects the non-operation state of the switching valve operating means. Is limited to the idling speed, and when the auto idle switch is OFF, and when the auto idle switch is ON and the operation state of the switching valve operation means is detected by the operation state detection means, the engine A hydraulic drive system for a construction machine, characterized in that the above-mentioned limitation on the number of rotations is lifted. 3. The hydraulic drive system for a construction machine according to claim 1, wherein a rotation speed operation means for operating the rotation speed of the engine, and a rotation speed operation amount detection for detecting an operation amount of the rotation speed operation means. A third target rotation speed for calculating the third target rotation speed of the engine according to the operation amount detected by the rotation speed operation amount detection means. Number calculation means, and the first to the first
A hydraulic drive system for a construction machine, further comprising: a minimum target rotation speed selection unit that selects a minimum one of the third target rotation speeds and outputs it to the engine control unit. 4. The hydraulic drive system for a construction machine according to claim 1, further comprising a switching valve operation amount detection means for detecting an operation amount of the switching valve operation means, and the displacement volume setting means is Of the third target displacement volume calculating means for calculating the third target displacement volume of the hydraulic pump according to the operation amount detected by the switching valve operation amount detecting means, and the first to third target displacement volumes. A hydraulic drive system for a construction machine, further comprising: a minimum displacement selecting means for selecting the smallest one and outputting it to the pump control means.