JPS63106405A - Controlling method for hydraulic device for driving inertial body - Google Patents

Abstract

PURPOSE:To eliminate any abrupt speed change of a hydraulic motor by gradually reducing the pressure of released pressure oil, and forcing discharge pressure oil of a hydraulic pump to work on the hydraulic motor in the case when stored pressures decreases while the hydraulic motor is accelerated by the pressure oil released from an accumulator. CONSTITUTION:An accumulator 20 is connected to the release pipe line 23 of a hydraulic pump 1 through a release valve 21. In the case when the pressure stored in the accumulator 20 decreases to be less than the preset value while a hydraulic motor 9 is accelerated by the pressure oil released from accumulator 20, the pressure of the released pressure oil is gradually reduced and the oil pressure discharged from the hydraulic pump 1 is applied on the hydraulic motor 9. As the driving pressure of the hydraulic motor 9, therefore, does not decrease temporarily at the time of changeover operation, the abrupt speed change of the hydraulic motor 9 can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of controlling a hydraulic system in which an inertial body is driven by a hydraulic motor.

[Conventional technology]

In a hydraulic system in which an inertial body such as a rotating body of a power shovel is driven by a hydraulic motor, the motor is rotated by the inertial force of the inertial body when the hydraulic motor is braked.

When the hydraulic motor is rotated by the inertial force, the motor operates as a pump. At this time, the energy of the pressure oil discharged from the motor means the inertial energy of the inertial body, and conventionally this inertial energy is recovered in an accumulator and utilized as energy for the hydraulic motor.

[Problem that the invention seeks to solve]

By the way, if the hydraulic motor is accelerated by both the inertial energy recovered in the accumulator and the discharge energy of the hydraulic pump, the motor will overrun.

Therefore, first, the motor is accelerated by the discharge pressure oil of the accumulator, and when the discharge pressure of this accumulator becomes below a certain level, the discharge of the accumulator is stopped.
It is effective to accelerate the motor using pressure oil discharged from a hydraulic pump.

However, when the driving pressure source for the motor is switched in this manner, the following disadvantages occur.

In other words, a hydraulic pump has a response delay due to the inertia of the oil and the response delay of the valve that controls itself.
After the accumulator stops discharging, its output pressure does not increase immediately.

Therefore, when switching to acceleration using the hydraulic pump, the acceleration pressure of the hydraulic motor temporarily decreases, which causes a sudden change in the acceleration performance of the motor.

Additionally, when driving an inertial body against gravity, for example when rotating a power excavator's rotating body upwards on a slope, the load torque acting on the hydraulic motor drives the inertial body on a flat road. It is considerably larger than the case.

Therefore, depending on the slope slope and the magnitude of the load acting on the packet, the swing drive torque based on the pressure oil discharged from the accumulator, that is, (swing drive pressure) x (hydraulic motor capacity) x the distance between the hydraulic motor and the swing body. (reduction ratio) and the load torque are balanced.

At this time, the discharge pressure of the accumulator does not decrease to the above-mentioned constant pressure, which causes the inconvenience that the motor is not accelerated by the above-mentioned hydraulic pump, that is, it becomes impossible to turn the rotating body. It turns out.

Furthermore, contrary to the above, when the rotating body of the power excavator is turned in the direction of the block on a slope, the load torque acting on the hydraulic motor is smaller than that on a flat road, so the hydraulic motor is This causes the inconvenience of rotating at a speed higher than the rated rotational speed (overrun).

Incidentally, an amount of pressure oil is released from the accumulator according to the difference between the accumulated pressure and the driving pressure of the hydraulic motor. For example, when the load torque is small and the driving pressure of the motor is low, a large amount of pressure oil is released from the accumulator, and in the opposite case, the amount of pressure oil released is small.

On the other hand, in the case of a fixed displacement hydraulic pump, its discharge ffi Q is constant regardless of the magnitude of the load.

In the case of a variable displacement type, the tilt angle of the swash plate is controlled so that an amount of pressure oil corresponding to the amount of operation of a directional control valve interposed between itself and the hydraulic motor is discharged.

Therefore, when the hydraulic motor is driven at a very low speed by slightly operating the directional control valve, there will be a difference between the amount of pressure oil released from the accumulator and the amount of pressure oil released by the pump depending on the magnitude of the load torque. This becomes a hindrance to fine control of the motor speed.

[Means for solving problems]

In the present invention, when the accumulated pressure decreases to a pressure lower than the preset pressure while the hydraulic motor is being accelerated by the discharge pressure oil of the accumulator, the pressure of the discharge pressure oil is gradually decreased, and the pressure of the discharge pressure oil is gradually decreased. The pressure oil discharged from the hydraulic pump is applied to the hydraulic motor.

Further, in the present invention, when the pressure change in the accumulated pressure becomes less than 2 constant while the hydraulic motor is being accelerated by the discharge pressure oil of the accumulator, the discharge pressure oil of the hydraulic pump is used instead of the discharge pressure oil of the accumulator. It is made to act on the above motor.

Furthermore, in the present invention, when the pressure change in the accumulated pressure exceeds a certain level while the hydraulic motor is being accelerated by the discharge pressure oil of the accumulator, the discharge pressure oil of the hydraulic pump is used instead of the discharge pressure oil of the accumulator. It is made to act on a hydraulic motor.

Further, in the present invention, the pressure oil released from the accumulator is transferred to the hydraulic motor only when the directional control valve is operated by a preset operation amount or more within a preset time while the accumulated pressure in the accumulator is greater than or equal to the preset pressure. I am trying to make it work.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an example of an inertial body drive hydraulic system to which the method according to the present invention is applied.

In the figure, a variable displacement hydraulic pump 1 is driven by a prime mover (not shown), and a swash plate control section 2 controls the tilt angle of its swash plate 1a.

The swash plate control unit 2 includes a CO valve (cutoff valve) 201,
An NC valve (negative control valve) 202, a guide valve 203, a servo actuator 204, and an electromagnetic switching valve 205 are provided.

The set pressure of the CO valve 201 is changed in two stages by the electromagnetic switching valve 205. That is, this switching valve 2
05 is in the state shown in the figure, the high set pressure P shown in FIG. 2 is selected, and when the vent valve 205 is switched, the low set pressure P shown in the same figure is selected.

-L This CO valve 201 is connected to the pump 1 as shown in the figure.
While the pressure P in the discharge side pipe line 23 is higher than the high set pressure P or higher than the low set pressure P, the C-I
CL has its output pressure P as low pressure P. 1 and pressure P is high set pressure P or low set pressure P
A magnitude P that makes the output pressure Pc equal to the input pressure when C-I C-L becomes smaller than C-I C-L. It has the effect of rapidly increasing the amount up to 2.

The NC valve 202 controls the output pressure P of the jet sensor 3, which will be described later.
t and Pd are manually applied as pilot pressures, and the output pressure P1 is lowered in proportion to the difference (Pj-Pd) between the pilot pressures Pt and Pd, as shown in FIG.

The output pressure Pi of the NC valve 202 is inputted to the guide valve 203 as a control pressure. Then, the servo actuator 204 is actuated by the pressure oil output from the guide valve 203.
This drives the swash plate 1a of the motor 1.

The jet sensor 3 described above has an orifice 301.30
2 and a relief valve 303, and outputs the pressures Pt and Pd using the carryover flow rate of the directional control valve 4 supplied to the pipe line 27 as an input parameter.

FIG. 4 shows the carryover flow rate and the output pressure difference (Pt
-Pd).

As shown in FIG. 5, the carryover flow rate decreases as the stroke amount of the directional control valve 4 from the neutral position increases. Therefore, from the relationship shown in FIG. 4, the pressure difference Pt-Pd decreases as the stroke amount increases, and from the relationship shown in FIG.
will increase. Then, when the output pressure P1 of the NC valve 202 increases while the CO valve 201 is open, the swash plate tilting angle of the pump 1 is increased via the guide valve 203 and the servo actuator 204. The discharge amount per rotation becomes larger.

As a result, when the directional control valve 4 is operated to the position 4B or 4C, the NC valve 202 is opened by an amount corresponding to the operation amount, so that the directional control valve 4 is moved to the position 4B.
Or, when it is at 4C, it becomes fully open. And N.C.
When the valve is fully open, the output pressure PC of the CO valve 201 is at the second level.
The minimum pressure P shown in the figure. 1, the swash plate tilting angle of the pump 1 is the minimum state, and when the output pressure Pc shows the maximum pressure Pc2 shown in the figure, the swash plate tilt angle is the maximum state. become.

On the other hand, the output pressure P of the CO valve 201. When the opening degree of the NC valve 202 is reduced to, for example, 1/2 when the maximum pressure PC2 is indicated, the tilting angle of the swash plate of the pump 1 becomes as shown by the dashed line in FIG.

The pilot valve 5 generates pilot pressure for operating the directional control valve 4, and its operating lever 50
1 is operated to the position B side and the C side, the switching valve 4 is operated to the position 4B side and the 4C side, respectively.

The pressure sensor 6 detects the pilot pressure acting on the switching valve 4 via the shuttle valve 7, and its output signal is input to a controller 8, which will be described later, as a signal indicating the switching operation of the switching valve 4.

The bidirectional rotary hydraulic motor 9 drives an inertial body 29 such as a rotating body of a power shovel.

A normal rotation side port 9a and a reverse rotation side port 9b of this hydraulic motor 9 are connected to the directional control valve 4 via a conduit 10.11, respectively, and check valves 12.13 that allow inflow from the motor 9 side. It is connected to the sequence valve 14 via. On the other hand, the motor 9 has a safety valve 15 which limits the magnitude of the driving oil pressure of the motor 9. IEI is installed in parallel, and check valve 1 is installed in each of the safety valves 15 and 16.
7.18 are arranged in parallel, and a suction line 19 is connected to a common connection point 28 of the safety valve 15.16 and the check valve 17.18.

The sequence valve 14 is equipped with a solenoid 14a for changing the set pressure in two stages. When the solenoid is de-energized, a low set pressure P is set, and when the solenoid is energized, a high set pressure P is set. A pressure P is selected respectively.

-H In FIG. 6, low set pressure P and high set pressure P are selected as the set pressure of the sequence valve 14 S -L
The pressure-flow characteristics of the opposite valve 40 when S-1 is selected are indicated by the symbol E, and the same characteristics of the safety valves 15 and 16 are indicated by the symbol F. As shown in the figure, the low set pressure PS-L of the sequence valve 14 is set lower than the set pressure P of the safety valve 15.16, and the high set pressure P is set higher than the set pressure Pp.

The output port of this sequence valve 14 is connected to the accumulator 2.
0, and is also connected to the discharge side pipe line 23 of the hydraulic pump 1 via the discharge valve 21.

The accumulator 20 is for recovering the inertial energy of the inertial body 29, and FIG. 7 shows the relationship between the accumulated pressure PA and the capacity V of this accumulator.

A pressure sensor 35 is provided in the conduit 25 to which the accumulator 20 is connected, and the accumulated pressure PA of the accumulator 20 is detected by this sensor 35.

The discharge valve 21 is connected to a main valve 211 interposed between the accumulator 20 and the pump 1, and a main valve 211 via a throttle 212.
1 and an electromagnetic pilot valve 213 arranged in parallel.

This discharge valve 21 is opened by switching the pilot valve 213. That is, the pilot valve 21
When No. 3 is switched, the pressure in the oil chamber 211a of the main valve 211 decreases, causing the main valve 211 to open, thereby opening the discharge valve 211.

Note that the fixed pump 22 is a hydraulic pressure source for the swash plate control section 2.

Further, the orifice 212 provided in the discharge valve 21 functions to maintain the upstream pressure of the main valve 211 when the pilot valve 213 is switched.

Furthermore, a safety valve 24 is provided to prevent the conduit 25 from becoming abnormally pressured, and a manual pressure relief valve 26 is used to relieve the pressure of the conduit 25 during transportation or the like.

Here, the high set pressure P and low set pressure P of the CO valve 201 in this embodiment
CL High set pressure P and low set pressure of the safety valve 14 -H P 1 Set pressure P of the safety valve 15.16 mentioned above P p --
L The magnitude relationship of the discharge stop pressure PAl of the accumulator 20, which will be described later, is summarized and shown as follows.

FIG. 8 shows the processing procedure of the controller 8 shown in FIG. 1, and the operation of this embodiment will be explained below with reference to the same figure.

In this procedure, after the flag F is initialized to "O" (step 100), it is determined whether the lever 501 of the pilot valve 5 is in the neutral position based on the output of the pressure sensor 6 (step 100). 101), the judgment result is NO.
In this case, the directional control valve 4 is in position 4B or 4c.
If it is determined that the pressure sensor 35 is operated to the side, it is determined based on the output of the pressure sensor 35 whether or not the accumulated pressure PA of the accumulator 2o is equal to or higher than the discharge stop pressure PA1 (step 102).

If P t, < P At, it is determined in step 104 whether or not the flag F is "1";
Since the flag F is currently at 0°, the determination result is NO. Therefore, in step 107, the high set pressure P is selected as the set pressure of the CO valve 201, and the discharge valve 21-H is closed. The process and the process of selecting the high set pressure P as the set pressure of the sequence valve 14 are executed, whereby the motor 9 is driven by the discharge pressure oil of the pump 1.

On the other hand, if PA≧PA1, the flag F is “1#
At the same time, as shown in FIG. 9(b), the solenoid 205a of the electromagnetic switching valve 205 is energized and the CO
A low set pressure P is selected as the set pressure of the valve 201, and at the same time, as shown in FIG. (Step 103).

When the discharge valve 21 is opened, the accumulator 20 and the pipe line 23 are directly connected, so the discharge pressure oil of the accumulator 20 is supplied to the hydraulic motor 9 via the directional control valve 4 and the pipe lines 10 and 11. This accelerates the motor 9.

At this time, the swash plate tilt angle of the pump 1 is at its minimum state as shown in FIG. 9(c), and therefore the hydraulic motor 9 is accelerated solely by the pressure oil discharged from the accumulator 2G.

That is, at present, the discharge pressure P of the accumulator 20 is
t, is PA≧PA1, and in step 103 CO
Low set pressure P (-F
Since AI) is selected, it becomes clear from Fig. 2-L that the swash plate tilting angle of the pump 1 is in the minimum state, so that the motor 9 is exclusively driven by the accumulator 2.
Accelerated by 0 release pressure oil.

The purpose of minimizing the tilt angle of the swash plate of the pump 1 as described above is to prevent the motor 9 from overrunning.

That is, if the swash plate tilt angle of the pump 1 is at the maximum when the discharge valve 21 is opened, the pressure oil discharged from the accumulator 20 is added to the maximum flow rate of pressure oil discharged from the pump 1 in the pipe line 23. Since they merge, a large flow of pressure oil is supplied to the motor 9, causing the motor to overrun. - However, if the tilting angle of the swash plate of the pump 1 is minimized as described above, the motor 9 will be driven exclusively by the pressure oil discharged from the accumulator 20, so the above-mentioned overrun will be prevented.

After the release valve 21 is opened, the release pressure PA of the release valve gradually decreases. Then, in step 102, the discharge pressure P
If it is determined that the release stop pressure PA1 has become lower than the release stop pressure PA1, it is determined in step 104 whether the flag F is "1°", but since the flag F is "1" at the moment After the flag F is set to "0°" in step 105, the following process is executed in step 106.

That is, as shown in FIG. 9(b), the electromagnetic switching valve 205
The solenoid 205a is deenergized and the CO valve 210 set pressure is changed to the high set pressure P. In the meantime, a process of gradually decreasing the pressure and a process of selecting a high set pressure P as the set pressure of the sequence valve 14 are executed.

The reason for gradually decreasing the driving current of the pilot valve 213 is as follows.

Even if the set pressure of the CO valve 201 is changed to the high set pressure P in step 104, the -H discharge pressure of the pump does not increase immediately. That is, the pump discharge pressure increases transiently as shown in FIG. 9(C) due to the response delay of the Co valve 201, the response delay of the cylinder 11 itself, and the inertia of the oil. Therefore, when the discharge valve 21 is suddenly closed, the motor driving pressure is temporarily reduced as shown by the dashed line in FIG. 9(d), and the acceleration of the motor 9 is suddenly changed.

However, if the driving current of the pilot valve 213 is gradually decreased, the discharge valve 1 is gradually closed, and the discharge pressure oil of the accumulator is gradually decreased, as shown by the solid line in FIG. A temporary drop in the motor driving pressure is prevented.

In FIG. 9(e), the solid line shows the change in the rotational speed of the motor 9 when the drive current is gradually reduced, and the dashed line shows the same change when the same control is not performed. There is. As is clear from the figure, according to this embodiment, the transition from acceleration of the motor 9 by the pressure oil discharged from the accumulator to acceleration of the motor 9 by the pressure oil discharged from the pump 1 is performed smoothly. In other words, the acceleration of the motor 9 does not suddenly change during this transition.

Note that the time ΔT1 for performing the gradual reduction control of the drive current is as follows:
The time is set to be longer than the time required to increase the tilt angle of the swash plate of the pump 1.

Next, a case will be described in which the lever 501 of the pilot valve 5 is returned to the neutral position. In this case, since the determination result in step 101 is YES, the high set pressure P is selected as the set pressure of the CO valve 201, and the sequence valve 1 is selected as the set pressure of the CO valve 201.
The low set pressure P is selected as the set pressure of No. 4 (Step-L 108).

On the other hand, when the lever 501 is set to the neutral position, the directional control valve 4 is returned to the neutral position 4A, and the supply of pressure oil to the motor 9 is stopped. Furthermore, the carryover flow rate of the directional control valve 4 is maximized from the relationship shown in FIG. 5, and therefore, the output pressure difference Pj-Pd of the jet sensor 3 is also maximized from the relationship shown in FIGS. 3 and 4. As a result, the NC valve is closed and the swash plate tilt angle of the pump 1 becomes the minimum state.

When the supply of pressure oil to the motor 9 is stopped, this motor is braked, and at this time, the motor performs a pumping action due to the inertial force of the inertial body.

In other words, if the directional control valve 4 is returned from the position 4C side to the neutral position 4A, pressure oil is discharged from 9b based on the inertial force (by the pumping action of the motor 9, the reverse side bow of the motor 9). be done.

As shown in FIG. 6, the low set pressure P of the sequence valve 14 is -L lower than the set pressure Pp of the safety valve 16 (since it is set, in the current situation where the paper set pressure P is selected in step 108) , upper S The sequence valve 14 is opened by the discharge pressure caused by the pump action of the motor 9. As a result, the pressure oil discharged from the motor 9 flows through the sequence valve 14 to the accumulator 2.
0, and thereby the inertial energy (braking energy) of the inertial body 29 is recovered into the accumulator 20.

The inertial energy recovered in the accumulator 20 is transferred to the lever 50 of the pilot valve 5 as described above.
When 1 is operated from position A to position B or C side,
That is, the directional control valve 4 moves from the neutral position 4A to the positions 4B and 4.
When operated to the C side, it is used as driving energy for the motor 9.

By the way, in steps 103, 106 and 107 shown in FIG. 8, the high set pressure P is selected as the set pressure of the sequence valve 14. This is for the following reason.

That is, the accumulated pressure PA of the accumulator 20 is P<PA
When the directional control valve 4 is operated to the position 4B or 4C at the start of work in the state 1, or when the directional control valve 4 is operated, the accumulated pressure of the accumulator changes from PA≧PA1 to PA1. If <P At, the discharge valve 21 is closed in step 106 or 108, and the motor 9 is driven exclusively by the pressure oil discharged from the pump 1. At this time, if the set pressure of the sequence valve 14 remains at the low set pressure P -L, the relationship between this pressure P and the set pressure P of the safety valve 15° -L16 is P
Since S-L F , the sequence valve 14 operates, and the motor 9 is thereby accelerated at the low set pressure P of the sequence valve 14 .

-L On the other hand, if the directional control valve 4 is operated under the condition where the accumulated pressure PA of the accumulator 20 is greater than or equal to the low set pressure P (>PA,) of the sequence valve 14, even if the sequence valve 14 Even if the set pressure is a low set pressure P, the sequence valve 14 does not operate due to the accumulated pressure -L force PA in the accumulator 20.

Therefore, in such a case, the motor 9 will be accelerated by the set pressure Pp of the safety valves 15 and 16.

As is clear from the above explanation, when the set pressure of the sequence valve 14 is fixed at the low set pressure P, in the case S-1, the motor 9 This will cause a difference in the acceleration pressure.

However, as mentioned above, step 103゜106.1
At 07, the high set pressure P is set as the set pressure of the sequence valve 14.
If (>P,) is selected, the sequence valve 1
4 will not be activated, and therefore the motor 9 will always be accelerated at the set pressure Pp of the safety valves 15 and 16.

Note that when the discharge pressure of the motor 9 becomes higher than the set pressure PF of the safety valve 15 or 16, this safety valve performs a relief operation. Therefore, the accumulated pressure PA of the accumulator 20
The upper limit of is the set pressure PF of this safety valve 16.

In addition, the safety valves 15, 16 and check valves 17, 18 installed in parallel with the motor 9 may prevent the pressure oil discharged from the motor 9 from being recovered to the accumulator side due to some reason, such as failure of the check valve 12, 13 or the sequence valve 14. It also works in case. That is, in such a case, the discharge pressure oil of the motor 9 is returned to the drive side boat 9b (or 9a) of the pump through the safety valve 15 (or 16) and the check valve 18 (or 17), and thereby the braking energy is transferred to the safety valve. 15 (or 16) is consumed as heat loss.

During the return of the pressure oil, there may be a slight leakage of pressure oil from the motor 9, etc., but the shortage of return pressure oil due to the leakage will be automatically replenished from the tank 32 via the suction pipe 19. , so-called cavitation does not occur due to this lack of pressurized oil.

By the way, if the inertial body 29 is, for example, the upper rotating body of a power shovel, the load torque of the motor 9 when the rotating body is turned upward on a slope is considerably larger than the load torque on a flat road. Therefore, depending on the gradient of the slope and the magnitude of the load acting on the packet, a situation may occur in which it becomes impossible for the revolving structure to turn.

That is, when the discharge valve 21 is opened in step 103 and the motor 19 is driven by the discharge pressure oil of the accumulator 20, the motor 9 is driven before the pressure of the discharge pressure oil decreases to the discharge stop pressure PA1. When the driving torque and the reverse turning torque based on the weight of the rotating body are balanced, at that point the release of pressure oil from the accumulator 20 is stopped and the operation of the rotating body 29 becomes impossible. In other words, pump 1
Since the transition to motor acceleration is not performed, the rotating body remains in a stopped state.

FIG. 10 shows an embodiment of the present invention in which the inertial body 29 can be continuously driven even when the inertial body 29 is driven against gravity as described above.

When the inertial body 29 stops due to the above-mentioned balance, there is no change in the accumulated pressure PA of the accumulator 29 over time, and even if the inertial body 29 does not come to a stop, the accumulator 20 increases as it approaches the above-mentioned balanced state. Pressure changes become gradual.

Therefore, in this embodiment, in step 109 following step 103, it is determined whether the amount of change p'-p' of the accumulated pressure PA per unit time T is less than or equal to the preset value St A A ΔP1. There is. That is, as shown in FIG. 11, the accumulated pressure PA is sampled at minute time intervals T8□, and the difference P'-P' between the accumulated pressure P' one sampling time ago and the accumulated pressure P' at the present moment is calculated.
is determined, and it is determined whether this difference is less than or equal to the value ΔP1 described in A above.

The above-mentioned value ΔP1 is set to a value that allows it to be determined that the above-mentioned balanced state is approached, and therefore, the judgment result in step 109 is YES before the above-mentioned inertial body 29 stops.
become.

If the judgment result in step 109 is YES,
Since the processes of steps 105 and 106 shown in FIG. 8 are executed, the acceleration of the motor 9 by the pressure oil discharged from the accumulator 20 shifts to the acceleration of the motor 9 by the pressure oil discharged from the pump 1.

In addition, since the pump 1 discharges oil in an amount determined by the product of the volume and the rotational speed, the motor 9 can be accelerated thereafter.

On the other hand, if the determination result in step 109 is NO, it is possible to drive the motor 9 by the discharged pressure oil from the accumulator 20, so that the motor continues to be driven by the discharged pressure oil.

By the way, when gravity acts in the driving direction of the inertial body 29 contrary to the above, that is, when the above-mentioned rotating body of a power excavator is turned in the direction of the printing plate on a slope, the motor 9 is moved to the accumulator. The inertial body 29 will overrun because it will be accelerated by both the release pressure oil and the gravity.

FIG. 12 shows an embodiment of the present invention that can prevent such overruns.

When approaching the state where the above-mentioned overrun occurs, the pressure drop in the accumulator 20 becomes large.

Therefore, in this embodiment, contrary to the embodiment shown in FIG. It is judged whether it is above or not. Note that the pressure P' shown in FIG.
, P' sampling interval T8□ is the above-mentioned A
A It is set to the same size as the sampling interval T8□ in the embodiment.

The value ΔP2 is set to a value that allows it to be determined that the state is approaching an overrun state.

Therefore, just before an overrun occurs, step 1
The result of the determination at step 09' is YES, and in this case, the processing at step 105 is executed and the acceleration of the motor 9 is switched to the acceleration of the motor 9 by the pressure oil discharged from the pump 1.

As mentioned above, the maximum discharge amount of the pump 1 is regulated by (displacement volume) x (rotational speed), so even if the inertial body 29
Even when the motor 9 is accelerated in the direction of gravity, excess pressure oil
Therefore, according to this embodiment, the above-mentioned overrun is effectively prevented.

Note that if the determination result in step 109' is No, the motor 9 continues to be driven by the pressure oil released from the accumulator 20.

By the way, when the motor 9 is accelerated by the pressure oil released from the accumulator 20, an amount of pressure oil is released from the accumulator 20 according to the accumulated pressure PA of the accumulator and the magnitude of the load acting on the motor 9 (motor drive pressure). In the embodiments shown in FIGS. 10 and 12, it is detected that the motor 9 tends to overload or overrun based on the discharge characteristics of the accumulator and utilizes changes in the accumulated pressure PA. ing.

On the other hand, the pump 1 discharges an amount of pressure oil into the pipe line 23 according to the operation amount of the directional control valve 4 by the action of the jet sensor 3 and the motor control section 2 .

Therefore, when the directional control valve 4 is minutely operated to finely control the speed of the inertial body 29, the motor 9 is driven by the pressure oil discharged from the akinimulator 20 and the motor 9 is driven by the pressure oil discharged from the pump 1. The amount of pressure oil supplied to the motor 9 differs depending on the time, and this causes the fine control characteristics at each drive time to differ.

Note that the discharge amount of a fixed displacement pump is constant regardless of the magnitude of the load. Therefore, even when this fixed displacement pump is used, the above-mentioned fine control characteristics still differ.

FIG. 14 shows an embodiment of the present invention that can solve such problems.

In this embodiment, after the flag F is initialized to "O" (step 200), it is determined whether the lever 501 of the pilot valve 5 is in the neutral position based on the output of the pressure sensor 6, that is, the direction is changed. It is determined whether the valve 4 is in the neutral position (step 201). Then, the lever 501 is operated from the neutral position, and the determination result in step 201 is N.
.

In this case, the lever 501 is operated by a predetermined amount (for example, the operation ff at full operation) based on the output of the sensor 6.
It is determined whether or not up to 1) has been operated (step 20).
2).

If the determination result in step 202 is NO, the same process as that in step 107 in FIG. 8 is performed in step 2.
08, and the motor 9 is thereby driven by the pressure oil discharged from the pump 1.

As long as the operating amount of the lever 501 is within the range of the predetermined operating amount, the motor 9 continues to be driven by the pressure oil discharged from the pump 1.

On the other hand, when the lever 501 is operated until the predetermined operation amount is reached, it is determined whether the time ΔT2 required for the operation is less than or equal to the preset time To (step 20
3).

Note that the determination in step 203 is made as follows. That is, the time point when the lever 501 starts operating from the neutral position and the time point when the lever is operated by the predetermined amount of operation are detected based on the output of the pressure sensor 6, and the time ΔT2 between these times and the preset time To are detected. This is done by comparing the

In step 203, if it is determined that ΔT2>”r□, that is, if the lever 501 is operated over a preset amount of operation over a period of time longer than time To, the process in step 208 is performed. This is executed, and the motor 9 continues to be driven by the pressure oil discharged from the pump 1.

On the other hand, if it is determined that ΔT2≦To, steps 204 to 208 similar to steps 102 to 107 shown in FIG.
is executed.

Note that when the lever 501 is returned to the neutral position, the eighth
Step 20 is similar to step 108 shown in the figure.
9 is executed.

Further, the predetermined operation amount shown in step 20.2 is the lever 5
For example, 50% of the operation amount when 01 is fully operated.
It is set to a range of about 100%.

After all, according to this embodiment, when the directional control valve 4 is operated by a predetermined operation amount or more within the preset time 10 under a condition where the accumulated pressure P of the accumulator 20 is greater than or equal to the preset pressure PA1, Only then, the motor 9 is driven by the pressure oil released from the accumulator 20. therefore,
During fine control, the motor 9 is driven only by the pressure oil discharged from the pump 1, so that constant fine control characteristics can be obtained at all times.

Here, the reason for performing the determination process shown in step 203 will be explained.

If this judgment process is not performed, the following inconvenience will occur. That is, when the fine control described above is continued for a certain period of time, the motor 9 is in a state of being accelerated by the pressure oil discharged from the pump 1. If the lever 501 is operated by more than the predetermined operation amount in such a state, the motor 9, which has already reached a certain rotational speed, will be further accelerated by the pressure oil released from the accumulator 20, resulting in overrun.

However, if the judgment process shown in step 203 is performed, the above-mentioned inconvenience can be prevented by appropriately setting the time To.

In each of the embodiments shown in FIGS. 8, 10, 12, and 14, a variable displacement type pump 1 is used, and the tilting angle of the swash plate 1a of this pump is set by Control unit 2
However, the above variable displacement pump 1
It is of course possible to use a fixed displacement pump instead.

As shown in FIG. 15, when this fixed displacement pump 50 is used, an electromagnetic switching valve 51 is interposed between the pump 50 and the directional switching valve 4, and the jet sensor 3 is omitted. In the examples shown in FIGS. 9, 10, and 12, the solenoid 51a of the electromagnetic switching valve 51 is energized in steps 106 and 107, and the valve removal is switched. Also the 14th
In the illustrated example, the facing valve 51 is switched in steps 207 and 208.

The present invention can be applied to driving not only a rotating body of a power shovel but also any inertial body.

〔Effect of the invention〕

According to the present invention, the discharge pressure oil of the accumulator is gradually reduced when switching from driving the hydraulic motor by the hydraulic pressure to the motor driven by the discharge pressure oil of the pump. Therefore, it is possible to avoid the inconvenience that the driving pressure of the hydraulic motor temporarily decreases during the switching and the speed of the motor suddenly changes.

Further, in the present invention, when the time change in the discharge pressure of the accumulator becomes less than a predetermined value, the hydraulic motor is driven by the discharge pressure oil of the pump 1. Therefore, it is possible to prevent the inertial body from stopping when the inertial body is driven against gravity on a slope or the like.

Further, in the present invention, when the time change in the discharge pressure of the accumulator exceeds a predetermined value, the hydraulic motor is moved by one stroke using the discharge pressure oil of the pump 1. Therefore, overrun of the hydraulic motor can be prevented when the inertial body is driven in the direction of gravity on a slope or the like.

Furthermore, in the present invention, the hydraulic motor is driven by the pressure oil discharged from the accumulator only when the directional switching valve is operated by a preset amount of operation within a preset time, so fine control of the motor is performed. It can be performed smoothly and appropriately.

[Brief explanation of the drawing]

Fig. 1 is a hydraulic circuit diagram showing an example of a hydraulic system to which the method according to the present invention is applied, Fig. 2 is a graph illustrating the characteristics of a CO valve, and Fig. 3 is a graph illustrating the characteristics of an NC valve. graph,
Figure 4 is a graph illustrating the relationship between the carryover flow rate of the switching valve and the output pressure difference of the jet sensor, Figure 5 is a graph illustrating the relationship between the stroke of the switching valve and the carryover flow rate, and Figure 6 is the sequence valve and safety valve. 7 is a graph illustrating the relationship between the accumulated pressure and capacity of the accumulator, FIG. 8 is a flowchart illustrating an embodiment of the control method according to the present invention, and FIG. 9 is a waveform diagram showing the operation of the embodiment shown in FIG. 8, FIG. 10 is a flowchart showing the embodiment of the second invention of the present invention,
Fig. 11 is a diagram showing a method for detecting the amount of pressure change in the embodiment of Fig. 10, Fig. 12 is a flowchart showing an embodiment of the third invention of the present invention, and Fig. 13 is an example of the embodiment of Fig. 12. 14 is a flowchart showing an embodiment of the fourth invention of the present invention, and FIG. 15 is a hydraulic circuit diagram showing an example of using a fixed capacity pump. be. DESCRIPTION OF SYMBOLS 1... Hydraulic pump, 1a... Swash plate, 2... Swash plate control part, 3... Jet sensor, 4... Directional switching valve,
5...Pilot valve, 6.35...Pressure sensor, 8
...Controller, 12,13.17.18...Check valve, 14...Sequence valve, 20...Accumulator, 21...Discharge valve, 29...Inertia body, 50
... Fixed capacity hydraulic pump, 51 ... Solenoid valve switching valve. LE sword P (Niri/cm) Figure 2 Figure 3 KiT Rio JYSt amount Force/direction Manchange valve stroke Figure 4 Figure 5 Pressure (in g/cm') Figure 6 M'' Pressure Pa (in g/cm2) Figure 15 Time Figure 13

Claims (4)

[Claims] (1) A hydraulic motor that drives an inertial body, and an accumulator that recovers the pressure oil discharged from the hydraulic motor based on the inertia of the inertial body, and the pressure oil discharged from the accumulator or the hydraulic pump is A control method for a hydraulic system in which discharge pressure oil is applied to the hydraulic motor, wherein the accumulator is operated only when the directional control valve is operated while the accumulated pressure in the accumulator is equal to or higher than a preset pressure. Release pressure oil is applied to the hydraulic motor, and when the accumulated pressure decreases to a pressure lower than the preset pressure while the hydraulic motor is being accelerated by the release pressure oil of the accumulator, the pressure of the release pressure oil is reduced. A method for controlling a hydraulic device for driving an inertial body, characterized in that the pressure oil discharged from the hydraulic pump is made to act on a hydraulic motor while gradually decreasing the pressure. (2) A hydraulic motor that drives an inertial body, and an accumulator that recovers pressure oil discharged from the hydraulic motor based on the inertia of the inertial body, and the pressure oil discharged from the accumulator or the hydraulic pump is A control method for a hydraulic system in which discharge pressure oil is applied to the hydraulic motor, wherein the accumulator is operated only when the directional control valve is operated while the accumulated pressure in the accumulator is equal to or higher than a preset pressure. Release pressure oil is applied to the hydraulic motor, and when the pressure change of the accumulated pressure becomes below a certain level while the hydraulic motor is being accelerated by the release pressure oil of the accumulator, the above-mentioned pressure oil is applied instead of the release pressure oil of the accumulator. A method for controlling an inertial body and a driving hydraulic device, characterized in that pressure oil discharged from a hydraulic pump acts on the motor. (3) A hydraulic motor that drives an inertial body, and an accumulator that recovers the pressure oil discharged from the hydraulic motor based on the inertia of the inertial body, and the pressure oil discharged from the accumulator or the hydraulic pump is A control method for a hydraulic system in which discharge pressure oil is applied to the hydraulic motor, wherein the accumulator is operated only when the directional control valve is operated while the accumulated pressure in the accumulator is equal to or higher than a preset pressure. Release pressure oil is applied to the hydraulic motor, and when the pressure change of the accumulated pressure exceeds a certain level while the hydraulic motor is being accelerated by the release pressure oil of the accumulator, the above-mentioned pressure oil is applied instead of the release pressure oil of the accumulator. A method for controlling a hydraulic device for driving an inertial body, characterized in that pressure oil discharged from a hydraulic pump acts on the hydraulic motor. (4) A hydraulic motor that drives an inertial body, and an accumulator that collects discharge pressure oil of the hydraulic motor based on the inertia of the inertial body, and discharges pressure oil or a hydraulic pump with the accumulator via a directional control valve. A control method for a hydraulic system in which a discharge pressure oil is applied to the hydraulic motor, wherein the directional control valve performs a preset operation within a preset time when the accumulated pressure in the accumulator is equal to or higher than a preset pressure. A method of controlling a hydraulic device for driving an inertial body, characterized in that the pressure oil discharged from the accumulator is made to act on the hydraulic motor only when the accumulator is operated by more than a certain amount.