JP3500201B2 - Hydraulic drive - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic actuator driven by pressure oil discharged from a hydraulic pump, and a control lever for controlling the flow rate of pressure oil supplied to the hydraulic actuator and the flow rate of discharged pressure oil. The present invention relates to a hydraulic drive system that controls in accordance with the amount and discharges excess pressure oil when the hydraulic pressure of a hydraulic circuit on the inflow side or the outflow side of a hydraulic actuator exceeds a predetermined pressure.

[0002]

2. Description of the Related Art A hydraulic machine such as a hydraulic excavator is driven by a hydraulic motor such as a traveling motor or a hydraulic cylinder such as an arm cylinder. Such a hydraulic actuator is usually designed so that the direction of the load pressure can be changed according to the normal and reverse directions of the operation. In addition, the speed control of the hydraulic actuator is mainly performed by controlling the inflow flow rate into the hydraulic actuator by the direction switching valve etc. provided on the meter-in side, and during deceleration, the braking control is performed by the brake valve provided on the meter-out side oil passage. Done. FIG. 11 is a hydraulic circuit diagram showing an example of a hydraulic drive circuit of a hydraulic actuator in which the direction of load pressure changes. The hydraulic drive device shown in the figure is specifically a hydraulic excavator traveling device, which controls the flow rate of the pressure oil supplied from the hydraulic pump 10 to the traveling motor 11 by the direction switching valve 42 and controls the hydraulic pressure on the meter-in side. Based on this, the brake valve 41 (a, b) controls the hydraulic excavator for braking. By the way, when the hydraulic excavator travels on a flat ground or runs up a slope, the traveling motor 11
A resistance load acts on the traveling motor 11, but a negative load acts on the traveling motor 11 in the case of sudden deceleration traveling or slope descending traveling. That is, in the case of sudden deceleration traveling or slope descending traveling, since the traveling motor 11 works as a pump, the traveling motor 1
The meter-in side of 1 is likely to be negative pressure. For example, when the hydraulic excavator that has traveled on a level ground shifts to slope down travel, the hydraulic pressure on the meter-in side of the travel motor 11, for example, p
₁ begins to drop. When the hydraulic pressure p ₁ becomes smaller than the set pressure of the brake valve 41a, the brake valve 41a operates toward the throttle side. Therefore, a braking force is applied to the traveling motor 11 so that the meter-in side hydraulic pressure p ₁ is controlled to maintain a predetermined pressure. It Even when the hydraulic excavator, which has been traveling at a constant speed, shifts to deceleration traveling, similar braking control by the brake valve 41 (a, b) is performed. However, in such a hydraulic drive system, since braking control by a brake valve is adopted,
In particular, when driving a traveling motor or swing motor with a large load inertia, for example, the brake valve closing operation due to a decrease in the oil pressure on the meter-in side during deceleration, the subsequent increase in the oil pressure on the meter-in side, and the opening of the brake valve following it. A large-amplitude vibration (hunting) phenomenon in which the operation continuously and periodically occurs is likely to occur. In addition, such a hunting phenomenon may occur even during rapid acceleration.

[0003]

Therefore, in consideration of pressure feedback control in addition to flow rate control, which is the basis of drive control, a pressure signal for detecting the inflow side pressure of a hydraulic actuator is passed through a high-pass filter, an all-pass filter or the like. A method has been proposed to prevent the occurrence of the hunting phenomenon by negatively feeding back the flow rate control, but if the hunting frequency is low, the sufficient filtering effect by the above filter cannot be obtained, so smooth acceleration / deceleration control by such a method is required. It was difficult to realize. Also, a method has been proposed in which target values of flow rate and pressure are calculated according to the lever operation amount, and electronic hydraulic pressure control is performed so that the actual flow rate and pressure follow these target values. For example, the lever operation amount is differentiated with respect to the target pressure value to obtain acceleration information of the hydraulic actuator, and the target pressure value is calculated from this acceleration information. However, actually, not only the control program becomes complicated, but it is difficult to realize the pressure control corresponding to the operation of the operator. For example, when the operator slowly operates the lever, it becomes difficult to calculate the differential value of the lever operation amount. Even if the hunting phenomenon does not occur, sudden operation of the lever causes a rapid increase or decrease in the flow rate of the pressure oil flowing into the hydraulic actuator. Become. The present invention has been made to solve such problems in the prior art, and it is an object of the present invention to provide a hydraulic drive device that prevents the occurrence of a hunting phenomenon that occurs during sudden acceleration or sudden deceleration, and that has excellent ride comfort. To aim.

[0004]

In order to solve the above problems, the present invention provides a flow rate and discharge of pressure oil supplied to a hydraulic actuator driven by pressure oil discharged from a hydraulic pump driven by a drive means. The flow rate of pressure oil to be controlled is controlled according to the operation amount of the operating lever, and excess pressure oil is discharged when the hydraulic pressure of the hydraulic circuit on the inflow side or the outflow side of the hydraulic actuator exceeds a predetermined pressure. In a hydraulic drive device, flow rate setting means for setting a set flow rate of pressure oil supplied to a hydraulic actuator according to an operation amount of an operation lever, and setting of an inflow side or an outflow side of the hydraulic actuator according to an operation amount of an operation lever. The oil pressure setting means for setting the oil pressure, the oil pressure detecting means for detecting the oil pressure on the inflow side or the outflow side of the hydraulic actuator, and the oil pressure detecting means If the detected hydraulic pressure is greater than the set hydraulic pressure by comparing the detected hydraulic pressure with the set hydraulic pressure set by the hydraulic pressure setting means, the hydraulic pressure on the inflow side or the outflow side of the hydraulic actuator is determined as the differential pressure between the detected hydraulic pressure and the set hydraulic pressure. The flow rate correction means is provided to correct the flow rate controlled by the inflow flow rate control means or the outflow flow rate control means in accordance with the set flow rate set by the flow rate setting means.

[0005]

When the operation lever is operated by the operator, the flow rate setting means sets the set flow rate of the pressure oil supplied to the hydraulic actuator according to the operation amount of the operation lever. Further, the hydraulic pressure setting means sets the set hydraulic pressure on the inflow side or the outflow side of the hydraulic actuator according to the operation amount of the operation lever. The hydraulic pressure detection means detects the hydraulic pressure on the inflow side or the outflow side of the hydraulic actuator. The flow rate correction means compares the detected oil pressure detected by the oil pressure detection means with the set oil pressure set by the oil pressure setting means, and when it determines that the detected oil pressure is higher than the set oil pressure, the oil pressure on the inflow side or the outflow side of the hydraulic actuator is set. The flow rate controlled by the inflow flow rate control means or the outflow flow rate control means is corrected in accordance with the set flow rate set by the flow rate setting means so as to decrease according to the differential pressure between the detected hydraulic pressure and the set hydraulic pressure.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a conceptual diagram of a drive control mechanism of a hydraulic excavator according to a first embodiment of the present invention. In the figure, 10 is a hydraulic pump serving as a pressure oil supply source, 11 is a hydraulic actuator having a large inertia load represented by a traveling motor, 12 is a pressure compensation valve that is electronically controlled, 13 is a main hydraulic valve on the meter-in side, 14 is a meter-out side hydraulic main valve, and 12a, 13a and 14a are pressure compensation valves 1 respectively.
2. Electro-hydraulic interface for converting control signals of the hydraulic main valves 13 and 14 into valve driving force; 15 (a, b) are make-up valves; 16 and 17 are meter-in side hydraulic sensor and meter-out side hydraulic sensor, 18 respectively. (A,
b) is a relief valve and 19 is an oil tank. Further, the pressure compensating valve 12, the electro-hydraulic interfaces 12a, 13a, 14a of the hydraulic main valves 13, 14 and the meter-in side and meter-out side hydraulic sensors 16, 17 are respectively connected to the controller 1 shown on the right side of the broken line in FIG. It receives a control signal and sends out a detection signal. Blocks shown in the control unit 1 are functional blocks representing a control function, and 21,23,25 are subtractors, 22 is a meter-out pressure calculation unit, 24 is a meter-in pressure calculation unit, and 26 is an adder. . As described above, FIG. 1 shows the concept of the drive control mechanism of the hydraulic excavator. Since the hydraulic actuator 11 is configured such that the meter-in side and the meter-out side can be reversed, the actual hydraulic circuit is the meter-in side and the meter-in side. The outer side is symmetrical.

FIG. 2 is a block diagram showing an internal circuit of the control unit. In the figure, 2 is a central processing unit (CPU),
Reference numeral 3 is a random access memory (RAM) for temporarily storing data of the calculation process, and 4 is a lead in which data of a conversion procedure that gives a value of a flow rate command and a pressure command for a control procedure program and an operation amount of an operation lever described later is stored. Only memory (ROM), 5 is an output I / O interface, 6 to 8 are amplifiers, 9 is an input A / D converter, and 90 is an operation lever. The pressure compensating valve 12 and the hydraulic main valves 13 and 14 are connected to the amplifiers 6, 7 and 8, respectively, and the operating lever 90 and the meter-in side and meter-out side hydraulic sensors 16 and 17 are connected to the A / D converter 9. There is. Operation amount y signal of operation lever 90, meter-in side and meter-out side oil pressure sensors 16 and 17
The meter-in side (MI) and meter-out side (MO) hydraulic pressures p _la and p _lb signals detected by are converted into digital signals by the A / D converter 9 and input to the CPU 2, where the hydraulic pressure is read according to the program read from the ROM 4. Calculation for flow rate / pressure control (PQ control) of the actuator 11 is performed. The MI correction differential pressure command Δp _C ′, the meter-in side (MI) flow rate command q _i , and the meter-out side (MO) flow rate control command y ₀ obtained as a result are respectively I /
It is output to and amplified by the amplifiers 6, 7, and 8 via the O interface 5, and is supplied to the pressure compensating valve 12 and the hydraulic main valves 13 and 14 as control currents of the respective electric oil interfaces.

FIG. 3 is a conceptual diagram showing the basic control concept of this embodiment, FIG. 4 is a conceptual diagram showing the detailed control concept, and FIG. 5 is a PQ.
It is a flow chart of control. First, as shown in FIG. 3, the basic concept of control of the present embodiment (invention) is based on flow rate control (Q control), which is a basic and most stable control method when hydraulically controlling a hydraulic actuator. The disadvantage of Q control is to compensate for it with pressure control (P control) and to perform mixed control of both. As a result, it is possible to perform the mixed control of the respective valves by coordinating the two control methods of the Q control and the P control based on one control command corresponding to the operation amount of the operation lever 90 without contradiction. The operation (PQ control) of this embodiment will be described with reference to FIGS. 4 and 5. First, RO
Conversion tables T _qi , T _pi , and T _po of the MI flow rate command q _i , the MI pressure command p _Ci, and the meter-out side (MO) pressure command p _Co with respect to the operation amount y of the operation lever 90 stored in M4.
The converted value based on is read and stored in the RAM 3 (S1). In this embodiment, the MO flow rate command q _o is MI.
It is set to a value equal to the flow rate command q _i . Further, the above conversion tables T _qi , T _pi , and T _po empirically show the expected speed, acceleration, and deceleration of the hydraulic actuator 11 with respect to the operation amount y when the operator operates the operation lever 90. It is determined and determined, and stored in the ROM 4 in advance. As shown in FIG. 4, the conversion characteristics shown in the conversion tables T _qi , T _pi , and T _po have the MI pressure command p _Ci and the MO pressure command p _Co saturated with the increasing operation amount y in this embodiment. In contrast, the MI flow rate command q _i (MO flow rate command q
_o ) has the property of increasing rapidly as the manipulated variable y increases. Next, the MI hydraulic pressure p _la and the MO hydraulic pressure p _lb detected by the meter-in side and meter-out side hydraulic pressure sensors 16 and 17 are fetched and stored in the RAM 3 (S2). Then, the MI hydraulic pressure p _la is subtracted from the MI pressure command p _Ci ,
It is determined whether (p _Ci −p _la ) <0 (S3). If the result is Yes, the MI flow rate command q _{i is set} to (p _la −p _Ci ).
It is replaced with the corrected MI flow rate command q _i ′ reduced by the flow rate proportional to (S4). That is, the corrected MI flow rate command q _i ′ is M
The flow rate command is such that the I hydraulic pressure p _la approaches the MI pressure command p _Ci . If the decision result is No, MI flow command the MI flow rate instruction q _i read in step S1 q _i
(S5). Next, the meter-out side (MO) hydraulic pressure p _lb is subtracted from the MO pressure command p _Co , and (p _Co −p _lb ) <0
It is determined whether or not (S6). If the result is Yes,
The MO flow rate command q _o replace the corrected increased by the flow rate proportional to (p _lb -p _Co) MO flow rate command q _o '(S
7). That is, the corrected MO flow rate command q _o ′ is a flow rate command that brings the MO hydraulic pressure p _lb closer to the MO pressure command p _Co. If the determination result is No, the MO read in step S1
The flow rate command q _o is directly used as the MO flow rate command q _o (S
8). Then, it is determined whether the MI flow rate Q _i and the MO flow rate Q _o detected by the meter-in side and meter-out side oil amount sensors (not shown) are both 0, that is, whether or not the hydraulic actuator 11 has stopped (S9). Y
If it is es, the PQ control process is terminated and the determination result is No.
If so, the procedure returns to step S2 to repeat the above operation.

FIG. 6 is a functional block diagram showing the control flow of the control section showing in detail the process of calculating the flow rate command correction (PQ control) in the MI / MO pressure control described above. As described above, first, the manipulated _variable y is _calculated based on the conversion tables T _pi and T _po.
The converted values of the MI pressure command p _Ci and the MO pressure command p _Co are read, and the subtractors 21 and 23 subtract from the MI hydraulic pressure p _la and the MO hydraulic pressure p _lb , respectively. The respective subtracted values (p _Ci −p _la ) and (p _Co −p _lb ) are on the meter-in side (M
I) Input to the pressure calculation unit 24 and the meter-out side (MO) pressure calculation unit 22. As shown in FIG. 6, the MI pressure calculation unit 24 and the MO pressure calculation unit 22 have the functions of the MI correction limit block 24a, the MI pressure control block 24b, the MO correction limit block 22a, and the MO pressure control block 22b, respectively. , MI correction limit block 24
The a and MO correction limiting block 22a limits the output value to 0 when the input subtraction values (p _Ci -p _la ) and (p _Co -p _lb ) are positive values. Subtracted value (p _Ci −
p _la ), (p _Co −p _lb ) is the MI correction limiting block 24a
And the MO correction limit block 22a is limited to a negative value or 0, and then the MI pressure control block 24b and MO
The pressure control block 22b performs calculation according to the PI control, and the MI pressure correction command Δp _cp and the MO pressure command y _cp are obtained, respectively. The PI control arithmetic expression is generally represented by the following expression. Φ = K _I / s + K _p (K _I ; integral gain, K _p ; proportional gain, s; Laplace operator) K _p also has a vibration suppressing effect in hydraulic control. The MI pressure correction command Δp _cp output from the MI pressure calculation unit 24 is added to the differential pressure command Δp _c (corresponding to the MI flow rate command q _i ) by the adder 26. The output of the adder 26 becomes the MI correction differential pressure command Δp _c ′ output to the electric oil interface 12 a of the pressure compensation valve 12.

The pressure compensating valve 12 receives the MI correction differential pressure command Δ
differential pressure according to p _c 'compensation block 27 and MI flow rate conversion is known as shown by block 28 first-order lag element 1
/ (1 + Ts) and the pressure compensation operation according to the following Bernoulli's equation. Thus, the MI correction differential pressure command Δp _c ′
The hydraulic fluid of MI flow rate Q _i according to
It will flow into 1. Q _i = Cv · A (y) √ (2Δp / ρ) (Cv; flow coefficient, A (y); opening area, ρ; oil density) (Corresponding to the command q _o ), the MO flow rate correction command y _cp output from the MO pressure calculation unit 22 is subtracted, and the electro-hydraulic interface 14 a of the hydraulic main valve 14 is used as the MO flow rate control command y _o.
Is output to. The hydraulic main valve 14 is the MO flow rate conversion block 2
According to Bernoulli's equation shown in FIG. 9, the flow rate of the pressure oil flowing out from the hydraulic actuator 11 is changed to the MO flow rate Q _O.
To control. Q _O = Cv · B (y) √ (2p _lb / ρ) (B (y); opening area) Next, the operation of the embodiment will be further described based on an actual example.
FIG. 7 shows the operation amount y corresponding to the flow rate command q and the pressure command _pc , the MI hydraulic pressure _pla , the MO hydraulic pressure _plb, and the MI when the hydraulic excavator travels on the ground in the order of accelerated traveling-steady traveling-decelerated traveling. FIG. 7 is a characteristic diagram showing the time change of the flow rate Q _i (Q _O ) in association with the PQ control of the present embodiment and the conventional Q control. (a) shows MI flow rate command q
_i (q _o) operation amount of the operation lever 90 corresponding to y (thin line) and the flow pressure command p _c in consideration of the pressure correction (thick line)
(B) is the MI hydraulic pressure p _la , and (c) is the MO hydraulic pressure p _la.
lb and (d) show the MI flow rate Q _i (Q _O ), respectively. In (b) to (d), the solid line shows the characteristics of this embodiment (PQ control), and the broken line shows the characteristics when only the flow rate control (Q control) corresponding to the conventional example is performed. First,
The operation during acceleration will be described. During acceleration, the operator gradually pushes the operation lever 90 to increase the operation amount y. Corresponding to this, MI flow rate command q _i (MO flow rate command q _o )
Also increases. The MI flow rate command q _i is transmitted to the electro-hydraulic interface 13a of the hydraulic main valve 13, and its opening area A (y)
Increase. If p _la ≦ p _Ci , MI pressure correction command Δp
_{Since cp} = 0, the MI correction differential pressure command Δp _c ′ output to the electro-hydraulic interface 12a of the pressure compensation valve 12 is M
The differential pressure command Δp _c corresponds to the I flow rate command q _i . That is, the upstream hydraulic pressure p _z and the downstream hydraulic pressure of the hydraulic main valve 13, that is, MI
The MI flow rate Q _i for controlling the pressure compensating valve 12 is controlled so that the oil pressure difference between the oil pressures p _la becomes equal to the pressure difference command Δp _c according to the MI flow rate command q _i . By the way, when the operator pushes the operation lever 90 abruptly, the load pressure, that is, the MI hydraulic pressure p _la rapidly increases. Conventionally, as shown by a broken line, the MI hydraulic pressure p _la rapidly rises to reach the relief pressure p _rl, and excess pressure oil is discharged to the meter-out side by the relief valve 18a. However, in this embodiment, p _la
When> p _Ci , P control, that is, MI flow rate command q _i
As a result of the addition of the MI pressure correction command Δp _cp <0, which is a value proportional to (p _la −p _Ci ), the sum of the differential pressure commands Δp _c and Δp _cp is added to the electric oil interface 12a of the pressure compensation valve 12. , Actually the difference M between the differential pressure command Δp _c and (−Δp _cp )> 0
The I correction differential pressure command Δp _c ′ is given. Thus, MI
The hydraulic excavator continues to accelerate in a state where the hydraulic pressure p _la does not reach the relief pressure p _rl and reaches a steady running state. Meanwhile, MI
The flow rate Q _i increases slowly at first and then rapidly.
Since the load pressure of the hydraulic actuator 11 is large, the MO hydraulic pressure p _lb gradually increases while maintaining a low value. When the hydraulic excavator reaches a steady traveling state, the MI hydraulic pressure p _la maintains a constant value commensurate with the load pressure during flatland traveling. The MO hydraulic pressure p _lb and the MI flow rate Q _i also change similarly. At this time, when the operator slowly operates the operation lever 90, the MI hydraulic pressure p
_{Since la} and MO hydraulic pressure p _lb do not change significantly, MI correction differential pressure command Δp _c ′ = Δp _c , that is, MI flow rate command q _i
Q control is performed based on

Next, the operation during deceleration traveling will be described. During deceleration, the operator gradually pulls back the operation lever 90 to decrease the operation amount y. Corresponding to this, MI flow rate command q
_i (MO flow rate command q _o ) also decreases. MI flow rate command q _i
The differential pressure command Δp _c corresponding to and the operation amount y corresponding to the MO flow rate command q _o are transmitted to the electro-hydraulic interface 12a of the pressure compensating valve 12 and the electro-hydraulic interface 14a of the hydraulic main valve 14, respectively. The opening area of 14 is reduced. MO pressure command y while p _lb ≤ p _Co
because it is _cp = 0, MO flow control command y _o is output to the electro-hydraulic interface 14a of the hydraulic main valve 14 is manipulated variable y
(Q _o , q _i ), and the MI flow rate Q _i , MO of the pressure oil passing through the hydraulic main valves 13 and 14 corresponding to the decrease of the MI flow rate command q _i and the MO flow rate command q _o corresponding to the manipulated variable y. The flow rate Q _O is controlled. When the operator abruptly pulls back the operation lever 90 during deceleration, the MI flow rate Q _i , MO of the pressure oil passing through the hydraulic main valves 13 and 14 is increased according to the decrease in the operation amount y.
Although the flow rate Q _O sharply decreases, the MO hydraulic pressure p _lb sharply increases because the traveling motor tries to maintain the rotation due to the inertial load of the hydraulic excavator. Therefore, conventionally, as shown by the broken line in FIG. 7 (c), the MO hydraulic pressure p _lb rapidly rises to reach the relief pressure p _rl, and excessive pressure oil is discharged to the meter-in side by the operation of the relief valve 18b. However, in this embodiment, when p _lb > p _Co , P control, that is, the MO pressure command y _cp is subtracted from the manipulated _variable y, that is, (−y _cp )> 0.
There summed MO flow control command y _o is output to the electro-hydraulic interface 14a of the hydraulic main valve 14. as a result,
As shown in (d), the MO flow rate Q _O becomes larger than the flow rate commanded by the manipulated variable y. Therefore, the MO hydraulic pressure p _lb decreases after reaching the maximum value without reaching the relief pressure p _rl . Braking of the hydraulic actuator 11 becomes slower than in the case where the conventional Q control is performed, so the traveling distance until the hydraulic excavator stops is extended by the distance corresponding to the time indicated by A → B. On the other hand, on the meter-in side, as described above, the Q control based on the MI flow rate command q _i according to the decrease in the manipulated variable y is performed.
_{Since i} is limited to the flow rate according to the MI flow rate command q _i ,
As shown in (b), the MI hydraulic pressure p _la may suddenly decrease and become negative. At that time, the make-up valve 15a is operated to supply the pressure oil from the tank 19 to the meter-in side oil passage.

FIG. 8 shows changes in flow rate and pressure at the time of sudden acceleration and sudden deceleration, respectively, when only the conventional Q control is performed and when the PQ control of this embodiment is performed. In FIG. 8, (a1) and (a2) respectively show the flow rate characteristic and the pressure characteristic in the present embodiment,
(B1) and (b2) show the flow rate characteristic and the pressure characteristic in the conventional example, respectively. (A1), (b
As shown in 1), in this specific example, the flow rate command q (= q _i
= Q _o ) is the one in which the operating lever 90 is operated such that it rapidly rises and then immediately falls. When only the flow rate control is performed, the MI hydraulic pressure p _la suddenly _{rises due to} the rapid rise of the flow rate command q and the relief pressure p _rl.
And the MI pressure oil is discharged to the MO via the relief valve 18a to be maintained at a constant pressure (p _rl ) and then _gradually decreases (b2). On the other hand, when the PQ control is performed, the MI hydraulic pressure p _la rises rapidly, but after reaching the maximum hydraulic pressure without reaching the relief pressure p _rl , it gradually decreases (a2). When the flow rate command q is rapidly lowered, when only the flow rate control is performed, the MO flow rate Q _O is rapidly reduced due to the rapid fall of the flow rate command q, and the MO hydraulic pressure p _lb is increased. Relief pressure p at once
_rl , and the MO pressure oil passes through the relief valve 18b to MI.
After being maintained at a constant pressure (p _rl ) by being discharged, the hydraulic actuator 11 vibrates violently due to the contraction stress of the pressure oil. On the other hand, when the PQ control is performed, the MO oil pressure p _lb rises rapidly, but the MO flow rate Q _O does not decrease sharply, so the relief pressure p _rl
It reverses without reaching, and gradually declines. As described above, in this embodiment, P is set during the rapid acceleration / deceleration driving.
Since control is added and Q control, which is the basic control system of the hydraulic system, is performed at other times, the drive control is performed by operating one operating lever 90, but without relying on a complicated control system. Moreover, it is possible to perform the acceleration / deceleration control in accordance with the control feeling expected when the operator operates the operation lever 90 by the relatively simple automatic switching control. Also,
Since speed control during acceleration / deceleration driving is performed smoothly, a mechanical shock is given to the operator while riding during sudden acceleration or deceleration, and the hydraulic actuator mechanically oscillates (hunting) during acceleration / deceleration control operation. Since no movement occurs, the ride comfort of a hydraulic machine such as a hydraulic excavator becomes excellent. Furthermore, since the MI hydraulic pressure p _la and the MO hydraulic pressure p _lb never reach the relief pressure p _rl , the energy loss in the hydraulic control can be made smaller than in the conventional example in which the Q control is performed.

Next, a second embodiment of the present invention in which the PQ control of MI of the hydraulic actuator 11 is performed only by the hydraulic main valve 13 will be described. FIG. 9 is a conceptual diagram of the drive control mechanism of the hydraulic excavator according to the second embodiment, and FIG. 10 is a functional block diagram showing a control flow of the control unit. In these figures, 30 is a differential pressure sensor for detecting a hydraulic pressure difference between the upstream side and the downstream side of the hydraulic main valve 13, and 31 is a correction for the operation amount y by the differential pressure Δp detected by the differential pressure sensor 30. Differential pressure correction unit, 32 MI flow rate calculation unit, 33 differential pressure feedback unit, 34
Is a subtracter, and 40 is an MI pressure correction unit. In addition, the same reference numerals are given to the portions which are the same as or can be regarded as the same as those in the first embodiment, and the duplicate description thereof will be omitted. Differential pressure sensor 3
The differential pressure Δp detected at 0 is input to the differential pressure feedback unit 33,
Therefore, the feedback command y _f ′ is calculated according to the following equation. y _f ′ = A (y _i ) / A (y) √ (Δp / Δp _N ) (Δp
_N : standard differential pressure) The feedback command y _f ′ is input to the subtractor 34, and the operation amount y is subtracted. The result is input to the flow rate calculation unit 32, and the MI flow rate command y _f is calculated according to the following equation. y _f = K _I / s The MI flow rate command y _f is added to the MI pressure correction command y _cp calculated by the MI pressure calculator 24 in the adder 26 and output to the electric oil interface 13 a of the hydraulic main valve 13. As a result, the hydraulic main valve 13 controls the MI flow rate Q _i according to the MI corrected flow rate control command y _i . The operation of the hydraulic main valve 13 can be expressed by the following arithmetic expression, and the same operation as the pressure compensating valve 12 and the hydraulic main valve 13 in the first embodiment is performed. Q _i Cv · A (q _i ′) √ (Δp) The operation in the MO flow rate control is the same as that of the first embodiment. As described above, in the present embodiment, the MI flow rate is controlled in response to the change in the differential pressure Δp of the hydraulic main valve 13, and the MI flow rate control similar to that in the first embodiment can be performed without using the pressure compensation valve. It is possible.

[0014]

As described above, according to the invention of claim 1, the set flow rate of the pressure oil supplied to the hydraulic actuator and the setting of the inflow side or the outflow side of the hydraulic actuator according to the operation amount of the operation lever. When the hydraulic pressure is set, the detected hydraulic pressure on the inflow side or the outflow side of the hydraulic actuator is detected, the detected hydraulic pressure is compared with the set hydraulic pressure, and when it is determined that the detected hydraulic pressure is higher than the set hydraulic pressure, the inflow side or outflow of the hydraulic actuator is detected. Since the flow rate controlled by the inflow flow rate control means or the outflow flow rate control means is corrected so that the hydraulic pressure on the side decreases according to the differential pressure between the detected hydraulic pressure and the set hydraulic pressure, it does not depend on a complicated control mechanism. , It is possible to prevent the load pressure against the hydraulic pressure of the hydraulic actuator or the main valve of the outflow side from becoming excessive without suppressing unnecessary flow rate.
Since a smooth flow rate correction can be performed, it is possible to prevent the occurrence of a hunting phenomenon that occurs during sudden acceleration or sudden deceleration, and to provide a hydraulic drive system that excels in riding comfort. According to the second aspect of the invention, the set hydraulic pressure on the inflow side of the hydraulic actuator is set according to the operation amount of the operating lever, the detected hydraulic pressure on the inflow side of the hydraulic actuator is detected, and the detected hydraulic pressure is larger than the set hydraulic pressure. When the determination is made, the flow rate controlled by the inflow flow rate control means is decreased so that the oil pressure on the inflow side of the hydraulic actuator decreases in accordance with the pressure difference between the detected oil pressure and the set oil pressure. In addition, since the positive load pressure of the hydraulic actuator will not be excessive and released by the pressure release means, it is possible to prevent waste of drive energy. According to the third aspect of the present invention, a throttle valve whose opening amount changes in the upstream oil passage of the hydraulic actuator according to a flow rate control command, and a difference between the inflow side hydraulic pressure and the outflow side hydraulic pressure of the throttle valve. A pressure compensating valve that controls the flow rate of pressure oil supplied to the hydraulic actuator so that the pressure becomes a predetermined differential pressure is provided, and the inflow flow rate control means is supplied to the hydraulic actuator by controlling the opening amount of the pressure compensating valve. Since the flow rate of the pressure oil to be controlled is controlled, the inflow rate can be controlled accurately and the structure of the inflow rate control means can be simplified. According to the invention described in claim 4, a throttle valve which is provided in an upstream oil passage of the hydraulic actuator and whose opening amount changes according to a flow control command, and an inflow hydraulic pressure and an outflow hydraulic pressure of the throttle valve. Since it has a differential pressure detection means for detecting the differential pressure of the, and the inflow flow rate control means is configured to issue a flow rate control command according to the differential pressure detected by the differential pressure detection means to the throttle valve, The configuration of the hydraulic circuit can be simplified. According to the invention of claim 5, when it is determined that the detected hydraulic pressure detected by the downstream hydraulic pressure detecting means is higher than the set hydraulic pressure set by the downstream hydraulic pressure setting means, the hydraulic pressure on the outflow side of the hydraulic actuator is the detected hydraulic pressure and the set hydraulic pressure. Since the correction is made to increase the flow rate so as to decrease in accordance with the pressure difference between and, it is possible to prevent the negative load pressure of the hydraulic actuator from becoming excessive and the hunting phenomenon from occurring during sudden deceleration or the like.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a drive control mechanism of a hydraulic excavator according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing an internal circuit of a control unit.

FIG. 3 is a conceptual diagram showing the basic concept of control of the first embodiment.

FIG. 4 is also a conceptual diagram showing a detailed control concept.

[Fig. 5] Similarly, a flow chart of PQ control

FIG. 6 is a functional block diagram showing in detail the calculation process of flow rate command correction.

FIG. 7 is a characteristic diagram showing changes with time of commands and responses according to a specific example of this embodiment.

FIG. 8 is a characteristic diagram showing changes in flow rate and pressure when rapid acceleration and rapid deceleration are performed in this example and the conventional example.

FIG. 9 is a conceptual diagram of a drive control mechanism of a hydraulic excavator according to a second embodiment of the present invention.

FIG. 10 is a functional block diagram showing a control flow of the control unit.

FIG. 11 is a hydraulic drive circuit diagram of a hydraulic actuator according to a conventional example.

[Explanation of symbols]

1 control unit 2 CPU 4 ROM 10 hydraulic pump 11 Hydraulic actuator 12 Pressure compensation valve 13,14 Hydraulic main valve 12a, 13a, 14a Electro-oil interface 15 (a, b) Make-up valve 16 Meter-in side oil pressure sensor 17 Meter-out side oil pressure sensor 18 (a, b) relief valve 19 oil tank 21,23,25,34 Subtractor 22 Meter-out pressure calculator 24 Meter-in pressure calculator 26 adder 30 differential pressure sensor 31 Differential pressure correction unit 32 Meter-in side flow rate calculation unit 33 Differential pressure feedback section 40 Meter-in side pressure compensator 90 Operation lever

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) F15B 11/00-11/22 E02F 9/22

Claims (5)

(57) [Claims] 1. A hydraulic pump driven by a drive means, a hydraulic actuator driven by pressure oil discharged from the hydraulic pump, and pressure oil supplied to the hydraulic actuator according to an operation amount of an operating lever. Inflow flow rate control means for controlling the flow rate, outflow flow rate control means for controlling the flow rate of the pressure oil discharged from the hydraulic actuator, and the hydraulic pressure of the hydraulic circuit on the inflow side or the outflow side of the hydraulic actuator exceeds a predetermined pressure. In a hydraulic drive device equipped with a pressure release means for releasing an excess pressure oil when the pressure is increased, a flow rate setting means for setting a set flow rate of the pressure oil supplied to the hydraulic actuator according to an operation amount of the operation lever; A hydraulic pressure setting means for setting a set hydraulic pressure on the inflow side or the outflow side of the hydraulic actuator according to the operation amount of the operation lever; By comparing the hydraulic pressure detecting means for detecting the detected hydraulic pressure on the inflow side or the outflow side of the actuator with the detected hydraulic pressure detected by the hydraulic pressure detecting means and the set hydraulic pressure set by the hydraulic pressure setting means, the detected hydraulic pressure is higher than the set hydraulic pressure. When it is determined that the flow rate is large, the inflow side or the outflow side of the hydraulic actuator is decreased according to the set flow rate set by the flow rate setting means so as to be decreased according to the differential pressure between the detected hydraulic pressure and the set hydraulic pressure. A hydraulic drive device comprising flow rate control means or flow rate correction means for correcting the flow rate controlled by the outflow flow rate control means. 2. The hydraulic pressure setting means is an upstream hydraulic pressure setting means for setting the set hydraulic pressure on the inflow side of the hydraulic actuator according to the operation amount of the operating lever, and the hydraulic pressure detecting means sets the detected hydraulic pressure on the inflow side of the hydraulic actuator. When the flow rate correction means determines that the detected hydraulic pressure detected by the upstream hydraulic pressure detection means is higher than the set hydraulic pressure set by the upstream hydraulic pressure setting means, the hydraulic pressure on the inflow side of the hydraulic actuator is detected. 2. The hydraulic drive system according to claim 1, wherein a correction is made to reduce the flow rate controlled by the inflow flow rate control means so as to reduce the pressure in accordance with the differential pressure between the detected hydraulic pressure and the set hydraulic pressure. . 3. An oil passage upstream of the hydraulic actuator,
A throttle valve whose opening amount changes according to a flow rate control command, and pressure oil supplied to the hydraulic actuator so that the differential pressure between the inflow side hydraulic pressure and the outflow side hydraulic pressure of the throttle valve becomes a predetermined differential pressure. And a flow rate control means for controlling the flow rate of the pressure oil supplied to the hydraulic actuator by controlling the opening amount of the pressure compensation valve. The hydraulic drive system according to claim 2. 4. A throttle valve which is provided in an oil passage upstream of a hydraulic actuator and whose opening amount changes according to a flow rate control command, and a differential pressure between an inflow hydraulic pressure and an outflow hydraulic pressure of the throttle valve is detected. 3. The inflow flow rate control means issues a flow rate control command to the throttle valve according to the differential pressure detected by the differential pressure detection means.
The hydraulic drive described. 5. The hydraulic pressure setting means is a downstream hydraulic pressure setting means for setting the set hydraulic pressure on the outflow side of the hydraulic actuator according to the operation amount of the operation lever, and the hydraulic pressure detection means detects the detected hydraulic pressure on the outflow side of the hydraulic actuator. When the flow rate correction means determines that the detected hydraulic pressure detected by the downstream hydraulic pressure detection means is higher than the set hydraulic pressure set by the downstream hydraulic pressure setting means, the hydraulic pressure on the outflow side of the hydraulic actuator is The hydraulic drive system according to claim 1, wherein correction is performed to increase a flow rate controlled by the outflow flow rate control unit so that the flow rate is controlled according to a pressure difference between the detected hydraulic pressure and the set hydraulic pressure.