JPH0536642B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a hydraulic control device that drives a plurality of actuators with a single pump.

(Prior Art) Conventionally, in a hydraulic control device in which a plurality of actuators are connected to a plurality of parallel circuits branched from a single pump through directional control valves, a pressure compensation valve is provided on the pump side of each directional control valve. By providing a device that allows each actuator to be driven at the required speed according to the spool opening of each directional control valve, regardless of changes in load, even if multiple actuators are operated simultaneously (for example, a special Publication No. 52-40381) is known.

In this control device, when multiple actuators are operated simultaneously, if the pump discharge flow rate is greater than the sum of the required flow rates supplied to each actuator via each directional control valve, mutual flow interference between the actuators will occur. However, since the entire circuit is constructed of parallel circuits, the following problems arise.

In other words, as the engine speed decreases,
When the pump discharge flow rate becomes less than the sum of the above-mentioned required flow rates, the flow rate flows first to the actuator side with a lower load pressure, and the flow rate to the actuator side with a higher load pressure becomes insufficient, and the desired control is no longer performed. Also,
Even if the pump discharge flow rate is greater than the sum of the required flow rates, the maximum value of the required flow rates will vary due to accuracy errors, setting errors, etc. of the pressure compensating valves on the pump side of each directional control valve. Therefore, even if two actuators are operated to synchronize, for example, the same flow rate may not flow through both actuators due to the above-mentioned reasons, and synchronization is impaired. Therefore, when the conventional control device described above is applied to the main hoist and catch hoist of a truck crane, and the main hoist and catch hoist are synchronized to suspend a long object together, or when the main hoist and catch hoist are used to open and close a bucket. When performing clamshell work using ropes and support ropes, as mentioned above, there is a risk that the synchronization will be impaired and the balance of the suspended load will be lost, or that the opening/closing rope of the bucket may come loose and the load will spill.

(Object of the Invention) The present invention has been made to solve such problems, and the first object of the invention is to reduce the pump discharge flow rate due to a decrease in engine speed etc. when operating multiple actuators. Even if the required flow rate is less than the sum of the required flow rates of multiple actuators, it is possible to properly supply the required flow rate to each actuator and operate each actuator accurately, improving synchronization and improving truck crane operation. To safely and smoothly carry out co-hanging clam shell work using a main hoist and a catch hoist.

In addition, an object of the second invention is to operate multiple actuators in synchronization in a series circuit while performing pressure compensation control in the same way as in the case of the first invention, in work that requires synchronization, so that the pressure required can be adjusted. For work that requires a parallel circuit, each actuator can be operated properly at a pressure that corresponds to its load pressure, and by simply switching the switching valve according to the work content, the work can be performed in the optimal condition and work efficiency can be improved. The goal is to

(Structure of the Invention) The first invention provides a hydraulic control device in which three or more actuators are connected to a single pump in parallel through directional control valves, () a discharge circuit of the pump is provided with a main bleed-off type. Pressure compensation valves are connected in parallel, () A meter-in type pressure compensation valve is provided on the pump side of each directional control valve to keep the differential pressure before and after each directional control valve constant, and () the load on the actuator is A shuttle valve is provided that guides the high-pressure side load pressure of the main bleed-off type pressure compensation valve to the back pressure chamber; The tank port of the upstream directional control valve is connected in a series circuit between the pump port of the downstream directional control valve and the meter-in type pressure compensation valve, and () the load of the downstream actuator is connected to this series circuit. An auxiliary bleed-off pressure compensation valve that controls the bleed-off flow rate from the upstream directional control valve to the tank based on pressure is connected in parallel. The pressure is set higher than the pressure compensation valve setting value.

With this configuration, pressure compensation control is performed by a meter-in type pressure compensation valve for each actuator,
Each actuator does not interfere with each other,
It operates properly at the required flow rate determined by the directional control valve. Also, when synchronizing a specific actuator among three or more actuators connected in parallel, the series circuit allows the flow rate used on the upstream side to directly flow into the downstream side, ensuring accurate synchronization between the upstream and downstream sides. is activated. Also, during synchronization, if the return flow rate from the upstream side is greater than the required flow rate downstream, the excess oil is returned to the tank via the auxiliary bleed-off type pressure compensation valve, and if it is low, the insufficient flow rate is returned to the meter from the pump side. It flows into the downstream side through a type pressure compensation valve, and the upstream and downstream sides are always operated in synchronization and properly.

A second invention is a second invention in which, in the first invention, a position a where downstream load pressure is introduced into the back pressure chamber of the auxiliary bleed-off pressure compensation valve and a position b where the back pressure chamber is communicated with the tank are provided. It is equipped with a switchable switching valve.

With this configuration, in the second invention, the switching valve a
At position b, a series circuit performs the same control as in the first invention, making it an optimal circuit for tuning work, and at position b, a parallel circuit leads to pressures corresponding to their load pressures to each actuator, This circuit is suitable for hoisting heavy objects, etc., and by switching the switching valve, it becomes possible to select and use a series circuit or a parallel circuit for a specific plurality of actuators, improving the versatility of the device.

(Embodiment) FIG. 1 shows an embodiment in which the first invention is applied to a truck crane, in which a single pump 10 operates four actuators, namely a boom telescoping cylinder 51, a boom elevating cylinder 52, and a main hoisting cylinder. The case where the motor 53 and the auxiliary winding motor 54 are driven is illustrated, and in particular, the main winding motor 53 and the auxiliary winding motor 54 are controlled according to the first invention.

A plurality of parallel circuits 20, 21, 22, 23, 24 are branch-connected to the discharge circuit 11 of the pump 10,
The circuit 20 is connected to the tank 60 via a main bleed-off pressure compensation valve 61, and the other circuits 21, 2
Meter-in type pressure compensation valves 31, 32, 33, 34 and directional control valve 4 are installed at 2, 23, 24, respectively.
The actuators 51, 52, 53, and 54 are connected to each other via the actuators 1, 42, 43, and 44, respectively.

Each of the meter-in type pressure compensating valves 31 to 34 is located on the pump side of each of the directional control valves 41 to 44, and introduces the pressure on the inlet side of each of the directional control valves 41 to 44 into one end of the plunger, and introduces the pressure on the outlet side. In other words, the load pressure of each actuator 51 to 54 is introduced into the back pressure chamber on the spring side at the other end of the plunger, and each directional control valve 41 to 4
This is to control so that the differential pressure before and after No. 4 is constant. In addition, each meter-in type pressure compensation valve 31~
The back pressure chamber 34 is connected to the back pressure chamber of the main bleed-off type pressure compensating valve 61 via shuttle valves 63, 64, and 65, and the load pressure of each of the actuators 51 to 54 is selected as a high pressure, so that the main bleed-off type It is designed to be guided to the back pressure chamber of the pressure compensating valve 61. 6
6 is a main relief valve. This main relief valve 66 may be connected in parallel to the discharge circuit 11 of the pump 10, but by connecting it in parallel to the back pressure chamber of the main bleed-off type pressure compensation valve 61 as shown in the figure, a small relief valve can be provided. Valve can be used.

In the above configuration, the direction control valves 41, 42,
43 is connected in parallel to the pump 10 as in the conventional case. On the other hand, the directional control valve 43 and the directional control valve 44 are substantially connected in series based on the present invention. That is, the tank port of the directional control valve 43 on the upstream side is connected to the pump port of the directional control valve 44 on the downstream side by the series circuit 25 having the check valve 26, and the flow rate used on the upstream side is directly transferred to the circuit 25 and the check valve 26. It is configured to be guided to the directional control valve 44 on the downstream side via the directional control valve 44. The secondary side of the meter-in type pressure compensation valve 34 is connected in parallel to the circuit 25 to the pump port of the directional control valve 44 on the downstream side.

The circuit 25 includes an auxiliary bleed-off type pressure compensation valve 6.
2 are connected in parallel, and the back pressure chamber of this valve 62 is connected in parallel to the back pressure chamber of the meter-in type pressure compensation valve 34. Furthermore, the setting value of the auxiliary bleed-off type pressure compensation valve 62 is the same as that of the meter-in type pressure compensation valve 34.
is set higher than the setting value.

Next, the operation of the embodiment of the first invention will be explained.

Neutral When each of the directional control valves 41 to 44 is in neutral, the oil discharged from the pump 10 is
44, the flow does not flow into each actuator 51 to 54, and each actuator remains stopped, and the back pressure chamber of the main bleed-off pressure compensation valve 61 is communicated with the tank 60, and this pressure The compensation valve 61 is closed only by spring force, and its installed value is a low pressure. Therefore, the entire amount of oil discharged from the pump 10 is bleed-off at low pressure into the tank 60 via the main bleed-off type pressure compensating valve 61.

Driving the upstream actuator For example, when the main winding directional control valve 43 is switched to the upper or lower position, the oil discharged from the pump 10 flows into the main winding motor 53 via the meter-in type pressure compensation valve 33 and the directional control valve 43. The motor 53 is driven. At this time, the pressure on the inlet side of the direction control valve 43 and the pressure on the outlet side, that is, the load pressure of the main motor 53
Pa ₃ is led to both ends of a meter-in type pressure compensation valve 33, and this pressure compensation valve 33 causes a directional control valve 43.
Pressure compensation control is performed such that the differential pressure before and after is constant, and the pressure is determined by the spool opening degree of the direction control valve 43 for the main winding motor 53 regardless of whether or not the other actuators 51, 52, and 54 operate. The requested flow rate Qa ₃ is appropriately supplied.

When the main winding motor 53 is driven, the main winding motor 5
The load pressure Pa ₃ of 3 is led to the back pressure chamber of the main bleed-off type pressure compensation valve 61 via the shuttle valves 65, 64, 63, and this load pressure Pa ₃ causes the pressure compensation valve 61 to be
The setting value of pump 1 is increased, and along with this, the setting value of pump 1 is increased.
The discharge pressure Pp of 0 rises to the set value of the pressure compensation valve 61, that is, the pressure corresponding to the load pressure _Pa3 of the main winding motor 53, and this pressure is guided to the main winding motor 53, and the main winding motor 53 is acceleratedly driven. be done. moreover,
Of the discharge flow rate Qp of the pump 10, the required flow rate is determined by the spool opening degree of the directional control valve 43.
As Qa ₃ flows into the motor 53, its surplus flow rate (Qp-Qa ₃ ) is bled off to the tank 60 by the pressure compensation valve 61 at a pressure corresponding to the load pressure Pa ₃ .

On the other hand, since the downstream directional control valve 44 is in the neutral position, the auxiliary winding motor 54 remains stopped and the back pressure chamber of the auxiliary bleed-off type pressure compensation valve 62 is communicated with the tank 60. For this reason,
Return oil led from the upstream main winding motor 53 to the circuit 25 via the directional control valve 43 is bleed off to the tank 60 at low pressure via the auxiliary bleed-off type pressure compensation valve 62.

During this control, the load pressure of the main motor 53
When a change occurs in Pa ₃ , the load pressure Pa ₃ is always guided to the back pressure chamber of the main bleed-off pressure compensation valve 61, so the pressure compensation control by the pressure compensation valve 61 reduces the discharge pressure of the pump 10. Pp is always maintained at a pressure corresponding to the load pressure Pa ₃ of the main winding motor 53, and the required flow rate Qa ₃ according to the spool opening of the directional control valve 43 is mainly maintained by pressure compensation control by the meter-in type pressure compensation valve 33. The air flows into the winding motor 53, and the motor 53 is appropriately driven at a speed corresponding to the amount of operation of the directional control valve 43.

Driving the downstream actuator When the upstream main winding directional control valve 43 is held in the neutral position and the downstream auxiliary winding directional control valve 44 is switched to the upper or lower position, the control is similar to the above control. The load pressure Pa ₄ of the auxiliary motor 54 is guided to the back pressure chamber of the main bleed-off type pressure compensation valve 61 via the shuttle valves 65, 64, 63, and the pressure compensation valve 61
The discharge pressure of the pump 10 due to pressure compensation control by
Pp is maintained at a pressure corresponding to the load pressure Pa ₄ , and the meter-in type pressure compensation valve 34 performs pressure compensation control to maintain a constant differential pressure across the directional control valve 44, which is a request determined by the spool opening of the directional control valve 44. The flow rate Qa ₄ is appropriately flowed into the auxiliary winding motor 54, and the auxiliary winding motor 54 is appropriately driven at a speed corresponding to the above-mentioned inflow flow rate Qa ₄ regardless of its load pressure.

Simultaneous driving of two actuators For example, when driving the main winding and auxiliary winding at the same time, the upstream main winding directional control valve 43 and the downstream auxiliary winding directional control valve 44 are substantially configured in a series circuit. Therefore, when the downstream auxiliary winding directional control valve 44 is switched to the upper or lower position with the main winding driven as described above, the wind is guided from the upstream main winding motor 53 to the circuit 25 via the directional control valve 43. Return oil flows into the auxiliary motor 54 via the check valve 26 and the downstream directional control valve 44.

At this time, the load pressure Pa ₄ of the auxiliary winding motor 54 is guided to the back pressure chamber of the auxiliary bleed-off type pressure compensation valve 62 and the set value of the pressure compensation valve 62 is increased. Return oil from the winding motor 53 is once blocked by the auxiliary bleed-off type pressure compensation valve 62 and guided to the pump port of the directional control valve 44 downstream. The pressure of the return oil guided to the downstream directional control valve 44 is determined by an auxiliary bleed-off type pressure compensation valve 62, and the set value of this pressure compensation valve 62 is determined by the downstream auxiliary oil flow guided to the back pressure chamber. Since it is controlled by the load pressure Pa ₄ of the motor 54,
The pressure of the return oil is the load pressure of the auxiliary motor 54 Pa ₄
The pressure rises to a level corresponding to the pressure, and the auxiliary winding motor 54 is driven by that pressure.

On the other hand, due to the increase in the pressure of the return oil, the back pressure of the main winding motor 53 will rise, but along with this rise in back pressure, the pressure on the suction side of the main winding motor 53 will also rise, and the suction side The pressure corresponds to the sum of the load pressure Pa ₄ of the downstream auxiliary motor 54 and the original load pressure Pa ₃ of the main motor 53 (Pa ₃ + Pa ₄ )
, and the pressure increases to the shuttle valves 65, 64,
63 to the back pressure chamber of the main bleed-off type pressure compensation valve 61, and under pressure compensation control by the pressure compensation valve 61, the discharge pressure Pp of the pump 10 increases to a pressure corresponding to the sum of the load pressures.

The discharge flow rate Qp of the pump 10 first flows into the upstream main motor 53 under the above control, the main motor 53 is driven at a predetermined speed, and the return oil flows into the downstream auxiliary motor 54. , the auxiliary winding motor 54 is driven. Here, when the flow rate Qa ₃ of the return oil from the upstream main motor 53 is greater than the required flow rate Qa ₄ of the auxiliary motor 54 determined by the spool opening of the downstream directional control valve 44, the return oil flow from the upstream Of the returned oil, a flow rate corresponding to the downstream required flow rate Qa ₃ flows into the auxiliary winding motor 54, and the flow rate Qa ₄
The auxiliary winding motor 54 is driven at a speed corresponding to. In addition, among the return oil flow rate Qa ₃ from the upstream, the remaining surplus flow that has flowed into the downstream auxiliary motor 54 (Qa ₃ −
Qa ₄ ) is the above auxiliary bleed-off type pressure compensation valve 62
This bleeds off to the tank 60 at a pressure corresponding to the load pressure Pa ₄ of the downstream auxiliary winding motor 54.

Return oil flow rate Qa ₃ from upstream is downstream required flow rate
If it is less than Qa ₄ , the meter-in type pressure compensation valve 3 provided on the pump side of the downstream directional control valve 44
4, the insufficient flow is transferred from the pump 10 to the auxiliary motor 5 via the meter-in type pressure compensation valve 34 and the direction control valve 44.
4 will be replenished.

During the simultaneous operation of the main winding and auxiliary winding, even if the load pressures Pa ₃ and Pa ₄ of the motors 53 and 54 fluctuate, the upstream bleed-off pressure compensation valves 61 and 62
Due to the pressure compensation control of the meter-in type pressure compensation valves 33 and 34 to maintain a constant differential pressure, each directional control valve 4 is always connected to each motor 53 and 54.
The required flow rates Qa ₃ and Qa ₄ determined by 2 and 43 are inflowed, and each motor 53 and 54 is driven at a predetermined speed, respectively.

Next, when the main winding and the auxiliary winding are synchronized, such as when performing co-suspension work on long objects or clamshell work, each directional control valve 43 of the main winding and the auxiliary winding,
By making the operating amounts of 44 the same, the required flow rate Qa ₃ determined by the directional control valve 43 flows into the main winding motor 53, and the same return oil flow rate is made in the series circuit and directly flows into the auxiliary winding motor 53. It flows into the motor 54, and the main winding motor 53 and the auxiliary winding motor 54 are driven in complete synchronization.

In this case, in the series circuit, the upstream main winding motor 5
Since the return flow rate corresponding to the flow rate Qa ₃ flowing into Qa 3 flows directly into the downstream auxiliary motor 54, the required flow rate of the main motor 53 is reduced as in the conventional parallel circuit.
The total flow rate of Qa ₃ and the required flow rate Qa ₄ of the auxiliary winding motor 54 is not required, as long as the discharge flow rate Qp of the pump 10 is equal to or higher than the required flow rate Qp ₃ of the upstream main winding motor 53. Both motors 53 and 54 of the auxiliary winding are synchronously driven. In other words, the pump discharge flow rate
Required flow rate of one actuator among Qp
Two actuators are synchronously driven with only Qa ₃ . Note that the remaining discharge flow rate of the pump 10 (Qp−
Qa ₃ ) is bled off to the tank 60 by the main bleed-off type pressure compensating valve 61 at a pressure (Pa ₃ +Pa ₄ ) corresponding to the sum of the load pressures.

Therefore, even if the engine speed decreases and the discharge flow rate Qp of the pump 10 decreases, the main bleed-off type pressure compensating valve 61 ensures that the tank 60
bleed-off flow rate is reduced.
If the pump discharge flow rate Qp is equal to or higher than the required flow rate Qa ₃ of the main winding, both the main winding and auxiliary winding motors 53 and 54 can be reliably driven in synchronization. Furthermore, even if the boom elevation cylinder 52 is driven by operating the boom elevation direction control valve 42 further upstream from the main hoist, the remaining pump discharge flow rate (Qp - _{Qa 2} ) is the main hoist's required flow rate Qa ₃ or more, the boom elevation and the main hoist and auxiliary hoist's 3
Can perform two tasks at the same time.

By the way, when the main winding and auxiliary winding are operated simultaneously (synchronized) as described above, they are used in a series circuit, so
The discharge pressure Pp of the pump 10 attempts to rise to a pressure corresponding to the sum of the main winding load pressure Pa ₃ and the auxiliary winding load pressure Pa ₄ . However, the discharge pressure Pp of the pump 10
The maximum value of is determined by the main relief valve 66, so if the sum of the load pressures (Pa ₃ + Pa ₄ ) is higher than the set value of the main relief valve 66, for example when lifting a heavy object, the main relief valve There is a possibility that both the motors 53 and 54 cannot be driven because the motor 66 is not working.

The second invention solves this problem, and an embodiment thereof will be explained with reference to FIG. 2.

In FIG. 2, a switching valve 70 is added to the circuit shown in FIG. 1, and the other configurations are substantially the same as the embodiment shown in FIG. Therefore, in FIG. 2, the same parts as those in FIG. 1 are given the same reference numerals, redundant explanation thereof will be omitted, and different parts will be explained below.

The switching valve 70 connects a pilot circuit 71 for deriving load pressure, which communicates with the back pressure chamber of the meter-in type pressure compensation valve 34 on the downstream side, and a pilot circuit 72, which communicates with the return oil circuit 67 to the tank 60, for auxiliary bleed-off. It is selectively connected to the back pressure chamber of the shaped pressure compensation valve 62.

In this embodiment, when the switching valve 70 is in the position shown, the downstream load pressure deriving pilot circuit 71 is communicated with the back pressure chamber of the auxiliary bleed-off type pressure compensation valve 62, thereby substantially The circuit is the same as the circuit shown in FIG. 1, and the upstream and downstream, that is, the main winding and the auxiliary winding, are series circuits, and moreover, the pressure compensation is controlled, and the tuning work is performed properly.

Next, when the switching valve 70 is switched to the position shown in the drawing,
The back pressure chamber of the auxiliary bleed-off type pressure compensation valve 62 is connected to the tank 6 via the circuits 72 and 67 by the switching valve 72.
0, and the set value of this pressure compensation valve 62 becomes low pressure. Therefore, the return oil led from the upstream main winding motor 53 to the circuit 25 does not flow into the downstream directional control valve, but instead flows into the auxiliary bleed-off type pressure compensation valve 62.
bleed off to tank 60 at low pressure.
Therefore, the upstream main winding motor 53 is driven at a pressure corresponding to its own load pressure Pa ₃ without being influenced by the downstream load pressure. Further, the discharge side of the pump 10 flows into the downstream auxiliary motor 54 via the meter-in type pressure compensation valve 34 and the direction control valve 44 .

That is, if the switching valve 70 is switched to the upper position, the upstream directional control valve 43 and the downstream directional control valve 44 will be connected in a parallel circuit, and the oil discharged from the pump 10 will be transferred to the upstream main motor 53. They will be individually supplied to the downstream auxiliary winding motors 54.
In this case, the main winding load pressure Pa ₃ and the auxiliary winding load pressure
The load pressure on the high pressure side of Pa ₄ is led to the back pressure chamber of the main bleed-off type pressure compensation valve 61, and the excess oil from the pump 10 is transferred to the tank 6 at a pressure corresponding to the load pressure on the high pressure side.
Bleed off to 0.

By switching to the parallel circuit in this way, the discharge force Pp of the pump 10 does not need to rise to the pressure corresponding to the sum of the load pressures as in the case of the above-mentioned series circuit, but only needs to be equal to or higher than the pressure on the high pressure side. In addition, since the set value of the main relief valve 66 is set in advance to be higher than the maximum value of the load pressure of each actuator 51 to 54, the main winding and auxiliary winding are simultaneously operated within the range below the set value of the main relief valve 66. And it can be driven reliably.

In this way, by switching the switching valve 70, it is possible to use either the series circuit or the parallel circuit.

Although each of the above embodiments has been described with reference to a case where it is applied to a truck crane, the first and second inventions are not limited to the above embodiments, but can be applied to various types of construction machinery and the like, and the actuator to be controlled is also a hydraulic motor. , hydraulic cylinder may be used, 3
It can also be applied to control of more than one actuator.

(Effects of the Invention) As described above, according to the first invention, pressure compensation control is performed by the meter-in type pressure compensation valve for each actuator, and each actuator is controlled by each directional control valve without interference with each other. It can be operated properly at the required flow rate determined by the flow rate. In addition, when synchronizing a specific actuator in a group of actuators, it can essentially be used in a series circuit, and even if the pump discharge flow rate decreases slightly due to a decrease in engine speed, the flow rate used on the upstream side It is possible to flow directly into the downstream side and operate the upstream and downstream sides in precise synchronization, making it possible to safely and efficiently carry out work such as co-hanging of long objects and clamshell work using buckets.

In addition, according to the second invention, it is possible to use a series circuit and a parallel circuit properly in one circuit by simply switching the switching valve, and when performing tuning work, the series circuit can be properly tuned and the weight is reduced. When pressure is required, such as when hoisting objects, a parallel circuit can be used at high pressures up to the set value of the main relief valve, greatly improving work efficiency and increasing the versatility of the device.

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of the first invention, and FIG. 2 is a hydraulic circuit diagram showing an embodiment of the second invention. 10...Pump, 11...Discharge circuit, 20,2
1, 22, 23, 24... Parallel circuit, 25... Series circuit, 31, 32, 33, 34... Meter-in type pressure compensation valve, 41, 42, 43, 44...
Directional control valve, 51...Boom telescopic cylinder, 52
...Boom elevation cylinder, 53...Main winding motor (upstream actuator), 54...Auxiliary winding motor (downstream actuator), 60...Tank, 61
...Main bleed-off type pressure compensation valve, 62...Auxiliary bleed-off type pressure compensation valve, 63, 64, 65...
...Shuttle valve, 66...Main relief valve.

Claims (1)

[Scope of Claims] 1. A hydraulic control device in which three or more actuators are connected to a single pump in parallel through directional control valves, () a main bleed-off type pressure compensation valve is provided in the discharge circuit of the pump. () A meter-in type pressure compensation valve is provided on the pump side of each directional control valve to keep the differential pressure across each directional control valve constant. A shuttle valve is provided that guides the side load pressure to the back pressure chamber of the main bleed-off pressure compensation valve, The tank port of is connected in a series circuit between the pump port of the downstream directional control valve and the meter-in type pressure compensation valve, and the upstream direction is connected to this series circuit by the load pressure of the downstream actuator. An auxiliary bleed-off type pressure compensation valve that controls the bleed-off flow rate from the control valve to the tank is connected in parallel, and () the setting value of this auxiliary bleed-off type pressure compensation valve is greater than or equal to the setting value of each meter-in type pressure compensation valve mentioned above. A hydraulic control device characterized by being set to. 2. In a hydraulic control system in which three or more actuators are connected in parallel to a single pump through directional control valves, () a main bleed-off type pressure compensation valve is connected in parallel to the discharge circuit of the pump, ( ) A meter-in type pressure compensation valve is installed on the pump side of each directional control valve to keep the differential pressure before and after each directional control valve constant. A shuttle valve that guides the main bleed-off pressure compensation valve to the back pressure chamber is provided, () A tank port of the upstream direction control valve of each direction control valve that controls a plurality of specific actuators in the actuator group. is connected in a series circuit between the pump port of the downstream directional control valve and the meter-in type pressure compensating valve, and () the voltage from the upstream directional control valve is connected to this series circuit by the load pressure of the downstream actuator. An auxiliary bleed-off type pressure compensation valve that controls the bleed-off flow rate to the tank is connected in parallel, and the back pressure chamber is located at the same position as the position where downstream load pressure is introduced into the back pressure chamber of this auxiliary bleed-off type pressure compensation valve. A changeover valve is provided at a position where the auxiliary bleed-off pressure compensation valve communicates with the tank, and () the set value of the auxiliary bleed-off type pressure compensation valve is set to be higher than the set value of each of the meter-in type pressure compensation valves. Hydraulic control device.