JPH11230108A - Bleed-off control device for actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize bleed-off control which can obtain a stable operational feeling, and besides, has high degree of freedom to set control characteristic. SOLUTION: This control device controls a flow of hydraulic fluid returned from a pump 12 to a tank 10 without going by way of an actuator such as a revolving motor 14 by using a directional flow control valve 20 and the like. In this case, relationship between control input of an electric lever 44 and the like and differential pressure before and after bleed-off restriction is previously set, and the opening area of the bleed-off restriction is adjusted based on the control input and the delivery of the pump 12 so as to retain this relationship regardless of the delivery of the pump 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bleed-off control device for an actuator used in a work boat or other hydraulic cranes, hydraulic shovels, or the like.

[0002]

2. Description of the Related Art Heretofore, as a speed control method of an actuator which operates by receiving a supply of a working fluid, a bleed-off control for controlling a flow rate of a fluid returning from a pump to a tank without passing through the actuator is well known. . For example, Japanese Patent Publication No. 7-6525 discloses that a directional flow control valve having a bleed-off passage therein is provided between a hydraulic motor and a hydraulic pump, and the above-described directional flow control valve is provided in accordance with the operation amount of a lever operated by an operator. There is disclosed an apparatus in which the opening area of a bleed-off flow path is controlled by changing the pilot pressure of a directional flow control valve.

[0003]

In the apparatus disclosed in the above publication, the lever operation and the opening area of the bleed-off flow path are associated with each other on a one-to-one basis. The bleed-off pressure (differential pressure before and after the bleed-off flow path) corresponding to the amount differs. In other words, the relationship between the lever operation and the opening area of the bleed-off flow path is not constant, so that there is a disadvantage that it is difficult to perform an appropriate operation.

In the above publication, pressure control is performed to control the pump discharge pressure during acceleration and the pressure in the motor discharge side flow path during deceleration in accordance with the amount of operation of the operation lever, thereby enabling smooth deceleration stop and load deflection prevention. However, even in such pressure control, the pressure relationship fluctuates depending on the pump discharge flow rate.
Even if the operator intends to perform the same operation, the feeling of acceleration and the feeling of deceleration may change.

In the apparatus disclosed in this publication, the flow rate characteristic and the pressure characteristic are determined by the relationship between the pilot pressure and the spring reaction force, so that the degree of freedom in setting the characteristic is low. Therefore, in order to set various types of characteristics, it is necessary to add hydraulic devices by the number of the characteristics, which causes a problem of high cost.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a bleed-off control device for an actuator which can obtain a stable operation feeling and has a high degree of freedom in setting its control characteristics.

[0007]

As means for solving the above problems, the present invention provides an actuator, a pump for supplying a working fluid to the actuator, and a pump for supplying a working fluid from the pump without passing through the actuator. Bleed-off restrictor for changing the opening area of the bleed-off flow path for returning to the tank, operating means operated to operate the actuator, discharge flow detecting means for detecting the discharge flow of the pump, On the basis of the discharge flow rate detected by the discharge flow rate detection means and the operation amount of the operation means, the relationship between the operation amount of the operation means and the differential pressure before and after the bleed-off throttle means becomes a predetermined relation. And control means for operating the bleed-off throttle means.

In this configuration, the relationship between the amount of operation of the operating means and the differential pressure before and after the bleed-off throttle means is predetermined, and the bleed-off flow passage is controlled in accordance with the pump discharge flow rate so as to maintain this relationship. Since the opening area of is determined,
The characteristic of the manipulated variable-bleed-off pressure does not fluctuate greatly with the change of the pump discharge flow rate as in the prior art, and a stable operation feeling can be obtained, and the above-mentioned characteristics can be set with a high degree of freedom. it can.

The term "differential pressure before and after the bleed-off throttle means" means a differential pressure when it is assumed that the entire amount of the pump discharge passes, and the actual flow rate after the actuator starts moving. Irrespective of this, the differential pressure is calculated assuming that the entire pump discharge amount has passed through the bleed-off restrictor.

As the bleed-off restricting means, a directional flow control valve having a bleed-off flow path may be provided between the actuator and the pump, or separately from the directional flow control valve. A bleed-off control valve for changing the flow rate of the working fluid returning from the pump to the tank without passing through the actuator may be provided.

The bleed-off passage may be provided inside the directional flow control valve as in the former case. The directional flow control valve may be a pilot switching valve in which the opening area of the bleed-off passage changes according to the pilot pressure. Preferably, the control means is configured to change the pilot pressure of the directional flow control valve based on the discharge flow rate detected by the discharge flow rate detection means and the operation amount of the operation means. If a bleed-off control valve is provided separately from the directional flow control valve as in the latter, the bleed-off control can be performed independently of the operation of the directional flow control valve. Get higher. Further, the disadvantage that the bleed-off flow varies depending on the operation direction of the directional flow control valve can be avoided.

Although it is very difficult to directly detect the discharge flow rate, the means for detecting the discharge flow rate is determined based on the value corresponding to the operating speed of the drive source of the pump and the value corresponding to the pump displacement. With the provision of a calculator, it is possible to easily determine the pump discharge flow rate.

As described above, in the present invention, since the characteristics of the operation amount of the operation means and the differential pressure before and after the bleed-off throttle means can be freely set, for example, a plurality of types of control patterns having different characteristics are stored. It is also possible to control the operation of the bleed-off aperture means based on the control pattern selected among them. According to such a configuration, more appropriate actuator control can be performed by selecting an appropriate control pattern according to the driving situation and the like.

For example, a flow rate control pattern for increasing the differential pressure before and after the bleed-off restrictor in response to an increase in the operation amount of the operating means, and maintaining a sufficiently high differential pressure before and after the bleed-off restrictor. By preparing a pressure control pattern that increases the relief pressure (for example, the set pressure of a relief valve installed in parallel with the bleed-off throttle means) in accordance with the increase in the operation amount of the control means, speed-oriented operations and operation It is possible to perform any of the power-oriented operations. Further, the flow control pattern may include a composite control pattern for increasing both the differential pressure and the relief pressure before and after the bleed-off restrictor in response to an increase in the operation amount of the operating means.

As the actuator, for example, a turning motor in a working machine is suitable. In this case, as the pressure control patterns, a first pressure control pattern having a high increase rate of the relief pressure when the relief pressure rises and a second pressure control pattern having a low increase rate of the relief pressure when the relief pressure rises
And if the turning direction corresponding to the operating direction of the operating means is the same direction as the current turning direction, the first pressure control pattern is executed to correspond to the operating direction of the operating means. If the control means is configured to execute the second pressure control pattern when the turning direction to be performed is the opposite direction to the current turning direction, in the former case, the acceleration performance is increased and the In the latter case, it is possible to alleviate the deceleration shock while avoiding inconveniences such as load swing caused by the shock while allowing the vehicle to reach the speed.

This effect is obtained by the first flow control pattern having a high rate of increase in the differential pressure when the differential pressure rises before and after the bleed-off restrictor, and the flow control pattern before and after the bleed-off restrictor. The second flow rate control pattern in which the rate of increase of the differential pressure at the time of the rise of the differential pressure is low is stored. If the turning direction corresponding to the operating direction of the operating means is the same as the current turning direction, the second Even if the first flow control pattern is executed and the turning direction corresponding to the operation direction of the operating means is the opposite direction to the current turning direction, the second flow control pattern may be executed similarly. It is possible to get.

[0017]

FIG. 1 shows a first embodiment of the present invention.
This will be described with reference to FIG.

The hydraulic circuit shown in FIG. 1 includes a tank 10, a hydraulic pump 12, and a swing motor 14. The hydraulic pump 12 is connected to an engine 16 mounted on a working machine or the like as a drive source thereof, and
4 is a revolving body 18 provided in the working machine or the like.
It is connected to.

The actuator to be controlled in the present invention is not limited to the swing motor 14, but the present invention can be applied to speed control of a hydraulic cylinder, for example.

A directional flow control valve 20 is provided between the hydraulic pump 12 and the swing motor 14. In the illustrated example, as the directional flow control valve 20, a three-position pilot switching valve having a pilot portion 21 for turning left and a pilot portion 22 for turning right is used. The directional flow control valve 20 has two P ports (pump ports) and one T port (tank port) as inlet ports,
It has a T port, an A port, and a B port as outlet ports. The A port is connected to the MA port of the swing motor 14, and the B port is connected to the MB port of the motor 14.

The directional flow control valve 20 has a neutral position, a right turning position (a position mainly connecting the P port and the A port) and a left turning position (the P port and the B port are mainly connected). (A communicating position) also has a bleed-off flow path for returning some of the hydraulic oil to the tank 10 without passing through the rotation motor 14, and the opening area of each flow path including this bleed-off flow path and the spool stroke (Spool movement from neutral position)
Is set as shown in FIG. That is, in the neutral range in which the spool stroke is less than a certain value (the range in which neither the P-> A flow path nor the P-> B flow path is completely open), the opening area of the P-> T flow path is large and the spool stroke is equal to or more than a certain value. In the range (the range in which the P → A flow path or the P → B flow path is completely open), the opening area of the P → T flow path (bleed-off flow path) is small, and the opening area increases the spool stroke. Directional flow control valve 2
No spool and sleeve shapes are set.

A common pilot hydraulic pressure source 30 is connected to both pilot portions 21 and 22 of the directional flow control valve 20, and an electromagnetic proportional power source is connected between the pilot hydraulic pressure source 30 and each of the pilot portions 21 and 22. Pressure reducing valves 31, 32
Is provided. Therefore, these electromagnetic proportional pressure reducing valves 3
Pilot pressures input to the pilot sections 21 and 22 can be adjusted by solenoid excitation currents input to the solenoids 1 and 32, respectively.

An electromagnetic proportional relief valve 40 for varying the relief pressure is provided between the discharge side of the hydraulic pump 12 and the tank return oil passage. In addition, a flow path connecting the A port and the B port of the directional flow control valve 20 to the MA port and the MB port of the swing motor 14 is connected via a check valve 42 in order to prevent the flow path from becoming negative pressure. Connected to the tank.

An operating lever of the working machine on which the hydraulic circuit is mounted is provided with an electric lever (operating means) 44 operated by a driver or the like. The electric lever 44 is configured to output an electric signal according to the operation amount. In addition, this device is provided with sensors such as a turning direction detecting sensor 46 for detecting the turning direction of the turning motor 14 and an engine speed sensor 48 for detecting the number of revolutions of the engine 16. A signal and an electric signal output from the electric lever 44 are input to the controller 50.

The controller 50 is configured to output control signals to the solenoids of the electromagnetic proportional pressure reducing valves 31, 32 and the electromagnetic proportional relief valve 40 based on the input signals. Specifically, this controller 50
Includes a differential pressure calculating means 51, a discharge flow rate calculating means 52, a pilot pressure control means 53, and a relief pressure control means 54 as shown in FIG.

The differential pressure calculating means 51 provides two types of relationships between the lever input signal (signal corresponding to the lever operation amount) Vin and the target value (target differential pressure) Pb of the differential pressure before and after the bleed-off flow path. , That is, a flow control pattern and a pressure control pattern. Based on the selected pattern and the lever input signal Vin, the lever input signal V
The target differential pressure Pb corresponding to in is calculated.

The pattern for controlling the flow rate (FIG. 4A)
4D), as shown in FIG. 4D, regardless of the magnitude of the pump discharge flow rate Qp, the lever input signal Vin
Is a pattern set so as to increase or decrease the steady-state turning speed substantially in proportion to. On the other hand, the pressure control pattern (the pattern shown in FIG. 3B) is such that the target differential pressure Pb is increased to a pressure sufficiently higher than the maximum value of the relief pressure when the lever input signal Vin becomes equal to or higher than a certain value. This pattern is set to start up.
As shown in (d), the steady turning speed is determined by the lever input signal Vin.
Is constant regardless of

The selection of the pattern may be performed by a driver operating a provided switch, or may be automatically determined by the controller 50 according to the driving state. . For example, during steady operation with low acceleration and deceleration, select a flow control pattern,
The controller 50 may be configured to select a pressure control pattern during work in which acceleration and deceleration are large.

The discharge flow rate calculating means 52 calculates the discharge flow rate Qp of the pump 12 based on the engine speed Ne detected by the engine speed sensor 48 and the following equation.

[0030]

[Number 1] _{Qp = η v · q p ·} Ne However, eta _v: volume efficiency q _p: wherein the pump volume, the pump volume q _p, using the specific values of the pump 12 to be used. The method of obtaining the volumetric efficiency η _v
May be determined according to the accuracy required for the calculation of. For example, when high accuracy is required, the engine rotation speed Ne and the pump discharge pressure corresponding to the pump rotation speed are detected by a sensor from time to time, and these are taken into the controller 50 and based on the volumetric efficiency characteristics of the pump. What is necessary is just to calculate volumetric efficiency (eta) _v . If less high accuracy is not required, this as a parameter to detect only one of the engine speed Ne and the pump discharge pressure, may be calculated volumetric efficiency eta _v and the other as a fixed value Alternatively, the volume efficiency η _v itself may be treated as a fixed value.

The pilot pressure control means 53 calculates an opening area Ab of the bleed-off flow path corresponding to the set pressure Pb and the pump discharge flow rate Qp, determines a spool stroke at which the opening area Ab is obtained, and calculates the spool stroke. And outputs a control signal to the electromagnetic proportional pressure reducing valve 31 or 32 so as to obtain a pilot pressure corresponding to.

Here, the opening area Ab of the bleed-off flow path is obtained by the following equation.

[0033]

Ab = Qp / (C√Pb) where C is a coefficient according to the orifice equation. The opening area Ab calculated by this equation and the electric lever input Vin
4 (e) in the case of the flow control pattern.
In the case of the pressure control pattern as shown in FIG. That is, in this device, unlike the conventional device, the electric lever input Vin and the bleed-off flow passage opening area A
The relationship with b depends on the pump discharge flow rate Qp.

The relief pressure control means 54 calculates the target relief pressure Pr corresponding to the lever input signal Vin, and outputs a control signal to the electromagnetic proportional relief valve 40 so as to obtain the target relief pressure Pr. Specifically, when the flow control pattern is selected from the above control patterns, the relief pressure control means 54 sets the target relief pressure Pr to the highest value regardless of the electric lever input Vin as shown in FIG. Set to a value. On the other hand, when the pressure control pattern is selected, a pattern selected from the three patterns a, b, and c as shown in FIG. 3 is adopted, and based on this pattern and the lever input signal Vin. The target relief pressure Pr is calculated. Of the patterns a, b, and c shown here, the pattern a is the lever input signal Vin.
This is a pattern in which the lever input signal Vin is proportional to the target relief pressure Pr in a range where is equal to or more than a certain value. Pattern b
Is a pattern (first pressure control pattern) in which the increase rate of the target relief pressure Pr with respect to the increase of the lever input signal Vin in a region where the lever input signal Vin is relatively small (when the relief pressure rises), The pattern c is a pattern (second pressure control pattern) in which the rate of increase of the target relief pressure Pr with respect to the increase in the lever input signal Vin in a region where the lever input signal Vin is relatively small is lower than the first pressure control pattern. is there.

These patterns a to c may be performed by operating a switch provided by the driver, or may be automatically determined by the controller 50 according to the driving state. . For example, the turning direction detected by the turning direction detection sensor 46 and the electric lever 44
If the turning direction (command turning direction) corresponding to the operation direction is the same, the pattern b is automatically selected so that a speed close to the maximum speed can be obtained at a relatively early stage from the start of lever operation. If the turning direction detected by the turning direction detection sensor 46 is opposite to the turning direction (command turning direction) corresponding to the operation direction of the electric lever 44, the load may shake due to a shock due to rapid deceleration. Controller 5 automatically selects pattern c in order to prevent
0 may be configured.

The same can be said for a flow control pattern, for example. That is, in the flow control pattern, a pattern in which the rate of increase of the target differential pressure Pb with respect to the increase of the lever input signal Vin in a region where the lever input signal Vin is relatively small is relatively high (first flow control pattern).
And a pattern in which the rate of increase of the target differential pressure Pb with respect to an increase in the lever input signal Vin in a region where the lever input signal Vin is relatively small is lower than the first flow rate control pattern (second flow rate control pattern). And turning direction detection sensor 4
6 is the same as the turning direction (command turning direction) corresponding to the operation direction of the electric lever 44, the first flow control pattern is selected to start the lever operation. , A speed close to the maximum speed can be obtained at a relatively early stage, and when the turning direction (command turning direction) corresponding to the operation direction of the electric lever 44 is opposite, the second flow control pattern By selecting, it is possible to prevent load swing from occurring due to shock due to rapid deceleration.

Next, the operation of this device will be described.

When the electric lever 44 is operated, a lever input signal Vin corresponding to the operation direction and operation amount is input to the controller 50. Upon receiving this signal, the controller 50 outputs a control signal to the electromagnetic proportional pressure reducing valves 31 and 32 to control the pilot pressure of the directional flow control valve 20, and outputs a control signal to the electromagnetic proportional relief valve 40 to release the relief pressure. Control.

Here, when the flow control pattern is selected, the target differential pressure (the target value of the differential pressure across the bleed-off passage) Pb is calculated based on the relationship shown in FIG. Based on the calculated value, the opening area Ab of the bleed-off flow path shown in FIG. 4E is calculated, and the pilot pressure of the directional flow control valve 20 is controlled so that a spool stroke corresponding to the opening area Ab is obtained. Is done.

On the other hand, as shown in FIG. 4B, the target relief pressure Pr is set to the maximum value regardless of the lever input signal Vin. The operating pressure of the swing motor 14, that is, the actual acceleration force and deceleration force, is governed by the lower one of the differential pressure across the bleed-off flow path and the target relief pressure. The characteristic of the deceleration force is almost equal to the characteristic of the differential pressure Pb before and after the bleed-off flow path in most regions, as shown in FIG. Therefore, at the time of this flow rate control, the steady turning speed increases and decreases substantially in proportion to the lever input signal Vin at a rate corresponding to the pump discharge flow rate Qp, as shown in FIG.

When the pressure control pattern is selected, the target differential pressure Pb is calculated based on the relationship shown in FIG. 5A, and the bleed-off shown in FIG. The opening area Ab of the flow path is calculated, and the pilot pressure of the directional flow control valve 20 is controlled so that a spool stroke corresponding to the opening area Ab is obtained.

On the other hand, as shown in FIG. 4B, the target relief pressure Pr is set to a value substantially proportional to the lever input signal Vin. As described above, the actual acceleration force and deceleration force are governed by the lower one of the pressure difference between the front and rear of the bleed-off flow path and the target relief pressure. As shown in FIG. 3C, the characteristics of the relief pressure Pr are almost equal to those in most regions. That is, at the time of this pressure control, an acceleration force and a deceleration force substantially proportional to the lever input signal Vin are obtained.

As described above, in the apparatus according to this embodiment, the relationship between the lever input signal Vin and the pressure difference Pb before and after the bleed-off flow path is determined in advance, and the pump discharge flow rate Qp is maintained so as to maintain this relationship. , The relationship between the lever input signal Vin and the bleed-off flow path differential pressure Pb greatly changes depending on the pump discharge flow rate Qp as in the prior art. There is no such thing. Therefore, an effect that a stable operation feeling can always be obtained is obtained.

Further, in this embodiment, two types of patterns, ie, a flow control pattern and a pressure control pattern, are prepared as a relationship between the lever input signal Vin and the bleed-off flow path differential pressure Pb. Since the pattern can be selected as appropriate, it is possible to perform bleed-off control more suitable for the operation state.

When a plurality of types of patterns are prepared as described above, the number of types is not limited to two but may be set to three or more. In addition, a plurality of types of flow control patterns may be set, or a pattern other than the flow control pattern and the pressure control pattern may be set depending on the setting of the characteristics of the relief pressure. .
For example, as shown in FIG. 6A, the relationship between the lever input signal Vin and the target differential pressure Pb is set in the same manner as that shown in FIG. 4A, and as shown in FIG. If the relationship between the input signal Vin and the target relief pressure Pr is set in the same manner as the pressure control pattern shown in FIG. 5B, the finally obtained acceleration force and deceleration force are shown in FIG. As a result, it has characteristics in which flow control and pressure control are combined. If such a composite control pattern is included in the flow control pattern, more versatile control becomes possible.

Next, a second embodiment will be described with reference to FIGS.

As shown in FIG. 7A, in the directional flow control valve 20 in which the spool 25 is loaded in the sleeve 26, for example, a left turning notch 25 is formed on the surface of the spool 25.
a and the right turning notch 25b are machined, and the left turning notch 2 is formed.
5a secures a bleed-off passage when turning left,
In the case where the bleed-off passage at the time of turning right is secured by the notch 25b for turning right, both notches 25a, 25 for turning are used.
Since there is always an error in the machining of b, both notches 25a, 25
It is extremely difficult to make the shape of b exactly the same,
Actually, for example, as shown by a two-dot chain line in the figure, the left turning notch 25a may be larger than the right turning notch 25b. In such a case, even if the spool stroke is the same, a difference occurs in the opening area of the bleed-off flow passage between the left turn and the right turn. In the example of FIG. As the area increases, the differential pressure across the bleed-off flow path decreases.

On the other hand, as shown in FIG. 7B, the lever stroke in the turning range is So, the spool stroke in the turning range when the pump discharge flow Qp is relatively large is S ₁ , and the pump discharge flow Qp is relatively high. Assuming that the spool stroke in the turning range when small is S ₂ (<S ₁ ),
The enlargement ratio R of the lever stroke with respect to the spool stroke is R ₁ = So / S ₁ at a large discharge flow rate, and R ₂ = So / S ₂ (> R ₁ ) at a small discharge flow rate. Therefore, when viewed in terms of lever stroke, even the difference in the opening area of the bleed-off flow path is enlarged by the enlargement rate R, and especially at a small discharge flow rate, is enlarged at a large rate. Such inconvenience is not limited to the case where the bleed-off flow path is formed on the outer surface of the spool 25, but may also occur when the bleed-off flow path is formed on the inner surface of the sleeve 26.

Therefore, in this embodiment, instead of forming a bleed-off flow path inside the directional flow control valve 20 as in the above-described embodiment, or in addition to this, as shown in FIG. A separate bleed-off control valve 60 is provided outside the flow control valve 20 in parallel with the electromagnetic proportional relief valve 40, and the bleed-off control valve 60 performs bleed-off control independently of the directional flow control valve 20. Like that. By doing so, it is possible to prevent or suppress the inconvenience of causing a difference in the bleed-off flow rate between the left turn and the right turn.

Further, as shown in the figure, as the bleed-off control valve 60, a variable flow rate pilot switching valve whose flow path opening area is changed by the pilot pressure input to the pilot section 63 is used.
If a shuttle valve 63 is provided in the pilot circuit on the secondary side of 32 and the higher pressure is selected from among the pilot pressures input to the pilot sections 21 and 22 and is input to the pilot section 63, the directional flow control can be performed. The effect is obtained that the bleed-off control can be executed by using the pilot circuit for operating the valve 20 as it is.

Of course, the bleed-off control can be freely performed using means other than the pilot pressure of the directional flow control valve 20. For example, FIG. 9 shows a third embodiment.
As shown in the figure, an electromagnetic proportional pressure reducing valve 33 dedicated to bleed-off control is connected to a common pilot hydraulic pressure source 30 in parallel with the electromagnetic proportional pressure reducing valves 31 and 32.
The pilot pressure of the bleed-off control valve 60 may be controlled by inputting a control signal from the controller 50 to the controller. In this configuration, the bleed-off diaphragm can be independently controlled without being affected by the meter-in / meter-out diaphragm opening, and therefore, there is an advantage that the degree of freedom of the control is further increased.

FIG. 10 shows a fourth embodiment. In this embodiment, a remote control valve 64 whose secondary pressure changes in accordance with the operation amount is used as the operation means instead of the electric lever 44.
Is provided, and the secondary side pressure of the pressure sensor 66,
The detection signal, that is, the signal corresponding to the operation amount of the remote control valve 64 is input to the controller 50.

On the other hand, an electromagnetic switching valve 7 is provided between each of the pilot sections 21 and 22 and the electromagnetic proportional pressure reducing valves 31 and 32.
1, 72 are provided, and these electromagnetic switching valves 71, 7 are provided.
2, when a control signal is input from the controller 50 to the electromagnetic proportional pressure reducing valves 31 and 32 and the pilot units 21 and
2 is secured, and the electromagnetic switching valve 7
When the control signal is not input to the controllers 1 and 72 from the controller 50, a pilot oil passage for inputting the secondary pressure of the remote control valve 64 as it is to the pilot units 21 and 22 as the pilot pressure is secured.

According to such an apparatus, the controller 5
When 0 operates normally and a control signal is input to the electromagnetic switching valves 71 and 72, the same control as in the first embodiment can be executed, but, for example, the controller 50 fails and does not operate. In an emergency, the electromagnetic switching valves 71 and 72
Input of the control signal to the remote control valve 64 automatically stops.
Are connected to the pilot units 21 and 22, so that the minimum control can be performed only by the hydraulic circuit without passing through the controller 50. Therefore, it is possible to avoid the inconvenience that the machine does not operate at all when the controller 50 is abnormal, and it is possible to quickly perform emergency safety processing such as evacuation to a safe place for the time being.

In each of the above embodiments, the directional flow control valve 20 is connected to the two ports MA, MA of the swing motor 14 at the neutral position.
Although a so-called neutral-free type, which communicates the MB with the pump port and the tank port, is used in the present invention, for example, as shown in FIG. It can also be effectively applied to a neutral block type that blocks (although the overload relief valve is omitted in the figure for convenience).

To explain this concretely, first, in the conventional device, the electric lever input V
The opening area Ab (FIG. 12) of the bleed-off flow path corresponding to
(A) (solid line L1) and the opening area of the meter-in and meter-out flow paths (solid line L2 in FIG. 3 (a)) were fixed, so that even with the same electric lever input Vin as shown in FIG. However, the pressure difference before and after the pump discharge flow rate (curve C _H ) is higher than the pressure difference before and after the pump discharge flow rate (curve C _L ), and especially in the latter case,
The bleed-off differential pressure at the time when the meter-in or meter-out channel starts to be opened becomes a pressure higher than necessary than the starting resistance of the actuator, and there is a disadvantage that energy is consumed by that much. Also, if the pressure difference before and after the pump discharge flow rate is set low is low to suppress this energy consumption, the pressure difference before and after the pump discharge flow rate is low becomes insufficient, and the lever is operated to the predetermined operation position. However, the actuator may not be able to start up.

On the other hand, in the present invention, the opening area Ab of the bleed-off flow path is made larger when the pump discharge flow rate is high than when the pump discharge flow rate is low (two-dot chain line L1 'in FIG. 12A). Since the relation between the electric lever input Vin and the bleed-out differential pressure Pb is set to a predetermined relation irrespective of the pump discharge flow rate (curve C in FIG. 9C), a good start of the actuator is achieved. It is possible to prevent unnecessary consumption of energy while securing.

[0058]

As described above, the present invention detects the discharge flow rate of the pump and, based on the discharge flow rate detected by the discharge flow rate detection means and the operation amount of the operation means, determines the operation amount of the operation means. Since the bleed-off throttle means is operated such that the relationship with the differential pressure before and after the bleed-off throttle means becomes a predetermined relationship,
It is possible to prevent the disadvantage that the characteristic of the manipulated variable-bleed-off pressure fluctuates greatly with the change of the pump discharge flow rate as in the related art, to obtain a stable operation feeling, and to set the above characteristic with a high degree of freedom. There is an effect that can be done.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram showing a first embodiment of the present invention.

FIG. 2 is a graph showing a relationship between a spool stroke of the directional flow control valve shown in FIG. 1 and an opening area of each flow path.

FIG. 3 is a block diagram illustrating a functional configuration of a controller illustrated in FIG. 1;

FIGS. 4A to 4E are graphs showing characteristics of respective parameters when a flow control pattern is selected in the controller.

FIGS. 5A to 5E are graphs showing characteristics of each parameter when a pressure control pattern is selected in the controller.

FIGS. 6A to 6C are graphs showing characteristics of respective parameters when a composite control pattern is selected in the controller.

7A is a front view showing an example in which a notch for a bleed-off flow path is provided on a spool of a directional flow control valve, and FIG.
Is a graph showing a relationship between a lever stroke and a spool stroke of the directional flow control valve.

FIG. 8 is a hydraulic circuit diagram showing a second embodiment of the present invention.

FIG. 9 is a hydraulic circuit diagram showing a third embodiment of the present invention.

FIG. 10 is a hydraulic circuit diagram showing a fourth embodiment of the present invention.

FIG. 11 is a hydraulic circuit diagram showing a fifth embodiment of the present invention.

12A is a graph showing a relationship between an electric lever input set in the fifth embodiment and a bleed-off passage opening area, and FIG. 12B is a graph showing an electric lever input obtained in a conventional apparatus and an actual electric lever input. 7C is a graph showing the relationship between the pressure difference before and after the bleed-off, and FIG. 7C is a graph showing the relationship between the electric lever input and the pressure difference before and after the bleed-off set in the fifth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Tank 12 Hydraulic pump 14 Swing motor 16 Engine (pump drive source) 18 Revolving unit 20 Directional flow control valve 21, 22 Pilot unit 30 Pilot hydraulic source 31, 32 Electromagnetic proportional pressure reducing valve 40 Electromagnetic proportional relief valve 44 Electric lever (operating means) 48) engine speed sensor 50 controller (control means) 60 bleed-off control valve 62 shuttle valve (pilot pressure input means) 63 pilot section 64 remote control valve (operating means)

Continued on the front page (72) Inventor Shigeki Kitagawa 2-3-1, Shinhama, Arai-machi, Takasago City, Hyogo Prefecture Inside Kobe Steel, Ltd. Takasago Works (72) Inventor Seiichi Kinshino 2-3-1, Shinama, Arai-machi, Takasago City, Hyogo Prefecture No. Kobe Steel, Ltd. Takasago Works (72) Inventor Soji Kimura 2-3-1, Shinhama, Araimachi, Takasago City, Hyogo Prefecture Kobe Steel Works, Takasago Works

Claims (10)

[Claims] 1. An actuator, a pump for supplying a working fluid to the actuator, and a bleed-off restrictor for changing an opening area of a bleed-off flow path for returning the working fluid from the pump to the tank without passing through the actuator. Means, operating means operated to operate the actuator, discharge flow rate detecting means for detecting a discharge flow rate of the pump, discharge flow rate detected by the discharge flow rate detecting means, and an operation amount of the operating means. Based on
An actuator comprising: control means for operating the bleed-off restrictor so that the relation between the operation amount of the operating means and the differential pressure before and after the bleed-off restrictor has a predetermined relationship. Bleed-off control device. 2. The bleed-off control device according to claim 1, further comprising a directional flow control valve having a bleed-off flow passage between the actuator and the pump. apparatus. 3. The bleed-off control device according to claim 2, wherein said directional flow control valve is a pilot switching valve whose opening area of a bleed-off flow path changes in accordance with pilot pressure, and said discharge flow detecting means detects said directional flow control valve. A bleed-off control device for an actuator, wherein the control means is configured to change a pilot pressure of the directional flow control valve based on a detected discharge flow rate and an operation amount of the operation means. 4. The bleed-off control device according to claim 1, further comprising a directional flow control valve provided between the actuator and the pump, and separately from the directional flow control valve via the pump and the actuator. A bleed-off control device for an actuator, comprising a bleed-off control valve for changing a flow rate of a working fluid returned to a tank without performing the bleed-off control. 5. The bleed-off control device for an actuator according to claim 1, wherein said discharge flow rate detecting means has a value corresponding to an operating speed of a drive source of said pump and a value corresponding to a pump displacement. A bleed-off control device for an actuator, which calculates a discharge flow rate of a pump based on the following. 6. The bleed-off control device for an actuator according to claim 1, wherein the control means has a different relationship between an operation amount of an operation means and a differential pressure before and after the bleed-off throttle means. A bleed-off control device for an actuator, wherein a plurality of types of control patterns are stored, and the operation of the bleed-off throttle means is controlled based on the selected control pattern. 7. A bleed-off control device for an actuator according to claim 6, wherein said control means increases a differential pressure across said bleed-off throttle means in response to an increase in an operation amount of said operation means. And a pressure control pattern for increasing the relief pressure in response to an increase in the operation amount of the control means while maintaining the differential pressure before and after the bleed-off throttle means sufficiently high. Control device. 8. The bleed-off control device for an actuator according to claim 1, wherein the actuator is a turning motor in a work machine. 9. The bleed-off control device for an actuator according to claim 7, wherein the actuator is a swing motor of a work machine, and both ports of the swing motor and the pump port are in a state where the operating means is operated to a neutral position. And the control means includes a first pressure control pattern having a high increase rate of the relief pressure when the relief pressure rises, and a pressure control pattern when the relief pressure rises as the pressure control pattern. The second pressure control pattern in which the increase rate of the relief pressure is low is stored, and when the turning direction corresponding to the operation direction of the operation means is the same as the current turning direction, the first pressure control pattern is changed. The second pressure control pattern is executed when the turning direction corresponding to the operating direction of the operating means is opposite to the current turning direction. Bleed-off control device for an actuator. 10. The bleed-off control device for an actuator according to claim 7, wherein the actuator is a turning motor of a work machine, and both ports of the turning motor and the pump port are in a state where the operating means is operated to a neutral position. And the control means is configured to communicate with the tank port as the flow control pattern, wherein the rate of increase of the differential pressure at the time of rising of the differential pressure before and after the bleed-off throttle means is high. A pattern and a second flow rate control pattern having a low rate of increase in the differential pressure at the time of rising of the differential pressure before and after the bleed-off throttle means are stored, and the turning direction corresponding to the operating direction of the operating means is the current turning direction. If the direction is the same as the direction, the first flow control pattern is executed, and the turning direction corresponding to the operating direction of the operating means is opposite to the current turning direction. Bleed-off control device for an actuator, wherein the second flow control pattern is executed when the direction is the direction.