JPH10219755A - Oil-pressure circuit of construction machinery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the simplification or cost reduction of detection/decision control construction for travelling boost control in an L/S system and A/L control by reviewing an oil-pressure circuit. SOLUTION: In an L/S system with A/L, when controlling valves except for travelling are all in a neutral state, a center bypass controlling oil-pressure circuit passing through open and close valves 9v and 34v formed in spools of them, an auxiliary oil-pressure gauge 49 for detecting oil passage pressure thereof and a main pressure gauge 23 for detecting pressure variations in a main oil-pressure circuit S acting on a travelling controlling valve 34 are provided. A working state detection device G is constituted of decision made on the existence of pressure in the controlling oil-pressure circuit, and an operation detection device C is constituted of decision made on the existence of pressure in the main oil-pressure circuit S and decision made on the existence of pressure in the controlling oil-pressure circuit H.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit structure of a construction machine such as a backhoe or the like, and more particularly to load control for pump discharge of hydraulic power corresponding to a load, so-called load sensing (hereinafter referred to as L / L). S).
The present invention relates to an automatic idle (A / I) system that increases the engine speed according to an accelerator lever when a hydraulic actuator such as a boom cylinder or a traveling hydraulic motor operates, and drops the engine near idle when stopped. More specifically, the device is made compact by partially using the detecting means for the running pressure increase control and the detecting means for the A / I control in the L / S system.

[0002]

2. Description of the Related Art An apparatus having both the L / S and A / I systems is proposed in Japanese Patent Application No. 7-259662 filed earlier. This is because when the left and right traveling levers are operated at different positions from each other, the relief pressure of the first relief valve (reference numeral 40 in FIG.
Relieving pressure) is increased, and even during high-load turning on muddy roads, the L / S system is used so that the relief cut control (described later) does not cause a significant drop in speed, and turning is performed. It is equipped with running boost control that improves performance.

In addition, a means for detecting the pressure of the differential pressure oil passage on the low pressure side in the L / S system (reference numeral 23 in the above-mentioned prior application) is provided, and it is determined whether or not the hydraulic actuator is moving based on the pressure fluctuation. As a result, A / I control for automatically adjusting the engine speed to a high or low level is performed.

[0004]

In the above prior art, L
The system has both the detection determination means for running pressure increase control that can improve turning performance in the / S system and the detection determination means for A / I control. As shown in the principle diagram, it was conceived that both means were integrated. That is, three-position switching type on-off valves 30v, 34v1, 32v1, 10v are formed on the spools of the control valves 30.34, 32, 10 of the hydraulic actuator, and each on-off valve is connected to a center bypass type so that A / A
A first control hydraulic circuit HA for the I system is formed, and another pair of traveling control valves 34 and 32 is additionally formed with another on-off valve 34v2, 32v2, and the two additional on-off valves 34v2, 32v2. And a second control hydraulic circuit HS for traveling pressure increase control.

That is, when one of the two traveling control valves 34 and 32 is switched to a position other than the neutral position, the second control hydraulic circuit HS is closed, and control is performed based on the increase in circuit pressure by the second hydraulic pressure gauge 23S. The device 26 switches the solenoid valve Ve and applies a preload by the control pump 60 so that the first relief valve 40
Increase the relief pressure. If both of the traveling control valves 34 and 32 are in the neutral position, the second control hydraulic circuit HS is opened, and the control device 26 switches the solenoid valve Ve according to the circuit pressure drop information from the second hydraulic pressure gauge 23S. Travel pressure increase control is performed to reduce the relief pressure of one relief valve 40 to a low pressure at which no preload is applied by the control pump 60.

Further, when all the control valves for working and traveling are operated in a neutral manner, the first control hydraulic circuit HA is opened, and the engine speed is reduced to the idling side by the information on the decrease of the circuit pressure by the first oil pressure gauge 23A. If any one of the control valves is operated to a position other than neutral, the first control hydraulic circuit HA is closed, and the A / I raises the engine speed according to the accelerator lever according to the increase in circuit pressure by the first hydraulic pressure gauge 23A.
Control is performed.

However, in the above-mentioned comparative example technology, two types of control circuits HS and HA for running boost control and A / I control are required, which complicates the structure. In particular, the running control valve is considerably increased in size. At the same time, it seems that there is room for further improvement, such as the necessity of an expensive solenoid valve Ve for increasing the pressure of the first relief valve 40. Accordingly, an object of the present invention is to simplify the structure and reduce the cost of the detection / judgment means for running boost control and A / I control in the L / S system by reviewing the hydraulic circuit.

[0008]

[Means for Solving the Problems]

[Configuration] A first aspect of the present invention provides a control valve including a plurality of hydraulic actuators, a variable displacement hydraulic pump, a throttle valve for a hydraulic oil supply path to the hydraulic actuator, and a discharge amount per unit time of the hydraulic pump. A flow rate adjusting mechanism for variably setting the pressure difference between a first oil passage communicating with a lower portion of the pressure oil supply to the throttle valve and a second oil passage communicating with a supply port of the control valve at a predetermined value. Control means for operating the flow rate adjusting mechanism, and the first oil passage and the second oil passage
An unload valve that acts on the second oil passage by a differential pressure greater than a predetermined value with respect to the oil passage, and a first unload valve that acts on the first oil passage.
An operation amount detection unit that includes a relief valve and a second relief valve that acts on a second oil passage, detects an operation amount of an accelerator operation tool, an operation actuator that drives and operates an engine speed adjustment unit, and a hydraulic actuator. Operation detection means for detecting whether or not the engine is operating, when the hydraulic actuator is stopped, the engine speed is changed to the idling side, and when the hydraulic actuator is operated, the engine speed is set to a value set by the accelerator operation tool. An accelerator control means is provided for linking the operation amount detection means and the operation actuator so as to perform the return operation, and the sum of the first relief pressure and the predetermined differential pressure is determined by the relief pressure of the second relief valve (hereinafter referred to as the second relief pressure).
Relief pressure adjusting means capable of variably setting the first relief pressure so that a low pressure state lower than the relief pressure) and a high pressure state higher than the relief pressure can be selected and set, and a work state controlling the adjusting operation of the relief pressure adjusting means. Detecting means, and forming, on each spool of a working control valve of a hydraulic actuator other than the traveling hydraulic actuator among the hydraulic actuators, an opening / closing valve having a number of switching positions in response to the working control valve, When all of the control valves are in the neutral position, a control hydraulic circuit of a center bypass type in which the pressure oil passes all the way through the spool is provided, a sub-hydraulic sensor for detecting pressure fluctuation of the control hydraulic circuit, and a hydraulic actuator for traveling. A main oil pressure sensor for detecting pressure fluctuations of the main oil pressure circuit acting on the control valve is provided. The operation detection means is configured to determine whether the pressure is raised in the main hydraulic circuit and whether the pressure is raised for the control hydraulic circuit. It is characterized by having been done.

According to a second aspect of the present invention, in the first aspect, the sub-hydraulic sensor is constituted by an oil pressure gauge connected to a lower portion of the lowermost opening / closing valve in a pressure supply direction in an oil path of the control hydraulic circuit. An orifice is provided on the lower side of the connection point of the oil pressure gauge, and a pressure-increasing oil path is provided for connecting a connection oil path to the oil pressure gauge and an oil chamber formed on the relief spring side of the first relief valve to constitute relief pressure adjusting means. Then, when pressure rises in the oil pressure gauge, the first relief pressure increases and a high pressure state appears,
Further, the work state detecting means is characterized in that the first relief pressure is reduced when a pressure does not rise in the hydraulic pressure gauge, and a low pressure state appears.

According to a third aspect of the present invention, in the first aspect, the sub-hydraulic sensor is constituted by an oil pressure gauge connected to an upper portion of the uppermost opening / closing valve in a pressure supply direction in an oil passage of the control hydraulic circuit. A relief pressure adjusting means is provided by providing a pressure-reducing oil passage that communicates the connection oil passage with the first relief pressure working oil chamber. When the oil pressure gauge rises, the first relief pressure is reduced and the low pressure state is established. The work state detecting means is configured so that the first relief pressure is increased when a pressure is not generated in the oil pressure gauge and a high pressure state appears.

[0011] In a fourth aspect based on the first aspect, the first relief valve is configured by connecting a high-pressure relief valve having a high relief pressure and a low-pressure relief valve having a low relief pressure in parallel. A selection valve capable of switching between a first state in which the circuit is connected and a second state in which the low-pressure relief valve is circuit-connected is provided. When the first state is selected, the sum of the first relief pressure and the predetermined differential pressure becomes the second state. A high pressure state higher than the relief pressure appears, and when the second state is selected, the relief is performed so that the sum of the first relief pressure and the predetermined differential pressure is lower than the second relief pressure. The working state detecting means is constituted by forming a pressure adjusting means and linking the selection valves so as to be switched depending on whether or not the pressure of the control hydraulic circuit rises.

[Operation] According to the configuration of claim 1, the following operation is obtained, which will be described in detail in the embodiment. (1) There is only one type of oil passage through the on-off valve, and only one on-off valve per control valve is required for each spool.
The size of the control valve can be reduced as compared with the conventional case where two on-off valves are provided in the traveling control valve.

(2) Since the control hydraulic circuit does not take the traveling control valve into consideration, as shown in FIG. 6, when the vehicle is in neutral and traveling, that is, when the working device does not move, the first relief pressure becomes high. The first relief pressure is controlled to a non-running boosted state in which the first relief pressure is low at the time of work and at the time of work / running, that is, when the work apparatus moves. In the above-described comparative example technology, the first relief pressure is controlled to a high pressure during work / running, and there is a possibility that the high-pressure oil exceeding a prescribed level acts on the hydraulic actuator for the working device, thereby lowering the durability. The operation of the working device such as the compensator itself being closed and the boom lifting / lowering speed being significantly reduced may occur, but the inconvenience does not occur in the present invention.

(3) For example, the means for judging the operation and stop of the hydraulic actuator based only on the pressure fluctuation of the main hydraulic circuit with a large flow rate passing through the control valve may use hydraulic pressure by its own weight, such as boom lowering or arm scraping. Negative pressure may act on the actuator, and even if the hydraulic actuator is driven in that direction, no pressure is generated in the circuit, and even though the working hydraulic actuator is moving, it is "not moving" A /
There is a risk of malfunction determined on the I control.

On the other hand, in the case of the present invention, the judgment is made in consideration of the pressure fluctuation of the control hydraulic circuit in addition to the pressure fluctuation of the main hydraulic circuit. It is possible to reliably detect whether the working hydraulic actuator is operating. The traveling control valve is omitted from the control hydraulic circuit because the counter balance valve always generates pressure even when a negative pressure is applied to the hydraulic motor, for example, when the hydraulic motor is traveling uphill. Can be dealt with by observing the pressure fluctuation of the main hydraulic circuit. That is, it is possible to determine whether the hydraulic actuator is operating or not for all actuators.

The structure of claim 2 is a means for increasing the travel pressure by using the pressure detected by the control hydraulic circuit in a direction to increase the first relief pressure, which will be described in detail in the embodiment. That is, when all of the working on-off valves are in a neutral state, a pressure builds up in the oil pressure gauge, so that the pressure is supplied to an oil chamber formed on the spring side of the first relief valve to increase the first relief pressure. When any of the working on-off valves is at a position other than neutral, no pressure is applied to the oil pressure gauge, so that no pressure acts on the spring-side oil chamber of the first relief valve, and a low relief pressure due to only the relief spring is generated. Acts to appear. By this mechanical means, it is possible to perform traveling pressure increase control without using an expensive solenoid valve.

According to a third aspect of the present invention, which will be described in detail in the embodiment, the traveling pressure is increased by using the pressure detected by the control hydraulic circuit in the direction of decreasing the first relief pressure. That is, when all of the working on-off valves are in neutral, no pressure is applied to the oil pressure gauge, so that no pressure acts on the relief pressure working side oil chamber of the first relief valve. When the oil pressure gauge is at the position, the pressure acts on the oil pressure gauge, so that the pressure acts on the relief-pressure-operating-side oil chamber, and the first relief pressure can be reduced.

Therefore, the sum of the first relief pressure and the predetermined differential pressure only by the relief spring is higher than the second relief pressure, and the sum of the first relief pressure and the predetermined differential pressure reduced by the pressure rise. However, by setting the pressure to be lower than the second relief pressure, it is possible to perform the running pressure increase control without using an expensive solenoid valve by a mechanical means for directly applying the pressure to the first relief valve.

According to the second and third aspects of the present invention, since a general relief valve is a custom-built part for newly installing an oil chamber or an oil passage,
The cost of a single valve with a dedicated mold is considerably high. On the other hand, in the configuration of claim 4, three ordinary valves, ie, two relief valves and one selection valve, can be configured, and the number of valves increases, but the total cost can be reduced. Becomes possible.

In the second and third aspects of the present invention, the balance between the relief spring of the first relief valve and the pressure in the control hydraulic circuit must be adjusted with relatively high precision. By providing separate valves for each of the high pressure relief, low pressure relief, and high / low selection functions, high accuracy is not required for each valve, and travel pressure control can be performed reliably.

[Effect] In the hydraulic circuit for a construction machine according to any one of claims 1 to 4, the control valve can be made compact by the operation of (1), and the working device can be driven favorably by the operation of (2). It is possible to prevent a decrease in speed during cornering while keeping the vehicle in the state.
Something that can execute the control was obtained.

In the hydraulic circuit for a construction machine according to the second aspect, there is an advantage that the relief pressure adjusting means can be constituted at a relatively low cost by mechanical means for applying the pressure of the control hydraulic circuit to a state in which the first relief pressure is increased. is there.

In the hydraulic circuit for a construction machine according to the third aspect, there is an advantage that the relief pressure adjusting means can be constituted relatively inexpensively by the mechanical means for applying the pressure of the control hydraulic circuit to the state where the first relief pressure is reduced. is there.

In the hydraulic circuit for a construction machine according to the fourth aspect, the relief pressure adjusting means is provided by mechanical means by devising a function of the first relief valve utilizing the pressure of the control hydraulic circuit by a plurality of simple valves. In this case, an economical advantage due to low cost and an advantage with high reliability that the traveling boost control can be reliably performed can be obtained.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION

-First Embodiment-Hereinafter, a first embodiment of the present invention will be described with reference to the drawings for a case of a backhoe as an example of a construction machine.

FIG. 1 shows a small backhoe, 1 is an excavating work device, 2 is a turntable, 3 is a traveling machine stand, 4 is a crawler traveling device, 28 is a dozer, and the excavating work device 1 is a boom 5 , Arm 6, bucket 7 and the like. The boom 5 includes a base end boom section 5x and an intermediate boom section 5x.
y and a distal end boom section 5z, and the offset cylinder 36 is configured to be capable of moving the distal end boom section 5z in parallel offset with respect to the proximal end boom section 5x.

FIGS. 2 and 3 schematically show the entire hydraulic circuit. The control valve 29 for the dozer cylinder, the bucket cylinder 7
c control valve 30, left traveling motor 31 control valve 32, boom cylinder 5c control valve 9, arm cylinder 6c control valve 10, right traveling motor 33 control valve 34, swing motor control valve 35, offset cylinder 36 / L system equipped with a variable displacement twin hydraulic pump 8 that discharges at a pressure slightly higher than the load pressure is adopted for each of the control valves 37 and 38 for service. ing. An A / I system that is preferable in terms of noise and energy saving is also adopted, and will be described below.

FIG. 4 shows a principle circuit diagram of a main part of a part related to the boom cylinder 5c and the right traveling hydraulic motor 33 shown in FIG. The hydraulic pump 13 is a flow rate adjusting mechanism for variably setting the discharge oil amount per unit time of the hydraulic pump 8. The flow control mechanism 13 includes a horsepower control cylinder 13 </ b> A operated by the discharge pressure of the main pump 8, and a flow control cylinder 13 </ b> B driven by the control pump 18. Also, a pressure compensation type flow control valve 14 for the control cylinder 13 is provided.

Numeral 11 denotes a boom, and 12 denotes a compensator (pressure compensating valve) for a right traveling motor. Throttle valves 9 s and 34 s are provided in a supply side oil passage in the boom control valve 9 and the right traveling motor control valve 34. Equipped. Both compensators 11 and 12 are located on the lower side of the pressure oil supply with respect to the respective supply-side throttle valves 9 s and 34 s, and each actuator 5
c, 33 are arranged on the upstream side of the pressure oil supply. A low-pressure side oil passage 11t which is on the lower side of the supply of pressure oil to the compensators 11 and 12 and communicates the upper side of the supply of pressure oil to the actuators 5c and 33 with the spring-side oil chambers of the compensators 11 and 12. , 12t are provided.

The throttle valves 9 s, 9 b, 9 b, 9 b, 9 b, 9 b, 9 b, 9 b, and 11 b on the supply side of the hydraulic oil to the compensators 11, 12 are good.
The high-pressure side oil passage 1 that communicates the lower side of the pressure oil supply for 34 s with the non-spring side oil chamber of each of the compensators 11 and 12.
1k and 12k are provided. And each compensator 1
1 and 12 are configured as a constant pressure reducing valve provided with a compression spring 17 for biasing the flow path to the cutoff side, thereby forming an after-orifice type L / S circuit.

A first oil passage 14t on the low-pressure side is provided for communicating the spring-side oil chamber 14x of the flow rate control valve 14 with the lower part of the supply of pressure oil to the supply-side throttle valves 9s and 34s. A first oil passage 14t communicates with the passages 11t and 12t. A high-pressure side second oil passage 15 communicated with the supply ports 9p and 34p of the control valves 9 and 34, and an oil chamber on the opposite side of the spring-side oil chamber 14x of the flow control valve 14 are connected to a dedicated connection oil passage 16 Are in communication. Further, the pressure of the flow control valve 14 with respect to the adjusting cylinder 13 is supplied by a dedicated auxiliary pump 18 driven by the engine. That is, the first oil passage 14t and the supply ports 9p, 34p of the control valves 9, 34 are provided.
The load control means A is provided with a flow control valve 14 for operating the adjusting cylinder 13 so as to maintain a differential pressure between the second oil passage 15 and the second oil passage 15 at a predetermined value.

An unload valve which acts on the second oil passage 15 by a differential pressure (20 kg) larger than a predetermined pressure difference (14 kg) between the first oil passage 14t and the second oil passage 15 due to L / S. 39, a first relief valve 40 acting on the first oil passage 14t, and a second relief valve 41 acting on the second oil passage 15.

As shown in FIG. 5, the bucket control valve 3
0, the boom control valve 9, the arm control valve 10, the turning control valve 35, and the offset control valve 37 are configured as pilot operated valves that can be switched by pilot pressure.
A cross control lever 50 for a bucket, a cross control lever 51 for an arm / turn, and an offset pedal 52 are provided. Then, each of the pilot valves 50a to 50d, 51
Pilot pumps for a to 51d, 52a, and 52b are shared by the auxiliary pump 18.

In this backhoe, the first relief pressure is increased during turning during traveling and traveling, so that the turning speed does not become too slow even under a high load, that is, relief cut control (described later) does not occur. And will be described below.

As shown in FIG. 5, the traveling control valves 32, 3
7 working control valves 30, 9, 10, 38, excluding 4
Each of the spools 37, 29, and 35 has a three-position switching type on-off valve 30v, 9v, 10v, 38v, 37v, 29
v, 35v (hereinafter abbreviated as 30v to 35v), and a control hydraulic circuit H of a center bypass type is provided, in which all hydraulic oil passes through the spool when all of the working control valves are in the neutral position.

Each open / close valve 30 v to 35 v of the working control valve
Is configured such that the flow path is closed at a position other than the neutral position, and a portion between the control valve 48 and the bucket opening / closing valve 30v on the uppermost side in the pressure supply direction in the control oil passage 47,
A sub-hydraulic meter (an example of a sub-hydraulic sensor) 49 for detecting a pressure fluctuation of the control hydraulic circuit H is connected.

A working state detecting means G for detecting whether or not a working hydraulic actuator Vs other than the traveling hydraulic motors 31, 33 is operating, and a relief pressure adjusting means E capable of variably setting a first relief pressure. When the running state appears, the sum of the first relief pressure and the predetermined differential pressure becomes
The work state detecting means G and the relief pressure adjusting means E are linked so as to exceed the relief pressure of the second relief valve 41 (hereinafter, abbreviated as the second relief pressure).

As shown in FIG. 4, the relief pressure adjusting means E
Are connected to the auxiliary oil pressure gauge 49 and the first relief valve 4
Pressure-reducing oil passage 40a communicating with the relief-pressure-operating-side oil chamber 0
Is provided. The work state detecting means G is constituted by the sub-hydraulic gauge 49, and functions as outputting detection information as to whether or not pressure is applied to the uppermost part of the control oil passage 47 (corresponding to the third aspect).

As described above, the working on-off valves 30v to 35v
If at least one of them is in the neutral position, a pressure will be applied to the sub-hydraulic gauge 49, so that the relief spring 4
The first relief pressure becomes low corresponding to the fact that 0A becomes weak, and the low pressure state described above appears. If all the on-off valves are in the neutral position and no pressure rises on the sub-hydraulic gauge 49, this corresponds to the fact that the urging force of the relief spring 40A acts as it is and the first relief pressure becomes high, which corresponds to the high pressure state described above. Will appear.

That is, as shown in FIG. 6, when "neutral" when all the control valves are neutral, and when "running" when only one or both of the traveling control valves 32 and 34 are at positions other than neutral. , The control valve Vs for all operations becomes neutral and the control hydraulic circuit H
, And the first relief pressure becomes "high" in any case. Further, when the traveling control valves 32 and 34 are both neutral and one of the operation control valves Vs is at a position other than the neutral position, and when at least one of the traveling control valves 32 and 34 is not the neutral position. In the "working / running" state in which any of the work control valves Vs is in a position other than the neutral position, the pressure rises in the control hydraulic circuit H, and in any case, the first relief pressure is "low". become.

Here, the necessity of the running boost control in the L / S system will be described with reference to FIGS.

First, as a specific example, the operating pressure (predetermined differential pressure or L / S differential pressure) of the flow control valve 14 for producing a differential pressure is 14 kg, the unload pressure is 20 kg, the first relief pressure is 230 kg, It is assumed that the second relief pressure is set to 260 kg. Then, for example, when the traveling load of the right traveling hydraulic motor 33 increases and exceeds 230 kg, the first relief valve 40, which is a system relief valve, opens, but the low pressure side originally including the first oil passage 14t is opened. The oil passage (the oil passage drawn by the broken line in FIG. 4) is for detecting a differential pressure, and is a narrow flow passage as compared with the oil passage for driving the actuator, and it is difficult to sufficiently discharge the oil passage. Therefore, the discharge pressure still increases even though the first relief valve 40 is opened.

Then, the L / S differential pressure rises to 20 kg
(That is, the pressure of the second oil passage 15 becomes 250 kg)
This time, the unload valve 39 is opened and sufficient discharge is performed. However, since the second relief valve 41 having the opening pressure of 260 kg is closed, the L / S differential pressure is set to 14 times the set pressure.
Thus, the discharge amount of the hydraulic pump 8 is controlled to the minimum. Therefore, the driving speed of the traveling hydraulic motor 33 also becomes the minimum speed,
Powerful but slow running speed when turning with high load. This is the relief cut control described in the section "Prior Art".

In order to solve this problem, the sum of the first relief pressure and the predetermined differential pressure should be higher than the second relief pressure. That is, the opening pressure of the first relief valve 40 is set to 250 kg. Then, the running load at the time of turning increases, the first relief valve 40 opens, and the pressure still rises as described above, but the discharge pressure of the hydraulic pump 8 reaches 264 kg for generating the set differential pressure of 14 kg. Previous 26
When the pressure becomes 0 kg, the second relief valve 41 is opened, and the L / S differential pressure is maintained at 10 kg.

Therefore, the control is performed so as to increase the discharge amount of the hydraulic pump 8 in order to produce the set differential pressure of 14 kg, but the L / S differential pressure does not become larger than 10 kg. As a result, the pump discharge amount is controlled to the maximum, so that the driving speed of the hydraulic motor 33 is increased, and the turning speed is increased. That is, in a normal state in which the relief cut control operates, the unload valve 39 is opened before the second relief valve 41 is opened. When the unload valve 39 is opened first, the L / S differential pressure becomes a predetermined value. It becomes larger than the differential pressure, and the pump discharge amount is controlled to the minimum.

On the other hand, if the second relief valve 41 is opened before the unload valve 39, the L / S
The differential pressure becomes smaller than the predetermined differential pressure, and the pump discharge amount is controlled to the maximum. This series of control is referred to as traveling pressure increase control.

-A / I control-

As shown in FIG. 4, an accelerator lever 24 for adjusting and setting the engine speed by manual operation, an accelerator adjusting mechanism B for driving and adjusting the engine speed and a hydraulic actuator such as a boom cylinder 5c are provided. Operation detecting means C for detecting whether or not the engine is operating, that is, whether or not a load is acting, and when the hydraulic actuator is stopped and there is no load, the engine speed is changed to the idling side, and An accelerator control means D for operating an accelerator adjusting mechanism B is provided to operate the engine speed to a set value by the accelerator lever 24 when the hydraulic actuator is operated.

That is, the governor 20 of the engine 19 is provided with a governor lever 21, and a geared motor 22 which is an accelerator adjusting mechanism for driving and operating the governor lever 21.
The auxiliary oil pressure gauge 49 for detecting the pressure of the control oil passage 47, the potentiometer 25 for detecting the operation position of the hand accelerator lever 24, the feedback potentiometer 27 for detecting the operation amount of the governor lever 21, and the first oil passage 15 Main oil pressure gauge that detects pressure (an example of main oil pressure sensor) 2
3 is connected to the control device 26 to constitute accelerator control means D.

That is, by operating the hand accelerator lever 24 at the idling position i, the engine speed in the working state (usually set to the full accelerator position m in many cases) is set. The engine speed is maintained and the engine speed is reduced to the idling state while the accelerator lever 21 is set at the position m during non-operation (when no load is applied). It is set so that the control device 26 determines from the detection information of the oil pressure gauges 23 and 49.

That is, basically, it is determined whether or not the hydraulic actuator is operating based on whether or not pressure is applied to the main oil pressure gauge 23. As mentioned in part (3),
At the time of "work", the main oil pressure gauge 23 may not have a pressure even though the boom cylinder is moving. Therefore, FIG.
As shown in the figure, even if the main oil pressure gauge 23 does not have a pressure, if the sub oil pressure gauge 49 has a pressure, the engine speed is controlled to the work speed, and the main and auxiliary oil pressure meters 23, 49 are controlled. Constitute an operation detecting means C.

A counter balance valve 60 is provided in the circuit of the traveling motors 31 and 33, and the pressure always rises in the first oil passage 15 which is the main hydraulic circuit S during traveling. The operation and stop of the traveling motors 31 and 33 can be determined based on the detection information.

-Second embodiment (corresponding to the configuration of claim 2)
-The following description focuses on differences from the first embodiment. As shown in FIG. 7, the auxiliary hydraulic pressure sensor is connected to the lowermost swivel on-off valve 3 in the control oil passage 47 of the control hydraulic circuit H.
An auxiliary orifice 59 is provided in the control oil passage 47 at a position on the lower side of the connection point of the auxiliary oil pressure gauge. Then, a relief oil pressure adjusting means E is provided by providing a pressure-increasing oil passage 40b which communicates an oil passage connected to the sub-hydraulic gauge 49 with an oil chamber formed on the relief spring 40A side of the first relief valve 40.

As shown in FIG. 7, the first relief valve 40 in this case has a slide valve body 55 for opening and closing the input and output oil passages 53 and 54, a relief spring 56, and a variable base position of the relief spring 56. The pressurized oil passage 40b is connected to a hydraulic chamber 58 for moving the piston 57. That is, while the first embodiment acts on the side where the pressure of the control hydraulic circuit H decreases the first relief pressure, the second embodiment acts on the side where the relief pressure is increased. I have.

Thus, the seven working on-off valves 30v to 3v
When all 5v are neutral, the orifice 59 raises the pressure on the sub-hydraulic gauge 49, and the pressure increases the first relief pressure to produce a high pressure state, and the seven working on-off valves 30v to 35v When any of them is at a position other than the neutral position, the control oil passage 47 is closed and the pressure on the sub-hydraulic gauge 49 does not rise, so that the first relief pressure is lowered and a low pressure state comes to appear. Thus, the work state detecting means G is constituted.

-Third Embodiment- (corresponding to Claim 3) This third embodiment is a modification of the structure of the first relief valve 40 in the first embodiment. The explanation will be focused.

As shown in FIG. 9, when the relief pressure is high (2
50 kg) high-pressure relief valve 61 and low-pressure (230 kg) low-pressure relief valve 62 having a low relief pressure are connected in parallel, and a circuit in which only high-pressure relief valve 61 is connected in circuit.
The first relief valve 4 is provided by providing a selection valve 63 capable of switching between a state and a second state in which the low-pressure relief valve 62 is connected to the circuit.
0. The portion between the oil passage y and the oil passage z in FIG. 4 is different.

The selection valve 63 is switched by using the pressure of the control hydraulic circuit H as a pilot pressure. When the pressure in the control hydraulic circuit H rises, the selection valve 63 is in a closed position where the flow path is shut off, and the pressure does not rise. And the structure is returned to the open position where the flow path is opened, and constitutes the relief pressure adjusting means E. in addition,
By providing a detection oil passage 64 connecting the sub-hydraulic gauge 49 and the selection valve 63 so that the selection valve 63 is switched according to whether or not the pressure of the control hydraulic circuit H rises, the work state is detected. Means G are constituted.

When the seven on-off valves 30v to 35v are neutral and no pressure is applied to the control hydraulic circuit H, that is, when "neutral" or "running", the selection valve 63 is in the closed position and the high-pressure relief The first state is such that only the valve 62 can operate, and the first relief pressure (250 kg) and the predetermined differential pressure (1
4 kg) exceeds the relief pressure (260 kg) of the second relief valve 41.

When one of the seven on-off valves 30v to 35v is set to a position other than the neutral position and pressure is applied to the control hydraulic circuit H, the selection valve 63 is opened by the pressure, and both relief valves are opened. The valves 61 and 62 are in the second state in which they can operate, and the first relief pressure (230 kg) and the predetermined differential pressure (1
4 kg) is lower than the second relief pressure (260 kg).

Fourth Embodiment (corresponding to claim 1) The first to third embodiments described above are all mechanical means for switching valves by the control hydraulic circuit H. 10
As shown in (1), an electric means for adjusting the first relief pressure from the detection information of both the main and sub hydraulic gauges 23 and 49 is also possible. That is, the solenoid 65 capable of compressing the relief spring 56 of the first relief valve 40 and the two hydraulic gauges 2
3 and 49 are connected to the control device 26, and the solenoid 65
Means that the first spring pressure is adjusted from a low pressure (230 kg) to a high pressure (250 kg) by compressing the relief spring 56 by energization.

In this case, as shown in FIG.
When the pressure on the sub oil pressure gauge 49 rises, the solenoid 65 is not energized regardless of the information of the main oil pressure gauge 23, and
Control the relief pressure to "low". And the sub-hydraulic gauge 49
When the pressure does not rise and the main oil pressure gauge 23 rises, the solenoid 65 is energized to increase the first relief pressure to “high”.
When the pressure does not rise at the sub-hydraulic gauge 49 and the pressure does not rise at the main hydraulic gauge 23, the solenoid 65 is not energized, and the first relief pressure is controlled to "low".

According to this electric means, the first relief pressure is set to “high” when the hydraulic actuator does not operate and is “neutral”.
, And a more sophisticated running boost control state can be obtained.

[Brief description of the drawings]

FIG. 1 is a side view of a backhoe.

FIG. 2 is a schematic overall view of a hydraulic circuit.

FIG. 3 is a schematic overall view of a hydraulic circuit.

FIG. 4 is a partial hydraulic circuit diagram showing the principle of L / S with A / I.

FIG. 5 is a circuit diagram showing an operation structure of a pilot control valve.

FIG. 6 shows the engine speed and first engine speed according to work and running conditions.
Change in relief pressure

FIG. 7 is a circuit diagram showing a main part of a traveling boost control device according to a second embodiment.

FIG. 8 (a) A diagram showing a logical judgment table of engine speed adjustment (b) A diagram showing a logical judgment table of first relief pressure adjustment in the fourth embodiment

FIG. 9 is a circuit diagram showing a main part of a traveling boost control device according to a third embodiment.

FIG. 10 is a circuit diagram showing a main part of a traveling boost control device according to a fourth embodiment.

FIG. 11 is a circuit diagram illustrating the principle of a working state detecting unit and an operation detecting unit according to a comparative example.

[Explanation of symbols]

 5c, 33, 6c Hydraulic actuator 8 Hydraulic pump 9, 10, 34 Control valve 9s, 10s, 34s Throttle valve 9p, 10p, 34p Supply port 9v, 10v, 35v Open / close valve 13 Flow control mechanism 14t First oil passage 15 Second Oil passage 20 Engine rotation speed adjusting means 22 Operating actuator 23 Main oil pressure sensor 24 Accelerator tool 25 Operating amount detecting means 39 Unload valve 40 First relief valve 40a Step-down oil passage 40b Boost oil passage 41 Second relief valve 47 Oil passage 49 Secondary oil pressure sensor 59 Orifice 61 High pressure relief valve 62 Low pressure relief valve 63 Selection valve A Load control means C Actuation detection means D Accelerator control means E Relief pressure adjustment means G Work state detection means H Control hydraulic circuit S Main hydraulic circuit

Claims (4)

[Claims] 1. A control valve having a plurality of hydraulic actuators, a variable displacement hydraulic pump, a throttle valve for a pressure oil supply path to the actuator, and a discharge amount per unit time of the hydraulic pump variably set. And a differential pressure between a first oil passage communicating with a lower portion of the pressure oil supply to the throttle valve and a second oil passage communicating with a supply port of the control valve is maintained at a predetermined value. Load control means for operating the flow rate adjusting mechanism as described above, and an unload acting on the second oil passage by a pressure difference between the first oil passage and the second oil passage that is larger than the predetermined value. A valve, a first relief valve acting on the first oil passage, and a second relief valve acting on the second oil passage, an operation amount detecting means for detecting an operation amount of an accelerator operation tool,
An operation actuator for driving and operating the engine speed adjusting means, and an operation detecting means for detecting whether or not the hydraulic actuator is operating, when the hydraulic actuator is stopped, the engine speed is changed to the idling side, and An accelerator control unit that links the operation amount detection unit and the operation actuator so as to return the engine speed to a set value by the accelerator operation tool when the hydraulic actuator is operated; The relief pressure of the first relief valve can be variably set so that the sum of the relief pressure and the predetermined differential pressure can be selectively set between a low pressure state below the relief pressure of the second relief valve and a high pressure state above the relief pressure of the second relief valve. And a work state detecting means for controlling the operation of the relief pressure adjusting means. In the spool of each of the working control valves of the hydraulic actuators other than the traveling hydraulic actuator among the hydraulic actuators, an opening / closing valve having a number of switching positions in response to the working control valves is formed. When all of the control valves are in the neutral position, a pressure hydraulic oil is provided with a center-bypass-type control hydraulic circuit that passes through the spool entirely,
A sub-hydraulic sensor for detecting a pressure fluctuation of the control hydraulic circuit, and a main hydraulic sensor for detecting a pressure fluctuation of a main hydraulic circuit acting on a control valve of the traveling hydraulic actuator; It is configured to determine based on whether or not pressure is raised for a hydraulic circuit, and the operation detecting means determines whether or not pressure is raised in the main hydraulic circuit,
A hydraulic circuit of a construction machine configured to determine whether or not pressure is generated for the control hydraulic circuit. 2. The hydraulic pressure sensor according to claim 1, wherein the auxiliary hydraulic pressure sensor comprises a hydraulic pressure gauge connected to a lower side portion of a lowermost opening / closing valve in a pressure supply direction in an oil path of the control hydraulic circuit, and the hydraulic pressure gauge connection point in the oil path. An orifice is provided in the lower portion of the first relief valve, and a pressure-increasing oil passage communicating between an oil passage connected to the oil pressure gauge and an oil chamber formed on the relief spring side of the first relief valve is provided to constitute the relief pressure adjusting means. When the pressure gauge rises, the relief pressure of the first relief valve increases and the high pressure state appears, and when the pressure gauge does not rise, the relief pressure of the first relief valve decreases. The hydraulic circuit for a construction machine according to claim 1, wherein the work state detecting means is configured so that the low-pressure state appears. 3. The hydraulic pressure sensor according to claim 1, wherein the auxiliary oil pressure sensor comprises an oil pressure gauge connected to an upper side portion of an uppermost opening / closing valve in a pressure supply direction in an oil path of the control hydraulic circuit. The pressure reducing oil passage communicating with the relief pressure working side oil chamber of the first relief valve is provided to constitute the relief pressure adjusting means, and when the pressure gauge rises, the relief pressure of the first relief valve decreases. The work state detecting means is configured such that the low pressure state appears and the pressure in the oil pressure gauge does not rise, so that the relief pressure of the first relief valve increases and the high pressure state appears. The hydraulic circuit for a construction machine according to claim 1, wherein the hydraulic circuit is provided. 4. A first state in which the first relief valve is configured by connecting a high-pressure relief valve having a high relief pressure and a low-pressure relief valve having a low relief pressure in parallel and connecting only the high-pressure relief valve in a circuit. And a selection valve capable of switching between a second state in which the low-pressure relief valve is connected to the circuit. When the first state is selected, the sum of the relief pressure of the first relief valve and the predetermined differential pressure becomes When a high pressure state higher than the relief pressure of the second relief valve appears and the second state is selected, the sum of the relief pressure of the first relief valve and the predetermined differential pressure becomes the relief pressure of the second relief valve. The relief pressure adjusting means is constituted so that a low pressure state lower than the above appears, and the selection valve is operated so as to be switched depending on whether or not the pressure of the control hydraulic circuit rises, whereby Hydraulic circuit for construction equipment according to claim 1 that is configured to work state detection means.