JPH0971978A - Hydraulic circuit of construction machine - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To solve the inconvenience that the engine is lowered to the idling state even when the boom cylinder is in the shortening drive state when the boom is lowered. A throttle valve 9s is provided in a supply-side oil passage in a control valve 9 for a boom cylinder 5c, and a flow rate adjusting mechanism 13 for adjusting a variable displacement hydraulic pump 8 is provided.
Load sensing for maintaining the differential pressure between the first oil passage 14t on the lower side of the pressure oil supply side and the second oil passage 15 of the pressure oil supply port 9p of the control valve 9 at a predetermined value, and the engine when the boom cylinder 5c is stopped. Is idling, and at the time of operation, it is equipped with an auto idle that sets the engine speed to a set value that matches the accelerator lever. The pressure sensor 23, which controls the operation and non-operation of the auto idle, is configured to detect the pressure in the first oil passage 14t so that the pressure sensor 23 shifts to the idling state after a predetermined time elapses after the pressure detection operation of the pressure sensor 23 is stopped. In addition, a timer means 27 for linking the pressure sensor 23 and the accelerator control means D is provided.

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. More specifically, the present invention relates to load control in which hydraulic power corresponding to a load is discharged by a pump, so-called load sensing, and an actuator are operated. The present invention relates to a control provided with a control for reducing the engine speed to an idling state when the load is not applied, that is, a so-called auto idle.

[0002]

2. Description of the Related Art A backhoe disclosed in Japanese Unexamined Patent Publication No. 7-103204 is known as one that employs load sensing, in which a throttle valve provided in a supply-side oil passage in a control valve is used. The flow rate of the pump is variably adjusted so as to maintain the differential pressure set by the sum of the pressure difference and the pressure difference by the pressure compensating valve arranged on the pressure oil supply lower side of the control valve. In addition, in Japanese Patent Application No. 6-204072 filed previously, a technique is proposed in which the engine speed is reduced to improve fuel consumption and noise when the actuator is not operating, that is, when no load is applied. .

[0003]

Therefore, it is preferable to incorporate an auto idle into a construction machine that employs load sensing, in order to achieve further energy saving and noise reduction while having the necessary functions. It is an object of the present invention to rationally integrate a load sensing system and an auto idle system without functional problems.

[0004]

[Means for Solving the Problems]

[Configuration] To achieve the above object, the present invention provides a hydraulic actuator, a variable displacement hydraulic pump, a control valve having a throttle valve for a pressure oil supply path to the actuator,
A first oil passage that communicates with a lower portion of the pressure oil supply to the throttle valve, and a second fluid communication port that communicates with the pressure oil supply port of the control valve. Load control means for operating the flow rate adjusting mechanism so as to maintain the differential pressure with the oil passage at a predetermined value, an accelerator operating tool for adjusting and setting the engine speed by manual operation, and an adjusting setting by driving the engine speed. It has an accelerator adjustment mechanism and an operation detection unit that detects whether the hydraulic actuator 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 changed. To operate the accelerator with the set value,
And an accelerator control means for operating the accelerator adjusting mechanism, and the operation detecting means is configured to detect whether or not pressure is present in the first oil passage, and the pressure detecting operation by the operation detecting means is eliminated. In order to activate the accelerator control means after a lapse of a predetermined time from the above, a timer means for connecting the operation detecting means and the accelerator control means is provided.

[Operation] According to the first aspect of the present invention, whether the operation detecting means for controlling the operation of the auto idle has a pressure in the lower portion of the pressure oil supply side with respect to the throttle valve of the supply side oil passage in the control valve. It is configured by detecting whether or not it stands. In other words, it is to judge whether the circuit pressure, which is the basic pressure for producing the differential pressure, stands or does not stand.Therefore, even if one has a plurality of actuators such as a backhoe, it is necessary to use either actuator. Since pressure acts, the presence or absence of a load can be detected without exception. However, in some cases, it may not always be possible to accurately determine the operating and non-operating states of the actuator.

For example, when the boom cylinder is operated to move down the boom in the backhoe, the boom is originally moved down by its own weight, and if the moving speed of the boom is equal to or higher than the driving speed of the boom cylinder. In reality, no pressure will be built up in the first oil passage described above, and it is predicted that the engine will fall to the idling state even though the actuator is in the operating state. In this case, when the boom is next raised without delay, the engine speed will be restored to the set value accordingly, and unnecessary control will be performed, and the operation lag will be slowed by the time lag required for the recovery. There is an inconvenience.

Therefore, when the actual circuit pressure fluctuation was examined, it was confirmed that when the control valve was switched from the neutral position to another operating position, the starting pressure was always raised for a moment immediately after the switching operation. That is, in the state where a negative pressure acts like the boom lowering described above, as shown in the circuit pressure graph shown in FIG. 3, the pressure is remarkably raised immediately after the switching operation, but the pressure is immediately lost and the control accompanying the end of operation is performed. The behavior is such that a little pressure is applied during the return switching operation of the valve.

Therefore, in the present application, since the timer means for activating the accelerator control means after a lapse of a predetermined time from the pressure detection operation by the operation detecting means is provided, as described above, the actuator is operated by a negative pressure. Even when the pressure detection operation is stopped, the idling state is restricted immediately, and the set rotation speed can be maintained while the actuator is operating. Therefore, the inconvenience that the actuator is in the idling state even if it is in the operating state is solved, unnecessary control is not performed, and the operation response is improved.

[Effect] As a result, by a relatively simple modification of providing a timer means in the control system, the operation or non-operation can be detected regardless of the presence or absence of the operating pressure in the actuator, and the hydraulic pressure of the load sensing system can be adopted. In the circuit, the auto idle system came to function correctly, and it was possible to provide it with better operability.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.
A case of a backhoe as an example of a construction machine will be described with reference to the drawings. FIG. 1 shows a backhoe, 1 is an excavating work device, 2 is a turning table, 3 is a traveling machine stand, 4 is a crawler traveling device, and the excavating work device 1 includes a boom 5, an arm 6, a bucket 7, and the like. It is configured. In this backhoe, a boom cylinder 5c, an arm cylinder 6c,
A load sensing system and an auto idle system are incorporated in a hydraulic circuit for driving an actuator such as a bucket cylinder 7c and a traveling hydraulic motor or a swing cylinder (not shown), and the hydraulic circuit will be described based on the principle diagram shown below.

FIG. 2 shows a principle circuit diagram in which circuits related to the boom cylinder 5c and the arm cylinder 6c are extracted. 8 is a variable displacement hydraulic pump driven by an engine 19, 13 is a unit time of the hydraulic pump 8. It is a flow rate adjusting mechanism that variably sets the amount of discharged oil per hit. Flow control mechanism 13
Is constituted by an adjustment cylinder 13 composed of a horsepower control cylinder 13A operated by the discharge pressure of the main pump 8 and a flow control cylinder 13B driven by the adjustment pump 18. The flow control mechanism A and the pressure compensation type flow control valve 14 corresponding thereto constitute a load control means A. 9 is a control valve for the boom, 10 is a control valve for the arm, 11 is a compensator for the boom and 12 is a compensator (pressure compensating valve) for the arm, and a throttle valve 9s is provided in the supply-side oil passage in both control valves 9 and 10. , 10s.

The compensators 11 and 12 are located on the lower side of the pressure oil supply to the supply side throttle valves 9s and 10s, respectively.
In addition, they are arranged on the upstream side of the pressure oil supply to the actuators 5c and 6c. And each compensator 1
The low pressure side oil passages 11t and 12t are provided on the lower side of the pressure oil supply for the actuators 1 and 12 and for communicating the pressure oil supply upper side portion for the actuators 5c and 6c and the spring side oil chambers of the compensators 11 and 12, respectively. There is.

Throttle valves 9s, which are on the good side of the pressure oil supply to the compensators 11 and 12, and also on the oil passages on the supply side.
The high-pressure side oil passage 1 that communicates the lower side of the pressure oil supply for 10 s with the non-spring side oil chamber of each of the compensators 11 and 12.
1k and 12k are provided. Each compensator 11,1
2, a constant pressure reducing valve provided with a compression spring 17 for biasing the flow path to the disconnection side, thereby forming an after-orifice type load sensing circuit.

There is provided a first low pressure side oil passage 14t which connects the spring side oil chamber 14x of the flow rate control valve 14 and the pressure oil supply lower side portion to the respective supply side throttle valves 9s, 10s, and each low pressure side oil passage. The first low-pressure side oil passage 14t communicates with 11t and 12t. Pressure oil supply ports 9p, 10 of each control valve 9, 10
A communication oil passage 15 communicated with p and a non-spring-side oil chamber of the pressure control valve 14 communicate with a dedicated connection oil passage 16. or,
Adjusting cylinder 13 at the time of switching of flow control valve 14
Is supplied by a dedicated adjustment pump 18 driven by the engine together with the hydraulic pump 8.

As shown in FIG. 2, an accelerator lever (an example of an accelerator operating tool) 24 for adjusting and setting the engine speed by artificial operation, an accelerator adjusting mechanism B for driving and adjusting the engine speed, and a boom. Cylinder 5c
And the like, that is, whether or not a hydraulic actuator is operating, that is, whether or not a load is acting, and an operation detecting means C. When the hydraulic actuator is stopped and there is no load, the engine speed is set to the idling side. There is provided accelerator control means D for operating the accelerator adjusting mechanism B so that the engine speed can be changed to a set value by the accelerator lever 24 when the hydraulic actuator is operated.

That is, a governor 20 of the engine 19 is provided with a governor lever 21, and a geared motor for driving and operating the governor lever 21 (an example of the accelerator adjusting mechanism B).
22, the first low pressure side oil passage (corresponding to the first oil passage) 14 described above
A pressure sensor 23 for detecting the pressure of t and a potentiometer 25 for detecting the operation position of a hand accelerator lever (an example of an accelerator operation tool) 24 are connected to a control device 26 to constitute an accelerator control means D.

That is, by operating the hand accelerator lever 24 in the idling position i, the engine speed in the working state (usually set to the full accelerator position m) is set, and in the working state, it is set. The engine speed is kept idling, and the engine speed is lowered to the idling state while the accelerator lever 24 is kept set to the position m when not working (no load). In this case, the pressure sensor 23 constitutes the operation detecting means C. Then, the accelerator control means D is activated after a predetermined time has elapsed since the pressure detection operation by the pressure sensor 23 was stopped, specifically, the engine is brought into an idling state 3 to 4 seconds after the pressure is exhausted. A timer means 27 for connecting the pressure sensor C and the accelerator control means D is connected to the control device 26.

For example, when the boom control valve 9 is switched and the boom cylinder 5c is shortened so as to lower the boom 5, the speed at which the piston rod 5r is pushed depends on the weight of the excavation work device 1 and the boom cylinder 5c is shortened. It may be faster than the driving speed. Then, the boom cylinder 5 is placed in the oil passage on the upstream side of the pressure oil supply of the boom control valve 9.
Since the pressure due to the drive load of c does not stand up, the change in the pressure due to the switching operation of the control valve 9 in this case, as shown in the graph in FIG. When the control valve 9 disappears and the control valve 9 is returned to the neutral position, a slight pressure rises again for a moment.

Therefore, by setting the interval between the front and rear peak pressures in FIG. 3 to a predetermined time (3 to 4 seconds) required to move the boom 5 from the highest position to the lowest position, the circuit pressure is established. Even when the boom is not lowered, the engine speed can be maintained at the set value. Of course, if the "boom lift" is switched to during the predetermined time, the pressure rises again, so that the set rotational speed is continuously maintained. That is, if the maximum continuous operation time of the actuator to be operated is actually set as the predetermined time, it is possible to avoid the situation of idling against the intention during the operation of the actuator.

Further, there is provided a correction control means E for preventing a false operation of the auto idle when the operating oil is at a low temperature immediately after the engine is started. That is, the tank back pressure, which is the drain oil passage, increases due to the increase in the viscosity of the hydraulic oil at low temperature, and the pressure sensor 23 detects the pressure even when the actuator is not operating, and the engine speed is the operation of the hand accelerator lever 24. It rises to the street value.

Therefore, from the state that the pressure detected by the pressure sensor 23 is below a predetermined value, the auto idle is activated by determining that some operation lever has been operated because the time during which the pressure has increased above the specified pressure continues for some time. is there.
That is, the pressure detecting means a for detecting the circuit pressure, the fluctuation detecting means b for detecting the change of the circuit pressure, and the measuring means c for measuring the time after the pressure fluctuation are provided, and the circuit pressure is below a predetermined value. If the increase value of the pressure is greater than or equal to a preset specified value and the increased pressure is continued for a preset time or longer, the pressure detection is performed so as to increase the engine speed to a value corresponding to 24 kinds of accelerator levers. The auxiliary control means E links the means a, the fluctuation detection means b, the measurement means c, and the accelerator control means D.

Actually, the pressure detecting means a and the fluctuation detecting means b
The pressure sensor 23 takes charge of the pressure sensor 23, and the auxiliary control means E and the measuring means c provided in the control device 26 are connected. To give a specific example, the circuit pressure is 5k from the range of 10kg or less.
If the state of rising by g or more and 5 kg or more continues for several ms (millisec), it is determined that the boom cylinder 5c, the arm cylinder 6c or the like has been operated, and the engine speed set by the hand accelerator lever 24 is reached. Raise it.

In the above-described embodiment, the boom cylinder 5c and the arm cylinder 6c constitute a hydraulic actuator. However, the traveling hydraulic motor, the swing cylinder, etc. are also hydraulic actuators, and even if there is only one hydraulic actuator. good.

It should be noted that reference numerals are added to the claims for convenience of comparison with the drawings, but the present invention is not limited to the configurations of the accompanying drawings by the entry.

[Brief description of drawings]

1] Side view of backhoe

FIG. 2 is a partial hydraulic circuit diagram showing the principle of load sensing and auto idle.

FIG. 3 is a diagram showing a change graph of the detected pressure of the control valve.

[Explanation of symbols]

 5c, 6c Hydraulic actuator 8 Hydraulic pump 9,10 Control valve 9s, 10s Throttle valve 9p, 10p Pressure oil supply port 13 Flow rate adjusting mechanism 14t 1st oil passage 15 2nd oil passage 24 Accelerator operation tool 27 Timer means A Load control means B accelerator adjustment mechanism C operation detection means D accelerator control means

Claims (1)

[Claims] 1. Hydraulic actuators (5c), (6c)
, A variable displacement hydraulic pump (8), and control valves (9), (1) equipped with throttle valves (9s), (10s) for the pressure oil supply paths to the actuators (5c), (6c).
0) and a flow rate adjusting mechanism (13) that variably sets the discharge amount of the hydraulic pump (8) per unit time, and communicates with the lower side of the pressure oil supply to the throttle valves (9s) and (10s). The first oil passage (14t) and the pressure oil supply ports (9p), (10) of the control valves (9), (10).
p), the load control means (A) for operating the flow rate adjusting mechanism (13) so as to maintain the differential pressure with the second oil passage (15) at a predetermined value, and the engine speed is manually adjusted. Operation for detecting whether or not the accelerator operation tool (24) to be set, the accelerator adjustment mechanism (B) to drive and set the engine speed, and the hydraulic actuators (5c) and (6c) are operating. And a detection means (C) for changing the engine speed to the idling side when the hydraulic actuators (5c), (6c) are stopped, and for operating the hydraulic actuators (5c), (6c). An accelerator control means (D) for actuating the accelerator adjusting mechanism (B) so as to operate the accelerator operating tool (24) to a set value. The stage (C) is configured to detect whether or not the pressure is present in the first oil passage (14t), and after a predetermined time has elapsed since the pressure detecting operation by the operation detecting means (C) disappeared. The accelerator control means (D)
Timer means (27) for connecting the operation detecting means (C) and the accelerator control means (D) so that
The hydraulic circuit of the construction machine equipped with.