JP3286146B2 - Construction machine hydraulic circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit structure of a construction machine such as a backhoe or the like, and more particularly to a so-called load sensing system employing a load control for pumping hydraulic power corresponding to a load. A technique for lowering the driving speed of the working device by lowering the engine speed in order to improve operability (for example, Japanese Patent Application Laid-Open No. 7-3)
No. 4489).

[0002]

2. Description of the Related Art In Japanese Patent Application No. 7-230188 filed earlier, an electric operation control technique capable of performing a light accelerator operation by an electric actuator is applied to the above-mentioned technique, and excavation work is performed in response to an increase or decrease in an engine speed. A system has been proposed in which the operability of a load sensing system (hereinafter, abbreviated as E-compliant LS / S) corresponding to the engine speed, in which the drive speed of the device increases and decreases, is further improved.

[0003]

According to the above prior art, the rotational speed adjusting means is operated by an electric actuator (geared motor). Therefore, the differential pressure of load sensing is changed and set by driving the electric actuator. The drive speed of a hydraulic actuator such as a boom cylinder can be changed. With this structure, if the geared motor may move due to gear backlash, engine vibration, or other causes, the detection value of the feedback potentiometer that detects the position of the rotation speed adjusting means changes, The control function of the accelerator control means, that is, the geared motor is automatically operated so as to return to the original designated position and to be driven to the position corresponding to the accelerator operation tool.

Therefore, in the conventional control device, when the geared motor shifts, the geared motor is repeatedly driven in small increments. As a result, there is a disadvantage that the speed of the hydraulic actuator becomes faster or slower, resulting in speed hunting. there were. An object of the present invention is to provide a highly efficient and easy-to-use E
It is to improve the operability of the working device by eliminating the speed hunting due to the unexpected movement of the electric actuator while having the corresponding LS / S and the electric operation control device.

[0005]

[Means for Solving the Problems]

[Configuration] To achieve the above object, the present invention provides a hydraulic actuator, a variable displacement hydraulic pump, and a control valve including a throttle valve for a hydraulic oil supply path to the actuator,
A flow control mechanism for variably setting a discharge amount per unit time of the hydraulic pump, a first oil passage communicating with a lower portion of the hydraulic oil supply to the throttle valve, and a second oil passage communicating with a pressure oil supply port of the control valve. First detection means for electrically detecting an operation amount of a manually operated accelerator operation tool, comprising: load control means for operating a flow rate adjusting mechanism so as to maintain a differential pressure between the oil passage and a predetermined value; An electric actuator for driving and operating the number adjusting means; a second detecting means for detecting an operated amount of the engine speed adjusting means such that the electric actuator is driven by an amount corresponding to the operation amount of the accelerator operating tool; An accelerator control means for linking the detection means and the electric actuator; an adjusting means for changing and regulating the throttle amount or the differential pressure of the throttle valve; and a hydraulic actuator when the engine speed is increased. Speed control means for linking the second detection means and the adjustment means so that the drive speed of the hydraulic actuator becomes low when the engine speed is reduced and the engine speed is reduced. A dead zone is set so that the electric actuator in a stopped state starts to move by a displacement of the detection means by a predetermined amount or more.

According to the first aspect of the present invention, even if the electric actuator slightly moves due to vibration or the like to move the second detecting means due to the setting of the dead zone, the feedback is provided when the amount of movement is equal to or less than the predetermined amount. Therefore, the speed hunting of the hydraulic actuator described above does not occur. Therefore, the scooped object falls due to the vibration of the boom and the arm while being jerky, and the non-smooth and unpleasant turning behavior is improved or eliminated.

Further, the feedback function in the electrically operated accelerator device for operating the engine speed adjusting means by the electric actuator is performed by the second detecting means for detecting the operated amount of the engine speed adjusting means. For example, a value closer to the actual number of revolutions can be taken in as compared with the means using the operation amount of the operation side portion such as an accelerator lever as a feedback reference, which is preferable in that it can contribute to improvement in control accuracy. .

[Effects] As a result, the electric operation control which can operate the accelerator lightly in an economical state without equipment modification by means of the control for providing the dead zone, and the E-compatible LS
The speed hunting of the hydraulic actuator can be suppressed while adopting / S, and a hydraulic circuit with even better operability can be provided.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS 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 swivel base, 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, an arm 6, a bucket. 7 and the like.

FIG. 2 schematically shows the hydraulic circuit. The control valve 29 for the dozer cylinder, the control valve 3 for the bucket cylinder 7c,
0, control valve 32 for left running motor 31, boom cylinder 5
c control valve 9, arm cylinder 6c control valve 10, right traveling motor 33 control valve 34, swing motor control valve 35,
For each control valve of the swing cylinder 36 and the service control valve 38, a load sensing system including a variable displacement hydraulic pump 8 that is discharged at a pressure slightly higher than the load pressure is employed. ing. Also, an auto idle system which is preferable in terms of noise and energy saving is adopted, and will be described below.

FIG. 3 shows a principle circuit diagram of a main part of a part related to the boom cylinder 5c and the arm cylinder 6c surrounded by a virtual line in FIG.
9, the variable displacement hydraulic pump driven by 9
Is a flow rate adjusting mechanism for variably setting the amount of oil discharged per unit time of the hydraulic pump 8. The flow control mechanism 13 is provided with a horsepower control cylinder 13 </ b> A operated by the discharge pressure of the main pump 8.
And the flow control cylinder 13 driven by the regulating pump 18
B.

Further, a pressure compensating type flow control valve 14 for the control cylinder 13 is provided. 11 is for the boom and 12
Is each compensator (pressure compensation valve) for the arm,
Throttle valves 9 s and 10 s are provided in supply-side oil passages in the boom control valve 9 and the arm control valve 10. Each control valve 2 other than the control valves 9 and 10 for the boom and the arm is used.
The structures of 9, 30, 32, 34, 35, 37, 38 are all the same as the control valves 9, 10 for the boom and the arm.

Each of the compensators 11 and 12 is located on the lower side of the pressure oil supply to each of the supply side throttle valves 9s and 10s.
In addition, they are arranged on the upstream side of the pressure oil supply to the actuators 5c and 6c. And each compensator 1
Low-pressure-side oil passages 11t and 12t are provided on the downstream side of the pressure oil supply to the actuators 1 and 12 and communicate the upper side of the pressure oil supply to the actuators 5c and 6c with the spring-side oil chambers of the compensators 11 and 12. It is.

The throttle valve 9s, which is on the upstream side of the pressure oil supply to each of the compensators 11 and 12,
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 constituting an after-orifice type load sensing circuit.

A first low-pressure side oil passage 14t is provided for communicating the spring-side oil chamber 14x of the flow control valve 14 with the lower side of the pressure oil supply to each of the supply-side throttle valves 9s and 10s. A first low-pressure side oil passage 14t communicates with 11t and 12t. A dedicated connection oil passage 16 is provided between the second oil passage 15 communicating with the supply ports 9p and 10p of the control valves 9 and 10 and the oil chamber on the flow control valve 14 opposite to the spring-side oil chamber 14x.
Are in communication. The pressure on the adjusting cylinder 13 when the flow control valve 14 is switched is supplied by a dedicated adjusting pump 18 driven by the engine together with the hydraulic pump 8. That is, the flow control valve that operates the adjusting cylinder 13 so as to maintain the pressure difference between the first oil passage 14t and the second oil passage 15 communicating with the supply ports 9p and 10p of the control valves 9 and 10 at a predetermined value. 14 and load control means A
Is configured.

A first potentiometer (an example of a first detecting means) 25 for electrically detecting an operation amount of an accelerator lever (an example of an accelerator operation tool) 24 for adjusting and setting the engine speed by manual operation, and a governor (an example). An example of the engine speed adjusting means) a geared motor (an example of an electric actuator) 22 for driving and operating the governor lever 21 of the engine 20, and an operation detecting means 23 for detecting whether or not a hydraulic actuator such as the boom cylinder 5c is operating. The first potentiometer 25 and the geared motor 22 are operated so that the engine speed is changed to the idling side when the hydraulic actuator is stopped, and the engine speed is operated to the set value by the accelerator lever 24 when the hydraulic actuator is operated. It is provided with an associated accelerator control means C. .

That is, a feedback second potentiometer (an example of a second detection means) 27 for detecting the operating position of the governor lever 21, a geared motor 22, and the above-described first low-pressure side oil passage (corresponding to the first oil passage) 14t. Pressure sensor 23 for detecting the pressure of the first and the first potentiometer 25
Is provided in the control device 26.

That is, the operator operates the hand accelerator lever 24 at the idling position i to set the engine speed in the working state (usually often set to the full accelerator position m). When the engine speed is maintained, and when the engine is not working (when no load is applied), the engine speed is substantially reduced to an idling state while the accelerator lever 24 remains set at the position m. In this case, the pressure sensor 23 forms an operation detecting unit.

An adjusting means B for changing and adjusting the throttle amount of the throttle valves 9s and 10s is provided. When the engine speed is increased, the drive speed of a hydraulic actuator such as the boom cylinder 5c is increased, and the engine speed is decreased. The control device 26 is provided with a speed control means E for linking the second potentiometer 27 and the adjustment means B so that the driving speed of the hydraulic actuator becomes slower when it is operated.

The adjusting means B is provided for each of the compensators 11, 1
2 each low-pressure oil passage 11t, 12t and the first low-pressure oil passage 14
and t via an electromagnetic high-speed response valve 28. The electromagnetic high-speed response valve 28 communicates with each of the low-pressure oil passages 14t, 11t, and 12t at the normal position b, and the low-pressure oil passages 11t and 12t and the second high-pressure oil passage at the high-pressure position a. The oil passage 15 is configured to have a two-position switching valve structure communicating with the communication oil passage 21a.

By operating the electromagnetic high-speed response valve 28, the hydraulic pressure acting on the low-pressure side oil passages 11t, 12t of the compensators 11, 12 can be set to an intermediate value between the load pressure of the actuators 5c, 6c and the discharge pressure of the pump. 1
Compensator 1 by the differential pressure maintaining action by 1 and 12
The supply pressure to the valves 1 and 12 is higher than when the electromagnetic high-speed response valve 28 is at the normal position b. Then, in order to keep the differential pressure between the first low-pressure side oil passage 14t and the discharge pressure of the hydraulic pump 18 constant, the differential pressure at the throttle valves 9s, 10s on the upstream side of the compensators 11, 12 is reduced. That is, control is performed so that the throttle amounts of the throttle valves 9s and 10s are reduced, that is, the opening degrees of the control valves 9 and 10 are reduced. As a result, the amount of oil supplied to the actuators 5c and 6c is reduced, and the driving speed is reduced. It becomes. This action is maintained even if the load fluctuates due to the control structure based on the differential pressure between the load pressure and the pump differential pressure.

Conversely, when the supply pressure to the compensators 11 and 12 is reduced, the differential pressure at the throttle valves 9s and 10s is increased, that is, the throttle amounts of the throttle valves 9s and 10s are increased.
That is, the control valves 9 and 10 are controlled so as to increase their opening degrees, the amount of oil supplied to the actuators 5c and 6c increases, and the driving speed increases.

A second potentiometer 27 for detecting the rotational speed of the engine 19, an electromagnetic high-speed response valve 28,
Setting device 3 for variably adjusting the duty ratio of intermittent operation time
9 and a switch 40 for switching between an automatic control mode and a manual control mode are connected to the control device 26 so that the compensator 1
The partial pressures 1 and 12 are configured to be changed and set. That is, by changing the partial pressure, the throttle valves 9s, 1
The adjusting means B capable of changing and adjusting the opening of 0 s is configured. The adjusting means B intermittently energizes the electromagnetic high-speed response valve 28 which is urged to return to the high-pressure position a to the normal position b where the high-pressure oil path which is the discharge oil path of the hydraulic pump 8 is connected. It has a function of performing intermittent operation and intermittent control for variably setting the intermittent time.

The operation of the speed control means E will be described. First, the changeover switch 40 is operated to the automatic control mode to intermittently energize the electromagnetic high-speed response valve 28.
The energization time ratio in one cycle of the intermittent time, that is, the duty ratio is linked so as to decrease when the rotation speed of the engine 19 is low. Thus, if it is desired to reduce the turning speed during the excavation work, the engine speed may be reduced by operating the accelerator lever 24, and if it is desired to increase the driving speed, the engine speed may be increased. .

When it is desired to intentionally change the driving speed of the actuator, the changeover switch 40 is operated to a manual operation mode, and the second potentiometer 27 and the control device 2 are operated.
Disconnect with 6. Then, the duty ratio changes to the setting device 3
9, the supply pressure to the compensators 11, 12 can be set to an arbitrary value between the load pressure of the actuators 5c, 6c and the pump discharge pressure by the manual operation of the setting device 39. 5c, 8
The drive speed of c can be adjusted independently of the engine speed.

A dead zone is set in the accelerator control means C so that the stopped geared motor 22 starts to move when the second potentiometer 27 is displaced by a predetermined amount or more. That is, when the geared motor 22 stops at a certain position, the position is detected by the second potentiometer 27 and a holding current for maintaining the stop position of the governor lever 21 is supplied to the geared motor 22. The engine speed can be displayed as operated by the lever 24.

However, when the geared motor 22 slightly moves due to gear backlash, machine vibration, or the like, the detection value of the second potentiometer 27 changes, so that the detection value of the second potentiometer 27 is changed to the first potentiometer 25. The function of the accelerator control means C that matches the detected value of the above causes the geared motor 22 to be started in the reverse direction by the amount of movement, so that the engine speed fluctuates and the driving speed of the working device causes hunting. is there. For example, while the boom is being raised, hunting occurs in which the speed of the boom rises or falls, and it is difficult to operate the boom. In other words, the control for accurately displaying the engine speed according to the operation of the accelerator will rather induce hunting.

Referring to the graph of FIG. 4 showing the relationship between the position of the geared motor 22 (the operating position of the governor lever 21) and the supply current (holding current), the dead zone is provided as described above. If the geared motor 22 stops at the position α, a range of α1 to α is a range of a current value of ± 5% of the supply current value β at that time.
2 is set to the dead zone, so that even if the geared motor 22 moves
If it is within the range of .alpha.2, the feedback control will not operate, and the speed hunting of the working device due to the fluctuation of the engine speed will not occur. Although the slope of the relationship graph of FIG. 4 is downward-sloping, it may be downward-sloping.

That is, by adopting the E-compatible LS / S and the electric accelerator device, the technology can be operated lightly and the operation is easy, and the speed hunting of the actuator caused by its structure is set to the dead zone. This is resolved by The dead zone can be set by, for example, "two dead zones in each of the forward and reverse rotation directions from the stop position of the geared motor 22" or "3% of the entire lever swing range from the stop position of the governor lever 21". Angle
And the area moved to the high-speed side and the low-speed side. "

As shown in FIG. 3, a controller 41 is connected to the controller 26. This is because the driving speed of the front device (running, dozer, turning, etc.) may be different for each backhoe due to mechanical variations, so that the actuator speed fluctuation control accompanying the fluctuation of the engine speed,
That is, the reference point of the E corresponding LS / S is changed. That is, by operating the volume regulator 41 connected when the changeover switch 40 is switched to the automatic control mode, the drive speed of the front device at the time of the reference engine speed is the same at the time of shipment. It adjusts to become.

As a technique for adjusting the speed of the front apparatus, in addition to the means for adjusting each model as described above, the drive speed of a certain section (for example, a range of 45 degrees to the right from the front in turning) is controlled by a microcomputer. Self-correction circuit that automatically measures and automatically corrects the supply current (gain current) to the geared motor 22 so that it matches the design reference speed.
Means may be incorporated in the control device 26 in advance.

In the above-described embodiment, the hydraulic actuator is constituted by the boom cylinder 5c. However, the arm cylinder 6c, the traveling hydraulic motors 31, 33, the swing cylinder 36 and the like are also hydraulic actuators. It is good even in the case of. Further, the second potentiometer 27 may be configured to detect the position of the geared motor 22.

Incidentally, reference numerals are written in the claims for convenience of comparison with the drawings, but the present invention is not limited to the configuration of the attached drawings by the entry.

[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 partial hydraulic circuit diagram showing the principle of load sensing with auto idle.

FIG. 4 is a diagram showing a relationship graph between a position of a geared motor and a current.

[Explanation of symbols]

 5c Hydraulic actuator 8 Hydraulic pump 9 Control valve 9s Throttle valve 9p Hydraulic oil supply port 13 Flow rate adjusting mechanism 14t First oil path 15 Second oil path 20 Engine speed adjusting means 22 Electric actuator 24 Accelerator tool 25 First detecting means 27 Second detection means A Load control means B Adjustment means C Accelerator control means E Speed control means

Continued on the front page (72) Inventor Keiji Horii 64 Ishizukita-cho, Sakai-shi, Osaka Kubota Sakai Works (56) References JP-A-7-34489 (JP, A) JP-A 5-187406 (JP) JP-A-6-313326 (JP, A) JP-A-4-203502 (JP, A) JP-A-5-26068 (JP, A) JP-A-2-63114 (JP, U) (58) Field surveyed (Int.Cl. ⁷ , DB name) E02F 9/20-9/22 E02F 3/43 F15B 11/00 B60K 41/00-41/28

Claims (1)

(57) [Claims] 1. A hydraulic actuator (5c), a variable displacement hydraulic pump (8), and said actuator (5c).
c) a control valve (9) including a throttle valve (9s) for a pressure oil supply path to the pressure oil supply path, and a flow rate adjusting mechanism (13) for variably setting a discharge amount per unit time of the hydraulic pump (8). A first oil passage (14t) communicating with a lower portion of the pressure oil supply to the throttle valve (9s), and a second oil passage (15) communicating with a pressure oil supply port (9p) of the control valve (9). The flow control mechanism (1) maintains the pressure difference between
A first detecting means (25) for electrically detecting an operation amount of an accelerator operation tool (24) which is manually operated, comprising: a load control means (A) for operating 3); and an engine speed adjusting means (20). An electric actuator (22) for driving and operating the engine speed adjusting means (20) such that the electric actuator (22) is driven by an amount corresponding to the operation amount of the accelerator operation tool (24). An accelerator control means (C) for linking the second detection means (27) for detecting an operation amount, the first detection means (25), and the electric actuator (22) is provided, and a throttle of the throttle valve (9s) is provided. An adjusting means (B) for changing and adjusting the amount or the differential pressure is provided, and when the engine speed is increased, the driving speed of the hydraulic actuator (5c) is increased, and when the engine speed is decreased, the driving speed is reduced. As the driving speed of the pressure actuator (5c) is slow, the second
A speed control unit (E) for linking a detection unit (27) with the adjustment unit (B); and the accelerator control unit (C) is provided with a displacement of the second detection unit (27) by a predetermined amount or more. A hydraulic circuit of a construction machine in which a dead zone for setting the electric actuator (22) in a stopped state to start moving is set.