JPH0132361B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for a working machine that uses hydraulic pressure and is capable of automatically controlling the working machine.

[Conventional technology]

Various hydraulic working machines often require extremely complex and precise operations in order to make the machine perform the desired operation, making it difficult for operators to perform such operations. is often the case. For this reason, it has become possible to equip work machines with control devices to make them perform the desired operations, and to drive the work machines by selecting either manual operation or automatic control using this control device. It is normal that Such a device will be explained using a hydraulic excavator as an example.

FIG. 1 is a schematic system diagram of a conventional hydraulic excavator control device.

In the figure, 1 is a hydraulic pump, 2 is an actuator of a hydraulic excavator, for example, a bucket cylinder, and 3 is a directional control valve that guides pressure oil from the hydraulic pump 1 to the actuator 2 and drives the actuator 2. 3
Reference numerals a and 3b are pilot ports of the directional control valve 3, and the directional control valve 3 is switched from the illustrated neutral position N to the left position L or the right position R in accordance with the applied pilot pressure. 4 is a lever for manually operating the actuator 2, and 5 is a pilot valve that outputs pilot pressure in response to the operation of the operating lever 4. The pilot pressure of the pilot valve 5 is applied to the pilot ports 3a, 3b of the directional control valve 3.
Reference numeral 6 denotes a control calculator that calculates numerical values necessary for controlling the actuator 2 in order to cause the hydraulic excavator to perform a desired operation. This control calculator 6 will be described later. Reference numeral 7 denotes an electric/hydraulic conversion valve which inputs an electric signal _Ib corresponding to the value calculated by the control calculator 6 and outputs a pilot pressure corresponding to the electric signal Ib. 8 is the pilot pressure of the pilot valve 5 and the electrical
The higher pilot pressure of the hydraulic conversion valve 7 is transferred to the pilot port 3b of the directional control valve 3.
It is a shuttle valve added to the In addition, the directional control valve 3
An electric/hydraulic conversion valve 7 and a shuttle valve 8 are provided on the pilot port 3a side in the same manner as on the pilot port 3b side, but they are not shown.

Here, the control calculator 6 will be described. Hydraulic excavators are equipped with various control calculators depending on the content of the work, such as a control calculator for excavation locus control, a control calculator for bucket angle control, and the like. Among these, the control calculator for bucket angle control will be briefly explained. When raising the boom of a loading hydraulic excavator, it is necessary to keep the angle of the bucket from the horizontal plane, that is, the absolute angle, constant even while the boom is operating, in order to prevent earth and sand from falling. To do this, the bucket must be constantly operated appropriately in response to the operation of the boom, and such operation requires advanced technology and a great deal of effort. To deal with this, the absolute angle of the bucket can be automatically made constant without performing the bucket operation. For this purpose, a control calculator for bucket angle control is provided, which detects the respective angles of the front mechanism of the hydraulic excavator, that is, the boom, arm, and bucket, and depending on the angles of the boom and arm, This method calculates the buckett angle such that the absolute angle of the buckett is constant, and calculates the difference from the current buckett angle. Therefore, the output signal I _b of the control calculator 6 shown in FIG. 1 corresponds to this difference signal. In this case, the operating lever 4 corresponds to a bucket operating lever, and the actuator 2 corresponds to a bucket cylinder. In order to selectively perform both automatic control and manual operation by the control calculator 6 of the bucket, the signal I _b is generated when either the boom operating lever or the arm operating lever is in the operating position, and The output is made only when the bucket control lever is not in the operating position. In the following description, the case where the control calculator 6 is for bucket angle control will be exemplified and explained.

In FIG. 1, when manually driving the bucket, the operating lever 4 is operated. In this case, the signal
I _b is not output and the shuttle valve 8 is the pilot valve 5.
The pilot pressure is transmitted to the pilot port 3b of the directional control valve 3, and the directional control valve 3
The bucket cylinder 2 is operated by switching to the right side position R according to the amount of operation, and the bucket can be arbitrarily driven. On the other hand, when automatically controlling the bucket, the operating lever 4 is set to the neutral position, and when the boom or arm operating lever is operated, the difference signal I _b
is output from the control calculator 6. The electric/hydraulic conversion valve 7 outputs a pilot pressure according to the signal _Ib , and this pilot pressure is applied to the pilot port 3b of the directional control valve 3 via the shuttle valve 8, and the directional control valve 3 is controlled according to this pilot pressure. Then, the bucket cylinder 2 is operated by switching to the right position R, and the bucket is controlled so that the bucket always maintains a predetermined absolute angle. Control in the reverse direction is similarly performed via an electric/hydraulic conversion valve and a shuttle valve (not shown).

[Problem to be solved by the invention]

By the way, if the directional control valve 3 is in one direction (left side position L)
The flow rate characteristics in the direction (or right side position R direction) are as shown in FIG. That is, in FIG. 2, P is the pilot pressure applied to the directional control valve 3, and Q is the flow rate of the directional control valve 3. Pilot pressure P is pressure P ₁
When the pressure is lower, the directional valve 3 blocks the pressure oil from the hydraulic pump 1 and only allows the pressure oil to flow when the pressure is above _P1 . Thereafter, the flow rate Q of the pressure oil from the directional control valve 3 is proportional to the pilot pressure P. The area between pressure 0 and pressure P ₁ is a dead zone, and this dead zone is usually made as large as possible in order to reduce the leakage of pressure oil when the directional control valve 3 is in the neutral position. . In order to explain the relationship between the pilot pressure in this dead zone and the displacement of the operating lever 4, the characteristics of the pilot pressure with respect to lever displacement are shown in FIG.

In FIG. 3, the lever displacement X is plotted on the horizontal axis, and the pilot pressure P is plotted on the vertical axis. As can be seen from this figure, the pilot pressure _P1 shown in FIG. 2 is output when the lever displacement reaches the displacement _X1 . When the lever displacement is smaller than the displacement _X1 , the pilot pressure does not reach the pressure _P1 , so the directional control valve 3 cannot be switched. That is, the directional control valve 3 will not be switched even if the operating lever 4 moves very slightly from the neutral position. Theoretically, when the lever displacement is smaller than displacement X ₁ , the pilot pressure is 0,
It is sufficient that the pilot pressure _P1 is outputted from the pilot valve 5 when the displacement _X1 is reached. However, in reality, there is some time delay for the pilot pressure to reach the pressure P ₁ , and this has an unfavorable effect on the operating feeling, so the pilot pressure P ₀ is output at a displacement X ₀ that is smaller than the displacement X ₁ .
Usually, the design is such that the pilot pressure P ₁ is obtained immediately when the displacement X ₁ is reached.

Therefore, if we consider the control device shown in Fig. 1 on the premise that the directional control valve 3, the operating lever 4, and the pilot valve 5 have the characteristics shown in Figs. 2 and 3, if the operator of the hydraulic excavator If you touch the operating lever 4 and it moves beyond displacement X ₀ (displacement X ₀ is extremely small,
Moreover, such a situation often occurs during operation of a hydraulic excavator. ), pilot pressure from pilot valve 5
P _a (P ₀ ≦P _a <P ₁ ) will be output. now,
The bucket is automatically controlled, and the pilot pressure P _b corresponding to the signal I _b is applied from the electric/hydraulic conversion valve 7 to the pilot port 3 b of the directional control valve 3. In this state, the pilot pressure P is changed as described above. Suppose that _a is applied to the pilot port 3a of the directional control valve 3. As a result, the pilot pressure actually applied to the directional control valve 3 is the pressure P _b ′ (P _b ′ = P _b − P _a )
As a result, the flow rate of the directional control valve 3 does not become the required flow rate Q _b as shown in FIG. 4, but becomes a lower flow rate Q _b '. Such a situation occurs even more frequently when the operating lever 4 is a so-called joystick lever that operates different actuators by operating in a right angle direction. This will be explained with reference to FIG.

Fig. 5 is an operating diagram of the joystick lever, where 4 _J represents the joystick lever knob, and O represents the operator of the hydraulic excavator. The joystick lever 4 _J is in the neutral position as shown in the figure, and for example, by operating it in the directions of arrows A and B, it drives the bucket cylinder, and by operating it in the directions of arrows C and D, it drives the boom cylinder. It is assumed that it is familiar. Now, when the boom is operated by operating the lever _4J in the direction of arrow C, the control calculator 6 starts calculation at the same time and outputs the signal _Ib , and the corresponding pilot pressure _Pb is generated. do. In this case, if the lever _4J is not operated accurately in the direction of arrow C and the operator unconsciously operates it in the direction of arrow E, a slight component in the direction of arrow A will occur, so that the lever _4J will be moved by that amount. It is the same as if it were operated in the direction of arrow A, and pilot pressure is transferred from the pilot valve 5 to the pilot port 3a of the directional control valve 3.
P _a is added, which results in exactly the same result as above.

As mentioned above, with the conventional control device shown in Fig. 1, due to the driver's unconscious movement of the operating lever, large errors occur in the automatic control and the desired work cannot be achieved. When performing control that adds safety by preventing the falling of earth and sand, such as the example of bucket angle control, there is a drawback that there is a risk of a dangerous situation occurring.

SUMMARY OF THE INVENTION An object of the present invention is to provide a control device for a working machine that eliminates the above-mentioned conventional drawbacks and can accurately and automatically control a working machine without causing errors even if unexpected pilot pressure occurs. .

[Means to solve the problem]

In order to achieve the above object, the present invention provides a directional control valve that drives an actuator in response to pilot pressure applied to a pilot port, an operating section that generates a desired pilot pressure, and a control that controls the operation of the actuator. A control device for a working machine comprising: a control unit that generates a pilot pressure in accordance with a signal; and means for guiding a higher pressure of the pilot pressure of the operating unit and the control unit to the directional control valve. a detection device for detecting pilot pressure from the operating section applied to the switching valve; and a detection device for generating this pilot pressure when the operating section is not in a state of driving the directional switching valve and the pilot pressure is detected by the detection device. The present invention is characterized in that a correction means is provided for adding a signal that invalidates the detected pilot pressure to the control signal of the control unit for the pilot port on the opposite side.

[Effect]

When the pilot pressure is detected by the detection device,
This pilot pressure is converted into a signal proportional to it or a signal of a predetermined magnitude, and this converted signal is added to the control signal for the pilot port on the opposite side from the side where the detected pilot pressure is generated. Ru. As a result, the detected pilot pressure is almost completely canceled or substantially canceled, and accurate automatic control is achieved.

〔Example〕

The present invention will be explained below based on the embodiment shown in FIG.

In FIG. 6, parts that are the same as those in FIG. 1 are given the same reference numerals and explanations will be omitted. Note that, as in FIG. 1, the illustration of the electro-hydraulic conversion valve 7 and the shuttle valve 8 for the pilot port 3a of the directional control valve 3 is omitted. A pressure detector 9 detects the pilot pressure applied to the pilot port 3a of the directional control valve 3. The pressure detector 9 outputs a signal corresponding to the detected pressure, and this signal is input to the control calculator 10. A similar pressure detector 9 is used to detect the pilot pressure at the other pilot port 3b, but is not shown. 10 is a control calculator. The control calculator 10 in this embodiment differs from the control calculator 6 shown in FIG. 1 in that it has a function of correcting the control signal based on the signal from the pressure detector 9.

Next, the operation of this embodiment will be described in the case of the bucket angle control described above with reference to the flowchart shown in FIG.

The control calculator 10 first determines whether or not to automatically control the bucket angle (first step S ₁ ; hereinafter, each step will be expressed as S ₂ , S ₃ , etc.). As described above, this determination is made based on the operating states of the boom operating lever, arm operating lever, and bucket operating lever. If it is determined in step _S1 that automatic control is to be performed, a predetermined calculation is performed to calculate a control signal _Ib ( _S2 ). Next, it is checked whether the pilot pressure P _a is detected at the pilot port 3a of the directional control valve 3 by the pressure detector 9 (S ₃ ). If pilot pressure P _a is detected,
A signal I _a corresponding to this value is obtained, and this signal I _a is added to the control signal I _b calculated in step S ₂ to calculate a corrected control signal (I _b +I _a ) (S ₄ ). next,
This corrected signal (I _b + I _a ) is output (S ₅ ).
If it is determined in step _S3 that the pilot pressure P _a is not detected, the process moves to step _S5 and outputs the control signal I _b calculated in step _S2 . The output control signal is converted into a corresponding pilot pressure by the electric/hydraulic conversion valve 6 to drive the directional control valve 3 and control the bucket angle. In this way, when the operator unconsciously manipulates the control lever, the pilot pressure, which causes errors, can be reduced.
Even if P _a occurs, the control pressure will be P _b + P _a , so
The actual control pressure P _b ' becomes P _b '=P _b +P _a -P _a =P _b , and the drawback caused by the pilot pressure P _a is completely eliminated.

Note that during automatic control, if the displacement of the bucket control lever is greater than or equal to the displacement X ₁ shown in FIG. 3, it can be considered that the automatic control is stopped and a manual correction operation using the bucket control lever is performed. Therefore, the pressure to be removed that is subject to correction in this embodiment is exclusively the pressure shown in FIG.
It can be seen as P ₀ ~ P ₁ . So this pressure
Even if P ₀ to _{P 1} are represented by the pressure P ₀ (the above-mentioned pressure P _a is taken as the pressure P ₀ ) and the signal I ₀ corresponding to this pressure P ₀ is used as a correction signal (the above-mentioned signal I _a is used as the signal Even if I ₀ ), it can be sufficiently tolerated in practice.
In this case, the pressure detector 9 can be a simple pressure switch.

In this way, in this embodiment, the pilot pressure from the operating lever of the directional control valve is detected using a pressure detector, and the control signal calculated by the control calculator is corrected according to this pilot pressure. , accurate bucket angle control is possible, and there is no risk of dangers such as falling earth and sand.

In the above explanation, the case of controlling the bucket angle of a hydraulic excavator was particularly described, but the present invention is not limited to this, and it is natural that the present invention can be applied to various types of control in other working machines. be.

〔Effect of the invention〕

As described above, in the present invention, the pilot pressure from the operating part of the directional control valve is detected using a pressure detector, and the control signal of the control part is corrected according to this pilot pressure, so that the expected Even if the pilot pressure is generated, the working machine can be accurately controlled without malfunctioning, and especially in control that adds safety, the occurrence of danger can be prevented.

[Brief explanation of drawings]

Fig. 1 is a schematic system diagram of a conventional hydraulic excavator control device, Fig. 2 is a flow characteristic diagram of the directional control valve of the control device shown in Fig. 1, and Fig. 3 is a diagram showing the displacement of the operating lever shown in Fig. 1. Pilot pressure characteristic diagram, 4th
The figure is the same flow rate characteristic diagram as Figure 2, which explains changes in flow rate due to pilot pressure errors, Figure 5 is an explanatory diagram showing the operation of the joystick lever, and Figure 6 is a diagram of the hydraulic excavator according to the embodiment of the present invention. A schematic system diagram of the control device, FIG. 7 is a flowchart explaining the operation of the control device shown in FIG. 2... Actuator, 3... Directional switching valve, 4
...Operation lever, 5...Pilot valve, 7...Electric/hydraulic conversion valve, 8...Shuttle valve, 9...Pressure detector, 10...Control calculator.

Claims (1)

[Claims] 1. A directional control valve that drives an actuator in response to pilot pressure applied to a pilot port, an operating section that generates a desired pilot pressure, and a control section that generates pilot pressure in response to a control signal that controls the operation of the actuator. and means for guiding the higher pressure of the pilot pressure of the operating section and the control section to the directional switching valve, wherein the pilot pressure from the operating section that is applied to the directional switching valve is a detection device for detecting the directional control valve; 1. A control device for a working machine, comprising: a correction means for adding a signal that invalidates a detected pilot pressure to a control signal of a control section.