JP2514915B2 - Floor circuit for construction machine boom - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boom circuit for a boom of a hydraulic excavator among construction machines.

2. Description of the Related Art FIG. 5 is a side view of a hydraulic excavator in a construction machine. In the figure, 1 is a lower traveling body of a hydraulic excavator, 2 is an upper swing body, 3 is a work attachment mounted on the front portion of the upper swing body 2, 4 is a boom of the work attachment 3, 5 is a boom cylinder, 6 is an arm, 7 is a bucket. FIG. 6 is a circuit diagram of essential parts of the hydraulic excavator. In the figure, 8 is a directional switching valve of the boom cylinder 5, 9 and 10 are pilot pressure receiving portions of the directional switching valve 8, 11 is a remote control valve, and 12 is a main pump. The operation lever 14 of the remote control valve 11 is tilted to the (a) position or the (b) position direction. As a result, the pilot pressure from the pilot pump 13 acts on the pilot pressure receiving portion 9 or 10 of the directional control valve 8 via the oil passage 15, the pilot valve 16 or 17 of the remote control valve 11, and the oil passage 18 or 19. The direction switching valve 8 is switched and the pressure oil from the main pump 12 is supplied to the boom cylinder 5 via the operation circuits 20 and 21.

FIG. 7 is a circuit diagram of essential parts of a wheel loader (not shown) of the work vehicle. In the figure, 22 is a boom cylinder of the wheel loader, 23 is a control valve of the boom cylinder 22, 24 is an operating lever of the control valve 23, 25 is a detent coil, (c) is the neutral oil passage position of the control valve 23, and ) Is an ascending oil passage position, (e) is a descending oil passage position, and (f) is a float oil passage position. When performing snow removal work or back dozer work with the wheel loader, the control valve 23 is switched to the float oil passage position (f) to perform the work.

Problems to be Solved by the Invention When performing earthmoving work with a hydraulic excavator, if the boom can be floated, the excavator can be run to perform earthmoving work like a bulldozer. Further, in the above case, the leveling can be performed by stopping the traveling of the hydraulic excavator and performing the operation of retracting the arm.

However, in a hydraulic excavator, the operating angle of the boom arm is large, and therefore each cylinder is often operated in multiple motions. Moreover, as a general means for controlling the switching of the directional control valve for the boom, the operating lever of the remote control valve is used. It is designed to tilt. Therefore, if the float oil passage position is provided in the boom directional control valve, it may cause an erroneous operation. Therefore, the float oil passage position could not be provided in the boom directional control valve.

In order to solve the above problems, it is an object of the present invention to provide a boom float circuit that allows a boom of a hydraulic excavator to float in a float state that allows easy and reliable repeated operation.

Means for Solving the Problems This invention has taken the following means in order to solve the above problems. That is, a. A hydraulic excavator in which a work tool is provided at the tip of the arm, and the base end of the boom that pivotally supports the arm at the tip of the boom is pivotally attached to the front part of the upper swing body through a boom cylinder so as to be vertically rotatable. In the boom cylinder operating circuit, b. A switching valve with a float oil passage position, which is provided with an oil passage that interconnects two hydraulic operating circuits that communicate the boom cylinder and the direction switching valve thereof, and is provided with a cutoff oil passage position and a float oil passage in the oil passage. To provide.

C. The float oil passage position switching valve is normally in a position to shut off the oil passage, but it is switched when a signal from the outside acts on the receiving portion, and the float oil passage connects the two hydraulic operating circuits to the tank circuit. A switching valve with a float oil passage position for forming the passage position; and d. A signal from an electric signal switching means for generating a signal using pilot oil pressure or electricity as a medium is guided to the receiving portion of the float position directional control valve.

E. Further, an electric circuit communicating with the output section of the electric signal switching means and the power source is provided, and In the middle of the electric circuit, a manual contact type switch and a manual operation automatic return contact type switch are electrically arranged in series as opening / closing means which can be arbitrarily and easily operated by a driver.

Action a. When a signal from the electric signal switching means is not input to the receiving part of the switching valve with float position, that is, even when the opening / closing means in the electric circuit leading to the power source is open or the means is closed, manual operation is automatically performed. When the return contact type switch is not operated, the switching valve with float position is in the shutoff oil passage position, so that the boom cylinder is independent of the pipe passage leading to each oil chamber, as in the normal backhoe work. Does not float.

B. On the other hand, depending on the work content of the backhoe illustrated above, when the boom cylinder is in a floating state and the self-weight of the work device supported by the cylinder is used to finish the grounding surface of the work tool, or When the tool is raised to a predetermined height and then repeatedly dropped to perform pile driving, rolling compaction, etc., the opening / closing means in the power circuit is opened / closed, or the opening / closing means is closed. Since it is only necessary to close the manual operation automatic return contact type switch whenever necessary, the operation for such work is easy and reliable.

EXAMPLES Examples of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a hydraulic tilting diagram showing the basic concept of the boom float circuit according to the present invention, and the same components as those described in the section of the prior art are designated by the same reference numerals. Reference numeral 26 indicates a switching valve with float oil passage position. Next, the basic configuration and function of the float circuit according to the present invention will be described below.
Referring to FIG. In the operating circuits 20 and 21 that connect the boom cylinder 5 and the direction switching valve 8 to each other,
A switching valve 26 with a float oil passage position is provided in the middle of the oil passage communicating with the boom cylinder 5 when the switching valve 26 with the float oil passage position is in the cutoff oil passage position (G). In that state, the function is the same as that of the conventional hydraulic excavator since it does not float. However, when the switching valve 26 is switched from the shutoff oil passage position (G) to the float oil passage position (H), the two operating circuits leading to the oil chamber of the boom cylinder 5 both communicate with the tank, and the boom cylinder 5 is Float. Therefore, when performing the earthmoving work or the like using the bottom surface of the bucket of the hydraulic excavator, the work can be easily performed without applying an extra pressing force by the cylinder.

FIG. 2 is a float circuit diagram of an embodiment according to the present invention, in which the basic concept of FIG. 1 can be more specifically and easily operated. In the figure, 27 is a solenoid valve with a float oil passage position, (i) is a shutoff oil passage position of the solenoid valve 27, (n) is a float oil passage position, 28 is a solenoid of the solenoid valve 27, 29 is an electric circuit, 30 is A manual contact switch in the electric circuit 29 and a power source 31. The solenoid valve 27 with the float oil passage position normally holds the (i) position, but when the manual contact switch 30 is turned on, the shutoff oil passage position (li) is switched to the float oil passage position (n). Instead, the function thereof is the same as that of the switching valve 26. Instead of the solenoid valve 27, it is also possible to replace it with a pilot valve with a float oil passage position, which is operated by switching the pilot pressure as described in FIG.

FIG. 3 is a boom float circuit diagram showing another embodiment according to the present invention. In the figure, the same reference numerals are given to those using the same constituent elements as the elements in the float circuit in FIGS. 1 and 2 of the embodiment. 32 is an electric circuit, and 33 is a manually operated automatic return contact switch. Next, the configuration and function of the float circuit according to this embodiment will be described with reference to FIG. A manual contact type switch 30 and a manual operation automatic return contact type switch 33 (hereinafter referred to as return contact type switch 33) are connected in series to an electric circuit 32 for switching and operating the solenoid valve 27 with the float oil passage position. did. Therefore, the manual contact switch 30 in the electric circuit 32
Is off, the solenoid valve 27 is in the shutoff oil passage position (re), the solenoid 28 is not excited even if the return contact type switch 33 is turned on, and the solenoid valve 27 with float position is ) The boom cylinder 5 does not float because it holds the position. However, with the above-mentioned manual contact type switch 30 in the ON state,
When 33 is turned on, the solenoid valve 27 with a float position is switched to the (n) position and the boom cylinder 5 is floated only while the return contact switch 33 is turned on. Therefore, after operating only the manual contact switch 30 to the ON state, the boom direction switching valve 8 is switched to the boom raising oil passage position (L) to raise the boom, and the bucket at the tip of the work attachment reaches the required height. When rising, the return contact switch 33 is turned on. At this time, since the boom cylinder 5 is in a floating state, the bucket will fall freely with the boom. Therefore, if the manual contact switch 30 is turned on as described above, regardless of whether the boom direction switching valve 8 is in the boom up oil passage position (L) or not,
If the return contact switch 33 is turned on and off in consideration of the required timing, it is possible to perform compaction work such as the ground by the bucket falling from the height of the ground at that time and piling work.

FIG. 4 is a float circuit diagram of still another embodiment according to the present invention. In the figure, 34 is a pilot valve with float oil passage position, 35 is a pilot pressure receiving part of the pilot valve 34, 36 is an electromagnetic switching valve, 37 is a solenoid of the electromagnetic switching valve 36, 32 'is an electric circuit, 30 is a manual contact type. A switch and 33 are reset contact type switches. Circuit diagram of this embodiment (Fig. 4)
Is different from the embodiment shown in FIG. 3 in that the pilot valve 34 is used as the switching valve with float oil passage position and the pilot valve 34 is used for the switching operation, and the pilot pressure receiving portion 37 is operated by the pilot valve 34. The point is that the pressure can be controlled by the electromagnetic switching valve 36. The construction of the electric circuit 32 'for switching the electromagnetic switching valve 36 is the same as that of the embodiment (FIG. 3).
The electric circuit 32 of FIG. The function of the boom float circuit is also the same as that of the above-described embodiment (FIG. 3).

EFFECTS OF THE INVENTION In a machine similar to a hydraulic excavator provided with a boom circuit for a boom of a construction machine according to the present invention, when a work is performed by switching a switching valve with a float position to a cutoff oil passage position, an original operating function is exerted. Needless to say, if the switching valve is operated to close the electric signal circuit according to the driver's intention, the switching valve with the float position switches to the float oil passage position. Instead, the work tool always receives a downward force toward the ground, which does not exceed a certain value corresponding to the weight of the work front of the machine.
It is easy to perform leveling work similar to a tractor system machine such as a bulldozer by running the machine, and even when performing the leveling work by stopping the machine and retracting the arm, it does not matter to the attitude of the work attachment. A force corresponding to the weight of the work attachment acts on the work tool in the same manner as above.

In addition, there is a manual contact switch and a manual operation automatic return contact switch in the electrical circuit that normally or indirectly switches the switching valve with float oil passage position that is in the shutoff oil passage position to the float oil passage position. Since they have a circuit configuration in which they are arranged in series, when both of these switches or one of them is in the open state, a normal boom operation circuit is formed and the original function is exhibited. Only when the circuit is closed, the switching valve with the float oil passage position is switched to the float oil passage position, and as described above, the boom cylinder is in the float state and the leveling work can be easily performed, as described above. On the other hand, the manual contact type switch on the electric signal circuit is closed by the driver's intention while the work attachment is raised to a predetermined height, and then the manual operation automatic return contact type switch is closed to operate, for example, a bucket. It is possible to perform compacting work such as the ground and piling work by repeating dropping the car, and unless the driver intentionally operates the two switches, keep pressing the manual operation automatic return contact type switch. Since the switching valve with float position cannot hold the float position only when it is present, no erroneous operation occurs.

As described above, in the construction machine equipped with the float circuit according to the present invention, the boom cylinder can be floated as needed or repeatedly according to the driver's intention. It is effective in improving the work function of construction machinery, expanding the range of support for various work types, and preventing erroneous operations.

[Brief description of drawings]

FIG. 1 is a hydraulic system diagram showing the basic concept of a boom float circuit according to the present invention, FIG. 2 is a float circuit diagram showing one embodiment of the present invention, and FIG. 3 is a float showing another embodiment of the present invention. Circuit diagram, FIG. 4 is a float circuit diagram showing a modified embodiment of the switching means of FIG. 3, FIG. 5 is a side view of the hydraulic excavator, FIG. 6 is a circuit diagram of essential parts of the hydraulic excavator, and FIG. 7 is a wheel. It is a principal part circuit diagram of a loader. 4 …… Boom 5,22 …… Boom cylinder 8 …… Direction switching valve 20,21 …… Operating circuit 26 …… Switching valve with float oil passage position 27 …… Solenoid valve with float oil passage position 29,32,32 ′ ...... Electrical circuit 30 ...... Manual contact type switch 33 ...... Manual operation Automatic return contact type switch 34 ...... Pilot valve with float oil passage position

Claims (2)

(57) [Claims] 1. A construction in which a work attachment including an arm having a work tool at a tip thereof and a boom holding the arm is provided on a front portion of an upper swing body, and the boom is pivotally mounted by a boom cylinder. In the machine, an oil passage is provided to connect two operation circuits that independently communicate the two oil chambers of the boom cylinder and the directional switching valve for operating the cylinder, and the oil passage is normally provided in the middle of the oil passage. And a float oil passage position switching valve that connects the front and rear oil passages to the tank circuit when a signal from the outside acts on the receiving portion. , Remotely supply switching operation signal to the receiving part of the valve.
An electric signal circuit which can be cut off, and an electric signal circuit arranged in the middle of the electric signal circuit and electrically arranged in series by the driver,
And a manually operated automatic return contact type switch for closing the internal circuit only while applying an operating force, and a manual contact type switch for opening and closing the circuit which is easily operated. Float circuit for boom frome. 2. A receiving part of the switching valve with float oil passage position according to claim 1 is provided with a switching signal via a hydraulic pilot valve and is supplied to the receiving part of the hydraulic pilot valve. The float circuit for a boom of a construction machine according to claim (1), characterized in that an electric signal circuit is provided.