JPH0978633A - Running vibration limiting hydraulic circuit for wheel type construction machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a boom from falling down when the action of a running damper of a wheel type work machine is changed over. SOLUTION: A first on/off valve 22 is provided in a connection circuit 21 between the bottom side of a boom cylinder 13 and an accumulator 20, and a second on/off valve 26 and a pressure switch 28 are provided in a connection circuit 25 between a hydraulic pump 10 and the accumulator 20. During an excavation work, the first on/off valve 22 is closed and the second on/off valve 26 is opened. Oil of high pressure delivered from the hydraulic pump flows into the accumulator 20 and the pressure of the oil rises to a pressure determined by the pressure switch 28. During running, the valve 22 is opened and the valve 26 is closed so that the bottom side of the cylinder 13 is brought into communication with the accumulator 20 to prevent a boom from falling down.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a traveling vibration suppressing hydraulic circuit for a wheel type construction machine, and more particularly, to a traveling vibration suppressing hydraulic circuit for preventing a boom from falling when switching a traveling damper operation.

[0002]

2. Description of the Related Art FIG. 3 is a side view of a wheel type tractor excavator. A boom 2 is rotatably mounted by a pin 3 in front of a body 1 of a vehicle. It is connected. A bucket 5 is rotatably attached to the tip of the boom 2 by a pin 6, and the boom 2 and the bucket 5 are connected by a bucket cylinder 7 via a link 8. When the boom cylinder 4 expands and contracts, the boom 2 rotates about the pin 3, and when the bucket cylinder 7 expands and contracts, the bucket 5 rotates about the pin 6.

In the above wheel type tractor shovel, the working device projects forward from the front axle, the weight ratio is large, and the axle is non-buffering type and is entirely supported by rubber tires. Therefore, when traveling on an uneven road surface, the vehicle body is likely to generate vertical vibration. And as the vehicle speed increases, the vibration becomes more intense. In order to absorb the vibration energy at this time and damp the vibration, a traveling damper has been conventionally used. That is, the load side oil chamber of the boom cylinder 4 that supports the boom 2 and the vibration suppressing accumulator are openably and closably connected via the switching valve, and are connected to the load side oil chamber of the hydraulic cylinder only during traveling in which vibration occurs. It was in communication with the accumulator to suppress vibration.

However, in the above structure, there is a problem that the boom temporarily drops when the work device is loaded with the accumulator having a low accumulated pressure and communicates with the load side oil chamber of the boom cylinder having a high hydraulic pressure.

As an example of measures for solving the problem, there is a boom fall prevention device of a traveling vibration suppressing device (traveling damper) shown in the hydraulic circuit diagram of FIG. The discharged oil from the working machine hydraulic pump 50 is connected to the boom cylinder 53 and the bucket cylinder 54 via the working machine operation valve 52. An opening / closing valve 58 is arranged between the bottom side of the boom cylinder 53 and the vibration suppressing accumulator 55. In a normal state, the open / close valve 58 is in the (b) position, and shuts off the bottom side of the boom cylinder 53 and the vibration suppressing accumulator 55. When the traveling vibration suppressing device (traveling damper) is operated during traveling, the open / close valve 58 is switched to the (a) position by a signal from a command device (not shown).
At the position (a), the circuit 56 connecting the bottom side of the boom cylinder 53 and the vibration suppressing accumulator 55, and the circuit 57 from the vibration suppressing accumulator 55 are connected via the opening / closing valve 58 having the open / close two positions. In addition, the head side of the boom cylinder 53 and the oil tank 51 are
A circuit 60 for connecting to and a circuit 61 to the oil tank 51 are connected via an on-off valve 58.

In the above description, the on-off valve 58 is adapted to switch in response to the vehicle speed, and at a predetermined speed (for example, 6 km / h) or less, it is in the closed position at the (b) position and exceeds the predetermined speed. And it becomes the open position at position (a). The normal filling pressure of the accumulator 55 is a pressure corresponding to the hydraulic pressure generated on the bottom side of the boom cylinder 53 when the bucket is empty. The filling circuit 62 connected to the discharge port of the hydraulic pump 50 includes a pressure reducing valve 63 and a filling circuit 64.
Is connected to the accumulator 55 via a check valve 65 on the filling circuit 64. Pressure reducing valve 6
3 and the oil tank 51 are connected by a return circuit 66. The pressure reducing valve 63 is adjusted to a limit pressure corresponding to a supporting pressure generated on the bottom side of the boom cylinder 53 when a load is loaded on a bucket and the boom is lifted.

[0007] When the vehicle is initially started, the discharge pressure of the hydraulic pump 50 is low, and therefore the accumulator 5
The filling pressure of 5 is also low. The bucket runs with no load,
When the vehicle speed exceeds a predetermined speed, the opening / closing valve 58 is switched to the position (a), the circuit is opened, and the bottom side of the boom cylinder 53 and the accumulator 55 communicate with each other. At this time, since the hydraulic pressure on the bottom side of the boom cylinder 53 is lower than the filling pressure of the accumulator 55, the boom cylinder does not drop. In this state, the accumulator 55 exerts a vibration suppressing function.

When the vehicle is excavating, the vehicle speed decreases, so the on-off valve 58 is in the (b) position and the circuit is closed. At this time, when the work implement operation valve 52 is operated to start the excavation work, the discharge pressure of the hydraulic pump 50 rises. This pressure is higher than the above limit pressure, but the filling pressure of the accumulator 55 is the limit pressure adjusted by the pressure reducing valve 61. The pressure oil in the filling circuit 64 does not flow back to the tank 51 by the check valve 65.

When excavation and loading are completed, the work machine operation valve 5
The vehicle is run with the holding position of 2. When the traveling speed reaches a predetermined speed, the opening / closing valve 58 is switched to the position (a) and opened. The bottom side of the boom cylinder 53 and the accumulator 55 communicate with each other, and the traveling damper is activated (ON). Hereinafter, when the traveling damper is in the operating state, it is referred to as traveling damper ON, and when the traveling damper is not in the operating state, it is referred to as traveling damper OFF. At this time, the support pressure on the bottom side of the boom cylinder 53 and the limit pressure of the accumulator 55 are substantially equal to each other, so that the boom does not drop.

[0010]

However, in the above configuration, the traveling damper is ON when the bucket is empty, the vehicle speed exceeds a predetermined speed, and the opening / closing valve is opened (a position).
In this state, for example, when the bucket is operated, the discharge pressure of the hydraulic pump rises to the set pressure of the pressure regulating valve (not shown), the set pressure is reduced, and reaches the accumulator via the check valve. This reduced pressure acts on the bottom side of the boom cylinder 53 from the opening (a position) of the open / close valve through the circuit 56 to raise the boom.

The present invention has been made in view of the above problems. The boom does not drop when the traveling damper is turned on, and even if the bucket is operated while traveling with the traveling damper on. An object of the present invention is to provide a hydraulic circuit for suppressing traveling vibration of a wheel-type construction machine in which the boom is not displaced.

[0012]

In order to achieve the above object, in a traveling vibration suppressing hydraulic circuit for a wheeled construction machine according to the present invention, a base end of a boom of a working machine is mounted on a vehicle body of the wheeled construction machine. Part is rotatably mounted, and the load side oil chamber of the hydraulic cylinder that receives the pressure oil from the hydraulic pump for operating the work machine and rotatably operates the boom and the accumulator for vibration suppression are connected to the first opening / closing valve. In a traveling vibration suppressing hydraulic circuit of a wheel-type construction machine connected via a traveling damper control switch for switching the first on-off valve, a working machine actuating hydraulic pump, and an accumulator connected circuit. Two on-off valves, a pressure switch provided on the connection circuit between the accumulator and the second on-off valve, and the first on-off valve are communicated with each other when the traveling damper changeover switch is turned on. When the travel damper selector switch is turned off, the first on-off valve is shut off, and when the hydraulic pressure applied to the pressure switch is below a predetermined pressure, the second on-off valve is opened. And a controller that outputs a command signal to cause the command.

[0013]

With the above-mentioned structure, the traveling damper OF
When the filling pressure of the accumulator is equal to or lower than the predetermined pressure at F, the second opening / closing valve is opened to increase the filling pressure to the predetermined pressure. Therefore, the boom will not drop when the traveling damper is switched on with the load applied to the boom and the hydraulic cylinder bottom side and the accumulator are in communication. Further, since the second opening / closing valve is closed when the traveling damper is ON, the boom does not rise even if the bucket is operated.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a traveling vibration suppressing hydraulic circuit for a wheel-type construction machine according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a hydraulic circuit diagram for suppressing traveling vibration of a wheel-type construction machine. The discharge circuit 11 of the working machine hydraulic pump 10 is connected to the boom cylinder 13 and the bucket cylinder 14 via the working machine operation valve 12. On the circuit 21 connecting the vibration suppressing accumulator 20 and the bottom side 13a of the boom cylinder 13, there is an electromagnetic first on-off valve 2 having two positions, an open (a position) and a closed (b position).
2 is provided, and a solenoid valve 24 having two positions, an open (a position) and a closed (b position), is provided on a circuit 23 connecting the head side 13b of the boom cylinder 13 and the oil tank 15. ing. The filling pressure of the accumulator 20 is normally set to a pressure substantially corresponding to the hydraulic pressure generated on the bottom side 13a of the boom cylinder 13 when the bucket 5 (shown in FIG. 3) is empty. A check valve 24a is provided inside the solenoid valve 24 at the open position (a position).

On the circuit 25 branching from the discharge circuit 11 of the hydraulic pump 10 and connected to the accumulator 20, there is provided an electromagnetic second on-off valve 26 having two positions, an open (a position) and a closed (b position). The second accumulator 20 and the second
A pressure switch 28 is provided between the on-off valve 26 and the on-off valve 26. The pressure switch 28 is set to a predetermined set pressure Po (for example, 70 kg / cm ² ). The predetermined set pressure Po is substantially equal to the pressure generated on the bottom side of the boom cylinder 13 when a load is loaded on the bucket. Second
A check valve 26a is internally provided on the open (a position) side of the on-off valve 26. The main monitor 30 is provided with a traveling damper operation changeover switch 31 and is connected to the controller 34. Further, the controller 34 uses the shift control switch 3
2, vehicle speed sensor 33, first opening / closing valve 22, second opening / closing valve 2
6, pressure switch 28, and solenoid valve 24, respectively.

Next, the operation of the traveling damper will be described with reference to the traveling vibration suppressing hydraulic circuit diagram of FIG. 1 and the traveling damper operation table of FIG.

At the beginning of starting the vehicle, the traveling damper is off, the discharge pressure Pp of the hydraulic pump 10 (hereinafter referred to as pump discharge pressure Pp) is low, and the filling pressure Pa filling the accumulator 20 is also low. The controller 34 is
The signal from the pressure switch 28 is received and the filling pressure Pa is compared with a predetermined set pressure Po. When the vehicle is started, it is determined that the filling pressure Pa <the predetermined set pressure Po, and the second opening / closing valve 26 is set to the (a) position to be opened. As a result, the accumulator 20 becomes the pump discharge pressure P.
The filling pressure Pa increases as the pressure is increased to p. For example, when the working machine operation valve 12 is operated to raise the bucket 5 via the boom cylinder 13 for traveling, the hydraulic pump 10 generates a pressure necessary to raise the working machine, and the pump discharge pressure Pp is generated. As a result, the accumulator 20 is filled, and the filling pressure Pa rises to the pressure required to hold the bucket 5.

When the vehicle starts traveling, the operator operates the traveling damper operation changeover switch 31 of the main monitor 30 to turn on the traveling damper, and when the traveling speed exceeds a predetermined speed (for example, 6 km / h), the vehicle speed sensor 33 detects it. Upon receiving the signal, the controller 34 sends a command signal to open the first opening / closing valve 22 (position A), closes the second opening / closing valve 26 (position B), and opens the solenoid valve 24 (position A). . Then, the bottom side 13a of the boom cylinder 13 communicates with the accumulator 20, and the head side 1 of the boom cylinder 13
Since 3b and the oil tank 15 communicate with each other, the accumulator 20 exhibits a vibration suppressing function. At this time, since the hydraulic pressure on the bottom side 13a of the boom cylinder 13 and the filling pressure Pa of the accumulator 20 are substantially equal to each other, the boom cylinder 13 does not drop.

When the vehicle arrives at the work site and starts excavation work, the operator operates the travel damper operation changeover switch 31 to turn off the travel damper. The first opening / closing valve 22 is closed (position B) in response to a command from the controller 34, and the controller 34 receives a signal from the pressure switch 28 and compares the pump discharge pressure Pp with a predetermined set pressure Po. At this time, if the pump discharge pressure Pp is lower than the predetermined set pressure Po, the controller 3
4 sends a command for opening (a position) to the second opening / closing valve 26, and sends a command for closing (b position) to the solenoid valve 24. As a result, the pump discharge pressure Pp fills the accumulator 20 and raises the filling pressure Pa to a predetermined set pressure Po that is initially set. For example, when the excavation work is started at this time, the pump discharge pressure Pp of the hydraulic pump 10 increases. Therefore, the pressure oil is supplied to the check valve 26a of the second opening / closing valve 26 and the circuit 2
It flows into the accumulator 20 via 5 and raises a filling pressure. When the filling pressure rises and the filling pressure Pa filled in the accumulator 20 becomes equal to or more than the set pressure Po, the controller 34 receives the signal from the pressure switch 28 to close the second opening / closing valve 26 (position B), and the accumulator 20.
The inflow of pressure oil to the machine stops.

When the excavation and loading work is completed and the vehicle starts traveling, the operator turns on the traveling damper operation changeover switch 31. When the vehicle speed exceeds a predetermined speed, the speed sensor 33 sends a signal to the controller 34, and the controller 34 sends a command signal to open the first opening / closing valve 22 (a position) and the second opening / closing valve 26 remains closed. To The solenoid valve 24 is opened (a position). Therefore, the bottom side 13a of the boom cylinder 13 and the accumulator 20 communicate with each other. Since the pressures of the two are substantially equal as described above, the boom 2 does not drop when the traveling damper is switched on.

Since the second opening / closing valve 26 is closed,
The boom 2 does not rise even if the bucket is operated.

[0022]

Since the present invention is configured as described in detail above, the hydraulic pressure on the side of the boom cylinder bottom and the filling pressure of the accumulator can be made substantially equal both when the bucket is empty and when it is loaded. Therefore, the boom does not drop when the travel damper operation is switched, and the circuit between the hydraulic pump and the accumulator is shut off while the travel damper is operating, so that the boom does not rise even if the bucket is operated. A machine vibration suppressing device is obtained.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram for suppressing traveling vibration of a wheeled construction machine according to the present invention.

FIG. 2 is a traveling damper operation table for explaining the operation of the traveling vibration suppressing hydraulic circuit of the wheeled construction machine of the present invention.

FIG. 3 is a side view of a wheeled tractor shovel.

FIG. 4 is a hydraulic circuit diagram showing an example of a conventional boom fall prevention device.

[Explanation of symbols]

 10 hydraulic pump 12 working machine operation valve 13 boom cylinder 14 bucket cylinder 20 accumulator 22 first opening / closing valve 24 solenoid valve 26 second opening / closing valve 26a check valve 28 pressure switch 30 main monitor 31 traveling damper operation changeover switch 33 vehicle speed sensor 34 controller

Claims (1)

[Claims] 1. A basal end of a boom of a working machine is rotatably mounted on a vehicle body of a wheel-type construction machine, and the boom is rotatably operated by receiving pressure oil from a hydraulic pump for operating the working machine. In a traveling vibration suppressing hydraulic circuit of a wheel-type construction machine in which a load side oil chamber of a hydraulic cylinder and an accumulator for suppressing vibration are connected via a first opening / closing valve, a traveling damper changeover switch for switching the first opening / closing valve, A second opening / closing valve provided on a connection circuit between the working machine operating hydraulic pump and the accumulator; a pressure switch provided on a connection circuit between the accumulator and the second opening / closing valve; and the traveling damper switching When the switch is turned on, the first on-off valve is communicated with and the second on-off valve is shut off; when the travel damper changeover switch is turned off, the first on-off valve is shut off, and A traveling vibration suppressing hydraulic circuit for a wheeled construction machine, comprising: a controller that outputs a command signal for communicating the second opening / closing valve when the hydraulic pressure applied to the pressure switch is equal to or lower than a predetermined pressure.