JPH0449336A - Pressure controller for working machine - Google Patents

Abstract

PURPOSE:To cut down the consumption of electric power by a method which the working pressure of an actuator is controlled by a solenoid regulating valve consisting of a valve seat, a poppet, a pressure-setting spring, and a proportion solenoid to generate magnetic force corresponding to current. CONSTITUTION:A solenoid control valve to control working pressures consists of an inlet port 61, a valve chamber 62, a valve seat 64, a poppet 70, a pressure- setting spring 71, and a solenoid 80 for regulating set pressures. The solenoid 80 is a proportion solenoid to generate magnetic forces corresponding to current. Pressure oil from the port 60 is sent through the peripheral groove 65 of the seat 64 to the valve port 67, the poppet 70 is retracted backwards, and when the pressure reaches more than the valve port-closing force of the poppet 70, current flows in the coil 83 of the solenoid 80 to generate magnetic forces, where the magnetic force is relieved to the outlet port 63 to control the pressure on the inlet side. Energy-saving effect can thus be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pressure control device for working machines such as hydraulic excavators and hydraulic cranes.

[Conventional technology]

Conventionally, this type of working machine is constructed by attaching a front attachment to a Heas machine consisting of a lower traveling body and an upper revolving body. For example, in the case of a hydraulic excavator, the standard front attachment consists of a boom, arm, and packet, but depending on the purpose of the work, other attachments such as a long arm, attachments for building demolition, and breakers can be attached. Here, if a specific front attachment/nuclement is installed, will there be any problems during normal work? For example, if unreasonable force is applied to a specific structure such as a boom when the arm is fully extended. There is. In such cases, it is necessary to lower the circuit pressure of the actuator for operating the particular structure in question, such as the boom. As described above, depending on the type of front attachment, for example, in order to set the output to a desired value, it may be necessary to change the pressure of a specific circuit from the standard specification pressure to a desired pressure.

Therefore, the actuator circuit for operating each front attachment is provided with an overload relief valve that sets the circuit pressure, and in order to change the set pressure of the overload relief valve, for example, a port relief valve is added to the overload relief valve. , and adjust the set pressure with an adjustment spring, or
As shown in Publication No. 7-199283, a high pressure relief valve and a low pressure relief valve are switchably connected to the pilot pipe of the overload relief valve via a pair of electromagnetic switching valves, and the switching of the electromagnetic switching valves is performed. There are two known methods: a method of changing the set pressure by using an electromagnetic proportional relief valve, and a method of adjusting the set pressure by using an electromagnetic proportional relief valve and sending an electric signal to the electromagnetic proportional relief valve.

[Problem to be solved by the invention]

In the conventional method described above, in which a port relief valve whose set pressure is adjusted with an adjustment spring is used as an overload relief valve, the adjustment spring must be manually adjusted every time the front attachment is replaced. First, in this case, the main control valve, including the port relief valve, is installed inside the base machine, making it difficult to work on it, and it is necessary to make adjustments while measuring the pressure, making the adjustment work very time-consuming. It's complicated.

Furthermore, as shown in Japanese Utility Model Application No. 57-199283, in a method in which two relief valves with different set pressures are selectively connected to the pilot line of an overload relief valve to switch the set pressure, for example, If you want to switch the pressure in two ways, you will need one or two electromagnetic switching valves, one for high pressure and one for low pressure, for one overload relief valve.
In addition, in order to switch the set pressure in three ways, one to three electromagnetic switching valves and three relief valves for high pressure, medium pressure, and low pressure are required. A number of electromagnetic switching valves and relief valves are required depending on the number of changes in the set pressure, which is disadvantageous in terms of cost and installation space.

Note that if an electromagnetic proportional relief valve is used as an overload relief valve, the number of valves can be reduced, but in a conventional electromagnetic proportional relief valve, when the current input to it is 0, the set pressure is 0, and the current is Since the set pressure increases as the pressure increases, for example, set the set pressure to the lowest value (200k
g/cd) and the highest value (315kg/al), the input current is a certain value (0.6A)
The set pressure is set to the lowest value until the current reaches the above value (0.6A
), the set pressure increases as the current increases, and when the current value is at its maximum (0.8 A), the set pressure reaches its maximum value (
315kg/aIr).

Furthermore, in this case, in the normal design of hydraulic excavators, it is common sense to determine the pressure resistance value of hydraulic equipment by considering the balance of each circuit pressure when using the standard front attachment and the standard specification. When using the front attachment, the set pressure of the relief valve above is at its maximum value (3
15kg/car), and when a special front attachment is installed, the set pressure is set to the minimum value (200kg/car).
m). Then, when the usage is frequently used, the maximum current (0.8A) is passed through the relief valve and the maximum power (0.8Ax
24V=19.2W/unit), and when the device is used infrequently, a low current is passed or no current is passed, resulting in wasted power consumption.

The present invention solves the above conventional problems and provides a work machine that can easily change the circuit pressure of each actuator and reduce power consumption when the front attachment of the work machine is changed. A pressure control device is provided.

[Means to solve the problem]

The present invention provides a working machine in which a rotating body is rotatably supported on a traveling body and a front attachment is replaceably mounted on the rotating body, including a hydraulic pump, an actuator for operating the front attachment, and an actuator from the hydraulic pump to the actuator. The electromagnetic pressure control valve includes a control valve that controls the supply and discharge of pressure oil to the valve, an electromagnetic pressure control valve that controls the operating pressure of the actuator, and a work selection switch. A pressure setting spring that is biased in the direction of closing the valve opening to set the set pressure to a high pressure, and an input of an electric signal generates a magnetic force that attracts the poppet in a direction that reduces the closing force of the valve opening exerted by the spring, and the electric signal increases. and a set pressure adjustment solenoid that lowers the set pressure accordingly, and controls the set pressure of the electromagnetic pressure control valve by changing the electric signal to the set pressure adjustment solenoid based on the selection signal from the work selection switch. It is characterized in that it includes a control means.

[For production]

With this configuration, when replacing the front attachment to perform special work, simply operate the work selection switch according to the work content, and the set pressure of the electromagnetic pressure control valve installed in the circuit of the designated actuator will be automatically adjusted. This prevents excessive force from being applied to certain attachments and their actuators, facilitating smooth operation. In particular, in order to change the set pressure, a so-called negative control type electromagnetic pressure control valve is used, in which the set pressure reaches its maximum value when the current is increased, and the set pressure decreases as the current increases, so it is frequently used. When using a standard specification attachment, the set pressure of the electromagnetic pressure control valve is set to the maximum value without passing current, and the above set pressure is changed by passing a specified current only when using a special actuator that is rarely used. It is possible to reduce power consumption and increase energy-saving effects. Also, while working,
If an electrical problem occurs such as a poor connection or disconnection of the electric wire to the electromagnetic pressure control valve, the electromagnetic pressure control valve automatically becomes the maximum setting pressure, and the actuator, or attachment, can be held at that maximum setting pressure, improving safety. It will be possible.

〔Example〕

FIG. 5 shows an example of a working machine to which the present invention is applied. This work machine is configured as a base machine in which an upper rotating body 12 is rotatably mounted on a lower traveling body 11, and a boom 13, an arm 14, and a packet 15 are each rotatable as standard front attachments on this base machine. Equipped with freely movable equipment. In this work machine, the lower traveling body 11 travels, the upper rotating body 12 rotates, the boom 13,
In order to rotate the arm 14 and the packet 15, actuators, ie, travel motors 21 and 22 shown in FIG.
A swing motor 23, a boom cylinder 24, an arm cylinder 25, a packet cylinder 26, and a control circuit thereof are provided.

In FIG. 1, 16 is a tank, 17.18 is a main pump, and each pump 17.18 is connected to a main control valve 30.40.

One of the main control valves 30 has a traveling section having one traveling directional control valve 32 arranged at the most upstream side in a tandem circuit, and downstream thereof directional control valves for boom 1st speed, packet 2nd speed, and arm 2nd speed. 33, 34, and 35 are connected by a parallel circuit, the traveling relief valve 31 is connected to the inlet section, and the working equipment IJ IJ- common to each of the boom 1st speed, packet, and arm 2nd speed working equipment is connected to the outlet section. A valve 36 is connected.

In addition, the other main control valve 40 has a traveling section having the other traveling direction control valve 42 disposed at the most upstream position in the tandem circuit, and downstream of the travel section having the other traveling direction control valve 42, valves for swinging, arm 1st speed, and boom 2nd speed are provided in each direction. Control valve 43.44.45
The inlet section is connected to the working equipment section with a parallel circuit, the travel relief valve 41 is connected to the inlet section, and the working equipment relief valve 41 common to the swing, arm 1st speed, and boom 2nd speed working equipment is connected to the outlet section. 46 are connected.

The set pressure of the travel relief valve 31.41 is set higher than the set pressure of each working device relief valve 36.46. Each implement relief valve 36,46 may be provided between the travel section and the downstream implement section.

Each of the directional control valves 32 to 35 and 42 to 45 is provided with a predetermined actuator, that is, a travel motor 21, 22, respectively.
, boom cylinder 24, arm cylinder 25. A packet cylinder 26 and a swing motor 23 are connected, and by operating each directional control valve, pressure oil is supplied from the main pump 17, 18 to each actuator, and each actuator is operated to perform a desired work.

In the above hydraulic circuit, between the boom 1st speed directional control valve 33 and the boom cylinder 24, the arm 1st speed directional control valve 4
4 and the arm cylinder 25, and between the packet directional control valve 34 and the packet cylinder 26, variable overload relief valves 51, 52, 53, 54 are provided in each pipe line, respectively.
, 55, 56 are connected. Each of these variable overload relief valves 51 to 56 has the same structure and is configured as follows.

FIG. 2 shows an example of an electromagnetic pressure control valve V used in a variable overload relief valve. This electromagnetic pressure control valve V includes a valve case 60, a valve seat 64, a poppet 70,
It includes a valve cover 68, a solenoid 80 for adjusting set pressure, a spring 71 for pressure setting, and a spring cover 75.

Valve case 60 has an inlet port 61, a valve chamber 62, and an outlet port 63. The valve seat 64 has a circumferential groove 65, a passage 66, and a valve port 67 communicating with the inlet boat 61, and is inserted into the valve chamber 62 of the valve case 60. The poppet 70 is slidably supported in the valve chamber 62 in the axial direction so as to open and close the valve port 67 at its tip.

The set pressure adjustment solenoid 80 includes a stator 81, a coil 83 attached to the outer periphery of the stator 81 via a cover 82, and a rod 84 supported by the stator 81 so as to be slidable in the axial direction. The plunger 85 is attached to the outside of the valve cover 68. Note that the plunger 85. The rod 84 is integrally connected to the middle part of the hood 84 by press fitting, shrink fitting, set screw, etc.
Both ends of the valve cover 68 and the stator 8 are connected to each other.
It is slidably supported in the axial direction by a bearing portion formed in 1. The tip of the rod 84 is brought into contact with the back surface of the poppet 70, and the retainer 72 is engaged with the rear end of the rod 84. Further, a retainer 73 is supported by the spring cover 75 via an adjustment screw 74, and the pressure setting spring 7
1 is provided between both retainers 72 and 73. The spring 71 biases the plunger 85 and rod 84 of the solenoid 80 to the left in the drawing, thereby biasing the poppet 70 in a direction to close the valve port 67 of the valve seat 64.

The coil 83 generates a magnetic force that attracts the plunger 85 in a direction (to the right in the drawing) through the stator 81 against the spring 71 when an electric signal (current) is input. Outer periphery or stator 81
It is provided on the outer periphery of the Reference numeral 86 indicates a connector electrically connected to the coil 83, and a lead wire for inputting an electric signal from a controller 90 to the coil 83, which will be described later, is connected to this connector 86. The plunger 85 is provided with a damper throttle 87. 88 indicates a spacer made of a non-magnetic material.

In the electromagnetic pressure control valve V having the above configuration, the inlet port 461
The pressure oil flowing into the valve seat 64 has a circumferential groove 65 and a passage 66.
and reaches the valve port 67, which acts to move the poppet 70 backward in the right direction in the drawing against the spring 71, and when the pressure P exceeds the valve port closing force of the poppet 70 due to the spring 71, the exit boat 63 side, and the pressure P on the inlet side is controlled by this relief.

Here, when no electric signal is input to the coil 83, the force of the spring 71 remains at its maximum and acts as a force to press the poppet 70 to the left in the drawing and close the valve port 67. As a result, the set pressure Ps of the electromagnetic pressure control valve ■ becomes the maximum set pressure PS2, and this valve V
It becomes a relief valve that is relieved at the pressure P on the first side or the highest set pressure P2.

Next, when an electric signal, for example, a current 2, is input to the coil 83, a magnetic force corresponding to the current 2 is generated, and the plunger 85 is attracted to the right in the drawing by the magnetic force. The pressing force of the spring 71 acting on the electromagnetic pressure control valve V is reduced, and the set pressure P5 of the electromagnetic pressure control valve V is reduced. The pressure P on the inlet boat 61 side is controlled according to the magnetic force of the coil 83, that is, according to the current i input to the coil 83.

Furthermore, in this case, if the solenoid 80 is a proportional solenoid that generates a magnetic force according to the current i input to its coil 83, the set pressure P5 of this electromagnetic pressure control valve
As shown in the figure, it is controlled in proportion to the current i, and the current i is 0.
The maximum set pressure PS2 is reached, and the larger the current i,
An electromagnetic proportional pressure control valve is obtained which is controlled by a so-called negative control method so that the set pressure P is lowered.

In this pressure control valve V, the maximum set pressure PS2 can be changed in the direction of arrow A in FIG. 3 by adjusting the force of the spring 71 with the adjusting screw 74. Also, the lowest value PS□ of the set pressure P5 of this valve V is the plunger 85
It is determined by the minimum value of the gap between the right end surface of the figure and the inner wall surface of the stator 81 facing thereto, that is, the thickness of the spacer 88. Therefore, by changing the thickness of the spacer 88 and adjusting the stroke end of the plunger 85 to the right in the drawing, the minimum set pressure PS□ can be changed in the direction of the arrow in FIG. 3. Furthermore, spring 71
By replacing the set pressure Ps, the control gradient of the set pressure Ps can be changed as shown by the broken line in FIG.

Next, using the electromagnetic pressure control valve V configured as described above, a variable overload relief valve 5 as shown in FIG.
1 (same for 52 to 56). Note that FIG. 4 shows hydraulic symbols. That is, the variable overload relief valve 51 is composed of a balanced piston type relief valve, and the above-mentioned electromagnetic pressure control valve (2) is used as its child valve, and the inlet port 61 of this valve V is connected to the pressure control section 7 of the parent valve 77.
8 and is connected to the outlet port 63 or the secondary passage of the master valve 77. 79 indicates a check valve.

The variable overflow relief valves 51 to 56 configured in this way are connected to predetermined locations shown in FIG. 1, respectively.

In Fig. 1, 90 is a controller, 91 is for normal work, 92 is for long arm work, 93 is for vibro work, 94 is for breaker work, and 95 is a spare work selection switch. In response to signals from the switches 91 to 95, the controller 90 outputs a predetermined electric signal to the variable overload relief valves 51 to 56 of a predetermined actuator, and the overload relief valve 5
It is designed to control a set pressure of 1 to 56.

When performing normal work with the standard specification boom 13, arm 14, and front attachment of the packet 15 attached as shown in Fig. 5, turn on the normal work switch 91 shown in Fig. 1. If the controller 90 does not output an electric signal, the set pressure P of each variable overload relief valve 51 to 56 will be reduced.
5 is the highest setting pressure, allowing normal work to be carried out efficiently. During this normal work, there is no need to output electrical signals from the controller 90, so power consumption can be reduced.

By the way, if a long arm (not shown), for example, is used instead of the standard arm 14 shown, there is a risk that an excessive load will be applied to the boom 13.

In such a case, the long arm work switch 92
By operating the controller 90, a predetermined electric signal is sent from the controller 90 to the variable overload relief valves 51 and 53 that act, for example, during boom-raising and arm-pushing work, and the set pressure P of the IJ-IJ-F valves 51 and 53 is adjusted.
s can be lowered respectively.

Note that no electrical signal is sent to the other relief valves 52, 54, 55, and 56, and their set pressures are maintained at the highest value. As a result, the relief valves 51 and 53 are relieved at a lower pressure than in standard use when raising the boom and pushing the arm, preventing excessive load pressure from being applied to the boom cylinder 24 and arm cylinder 25, and causing damage to the machine. This prevents troubles and allows the desired work to be carried out safely. Also, when Mr. J performs other special work, he sends an electric signal only to a specific overload relief valve to change its set pressure depending on the work.

This prevents damage to the machine and saves energy.

During the special work mentioned above, if the signal from the controller 9o is no longer input due to a problem with the electrical system, the set pressure of the variable overload relief valve, which had been lowered to a low set pressure, will return to the original maximum set pressure. is,
This ensures that a particular attachment, such as a long arm, is held by the variable overload relief valve with the highest set pressure.

The present invention is not limited to the case where a hydraulic excavator is used as a base machine as described above, but also when a hydraulic crane is used as a base machine,
Needless to say, by replacing the front attachment, it can also be applied to working machines that perform work at heights, earth auger work, and clamshell work.

〔Effect of the invention〕

As described above, according to the present invention, when various front attachments of a work machine are changed, the circuit pressure of each actuator can be easily changed, and it is possible to prevent excessive force from being applied to each attachment. Able to work smoothly. Moreover, it is not necessary to send an electric signal to only the electromagnetic pressure control valve that requires change, and it is not necessary to send an electric signal to other valves. Therefore, power consumption can be reduced and an energy saving effect can be obtained. Furthermore, if an electrical trouble occurs, the set pressure of the valve is returned to the highest set pressure, and the actuator can be reliably held at that pressure, thereby increasing safety.

[Brief explanation of drawings]

Fig. 1 is a hydraulic circuit diagram showing an embodiment of the present invention, Fig. 2 is a sectional view showing a specific example of an electromagnetic pressure control valve, Fig. 3 is a control characteristic diagram of the electromagnetic pressure control valve, and Fig. 4 is an electromagnetic pressure control valve. A hydraulic symbol diagram of a variable overload relief valve using a control valve, and FIG. 5 is a side view showing an example of a working machine to which the present invention is applied. 11... Lower traveling body, 12... Upper revolving body, 13.
...Boom, 14...Arm, 15...Packet,
17° 18... Main pump, 24... Boom cylinder, 25... Arm cylinder, 26... Packet cylinder, 30.40... Main control valve, 32° 33.34, 35, 42. 43,44.45・
... Directional control valve, 51, 52, 53, 54. '55.5
6... Variable overload relief valve, ■... Solenoid pressure control valve, 61... Inlet boat, 62... Valve chamber,
63...Outlet port, 64...Valve seat, 7o...
・Poppet, 71...Pressure setting spring, 8o・
- Set pressure adjustment solenoid, 90...controller, 91, 92.93, 94.95-...work selection switch. Patent applicant: Kobe Steel, Ltd. Agent
Patent Attorney Etsushi Kotani Patent Attorney Chief 1
) Masaru Patent Attorney Takao Ito No. 5 Figure 2 Bow

Claims (1)

[Claims] 1. In a work machine in which a rotating body is rotatably supported on a traveling body and a front attachment is attached to the rotating body in a replaceable manner, there is a hydraulic pump, an actuator for operating the front attachment, and pressure from the hydraulic pump to the actuator. Equipped with a control valve that controls oil supply and discharge, an electromagnetic pressure control valve that controls actuator operating pressure, and a work selection switch, the electromagnetic pressure control valve has a poppet that opens and closes the valve port, and a poppet that closes the valve port. There is a pressure setting spring that biases the valve in a direction to set the set pressure to a high pressure, and an electric signal input generates a magnetic force that attracts the poppet in a direction that reduces the valve closing force exerted by the spring, and as the electric signal increases. and a set pressure adjusting solenoid that lowers the set pressure by changing the electric signal to the set pressure adjusting solenoid based on the selection signal from the work selection switch to control the set pressure of the electromagnetic pressure control valve. A pressure control device for a working machine, characterized by comprising: