JPH071701Y2 - Electric circuit for control switch protection of construction machinery - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electric circuit for protecting a control switch of a construction machine.

2. Description of the Related Art FIG. 2 is a circuit diagram showing a main part of a conventional electric circuit. In the figure, 1 is a power supply, 2 is a key switch, 3 is a fuse, 4 is a switch for heavy load, 5 is various solenoid valves, 6
Is a relay, and 7 is a control switch. Control switch 7
Is a switch such as a pressure switch or a proximity switch provided for an actuator mounted on a construction machine.

Next, the configuration of the circuit shown in FIG. 2 will be described. A power source 1, a key switch 2, a fuse 3 and a heavy load switch 4 were connected in series, and various solenoid valves 5 and an exciting coil 8 of a relay 6 were connected in parallel downstream of the switch 4. On the other hand, the upstream side and the downstream side of the heavy load switch 4 are connected via the contact portion 9 of the relay 6 and the control switch 7.

Next, the operation function of the circuit of FIG. 2 will be described. When the key switch 2 is turned on and the heavy load switch 4 is turned on, the current from the power source 1 energizes the exciting coil 8 for the relay 6 and various solenoid valves 5. Therefore, the contact portion 9 for the relay 6 closes the circuit. Further, since a specific actuator (not shown) is heavily loaded, the control switch 7 also closes the circuit. As a result, the relay 6 and the control switch 7
Form a self-holding circuit. Therefore, if the operation of a specific actuator under heavy load is stopped,
For example, when a heavy load is suspended from a boom of a construction machine and stopped, the heavy load is held in a suspended state and the heavy load is prevented from falling. That is, the current from the power supply 1 passes through the key switch 2 and the fuse 3,
Power is transmitted to the various solenoid valves 5 from the heavy load switch 4 side, the relay 9 contact portion 9 and the control switch 7 side. When the heavy load applied to the specific actuator disappears, the control switch 7 opens the circuit, so that the current flowing through the solenoid valve 5 is de-energized by the control switch 7.

Problems to be Solved by the Invention The circuit shown in FIG. 2 is provided to prevent falling when a heavy load is lifted by a specific actuator of a construction machine, such as a boom, or when the engine is stopped. That is,
When lifting a heavy object with the boom, the heavy load switch is turned on to perform heavy load work. With respect to the operation, the control switch opens and closes in the electric path of the load current flowing to various solenoid valves. Also, if the heavy load switch is opened due to an operation error, the current from the power supply will pass through the relay contact and the control switch,
Electric power is transmitted to a plurality of various solenoid valves. Since the control switch does not have a plurality of contact parts for the plurality of various solenoid valves, an accidental burnout of the control switch has occurred due to an insufficient load capacity. As described above, since the load current is opened and closed by the control switch, the contacts of the control switch may be burned out.

An object of the present invention is to solve the above problems and provide an electric circuit for protecting a control switch in which a load current supplied to various solenoid valves does not pass through the control switch.

In the present invention, a power supply, a key switch, a heavy load switch, and a relay exciting coil are connected in series, and
The relay contact part and the control switch are connected and arranged in series from the upstream side of the heavy load switch, and the specific actuator that drives the heavy load and other required components are connected between the electric path and the ground on the downstream side of the key switch. In a heavy load electric circuit in which a plurality of solenoid valves for controlling an actuator are provided in parallel, in the electric circuit between the downstream side contact part of the relay relay contact part and the control switch, Connect the individual solenoid valves and ground the downstream sides of the multiple solenoid valves, respectively, and (c) connect the solenoid valve to the downstream contact point of the control switch and the downstream contact point of the heavy load switch. A diode is provided between the control switch and the heavy load switch so that a current flows in the diode.

Function a When the key switch and heavy load switch are turned on during heavy load work, the relay contact and control switch close the circuit. The load current from the power source is supplied to various solenoid valves via the relay contact portion. In addition, the relay, control switch and diode
Form a self-holding circuit.

(B) In the state of the above item (a), even if the heavy load switch is turned off, the load current supplied to the various solenoid valves does not pass through the control switch because it is transmitted through the relay contact portion. Part of the current flows to the relay exciting coil via the control switch and sneak prevention diode.

Embodiment Hereinafter, an electric circuit for protecting a control switch according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a circuit diagram showing a main part of an electric circuit according to the present invention. Next, the configuration of the electric circuit of the present invention will be described with reference to FIG. In the present invention,
Downstream contact portion of the contact portion 9 for the relay 6 and the control switch 7
In parallel with the control switch 7, a plurality of various solenoid valves 5 for controlling a specific actuator that drives a heavy load (for example, a boom of a construction machine, etc.) and other required actuators are provided in an electric path between and. Between the electric circuits connecting the downstream side contact portion of the control switch 7 and the downstream side contact portion of the heavy load switch 4 to each other. In addition, the diode 11 for preventing so-called current sneak in the direction in which the current flows from the control switch 7 to the heavy load switch 4 is provided.
It is configured by interposing. A diode provided in an electric path that connects the upstream side and the downstream side of the exciting coil 8 for the relay 6
12 is for spark extinguishing.

Next, the operation function of the circuit according to this invention will be described with reference to FIG. During heavy load work, turn on the key switch 2,
When the heavy load switch 4 is turned on, the current from the power supply 1 energizes the exciting coil 8 for the relay 6. Relay 6
Since the contact point section 9 for the circuit closes the circuit, the load current from the power source 1 passes through the contact point section 9 for the relay 6 and the electric path 10 and then the various solenoid valves 5
Is supplied to. Moreover, since a heavy load is applied to a specific actuator, the control switch 7 also closes the circuit. As a result, the relay 6, the control switch 7, and the sneak-in prevention diode 11 form a self-holding type circuit. Even when the heavy load switch 4 is opened in the above state, the load current supplied to the various solenoid valves 5 is transmitted through the relay 6 contact portion 9. Therefore, the load current does not pass through the control switch 7. Part of the current flows to the exciting coil 8 for the relay 6 via the control switch 7 and the sneak-prevention diode 11. This prevents a contact burnout accident at the contact portion of the control switch 7 and protects the control switch 7.

Effect of the Invention In the heavy load circuit of the prior art, the load current supplied to each solenoid valve was passed through the control switch. In addition, since the control switch does not have a plurality of contact parts for a plurality of various solenoid valves, there is a risk that the contacts of the control switch may be burned out due to an insufficient load capacity.

However, in the control switch protection electric circuit according to the present invention, even when the heavy load switch is opened, the load current supplied to the various solenoid valves is transmitted through the relay contact portion. Therefore, the load current does not pass through the control switch. A part of the current flows to the relay exciting coil through the control switch and the sneak prevention diode.
This prevents accidental burnout of the control switch contacts, thus improving the safety of the heavy load electric circuit.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an essential part of a control switch protection electric circuit according to the present invention, and FIG. 2 is a circuit diagram showing an essential part of a conventional electric circuit. 4 …… Switch for heavy load 5 …… Various solenoid valves 6 …… Relay 7 …… Control switch 8 …… Excitation coil 9 …… Contact point 11 …… Diode

Claims (1)

[Scope of utility model registration request] 1. A power source, a key switch, a heavy load switch and a relay exciting coil are connected in series, and a relay contact portion and a control switch are connected in series from the upstream side of the heavy load switch. , In the electric circuit for heavy load in which a plurality of solenoid valves for controlling a specific actuator for driving a heavy load and other required actuators are provided in parallel between the electric path on the downstream side of the key switch and the ground, In the electric path between the downstream contact portion of the relay contact portion and the control switch, the plurality of solenoid valves are connected in parallel with the control switch, and the downstream sides of the plurality of solenoid valves are grounded respectively. Also, with the downstream contact of the control switch,
A control switch for a construction machine characterized in that a diode is provided between a control switch and a switch for heavy load, in the direction of which a current flows, between an electric path communicating with a downstream contact portion of the switch for heavy load. Electrical circuit for protection.