JPS6116182Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a brake lamp circuit for a hydraulically driven vehicle such as a wheel loader.

This type of hydraulically driven vehicle is also equipped with a brake light at the rear of the vehicle body, similar to general engine-driven vehicles. On the other hand, in the case of a vehicle driven by a hydraulic motor, a counterbalance valve as a brake valve is built into the motor circuit to prevent cavitation of the motor due to running inertia, etc.
This valve also exerts a braking action. In such a configuration, if the engine speed suddenly decreases when driving down a slope, for example, the amount of oil discharged from the pump will decrease, and the brake action of the counterbalance valve will cause sudden braking while driving. This creates a risk of a rear-end collision.

The present invention aims to create a brake lamp circuit that can illuminate the brake lamp and issue a warning even when braking force is applied by the action of the counterbalance valve, in the same way as when a mechanical brake is applied. It is something to do.

Embodiments of the present invention will be described below with reference to the drawings. 1 is a hydraulic pump, 2 is a hydraulic motor, and 3 is a control valve. This control valve 3 is switched between a forward rotation position a, a neutral position b, and a reverse rotation position c by operating a lever, etc. In the forward rotation position a, the vehicle moves forward due to the rotation of the motor 2, and in the reverse rotation position c, the vehicle moves backward. do. Then, pump 1 at neutral position b
The discharged oil carries over and the motor 2 stops. Reference numeral 4 designates a counterbalance valve as a brake valve, which is provided in the hydraulic circuits 5 and 6 between the control valve 3 and the hydraulic motor 2. This counterbalance valve 4 is moved to a normal rotation position d with a counterbalance part by the pressure in the circuits 5 and 6.
The motor circuit is automatically switched to a neutral position e with a brake section and a reverse position f with a counterbalance section, and when the circuit pressure decreases, the motor circuit is switched to the neutral position e. When closed, it prevents cavitation and exerts a braking action.

On the other hand, in the electric circuit, 7 is an engine switch, 8 is a limiter switch, 9 is a pressure switch,
Reference numeral 10 designates a brake lamp. These series circuits are connected between power sources, and the brake lamp 10 is turned on only when the above-mentioned switches 7, 8, and 9 are all closed. The limiter switch 8 is operated by operating the control valve 3, and is turned off when the valve 3 is in the neutral position b, and turned on when it is set in the forward rotation and reverse rotation positions a and c. The pressure switch 9 is in the form of a so-called normally closed switch.
It turns off only when pressure above a certain level is applied. An operating pressure extraction circuit 11 of the pressure switch 9 has a shuttle valve 12 and is connected to the hydraulic circuits 5 and 6, so that the circuit pressure is applied to the pressure switch 9. In this case, pressure switch 9
The set operating pressure, that is, the pressure _Ps at which the switch 9 is turned off, is set to a value slightly lower than the cracking pressure _Pc of the counterbalance valve 4. Therefore, as long as the circuits 5 and 6 are equal to or higher than the cracking pressure of the counterbalance valve 4, the pressure switch 9 is kept off, and when the circuit pressure drops to a low value below the cracking pressure, the switch is turned off. 9 is turned on.

13 is a timer for preventing the brake lamp 10 from blinking frequently;
0 and a disc switch 15 driven by the motor 14, and the switch 15 is connected in parallel with the pressure switch 9. The disc switch 15 is turned on when the disc begins to rotate by the motor 14.
When the disk rotates once, the contacts open and turn off. In other words, the disc is turned on for one rotation to exert a timer effect, and during this time the pressure switch 9 is turned on.
Even if the brake lamp 10 is turned on and off repeatedly, the energizing circuit of the brake lamp 10 is maintained.

To explain the operation of this circuit, when the control valve 3 is in the neutral position b, the limiter switch 8 is turned off, so the brake lamp 10 does not light up. Next, when the control valve 3 is set to the normal rotation position a or the reverse rotation position, the motor 2 rotates. At this time, even if the motor is idling, the pressure in the circuits 5 and 6 will not fall below the cracking pressure. Therefore, during normal driving in this state, the brake lamp 10 does not light up because the pressure switch 9 is turned off.

However, when driving down a slope, etc., the engine speed decreases and the motor 2 rotates at a rate greater than the amount of oil discharged from the pump.
When this occurs, that is, when the amount of oil discharged from the pump 1 cannot keep up with the rotation of the motor 2, the counterbalance valve 4 is switched to the neutral position e based on the pressure drop in the circuits 5 and 6 to prevent cavitation. It exerts a braking action for. At the same time, the pressure switch 9 is turned on due to the decrease in the circuit pressure, so that an energizing circuit for the brake lamp 10 is formed and the lamp 10 is turned on. Then, when the running speed of the vehicle decreases due to the braking action of the counterbalance valve 4, the amount of oil discharged from the pump catches up with the motor rotation again, and the pressure in the circuits 5 and 6 returns to the original level, and the counterbalance valve 4
Since the pressure switch 9 returns to its original position, the pressure switch 9 is turned off and the brake lamp 10 goes out.

In this way, when using this circuit, even when braking force is applied to the vehicle by the action of the counterbalance valve 4, the brake lamp is turned on to warn the following vehicle, just as when mechanical brakes are applied. 10 can be turned on.

By the way, in the above operation, the opening/closing speed of the counterbalance valve 4 is fast, and the pressure switch 9
When the circuit pressure rises and falls around the set pressure, the brake lamp 10 will blink frequently. If this happens, not only will the brake lamp 10 become useless, but it will also have a negative effect on the lifespan of the lamp 10 and the like. In this circuit, such a so-called chattering phenomenon can be prevented by the timer 13.

That is, when the brake lamp 10 lights up,
The motor 2 connected in parallel with the lamp 10 rotates, and the disc switch 15 is turned on for a certain period of time as described above. Therefore, even if the hydraulic circuit pressure rises and the pressure switch 9 is turned off again before the disc switch 15 is next turned off, the disc switch 15 will maintain the energization circuit of the lamp 10. Ru. Therefore, once the lamp 10 is lit, it will always remain lit for a certain period of time, and the above-mentioned chattering phenomenon can be prevented.

Note that this timer 13 may be replaced with another one having a function similar to that described above and illustrated.

As described above, according to the present invention, in a hydraulically driven vehicle such as a wheel loader, even when a counterbalance valve acting as a brake valve acts and a substantial braking force is applied to the vehicle, the mechanical brake is applied. The brake lamp can be turned on in the same way as when the vehicle is in use, thereby increasing the effect of preventing rear-end collisions and improving driving safety.

[Brief explanation of the drawing]

The figure is a hydraulic and electrical circuit diagram showing an embodiment of the present invention. 1...Hydraulic pump, 2...Hydraulic motor, 3...
Control valve, 4... Counter balance valve, 5, 6... Motor hydraulic circuit, 9... Pressure switch, 10... Brake lamp, 11... Operating pressure extraction circuit for the pressure switch.

Claims (1)

[Scope of utility model registration request] In a hydraulically driven vehicle that has a hydraulic pump, a hydraulic motor, and a control valve, and a counterbalance valve as a brake valve is provided between the control valve and the hydraulic motor, the brake lamp is activated by the cracking pressure of the counterbalance valve. A hydraulic drive characterized in that the pressure switch is connected to a power source via a pressure switch that operates at a lower pressure, and the operating pressure extraction circuit of the pressure switch is connected to a hydraulic circuit between the control valve and the counterbalance valve. Brake light circuit for vehicle.