JPH0351225Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a driving device for a barrel containing concrete in a concrete mixer truck.

As shown in the first diagram, a conventional drive device of this kind connects a double-discharge type variable displacement hydraulic pump c to a hydraulic motor a that rotates a barrel i in forward and reverse directions via a closed circuit b, and also connects a hydraulic motor a that rotates a barrel i in forward and reverse directions. Generally, a fixed capacity replenishment pump d is connected to replenish fluid to the
The flow rate and flow direction of the closed circuit b are controlled by controlling the control piston e of the variable displacement hydraulic pump c by the servo valves f, g and the joystick valve h. Therefore, when the driving motor j of the mixer truck is in an idling state, the variable displacement hydraulic pump c and the replenishment pump d tend to be insufficient in the replenishment amount of the replenishment pump d, and there is a risk of cavitation in the closed circuit b. , the oil temperature increases due to the replenishment pump d, which is not preferable. Furthermore, even if the control piston e is controlled to reduce the discharge amount to zero, the variable displacement hydraulic pump c still releases some fluid into the closed circuit b.
Therefore, there is an inconvenience that the hydraulic motor a cannot be completely stopped.

It was thought that these inconveniences and inconveniences could be solved by connecting the hydraulic pump c to the closed circuit b via a switching valve and omitting the replenishment pump d by directly connecting the suction circuit of the hydraulic pump c to the tank. If the switching valve is switched instantaneously, there is a risk that a shock will occur in the closed circuit b, and even if the barrel i is stopped, there is a risk that the barrel i will reverse due to the unevenness of the ready-mixed concrete inside, and the ready-mixed concrete will be discharged carelessly.

The present invention aims to eliminate the above-mentioned disadvantages and provide a drive device free from the above-mentioned risks, in which the barrel A of a concrete mixer truck is connected to a hydraulic motor 2 driven by a variable displacement hydraulic pump 1. In this system, the discharge circuit 3 and suction circuit 4 of the variable displacement hydraulic pump 1 are controlled to operate the hydraulic motor 2 via a pilot operated switching valve 5 having a spool type flow rate adjustment function. An orifice 11 is connected to the circuits 6, 7 and is connected to a pilot circuit 10, 10 for switching operation of the switching valve 5.
11 and both pilot circuits 10, 10.
is connected to the discharge circuit 3 via a pilot valve 12.

The pilot-operated switching valve 5 has a discharge circuit 3, a suction circuit 4, and operating circuits 6, 7, as shown in the second figure.
At the neutral position 5a, the discharge circuit 3 and the suction circuit 4 are connected to the operating circuits 6 and 7 in the forward and reverse directions, and the barrel A, which is connected to the hydraulic motor 2, is rotated forward for concrete suction and for concrete discharge. The hydraulic motor 2 is provided with switching positions 5b and 5c for performing reverse rotation and reverse rotation, and a low rotation position 5d equipped with a throttle for normal rotation of the hydraulic motor 2 at a relatively low speed when the mixer truck is running.
It is assumed that the valve is switched to each position by operating the pilot valve 12 against the force of the spring 5e, and at the intermediate position between the positions, the opening area changes according to the distance of movement, and a flow rate corresponding to the flow rate flows through the flow rate adjustment function. I made sure that it was fulfilled. The pilot valve 12 is a lever-operated pressure reducing valve, and when the lever 12a is tilted to one side, the pressure in the discharge circuit 3 is reduced and the switching valve 5 is operated via one pilot circuit 10 to perform a switching operation. Reportedly. In this case, if the inclination of the lever 12a is small, the pressure will be greatly reduced, and as the inclination increases, the degree of pressure reduction will become smaller and the switching valve 5 will be operated to switch to a greater extent, and if there is no inclination, the switching valve 5 will be operated.
The neutral position 5a is held by the spring 5e. When the lever 12a is tilted greatly and rapidly, the pressure in one pilot circuit 10 rises rapidly, but since the circuit 10 is provided with an orifice 11, the rapid switching operation of the switching valve 5 can be suppressed, and a closed circuit is formed. This prevents a shock from occurring due to rapid disconnection between the operating circuits 6 and 7 and the discharge circuit 3 and the suction circuit 4. Furthermore, since the pressure acting on the pilot circuit 10 is led from the discharge circuit 3, when the prime mover 13 that drives the hydraulic pump 1 stops and the pressure in the discharge circuit 3 decreases, the pressure in the pilot circuit 10 automatically decreases. , the switching valve 5 is returned to the neutral position 5a by a spring 5e. Therefore, the operating circuits 6 and 7 are cut off, and the reverse rotation of the barrel A due to the gravity of the fresh concrete and the accidental discharge of the ready-mixed concrete are prevented. Control pistons 14 and 15 move the swash plate and other means for varying the displacement of the variable displacement hydraulic pump 1 in opposite directions; one control piston 1
4, the pressure of the discharge circuit 3 is introduced, and a control piston 15 is formed to have a larger pressure-receiving area than the control piston 14, and the pressure of the discharge circuit 3 or tank pressure is selectively applied thereto via a servo valve 16. When the pressure of the discharge circuit 3 acts on both pistons 14 and 15, the control piston 15, which has a large pressure-receiving area, moves the means such as a swash plate in the direction of decreasing the discharge amount by the spring 14a of the control piston 14. When tank pressure acts on the control piston 15, the pressure of the discharge circuit 3 acting on the other control piston 14 causes the means to tilt in the direction of increasing the discharge amount. The servo valve 16 is a first servo valve which, when the pressure in the discharge circuit 3 exceeds a set pressure, introduces the pressure to the control piston 15 to reduce the pump discharge amount and prevent waste of pump power.
The servo valve 16a and the pilot circuit 19 to the control piston 15 are connected to each other when the pressure of the discharge circuit 3 takes the sum of the higher pressure of the operating circuits 6, 7 extracted via the shuttle valve 17 and the force of the spring 18. The second servo valve 16b is connected to the tank and increases the pump discharge amount.

To explain its operation, when the pilot valve 12 is not operated, the switching valve 5 is in the neutral position 5a shown in the figure.
The operating circuits 6 and 7 are disconnected from the discharge circuit 3 and the suction circuit 4, the rotation of the hydraulic motor 2 and the barrel A is stopped, and the hydraulic pump 1 is automatically stopped by the operation of the servo valve 16. Control the discharge amount to zero. When the pilot valve 12 is operated, the switching valve 5 gradually slides from the neutral position 5a toward the switching position 5b or 5c depending on the amount of operation, and the operating circuits 6, 7, the discharge circuit 3, and the suction circuit 4 are connected to each other. The connection area of hydraulic motor 2 and barrel A gradually increases.
The rotation speed increases. In this case, the flow rate that is insufficient due to oil leakage in the circuit, etc., is self-primed by the hydraulic pump 1 via the replenishment circuit 9, so even if the prime mover 13 of the mixer truck that drives the pump 1 becomes idling and the rotation speed drops, there will be insufficient flow. You can continue to replenish the amount.

Furthermore, even if the pilot valve 12 is suddenly actuated, the switching valve 5 will not be switched suddenly due to the action of the orifice 11 of the pilot circuit 10, and no shock will occur in the circuit. Furthermore, while the barrel A is rotating under suction, the prime mover 13
Even if the switching valve 5 stops, since the switching valve 5 is of a pilot operated type and is operated by the pressure from the discharge circuit 3, it automatically returns to the switching position 5a, and the barrel A will not be reversed by the gravity of the fresh concrete.

In this way, according to the present invention, the operating circuit 6,
7 is provided with a spool-type pilot operated switching valve 5 having a flow rate adjustment function, which is connected to the pilot circuit 1.
Since the pressure of the discharge circuit 3 is controlled by the pilot valve 12 through the orifice 11 of 0, the barrel A can be stopped and unnecessary power consumption can be prevented, and a shock can be generated in the circuit. Since the suction circuit 4 is connected to the tank 8 via the replenishment circuit 9, it is possible to automatically stop the barrel when the prime mover is stopped without having to use a replenishment pump. It has the effect of being able to replenish the flow rate.

[Brief explanation of the drawing]

FIG. 1 is a diagram of a conventional barrel drive device, and FIG. 2 is a diagram of an embodiment of the present invention. A... Barrel, 1... Variable displacement hydraulic pump,
2... Hydraulic motor, 3... Discharge circuit, 4... Suction circuit, 5... Pilot operation switching valve, 6, 7...
Operating circuit, 8... Tank, 9... Replenishment circuit, 10
... Pilot circuit, 11 ... Orifice, 12
...Pilot valve.

Claims (1)

[Scope of utility model registration request] The barrel A of a concrete mixer truck is connected to a hydraulic motor 2 driven by a variable displacement hydraulic pump 1 for forward and reverse rotation, and the discharge circuit 3 and suction circuit 4 of the variable displacement hydraulic pump 1 are connected to a hydraulic motor 2 driven by a variable displacement hydraulic pump 1. The operating circuits 6 and 7 of the hydraulic motor 2 are connected to the hydraulic motor 2 via a pilot-operated switching valve 5 having a spool-type flow rate adjustment function.
A replenishment circuit 9 connected to the tank 8 is connected to the suction circuit 4, and orifices 11, 11 are connected to the pilot circuit 10, 10 for switching operation of the switching valve 5.
A barrel drive device for a concrete mixer truck, comprising: a concrete mixer truck; and both pilot circuits 10, 10 connected to the discharge circuit 3 via a pilot valve 12.