JPH0417886Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field This invention relieves the hydraulic oil when the pressure of the hydraulic oil pumped from the hydraulic pump to the hydraulic cylinder exceeds a set value, and when the loading platform becomes larger than a predetermined angle. It is used in the field of dump trucks to bypass hydraulic oil when tilting.

(b) Prior art In conventional dump trucks, there is a gap between the hydraulic pump and the hydraulic cylinder driven by the hydraulic pump.
A relief valve that relieves the hydraulic oil when the pressure of the hydraulic oil from the hydraulic pump exceeds a set pressure, and a bypass valve that bypasses the hydraulic oil when the loading platform tilts beyond a predetermined angle are separately provided. As a result, the entire hydraulic system of the dump truck becomes large, making it difficult to use in a narrow space, and also requiring a large number of man-hours to manufacture.

(c) Purpose of the invention The present invention was made in order to eliminate the above-mentioned drawbacks, and the poppet that closes the communication port for releasing the hydraulic oil is pushed by the internal pressure of the hydraulic oil and the tilting movement of the hydraulic cylinder. It is an object of the present invention to provide a bypass relief control valve for hydraulic oil in a dump truck that can be opened at any pressure.

(d) Structure of the invention In this invention, the casing is provided with a first port and a second port that can be communicated at all times, and a third port that can be communicated with the valve chamber in the casing, and the first port is connected to a hydraulic pump. The second port communicates with the hydraulic cylinder side and the third port communicates with the tank side, and the valve chamber is provided with a communication port that communicates the valve chamber with the first port, and the communication port is closed. A poppet is provided which is biased by a spring in the closing direction, and the poppet is integrally provided with a rod having a smaller diameter than the communication port and extending on the center line of the poppet, and the free end of the rod is located at a position opposite to the communication port. The poppet is inserted into and supported by a hole opened in the casing, and is brought into contact with one end of a press rod that partially protrudes from the casing and is pressed in conjunction with the tilting movement of the hydraulic cylinder, thereby causing the poppet to rise above the set pressure at the first port. This is a bypass relief control valve for hydraulic oil in a dump truck, characterized in that it can be opened by internal pressure and can also be opened by pressure from a push rod.

(e) Embodiment The following embodiment will be explained with reference to the drawings. 1 is a loading platform tiltably mounted on the body 2 of a dump truck;
A hydraulic cylinder 3 for tilting the loading platform 1 is provided between the loading platform 1 and the vehicle body 2.

A bypass relief control valve 4, which will be described later, is provided at the base of the hydraulic cylinder 3.
is tilted by a predetermined angle α or more, the bypass relief control valve 4 is opened via the bell crank 5.

FIG. 3 shows a hydraulic circuit for a hydraulic cylinder, in which the hydraulic pump 6 and the hydraulic cylinder 3 are communicated with each other through a main flow path 7.
A switching valve 8 and a bypass relief control valve 4 are provided to control lowering and stopping.

Next, the bypass relief control valve 4 of the present invention will be explained with reference to FIGS. 4 and 5. 9 is a casing, and the casing 9 has a first port 10 communicating with the hydraulic pump 6 side and a first port 10 communicating with the hydraulic cylinder 3 side. A second port 11 communicating with the tank 12 and a third port 13 communicating with the tank 12 side are provided.

The first port 10 and the second port 11 are always in communication, and the third port 13 is communicated with a valve chamber 14 in the casing 9.

The valve chamber 14 is provided with a communication port 15 for communicating with the first port 10, and the communication port 15 has a poppet that is biased by a spring 16 at an arbitrarily set pressure in the direction of closing the communication port. 17 is provided, and the communication port 15 is opened and closed by movement of the poppet 17.

The poppet 17 is integrally provided with a rod 18 that extends forward on the center line of the poppet 17 and has a smaller diameter l than the diameter L of the communication port 15.
The free end of 8 is inserted and supported in a hole 19 provided at a position opposite to communication port 15.

Also, a pressing rod 20 is placed on the same axis as the rod 18.
is slidably provided, and one end of the press rod 20 is brought into contact with the free end of the rod 18, and the other end is made to protrude from the casing 9 and come into contact with a part of the bell crank 5, thereby controlling the tilting of the hydraulic cylinder 3. The poppet 17 is opened via the push rod 20 and the rod 18 by the rotation of the bell crank 5 upon operation.

The present invention has the above-mentioned structure, and its operation will be explained next. When the loading platform 1 is to be raised, the switching valve 8 is switched to the raised position (left position) as shown in FIG. 7 to the hydraulic cylinder 3 to tilt the loading platform 1.

At that time, if the pressure inside the main flow path 7 becomes higher than the set pressure for some reason, the internal pressure of the main flow path 7 acts on the poppet 17, resisting the force of the spring 16, and opens the poppet 17, opening the first port 10 side. The hydraulic fluid on the second port 11 side is returned to the tank 12 through the communication port 15, the valve chamber 14, and the third port 13 to avoid abnormally high pressure in the main flow path 7.

Furthermore, if the loading platform 1 is tilted by a predetermined angle or more, that is, if the hydraulic cylinder 3 is tilted by a predetermined angle α or more, there is a risk that the vehicle body 2 will overturn. Therefore, as shown in FIG. 2
The push rod 20 is rotated from the solid line position to the dashed-dotted line position in the figure, and the push rod 20 is pushed into the poppet 17 via the rod 18.
is pushed open, the first port 10 and the third port 13 are communicated with each other through the communication port 15, the hydraulic oil from the hydraulic pump 6 is returned to the tank 12, the extension of the hydraulic cylinder 3 is stopped, and rollover is prevented. It's getting old.

(f) Effects of the invention As described above, the present invention allows the poppet that opens and closes the communication port for releasing hydraulic oil to be opened by both the internal pressure of the hydraulic oil and the pressing force due to the tilting movement of the hydraulic cylinder. As a result, a single control valve can serve as both a relief valve and a bypass valve, and the entire hydraulic system of a dump truck can be made compact.

In addition, a rod is provided on the poppet, and the free end of the rod is inserted through the hole and supported, so the poppet can move in a stable state and the pressure-receiving area of the poppet is increased by increasing the contact surface of the poppet. It can be made small, and the communication port can be reliably closed with a spring of small force.

Furthermore, since the force of the spring is reduced, only a small amount of external force is required to open the poppet, making it extremely easy to open and close the poppet.

[Brief explanation of drawings]

Figure 1 is an overall view of the present invention in a dump truck.
2 is a partially enlarged view of FIG. 1, FIG. 3 is a hydraulic circuit diagram, FIG. 4 is an overall cross-sectional view of the bypass relief control valve, and FIG. 5 is an operating state diagram. 3 is a hydraulic cylinder, 4 is a bypass relief control valve, 6 is a hydraulic pump, 10 is a first port, 11 is a second port, 12 is a tank, 13 is a third port,
15 is a communication port, 17 is a poppet, 18 is a rod,
19 is a hole, and 20 is a pressing rod.

Claims (1)

[Scope of utility model registration request] The casing is provided with a first port and a second port that can communicate at all times, as well as a third port that can communicate with the valve chamber in the casing, with the first port being connected to the hydraulic pump side and the second port being connected to the hydraulic cylinder side. the third port to the tank side,
The valve chamber is provided with a communication port that communicates the valve chamber with the first port, and a poppet biased by a spring in the closing direction to close the communication port, and the poppet has a diameter smaller than that of the communication port. A rod extending on the center line of the poppet is integrally provided, and the free end of the rod is inserted and supported through a hole opened at a position opposite to the communication port, and partially protrudes from the casing, and the rod is configured to move the hydraulic cylinder in a tilting motion. abutting one end of a pressing rod that is pressed in relation to the
A bypass relief control valve for hydraulic oil in a dump truck, characterized in that the poppet can be opened at an internal pressure equal to or higher than the set pressure in the first port, and can also be opened by pressure from a press rod.