JPS581379Y2 - Platform lifting speed control device for dump trucks, etc. - Google Patents

Description

[Detailed description of the invention] The present invention is a loading platform elevation speed control device for a dump truck, etc., and more specifically, in a hydraulic circuit connecting a dump cylinder and a control valve. If the passing flow rate is small during the platform lowering operation, a free flow with low flow path resistance can be obtained, and if a certain amount of passing flow is about to flow, the flow path is narrowed down to reduce the flow rate. The present invention relates to a control device that is capable of automatically controlling the lifting and lowering speed of a loading platform in accordance with the amount of cargo on the loading platform by interposing a flow rate control valve mechanism that can restrict the flow rate.

Generally, the control of the dump cylinder in a dump truck was carried out only by the control valve, so the lifting and lowering speed of the loading platform, especially the descending speed, was controlled by the driver using the control lever to adjust the degree of port opening using the spool inside the control valve. I was relying on it.

Therefore, when dump trucks are frequently used for road repair, for example, when asphalt, etc. is not discharged all at once, but is discharged in small quantities at the required location, the asphalt, etc. must be lowered while still being loaded on the platform.
Due to its weight, a large amount of pressurized oil in the dump cylinder flows into the tank at once, causing the loading platform to drop rapidly. Even if the dump cylinder stops midway, it will cause a severe shock to the vehicle and the driver, causing the vehicle to crash. damage or cause significant discomfort to the driver.

In order to solve this drawback, it is necessary to limit the amount of oil flowing out from the dump cylinder, but if a generally well-known flow control valve is used as the limiting device, the above drawback can be solved to some extent. Even during the lowering operation when all the cargo on the loading platform is discharged, regardless of the amount of pressure oil flow from the dump cylinder, it must pass through the small diameter orifice that was the main problem solved during the operation, and the flow is always low. This will result in road resistance.

Further, when the loading platform is raised, it is necessary to pass through the orifice or press a poppet provided with the orifice against a spring, and in either case, flow path resistance is encountered.

Therefore, from the viewpoint of workability of dump trucks, when raising the loading platform, the loading platform should be raised quickly by reducing the flow resistance in the middle of the circuit, and when the loading platform has been raised and all the cargo has been released, the loading platform should be raised as quickly as possible. The advantage of conventional dump trucks, which do not have control valves that allow them to lower the flow rate, is negated by the flow control valves used to solve the above disadvantages.

This proposal maintains the advantages of conventional dump trucks,
It is also an object of the present invention to provide a control device that can solve the drawbacks during the lowering operation when there is a load on the platform.

An embodiment of the present invention will be explained in detail below based on the drawings.

The cargo platform 1 has one end pivotally supported by the vehicle body frame 2, and is tilted by the operation of the dump cylinder 3.

The dump cylinder 3 is operated by a hydraulic circuit switching operation of a control valve 4 using a control lever (not shown) disposed at a driver's seat or the like.

Each of the above configurations is a well-known dump operation mechanism installed in a dump truck, and is not a new configuration at all.

5 is a flow control valve mechanism disposed in the hydraulic circuit connecting the dump cylinder 3 and the control valve 4;
The outer cylinder 6 is generally composed of a poppet 7 and a spring 8, and the outer cylinder 6 has a continuous large-diameter flow passage part 6A communicating with the piston chamber of the dump cylinder 3 and a small-diameter flow passage part 6B connected to the control valve 4 at its axial center. The boundary between the two flow path portions 6A and 6B forms a valve seat 6C which serves both as a receiver for the spring 8 and as a stopper for the poppet 7.

Note that 6D is a joint between the valve seat 6C and the small diameter flow path portion 6B,
For the sake of explanation, it is called the valve seat port.

The poppet 7 has a flange portion 7A that slidably fits into the large diameter flow path portion 6A of the outer cylinder 6, and a diameter that is approximately the same or larger than the small diameter flow path portion 6B, and a diameter smaller than the large diameter flow path portion 6A. The movement range in the axial direction is restricted by the retaining ring 9 and the valve seat 6C.

A bottomed channel 10 is bored in the axial center of the poppet 7 along the axial direction and has an open opening facing the large diameter channel section 6A,
An appropriate number of poppet outlets 10B are bored in the side wall near the bottom 10C of the channel 10, and the outer periphery of the bottom 10C has a conical shape, with an appropriate number of stripes along the conical surface. A slit 11 is carved therein.

Moreover, this poppet 7 is always attached in a direction away from the small diameter flow path section 6B, that is, the flange section 7A is in contact with the retaining ring 9 by a spring 8 whose one end is connected to the valve seat 6C and the other end is connected to the flange section 7A. The situation is maintained.

Since the present invention is configured as described above, in order to raise the loading platform, pressurized oil from the pump P is supplied by switching the control valve 4 using the control lever.
When oil is supplied to the small diameter flow path section 6B of the flow path control valve mechanism 5, the poppet 7 is urged toward the retaining ring 9 by the spring 8, so the conical surface of the poppet bottom surface 10C is separated from the valve seat 6C, and the valve is closed. Open the seat opening 6D to the maximum extent possible.

Therefore, the pressure oil enters the bottomed flow path 10 from the poppet outlet 10B of the poppet 7 through the valve seat opening 6D, is sent from the poppet inlet 10A to the large diameter flow path 6A of the outer cylinder 6, and from there flows into the dump cylinder 3. enters the piston chamber.

Therefore, the flow direction of the pressure oil pumped from the pump P changes only slightly, and the flow path resistance is low and it flows smoothly, so the dump cylinder operates quickly and the cargo platform rises quickly.

Next, let's talk about lowering the loading platform.

[When there is no cargo on the loading platform]

Since the platform load applied to the dump cylinder 3 is small, the flow rate of pressure oil discharged from the cylinder 3 per unit time is small, and the inlet 1 of the poppet 7 is smaller than the large diameter flow path 6A of the outer cylinder 6.
The pressure oil entering 0A hits the poppet bottom surface of the bottomed channel 10 and is deflected at right angles, and when flowing out from the poppet outlet 10B, the poppet 7 receives a force in the flow direction (in the direction of the small diameter channel 6B).

F-ρQ2/A F: Force applied to the poppet ρ: Original fluid density Q: Flow rate of fluid per unit time A: Cross-sectional area of the bottomed channel 10 However, this force F is The poppet 7 is not large enough to overcome the biasing force of the spring 8, and the poppet 7 is biased by the spring 8 in a direction away from the small diameter flow path portion 6B, opening the valve seat opening 6D widely.

Therefore, the pressure oil that has exited the poppet outlet 10B flows through the valve seat port 6D to the small diameter flow path section 6B, and then flows down through the control valve 4 to the tank.

Therefore, the flow direction of the pressure oil discharged from the dump cylinder 3 only slightly changes as when the loading platform is raised, and the flow path resistance is small and the flow smoothly flows, so that the loading platform is lowered speedily.

[When there is cargo on the loading platform]

Since the loading platform load on the dump cylinder 3 is large, the flow rate of the pressure oil discharged from the cylinder 3 per unit time is large, and the force F applied to the poppet 7 becomes large, and this force F is applied to the spring 8. If the biasing force becomes stronger than the biasing force, the poppet 7 will move toward the small-diameter flow path portion 6B against the biasing force of the spring 8, and the conical portion at the bottom of the poppet 7 will fit into the valve seat opening 6D, so the slit 11 will be closed. Except for this, the valve seat port 6D is closed.

Therefore, the bottomed flow path 10 and the small diameter flow path portion 6B are formed by the slit 11.
The discharge flow rate from the dump cylinder 3 is limited since the dump cylinder 3 is in communication only with the dump cylinder 3.

At this time, the pressure on the bottomed flow path 10 side of the valve seat port 6D increases,
Since the pressure on the small-diameter flow path portion 6B side becomes low, the poppet 7 maintains a state pressed against the valve seat opening 6D.

Therefore, the descending speed of the loading platform is slow because only the flow rate passing through the slit 11 becomes the allowable descending discharge amount, and even though a large amount of cargo such as asphalt is loaded on the loading platform, the loading platform descends slowly. It's coming.

As described above, during the lifting operation of the loading platform and the lowering operation when most of the cargo on the loading platform has been released, a free flow with low flow path resistance can be obtained at all times, and the lifting operation of the loading platform can be carried out speedily. When lowering the platform with cargo loaded, the flow path is immediately throttled in response to the flow rate that passes through according to the load of the platform, and the rate of descent of the platform is slowed down to limit the amount of discharge from the cylinder. The cargo platform can be lowered slowly.

Therefore, the driver can safely raise and lower the loading platform simply by operating the control lever to the up and down positions.In particular, when lowering the loading platform, the lowering speed is automatically controlled according to the load on the loading platform. Therefore, there is no need to be nervous when operating the control lever, and since the descending speed is slow when loaded, the impact force is small even when descending and stopping at any position, and there is no risk of damaging the vehicle or injuring the driver. It doesn't cause any discomfort.

In addition, the loading platform lifting operation and loading platform lowering operation in an unloaded state are carried out speedily even though a flow control valve mechanism is interposed in the hydraulic circuit, so that there is no loss in work efficiency.

Furthermore, if the flow rate control valve mechanism of the present invention is directly attached to the dump cylinder, it can function as a safety valve to prevent the platform from dropping suddenly even if the pipe between the control valve and the dump cylinder ruptures.

The embodiment of the present invention has been described in detail based on the case where the flow control valve mechanism is installed in the piping to the dump cylinder of a dump truck, but the device of the present invention can also be installed in the lift cylinder of a forklift truck, the lifting cylinder of an autojacket, etc. Since the same effects can be obtained, the present invention is not limited to a loading platform elevating device for a dump truck.

[Brief explanation of drawings]

The drawings show one embodiment of the present device, with FIG. 1 being an explanatory diagram when it is installed on a dump truck, and FIG. 2 being a sectional view of the main part of the present device. 3... Dump cylinder, 4... Control valve, 5... Flow rate control valve mechanism, 6...
...Outer tube, 7...Poppet, 8...
·spring.

Claims (1)

[Scope of utility model registration request] An outer cylinder has a large-diameter flow path section 6A and a small-diameter flow path 6B continuously formed at the axis, and a valve seat section 6C that serves as a spring receiver at the joining point of both flow path sections; It has a bottomed flow path 10 that is fitted into the large diameter flow path and is bored along the axis with a bottom.
A flange portion is provided on the outer periphery of the open side of the bottomed flow path and that slides along the large diameter flow path portion 6A, and a flange portion that can be fitted with the small diameter flow path portion 6B and that slides along the large diameter flow path portion 6A is provided on the outer periphery of the bottom side of the bottomed flow path. Slit 11 that controls the flow rate when fitted with the flow path portion 6B
A poppet formed with , and one end attached to the valve seat portion 6C,
The large diameter flow path section 6A of the flow rate control valve mechanism is constituted by a spring whose other end is joined to a flange portion and biases the poppet in a direction away from the small diameter flow path section 6B. A loading platform elevation speed control device for a dump truck or the like, which is interposed in a conduit to connect the passage portion 6B to a control valve.