JPS6346302Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Technical Field> The present invention relates to a cab tailing device using hydraulic pressure.

<Background Art> A cab tail device using a hydraulic cylinder is configured as shown in FIG. 1, for example. That is, the cab 2 hinged to the tip of the vehicle body frame 1 is raised and lowered around the hinge by a hydraulic cylinder 3.
The cylinder body side is rotatably connected to the vehicle body frame 1, and the rod side is rotatably connected to the cab 2. The cab 2 is raised and lowered by selectively supplying hydraulic oil to the head side chamber or the rod side chamber of the hydraulic cylinder 3. A locking device 4 locks the cab 2 to the vehicle body frame 1.

By the way, in a cab tailing device using such a hydraulic cylinder, the rod position of the hydraulic cylinder 3 is detected and the operation of the oil supply pump is automatically activated so that the cab automatically stops at the tailing position or the traveling position when the cab is raised or lowered. It is configured to stop automatically.

However, such a conventional stopper mechanism uses two limit switches to detect the extended position and the retracted position of the rod using separate limit switches. For this reason, two switches for position detection are required, which is uneconomical, and the switch must be installed near the hydraulic cylinder because it is necessary to detect the extended and contracted positions of the rod. A cover, etc. was necessary because it easily got dirty. This type of stopper mechanism is disclosed in Japanese Unexamined Patent Publication No. 57-155168 and Japanese Utility Model Application No. 58-58982.

<Purpose of the invention> This invention was made in view of the above circumstances.
The purpose of this system is to solve the problems of the conventional hydraulic cylinder by detecting the rod position based on the state of the current flowing through the drive circuit of the electric motor that drives the refueling pump, rather than the extended and retracted positions of the rod in the hydraulic cylinder. do.

<Summary of the invention> For this reason, in the present invention, in a cab tilt device that uses a hydraulic cylinder to raise and lower a cab, the circuit is added to the drive circuit of the electric motor that drives the oil supply pump that supplies hydraulic oil to the hydraulic cylinder for raising and lowering the cab. A circuit interrupting means is provided for detecting that the current flowing through the motor exceeds a predetermined value and interrupting the drive circuit, and the supply current value increases as the load on the motor increases due to the bottoming out state of the hydraulic cylinder. By taking advantage of this fact, the cab is automatically stopped at the tilt position or the traveling position, thereby reducing the number of detection means and preventing contamination, thereby improving reliability and economic efficiency.

<Example> Hereinafter, an example of the present invention will be described based on FIG. 2. Incidentally, the same elements as in FIG. 1 are given the same reference numerals and their explanations will be omitted.

In FIG. 2, the oil supply pump 11 provided in the oil supply circuit of the hydraulic cylinder 3 has its suction side communicating with, for example, an oil pan 13 for storing hydraulic oil through an oil supply passage 12, and its discharge side communicating with an oil supply passage 14 interposed therein. It is connected via a switching valve 15 to a head side chamber 3A and a rod side chamber 3B of the hydraulic cylinder 3 for cab elevation. 16 is an oil return passage connecting the passage switching valve 15 and the oil pan 13.

On the other hand, a motor drive circuit that supplies current to the motor that drives the oil supply pump 11 is configured as follows.

Relay 1 is installed between battery 17 and motor 18.
9 normally open contacts 19a are connected in series. Further, in parallel with the normally open contact 19a, an automatic return type push button type motor operating switch 20 and a relay 1 are connected.
A series circuit of 9 excitation coils 19b is connected. Further, for example, a circuit breaker 21 is connected in series with the motor 18 as a circuit interrupting means for detecting that the current supplied to the motor 18 exceeds a predetermined value and interrupting the motor drive circuit.

Next, the effect will be explained.

Cab lifting and lowering operations are performed in the same manner as before.

First, when the cab 2 is to be tilted, the passage switching valve 15 is set to the lower position as shown in the second figure.
Next, when the operating switch 20 is pressed to turn on, the excitation coil 19b of the relay 19 is energized, the normally open contact 19a is closed, the motor 18 is connected to the battery 17, and the motor 18 starts the oil supply pump 11. Then, hydraulic oil is sucked from the oil pan 13 through the oil supply passage 12, and is supplied from the oil supply passage 14 on the discharge side to the head side chamber 3A of the hydraulic cylinder 3 via the switching valve 15, and the rod 3C extends and closes the cab. 2 rises. At this time, the hydraulic oil in the rod side chamber 3B is returned to the oil pan 13 from the oil return passage 16 via the switching valve 15.

On the other hand, when lowering the cab 2, the passage switching valve 15 is switched to the upper position, contrary to the above.
As a result, the hydraulic oil discharged from the oil supply pump 11 passes through the switching valve 15 and is then supplied from the oil supply path 14 to the rod side chamber 3B of the hydraulic cylinder 3, causing the rod 3C to contract and the cab 2 to descend. The hydraulic oil in the head side chamber 3A is returned to the oil pan 13 from the oil supply path 14 through the switching valve 15 and the oil return path 16 as the rod 3C moves. Note that the operating switch 20 is kept pressed while the cab is being moved up and down.

In such a cab raising/lowering operation, when the rod 3C of the hydraulic cylinder 3 becomes fully extended or compressed, a condition called bottoming out occurs in the hydraulic cylinder 3. Then, the oil pressure on the discharge side of the oil supply pump 11 increases, and as the load on the motor 18 increases due to this increase in oil pressure, the current supplied to the motor 18 also increases. This current also flows through the circuit breaker 21, and when it exceeds a predetermined value, the circuit breaker 21 operates to cut off the motor drive circuit. Therefore, the power to the motor 18 is cut off and stopped, the oil supply to the hydraulic cylinder 3 by the oil supply pump 11 is stopped, and the raising or lowering operation of the cab 2 is automatically stopped.

In this way, by detecting the amount of current in the motor drive circuit that rapidly increases due to an excessive rise in the oil pressure in the hydraulic cylinder 3, and detecting the up/down position of the cab 2, only one detection switch is required, reducing costs. In addition to reducing the installation location of the detection switch, it is not limited to the vicinity of the hydraulic cylinder 3, increasing the degree of freedom in layout.Moreover, it can be installed in a location that is difficult to get dirty, improving reliability and durability. can.

<Effects of the invention> As described above, according to the invention, the current flowing through the motor increases due to the increase in oil pressure as the hydraulic cylinder bottoms out, and this current value is used to increase the current flow when the cab is raised and lowered. Because it is configured to detect the cab stop position, only one position detection means is required, unlike the conventional detection mechanism using a limit switch.Moreover, the position detection means can be installed in locations other than the vicinity of the hydraulic cylinder, where it is easy to get dirty. It becomes possible. Therefore, layout constraints are relaxed, design freedom is improved, and it is possible to prevent dirt from being soiled even without a cover, improving reliability and economical efficiency.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating a cab tail device using a hydraulic cylinder, and FIG. 2 is a motor drive circuit diagram showing one embodiment of the cab tail device according to the present invention. 2... Cab, 3... Hydraulic cylinder, 3A...
Head side chamber, 3B... Rod side chamber, 3C... Rod, 11... Fuel pump, 17... Battery, 1
8...Motor, 20...Operation switch, 21...
circuit breaker.

Claims (1)

[Scope of utility model registration request] In a cab tilt device in which a cab hinged to a vehicle body frame is raised and lowered around the hinge by a hydraulic cylinder, an electric motor drive circuit for supplying current to an electric motor that drives an oil supply pump that supplies hydraulic oil to the hydraulic cylinder for raising and lowering the cab. ,
1. A cab tailing device, comprising a circuit interrupting means for detecting that the current flowing through the circuit exceeds a predetermined value and interrupting the circuit.