JPS5914474Y2 - Truck crane hydraulic jack control device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a hydraulic jack control system for a truck crane, in which a hydraulic jack is attached to the front end of the vehicle body, and hydraulically operated outriggers on both sides are attached to the middle and rear ends of the vehicle body, respectively.

In general, the bending rigidity of the front end of a truck crane is significantly smaller than that of the rear of the vehicle, which is supported on the ground via outriggers. Therefore, front end hydraulic jacks are used when the load is large during front-hanging cargo handling operations, and the center of gravity of the truck crane is moved to the middle of the outriggers on both sides. It is desirable to support the front end of the vehicle body with a corresponding force only when the vehicle moves further forward to prevent the initial forward tilting movement of the vehicle body.

However, if the ground pressure at the lower end of the front end hydraulic jack is too low, the lower end of the front end hydraulic jack will sink into the ground due to the permissible front suspension load on soft or uneven ground, causing an initial forward tilting movement of the vehicle body. The center of gravity of the truck crane may move further forward than the IJ (IJ), causing the front end of the truck to bend.

In order to prevent this, even if reduced pressure oil is supplied to the front end hydraulic jack at the same time as the outrigger is extended, the pressure oil tends to flow first to the front end hydraulic jack, which has less extension resistance, so the front end hydraulic jack is on the side of the outrigger. There is a tendency for the front end hydraulic jack to extend before the hydraulic jack, but once it has extended, the front end hydraulic jack cannot be contracted immediately, so if there is a difference in the extension speed of the intermediate outrigger and the rear end outrigger, the front end hydraulic jack or There is a risk that an unexpected load will be applied to the front end of the vehicle.

The present invention addresses these problems by connecting the upper and lower cylinder chambers 4 of the front end hydraulic jack 3 to the hydraulic power source 1 via the pressure reducing valve 2.
, 5, the pressure reducing valve and the upper cylinder chamber 4.
A switching valve 6 is inserted into the oil passage between the upper and lower cylinder chambers 4 and 5, and has a normal position for blocking the upper and lower cylinder chambers 4 and 5 and a switching position for communicating both the upper and lower cylinder chambers with the secondary side of the pressure reducing valve 2. A device that generates a signal when the directional switching valve 8 that controls the outrigger side hydraulic jack 7 is switched to the extended or retracted position, and a device that switches the switching valve 6 based on the signal from the signal generating device are attached,
An IJ valve 9 whose set pressure is slightly higher than that of the pressure reducing valve 2 is connected to the upper cylinder chamber 4 of the front end hydraulic jack 3, and is placed between the hydraulic power source 1 and the front end hydraulic jack 3 in a permanent position that blocks the gap between them. The present invention is characterized in that a hydraulic circuit controlled by a switching valve 10 having a switching device for reducing front end hydraulic jack is provided in parallel with a front end hydraulic jack operating circuit including a pressure reducing valve 2.

An embodiment of the present invention will be described below with reference to the drawings.

Reference numeral 11 denotes a truck crane body, and the body 11 has a portion approximately in front of the front wheels 12 that has significantly lower bending rigidity than a portion behind it.

Reference numeral 13 denotes a pair of left and right outriggers attached to the intermediate and rear ends of the vehicle body 11, which have high bending rigidity.
are outer cylinders 14 fixed to the lower surface of the vehicle body 11 as shown in FIG.
A telescopic beam in which the inner cylinder 15 is slidably inserted and the inner and outer cylinders are connected by a telescopic cylinder 16;
The hydraulic jack 7 has a cylinder portion fixed to the tip thereof, and a ground plate 18 is tiltably attached to the lower end of the piston rod 17 of the hydraulic jack.

There are two front end hydraulic jacks 3, each having a cylinder portion fixed to both sides of the front end of the vehicle body 11, and a grounding plate 20 is attached to the lower end of the piston rod 19 so as to be tiltable.

Reference numeral 21 denotes a swivel base mounted on the vehicle body 11 above the rear wheels 22 located between the intermediate and rear end outriggers 13;
Reference numeral 3 denotes a telescopic telescoping boot 4 which is supported by a cantilever on the swivel base 21 so as to be adjustable in elevation. 24 is an automobile driver's cab attached to the right side of the front end of the vehicle body 11.

The illustrated switching valve 10 is a three-position directional switching valve so that the front end hydraulic jack 3 can be controlled to extend. The position direction switching valve 25- and the three position direction switching valve 8 for controlling each hydraulic jack 7 are connected to a hydraulic power source (
hydraulic pump) °1 in parallel via an oil line 26,
A switching valve 6 is provided for each operating circuit of each front end hydraulic jack 3.

In FIG. 4, A indicates the connection range of each directional switching valve 10, B indicates a connection range of each directional switching valve 25, and C indicates a connection range of each directional switching valve 8.

The switching device of each switching valve 6 and its operation signal generating device are connected to its neutral position circulation oil passage (center bypass oil passage) so that the directional switching valve 8 group is located downstream of the other directional switching valve 10.25 group. 27 is connected, and the switching valve 6 is pilot-operated, and its pilot oil passage 28 is connected to the circulation oil passage 27 between the omnidirectional switching valve 8 and the omnidirectional switching valve 25.

For this reason, even if any of the directional switching valves 8 is switched from the neutral position shown in the figure where the circulation oil passage 27 is conducted to either the extended or retracted position, pilot pressure is generated in the pilot oil passage 28 and the switching valve 6
is switched to the right position in FIG. 4, but no pilot pressure is generated even if the directional control valve 25 or 10 is switched.

In the figure, 29 is a pilot check valve inserted into the high pressure oil passage 30 when the hydraulic jack 7 is extended, and 31 is the oil passage 3 on the opposite side.
2 is a pilot oil passage; 33 is a pilot check valve inserted into the high pressure side oil passage 34 when the hydraulic jack 3 is extended;
5 is a pilot oil passage from the primary side of the pressure reducing valve 2, 36 is a drain oil passage of the pilot operated pressure reducing valve 2, and 37 is a relief valve.

According to the above configuration, after controlling the omnidirectional switching valve 25 to extend the telescopic beam (14, 15), when the omnidirectional switching valve 8 is switched to the extended position (lower position in FIG. 4), the hydraulic source 1 ．． The circulation oil passage 27 between the directional switching valves 8 also becomes a high pressure side and generates pilot pressure in the pilot oil passage 28, and the pilot pressure switches the switching valve 6 to the right position (switching position) in FIG. 4. Since the upper and lower cylinder chambers 4 and 5 of the front end hydraulic jack 3 are connected to the secondary side of the pressure reducing valve 2 and communicate with each other, the front end hydraulic jack receives the weight of its piston rod 19 and grounding plate 20, and the pressure receiving area of the upper and lower pistons. The piston rod expands due to the difference in pressure or the reduced hydraulic pressure acting on the cross-sectional area of the piston rod.

In this way, the vehicle body 1 is moved by the full hydraulic jack 7 from Figures 1 to 3.
When it is lifted as shown in the figure and the lower end of the front end hydraulic jack 3 touches the ground, the omnidirectional switching valve 8 is returned to the neutral position and the hydraulic jack 7 is locked.

Then, the pilot oil pressure disappears, so the switching valve 6 returns to the normal position shown and locks the front end hydraulic jack 3.

Next, when retracting the outriggers, switch the omnidirectional switching valve 8 to the retracted position (upper position in Figure 4), the pilot check valve 29.33 opens and the full hydraulic jack 7 begins to retract, and at the same time the pilot Since a pilot pressure equal to the pilot pressure for opening the check valve is generated in the pilot oil passage 28, the switching valve 6 is switched to the right position in FIG. 4, and the upper and lower cylinder chambers 4 and 5 communicate with each other.

Therefore, as the vehicle body 1 descends due to the reduction of the total hydraulic jack 7, the front end hydraulic jack 3 is compressed and compressed by the ground.
Excess oil based on the difference in cross-sectional area between the upper and lower cylinder chambers 4 and 5 returns to the tank T by opening the relief valve 9.

After the wheels 12.22 touch the ground in this way, when the full hydraulic jack 7 is fully contracted and the omnidirectional switching valve 8 is returned to the neutral position,
As described above, since the pilot pressure in the pilot oil passage 28 disappears, the switching valve 6 returns to the normal position shown in the figure, but at this time, the lower end of the front end hydraulic jack 3 is still in contact with the ground.

Therefore, when the full switching valve 10 is switched to the upper position (reduced position) in FIG. 4, the pilot check valve 33 opens again.
The lower cylinder chamber 5 becomes the high-pressure side, and the oil in the upper cylinder chamber 4 returns to the tank via the switching valves 6 and 10. While the front end hydraulic jack 3 is completely reduced, the omnidirectional switching valve 25 moves the oil into the telescopic beam (14, 15). ).

In the figure, for convenience of explanation, each directional switching valve 10, 25.8 is manually controlled, but if each directional switching valve is a three-position electromagnetic directional switching valve commonly used in the past, the switching valve 10, 25. Since the and direction switching valve 25 can be operated simultaneously, the front end hydraulic jack 3 can be completely reduced while the telescopic beam is being reduced.

Further, the switching device of the switching valve 6 and its operation signal generating device are not limited to the above-mentioned pilot control method, and the switching device of the switching valve 6. The directional control valve 8 is controlled by an electromagnetic control system, and the directional control valve 6
, 8 can be simultaneously switched with one changeover switch.

According to the present invention, whenever the outrigger side hydraulic jack 7 is extended or contracted, the upper and lower cylinder chambers 4 and 5 of the front end hydraulic jack 3 communicate with each other, so that the front end hydraulic jack responds to the reduced pressure pressure acting on the cross-sectional area of the piston rod. Since the extension is applied with a corresponding force, when the hydraulic jack 7 expands and contracts, the bending stress acting on the front part of the car body, which has low bending rigidity, is significantly reduced, preventing a decrease in fatigue strength. The ground pressure of the front end hydraulic jack 3 can be increased to such an extent that the initial forward tilting movement of the vehicle body 1 can be prevented in accordance with the allowable load.

[Brief explanation of drawings]

1 and 2 are a side view and a plan view, respectively, of the truck crane when the outriggers are extended, FIG. 3 is a sectional view taken along line XX in FIG. 1, and FIG. 4 is a hydraulic circuit diagram. 11... Vehicle body, 13... Outrigger,
16...Telescopic cylinder, 21...Swivel base, 23...Telescopic boom, 25...Telescopic cylinder directional switching valve, 28...・Pilot oil passage.

Claims (1)

[Scope of utility model registration request] In a truck crane that has a hydraulic jack installed at the front end and hydraulically operated outriggers on both sides installed at the middle and rear ends of the vehicle body, the upper and lower cylinder chambers 4.5 of the front end hydraulic jack 3 are connected to the hydraulic source 1 through a pressure reducing valve 2. Among the communicating oil passages, in the oil passage between the pressure reducing valve and the upper cylinder chamber 4, there is a permanent position where the upper and lower cylinder chambers 4 and 5 are cut off, and the upper and lower cylinder chambers are both on the secondary side of the pressure reducing valve 2. A switching valve 6 having a communicating sliding switching position is inserted, and a device for generating a signal when the directional switching valve 8 that controls each outrigger side hydraulic jack 7 is switched to the extended or linear position, and a device that generates a signal by the signal of the signal generating device. A relief valve 9 having a set pressure slightly higher than that of the pressure reducing valve 2 is connected to the upper cylinder chamber 4 of the front end hydraulic jack 3, and between the hydraulic power source 1 and the front end hydraulic jack 3, A truck characterized in that a hydraulic circuit controlled by a switching valve 10, which has a constant position for blocking the gap between the two and a switching position for reducing the front end hydraulic jack, is provided in parallel with a front end hydraulic jack operating circuit including a pressure reducing valve 2. Crane hydraulic jack control device.