JPS62198508A - Suspension cylinder control device for heavy load carrying vehicle - Google Patents

Abstract

PURPOSE:To raise running stability of a vehicle, by connecting an accumulator to a hanging cylinder oil chamber through a no-leak valve, and constituting a suspension cylinder control device as filling up the accumulator with oil whose pressure is the same as the oil pressure fed to the suspension cylinder, in the heavy load carrying vehicle on which a carrier is taken in/out under a pallet or the like. CONSTITUTION:When the first directional change valve 8 is changed to the oil feed side, to lay a heavy load on a carrier in a condition that a suspension cylinder 1 is contracted, and oil is fed to the oil chamber 1a, an accumulator 4 is also filled up with oil through a no-leak valve 3. Accordingly, when the first directional change valve 8 is neutrally positioned, the oil pressure in the accumulator 4 is kept at the same degree as the oil pressure in the suspension cylinder 1. Then, if the oil pressure in the suspension cylinder 1 is varied over the preset range comparing with the oil pressure in the accumulator 4, while the vehicle is running, differential pressure is absorbed by the motion of a double rod hydraulic cylinder 5 and switches 6, 7. With this constitution, running stability of the vehicle is raised.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heavy goods transport vehicle that can move a loading platform into and out of the underside of a pallet, etc. for loading and unloading a pallet carrying a large, heavy object.

[Conventional technology]

A plurality of hydraulic suspension devices i', which also serve as jacks, are provided on both sides of the loading platform to raise and lower the loading platform relative to the separated axle by means of suspension cylinders, and one first hydraulic suspension system i' is capable of simultaneously supplying and discharging pressure oil to the hydraulic oil chambers of all the suspension cylinders. A heavy goods transport vehicle equipped with a directional control valve is disclosed in Japanese Patent Laid-Open No. 51-137223, etc., but the suspension system is divided into three or more groups, and the hydraulic suspension system of each group is controlled by hydraulic pressure. It is designed to form a jack and hydraulic balance device.

[Problem that the invention seeks to solve]

In this prior art, in the four-axle vehicle shown in FIGS. 2 and 3, each suspension device 22 attached to the loading platform 21 is
Divide into three groups, B and C groups on both sides of the rear,
The hydraulic oil chamber 1a of the suspension cylinder 1 in each group is
As shown in the figure, each group has a first pilot check valve 9 for holding pressure oil and a flow control valve 10 that can regulate the flow rate when supplying or discharging pressure oil. When the suspension cylinders and cylinders 1 in each group are connected in parallel to one first directional control valve 8 by sequentially connecting the suspension cylinders and cylinders 1 in parallel, the loading platform 21 is supported at three points a, b, and c, so each wheel 26 is Triangle ab that receives a load but has a narrow center of gravity
c. In FIG. 4, 11 is a hydraulic bonder, 12 is a relief valve, 16 is a pilot oil passage of the first pilot reverse valve 9, and T is a tank.

In order to eliminate the above drawback, each suspension e22 is divided into groups A and D on both sides of the front and groups B and D on both sides of the rear, as shown in Fig. 5.
If the suspension cylinders in each group are divided into four groups, the hydraulic oil chambers of the suspension cylinders in each group are connected to each other, and the control device for the suspension cylinders in each group is provided as described above, the loading platform 21 can be divided into four groups a, b, and c. .

Since the load is supported at four points d, the variation range of the center of gravity position of the load is wide as in the rectangle abcd, but if any one group, for example the wheels 26 of A, is If the load runs over or falls onto Ga or Gb where there is a step on the ground G, one of the groups B and C will rise depending on the position of the center of gravity of the load, and that axle will no longer receive the load. This not only causes the load on the axle to increase and exceed the allowable load, but also causes unstable running.

Also, since the permissible load on each axle when driving on the road is limited, if the cargo load is extremely large.

The number of axles of the four-axle vehicle shown in Figure 3 must be increased to make it a six-axle or eight-axle vehicle, but in this case, the fifth
A similar problem occurs to the vehicle shown in the figure.

Each of the illustrated suspension systems has an arm 25 pivoted to the lower end of a fork-shaped suspension frame 24 attached under the floor of the loading platform so as to be movable up and down on a shaft 26, and a separation axle 27 supported at the tip of the arm. Wheels 26 are attached to both sides of the frame, and a clevis-shaped suspension cylinder 1 is attached between the suspension frame 24 and the arm 25.

[Means for solving problems]

The present invention deals with the above-mentioned problem, and provides pressure oil for the hydraulic oil chamber 1a of the suspension cylinder 1 in at least a pair of left and right suspension devices or in each suspension device group formed by communicating and connecting the hydraulic oil chambers of the respective suspension cylinders. an accumulator 4 connected to the hydraulic oil chamber of the suspension cylinder via a no-leak valve 6, and an accumulator 4 connected to the hydraulic oil chamber of the suspension cylinder through the no-leak valve 6; Both rond type hydraulic cylinders 5 each having an oil chamber 1a connected to the oil chamber on the other side, and switches 6 which are respectively switched when a constant positive and negative pressure difference is generated between the oil chambers on both sides of the rond type hydraulic cylinders.
7 and a circuit for switching the second directional control valve 2 so that the pressure in the hydraulic oil chamber of the suspension cylinder becomes approximately equal to the accumulator pressure by the signals issued by the respective switches, and the first directional control valve 8 is provided. Supply of pressure oil to fully suspended cylinders.

The main feature is that a circuit is provided that opens all the no-leak valves 6 only while switching to the exhaust position.

[For production]

After the vehicle enters the underside of a heavy object supported by a pallet or the like on the ground with the suspension cylinder 1 in the contracted state,
In order to load the heavy object onto the loading platform 21, the loading platform 21 is raised by switching the first directional control valve 8 to the left position in FIG. 1 and supplying pressure oil to the hydraulic oil chamber 1a of the fully suspended cylinder. However, in at least a pair of left and right suspension systems equipped with the device of the present invention, the no-leak valve 6 is activated when the loading platform is raised.
is opened and the accumulator 4 is filled with cylinder operating pressure. Therefore, when the loading platform has finished rising and the first directional switching valve 8 is returned to the neutral position, and all the no-leak valves 6 are closed, the hydraulic pressure Po corresponding to the load is generated in each suspension cylinder 1. The same pressure Po is confined in the accumulator 4. On the other hand, both rond type hydraulic cylinders 5
0 Since the same oil pressure acts on both side oil chambers 5a and sb as in the middle chamber for lifting the loading platform, the switches 6.7 do not issue a signal, and each second
The directional control valve 2 maintains its neutral position so that there is no risk of interfering with the extension of the suspension cylinder.

In addition, in order to unload this heavy cargo, the first directional control valve 8 is switched to the right position in Fig. 1, and the hydraulic oil chamber 1 of the fully suspended cylinder is
Even when the suspension cylinder is contracted by the weight of the loading platform or cargo by connecting the terminal A to the tank T, all the no-leak valves 6 open at the same time to discharge the accumulator pressure, so when the loading platform has finished lowering, the first directional control valve 8 is returned to the neutral position, and therefore all the no-leak valves 6 are closed, the load hydraulic pressure of the suspension cylinder corresponding to the empty load is contained in the accumulator 4. Therefore, each accumulator stores the hydraulic oil chamber pressure of the corresponding suspension cylinder in accordance with the presence or absence of a load, the weight distribution of the load, etc. each time the jack is operated.

Therefore, when the vehicle travels in the direction of the arrow in FIG. 6 and the wheel 26 of the - side suspension system runs onto a step Ga above, the internal pressure Po of the suspension cylinder increases by ΔP and Pl
On the other hand, since the memorized pressure on the accumulator side is Pa, the pressure in the oil chamber 5a of both Rondo type hydraulic cylinders 5 increases by ΔP than the pressure in the other oil chamber 5b.

When this pressure difference ΔP reaches a certain value or more, the piston moves to the right against the elasticity of the right neutral position return spring 5C, closes the switch 7 via the piston rond, and issues a signal. Since the two-way switching valve 2 is switched to the left position in FIG. 1 and the hydraulic oil chamber 1a of the suspension cylinder communicates with the tank T, the suspension cylinder contracts due to the load.Thus, the pressure in the hydraulic oil chamber 1a and 7 cutiator 4
When the difference from the stored pressure becomes less than the neutral position return force due to the spring 5C, the piston of the hydraulic cylinder 5 returns to the neutral position, the switch 7 opens, and the second directional control valve 2 returns to the neutral position. Therefore, if an excessive load is applied only to the separated axle that rides on Ga where there is a step, the suspension cylinder will contract and the wheel will not be lifted, thereby preventing excessive load from being applied to the axle.

In addition, when the vehicle travels in the direction of the arrow in Fig. 7 and the wheel of the - side suspension system is floating at a point Gb where there is a step below, the internal pressure of the suspension cylinder becomes lower than the memorized pressure of the accumulator. . When this pressure difference resists the elasticity of the left neutral position return spring of the hydraulic cylinder 5 and pushes the piston to the left, the switch 6 is closed and a signal is issued, and this signal causes the switch to switch to the second direction. The valve 2 is switched to the right position in FIG. 1, and pressure oil is supplied to the hydraulic fluid chamber 1a of the suspension cylinder, which extends and presses its wheels against the ground. Therefore, when the internal pressure of the suspension cylinder increases and the piston of the hydraulic cylinder 5 returns to the neutral position, the switch 6 opens and returns the second directional control valve 2 to the neutral position. The pair of left and right suspension systems or the suspension cylinders of a suspension system group always support the loading platform with hydraulic pressure approximately equal to the memorized pressure of the accumulator, regardless of the unevenness of the ground. [Example] Figure 1 shows a fully suspended system. Each of the devices is equipped with a double rod-type differential pressure switch control device (5, 6
, 7) show embodiments in which devices of the present invention for controlling the second directional control valve 2 are respectively attached, and members with the same reference numerals as in FIG. 4 are corresponding members.

14 is an oil line that connects a flow control valve that regulates the flow rate to another suspension cylinder (not shown) to the A boat of the first direction switching box 8 in parallel with the flow control valve 10 (not shown); An oil passage connects the pilot oil passage of the first pilot reverse valve, which is to hold the built-in pressure oil of the cylinder, to the first directional control valve 80B boat in parallel with the pilot oil passage 16 shown, and 16 is the other suspended cylinder. An oil passage 17 connects a second directional switching valve for each suspension cylinder 1 to the discharge port of the hydraulic pump 11 in parallel with the second directional switching valve 2 shown in the figure.
The primary side of the second pilot reverse valve 17 and its pilot oil passage 18 are connected to the B boat of the corresponding second directional control valve 2, respectively. Connected to A boat.

A normally closed no-leak valve 6 inserted into an oil passage connecting the hydraulic oil chamber 1a of the suspension cylinder 1 and the accumulator 4,
The no-leak valve switching solenoid 6a of the full suspension system, which opens only when the switching solenoid 6a is energized, is simultaneously energized when either side switching solenoid 8a or 8b of the first directional switching valve 8 is energized. and is controlled by a circuit that becomes non-conductive when the first directional control valve returns to the neutral position shown.

Both rond type hydraulic cylinders 5 have springs 5C symmetrically built therein which always urge the pistons to return to the neutral position, and contact pieces of switches 6.7 are attached to the piston travel distances on both sides, respectively. Therefore, when the piston slides to the right in the figure and closes the switch 7, the solenoid 2a which switches the second directional control valve 2 to the left position in the figure is energized via the signal transmission line 19'. When the piston slides to the left and closes the switch 6, the solenoid 2b which switches the second directional control valve to the right position is energized via its signal transmission line 20. In the figure, E indicates the power source. By using a proportional solenoid valve in place of the second directional switching valve 20, the flow rate of pressure oil sent to the suspension cylinder 1 or the cylinder depending on the amount of piston movement of the two rond type hydraulic cylinders 5. You can also subtly adjust the flow lid that returns to the tank.

Although one embodiment has been described above, in the four-axle vehicle shown in FIG. 5, the above-described device jIL of the present invention can be attached to each of the suspension groups A to D.

Further, between the front suspension group A and the rear suspension group (B r c) of the 4-axle vehicle shown in FIG. 3, a suspension group that is the same as the rear suspension group is added to form a 6-axle vehicle. In this case, the device of the present invention may be attached only to each of the added suspension groups to widen the variation range of the load center position.

〔Effect of the invention〕

According to the present invention, the loading platform supporting force of at least a pair of left and right suspension devices or each suspension cylinder of a suspension device group is made to be approximately equal to the loading platform supporting force when the load is jacked up, regardless of the unevenness of the traveling road surface. As a result, the range of variation in the load center position is widened, which not only makes it possible to cope with changes in the type of cargo and increases in the amount of cargo load, but also eliminates the risk of unstable running. Furthermore, since the hydraulic pressure of the suspension cylinder when the load is jacked up is stored in the accumulator, there is no risk of failure and maintenance is easy.

[Brief explanation of drawings]

Figure 1 is a hydraulic circuit diagram of one embodiment of the present invention, Figures 2 and 3 are
The figures are a side view and a plan view of a conventional vehicle, FIG. 4 is a hydraulic circuit diagram thereof, FIG. 5 is a plan view of a vehicle to which the present invention can be applied, and FIGS. 6 and 7 are a vehicle in motion. FIG. 3 is a side view of main parts. DESCRIPTION OF SYMBOLS 10... Flow control valve, 11... Hydraulic pump, 21... Loading platform, 22... Suspension device, 26...
Wheel, 27... Separate axle. Figure 1 2 Figure ν G 4- Figure

Claims (1)

[Claims] A plurality of suspension devices that also serve as jack devices are provided on both sides of the loading platform to enable the loading platform to be raised and lowered relative to the separated axle by means of suspension cylinders, and a single first direction switch is provided that can simultaneously supply and discharge pressure oil to the hydraulic oil chambers of all the suspension cylinders. In a heavy goods transport vehicle equipped with a valve, each suspension system group formed by connecting at least a pair of left and right suspension systems or the hydraulic fluid chambers of respective suspension cylinders is provided with a hydraulic fluid chamber (1a) of a suspension cylinder (1). a second directional switching valve (2) capable of supplying and discharging pressurized oil to and from the hydraulic oil chamber of the suspension cylinder; A double rod type hydraulic cylinder (5) in which the hydraulic oil chamber (1a) of the suspended cylinder is connected to the oil chamber on the other side.
and a switch (6) that is switched when a certain positive and negative pressure difference occurs between the oil chambers on both sides of the double rod type hydraulic cylinder.
, (7), and a circuit for switching the second directional control valve (2) so that the pressure in the hydraulic oil chamber of the suspension cylinder becomes approximately equal to the accumulator pressure by the signals issued by the respective switches, and Suspended cylinder control for a heavy goods transport vehicle, characterized in that a circuit is provided that opens all no-leak valves (3) only while the directional switching valve (8) is switched to the position of supplying and discharging pressure oil to the fully suspended cylinder. Device.