Aerial work platform

Abstract

To provide a vehicle for working at height that has a simple configuration and exhibits a stable oscillation function even when the temperature of the working environment changes. [Solution] The pressure of the pressurized oil sealed in the extension-side closed line 7 and compression-side closed line 8 that make up the axle sway absorbing hydraulic circuit is set arbitrarily within a pressure change range W that corresponds to the allowable operating temperature range set for the aerial work vehicle. The valve switching state maintenance pressure of the extension-side hydraulic control valve and compression-side hydraulic control valve at the upper limit value A of the allowable operating temperature range is set to a pressure at which the extension-side hydraulic control valve and compression-side hydraulic control valve operate in response to pilot pressure. Furthermore, the pressure of the pressurized oil in the first hydraulic cylinder 6L and the second hydraulic cylinder 6R at the lower limit value B of the allowable operating temperature range is set to a pressure at which the operating state of the first hydraulic cylinder 6L and the second hydraulic cylinder 6R is maintained without being affected by air bubbles remaining in the cylinders.

Description

[Technical Field]

[0001] The present invention relates to a high-altitude work vehicle in which hydraulic cylinders are mounted between both ends of an axle on which wheels are mounted and the vehicle body for hydraulic suspension. [Background technology]

[0002] BACKGROUND ART Conventionally, an example of a work vehicle equipped with this type of hydraulic cylinder between the axle and the vehicle body is the work vehicle disclosed in Patent Document 1.

[0003] This work vehicle is equipped with a suspension spring mechanism that supports the axle on the vehicle body so that it can swing freely, and a pair of lock cylinders arranged between both ends of the axle and the vehicle body. The bottom chambers and rod chambers of the pair of lock cylinders are connected by a pair of pipes. Each pipe is connected to an oil tank via a pair of switch valves, and during work, the pipes are closed by the pair of switch valves to form a closed circuit. When the work vehicle is traveling with the closed circuit formed, if a rolling motion occurs, each rod of the pair of lock cylinders will follow that rolling motion, giving the work vehicle an oscillation function. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-136932 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above-mentioned conventional work vehicles, in order to provide the work vehicle with an oscillation function, it is necessary to connect an oil tank via a switching valve to each hydraulic closed circuit formed between the bottom chamber and rod chamber of the lock cylinder. Meanwhile, there is a constant demand for work vehicles with a simpler configuration.

[0006] Furthermore, work vehicles are used in a variety of environments, and it is necessary for the work vehicle to have a stable oscillation function even if the temperature of the operating environment changes and the pressure of the pressurized oil sealed in the hydraulic closed circuit changes.

[0007] The present invention has been made to solve such problems, and aims to provide an aerial work platform with a simple configuration that can stably perform oscillation functions even when the ambient temperature changes during use. [Means for solving the problem]

[0008] To this end, the present invention provides: a first hydraulic cylinder for a hydraulic suspension, the first hydraulic cylinder having a rod connected to one end of an axle on which a wheel is mounted and a bottom of a cylinder tube attached to a vehicle body; a second hydraulic cylinder for a hydraulic suspension, the second hydraulic cylinder having a rod connected to the other end of the axle and a bottom of a cylinder tube attached to the vehicle body; a closed extension-side pipe line that connects the extension-side oil chambers of the first hydraulic cylinder and the second hydraulic cylinder, and through which no sealed pressure oil flows in or out; a closed retraction-side pipeline that connects the retraction-side oil chambers of the first hydraulic cylinder and the second hydraulic cylinder, and through which no sealed pressure oil flows in or out; an extension-side hydraulic control valve provided in the extension-side closed line; a compression side hydraulic control valve provided in the compression side closed line; Equipped with The extension side hydraulic control valve and the compression side hydraulic control valve are set, according to the applied pilot pressure, so that the flow direction of pressure oil in the extension side closed line is from the first hydraulic cylinder to the second hydraulic cylinder and the flow direction of pressure oil in the compression side closed line is from the second hydraulic cylinder to the first hydraulic cylinder, or the flow direction of pressure oil in the extension side closed line is from the second hydraulic cylinder to the first hydraulic cylinder and the flow direction of pressure oil in the compression side closed line is from the first hydraulic cylinder to the second hydraulic cylinder, The pressure of the pressure oil sealed in the extension side closed line and the contraction side closed line is set within a pressure change range corresponding to a set allowable operating environmental temperature range, The valve switching state holding pressure of the extension side hydraulic control valve and the compression side hydraulic control valve at the upper limit value of the allowable operating environmental temperature range is set to a pressure at which the extension side hydraulic control valve and the compression side hydraulic control valve operate in accordance with the pilot pressure, The pressure of the hydraulic oil in the first and second hydraulic cylinders at the lower limit of the allowable operating temperature range is set to a pressure that maintains the operating state of the first and second hydraulic cylinders without being affected by air bubbles remaining in the cylinders. We have configured a high-altitude work vehicle.

[0009] According to this configuration, the direction of pressure oil flow through the extension-side closed line is set from the first hydraulic cylinder to the second hydraulic cylinder, and the direction of pressure oil flow through the compression-side closed line is set from the second hydraulic cylinder to the first hydraulic cylinder, depending on the pilot pressure applied to the extension-side hydraulic control valve and the compression-side hydraulic control valve. This flow of pressure oil operates the first and second hydraulic cylinders, causing an upward force from the wheel that lifts one end of the axle off the ground, causing the one end of the axle to swing upward. Even if this swing lifts the one end of the axle upward, the swing is absorbed by the first hydraulic cylinder retracting and the second hydraulic cylinder extending. Therefore, even if the one end of the axle swings upward, the posture of the vehicle body supported by the first and second hydraulic cylinders remains horizontal.

[0010] Furthermore, depending on the pilot pressure applied to the extension-side hydraulic control valve and the compression-side hydraulic control valve, the direction of pressure oil flow through the extension-side closed line is set from the second hydraulic cylinder to the first hydraulic cylinder, and the direction of pressure oil flow through the compression-side closed line is set from the first hydraulic cylinder to the second hydraulic cylinder. This flow of pressure oil operates the first and second hydraulic cylinders, causing the other end of the axle to receive an upward force from the wheel, lifting it off the ground. Even if this causes the other end of the axle to swing upward, this swing is absorbed by the second hydraulic cylinder retracting and the first hydraulic cylinder extending. Therefore, even if the other end of the axle swings upward, the vehicle body supported by the first and second hydraulic cylinders remains horizontal.

[0011] In addition, the pressure of the enclosed pressure oil in the closed extension-side pipes and the closed compression-side pipes that connect the extension-side oil chambers and the compression-side oil chambers of the first hydraulic cylinder and the second hydraulic cylinder, and that do not allow the enclosed pressure oil to flow in or out, is set within a pressure change range that corresponds to the allowable operating temperature range set for the aerial work platform. The valve switching state holding pressure of the extension-side hydraulic control valve and the compression-side hydraulic control valve at the upper limit of the allowable operating temperature range is set to a pressure at which the extension-side hydraulic control valve and the compression-side hydraulic control valve operate in accordance with the pilot pressure applied to the extension-side hydraulic control valve and the compression-side hydraulic control valve. Furthermore, the pressure of the pressure oil in the first hydraulic cylinder and the second hydraulic cylinder at the lower limit of the allowable operating temperature range is set to a pressure that maintains the operating state of the first hydraulic cylinder and the second hydraulic cylinder without being affected by air bubbles remaining in the cylinder.

[0012] Therefore, without the need to connect an oil tank or the like via a switching valve to supply pressure oil to each hydraulic closed circuit formed between the extension oil chambers of the first hydraulic cylinder and the compression oil chambers of the second hydraulic cylinder, as in the past, this system can respond to changes in the actual operating temperature by simply setting the pressure of the pressure oil sealed in each hydraulic closed circuit within a pressure change range corresponding to the allowable operating temperature range. In other words, even if the operating temperature rises, the applied pilot pressure overcomes the valve switching state maintenance pressure of the extension hydraulic control valve and the compression hydraulic control valve, and they operate according to the pilot pressure, as long as the actual operating temperature is lower than the upper limit of the set allowable operating temperature range. Furthermore, even if the operating temperature drops, the pressure of the pressure oil in the first hydraulic cylinder and the second hydraulic cylinder is set to a pressure that maintains the operating state of the first hydraulic cylinder and the second hydraulic cylinder without being affected by air bubbles remaining in the cylinder, as long as the actual operating temperature is higher than the lower limit of the set allowable operating temperature range.

[0013] This makes it possible to provide a vehicle for working at height that has a simple configuration and that can stably perform its oscillation function even when the temperature of the environment in which it is used changes.

[0014] The present invention also provides The extension side hydraulic control valve comprises: a first sequence valve provided corresponding to the first hydraulic cylinder and interrupting the flow of pressure oil through the extension side closed line in a direction from the first hydraulic cylinder to the second hydraulic cylinder; a first check valve connected in parallel to the first sequence valve and allowing the flow of pressure oil from the second hydraulic cylinder to flow from the second hydraulic cylinder to the first hydraulic cylinder and stopping the flow of pressure oil from the first hydraulic cylinder to the second hydraulic cylinder; a second sequence valve provided corresponding to the second hydraulic cylinder and interrupting the flow of pressure oil through the extension side closed line in a direction from the second hydraulic cylinder to the first hydraulic cylinder; and a second check valve connected in parallel to the second sequence valve and allowing the flow of pressure oil from the first hydraulic cylinder to flow from the second hydraulic cylinder to the second hydraulic cylinder and stopping the flow of pressure oil from the second hydraulic cylinder to the first hydraulic cylinder; The compression side hydraulic control valve is composed of: a third sequence valve provided corresponding to the first hydraulic cylinder and interrupting the flow of pressure oil through the compression side closed line in the direction from the first hydraulic cylinder to the second hydraulic cylinder; a third check valve connected in parallel to the third sequence valve and allowing the flow of pressure oil from the second hydraulic cylinder to flow from the second hydraulic cylinder to the first hydraulic cylinder and stopping the flow of pressure oil from the first hydraulic cylinder to the second hydraulic cylinder; a fourth sequence valve provided corresponding to the second hydraulic cylinder and interrupting the flow of pressure oil through the compression side closed line in the direction from the second hydraulic cylinder to the first hydraulic cylinder; and a fourth check valve connected in parallel to the fourth sequence valve and allowing the flow of pressure oil from the first hydraulic cylinder to flow from the first hydraulic cylinder to the second hydraulic cylinder and stopping the flow of pressure oil from the second hydraulic cylinder to the first hydraulic cylinder. It is characterized by:

[0015] When one end of the axle receives an upward force from the wheel, which moves it away from the ground, the end of the axle swings upward. In this case, the rod of the first hydraulic cylinder receives a force from the end of the axle in a direction that causes it to contract.

[0016] According to this configuration, the first sequence valve opens the extension-side closed line in a continuity state, allowing pressure oil to flow from the first hydraulic cylinder to the second hydraulic cylinder, depending on the pilot pressure applied to the extension-side hydraulic control valve. The second check valve allows pressure oil to flow from the first hydraulic cylinder to the second hydraulic cylinder, so the extension-side closed line forms a closed line through which pressure oil flows from the first hydraulic cylinder to the second hydraulic cylinder. Therefore, pressure oil filling the extension-side oil chamber of the first hydraulic cylinder flows from the first hydraulic cylinder to the second hydraulic cylinder through the extension-side closed line via the first sequence valve. Then, the pressure oil flows into the extension-side oil chamber of the second hydraulic cylinder through the second check valve connected in parallel to the second sequence valve.

[0017] At the same time, in response to the pilot pressure applied to the compression-side hydraulic control valve, the fourth sequence valve opens the compression-side closed line, allowing pressure oil to flow from the second hydraulic cylinder to the first hydraulic cylinder. The third check valve allows pressure oil to flow from the second hydraulic cylinder to the first hydraulic cylinder, forming a closed line through which pressure oil flows from the second hydraulic cylinder to the first hydraulic cylinder. Therefore, the pressure oil filling the compression-side oil chamber of the second hydraulic cylinder is compressed by the pressure oil flowing from the first hydraulic cylinder into the extension-side oil chamber and flows out of the compression-side oil chamber. The pressure oil then flows from the second hydraulic cylinder to the first hydraulic cylinder through the fourth sequence valve in the compression-side closed line, passes through the third check valve connected in parallel to the third sequence valve, and flows into the compression-side oil chamber of the first hydraulic cylinder.

[0018] Therefore, the first hydraulic cylinder contracts its rod and retracts, while the second hydraulic cylinder extends its rod. As a result, the upward swing of one end of the axle is absorbed by the first hydraulic cylinder retracting and the second hydraulic cylinder extending, and the position of the vehicle body supported by the first and second hydraulic cylinders is kept horizontal.

[0019] When the other end of the axle receives an upward force from the wheel, which moves it away from the ground, the other end of the axle swings upward. In this case, the rod of the second hydraulic cylinder receives a force from the other end of the axle in a retracting direction.

[0020] According to this configuration, the second sequence valve opens the extension-side closed line, allowing pressure oil to flow from the second hydraulic cylinder to the first hydraulic cylinder, depending on the pilot pressure applied to the extension-side hydraulic control valve. Because the first check valve allows pressure oil to flow from the second hydraulic cylinder to the first hydraulic cylinder, the extension-side closed line forms a closed line allowing pressure oil to flow from the second hydraulic cylinder to the first hydraulic cylinder. Therefore, pressure oil filling the extension-side oil chamber of the second hydraulic cylinder flows from the second hydraulic cylinder to the first hydraulic cylinder through the extension-side closed line via the second sequence valve. Then, the pressure oil flows into the extension-side oil chamber of the first hydraulic cylinder through the first check valve connected in parallel to the first sequence valve.

[0021] At the same time, in response to the pilot pressure applied to the compression-side hydraulic control valve, the third sequence valve opens the compression-side closed line, allowing pressure oil to flow from the first hydraulic cylinder to the second hydraulic cylinder. The fourth check valve allows pressure oil to flow from the first hydraulic cylinder to the second hydraulic cylinder, forming a closed line through which pressure oil flows from the first hydraulic cylinder to the second hydraulic cylinder. Therefore, the pressure oil filling the compression-side oil chamber of the first hydraulic cylinder is compressed by the pressure oil flowing from the second hydraulic cylinder into the extension-side oil chamber and flows out of the compression-side oil chamber. The pressure oil then flows from the first hydraulic cylinder to the second hydraulic cylinder through the third sequence valve in the compression-side closed line, and then flows into the compression-side oil chamber of the second hydraulic cylinder through the fourth check valve connected in parallel to the fourth sequence valve.

[0022] Therefore, the second hydraulic cylinder contracts its rod and retracts, while the first hydraulic cylinder extends its rod. As a result, the upward swing of the other end of the axle is absorbed by the second hydraulic cylinder retracting and the first hydraulic cylinder extending, and the position of the vehicle body supported by the first and second hydraulic cylinders is kept horizontal.

[0023] The present invention is also characterized by comprising a first pressure adjustment port provided in the extension side closed line for adjusting the pressure of the pressure oil in the extension side closed line, a first pressure detection port provided in the extension side closed line for detecting the pressure of the pressure oil in the extension side closed line, a second pressure adjustment port provided in the compression side closed line for adjusting the pressure of the pressure oil in the compression side closed line, and a second pressure detection port provided in the compression side closed line for detecting the pressure of the pressure oil in the compression side closed line.

[0024] With this configuration, the allowable operating ambient temperature range set for the aerial work vehicle is set relatively high, and the pressure of the pressurized oil in the extension side closed line and the compression side closed line can be lowered to an appropriate value by adjusting the opening of the first pressure adjustment port and the second pressure adjustment port while detecting it with the first pressure detection port and the second pressure detection port according to the actual ambient temperature of the aerial work vehicle used. As a result, if the ambient temperature range of the actual environment is lower than initially set, the pressure of the pressurized oil in the extension side closed line and the compression side closed line, which was set relatively high, can be adjusted lower according to the actual environment, and the oscillation function can be performed appropriately according to the ambient temperature.

[0025] The present invention is also characterized by including a first air vent port provided in the extension-side closed conduit and a second air vent port provided in the compression-side closed conduit.

[0026] According to this configuration, the pressure of the pressure oil in the extension side closed line and the compression side closed line can be increased by supplying pressure oil to the extension side closed line and the compression side closed line via the first air bleed port and the second air bleed port. As a result, if the adjustment of the pressure of the pressure oil in the extension side closed line and the compression side closed line is made too low, the pressure can be increased to perform fine pressure adjustment and set to an appropriate value. [Effects of the Invention]

[0027] According to the present invention, it is possible to provide an aerial work platform that has a simple configuration and is capable of stably exhibiting an oscillation function even when the ambient temperature in which it is used changes. [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a schematic structural diagram of a traveling device in an aerial work vehicle according to an embodiment of the present invention; [Figure 2] FIG. 2 is a circuit diagram of a hydraulic circuit provided in the traveling device shown in FIG. [Figure 3] 3 is a diagram for explaining the pressure setting of pressure oil sealed in the pipelines of the hydraulic circuit shown in FIG. 2.

[0023] FIG. [Figure 4] 2 is a schematic diagram showing a state in which an axle of the traveling device shown in FIG. 1 is swinging. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0029] Next, an embodiment of the aerial work vehicle according to the present invention will be described. In the drawings, the same or corresponding parts will be denoted by the same reference numerals.

[0030] FIG. 1 is a conceptual diagram showing a schematic structure of a wheeled traveling device 1 in an aerial work vehicle according to one embodiment of the present invention.

[0031] The wheeled traveling device 1 is configured by connecting an axle 3 to a vehicle body frame 2 via a swing shaft 4. A pair of wheels 5L, 5R are attached to both ends of the axle 3. The axle 3 is configured to be able to swing freely in the width direction of the vehicle body together with the wheels 5L, 5R around the swing shaft 4. In this embodiment, a case will be described in which the wheels 5L, 5R are the front wheels of a vehicle for working at height.

[0032] A first hydraulic cylinder 6L for hydraulic suspension is provided between one end of the axle 3 and the body frame 2. A second hydraulic cylinder 6R for hydraulic suspension is provided between the other end of the axle 3 and the body frame 2. The first hydraulic cylinder 6L has a rod connected to one end of the axle 3, and the bottom of the cylinder tube is attached to the body frame 2. The second hydraulic cylinder 6R has a rod connected to the other end of the axle 3, and the bottom of the cylinder tube is attached to the body frame 2.

[0033] The extension-side oil chambers 6L1 and 6R1, which are oil chambers on the cylinder cap side of the first hydraulic cylinder 6L and the second hydraulic cylinder 6R, are connected by an extension-side closed line 7, allowing pressure oil to pass between them. The compression-side oil chambers 6L2 and 6R2, which are oil chambers on the cylinder rod side of the first hydraulic cylinder 6L and the second hydraulic cylinder 6R, are connected by a compression-side closed line 8, allowing pressure oil to pass between them. The extension-side closed line 7 and the compression-side closed line 8 each form a closed hydraulic circuit where the enclosed pressure oil does not flow in or out.

[0034] FIG. 2 is a circuit diagram of an axle vibration absorbing hydraulic circuit formed by the first hydraulic cylinder 6L, the second hydraulic cylinder 6R, the extension-side closed pipe line 7, and the compression-side closed pipe line 8.

[0035] An extension-side hydraulic control valve is provided in the extension-side closed line 7, and a compression-side hydraulic control valve is provided in the compression-side closed line 8.

[0036] The extension side hydraulic control valve is composed of a first sequence valve 10L and a first check valve 11L which constitute a first counterbalance valve, and a second sequence valve 10R and a second check valve 11R which constitute a second counterbalance valve. The compression side hydraulic control valve is composed of a third sequence valve 12L and a third check valve 13L which constitute a third counterbalance valve, and a fourth sequence valve 12R and a fourth check valve 13R which constitute a fourth counterbalance valve.

[0037] The first to fourth sequence valves 10L, 10R, 12L, and 12R are supplied with the same pilot signal P as hydraulic pressure, that is, pilot pressure, from a hydraulic pump (not shown). In Fig. 2, this pilot signal P is indicated by a dotted line. The pilot signal P is supplied to the first to fourth counterbalance valves as appropriate, by turning on and off the pressure oil output from the hydraulic pump using the pilot valve.

[0038] The first sequence valve 10L constituting the first counterbalance valve is provided corresponding to the first hydraulic cylinder 6L, and in response to an applied pilot pressure, connects and disconnects the flow of pressure oil through the extension-side closed line 7 in the direction from the first hydraulic cylinder 6L to the second hydraulic cylinder 6R. The first check valve 11L is connected in parallel to the first sequence valve 10L, and allows the flow of pressure oil from the second hydraulic cylinder 6R to the first hydraulic cylinder 6L, but blocks the flow of pressure oil from the first hydraulic cylinder 6L to the second hydraulic cylinder 6R. The second sequence valve 10R constituting the second counterbalance valve is provided corresponding to the second hydraulic cylinder 6R, and in response to an applied pilot pressure, connects and disconnects the flow of pressure oil through the extension-side closed line 7 in the direction from the second hydraulic cylinder 6R to the first hydraulic cylinder 6L. The second check valve 11R is connected in parallel to the second sequence valve 10R and allows the flow of pressure oil from the first hydraulic cylinder 6L to the second hydraulic cylinder 6R, but blocks the flow of pressure oil from the second hydraulic cylinder 6R to the first hydraulic cylinder 6L.

[0039] Furthermore, the third sequence valve 12L constituting the third counterbalance valve is provided corresponding to the first hydraulic cylinder 6L, and in response to the applied pilot pressure, connects and disconnects the flow of pressure oil through the compression-side closed line 8 in the direction from the first hydraulic cylinder 6L to the second hydraulic cylinder 6R. The third check valve 13L is connected in parallel to the third sequence valve 12L, and allows the flow of pressure oil from the second hydraulic cylinder 6R to the first hydraulic cylinder 6L, but blocks the flow of pressure oil from the first hydraulic cylinder 6L to the second hydraulic cylinder 6R. The fourth sequence valve 12R constituting the fourth counterbalance valve is provided corresponding to the second hydraulic cylinder 6R, and in response to the applied pilot pressure, connects and disconnects the flow of pressure oil through the compression-side closed line 8 in the direction from the second hydraulic cylinder 6R to the first hydraulic cylinder 6L. The fourth check valve 13R is connected in parallel to the fourth sequence valve 12R, and allows the flow of pressure oil from the first hydraulic cylinder 6L to the second hydraulic cylinder 6R, but blocks the flow of pressure oil from the second hydraulic cylinder 6R to the first hydraulic cylinder 6L.

[0040] The extension side hydraulic control valve and the compression side hydraulic control valve are configured by the first to fourth counterbalance valves to set the flow direction of pressure oil through the extension side closed line 7 from the first hydraulic cylinder 6L to the second hydraulic cylinder 6R, and the flow direction of pressure oil through the compression side closed line 8 from the second hydraulic cylinder 6R to the first hydraulic cylinder 6L, depending on the pilot pressure applied. Alternatively, the flow direction of pressure oil through the extension side closed line 7 is set from the second hydraulic cylinder 6R to the first hydraulic cylinder 6L, and the flow direction of pressure oil through the compression side closed line 8 is set from the first hydraulic cylinder 6L to the second hydraulic cylinder 6R, depending on the pilot pressure applied.

[0041] Furthermore, the pressure of the pressurized oil filled in the extension side closed conduit 7 and the compression side closed conduit 8 can be set arbitrarily within a pressure change range corresponding to the allowable ambient temperature range set for the aerial work platform. The extension side closed conduit 7 and the compression side closed conduit 8 can be formed, for example, by a flexible hose. A flexible hose generally has an inner layer made of synthetic rubber or resin, which is covered and reinforced by a reinforcing layer made of woven wire or synthetic fiber. By increasing the diameter of the flexible hose and various joints to reduce piping resistance in the extension side closed conduit 7 and the compression side closed conduit 8, thereby reducing pressure oil pressure loss, and by utilizing the accumulator effect created by the expansion of the flexible hose due to hydraulic pressure, the pressure of the pressurized oil filled in the extension side closed conduit 7 and the compression side closed conduit 8 can be set arbitrarily.

[0042] The valve switching state maintaining pressure of the extension side hydraulic control valve and the compression side hydraulic control valve at the upper limit of the allowable operating temperature range is set to a pressure at which the extension side hydraulic control valve and the compression side hydraulic control valve operate according to the pilot pressure. Also, the pressure of the pressure oil in the first hydraulic cylinder 6L and the second hydraulic cylinder 6R at the lower limit of the allowable operating temperature range is set to a pressure at which the first hydraulic cylinder 6L and the second hydraulic cylinder 6R maintain their operating state without being affected by air bubbles remaining in the cylinders.

[0043] FIG. 3 is a diagram illustrating the pressure setting of the pressure oil sealed in the extension-side closed pipe line 7 and the compression-side closed pipe line 8.

[0044] The up and down directions in the diagram indicate the magnitude of the pressure of the pressurized oil sealed in the extension side closed pipe line 7 and the compression side closed pipe line 8, and the ambient temperature in which the aerial work platform is used. As the internal pressure increases along the arrows, the pressure of the pressurized oil in the extension side closed pipe line 7 and the compression side closed pipe line 8 increases. Also, as the ambient temperature increases along the arrows, the ambient temperature in which the aerial work platform is used increases.

[0045] The shaded area in the figure represents the allowable operating temperature range set for the aerial work platform. The upper limit A and lower limit B of this allowable operating temperature range are set as described above. The pressure of the pressure oil in the extension-side closed line 7 and the compression-side closed line 8 is set corresponding to the upper limit A and lower limit B, and is set within the set pressure range W.

[0046] When the operating temperature of the aerial work platform is high and the internal pressure of the extension closed line 7 and the compression closed line 8 is equal to or greater than the internal pressure C, the valve switching state holding pressure of the extension side hydraulic control valve and the compression side hydraulic control valve and the pilot pressure of the pilot signal P are in conflict, and the extension side hydraulic control valve and the compression side hydraulic control valve will not operate.

[0047] When the operating temperature of the aerial work platform is low and the internal pressure of the extension closed line 7 and the retraction closed line 8 is equal to or lower than the internal pressure D, the hydraulic oil inside the first hydraulic cylinder 6L and the second hydraulic cylinder 6R contracts, causing the internal pressure to drop. Therefore, air bubbles that were crushed by the pressure of the hydraulic oil inside the cylinders and were unable to completely escape inside the cylinders grow larger as the internal pressure drops. This causes rattles in the first hydraulic cylinder 6L and the second hydraulic cylinder 6R, preventing the first hydraulic cylinder 6L and the second hydraulic cylinder 6R from fully maintaining their operating state.

[0048] 2 includes a first pressure adjustment port 14L and a first pressure detection port 15R in the extension side closed line 7, and a second pressure adjustment port 14R and a second pressure detection port 15L in the compression side closed line 8. The first pressure adjustment port 14L adjusts the pressure of the pressure oil in the extension side closed line 7, and the first pressure detection port 15R detects the pressure of the pressure oil in the extension side closed line 7. The second pressure adjustment port 14R adjusts the pressure of the pressure oil in the compression side closed line 8, and the second pressure detection port 15L detects the pressure of the pressure oil in the compression side closed line 8.

[0049] Furthermore, in this embodiment, the axle vibration absorbing hydraulic circuit is provided with a first hydraulic cylinder extension-side air bleed port 16L and a second hydraulic cylinder extension-side air bleed port 16R as first air bleed ports in the extension-side closed line 7, and is provided with a first hydraulic cylinder compression-side air bleed port 17L and a second hydraulic cylinder compression-side air bleed port 17R as second air bleed ports in the compression-side closed line 8.

[0050] In an aerial work vehicle equipped with the wheeled traveling device 1 according to this embodiment, the direction of pressure oil flow through the extension-side closed line 7 is set from the first hydraulic cylinder 6L to the second hydraulic cylinder 6R according to the pilot pressures applied to the extension-side hydraulic control valve and the compression-side hydraulic control valve, and at the same time, the direction of pressure oil flow through the compression-side closed line 8 is set from the second hydraulic cylinder 6R to the first hydraulic cylinder 6L. This flow of pressure oil operates the first hydraulic cylinder 6L and the second hydraulic cylinder 6R, causing one end of the axle 3 to receive an upward force from the wheel 5L that moves it away from the ground as shown in Figure 4. Even if this causes a swing that lifts one end of the axle 3 upward, this swing is absorbed by the first hydraulic cylinder 6L retracting and the second hydraulic cylinder 6R extending.

[0051] More specifically, when one end of the axle 3 receives an upward force from the wheel 5L that causes it to leave the ground, the one end of the axle 3 swings upward as shown in Figure 4. In this case, the rod of the first hydraulic cylinder 6L receives a force from the one end of the axle 3 in a contracting direction.

[0052] At this time, according to this embodiment, in response to the pilot pressure applied to the extension side hydraulic control valve, the first sequence valve 10L enters a conducting state in which pressure oil passes through the extension side closed line 7 in the direction from the first hydraulic cylinder 6L to the second hydraulic cylinder 6R. The second check valve 11R passes pressure oil through the extension side closed line 7 in the direction from the first hydraulic cylinder 6L to the second hydraulic cylinder 6R, so the extension side closed line 7 forms a closed line through which pressure oil passes in the direction from the first hydraulic cylinder 6L to the second hydraulic cylinder 6R. Therefore, pressure oil filling the extension side oil chamber 6L1 of the first hydraulic cylinder 6L flows through the extension side closed line 7 from the first hydraulic cylinder 6L to the second hydraulic cylinder 6R via the first sequence valve 10L. Then, the pressure oil flows into the extension side oil chamber 6R1 of the second hydraulic cylinder 6R through the second check valve 11R connected in parallel to the second sequence valve 10R.

[0053] At the same time, in response to the pilot pressure applied to the compression-side hydraulic control valve, the fourth sequence valve 12R enters a conducting state, allowing pressure oil to pass through the compression-side closed line 8 in the direction from the second hydraulic cylinder 6R to the first hydraulic cylinder 6L. The third check valve 13L allows pressure oil to pass through the compression-side closed line 8 in the direction from the second hydraulic cylinder 6R to the first hydraulic cylinder 6L, so the compression-side closed line 8 forms a closed line through which pressure oil passes in the direction from the second hydraulic cylinder 6R to the first hydraulic cylinder 6L. Therefore, the pressure oil filling the compression-side oil chamber 6R2 of the second hydraulic cylinder 6R is compressed by the pressure oil flowing from the first hydraulic cylinder 6L into the extension-side oil chamber 6R1, flows out of the compression-side oil chamber 6R2, and flows through the compression-side closed line 8 from the second hydraulic cylinder 6R to the first hydraulic cylinder 6L via the fourth sequence valve 12R. Then, the oil passes through the third check valve 13L connected in parallel to the third sequence valve 12L and flows into the compression-side oil chamber 6L2 of the first hydraulic cylinder 6L.

[0054] Therefore, even if one end of the axle 3 swings upward, the posture of the body frame 2 supported by the first hydraulic cylinder 6L and the second hydraulic cylinder 6R is kept horizontal by the oscillation function described above. That is, the first hydraulic cylinder 6L contracts its rod and retracts, while the second hydraulic cylinder 6R extends its rod and extends. As a result, the swing of one end of the axle 3 swinging upward is absorbed by the first hydraulic cylinder 6L retracting and the second hydraulic cylinder 6R extending, and the posture of the body frame 2 supported by the first hydraulic cylinder 6L and the second hydraulic cylinder 6R is kept horizontal as shown in Figure 4.

[0055] Furthermore, depending on the pilot pressures applied to the extension side hydraulic control valve and the compression side hydraulic control valve, the direction of pressure oil flow through the extension side closed line 7 is set to flow from the second hydraulic cylinder 6R to the first hydraulic cylinder 6L, and at the same time, the direction of pressure oil flow through the compression side closed line 8 is set to flow from the first hydraulic cylinder 6L to the second hydraulic cylinder 6R. As a result of this flow of pressure oil operating the first hydraulic cylinder 6L and the second hydraulic cylinder 6R, an upward force is applied from the wheel 5R to lift the other end of the axle 3 off the ground, and even if this causes a swing that lifts the other end of the axle 3 upward, this swing is absorbed by the second hydraulic cylinder 6R retracting and the first hydraulic cylinder 6L extending.

[0056] More specifically, when the other end of the axle 3 receives an upward force from the wheel 5R that moves it away from the ground, the other end of the axle 3 swings upward. In this case, the rod of the second hydraulic cylinder 6R receives a force from the other end of the axle 3 in a contracting direction.

[0057] At this time, according to this embodiment, in response to the pilot pressure applied to the extension side hydraulic control valve, the second sequence valve 10R enters a conducting state in which pressure oil passes through the extension side closed line 7 in the direction from the second hydraulic cylinder 6R to the first hydraulic cylinder 6L. Because the first check valve 11L passes pressure oil through the extension side closed line 7 in the direction from the second hydraulic cylinder 6R to the first hydraulic cylinder 6L, the extension side closed line 7 forms a closed line through which pressure oil passes in the direction from the second hydraulic cylinder 6R to the first hydraulic cylinder 6L. Therefore, pressure oil filling the extension side oil chamber 6R1 of the second hydraulic cylinder 6R flows through the extension side closed line 7 from the second hydraulic cylinder 6R to the first hydraulic cylinder 6L via the second sequence valve 10R. Then, the pressure oil flows into the extension side oil chamber 6L1 of the first hydraulic cylinder 6L through the first check valve 11L connected in parallel to the first sequence valve 10L.

[0058] At the same time, in response to the pilot pressure applied to the compression-side hydraulic control valve, the third sequence valve 12L enters a conducting state, allowing pressure oil to pass through the compression-side closed line 8 in the direction from the first hydraulic cylinder 6L to the second hydraulic cylinder 6R. The fourth check valve 13R allows pressure oil to pass through the compression-side closed line 8 in the direction from the first hydraulic cylinder 6L to the second hydraulic cylinder 6R, so the compression-side closed line 8 forms a closed line through which pressure oil passes in the direction from the first hydraulic cylinder 6L to the second hydraulic cylinder 6R. Therefore, the pressure oil filled in the compression-side oil chamber 6L2 of the first hydraulic cylinder 6L is compressed by the pressure oil flowing from the second hydraulic cylinder 6R into the extension-side oil chamber 6L1, and flows out of the compression-side oil chamber 6L2. Then, the oil flows through the compression-side closed line 8 from the first hydraulic cylinder 6L to the second hydraulic cylinder 6R via the third sequence valve 12L, and then flows into the compression-side oil chamber 6R2 of the second hydraulic cylinder 6R through the fourth check valve 13R connected in parallel to the fourth sequence valve 12R.

[0059] Therefore, even if the other end of the axle 3 swings upward, the posture of the body frame 2 supported by the first hydraulic cylinder 6L and the second hydraulic cylinder 6R is kept horizontal by the oscillation function described above. That is, the second hydraulic cylinder 6R contracts its rod and retracts, while the first hydraulic cylinder 6L extends its rod and extends. As a result, the swing of the other end of the axle 3 swinging upward is absorbed by the second hydraulic cylinder 6R retracting and the first hydraulic cylinder 6L extending, and the posture of the body frame 2 supported by the first hydraulic cylinder 6L and the second hydraulic cylinder 6R is kept horizontal.

[0060] Furthermore, according to this embodiment, the pressure of the enclosed pressure oil in the closed extension-side pipe line 7 and the closed compression-side pipe line 8, which connect the extension-side oil chambers 6L1 and 6R1 of the first hydraulic cylinder 6L and the compression-side oil chambers 6L2 and 6R2 of the second hydraulic cylinder 6R and through which no pressure oil flows, is set within a pressure change range W (see FIG. 3) corresponding to the allowable operating temperature range set for the aerial work platform. The valve switching state holding pressures of the extension-side hydraulic control valve and the compression-side hydraulic control valve at the upper limit value A of the allowable operating temperature range are set to a pressure at which the extension-side hydraulic control valve and the compression-side hydraulic control valve operate, according to the pilot pressure of the pilot signal P given to the extension-side hydraulic control valve and the compression-side hydraulic control valve. Furthermore, the pressure of the pressurized oil in the first hydraulic cylinder 6L and the second hydraulic cylinder 6R at the lower limit value B of the allowable operating ambient temperature range is set to a pressure that maintains the first hydraulic cylinder 6L and the second hydraulic cylinder 6R in an operating state without being affected by air bubbles remaining in the cylinders.

[0061] Therefore, without the need to connect an oil tank or the like via a switching valve to supply pressure oil to each hydraulic closed circuit formed between the extension-side oil chambers 6L1 and 6R1 of the first hydraulic cylinder 6L and the compression-side oil chambers 6L2 and 6R2 of the second hydraulic cylinder 6R, as in the past, this system can respond to changes in the actual operating temperature by simply setting the pressure of the pressure oil sealed in each hydraulic closed circuit within the pressure change range W corresponding to the allowable operating temperature range. In other words, even if the operating temperature rises, the extension-side hydraulic control valve and the compression-side hydraulic control valve will operate according to the applied pilot pressure, overcoming the valve switching state holding pressure, as long as the actual operating temperature is lower than the upper limit A of the set allowable operating temperature range. Furthermore, even if the operating temperature drops, the first hydraulic cylinder 6L and the second hydraulic cylinder 6R will maintain their operating state without being affected by air bubbles remaining in the cylinders as long as the actual operating temperature is higher than the lower limit B of the set allowable operating temperature range.

[0062] This makes it possible to provide a vehicle for working at height that has a simple configuration and that can stably perform its oscillation function even when the temperature of the environment in which it is used changes.

[0063] Furthermore, according to this embodiment, the allowable operating ambient temperature range set for the aerial work vehicle is set relatively high, and the pressure of the pressure oil in the extension-side closed line 7 can be manually lowered to an appropriate value by adjusting the opening of the first pressure adjustment port 14L while detecting it at the first pressure detection port 15R in accordance with the actual ambient temperature of the aerial work vehicle being used. Also, the pressure of the pressure oil in the compression-side closed line 8 can be manually lowered to an appropriate value by adjusting the opening of the second pressure adjustment port 14R while detecting it at the second pressure detection port 15L.

[0064] As a result, if the ambient temperature range of the actual environment is lower than the initial setting, the pressure of the pressurized oil in the extension side closed line 7 and the contraction side closed line 8, which was set high, can be adjusted to a lower pressure according to the actual environment, allowing the oscillation function of the aerial work platform to be performed appropriately according to the ambient temperature.

[0065] Furthermore, according to this embodiment, by supplying pressure oil to the extension-side closed line 7 via the first hydraulic cylinder extension-side air bleed port 16L or the second hydraulic cylinder extension-side air bleed port 16R, which constitute the first air bleed port, it is possible to increase the pressure of the pressure oil in the extension-side closed line 7. Furthermore, by supplying pressure oil to the compression-side closed line 8 via the first hydraulic cylinder compression-side air bleed port 17L or the second hydraulic cylinder compression-side air bleed port 17R, which constitute the second air bleed port, it is possible to increase the pressure of the pressure oil in the compression-side closed line 8.

[0066] As a result, if the adjustment of the pressure of the pressure oil in the extension-side closed pipe line 7 and the compression-side closed pipe line 8 is made too low, the pressure can be increased to perform fine pressure adjustment and set to an appropriate value.

[0067] Furthermore, according to this embodiment, by alternately operating the rods of the first hydraulic cylinder 6L and the second hydraulic cylinder 6R and retracting one rod when the other is extended, air remaining inside the first hydraulic cylinder 6L and the second hydraulic cylinder 6R can be efficiently bled through the first hydraulic cylinder extension-side air bleed port 16L, the second hydraulic cylinder extension-side air bleed port 16R, the first hydraulic cylinder retraction-side air bleed port 17L, and the second hydraulic cylinder retraction-side air bleed port 17R.

[0068] In the above embodiment, the axle 3 and wheels 5L, 5R are on the front wheel side. However, the present invention can be similarly applied to the rear wheel and axle to provide the oscillation function instead of the front wheel side. In this case, the same effects as those of the above embodiment can be achieved. [Explanation of symbols]

[0069] 1...wheeled traveling device, 2...body frame, 3...axle, 4...oscillating shaft, 5L, 5R...wheel, 6L...first hydraulic cylinder, 6R...second hydraulic cylinder, 6L1, 6R1...extension oil chamber, 6L2, 6R2...compression oil chamber, 7...extension closed line, 8...compression closed line, 10L...first sequence valve, 10R...second sequence valve, 11L...first check valve, 11R...second check valve, 12L...third sequence valve, 12R...fourth sequence valve, 13L...third check valve, 13R ...Fourth check valve, 14L...First pressure adjustment port, 14R...Second pressure adjustment port, 15R...First pressure detection port, 15L...Second pressure detection port, 16L...First hydraulic cylinder extension side air bleed port (first air bleed port), 16R...Second hydraulic cylinder extension side air bleed port (first air bleed port), 17L...First hydraulic cylinder retraction side air bleed port (second air bleed port), 17R...Second hydraulic cylinder retraction side air bleed port (second air bleed port)

Claims

1. a first hydraulic cylinder for a hydraulic suspension, the first hydraulic cylinder having a rod connected to one end of an axle on which a wheel is mounted and a bottom of a cylinder tube attached to a vehicle body; a second hydraulic cylinder for a hydraulic suspension, the second hydraulic cylinder having a rod connected to the other end of the axle and a bottom of a cylinder tube attached to the vehicle body; a closed extension-side pipe line that connects the extension-side oil chambers of the first hydraulic cylinder and the second hydraulic cylinder, and through which no sealed pressure oil flows in or out; a closed retraction-side pipeline that connects the retraction-side oil chambers of the first hydraulic cylinder and the second hydraulic cylinder, and through which no sealed pressure oil flows in or out; an extension side hydraulic control valve provided in the extension side closed line; a compression side hydraulic control valve provided in the compression side closed line; Equipped with The extension side hydraulic control valve and the compression side hydraulic control valve are configured, in accordance with an applied pilot pressure, so that the flow direction of pressure oil through the extension side closed line is set to a direction from the first hydraulic cylinder to the second hydraulic cylinder and the flow direction of pressure oil through the compression side closed line is set to a direction from the second hydraulic cylinder to the first hydraulic cylinder, or so that the flow direction of pressure oil through the extension side closed line is set to a direction from the second hydraulic cylinder to the first hydraulic cylinder and so that the flow direction of pressure oil through the compression side closed line is set to a direction from the first hydraulic cylinder to the second hydraulic cylinder, the pressure of the pressure oil sealed in the extension-side closed line and the compression-side closed line is set within a pressure change range corresponding to a set allowable operating environmental temperature range, a valve switching state holding pressure of the extension side hydraulic control valve and the compression side hydraulic control valve at an upper limit value of the allowable operating environmental temperature range is set to a pressure at which the extension side hydraulic control valve and the compression side hydraulic control valve operate in response to the pilot pressure, The pressure of the pressure oil in the first hydraulic cylinder and the second hydraulic cylinder at the lower limit of the allowable operating temperature range is set to a pressure that maintains the first hydraulic cylinder and the second hydraulic cylinder in an operating state without being affected by air bubbles remaining in the cylinders. Aerial work platform.

2. The extension side hydraulic control valve is composed of: a first sequence valve provided corresponding to the first hydraulic cylinder and interrupting the flow of pressure oil through the extension side closed line in a direction from the first hydraulic cylinder to the second hydraulic cylinder; a first check valve connected in parallel to the first sequence valve and allowing the flow of pressure oil from the second hydraulic cylinder to flow from the second hydraulic cylinder to the first hydraulic cylinder and stopping the flow of pressure oil from the first hydraulic cylinder to the second hydraulic cylinder; a second sequence valve provided corresponding to the second hydraulic cylinder and interrupting the flow of pressure oil through the extension side closed line in a direction from the second hydraulic cylinder to the first hydraulic cylinder; and a second check valve connected in parallel to the second sequence valve and allowing the flow of pressure oil from the first hydraulic cylinder to flow from the first hydraulic cylinder to the second hydraulic cylinder and stopping the flow of pressure oil from the second hydraulic cylinder to the first hydraulic cylinder, The compression side hydraulic control valve is composed of: a third sequence valve provided corresponding to the first hydraulic cylinder and interrupting the flow of pressure oil through the compression side closed line in a direction from the first hydraulic cylinder to the second hydraulic cylinder; a third check valve connected in parallel to the third sequence valve and allowing the flow of pressure oil from the second hydraulic cylinder to flow from the second hydraulic cylinder to the first hydraulic cylinder and stopping the flow of pressure oil from the first hydraulic cylinder to the second hydraulic cylinder; a fourth sequence valve provided corresponding to the second hydraulic cylinder and interrupting the flow of pressure oil through the compression side closed line in a direction from the second hydraulic cylinder to the first hydraulic cylinder; and a fourth check valve connected in parallel to the fourth sequence valve and allowing the flow of pressure oil from the first hydraulic cylinder to flow from the first hydraulic cylinder to the second hydraulic cylinder and stopping the flow of pressure oil from the second hydraulic cylinder to the first hydraulic cylinder. The aerial work platform according to claim 1.

3. 3. The aerial work vehicle according to claim 1, further comprising: a first pressure adjustment port provided in the extension side closed line to adjust the pressure of the pressure oil in the extension side closed line; a first pressure detection port provided in the extension side closed line to detect the pressure of the pressure oil in the extension side closed line; a second pressure adjustment port provided in the compression side closed line to adjust the pressure of the pressure oil in the compression side closed line; and a second pressure detection port provided in the compression side closed line to detect the pressure of the pressure oil in the compression side closed line.

4. 4. The vehicle for working at height according to claim 3, further comprising: a first air vent port provided in the extension-side closed conduit; and a second air vent port provided in the retraction-side closed conduit.

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