JP3723709B2 - Hydraulic cylinder operation control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydraulic cylinder configured by fitting and disposing a piston portion of a cylinder rod in an axially movable manner in a hollow cylindrical space of a cylinder tube, and more specifically, in a cylinder oil chamber of the hydraulic cylinder. The present invention relates to an operation control device for a hydraulic cylinder that performs supply control of hydraulic oil and performs the operation control.
[0002]
[Prior art]
Such a hydraulic cylinder is used for various applications, for example, as a hoisting cylinder for performing an hoisting operation of a boom in an aerial work vehicle, and an expansion cylinder for performing an expansion and contraction operation of a boom. These hydraulic cylinders are expanded and contracted by controlling the supply of hydraulic oil in the cylinder oil chamber, and the boom is operated up and down or expanded and contracted.
[0003]
[Problems to be solved by the invention]
By the way, in such a hydraulic cylinder, when the cylinder rod is expanded and contracted from a state where the piston portion is located at the end in the hollow cylindrical space in the cylinder tube, that is, a state where the cylinder rod is located at the stroke end, Due to structural effects such as a sudden change in the pressure receiving area, a phenomenon occurs in which the cylinder rod suddenly starts operating after a slight time delay and an impact is generated. For this reason, for example, when the operation of raising and lowering the boom is performed from the state where the hoisting cylinder is located at the stroke end, the boom suddenly performs hoisting operation after a slight time delay from this operation, and boarded the work table. There is a problem that the rider's ride comfort is reduced due to the impact on the worker.
[0004]
In order to suppress such a problem, it is conceivable to perform control for gradual supply of hydraulic oil into the cylinder oil chamber. However, when the cylinder rod is located at the normal stroke position (that is, the position excluding the vicinity of the stroke end), the supply of hydraulic oil into the cylinder oil chamber is moderated even though the above-described impact does not occur. For this reason, the start of the operation becomes gentle within the entire stroke range of the hydraulic cylinder, and there is a problem that, for example, the undulation and expansion / contraction operation of the boom becomes slow, and the workability is lowered.
[0005]
The present invention has been made in view of such a problem, and it is possible to prevent a shock from being generated when the cylinder rod starts its operation from the stroke end and reduce the operation start speed in a normal stroke region. It is an object of the present invention to provide an operation control device for a hydraulic cylinder having such a configuration.
[0006]
[Means for Solving the Problems]
In order to achieve such an object, the present invention relates to a hydraulic cylinder configured by fitting and disposing a piston portion of a cylinder rod in an axially movable manner in a hollow cylindrical space of a cylinder tube. A hydraulic control valve that controls the supply of hydraulic oil into a cylinder oil chamber formed by a hollow cylindrical space partitioned by a piston portion, a control device that controls the operation of the hydraulic control valve, and a hydraulic control valve that controls the hydraulic control valve The supply amount increase characteristic setting means for setting the hydraulic supply amount increase characteristic when starting the hydraulic oil supply to the cylinder oil chamber by performing the operation control, and whether the piston part is located near the end of the hollow cylindrical space The hydraulic cylinder operation control device is configured to have stroke end detection means for detecting whether or not. When the piston part is located at the end of the hollow cylindrical space, it abuts against the end side end face in the cylinder tube, and the pressure receiving area of the piston part with respect to the hydraulic pressure in the cylinder oil chamber is away from the end side end face. The hydraulic pressure that is set by the supply amount increase characteristic setting means when the stroke end detection means detects that the piston portion is located in the vicinity of the end of the hollow cylindrical space. The supply amount increase characteristic is a hydraulic supply amount that is set by the supply amount increase characteristic setting means when the stroke end detection means detects that the piston portion is located at the intermediate position (position within the normal stroke range). It is configured to have a gradual increase characteristic than the increase characteristic.
[0007]
According to the operation control device having such a configuration, when the cylinder rod (or the piston portion) is located in the vicinity of the stroke end, the hydraulic oil is supplied with a slowly increasing characteristic. The operation can be started smoothly even at the stroke end where a rapid operation is likely to occur. On the other hand, when the cylinder rod is in a normal stroke position excluding the stroke end, hydraulic oil is supplied with a normal increase characteristic, that is, an increase characteristic larger than the increase characteristic set at the stroke end, and the hydraulic cylinder starts operating quickly. Therefore, the hydraulic cylinder can be efficiently operated with a good response.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 2 shows an aerial work vehicle to which the present invention is applied. The aerial work vehicle 1 includes a swivel base 3 that is disposed on a vehicle body 2 of a vehicle that has a driving cabin 2a so that the vehicle can turn horizontally with respect to the vehicle body by an operation of a turn motor (not shown). 3, a boom 4 that is raised and lowered by a raising and lowering cylinder 12 is pivotally attached. The boom 4 includes a proximal boom 4a, an intermediate boom 4b, and a distal boom 4c configured in a telescopic manner, and is expanded and contracted by a built-in telescopic cylinder 13. A base end portion of the base end boom 4 a is pivotally connected to the swivel 3.
[0009]
A vertical post 6 that is always vertically held by a leveling cylinder (not shown) is pivotally connected to the tip of the tip boom 4c, and a work table 8 can be swung horizontally through a swing arm 7 (swinging). It is attached freely. A lifting device 9 is provided at the upper end of the tip boom 4c, and a heavy object can be lifted. Outrigger jacks 18 are provided on the front, rear, left, and right sides of the vehicle body 2, and the outrigger jacks 18 extend downward to stably support the vehicle body 2 when working at a high place.
[0010]
The work table 8 is provided with an upper operating device 20, and the lower part of the vehicle body 2 is provided with a lower operating device 21. Therefore, an operator who has boarded the work table 8 can operate the upper operation device 20 to perform the turning operation of the turntable 3, the raising and lowering operation of the boom 4, and the work vehicle on the ground can operate the lower operation. A similar operation can be performed by operating the device 21. A jack operating device 22 is also provided at the rear part of the vehicle body 2, thereby operating the outrigger jack 18.
[0011]
In the aerial work vehicle 1 having the above configuration, the hoisting cylinder 12, the telescopic cylinder 13 and the like are constituted by the hydraulic cylinder according to the present invention, and the hoisting cylinder 12 will be described below as an example. FIG. 1 shows the structure of the hoisting cylinder 12 and its operation control device. The undulating cylinder 12 is a cylinder tube 31 having a hollow cylindrical space 32 and a cylinder that is movable in the axial direction by fitting and disposing a piston portion 34 in the hollow cylindrical space 32 so as to be movable in the axial direction. The cylinder rod 33 protrudes outward from the cylinder tube 31. The hollow cylindrical space 32 is divided by a piston portion 34 to form a rod side cylinder oil chamber 32a and a bottom side cylinder oil chamber 32b.
[0012]
The cylinder oil chambers 32a and 32b are provided with ports 31a and 31b, respectively, and the cylinder rod 33 is moved in the axial direction by supplying hydraulic oil from the ports 31a and 31b into the cylinder oil chambers 32a and 32b. . For this reason, a hydraulic control valve 41 is connected to both ports 31a and 31b via oil passages 45 and 46, and hydraulic oil supplied from the hydraulic pump 40 is supplied to both cylinder oil chambers 32a and 32b according to the operation of the hydraulic control valve 41. The control is performed by selectively supplying to 32b and moving the cylinder rod 33 in the axial direction. The hydraulic control valve 41 is an electromagnetic control valve whose operation is controlled by performing excitation control of the left and right solenoids 41 a and 41 b, and excitation control signals for the left and right solenoids 41 a and 41 b are output from the controller 50.
[0013]
An operation signal corresponding to the operation of the operation levers 20a and 21a is input from the upper or lower operation devices 20 and 21 to the controller 50, and the left and right solenoids 41a and 41b of the hydraulic control valve 41 are excited according to the operation signal. Output a control signal. As a result, for example, when an operator who has boarded the work table 8 operates the hoisting operation lever 20a of the upper operation device 20, the hoisting cylinder 12 is expanded and contracted in response to this operation, and the boom 4 is hoisted.
[0014]
In the operation control device having such a configuration, as shown in FIG. 3, the cylinder rod 33 is contracted to the stroke end, and the piston portion 34 is in a state of being substantially in contact with the end side end surface of the cylinder tube 31. Consider the case where the extension is operated. To extend the cylinder rod 33, hydraulic oil is supplied from the port 31b into the bottom cylinder oil chamber 32b. At this time, as shown in the figure, the piston portion 34 is in contact with the end side end surface of the cylinder tube 31 and the pressure receiving area of the piston portion 34 in the bottom side cylinder oil chamber 32b is small. The cylinder rod 33 extends only when the hydraulic pressure reaches a predetermined high pressure. However, when the piston part 34 is separated from the end side end surface through the extension operation of the cylinder rod 33, the pressure receiving area of the piston part 34 increases, and the pressing force acting on the piston part 34 increases rapidly. Is suddenly moved in the direction of extension. As a result, the boom 4 is suddenly moved up and down after a slight time delay, and there is a problem that the ride comfort is lowered by giving an impact or shock to the worker who is on the work table 8.
[0015]
For this reason, the hoisting cylinder 12 of this example is provided with a position detection sensor 55 for detecting the axial movement position of the cylinder rod 33 with respect to the cylinder tube 31, and the detection signal of this position detection sensor 55 is the controller 50. To be sent out. The controller 50 determines whether or not the cylinder rod 33 is in the vicinity of the stroke end based on a transmission signal from the position detection sensor 55. That is, it is determined whether the piston portion 34 is in the stroke end vicinity region A or the normal stroke region B in FIG. When it is determined that the region is in the stroke end vicinity region A, the operation of the hydraulic control valve 41 is controlled so as to supply the hydraulic oil having the characteristics shown in FIG. On the other hand, when it is determined that it is in the normal stroke region B, the operation of the hydraulic control valve 41 is controlled so as to supply hydraulic oil having characteristics as shown in FIG.
[0016]
4 (A) and 4 (B) show the hydraulic oil supply speed (ie, the supply oil amount per unit time) dQ / dt from the hydraulic control valve 41 to the left and right cylinder oil chambers 32a, 32b at the start of operation. The relationship with the elapsed time t is shown. As can be seen from these figures, when it is determined that the region is in the region A near the stroke end and hydraulic oil supply having the characteristics shown in FIG. 4A is performed, the hydraulic oil supply speed dQ / dt is increased from the start of the operation. Slowly increasing control is performed. As a result, even when the piston portion 34 is positioned near the stroke end, the expansion / contraction operation can be started smoothly without shock.
[0017]
If it is determined that the stroke is in the normal stroke region B, there is little problem of occurrence of shock even if the hydraulic oil is supplied relatively quickly. For this reason, the hydraulic oil supply speed dQ / dt is controlled to increase rapidly from the start of the operation as shown in FIG. 4B, and the undulation operation with good response to the operation of the operation lever 20a is performed. Efficient work can be performed.
[0018]
The means for detecting whether or not the cylinder rod is at the stroke end is not limited to the position detection sensor as described above, but a proximity switch such as a limit switch or a boom undulation angle sensor is used. It is also possible to detect the stroke position. In addition, as the hydraulic oil supply control in the vicinity of the stroke end, the dQ / dL control may be performed based on the stroke length L as well as the dQ / dt control as described above. You may perform control which stops hydraulic oil supply in a near field.
[0019]
【The invention's effect】
As described above, according to the present invention, when the stroke end detecting means detects that the piston portion is positioned in the vicinity of the end of the hollow cylindrical space, it is set by the supply amount increasing characteristic setting means. The hydraulic supply amount increase characteristic is set by the supply amount increase characteristic setting means when the stroke end detecting means detects that the piston portion is located at an intermediate position excluding the vicinity of the end of the hollow cylindrical space. Therefore, when the cylinder rod (or piston part) is located near the stroke end, hydraulic oil is supplied with a gradually increasing characteristic. The operation can be started smoothly even at the stroke end where the rapid operation is likely to occur due to the structural influence. On the other hand, when the cylinder rod is in a normal stroke position excluding the stroke end, hydraulic oil is supplied with a normal increase characteristic, that is, an increase characteristic larger than the increase characteristic set at the stroke end, and the hydraulic cylinder starts operating quickly. Therefore, the hydraulic cylinder can be efficiently operated with a good response.
[Brief description of the drawings]
FIG. 1 is a hydraulic circuit diagram showing a configuration example of a hydraulic cylinder operation control apparatus according to the present invention.
FIG. 2 is a perspective view of an aerial work vehicle using the hydraulic cylinder.
FIG. 3 is a cross-sectional view showing a configuration of the hydraulic cylinder.
FIG. 4 is a graph showing a hydraulic oil supply amount increase characteristic set according to a stroke position of a cylinder rod of the hydraulic cylinder.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Aerial work vehicle 12 Hoisting cylinder 13 Telescopic cylinder 31 Cylinder tube 32 Hollow cylindrical space 33 Cylinder rod 34 Piston part 41 Hydraulic control valve 50 Controller 55 Position detection sensor

Claims (1)

Cylinder tube having a hollow cylindrical space, and a cylinder rod extending in the axial direction and having a piston portion fitted and disposed in the hollow cylindrical space of the cylinder tube so as to be movable in the axial direction And a hydraulic control valve that controls the supply of hydraulic oil into a cylinder oil chamber formed by the hollow cylindrical space partitioned by the piston portion, and a control device that controls the hydraulic control valve. In the hydraulic cylinder operation control device,
Supply amount increase characteristic setting means for setting a hydraulic supply amount increase characteristic when starting operation of supplying hydraulic oil into the cylinder oil chamber by performing operation control of the hydraulic control valve by the control device;
Stroke end detecting means for detecting whether or not the piston portion is positioned near the end of the hollow cylindrical space;
When the piston portion is located at the end of the hollow cylindrical space, it abuts on the end side end surface in the cylinder tube, and the pressure receiving area of the piston portion with respect to the oil pressure in the cylinder oil chamber is such that the piston portion is the end side end surface. Configured to be smaller than when away from
The hydraulic pressure supply amount increase characteristic set by the supply amount increase characteristic setting unit when the stroke end detection unit detects that the piston portion is located near the end of the hollow cylindrical space is: When the stroke end detecting means detects that the piston portion is located at an intermediate position of the hollow cylindrical space, the pressure supply amount increasing characteristic set by the supply amount increasing characteristic setting means is more gradual. A hydraulic cylinder operation control device characterized by having an increase characteristic.

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