JP2004301215A - Hydraulic driving device for work vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To switch between a case where a function of a counter balance valve is made effective in accordance with type of attachment and a case where it is quickly turned by gravity to enable operation suitable for work contents by the attachment in a work vehicle such as a lift truck provided with the counter balance valve. <P>SOLUTION: An operate check valve 16a is arranged in the counter balance valve 16 provided in a tilt cylinder 8, and an electromagnetic selector valve 20, a controller 40 driving and controlling the electromagnetic selector valve 20, and an attachment setting switch 41 are additionally provided. An output port of the electromagnetic selector valve 20 and a Pc port which is a pilot port of the operate check valve 16a are mutually connected by a pilot pipe passage 37. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention has a boom rotatably attached to a vehicle body and an attachment exchangeably attached to a tip of the boom, and a hydraulic pressure of a working vehicle for performing a cargo handling operation by operating these. It relates to a driving device.
[0002]
[Prior art]
2. Description of the Related Art A lift truck (also known as a telescopic handler) is known as a work vehicle that performs a cargo handling operation by operating a boom rotatably attached to a vehicle body and an attachment that is exchangeably attached to a tip of the boom. . This lift truck is provided with a hydraulic drive device as a drive means for a working member such as a boom and an attachment. The hydraulic drive device includes a hydraulic cylinder for rotating the boom and the attachment as described in, for example, JP-A-11-71100. A hydraulic pump for supplying hydraulic oil to each hydraulic cylinder for the boom and the attachment; a directional control valve for controlling a flow of hydraulic oil supplied from the hydraulic pump to each hydraulic cylinder for the boom and the attachment; A counterbalance valve is provided between the directional control valve and the cylinder chamber on the load holding side of each hydraulic cylinder for attachment and attachment.
[0003]
The counterbalance valve prevents the boom or attachment from escaping due to gravity when rotating the boom or attachment in the downward direction while holding a heavy object (escape prevention function), or for each of the boom and attachment. If the piping (hydraulic hose) connecting the cylinder chamber on the load holding side of the hydraulic cylinder and the directional control valve breaks, the hydraulic cylinder will suddenly shrink and prevent the boom and load from falling (when the piping breaks) Fall prevention function).
[0004]
[Patent Document 1]
JP-A-11-71100
[0005]
[Problems to be solved by the invention]
By the way, the lift truck is characterized in that various operations can be performed by one machine by exchanging the attachment at the tip. For example, the attachment for performing the cargo handling operation is a fork, but when the attachment is replaced with a bucket, the attachment can be used for a loading operation for loading earth and sand on a truck or the like instead of a tractor shovel such as a wheel loader.
[0006]
In the work performed by such a work vehicle such as a lift truck, when the attachment is moved in the direction of gravity depending on the type of the attachment, if the attachment can be moved quickly in the direction of gravity, the work speed increases, and there is a convenient work.
[0007]
For example, in a loading operation performed by attaching a bucket as an attachment, when the earth and sand is unloaded, the bucket into which the sand has been scooped is moved to the unloading position, and then the bucket is rotated in the direction of gravity (forward) to release the unloaded soil. However, at this time, if the bucket can be quickly rotated by its own weight, the work speed is increased, and the operability and work efficiency are improved. In addition, when scooping in earth and sand, the bucket may be lowered to a required height by a boom lowering operation.In this case, if the boom and the bucket can be lowered quickly by their own weight, the working speed increases, and the operability increases. And work efficiency is improved.
[0008]
In the conventional lift truck described above, a counterbalance valve is provided to prevent runaway and fall when piping breaks, so when moving the boom or attachment in the direction of gravity during loading work etc., the counterbalance valve will be in the way. As a result, the boom and the attachment cannot be quickly rotated by gravity, resulting in a problem that operability and work efficiency are poor.
[0009]
An object of the present invention is to make it possible to switch between a case where the function of the counterbalance valve is activated and a case where the counterbalance valve is quickly rotated by gravity in a work vehicle such as a lift truck having a counterbalance valve, depending on the type of the attachment. It is an object of the present invention to provide a hydraulic drive device for a working vehicle that enables an operation suitable for the work content by the attachment.
[0010]
[Means for Solving the Problems]
(1) In order to achieve the above object, the present invention provides a working vehicle having a boom rotatably attached to a vehicle body and an attachment exchangeably attached to a tip of the boom. In the driving device, a hydraulic cylinder for rotating the boom and the attachment, a hydraulic pump for supplying pressure oil to the hydraulic cylinder for the boom and the attachment, and a hydraulic cylinder for the boom and the attachment from the hydraulic pump A directional control valve for controlling the flow of the pressure oil supplied to the boom and the hydraulic cylinder for the boom and the attachment, at least one of the load-holding cylinder chambers of the hydraulic cylinder, and a pipeline connected to the directional control valve. A counterbalance valve, an external signal generating means for generating an external signal, and the counterbalance valve. It shall have an opening and closing means for enabling communication with an external signal.
[0011]
When the external signal is not generated by the external signal generating means, the counterbalance valve works as usual, and the function of the counterbalance valve is effective.For work that requires the function of the counterbalance valve, such as loading and unloading work with a fork, The lowering operation is performed at a safe speed irrespective of the weight of the luggage to be handled, and the cargo handling work can be performed safely. When an external signal is generated by the external signal generator, the opening / closing means connects the counterbalance valve, so in work that does not require the function of the counterbalance valve, such as loading work with a bucket, the attachment is quickly rotated by gravity. Operability and work efficiency can be improved.
[0012]
As described above, according to the present invention, in a work vehicle such as a lift truck equipped with a counterbalance valve, it is possible to switch between a case where the function of the counterbalance valve is activated and a case where it is quickly rotated by gravity according to the type of attachment. Then, an operation suitable for the work content by the attachment is enabled.
[0013]
(2) In the above (1), preferably, the hydraulic drive device further includes input means by an operator, and control means for activating the external signal generation means based on a signal from the input means.
[0014]
By operating the input means, the operator can switch between a case where the function of the counterbalance valve is activated and a case where the counterbalance valve is quickly rotated by gravity according to the type of the attachment, and an operation suitable for the work content by the attachment. Becomes possible.
[0015]
(3) In the above (1), the hydraulic drive device may include an information reading unit that generates a signal when a specific attachment is mounted on the boom, and the external signal generation unit based on a signal from the information reading unit. Control means for operating the means.
[0016]
By this means, when the attachment is attached, the communication means automatically switches the counter balance valve function or the counter balance valve to the communication state, so the type of attachment and counter balance valve State mismatch can be prevented.
[0017]
(4) In the above (3), preferably, the information reading means is a shape feature provided in a mounting portion between the tip of the boom and the attachment, and a sensor means which is turned on / off by the shape feature. .
[0018]
Thus, it is possible to reliably determine whether the function of the counterbalance valve is effective or communicate without being affected by the use environment.
[0019]
(5) In the above (1), preferably, the counterbalance valve includes a pressure control valve and a check valve connected in parallel with each other, and the opening / closing means is a check valve of the counterbalance valve based on the external signal. It is a means to open.
[0020]
Thereby, the opening / closing means can communicate the counterbalance valve.
[0021]
(6) In the above (1), the counterbalance valve includes a pressure control valve and a check valve connected in parallel to each other, and the opening / closing means is connected in parallel to the pressure control valve and the check valve of the counterbalance valve, An on-off valve that can be switched from the closed position to the open position by an external signal may be used.
[0022]
This also allows the opening / closing means to communicate the counterbalance valve.
[0023]
(7) In the above (1), the counterbalance valve includes a pressure control valve and a check valve connected in parallel with each other, and the external signal generating means is means for generating a pilot pressure as an external signal, The opening / closing means may be means for guiding a pilot pressure generated by the external signal generating means to a valve-opening-side pressure receiving portion of a pressure control valve of the counterbalance valve.
[0024]
This also allows the opening / closing means to communicate the counterbalance valve.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0026]
FIG. 1 is a circuit diagram showing an entire system of a hydraulic drive device for a working vehicle according to a first embodiment of the present invention.
[0027]
In FIG. 1, a hydraulic drive device according to the present embodiment includes a hydraulic cylinder 7, 8 used as an up-and-down cylinder of a boom of a lift truck and a tilt cylinder of an attachment, and a main unit for supplying hydraulic oil to the hydraulic cylinders 7, 8. Hydraulic pump 10, directional control valves 11 and 12 for controlling the flow of hydraulic oil supplied from hydraulic pump 10 to hydraulic cylinders 7 and 8, operation levers 13 and 14 for commanding the operation of hydraulic cylinders 7 and 8, and remote control Valves 25 and 26, counterbalance valves 15 and 16, relief valve 17 for regulating the maximum discharge pressure of hydraulic pump 10, pilot pump 19 for supplying pressure oil to remote control valves 25 and 26, direction control by external force, etc. Overpressure preventing the pressure in the pipelines 33 and 34 between the valve 12 and the hydraulic cylinder 8 from becoming abnormally high or negative pressure. And a load relief and anti-cavitation valve 21, 22.
[0028]
2 and 3 show the appearance of the lift truck.
[0029]
In the present embodiment, the work vehicle is a lift truck, and the lift truck includes a vehicle body 1, front wheels 2 and rear wheels 3 attached to the vehicle body 1, a cab 4 located on the vehicle body 1, and a vehicle body 1. And a telescopic boom 5 attached to the side of the driver's cab 4 so as to be able to raise and lower, and an attachment 6A or 6B rotatably attached to the tip of the boom 5 (hereinafter, appropriately represented by reference numeral "6"). The vehicle travels by driving one or both of the front wheel 2 and the rear wheel 3 by an engine (not shown). The attachment 6A in FIG. 2 is a fork used for cargo handling, and the attachment 6B in FIG. 3 is a bucket used for loading or the like.
[0030]
The boom 5 is extended and contracted by a telescopic cylinder (not shown), and can be raised and lowered by the expansion and contraction of the hydraulic cylinder 7 (hereinafter, appropriately referred to as a lifting cylinder). The attachment 6 can be tilted by expanding and contracting a hydraulic cylinder 8 (hereinafter, appropriately referred to as a tilt cylinder). In the hydraulic circuit shown in FIG. 1, only a portion that expands and contracts the up-and-down cylinder 7 and the tilt cylinder 8 is shown, and other actuators such as the telescopic cylinder and a circuit for driving the actuator are omitted. In FIG. 1, reference numeral 9 denotes a leveling cylinder for keeping the angle of the attachment 6 constant when the boom 5 is raised and lowered.
[0031]
The counterbalance valves 15 and 16 are provided in the up-and-down cylinder 7 and the tilt cylinder 8, respectively. The bottom chamber 7a, which is a cylinder chamber on the load holding side of the up-and-down cylinder 7, is connected to the pipe 31 via the counterbalance valve 15 and The passage 31 is connected to one of the actuator ports of the directional control valve 11. Similarly, the bottom chamber 8a, which is the cylinder chamber on the load holding side of the tilt cylinder 8, is connected to the pipe 33 via the counterbalance valve 16, and the pipe 33 is connected to one of the actuator ports of the direction control valve 12. I have. That is, the counterbalance valve 15 is located between the bottom chamber 7 a of the undulating cylinder 7 and the pipe 31, and the counterbalance valve 16 is located between the bottom chamber 8 a of the tilt cylinder 8 and the pipe 33. Rod chambers 7b and 8b, which are cylinder chambers on the rod side of the up-and-down cylinder 7 and the tilt cylinder 8, are directly connected to pipes 32 and 34, respectively, and the pipes 32 and 33 are connected to the other direction control valves 11 and 12, respectively. Connected to actuator port. The conduits 31 to 34 are hydraulic hoses.
[0032]
The counterbalance valves 15 and 16 have a function of preventing the boom 5 or the attachment 6 from escaping due to gravity when rotating the boom 5 or the attachment 6 in a downward direction while holding a heavy object (an escape prevention function). Function to prevent the boom 5, attachment 6, and load from dropping due to rapid contraction of the up-and-down cylinder 7 and the tilt cylinder 8 when the pipelines 31 and 33 (hydraulic hoses) are broken (fall prevention function when the pipe is broken). ) And has the following configuration.
[0033]
The counterbalance valve 15 has a check valve 15a and a pressure control valve 15b with a relief function. The counterbalance valve 16 has an operate check valve 16a and a pressure control valve 16b with a relief function. The valve 15b, the operation check valve 16a, and the pressure control valve 16b are connected in parallel with each other. The check valve 15a permits only the flow of pressure oil from the pipe line 31 to the cylinder chamber 7a, and the operation check valve 16a has a built-in opening / closing means (described later) that is operated by a pilot pressure which is an external signal. When it is not, it functions as a normal check valve, allows only the flow of pressurized oil from the pipe line 33 to the cylinder chamber 8a as in the case of the check valve 15a, and opens and reverses when pilot pressure is applied. Flow is also possible. Each of the pressure control valves 15b and 16b has a valve-opening-side pressure receiving portion to which the pressure of the hydraulic oil in the pipelines 32 and 34 is led, and is opened by the pressure of the rod chambers 7b and 8b of the hydraulic cylinders 7 and 8. It has become. Further, the inlet pressure of the pressure control valves 15b and 16b is guided to the valve-opening-side pressure-receiving portions of the pressure control valves 15b and 16b, and the pressure is opened by the own pressure. It has a relief function to prevent the pressure from exceeding the set pressure.
[0034]
Conventionally, the counterbalance valve 16 is provided with a normal check valve instead of the operation check valve 16a. The operation of the present embodiment when the pilot pressure does not act on the operation check valve 16 is the same as that of the conventional one having a normal check valve.
[0035]
When the operator operates the operation lever 14, the direction control valve 12 is switched by the pilot pressure output from the remote control valve 26. When the directional control valve 12 is switched from the neutral position 12b to the position 12a, the pressure oil discharged from the hydraulic pump 10 passes through the pipe 30, the directional control valve 12, the pipe 33, and the check valve 16a of the counterbalance valve 16. Then, it flows into the bottom chamber 8a of the tilt cylinder 8. As a result, the tilt cylinder 8 operates in the extending direction, and the oil discharged from the rod chamber 8b of the tilt cylinder 8 returns to the tank 18 through the pipe 34 and the directional control valve 12. As a result, the attachment 6 rotates in the A (up) direction.
[0036]
Similarly, when the directional control valve 12 is switched to the position 12c, the pressure oil discharged from the hydraulic pump 10 similarly passes through the pipe 30, the directional control valve 12, and the pipe 34 to the rod of the tilt cylinder 8. It flows into the chamber 8b. At this time, when the driving pressure of the rod chamber 8b and the pressure of the pipe line 34 are low, such as when the attachment 6 falls due to gravity and rotates, the pressure control valves 15b and 16b of the counter balance valves 15 and 16 are closed. In the valve state, the oil in the bottom chamber 8 a of the tilt cylinder 8 is blocked by the counterbalance valve 16, so that the pressure in the pipeline 34 increases, and this pressure acts on the pressure control valve 16 b of the counterbalance valve 16. The pressure control valve 16b opens, and the oil in the bottom chamber 8a of the tilt cylinder 8 returns to the tank 18 through the pipeline 33 and the direction control valve 12. As a result, the tilt cylinder 8 operates in the contracting direction, and the attachment 6 rotates in the B (down) direction due to gravity. When the attachment 6 rotates in the B (down) direction due to gravity and the tilt cylinder 8 is about to contract more than the flow rate of the pressure oil supplied to the rod chamber 8 b of the tilt cylinder 8, the pressure in the pipeline 34 decreases again. Then, the pressure control valve 16b of the counter balance valve 16 is switched to the closing direction, a back pressure is generated in the bottom chamber 8a of the tilt cylinder 8, and the operation speed of the tilt cylinder 8 is suppressed. When the operation speed of the tilt cylinder 8 is suppressed to a flow rate equal to or higher than the flow rate of the pressure oil supplied to the rod chamber 8b of the tilt cylinder 8, the pressure in the pipeline 34 increases again, and the pressure control valve 16b is switched in the opening direction. The back pressure of the bottom chamber 8a of the tilt cylinder 8 decreases, and the suppression of the working speed of the tilt cylinder 8 is eased. The switching of the closing direction and the opening direction of the pressure control valve 16b and the increase and decrease of the pressure in the pipeline 34 are repeated in a very short time. As a result, the pressure control valve 16b has a substantially constant throttle opening. As a result, the operation speed of the tilt cylinder 8 is suppressed to a substantially constant speed, and escape of the attachment 6 is prevented.
[0037]
When the operator operates the operation lever 13, the direction control valve 11 switches, and the boom 5 is similarly rotated by the up-and-down cylinder 7. When the boom 5 rotates, the leveling cylinder 9 is driven to move, and oil is supplied and discharged between the leveling cylinder 9 and the tilt cylinder 8 through the pipes 35 and 36 and the pipes 33 and 34. , The tilt cylinder 8 is moved. With this function, even when the angle of the boom 5 changes, the angle of the attachment 6 with respect to the ground is maintained, and the load placed on the attachment 6 can be prevented from falling. Further, when the direction control valve 11 is switched to the position 11c and the driving pressure of the rod chamber 7b of the boom cylinder 7 and the pressure of the pipe line 32 are low, such as when the boom 5 falls by gravity and rotates. As in the case of the counterbalance valve 16, the operation speed of the boom cylinder 7 is suppressed by the counterbalance valve 15, and the runout of the boom 5 is prevented.
[0038]
In the present embodiment, the operation check valve 16a is provided in the counterbalance valve 16 as described above. Further, an electromagnetic switching valve 20, a control device 40 for controlling and driving the electromagnetic switching valve 20, and an attachment setting switch 41 are additionally provided, and an output port of the electromagnetic switching valve 20 and a Pc port (FIG. 1) which is a pilot port of the operation check valve 16a. 4) is connected via a pilot line 37.
[0039]
FIG. 4 shows a cross-sectional structure of the counterbalance valve 16 including the operation check valve 16a.
[0040]
The counterbalance 16 has a housing 50, and the housing 50 is provided with each of Cb port, V port, Cr port, Pc port, and D port. The Cb port is connected to the port of the bottom chamber 8a of the tilt cylinder 8, the V port is connected to the pipe 33, the Cr port is connected to the pipe 34, the Pc port is connected to the pipe 37, and the D port is connected to the tank 18. In the housing 50, two valve bodies of a poppet 52 and a spool 53 are arranged as valve bodies of the operation check valve 16a and the pressure control valve 16b, respectively, and thereby open and close a passage between the V port and the Cb port. Further, a piston 51 is arranged as opening / closing means of the poppet 52. The Pc port is located on the back side of the piston 51, and the Cr port is located on the end side of the spool 53 in the valve opening direction.
[0041]
The spool 53 is composed of two parts, a small-diameter spool part 53a where the end in the valve-opening direction is located and a large-diameter spool part 53b where the end in the valve-closing direction is located. The pressure receiving area of the portion 53b in the valve opening direction is larger than the pressure receiving area of the spool portion 53a in the valve closing direction. A spring 53c for setting pressure is located on the side of the spool portion 53b.
[0042]
When a pressure equal to or higher than the pressure set by the spring 53c acts on the Cr port, the spool 53 opens and the flow of the pressure oil from the Cb port to the V port via the spool portion 53b becomes possible. On the other hand, when pressure is not acting on the Pc port, the poppet 52 functions as a normal check valve. When pressure acts on the V port, the pressure on the V port pushes the poppet 52 open, and V The flow of pressure oil from the port to the Cb port becomes possible. Further, even if pressure acts on the Cb port, the poppet 52 does not open, and the reverse flow from the Cb port to the V port via the poppet valve 52 is impossible. When pressure is applied to the Pc port, the piston 51 pushes the poppet 52 open, so that the reverse flow from the Cb port to the V port is performed regardless of the pressure applied to the Cr port, that is, regardless of the open / close state of the spool 53. Becomes possible.
[0043]
When the pressure at the Cb port rises to the set pressure of the spring 53c, the spool 53 opens due to the difference in the pressure receiving area between the spool portion 53a and the spool portion 53b, and the hydraulic oil flows from the Cb port to the V port via the spool portion 53b. (Relief function).
[0044]
Returning to FIGS. 1 and 2, the attachment setting switch 41 is provided in the cab 4 and operated by the operator.
[0045]
The control device 40 controls the excitation state of the electromagnetic switching valve 20 according to the state of the setting switch 41 as shown in FIG. That is, when the setting switch 41 is at the position a, the excitation of the electromagnetic switching valve 20 is turned on, and when the setting switch 41 is at the position b, the excitation of the electromagnetic switching valve 20 is turned off.
[0046]
In the above, the electromagnetic switching valve 20 constitutes an external signal generating means for generating an external signal (pilot pressure), and the piston 51 provides an opening / closing means for allowing the counterbalance valve 16 to communicate with the external signal (pilot pressure). Constitute.
[0047]
Further, the attachment setting switch 41 constitutes an input means by an operator, and the control device 40 constitutes a control means for operating the electromagnetic switching valve 20 which is an external signal generating means based on a signal from the input means.
[0048]
Next, the operation of the present embodiment will be described.
[0049]
Now, when carrying out the cargo handling work by attaching the fork 6A as an attachment, the operator switches the attachment setting switch 41 to the position b. As a result, the excitation is turned off by the control device 40, so that the electromagnetic switching valve 20 is at the position 20b. In this position 20b, the pilot line 37 connected to the operation check valve 16a is communicated with the tank 18, so that the operation check valve 16a does not open and does not allow reverse flow. In this case, as described above, the hydraulic circuit operates in the same manner as in the related art. When the fork 6A is turned in the lowering direction by weight, the counterbalance valve 16 operates, and the lowering operation is performed at a safe speed regardless of the weight of the luggage to be handled. And cargo handling work can be performed safely.
[0050]
When performing the loading operation by changing the attachment from the fork 6A to the bucket 6B, the operator switches the attachment setting switch 41 to the position a. As a result, since the excitation is turned ON by the control device 40, the electromagnetic switching valve 20 is at the position 20a. In this position 20a, since the pilot line 37 connected to the operation check valve 16a is connected to the pilot pump 19, the poppet 52 is pushed open by the piston 51, and the operation check valve 16a is opened to allow reverse flow. State. That is, the bottom chamber 8 a of the tilt cylinder 8 communicates with the pipeline 32. As a result, when soil or the like that has entered the bucket 6A is discharged, the speed can be quickly rotated using its own weight and discharged without being limited by the counterbalance valve 16.
[0051]
As described above, according to the present embodiment, when the operator sets the type of attachment with the setting switch 41, the work of the counterbalance valve 16 can be effectively performed during the cargo handling work with the fork 6A, and the work can be performed safely. At the time of the loading operation by the bucket 6B, the operation can be performed quickly by communicating with the counterbalance valve 16, and the operability and the operation efficiency can be improved.
[0052]
A second embodiment of the present invention will be described with reference to FIGS. In the figure, the same parts as those shown in FIG. 1 are denoted by the same reference numerals.
[0053]
FIG. 6 is a circuit diagram showing the entire system of the hydraulic drive device of the work vehicle according to the present embodiment. This embodiment is different from the first embodiment shown in FIG. 1 in that a photo sensor 42 and a light emitting diode 43 are provided in place of the attachment setting switch 41, and the control device 40A inputs a signal from the photo sensor 42 to calculate. The difference is in the processing, and the other configuration is the same as that of the first embodiment.
[0054]
FIG. 7 is a diagram showing the characteristics of the hitch at the end of the boom, the characteristics of the joint of the attachment with the hitch, and the installation positions of the photosensor 42 and the light emitting diode 43. FIG. FIG. 8 is a top view of the portion VIII of FIG. FIG. 9 is a diagram illustrating a state where the attachment and the hitch are joined when the attachment is a bucket.
[0055]
In FIG. 7, a hitch 46 is attached to the tip portion 45 of the boom 5 of the lift truck in many cases so that it can be easily replaced with various attachments. It has a joint 47 that can be easily attached to and detached from The hitch 46 includes left and right side plates 46a and 46b, and a concave portion 46c is formed in the side plates 46a and 46b. The joining portion 47 includes left and right brackets 47a and 47b and a rod 47c inserted between the brackets 47a and 47b. The rod 47c can be inserted into the concave portion 46c. Pin holes 61 and 62 are provided in the side plates 46a and 46b and the brackets 47a and 47b, respectively. When the attachment is attached, the pins 63 (see FIG. 9) are driven into these pin holes and fixed.
[0056]
As shown in FIGS. 7 and 8, the photo sensor 42 and the light emitting diode 43 are installed facing each other on the hitch 46 with a gap therebetween. In the illustrated example, a claw portion 48 is attached to one side plate 46a of the hitch 46, and the light-emitting diode 43 is installed on one of the opposing surfaces of the side plate 46a and the claw portion 48, for example, a surface on the side plate 46a side, and the other, for example, a claw The photo sensor 42 is installed on the surface on the part 48 side. When there is no object that blocks light in the space between the side plate 46a of the hitch 46 and the claw portion 48, the photo sensor 42 receives light emitted from the light emitting diode 43 and when there is an object that blocks light in that space. In other words, the photo sensor 42 cannot receive the light emitted from the light emitting diode 43.
[0057]
On the other hand, a joint 47 between the attachment 6 and the hitch 46 has a feature as shown in FIG. That is, in the case of an attachment that does not require the counter balance valve such as the bucket 6B to work, a hole 49 is provided in a portion of the bracket 47a that enters between the photosensor 42 and the light emitting diode 43 when joined to the hitch 46, and the fork 6A or the like is provided. If the attachment requires the counterbalance valve to work, do not provide a hole at that location. Therefore, when the fork 6A is attached as the attachment, there is a light blocking member in the space between the side plate 46a of the hitch 46 and the claw portion 48, and when the bucket 6B is attached as the attachment, as shown in FIG. There is no obstacle in the space between the side plate 46a of the hitch 46 and the claw portion 48.
[0058]
The control device 40A controls the excitation state of the electromagnetic switching valve 20 according to the signal from the photo sensor 42 as shown in FIG. That is, if the photo sensor 42 receives the light of the light emitting diode 43, the excitation of the electromagnetic switching valve 20 is turned ON, and if not, the excitation of the electromagnetic switching valve 20 is turned OFF.
[0059]
In the above, the photo sensor 42, the light emitting diode 43, and the hole 9 of the claw portion 48 constitute an information reading unit that generates a signal when a specific attachment is mounted on the boom 5, and the control device 40A includes the information reading unit. A control means for operating the electromagnetic switching valve 20, which is an external signal generation means, based on a signal from the control unit.
[0060]
Now, when the fork 6A is attached as an attachment, the bracket 47a of the attachment joint 47 enters the space between the photosensor 42 and the light emitting diode 43, and blocks light from the light emitting diode 43. Therefore, since the photo sensor 42 does not receive the light, the control device 40A controls the excitation state of the electromagnetic switching valve 20 to OFF according to the control table of FIG. As a result, the electromagnetic switching valve 20 is at the position 20b, and the pilot line 37 connected to the operation check valve 16a is communicated with the tank 18, so that the operation check valve 16a does not open and does not allow reverse flow. In this case, since the hydraulic circuit is equivalent to the conventional one, when the fork 6A is rotated in the lowering direction by weight, the counterbalance valve 16 works, and the lowering operation is performed at a safe speed regardless of the weight of the luggage to be handled. Cargo handling work can be performed safely.
[0061]
When the attachment is changed from the fork 6A to the bucket 6B, the result is as shown in FIG. 9. Since the hole 49 is formed in the plate of the joint 47 with the hitch 46 of the attachment, the light from the light emitting diode 43 is not blocked. Therefore, the photo sensor 42 receives the light from the light emitting diode 43, and the control device 40A controls the excitation state of the electromagnetic switching valve 20 to ON according to the control table of FIG. As a result, the electromagnetic switching valve 20 is at the position 20a, and the pilot line 37 connected to the operation check valve 16a is connected to the pilot pump 19. Therefore, the poppet 52 is pushed open by the piston 51, and the operation check valve 16a is opened. To allow reverse flow. That is, the bottom chamber 8 a of the tilt cylinder 8 communicates with the pipeline 33. As a result, when the soil or the like that has entered the bucket 6B is discharged, the speed can be quickly rotated using its own weight and discharged without being limited by the counterbalance valve 16.
[0062]
As described above, in the present embodiment, the attachment has information indicating whether or not the function of the counterbalance valve 16 is effective depending on the presence or absence of the hole 49 in the plate of the joint 47 with the hitch 46. Without receiving the force, it is possible to reliably determine whether the function of the counterbalance valve 16 is effective or to communicate with it. During the cargo handling work with the fork 6A, the function of the counterbalance valve 16 is effective, and the work can be performed safely. At the time of the loading operation by 6B, the operation can be performed quickly by connecting the counterbalance valve 16, and the operability and the operation efficiency can be improved.
[0063]
Several other embodiments of the present invention will be described with reference to FIGS. In the figure, the same parts as those shown in FIG. 1 are denoted by the same reference numerals.
[0064]
FIG. 11 is a circuit diagram showing an entire system of a hydraulic drive device for a work vehicle according to a third embodiment of the present invention. This embodiment is different from the first embodiment shown in FIG. 1 in the configuration of the opening / closing means that allows the counterbalance to communicate with an external signal.
[0065]
In FIG. 11, a counterbalance valve 16A provided in the tilt cylinder 8 has a pressure control valve 16b, a normal check valve 16c, and an on-off valve 16d, which are connected in parallel with each other. The on-off valve 16d is a pilot-pressure-operated two-position switching valve having a closed position and an open position, and its pressure receiving portion 16e is connected to the output port of the electromagnetic switching valve 20 via a pilot line 37. When the pilot pressure from the electromagnetic switching valve 20 is not acting on the pressure receiving portion 16e, the on-off valve 16d is in the illustrated closed position, and only the flow of the pressure oil from the pipe line 33 to the bottom chamber 8a by the check valve 16c is possible. When the pilot pressure acts on the pressure receiving portion 16e from the electromagnetic switching valve 20, the on-off valve 16d is switched to the open position, and the flow in the opposite direction is also possible.
[0066]
The function of the counterbalance 16A configured as described above is the same as that of the counterbalance 16 in the first embodiment, and the present embodiment also provides the same effects as those of the first embodiment.
[0067]
FIG. 12 is a circuit diagram showing an entire system of a hydraulic drive device for a work vehicle according to a fourth embodiment of the present invention. This embodiment also differs from the first embodiment shown in FIG. 1 in the configuration of the opening / closing means that allows the counterbalance to communicate with an external signal.
[0068]
In FIG. 12, a counterbalance valve 16B provided in the tilt cylinder 8 has a pressure control valve 16b and a normal check valve 16c connected in parallel to each other, and has the same structure as the counterbalance valve 15 on the undulating cylinder 7 side. ing.
[0069]
A shuttle valve 38 is provided at a portion that guides the pressure of the pressure oil in the pipe 34 to the valve-opening pressure receiving chamber of the pressure control valve 16b. One input port of the shuttle valve 38 is connected to the pipe 34, and the other input port is provided. Are connected to the pilot line 37, and the output port is connected to the pilot line 39. When the pilot pressure from the electromagnetic switching valve 20 is not acting on the shuttle valve 38, the pressure control valve 16b is in the illustrated closed position, and only the flow of pressure oil from the pipe line 33 to the bottom chamber 8a by the check valve 16c is performed. When the pilot pressure acts on the shuttle valve 38 from the electromagnetic switching valve 20, the pressure control valve 16b is switched to the open position, and the flow in the opposite direction is also possible.
[0070]
The function of the counterbalance 16B configured as described above is the same as that of the counterbalance 16 in the first embodiment, and the present embodiment also provides the same effects as those of the first embodiment.
[0071]
FIG. 13 is a circuit diagram showing an entire system of a hydraulic drive device for a work vehicle according to a fifth embodiment of the present invention. In the present embodiment, both the counterbalance valve for the tilt cylinder and the counterbalance valve for the up / down cylinder can be communicated by an external signal.
[0072]
In FIG. 13, the counterbalance valve 15A provided in the up / down cylinder 7 has a pressure control valve 15b and an operation check valve 15c connected in parallel with each other, like the counterbalance valve 16 on the tilt cylinder 8 side. A Pc port (see FIG. 4), which is a pilot port of 15c, is connected to the pilot line 37A, and the pilot line 37A is connected to the output port of the electromagnetic switching valve 20 via the line 37. The operation check valve 15c allows only the flow of the pressurized oil from the pipe line 31 to the bottom chamber 8a when the pilot pressure is not applied, like a normal check valve. Is also possible.
[0073]
According to this embodiment, when the attachment is changed from the fork 6A to the bucket 6B to perform the loading operation, when the attachment setting switch 41 is switched to the position a and the electromagnetic switching valve 20 is switched to the position 20a, the counter balance valve 15A, The 16 operation check valves 15c and 16a are both opened, and a state in which the reverse flow is allowed is established. Therefore, when discharging the earth and sand that has entered the bucket 6A, both the boom 5 and the bucket 6B rotate quickly by their own weight, and the working speed can be further increased.
[0074]
Further, according to the present embodiment, the boom can be quickly lowered during the scooping operation of the earth and sand in the loading operation, so that the operation speed is similarly increased, and the operability and the operation efficiency are improved.
[0075]
The present invention is not limited to the above embodiment, and various changes and modifications can be made within the spirit of the present invention. For example, in the third to fifth embodiments illustrated in FIGS. 11 to 13, the electromagnetic switching valve 20 is operated by the control device 40 based on the signal of the attachment setting switch 41, but is illustrated in FIG. 6. As in the second embodiment, the electromagnetic switching valve 20 may be operated by the control device 40A based on signals from the photo sensor 42 and the light emitting diode 43.
[0076]
【The invention's effect】
According to the present invention, in a working vehicle such as a lift truck having a counterbalance valve, it is possible to switch between a case where the function of the counterbalance valve is activated and a case where the counterbalance valve is quickly rotated by gravity according to the type of the attachment. The counterbalance valve function can be used safely when loading with a fork, and the work can be done safely by using the counterbalance valve. An operation suitable for the work content can be performed, safety can be maintained, and operability and work efficiency can be improved.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing an entire system of a hydraulic drive device of a working vehicle according to a first embodiment of the present invention.
FIG. 2 is a view showing an appearance of a lift truck as an example of a work vehicle, showing a state where a fork is attached as an attachment.
FIG. 3 is a view showing an appearance of a lift truck as an example of a work vehicle, and showing a state where a bucket is mounted as an attachment.
FIG. 4 is a view showing a cross-sectional structure of a counterbalance valve having an operation check valve provided in the hydraulic drive device according to the first embodiment of the present invention.
FIG. 5 is a diagram showing a control table of a control device provided in the hydraulic drive device according to the first embodiment of the present invention.
FIG. 6 is a circuit diagram showing an entire system of a hydraulic drive device of a working vehicle according to a second embodiment of the present invention.
FIG. 7 shows the characteristics of the hitch at the end of the boom of the lift truck, the characteristics of the joint with the hitch of the attachment, and the installation positions of the photo sensor and the light emitting diode provided in the hydraulic drive device according to the second embodiment of the present invention. FIG.
FIG. 8 is a top view showing details of a VIII section in FIG. 7;
FIG. 9 is a diagram showing a state where the attachment and the hitch are joined when the attachment of the lift truck including the hydraulic drive device according to the second embodiment of the present invention is a bucket.
FIG. 10 is a diagram showing a control table of a control device provided in a hydraulic drive device according to a second embodiment of the present invention.
FIG. 11 is a circuit diagram showing an entire system of a hydraulic drive device of a working vehicle according to a third embodiment of the present invention.
FIG. 12 is a circuit diagram showing an entire system of a hydraulic drive device of a working vehicle according to a fourth embodiment of the present invention.
FIG. 13 is a circuit diagram showing an entire system of a hydraulic drive device for a working vehicle according to a fifth embodiment of the present invention.
[Explanation of symbols]
1 Body
2 front wheels
3 Rear wheel
4 cab
5 Boom
6 Attachments
6A fork
6B bucket
7 Undulating cylinder
8 Tilt cylinder
9 Leveling cylinder
10 Hydraulic pump
11,12 directional control valve
13,14 Operation lever
15, 16 Counterbalance valve
15A counterbalance valve
16A; 16B Counterbalance valve
15a Check valve
15b Pressure control valve
16c operated check valve
16a Operate check valve
16b Pressure control valve
16c check valve
16d on-off valve
17 Relief valve
18 tanks
19 Pilot pump
20 Solenoid switching valve
21,22 Overload relief and anti-cavitation valve
25, 26 Remote control valve
30-36 pipe
37 Pilot pipeline
37A Pilot line
38 Shuttle valve
39 Pilot pipeline
40 control device
40A control device
41 Attachment setting switch
42 Photo Sensor
43 light emitting diode
45 Boom tip
46 hitch
47 joint
48 claws
49 holes
50 Housing
51 piston
52 Poppet
53 spool

Claims (7)

A hydraulic drive device for a working vehicle including a boom rotatably attached to a vehicle body and an attachment replaceably attached to a tip of the boom,
A hydraulic cylinder for rotating the boom and the attachment,
A hydraulic pump that supplies pressurized oil to each hydraulic cylinder for the boom and the attachment,
A directional control valve for controlling the flow of pressurized oil supplied from the hydraulic pump to each hydraulic cylinder for the boom and the attachment,
A counterbalance valve disposed between at least one load holding side cylinder chamber of the boom and attachment hydraulic cylinders and a conduit leading to the directional control valve;
External signal generating means for generating an external signal;
Opening / closing means for allowing the counterbalance valve to communicate with the external signal. The hydraulic drive device for a working vehicle according to claim 1,
Input means by an operator;
Control means for operating the external signal generating means based on a signal from the input means. The hydraulic drive device for a working vehicle according to claim 1,
Information reading means for generating a signal when a specific attachment is attached to the boom,
Control means for activating the external signal generating means based on a signal from the information reading means. The hydraulic drive device for a working vehicle according to claim 3,
The hydraulic drive device for a working vehicle, wherein the information reading means is a shape feature provided to a mounting portion between the end of the boom and the attachment, and a sensor means which is turned on / off by the shape feature. . The hydraulic drive device for a working vehicle according to claim 1,
The counterbalance valve includes a pressure control valve and a check valve connected in parallel with each other,
The hydraulic drive device for a working vehicle, wherein the opening / closing means is means for opening a check valve of the counterbalance valve in response to the external signal. The hydraulic drive device for a working vehicle according to claim 1,
The counterbalance valve includes a pressure control valve and a check valve connected in parallel with each other,
The hydraulic drive device for a working vehicle, wherein the opening / closing means is an opening / closing valve that is connected in parallel to the pressure control valve and the check valve of the counterbalance valve and is switched from a closed position to an open position by an external signal. The hydraulic drive device for a working vehicle according to claim 1,
The counterbalance valve includes a pressure control valve and a check valve connected in parallel with each other,
The external signal generating means is means for generating a pilot pressure as an external signal,
The opening / closing means is means for guiding a pilot pressure generated by the external signal generating means to a valve-opening-side pressure-receiving portion of a pressure control valve of the counterbalance valve.

Images