Patent Publication Number: US-8523139-B2

Title: Selector valve operating mechanism for working vehicle

Description:
TECHNICAL FIELD 
     The present invention relates to a selector valve operating mechanism for a working vehicle which operates a mechanical selector valve thr controlling a hydraulic actuator. 
     BACKGROUND ART 
     Conventionally, an art is known in which a working vehicle such as a backhoe loader has a PTO hydraulic port for supplying pressure oil to a hydraulic actuator of an external hydraulic apparatus such as a breaker or a grapple, and for supply and discharge of pressure oil to the PTO hydraulic port, an electromagnetic type selector valve with an electromagnetic solenoid is employed such as an electromagnetic selector valve in which a spool in the selector valve is moved directly by an electromagnetic solenoid so as to change the route of pressure oil or an electromagnetic hydraulic selector valve in which an electromagnetic pilot valve having an electromagnetic solenoid is actuated and a main spool is moved indirectly by hydraulic pressure from the electromagnetic pilot valve so as to change the route of pressure oil (for example, see the Patent Literature 1). 
     On the other hand, such an electromagnetic type selector valve requires complex oil paths and control construction, and the large valve is employed so as to drive directly an external hydraulic apparatus. Therefore, when large numbers of the valves are employed, the cost of parts is increased. Accordingly, art of a mechanical selector valve is also known in which the spool of the selector valve is moved mechanically by manual power transmitted through a pedal, a lever or the like (for example, see the Patent Literature 2).
     Patent Literature 1: the Japanese Patent Laid Open Gazette 2007-92763   Patent Literature 2: the Japanese Patent Laid Open Gazette 2003-176549   

     DISCLOSURE OF INVENTION 
     Problems to be Solved by the Invention 
     However, the structures of oil paths and switching control of a mechanical selector valve for controlling a hydraulic actuator and the cost of parts of the mechanical selector valve are respectively simplified and reduced to levels not achievable by an electromagnetic selector valve. However, simple and quick switching operation of the mechanical selector valve by the use of a nearby switch which requires small force to actuate such as the electromagnetic selector valve is difficult, and this makes the mechanical selector valve less easy to operate than the electromagnetic selector valve. 
     Means for Solving the Problems 
     The above problems are solved by the following means according to the present invention. 
     Namely, according to the present invention, a selector valve operating mechanism for a working vehicle which operates a mechanical selector valve for controlling a hydraulic actuator, includes a hydraulic piston connected through an operation link to a spool of the mechanical selector valve, an electromagnetic valve hydraulically controlling reciprocal action of the hydraulic piston, and a control device transmitting an action signal to the electromagnetic valve. By action control of the electromagnetic valve, the spool is moved via the hydraulic piston and the operation link so as to operate the mechanical selector valve. 
     According to the present invention, the hydraulic piston is constructed integrally with the electromagnetic valve. 
     According to the present invention, the hydraulic piston comprises two hydraulic pistons respectively for moving the spool forward and rearward in movement direction of the spool, and each of the hydraulic pistons is single acting type having a pressure oil chamber at only one of front and rear sides in the move direction of the piston. 
     According to the present invention, a selector valve operating mechanism for a working vehicle which operates a mechanical selector valve for controlling a hydraulic actuator, includes a motor connected through an operation link to a spool of the mechanical selector valve and controllable electrically, and a control device transmitting an action signal to the motor. The spool is moved via the operation link by rocking output of the motor so as to operate the mechanical selector valve. 
     Effect of the Invention 
     The present invention constructed as the above brings the following effects. Namely, according to the present invention, a selector valve operating mechanism for a working vehicle which operates a mechanical selector valve for controlling a hydraulic actuator, includes a hydraulic piston connected through an operation link to a spool of the mechanical selector valve, an electromagnetic valve hydraulically controlling reciprocal action of the hydraulic piston, and a control device transmitting an action signal to the electromagnetic valve. By action control of the electromagnetic valve, the spool is moved via the hydraulic piston and the operation link so as to operate the mechanical selector valve. Accordingly, the mechanical selector valve can be operated with the electromagnetic valve which is a small and cheap electromagnetic selector valve or the like. In comparison with the case of employing only a large and expensive electromagnetic selector valve, the oil path switching control construction can be simplified and the cost of parts thereof can be reduced. Furthermore, a nearby switch or the like is interlocked with the action of the electromagnetic valve so that the mechanical selector valve can be switched easily and quickly with small operation power similarly to the conventional electromagnetic selector valve, whereby switching operability can be improved widely. Moreover, the hydraulic pistons, the electromagnetic valve and the like can be subsequently attached easily to a current mechanical selector valve. Accordingly, the requirement of improvement of switching operability from a user can be measured quickly without changing the fundamental construction of the selector valve, whereby the working vehicle superior in general-purpose properties can be provided. 
     According to the present invention, the hydraulic piston is constructed integrally with the electromagnetic valve. Accordingly, the hydraulic pistons and the electromagnetic valve are made to be a single unit structure so as to be attachable and detachable easily in the selector valve operating mechanism, whereby the assemble ability and maintainability can be improved. Furthermore, members required for oil paths and attachment members concerning the hydraulic pistons and the electromagnetic valve can be made common, whereby the cost of parts can be reduced further. Moreover, the arrangement space for the hydraulic pistons and the electromagnetic valve can be reduced, whereby the whole selector valve operating mechanism can be made compact. 
     According to the present invention, the hydraulic piston comprises two hydraulic pistons respectively for moving the spool forward and rearward in movement direction of the spool, and each of the hydraulic pistons is single acting type having a pressure oil chamber at only one of front and rear sides in the move direction of the piston. Accordingly, unlike a double acting piston in which pressure oil chambers are provided at both front and rear sides in the move direction of the pistons, it is necessary to control only the hydraulic pressure in the pressure oil chamber at one of the sides and any complex position control mechanism for keeping the neutral position is not required, whereby the hydraulic pressure control construction can be simplified so as to improve responsibility of the pistons and to reduce the cost of parts further. 
     According to the present invention, a selector valve operating mechanism for a working vehicle which operates a mechanical selector valve for controlling a hydraulic actuator, includes a motor connected through an operation link to a spool of the mechanical selector valve and controllable electrically, and a control device transmitting an action signal to the motor. The spool is moved via the operation link by rocking output of the motor so as to operate the mechanical selector valve. Accordingly, the mechanical selector valve can be switched with a small and cheap motor. Therefore, in comparison with the case of employing only a large and expensive electromagnetic selector valve, the oil path switching control construction can be simplified and the cost of parts thereof can be reduced. Furthermore, a nearby switch or the like is interlocked with the action of the motor so that the mechanical selector valve can be switched easily and quickly with small operation power similarly to the conventional electromagnetic selector valve, whereby switching operability can be improved widely. Moreover, the motor and the like can be subsequently attached easily to a current mechanical selector valve, whereby the working vehicle superior in general-purpose properties can be provided. In comparison with the case that the small electromagnetic valve is employed for operating the mechanical selector valve, the hydraulic piping and the like can be reduced further, whereby the assemble ability and maintainability can be improved. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a side view of entire construction of a working vehicle according to the present invention. 
         FIG. 2  is a hydraulic circuit diagram of the entire working vehicle. 
         FIG. 3  is a hydraulic circuit diagram of a loader control valve section. 
         FIG. 4  is a front view partially in section of an operation part having a selector valve operating mechanism according to the present invention. 
         FIG. 5  is a front view partially in section of the selector valve operating mechanism. 
         FIG. 6  is a hydraulic circuit diagram of the selector valve operating mechanism. 
         FIG. 7  is a front view partially in section of an operation part having a selector valve operating mechanism of another embodiment. 
     
    
    
     THE BEST MODE FOR CARRYING OUT THE INVENTION 
     Next, explanation will be given on an embodiment of the present invention. 
       FIG. 1  is a side view of entire construction of a working vehicle according to the present invention.  FIG. 2  is a hydraulic circuit diagram of the entire working vehicle.  FIG. 3  is a hydraulic circuit diagram of a loader control valve section.  FIG. 4  is a front view partially in section of an operation part having a selector valve operating mechanism according to the present invention.  FIG. 5  is a front view partially in section of the selector valve operating mechanism.  FIG. 6  is a hydraulic circuit diagram of the selector valve operating mechanism.  FIG. 7  is a front view partially in section of an operation part having a selector valve operating mechanism of another embodiment. 
     Firstly, explanation will be given on entire construction of a working vehicle  1  according to the present invention referring to  FIGS. 1 ,  2  and  4 . 
     The working vehicle  1  is a backhoe loader. A loader  3  which is a loading unit and an excavator  4  are disposed at front and rear sides of a traveling vehicle  2  at the center of the working vehicle  1 . A body frame  5  is extended and provided from the front end to the real end of the traveling vehicle  2 . Left and right front wheels  8  and rear wheels  9  are attached respectively through a front axle casing and a rear axle casing (not shown) to the front and rear portions of the body frame  5 . The working vehicle  1  can travel while equipped with the loader  3  and the excavator  4 . 
     A steering wheel  11  and a seat  12  are disposed in a maneuvering part  14  covered by a canopy  42  in the traveling vehicle  2 . Various kinds of hydraulic operation members for controlling the loader  3  and the like, a meter (not shown) and the like are concentrically arranged at the side of the seat  12  as an operation part  10 . An accelerator lever  13 , a control valve unit  15  having a plurality of mechanical selector valves according to the present invention, and the like are arranged in the operation part  10 . Accordingly, traveling operation of the working vehicle  1  and loader work operation of the loader  3  can be performed by the maneuvering part  14 . 
     The loader  3  is connected to the side portion of the traveling vehicle  2  and extended forward, and includes a bracket  40 , a lift arm  41 , a bucket  16  attached to the tip of the lift arm  41  and the like so as to be employed as a front loader. An engine  6  is mounted in the front portion of the body frame  5  of the traveling vehicle  2 . The engine  6  is covered by a bonnet  7  on the body frame  5 , and the loader  3  is disposed outside the bonnet  7 . 
     The excavator  4  is detachably attached to the rear portion of the traveling vehicle  2  and includes a boom bracket  22 , a boom  24 , an arm  26 , a bucket  28  attached to the tip of the arm  26  and the like so as to be employed as a backhoe. Behind the seat  12 , an operation column  37  containing a control valve unit  43  for the excavator  4  is standingly provided, and excavating work operation can be performed by operating an operation lever on the operation column  37 . 
     Two stabilizers  20  are disposed at the left and right sides of the rear portion of the body frame  5 . By extending and contracting rods of two stabilizer cylinders  21  provided in the stabilizers  20 , at the excavating work, the excavator  4  can be moved vertically and rotated, and the stabilizers  20  can be stretched with the bucket  16  of the loader  3  so as to support the working vehicle  1 , thereby securing good stability of the vehicle body. 
     At the side of the maneuvering part  14 , a pressure oil tank  33  serving as a reservoir tank of pressure oil is disposed. Behind the engine  6 , a hydraulic pump unit  130  for supplying pressure oil to working machines such as the loader  3  and the excavator  4  is disposed. An output shaft  6   a  projected rearward from the engine  6  is connected to the hydraulic pump unit  130  and the hydraulic pump unit  130  is driven by power of the engine, whereby pressure oil is supplied from the hydraulic pump unit  130  to the working machines and the like. 
     In detail, in the loader  3 , pressure oil is supplied to left and right lift cylinders  17  and dump cylinders  18 , and in the excavator  4 , pressure oil is supplied to two swing cylinder  23 , which makes extend and contract a boom cylinder  25 , an arm cylinder  27 , a bucket cylinder  29  and a rod  34  so as to rotate laterally the excavator  4 , and the left and right stabilizer cylinders  21 . Furthermore, pressure oil is supplied to a power steering cylinder  141  for steering the front wheels  8 . 
     A hydraulic stepless transmission  101  in a transmission casing  31  is connected through a transmission shaft  30  and the like to the output shaft  6   a  of the engine  6 . A motor shaft  32  which is an output shaft of the hydraulic stepless transmission  101  is connected through a differential mechanism, a clutch mechanism, axles and the like (not shown) to the rear wheels  9 . The power of the engine is speed-changed and then transmitted as speed-changed power to the rear wheels  9 , whereby the working vehicle  1  is driven so as to travel. 
     Next, explanation will be given on a hydraulic circuit  100  of the working vehicle  1  referring to  FIGS. 2 and 3 . 
     The hydraulic circuit  100  includes the hydraulic stepless transmission  101 , the pressure oil tank  33 , the hydraulic pump unit  130 , a power steering control valve section  140 , a loader control valve section  200  which is a mechanical selector valve group form controlling the loader  3 , a backhoe control valve section  150  which is a mechanical selector valve group form controlling the excavator  4 , and the like. 
     In the hydraulic stepless transmission  101 , a hydraulic pump  59  and a hydraulic motor  60  each of which is variable capacity type are connected fluidly to each other through a pair of main oil paths  61   a  and  61   b  so as to construct a closed circuit. In the closed circuit, by controlling tilt angle of movable swash plates  59   a  and  60   a  of the hydraulic pump  59  and the hydraulic motor  60 , the rotational speed and rotational direction of the power of the engine inputted through the transmission shaft  30  and the like to the hydraulic pump  59  is changed freely, and then outputted as speed-changed power through the motor shaft  32 . 
     The pressure oil tank  33  is a vessel in which pressure oil used in the hydraulic circuit  100  is stored, and may also serve as the transmission casing  31  of the working vehicle  1  at need. 
     The hydraulic pump unit  130  includes two variable capacity type hydraulic pumps P 1  and P 2  and a fixed capacity type hydraulic pump P 3  such as a gear pump. The hydraulic pumps P 1  and P 2  are constructed integrally so that the mounting space of the hydraulic pump unit  130  is reduced in comparison with the case that hydraulic pumps are provided separately, whereby the hydraulic pump unit  130  is made compact. 
     The suction side of each of the hydraulic pumps P 1 , P 2  and P 3  is connected to a port  131 , and the port  131  is connected through a pipe  121  to the pressure oil tank  33 . Namely, pressure oil is supplied through the common pipe  121  to the hydraulic pumps P 1 , P 2  and P 3 , whereby the introduction route of pressure oil is simplified so as to reduce piping cost and suction resistance at the time of suction of pressure oil is reduced. 
     Furthermore, the discharge sides of the hydraulic pumps P 1 , P 2  and P 3  respectively have discharge ports  132 ,  133  and  134 . The discharge ports  132  and  133  are connected to the loader control valve section  200  respectively through pipes  137  and  136 , and the discharge port  134  is connected through a pipe  135  to the power steering control valve section  140 . 
     Accordingly, in the hydraulic pump unit  130 , pressure oil in the pressure oil tank  33  is sucked through the pipe  121  and the port  131  and supplied through the discharge ports  132 ,  133  and  134  to the loader control valve section  200  and the power steering control valve section  140 . 
     In the power steering control valve section  140 , a steering control valve (not shown) is provided, and the steering control valve controls slide of the power steering cylinder  141  corresponding to the operation of the steering wheel  11  so as to assist the steering power. The pipe  135  is connected to a port  142  provided in the power steering control valve section  140 , and pressure oil discharged from the hydraulic pump P 3  is supplied from the pipe  135  through the port  142  to the steering control valve. 
     A port  102  provided in the power steering control valve section  140  is connected through a pipe  103  whose middle portion is provided therein with a filter  104  to a charge circuit  64  of the hydraulic stepless transmission  101 . The charge circuit  64  includes two check valves  62  and a check release valve  63 , and pressure oil controlled to charge release pressure by the check release valve  63  is supplied through the check valves  62  to the closed circuit. 
     As described in detail later, the loader control valve section  200  includes selector valves  210 ,  220 ,  230  and  240  controlling pressure oil to the lift cylinders  17  and the dump cylinders  18  of the loader  3 , and the drive of the loader  3  is controlled by the selector valves  210 ,  220 ,  230  and  240 . 
     Furthermore, the loader control valve section  200  includes a pump port  251 , a tank port  252 , a carry-over port  253 , dump cylinder ports  254  and  255 , lift cylinder ports  256  and  257 , ports  258  and  259 , and PTO ports  260  and  261 . 
     The pump port  251  is connected to a pipe  136  communicated with the discharge port  133  of the hydraulic pump P 2 , the port  258  is connected to a pipe  137  communicated with the discharge port  132  of the hydraulic pump P 1 , and the tank port  252  is connected to a pipe  262  communicated with the pressure oil tank  33 . Pressure oil discharged from the hydraulic pumps P 1  and P 2  is supplied to the selector valves  210 ,  220 ,  230  and  240  of the loader control valve section  200 , whereby the lift cylinders  17 , the dump cylinders  18 , a hydraulic actuator of an external hydraulic apparatus and the like are driven. 
     The backhoe control valve section  150  includes selector valves  51  to  58 , which control the action of the stabilizer cylinders  21 , the swing cylinder  23 , the boom cylinder  25 , the arm cylinder  27  and the bucket cylinder  29 , and ports  151  and  152 . 
     The port  151  is connected to a pipe  263  communicated with the carry-over port  253  of the loader control valve section  200 , and the port  152  is connected to a pipe  264  communicated with the port  259  of the loader control valve section  200 . One of the stabilizer cylinders  21 , the swing cylinder  23  and the arm cylinder  27  are driven by pressure oil supplied from the port  151  through the pipe  263 , and the other stabilizer cylinder  21 , the bucket cylinder  29  and the boom cylinder  25  are driven by pressure oil supplied from the port  152  through the pipe  264 . 
     Next, explanation will be given on detailed construction of the loader control valve section  200  referring to  FIGS. 2 and 3 . 
     The loader control valve section  200  includes the dump cylinder selector valve  210 , the lift cylinder selector valve  220 , the mode selector valve  230  and the PTO selector valve  240 . 
     The dump cylinder selector valve  210  is a direction control valve with six ports and three positions (positions A, B and C) and interposed between the pump port  251  and the dump cylinders  18 . The pump port  251  and the dump cylinder selector valve  210  are connected through an oil path  270 . The oil path  270  and an oil path  272  connected to the tank port  252  are connected through an oil path  271 . A release valve  271   a  is provided in the middle portion of the oil path  271 . 
     Furthermore, the oil path  272  and the dump cylinder port  254  are connected through an oil path  274 . The middle portion of the oil path  274  is connected through an oil path  273  to the dump cylinder selector valve  210 . An anti-void release valve  274   a  is provided in the oil path  274  near the connection part to the oil path  272 . The oil path  272  and the dump cylinder port  255  are connected through an oil path  276 . The middle portion of the oil path  276  is connected through an oil path  275  to the dump cylinder selector valve  210 . An anti-void release valve  276   a  is provided in the oil path  276  near the connection part to the oil path  272 . 
     The dump cylinder port  254  is communicated through a pipe  265  with bottom chambers of the dump cylinders  18 . The dump cylinder port  255  is communicated through a pipe  266  with rod chambers of the dump cylinders  18 . 
     In this construction, pressure oil discharged from the discharge port  133  of the hydraulic pump P 2  is supplied through the pipe  136 , the pump port  251  and the oil path  270  to the dump cylinder selector valve  210 . When the dump cylinder selector valve  210  is switched to the position C, pressure oil is pressingly sent through the oil path  273 , the oil path  274 , the dump cylinder port  254  and the pipe  265  to the bottom chambers of the dump cylinders  18 . Accordingly, the rods of the dump cylinders  18  are extended. 
     When the dump cylinder selector valve  210  is switched to the position B, pressure oil is pressingly sent through the oil path  275 , the oil path  276 , the dump cylinder port  255  and the pipe  266  to the rod chambers of the dump cylinders  18 . Accordingly, the rods of the dump cylinders  18  are contracted. By the position selecting operation of the dump cylinder selector valve  210 , the rods of the dump cylinders  18  are extended and contracted, whereby the bucket  16  is rotated vertically about the lift arm  41 . 
     The lift cylinder selector valve  220  is a direction control valve with six ports and four positions (positions D, E, F and G) and interposed between the dump cylinder selector valve  210  and the lift cylinders  17 . The lift cylinder selector valve  220  is connected through an oil path  277  to the dump cylinder selector valve  210 . 
     Furthermore, the oil path  272  and the lift cylinder port  256  are connected through an oil path  279 . The middle portion of the oil path  279  is connected through an oil path  278  to the lift cylinder selector valve  220 . A check valve  279   a  is provided in the oil path  279  near the connection part to the oil path  272 . The lift cylinder selector valve  220  and the lift cylinder port  257  are connected through an oil path  280 . 
     The lift cylinder port  256  is communicated through a pipe  267  with rod chambers of the lift cylinders  17 . The lift cylinder port  257  is communicated through a pipe  268  with bottom chambers of the lift cylinders  17 . 
     In this construction, when the dump cylinder selector valve  210  is switched to the position A, pressure oil passing through the dump cylinder selector valve  210  is supplied through the oil path  277  to the lift cylinder selector valve  220 . Furthermore, when the lift cylinder selector valve  220  is switched to the position E, pressure oil is pressingly sent through the oil path  280 , the lift cylinder port  257  and the pipe  268  to the bottom chambers of the lift cylinders  17 . Accordingly, the rods of the lift cylinders  17  are extended. 
     When the lift cylinder selector valve  220  is switched to the position F, pressure oil is pressingly sent through the oil path  278 , the oil path  279 , the lift cylinder port  256  and the pipe  267  to the rod chambers of the lift cylinders  17 . Accordingly, the rods of the lift cylinders  17  are contracted. By the position selecting operation of the lift cylinder selector valve  220 , the rods of the lift cylinders  17  are extended and contracted, whereby the lift arm  41  is moved upward and downward vertically. 
     The mode selector valve  230  is a direction control valve with five ports and three positions (positions J, K and L) and interposed between the lift cylinder selector valve  220  and the carry-over port  253 . The mode selector valve  230  includes primary ports  230   a  and  230   b  and secondary ports  230   c ,  230   d  and  230   e . When the mode selector valve  230  is switched to the “working position H”, the port  230   a  is communicated with the port  230   c , the port  230   d  is communicated with the port  230   e , and the port  230   b  is blocked. When the mode selector valve  230  is switched to the “return position J”, the port  230   a , the port  230   b , the port  230   c , the port  230   d  and the port  230   e  are communicated with each other. When the mode selector valve  230  is switched to the “confluence position K”, the port  230   a  is communicated with the port  230   c  and the port  230   d  and the port  230   b  is communicated with the port  230   e . The port  230   a  is connected through an oil path  281  to the lift cylinder selector valve  220 . 
     Furthermore, the port  230   b  of the mode selector valve  230  is connected through an oil path  282  to the oil path  272 . The port  230   d  is connected through an oil path  283  to the port  258 . The port  230   e  is connected through an oil path  284  to a middle portion of an oil path  285 . The oil path  285  connects the oil path  272  to the port  259 . An anti-void release valve  285   a  is provided in the oil path  285  near the connection part to the oil path  272 . 
     The PTO selector valve  240  is a direction control valve with six ports and four positions (positions L, M, N and P) and interposed between the mode selector valve  230  and the carry-over port  253 . The PTO selector valve  240  includes primary ports  240   a ,  240   b  and  240   c  and secondary ports  240   d ,  240   e  and  240   f . When the PTO selector valve  240  is switched to the “position L”, the port  240   a  is communicated with the port  240   d  and the ports  240   b ,  240   c ,  240   e  and  240   f  are blocked. When the PTO selector valve  240  is switched to the “position M”, the port  240   b  is communicated with the port  240   f , the port  240   c  is communicated with the port  240   e  and the ports  240   a  and  240   d  are blocked. When the PTO selector valve  240  is switched to the “position N”, the port  240   b  is communicated with the port  240   e , the port  240   c  is communicated with the port  240   f  and the ports  240   a  and  240   d  are blocked. When the PTO selector valve  240  is switched to the “continuous position P”, the port  240   b  is communicated with the port  240   e , the port  240   c  is communicated with the port  240   f  and the ports  240   a  and  240   d  are blocked. The port  240   a  is connected through an oil path  286  to the port  230   c  of the mode selector valve  230 . 
     Furthermore, the port  240   b  of the PTO selector valve  240  is connected through an oil path  287  to the middle portion of the oil path  286 , and a check valve  287   a  is provided in the middle portion of the oil path  287 . The port  240   c  is connected through an oil path  288  to the oil path  272 . The port  240   d  is connected through an oil path  289  to the carry-over port  253 . The port  240   e  is connected through an oil path  290  to a middle portion of an oil path  291 . The oil path  291  connects the oil path  272  to the PTO port  260 . A plug  291   a  is provided in the oil path  291  near the connection part to the oil path  272 . The port  240   f  is connected through an oil path  292  to a middle portion of an oil path  293 . The oil path  293  connects the oil path  272  to the PTO port  261 . A plug  293   a  is provided in the oil path  293  near the connection part to the oil path  272 . 
     Explanation will be given on selection construction of the pressure oil route with the mode selector valve  230  and the PTO selector valve  240  constructed as mentioned above. 
     When excavating work or the like is performed with the excavator  4 , the mode selector valve  230  is set to the working position H and the PTO selector valve  240  is set to the position L. 
     Then, pressure oil discharged from the discharge port  133  of the hydraulic pump P 2  is supplied through the pipe  136 , the pump port  251 , the oil path  270 , the dump cylinder selector valve  210 , the oil path  277 , the bucket lift cylinder selector valve  220 , the oil path  281 , the mode selector valve  230 , the oil paths  286 , the PTO selector valve  240 , the oil path  289 , the carry-over port  253 , and the pipe  263  to the backhoe control valve section  150 . On the other hand, pressure oil discharged from the discharge port  132  of the hydraulic pump P 1  is supplied through the pipe  137 , the port  258 , the oil path  283 , the mode selector valve  230 , the oil path  284 , the oil path  285 , the port  259  and the pipe  264  to the backhoe control valve section  150 . Accordingly, pressure oil pressingly sent from the discharge ports  132  and  133  of the hydraulic pumps P 1  and P 2  can be supplied to the backhoe control valve section  150 , and the excavator  4  is driven by the supplied pressure oil. 
     In the case that an external hydraulic apparatus is connected to the PTO ports  260  and  261  and work is performed with the external hydraulic apparatus, the mode selector valve  230  is set to the working position H and the PTO selector valve  240  is set to the position M or N. 
     Then, pressure oil discharged from the discharge port  133  of the hydraulic pump P 2  is supplied through the pipe  136 , the pump port  251 , the oil path  270 , the dump cylinder selector valve  210 , the oil, path  277 , the bucket lift cylinder selector valve  220 , the oil, path  281 , the mode selector valve  230 , and the oil paths  286  and  287  to the PTO selector valve  240 . At the position M, the pressure oil is pressingly sent through the port  240   f  and the oil paths  292  and  293  to the PTO port  261 . At the position N, the pressure oil is pressingly sent through the port  240   e  and the oil paths  290  and  291  to the PTO port  260 . Accordingly, the pressure oil is extracted from the PTO port  260  or  261  so as to drive the external hydraulic apparatus. 
     In the case of conveying work of earth and sand with the loader  3  or the case of traveling, the mode selector valve  230  is set to the return position J. 
     Then, pressure oil discharged from the discharge port  133  of the hydraulic pump P 2  is supplied through the pipe  136 , the pump port  251  and the oil path  270  to the dump cylinder selector valve  210 , and is supplied through the oil path  277  to the bucket lift cylinder selector valve  220  so as to drive the loader  3 . 
     The pressure oil after passing through the dump cylinder selector valve  210  and the bucket lift cylinder selector valve  220  is supplied through the oil path  281  to the mode selector valve  230 . On the other hand, pressure oil discharged from the discharge port  132  of the hydraulic pump P 1  is supplied through the pipe  137 , the port  258  and the oil path  283  to the mode selector valve  230 . The pressure oil supplied from the discharge ports  132  and  133  of the hydraulic pumps P 1  and P 2  is returned through the oil path  282 , the oil path  272 , the tank port  252  and the pipe  262  to the pressure oil tank  33 . 
     In the case that the external hydraulic apparatus connected to the PTO ports  260  and  261  requires larger flow rate than the flow rate of pressure oil discharged from the discharge port  133  of the hydraulic pump P 2 , the mode selector valve  230  is set to the confluence position K and the PTO selector valve  240  is set to the continuous position P. 
     Then, pressure oil discharged from the discharge port  133  of the hydraulic pump P 2  is supplied through the pipe  136 , the pump port  251 , the oil path  270 , the dump cylinder selector valve  210 , the oil path  277 , the bucket lift cylinder selector valve  220 , and the oil path  281  to the mode selector valve  230 . On the other hand, pressure oil discharged from the discharge port  132  of the hydraulic pump P 1  is supplied through the pipe  137 , the port  258  and the oil path  283  to the mode selector valve  230 . Pressure oil supplied from the discharge ports  132  and  133  of the hydraulic pumps P 1  and P 2  is combined in the mode selector valve  230 , and the combined pressure oil is pressingly sent through the oil paths  286 , the oil paths  287 , the PTO selector valve  240 , the oil path  290 , the oil path  291  and the PTO port  260  to the external hydraulic apparatus so as to drive it. 
     Next, explanation will be given on the control valve unit  15  constructing the loader control valve section  200  referring to  FIGS. 2 to 4 . 
     As mentioned above, the control valve unit  15  is disposed in the operation part  10  and fixed to a vertical wall surface of an operation frame  105  constructing the frame body of the operation part  10  by a fastening member  106  such as a bolt. 
     In the left portion of the control valve unit  15 , the tank port  252  and the pump port  251  are provided respectively in the upper and lower sides of the portion, and the selector valves  210 ,  220 ,  230  and  240  are connected in series rightward so that the spool of each selector valve is slidable vertically. In the right portion of the PTO selector valve  240  at the most right, the carry-over port  253  is disposed. 
     In the lower and upper portions of the side surfaces of the selector valves  210 ,  220 ,  230  and  240 , the dump cylinder ports  255  and  254 , the lift cylinder ports  257  and  256 , the ports  259  and  258 , and the PTO ports  261  and  260  connected to hydraulic actuators of an external hydraulic apparatus are respectively formed. 
     Ones of ends of the spool of each of the dump cylinder selector valve  210  and the bucket lift cylinder selector valve  220  are interlockingly connected to a loader operation lever  44  respectively through links  107  and  108 . By slewing the loader operation lever  44 , the clump cylinder selector valve  210  and the bucket lift cylinder selector valve  220  are switched to the positions, whereby the rods of the dump cylinders  18  and the lift cylinders  17  are extended and contracted as mentioned above so as to drive the loader  3 . 
     One of ends of the spool of the mode selector valve  230  is interlockingly connected through a link  109  to a mode selector lever  45 . By slewing the mode selector lever  45 , the mode selector valve  230  can be switched to one of the working position H, the return position J and the confluence position K. Similarly, one of ends of the spool of the PTO selector valve  240  is interlockingly connected to a selector valve operating mechanism  110  according to the present invention. By operation means such as a nearby switch  124  discussed later, the spool  145  of the PTO selector valve  240  can be slid easily and quickly so as to switch to one of the positions L, M, N and P. By combining the set positions of the mode selector valve  230  and the spool of the PTO selector valve  240 , the pressure oil route can be switched as mentioned above so as to perform various kinds of work. 
     Next, explanation will be given on the selector valve operating mechanism  110  referring to  FIGS. 2 to 6 . 
     The selector valve operating mechanism  110  includes a solenoid valve  113  having a spool  112  driven by electromagnetic solenoids  111 , a pair of operating actuators  174  and  177  connected to the solenoid valve  113  respectively through oil paths  114  and  115 , an operation link  161  and the like. The operation link  161  includes a rocking part  180  rockingly driven by the operating actuators  174  and  177  and a connection part  148  interlockingly connecting the rocking part  180  to one of ends of the spool  145  of the PTO selector valve  240 . 
     The solenoid valve  113  has four ports and three positions. The spool  112  connected to the two electromagnetic solenoids  111  is formed to be inserted into a spool chamber  120   a  of a valve block  120 , which is arranged closely to the control valve unit  15 , from the side thereof. The electromagnetic solenoids  111  are connected through two wires  122  to a controller  123  controlling the traveling operation and various kinds of work, and the controller  123  is connected through a wire  128  to the nearby switch  124  provided in the operation part  10 . The nearby switch  124  should be provided in a position easy to be operated such as the grip of the loader operation lever  44  or the upper surface of the operation frame  105 , and the attachment position is not limited. 
     Furthermore, a pump port  169  opened in the lower surface of the valve block  120  is connected through a pipe  269  to the portion of the pipe  103  between the power steering control valve section  140  and the hydraulic stepless transmission  101  closer more the hydraulic stepless transmission  101  than the filter  104 , whereby a part of pressure oil discharged from the discharge port  134  of the hydraulic pump P 3  is supplied through the pipe  269  to the selector valve operating mechanism  110 . 
     In this case, the pipe  269  is connected to the charge circuit  64  of the hydraulic stepless transmission  101  similarly to the pipe  103 , whereby pressure oil controlled to charge release pressure by the check release valve  63  is supplied through the pipe  269  to the solenoid valve  113 . On the other hand, a tank port  170  formed in the lower surface of the valve block  120  adjacently to the pump port  169  is connected through a pipe  171  to the pressure oil tank  33 , whereby pressure oil from the solenoid valve  113  can be discharged to the pressure oil tank  33 . 
     The operating actuator  174  includes an operating cylinder  175 , including a cylinder chamber  120   b  opened upward in the upper portion of the valve block  120  and a plug  143  engaged downward with the cylinder chamber  120   b , and an operating piston  176  slidably inserted downward into the operating cylinder  175 . A pressure oil chamber  120   d  is provided in the cylinder chamber  120   b  at the side of lower end of the operating piston  176 , and the pressure oil chamber  120   d  is connected through the oil path  114  to one of actuator ports  125  of the solenoid valve  113 . 
     Similarly, the operating actuator  177  includes an operating cylinder  178 , including a cylinder chamber  120   c  arranged adjacently to the cylinder chamber  120   b  and a plug  144  engaged downward with the cylinder chamber  120   c , and an operating piston  179  slidably inserted downward into the operating cylinder  178 . A pressure oil chamber  120   e  is provided in the cylinder chamber  120   c  at the side of lower end of the operating piston  179 , and the pressure oil chamber  120   e  is connected through the oil path  115  to the other actuator port  126  of the solenoid valve  113 . Each of the operating pistons  176  and  179  is formed integrally with the solenoid valve  113  via the valve block  120 . 
     Accordingly, in the valve block  120 , pressure oil from the solenoid valve  113  is supplied to and discharged from the pressure oil chambers  120   d  and  120   e  of the operating actuators  174  and  177 . By the hydraulic pressure of the oil, the operating pistons  176  and  179  can be slid vertically in the operating cylinders  175  and  178 . 
     In the operation link  161 , the rocking part  180  includes a spindle  181 , projectingly provided horizontally from the vertical wall surface of the operation frame  105  toward a space above the valve block  120  and between the operating actuators  174  and  177 , and a rocking body  182  rotatably engaged around the spindle  181  by a boss  182   a.    
     In the rocking body  182 , backing plates  182   b  and  182   c  are projectingly provided radially at the positions on the outer perimeter of the boss  182   a  separated for 180°, and the lower surfaces of the backing plates  182   b  and  182   c  touch respectively the tops of the operating pistons  176  and  179 . On the other hand, a pressing plate  182   d  is projectingly provided radially at the part on the outer perimeter of the boss  182   a  closer to the control valve unit  15  than the backing plate  182   b.    
     An upper end of a connection stay  148   b  constructing the connection part  148  is rotatably connected through a connection shaft  148   a  to the pressing plate  182   d , and the lower end of the connection stay  148   b  is connected to the outer upper end of the spool  145  of the PTO selector valve  240 . 
     Accordingly, when the operating pistons  176  and  179  of the operating actuators  174  and  177  are slid vertically, the backing plates  182   b  and  182   c  of the rocking part  180  are pushed so that the rocking body  182  is rotated around the spindle  181 . Subsequently, the spool  145  of the PTO selector valve  240  is moved vertically via the pressing plate  182   d  and the connection part  148 . 
     In the construction as mentioned above, by stewing a switch lever  127  of the nearby switch  124 , a switch signal corresponding to one of positions  117 ,  118  and  119  is transmitted to the controller  123 . When the controller  123  transmits a switching signal to the electromagnetic solenoids  111  based on the received switch signal, the electromagnetic solenoids  111  are excited and the spool  112  is set to corresponding one of positions X 1 , X 2  and X 3 . 
     It may alternatively be constructed that the controller  123  is omitted and an operation signal is transmitted directly to the electromagnetic solenoids  111  by operating the nearby switch  124 . A safety device, a hydraulic pressure detection means, an oil temperature detection means, means for detecting the position of the mode selector lever  45  and the like are connected to the controller  123  so that any switching signal is not transmitted to the electromagnetic solenoids  111  at the time of occurrence of abnormality or at the time of excavation work with the backhoe. 
     For example, when the switch lever  127  is slewed to the position  117 , the spool  112  is set to the position X 1 . Then, pressure oil from the discharge port  134  of the hydraulic pump P 3  is supplied through the pipe  135 , the power steering control valve section  140 , the pipe  103 , the filter  104 , the pipe  269 , the solenoid valve  113  and the oil path  114  to the pressure oil chamber  120   d . Simultaneously, pressure oil in the pressure oil chamber  120   e  is discharged through the oil path  115 , the solenoid valve  113  and the pipe  171  to the pressure oil tank  33 . Accordingly, as shown in  FIG. 5 , the operating piston  176  is moved upward and the operating piston  179  is moved downward, whereby the rocking body  182  is rotated along direction  146 . Subsequently, the spool  145  is pulled upward via the backing plate  182   b  and the connection part  148  so that the PTO selector valve  240  is set to the position N, whereby pressure oil is supplied through the PTO port  260  to the external hydraulic apparatus and pressure oil is discharged through the PTO port  261 . 
     When the switch lever  127  is slewed to the position  118 , the spool  112  is set to the position X 2 , and pressure oil is not supplied to the pressure oil chambers  120   d  and  120   e , whereby the operating pistons  176  and  179  do not push the rocking body  182  and the neutral state is realized at which the backing plates  182   b  and  182   c  are kept horizontal as shown in  FIG. 4 . Subsequently, the spool  145  is set to the position N so as to realize the neutral state, whereby pressure oil is not supplied to and discharged from the PTO ports  260  and  261 . 
     When the switch lever  127  is slewed to the position  119 , the spool  112  is set to the position X 3 . Then, pressure oil in the pressure oil chamber  120   d  is discharged through the oil path  114 , the solenoid valve  113  and the pipe  171  to the pressure oil tank  33 , and pressure oil from the discharge port  134  of the hydraulic pump P 3  is supplied through the pipe  135 , the power steering control valve section  140 , the pipe  103 , the filter  104 , the pipe  269 , the solenoid valve  113  and the oil path  115  to the pressure oil chamber  120   e . Accordingly, the operating piston  176  is moved downward and the operating piston  179  is moved upward, whereby the rocking body  182  is rotated along direction  147  opposite to the direction  146 . Subsequently, the spool  145  is pushed downward via the pressing plate  182   d  and the connection part  148  so that the PTO selector valve  240  is set to the position M, whereby pressure oil is supplied through the PTO port  261  to the external hydraulic apparatus and pressure oil is discharged through the PTO port  260 . Accordingly, pressure oil can be supplied through the PTO ports  260  and  261  to the hydraulic actuator of the external hydraulic apparatus such as a breaker or a grapple. 
     Namely, in the selector valve operating mechanism  110  of the working vehicle  1  operating the PTO selector valve  240  which is a mechanical selector valve for controlling a hydraulic actuator driving a working machine attached as an attachment, the selector valve operating mechanism  110  includes the operating pistons  176  and  179  which are hydraulic pistons connected through the operation link  161  to the spool  145  of the PTO selector valve  240 , the solenoid valve  113  hydraulically controlling reciprocal action of the operating pistons  176  and  179 , and the controller  123  which is a control device transmitting an action signal to the solenoid valve  113 . By the action control of the solenoid valve  113 , the spool  145  is moved via the operating pistons  176  and  179  and the operation link  161  so as to operate the PTO selector valve  240 . Accordingly, the PTO selector valve  240  can be operated with the solenoid valve  113  which is a small and cheap electromagnetic selector valve or the like. In comparison with the case of employing only a large and expensive electromagnetic selector valve, the oil path switching control construction can be simplified and the cost of parts thereof can be reduced. Furthermore, the nearby switch  124  or the like is interlocked with the action of the solenoid valve  113  so that the mechanical selector valve can be switched easily and quickly with small operation power similarly to the conventional electromagnetic selector valve, whereby switching operability can be improved widely. Moreover, the operating pistons  176  and  179  which are hydraulic pistons, the solenoid valve  113  and the like can be subsequently attached easily to the PTO selector valve  240  which is a current mechanical selector valve. Accordingly, the requirement of improvement of switching operability from a user can be measured quickly without changing the fundamental construction of the selector valve, whereby the working vehicle  1  superior in general-purpose properties can be provided. 
     The operating pistons  176  and  179  which are hydraulic pistons are, constructed integrally with the solenoid valve  113 . Accordingly, the operating pistons  176  and  179  and the solenoid valve  113  are made to be a single unit structure so as to be attachable and detachable easily in the selector valve operating mechanism  110 , whereby the assemble ability and maintainability can be improved. Furthermore, members required for oil paths and attachment members concerning the operating pistons  176  and  179  and the solenoid valve  113  can be made common, whereby the cost of parts can be reduced further. Moreover, the arrangement space for the operating pistons  176  and  179  and the solenoid valve  113  can be reduced, whereby the whole selector valve operating mechanism  110  can be made compact. 
     The operation piston which is a hydraulic piston includes the two operating pistons  176  and  179  respectively for moving forward and rearward the spool  145 , and the operating pistons  176  and  179  are single acting type respectively having the pressure oil chambers  120   d  and  120   e  at only ones of the front and rear sides in the move direction of the pistons. Accordingly, unlike a double acting piston in which pressure oil chambers are provided at both front and rear sides in the move direction of the pistons, it is necessary to control only the hydraulic pressure in the pressure oil chamber at one of the sides and any complex position control mechanism for keeping the neutral position is not required, whereby the hydraulic pressure control construction can be simplified so as to improve responsibility of the pistons and to reduce the cost of parts further. However, of course, it may alternatively be constructed that the operating actuators  174  and  177  is constructed by an operation actuator having one operation piston of double acting type and is connected to the solenoid valve  113 , and the operation piston is connected to the connection part  148 . 
     Next, explanation will be given on a selector valve operating mechanism  110 A which is another mode of the selector valve operating mechanism  110  referring to  FIG. 7 . 
     In the selector valve operating mechanism  110 A, the spool  145  of the PTO selector valve  240  is moved by not the electromagnetic solenoids  111  but rotational power of an electric motor  190  so as to reduce the parts of hydraulic piping and the like. 
     In the selector valve operating mechanism  110 A, a main body  190   a  of the motor  190  is fixed to the vertical wall surface of the operation frame  105  constructing the frame body of the operation part  10  by a bolt or the like (not shown), and a motor shaft  190   b  is projectingly provided horizontally from the main body  190   a . The motor  190  is connected through a wire (not shown) to the controller  123 , and the controller  123  is connected through the wire  128  to the nearby switch  124  provided in the operation part  10 . Furthermore, the motor shaft  190   b  is connected through an operation link  149  to the outer upper end of the spool  145  of the PTO selector valve  240 . 
     The operation link  149  includes a rocking part  191  and the connection part  148 , and the rocking part  191  includes a boss  191   a  engaged around the motor shaft  190   b  and a pressing plate  191   b  projectingly provided radially from the outer perimeter of the boss  191   a . The upper end of the connection stay  148   b  constructing the connection part  148  is rotatably connected through the connection shaft  148   a  to the pressing plate  191   b , and the lower end of the connection stay  148   b  is connected to the outer upper end of the spool  145  of the PTO selector valve  240 . 
     Accordingly, when the switch lever  127  of the nearby switch  124  is slewed, the motor  190  is driven and the pressing plate  191   b  of the rocking part  191  is rotated around the motor shaft  190   b . Then, similarly to the selector valve operating mechanism  110 , the spool  145  of the PTO selector valve  240  is moved via the pressing plate  191   b  and the connection part  148 . 
     Namely, in the selector valve operating mechanism  110 A of the working vehicle  1  operating the PTO selector valve  240  which is a mechanical selector valve for controlling a hydraulic actuator driving a working machine attached as an attachment, the selector valve operating mechanism  110 A includes the motor  190  connected through the operation link  149  to the spool  145  of the PTO selector valve  240  and controllable electrically, and the controller  123  which is a control device transmitting an action signal to the motor  190 . The spool  145  is moved via the operation link  149  by rocking output of the motor  190  so as to operate the PTO selector valve  240 . Accordingly, the PTO selector valve  240  can be switched with a small and cheap motor. Therefore, in comparison with the case of employing only a large and expensive electromagnetic selector valve, the oil path switching control construction can be simplified and the cost of parts thereof can be reduced. Furthermore, the nearby switch  124  or the like is interlocked with the action of the motor  190  so that the mechanical selector valve can be switched easily and quickly with small operation power similarly to the conventional electromagnetic selector valve, whereby switching operability can be improved widely. Moreover, the motor  190  and the like can be subsequently attached easily to the PTO selector valve  240  which is a current mechanical selector valve, whereby the working vehicle  1  superior in general-purpose properties can be provided. In comparison with the case that the small solenoid valve  113  is employed for operating the mechanical selector valve, the hydraulic piping and the like can be reduced further, whereby the assemble ability and maintainability can be improved. 
     INDUSTRIAL APPLICABILITY 
     In addition to the backhoe loader described in the embodiment, in whole working vehicle such as a tractor, planting machine, a truck or the like, the present invention can be employed in whole selector valve operation mechanism for operating mechanical selector valves for controlling hydraulic actuators of an external hydraulic apparatus.