GB2134876A

GB2134876A - Swivelling-type work vehicle

Info

Publication number: GB2134876A
Application number: GB08333768A
Authority: GB
Inventors: Akihiko Ikeda; Yoshinobu Tabuchi; Akira Tsuda; Asahiro Tsutsumi; Kazushige Ikeda
Original assignee: Kubota Corp
Current assignee: Kubota Corp
Priority date: 1982-12-24
Filing date: 1983-12-19
Publication date: 1984-08-22
Also published as: FR2538575A1; DE3346800A1; GB8333768D0; FR2538575B1; GB2134876B; DE3346800C2

Abstract

A swivelling-type work vehicle has a swivelling superstructure comprising an excavation implement and a hydraulic motor 3 for causing the swivelling. There further is provided a control apparatus 20 which functions to automatically reduce the working hydraulic medium flow rate supplied to the hydraulic motor 3, whenever the swivelling superstructure has come to a respective preset vicinity of either one of given left and right halt positions, thus to reduce the swivelling speed in such vicinity range. <IMAGE>

Description

SPECIFICATION Swivelling-type work vehicle Background of the invention This invention relates to swivelling-type work vehicles each having: a base structure; a swivelling wagon equipped with an excavation implement; a hydraulic motor for driving the swivelling wagon in a swivelling movement relative to the base structure; and a maneuvering valve for such hydraulic driving.

The excavation implement of such work vehicle is supposed to repeat the work, in reversingly reciprocating strokes or stages, of, for example, digging a ditch and of transferring the excavated soil from the digging ditch position to a truck (or some other soil discharge means) loading position.

Thus, it is required to maneuver the swivelling wagon equipped with the excavation implement so as to perform the reversingly reciprocating stroke exactly between two halt angular positions relative to the base structure, thus alternatively from one the other of such given positions.

It is the conventional practice, in the sequentially repeated maneuvering of starting the swivelling wagon equipped with the excavation implement and of halting it, to manually maneuver a switchover valve at properly judged sequential timing intervals.

A drawback has been noticed at such swivelling-wagon halding maneuvering in that there occurs considerable shocking impact in the hydraulic system and the mechanical vehicle structure as caused by heavy inertial moment of the swivelling wagon and the parts ancillary thereto, on account that the switchover valve is shut up in practice inevitably very rapidly, thus also to make the operator quite uncomfortable.

There further has been a drawback as well in the operability, since very experienced skill is required in order to actually halt the swivelling wagon exactly in the given target angular position and since the operator gets nervously tired in properly judging the halting maneuver timing.

Summary of the invention In view of the actual status as described above, this invention has as its object to provide the work vehicle of the described type, which is capable of securely realizing automatic halting of the excavation implement exactly at the preset angular position in each of the reversingly reciprocating work stages or strokes, thus without requiring any particular skill of the operator in the manual maneuvering, and at the same time effectively suppressing uncomfortable vibrations at such halting, and which is yet of the structure as can quite economically be constructed by means of making wise and effective use of the component parts as are indispensably present in the conventional structure.

To attain the object, the swivelling-type work vehicle according to this invention is such as has: a vehicle body: an excavation implement disposed to be swivellable with respect to the vehicle body; hydraulic motor means for swivelling the excavation implement; a maneuvering valve of electric maneuvering type, capable of switching over the operational direction of, and of adjusting the hydraulic working medium flow rate to, the hydraulic motor means; a maneuvering device to maneuver by means thereof the maneuvering valve; a sensor of electric type adapted to give, as its output, information responsive to the maneuvering direction and maneuvering amount of the maneuvering device; and a control mechanism adapted to maneuver the maneuvering valve in response to the information from the sensor; and further comprises: setter apparatuses to set by means thereof a left and a right halt positions, respectively, relative to the vehicle body, between which positions, thus alternatively from one to the other of which, the excavation implement should move in shuttlewise shifting in its successive working stages; an angle-detecting apparatus adapted to detect the left- and right-movement angle, relative to the vehicle body, of the excavation implement; and a control apparatus adapted to automatically maneuver the maneuvering valve to the flow-ratereducing side whenever the information from the position-detecting apparatus shows that the excavation implement has come to a respective preset vicinity of either one of the half positions set by the setter apparatuses.

Thus, the automatic halting control apparatus receives and processes the information with respect both to the preset target halt angular positions of the excavation implement relative to the vehicle body, on the one hand, and to the actually detected operating implement position, on the other hand, and on the basis thereof makes it possible to reduce the flow rate of the working medium supplied to the hydraulic motor driving the excavation implement, whenever the excavation implement has come to the vicinity of the set target position, and thereby to halt the excavation implement automatically at the target halt position as set by means of the setter apparatus, while properly reducing the swivelling angular speed of the excavation implement.There accordingly is required no particular skill of the operator in the manual maneuvering for halting the excavation implement at the halt position as desired. Since violent rapid halting is thus evaded, it is now possible to securely attain the quite smooth halting, effectively suppressing uncomfortable vibrations.

Intended particularly in this invention is to make best effective use of the maneuvering valve, as is indispensably present in the conventional structure for effecting the automatic halting of the excavation implement according to this invention, thus to make it possible to simplify the structure than in the case of providing a flow-rate regulator specifically for the automatic halting.

Further advantages accruing from this invention will be apparent from the detailed description to follow hereunder.

Brief description of the drawings The accompanying drawings are given for illustration purposes of a couple of embodiments of the swivelling-type work vehicle according to this invention, in which: Fig. 1 is an overall side elevation of the vehicle; Fig. 2 is a diagram of a hydraulic circuit for driving the swivelling; Fig. 3 is a graphic illustration showing how the timing, as expressed by angular position, to start automatic speed-reducing control prior to halting the swivelling is shifted in response to the actual plateau-like highest angular speed; Fig. 4 is a detailed graphic illustration showing how the swivelling angular speed is controlled in a stroke of the swivelling movement; Fig. 5 is a schematic block diagram of the swivelling angular speed control; Fig. 6 is a flow chart showing the operation of a data processor used as a component for the control;; Fig. 7 is a side elevation, partly in section, of an embodiment of a swivei-angle-detecting apparatus used also as a component for the control; and Fig. 8 is a side elevation similar to Fig. 7 but showing a modified embodiment of the angledetecting apparatus.

Detailed description of the preferred embodiments Shown in Fig. 1 is a backhoe as a specific example of swivelling-type civial work vehicle, and it has a swivelling wagon 2 pivotally mounted on a base structure provided with a pair of left and right crawler-type running travel apparatuses 1, for swivelling about an upright axis P, as driven by a hydraulic motor 3. Fixedly or stationarily mounted on the swivelling wagon 2 are a riding operation quater 4 and a prime mover quarter 5.

Pivotally movably further mounted on a front tip of the swivelling wagon 2 is a backhoe implement 6, which in fact is maneuverable in pivotal or articulated rocking up and down and also in pivotal or articulated extension and retraction.

Still further, pivotally movably mounted on a front tip of the base structure is a dozer implement 7 which in fact is maneuverable in pivotal or articulated raising and lowering.

Hydraulic drive circuit for the swivelling wagon 2 is shown in Fig. 2. As is seen, a motor 3 is connected to a hydraulic pump 8 via hydraulic passages inciuding a maneuvering valve 10 which can switch over the movement of operational mode of the swivelling wagon 2 in alternative selection in between the rightward swivelling, leftward swivelling and halting. In this instance, the maneuvering valve 10 is constructed to serve dually as well as a flow-rate regulator valve as is maneuverable to adjust or regulate the flow rate of the hydraulic working medium, as supplied to the motor 3, in proportional response to the maneuvering amount or position in each of the respective driving modes.

Thus in the respective hydraulic lines to actuation terminals of the maneuvering valve 10 there are interposed a pair of proportional electromagnetic valves 11, 1 2 which perform, in response to their input pilot pressure, the switching over and the proportional control of the maneuvering valve 10. It is hereby made possible to effect the proper control for the swivelling drive of the swivelling wagon 2, namely the control of the swivelling angular speed and the halting, by means of giving a command to a drive controller 1 3 provided to control the electromagnetic valves 11, 12.

By the way, illustrated at 14 are braking valve mechanisms provided for prevention of inertial continued swivelling of the swivelling wagon 2 at halting the drive, while at 1 5 are relief valves provided for dampening excessively forced or violent drive halting of the swivelling wagon 2.

The drive controller 13 is supposed to be capable of performing both manually commanded maneuvering mode and automatically commanded maneuvering mode. Here, the automatically commanded maneuvering mode is further supposed to include the automatic halting while incorporating some manual maneuvering process therein and the true or further-advanced fully automatic maneuvering consisting entirely of automatic processes.

Described first is the function of the automatic halting incorporating some manual maneuvering process therein.

As illustrated in the righthand upper corner in Fig. 2, there are provided: a maneuvering device 1 50 manually maneuverable in left-and-right rocking in the illustration; and a potentiometer 1 60 to detect the maneuvering direction of the maneuvering device 1 50 with reference to its neutral position N and also the amount of the maneuvering.Shown as a block designated by 20 is a control apparatus which receives such detection information given by the potentiometer 1 60 and maneuvers, in response to such information, the hydraulic maneuvering valve 10 via the electromagnetic valves 11, 12 in such manner that upon leftward rocking of the maneuvering device 150, the swivelling wagon 2 is accordingly caused to swivel leftwards and upon rightward rocking to similarly swivel rightwards, and that in either direction the swivelling angular speed is so controlled as to be the higher as the maneuvering device 1 50 is rocked the remotorfrom the neutral position N. It is hereby possible to control the movement of the swivelling wagon 2 so as to realize proper leftward or rightward swivelling of the backhoe implement 6 as desired.

Looking further into the control apparatus 20, it has sufficiently ample information memory means and it functions such that it judges the operating direction of the hydraulic motor 3 and the amount of the working medium being supplied to the hydraulic motor 3, on the basis of the information given beforehand in the memory and also of the detection information of the maneuvering status of the maneuvering device 1 50 as detected by the potentiometer 1 60 and given in the form of variation in its output electrical voltage signal; that it maneuvers responsive to such judgement results, either the leftwards swivelling maneuvering means which is supposed to be the electromagnetic valve 1 2 or the right swivelling maneuvering means which is supposed to be the electromagnetic valve 11, in such manner as to intermittently energize same in the form of a train of pulse signal, while properly altering the repetition frequency of the pulse signals so as to adjust the overall energization time period per a unit time interval just as to match the judged situation; and that it has further information stored beforehand for its further aspect of the function of also maneuvering the maneuvering valve 10 as described just hereunder: Primary means provided for such aspect of the function are illustrated as blocks 18 and 1 9.

Meant by 1 8 is a sensor for detecting the angle of the swivelling of the swivelling wagon 2 relative to the base structure, by means of a potentiometer. Meant generally by 1 9 is setter means consisting of: a first setter apparatus 1 9a provided for setting a first halt or standard swivelling angular position, relative to the base structure, in which the swivelling wagon 2 should be halted for instance for effecting there the digging work; and a second setter apparatus 1 9b provided for setting a second halt or standard swivelling angular position, relative to the base structure, in which the swivelling wagon 2 should be halted for instance for effecting there the soil discharging work.In this connection, shown at 120 is a manual switch provided for switching over the control apparatus 20 between: its active or operative state of receiving the information from both the angle-detecting apparatus, namely the sensor 18, and the two setter apparatuses 1 spa, 1 9b and of performing the control on the basis of such information; and its inactive or inoperative state.Meant by the active or operative state, as selected by the corresponding maneuvering of the manual switch 120, is such that the control apparatus 20 functions so as to automatically maneuver the maneuvering valve 10 to the flow-rate-reducing side whenever the swivelling wagon 2 has come to a preset vicinity of the preset halt angular position, namely one of the two halt or standard angular positions preset by means of the respective setter apparatuses 1 9a, 1 9b, relative to the base structure, in the course of a stage or stroke of the reversingly reciprocating movements of the swivelling wagon 2, namely the stroke from the other of the two standard positions, which is thus the starting angular position in this specific stroke, to the said one of the two standard positions, which is thus the target halting angular position in this stroke, relative to the base structure.

Thus, it is possible-in the ditch-digging or hole-digging work where the backhoe implement 6 is transferred or swivelled in reversingly reciprocating strokes or stages between one lateral side position with respect to the vehicle, where the soil is excavated, and the other lateral side position with respect to the vehicle, where the excavated soil is discharged-more specifically in each stroke where the swivelling wagon 2 should be maneuvered to swivel relative to the base structure from one of its standard angular positions, namely the starting position in this stroke, to the other of its standard angular positions, namely the target halting position in this stroke, in order to thereby accordingly transfer the backhoe implement 6 in such swivelling stroke with respect to the vehicle body-to automatically halt the swivelling wagon 2 at the target halting angular position as desired, once the operator has initiated the maneuvering simply by means of maneuvering the manual maneuvering device 150, and in fact in such advantageous manner of the automatic halting that the swivelling angular speed of the swivelling wagon 2 is automatically reduced when the swivelling wagon 2 has come to the preset vicinity of such target halting angular position relative to the base structure and therefore that the halting of the swivelling wagon 2 is effected quite smoothly without causing any serious uncomfortable vibrations.

Here, it is supposed that the control apparatus 20 also has a program and information data therefore stored for properly setting the timing, as expressed by swivelling angular position, to start the automatic halting control on to the maneuvering valve 1 0. Meant by proper setting of the timing is such that the automatic halting control is started when the swivelling wagon 2 has come to a swivelling angular position upstream of the preset target halting position relative to the base structure, by an angle to be set in proper respect to the estimated plateau-like highest angular speed of the swivelling wagon 2; and therefore the stored program is such that is intended to receive also an output information of an apparatus 18' provided for calculating the actual swivelling angular speed by processing the signal from the swivelling-angle-detecting apparatus 1 8, and based on such information then to automatically correct the timing of starting the halting control on to the maneuvering valve 10 so as to properly be earlier as the plateau-like highest angular speed of the swivelling wagon 2 gets higher by some reason or other.

Fig. 3 is meant to illustrate such modification of the timing, in graphic representation with swivelling angle 0 of the swivelling wagon 2 relative to the base structure on the abscissa and the swivelling angular speed V on the ordinate, with the solid line representation supposed to show a normal automatic halting control as is started at the angular position shown at S, and the phantom line representation thus showing an abnormal case where the plateau-like highest angular speed is somewhat highest than in the normal case, with the automatic halting control accordingly started earlier than in the normal case.

Thus, it is hereby possible to securely cope with such abnormal case where the swivelling angular speed gets somewhat higher than in the normal case, on account for instance of abnornally undulated terrain of the working field, and to realize even in such abnormal case the proper automatic reducing down of the angular speed of the swiveiling wagon 2 to effect smooth, quiet and comfortable automatic halting properly as desired.

In actually practicing this invention, it as well is possible, in substitution for or in addition to swivelling the swivelling wagon 2 relative to the base structure as described above, to provide a hydraulic cylinder 3' (shown as so provided already in Fig. 1) for swivelling the backhoe implement 6 relative to the swivelling wagon 2, or else, in the case there is no such wagon 2 as is swiveílable relative to the base structure, thus anyhow relative to the vehicle body in general.

Needless to say, this invention may be practiced in quite a variety of work vehicle, such for instance as face-shovel-work vehicles, being by no means limited to the backhoe specifically illustrated and described hereinabove.

As the maneuvering valve 10, it as well is possible to use a valve as is maneuvered for instance by means of a servomotor, and as is obvious to these skilled in the art, the specific construction of the control mechanism for the valve maneuvering and for the automatic halting of the swivelling may properly be adapted, in a variety of ways, to such respective modifications of the maneuvering valve 1 0.

In repeating the work in reversingly reciprocating strokes of swivelling the backhoe implement 6, it as well is possible to provide according to this invention the function of the automatic halting of the swivelling only in the strokes in one single particular direction alone, thus starting from one given standard swivelling angular position on one specific side of the vehicle and aiming at the other given standard angular position on other side of the vehicle.

A specific rational manner of constructing the system incorporating the automatic control having the function of the automatic halting of the swivelling as described hereinabove, so as to cause the swivelling wagon to perform each swivelling stroke at such angular speed that is securely defined all over the stroke from the start to the halt by a preset function of the swivelling angle as is intended to be optimai for allowing the swivelling speed as high as possible and yet guaranteeing quite smooth starting up and halting of the swivelling wagon, with excellent precision of keeping the target halt position under the automatic halting, is described hereunder with reference also to Figs. 4-6 in addiiton to Figs. 2 and 3 referred to already herein-above.

As shown in Fig. 2, the maneuvering valve 10 is equipped, for detection of its actual swivelling status, with sensor means 1 7 as may be of limitswitch type. As has already been briefly described, represented by the block 1 8 is a potentiometer-type sensor, namely the angledetection sensor mounted on or in interlocking with the rotary shaft of the swivelling wagon 2 to thus detect the left-and-right swivelling angle of the wagon 2 relative to the base structure.Thus, upon starting up as has been initiated by means of the manual maneuvering or commanding as has already been described, the control apparatus 20 functions to automatically maneuver the drive controller 13 in response to the information given by both the sensors 17, 18, in such manner as to cause the swivelling wagon 2 to: swivel at such angular speed e, that is securely defined by a preset function of the swivelling angle 0"; and ultimately thus halt at the target finishing or halting position ef for that stroke as has been preset by setter means 19. in this way, it has become possible to quite easily and efficiently perform the frequent maneuvering of swivelling the swivelling wagon 2 from one to the other of the soil-digging and soil-discharging positions, without requiring troublesome manual maneuvering control of the swivelling angular speed and of the halting.

Graphic representation of Fig. 4 is meant to illustrate a specific example of how the swivelling angular speed 0, in a stroke which should start from a swivel-starting angular position 65 and finish at a swivel-finishing angular position ef is automatically controlled by the control apparatus 20 as a preset function of the swivelling angle e from the starting position Cs where () is therefore null (and though the successive swivelling movements are normally repeated in reversingly reciprocating strokes, the value of 0" after the starting is always considered to be positive and its value at the finishing position sf is designated simply also as Of). As is seen, the function of this specific example of the illustrated case, shown in solid line curve in Fig. 4, has its sections or parts corresponding respectively to: a smooth acceleration stage at starting the swivelling, shown as a section of a curve I representing a first preset formula referenced as A hereunder; a smooth deceleration stage at halting the swivelling, shown as a section of a curve m representing a second preset formula referenced as B hereunder; and a smooth constant speed stage at a plateau-like highest angular speed 0M properly preset for effecting the overall stroke rapidly and yet smoothly, shown as a section of a horizontal straight line n representing a third preset formula referenced as C hereunder:

wherein: K1, K2 are given constants (supposed in this specific instance to be K1=K2=K); a is an auxiliary parameter as is set to define the angular speed at the swivel-starting position ()5; and E is a given constant as is set to define an insensitivity range around the swivel finishing position O".

It is supposed that the control apparatus 20 has these formulas A, B, C beforehand stored in its memory means, and being given the information of the swivel-finishing position sf and of the swivelling direction by the setter means 1 9 and the maneuvering-status-detection sensor means 17, as is best seen in Figs. 5 and 6, it effects the operation of calculating the respective three values of CO according to these formulas A, B, C using the value of the actually detected swivelling angle e as is continuously given by the angle-detection sensor 18.As is clear from Fig. 6, shown simply as a block 20a in Fig. 5 is a calculation processor to select out always the smallest one of the three values of 190 calculated in the aforementioned manner and then to emit the value as its output to serve as the control command target angular speed CO. Shown also simply as a block 20b in Fig. 5 is a differentiator which receives as its input the information of the actual swivelling angle 0 from the angledetection sensor 1 8 and thus continuously gives as its output the actually detected swivelling angular speed value C".

As is now clear from Fig. 5, a section in phantom block designated at 20c is a correctionsignal composer which functions so as to: receive the output information both from the calculation processor 20a and the differentiator 20b, namely the angular speed values pf the control target CO and the actual detection (i; subtract the former from the latter to obtain the balance ,=-Qe; multiply this balance by a preset correction factor k to obtain the product Xk=k(ie; and subtract this product from the control target value 6o to ultimately obtain as its output a correction signal value

as is given as the command input to the drive controller 13.

Thus, the drive controller 1 3 is automatically maneuvered in such feedback principle so that the actually detected swivelling angular speed 0 may be controlled at any value of the detected swivelling angle 1O, so as to be brought close enough to the target value of CO which is defined always by such particular one of the three formulas A, B, C that then gives the smallest value CO, namely so as to correct the actual swivelling speed () in good response and correspondence to such command target speed C"O as mentioned above.In this way, it is made possible all over the swivelling stroke, thus throughout the acceleration stage at starting the swivelling, the constant speed stage in the middle way of the swivelling and the deceleration stage at halting the swivelling, to automatically and securely realize the swivelling angular speed control as is optimal for the respective stages so as to cause the swivelling wagon 2 to quite smoothly and efficiently swivel throughout the entire stroke and ultimately halt in excellent precision at the preset target halting position.

It is supposed that the control apparatus 20 has in addition to the three formulas A, B, C also beforehand further two formulas stored in its memory means, namely as illustrated in Fig. 4 as: a curve I' whose section shown in solid line corresponding to a smooth deceleration stage in reversingly restoring swivelling representing a fourth preset formula referenced as D hereunder; and a horizontal straight line n' whose section shown in solid line corresponding to a smooth constant speed stage at a plateau-like highest absolute angular speed but in negative value 0"M' (the value supposed in this specific instance to be 0"M=0"M') in the reversingly restoring swivelling representing a fifth formula referenced as E hereunder:

wherein: K3 is a given constant as is set to define the steepness of the angular speed variation in the final stage of the reversingly restoring movement (supposed in this specific instance to be K3=K1=K2=K); and it effects, in the case the swiveliing wagon 2 undergoes inadvertent overrunning beyond the target halting position ef on account of some external disturbance or other, the operation just as in the normal course of the forward swivelling as described hereinbefore, thus of calculating here the respective two values of OO according to these formulas D, E, to then select out always such one of the smallest absolute value out of the two values of C"O and automatically maneuvers the drive controller 1 3 in such feedback principle that actually detected swivelling angular speed 15) may at any value of the detected swivelling angle 19 be brought close enough to so selected particular one of the value of 90 defined by such formula D or E. In this way, it is made possible to automatically restore the swivelling wagon 2, without requiring any manual maneuvering for correcting the overrunning, rapidly and yet smoothly to the preset target halting position ef, in a manner just the same as was described with respect to the normal course of the forward swivelling.

As the sensors for detecting the swivelling angle e of the swivelling wagon 2 relative to the base structure and for detecting the switchover status of the maneuvering valves 10, it is by no means limited to use those of the potentiometer type or the limit-switch type but it as well is possible to use any proper known kind of non contacting type or contacting type sensors, and these sensors may thus in general be referenced to as an angle-detecting apparatus 1 8 for the swivelling angle relative to the vehicle body and a maneuvering valve-state detecting apparatus 17, respectively.

Still further, as the maneuvering valve-state detecting apparatus 17, it is by no means limited to use the one to directly detect the switchover status of the maneuvering valve 10 but it as well is possible to use any other proper one to indirectly detect the switchover status of the maneuvering valve 10 for instance by means of sensing the swivelling direction of the swivelling wagon 2 on the basis of the information given by the angle-detecting apparatus 1 8 for the swivelling angle relative to the vehicle body.

Yet further, instead of providing a single maneuvering valve 10 of pilot-pressure actuation type as described hereinbefore dually to serve as: a valve for maneuvering the swivelling wagon 2 in switching over in its forward and reverse rotations and its halting; and also as a valve for maneuvering in regulatingly adjusting, for the swivelling angular speed control, the working hydraulic medium supplied to the hydraulic motor 3; it as well is possible to provide separate valves specifically for the respective purposes.

It may be as obvious to those skilled in the art that the constants Ka, K2, K3, 8, E, C: M' C: M" adapted in the formulas A, B, C, D, E to be memorized beforehand in the control apparatus 20, may properly be selected in accordance with the specific conditions as are actually given.

Now, as a specific example of the sensor 1 8 for detecting the swivelling angle of the wagon 2, a rotary-encoder type angle-detecting apparatus is described hereunder, first with respect to its first further specific embodiment shown in Fig. 7: Illustrated here at 1 8 is a rotary encoder adopted as a specific embodiment of the swivelling-angle sensor, which is operatively connected to the control apparatus 20 to function for displaying the direction and angular speed of the swivelling of the swivelling wagon 2 relative to the base structure and for automatically halting the swivelling wagon 2 the preset target halting position.Designated generally at 110 is a speedreduction apparatus for driving the swivelling wagon 2, and it has: its output shaft 11 Oa; its covering case 1 1 orb; and its intermediary rotary shaft 11 Oc, thus disposed upstream of the output shaft 11 Oa with respect to the power transmission, with one end thereof protruding out through the case 11 Ob.As is seen, the rotary encoder 1 8 is secured, via a coupling 1 17, on to the protruding tip end of the intermediary rotary shaft 1 Oc. It is hereby possible to cause the rotary encoder 18 to rotate by an angle proportional to the swivelling rotation angle of the swivelling wagon 2 at such a high proportional rate so that the former angle is for larger than the latter, thus to detect the swivelling angle of the wagon 2 at quite a high resolution. Designated at 107 is a rotary joint for the lubrication purpose.

Specific structure of the speed-reduction apparatus 110 may properly selected from a variety of known ones, and there is no specific limitation or restriction as to which particular shaft in the speed-reduction apparatus 110, upstream of its output shaft 11 Oa with respect to the power transmission, should be adopted to secure thereto the rotary encoder 1 8.

Fig. 8 shows one specific form among such variety of possibilities, namely the particular structure of securing the rotary encoder 18 on to a motor-output shaft 3a.

Specific structure of the rotary encoder 1 8 may properly be selected from variety of known ones, such for instance as of optical type or magnetic type, and specific means for securing a base or outer casing of the rotary encoder 1 8 on to the covering case 11 Ob of the speed-reduction apparatus 110, as well as specific structure of the coupling 11 7, may also properly be selected from variety of known ones.

In any case, direct use of any commercially easily and economically available compact or conveniently small-sized rotary encoder is possible simply by modifying any conventional speed-reduction apparatus in such manner, as described hereinabove, as to extend properly selected one of its component rotary shafts to protrude through its covering case and as to secure, via a coupling, the rotary encoder on to the protruding tip end of such selected shaft, while securing a base or outer casing of the rotary encoder on to the covering case of the speedreduction apparatus. In this simple way it is now possible, as has already been mentioned, to make wise and effective use of the function of the speed-reduction apparatus, to cause the movable part of the rotary encoder to rotate by far larger angle in comparison with the angle of the swivelling of the swivelling wagon, and therefore to detect the swivelling angle of the wagon at quite high a resolution, even though the intrinsic resolution of the rotary encoder itself may not be very high.

As is clear from the above, it has now become possible to hereby provide a work vehicle of excellent swivelling operability, as can perform quite exactly and precisely the control of automatic halting of the swivelling wagon and the detection of the swivelling direction and amount, and as is yet very favourable in the viewpoint of the manufacturing cost as well as the component material cost.

Claims

1. A swivelling-type work vehicle, comprising: a vehicle body; an excavation implement (6) disposed to be swivelling with respect to the vehicle body; hydraulic motor means (3, 3') for swivelling the excavation implement (6); a maneuvering valve (10) of electric maneuvering type, capable of switching over the operational direction of, and of adjusting the hydraulic working medium flow rate to, the hydraulic motor means (3, 3'); a maneuvering device (1 50) to maneuver by means thereof the maneuvering valve (10); a sensor (1 60) of electric type adapted to give, as its output, information responsive to the maneuvering direction and maneuvering amount of the maneuvering device (150); and a control mechanism adapted to maneuver the maneuvering valve (10) in response to the information from the sensor (1 60);; the swivelling-type work vehicle further comprising: setter apparatuses (1 9a, 1 9b) to set by means thereof a left and a right halt positions, respectively, relative to the vehicle body, between which positions, thus alternatingly from one to the other of which, the excavation implement (6) should move in shuttle-wise shifting in its successive working stages; an angle-detecting apparatus (18) adapted to detect the left-and-right movement angle relative to the vehicle body, of the excavation implement (6); and a control apparatus (20) adapted to automatically maneuver the maneuvering valve (1) to the flow-rate-reducing side whenever the information from the position detecting apparatus (1 8) shows that the excavation implement (6) has come to a respective preset vicinity of either one of the halt positions set by the setter apparatuses (19a,(19b).

2. A work vehicle of Claim 1, wherein the control apparatus (20) is provided with a switch (120) capable of switchi-ng over the control apparatus (20) between its active or operative state and inactive or inoperative state.

3. A work vehicle of Claim 1 or 2, further comprising: a valve-state detecting apparatus (17) adapted to detect the state information, as its output, to the control apparatus (20); and wherein: the control apparatus (20) is adapted to automatically maneuver the maneuvering valve (10) so as to cause the excavation implement (6) to swivel at such angular speed that is defined by a preset function of the information from both the valve-state detecting apparatus (1 7) and the angle detecting apparatus (18).

4. A work vehicle of Claim 3 wherein the vehicle body comprises: a base structure; and a swivelling wagon (2) disposed for pivotal swivelling on the base structure; the excavation implement (6) is mounted on the swivelling wagon (2); and the control apparatus (20) is adapted to automatically maneuver the maneuvering valve (10) so as to cause the swivelling wagon (2) to swivel relative to the base structure, in a stroke which should start from a swivel-starting position (e)5 and finish at a swivel finishing position (C")f at such angular speed that is defined by the function which is selected from the following three formulas (A, B, C):

wherein:: 19 is the swivel angle from the starting position (C") where e is therefore null, and though the successive swivelling movement are normally repeated in reversingly reciprocating strokes, the value of 0 after starting each stroke is always considered to be positive and its value at the finishing position (C") is designated simply also as (9 is the swivelling angular speed at the position defined by angle 19; eM is given constant as is set as the rated highest angular speed of the swivelling wagon (2);; a is an auxiliary parameter as is set to define the angular speed of the swivelling wagon (2) at the swivel-starting position (95); E is a given constant as is set to define an insensitivity range around the swivel finishing position (C"); and K1, K2 are given constants as are set to define the steepness of the angular speed variation in the initial and final stages of the swivelling stroke; in such manner as to always adopt such particular one of these three (A, B, C) which gives the smallest value of CO for the specific value of O at that time.

5. A work vehicle of Claim 4, having a speedreduction apparatus (110) for driving the swivelling wagon (2), which is mounted on the swivelling wagon (2), and which has, in turn: its output shaft (1 1 Oa); its covering case 1 Ob); and its intermediary rotary shaft (1 1 Oc), thus disposed upstream of the output shaft (1 1 Oa) with respect to the power transmission, with one thereof protruding out through the case (1 1 Ob); wherein: a rotary encoder to serve as the angle detecting apparatus (18) is secured, via a coupling (117), on the protruding tip end of the intermediary rotary shaft (1 1 Oc).

6. A work vehicle of Claim 4, having a speed reduction apparatus (1 10) for driving the swivelling wagon (2), which is mounted on the swivelling wagon (2), and which has, in turn: its covering case 1 Ob); and its input shaft (3a) that is an output shaft of the hydraulic motor (3), disposed with one end thereof protruding out through the case (1 10b); wherein: a rotary encoder to serve as the angle detecting apparatus (18) is secured, via a coupling (117), on to the protruding tip end of the motor-output shaft (3a).

7. A swivelling-type work vehicle substantially as hereinbefore described, with reference to the accompanying drawings.