JP4604411B2 - Plowing depth control device for power agricultural machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a tilling depth control device such as a rotary working machine.
[0002]
[Prior art]
There is known a structure in which a rotary tiller is connected to a rear part of a tractor via a three-point link mechanism, and the rotary tiller is controlled to be set at a set depth.
[0003]
Such a conventional device is generally detected by electrically detecting the movement of the rear cover of the rotary tiller and feeding back the detected value to the controller on the tractor main unit side. The rotary tilling device is moved up and down by comparing the plowing depth detection value and operating the hydraulic lifting mechanism in a direction to eliminate the difference.
[0004]
[Problems to be solved by the invention]
By the way, in such an apparatus, when performing plowing depth control, it is necessary to set the reference position (height) before starting the control. Conventionally, after the rotary tiller is mounted on the tractor, the hydraulic lifting mechanism is operated and, for example, the rear cover of the rotary tiller comes closest to the rotary claw shaft side and does not move any further. The value was read by the controller and stored in the storage means as a value near the tillage depth of zero.
[0005]
Conventionally, this reference value can be read only once when the work implement is connected to the tractor and the electrical couplers are connected to each other, and the reading is also performed from the state where the coupler is not attached. Whether or not, for example, whether the detection voltage of the tilling depth sensor has changed from 0V to 5V can be determined, and after the determination, the rotary tilling device was lifted to set the tilling depth reference value. When a rotary tiller is connected to a tractor using a so-called quick hitch, it is necessary to determine whether the work implement is really connected when the work implement is mounted. Since the voltage has changed from 0V to 5V (or from 5V to 0V), the simple method of rewriting the reference value cannot cope with it.
[0006]
[Means for Solving the Problems]
The present invention has been proposed in view of the above-mentioned problems, and has taken the following technical means. That is, according to the first aspect of the present invention, the rotary work machine 30 is detachably connected via the quick hitch mechanism 14 provided in the tractor 1, and the vertical swing of the rear cover 40 on the rotary work machine 30 side is controlled on the tractor 1 side. In the configuration in which the rotary working machine 30 is configured to be automatically raised and lowered by transmitting to the tilling depth sensor 65, a controller 85 for tilling depth control is provided on the tractor 1 body side, and the tilling depth reference value is stored in the controller 85. A storage means 92 for storing is provided, The controller 85 stores the detected value of the tilling depth sensor 65 when the rotary working machine 30 is detached from the quick hitch mechanism 14 as a set value, and when the detected value of the tilling depth sensor 65 is less than this set value, the rotary working machine. 30 is configured to recognize that it is connected to the quick hitch mechanism 14, The rewriting of the reference value to the storage means 92 is performed at a position before the maximum ascending position in the process of raising the work machine 30 after the work machine 30 is connected by the quick hitch mechanism 14. Even in the process Controller 85 The tilling depth sensor 65 The set value Above Less than 1 second The plowing depth control device in the mobile agricultural machine is characterized in that the plowing depth reference value is not rewritten when detecting for a short time.
[0007]
[0008]
The effect | action by the said structure is as follows. A tractor equipped with a quick hitch mechanism is moved backward against a rotary work machine placed on a flat place, and the work machine is lifted by the quick hitch mechanism. The plowing depth sensor installed in the tractor body detects the mounting of the rotary plowing device, and in this state, activates the hydraulic working mechanism to raise the rotary working machine.
[0009]
In the process of lifting the work implement by the lift mechanism, the position before the maximum ascent position is regarded as a position where the tilling depth is shallow (a value near zero tilling depth), and this detected value is used as a reference value and stored in the storage means of the controller. Even if the working machine 30 is in the ascending process, the tilling depth sensor 65 is Set value (Eg 5V) or more Less than 1 second When detecting for a short time, the plowing depth reference value is not rewritten.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below based on the embodiments shown in the drawings. First, in terms of configuration, reference numeral 1 shown in FIG. 6 is a conventionally known tractor that transmits rotational power shifted to the rear wheel 3 via a transmission (not shown) in the transmission case 2.
[0011]
A hydraulic cylinder case 5 having a hydraulic cylinder 4 inside is fixed to the rear upper portion of the transmission case 2, and lift arms 7 and 7 are freely attached to the hydraulic cylinder case 5. When the operating pressure oil is supplied into the hydraulic cylinder 4, the lift arms 7 and 7 are rotated upward, and when the operating pressure oil is removed, the lift arms 7 and 7 are lowered. In the figure, reference numeral 8 is a top link hitch, 9 is a top link, 10 is a lower link, and 11 is a lift rod. A quick hitch 14 for lifting the work implement is detachably attached to a three-point link 12 including a top link 9 and a lower link 10.
[0012]
The quick hitch 14 locks a hook-like upper engaging portion 19 that locks a locking pin 17 provided on the top of the top mast 16 on the work machine side from below and connecting pins 20 and 20 on the rotary work machine side. Lower engagement portions 22 and 22 are provided, and the lower engagement portions 22 and 22 are opened at the rear, and the working pins 20 and 20 are accommodated in the openings. FIG. 2 shows the quick hitch 14 as viewed from the front. The main frame portion 23 having a mountain shape is formed of a steel pipe, and the left and right sides are connected by an intermediate pipe 24 to reinforce the main frame portion 23.
[0013]
A pair of plate bodies 26, 26 are attached to the intermediate pipe 24, and a bearing portion 29 that supports the rear portion of the universal joint 28 is formed on the plate bodies 26, 26. The bearing portion 29 is supported so as to be able to turn in the front-rear direction by a predetermined angle about shafts 31, 31 provided on the left and right, and a spline hole 33 into which the input shaft 32 of the rotary working machine 30 can be fitted is formed in the center portion. Has been. Accordingly, when the rotary work machine 30 is lifted by the quick hitch 14 and the work machines 30 are combined, the input shaft 32 of the rotary work machine 30 enters the spline hole 33 and the rotational power of the PTO shaft 34 of the tractor 1 is supplied to the universal joint 28. The spline hole 33 and the input shaft 32 are sequentially transmitted to the rotary work machine 30 side. Reference numeral 27 denotes a pin for attaching the lower link 10.
[0014]
The rotary working machine 30 includes a transmission case 36 that transmits power from the input shaft 32 to the tilling shaft 35, a plurality of tilling claws 38 attached to the tilling shaft 35, a main cover 39 that covers the top of the tilling portion, The rear cover 40 is pivotally attached to the rear portion of the cover 39, and the vertical swing of the rear cover 40 is transmitted to the wire 46 via the rod 42 and the bell crank 44. Reference numeral 47 is a connect pipe of the rotary working machine 30, and 48 is a hitch plate fixed to the connect pipe 47. A triangular plate 49 is attached to the left hitch plate 48 as viewed from the side, and a first swinging member 50 is pivotally attached to the plate 49 by a fulcrum pin 51 so as to be pivotable back and forth. A roller 53 is attached to the upper part of the first swing member 50, a pin 55 for attaching the front end of the wire 46 is fixed to the lower end, and the front end of the spring 56 is locked to the upper part of the first swing arm 50. The rear end of the spring 56 is fixed to the rotary work machine 30 side, and urges the upper part of the first swing arm 50 to be always attracted rearward. Therefore, when the rear cover 40 stands up with a shallow plowing depth, the first swinging member 50 is pulled rearward and is in a rearward tilted position when viewed from the side, and the deeper plowing depth increases the rear cover 40. When moved upward, the rod 42 is pushed, and the bell crank 44 is rotated counterclockwise about the fulcrum 45. As a result, the wire 46 is pulled rearward and the roller 53 portion of the first swing member 50 is moved forward. It is made to rotate.
[0015]
On the other hand, on the quick hitch 14 on the three-point link hitch mechanism side, a locking plate 57 is fixed to the lower left portion of the main frame 23 as shown in FIG. A moving member 60 is pivotally attached. A contact portion 60a bent in a reverse shape when viewed from the side is provided on the upper portion of the second swing member 60, and a roller 53 of the first swing member 50 is provided on the contact portion 60a from the back. It is comprised so that it may contact | abut.
[0016]
A pin 61 is fixed to the lower end of the second swing member 60, and the rear end of the wire 62 is connected to the pin 61. The front end of the wire 62 is connected to an arm 66 of a potentiometer 65 which is a tilling sensor attached to the side of the hydraulic cylinder case 5 of the tractor 1. The arm 66 is always biased toward the front side by a spring 68. Accordingly, as a result of the second swinging member 60 being pushed from behind by the roller 53 of the first swinging member 50, the arm 66 is moved to the spring 68 when the second swinging member 60 rotates around the pin 58 that is the rotation fulcrum. It is rotated counterclockwise while resisting Reference numeral 70 denotes a stopper for preventing the second swinging member 60 from reversing (clockwise rotation in FIG. 6). The stopper 70 is fixed horizontally and laterally from the locking plate 57, and mud is attached to the second swinging member 60. As a result of adhesion or external force acting, the stopper 70 regulates even if a force to rotate it clockwise is exerted. In this way, the second swinging member 60 is always held in the backward tilted posture to prevent the reversal of the second swinging member 60, thereby preventing the second swinging member 60 from being damaged and deformed when the work implement is connected.
[0017]
8 and 9 show the detailed structure of the second swinging member 60 and the locking plate 57 part that supports the second swinging member 60, and both 60 and 57 can be passed through a thin bar such as a small bolt or screwdriver. Holes 72 and 73 are formed, and the length of the wire 62 is adjusted so that these through holes 72 and 73 coincide with each other when viewed from the side. That is, the nuts 74 of the outer wire 62a fastened to the base portion of the locking plate 57 are loosened to adjust the position of the outer wire 62a and adjust the protruding amount of the inner wire 62b. Adjust so that the holes 72 and 73 overlap. The position where the through holes 72 and 73 coincide with each other is the position where the posture of the second swinging member 60 is optimal, and the roller 53 on the first swinging member 50 side abuts the second swinging member 60 accurately, and the rear part It is configured to accurately capture the change in tilling depth by the cover 40 and accurately feed back to the tilling depth sensor 65. 8 and 9, reference numeral 75 denotes a rubber boot that covers the outer periphery of the inner wire 62b.
[0018]
FIG. 10 illustrates the case where the position of the rod 42 is changed when the vertical swing of the rear cover 40 is transmitted to the tilling depth sensor 65 on the tractor 1 side. Briefly describing the structure, a metal fitting 77 having a folded piece 77a bent upward is fixed to the rear upper portion of the rear cover 40 with a bolt 76, and a bracket 78 having a triangular shape in side view is fixed to the rear end of the main cover 39. is doing. A rotating arm 82 having two through holes 79, 80 is pivotally supported on the bracket 78, and one of the through holes 79, 80 and the folded piece 77 a are connected by the rod 42.
[0019]
When the through hole 80 close to the pivot axis is selected, the rotary work machine 30 is connected using the quick hitch 14 as in the above embodiment, and the direct work type, in other words, the quick hitch 14 is not used. When the rotary work machine 30 is directly connected to the lower link 10 and the wire 46 on the rear cover 40 side is directly connected to the tilling depth sensor 65 of the tractor 1, the other through hole 79 is selected.
[0020]
Thus, by changing the connection position of the rod 42, the push-pull amount of the wire can be maintained appropriately, and it is possible to deal with both the direct mounting type and the quick type by sharing parts. Next, the working depth control system of the rotary working machine 30 will be described.
[0021]
FIG. 11 is a block diagram of the tilling depth control system. On the input side of the controller 85 made of a microcomputer, a check mode switch 86, a tilling depth sensor 65, and a tilling depth that are turned on and off when checking the operation status of the sensors and switches. A setting device 88 is connected. The plowing depth setting device 88 has a dial shape and can be set in 8 steps from the position of “plowing depth zero” to the “deep” state. The “cut” position to be set is set. Further, a position setter 83 and a position sensor 84 are connected to the input side of the controller 85. The position setter 83 is provided at the rotation base of the hydraulic operation lever 6, and the position sensor 84 is attached to the rotation base of the lift arm 7. The position control system is configured here so that when the hydraulic operation lever 6 is rotated in the front-rear direction, the lift arm 7 is rotated to the set position.
[0022]
On the other hand, an ascending proportional solenoid 89 for raising the work implement and a descending proportional solenoid 90 for lowering the implement are connected to the output side of the controller 85. When a rising signal is output in response to a control command from the controller 85, the raising proportional solenoid 89 is excited. Conversely, when a lowering signal is output, the lowering proportional solenoid 90 is excited to rotate the lift arm 7 up and down.
[0023]
Reference numeral 92 denotes a storage means for storing the tilling depth reference value. An electrically rewritable means such as an EEPROM is provided in the controller 85, and the tilling depth reference value (for example, by the method described later) Memorize value near zero tilling depth). Reference numeral 93 denotes a buzzer connected to the controller 85. This buzzer 93 is used when adjusting the initial value of the tilling depth sensor 65.
[0024]
That is, the working depth sensor 65 in this embodiment is located on the side of the single tractor, and the working machine is connected via the quick hitch mechanism 14, and the movement of the rear cover 40 on the working machine side is connected to the working depth sensor 65 by the wire 46. , 62, the lengths of the wires 46, 62 are indispensable for accurate feedback. Therefore, in this embodiment, the following operation is performed in order to notify the operator whether or not the adjustment work is possible.
[0025]
For this purpose, after lifting the work implement with the quick hitch 14, the operator first turns on the check mode switch 86, and then adjusts the tilling depth setting device 88 within the range of the dials 2-4. At this time, if the buzzer 93 sounds, the plowing depth sensor 65 can be adjusted. When the buzzer 93 does not ring, since the initial adjustment of the tilling depth sensor 65 cannot be performed, the lengths of the wires 46 and 62 are adjusted with the rear cover 40 suspended. Conventionally, when the operator performs the adjustment work, the microcomputer checker is brought to the work machine and is operated so that the value of the tillage sensor 65 is adjusted within an appropriate range while viewing the numerical value of the microcomputer checker. However, in this apparatus, if the buzzer 93 sounds, the operator can recognize that it is within the adjustment range, and adjustment is simple and convenient.
[0026]
In this embodiment, when the rotary working machine 30 is detached from the quick hitch 14, the detection value of the tilling depth sensor 65 is set to 5 V in terms of voltage. The wire 53 is pulled by the lifting and the roller 53 of the first swinging member 50 pushing the contact portion 60a of the second swinging member 60 slightly from the rear, and the arm 66 of the tilling depth sensor 65 is rotated slightly backward. When it moves As a setting value It becomes less than 5V, and the controller 85 recognizes that the work machine is connected.
[0027]
If the check mode switch 86 is turned on and the tilling depth setting device 88 is set to the range of the dials 2 to 4, and the buzzer 93 sounds at this time, the tilling depth sensor 65 can be adjusted. Next, how to set and rewrite a reference value (for example, a value near zero tilling depth) will be described.
[0028]
In this embodiment, the rotary working machine 30 is connected by the quick hitch 14, and the tilling depth sensor 65 value when the lift arm 7 is lifted only once from the maximum ascending position of the lift arm 7 to a position 10 degrees lower is used as the tilling depth reference value. The plowing depth sensor value is written in the storage means 92. FIG. 12 is a time chart showing the timing of rewriting. When the key switch is turned on and the controller 85 is turned on and the first ascending output is generated, the lift arm 7 is in front of the maximum ascending position (lower 10 degrees). ) Is read and the plowing depth sensor 65 value is written in the storage means 92 as a plowing depth reference value (near plowing depth zero value). The position where the tilling depth is zero is a position where the rear cover 40 is slightly rotated upward from the storage position.
[0029]
The reason for reading the tilling depth sensor value before the maximum ascent position is that if the reading is set at the maximum ascent position, the rear cover 40 vibrates due to the impact at the moment when the rear cover 40 stops at the upper limit position. This is because the vibration is fed back to the tilling depth sensor 65 and the stable reference value cannot be rewritten.
[0030]
In the following cases, the tilling depth sensor value was not rewritten. That is, this is a case where the tilling sensor value exceeds 5V, for example. This is because the rotary work machine 30 is in a state of being detached from the quick hitch 14, and in such a case, there is no need for rewriting. The second is the plowing sensor value As a setting value This is the case of a short time such as 5 V or more and less than 1 second. In this case, the suspended rotary work machine 30 vibrates violently, and rewriting is prohibited in this case as well. The third case is a case where the value to be rewritten is a very small value with respect to the currently stored tilling depth sensor value, for example, the scheduled rewriting value is 5 bits or less with respect to the current tilling depth stored value. In such a case, the amount of change is small and there is almost no influence on the control performance, so rewriting is not performed.
[0031]
Next, the operation when the rotary work machine 30 is attached and detached using the quick hitch 14 will be briefly described with reference to FIGS. When the rotary work machine 30 placed on the flat ground is mounted, the quick hitch 14 (not shown) is unlocked, the lift arms 7 and 7 are lowered, and the tractor 1 is moved backward.
[0032]
Then, the upper engaging portion 19 of the quick hitch 14 is submerged under the mast 16 of the rotary work machine 30, and the lift arms 7 and 7 are rotated up so as to scoop up the locking pin 17 on the mast 16 side. Then, as shown in FIG. 7, the rotary working machine 30 rotates clockwise around the locking pin 17, and the connecting pins 20, 20 of the rotary working machine 30 enter the lower engaging portions 22, 22 from the rear. In this state, a lock device (not shown) is operated to complete the connection between the tractor 1 and the work implement 30.
[0033]
At this time, since the connection between the PTO shaft 34 of the tractor 1 and the input shaft 32 on the rotary work machine 30 side is automatically performed, when the tractor 1 is advanced while the PTO shaft 34 is rotated, the tilling shaft of the rotary work machine 30 is moved. 35 is rotated and the soil is cultivated by the tilling claws 38.
[0034]
When plowing work is started and the plowing depth is gradually increased, the rear cover 40 is lifted by the soil (the phantom line in FIG. 7), and its movement is first swung via the rod 42, bell crank 44, and wire 46. It is transmitted to the member 50. By pulling the wire 46 backward, the roller 53 of the first swing member 50 rotates forward, and the roller 53 pushes the contact portion 60a of the second swing member 60 to rotate it counterclockwise. . When the second swinging member 60 is pushed along with the increase in tilling depth, the wire 62 is pulled, and the arm 66 of the tilling depth sensor 65 is rotated to inform the controller (not shown) that the tilling depth is deep. The controller reads the change, supplies the operating pressure oil into the hydraulic cylinder 4, and lifts and lifts the lift arms 7 and 7 until the set working depth is reached. In this way, tilling depth control is executed. In connecting the rotary working machine 30 to the tractor 1, the second swinging member 60 is prevented from reversing itself by the reversing prevention stopper 70 fixed to the locking plate 57. Even if a hand hits or mud adheres and tries to turn it downward (clockwise in FIG. 6), the movement is blocked by this stopper 70, and therefore the second swinging member 60 always moves backward. The tilted posture is maintained and the first swinging member 50 on the work machine 30 side can be linked.
[0035]
When the rotary work machine 30 is removed, the operation opposite to the above may be performed. If the lock device (not shown) is released and the lift arms 7 and 7 are operated to the lowering side, the rotary work machine 30 side can be easily removed. The locking pin 17 and the lower connecting pins 20, 20 are detached from the quick hitch 14.
[0036]
Finally, FIGS. 13 to 15 will be described. FIG. 13 and FIG. 14 explain the configuration of the main part of the rotary working machine 30 described above. Components having the same or similar configurations as those in the above embodiment are denoted by the same reference numerals, and only new components are denoted by different symbols.
[0037]
A plate 49 having a triangular shape in a side view is disposed on the outer side of the one-side hitch plate 48 of the rotary working machine 30, and the side view for supporting the first swinging member 50 is formed in a substantially square shape inside the hitch plate 48. The plate 97 is fixed by pins 98 and bolts 99. A wire 46 for transmitting the movement of the rear cover 40 to the first swinging member 50 is disposed so as to have an inverted S shape when viewed from the plane as shown in FIG. The clamp 100 attached to the lower part of the pipe 47 is configured to prevent the wire 46 itself from drooping. In FIG. 14, reference numeral 101 denotes a pin, 102 denotes a spring, and 103 denotes a nut.
[0038]
By supporting the wire 46 in a relatively long and inverted S shape in the above, the wire 46 can be prevented from being pulled when the rear cover 40 is rotated. Therefore, the rotation of the rear cover 40 becomes smooth, and the operation of the tilling depth control is ensured without fear of the cable being cut.
[0039]
In particular, as described in this embodiment, the triangular plate 49 and the substantially rectangular plate 97 are configured to sandwich the hitch plate 48 of the rotary working machine 30 and fix with the bolt 99 and the pin 98, so that the plate 97 is fixed. The positional relationship between the connected connecting pin 20 and the first swing member 50 becomes accurate, the tensile amount of the wire 46 is stabilized, and precise tilling control can be performed.
[0040]
FIG. 15 illustrates a method corresponding to a rotary work machine in which the quick hitch 14 cannot be used when plowing depth control is performed using a plowing depth sensor. The features of the control system shown in this figure are a first control system that connects the work machine with the quick hitch 14, and a second control system in which the operator directly connects the electrical coupler to the controller after the work machine is connected to the tractor. It is a point provided.
[0041]
Therefore, a detachable coupler 110 is provided between the controller 85 and the tilling depth sensor 65. The coupler 110 includes a male coupler 110a and a female coupler 110b. In the case of a completely different rotary work machine that cannot support the quick hitch 14, the coupler 110 is separated, and the male coupler 110a on the controller 85 side is replaced with the rotary coupler 120. It is configured to be combined with the female coupler 120b. In this case, the tilling depth sensor 130 is provided on the rotary side, and the movement of the rear cover is transmitted to the tilling depth sensor 130 and the signal is fed back to the controller 85 via the harness.
[0042]
With such a configuration, there is no quick hitch 14, and even if the working machine is completely different from the working machine that has been mounted so far, the working machine has only a coupler that can be separated from the working depth sensor. The plowing depth can be controlled.
[0043]
【The invention's effect】
According to the first aspect of the present invention, as described above, the rotary work machine 30 is detachably connected via the quick hitch mechanism 14 provided in the tractor 1, and the vertical swing of the rear cover 40 on the rotary work machine 30 side is controlled. In this configuration, the rotary working machine 30 can be automatically moved up and down by being transmitted to the plowing depth sensor 65, and a plowing depth control controller 85 is provided on the tractor 1 main body side. A storage means 92 for storing the value is provided; The controller 85 stores the detected value of the tilling depth sensor 65 when the rotary working machine 30 is detached from the quick hitch mechanism 14 as a set value, and when the detected value of the tilling depth sensor 65 is less than this set value, the rotary working machine. 30 is configured to recognize that it is connected to the quick hitch mechanism 14, Since the rewriting of the reference value to the storage means 92 is performed at a position before the maximum ascending position in the process of raising the work machine 30 after the work machine 30 is connected by the quick hitch mechanism 14, the working depth reference value is set. Can be rewritten smoothly and stably. That is, when the setting is made so that the reading is performed at the maximum ascending position, the rear cover 40 vibrates due to the impact at the moment when the rear cover 40 stops at the upper limit position, and the vibration is fed back to the tilling depth sensor 65 to rewrite the stable reference value. It is possible to eliminate the disadvantage that cannot be done.
[0044]
Even if the working machine 30 is in the ascending process Controller 85 The tilling depth sensor 65 The set value Above Less than 1 second Since the plowing depth reference value is not rewritten when detecting for a short time, rewriting is not performed when the suspended rotary work machine 30 vibrates violently.
[0045]
[Brief description of the drawings]
FIG. 1 is a side view of a three-point link hitch mechanism (quick hitch).
FIG. 2 is a front view of FIG.
FIG. 3 is a side view of the upper part of the rotary working machine.
4 is a front view of FIG. 3. FIG.
FIG. 5 is an enlarged side view of a main part.
FIG. 6 is a side view of a tractor and a rotary work machine.
FIG. 7 is a side view of a tractor and a rotary work machine.
FIG. 8 is an exploded perspective view of a main part.
FIG. 9 is an enlarged side view of a main part with a part cut away.
FIG. 10 is an exploded perspective view of a main part.
FIG. 11 is a control block diagram.
FIG. 12 is a time chart.
FIG. 13 is a perspective view of a main part.
FIG. 14 is a perspective view of a main part.
FIG. 15 is a block diagram of a control system.
[Explanation of symbols]
1 Tractor
2 mission case
3 Rear wheels
4 Hydraulic cylinder
14 Quick hitch mechanism
30 Rotary work machine
34 PTO axis
39 Main cover
40 Rear cover
50 First swing member
60 Second swing member
85 controller
86 Check mode switch
88 Working depth setting device
92 Memory means
93 Buzzer

Claims (1)

A rotary work machine (30) is detachably connected via a quick hitch mechanism (14) equipped to the tractor (1), and the vertical swing of the rear cover (40) on the rotary work machine (30) side is controlled. ) Side plowing depth sensor (65) and the rotary work machine (30) is configured so that it can be raised and lowered automatically, the tractor (1) main body side is provided with a plowing depth control controller (85), The controller (85) is provided with storage means (92) for storing the working depth reference value, and the controller (85) is a working depth sensor when the rotary working machine (30) is detached from the quick hitch mechanism (14). When the detected value of (65) is stored as a set value and the detected value of the tilling depth sensor (65) is less than this set value, it is recognized that the rotary work machine (30) is connected to the quick hitch mechanism (14). And so that configuration, after connecting a work implement (30) rewrites the reference value to said memory means (92) in the quick hitch mechanism (14), the maximum raised position before the course of raising the working machine (30) Even if the working machine (30) is in the ascending process, the controller (85) detects the plowing depth when the plowing depth sensor (65) detects the set value or more for a short time of less than 1 second. A plowing depth control apparatus in a mobile agricultural machine, characterized in that the reference value is not rewritten.

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