Signal converter for leveling work

Abstract

To provide a technology to use GNSS leveling control technology at low cost.SOLUTION: A signal converter for levelling work includes: a signal input terminal for receiving a positioning height signal output from an output terminal of a positioning control device; a signal output terminal for outputting a connection mechanism control signal for controlling an operation of a work machine connection mechanism for a connection mechanism control terminal of a tractor to which a signal corresponding to a tilling depth of a rotary tilling work machine is input in a state that the rotary tilling work machine is connected to the work machine connection mechanism; and a signal conversion circuit for converting the positioning height signal input from the signal input terminal to the connection mechanism control signal.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a technology for controlling the lifting and lowering operation of a leveling machine connected to a tractor based on height information measured by a satellite positioning system (GNSS (Global Navigation Satellite System)). Hereinafter, this technology will be referred to as GNSS leveling control technology. [Background technology]

[0002] To improve crop growth, field leveling is performed on paddy fields, farmlands, and other agricultural fields. This leveling work is performed using a leveling machine that can be attached to a tractor. In recent years, tractors or leveling machines that use GNSS leveling control technology have become available.

[0003] For example, Patent Document 1 below discloses a farm implement using GNSS leveling control technology. In this implement, a height position detection signal for the implement is acquired using radio waves received from a GPS (Global Positioning System) satellite, and the working height of the implement is controlled by driving a lift mechanism so that the deviation between the height indicated by the height position detection signal and the working height set by a position selection means (position control lever) equipped on the tractor is constant. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-8505 Summary of the Invention [Problem to be solved by the invention]

[0005] Existing devices that use GNSS leveling control technology, like the above-mentioned farm implement, require the addition of dedicated equipment to the tractor. For example, the tractor must be equipped with a dedicated terminal for inputting height information signals detected by a satellite positioning system, and a function for controlling the lifting and lowering operation of the leveling implement based on the signal input from that dedicated terminal.

[0006] However, under these conditions, tractor prices will rise even further, which could lead to a slowdown in the spread of GNSS leveling control technology. GNSS leveling control technology is expected to improve crop growth and agricultural work efficiency, but if its spread stagnates, these benefits will no longer be realized.

[0007] The present invention has been made in view of the above circumstances, and provides a technology that enables the use of GNSS leveling control technology at low cost. [Means for solving the problem]

[0008] One aspect of the present invention relates to a leveling signal conversion device connected between a positioning control device that outputs a positioning height signal based on height information measured using a positioning satellite when a tractor that can be connected to a rotary tillage machine or a leveling machine as a specific work machine via a work machine connection mechanism and can raise and lower the specific work machine by operating the work machine connection mechanism is connected to the leveling machine. The leveling signal conversion device comprises a signal input terminal that receives the positioning height signal output from the output terminal of the positioning control device, a signal output terminal that outputs a coupling mechanism control signal for controlling the operation of the implement coupling mechanism to the tractor's coupling mechanism control terminal, to which a signal corresponding to the tilling depth of the rotary tillage implement is input when the rotary tillage implement is connected to the implement coupling mechanism, and a signal conversion circuit that converts the positioning height signal input from the signal input terminal into a coupling mechanism control signal. [Effects of the Invention]

[0009] According to the present invention, GNSS leveling control technology can be used at low cost. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram showing a tractor and a leveling machine that use a leveling signal converter (the converter) according to the present embodiment. FIG. [Figure 2] FIG. 1 is a diagram showing a rotary tillage implement coupled to a tractor. [Figure 3] FIG. 10 is a view showing the leveling machine in a raised position. [Figure 4] 1 is a schematic diagram showing a connection configuration of a signal converter for leveling (the converter) according to the present embodiment. [Figure 5] 1 is a diagram showing the appearance of a signal converter for leveling (the converter) according to the present embodiment. [Figure 6] FIG. 2 is a circuit diagram showing a specific example of a signal conversion circuit. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described. As an example of this embodiment, a signal converter for leveling (hereinafter, sometimes referred to as the present converter) will be illustrated. Note that the embodiment described below is merely an example, and the present invention is not limited to the configuration of the following embodiment.

[0012] Figure 1 shows a tractor 1 and a leveling implement 2 that use a leveling signal conversion device (this converter) according to this embodiment, Figure 2 shows a rotary tiller 3 connected to the tractor 1, and Figure 3 shows the leveling implement 2 in a raised state. In this specification, in order to specify the relative positional relationship of each component, the forward / backward direction, left / right direction, and up / down direction are defined as follows: The forward direction is the direction of travel of the tractor 1 when traveling straight, and the backward direction is the opposite direction. The right direction is the right side of the direction of travel of the tractor 1 when traveling straight, and the left direction is the left side of that. The direction of gravity is defined as the downward direction, and the opposite direction is defined as the upward direction. That is, FIGS. 1, 2 and 3 show the right side of a tractor 1, a leveling implement 2 and a rotary tiller 3.

[0013] The tractor 1 is an agricultural work vehicle that can be driven by an operator and can be coupled to a specific work implement such as a leveler 2 or a rotary tiller 3, and can tow the specific work implement to perform various tasks in fields, etc. However, the tractor 1 is not limited to a vehicle that is driven by a person, and may also be an autonomous vehicle. In this specification, for ease of understanding, the work vehicle itself will be referred to as a tractor 1, and the work implement that can be connected to the work vehicle will be described separately from the tractor 1, but this does not exclude treating the work implement as one component of the tractor 1.

[0014] The tractor 1 includes a body frame, wheels, a prime mover, a clutch device, a transmission device, etc. The prime mover is a drive source of the tractor 1 such as an engine. Power from the prime mover is transmitted to the wheels via the clutch device and the transmission device, thereby driving the wheels. Either the front wheels or the rear wheels may be drive wheels, or both may be drive wheels. In this embodiment, there are no restrictions on the configuration related to the running of the tractor 1, and any configuration can be adopted, so detailed explanation will be omitted here.

[0015] The tractor 1 further includes a work implement coupling mechanism (hereinafter sometimes abbreviated as coupling mechanism) 5. The tractor 1 can be coupled to a specific work implement via this coupling mechanism 5, and the specific work implement can be raised and lowered by operating the coupling mechanism 5. In this embodiment, a leveling implement 2 and a rotary tiller implement 3 are given as examples of the specific work implement, but the specific work implement that can be coupled to the tractor 1 is not limited in any way.

[0016] The connecting mechanism 5 includes at least a lower link 51, a lift link 52, a lift arm 53, and a top link 54. One end of a lift link 52 is rotatably connected to the middle portion of the lower link 51 in the longitudinal direction (front-rear direction), and the other end of the lift link 52 is rotatably connected to the rear end of a lift arm 53. Two sets of lower link 51, lift link 52, and lift arm 53 connected in this manner are provided on the left and right, and the rear ends of the left and right lower links 51 are connected to the specific work machine together with the rear end of the top link 54. In other words, the left and right lower links 51 and the top link 54 form a three-point link mechanism for the specific work machine.

[0017] The front ends of the top link 54 and the left and right lower links 51 are each rotatably connected to the rear of the tractor 1. The left and right lift arms 53 are also rotatably connected to the rear of the tractor 1 at the front and rotate around their rotation axes by power from the mechanism drive unit 15. As the left and right lift arms 53 rotate, the left and right lower links 51 also rotate around their front end connecting axes via the lift links 52, thereby raising and lowering the specific working machine. In this way, the rotation angle of the lift arms 53 determines the raised and lowered position of the specific working machine. In the example of Figure 3, the lift arms 53 rotate so that the leveling machine 2, which serves as the specific working machine, is raised.

[0018] The mechanism drive device 15 that operates the connecting mechanism 5 in this manner transmits power input from a prime mover and outputs power via an actuator to realize the rotation of the lift arm 53. Such a mechanism drive device 15 is realized as a hydraulic system composed of hydraulic equipment such as a hydraulic pump, hydraulic valves, and hydraulic actuators. The mechanism drive device 15 controls the rotation angle of the lift arm 53, thereby controlling the lift position of the specific work machine. The mechanism drive device 15 is shown in Figure 4, which will be described later.

[0019] The connecting mechanism 5 further includes a PTO (Power Take-Off) drive shaft (not shown) for transmitting power to the connected specific implement. The PTO drive shaft outputs power input from the prime mover to the specific implement via the PTO shaft of the tractor 1. When the rotary tiller 3 is connected to the tractor 1, the power transmitted via the PTO drive shaft rotates the tiller tines 31 of the rotary tiller 3.

[0020] In this embodiment, the connecting mechanism 5 and the mechanism drive device 15 are capable of switching between the leveling machine 2 and the rotary tiller 3 and connecting them to the tractor 1, and are configured to be able to raise and lower the connected leveling machine 2 and rotary tiller 3, and their specific configurations are not limited in any way. Furthermore, the operation of the connecting mechanism 5 and the operation of the mechanism drive device 15 as described above are controlled by a control system (tractor control device) of the tractor 1, which will be described later, but in the following explanation, such control may be abbreviated as control over the connecting mechanism 5.

[0021] The tractor 1 further includes a control section 17. The control section 17 includes various operating sections in addition to a steering wheel and a seat for the operator (worker). The operating sections include a main speed change lever, a sub-speed change lever, a position control lever, a tilling depth adjustment dial, a PTO operating section, etc. The main speed change lever and sub-speed change lever are control parts for changing the travel speed. The position control lever is a control part for raising and lowering a specific implement to a desired position. In addition, as will be described in detail later, the safety mode is released by a specific operation on this position control lever. The tilling depth adjustment dial is a control part for adjusting the tilling depth of the rotary tiller implement 3. The PTO control part is a control part for switching between rotating and stopping the PTO shaft. However, the control unit 17 may further include other components, and the specific configuration of the control unit 17 is not limited in any way.

[0022] The leveling implement 2 is a work implement that is coupled to and pulled by the tractor 1 in order to make the height of the field level. The leveling implement 2 illustrated in Figures 1 and 3 is composed of a frame portion 21 connected to the connecting mechanism 5, and a leveling portion 25 connected to the frame portion 21 and capable of contacting the field surface to level it. The frame portion 21 is connected at the front to the rear ends of the top link 54 and the lower link 51 . The leveling unit 25 is connected to the rear of the frame unit 21 so as to extend downward. The leveling unit 25 includes a leveling plate whose lower end surface levels the soil in the field, and left and right side plates that are provided to move the soil leveled by the leveling plate without letting it leak out to the sides. The leveling plate is a plate-like body that is long in the left and right width directions and short in the up and down directions, and has a curved shape that protrudes gently to the rear. The left and right side plates are connected to the left and right ends of the leveling plate so as to sandwich the leveling plate from the left and right. However, the specific structure of the leveling machine 2 is not limited as long as it has a structure that can make the height of the field uniform. For example, the leveling machine 2 is not limited to the examples in Figures 1 and 3, and may further have a structure that allows cultivation or other structures.

[0023] The rotary tiller 3 is a work machine that is coupled to and pulled by the tractor 1 to till the field. The rotary tiller 3 illustrated in FIG. 2 includes a group of tiller tines 31, a tine cover 32, a rear cover 33, and the like. The tillage tine group 31 is fixed to a rotatable rotary shaft extending in the left-right direction and rotates integrally with the rotary shaft. The rotary shaft rotates by power transmitted from the PTO drive shaft of the connecting mechanism 5. The tine cover 32 is provided to cover the tillage tine group 31 from above, the front, and the left and right directions.

[0024] The rear cover 33 covers the tillage tines 31 from the rear and is rotatable relative to the tine cover 32. The rear cover 33 rotates when its lower end comes into contact with the field surface and moves up and down in response to the unevenness of the field surface. A rear cover sensor (not shown) is provided that can detect the rotation angle of the rear cover 33. However, the rotary tiller 3 is not limited to a specific structure as long as it has a structure that allows it to till a field. For example, the rotary tiller 3 is not limited to the example shown in Figure 2 and may further have other structures.

[0025] FIG. 4 is a schematic diagram showing the connection configuration of the leveling signal converter (present converter) 9 according to this embodiment. As shown in FIG. 4, the tractor 1 is provided with a tractor control device (hereinafter, sometimes abbreviated as the control device) 10 as a control system. The control device 10 may also be called an ECU (Electronic Control Unit) and includes a processor, memory, an input / output interface (I / F) unit, etc. The processor may be one or more central processing units (CPUs) or micro processing units (MPUs), or a combination thereof, and may further include a digital signal processor (DSP), a graphics processing unit (GPU), a field programmable gate array (FPGA), etc. The memory is a random access memory (RAM) and a read-only memory (ROM), and may also include an auxiliary storage device (such as a hard disk). The input / output I / F unit controls the input or output of signals to be processed or that have been processed by the processor. The control device 10 exchanges signals with various sensors, the control unit 17, etc. via the input / output I / F unit. The input / output I / F unit may include a communication unit for communicating with other devices. However, the hardware configuration of the control device 10 is not limited in any way.

[0026] The control device 10 executes various controls by reading out computer programs stored in a memory and executing them in a processor. The control device 10 includes a travel system control unit as well as a work machine system control unit, etc. These control units can also be distinguished as individual ECUs. The traveling system control unit controls other traveling systems, such as the control of the prime mover and the traveling speed, etc. In this embodiment, the traveling system control unit is not limited to any specific control content as long as it can perform general control related to the traveling of the tractor.

[0027] The work machine system control unit controls the mechanism drive device 15 and the PTO shaft described above. In this embodiment, the work machine system control unit is not limited to any specific control content as long as it can perform general control for the rotary tiller 3 when the rotary tiller 3 is connected. Well-known examples of common controls for the rotary tiller 3 include automatic leveling control that keeps the implement level, and tilling depth control, and tilling depth control will be described in detail later.

[0028] The control device 10 further includes a linkage control connector 11 as shown in FIG. The coupling mechanism control connector 11 includes at least a coupling mechanism control terminal and a power supply terminal, and may be referred to as a tractor-side connector 11 hereinafter. When the rotary tiller 3 is coupled to the tractor 1, a connector provided on the rotary tiller 3 (hereinafter referred to as the rotary side connector) is connected to the tractor side connector 11. A control device (hereinafter referred to as the rotary side device) mounted on the rotary tiller 3 uses power supplied from the power supply terminal of the tractor side connector 11 to generate a signal corresponding to the tilling depth of the rotary tiller 3, and outputs this signal to the coupling mechanism control terminal of the tractor side connector 11.

[0029] Here, "a signal corresponding to the tilling depth of the rotary tiller 3" means a signal that can indicate the depth position of the tiller tines 31 of the rotary tiller 3 from the field surface. One example is a feedback signal from a rear cover sensor. When the tillage tines 31 are located deep underground from the field surface, the tillage depth is deep, the rotation angle of the rear cover 33 is large, and the lower end of the rear cover 33 is positioned upward due to contact with the field surface after tillage. On the other hand, when the tillage tines 31 are located shallower from the field surface, the tillage depth is shallower and the rotation angle of the rear cover 33 is smaller. The feedback signal from the rear cover sensor indicates the rotation angle of the rear cover 33, and therefore can be said to be a signal that can indicate the depth position of the tillage tines 31 from the field surface. However, the "signal corresponding to the tilling depth of the rotary tiller 3" is not limited to a feedback signal from the rear cover sensor, but may be a signal obtained by other methods.

[0030] Here, a general tilling depth control for the rotary tiller 3 using a feedback signal from such a rear cover sensor will be described. Before describing the control content, first, the setting of the safety mode by the control device 10 (work machine system control section) and the setting of the reference point and neutral point will be described. The "safety mode" is a control mode for the connecting mechanism 5 in the control device 10, and is a mode in which the specific work machine connected to the connecting mechanism 5 is fixed so that it does not rise or fall or operate. The "neutral point" is a concept that indicates a specific position (specific angle) within the range of motion (rotation angle) of the connecting mechanism 5 that corresponds to the lifting range of a specific work machine, and indicates the target position (rotation angle) for the height position (lifting position) of the specific work machine. The "reference point" is a concept that indicates a specific position (specific angle) within the range of motion (rotation angle) of the connecting mechanism 5 that corresponds to the lifting range of a specific work machine, and indicates a position (angle) that serves as a reference for determining the "neutral point." For example, the neutral point is set at a predetermined relative position with respect to the reference point. The neutral point and reference point are set based on the signal input from the connection mechanism control terminal of the tractor side connector 11, and when setting the neutral point and reference point, for example, voltage values ​​corresponding to each of the neutral point and reference point are maintained.

[0031] The control device 10 (work machine system control unit) can set a safety mode as a control mode for the connecting mechanism 5. For example, when the safety mode is set, the control device 10 controls the connecting mechanism 5 so that the lift arm 53 and the PTO shaft are fixed and do not move. This safety mode is provided to ensure the safety of the worker by preventing the working machine and connecting mechanism 5 from moving unintentionally when not working.

[0032] The control device 10 sets the safety mode when the prime mover is stopped, when it detects that nothing is connected to the tractor-side connector 11, or the like, and cancels the safety mode when a specific operation is performed on the operating unit 17, or the like. In this embodiment, an example of the specific operation is lowering the position control lever from its uppermost position. When the position control lever is operated to the uppermost position, the lift arm 53 rotates under control of the mechanism drive device 15 by the control device 10, and the rotary tiller 3 rises to its uppermost position. When the position control lever is lowered from its uppermost position, the rotary tiller 3 descends, and the control device 10 cancels the safety mode.

[0033] The control device 10 (work machine system control unit) can also set a reference point and a neutral point. When the safety mode is released, the control device 10 sets a reference point based on a signal input from the coupling mechanism control terminal of the tractor-side connector 11, and further sets a neutral point based on the reference point. When a signal corresponding to the set neutral point is input from the coupling mechanism control terminal, the control device 10 controls the coupling mechanism 5 to stop the lifting or lowering of the specific work machine. Details regarding the setting of the reference point and neutral point will be described later.

[0034] When the control device 10 executes tillage depth control, the rotary tillage implement 3 is coupled to the tractor 1, and the rotary-side connector is connected to the tractor-side connector 11. In the rotary-side device, a feedback signal from the rear cover sensor is generated using power supplied from the power supply terminal of the tractor-side connector 11, and this feedback signal is output to the connection mechanism control terminal of the tractor-side connector 11. The feedback signal from the rear cover sensor is, for example, a voltage signal in the range of 0 (V) to 5 (V) corresponding to the rotation angle range of the rear cover 33.

[0035] When the safety mode is released, the control device 10 acquires a feedback signal from the rear cover sensor via the connecting mechanism control terminal and sets a reference point based on the content of the signal. Specifically, the control device 10 holds the voltage value of the acquired feedback signal as the reference point. Next, the control device 10 sets the neutral point at a predetermined relative position (relative angle) with respect to the reference point. Specifically, the control device 10 adds a predetermined voltage value (for example, 0.5 (V)) to the voltage value held as the reference point and holds the resulting voltage value as the neutral point. The reference point is set when the safety mode is released, and indicates the position where the tip of the rear cover 33 is not in contact with the field surface and the rotation angle of the rear cover 33 is at its smallest, whereas the neutral point indicates the position where the tilling depth is deeper than the reference point position and the rotation angle of the rear cover 33 is larger.

[0036] Thereafter, the control device 10 controls the coupling mechanism 5 in accordance with the feedback signal of the rear cover sensor input from the coupling mechanism control terminal to raise and lower the rotary tiller 3. For example, if the height position of the rotary tiller 3 indicated by the feedback signal is higher than the neutral point, the control device 10 controls the coupling mechanism 5 to lower the rotary tiller 3, and conversely, if the height position is lower than the neutral point, the control device 10 controls the coupling mechanism 5 to raise the rotary tiller 3. As a result, the rotary tiller 3 is towed by the tractor 1 while fixed at a height position corresponding to the neutral point, and the entire field is tilled appropriately.

[0037] In this tilling depth control, the control device 10 may change the set neutral point in response to the operation of the tilling depth adjustment dial on the operating unit 17. For example, if the operator determines that the tilling depth of the rotary tiller 3 is too deep, he or she operates the tilling depth adjustment dial to decrease the tilling depth, which results in the neutral point being changed to decrease the rotation angle of the rear cover 33. Alternatively, if the operator determines that the tilling depth of the rotary tiller 3 is too shallow, he or she operates the tilling depth adjustment dial to increase the tilling depth, which results in the neutral point being changed to increase the rotation angle of the rear cover 33. This allows the tilling depth to be finely adjusted as needed depending on the condition of the field.

[0038] Such tillage depth control for rotary tillers 3 has been widely used for a long time before the advent of GNSS leveling control technology, and typical tractors 1 are capable of carrying out such tillage depth control. Here, as mentioned above, the signal input from the coupling mechanism control terminal of the existing tractor-side connector 11 is a signal corresponding to the tillage depth, and is different from the signal corresponding to the height based on GNSS positioning. Therefore, in order to realize GNSS leveling control in the tractor 1, the usual idea is to provide the tractor 1 with a new control terminal or a new control mode. However, such an idea would further increase the price of the tractor 1. Therefore, the inventors came up with the revolutionary idea of ​​achieving GNSS leveling control at low cost by simply using the existing tractor-side connector 11 and existing tillage depth control provided for the rotary tiller 3, without adding a new control terminal or a new control mode to the tractor 1. In other words, the converter 9 achieves GNSS leveling control by the tractor 1 while still using the existing tractor-side connector 11 and existing tillage depth control provided for the rotary tiller 3. Furthermore, with this converter 9, other existing controls for the rotary tiller 3 can also be used as they are. For example, an existing automatic leveling control for the leveler 2 can also be used as is.

[0039] [Signal converter for leveling work (this converter)] FIG. 5 is a diagram showing the appearance of a leveling operation signal converter (present converter) 9 according to this embodiment. As shown in FIG. 5, the converter 9 includes a main body 90, a mode changeover switch 91, an adjustment dial 92, a tractor connector 93, a GNSS connector 94, and the like. When connecting the leveling implement 2 to the tractor 1, the converter 9 is connected between the GNSS controller 71 and the tractor 1. Specifically, the GNSS connector 94 of the converter 9 is connected to the output connector 75 of the GNSS controller 71, and the tractor connector 93 of the converter 9 is connected to the connecting mechanism control connector (tractor-side connector) 11 of the tractor 1.

[0040] The main body 90 is a box that houses the signal conversion circuit 98 of the converter 9. The mode selector switch 91 is an operation unit that allows a user to switch the operation mode of the signal conversion circuit 98, and can also be called a mode switching operation unit. The mode selector switch 91 can switch between a reference setting mode and a normal operation mode as the operation mode of the signal conversion circuit 98. Details of these operation modes will be described later. The adjustment dial 92 is an operation unit that allows the user to adjust the neutral point, and can also be called an adjustment operation unit. The neutral point is changed by the user rotating the adjustment dial 92. The method for changing the neutral point will be described later.

[0041] The tractor connector 93 includes at least a signal output terminal 96 and a power supply terminal 97, and is a connector that can be connected to the tractor-side connector 11. The tractor connector 93 corresponds to the converter-side connector. When the tractor connector 93 and the tractor-side connector 11 are connected, the signal output terminal 96 and the coupling mechanism control terminal of the tractor-side connector 11 become conductive, and the power supply terminal 97 and the power supply terminal of the tractor-side connector 11 become conductive. The GNSS connector 94 is a connector that includes at least a signal input terminal 95 and is connectable to the output connector 75 of the GNSS controller 71. When the GNSS connector 94 and the output connector 75 are connected, the signal input terminal 95 and the output terminal of the output connector 75 are brought into a conductive state.

[0042] The GPS satellite positioning system (GNSS) controller 71 outputs a positioning height signal based on height information measured using positioning satellites. The GNSS controller 71 can also be called a positioning control device. The GNSS controller 71 is connected to the GNSS display unit 72 and the GNSS antenna 73. The GNSS controller 71 acquires satellite signals received by the GNSS antenna 73, calculates three-dimensional positioning data based on the satellite signals, and outputs a positioning height signal based on the height information in the calculated positioning data from the output terminal of the output connector 75. The positioning height signal is not limited to any specific content, as long as it can indicate that the height indicated by the calculated three-dimensional positioning data is higher than the reference height, approximately the same as the reference height, or lower than the reference height. The reference height is stored as setting information in the GNSS controller 71. The reference height is the height of a surface that is used as a reference for leveling the field, and corresponds to the neutral point.

[0043] The GNSS display unit 72 can display setting information of the GNSS controller 71 and information on elevation differences in the field based on measured three-dimensional positioning data. The GNSS antenna 73 receives radio waves from positioning satellites such as QZSS, GPS, GLONASS, and Galileo. For example, the GNSS antenna 73 is installed on the upper surface of the leveling unit 25 of the leveling machine 2 as shown in FIG. As long as the GNSS controller 71 can output a positioning height signal based on height information measured using a positioning satellite, there are no limitations on the type of positioning satellite or the positioning method supported by the GNSS controller 71 and the GNSS antenna 73. Furthermore, the installation position of the GNSS antenna 73 is not limited to the example shown in Fig. 1 as long as it can measure the height position of the leveling machine 2. The same applies to the installation positions of the GNSS controller 71 and the GNSS display unit 72.

[0044] As described above, the converter 9 includes a signal input terminal 95, a signal output terminal 96, and a signal conversion circuit 98. The signal input terminal 95 receives the positioning height signal output from the GNSS controller 71, and the signal conversion circuit 98 converts the positioning height signal input from the signal input terminal 95 into a coupling mechanism control signal for controlling the operation of the coupling mechanism 5, and outputs the coupling mechanism control signal from the signal output terminal 96 to the coupling mechanism control terminal of the tractor-side connector 11 of the tractor 1. As described above, when the rotary tillage implement 3 is connected to the connecting mechanism 5, a signal corresponding to the tilling depth of the rotary tillage implement 3 (feedback signal of the rear cover sensor) is input to the connecting mechanism control terminal of the tractor side connector 11, from which the above-mentioned connecting mechanism control signal is output. In this embodiment, without providing the tractor 1 with a new control terminal for leveling or a new control mode for leveling, the tractor 1's coupling mechanism control terminal and tilling depth control, which input a signal corresponding to the tilling depth when the rotary tiller 3 is coupled, are used as is, thereby making it possible to inexpensively implement GNSS leveling control technology in the tractor 1. Furthermore, according to this embodiment, it is possible to use not only tilling depth control but also other existing controls for the rotary tiller 3, such as automatic leveling control, for the leveler 2 as is.

[0045] Furthermore, if the tractor-side connector 11 includes a power supply terminal as well as a coupling mechanism control terminal, the tractor connector 93 includes a power supply terminal 97 that is connected to the power supply terminal. When the tractor-side connector 11 and the tractor connector 93 are connected, the power supply terminal 97 receives power supplied from the power supply terminal of the tractor-side connector 11. The signal conversion circuit 98 generates the coupling mechanism control signal using the power supplied that is input from the power supply terminal 97 when the tractor connector 93 and the tractor-side connector 11 are connected. As described above, when the rotary tiller 3 and the tractor 1 are connected, a feedback signal is generated from the rear cover sensor using power supplied from the power supply terminal of the tractor-side connector 11. In this way, the same connector connection between the rotary tiller 3 and the tractor 1 is used as is to achieve the same connector connection between the leveler 2 and the tractor 1. This eliminates the need for the converter 9 itself to have a power source, making it possible to achieve an inexpensive and easy-to-use device.

[0046] When the safety mode is cancelled by the control device 10, the mode changeover switch 91 is operated to set the reference setting mode, and after the safety mode is cancelled, the mode changeover switch 91 is switched from the reference setting mode to the normal operation mode by a user operation. When the reference setting mode is set, the signal conversion circuit 98 outputs a signal corresponding to the reference point from the signal output terminal 96, and when the normal operation mode is set, it outputs a linkage mechanism control signal based on the positioning height signal input from the signal input terminal 95 from the signal output terminal 96.

[0047] As a result, in tillage depth control, the control device 10 of the tractor 1 acquires a signal corresponding to the reference point output from the signal output terminal 96 via the coupling mechanism control terminal when the safety mode is released, and can set the reference point based on the content of that signal. Furthermore, after the safety mode is released, the control device 10 controls the coupling mechanism 5 in accordance with the coupling mechanism control signal based on the positioning height signal so that the signal indicates the neutral point, thereby raising and lowering the rotary tillage implement 3 (tilling depth control). In other words, in this embodiment, it is possible to perform leveling work by using the same tilling depth control content used when a rotary tillage implement 3 is connected to the tractor 1 even when a leveling implement 2 is connected, and as a result, GNSS leveling control can be achieved at low cost.

[0048] The signal conversion circuit 98 further includes a setting means for a converter-side neutral signal that is output as a signal corresponding to the neutral point from the signal output terminal 96 to the coupling mechanism control terminal of the tractor-side connector 11. The signal conversion circuit 98 can adjust the setting means in accordance with the user's adjustment operation of the adjustment dial 92 so that the converter-side neutral signal corresponds to the neutral point set in the control device 10 of the tractor 1.

[0049] Here, in tillage depth control, the tractor 1 (control device 10) sets the neutral point to a predetermined relative value with respect to the reference point, but when the leveling implement 2 is coupled, if the positioning height signal from the GNSS controller 71 corresponds to the neutral point (reference height), the converter 9 must output a coupling mechanism control signal (converter-side neutral signal) corresponding to the neutral point set by the control device 10 from the signal output terminal 96. In other words, the converter-side neutral signal set by the converter 9 must correspond to the neutral point set by the control device 10. On the other hand, the method for setting the neutral point may differ depending on the manufacturer of the tractor 1 or the type of the tractor 1. Therefore, the signal conversion circuit 98 includes a setting means for the converter side neutral signal, and by allowing the user to operate the adjustment dial 92, the setting means can be adjusted so that the converter side neutral signal corresponds to the neutral point set in the control device 10 of the tractor 1.This makes it possible to use the tillage depth control of the tractor 1 as is for GNSS leveling control, and furthermore, makes it possible to realize GNSS leveling control without being limited to the manufacturer or type of tractor 1. The details of the converter-side neutral signal setting means in the signal conversion circuit 98 will be described later.

[0050] [Signal conversion circuit] The signal conversion circuit 98 will be described below using a specific example. FIG. 6 is a circuit diagram showing a specific example of the signal conversion circuit 98. As shown in FIG. The signal conversion circuit 98 has variable resistors VR1, VR2, VR3 and VR4, a changeover switch SW1, and relays RL1 and RL2.

[0051] The variable resistors VR1, VR2, VR3, and VR4 are each connected in parallel to a power supply terminal 97 to which the supply voltage from the tractor 1 is input. The variable resistors VR1, VR2, VR3, and VR4 each have a voltage dividing terminal that divides and extracts the voltage input from the power supply terminal 97, and can each be called a voltage dividing resistor.

[0052] The changeover switch SW1 is a single-pole, double-throw switch and has a changeover terminal a connected to the voltage-dividing terminal of the variable resistor VR1, a changeover terminal b connected to the voltage-dividing terminal of the variable resistor VR2, and a common terminal c. The changeover switch SW1 is a circuit part of the mode changeover switch 91, and by operating the mode changeover switch 91, the changeover terminal connected to the common terminal c is switched between the changeover terminals a and b.

[0053] Relays RL1 and RL2 are c-contact type relays and include switches SW10 and SW20 and coils L10 and L20. Switches SW10 and SW20 each have a normally closed (NC) terminal, a normally open (NO) terminal, and a common terminal. The NC terminal of relay RL1 is connected to the common terminal c of the changeover switch SW1, and the NO terminal of relay RL1 is connected to the voltage-dividing terminal of variable resistor VR3. The NC terminal of relay RL2 is short-circuited, and the NO terminal of relay RL2 is connected to the voltage-dividing terminal of variable resistor VR4.

[0054] The common terminals of the switches SW10 and SW20 of the relays RL1 and RL2 are both connected to a signal output terminal 96. The coils L10 and L20 of the relays RL1 and RL2 are connected to a signal input terminal 95. The signal input terminal 95 includes a LO side input terminal 95-1 and a HI side input terminal 95-2, with the LO side input terminal 95-1 connected to the coil L20 of the relay RL2 and the HI side input terminal 95-2 connected to the coil L10 of the relay RL1. If the height indicated by the three-dimensional positioning data calculated by the GNSS controller 71 is higher than the reference height, an HI side control voltage (e.g., 12 (V)) is applied to the HI side input terminal 95-2 as a positioning height signal, and if it is lower than the reference height, an LO side control voltage (e.g., 12 (V)) is applied to the LO side input terminal 95-1 as a positioning height signal. If it is approximately the same as the reference height, no control voltage is applied to either terminal, or a voltage significantly lower than the HI side control voltage and the LO side control voltage is applied.

[0055] When the common terminal c of the changeover switch SW1 is connected to the changeover terminal b, the reference setting mode is set, and when the common terminal c of the changeover switch SW1 is connected to the changeover terminal a, the normal operation mode is set. When the reference setting mode is set, the common terminals and NC terminals of the switches SW10 and SW20 of the relays RL1 and RL2 are connected, so that the voltage-dividing terminals of the variable resistor VR2 are in a conductive state with the signal output terminal 96. As a result, the voltage divided by the voltage-dividing terminals of the variable resistor VR2 is output from the signal output terminal 96 as a signal corresponding to the reference point. For this reason, the voltage dividing terminals of the variable resistor VR2 are set so that the voltage of the signal corresponding to the reference point is output.

[0056] On the other hand, when the normal setting mode is set and neither the HI side control voltage nor the LO side control voltage is applied to the signal input terminal 95, the common terminal and the NC terminal of the relays RL1 and RL2 remain connected, and the voltage dividing terminal of the variable resistor VR1 is in a conductive state with the signal output terminal 96. As a result, the voltage divided by the voltage dividing terminal of the variable resistor VR1 is output from the signal output terminal 96 to the tractor 1 as a coupling mechanism control signal (converter side neutral signal). In this way, the voltage divider terminals of the variable resistor VR1 are set so as to output a voltage corresponding to the converter-side neutral signal. However, as described above, there is a possibility that a deviation may occur between the converter-side neutral signal and the neutral point set in the tractor 1, so in this embodiment, the voltage output from the voltage divider terminals of the variable resistor VR1 is adjustable. That is, the variable resistor VR1 includes a slider electrically connected to the voltage divider terminals, and the slider is configured to slide on the resistance element in response to rotation of the adjustment dial 92. This makes it possible to adjust the voltage corresponding to the converter-side neutral signal, so the variable resistor VR1 (including the slider and voltage divider terminals) corresponds to a converter-side neutral signal setting means.

[0057] When the normal setting mode is set and a HI side control voltage is applied to the HI side input terminal 95-2, the coil of relay RL1 is excited and the common terminal and NO terminal are connected, and the common terminal and NC terminal of relay RL2 remain connected, bringing the voltage-dividing terminal of variable resistor VR3 into conduction with signal output terminal 96. As a result, the voltage divided by the voltage-dividing terminal of variable resistor VR3 is output from signal output terminal 96 to the tractor 1 as a connecting mechanism control signal, and the control device 10 of the tractor 1 controls the connecting mechanism 5 to lower the leveling implement 2. For this reason, the voltage dividing terminals of the variable resistor VR3 are set so as to output a voltage corresponding to the coupling mechanism control signal that commands the leveler 2 to lower. In this case, the coupling mechanism control signal corresponds to a feedback signal that indicates that the height position of the rotary tiller 3 is higher than the neutral point when the rotary tiller 3 is coupled to the tractor 1.

[0058] On the other hand, when the normal setting mode is set and an LO side control voltage is applied to the LO side input terminal 95-1, the common terminal and NC terminal of relay RL1 remain connected, and the coil of relay RL2 is excited, connecting the common terminal and NO terminal, and the voltage-dividing terminals of variable resistor VR4 and variable resistor VR1 are brought into a conductive state with the signal output terminal 96. As a result, the potential difference (voltage) between both voltage-dividing terminals is output from the signal input terminal 95 to the tractor 1 as a connecting mechanism control signal, and the control device 10 of the tractor 1 controls the connecting mechanism 5 to raise the leveling implement 2. For this reason, the voltage dividing terminals of variable resistor VR4 are set so that the potential difference with the voltage dividing terminals of variable resistor VR1 becomes a voltage corresponding to the coupling mechanism control signal that commands the leveling implement 2 to rise. In this case, the coupling mechanism control signal corresponds to a feedback signal that indicates that the height position of the rotary tiller 3 is lower than the neutral point when the rotary tiller 3 is coupled to the tractor 1.

[0059] From the above, the signal conversion circuit 98 can be expressed as follows: That is, the signal conversion circuit 98 includes a first voltage dividing resistor (variable resistor VR4), a second voltage dividing resistor (variable resistor VR3), a third voltage dividing resistor (variable resistor VR1), and a fourth voltage dividing resistor (variable resistor VR2), each of which is connected in parallel to the power supply terminal 97 and has a voltage dividing terminal for dividing and extracting the voltage input from the power supply terminal 97, and a first switch circuit (relay RL2) for switching between a first state in which a voltage dividing terminal of the first voltage dividing resistor (variable resistor VR4) is in a conductive state and a second state in which a voltage dividing terminal of the first voltage dividing resistor (variable resistor VR4) is in a cutoff state based on the positioning height signal. a third state in which a conduction state is established between the voltage dividing terminal of the second voltage dividing resistor (variable resistor VR3) and the signal output terminal 96 and a cutoff state is established between the voltage dividing terminals of the third voltage dividing resistor (variable resistor VR1) and the fourth voltage dividing resistor (variable resistor VR2) and the signal output terminal 96, based on the positioning height signal, or a fourth state in which a cutoff state is established between the voltage dividing terminal of the second voltage dividing resistor (variable resistor VR3) and the signal output terminal 96 and a conduction state is established between the voltage dividing terminal of the third voltage dividing resistor (variable resistor VR1) or the fourth voltage dividing resistor (variable resistor VR2) and the signal output terminal 96 a second switch circuit (switch SW10 of relay RL1) that switches between either one of the first and second states, and a fifth state in which the voltage dividing terminal of the third voltage dividing resistor (variable resistor VR1) and the signal output terminal 96 are in a conductive state and the voltage dividing terminal of the fourth voltage dividing resistor (variable resistor VR2) and the signal output terminal 96 are in a cutoff state, in response to a user operation on the mode switching operation unit (mode switching switch 91) when the second switch circuit (switch SW10 of relay RL1) is in a fourth state; and a third switch circuit (changeover switch SW1) that switches the state to either a first state or a sixth state in which a voltage dividing terminal of the fourth voltage dividing resistor (variable resistor VR2) and the signal output terminal 96 are in a conductive state. When the reference setting mode is set, the first switch circuit (switch SW20 of relay RL2) is in the second state, the second switch circuit (switch SW10 of relay RL1) is in the fourth state, and the third switch circuit (changeover switch SW1) is in the sixth state. When the normal operation mode is set, when the positioning height signal corresponds to the lowering of the leveling machine 2,When the first switch circuit (switch SW20 of relay RL2) is in the second state and the second switch circuit (switch SW10 of relay RL1) is in the third state, and the positioning height signal corresponds to the elevation of the leveling implement 2, the first switch circuit (switch SW20 of relay RL2) is in the first state, the second switch circuit (switch SW10 of relay RL1) is in the fourth state, and the third switch circuit (changeover switch SW1) is in the fifth state, and when the positioning height signal indicates neutral, the first switch circuit (switch SW20 of relay RL2) is in the second state, the second switch circuit (switch SW10 of relay RL1) is in the fourth state, and the third switch circuit (changeover switch SW1) is in the fifth state. In this way, it is possible to realize, with a simple circuit configuration, the signal conversion circuit 98 that can output a coupling mechanism control signal corresponding to the reference point, a coupling mechanism control signal corresponding to the neutral point (converter-side neutral signal), a coupling mechanism control signal indicating a command to lower the leveling machine 2, and a coupling mechanism control signal indicating a command to raise the leveling machine 2. Furthermore, with such a circuit configuration, it is possible to make the device more robust than a complex circuit configuration using an IC (Integrated Circuit) or the like.

[0060] In the circuit example of Figure 6, for example, when the voltage supplied from the power supply terminal 97 is 5 (V), the voltage-dividing terminal of variable resistor VR2 is set so that the voltage of the connecting mechanism control signal corresponding to the reference point is 4.8 (V), the voltage-dividing terminal of variable resistor VR1 is set so that the voltage of the converter side neutral signal is 4.5 (V), the voltage-dividing terminal of variable resistor VR3 is set so that the voltage of the connecting mechanism control signal indicating a command to lower the leveling tool 2 is 5 (V), and the potential difference between the voltage-dividing terminal of variable resistor VR1 and the voltage-dividing terminal of variable resistor VR4 is set so that the voltage of the connecting mechanism control signal indicating a command to raise the leveling tool 2 is 3.5 (V). However, this embodiment is not necessarily limited to such voltage values.

[0061] [Leveler lift control using tillage depth control] Next, the lifting and lowering control of the leveling implement 2 using the tillage depth control by the control device 10 of the tractor 1 as it is when the leveling implement 2 is connected to the tractor 1 will be described.

[0062] At this time, the GNSS controller 71, the converter 9, and the control device 10 are connected. Specifically, the output connector 75 of the GNSS controller 71 is connected to the GNSS connector 94 of the converter 9, and the tractor connector 93 of the converter 9 is connected to the tractor-side connector 11 of the control device 10. The signal conversion circuit 98 of the converter 9 receives power from the power supply terminal of the tractor-side connector 11 via a power supply terminal 97 (tractor connector 93), uses that power and generates a coupling mechanism control signal based on the positioning height signal from the GNSS controller 71 input via a signal input terminal 95 (GNSS connector 94), and outputs this coupling mechanism control signal via a signal output terminal 96 (tractor connector 93) to the coupling mechanism control terminal of the tractor-side connector 11. This coupling mechanism control signal corresponds to a feedback signal from the rear cover sensor when the rotary tiller 3 is connected, and is a voltage signal in the range of 0 (V) to 5 (V), for example.

[0063] At the start of this control, the control device 10 sets the safety mode as the control mode for the coupling mechanism 5 by, for example, plugging or unplugging the tractor-side connector 11. Meanwhile, in this converter 9, the mode selector switch 91 sets the reference setting mode as the operating mode of the signal conversion circuit 98, and a coupling mechanism control signal corresponding to the reference point (a voltage divided by the voltage-dividing terminal of the variable resistor VR2 in FIG. 6) is output from the signal output terminal 96.

[0064] When the safety mode is released, the control device 10 acquires a coupling mechanism control signal corresponding to the reference point from the converter 9 via the coupling mechanism control terminal, and sets the reference point based on the content of the signal. Specifically, the control device 10 holds the voltage value of the acquired coupling mechanism control signal as the reference point. Next, the control device 10 sets the neutral point at a predetermined relative position (relative angle) with respect to the reference point. Specifically, the control device 10 adds a predetermined voltage value (for example, 0.5 (V)) to the voltage value held as the reference point and holds the resulting voltage value as the neutral point.

[0065] In the converter 9, the mode selector switch 91 is operated to switch the operation mode of the signal conversion circuit 98 from the reference setting mode to the normal operation mode. At this time, the positioning height signal from the GNSS controller 71 indicates the neutral point, so in the converter 9, a converter-side neutral signal (a coupling mechanism control signal corresponding to the neutral point) (a voltage divided by the voltage-dividing terminal of the variable resistor VR1 in FIG. 6) is output from the signal output terminal 96.

[0066] When the converter-side neutral signal input from the connecting mechanism control terminal indicates the neutral point set by the control device 10, the control device 10 controls the connecting mechanism 5 to stop the leveling machine 2 from moving up and down. On the other hand, if the converter-side neutral signal is out of sync with the neutral point set by the control device 10, the control device 10 controls the connecting mechanism 5 in accordance with the converter-side neutral signal to raise and lower the leveler 2, so the adjustment dial 92 of the converter 9 is operated until the leveler 2 stops. When the leveler 2 stops due to the converter-side neutral signal output from the converter 9, this means that the converter-side neutral signal has been adjusted to correspond to the neutral point set by the control device 10.

[0067] Thereafter, the converter 9 outputs a coupling mechanism control signal based on the positioning height signal from the GNSS controller 71 to the control device 10, and the control device 10 controls the coupling mechanism 5 in accordance with the coupling mechanism control signal input from the coupling mechanism control terminal to raise and lower the leveling machine 2. As a result, when the positioning height signal input from the GNSS controller 71 to this converter 9 indicates the reference height (neutral point), the leveling machine 2 stops moving up and down (is fixed), when the positioning height signal indicates that the height is lower than the reference height, the leveling machine 2 rises, and when the positioning height signal indicates that the height is higher than the reference height, the leveling machine 2 descends. According to this embodiment, the leveling implement 2 is lifted and lowered using the tillage depth control by the tractor 1, and the leveling implement 2 is pulled by the tractor 1 while being fixed at a height position corresponding to the neutral point, thereby allowing the entire field to be properly leveled.

[0068] [Variations] The above-described embodiment is an example. The leveling signal converter (the converter) 9 is not limited to the above-described configuration, and may be partially modified as appropriate or may further include other configurations as long as it has at least some of the above-described configurations.

[0069] For example, the circuit configuration of the signal conversion circuit 98 is not limited to the example shown in FIG. In the signal conversion circuit 98, when the reference setting mode is set, the voltage divided by the fourth voltage dividing resistor (variable resistor VR2) is output from the signal output terminal 96 as a signal corresponding to the reference point due to electrical continuity between the voltage dividing terminal of the fourth voltage dividing resistor (variable resistor VR2) and the signal output terminal 96, and when the normal operation mode is set, the voltage divided by one or more voltage dividing resistors is output from the signal output terminal 96 as a linkage mechanism control signal based on the positioning height signal due to electrical continuity between the voltage dividing terminal of one or more of the first voltage dividing resistor (variable resistor VR4), the second voltage dividing resistor (variable resistor VR3) or the third voltage dividing resistor (variable resistor VR1) and the signal output terminal 96. For example, unlike the example of Figure 6, the circuit configuration may be such that the connecting mechanism control signal corresponding to the reference point, the connecting mechanism control signal corresponding to the neutral point (converter side neutral signal), the connecting mechanism control signal indicating an instruction to lower the leveling machine 2, and the connecting mechanism control signal indicating an instruction to raise the leveling machine 2 each correspond to only one voltage dividing resistor (variable resistor) and are output by electrical continuity between each voltage dividing resistor and signal output terminal 96.

[0070] In addition, in the example of Figure 6, a variable resistor is used as an example of a voltage dividing resistor, but other resistance elements or resistance configurations may be used as long as they can divide the power supplied via the power supply terminal 97 and use it as a connection mechanism control signal. In addition, although the example of FIG. 6 uses relays RL1 and RL2, other switch configurations may be used. Furthermore, the LO side input terminal 95-1 and the HI side input terminal 95-2 of the signal input terminal 95 may be configured inversely. A HI side control voltage (e.g., 12 (V)) may be applied to the input terminal 95-1, and a LO side control voltage (e.g., 12 (V)) may be applied to the input terminal 95-2. In this case, the correspondence between the variable resistors VR3 and VR4 corresponding to the lowering command and the raising command of the leveling machine 2 is reversed.

[0071] Furthermore, the converter 9 can also be used when a specific work machine having both tilling and leveling functions is connected to the tractor 1. Furthermore, in this embodiment, it is assumed that the tractor-side connector 11 of the tractor 1 that is used when the rotary tiller 3 is connected is also used when the leveler 2 is connected, but the converter 9 can also be used for a tractor 1 that is provided with separate connectors for the rotary tiller 3 and the leveler 2. In this case, the tractor connector 93 of the converter 9 can be connected to the connector provided for the rotary tiller 3. [Explanation of symbols]

[0072] 1 Tractor, 2 Leveling implement, 3 Rotary tiller implement, 5 Implement coupling mechanism (coupling mechanism), 7 GNSS, 9 Leveling signal converter (this converter), 10 Tractor control device (control device), 11 Coupling mechanism control connector (tractor side connector), 15 Mechanism drive device, 17 Control unit, 21 Frame unit, 25 Leveling unit, 31 Tiller tines, 32 Tine cover, 33 Rear cover, 51 Lower link, 52 Lift link, 53 Lift arm, 54 Top link, 71 GNSS controller, 72 GNSS display unit, 73 GNSS antenna, 75 Output connector, 90 Main unit, 91 Mode selector switch, 92 Adjustment dial, 93 Tractor connector, 94 GNSS connector, 95 Signal input terminal, 95-1 LO side input terminal, 95-2 HI side input terminal, 96 Signal output terminal, 97 power supply terminal, 98 signal conversion circuit VR1 variable resistor, VR2 variable resistor, VR3 variable resistor, VR4 variable resistor, SW1 changeover switch, RL1 relay, RL2 relay, SW10 switch, SW20 switch, L10 coil, L20 coil

Claims

1. A tractor can be connected to a rotary tiller or leveling machine as a specific machine via a machine connection mechanism, and can raise and lower the specific machine by operating the machine connection mechanism. When the tractor is connected to the leveling machine, a positioning control device outputs a positioning height signal based on height information measured using a positioning satellite, and a leveling signal conversion device is connected between the tractor and the tractor, a signal input terminal for receiving the positioning height signal output from an output terminal of the positioning control device; a signal output terminal for outputting a coupling mechanism control signal for controlling the operation of the working machine coupling mechanism to a coupling mechanism control terminal of the tractor to which a signal corresponding to the tilling depth of the rotary tillage machine is input when the rotary tillage machine is connected to the working machine coupling mechanism; a signal conversion circuit for converting the positioning height signal input from the signal input terminal into the connection mechanism control signal; A signal conversion device for leveling work comprising:

2. a power supply terminal for receiving power from a power supply terminal of the tractor; a converter-side connector including at least the signal output terminal and the power supply terminal; Further comprising: The tractor has a tractor-side connector including at least the connection mechanism control terminal and the power supply terminal, and when the rotary tillage implement is connected to the implement connection mechanism, a signal corresponding to the tilling depth of the rotary tillage implement, which is generated in a rotary side device connected to the tractor-side connector using power supplied from the power supply terminal of the tractor-side connector, is input from the connection mechanism control terminal of the tractor-side connector, the signal conversion circuit generates the coupling mechanism control signal using the supply power input from the power supply terminal in a state in which the converter side connector and the tractor side connector are connected.

2. A signal conversion device for leveling as claimed in claim 1.

3. a mode switching operation unit that enables switching of an operation mode of the signal conversion circuit by a user operation; Further comprising: The tractor is capable of setting a safety mode as a control mode for the work machine coupling mechanism in which the specific work machine is fixed and not raised or lowered, and is capable of setting a reference point and a neutral point within a range of motion of the work machine coupling mechanism corresponding to the lifting and lowering range of the specific work machine, and when the safety mode is released, the tractor sets a reference point based on a signal input from the coupling mechanism control terminal, and further sets a neutral point based on the reference point, and controls the work machine coupling mechanism so that the lifting and lowering of the specific work machine is fixed at a certain height position when a signal corresponding to the set neutral point is input from the coupling mechanism control terminal, the mode switching operation unit is operated to set a reference setting mode as an operation mode of the signal conversion circuit when the safety mode is released, and is switched from the reference setting mode to a normal operation mode by a user operation after the safety mode is released; the signal conversion circuit outputs a signal corresponding to the reference point from the signal output terminal when the reference setting mode is set, and outputs the linkage mechanism control signal based on the positioning height signal from the signal output terminal when the normal operation mode is set.

3. A signal conversion device for leveling according to claim 2.

4. The signal conversion circuit includes: the power supply terminal further includes first, second, third and fourth voltage dividing resistors each connected in parallel to the power supply terminal and each having a voltage dividing terminal for dividing and extracting a voltage input from the power supply terminal, When the reference setting mode is set, a voltage divided by the fourth voltage dividing resistor is output from the signal output terminal as a signal corresponding to the reference point due to conduction between the voltage dividing terminal of the fourth voltage dividing resistor and the signal output terminal, When the normal operation mode is set, a voltage divided by one or more of the voltage dividing resistors based on the positioning height signal due to conduction between the signal output terminal and one or more of the voltage dividing terminals of the first, second or third voltage dividing resistors is output from the signal output terminal as the connection mechanism control signal.

4. A signal conversion device for leveling according to claim 3.

5. The signal conversion circuit includes: a first switch circuit that switches between a first state in which a conduction state is established between the voltage dividing terminal and the signal output terminal of the first voltage dividing resistor and a second state in which a conduction state is established between the voltage dividing terminal and the signal output terminal of the first voltage dividing resistor and the second state is switched off based on the positioning height signal; a second switch circuit which switches, based on the positioning height signal, between either a third state in which the voltage dividing terminal of the second voltage dividing resistor and the signal output terminal are in a conductive state and the voltage dividing terminals of the third and fourth voltage dividing resistors and the signal output terminal are in a cut-off state, or a fourth state in which the voltage dividing terminal of the second voltage dividing resistor and the signal output terminal are in a cut-off state and the voltage dividing terminal of the third or fourth voltage dividing resistor and the signal output terminal are in a conductive state; a third switch circuit which, when the second switch circuit is in a fourth state, switches, in response to a user operation on the mode switching operation unit, to either a fifth state in which the voltage-dividing terminal of the third voltage-dividing resistor and the signal output terminal are in a conductive state and the voltage-dividing terminal of the fourth voltage-dividing resistor and the signal output terminal are in a cut-off state, or a sixth state in which the voltage-dividing terminal of the third voltage-dividing resistor and the signal output terminal are in a cut-off state and the voltage-dividing terminal of the fourth voltage-dividing resistor and the signal output terminal are in a conductive state; Further comprising: When the reference setting mode is set, the first switch circuit is in the second state, the second switch circuit is in the fourth state, and the third switch circuit is in the sixth state, When the normal operation mode is set, when the positioning height signal corresponds to a lowering of the leveling machine, the first switch circuit is in the second state and the second switch circuit is in the third state, when the positioning height signal corresponds to a raising of the leveling machine, the first switch circuit is in the first state, the second switch circuit is in the fourth state and the third switch circuit is in the fifth state, and when the positioning height signal indicates neutral, the first switch circuit is in the second state, the second switch circuit is in the fourth state and the third switch circuit is in the fifth state.

5. A signal conversion device for leveling according to claim 4.

6. an adjustment operation unit that allows a user to adjust the neutral point; Further comprising: The signal conversion circuit includes: a converter-side neutral signal setting means for outputting a signal corresponding to the neutral point from the signal output terminal to the coupling mechanism control terminal of the tractor; The setting means is adjustable so that the converter side neutral signal corresponds to the neutral point set in the tractor in accordance with the adjustment operation by a user to the adjustment operation unit.

4. A signal conversion device for leveling according to claim 3.

7. The signal conversion circuit includes: the power supply terminal further includes first, second, third and fourth voltage dividing resistors each connected in parallel to the power supply terminal and each having a voltage dividing terminal for dividing and extracting a voltage input from the power supply terminal, When the reference setting mode is set, a voltage divided by the fourth voltage dividing resistor is output from the signal output terminal as a signal corresponding to the reference point due to conduction between the voltage dividing terminal of the fourth voltage dividing resistor and the signal output terminal, when the positioning height signal indicates a neutral point in a state in which the normal operation mode is set, a voltage divided by the third voltage dividing resistor is output from the signal output terminal as the connecting mechanism control signal due to conduction between a voltage dividing terminal of the third voltage dividing resistor and the signal output terminal; the third voltage dividing resistor is a variable resistor having a slider that moves in response to an adjustment operation by a user on the adjustment operation unit, the voltage dividing terminal of the third voltage dividing resistor is electrically connected to a slider of the variable resistor; 7. A signal conversion device for leveling according to claim 6.

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