JP3310596B2 - Agricultural tractor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling sensor for measuring the rolling angle of a traveling vehicle body by connecting a tilling device to a traveling vehicle body by driving a lifting actuator to be able to move up and down and by driving a rolling actuator to freely rotate. And a grounding sensor that measures the ground height based on the ground surface behind the tillage device, and drives the actuator to move the tillage device up and down by driving the actuator so as to maintain the measurement signal from the grounding sensor at a predetermined value. Regarding an agricultural tractor having a control device for performing automatic plowing depth control for maintaining the depth and a control device for performing rolling control for maintaining a rolling posture of a tillage device by driving a rolling actuator based on a signal from a rolling sensor, The present invention relates to an improvement in technology for changing the form of lifting control of a tilling device.

[0002]

2. Description of the Related Art Conventionally, there is an agricultural tractor constructed as described above, which is disclosed in Japanese Patent Publication No. Hei 6-71363. In this conventional example, the dead zone width of the plowing depth control is changed based on the vehicle speed. The form of the lifting control is changed by adjusting the operating speed of the cylinder for raising and lowering the tilling device.

[0003]

In a plowing operation with a tractor equipped with a tillage device, when the vertical distance of the tillage device with respect to the field scene fluctuates, the tillage device is raised and lowered and the tillage device with respect to the field scene is lifted. Control for maintaining the height at a predetermined value is performed. In addition, the fluctuation of the relative distance in the vertical direction of the tillage device with respect to the field scene is caused by such a phenomenon that a wheel falls into a concave portion such as a rut of a field or a wheel rides on a convex portion such as a mass of soil in a field. Is changed.

Further, when raising and lowering the tilling device when the posture of the vehicle body changes, it is necessary to quickly raise and lower the tilling device in conjunction with the speed of the posture change of the vehicle body to maintain the height of the tilling device with respect to the field scene. Although it is thought that it is effective in the point that the tillage device of a heavy object is lifted and lowered at a high speed in reality, not only a large capacity actuator is required, but also when the tillage device of a heavy object is operated at a high speed. It is also difficult to suppress the overshoot of the vehicle, and it is difficult to perform the lifting control that appropriately follows the field scene. In particular, when performing the tilling work by running the vehicle at a high speed in a rough field, the frequency of the vibration of the vehicle is large, and the amplitude of the vibration is large because the vehicle is oscillated in a short time. In such a situation, when the tillage device is moved up and down at a high speed for the purpose of elevating and lowering the tillage device following the field, the control appropriately following the field scene not only by the overshoot but also by the influence of the control delay is performed. It is difficult to perform the operation. For example, a phenomenon occurs in which the tilling device descends at a timing when the cultivation is required.

An object of the present invention is to rationally configure an agricultural tractor in which a field scene after plowing is flattened even when a plowing operation is performed by running a vehicle body at high speed in a rough field.

[0006]

A first feature of the present invention (claim 1) is that a drive actuator of a lifting / lowering actuator is mounted on a traveling vehicle body.
It can be moved up and down by moving, and the rolling actuator is driven
Tilling device is connected to the rolling body freely to prepare for the running vehicle
Rolling cell that measures the rolling angle of the
Sensor and ground height based on the ground surface behind the tillage device
And a ground sensor for measuring the measured value of the ground sensor.
Drive the lifting actuator to maintain the specified value and plow
Automatic tillage depth control to maintain the tillage depth of the tiller, and rolling
Rolling actuator based on sensor measurement
An automatic row driven to maintain the rolling posture of the tilling device
Agricultural tractors equipped with a control device that performs ring control
Therefore, the present invention is configured as follows. Travel of the traveling body
Equipped with a speed sensor that measures the speed, the traveling speed of the traveling vehicle
Is 3 to 4 km / h for rolling sensor measurement
The more severe the rough surface is, the more the automatic plowing
The vertical control speed becomes slow, and the vertical
Rolling of automatic rolling control with smaller troke
It is configured so that the switching operation is suppressed.

A second aspect of the present invention (claim 2), running
The vehicle can be moved up and down by driving the up / down actuator.
Rolling freely by driving a rolling actuator
Tillage device connected to the traveling vehicle body
Rolling sensor to measure rolling angle and tillage device
Grounding sensor that measures the ground height based on the ground surface behind
And maintain the measured value of the ground sensor at a predetermined value.
Drive the lifting actuator to maintain the tillage depth of the tillage device.
Automatic tillage depth control to maintain
Drives the rolling actuator based on the tillage device
Automatic rolling control to maintain the rolling posture
In a farm tractor equipped with a control device,
Consists in configuring. Speed for measuring the traveling speed of the traveling vehicle
Equipped with a degree sensor, the traveling speed of the traveling body is 3 to 4 km / h
The rolling frequency measured by the rolling sensor
The higher the degree, the lower the speed of automatic tillage control
As a result, the vertical stroke of the automatic
Rolling operation of dynamic rolling control is suppressed
It is composed.

A third aspect of the present invention (claim 3), running
The vehicle can be moved up and down by driving the up / down actuator.
Rolling freely by driving a rolling actuator
Tillage device connected to the traveling vehicle body
Rolling sensor to measure rolling angle and tillage device
Grounding sensor that measures the ground height based on the ground surface behind
And maintain the measured value of the ground sensor at a predetermined value.
Drive the lifting actuator to maintain the tillage depth of the tillage device.
Automatic tillage depth control to maintain
Drives the rolling actuator based on the tillage device
Automatic rolling control to maintain the rolling posture
In a farm tractor equipped with a control device,
Consists in configuring. Speed for measuring the traveling speed of the traveling vehicle
Equipped with a degree sensor, the traveling speed of the traveling body is 3 to 4 km / h
Rolling angle measured by a rolling sensor with a meter
The lower the speed of the automatic tillage control
As a result, the vertical stroke of the automatic
The configuration is such that the rolling operation of the rolling control is suppressed.
It has been done.

According to the first, second, and third features , when the traveling speed of the traveling vehicle body is increased during the automatic plowing depth control, the rolling frequency measured by the rolling sensor increases, or As the measured rolling angle increases, the control mode changing means changes the control mode in a direction to suppress the raising and lowering operation of the tillage device. The lifting operation is suppressed. That is, when the traveling speed of the vehicle body increases, the rolling angle of the vehicle body and the increase in the rolling frequency mean that the number of irregularities in the field scene per unit traveling distance is large, or that the height difference between the irregularities is large. In such a case, it is difficult to raise and lower the tilling device in a state of appropriately following the change in the posture of the vehicle body. By slowing the elevating operation without performing tilling, the tilling device descends at a timing that requires ascent, etc. Is flattened.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIGS. 1 and 2, an engine 4 is disposed at a front portion of a vehicle body 3 having a front wheel 1 and a rear wheel 2, and a transmission case 5 to which power from the engine 4 is transmitted is provided at a rear portion of the vehicle body 3. The driver's seat 7 is disposed at an intermediate position between the left and right rear fenders 6 above the transmission case 5, the steering handle 8 is disposed at the front of the driver's seat 7, and the driver's seat 7 is disposed at the rear end position of the vehicle body 3. A single-acting lift cylinder 11 is connected to the rotary tilling apparatus 10 via a two-point link mechanism 9 so as to be able to move up and down and roll freely, and is arranged at an upper position of the transmission case 5. The pair of left and right lift arms 12 and the two-point link mechanism 9, which are lifted and lowered by the drive of one example), are connected to each other via the left and right lift rods 13 to support the suspension in a suspended state. By interposing a double-acting rolling cylinder 14 (an example of the rolling actuator of claim 1) on the lift rod 13, the drive up and down of the rotary tilling device 10 and the drive rolling around the rolling axis X in the front-back direction can be achieved. Constitute a flexible agricultural tractor.

[0011] As shown in FIG.
The hydraulic system for driving up and down and driving rolling includes a hydraulic pump P driven by the engine 4, a flow priority valve 17 for flow control, and a control flow from the flow priority valve 17 for rolling. It comprises a rolling solenoid valve 18 for supplying to the cylinder 14 and an electromagnetic proportional control valve V for supplying surplus flow from the flow priority valve 17 to the lift cylinder 11 or discharging oil from the lift cylinder 11. The electromagnetic proportional control valve V includes a first valve 19 for ascending control,
Second valve 20 for pilot pressure control for opening and closing valve 19
And a third valve 21 for lowering control, a fourth valve 22 for pilot pressure control for opening and closing the third valve 21, and a relief valve 23. A current is supplied to the electromagnetic solenoid 20A of the second valve 20, and the first valve 19 is controlled by adjusting the supplied current.
As a result of the change of the pilot pressure acting on the valve, the opening of the valve is obtained in proportion to the current value, and the ascending speed is obtained in proportion to the opening. Has an electromagnetic solenoid 22A of the fourth valve 22
While supplying current to the
As a result of the change of the pilot pressure acting on the second valve 20, the opening degree of the valve is obtained in proportion to this current value, and a descending speed proportional to the opening degree is obtained.

In this agricultural tractor, the rotary tilling device 1
Automatic tillage depth control for maintaining 0 at a predetermined height based on a field scene (ground), position control for raising and lowering the rotary tillage device 10 to a predetermined height based on the vehicle body 3, and a rolling shaft in a front-back posture. Rotary tilling device 10 around core X
And the rolling tillage device 10 is maintained at a predetermined rolling posture, and the rotary tillage device 10 is raised to a predetermined height with respect to the vehicle body in preference to the three types of control. And a control system for performing forced ascent control for setting and maintaining the rolling posture.

The driver's seat 7 is controlled so as to perform automatic plowing depth control.
The control box 24 is provided on the upper surface of the rear fender 6 on the right side of the vehicle, and the control box 24 is provided with a potentiometer-type tillage depth setting device 25. Rear cover 10 configured to be swingable about axis Y
A potentiometer-type grounding sensor 26 that measures the ground height of the rotary tillage device 10 based on the field scene (ground surface) after plowing from the swing amount of A is provided. At the base end of a lift lever 27 disposed on the right side of the driver's seat 7 is provided a potentiometer type position setting device 28, and at the base end of the lift arm 12, a rotary tilling device 10 is provided based on the swing amount of the lift arm 12.
The control box 24 is provided with a potentiometer-type rolling angle setting device 30 so as to perform rolling control. A rolling sensor 31 for electrically measuring the amount of rolling of the vehicle body 3 in the left-right direction, a stroke sensor 32 for measuring the amount of expansion and contraction of the rolling cylinder 14 at a position near the rolling cylinder 14, and As shown in FIG. 4, the post portion 33 of the steering handle 8 is vertically operable so as to perform forced ascent control, and is urged to return to the neutral position N, as well as the ascending position U and the descending position. Forced lifting lever 3 operable with D
4 is provided, and a forced lifting switch 35 for detecting the operation direction of the lever 34 is provided at the base end of the lever 34. Further, in this agricultural tractor, as shown in FIG. 5, a pickup type that measures the running speed of the vehicle body from the rotation speed of the input shaft 38 of the differential device 37 with respect to the rear wheel 2 from the gear type transmission 36 incorporated in the transmission case 5. The speed sensor 39 is used for setting the control sensitivity of the automatic plowing depth control and the automatic rolling control as described later.

As shown in FIG. 6, the tillage depth setting device 25,
Grounding sensor 26, position setting device 28, lift arm sensor 29, rolling angle setting device 30, rolling sensor 31, stroke sensor 32, forced lifting switch 3
5. The control device 40 includes a system for inputting a signal from each of the speed sensors 39, and a system for outputting control signals to the electromagnetic proportional control valve V and the rolling electromagnetic valve 18.

The outline of the automatic cultivation depth control is as follows.
The lift cylinder 11 is driven to move the rotary tillage device 10 up and down so that the measurement value from the ground contact sensor 26 changes toward the value of the target plowing depth set in the above, and the dead zone set based on the target plowing depth is set. When the measured value from the ground sensor 26 reaches the signal area, the operation is set so as to stop the raising and lowering of the rotary tilling device 10, and the outline of the position control is the same as the target height set by the position setting unit 28. The rotary tilling device 10 is moved up and down by driving the lift cylinder 11 so that the signal from the lift arm sensor 29 changes toward the value, and the signal from the lift arm sensor 29 is moved to the signal range of the dead zone set based on the target height. The operation of stopping the elevation of the rotary tillage device 10 when a signal is reached is set. The outline of the automatic rolling control is the rolling angle. A ground rolling angle of the rotary tiller 10 set in Joki 30, rolling sensor 31
The target length of the rolling cylinder 14 is obtained based on the rolling angle of the vehicle body 3 in the left-right direction measured by the above-described method, and the value of the rolling cylinder 14 is changed toward the value of the target length. 14 and an operation of stopping the rolling control when a signal from the stroke sensor 32 reaches a signal zone of a dead zone set based on the target length. By operating the lever 34 to the ascending position U, the rotary tiller 10 is raised until a signal from the lift arm sensor 29 reaches a signal range of a dead zone set based on a preset upper limit as a reference, and automatic rolling control is performed. When the rotary tilling device 10 is in a state of being inclined with respect to the vehicle body 3, it reaches a posture without inclination with respect to the vehicle body 3. Is intended to drive the rolling cylinder 14 to the lowering position D the forcible lift lever 34
To perform the control to lower the rotary tillage device 10 to the height before the forced ascent control is performed (to the height at which the automatic tillage control is performed when the forced ascent is performed in the automatic plowing control state). Has become.

Further, this agricultural tractor is configured to be capable of automatic plowing depth control in a relatively high-speed running state of 3 to 4 km / h (conventionally, the limit is about 1.8 km / h). When the vehicle body 3 is driven at a high speed in a field scene in which many irregularities due to ruts are formed like a headland and an automatic rolling control is performed simultaneously with an automatic plowing depth control, a plowing operation is performed. When the vehicle body 3 rolls a lot in a short time based on the above, or when the vehicle body 3 rolls a lot, the raising and lowering operation and the rolling operation in the automatic plowing depth control and the automatic rolling control are suppressed, so that the field after plowing is controlled. The surface is configured to be flat, and the control operation thereof will be described below.

When performing the automatic plowing depth control and the automatic rolling control, a parameter setting routine is executed prior to these controls to obtain data necessary for the control. That is, as shown in the flowchart of FIG. 7, first, a signal from the speed sensor 39 is input to determine whether the traveling speed of the vehicle body 3 is equal to or higher than the set value (Steps # 101 and # 102). In some cases, the rolling sensor 3
The signal from 1 is input and the number of times of rolling (frequency) per unit time and the rolling angle are measured, and it is determined whether any of them is greater than a set value. , The valve drive parameters and the dead zone parameters are set based on the table data, and the sampling parameters used for the automatic rolling control are set based on the table data (steps # 103 to # 107). Further, when the traveling speed of the vehicle body 3 measured by the speed sensor 39 is equal to or less than the set value, and when the rolling frequency (frequency) measured by the rolling sensor 31 per unit time and the rolling angle are both set values. If it is below, each of the valve drive parameter and the dead zone parameter is set to the initial value (# 108 step).

In step # 106, the table data for setting each of the valve drive parameter and the dead zone parameter includes large values of the measured value (vehicle speed), the number of rolling times (frequency), and the rolling angle measured by the speed sensor 39. The characteristic is set so as to reduce the flow rate of the hydraulic oil supplied / discharged by the electromagnetic proportional control valve V and at the same time expand the dead zone (width) (see the graph in the same step), and the number of rolling ( Frequency) or, if the rolling angle is greater than or equal to the set value, this rolling frequency,
Alternatively, the valve drive parameter and the dead zone parameter are read from the table data based on the rolling angle and the traveling speed of the vehicle body 3, and if both the number of times of rolling (frequency) and the rolling angle are equal to or larger than the set values, the rolling is performed. The valve drive parameters and the dead zone parameters are read from the table data based on the number of times (frequency), the rolling angle, and the running speed of the vehicle body.

Further, as the valve drive parameter increases, the power supplied to the electromagnetic proportional control valve V decreases as the number of rolling times (frequency) increases, as the rolling angle increases, or as the traveling speed increases. It is a numerical value for determining the duty ratio for reducing the opening degree of the valve V, and the dead zone parameter increases as the number of times of rolling (frequency) increases or as the rolling angle increases.
Alternatively, it is a numerical value for expanding the area (width) of the dead zone set based on the target plowing depth as the traveling speed increases.

In step # 107, the table data for setting the sampling parameters is such that the larger the measured value of the speed sensor (vehicle speed), the measured value of the number of times of rolling (frequency), and the measured value of the rolling angle, the larger the value in the unit time. The characteristic is set so as to increase the number of times of sampling. If the number of times of rolling (frequency) or the rolling angle is equal to or larger than a set value, the rolling frequency or the rolling angle and the traveling speed of the vehicle body 3 The sampling parameter is read from the table data based on the number of times (frequency) and the rolling angle are both equal to or greater than a set value, and based on the number of times of rolling (frequency), the rolling angle, and the traveling speed of the vehicle body. The sampling parameters are read from the table data.

In step # 108, the initial values set for each of the valve drive parameter and the dead zone parameter are preset numerical values. When the vehicle speed is low, or even when the vehicle speed is high, the number of times of rolling (frequency If the measured value of (1) and the measured value of the rolling angle are smaller than predetermined values, appropriate automatic lifting control and automatic rolling control are enabled.

As shown in the flowchart of FIG. 8, in the automatic tillage depth control, a signal from the tillage depth setting device 25 is input to set a target tillage depth, and based on the dead zone parameter based on the target tillage depth. Set the dead zone of the area (# 20
1, # 202 step) Further, a signal from the ground contact sensor 26 is input, and it is determined whether or not this signal value is set as described above and is within the dead zone of the target plowing depth. If the control is not performed and the power is outside the dead zone, the intermittent power of the duty ratio based on the valve drive parameter is changed to the electromagnetic proportional control valve V
, The tillage device is raised and lowered (steps # 203 to # 205). Steps # 202 and # 205 are an example of the control mode changing means E in claim 1. In step # 202, the range of the dead zone is expanded to suppress the elevation operation, and in step # 205 , the control valve V is controlled. through is set in the form to suppress the lifting operation by reducing the amount of hydraulic oil supply and discharge it.

As shown in the flowchart of FIG. 9, in the automatic rolling control, a signal from a rolling angle setting device is input, a measurement signal is input from a rolling sensor at a cycle based on the sampling parameter, and the measurement signal is averaged. Then, the target length of the rolling cylinder is calculated and obtained from the deviation between the processing result and the signal from the rolling setter (# 301 to # 304 steps).
In the averaging process, a sum of sampled data is obtained, and an average value is obtained by dividing (dividing) the value of the sum by the number of times of sampling.

Next, a dead zone of a range based on the parameter is set based on the target length, a signal from the stroke sensor 32 is input, and it is determined whether or not this signal value is within the dead zone of the target length. If it is within the dead zone, the rolling control is not performed, and if it is outside the dead zone, the intermittent power based on the valve drive parameter is supplied to the rolling solenoid valve 18 to perform rolling of the tilling device (#). 305 to # 208 steps).

As described above, according to the present invention, when the traveling speed of the vehicle body 3 is equal to or higher than the predetermined value, the degree of roughness (the degree of unevenness) of the field scene is determined based on the signal from the rolling sensor 31, and the roughness is severe. In this case, as the degree of roughness is worse, the start of lifting and lowering of the rotary tilling device 10 is delayed, and the end of raising and lowering is accelerated to reduce the lifting stroke of the rotary tilling device 10. As a result, it is possible to prevent an overshooting operation following a field scene, thereby suppressing the occurrence of overshoot, and at the same time, preventing an operation in a reverse direction such as a descent of the rotary tillage device 10 at a timing requiring ascent. And the field scene after plowing can be flattened.

[Alternative Embodiment] In the above embodiment, the data for setting the opening of the valve and the data for setting the dead zone are obtained from preset table data. However, in the present invention, the traveling speed, the number of rolling ( Frequency) and the rolling angle. It is also possible to implement the control mode changing means for suppressing the rolling operation only by limiting the supply / discharge amount of the hydraulic oil or by expanding the dead zone.

[0027]

Therefore, even when tilling work is performed by running the vehicle at high speed in a rough field, the unevenness of the field scene is determined based on the measurement result of the rolling sensor, and the control mode is changed to change the control mode. Thus, the agricultural tractor in which the field scene after plowing is flattened irrespective of the unevenness of the tractor is rationally configured .

[Brief description of the drawings]

FIG. 1 is an overall side view of an agricultural tractor.

FIG. 2 is a rear view of the agricultural tractor.

FIG. 3 is a hydraulic circuit diagram of a lifting system and a rolling system.

FIG. 4 is a side view showing an arrangement of a forced lifting lever.

FIG. 5 is a schematic diagram of a transmission system showing an arrangement of a speed sensor.

FIG. 6 is a block circuit diagram of a control system.

FIG. 7 is a flowchart of a parameter setting routine.

FIG. 8 is a flowchart of automatic plowing depth control.

FIG. 9 is a flowchart of automatic rolling control.

[Explanation of symbols]

 Reference Signs List 3 Running body 10 Tilling device 11 Elevating actuator 14 Rolling actuator 26 Ground sensor 31 Rolling sensor 39 Speed sensor 40 Control device

Continuation of the front page (56) References JP-A-5-103502 (JP, A) JP-A-3-198701 (JP, A) JP-A-3-193517 (JP, A) JP-A-63-129904 (JP) , A) Japanese Utility Model Hei 5-31505 (JP, U) Japanese Utility Model Application 57-97734 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) A01B 63/10 A01B 63/114

Claims (3)

(57) [Claims] 1. A tilling device is connected to a traveling vehicle body so as to be able to move up and down by driving an elevation actuator and to rotate freely by driving a rolling actuator, and is provided on the traveling vehicle body to measure a rolling angle of the traveling vehicle body. and rolling sensor, a ground sensor which measures the ground height relative to the rear of the ground surface of the plow, the <br/> lift actuator so as to maintain the measured value of the ground sensor to a predetermined value and automatic plowing depth control drive to achieve maintenance of Kofuka of the plow, the maintenance of the said rolling actuator driven based on a rolling sensor measurements <br/> rolling posture of the <br/> plow An agricultural tractor comprising a control device for performing automatic rolling control and a speed sensor for measuring a traveling speed of the traveling vehicle body, The running speed is 3 to 4 km / h,
Ground surface determined based on the measurement of the rolling sensor
The lower the roughness, the lower the elevating speed of the automatic plowing control
The vertical stroke of the automatic tillage control is small
And the rolling operation of the automatic rolling control is suppressed.
Agricultural tractor that is configured to be used. 2. A lift actuator for a traveling vehicle body.
It can be moved up and down by driving, and the driving of the rolling actuator
The tillage device is connected to the rolling body by rolling freely, and the rolling angle of the traveling body is provided on the traveling body.
And a rolling sensor for measuring the
A ground contact sensor that measures the ground height based on the ground surface
The ground sensor so as to maintain the measurement value of the ground sensor at a predetermined value.
Drive the lifting actuator to maintain the plowing depth of the tillage device
Automatic tillage depth control and the measured value of the rolling sensor
Driving the rolling actuator based on the
Automatic rolling to maintain the rolling posture of the tilling device
An agricultural tractor provided with a control device for controlling the vehicle , comprising a speed sensor for measuring a traveling speed of the traveling vehicle , wherein the traveling speed of the traveling vehicle is 3 to 4 km / h.
Rolling frequency measured by the rolling sensor increases
The lower the vertical speed of the automatic plowing control
Thus, the vertical stroke of the automatic plowing control is reduced,
The rolling operation of the automatic rolling control is suppressed.
Agricultural tractor configured as follows. 3. A lift actuator for a traveling vehicle body.
It can be moved up and down by driving, and the driving of the rolling actuator
The tillage device is connected to the rolling body by rolling freely, and the rolling angle of the traveling body is provided on the traveling body.
And a rolling sensor for measuring the
A ground contact sensor that measures the ground height based on the ground surface
The ground sensor so as to maintain the measurement value of the ground sensor at a predetermined value.
Drive the lifting actuator to maintain the plowing depth of the tillage device
Automatic tillage depth control and the measured value of the rolling sensor
Driving the rolling actuator based on the
Automatic rolling to maintain the rolling posture of the tilling device
An agricultural tractor provided with a control device for controlling the vehicle , comprising a speed sensor for measuring a traveling speed of the traveling vehicle , wherein the traveling speed of the traveling vehicle is 3 to 4 km / h.
The rolling angle measured by the rolling sensor increases.
The lower the elevating speed of the automatic plowing control,
The vertical stroke of the automatic plowing control is reduced,
Rolling operation of automatic rolling control is suppressed
Agricultural tractor.