JP2736884B2 - Harvester vehicle speed control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] TECHNICAL FIELD The present invention relates to a threshing section, a reaping section, etc.
The traveling speed is reduced according to the increase or decrease of the load in the working part of
The present invention relates to a vehicle speed control device for a harvester that automatically adjusts the speed. [0002] 2. Description of the Related Art Grain is cut while traveling on a field,
In a harvester for threshing and sorting rice to extract granules
Means that the load on the working units such as the reaping unit and threshing unit is
The amount of processed grain is mainly
Depends on the degree. Therefore, the load condition in the working unit is
It is kept close to its maximum allowable load, and
In order to obtain operational efficiency, based on the load
With a vehicle speed control device that automatically adjusts the running speed
There is a harvester. [0003] Such a vehicle speed control device is disclosed in the present application.
Publication of Japanese Patent Application Nos. 61-249848 and 61-304918
There is a light. These drive the running and working parts of the harvester
Speed control at rated speed (
(Ronas control)
The load on the working unit is
As the load, for example, the position of the fuel rack of the fuel injection pump
And according to the magnitude of the detected load, the traveling speed
Change the traveling speed adjustment position of the transmission so that
It is a configuration that closes. This vehicle speed control device
The engine speed is constant regardless of the load.
Is maintained and the traveling speed and the traveling speed adjustment position of the transmission match.
After changing the travel speed adjustment position.
Load prediction is possible and the engine power is
Harvesting work can be performed in a state where it is maintained near the power, and high work
The effect is that the efficiency can be realized. FIG. 6 shows the operation of the engine speed control unit.
Output characteristics of engine controlled isochronously by
Line to the output characteristic curve of the engine during normal operation.
It is shown. As shown by the solid line in this figure, the engine
When the rotation speed control is operating, the axis output is
Output E₀In the range up to
Rated speed N₀The Japanese Patent Application No. 61-
In the vehicle speed control device of 249848 and Japanese Patent Application No. 61-304918
The maximum output E₀Is indicated by the broken line in the figure.
On the output characteristic curve during rotation, the rated speed N₀Yo
Slightly lower rotational speed N₁Of shaft output occurring at
Value (rated output) E₁Set it to be slightly higher than
It is. This is the rated output E₁85% to 90% of
Vehicle speed control while maintaining a state in which a changing load is applied to the engine
Clogging in the threshing section during harvesting
Rated output E due to occurrence₁Excessive load exceeding
If it is added occasionally, without lowering the rotation speed
This is to make it acceptable. [0005] The vehicle speed control as described above.
For example, in a harvester equipped with a control device,
The vehicle speed manually, for example, when the
The engine may be decelerated or accelerated.
When the operation of the speed control unit is stopped, the engine speed
Suddenly changes to the speed corresponding to the accelerator position at that time.
It will greatly decrease or increase, and the handling cylinder and
Threshing section due to sudden change in the rotation speed of the conveying screw
May cause problems such as clogging of untreated grains
You. On the other hand, it is necessary to stop the operation of the engine speed control unit.
Transmission lever that changes the transmission speed adjustment position of the transmission
When the vehicle speed is reduced or increased by manual operation,
Since the engine speed does not change, clogging in the threshing section
Although the risk of occurrence of the
As a result, the rated output E₁Above the maximum output E₁With
Intermittent load may be applied to the engine. However, this
Also, the operation of the engine speed control unit
Is the rated speed N₀Is maintained by the worker
Notices excessive load on engine
The engine continues to operate and the engine is overloaded.
As a result of forcing a long operation, the engine failed.
Engine life without realizing it.
There was a fear. [0006] In addition, without running the harvester,
By manually feeding the harvested grain stalks to the grain section
When using this as a threshing machine,
Activates the engine speed control to keep the engine speed constant
It is advisable to do this while keeping
The culm is sent to the threshing unit at once, and the amount of culm fed becomes excessive.
If the engine is
There was a risk that the operation during the interim period would be forced. [0007] The present invention has been made in view of such circumstances.
Shift to the next mowing stroke while manually shifting gears
, When using a harvester as a stationary threshing machine, etc.
The engine for extended periods of overload
These are maintained at a constant speed without
To provide a harvester vehicle speed control device that can be performed
With the goal. [0008] SUMMARY OF THE INVENTION A harvester vehicle according to the present invention.
The speed control device controls the engine that drives the work unit and the traveling unit.
An engine that operates to maintain the detected value of the rotation speed at a predetermined rotation speed.
Manually change the running speed of the harvester equipped with
Automatically changing the adjustable speed of the transmission
Control to maintain the load on the working unit properly.
In the vehicle speed control device of the harvester to be controlled,
The engine speed control unit determines whether the output of the engine is
Checking the engine speed within the range of the first output or less
A first control mode operating to maintain the output value at a predetermined speed.
And a second power output of the engine exceeding the first power output.
The detected value of the engine speed within the range below the output
Switch to the second control mode that operates to maintain a constant speed.
And a work state of the work unit is detected.
A work condition detecting means;
When an operation state other than the
While stopping, the engine speed control unit
Means for instructing operation in the first control mode.
And features. In the present invention, it is used as a stationary threshing machine
If harvesting is not under normal conditions, such as when
Is recognized based on the detection result of each of the detection means
At the same time, the automatic change of the traveling speed
Check that the engine speed control does not exceed the rated output of the engine.
Command the operation in the first control mode in the force range. [0010] BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described with reference to its embodiments.
This will be described in detail with reference to the drawings. FIG. 1 shows a harvester according to the present invention.
Vehicle speed control device (hereinafter referred to as the device of the present invention)
FIG. 2 is a schematic right sectional view of the pass-through harvester, and FIG. 2 is a plan view. In the figure, reference numeral 1 denotes a pair of left and right traveling crawlers.
An aircraft mounted on the upper side of 2, 2 (only one side is shown)
The threshing section is located on the upper left side of the
3 and the driver's seat DS, grain tongue
The engine 7 and the engine 8 are installed in this order from the front.
The mowing part 4 is attached to the front side of the body 1 so as to be able to move up and down.
Have been. The traveling crawlers 2 and 2 include a main crawler (not shown).
Clutch, hydrostatic continuously variable transmission and separate left and right sides
The driving force of the engine 8 transmitted through the clutch
From the left and right at the same time or separately,
Reverse or turn. As the body 1 advances, the reaper 4
Grain stalks from between the pair of left and right dividers 41, 41
Is introduced, and the cereal stem is placed on the upper part of the cutting unit 4 in the axial direction leftward.
After the rotation of the raking reel 42 which is pivotally supported as the right direction,
While being pulled down toward the lower part of the reaper 4,
Is cut by the cutting blade 43 which moves repeatedly. Rear side of cutting blade 43
On the upper side of the platform 45 extended to the
Lateral transport with a spiral transport plate 44a formed on the peripheral surface
The auger 44 is axially supported with the axis length direction as the left and right direction,
The grains cut by the cutting blade 43 are moved by the action of the transport plate 44a.
On the platform 45 according to the rotation of the horizontal transport auger 44
Is transported laterally, and the rear part of the cutting unit 4 and the threshing unit 3
At the front end opening of feeder house 5 communicating with the front
Is transferred to the chain conveyor 50 and
Rear upper part in a state of being sandwiched between the bottom plate of Yida House 5 and
And threshing from the rear end opening of feeder house 5
It is designed to be introduced into the handling room 30 of the unit 3. The bottom plate of the feeder house 5 is provided with the feeder
The presence or absence of grain in the house 5, that is, the amount of grain sent to the threshing unit 3
Multiple grain sensors 51,51 ... to detect the presence
It is located side by side. As the grain sensors 51, 51, for example,
If the pressure receiving surface is installed facing the inside of the feeder house 5,
The feeder house 5 is connected to the chain conveyor 50 on the pressure receiving surface.
When the transported grain comes in contact with the grain,
Piezoelectric transducer that emits a signal at a level corresponding to pressure
A child can be used. The handling chamber 30 has a spiral shape on the peripheral surface of the cylinder.
Do not project a double pitch screw and a large number of teeth.
Screw handling cylinder 31
The grain introduced into the handling room 30 is
Due to the action of the screw, the rear
While being transported to the
You. After the threshing process, the grater is stretched under the drum 31.
After passing through the receiving net 33, it was arranged below the threshing unit 3.
It falls on the rocking sorting device 32, and rocks the device 32,
The wind is raised by the Karamin device 34 installed at the front of the bottom of 3
And the sorting wind blown as shown by the white arrow in FIG.
Specific gravity is selected by synergy. That is, a relatively specific gravity of the grated
The large granules are the first gutter 35 provided in the lower part on the upstream side of the sorting wind.
Dropped up and transported to the right, connected to the right end of this
It is conveyed upward in the fryer 35a,
Is stored. In addition, the second thing such as ear cutting grain, spike sticking grain,
On the second gutter 36 located downstream of the sorting gutter from the first gutter 35
And is conveyed to the right, and connected to the right end of
The transfer case 36a is transported upward and forward in the
Re-introduced to the front and reprocessed. More grated
The third thing such as straw waste and garbage contained in the
From the rear end of the screw handling cylinder 31
Downward to the end of the threshing unit 3 with the discharged straw etc.
It is discharged onto the field surface from the opening No. 3 37. [0016] As mentioned above, cutting and threshing, sorting
Speed of the harvester that performs
It depends on the traveling speed adjustment position of the continuously variable transmission.
You. Shift lever 60 for setting this traveling speed adjustment position
Is arranged on the operation column 6 provided on the left side of the driver seat DS.
The operator sitting in the driver's seat DS moves the lever 60 back and forth.
The traveling speed adjustment position is set to zero
Can be set in stages. Proximal pivot of shift lever 60
Is provided with a shift motor 17 for rotating the lever 60.
(See FIG. 3), the forward rotation of the shift motor 17
Or, in response to the reverse rotation, the travel speed adjustment position is
Alternatively, the speed is changed to the low-speed running side. Also strange
A travel speed adjustment position is located near the pivot of the speed lever 60.
When in the neutral position and when in the reverse position, respectively
On neutral switch 14 and reverse switch 15
(See FIG. 3). Operation Photoshop
The operating status of the engine 8 is displayed on the
Accelerator lever 61 for manually setting the state
Automatic switch 11 for commanding operation start (see Fig. 3)
Various levers and switches are provided. FIG. 3 is a block diagram showing the configuration of the apparatus of the present invention.
In the figure, 10 is a vehicle speed control unit, and 20 is an engine speed control.
It is your part. The engine speed control unit 20
The detection result of the rotation speed is the rated rotation speed N₀If different from
The fuel rack of the fuel injection pump (not shown)
The fuel supply to the engine 8
By controlling the engine speed, the number of revolutions of
Number of turns N₀The so-called isochrome that operates to match
It performs eggplant control, and its input side has an engine
8 rack position sensor 21 for detecting the current operating state;
An output signal of the engine rotation sensor 22 is provided. La
For example, the rack position sensor 21 is coaxial with the rack.
Output voltage corresponding to the position of the rack
Using a differential transformer as the engine rotation sensor 22
Is mounted on the output shaft of the engine 8, for example.
Rotary device that outputs a number of pulse signals corresponding to the number of rotations
Use an encoder. The input side of the engine speed control unit 20
Is an output port b of the vehicle speed control unit 10 as described later._FourMoving from
Operation start command signal is also output port b_FiveFrom Mor
Command signals are given. On the other hand, engine speed
The output of the control unit 20 is a rack actuator for moving the rack.
It is given to tuator 23. Rack actuator
23 corresponds to the output signal of the engine speed control unit 20, for example.
A linear solenoid that moves linearly
It is configured by attaching to The engine speed control unit 20 controls the engine speed.
The current rotation of the engine 8 according to the input signal from the sensor 22
Recognize the number, this is the rated speed N₀Showed a different value from
In this case, the detected rotation speed and the rack position sensor 21
Depending on the current rack position recognized by the input signal,
Based on the arithmetic expression stored in advance, the rated rotational speed N ₀
The target rack position where the rack should be located to obtain
Then, a signal corresponding to the calculation result is output. Laqua
The actuator 23 moves the rack to the target according to this signal.
It operates to move it to the rack position,
As a result of adjusting the fuel supply amount, the engine 8
Rated speed N₀Is maintained. The engine speed control unit 20 includes an engine
8 is the rated output E₁Reaches (first output)
The first control mode for performing the above operation in the output range up to
And rated output E₁Over 10%
Force E₀In the output range up to (second output),
And a second control mode for performing the operation. Fig. 4
In these first and second control modes, the engine speed control unit 20
Is an output characteristic curve of the engine 8 when
The middle dashed line indicates the first control mode, and the solid line indicates the second control mode.
Control mode. Selection of both control modes is vehicle speed control
Output port b of unit 10_FiveThe mode command signal input from
Signal, and if the signal is low level
The operation in the first control mode is
In some cases, the operation in the second control mode is selected respectively.
It has become so. On the other hand, the vehicle speed control unit 10
Running of the continuously variable transmission based on the current load detection result
Change the speed adjustment position to reduce the load on the engine 8
Load E ₁Within the preset range of about 85 to 90% of
In order to maintain it, the running speed is automatically adjusted.
Input port a₁The automatic switch 11 is connected to
The switch 11 is turned on by a worker sitting in the driver's seat DS.
Input port a when turned on₁Turns to high level
I will. Input port a_Two~ A_FourThreshing section 3
And means for detecting the current working state of the reaper 4 are connected.
Have been. That is, the input port a_TwoAnd input port a_ThreeTo
Means that a threshing clutch that engages and disengages power to the threshing unit 3 is engaged.
To the threshing switch 12 and the mowing unit 4 that are turned on when
When the mowing clutch that engages and disengages the power of the
Cutting switches 13 are connected to each other,
Switch 11 turns input port a_TwoBut the reaping switch
Input port a by turning on switch 12_ThreeTurned to high level respectively
Input port a_FourIs a comparator
 Connected to the output side of the comparator 51a.
Turn to a high level according to the bell output.
You. The + input of the comparator 51a is on the bottom plate of the feeder house 5.
A voltage obtained by superimposing the outputs of the grain sensors 51, 51,.
The negative input is set by the voltage divider 51b.
Is a predetermined voltage. Therefore, input port a
_FourAre transported grains on the pressure receiving surface of each of the grain sensors 51, 51.
Abuts and the output voltage is the voltage set by the voltage divider 51b
Higher, that is, the grain is fed to the threshing unit 3
High level if Therefore, the vehicle speed control unit 10 controls the input port a
_Two, A_Three, a_FourAre all high level, normal
The automatic switch 11 recognizes that harvesting is in progress.
Turns on the input port a₁Is at a high level
Only the vehicle speed control operation described later is performed. Input port a of the vehicle speed control unit 10_Five~ A₇To
Are connected to means for detecting the current running state of the harvester
Have been. That is, input port a_FiveAnd input port a₆To
Is the neutral switch 14 and the reverse switch 15
Are connected to each other, and when these switches are turned on,
Input port a_Five, a₆Without turning to a high level
And the vehicle speed control unit 10 has an input port a_FiveAnd a₆No
Recognizes that the vehicle is moving forward, backward, or stopped based on the bell
I do. Also, input port a₇The car that detects the traveling speed
An output signal of the speed sensor 16 is provided. Vehicle speed sensor 16
For example, the teeth fixed to the axle of the traveling crawler 2
The teeth of the car are detected by an electromagnetic pickup and the rotation of the axle is detected.
Uses a speed detector that outputs a pulse signal that is an integral multiple of the number of turns.
This pulse is counted for a predetermined time in the vehicle speed control unit 10.
Then, the vehicle speed is calculated from the counting result and recognized. Further, an input port a of the vehicle speed control unit 10₈In
An output signal of the rack position sensor 21 is given,
The vehicle speed control unit 10 determines the current rack position based on this signal.
recognize. The vehicle speed control unit 10 performs the control operation as described below.
The engine speed control unit 20 operates.
The engine 8 always has its rated speed N₀Keep in
The rack position is the output of the engine 8,
In other words, according to the load applied to the engine 8, the vehicle
The speed control unit 10 has an input port a₈Input signal to
The current load state of the gin 8 can be recognized. On the other hand, the output port b of the vehicle speed controller 10₁, B_Two
Does not show the shift motor 17 for rotating the gearshift lever 60.
Output port b
₁(Or output port b_Two) According to the high level output.
The lift motor 17 rotates forward (or reverse) and the traveling speed adjustment position
Is changed to the high-speed (or low-speed) running side, and the running speed of the harvester
The speed is increased (or decelerated). Come out again
Power port b_ThreeIndicates that the vehicle speed control unit 10 is in the operating state.
Connected to the vehicle speed lamp 18 to inform the worker,
Output port b_ThreeThe lamp 18 according to the high level output of
It is lit. Further, output port b_FourAnd b_FiveIs the engine
Connected to the input side of the
The gin rotation speed control unit 20 has an output port b_FourOut of the high level
Depending on the force, the output port b_FiveAt the level of
Control operation in the appropriate control mode.
You. The engine 8 has a rating in the vehicle speed control unit 10.
Revolution N₀If the vehicle speed and engine 8
And the working load of the threshing unit 3, reaping unit 4, etc.
Harvesting under various different loading conditions
As a plurality of load characteristic curves obtained by performing
It is stored in advance in the form of an approximate expression. And the vehicle speed control unit 10
Is the input port a₇Output of the vehicle speed sensor 16
The current vehicle speed is recognized by the force signal, and the input port
a₈According to the output signal of the rack position sensor 21
Recognizing the current load on the engine 8,
Select the load characteristic curve that corresponds to these recognition results
After that, on this selected load characteristic curve,
The load on the gin 8 is the rated output E₁About 85-90% of
Calculates the target vehicle speed within the predetermined range of
And the current vehicle speed, the target vehicle speed is higher (or lower)
If, increase (or decelerate) the vehicle speed
Input port a₇The current vehicle speed from the signal input to
And output until it matches the target vehicle speed.
Port b₁(Or b_Two) Is set to high level and shift mode
The data 17 is rotated forward (or reverse). This vehicle speed control unit 10
By operation, the engine 8 during harvesting is always rated
Output E₁Operation under appropriate load condition slightly smaller than
As a result, a highly efficient harvesting operation is realized. The vehicle speed control unit 10 configured as described above operates
According to the working conditions of the department and the running condition of the harvester
Thus, the operation as shown in the flowchart of FIG. 5 is performed. Vehicle speed
The control unit 10 first sets the input port a₁Before by the level of
Check the on / off status of the automatic switch 11, and
If 11 is off, its output port b_ThreeThe low level
The vehicle speed lamp 18 is turned off and its output port
Auto b_FourAt low level and the automatic switch 11 is turned on.
Wait until In this case, the engine speed control unit 20
Does not perform the control operation, so the product sitting on the driver's seat DS
The trader operates the shift lever 60 and the accelerator lever 61
To set the running speed appropriately and run the harvester.
Can be On the other hand, when the automatic switch 11 is turned on,
In this case, the vehicle speed control unit 10_ThreeTo a high level
To turn on the vehicle speed lamp 18, and the operator operates the vehicle speed control unit 10.
Notifies that the printer is in the working state, and outputs
_FourIs set to high level and operation is started by the engine speed control unit 20.
Command the beginning. And after this, it will be selected as described below
Engine speed according to the first or second control mode
By the operation of the control unit 20, the rotation position of the accelerator lever 61 is determined.
Regardless, the engine 8 has a rated output E₁Output up to
Range or rated output E₁Output E of about 10% increase₀
Up to the rated speed N₀At constant speed
I'm sullen. Next, the vehicle speed control unit 10 controls the input port a
_Two~ A_FourThe working state in the working part by the level of
You. And input port a_Two, A_ThreeIs at a high level,
It is detected that the threshing unit 3 and the mowing unit 4 are operating.
And input port a_FourIs at a high level and grain
Feeding of harvested cereal to threshing unit 3 is detected by sensors 51, 51 ...
If so, it is considered normal harvesting conditions.
And proceed to the next step, while selecting one of the above conditions.
If one is not satisfied, that is, input port a _Two~ A_Four
Is low level, the output port b
_FiveTo the low level, and the first
After the operation in the control mode is commanded, the vehicle speed control
Return to the first stage of the flowchart without performing any operation. If the above conditions are satisfied, the vehicle speed control
The control unit 10 then has its input port a_Five, A₆Depending on the level of
Check the running condition of the harvester. And input port a_Fiveor
Is a₆Is at a high level and the harvester is stopped
Or, if it is recognized that the vehicle is moving backwards,
B_FiveTo low level before the engine speed control unit 20
After instructing the operation in the first control mode, the vehicle speed control operation is started.
Return to the first stage of the flowchart without performing any operation. Conversely, output port a_Five, A₆Are both Lorebe
Where it is recognized that the harvester is advancing.
Then, the vehicle speed control unit 10
A flag that is set when the shift lever 60 is manually operated.
Check the setting state of the tag F, and if it is set
Has an output port b_FiveAs low level and engine rotation
Commanded the number control unit 20 to operate in the first control mode.
After that, the flowchart starts without performing the vehicle speed control operation.
Return to the stage. The flag is, for example, during a vehicle speed control operation.
A drive signal is supplied to the shift motor 17 to achieve the target vehicle speed.
The vehicle speed detected by the vehicle speed sensor 16
Set when the target vehicle speed does not match
It is automatically reset later. Then, the flag F is reset.
In this case, the vehicle speed control unit 10_FiveThe high level
In the second control mode, the engine speed control unit 20
Command, the vehicle speed sensor 16 and the rack position
Input port a from sensor 21 ₇And input port a₈Husband
We take in the signals that are input each time, and based on these,
Perform speed control operation. This operation of the vehicle speed control unit 10 allows the normal
During harvesting, manual operation of the shifting lever 60
If not, the engine speed control unit 20
2 is operated in the control mode 2, and the engine 8
The number of turns is the rated output E₁Greater than
E₀The harvest is kept constant until reaching
Excessive momentary addition to the threshing unit 3 or reaping unit 4 during work
The rotation speed of the engine 8 does not change even with the load.
No. On the other hand, after one cycle of reaping is completed,
When shifting gears 60 manually, such as when shifting
In this case, since the flag F is set,
Whether the number-of-turns control unit 20 operates in the first control mode
The output of the engine 8 is the rated output E₁Exceeding
There is no. The flag F is reset after a predetermined time has elapsed.
However, at that time, the supply of grain to the threshing unit 3 was already stopped.
State that the grain sensors 51,51… do not detect the fed grain
Input port a_FourBecomes low level
The engine speed control unit 20 is in the first control mode.
Harvesting of the next process is started, and the grain sensors 51,51
... is in the second control mode when it has detected the feed grain again
Transition. In the embodiment, a reel is provided.
About the case where the device of the present invention is applied to
Solid, but the device of the present invention can be applied to self-removing harvesters
Needless to say, the self-equipped
A place to use as a stationary threshing machine without running the demolding harvester
Gear shift lever 60 is in the neutral position,
Switch 14 is off, and the input port of the vehicle speed
Toa_FiveIs low level, so engine speed control
The unit 20 operates in the first control mode and the engine 8
Output E₁Does not occur. [0038] According to the present invention, an engine speed control unit is provided.
By switching and controlling the first and second control modes.
Harvester is used during harvesting or as a stationary threshing machine
Regardless of whether the load is increased,
Gin is not overloaded and engine life is
Deterioration and occurrence of a failure can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a right side sectional view of a conventional harvester equipped with the device of the present invention. FIG. 2 is a plan view of a conventional harvester equipped with the device of the present invention. FIG. 3 is a block diagram showing a configuration of the device of the present invention. FIG. 4 is a graph showing the output characteristics of the engine when the engine speed control unit operates in the first and second control modes. FIG. 5 is a flowchart for explaining the operation of the device of the present invention. FIG. 6 is a graph showing an output characteristic of an engine under isochronous control and an output characteristic of an engine during normal operation. [Description of Signs] 3 Threshing unit 4 Reaping unit 8 Engine 10 Vehicle speed control unit 11 Automatic switch 12 Threshing switch 13 Reaping switch 14 Neutral switch 15 Reverse switch 17 Shift motor 20 Engine speed control unit 51 Grain sensor 60 Shift lever

   ────────────────────────────────────────────────── ─── Continuation of front page    (56) References JP-A-57-174019 (JP, A)                 JP-A-57-63020 (JP, A)                 54-33339 (JP, U)

Claims (1)

(57) [Claims] Adjusting the traveling speed of a transmission capable of manually changing the traveling speed of a harvester having an engine speed control unit that operates to maintain the detected value of the engine speed for driving the working unit and the traveling unit at a predetermined speed. In a vehicle speed control device for a harvester that adjusts by automatically changing a position and controls to properly maintain a load on the working unit, the engine speed control unit may be configured so that an output of the engine is related to a characteristic of the engine. A first control mode in which the detected value of the engine speed is maintained at a predetermined value within a range equal to or less than the first output; and a second control mode in which the engine output exceeds the first output. Work state detection means for switching to a second control mode operating to maintain the detected value of the engine speed within the range at the predetermined speed, and for detecting the work state of the work unit; Condition Means for instructing the engine speed control section to operate in the first control mode when the detecting means detects an operation state other than the harvesting operation, and stopping the automatic change. A vehicle speed controller for a harvester.