Patent Publication Number: US-2022210973-A1

Title: Combine

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the United States national phase of International Application No. PCT/JP2020/019934 filed May 20, 2020, and claims priority to Japanese Patent Application Nos. 2019-119006 filed Jun. 26, 2018, and 2019-121787 filed Jun. 28, 2019, the disclosures of which are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a combine. 
     2. Description of Related Art 
     Conventionally, there is a combine that can calculate a unit yield, which is a grain yield per unit plot in a cultivated field. 
     In advanced cultivated field management supported by computers, the yield distribution per unit plot in the cultivated field is important data. Therefore, a combine according to WO 2016/147521 (Patent Document 1) includes a yield measuring device, for example. Before the grains obtained by threshing reaped stalks reaped from the cultivated field while the combine is travelling are stored in a grain tank, the amount of grain is measured by a yield measuring device. Based on the amount of grain thus measured, a unit travel yield, which is the yield per unit mileage, is calculated, and yield map data is obtained from this unit travel yield and harvest travel positions (travel locus) calculated by a GPS unit. The yield measuring device is configured to measure the grain that has been conveyed from the threshing apparatus and has been input to the grain tank. Therefore, a yield, which is the amount of grain obtained in a unit plot at a harvest position (cultivated field position) calculated by the GPS unit, is assigned to the unit plot, considering the time delay between the time at which stalks are harvested and the time at which yield is measured. 
     In a combine, such a time delay is not necessarily constant. That is, in threshing processing performed by a combine, as shown in JP 2003-284424A (Patent Document 2), for example, the opening degree of a chaff sheave is adjusted and the volume of sorting air blown from a fanning mill is adjusted through grain sort control for preventing straw from being mixed in with the grains to be stored in the grain tank, as much as possible. Grain sort performance is improved by adjusting the opening degree of the chaff sheave and the wind power of the fanning mill based on a threshing condition. However, if the processing amount of the second product to be threshed is increased as a result, the delay time between the time at which stalks are harvested and the time at which yield is measured changes, and an error will occur in the assignment of yield at the harvest position. 
     Conventionally, there is a combine that can calculate a unit yield, which is a grain yield per small plot in a cultivated field. 
     A combine according to JP 2005-278539A (Patent Document 3) includes a yield measuring unit that measures the flow rate of grains obtained through threshing, flowing into a grain tank, and a machine body position measuring means for measuring the position of the machine body in a cultivated field. The yield measured by the yield measuring unit indicates the yield at a time that is early than the time of this yield measurement (the time at which the yield is measured by the yield measuring unit) by a predetermined time (delay time). This delay time is the total of threshing processing time, conveyance time that is taken to convey grains to the yield measuring unit, and so on. Considering such a situation, the yield measured by the yield measuring unit is corrected to be the yield in the cultivated field&#39;s small plot in which the machine body was located at the time that is earlier than the time of the yield measurement by the delay time. The yield increases from zero at the start of reaping of stalks, and therefore it is difficult to stabilize the yield. However, the combine according to Patent Document  3  does not take such a situation into consideration. If the reaping start area is located at the position of the machine body as of the time that is earlier than the time of the yield measurement by the delay time, the yield assigned to the small plot will include an error, and an accurate yield distribution for the entire cultivated field cannot be obtained. 
     In order to solve the problem in Patent Document 3, the combine according to JP 2017-060443A (Patent Document 4) includes a unit yield correction unit that corrects the unit yield at the start of reaping upon detection of the start of reaping of planted stalks by a reaping part. This unit yield correction unit replaces the unit yield corresponding to the small plot at the start of reaping of planted stalks with the unit yield measured in the next small plot. As a result, the measured yield value corresponding to the start of reaping may deviate from the actual value. 
     Patent Document 1: WO 2016/147521 
     Patent Document 2: JP 2003-284424A 
     Patent Document 3: JP 2005-278539A 
     Patent Document 4: JP 2017-060443A 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a combine capable of calculating the yield per unit plot in a cultivated field as accurately as possible regardless of the state of threshing. 
     In the combine according to Patent Document 4, the yield assigned to a small plot at the start of reaping is replaced with the yield assigned to the next small plot, and therefore, in order to obtain an accurate yield distribution in the entire cultivated field, it is a prerequisite that the yields of the small plots continuous from the reaping start position are substantially the same. Also, if the small plot length is short, the yield assigned to the next small plot at the start of reaping may include the same error as the first small plot at the start of reaping. 
     For this reason, there is demand for a combine that employs a yield correction technique that makes the yield assigned to the small plot at the start of reaping more accurate. 
     A combine according to the present invention includes: a reaping unit that reaps planted stalks; a threshing apparatus including a threshing cylinder unit that processes reaped stalks and a sort unit that swings to sort grains falling from the threshing cylinder unit; a grain tank that stores grains sorted by the sort unit; a yield measuring device that measures an amount of grain put in the grain tank; a unit yield calculation unit that calculates a unit yield per unit plot in a cultivated field based on the amount of grain; an opening degree adjustment unit that adjusts an opening degree of a chaff sheave of the sort unit in accordance with a threshing state of the threshing apparatus; a mode setting unit that sets a yield accuracy priority mode in which priority is given to accuracy of the unit yield calculation performed by the unit yield calculation unit; and a yield accuracy maintenance unit that in response to the mode setting unit setting the yield accuracy priority mode, forcibly fixes the opening degree of the chaff sheave at a specific opening degree in preference to the opening degree as adjusted by the opening degree adjustment unit. 
     Also, regarding a yield calculation method for calculating the yield of a combine according to the invention, the combine includes a reaping unit that reaps planted stalks; a threshing apparatus including a threshing cylinder unit that processes reaped stalks and a sort unit that swings to sort grains fallen from the threshing cylinder unit; a grain tank that stores grains sorted by the sort unit; and a yield measuring device that measures an amount of grain put in the grain tank, the yield calculation method including: calculating a unit yield per unit plot in a cultivated field, using the amount of grain; adjusting an opening degree of a chaff sheave of the sort unit in accordance with a threshing state of the threshing apparatus; setting a yield accuracy priority mode in which priority is given to accuracy of the unit yield calculation performed in the unit yield calculation step; and in response to the yield accuracy priority mode being set in the mode setting step, forcibly fixing the opening degree of the chaff sheave at a specific opening degree in preference to the opening degree as adjusted in the opening degree adjustment step. 
     With this configuration, when the yield accuracy priority mode is set, the opening degree of the chaff sheave of the sort unit is fixed at the specific opening degree, and thus the amount of the second product that varies depending on the opening degree of the chaff sheave becomes substantially constant or decreases to a negligible degree. As a result, variation of transit time (variation of delay time) from the time of harvest to the time of yield measurement, which is caused by variation in the ratio between the amount of grain sent to the grain tank as the first product and the amount of grain sent to the grain tank as the second product in the threshing apparatus, is substantially eliminated. As a result, the unit yield calculated by the unit yield calculation unit is accurately assigned to the harvest plot (reaping plot). 
     The opening degree of the chaff sheave is set based on the growth state of the stalks to be harvested for each cultivated field, and therefore it is preferable that the specific opening degree used in the yield accuracy priority mode is also set at least for each cultivated field. Therefore, in one preferable embodiment of the present invention, the specific opening degree is selectable. 
     In addition to adjusting the opening degree of the chaff sheave, for example, the wind power of the sorting wind produced by the fanning mill is also changed in order to optimize the threshing performance in the combine. If the ratio between the amount of the first product and the amount of the second product varies due to frequent changes in the wind power of the sorting wind, the transit time of the grains from the time of harvest to the time of yield measurement also varies, and the assignment of yields to harvest plots may be inaccurate. This problem is solved by keeping the wind power of the sorting wind constant. Therefore, a preferable embodiment of the present invention includes a wind power changing unit that changes the wind power of a fanning mill that supplies sorting wind to the sort unit, and in response to the mode setting unit setting the yield accuracy priority mode, the yield accuracy maintenance unit forcibly fixes the wind power of the fanning mill at a specific wind power in preference to the wind power adjusted by the wind power adjustment unit. Furthermore, if a configuration in which the specific wind power is selectable is employed, the sorting wind power can be fixed at a value that is suitable for the growing state of the planted stalks for each cultivated field. 
     When the reaping unit is in the non-reap work state, the reaped stalks are not supplied to the threshing apparatus except immediately after the transition from the reap work state to the non-reap work state. Therefore, there is no need to fix the threshing control parameters (the opening degree of chaff sheave and the rotation speed of the fanning mill) in the yield accuracy priority mode. Therefore, in one preferable embodiment of the present invention, the mode setting unit has a function of determining whether the reaping unit is in a reap work state or a non-reap work state, and sets the yield accuracy priority mode when the reaping unit is in the reap work state, and cancels the yield accuracy priority mode when the reaping unit is in the non-reap work state. 
     One preferable method for determining the reap work state or the non-reap work state of the reaping unit is to use a signal from a stalk detection sensor that detects the presence of reaped stalks. The stalk detection sensor can be formed using a contact type sensor such as a limit switch or a non-contact type sensor that employs light or ultrasonic waves. One preferable embodiment of the present invention includes a stalk detection sensor that detects presence or absence of the reaped stalks in the reaping unit or the threshing apparatus, wherein in response to the stalk detection sensor detecting the absence, the mode setting unit determines that the reaping unit is in the non-reap work state. 
     Even if the grain detection sensor detects a transition from the presence of reaped stalks to the absence of reaped stalks, i.e., the transition from the reap work state to the non-reap work state of the reaping unit, grains and stalks still remain in the sorting area of the threshing apparatus immediately after the transition. Considering such temporary retention, one preferable embodiment of the present invention includes a stalk detection sensor that detects presence or absence of the reaped stalks in the reaping unit or the threshing apparatus, wherein, after the stalk detection sensor detects the absence, the mode setting unit determines upon a predetermined period of time elapsing that the reaping unit is in the non-reap work state. Alternatively, in response to the stalk detection sensor detecting the absence, the mode setting unit determines upon a certain distance being travelled that the reaping unit is in the non-reap work state. 
     A combine that can travel automatically, which has begun to spread in recent years, can calculate the self-position thereof, using satellite radio waves, or the like. Furthermore, by using a cultivated field map and a travel locus, it is possible to detect that the reaping unit has entered a non-work area from a work area. Therefore, one preferable embodiment of the present invention includes a self-position calculation unit that detects entrance of the reaping unit from a work area into a non-work area in a reap work passage, wherein the mode setting unit determines upon the self-position calculation unit detecting the entrance of the reaping unit into the non-work area that the state is the non-reap work state. 
     A yield calculation program according to the present invention causes a computer to carry out the yield calculation method according to the present invention. A computer-readable recording medium according to the present invention is a computer-readable recording medium on which the yield calculation program according to the present invention is recorded. 
     A combine according to the present invention includes: a reaping unit that reaps planted stalks from a cultivated field; a threshing unit that threshes stalks reaped by the reaping unit; a grain tank that stores grains threshed by the threshing unit; a yield measuring unit that measures, as a measured yield, an amount of grain sent from the threshing unit to the grain tank; a yield assigning unit that assigns, to a measurement point that is calculated with use of satellite positioning, the measured yield at the measurement point; a designation unit that designates, as a correction point, the measurement point that is located in a reaping start area and designates, as designated measurement points, a plurality of measurement points that are located around the correction point; and a yield correction unit that, based on the measured yields assigned to the designated measurement points, corrects the measured yield assigned to the correction point. 
     Regarding a yield correction method for correcting a yield of a combine according to the present invention, the combine includes: a reaping unit that reaps planted stalks from a cultivated field; a threshing unit that threshes stalks reaped by the reaping unit; a grain tank that stores grains threshed by the threshing unit; and a yield measuring unit that measures, as a measured amount, an amount of grain sent from the threshing unit to the grain tank, the yield correction method including: a yield assigning step of assigning, to a measurement point that is calculated with use of satellite positioning, the measured yield at the measurement point; a designation step of designating, as a correction point, the measurement point that is located in a reaping start area and designating, as designated measurement points a plurality of measurement points that are located around the correction point; and a yield correction step of correcting the measured yield assigned to the correction point, based on the measured yields assigned to the designated measurement points. 
     With this configuration, a measurement point that is located in the reaping start area, of the measurement points to which the measured yields are sequentially assigned by the yield measuring unit, is the target (correction point) for which the measured yield is to be corrected. The new measured yield of the correction point is calculated based on the measured yields of the plurality of measurement points (designated measurement points) located around the correction point. By using the value derived from the measured yields assigned to the plurality of measurement points distributed around the correction point as the new measured yield of the correction point, an error is prevented from occurring in yield measurement at the start of reaping. In particular, the measured yields of a plurality of measurement points are used for correction, and therefore, even if there is an error in the yield measurement of the measured yields of adjacent measurement points, the influence of the error can be suppressed. 
     In general work travel of a combine, first, the combine performs turn reaping to reap planted stalks in an outer peripheral area of the cultivated field. The reaped area created through this travel is called a turning area (headland). Planted stalks in an unreaped area that exists inside the reaped area are reaped through reciprocating straight travel (or travel similar to straight travel), using the turning area as an area in which the combine makes a turn (U-turn, α-turn). The travel state of the combine immediately after finishing reaping in the unreaped area (unworked area) from this turning area and entering the turning area is referred to as the “start of reaping”, and the travel state of the combine immediately after entering the turning area from this unreaped area is referred to as the “end of reaping”. 
     The growth state of the planted stalks depends on the growth position in the cultivated field, and therefore, if the yield at a point that is excessively far from the point to be corrected is referred to, a large deviation may occur. For this reason, in one preferable embodiment of the present invention, the designation unit selects, as the designated measurement points, measurement points that are located within a predetermined distance from the correction point. 
     The greater the number of designated measurement points used to calculate the new measurement yield at the correction point is, the greater the computational load is. To avoid this problem regarding the computational load, in one preferable embodiment of the present invention, the designation unit selects, as the designated measurement points, a predetermined number of measurement points selected in ascending order of the distance from the correction point. 
     As described above, when the combine performs reciprocating straight travel in an area in the turning area after setting the turning area as an area in which the combine turns (U-turn, α-turn), the reaping start area and the reaping end area are close to each other. The measured yield at the measurement point located in the reaping end area is affected by the delay in the conveyance from the reaping unit to the grain tank, and is not an accurate measured yield. For this reason, in one preferable embodiment of the present invention, the designation unit determines, as an invalid measurement point, a measurement point that is located in a reaping end area, and excludes the invalid measurement point from the designated measurement points. 
     The measured yield at the measurement point designated as the correction point is corrected by the yield correction unit. The corrected measured yield does not necessarily indicate an actual value. Therefore, it is preferable that such a measured yield is not used to correct the measured yields at other measurement points. For this reason, in one preferable embodiment of the present invention, the designation unit determines, as an invalid measurement point, a measurement point to which the measured yield corrected by the yield correction unit is assigned, and excludes the invalid measurement point from the designated measurement points. 
     When calculating the measured yield at the correction point based on the measured yields of a plurality of designated measurement points, it is preferable to use a statistical representative value regarding the measured yield at the designated measurement point. In such a case, if there is little variation in the yields at the designated measurement points in the area where the designated measurement points are scattered, the arithmetic mean value can be used as the statistical representative value. However, the variation in yield in the cultivated field tends to increase depending on the distance from the correction point. Therefore, it is preferable to use a weighted average value using a weight determined based on the distance from the correction point, as a statistical representative value. For this reason, in one preferable embodiment of the present invention, the yield correction unit calculates, based on a weighted average of the measured yields assigned to the designated measurement points, the measured yield to be assigned to the correction point, the weighted average being such that a weight in the weighted average increases as the distance from the correction point increases. 
     In one preferable embodiment of the present invention, a small plot that is divided from the cultivated field includes at least one measurement point. As a result, it is possible to assign an accurate yield to each small plot. 
     In farm management, it is important to examine the variation in yield in the cultivated field and use it for the next farming operation. For this reason, one preferable embodiment of the present invention includes a yield map generation unit that generates a yield distribution map of the cultivated field based on the measured yields assigned to the measurement points. 
     A yield correction program according to the present invention causes a computer to carry out the yield correction method according to the present invention. A computer-readable recording medium according to the present invention is a computer-readable recording medium on which the yield correction program according to the present invention is recorded. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram showing a first embodiment (the same applies up to  FIG. 7 ), and is a side view showing the entirety of a combine. 
         FIG. 2  is a plan view showing the entirety of the combine. 
         FIG. 3  is a longitudinal side view showing a threshing apparatus. 
         FIG. 4  is a cross-sectional view showing a yield measuring device and a grain quality measuring device that are provided in a grain tank. 
         FIG. 5  is a plan view showing the yield measuring device. 
         FIG. 6  is a functional block diagram illustrating a control function for obtaining a yield map of a cultivated field. 
         FIG. 7  is a schematic diagram illustrating a process in which reaped stalks are subjected to threshing as the first or second product and sent to the grain tank. 
         FIG. 8  is a diagram showing a second embodiment (the same applies up to  FIG. 12 ), and is a side view showing the entirety of a combine. 
         FIG. 9  is a plan view showing the entirety of the combine. 
         FIG. 10  is a schematic diagram showing a yield measuring unit and a taste value measuring unit that are provided in a grain tank. 
         FIG. 11  is a functional block diagram illustrating a control function for obtaining a yield map of a cultivated field. 
         FIG. 12  is an illustration diagram for illustrating correction processing that is performed to correct the measured yield at a measurement point in a reaping start area. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     First Embodiment 
     The following describes a first embodiment with reference to  FIGS. 1 to 7 . 
     Hereinafter, a normal type combine is taken as an example of a combine according to the present invention, and is illustrated based on the drawings.  FIG. 1  is a left side view showing the entirety of the combine.  FIG. 2  is a plan view showing the entirety of the combine. The direction indicated by F in  FIGS. 1 and 2  is defined as a forward direction of the travel machine body  1 , the direction indicated by B is defined as a rearward direction of the travel machine body  1 , the direction indicated by L in  FIG. 2  is defined as a direction to the left of the travel machine body  1 , and the direction indicated by R in  FIG. 2  is defined as a direction to the right of the travel machine body  1 . 
     As shown in  FIGS. 1 and 2 , the combine includes a travel machine body  1  that is provided with a pair of left and right crawler travel apparatuses  2 . A driver section  3  is formed in a right side portion of a front portion of the travel machine body  1 . A driver&#39;s seat  4  is formed in the driver section  3 . The driver section  3  is covered by a cabin  5 . An engine (not shown) is provided below the driver&#39;s seat  4 . A threshing apparatus  6  and a grain tank  7  are provided in a rear portion of the travel machine body  1 . The threshing apparatus  6  and the grain tank  7  are arranged in a width direction of the travel machine body  1  such that the grain tank  7  is located rearward of the driver section  3 . A discharged straw shredding apparatus  8  is provided rearward of the threshing apparatus  6 . A reaping conveyance apparatus  9  extends forward from a threshing apparatus-side portion of the front portion of the travel machine body  1 . The reaping conveyance apparatus  9  includes a conveyance unit  10  that extends forward from the travel machine body  1  so as to be able to be operated to swing upward and downward, and a reaping unit  11  that is provided on the front side of the travel machine body  1  and whose rear portion thereof is coupled to a front end portion of the conveyance unit  10 . The reaping unit  11  is operated so as to be in a lowered working state and a raised non-working state in response to the conveyance unit  10  being operated to swing due to the extension and contraction of a lifting/lowering cylinder  12 . 
     In the combine, harvesting work is performed to harvest rice, wheat, soybeans, etc. by causing the travel machine body  1  to travel in a state where the reaping unit  11  has been lowered to be in the lowered working state. In the reaping unit  11 , ear tip-side portions of the planted stalks located forward of the travel machine  1  of the planted stalks in the cultivated field are shoveled rearward by a rotary reel  13 , and root-side portions of the planted stalks are cut by the reaping apparatus  14 , thus the planted stalks are reaped, and the entire reaped stalks from the roots to the ear tips are conveyed to the conveyance unit  10  by an auger  15 . The reaped stalks conveyed to the conveyance unit  10  are conveyed rearward and supplied to the threshing apparatus  6  by the conveyance unit  10 . In the threshing apparatus  6 , the reaped stalks thus supplied are subjected to threshing processing, and sort processing is performed to distinguish the grains obtained through threshing processing, from dust and stalk pieces. The discharged threshed straw is subjected to shredding processing by the discharged straw shredding apparatus  8 . Pieces of shredded straw are guided by a discharge port cover  8   a  and discharged rearward of the travel machine body  1 . The threshed grains subjected to sort processing are conveyed by a winnowing apparatus  16  to the grain tank  7 , and are stored in the grain tank  7 . The threshed grains stored in the grain tank  7  can be taken out of the grain tank  7  using a threshed product discharge apparatus  17 . 
     As shown in  FIG. 3 , the threshing apparatus  6  includes a threshing machine body  20 . A threshing cylinder unit  6 A is provided in an upper portion of the threshing machine body  20 , and a sort unit  6 B is provided in a lower portion of the threshing machine body  20 . 
     As shown in  FIG. 3 , the threshing cylinder unit  6 A includes a threshing chamber  21 , a threshing cylinder  22  that is provided in the threshing chamber  21 , and a receiving net  24  that is provided below the threshing cylinder  22 . The threshing chamber  21  is formed by left and right side walls  20   s  of the threshing machine body  20 , a front wall  20   f , a rear wall  20   r , a top plate  25 , and the receiving net  24 . The threshing cylinder  22  is supported by the front wall  20   f  and the rear wall  20   r  with a rotation support shaft  22   c  interposed therebetween, and is driven by a threshing cylinder drive unit  22   d  so as to rotate about the axis that extends in the front-rear direction of the threshing apparatus of the rotation shaft  22   c , which is defined as a rotation axis Y. The threshing cylinder  22  includes a shoveling portion  22   a  that is provided in a front portion thereof and a threshing processing portion  22   b  that is provided on the rear side of the shoveling portion  22   a . A plurality of dust feed valves  25   a  that are arranged in the front-rear direction of the threshing chamber  21  are supported on the inner surface side of the top plate  25 . The left side of the threshing chamber  21  is covered with a threshing cover  28  (see  FIGS. 1 and 2 ). 
     As shown in  FIG. 3 , in the threshing cylinder unit  6 A, the reaped stalks supplied by the conveyance unit  10  to the front end portion of the threshing chamber  21  are shoveled by the shoveling portion  22   a  toward the rear side of the threshing cylinder  22 , and are supplied to the threshing processing portion  22   b . The reaped stalks supplied to the threshing processing portion  22   b  are subjected to threshing processing that is performed by threshing teeth  23  and the receiving net  24 , as a threshing product. The threshing product to which a rotational force is applied by the threshing processing portion  22   b  comes into contact with the dust feed valves  25   a , is guided by the dust feed valves  25   a  so as to flow toward the rear side of the threshing chamber  21 , and is subjected to threshing processing while being transported toward the rear side of the threshing chamber  21 . The grains obtained through threshing processing fall to the sort unit  6 B through processed product leak holes in the receiving net  24 . Straw dust, which is threshing dust generated as a result of threshing processing, is discharged from a dust discharge port  26  that is located in a rear portion of the threshing chamber  21 , toward the rear side of the threshing chamber  21 . The straw dust discharged from the threshing chamber  21  flows into the discharged straw shredding apparatus  8  from a discharge port  27  that is located in a rear portion of the threshing machine body  20 . 
     As shown in  FIG. 3 , in the sort unit  6 B, the threshed product leaked from the receiving net  24  is shaken by a grain pan  33 , a sieve wire portion  34 , a chaff sheave  35 , and a grain sheave  36  of a swing sort apparatus  30 , and is subjected to sorting wind from a fanning mill  38 , and is thus subjected to sort processing through which grains and dust such as straw dust are distinguished from each other, while being transported rearward. The refined grains (grains) obtained as a first processed product through sort processing fall to a first product collecting unit  391  and are collected, and are discharged to the outside of the threshing machine body  20  by the first product collecting unit  391 . The discharged grains are passed to the winnowing apparatus  16  (see  FIG. 2 ). The second processed product obtained through sort processing falls to a second product collection unit  392  and is collected, is discharged to the outside of the threshing machine body  20  by the second product collection unit  392 , is passed to a reduction apparatus (not shown), and is returned to the front portion of the swing sort apparatus  30  by the reduction apparatus. The dust selected in the swing sort apparatus  30 , such as straw dust, flows into the discharged straw shredding apparatus  8  from the discharge port  27 . 
     Although  FIG. 3  only shows a schematic diagram, a stalk detection sensor  51  that detects the presence/absence of reaped stalks in the threshing apparatus  6  is provided. This stalk detection sensor  51  has a swing lever that extends downward from the top plate  25  of the threshing chamber  21 . The swing lever swings as a result of coming into contact with reaped stalks that enter the gap between the threshing cylinder  22  and the top plate  25 . The presence of reaped stalks is detected by detecting this swing displacement. When the swing lever is not in contact with reaped stalks, the swing lever is returned to the home position thereof by a spring. The absence of reaped stalks is detected by detecting the returning of the swing lever. Furthermore, a processing amount detection sensor S 2  that detects the amount of threshing product that has fallen to the chaff sheave  35  in a threshed state is provided above the chaff sheave  35 . 
     Although  FIG. 3  only shows a schematic diagram, the opening degree of the chaff sheave  35  can be adjusted using a chaff motor M 1 . Furthermore, the wind power of the fanning mill  38  can be changed using a fanning mill motor M 2 . The wind power of the fanning mill  38  can be changed by adjusting the rotation speed of the fanning mill  38  or adjusting the opening degree of the blower port. The chaff motor M 1  and the fanning mill motor M 2  are controlled based on the detection result of the processing amount detection sensor S 2  (a threshed state). For example, if the processing amount detection sensor S 2  detects that the amount of threshing product is large, the opening degree of the chaff sheave  35  and the wind power of the fanning mill  38  are controlled to increase. If the processing amount detection sensor S 2  detects that the amount of threshing product is small, the opening degree of the chaff sheave  35  and the wind power of the fanning mill  38  are controlled to decrease. 
     As shown in  FIGS. 3 and 4 , a yield measuring device  50  that measures a yield amount, which is the amount of grain input to the grain tank  7  from the threshing apparatus  6  via the first product collecting unit  391  and the winnowing apparatus  16  (see  FIG. 2 ), is provided at an upper position in the grain tank  7 . Furthermore, in this embodiment, a grain quality measuring device  40  that measures the quality (moisture, protein content, etc.) of grain is provided at a position where the grain quality measuring device  40  faces the yield measuring device  50 . 
     As shown in  FIG. 5 , the yield measuring device  50  includes a flat detection plate  51 , a load cell  52 , a support bracket  53  that supports the detection plate  51  and the load cell  52 , and an attachment bracket  54  for attaching the yield measuring device  50  to the inner wall of the grain tank  7 . The load cell  52  extends from a connection point of the load cell  52  and the support bracket  53 , which serves as a base end, and is supported in a cantilever-like manner. With this configuration, when a load acts on the detection plate  51 , the distortion of the load cell  52  increases. Grains are input to a storage space Q by a feeding blade  16   a  that is provided at the upper end of the winnowing apparatus  16 . At this time, a certain percentage of the grains flung by the feeding blade  16   a  collide with the detection plate  51 . The load cell  52  is distorted by the collision force (pressing force) of the grains bounced against the detection plate  51 , and an electric signal is generated. This electric signal is used as a detection signal for calculating the flow rate of grains. The electric signal indicates a voltage value or a current value, for example. As the input amount of grain sent from the winnowing apparatus  16  increases, the pressing force of the grains on the detection plate  51  increases proportionally, and the detection signal of the load cell  52  also increases. Based on such a measurement principle, the yield measuring device  50  measures the amount of grain input to the grain tank  7 . 
     The grain quality measuring device  40  includes a temporary storage unit  41  that temporarily stores the grains to be measured, and a measuring unit  42  that measures the quality of the grains stored in the temporary storage unit  41 . The temporary storage unit  41  is located on the inner side of the grain tank  7 , and the measuring unit  42  is located on the outer side of the grain tank  7 . The measuring unit  42  is housed in a storage case  43  that is formed so as to be hermetically sealed. The temporary storage unit  41  includes a substantially square cylindrical storage case  44  that is integrally coupled to the inner side surface of the storage case  43 , and grains can be stored in the storage case  44 . A vertical passage  45  that penetrates through the storage case  44  in the vertical direction is formed in the storage case  44 , and a shutter  46  is provided at an intermediate position of the vertical passage  45 . The shutter  46  is configured to be repositionable to a closed position that closes the vertical passage  45  at the intermediate position thereof and an open position that opens the vertical passage  45  at the intermediate position thereof. A grain intake port  45   a  for intaking grains is formed at the upper end of the vertical passage  45 . Some of the grains released by the feeding blade  16   a  of the winnowing apparatus  16  are taken into the intake port  45   a . With the shutter  46  switched to the closed state, the grains are stored in a temporary storage space  45 S created above the shutter  46  in the vertical passage  45 . When the shutter  46  is switched to the open state, the stored grains fall. The measuring unit  42  irradiates the grains temporarily stored in the temporary storage space  45 S with light, and measures the taste value (moisture and protein) of the grains as the grain quality based on the light returned through the grains, using a known spectroscopic analysis technique. 
       FIG. 6  shows a functional block diagram illustrating the control function for measuring the grain amount (yield) per unit plot (small plot) in the cultivated field to obtain the yield map (grain amount distribution map) of the cultivated field. 
     This combine can automatically travel along a preset travel route (travel map). For this reason, a GNSS unit  19  that receives satellite radio waves and calculates position coordinates is provided, and a control apparatus  100  is provided with an automatic travel management unit AU. The automatic travel management unit AU includes a self-position calculation unit  61 , a travel map setting unit  62 , a travel locus management unit  63 , and so on. The self-position calculation unit  61  calculates the self-position in the cultivated field, more specifically, the reaping position (harvest position) of the planted stalks based on the position coordinates output from the GNSS unit  19 . The travel map setting unit  62  sets a target travel route when automatic travel is being performed. The travel locus management unit  63  generates a travel locus of the travel machine body  1  (see  FIG. 1 ), and manages an unworked area, an existing worked area, and a turning area (an area used when shifting from a work route to the next work route, also called a headland) in the cultivated field. Reaping work is not performed in the turning area, and therefore the turning area can be regarded as a non-work area in principle. With this configuration, the self-position calculation unit  61  can output a signal or a flag indicating entrance into the non-work area when the reaping unit  11  enters a non-work area from a work area. 
     Furthermore, the control apparatus  100  includes a travel control unit RU, a reaping control unit CU, a threshing control unit SU, and a harvest data generating unit HU. The travel control unit RU generates a control signal related to travel control and transmits the control signal to a travel operation device D 3  via an input/output signal processing unit  90  to control the travel of the travel machine body  1 . The reaping control unit CU generates a control signal related to reaping control and transmits the control signal to a reaping unit operation device D 1  via the input/output signal processing unit  90  to control the operation of the reaping unit  11 . The processing amount detection sensor S 2 , the stalk detection sensor  51 , the yield measuring device  50 , and the grain quality measuring device  40  described above also transmit/receive signals and data to and from the control apparatus  100  via the input/output signal processing unit  90 . 
     Furthermore, as shown in  FIGS. 1 and 3 , the threshing control unit SU shown in  FIG. 6  generates a control signal related to threshing control and transmits the control signal to a threshing apparatus operation device D 2  via the input/output signal processing unit  90  to control the threshing apparatus  6 . The threshing apparatus operation device D 2  includes the chaff motor M 1  and the fanning mill motor M 2  described above. The threshing control unit SU includes an opening degree adjustment unit  71 , a wind power changing unit  72 , a mode setting unit  73 , and a yield accuracy maintenance unit  74 . The opening degree adjustment unit  71  adjusts the opening degree of the chaff sheave  35  of the sort unit  6 B according to the threshing state of the threshing apparatus  6 . Specifically, the chaff motor M 1  is controlled so that the opening of the chaff sheave  35  increases as the detection value of the processing amount detection sensor S 2  that detects the amount of threshing product that has fallen to the chaff sheave  35  increases, to prevent the threshing product from being held in the chaff sheave  35 . If the opening degree of the chaff sheave  35  is large, the amount of grain collected by the first product collecting unit  391  increases, and if the opening degree of the chaff sheave  35  is small, the amount of threshing product collected by the second product collecting unit  392  and to be re-threshed increases. The wind power changing unit  72  also changes the wind power of the fanning mill  38  according to the threshing state of the threshing apparatus  6 . Specifically, the fanning mill motor M 2  is controlled so that the wind power of the fanning mill  38  increases as the detection value of the processing amount detection sensor S 2  increases, and the threshing product that has not been sufficiently threshed is sent to the second product collecting unit  392 . That is to say, the amount of threshed product collected by the second product collection unit  392  increases as the wind power of the fanning mill  38  increases. 
     As schematically shown in  FIG. 7 , the threshing product collected by the second product collecting unit  392  (see  FIG. 3 ) is re-threshed and re-sorted, and thereafter collected by the first product collection unit  391  (see  FIG. 3 ) as re-threshing grains. Therefore, the retention time of such grains in the threshing apparatus  6  is longer than that of the grains directly collected by the first product collection unit  391 . That is to say, the average conveyance time (delay time) taken for grains obtained as a result of threshing the reaped stalks reaped by the reaping unit  11  and sent to the threshing apparatus  6  to be sent from the threshing apparatus  6  to the grain tank  7  varies depending on the amount of the collected second product. This variation has a direct influence on the retention time (delay time) of the reaped stalks or grains from the reaping unit  11  to the grain tank  7 , which is required when the yield measured by the yield measuring device  50  is assigned as the yield at the reaping position. 
     Upon an instruction being input from an operator or a preset condition being satisfied, the mode setting unit  73  sets a yield accuracy priority mode in which the calculation accuracy of the amount (yield) of the grains obtained from the reaped stalks reaped by the reaping unit  11  is improved by suppressing the amount of the second product collected by the second product collecting unit  392 . When the yield accuracy priority mode is set by the mode setting unit  73 , the yield accuracy maintenance unit  74  forcibly fixes the opening degree of the chaff sheave  35  at a specific opening degree. The specific opening degree may be the complete closure of the chaff sheave  35 , and is smaller than the average opening degree in conventional threshing control. Opening degrees at a plurality of levels may be set in advance as the specific opening degree so that the operator can freely determine and select the specific opening degree to be used, based on the state of the crops or the like. Furthermore, when the yield accuracy priority mode is set by the mode setting unit  73 , the yield accuracy maintenance unit  74  fixes the opening degree of the chaff sheave  35  at the specific opening degree, and sets the wind power of the fanning mill  38  at a predetermined specific wind power as well. Regarding the specific wind power as well, a plurality of levels may be prepared so that the operator can freely determine and select the specific wind power to be used, based on the state of the crops. 
     When the combine is in the non-reap work state, the planted stalks are substantially not reaped and no grain is obtained. Therefore, when the combine is in the non-reap work state, the yield accuracy priority mode need not be set. Therefore, the mode setting unit  73  has a function of determining whether the combine is in a reap work state or a non-reap work state, and is configured to set the yield accuracy priority mode when it is determined that the combine is in a reap work state, and to cancel the yield accuracy priority mode when it is determined that the combine is in a non-reap work state. 
     The conditions for the mode setting unit  73  to set the yield accuracy priority mode are listed below. At least one of these conditions is actually used as a condition for determining the non-reap work state. 
     (1) When the stalk detection sensor  51  that detects the presence or absence of stalks in the threshing apparatus  6  detects the absence of stalks, the mode setting unit  73  determines that the combine is in the non-reap work state. 
     (2) Once the stalk detection sensor  51  detects the absence of stalks, the mode setting unit  73  determines that the state is in a non-reap work state upon a predetermined period of time elapsing. Thus, it is possible to resolve the inconvenience that the yield accuracy priority mode is not applied in threshing processing of a small amount of reaped stalks that are retained immediately after the absence of stalks is detected. 
     (3) Substantially the same measure as in (2). Once the stalk detection sensor  51  detects the absence of stalks, the mode setting unit  73  determines the non-reap work state upon a certain distance being travelled. 
     (4) As described above, the self-position calculation unit  61  can output a signal or a flag indicating the entrance into the non-work area when the reaping unit  11  enters a non-work area from a work area. Using the output of the signal or flag as a trigger, the mode setting unit  73  determines that the combine is in the non-reap work state. 
     The harvest data generating unit HU includes a unit yield calculation unit  81 , a grain quality calculation unit  82 , a plot assigning unit  83 , a yield map generation unit  84 , and a quality map generation unit  85 . The unit yield calculation unit  81  calculates the unit yield per unit plot of the cultivated field based on pieces of grain amount data sequentially sent from the yield measuring device  50 . Here, as a unit section, a square or rectangular plot in which the reaping width of the reaping unit  11  or half to several times the reaping width is one side, and half to several times the reaping width is the other side is adopted as the unit plot. The amount of grain measured while the combine travels in this unit plot is calculated as a unit yield. The grain quality calculation unit  82  calculates the taste value of the grains acquired in this unit plot as a unit taste value. 
     The plot assigning unit  83  assigns the unit yield calculated by the unit yield calculation unit  81  to the unit plot which is the actual reaping plot, using the delay time which is the grain residence time from the cutting point to the yield measurement point. Similarly, the plot assigning unit  83  also assigns the unit taste value calculated by the grain quality calculation unit  82  to the unit plot, which is the actual reaping plot. 
     The yield map generation unit  84  creates a yield map showing the yield distribution in each unit plot, using the unit yield assigned to the unit plot, which is the actual reaping plot calculated by the unit yield calculation unit  81 . The quality map generation unit  85  creates a grain quality map showing the taste value distribution in each unit plot, using the unit taste value assigned to the unit section, which is the actual cutting section. 
     In addition, a yield calculation method for calculating a yield of the combine includes: a unit yield calculation step of calculating a unit yield per unit plot in a cultivated field, using the amount of grain; an opening degree adjustment step of adjusting the opening degree of the chaff sheave of the sort unit  6 B according to the threshing state of the threshing apparatus  6 ; a mode setting step of setting a yield accuracy priority mode in which priority is given to the accuracy of the unit yield calculation performed in the unit yield calculation step; and a yield accuracy maintenance step of, when the yield accuracy priority mode is set in the mode setting step, forcibly fixing the opening degree of the chaff sheave at a specific opening degree in preference to the opening degree adjusted in the opening degree adjustment step. 
     A yield calculation program according to the present embodiment causes a computer to carry out the yield calculation method according to the present embodiment. A computer-readable recording medium according to the present embodiment is a computer-readable recording medium on which the program that causes a computer to carry out the yield calculation method according to the present embodiment is recorded. 
     Other Embodiments Modified from First Embodiment 
     (1) In the above-described embodiment, the yield measuring device  50  is configured to obtain the grain amount based on a pressing force that is applied to the detection plate  51  by the grains fed by the feeding blade  16   a . Instead, it is possible to employ a yield measuring device  50  that determines a grain amount per unit time or a grain amount per unit mileage based on the time when the grain amount reaches a predetermined volume, using a temporary storage unit  41  of the grain quality measuring device  40  shown in  FIG. 4 . Of course, instead of sharing the temporary storage unit  41  with the grain quality measuring device  40 , it is possible to employ a configuration in which the yield measuring device  50  has its own temporary storage unit  41 , and measures a grain amount per unit time or a grain amount per unit mileage. Also, a granular material flow measuring device may be installed on a grain transport path extending from the threshing apparatus  6  to the grain tank  7  to measure the grain amount per unit time or the grain amount per unit mileage. 
     (2) In the above-described embodiment, a normal type combine is used as a combine. However, a head-feeding type combine may be used instead. In a head-feeding combine, a swing lever type sensor that is provided in the reaping unit  11  and detects the entry of stalks is used as the stalk detection sensor  51 . 
     In the above-described embodiment, when the mode setting unit  73  sets the yield accuracy priority mode, the second product is prevented from being generated, by fixing the chaff sheave  35  to a specific opening degree and fixing the wind power of the fanning mill  38  to a specific wind power. In another embodiment regarding the case in which the yield accuracy priority mode is set, it is possible to employ a configuration with which only one of the fixing of the opening degree of the chaff sheave  35  and the fixing of the wind power of the fanning mill  38  is performed. Alternatively, when the dust feed valves  25   a  are of a variable attitude type, fixing the dust feed valves  25   a  to a specific attitude may be added as another embodiment in the case where the yield accuracy priority mode is set. 
     (3) The present invention is applicable to a combine that can calculate the yield per unit area in a cultivated field. 
     Second Embodiment 
     The following describes a second embodiment with reference to  FIGS. 8 to 12 . 
     Hereinafter, a normal type combine is taken as an example of a combine according to the present invention, and is illustrated based on the drawings.  FIG. 8  is a left side view showing the entirety of the combine.  FIG. 9  is a plan view showing the entirety of the combine. The direction indicated by F in  FIGS. 8 and 9  is defined as a forward direction of a travel machine body  201 , the direction indicated by B is defined as a rearward direction of the travel machine body  201 , the direction indicated by L in  FIG. 9  is defined as a direction to the left of the travel machine body  201 , and the direction indicated by R in  FIG. 9  is defined as a direction to the right of the travel machine body  201 . 
     As shown in  FIGS. 8 and 9 , the combine includes a travel machine body  201  that is provided with a pair of left and right crawler travel apparatuses  202 . A driver section  203  is provided in a right side portion of a front portion of the travel machine body  201 . A driver&#39;s seat  204  is provided in the driver section  203 . The driver section  203  is covered by a cabin  205 . An engine (not shown) is formed below the driver&#39;s seat  204 . A threshing apparatus  206  and a grain tank  207  are provided in a rear portion of the travel machine body  201 . The threshing apparatus  206  and the grain tank  207  are arranged in a width direction of the travel machine body  201  such that the grain tank  207  is located rearward of the driver section  203 . A discharged straw shredding apparatus  208  is provided rearward of the threshing apparatus  206 . A reaping conveyance apparatus  209  extends forward from a threshing apparatus  206  side portion of the front portion of the travel machine body  201 . The reaping conveyance apparatus  209  includes a conveyance unit  210  that extends forward from the travel machine body  201  so as to be able to be operated to swing upward and downward, and a reaping unit  211  that is provided on the front side of the travel machine body  201  and whose rear portion thereof is coupled to a front end portion of the conveyance unit  210 . The reaping unit  211  is operated so as to be in a lowered working state and a raised non-working state in response to the conveyance unit  210  being operated to swing due to the extension and contraction of a lifting/lowering cylinder  212 . 
     In the combine, harvesting work is performed to harvest rice, wheat, soybeans, etc. by causing the travel machine body  201  to travel in a state where the reaping unit  211  is lowered to be in the lowered working state. In the reaping unit  211 , ear tip-side portions of the planted stalks located forward of the travel machine  201  of the planted stalks in the cultivated field are shoveled rearward by a rotary reel  213 , and root-side portions of the planted stalks are cut by the reaping apparatus  214 , thus the planted stalks are reaped, and the entire reaped stalks from the roots to the ear tips are conveyed to the conveyance unit  210  by an auger  215 . The reaped stalks conveyed to the conveyance unit  210  are conveyed rearward by the conveyance unit  210  and are supplied to a threshing unit  206 A of the threshing apparatus  206 . In the conveyance unit  210 , the reaped stalks thus supplied are subjected to threshing processing, the grains that have been subjected to sort processing are conveyed by a winnowing apparatus  216  to the grain tank  207 , and the grains are stored in the grain tank  207 . The grains stored in the grain tank  207  can be taken out of the grain tank  207  using a threshed product discharge apparatus  217 . 
     Although  FIG. 8  only shows a schematic diagram, a stalk detection sensor 
     S 12  that detects the presence/absence of reaped stalks in the threshing apparatus  206  is provided. This stalk detection sensor S 12  swings as a result of coming into contact with reaped stalks that enter the threshing unit  206 A. The working state of the combine is detected based on the presence of reaped stalks, and the non- working state of the combine is detected based on the absence of reaped stalks. 
       FIG. 10  shows the yield measuring unit  250  that measures the yield, which is the amount of grain input from the threshing apparatus  206  to the grain tank  207  through the winnowing apparatus  216 , and a taste value measuring unit  240  that measures the quality (moisture, protein amount, etc.) of grains input to the grain tank  207 . 
     The yield measuring unit  250  is built into a grain discharge apparatus  207   a . The grain discharge apparatus  207   a  scatters and discharges the conveyed grains into the grain tank  207 , using a rotating plate. The yield measuring unit  250  calculates the flow rate of grains based on the signal of a load cell that is distorted by the collision force of grains that are scattered and discharged each time the rotating plate rotates. The yield measuring unit  250  calculates the measured yield based on the flow rate of the grains in a predetermined cycle that is the rotation cycle of the rotating plate for the grains input to the grain tank  207 . 
     The taste value measuring unit  240  temporarily stores some of the grains scattered and discharged by the grain discharge apparatus  207   a , irradiates the stored grains with light, and measures the taste value (moisture and protein) of the grains by performing spectral analysis on the light returned through the grains Such temporary storage and measurement of the taste value of grains are performed periodically. 
       FIG. 11  shows a functional block diagram illustrating the control function for measuring the grain amount (yield) per unit plot (small plot) in the cultivated field to obtain the yield map (grain amount distribution map) of the cultivated field. 
     This combine can automatically travel along a preset travel route (travel map). For this reason, as shown in  FIGS. 8 and 9 , a GNSS unit  219  that has a satellite positioning function that is the function of receiving satellite radio waves and calculating position coordinates is provided on the upper surface of the top plate of the cabin  205 . As shown in  FIG. 11 , a control apparatus  300  includes an automatic travel management unit AU 2 . The automatic travel management unit AU 2  includes a self-position calculation unit  261 , a travel map setting unit  262 , a travel locus management unit  263 , and so on. The self-position calculation unit  261  calculates the self-position in the cultivated field, more specifically, the reaping position (harvest position) of the planted stalks based on the position coordinates output from the GNSS unit  219 . The travel map setting unit  262  sets a target travel route when performing automatic travel. The travel locus management unit  263  generates a travel locus of the travel machine body  201 , and manages an unworked area, an existing worked area, and a turning area (an area used when shifting from a work route to the next work route, also called a headland. See  FIG. 12 ) in the cultivated field. As described above, the turning area is a worked area in which reaping work has been performed. With this configuration, the self-position calculation unit  261  can manage a “reaping start” state, which is the travel state immediately after the reaping unit  211  enters the unreaped area (unworked area) from the turning area, and a “reaping end” state, which is the travel state immediately after the reaping unit  211  finishes reaping in the unreaped area and enters the turning area, and outputs a signal or a flag indicating the state. 
     The “start of reaping” and the “end of reaping” can also be determined from the detection result of the stalk detection sensor S 12 . For example, the stalk detection sensor S 12  can detect the absence of roots and determine the “end of reaping” when the combine has travelled 1 to 2 m. 
     Furthermore, the control apparatus  300  includes a travel control unit RU 2 , a work control unit CU 2 , a yield map generating unit HU 2 , and a taste value map generation unit FU 2 . The travel control unit RU 2  generates a control signal related to travel control and transmits the control signal to a travel operation device D 22  via an input/output signal processing unit  290  to control the travel of the travel machine body  201 . The work control unit CU 2  generates a control signal related to work such as reaping control and threshing control and transmits the control signal to the work operation device D 12  via the input/output signal processing unit  290  to control the operations of the reaping unit  211  and the threshing apparatus  206 . The yield measuring unit  250  and the taste value measuring unit  240  described above also exchange signals and data with the control apparatus  300  via the input/output signal processing unit  290 . 
     The yield map generating unit HU 2  includes a yield assigning unit  271 , a designation unit  272 , a yield correction unit  273 , and a yield map generation unit  274 . The yield assigning unit  271  determines the position of the reaping unit  211  calculated and set by the self-position calculation unit  261  as a measurement point, and assigns the measured yield sent from the yield measurement unit  250  to the measurement point. 
     Note that the yield measuring unit  250  measures the amount of grain based on the maximum value of the load cell in the cycle in which the rotating plate makes one rotation. If the rotation cycle of the rotating plate is approximately a fraction of a second, the amount of grain is measured several times per second. Therefore, in this embodiment, the amount of grain per second obtained by accumulating the amounts of grain measured per second is transmitted to the yield map generating unit HU 2  as the measured yield. Therefore, the measurement point to which the measured yield is assigned is also set based on the position of the reaping unit  211  calculated approximately every second. 
     At the start of reaping, almost no grains are retained in the route from the reaping unit  211  to the grain tank  207 , and even if the delay time of the grains from the reaping unit  211  to the grain tank  207  is considered, it is highly likely that an error will occur in the measured yield assigned to the measurement point. For this reason, there is a need to correct the measured yield assigned to the measurement point set at the start of reaping. In this embodiment, the measured yield assigned to the measurement point set at the start of reaping is replaced with a new measured yield calculated based on the measured yields assigned to the surrounding measurement points. 
     The designation unit  272  determines a measurement point located in the reaping start area that is to be corrected, as a correction point, and designates a plurality of measurement points located around the correction point as designated measurement points. The yield correction unit  273  corrects (rewrites) the measured yield assigned to the correction point to be corrected, based on the measured yields assigned to the designated measurement points. 
     Hereinafter, an example of the correction calculation of the measured yield assigned to the correction point will be described with reference to  FIG. 12 . In  FIG. 12 , the measurement points are indicated with reference numerals P 11  to P 4   m . The correction point is the measurement point P 24  located in the reaping start area, which is the correction target area, and is indicated by a circle filled with black. 
     The measurement points that are to be designated by the designation unit  272  are measurement points within a predetermined distance from the correction point P 24 . As for the measurement points within the predetermined distance from the correction point P 24 , the measurement points within the circle centered around the correction point P 24  and having a radius of the predetermined distance are the designated measurement points. However, here, for simplification, the measurement points indicated by P 11  to P 16 , P 21  to P 26 , and P 31  to P 36  are indicated as designated measurement points. Furthermore, in this correction processing, an invalid measurement point is selected from among the measurement points that are to be the designated measurement points. The invalid measurement points are the measurement points located in the reaping end areas (P 31  and P 32  in  FIG. 12 ) and the measurement points to which the measured yield corrected by the yield correction unit  273  is assigned (P 11  to P 14  and P 21  to P 23  in  FIG. 12 ), and these points are excluded from the designated measurement points. 
     As a result, the designated measurement points to ultimately be used to correct the correction point are the measurement points indicated by P 11  to P 16 , P 25 , P 26 , and P 31  to P 36 . 
     A weighted average is used in the correction algorithm in this embodiment, in which the measured yield newly assigned to the correction point is obtained from the measured yields assigned to the designated measurement points. Here, the measured yields assigned to the measurement points indicated by P 11  to P 16 , P 25 , P 26 , and P 31  to P 36  are Q 11  to Q 16 , Q 25 , Q 26 , and Q 31  to Q 36 , respectively, and the weights w given to the measurement points are values of a function in which the distance from the correction point is a variable, and are w 11  to w 16 , w 25 , w 26 , and w 31  to w 36 , respectively. 
     The measured yield newly assigned to the correction point is 
       ( Q 11+ w 11+ . . . + Q 31 ·w 31)/( w 11+ . . . + w 31). 
     In this way, all the measured yields initially assigned to the measurement points located in the reaping start area are corrected (rewritten) by the yield correction unit  273 . 
     The weight in the weighted average can be determined using various methods as follows. 
     (a) A weight “w 24 =1.0” is given to the correction point P 24 , and the weight “w 36 =0.0” is given to the measurement point farthest from the correction point (for example, P 36 ) of the designated measurement points. The weights of the remaining designated measurement points are values obtained by subtracting the ratio ρ between the distance from the correction point P 24  to the measurement points and the distance from the correction point P 24  to the measurement point P 36 , from “1.0” (1.0&gt;1.0·ρ&gt;0.0). 
     (b) A weight “w 24 =1.0” is given to the correction point P 24 , and the weight “w 36 =0.5” is given to the measurement point farthest from the correction point (for example, P 36 ) of the designated measurement points. The weights of the remaining designated measurement points are obtained through proportional distribution, using the values obtained by subtracting the ratio p between the distance from the correction point P 24  to the measurement points and the distance from the correction point P 24  to the measurement point P 36 , from “1.0” (1.0·ρ). That is to say, the weights of the remaining measurement points are “0.5+0.5×(1.0·ρ)=0.5×(2.0·ρ). 
     (c) As a more general method for obtaining the weight, it is possible to use a function G for deriving the weight of each of the remaining measurement points, in which the above ratio (1.0·ρ) is used as a variable. This function may be a linear function, but it may also be a non-linear function such as a quadratic function or a step function. 
     Furthermore, the above-described correction algorithm for calculating the measured yield assigned to the correction point to be corrected is an example, and other correction algorithms are listed below. However, the present invention is not limited thereto. For example, 
     (1) First, the designated measurement points to be determined may be determined as measurement points in the entire cultivated field, and a predetermined number of measurement points with a short distance from the correction points may be selected, and furthermore, the determination of invalid measurement points may be performed by narrowing down the number of points, and thereafter a number of designated measurement points corresponding to the number invalid measurement points may be added. 
     (2) When the travel locus management unit  263  has detected the boundary line between the turning area and the internal area in the turning area, i.e., the reaping end boundary line or the reaping start boundary line, only the measurement points located in the internal area of the turning area may be the points to be determined as the designated measurement points, from the beginning. 
     (3) When the target area for the designated measurement points is small (when the distance from the correction point for designating the designated measurement points is set to be small), the arithmetic mean may be used instead of the weighted average. 
     The yield map generation unit  274  calculates the yield for each small plot in the cultivated field based on the measured yields assigned to all of the measurement points including the measurement points corrected by the yield correction unit  273 , and generates the yield distribution map of the cultivated field. 
     The taste value map generation unit FU 2  includes a taste value assigning unit  281  and a quality map generation unit  282 . The taste value assigning unit  281  assigns taste values to the small plots in the cultivated field, using the taste values sent from the taste value measuring unit  240 , the self-position (the position of the reaping unit  211 ) sent from the self-position calculation unit  261 , and the delay time for the grains threshed from the reaped stalks to reach the taste value measuring unit  240 . The quality map generation unit  282  generates a taste value distribution map of the cultivated field, using the taste values assigned to the small plots in the cultivated field. The above-described correction method regarding the assignment of the yields to the small plots may also be adopted in the assignment of the taste values to the small plots. 
     If the yield distribution map and the taste value distribution map are to be created after the harvest work is complete, the yield map generation unit  274  and the quality map generation unit  282  do not necessarily have to be provided in the combine. The yield map generation unit  274  and the quality map generation unit  282  may be provided in a tablet computer or smartphone owned by a farm worker, or a computer of a cloud service. 
     In addition, a yield correction method for correcting a yield of the combine includes: a yield assigning step of assigning, to a measurement point that is calculated with use of satellite positioning, the measured yield at the measurement point; a designation step of designating, as a correction point, the measurement point that is located in a reaping start area and designating, as designated measurement points, a plurality of measurement points that are located around the correction point; and a yield correction step of, based on the measured yields assigned to the designated measurement points, correcting the measured yield assigned to the correction point. 
     A yield correction program according to the present embodiment causes a computer to carry out the yield correction method according to the present embodiment. A computer-readable recording medium according to the present embodiment is a computer-readable recording medium on which the program that causes a computer to carry out the yield correction method according to the present embodiment is recorded. 
     Other Embodiments 
     (1) In the above-described embodiments, the yield measuring unit  250  is configured to calculate the flow rate of grains based on the signal of the load cell that is distorted by the collision force of grains that are scattered and discharged each time the rotating plate rotates. Instead, it is possible to install a temporary storage chamber that temporarily stores grains that have been scattered and discharged, and employ a yield measuring unit  250  that determines a grain amount per unit time or a grain amount per unit mileage based on the time taken for the grain amount to reach a predetermined volume. Also, a granular material flow measuring device may be installed on a grain transport path extending from the threshing apparatus  206  to the grain tank  207  to measure the grain amount per unit time or the grain amount per unit mileage. 
     (2) In the above-described embodiment, a normal type combine is used as a combine. However, a head-feeding type combine may be used instead. In a head-feeding combine, a swing lever type sensor that is provided in the reaping unit  211  and detects the entry of stalks is used as the stalk detection sensor S 12 . 
     (3) The present invention is applicable to a combine that can calculate the yield per small plot in a cultivated field. 
     DESCRIPTION OF REFERENCE SIGNS cl First Embodiment 
       6 : Threshing Apparatus 
       6 A: Threshing Cylinder Unit 
       6 B: Sort unit 
       7 : Grain Tank 
       11 : Reaping Unit 
       22 : Threshing Cylinder 
       25   a : Dust Feed Valve 
       35 : Chaff Sheave 
       38 : Fanning Mill 
       40 : Grain Quality Measuring Device 
       50 : Yield Measuring Device 
       61 : Self-position Calculation Unit 
       71 : Opening Degree Adjustment Unit 
       72 : Wind Power Changing Unit 
       73 : Mode Setting Unit 
       74 : Yield Accuracy Maintenance Unit 
       81 : Unit Yield Calculation Unit 
       83 : Plot Assigning Unit 
       84 : Yield Map Generation Unit 
       85 : Quality Map Generation Unit 
       100 : Control Apparatus 
       391 : First Product Collection Unit 
       392 : Second Product Collection Unit 
     M 1 : Chaff Motor 
     M 2 : Fanning Mill Motor 
     S 1 : Stalk Detection Sensor 
     S 2 : Processing Amount Detection Sensor 
     SU: Threshing Control Unit 
     Second Embodiment 
       206 : Threshing Apparatus 
       206 A: Threshing Unit 
       207 : Grain Tank 
       211 : Reaping Unit 
       219 : GNSS Unit 
       250 : Yield Measuring Unit 
       261 : Self-position Calculation Unit 
       262 : Travel Map Setting Unit 
       263 : Travel Locus Management Unit 
       271 : Yield Assigning Unit 
       272 : Designation Unit 
       273 : Yield Correction Unit 
       274 : Yield Map Generation Unit 
       281 : Taste Value Assigning Unit 
       282 : Quality Map Generation Unit 
       300 : Control Apparatus 
     FU 2 : Taste Value Map Generation Unit 
     HU 2 : Yield Map Generation Unit