JPH056731Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) This invention is a cutting height control device for a reaper, specifically, a cutting height control device for a reaper in which the reaping part is supported so as to be movable up and down with respect to the machine body via a lifting device. Regarding a control device.

(Prior Art) Conventionally, as a cutting height control device for this type of reaper, an automatic cutting machine has a setting input device for setting the cutting height of the cutting section, and a cutting height position sensor for detecting the position of the cutting section. In addition to being equipped with a control mechanism, we have previously proposed a mechanism that is connected to the reaping clutch of the reaping section and is equipped with a reaping clutch operation priority mechanism and a manual operation mechanism that give priority to the automatic control mechanism. (Patent Application No. 59-44870) However, in this cutting height control device, when automatically controlling the cutting height of the cutting section, the cutting height is set using the setting input device of the automatic control mechanism, and the cutting height is set by the setting input device of the automatic control mechanism. When the reaping section reaches the position set by the input device, this position is detected by the cutting height position sensor, the operation of the lifting device is stopped, and the reaping section is moved to the position set by the setting input device. The operation of the reaping clutch operation priority mechanism causes the reaping section to be raised and lowered in priority over the automatic control mechanism.

If the reaping position of the reaping unit is to be adjusted up or down separately from the operations of the automatic control mechanism and the reaping clutch operation priority mechanism, the manual operation mechanism is turned on and off to operate the lifting device. , the reaping position of the reaping section is adjusted.

(Problems to be Solved by the Invention) In the conventional cutting height control device, the lifting speed of the reaping section by the reaping clutch operation priority mechanism and the lifting speed of the reaping section by the manual operation mechanism are as follows. Both are assumed to have the same speed,
As a result, the following problems arose.

That is, when raising and lowering the reaping section using the reaping clutch operation priority mechanism, it is desirable to do it as fast as possible in order to improve the workability of the reaper. On the other hand, if the reaping position of the reaping section is finely adjusted by the manual operation mechanism after the reaping section has been raised or lowered, a problem arises in which it is difficult to perform accurate fine adjustment. When the lifting speed of the reaping section by the mechanism is made low, the lifting speed of the reaping section by the manual operation mechanism due to the priority mechanism becomes low, resulting in the disadvantage that the workability of the reaping machine is reduced. .

The present invention was devised in view of the above-mentioned problems, and its purpose is to lower the lifting speed of the reaping section by the manual operation mechanism compared to the lifting speed of the reaping section by the reaping clutch operation priority mechanism. By doing this, while improving the workability of the reaper,
Furthermore, fine adjustment of the reaping position of the reaping section can be performed accurately with one manual operation mechanism,
In addition, it is possible to manually raise and lower the entire stroke of the reaping unit to inspect the raising and lowering movement of the reaping unit while the drive of the reaping unit is stopped, and to manually raise and lower the reaping unit at high speed to significantly adjust the cutting position of the reaping unit. An object of the present invention is to provide a cutting height control device that can control cutting height.

(Means for Solving the Problems) The mowing height control device of the present invention has a setting input device 13 for setting the mowing height and a mowing height detection sensor 9, and automatically controls the operation of the lifting device. a reaping clutch operation priority mechanism 28 that is linked to the operation of the reaping clutch that inputs power to the reaping section 6 and operates the lifting device at high speed in priority to the automatic control mechanism; One manual operation mechanism 23 is provided to operate the lifting device with priority over the control mechanism, and a low speed switching means 34 is provided in the drive system of the lifting device to reduce the operating speed of the lifting device. During manual operation by the manual operation mechanism 23, the low speed switching means 34 is switched to the low speed side, the lifting device is operated at a low speed for a certain period of time, and after a certain period of time, it is switched to the high speed side, and the lifting device is operated at a low speed at a high speed. An operating circuit 35 is provided.

(Function) Therefore, during reaping work in the automatic mode of the reaper, the reaping section can be automatically raised and lowered to the position set by the setting input device of the automatic control mechanism, and the reaping unit can be automatically moved up and down to the position set by the setting input device of the automatic control mechanism. During work, when operating the reaping clutch operation priority mechanism, the reaping section is raised and lowered at high speed, and while the priority mechanism can quickly raise and lower the reaping section, the manual operation mechanism is used to raise and lower the reaping section. When finely adjusting the reaping position, the reaping section can be raised and lowered at low speed, and the fine adjustment can be made accurately.

Further, as described above, the vertical movement of the lifting device is adjusted to a low speed only for a certain period of time from the time when the manual operating mechanism is operated, and even after this certain period of time has elapsed, the manual operating mechanism cannot be switched. When continuing operation, the switch is again made to high speed.

In other words, if the manual operating mechanism is operated for longer than a certain period of time, it can be switched to a high speed, so that it is possible to check the raising and lowering movement of the reaping section while the reaping section is stopped, so that the entire stroke of the reaping section can be manually operated. When raising and lowering the mower or when greatly adjusting the cutting position of the cutting section, it can be raised and lowered at high speed.

Further, the fine adjustment at low speed can generally be completed within the above-mentioned time, but if the fine adjustment is not completed within this time, the operation of the manual operation mechanism 23 is temporarily released and then operated again. This again makes it possible to make low-speed fine adjustments within the above-mentioned fixed period of time.

(Example) The cutting height control device for a reaper according to the present invention will be described below with reference to an example shown in the drawings.

FIG. 1 shows a combine harvester as an example of a reaping machine, in which a traveling device 2 is provided at the lower part of the machine body 1, a threshing section 3 is provided at the upper part, and a grain culm pulling device 4 and a cutting blade 5 are provided at the front part of the machine body 1. Reaping section 6 equipped with etc.
is supported so that it can be raised and lowered via a lifting device 42, which will be described later.A pilot seat 7 and an operation column 8 are provided at the front of the fuselage 1 at a position to the side of the front reaping section 6.

As the machine body 1 advances, the cutting blade 5 is raised while the grain culm is raised by the grain culm lifting device 4 of the reaping section 6.
The harvested grain culm is conveyed and supplied to the threshing section 3, where it is threshed.

Further, the combine harvester is equipped with a cutting height control device, and the lifting device 42 of the cutting section 6 is controlled by the cutting height control device, so that the cutting section 6 is adjusted up and down.

Therefore, the cutting height control device was constructed as follows.

That is, it has a setting input device 13 for setting the cutting height of the reaping section 6 and a cutting height detection sensor 9, an automatic control mechanism that automatically operates the lifting device 42, and a power supply to the reaping section 6. A reaping clutch operation priority mechanism 28 that operates the lifting device 42 at high speed in priority to the automatic control mechanism in conjunction with the operation of the reaping clutch that turns on and off; and one manual operation mechanism 23 that allows the lifting device 42 to
A low-speed switching means 34 is provided in the drive system for lowering the operating speed of the lifting device 42, and a manual circuit for raising or lowering the lifting device 42 by operating the manual operation mechanism 23 is provided with a low-speed switching means 34 for lowering the operating speed of the lifting device 42. A low-speed operation circuit 35 is connected to operate the circuit.

Specifically, as shown in FIG. 3, the mowing height detection sensor 9 and the mowing height detection sensor 9 are connected to a connection circuit in which a key switch SW-4 is connected to a power source E via a threshing switch SW-5 that is linked to a threshing clutch. Part 6
A setting input device 13 for setting the cutting height is connected in parallel, and an input signal from the setting input device 13 and the cutting height are connected to the output sides of the cutting height detection sensor 9 and the setting input device 13. A comparator 14 that compares the detection signal from the detection sensor 9 and outputs an output signal for operating the lifting device 42 is connected, and the mowing height detection sensor 9, setting input device 13, comparator 14, etc. , forming the automatic control mechanism described above.

The setting input device 13 has four switching terminals for a cut position, a high position, a medium position, and a low position, and by switching these terminals, the reaping section 6 can be set to a predetermined cutting height position.

As the cutting height detection sensor 9, a cutting height position sensor is used as shown in FIG. Piece 1
and a sensor body 12 having a sensor arm 11 which is activated by the sensor body 12, and three first to third switches which operate when the reaping section 6 reaches the high, middle and low positions. SW−
1, SW-2 and SW-3 are provided.

The cutting height position sensor 9 has its sensor main body 12 attached to the side of the operating column 8 on the machine body 1 side, and the actuating piece 10 is attached to the lifting case 4a of the grain culm lifting device 4 of the reaping section 6.
Each switch SW provided on the main body 12 is attached to the side of the main body 12 and swings the sensor arm 11 of the sensor main body 12 in the vertical direction with the actuating piece 10 as the reaping section 6 rises and falls.
-1, SW-2, and SW-3 are operated.

and the actuating piece 1 of the sensor arm 11
The above-mentioned switches SW-1,
By operating SW-2 and SW-3, the reaping section 6
The position of the reaping section 6 relative to the machine body 1, that is, the height of the reaping section 6 above the ground, is detected, and the elevating device 42 of the reaping section 6 is automatically controlled based on the detection result.

In addition, smoothing circuits 15, 15, 15 are connected to the output sides of the switches SW-1, SW-2, SW-3 in the cutting height position sensor 9, respectively. Each switch
The signals from SW-1, SW-2, and SW-3 are outputted to the comparator 14.

The comparator 14 includes three first to third AND circuits 16, 17, 18, and each of the circuits 16, 1
One of the input terminals 7 and 18 is connected to the setting input device 1.
3, respectively, and the other input terminal is connected to the output side of each of the smoothing circuits 15, respectively, and the AND circuits 16, 17, 18
When signals are input from both the setting input device 13 and the cutting height position sensor 9 to the respective input terminals of the AND circuits 16, 17,
A signal is output from the output side of the AND circuit 18, and the output side of each AND circuit 16, 17, 18 is connected to an OR circuit 19 having three input terminals.

Further, a fourth AND circuit 20 having three input terminals is connected to the output side of the OR circuit 19, and the output side of the AND circuit 20 is used to switch the lifting device 42 to the lowering side to lower the reaping section 6. The AND circuit 1 of the setting input device 13 and the comparator 14 is connected to the first solenoid SoI-1 to be lowered.
An OR circuit 21 is connected to each connection circuit connecting 6, 17, and 18, and 3 is connected to the output side of this OR circuit 21.
A NAND circuit 22 having two input terminals is connected, and an automatic lamp L is connected to the output side of the NAND circuit 22.

The mowing height control device is provided with a manual operation mechanism 23 and a manual operation holding mechanism 24 that operate the lifting device 42 with priority over the automatic control mechanism, and has a manual operation holding mechanism 24 on the output side that operates the lifting device 42 on the raising and lowering side. The first and second
Provide solenoids SoI-1 and SoL-2.

The manual operation mechanism 23 has two switching contacts and operates a manual switch SW-6 that raises or lowers the lifting device 42. The manual operation mechanism 23 switches each contact of the manual switch SW-6 through a manual circuit. It is connected to each of the solenoids SoI-1 and SoI-2, and by switching the switch SW-6 to any of the contacts, the automatic control by the automatic control mechanism is interrupted and priority is given to this automatic control. Then, each solenoid SoI-1, SoI is manually operated.
-2 is excited to operate the elevating device 42.

Further, the manual operation holding mechanism 24 has a reset/reset function.
Set flip-flop (RSFF) circuit 25
and a first and second inverter 26, 27 connected to the set position and reset position of the circuit 25, the first inverter 26 is connected to the manual switch SW-6, and the RSFF circuit 25 is While the output side is connected to one input terminal of the NAND circuit 22, this NAND circuit 22 and the
Connect to one input terminal of the RSFF circuit 20.

Further, the cutting height control device includes the cutting section 6.
In conjunction with the operation of the reaping clutch, which turns the power on and off to the
In priority to the automatic control mechanism, the lifting device 42
A reaping clutch operation priority mechanism 28 is provided to operate the reaping clutch.

The priority mechanism 28 connects a first differentiating circuit 29 to the reaping switch SW-7 which is interlocked with the reaping clutch, connects an inverter 30 and a second differentiating circuit 31 in parallel with the differentiating circuit 29, and connects the reaping switch SW-7 to the reaping switch SW-7. -7 and the first differentiating circuit 29 are respectively connected to one input terminal of the fourth AND circuit 20 and to one input terminal of the NAND circuit 22, while the inverter 30 and the second differentiating circuit 31 is connected to one input terminal of a fifth AND circuit 33 via a monomulti circuit 32, and the other input terminal of the circuit 33 is connected to the RSFF circuit 2.
The output side of the circuit 33 is connected to the second solenoid SoI-2, and the output side of the circuit 33 is connected to the second solenoid SoI-2.

Further, the cutting height control device is provided with a low speed switching means 34 that lowers the operating speed of the lifting device 42 in the reaping section 6, and a manual switch SW-6 which is switched by operating the manual operating mechanism 23.
A low-speed switching circuit 35 for operating the low-speed switching means 34 is connected to the manual circuit connected to.

The low speed switching circuit 35 is connected to the manual switch.
Two mono multi circuits 36 connected to each contact of SW-6, and two third and fourth solenoids connected to each mono multi circuit 36 and switching the lifting device 42 of the reaping section 6 from high speed to low speed. SoI−
3. Consisting of SoI-4, the manual switch SW
-6 switching operation allows each solenoid SoI-
3. Hold any of SoI-4 for a certain period of time (e.g. 5 seconds)
Thus, the elevating device 42 is operated at a low speed both in ascending and descending. Incidentally, when the above-mentioned certain period of time is exceeded, the elevating device 42 is switched to high speed.

As shown in FIG. 4, the low-speed switching means 34 is connected in parallel to the secondary side of a 3-position, 4-port first switching valve 37 that is connected to the pump P and switches the lifting device 42 to the ascending or descending side. Two connected second and third switching valves 38 and 39, and a first hydraulic circuit 4 that does not have a throttle on the output side of the second switching valve 38.
0 and a second hydraulic circuit 41 having a throttle 41a, each of these hydraulic circuits 40, 41 is connected to a head side chamber of the lifting device 42 that lifts and lowers the reaping section 6, and the second switching valve 38 with the third solenoid SoI-3, the hydraulic circuits 40 and 41 are selected, and pressure oil is supplied from one of the circuits 40 and 41 to the lifting device 42, and the lifting device This is done by switching the rising speed of 42 between high and low speeds.

Also, to the output side of the third switching valve 39, a first hydraulic circuit 43 without a throttle and a second hydraulic circuit 44 having a throttle 44a are connected, as with the second switching valve 38. Each hydraulic circuit 43, 44
is connected to the rod side chamber of the lifting device 42, and the third switching valve 39 is switched by the fourth solenoid SoI-4, thereby controlling each of the hydraulic circuits 43, 4.
4 is selected, pressure oil is supplied to the lifting device 42 from one of the circuits 43 and 44, and the lifting device 4
2. Switch the descending speed between high and low speed.

In this way, each solenoid of the low speed operation circuit 35
By selectively operating SoI-3 and SoI-4, the second and third switching valves 3 of the low-speed switching means 34
By switching between 8 and 39, the lifting speed of the lifting device 42 is controlled to be switched between high and low speeds.

In the embodiment shown in FIG.
A storage space 46 for the fuel tank 45 is formed in the lower part of the storage space 46, and controllers 47 are arranged on both sides of the fuel tank 45 within this storage space 46, and the upper part of each controller 47 and the side on the fuel tank 45 side are arranged. A cover 48 is provided to cover the controller 47, and the cover 48 prevents fuel spilled from the fuel tank 45 from coming into contact with the controller 47.

The cutting height control device of the present invention is constructed as described above, and when the cutting height of the cutting section 6 is automatically controlled by the automatic control mechanism, the key switch is activated.
SW-4, threshing switch SW-5, and reaping switch SW-7 are turned on, and the setting input device 13 is turned on.
For example, select the low position and switch to that position.Then, the third position corresponding to the low position of the setting input device 13 is selected.
A signal is output to one input terminal of the AND circuit 18, and the cutting height position sensor 9 detects the cutting height until the cutting section 6 is positioned at the low position set by the setting input device 13. The third switch SW-3 of the position sensor 9 is held in the ON operating state, and a signal is output to the other input terminal of the third AND circuit 18, so that the AND circuit 18 outputs an output signal. The output signal is passed through the OR circuit 19 to the output signal 1 of the first output device 20.
input to two input terminals.

Further, when the reaping switch SW-7 is turned on, the reaping switch SW-7 is transferred to the first output device 20.
It is input to the input terminal corresponding to the switch SW-7 of the holding mechanism 24.
The RSFF circuit 25 outputs a signal from the output side when the manual switch SW-6 is in an inactive state, that is, in a neutral state, and this signal is transmitted to the RSFF circuit of the first output device 20.
The signal is input to the input terminal corresponding to the circuit 25, that is, the signal is input to all the input terminals of the first output device 20, and therefore the signal is output from the output side of the first output device 20. The first solenoid SoL-1 is energized by the signal, the lifting device 42 is switched to the lowering side, and the reaping section 6
It is lowered from the upper retracted position.

When the reaping section 6 is lowered to the low position set by the setting input device 13, the third switch SW-3 of the cutting height position sensor 9 is turned off, and accordingly, the third switch SW-3 of the cutting height position sensor 9 is turned off. circuit 18
The output of the signal to one input terminal of Moved and held.

Further, when the reaping operation of the reaping section 6 is temporarily stopped, the reaping clutch is disengaged to stop the reaping section 6, and then the reaping switch SW-7 is turned off in conjunction with the reaping clutch.
Accordingly, a signal is output from the inverter 30 to one input terminal of the fifth AND circuit 33 via the monomulti circuit 32, and the manual operation mechanism 2
The manual switch SW-6 operated by the holding mechanism 2 is in the inactive state, that is, the neutral position.
A signal is output from the No. 4 RSFF circuit 25 to the other input terminal of the second output device 33, and therefore the signal is output from the No. 5 AND circuit 33 to the second solenoid SoL.
-2, the lifting device 42 is switched to the rising side, and the reaping unit 6 is outputted via the lifting device 42.
When the reaping operation is to be resumed, the reaping switch SW-7 is turned on in conjunction with the reaping clutch, and the reaping section 6 is moved to the position set by the setting input device 13. It will be lowered.

Therefore, when the reaping section 6 is raised and lowered by the on/off operation of the reaping switch SW-7, the first and second solenoids SoL-1, SoL
-2 excitation, the first switching valve 37 shown in FIG. 4 is switched, and the second and third switching valves 3
8, 39 to a first hydraulic circuit 40 without a throttle;
43, a large amount of pressure oil is supplied to the lifting device 42, and the lifting device 42 is raised and lowered at high speed.

In addition, when finely adjusting the cutting height position of the reaping section 6 after raising and lowering the reaping section 6 by switching the reaping clutch, the manual switch
SW-6 is switched to the ascending and descending sides, and by doing so, the third and fourth solenoids SoL-3 and SoL-4 are energized, and the second and third switching valves 38 shown in FIG. 4 are energized. , 39 are switched,
A small amount of pressure oil is supplied from the switching valves 38, 39 to the lifting device 42 through hydraulic circuits 41, 44 having throttles 41a or 44a, so that the lifting device 42 can be adjusted up and down accurately at low speed. .

The reason why the vertical movement of the lifting device 42 is adjusted to a low speed as described above is because the manual switch SW-
6, the mono multi circuit 3
The manual switch cannot be activated even after the specified period of time (for example, 5 seconds) set in step 6 has passed.
When the switching operation of SW-6 is continued, the switching is performed again at high speed.

Therefore, the fine adjustment at low speed can generally be completed within the above-mentioned time, but if the fine adjustment is not completed within this time, the switching operation of the manual switch SW-6 is temporarily released, By performing the operation again, the low speed fine adjustment within the above-mentioned fixed time can be performed again.

In addition, as described above, the manual switch SW-6
If you operate it for longer than a certain period of time, you can switch to a high speed, so you can check the raising and lowering operation of the reaping unit with the reaping unit stopped, or when you manually raise and lower the reaping unit over the entire stroke. If the mowing position is to be adjusted significantly, the mower can be raised and lowered at high speed.

(Effect of the invention) As explained above, the cutting height control device for a reaper according to the invention has a setting input device 13 for setting the cutting height and a cutting height detection sensor 9, and controls the operation of the lifting device. An automatic control mechanism that automatically controls the
A reaping clutch operation priority mechanism 28 is linked to the operation of the reaping clutch that inputs power to the reaping section 6, and operates the lifting device at high speed in priority over the automatic control mechanism; A manual operation mechanism 23 for operating the lifting device is provided, and a low speed switching means 34 for slowing down the operating speed of the lifting device is provided in the drive system of the lifting device.
is provided, and when manually operated by the manual operation mechanism 23, the low speed switching means 34 is switched to the low speed side, the lifting device is operated at a low speed for a certain period of time, and after a certain period of time has passed, it is switched to the high speed side, and the lifting device is operated. Since the low-speed operation circuit 35 is provided to operate at high speed, when operating the reaping clutch operation priority mechanism 28 during reaping work in automatic mode, the lifting device is operated at high speed, and the reaping section 6 is operated up and down at high speed. However, while the priority mechanism 28 can quickly raise and lower the reaping section 6 and improve work performance, the single manual operation mechanism 23 allows the reaping section 6 to be raised and lowered at a low speed to accurately determine the reaping position. It is possible to make fine adjustments and to manually raise and lower the entire stroke of the reaping section 6 by raising and lowering it at high speed and with a wide range of adjustment.

That is, one manual operation mechanism 23, that is, a manual switch SW that has two switching contacts as shown in the embodiment and raises or lowers the lifting device 42.
-6, the reaping section 6 can be raised and lowered manually. Since a low-speed operation circuit 35 is provided that operates the lifting device at a low speed for a certain period of time and switches to a high speed side after a certain period of time has elapsed, the lifting device is operated at high speed. It is possible to finely adjust the elevation and descent at low speeds and at high speeds.

More specifically, when finely adjusting the reaping position of the reaping section 6, the manual operation mechanism 23
With this operation, the low-speed operation circuit 35 operates, switches the low-speed switching means 34 to the low-speed side, lowers the operating speed of the lifting device, raises and lowers the reaping section 6 at low speed, and raises and lowers the reaping section accurately. In addition, as described above, the vertical movement of the lifting device 42 is adjusted to a low speed only within a certain period of time from the time when the manual operating mechanism 23 is operated. When the manual operation mechanism 23 is operated for a longer time than a certain time, the low speed switching means 34 switches from the low speed side to the high speed side and operates the lifting device at high speed.
As a result, while the manual operating mechanisms 23 are unified, the reaping section 6 can be operated by this single manual operating mechanism 23.
can be raised and lowered manually over the entire stroke, and in this case the reaping section 6 can be finely adjusted and adjusted at high speed.

As a result, the reaping section can be operated by one manual operation mechanism 23 without having to take the trouble to provide a high-speed manual operation mechanism separately from a low-speed manual operation mechanism and operate these high-speed and low-speed manual operation mechanisms separately. 6. Fine adjustment of the reaping position by raising and lowering the reaping unit at low speed, manual raising and lowering of the entire stroke of the reaping unit, and adjusting the reaping position of the reaping unit to check the raising and lowering movement of the reaping unit with the drive of the reaping unit stopped. It can be raised and lowered at high speed without manual lifting for large adjustments.

Further, the fine adjustment of the reaping section 6 at low speed can generally be completed within the above-mentioned time, but if the fine adjustment is not completed within this time,
By once releasing the operation of the manual operation mechanism 23 and operating it again, the fine adjustment at low speed within the above-mentioned fixed time can be performed again.

[Brief explanation of the drawing]

Fig. 1 is a front view of a combine harvester incorporating the cutting height control device according to the present invention, Fig. 2 is a partially cutaway front view showing the cutting height position sensor, and Fig. 3 is the cutting height control device. Circuit Diagram FIG. 4 is a circuit diagram showing a hydraulic circuit. 1... Machine body, 6... Reaping section, 9... Cutting height position sensor (cutting height detection sensor), 13...
...Setting input device, 23...Manual operation mechanism, 28...
Reaping clutch operation priority mechanism, 34...Low speed switching means, 35...Low speed operation circuit, 42... Lifting device.

Claims (1)

[Scope of utility model registration request] This is a cutting height control device for a reaper in which a reaping part 6 is supported so as to be movable up and down with respect to a machine body 1 via a lifting device, and has a setting input device 13 for setting the cutting height and a cutting height detection sensor 9. , an automatic control mechanism that automatically controls the operation of the lifting device and an operation of a reaping clutch that inputs power to the reaping section 6, and operates the lifting device at high speed in priority to the automatic control mechanism. Reaping clutch operation priority mechanism 28
and one manual operation mechanism 23 that operates the lifting device with priority over the automatic control mechanism, and a low speed switching means 34 that lowers the operating speed of the lifting device in the drive system of the lifting device. hand,
During manual operation by the manual operation mechanism 23, the low speed switching means 34 is switched to the low speed side, the lifting device is operated at low speed for a certain period of time, and after a certain period of time has passed, it is switched to the high speed side, and the lifting device is operated at high speed. A cutting height control device for a reaper, characterized in that a low speed operation circuit 35 is provided.