GB2107489A

GB2107489A - Automatic speed control of combine harvesters

Info

Publication number: GB2107489A
Application number: GB08225805A
Authority: GB
Inventors: Richard Christopher Gowe Danby
Original assignee: RDS FARM ELECTRONICS Ltd
Current assignee: RDS FARM ELECTRONICS Ltd
Priority date: 1981-09-09
Filing date: 1982-09-09
Publication date: 1983-04-27

Abstract

A combine harvester is equipped with grain loss sensors and their response is used to govern the speed of the combine to keep the loss to acceptable limits. To overcome the inherent delay factor, the harvested crop volume, which has a short term correlation with grain loss, is also monitored, and the combine speed is increased or decreased according to whether this volume is below or above a norm. A further control can be applied by monitoring the power applied to the threshing mechanism and reducing combine speed when this attains a maximum.

Description

SPECIFICATION Automatic speed control of combine harvesters This invention relates to the automatic speed control of combine harvesters.

It is important that a combine should be driven at an optimum speed to minimise grain loss, and various devices for determining this loss are known.

It is comparatively simple to use the signal from a grain loss sensor as one parameter in controlling the combine speed. However, the response is generally too slow, for it takes about 8 seconds for the straw to pass through the machine from being cut at the front end to being discharged at the rear end, and it is the grain being lost with this straw that is generally the most significant of the detected variables. Thus, the combine may have been operating at too fast or too slow a speed for about 8 seconds before any corrective action is generated. It would therefore be desirable to anticipate the detected grain loss and to control the combine speed by some early warning means.

According to the present invention there is provided a combine harvester speed control system wherein grain loss detection means are arranged to give an indication of acceptable or unacceptable grain loss and to govern the speed of the combine to maintain such loss in an acceptable band, and wherein harvested crop volume is monitored at the forward end of the combine and used to increase or decrease the combine speed according to whether that volume is below or above a level or range producing grain loss in the acceptable band.

It has been observed that as a general rule the more crop there is harvested the bigger is the grain loss, and vice versa, and that the relationship between crop volume and grain loss remains reasonably constant over a short term. Therefore, if a sudden upsurge in crop volume is detected as soon as it is harvested, then it is a reasonable assumption that there will be excessive grain loss.

This system immediately reduces the combine speed and therefore the resultant excess grain loss, before the sensors at the rear end of the machine can detect and transmit the information.

It has already been proposed to govern the speed of a combine, and in some cases the speed of its threshing cylinder, in response to harvested crop volume, decreasing the combine speed and increasing the cylinder speed, where that is possible, when the volume is high, and vice versa. But that was intended to reduce overloading the threshing devices, and took no account of grain loss. While there is a loose correlation between crop volume and grain loss it is by no means steady in the long term, and simply keeping the crop volume to a constant figure will not stabilise the grain loss. Therefore, aithough the sensors may not be called into play to such a great extent as a result of this early warning, nevertheless they do still have a control function whenever the grain loss does stray out of the acceptable band.Also, before this control system is switched into operation, it will usually be necessary to run the combine under manual control to determine the speed and crop volume level or range which will produce the minimum grain loss. The sensors heip supply this information, and the optimum crop volume level or range can then be registered in the system as a reference for the subsequent automatic control. This reference can be retained during interruptions in harvesting.

Over the long term, as noted above, the crop volume/grain loss relationship may change and the system will need adjustment. This could be done manually, but the preferred means will be automatic within the instrument, using the information from the sensors to override the original volume setting.

For example, if the grain loss is detected as being too high, the crop volume giving rise to that situation (the volume detected some seconds beforehand) can have been recorded and be available to compare with the existing crop volume norm. If it is equal, then that norm must be considered out-of-date and require adjusting. A new, lower volume can be set automatically, which will cause the combine to slow to a speed which will give less crop volume but acceptable grain loss. If, however, the comparison shows there was crop volume substantially above the existing norm, and the slowing of the combine was insufficient to keep the grain loss within bounds, the norm will be temporarily assumed to be still correct and the grain sensors will slow the combine further than that just caused by the crop volume detection.

The grain loss will then fall again into the acceptable band. When this is achieved, the crop volume just harvested may still not match the existing norm and may thus try to generate another change in combine speed. This would upset the grain loss again, and so the crop volume norm is adjusted to the new volume giving tolerable grain loss.

When there is negligible grain loss, this system will generate a higher forward speed, and if the loss remains low there is a tendency to ever-increasing speed. This can be checked by a maximum speed setting on a control module. Also with combines having distinct gear ratios, some form of warning, such as a light, can be arranged to be activated when the maximum or minimum speed for any particular gear ratio is achieved and the machine should be driven faster or slower.

Another limiting factor that can be fed into this system is the power applied to the threshing cylinder. Modern cylinders are very efficient at separating grain from straw, and so often there is very little grain loss. As noted above, this tends to increase the combine speed, and hence the power applied to the cylinder. Too much power, however, can be very damaging, and therefore a limit should be placed on it. Therefore, by measuring the power, for example by means of a pressure transducer in a hydraulically driven threshing mechanism, control can be exercised when that power reaches a maximum. This can override the grain loss signal, for obviously some slightly excessive grain loss is preferable to losing a much larger proportion through excessive threshing.

There are various ways of ascertaining harvested crop volume. Immediately after cutting, the crop is urged towards the centre line of the machine by an auger, and the torque on this could be measured to give an indication of the crop it is handling. After this, the crop is conveyed upwardly and rearwardly, and the torque on the drive for the intake elevator which performs this task could also be measured.

Alternatively, where the elevator is mounted to "float" and so accommodate variations in crop volume, the amount of deflection of that elevator can be detected and used to give an indication of volume. Another signal could be derived from the concave with which the rotating drum co-operates to thresh the crop. The concave could be mounted through strain gauges to the chassis of the machine, and these would give an indication of the volume of crop being threaded.

Claims

1. A combine harvester speed control system wherein grain loss detection means are arranged to give an indication of acceptable or unacceptable grain loss and to govern the speed of the combine to maintain such loss in an acceptable band, and wherein harvested crop volume is monitored at the forward end of the combine and used to increase or decrease the combine speed according to whether that volume is below or above a level or range producing grain loss in the acceptable band.

2. A system as claimed in claim 1, wherein the grain loss detection means exerts a control over said level or range to adjust the latter if the grain loss would otherwise persist at an unacceptable level.

3. A system as claimed in claim 1 or 2, wherein the power applied to the threshing mechanism is also monitored and used to decrease the combine speed when the power reaches a predetermined maximum.