GB2047427A - Automatic control of speed - Google Patents

Abstract

A combine harvester incorporating an automatic travelling speed control system is adapted to reduce its travelling speed with an increase in the threshing load. The travel speed control includes a unit for detecting the output speed of a first speed change unit 10 before the output is subjected to a speed change by a second speed change unit 11. The first speed change unit is preferably an hydraulic stepless speed change unit whose control linkage is automatically adjusted by an electric motor 23 when the torque changes. Electric transducers are used to provide signals of torque and speed. <IMAGE>

Description

SPECIFICATION Combine incorporating automatic running speed control system.

The present invention relates to a combine equipped with an automatic running speed control system comprising a first running speed change unit, a second running speed change unit for subjecting the output from the first speed change unit to speed change, a unit for detecting the speed change of the first speed change unit, a unit for detecting the load on a threshing unit and a drive assembly for operating the first speed change unit, the drive assembly being automatically operable in accordance with the speed change and the threshing load detected by the detecting units to maintain the speed change and the threshing load under preset control and obtain a reduced speed with an increase in the threshing load value.

When the running speed is controlled in this way, the amount of stalks to be reaped per unit time is variable with variations in the running speed, with the result that the amount of stalks to be fed to the threshing unit is variable to stabilize the threshing load.

Since the running speed is variable under preset control, the speed control can be effected with lesser hunching and with greater stability than the so-called on-off control in which when the threshing load varies to a value outside a preset range, the running speed is altered continuously until the threshing load varies to the preset range. The second speed change unit also gives a variable speed, such that the proper running speed set for a given threshing load value is variable.

While the threshing load value at the same running speed varies from field to field because of changes in the conditions of crops such as the wetness of stalks and the density of plantation, the second speed change unit, when operated for a speed change suited to a particular field, controls the speed properly for the particular threshing load. However, conventional means for detecting the speed change of the first speed change unit involve problems.

Stated more specifically, conventional detecting means comprise a potentiometer or stroke sensor for detecting the position of a member for operating the first speed change unit or the position of a link included in the link assembly for coupling the operating member to the speed change unit. Thus the operating member or the link is adapted to operate the potentiometer or the stroke sensor, so that for accurate detection there is the necessity of installing the potentiometer or the stroke sensor with high accuracy and making the operating member and the link with high precision.

This entails an increase in the manufacturing cost. While a stepless speed change unit of the hydraulic or belt type is generally used as the first speed change unit for smooth control, such a stepless speed change unit is liable to involve variations in transmission efficiency due to variations of load. Consequently, even if the components are installed or built with high accuracy, difficulties are encountered in assuring accurate detection and therefore in ensuring accurate control.

The present invention contemplates an improvement in the means for detecting the speed change afforded by the first speed change unit and provides a combine equipped with an automatic running speed control system of the foregoing type which is characterized in that the unit for detecting the speed change of the first speed change unit is adapted to detect the speed of rotation of a rotary member to be driven by the output of the first speed change unit before the output is subjected to a speed change by the secod speed change unit.

Accordingly the rotary member is rotatable with the first speed change unit accurately in synchronism therewith. Moreover the unit for detecting the speed of rotary member need not be attached to the rotary member with very high accuracy but nevertheless inherently assures detection with substantially high precison. The detecting unit is therefore less costly than the conventional means described above and yet is capable of accurately detecting the speed change provided by the first speed change unit. This assures speed control with improved accuracy while rendering the overall system inexpensive.

The invention will be described below in greater detail, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side elevation showing a combine incorporating an automatic running speed control system according to the invention; Figure 2 is a perspective view schematically showing a running power transmission system and a running speed change system; Figure 3 is a front view in vertical section showing a running transmission case; Figure 4 is a front view showing a torque detecting unit as installed in place; Figure 5 is a view in section taken along the line V-V in Fig. 4; Figure 6 is a view in section taken along the line VI-VI in Fig. 4; Figure 7 is a diagram showing the torque detecting unit; Figure 8 is a front view in vertical section showing a unit for detecting the speed of rotation; Figure 9 is a block diagram;; Figure 10 is a graph showing the relation between the torque and the speed change detected for control; and Figure 11 is a graph showing the relation between the detected torque value and the controlled running speed.

Fig. 1 is a side elevation showing a combine comprising a main body including a pair of opposite crawlers 1, 1, a threshing unit 2, etc. A reaping assembly connected to the front portion of the main body comprises means 3 for raising stalks, reaping means 4 for cutting stalks at the stub portions, a conveyor 5 for sending the cut stalks rearward toward the threshing unit 2, etc.

The threshing unit 2 is adapted to thresh the stalks with a rotary drum 7 while the stalks are being conveyed by a feed chain 6 provided on one side of the unit 2. After threshing, the stalks are fed to a cutter 8 and cut to small pieces.

With the travel of the combine, stalks are raised, reaped and then fed to the unit 2 for threshing.

Fig. 2 is a perspective view schematically showing a system for transmitting power to the crawlers 1, 1 and a running speed change system. An engine 9 is operatively connected to a hydraulic stepless speed change unit 10 serving as a first running speed change unit by a belt. The stepless speed change unit to is coupled to an input shaft 12 on a running transmission case 11 by a gear mechanism housed in a transmission case 1 3. The stepless speed change unit 10 has a speed change arm 1Qa connected by a link assembly 1 5 to a first speed change lever 14 which is pivotally movable forward or backward.The speed change unit 10 gives a forward higher speed as the first speed change lever 14 is turned forward from a neutral position N for affording a zero speed, while providing a rearward increasing speed as the lever 14 is turned backward from the neutral position N.

The running transmission case 11 houses a gear speed change unit 16 serving as a second running speed change unit as seen in Fig. 3. The unit 1 6 comprises a gear 1 7 which is composed integrally of three gears of different diameters, namely large, medium and small gears, and which is slidable axially thereof to give three different speeds. The speed change unit 1 6 has a speed change arm 1 6a connected by a link assembly 1 8 to a speed change lever 47 which is pivotally movable forward or backward for providing a variable speed.

Accordingly the running speed of the combine is variable by the stepless speed change unit 10 and by the gear speed change unit 1 6 for subjecting the output of the unit 10 to a speed change. For a reaping operation, the gear speed change unit 16 is set for a medium or low speed, while the unit 1 6 is usually set for a high speed when the combine is driven on roads. With the gear speed change unit 10 set for the desired speed, the stepless speed change untt 10 affords a steplessly variable speed.

Fig. 3 further shows drive shafts 19, 1 9 for the pair of crawlers 1, 1 and a pair of opposite steering transmission clutches 20, 20 for transmitting the output of the gear speed change unit 1 6 to the drive shafts 19, 1 9 or interrupting the transmission selectively.

The automatic running speed control system will now be described.

The system comprises a torque detecting unit 21 for detecting variations in the torque of the drum 7 as variations in the threshing load, a speed detecting unit 22 for detecting the speed of rotation of the input shaft 1 2 of the running transmission case 11 as the speed provided by the stepless speed change unit 10, and an electric motor 23 serving as drive means for operating the stepless speed change unit 10.

The torque detecting unit 21 will be described with reference to Figs. 4 to 7.

The rotary shaft 24 of the drum 7 is fixedly provided at its one end with a boss member 25, around which a pulley 26 for receiving power from the engine 9 is freely rotatably fitted with bearings provided therebetween.

Provided between the boss member 25 and the pulley 26 are coil springs (elastic members) 28 through which the power delivered to the pulley 26 is transmitted to the shaft 24. Gears 29, 30 of identical shape and size are secured to the pulley 26 and the boss member 25 respectively. Detectors 31, 32 are opposed to the peripheries of the gears 29, 30 for electrically detecting the passage of the teeth of the gears 29, 30.

The drive torque variations are detected in terms of the variations in the amount of elastic deflection of the coil springs 28, and the detected variations are delivered as voltage signals based on the phase differences of the pulse signals produced by the detectors 31 and 32.

The speed detecting unit 22 will now be described with reference to Fig. 8.

A support rod 40 is engaged in and fixed to one end of the input shaft 1 2. The rod 40 fixedly carries a gear 33. A detector 34 is provided as opposed to a peripheral portion of the gear 33 to electrically detect the passage of the teeth of the gear 33.

The variations in the speed of rotation of the input.-shaft 1 2 are detected in terms of the variations in the frequency per unit time of the pulse signals produced by the detector 34. The variations are delivered as voltage signals in accordance with the frequency.

The electric motor 23 is coupled to a pivotable link 15a of the link assembly 1 5 by way of worm speed reduction means 35 and frictional transmission means 36. The motor 23, when driven in a positive or reverse direction, operates the stepless speed change unit 10 to give an increased or reduced speed. The frictional transmission means 36 is provided to render the lever 14 operable as desired de spite the operation of the motor 23, for example, in the event of an emergency.

With reference to the block diagram of Fig.

9, the output from the speed detecting unit 22 and the output from the torque detecting unit 21 are fed to a checking circuit 37 for checking whether or not the relation between the threshing load value and the speed change afforded by the stepless speed change unit 10 is under preset control so as to give a lower speed with an increase in the threshing load value. In accordance with the check result provided by the circuit 37, the motor 23 is driven positively by a circuit 38a to give an increased speed or reversely by a circuit 38b to give a reduced speed. Pulse signal generator circuits 39a, 39b are interposed between the drive circuits 38a, 38b and the checking circuit 37 for driving the motor 23 intermittently.

The graph of Fig. 10 shows the control relation to be established by the checking circuit 37. The threshing load, namely the detected torque value Tis plotted as abscissa vs. the speed change. namely the speed of rotation, N, of the stepless speed change unit 10 as ordinate. The control relation is indicated at SO. Fig. 11 shows the relation between the detected torque value Tand the controlled actual running speed Vwhen the gear speed change unit 1 6 is set for the medium speed and when it is set for the low speed. Indicated at S1 is the relation at the low speed setting, and at S2 the relation at the medium speed setting.

With the automatic running speed control system described, the stepless speed change unit 10 operates for an increased or decreased speed in accordance with the variation of the threshing load to alter the amount of stalks to be repeated per unit time and thereby automatically stabilize the threshing load. Further in accordance with the density of the stalks planted and the wetness of the stalks, the operator sets the gear speed change unit 1 6 for the desired speed change to assure proper control under which a proper threshing load is available.When the density of the stalks is higher than the standard level or when the wetness of the stalks is greater than the standard degree, the threshing load is likely to vary with the tendency P1 indicated in Fig. 11 relative to the variation of the running speed, so that the operator will set the gear speed change unit 1 6 for the low speed. If the state of the stalks is standard, the variation of the threshing load relative to the variation of the running speed will exhibit the tendency P2 shown in Fig. 11. The operator will then set the unit 1 6 for the medium speed.

The first speed change unit 10, which is stepless speed change means in the embodiment described, may alternatively be a stepwise speed change unit.

The rotary member utilized for detecting the speed change of the first speed change unit 10 is not limited to the input shaft 1 2 used in the embodiment but may be any member which is driven by the output of the first speed change unit 10 before the output is subjected to a speed change by the second speed change unit 16.

Claims (4)

1. A combine incorporating an automatic running speed control system comprising a first running speed change unit, a second running speed change unit for subjecting the output from the first speed change unit to a speed change, a unit for detecting the speed change of the first speed change unit, a unit for detecting the load on a threshing unit and drive means for operating the first speed change unit, the drive means being automatically operable in accordance with the speed change and the threshing load detected by the detecting units to maintain the speed change and the threshing load under preset control and obtain a reduced speed with an increase in the threshing load value, the combine being characterized in that the speed change detecting unit for the first speed change unit is adapted to detect the speed of rotation of a rotary member to be driven by the output of the first speed change unit before the output is subjected to a speed change by the second speed change unit.

2. A combine as defined in claim 1 wherein the first speed change unit is a hydraulic stepless speed change unit.

3. A combine as defined in claim 1 wherein the speed change detecting unit for the first speed change unit is provided with a support rod at least rotatable with the rotary member, a gear mounted on the support rod and a detector opposed to a peripheral portion of the gear for electrically detecting the passage of the teeth thereof.

4. A combine incorporating an automatic running speed control system constructed and arranged to operate substantially as herein described with reference to and as illustrated in the accompanying drawings.