Agricultural working machine

Abstract

An agricultural working machine has a first axle and a second axle, multiple ground-engaging means disposed at the first and second axles that are at least partially drivable by a drive engine or are steerable using steering-knuckle steering, a steering-angle sensor disposed at a steerable ground-engaging means for detecting a set steering angle (.sub.th) and a steering brake for the selective braking of one or more drivable, ground-engaging means for steering support. A control unit controls and regulates the at least one steering brake based on a steering angle (.sub.th, .sub.tat) or a slip angle () of at least one of the steerable ground-engaging means.

Claims

1. An agricultural working machine comprising: a first axle disposed at a front of the machine; a second axle disposed at a rear of the machine; multiple ground-engaging means disposed at the first axle and the second axle, wherein the multiple ground engaging means are configured to be drivable by a drive engine or are configured to be steerable using steering-knuckle steering means or are configured to be both drivable by a drive engine and steerable using steering-knuckle steering means; at least one steering-angle sensor disposed at an associated steerable ground-engaging means for detecting a set steering angle (.sub.th) of the associated steerable ground-engaging means; at least one steering brake for the selective braking of one or more of the drivable ground-engaging means on the second axle for steering support; and a controller for controlling and regulating the at least one steering brake; wherein a slip angle () of the steerable ground-engaging means is determined, and the controller is configured for automatically activating the at least one steering brake during a turning action of the agricultural machine in response to an operator turning a steering wheel, depending on the slip angle () or both the set steering angle (.sub.th) and the slip angle (), wherein based on said configuration of the controller, manual activation of the steering brake during the turning action is not required, and the turning rate can be increased due to activation of the at least one steering brake.

2. The agricultural working machine according to claim 1, wherein the controller controls and regulates the at least one steering brake depending on the set steering angle (.sub.th), an output speed of a transmission of the working machine and a circumferential speed (v.sub.i, v.sub.a) of at least one drivable ground-engaging means, which is disposed on an inside of a curve.

3. The agricultural working machine according to claim 2, wherein the slip angle () of the at least one steerable ground-engaging means is determined depending on the steering angle (.sub.th), a working machine geometry (I, s) and the circumferential speeds (v.sub.i, v.sub.a) on an inside of a curve and on an outside of a curve of the at least one steerable ground-engaging means.

4. The agricultural working machine according to claim 1, wherein an activation of the at least one steering brake is carried out depending on a ratio between a theoretical circumferential speed (v.sub.i, th, v.sub.a, th) and an actual circumferential speed (v.sub.i, tat, v.sub.a, tat) of at least one driven ground-engaging means.

5. The agricultural working machine according to claim 1, wherein the at least one steering brake is activated if the machine speed drops below a limiting speed (v.sub.G).

6. The agricultural working machine according to claim 1, wherein the at least one steering brake is activated if a steering angle exceeds a limiting steering angle (.sub.G), if a slip angle exceeds a limiting slip angle (.sub.G) or both.

7. The agricultural working machine according to claim 1, further comprising a gyroscope for detecting an angular velocity () of the working machine.

8. The agricultural working machine according to claim 7, wherein the gyroscope determines an actual steering angle (.sub.i, tat, .sub.a, tat).

9. The agricultural working machine according to claim 1, further comprising a navigation system that is satellite-supported and provides position data for determining a curve radius (R.sub.HA, R.sub.VA) of one of the first axle and the second axle.

10. The agricultural working machine according to claim 8, wherein the actual steering angle (.sub.i, tat, .sub.a, tat) is determined by a curve radius (R.sub.HA, R.sub.VA).

11. The agricultural working machine according to claim 1, wherein one of the multiple ground-engaging means is a wheel or a crawler track.

12. A steering-support method for an agricultural working machine comprising at least a first axle located at a front of the machine and a second axle located at a rear of the machine, multiple ground-engaging means disposed at the at least first and second axles (12, 14) that are at least partially drivable by a drive engine, are steerable using steering-knuckle steering, or both, at least one steering-angle sensor disposed at a steerable one of the multiple ground-engaging means for detecting a set steering angle (.sub.th) of the steerable one of the multiple ground-engaging means, at least one steering brake for the selective braking of a driving one of the multiple ground-engaging means on the second axle for steering support and a control unit for the controlling and regulating the at least one steering brake, the method comprising the steps of: determining a slip angle () of at least one steerable ground-engaging means or determining a set steering angle (.sub.th) and a slip angle () of at least one steerable ground-engaging means; and automatically controlling and activating the at least one steering brake depending on the slip angle () or both the set steering angle (.sub.th) and the slip angle () during a turning action of the agricultural machine in response to an operator turning a steering wheel of the agricultural working machine, wherein manual activation of the steering brake during the turning action is not required.

13. The steering-support method according to claim 12, further comprising activating the at least one steering brake depending on one or more of the group consisting of at least one of the following: a ratio between a set circumferential speed (v.sub.i, th, v.sub.a th) and an actual circumferential speed (v.sub.i, tat, v.sub.a, tat) of at least one driven ground-engaging means, a limiting speed (v.sub.G), a limiting steering angle (.sub.G) and a limiting slip angle (.sub.G).

14. The steering-support method according to claim 13, further comprising determining an angular velocity of the working machine using a gyroscope.

15. The steering-support method according to claim 14, further comprising determining the slip angle () of the at least one ground-engaging means using the gyroscope.

16. The steering-support method according to claim 14, further including determining a curve radius (R.sub.HA, R.sub.VA) of at least one of the first axle and the second axle using a satellite-supported navigation system.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features and advantages of the invention will become apparent from the description of embodiments that follows, with reference to the attached figures, wherein:

(2) FIG. 1 shows a schematic side view of an agricultural working machine;

(3) FIG. 2 shows a schematic view of an axle arrangement of an agricultural working machine comprising a steered and a driven axle;

(4) FIG. 3a shows a schematic depiction of an axle arrangement of a working machine for the slip angle-based control and regulation of the steering brake;

(5) FIG. 3b shows a schematic detailed view of a steered ground-engaging means of the axle arrangement shown in FIG. 3a; and

(6) FIG. 4 shows a diagram of the response characteristic of the steering brake depending on a slip angle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(7) The following is a detailed description of example embodiments of the invention depicted in the accompanying drawings. The example embodiments are presented in such detail as to clearly communicate the invention and are designed to make such embodiments obvious to a person of ordinary skill in the art. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention, as defined by the appended claims.

(8) A schematic side view of an agricultural working machine 10 in the form of a tractor constructed according to the inventive principles is depicted in FIG. 1. Please note, however, that an agricultural working machine 10 constructed according to the invention also can be a self-propelled harvesting machine such as a combine harvester or a forage harvester, or any other type of working machine used for agricultural work. The exemplary agricultural working machine 10 in the form of a tractor comprises a first axle 12 in the form of a steered front axle and a second axle 14 in the form of a rigid rear axle. In the case of a self-propelled harvesting machine such as a combine harvester, the first axle can be, for example, a steered rear axle and the second axle can be a rigid front axle. Ground-engaging means 16 are disposed at each of the axles 12, 14. The ground-engaging means 16 can be wheels or crawler tracks.

(9) The agricultural working machine 10 can be equipped exclusively with wheels or crawler tracks, or in the form of a so-called half-track. Where the agricultural working machine 10 is a half-track, ground-engaging means 16 in the form of wheels are disposed at one axle and ground-engaging means 16 in the form of crawler tracks are disposed at another axle. In the case of a working machine 10 in the form of a tractor comprising half-tracks, steerable wheels are disposed at the first axle 12, i.e., the front axle, and crawler tracks are disposed at the second axle 14, i.e., the rear axle. The ground-engaging means 16 at the first axle 12 are designed so as to be steerable using steering-knuckle steering.

(10) The working machine 10 comprises a drive engine 18, which is operatively connected to the second axle 14, i.e., the rear axle, via a transmission 20 and a drive train 22, in order to bring a drive torque provided by the drive engine 18 to the rear axle. While the working machine 10 is depicted in FIG. 1 having a rear-wheel drive, the steering support according to the invention also can be used for working machines having all-wheel drive, in which case one axle can be steerable and/or drivable. A differential gearbox (not illustrated) is usually disposed at the driven axle 14 in order to distribute the drive torque to the ground-engaging means 16. A steering brake 22 is disposed at the second axle 14, i.e., the rear axle, which provides for a unilateral braking of ground-engaging means 16 of the second axle 14. Assigned to each of the ground-engaging means 16 at the second axle 14 are braking devices 34, which are jointly actuated as a service brake in order to reduce the speed of the working machine 10, for example, during road travel. These braking devices 34 can be actuated individually, on a particular side, as a steering brake 22, whereby a unilateral deceleration of the working machine 10 is made possible in order to achieve a very small turning radius. Braking devices 34 of a service brake and/or a steering brake 22 of a modern agricultural working machine 10 are usually hydraulically actuatable, wherein, for the purpose of a brake engagement, a hydraulic brake pressure is built up, which results in a braking force at the corresponding ground-engaging means 16.

(11) At the driven second axle 14, a revolutions per minute sensor 26 is assigned to one or both ground-engaging means 16 disposed at the axle 14, in order to detect the speed of the particular ground-engaging means 16. The output speeds of the drive engine 18 and the transmission 20 are determined via a drive-motor sensor 28 and a transmission sensor 30. In addition, the operative gear ratio of the transmission 20 is determined via the transmission sensor 30 and the output speed of the drive engine 18. At the steerable first axle 12, i.e., the front axle, a steering-angle sensor 32 is disposed on one or both ground-engaging means 16, by which a steering angle set at the particular ground-engaging means 16 is determined. The steering angle is set depending on a steering movement of an operator of the working machine 10, for example, via a steering wheel, in order to change the direction of travel of the working machine 10. The steering angle in this case is the steering angle set at a ground-engaging means 16, i.e., the angle through which the ground-engaging means 16 is deflected out of its initial position for straight-ahead travel of the working machine 10.

(12) According to the invention, the steering brake 22 of the agricultural working machine 10 is automatically actuated by a control unit 24 depending on a steering angle .sub.th, which has been set and/or a slip angle , in order to support a steering movement of the working machine 10, which is specified via the first axle 12, i.e., the steerable front axle. The agricultural working machine 10 comprises a gyroscope 38 for the slip angle-based control and regulation of the steering brake 22, which gyroscope is connected to the control unit 24 for the purpose of signal transmission. A navigation system 40, which is satellite-based, in particular, of the working machine 10 is likewise connected to the control unit 24, and so position signals of the navigation system 40 are utilized by the control unit 24, in particular for a slip angle-based control and regulation of the steering brake 22.

(13) FIG. 2 shows a schematic top view of an axle arrangement of an agricultural working machine 10 having a steering brake 22 and the geometric relationships of the axle arrangement, such as the track s and the wheelbase I of the working machine 10. The first axle 12 is a steered front axle having ground-engaging means 16, for example, wheels or crawler tracks, disposed thereon. The ground-engaging means 16 are each deflected through a set steering angle , for example, by use of a steering-knuckle steering (not illustrated), wherein the ground-engaging means 16 on the inside of the curve is deflected through the steering angle .sub.i, which is greater than the steering angle .sub.a of the ground-engaging means 16 on the outside of the curve, since the curve radius of the inner ground-engaging means 16 is smaller than the curve radius of the outer ground-engaging means 16. For the front axle, a mean value .sub.m can be calculated on the basis of the steering angles .sub.i, .sub.a of the inner and the outer ground-engaging means 16 on which the curve radius R.sub.VA of the front axle is based. Due to the curve radius R.sub.HA passed through by the second axle 14, i.e., the rear axle, at the speed v.sub.m in the center point thereof, the circumferential speeds v.sub.i, v.sub.a of the ground-engaging means 16 on the inside of the curve and on the outside of the curve have different values. The circumferential speeds v.sub.i, v.sub.a of the ground-engaging means 16 are dependent on the set steering angles .sub.i, .sub.a, wherein the circumferential speed v.sub.i of the ground-engaging means 16 on the inside of the curve is set by the steering brake 22 for the purpose of providing steering support in accordance with the set steering angle .sub.i.

(14) The control and regulation of the steering brake 22 is based only on the geometric steering configuration and is carried out depending on the set steering angle .sub.i, .sub.a, of at least one ground-engaging means 16, which angle can be detected by a steering-angle sensor 32, for example, at the ground-engaging means 16 on the inside of the curve. The steering angle .sub.a of the ground-engaging means 16 located on the outside of the curve can be determined via the steering kinematics of the first axle 12, which is stored in the control unit 24. For the purpose of controlling and regulating the steering brake 22, the control unit 24 requires not only the theoretical circumferential speed v.sub.i,th, v.sub.a,th of the inner and the outer ground-engaging means 16, but also their actual circumferential speeds v.sub.i,tat, v.sub.a,tat, whereby, for example, the influence of excessive slip is compensated for and excessive braking of the inner ground-engaging means 16 is avoided. The theoretical circumferential speeds v.sub.i,th and v.sub.a,th of the inner and the outer ground-engaging means 16 are determined via the geometric relationships at the rear axle 14. The actual circumferential speed v.sub.i,tat, v.sub.a,tat of the ground-engaging means 16 on the inside of the curve and on the outside of the curve are determined on the basis of their measured speeds and the particular rolling radii, for example, of the wheels or crawler tracks. In this case, just one revolution per minute sensor 26 at a ground-engaging means 16 is sufficient, since the speed measured at the ground-engaging means 16 corresponds to the speed of an output shaft of the differential 36, which output shaft is driving the ground-engaging means 16. The speed of the other output shaft and, therefore, of the other ground-engaging means 16 is determined from the speed of the input shaft of the differential 36 and from the gear ratio of the differential 36. The speed of the input shaft of the differential 36 corresponds to the speed of the output shaft of the transmission 20, which is determined by the transmission sensor 30. Without a transmission sensor 30, the output speed of the transmission 20 is determined from the speed of the drive motor 12 and the operative transmission ratio.

(15) A control and regulation of the steering brake 22 is reliably carried out on the basis of the set steering angle .sub.i, th, .sub.a, th which is detected by a steering-angle sensor 32, the speed of a ground-engaging means of the second axle 14, which is detected by the revolutions per minute sensor 26, and the output speed of the transmission 20. In this case, the control unit 24, with the aid of the aforementioned sensor variables and the geometric relationships, determines at least both the theoretical, i.e., the set, as well as the actual circumferential speed v.sub.i,th, v.sub.i,tat of the ground-engaging means 16 on the inside of the curve and can regulate the steering brake 22 correspondingly. In this case, a deviation between the theoretical and the actual circumferential speed v.sub.i,th and v.sub.i,tat of the ground-engaging means 16 on the inside of the curve can be eliminated, for example, using a control loop, by actuating the steering brake 22 accordingly, in particular the braking device 34 on the inside of the curve. Another advantage is that the speed v.sub.m of the center point of the rear axle 14 also can be ascertained from the drive train, whereby the system is unsusceptible to the high slip values that often occur on muddy ground.

(16) FIG. 3a shows an embodiment of the steering brake 22 according to the invention, wherein a control and regulation of the steering brake 22 is carried out by the control unit 24 depending on at least one slip angle of a steered ground-engaging means 16 at the first axle 12, i.e., the front axle. The slip angle of a ground-engaging means 16 is the angle between the theoretical steering angle .sub.th, which is set via the steering, and the steering angle .sub.tat that is actually effectuating the movement of the working machine. A small slip angle is necessary in this case so that the ground-engaging means 16 can build up cornering forces in order to change the direction of travel.

(17) The regulation of the steering brake 22 and, in particular, of the brake pressure of each side of the steering brake 22 is carried out on the basis of a slip angle , which is determined by the control unit 24 and is formed from the difference of the set steering angle .sub.th and the actual steering angle .sub.tat. The speed of the ground-engaging means 16 is influenced via the control of the steering brake 22, the difference of which exerts an influence on the actual steering angle .sub.tat. Therefore, the actual steering angle .sub.tat is increased, for example, by a decelerationon the inside of the curveof the inner ground-engaging means 16 such that the actual steering angle is moved toward the set steering angle .sub.i, th, .sub.a, th is reduced as a result. The result thereof is that the working machine 10 changes its direction of travel substantially on the radius through the set ground-engaging means 16. The regulation of the steering brake 22 is carried out starting at a specified limiting slip angle .sub.G, whereby the build-up of cornering forces is made possible by a small slip angle .

(18) The regulation of the steering brake 22 depending on the slip angle has the advantage, as compared to a use of only a set steering angle, that a bulk of the yaw moment of the working machine 10 can thereby be realized via the steered first axle 12, which, due to the steering-knuckle steering disposed there, is more efficient than the steering brake 22. In order to regulate the steering brake 22, the set, theoretical steering angle .sub.i, th, .sub.a, th to of a ground-engaging means 16 is therefore compared, using the control unit 24, with its actual steering angle .sub.tat, and their difference is used to determine the slip angle . The portion of the working machine 10 schematically depicted in a top view in FIG. 3a comprises ground-engaging means 16 in the form of wheels on the front axle 12, i.e., the steered front axle. Ground-engaging means 16, for example, in the form of crawler tracks, are disposed at the second axle 14, i.e., the driven rear axle. The determination of the slip angle .sub.i for a ground-engaging means 16 disposed on the inside of the curve is described in the following, although the determination of the slip angle .sub.a can be carried out in an analogous manner.

(19) The slip angle .sub.i of the wheel 16 on the inside of the curve, which slip angle is supposed to be determined, is determined from the difference of the set steering angle .sub.i,th and the actual steering angle .sub.i,tat. The set steering angle .sub.i,th of the wheel 12 on the inside of the curve at the steered front axle 12 is determined directly by the steering-angle sensor 32. The actual steering angle .sub.tat is determined via the known geometric conditions of the working machine 10, such as the track s and the wheelbase I, values for both of which are be stored in the control unit 24, and on the basis of the circumferential speeds vi, v.sub.a of the two driven ground-engaging means 16 of the second axle 14, for example, the inner crawler track and the outer crawler track. The difference of the two circumferential speeds v.sub.i,a of the driven ground-engaging means 16, which can be determined via the curve radius R.sub.HA of the rear axle 14 and, if necessary, the track S, corresponds to the speed v.sub.L at the front axle 12, which is effective for the steering. Based on this speed v.sub.L (FIG. 3b), in combination with the speed v.sub.t acting in the actual steering direction, the actual steering angle .sub.i,tat can be determined, wherein the speed v.sub.t can be determined via an angular velocity of the working machine 10 about an instantaneous center M and the curve radius R.sub.i of the inner wheel.

(20) The angular velocity also can be determined, for example, by use of a gyroscope, for example, an inertial measuring unit or a gyro-stabilized platform. The curve radius R.sub.HA, for example, of the rear axle is determined by evaluating the position data using an available navigation system, which is satellite-supported, in particular.

(21) Threshold values can be specified in order to further improve an activation and the control and regulation of the steering brake. For example, a limiting speed can be specified, below which an activation of the steering brake is made possible, whereas activation is not possible at a speed of the working machine above the limiting speed, for example, during road travel of the working machine at a speed above the limiting speed. Likewise, a limiting angle .sub.G, .sub.G can be specified, for example, for the steering angle and/or the slip angle , wherein an activation of the steering brake 22 first takes place at an angle above the limiting angle .sub.G, .sub.G.

(22) FIG. 4 shows a diagram, in which the relationship of the slip angle with respect to a brake pressure P1, 2, which act on the steering brake 22, in particular the braking devices 34, is depicted. Below the limiting angle .sub.G for the slip angle , the steering brake 22 is not actuated, either in a left-hand curve (left side of the diagram) or in a right-hand curve (right side of the diagram). As a result, small slip angles or steering angles are tolerated, and so smaller steering movements take place exclusively via the steering, in particular, the steering-knuckle steering, of the front axle 12, which steers more efficiently than the steering brake 22. In addition, as a result, the efficiency of the working machine 10 during towing is increased, since a braking of the driven ground-engaging means 16 first takes place above the limiting angle .sub.G, .sub.G. If the limiting angle .sub.G, .sub.G is exceeded, a regulation of the steering brake 22 is carried out in accordance with the defined curve up to a maximum brake pressure for supporting the steering of the working machine 10.

LIST OF REFERENCE NUMBERS

(23) 10 agricultural working machine 12 first axle 14 second axle 16 ground-engaging means 18 drive engine 20 transmission 22 steering brake 24 control unit 26 revolutions per minute sensor 28 drive engine sensor 30 transmission sensor 32 steering-angle sensor 34 braking device 36 differential 38 gyroscope 40 navigation system .sub.i steering angle of the ground-engaging means on the inside of the curve .sub.a steering angle of the ground-engaging means on the outside of the curve .sub.m mean value of the steering angle .sub.th set steering angle .sub.tat actual steering angle .sub.G limiting steering angle slip angle .sub.G limiting slip angle R.sub.VA curve radius of the front axle R.sub.HA curve radius of the rear axle n curve radius of the inner ground-engaging means r.sub.a curve radius of the outer ground-engaging means v.sub.i circumferential speed of the ground-engaging means on the inside of the curve v.sub.a circumferential speed of the ground-engaging means on the outside of the curve v.sub.m speed of the rear axle v.sub.L speed of the front axle v.sub.r speed in the radial direction v.sub.t speed in the direction of the actual steering angle angular velocity M instantaneous center P.sub.1,2 brake pressure I wheelbase s track

(24) As will be evident to persons skilled in the art, the foregoing detailed description and figures are presented as examples of the invention, and that variations are contemplated that do not depart from the fair scope of the teachings and descriptions set forth in this disclosure. The foregoing is not intended to limit what has been invented, except to the extent that the following claims so limit that.