Method and system for reducing vehicle oscillations

Abstract

A method for reducing vehicle oscillations for an agricultural vehicle with a drive engine, a running gear cooperating with the drive engine for driving wheels having pneumatic tires, and a control unit for regulating a tire pressure of at least one tire requires a number of steps. For example, the method includes generating a sensor signal as a function of at least one determined vehicle oscillation and regulating a tire pressure of at least one tire by the control unit as a function of the sensor signal in order to reduce the determined vehicle oscillation.

Claims

1. A method for reducing vehicle oscillations for an agricultural vehicle comprising a drive engine and a running gear cooperating with the drive engine for driving wheels having pneumatic tires and a control unit for regulating a tire pressure of at least one tire, the method comprising the steps of: specifying a limit value (S.sub.G) for the sensor signal (S, S, S); storing the limit value in the control unit; using a tractive force sensor, generating a sensor signal (S, S, S) as a function of at least one determined vehicle oscillation; and regulating, by the control unit, a tire pressure of at least one tire as a function of the sensor signal (S, S, S) to reduce the at least one determined vehicle oscillation, until the limit value (S.sub.G) is exceeded, said step of regulating comprising: lowering the tire pressure of the at least one tire to a minimum tire pressure, wherein the minimum tire pressure depends on a tire load capacity limit of the tire; and raising, in a stepwise manner, the tire pressure when the sensor signal (S, S, S) continuously exceeds the limit value (S.sub.G), until the sensor signal (S, S, S) drops below the limit value (S.sub.G).

2. The method according to claim 1, wherein a tire load capacity limit, a corresponding minimum tire pressure or both is stored in the control unit.

3. The method according to claim 1, wherein the sensor signal (S, S, S) is generated as a function of a measured vertical acceleration of the agricultural vehicle.

4. The method according to claim 1, wherein the sensor signal (S, S, S) is generated as a function of one or more of the following: a measured wheel, a measured axle, and an overall tractive force (F.sub.Z) which is required to draw an implement connected to the agricultural vehicle.

5. The method according to claim 1, wherein the sensor signal (S, S, S) is generated as a function of one or more of the following: a measured wheel load, an axle load (F.sub.A) and a vehicle weight (F.sub.G).

6. A method for reducing vehicle oscillations for an agricultural vehicle comprising a drive engine and a running gear cooperating with the drive engine for driving wheels having pneumatic tires and a control unit for regulating a tire pressure of at least one tire, the method comprising the steps of: specifying a limit value (S.sub.G) for the sensor signal (S, S, S); storing the limit value in the control unit; generating a sensor signal (S, S, S) as a function of at least one determined vehicle oscillation; and regulating, by the control unit, a tire pressure of at least one tire as a function of the sensor signal (S, S, S) to reduce the at least one determined vehicle oscillation, until the limit value (S.sub.G) is exceeded; wherein the sensor signal (S, S, S), is generated as a function of a measured output torque of the running gear, and wherein the step of regulating comprises: lowering the tire pressure of the at least one tire to a minimum tire pressure, wherein the minimum tire pressure depends on a tire load capacity limit of the tire; and raising, in a stepwise manner, the tire pressure when the sensor signal (S, S, S) continuously exceeds the limit value (S.sub.G), until the sensor signal (S, S, S) drops below the limit value (S.sub.G).

7. A system for reducing vehicle oscillations for an agricultural vehicle, comprising a drive engine; a running gear cooperating therewith for driving wheels having pneumatic tires; a tractive force sensor; and a control unit for regulating a tire pressure of at least one tire; wherein a sensor signal (S, S, S) is generated as a function of at least one ascertained vehicle oscillation, wherein a limit value (S.sub.G) specified for the sensor signal (S, S, S) is stored in the control unit, and a tire pressure of at least one tire is regulated by the control unit as a function of the sensor signal (S, S, S) to reduce the ascertained vehicle oscillation, the regulating carried out until the limit value (S.sub.G) is exceeded, and wherein the control unit is configured to regulate the tire pressure by lowering the tire pressure of the at least one tire to a minimum tire pressure, wherein the minimum tire pressure depends on a tire load capacity limit of the tire; and raising, in a stepwise manner, the tire pressure when the sensor signal (S, S, S) continuously exceeds the limit value (S.sub.G), until the sensor signal (S, S, S) drops below the limit value (S.sub.G).

8. An agricultural vehicle comprising the system for reducing vehicle oscillations according to claim 7.

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: presents a schematic side view of an agricultural vehicle; and

(3) FIG. 2: presents a schematic flow chart for carrying out the method for reducing the vehicle oscillations.

DETAILED DESCRIPTION OF THE INVENTION

(4) 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.

(5) FIG. 1 presents a schematic illustration, from the side, of an agricultural vehicle 10 in the form of a tractor, wherein the basic design of a tractor is assumed to be known to a person skilled in the art. The agricultural vehicle 10 may embody any vehicle that useable for agricultural work, for example, a tractor, a telehandler, a construction machine or a self-propelled harvesting machine.

(6) The agricultural vehicle, i.e., tractor 10, comprises a closed driver's cab 12 for accommodating an operator, wherein a control terminal 14 for operating the agricultural vehicle 10 is arranged within the driver's cab 12. The agricultural vehicle 10 comprises a plurality of wheels 16 arranged on a front axle and a rear axle. The wheels 16 each have pneumatic tires 18, which are engaged with a ground 20, in particular in order to transfer drive forces. The wheels 16 are driven by a drive engine 22, which is designed in the form of an internal combustion engine, and by a running gear 24 cooperating therewith.

(7) The running gear 24 is designed in the form of a hydraulically-mechanically power-split transmission comprising hydrostatic units 42 in the hydraulic power branch. An output torque of the running gear 24 is transferred to the wheels 16 via a drive train 26, which is schematically illustrated, wherein the illustrated agricultural vehicle 10 is a four-wheel drive vehicle. The agricultural vehicle 10 comprises various coupling devices 28 for drawing an agricultural implement (not illustrated). The illustrated tractor comprises both a three-point lifting unit 30 and a swinging drawbar 32, for example at the rear. An implement coupled to the swinging drawbar, for example, induces a tractive force F.sub.Z which acts substantially horizontally on the swinging drawbar 32. The tractive force F.sub.Z is measured via a tractive force sensor 34, for example.

(8) During tillage of the ground 20, the agricultural vehicle 10 may begin to bounce substantially in the vertical direction, in particular given dry ground 20 and a moderate to high tractive force F.sub.Z. These substantially vertically occurring vehicle oscillations are also known by the term power hop. These vertical vehicle oscillations can not only become unpleasant for the operator of the agricultural vehicle 10, but also can result in a fluctuation of the forces that can be transferred onto the ground and, therefore, in a dynamic fluctuation of the axle load F.sub.A, the tractive force F.sub.Z, and the output torque in the running gear 24, whereby damage can also occur to the agricultural vehicle 10 and/or the implement coupled thereto.

(9) According to the invention, a sensor signal S is generated as a function of at least one ascertained vehicle oscillation, in particular, a vertical vehicle oscillation, and a tire pressure of at least one tire is automatically regulated as a function of the sensor signal S by a control unit 36, which is arranged in the driver's cab 12, in order to reduce the ascertained vehicle oscillation. The ascertained vehicle oscillation can be a substantially vertical vehicle oscillation and/or a substantially horizontal vehicle oscillation, for example caused by a dynamic fluctuation of the tractive force F.sub.Z which acts in the horizontal direction.

(10) Depending on the ascertained vehicle oscillation, a sensor signal S is generated, for example, by the control unit 36, which is used to regulate the tire pressure of at least one tire 18. In order to regulate the tire pressure of one or more tires 18, the agricultural vehicle 10 comprises a tire pressure control system 38, which can be regulated by the control unit 36. The control unit 36 can be integrated into the tire pressure control system, for example. As a result, the tire pressure of one or more tires 18 can be regulated within the permissible operating parameters. A regulation of the tire pressures of the tires 18 can be carried out continuously as a function of the sensor signal S.

(11) In order to avoid a sustained operation of the tire pressure control system 38, a limit value S.sub.G for the sensor signal S is specified and stored in the control unit 36. A regulation of the tire pressure of the tires 18 is then carried out only when the sensor signal S exceeds the limit value S.sub.G, whereby vehicle oscillations up to an extent corresponding to the limit value S.sub.G are tolerated without triggering a regulation of the tire pressures. The sensor signal S is generated by a manual input by the operator, for example into the control terminal 14, wherein the input by the operator also corresponds to the limit value S.sub.G of the sensor signal S being reached. In addition, the sensor signal S is generated as a function of a measured acceleration of the agricultural vehicle 10. In this case, an acceleration sensor 40 is arranged on the front side, for example, of the agricultural vehicle 10, whereby substantially vertical vehicle oscillations and/or horizontal vehicle oscillations can be directly measured.

(12) A regulation of the tire pressure of the tires 18 is carried out when suitably specified acceleration values are exceeded, the associated sensor signals S of which correspond to the limit value S.sub.G. The sensor signal S also can be generated as a function of a measured output torque of the running gear 24. In this case, the pressures can be measured at the hydrostatic units 42 of the hydraulically-mechanically power-split running gear 24 and, if specified limit values that correspond to the limit value S.sub.G are exceeded, a regulation of the tire pressure of the tires 18 can be carried out. Likewise, a sensor signal S is generated by the tractive force sensor 34 as a function of the measured tractive force F.sub.Z. The limit value S.sub.G in this case is a specified limit value S.sub.G of the permissible tractive force F.sub.Z, for example. The sensor signal S also can be generated as a function of a measured wheel load, axle load F.sub.A or a vehicle weight F.sub.G. A load sensor 44 for determining the wheel load and/or axle load F.sub.A is provided on each wheel 16 in order to ascertain the vehicle weight F.sub.G and/or the axle loads F.sub.A. The vehicle weight F.sub.G also can be ascertained from the values determined by the load sensors 44. The permissible minimum tire pressure for a given axle load F.sub.A of the agricultural vehicle 10 corresponds to the so-called tire load capacity limit, which is determined from a tire load capacity table. The tire load capacity table is stored in the control unit 36 and from the axle load F.sub.A, which is ascertained by the load sensors 44, and/or the vehicle weight F.sub.G.

(13) FIG. 2 presents a flow chart of the method for reducing the vehicle oscillation of the agricultural vehicle 10. In a first step 100, the occurring vehicle oscillations are determined, for example by the acceleration sensor 40 and/or the tractive force sensor 35, and an associated sensor signal S is generated as a function of the ascertained vehicle oscillations. In a first decision step 110, the control unit 36 compares the generated sensor signal S with a limit value S.sub.G stored in the control unit 36.

(14) Provided the limit value S.sub.G is not reached by the sensor signal S, the determination of the vehicle oscillations and the generation of the sensor signals S is continued in step 100. When the limit value S.sub.G is reached by the sensor signal S, which can correspond to the occurrence of the so-called power hop vehicle oscillations, then, in a second step of the method 120, the control unit 36 lowers the tire pressure of at least one tire 18 to a minimum tire pressure, which corresponds to the load capacity limit of the tire 18 for a given axle load F.sub.A.

(15) In a third step 130, the vehicle oscillations are measured again and a 1.sup.st associated sensor signal S is generated. In a second decision step 140, the 1.sup.st associated sensor signal S is compared with the specified limit value S.sub.G once more. If the limit value S.sub.G is still exceeded, at least one tire pressure is raised by a discrete value in the subsequent, fourth step 150. In a fifth step 160, the oscillations are measured again and a 2.sup.nd associated sensor signal S is generated. The tire pressure of the tire 18 is raised in discrete steps until the associated sensor signal S drops below the limit value S.sub.G, which is monitored in the third decision step 170.

LIST OF REFERENCE NUMBERS

(16) 10 agricultural vehicle 12 operator's cab 14 control terminal 16 wheel 18 tire 20 ground 22 drive engine 24 running gear 26 drive train 28 coupling device 30 three-point lifting unit 32 swinging drawbar 34 tractive force sensor 36 control unit 38 tire pressure control system 40 acceleration sensor 42 hydrostatic unit 44 load sensor S, S, S sensor signal S.sub.G limit value F.sub.Z tractive force F.sub.A axle load F.sub.G vehicle weight 100 First step 110 first decision step 120 second step 130 third step 140 second decision step 150 fourth step 160 fifth step 170 third decision step

(17) 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.