Method for controlling the engine speed of a utility vehicle

Abstract

A method is provided for controlling engine speed of a drive engine of a utility vehicle having a drivable loading apparatus. The method includes detecting or predicting a driving movement of the loading apparatus, and requesting an increase of engine speed if the movement of the loading apparatus is predicted or detected.

Claims

1. A method for controlling engine speed of a drive engine of a utility vehicle having a drivable loading apparatus, comprising: detecting or predicting a driving movement of the loading apparatus; requesting an increase of engine speed if the movement of the loading apparatus is predicted or detected; increasing the engine speed by a predetermined increase rate to an elevated engine speed; and predicting movement of the loading device before the detecting step.

2. The method of claim 1, further comprising controlling the engine speed at an idling speed when the utility vehicle is stationary.

3. The method of claim 1, further comprising: triggering a predetermined waiting period; determining if the elevated engine speed is elevated about a predetermined limit speed; reducing the engine speed if the predetermined waiting period has expired and no driving movement of the loading apparatus has been requested until the expiration of the waiting period.

4. The method of claim 1, wherein the driving movement of the loading apparatus is predicted or detected depending on a detected state signal, wherein the state signal is indicative of an operating state of the loading apparatus.

5. The method of claim 1, further comprising: hydraulically driving the loading apparatus; determining a target hydraulic flow of a hydraulic drive pump of the utility vehicle depending on the predicted or detected driving movement of the loading apparatus; and requesting the increase of engine speed based on the determined target hydraulic flow.

6. The method of claim 5, wherein the determining step comprises determining the target hydraulic flow based on a detected valve control signal for at least one hydraulic valve of the loading apparatus.

7. The method of claim 5, wherein the determining step comprises determining the target hydraulic flow based on at least one of a requested drive movement of the loading apparatus, a drive characteristic of the loading apparatus, and a requested target position of the loading apparatus.

8. The method of claim 5, wherein the determining step comprises determining the target hydraulic flow based on at least one hydraulic unit of the utility vehicle.

9. The method of claim 5, wherein the requesting step comprises requesting the increase of the engine speed for a request period that is determined based on the target hydraulic flow.

10. The method of claim 1, wherein the elevated engine speed is less than or equal to a predetermined limit speed.

11. The method of claim 1, further comprising lowering the engine speed at a predetermined decrease rate after being increased.

12. The method of claim 1, further comprising maintaining the elevated engine speed for a holding period.

13. The method of claim 12, wherein the maintaining step comprises maintaining the elevated engine speed after expiration of a predetermined holding period if the requested engine speed is at least as high as the elevated engine speed at the point when the holding period expires.

14. A method for controlling engine speed of a drive engine of a utility vehicle, comprising: providing the vehicle with a drivable loading apparatus and a hydraulic drive pump; hydraulically driving the loading apparatus; detecting a driving movement of the loading apparatus; determining a target hydraulic flow of the hydraulic drive pump of the utility vehicle based on a predicted or detected driving movement of the loading apparatus; requesting an increase of engine speed based on the determined target hydraulic flow if movement of the loading apparatus is detected; and predicting movement of the loading device before the detecting step.

15. The method of claim 14, wherein the determining step comprises determining the target hydraulic flow based on a detected valve control signal for at least one hydraulic valve of the loading apparatus.

16. The method of claim 14, wherein the determining step comprises determining the target hydraulic flow based on at least one of a requested drive movement of the loading apparatus, a drive characteristic of the loading apparatus, and a requested target position of the loading apparatus.

17. A method for controlling engine speed of a drive engine of a utility vehicle, comprising: providing the vehicle with a drivable loading apparatus and a hydraulic drive pump; hydraulically driving the loading apparatus; detecting a driving movement of the loading apparatus; determining a target hydraulic flow of the hydraulic drive pump of the utility vehicle based on a predicted or detected driving movement of the loading apparatus; requesting an increase of engine speed if movement of the loading apparatus is detected; and predicting movement of the loading device before the detecting step.

18. A method for controlling engine speed of a drive engine of a utility vehicle, comprising: providing the vehicle with a drivable loading apparatus and a hydraulic drive pump; hydraulically driving the loading apparatus; detecting a driving movement of the loading apparatus; determining a target hydraulic flow of the hydraulic drive pump of the utility vehicle based on a predicted or detected driving movement of the loading apparatus; requesting an increase of engine speed if movement of the loading apparatus is detected; determining a request period of time based on the target hydraulic flow; increasing the engine speed for a duration of the request period of time; and predicting movement of the loading device before the detecting step.

19. A method for controlling engine speed of a drive engine of a utility vehicle having a drivable loading apparatus, comprising: detecting or predicting a driving movement of the loading apparatus; requesting an increase of engine speed if the movement of the loading apparatus is predicted or detected; increasing the engine speed by a predetermined increase rate to an elevated engine speed; triggering a predetermined waiting period; determining if the elevated engine speed is elevated about a predetermined limit speed; and reducing the engine speed if the predetermined waiting period has expired and no driving movement of the loading apparatus has been requested until the expiration of the waiting period.

20. A method for controlling engine speed of a drive engine of a utility vehicle having a drivable loading apparatus, comprising: detecting or predicting a driving movement of the loading apparatus; requesting an increase of engine speed if the movement of the loading apparatus is predicted or detected; increasing the engine speed by a predetermined increase rate to an elevated engine speed; and lowering the engine speed at a predetermined decrease rate after being increased.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above-mentioned aspects of the present disclosure and the manner of obtaining them will become more apparent and the disclosure itself will be better understood by reference to the following description of the embodiments of the disclosure, taken in conjunction with the accompanying drawings, wherein:

(2) FIG. 1 shows a side view of a tractor with a front loader in different working positions,

(3) FIG. 2 shows a flow chart of the performance of the method in a first embodiment,

(4) FIG. 3 shows a representation similar to a block schematic diagram of components of an arrangement for performing the method, and

(5) FIGS. 4-8 show representations of the requested engine speed increase and the actually elevated engine speed as a function of time.

(6) Corresponding reference numerals are used to indicate corresponding parts throughout the several views.

DETAILED DESCRIPTION

(7) The embodiments of the present disclosure described below are not intended to be exhaustive or to limit the disclosure to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of the present disclosure.

(8) FIG. 1 shows a utility vehicle constructed as a tractor 10, on the front side of which a loading apparatus constructed as a front loader 12 is mounted. The front loader 12 has a pivotable arm 14, at the free end of which a tool in the form of a shovel 16 is pivotably mounted. The arm 14 and the shovel 16 are driven hydraulically to assume different positions, e.g., the positions Pos_1, Pos_2, Pos_3 and Pos_4 illustrated in FIG. 1. In the positions Pos_1, Pos_2, and Pos_3, the arm 14 assumes different pivot angles relative to the tractor 10. The shovel 16 assumes different pivot angles relative to the arm 14 in the positions Pos_1, Pos_2, Pos_3 and Pos_4. The position Pos_3 can constitute a maximum lift height of the arm 14 or the loading apparatus 12 for certain work, in order to avoid damage to adjoining buildings, gate entryways or the like. The hydraulic movement power is provided by means of suitable hydraulic cylinders 18, which are mounted on the loading apparatus 12.

(9) The method for controlling an engine speed n of a drive engine of the tractor 10, not shown in detail, provides that movement driving of the loading apparatus 12 is initially predicted or detected and then an increase of the engine speed n of the drive engine is requested. The increase of the engine speed n is thus requested, for example, if future movement driving is predicted or movement driving has actually been requested and detected.

(10) According to FIG. 2, this method is applied as follows in an idling mode of the drive engine. The engine speed n initially corresponds to an idle speed n_L when the tractor 10 is stationary (step S1). The idle speed n_L is 850 rpm (revolutions per minute), for example. In a step S2, it is checked whether a state signal S_Z indicates an activated operating state (On) of the loading apparatus 12 or a different drive state, e.g., a deactivated operating state (Off). In the event of a detected activated operating state, it is assumed that movement driving or a drive movement will be requested with a high probability thereafter. Therefore, future movement driving is predicted. According to the method, an increase of the engine speed n is requested. The engine speed n is increased to the engine speed n_H (step S3). It is 1000 rpm, for example. At the time when the engine speed n is increased to n_H, a time counter is also activated, which begins at t=0 and ends upon expiration of a waiting period Δt_W, e.g., 1 minute (step S4). It is checked in step S5 whether movement driving or a drive movement has already been carried out or at least requested upon expiration of the period Δt_W. If yes, the elevated engine speed n_H is maintained (step S6). If no, the elevated engine speed n_H is reduced (step S7) in order to further reduce the increased fuel consumption. The elevated engine speed n_H is in particular reduced to the original idle speed n_L. Then it is checked in step S8 whether the operating state of the loading apparatus is still activated (S_Z=On). If this is the case, control returns to step S5 to check whether movement driving has been carried out or at least requested. If yes, the engine speed n is again increased (step S6). If it is determined in step S8 that the operating state of the loading apparatus is no longer activated, control returns to step S2.

(11) FIG. 3 schematically shows parts of an arrangement 20 for carrying out the method for controlling the engine speed n. In particular, the arrangement 20 is used for performing the method at any desired engine speeds n other than the idle speed n_L. The working blocks 22, 24, 26, 28 that are shown are used for implementing a control of the engine speed n, which takes effect depending on a hydraulic flow to be described below. In another embodiment of the arrangement 20 not shown here, additional working blocks and components are provided, which also consider the control of the engine speed n in idle mode according to FIG. 2.

(12) The arrangement 20 according to FIG. 3 assumes that the loading apparatus 12 and optionally additional units as well (e.g., steering, brake) are hydraulically driven. The tractor 10 has a hydraulic drive pump 30 for this purpose. The pump characteristic thereof (in particular a characteristic curve with a hydraulic flow (liters/min) as a function of the engine speed) is taken into consideration in the working block 24 in order to determine the higher engine speed n_A that is to be requested. The engine speed n_A to be requested is calculated as a function of a determined target hydraulic flow F_S. In particular, the engine speed n_A is requested for the request period Δt_A, i.e., the engine speed n_A is to be in effect during the request period Δt_A.

(13) The request period Δt_A is used in particular as an output signal of the working block 24, especially if a required hydraulic volume V_hyd is being calculated in the working block 28, and the period is sent as a signal to the working block 24. In this case, the target hydraulic flow F_S can be determined while taking into account a current engine speed n_akt of the drive motor and a requested hydraulic flow F_A, and the request period Δt_A can be determined therefrom. The hydraulic volume V_hyd represents a hydraulic volume that is estimated or calculated in order to be able to perform the predicted or detected movement driving of the loading apparatus 12. In this regard, a drive characteristic S_Ch (e.g., drive type, drive geometry, geometry of the hydraulic cylinders 18, etc.) and a requested drive movement S_Bew (e.g., a request for specific pivot movements of the arm 14 or the tool 16 by means of corresponding operating elements) of the loading apparatus 12 can be considered as input signals. When determining the hydraulic volume V_hyd, an input signal S_Pos_S is taken into particular consideration in the working block 28. More specifically, this signal represents the request for a target position Pos_S of the loading apparatus 12 that has already been stored and is therefore known with respect to the hydraulic requests. For example, the loading apparatus is in the starting position Pos_1 prior to the request for the target position Pos_S. Based on the known hydraulic initial and target positions and the known drive characteristic S_Ch, the required hydraulic volume V_hyd can then be predicted especially accurately in working block 28.

(14) The requested hydraulic flow F_A is an output signal of the working block 22. Input signals regarding the operating state (S_Z) of the loading apparatus 12, of a steering system (S_L, e.g., a steering angle) of the tractor 10, of a brake unit (S_B, e.g., status of the brake) and valve control signals S_V of hydraulic valves of the loading apparatus 12 are considered as input signals for this output signal, for example.

(15) In summary and based on the above explanations, the target hydraulic flow F_S is determined on the basis of movement driving of the loading apparatus 12 predicted or detected in the working block 22 or in the working block 28.

(16) The requested engine speed n_A, optionally the request period Δt_A and a predetermined limit speed n_G, as well as additional parameters or variables if appropriate, are evaluated in the working block 26. Depending on consumption-oriented aspects (in particular the least possible extra consumption of fuel), performance-oriented aspects (in particular, the quickest possible implementation of the requested movement driving) or load-oriented aspects (in particular the lowest possible load on the drive engine), an elevated engine speed n_H that is actually to be implemented, a holding period Δt_H for maintaining the elevated engine speed n_H, a higher increase rate m_an of the engine speed n and a decrease rate m_ab of the elevated engine speed n_H are determined from the input signals of the working block 26, or are predetermined, and are transmitted as output signals for controlling the drive engine (e.g., an engine control unit).

(17) Different activations of the drive engine are shown for the sake of example with reference to FIGS. 4-8. The curves in broken lines show requested increases of the engine speed n and possibly request periods Δt_A. The curves in solid lines show the elevated engine speeds n_H and the holding periods Δt_H, with which the drive engine is actually controlled based on the evaluation in the working block 26.

(18) In FIG. 4, a higher speed n_A for a request period Δt_A is requested starting from a point in time to at a current speed n_akt. For the limit speed n_G, however, a lower value is predetermined in comparison to the requested higher speed n_A. The actually achieved elevated speed n_H thus corresponds to the limit speed n_G. Based on consumption-oriented overall conditions, the elevated speed n_H is maintained only for a holding period of elevated engine speed n_H that is shorter than the request period Δt_A. In addition, the current speed n_akt is increased at a smaller increase rate m_an than was requested, in order to limit the extra consumption of fuel and the extra load on the drive engine.

(19) In FIG. 5, a higher speed n_A is requested for the time t.sub.15. The speed n is actually increased with a lower increase rate m_an up to time t.sub.25. The engine speed n thus initially remains at an increased speed n_H below the limit speed n_G because a further decrease of the engine speed n was requested in this case and constant changes of engine speeds are to be avoided. Starting from time t.sub.35, the requested speed is again higher than the elevated speed n_H achieved between t.sub.25 and t.sub.35. The engine speed n therefore continues to increase and is limited at time t.sub.45 as an elevated engine speed n_H due to the predetermined limit speed n_G. Between times t.sub.45 and t.sub.55, the elevated engine speed n_H is maintained for the holding period Δt_H. Thereafter, the elevated engine speed n_H is again reduced at the decrease rate m_ab. For time t.sub.65, an increase of the engine speed n is again requested with a value n_A above the limit speed n_G. Accordingly, the engine speed is again increased at an increase rate m_an with a limitation by the limit speed n_G (time t.sub.75). After expiration of the holding period Δt_H at time t.sub.85, the elevated engine speed n_H is again reduced at a decrease rate m_ab.

(20) In FIG. 6, a higher engine speed n_A above the limit speed n_G is requested for time t16. Consequently, the engine speed n is increased at a predetermined increase rate m_an with the limit speed n_G as the elevated engine speed n_H. The holding period Δt_H begins at time t26 and ends at time t.sub.36. Since a higher speed n_A above the limit speed n_G was again requested for this latter time, the elevated engine speed n_H continues to be maintained. In FIG. 6, this is maintained for an additional holding period Δt_H.

(21) In FIG. 7, the value of the elevated engine speed n_H corresponds to the value of the requested higher engine speed n_A because the latter lies below the limit speed n_G. Starting from time t17, the elevated engine speed n_H is maintained for the time span of the holding period Δt_H. Since a higher engine speed n_A was still being requested upon expiration of this first holding period Δt_H at time t27, the elevated engine speed n_H—analogously to the sequence in FIG. 6—is maintained for an additional holding period Δt_H.

(22) FIG. 8 shows the same requested higher engine speed n_A with the same request period Δt_A as in FIG. 7. However, the maintenance of the elevated engine speed n_H over a multiple of the holding period Δt_H has the disadvantage in FIG. 7 that it is maintained over a longer period than was requested with the request period Δt_A. In order to proceed in a fuel saving manner in such cases, the time intervals for this maintenance of the elevated engine speed n_H can be predetermined or ascertained in working block 26, according to the principle described below.

(23) If the request period Δt_A is less than the holding period Δt_H, the elevated engine speed n_H is maintained over the period of a single holding period Δt_H. If the request period Δt_A is equal to or larger than the holding period Δt_A, the elevated engine speed n_H is maintained over the period of the request period Δt_A. In FIG. 8, this means that the elevated engine speed n_H is maintained after expiration of the holding period Δt_H only for the period t.sub.28 to t.sub.38, where the period t.sub.28 to t.sub.38 corresponds to the request period Δt_A. This principle of a shortening of the time interval, and thus a limitation of the temporarily increased fuel consumption, for maintaining the elevated engine speed n_H can of course also be used in different variants of an increase of the engine speed n, e.g. the variants according to FIGS. 4-7.

(24) While exemplary embodiments incorporating the principles of the present disclosure have been disclosed hereinabove, the present disclosure is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of the disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this disclosure pertains and which fall within the limits of the appended claims.