WO2019145153A1

WO2019145153A1 - Rotational speed control method

Info

Publication number: WO2019145153A1
Application number: PCT/EP2019/050487
Authority: WO
Inventors: Stephan Schinacher; Stefan Traub; Mario Brugger; Matthias MADLENER
Original assignee: Zf Friedrichshafen Ag
Priority date: 2018-01-24
Filing date: 2019-01-10
Publication date: 2019-08-01
Also published as: DE102018201035A1

Abstract

The present invention relates to a rotational speed control method for controlling the rotational speed of an internal combustion engine, mechanically coupled to an infinitely variable transmission of a machine. The method comprises acquiring a transmission ratio of the infinitely variable transmission, acquiring an upper rotational speed limiting value of the internal combustion engine for the acquired transmission ratio, wherein the acquisition is carried out on the basis of an upper rotational speed limiting curve which assigns an upper rotational speed limiting value to each transmission ratio of the infinitely variable transmission, acquiring a lower rotational speed limiting value of the internal combustion engine for the acquired transmission ratio, and acquiring the position of the accelerator pedal of the machine. In addition, the method comprises determining the rotational speed of the internal combustion engine on the basis of the acquired upper rotational speed limiting value, the acquired lower rotational speed limiting value and the acquired position of the accelerator pedal.

Description

Drehzahlsteuerunqsverfahren

Technical area

The present invention relates to a speed control method for controlling the rotational speed, in particular of an internal combustion engine. It is not only the use of internal combustion conceivable, but there are also hybrid and or electric drives in conjunction with a continuously variable drive conceivable. The internal combustion engine or other drive motor is mechanically coupled to a continuously variable transmission. Further, the present invention relates to a rotation speed control device and a drive device having such a rotation speed control device.

State of the art

Conventional drive trains of work machines often include a power shift transmission with an upstream hydrodynamic torque converter. The hydrodynamic torque converter is mechanically coupled to an internal combustion engine. A driver of the work machine can influence an engine characteristic of the internal combustion engine via a control element. More specifically, it can select from various preset operating modes via the control. Different operating modes have different operating points of the internal combustion engine for a particular accelerator pedal position. The internal combustion engine is thus required for a certain accelerator pedal position depending on the selected operating mode different amount of power. This allows the driver, for example, in light work, in which the full engine power is not needed, in an "ECO mode" switch and thus save fuel, without the handling capacity is reduced. Furthermore, it is known to equip a work machine with a continuously variable transmission, for example, a hydrostatic-mechanical power split transmission. Thus, a continuously variable transmission can be provided with high efficiency. Such a continuously variable transmission is for example from the

DE 10 2015 223 249 A1. Presentation of the invention

The present invention relates to a speed control method for an internal combustion engine of a work machine mechanically coupled to a continuously variable transmission. The continuously variable transmission can be a power-split, for example, a hydrostatic-mechanical power-split transmission. The internal combustion engine can be a diesel engine. The work machine may be a construction machine, such as a wheel loader or a grader. Likewise, the work machine can be an agricultural machine. A mechanical coupling between two elements allows torque transmission between them. In a continuously variable transmission, the ratio is infinitely adjustable.

The method includes determining a ratio of the continuously variable transmission. As part of the investigation step, the reciprocal ratio of the continuously variable transmission can be determined. Under a reciprocal ratio of the quotient of output speed and input speed of the continuously variable transmission is understood. Alternatively, the quotient of input speed and output speed can also be determined here. The reciprocal ratio of the continuously variable transmission can increase with increasing speed of the work machine. In addition to the translation or the reciprocal ratio, the actual or the desired driving speed can also be used. The goal is to optimally choose the engine speed.

Furthermore, the method comprises determining an upper speed limit value of the internal combustion engine for the determined gear ratio. An upper speed limit value is understood as meaning a maximum speed of the internal combustion engine which should not be exceeded when the accelerator pedal is fully activated. The upper speed limit depends on the ratio of the continuously variable transmission. The determination is based on an upper speed limit curve. The upper speed limit curve assigns an upper speed limit to each possible gear ratio or each possible reciprocal ratio of the continuously variable transmission. If the gear ratio applied to the continuously variable transmission is known, the associated upper speed limit value can thus be determined via the upper speed limit curve. In addition, the method comprises determining a lower speed limit of the internal combustion engine for the determined ratio. A lower speed limit value is understood to mean a minimum speed of the internal combustion engine which should not be undershot when the gas pedal is not actuated. The lower speed limit may be dependent on or independent of the ratio of the continuously variable transmission.

Furthermore, the method comprises determining the accelerator pedal position of the working machine. An accelerator pedal position is the extent to which the accelerator pedal is depressed. For example, if the accelerator pedal is depressed to 50% of its maximum displacement, the accelerator pedal position is 50%.

In addition, the method includes determining the speed of the engine based on the determined upper speed limit, the determined lower speed limit, and the detected accelerator pedal position. In other words, the speed of the engine is made dependent on the determined upper and the determined lower speed limit. At least the upper speed limit is in turn dependent on the determined ratio of the continuously variable transmission.

As a result, the method of the present invention thus allows an adaptation of the speed of the internal combustion engine to the state of the continuously variable transmission. Thus, the entire system of internal combustion engine and continuously variable transmission can always be operated in a driving situation adapted and consumption-optimal operating point with a low specific fuel consumption.

Determining the speed may include interpolating between the determined upper speed limit and the determined lower speed limit depending on the detected accelerator pedal position. The interpolation can be a linear interpolation. Thus, the speed of the internal combustion engine can be determined in a simple manner. The upper speed limit curve may have a first range extending from a minimum reciprocal ratio of the continuously variable transmission to a larger reciprocal transmission ratio. In this first range, the speed limit curve may have a direct proportionality between the reciprocal ratio and the upper speed limit. A direct proportionality between reciprocal ratio and upper speed limit value is understood to mean a behavior in which an increase in the reciprocal ratio is accompanied by an increase in the upper speed limit value, the ratio of the two variables always being the same.

With this embodiment, a lower upper speed limit can be provided at low speeds and thus small reciprocal translations than with larger reciprocal ratios. In continuously variable transmissions, only a fraction of the power that can be supplied by the internal combustion engine is required at low driving speeds and thus low reciprocal ratios. Namely, continuously variable transmissions, unlike hydrodynamic torque converters, do not exhibit high power loss due to slippage at low speeds. Consequently, with this embodiment, the engine can be operated at low engine speeds at low reciprocal ratios. Such a lowering of the engine speed allows the engine to operate at a lower power hyperbola and thus lower specific fuel consumption (g / kW).

The lower speed limit may have a minimum speed of the engine regardless of a position of the accelerator pedal. As a result, sufficient power can be provided by the internal combustion engine for working hydraulics of the working machine at each operating point. Thus, the internal combustion engine has a minimum speed even when the accelerator pedal is not actuated

The lower speed limit can be determined based on a lower speed limit curve. The lower speed limit curve has a lower speed limit for each gear ratio or each reciprocal ratio of the continuously variable transmission. worth to. Thus, for each reciprocal ratio, an optimum minimum engine speed can be provided.

In addition, the lower speed limit curve may have a first range of travel extending from a minimum reciprocal ratio to a larger reciprocal transmission ratio. In the first driving range, the lower speed limit curve may have a direct proportionality between the reciprocal gear ratio and the lower speed limit value. With increasing reciprocal translation and thus with increasing speed of the work machine more power in the drive train may be required.

The method may further comprise determining which upper speed limit curve has been selected from a plurality of upper speed limit curves. In other words, a plurality of upper speed limit curves are stored, which respectively assign different upper speed limit values to a certain reciprocal ratio. The selection of one of the upper speed limit curves may be made by a driver of the work machine. Alternatively, the selection of one of the speed limit curves can also be done automatically. The different upper speed limit curves may provide different operating modes of the work machine. The determination of the upper speed limit is made in this embodiment based on the selected upper speed limit curve.

By selecting one of the upper speed limit curves from the plurality of upper speed limit curves, the speed level of the engine can be adjusted. By way of such an adaptation of the speed level, in turn, the maximum available power and the fuel consumption can be controlled. For example, selecting the upper speed limit curve at the lowest speed level results in a relatively low maximum available power, but also low specific fuel consumption. The opposite is the case when selecting the upper speed limit curve with the highest speed level. There is also the option of applying this to the optimum consumption when selecting the upper limit curve. For example, if the engine has a range of constant, maximum power. A variety of engines Already starting at about 1400 rpm up to the maximum engine speed (eg 2200 rpm), it can deliver constant power, but have the fuel-efficient point at 1500 rpm.

According to an embodiment, the plurality of upper speed limit curves may each have a profile over the reciprocal transmission, so that they do not intersect over the entire transmission range. In other words, the various upper speed limit curves are all arranged one above the other. Although the upper speed curves may touch in the context of this embodiment, they must not intersect. By touch is meant that multiple speed limit curves assign the same upper speed limit to a particular reciprocal ratio. This embodiment has the advantage that a speed level for the entire transmission range is selected by selecting the upper speed limit curve.

It is also possible in a further embodiment that the speed limit curves intersect. This is advantageous, for example, when a particularly fuel-efficient mode, a so-called "ECO-Pro Mode", is required, in which low engine speeds are to be controlled at low driving speeds, but at high driving speeds the maximum engine speed is to be used.

The upper speed limit curve may be automatically selected from the plurality of upper speed limit curves depending on a speed of change of the accelerator pedal. For example, at a high rate of change, an upper speed limit curve having a high speed level may be selected. Alternatively or additionally, an automatic selection of the upper speed limit curve can also be adaptive in dependence on the driving style of the driver. If, for example, the accelerator pedal is not fully stepped on by the driver during certain maneuvers, an upper speed limit curve with a lower speed level can be automatically selected. Alternatively or additionally, it is conceivable that an automatic selection of the upper speed limit curve takes place as a function of the retrieved power. For example, not the full power of the engine If required, an upper speed limit curve with a lower speed level can be selected automatically.

Furthermore, the aggressiveness of the work machine can be adapted to the selected upper speed limit curve. The aggressiveness is a measure of the dynamic driving behavior of the working machine. The aggressiveness can be reflected, for example, in the acceleration behavior of the working machine. For a consumption-optimal operation, it may be advantageous if the acceleration of the vehicle is reduced with decreasing speed level of the upper speed limit curve. Furthermore, the aggressiveness in the deceleration of the vehicle can be reflected. The delay is a measure of the Abbremsstärke the machine. Here it is also conceivable that the deceleration is reduced with decreasing speed level of the upper speed limit curve. Alternatively or additionally, it may be provided that reversing aggressiveness is reduced to lower rotational speed levels. Under Reversieraggressivität is a reduction in the speed and subsequent increase in speed in the opposite direction per unit time to understand.

Furthermore, the maximum tractive force of the work machine can be adapted to the selected upper speed limit curve. This adjustment can be made over the entire speed range or only for a subrange. For example, the maximum tractive effort can only be reduced for low driving speeds.

An above-described adaptation of the aggressiveness, the maximum tractive force as well as a previously described automatic selection of the upper speed limit curve can each be provided alone or in any combination with one another.

Furthermore, the present invention relates to a speed control device for controlling the rotational speed of a mechanically coupled to a continuously variable transmission internal combustion engine of a work machine. The speed control device includes a translation interface for providing a ratio of the continuously variable transmission and an accelerator pedal interface for providing an accelerator pedal position of an accelerator pedal. In addition, the control device has a motor rotation Number interface to output a certain engine speed to the internal combustion engine.

Within the scope of the present invention, the interfaces may be an input / output device which, for example, may be designed to transmit and receive data streams in a packetized or unpacked form. The interfaces can be designed as separate devices. Alternatively, some or all of the interfaces of the present invention may also be implemented via a single device, for example a bus.

The control device further comprises a computer device that is configured to determine an upper speed limit value of the internal combustion engine for the provided translation. A device of the control device for carrying out a specific function is the specific programming of the control device for carrying out this function. The control device is set up to carry out the determination of the upper speed limit value on the basis of an upper speed limit curve stored in the computer device. Furthermore, the control device is set up to determine a lower speed limit value of the internal combustion engine for the provided ratio. In addition, the control device is set up to determine the rotational speed of the internal combustion engine on the basis of the ascertained upper rotational speed limit value, the determined lower rotational speed limit value and the ascertained accelerator pedal position. The controller may be further configured to perform the method according to any of the previously described embodiments. With regard to the understandings and advantages of the individual features, reference is made to the above statements in connection with the method.

Moreover, the present invention relates to a drive arrangement for a work machine. The drive arrangement has an internal combustion engine, a continuously variable transmission mechanically coupled thereto and an accelerator pedal. Further, it includes a speed control device according to the above-described embodiment. The accelerator pedal interface of the control device is equipped with the accelerator pedal, the transmission interface with the continuously variable transmission and the engine speed Interface connected to the combustion engine. With regard to the understandings and advantages of the individual features, reference is also made to the above statements in connection with the method.

Brief description of the figures

Fig. 1 shows a drive arrangement according to an embodiment of the present invention.

FIG. 2 shows process steps of a speed control method for the internal combustion engine of FIG. 1 according to an embodiment of the present invention.

Fig. 3 shows a lower and a plurality of upper speed limit curves according to a

Embodiment of the present invention.

Detailed description of an embodiment

Fig. 1 shows a drive assembly 1 according to an embodiment of the present invention. The drive arrangement 1 comprises an accelerator pedal 2 with an accelerator pedal sensor 3 for determining an accelerator pedal position. Furthermore, the arrangement 1 comprises an internal combustion engine 4 and a continuously variable transmission 5 mechanically coupled thereto. The output of the transmission 5 can be mechanically coupled to wheels, not shown. In the present embodiment, it is a drive assembly 1 for a construction machine, in particular a wheel loader. The continuously variable transmission 5 comprises a transmission detection device 6 for detecting a reciprocal transmission ratio.

In addition, the drive arrangement 1 comprises an operating device 7, via which an operating mode of the drive arrangement 1 can be selected, as described below. The operating device 7 is arranged in the cab of the construction machine and can be operated by a driver. It is also possible that not the driver via the operating device 7, but, for example, a fleet management selects the operating mode based on collected data and this wirelessly, for example by means of radio This has the advantage that, for example, a fleet management all vehicles would operate optimized consumption.

Furthermore, the drive arrangement 1 comprises a control device 8. The control device 8 comprises an accelerator pedal interface 9, via which an accelerator pedal position detected by the accelerator pedal sensor 3 can be provided. In addition, the control device 8 comprises a translation interface 10. About the translation interface 10 can be provided with the translation detection means 6 detected reciprocal ratio of the continuously variable transmission 5. In addition, the control device 8 has a mode interface 1 1, via which a selected by the driver via the operating device 7 operating mode can be provided.

Furthermore, the control device 8 comprises an engine speed interface 12 for outputting a rotational speed determined by the control device 8 to the internal combustion engine 4. For determining the rotational speed to be output, the control device 8 is set up in order to carry out the following with reference to FIGS. 2 and 3 described method.

In a first step I, the reciprocal ratio of the continuously variable transmission 5 is determined by means of the ratio detection device 6 and the control device 8 is provided via the translation interface 10.

In the control device 8 of this embodiment, three different upper speed limit curves 13.1, 13.2, 13.3 are deposited. The upper speed limit curves 13.1, 13.2, 13.3 respectively have each reciprocal ratio of the continuously variable transmission 5 an upper speed limit value of the internal combustion engine 4. By means of the operating device 7, the driver can select one of these three upper speed limit curves 13.1, 13.2, 13.3 by selecting an operating mode.

In Fig. 3, the three upper speed limit curves 13.1, 13.2 and 13.3 are shown. Increasing abscissa values in this figure correspond to a larger denden reciprocal ratio and increasing ordinate values correspond to a higher speed of the internal combustion engine 4. With greater reciprocal translation in this embodiment also increases the driving speed (not shown) of the working machine. As shown in Fig. 3, the second upper speed limit curve 13.2 extends below the first upper speed limit curve 13.1. The third upper speed limit curve 13.3 again runs below the second upper speed limit 13.2. The ordinate and its values can also be a velocity.

From Fig. 3 it is further apparent that in the control device 8, a lower speed limit curve 14 is deposited. The lower speed limit curve 14 assigns a lower speed limit value of the internal combustion engine 4 to each reciprocal transmission ratio.

All speed limit curves, so the three upper speed limit curves 13.1, 13.2 and 13.3 and the lower speed limit curve 14, each have two driving ranges 15 and 16. In a first travel range 15, which ranges from a minimum reciprocal ratio m to a first transition ratio c, all speed limit curves 13.1, 13.2, 13.3 and 14 have a linear course. More specifically, the lower 14 and upper speed limit curves 13.1, 13.2 and 13.3 increase linearly with increasing reciprocal gear ratio in this first driving range 15.

In a second driving range 16, which extends from the first transition ratio c in the direction of increasing reciprocal translations, the lower 14 and the first upper speed limit curve 13.1 have a constant speed limit value. The second 13.2 and the third upper speed limit curve 13.3 have from the first transition ratio c with increasing reciprocal ratio up to a second transition ratio f to a constant speed limit. As of the second transition ratio f, however, they have a further linearly increasing section as the reciprocal translation increases. In this further linear section, the second 13.2 and third upper speed limit curve 13.3 linearly increase with increasing reciprocal ratio to a convergence point 17 on the first upper speed limit curve 13.1. Thus, even with the upper speed limit curves 13.2 and 13.3, which have a relatively low speed level, high driving speeds can be achieved. In a step II it is determined which operating mode and thus which of the upper speed limit curves 13.1, 13.2, 13.3 the driver has selected via the operating device 7. Subsequently, in a step III, the upper speed limit value for the reciprocal transmission determined in step I is determined via the upper speed limit curve 13.1, 13.2, 13.3 selected in step II.

Furthermore, in a step IV, the lower speed limit value for the reciprocal transmission determined in step I is determined on the basis of the lower speed limit curve 14 stored in the control device 8. In a step V, the accelerator pedal position is determined via the accelerator pedal sensor 3.

Subsequently, in a step VI, the target rotational speed of the internal combustion engine 4 is determined based on the determined in step III upper speed limit, the determined in step IV lower speed limit and the accelerator pedal position determined in step V. More specifically, between the determined upper speed limit value and the determined lower speed limit value is linearly interpolated depending on the detected accelerator pedal position to obtain the engine speed. In a step VII, the determined engine speed is output via the engine speed interface 12 to the engine 4.

REFERENCE CHARACTERS

1 drive arrangement

2 accelerator pedal

3 accelerator pedal sensor

4 internal combustion engine

5 continuously variable transmission

6 Translation detection device

7 operating device

8 control device

9 accelerator pedal interface

10 translation interface

11 mode interface

12 engine speed interface

13.1, 13.2, 13.3 upper speed limit curve

14 lower speed limit curve

15 first driving range

16 second driving range

17 merge point

m minimum reciprocal translation

c first transitional translation

f second transitional translation

I determine translation

II Determine operating mode

III Determine upper speed limit

IV Determine lower speed limit

V Determine accelerator pedal position

VI Determine speed of combustion engine

VII Output specific speed to internal combustion engine

Claims

claims

1 . Speed control method for a combustion engine (4) of a work machine mechanically coupled to a continuously variable transmission (5), comprising

Determining (I) a ratio of the continuously variable transmission (5);

Determining (III) an upper speed limit of the detected ratio engine (4), the determination being based on an upper speed limit curve (13.1; 13.2; 13.3) assigning each transmission of the continuously variable transmission (5) an upper speed limit;

Determining (IV) a lower speed limit of the internal combustion engine (4) for the determined gear ratio;

Determining (V) the accelerator pedal position of the work machine;

Determining (VI) the speed of the internal combustion engine (4) based on the determined upper speed limit, the determined lower speed limit and the detected accelerator pedal position.

2. Speed control method according to claim 1, characterized in that the determination (VI) of the rotational speed comprises the interpolation between the determined upper speed limit value and the determined lower speed limit value as a function of the ascertained accelerator pedal position.

A speed control method according to claim 1 or 2, characterized in that the upper speed limit curve (13.1; 13.2; 13.3) in a range from a minimum reciprocal ratio (m) to a reciprocal transition ratio (c) has a direct proportionality between the reciprocal ratio and has the upper speed limit.

4. Speed control method according to one of the preceding claims, characterized in that the lower speed limit value has a minimum speed of the motor (4) regardless of a position of the accelerator pedal (2).

5. Speed control method according to one of the preceding claims, characterized in that the lower speed limit value is determined on the basis of a lower speed limit curve (14), which assigns each transmission of the continuously variable transmission (5) has a lower speed limit.

The speed control method according to claim 5, characterized in that the lower speed limit curve (14) has a direct proportionality between the reciprocal gear ratio and the lower speed limit value in a range from a minimum reciprocal gear ratio (m) to a reciprocal transmission gear ratio (c).

7. Speed control method according to one of the preceding claims, further with

Determining (II) which upper speed limit curve has been selected from a plurality of upper speed limit curves (13.1, 13.2, 13.3); wherein the determination (III) of the upper speed limit value is based on the selected upper speed limit curve.

8. Speed control method according to claim 7, characterized in that the plurality of upper speed limit curves (13.1, 13.2, 13.3) does not intersect over the entire transmission range.

9. A speed control method according to claim 7 or 8, characterized in that the upper speed limit curve of the plurality of upper speed limit curves (13.1, 13.2, 13.3) is automatically selected in response to a rate of change of the accelerator pedal.

10. Speed control method according to one of claims 7 to 9, characterized in that the aggressiveness of the working machine is adapted to the selected upper speed limit curve.

11. Speed control method according to one of claims 7 to 10, characterized in that the maximum tractive force of the working machine is adapted to the selected upper speed limit curve.

12. A speed control device (8) for controlling the speed of a with a continuously variable transmission (5) mechanically coupled combustion engine (4) of a work machine, comprising a translation interface (10) for providing a ratio of the continuously variable transmission (5); an accelerator pedal interface (9) for providing an accelerator pedal position of an accelerator pedal (2); a computer device which is set up in order to determine an upper speed limit value of the internal combustion engine (4) for the provided gear ratio, the determination taking place on the basis of an upper speed limit curve (13.1; 13.2; 13.3) stored in the computer device, that of each gear ratio of the continuously variable transmission (5) assigns an upper speed limit to determine a lower speed limit of the provided translation engine (4) and to determine the speed of the engine (4) based on the determined upper speed limit, the determined lower speed limit, and the detected accelerator pedal position; and an engine speed interface (12) for outputting the determined engine speed to the engine (4).

13. A drive arrangement (1) for a work machine, comprising an internal combustion engine (4), with this mechanically coupled continuously variable transmission (5), an accelerator pedal (2) and a speed control device (8) according to claim 12, wherein the accelerator pedal interface (9) the accelerator pedal (2), the transmission interface (10) with the continuously variable transmission (5) and the engine speed interface (12) with the internal combustion engine (4) are connected.