DE102019112165A1 - Method for controlling a hybrid drive train - Google Patents

Abstract

The invention relates to a method for controlling a hybrid drive train with an internal combustion engine and an electric machine as well as a continuously adjustable belt drive connected downstream with a hydraulically controlled variator and a belt clamped between cone pulley sets of the variator depending on the ratio on different radii. In order to enable an increased input torque applied to a drive shaft of the variator with an unchanged design of the belt drive, the maximum adjustable input torque (M) is increased depending on the ratio (i) of the variator in at least one ratio range compared to the maximum adjustable input torque according to the design of the variator .

Description

The invention relates to a method for controlling a hybrid drive train with an internal combustion engine and an electric machine as well as a continuously adjustable belt drive connected downstream with a variator controlled by a hydraulic system and a belt clamped between cone pulley sets of the variator depending on the ratio on different radii.

Hybrid drive trains with an internal combustion engine and an electric machine that can be operated as a generator and as an electric motor as well as a continuously variable belt transmission (CVT) are well known. For example, such a CVT is in the document WO 2015/110108 A1 disclosed. The internal combustion engine and the electric machine are connected upstream of the CVT, so that the variator of the CVT transmits the engine torque of the internal combustion engine and the drive torque of the electric machine. Due to the typical properties of the CVT with a frictional connection between the belt, for example rocker parts of a link chain and the surfaces of the conical pulley sets of the variator, the maximum input torque at the variator is limited, so that with conventional CVTs, correspondingly small electric machines have to be combined with the internal combustion engine. The variator is designed for critical operating points, preferably in the extreme gear ratios with small running radii of the belt on one of the conical pulley sets.

A method for controlling the hybrid drive train is used, among other things, to control the transmission ratio of the belt transmission. For this purpose, a contact pressure is preferably generated by means of at least one oil pump in order to preload one loose disk of the conical disk sets against a fixed disk while the belt is being clamped. By means of the at least one oil pump, the loose disks of the conical pulley sets are subjected to different contact pressure, so that depending on the contact pressure, the belt on the corresponding conical pulley sets is shifted to different radii and a desired gear ratio is set.

The object of the invention is to develop a method for controlling a hybrid drive train. In particular, the object of the invention is to propose a method for increasing the maximum input torque of the CVT with a given design of the CVT.

The object is achieved by the subject matter of claim 1. The claims dependent on claim 1 reproduce advantageous embodiments of the subject matter of claim 1.

The proposed method is used to control a hybrid drive train. A hybrid drive train in the sense of this invention contains at least the following drive train components: an internal combustion engine, an electric machine and a continuously adjustable belt drive connected downstream with a variator controlled by a hydraulic system and a belt clamped between cone pulley sets of the variator depending on the ratio on different radii. The electric machine can be operated as a motor and generator and can be arranged in the pulley plane or at the output of the internal combustion engine on the transmission side, for example coaxially to the crankshaft. The looping means can preferably be designed as a link chain with one of the links connected to one another by means of two rocker pieces rolling on each other, or as a push link belt, the end faces of the rocker pieces rolling between the surfaces of the cone pulley sets. The radius of the belt on the two sets of conical pulleys and thus the transmission ratio of the belt drive is set hydraulically by applying a contact pressure and an additional control pressure to one loose disk of the two sets of conical pulleys.

A starting element, for example a starting clutch or a hydrodynamic torque converter, can be arranged between the internal combustion engine and the electric machine and the belt drive. An additional friction clutch can be provided between the internal combustion engine and the electric machine.

The electric machine can be used for purely electric driving, as a booster for the internal combustion engine, as a starter for the internal combustion engine, as a generator during recuperation when the internal combustion engine is switched off or separated from the rest of the drive train by means of a friction clutch and / or as a generator for charging an electrical accumulator.

In order to make better use of the possibilities of the belt transmission with regard to its transmission of torque, a maximum input torque applied to the input side of the variator is set as a function of the ratio of the variator. This means that the applied maximum input torque compared to the originally specified maximum according to the design of the variator The input torque is set in such a way that with each gear ratio of the variator, for example preferably with gear ratios between 2.8 and 0.40, the maximum transferable torque which is harmless to the variator is transferred. In this way, depending on the translation of the variator, the maximum input torque originally specified by a corresponding design of the variator can be set higher for a specified translation. In this way, for example, a torque greater than the originally specified input torque can be transmitted to the variator, for example during boost operation of the internal combustion engine and electric machine, that is, increased input torques can be applied at specified gear ratios compared to the input torque originally specified by the design of the variator without the variator having to design and redesign more. It has been shown here that if the belt transmission is designed for the original maximum input torque, which can be applied without damaging the variator, it is limited to the largest and smallest ratio of the variator, and an input torque that is larger than this input torque can be applied without damage if the ratio is medium . It is therefore proposed that in a transmission range of the underdrive and the overdrive of the variator, in which the belt has a minimum radius on a conical pulley set, the input torque should be transmitted in accordance with the design of the belt transmission and, in the case of transmissions in between, an enlarged one that may be dependent on other operating parameters Allow or set input torque.

In a preferred manner, it is proposed in such a method that for this purpose several torque curves of the maximum input torque are assigned to corresponding gear ratio ranges. For example, a first torque curve is set in a first gear ratio range of the variator between the underdrive and a gear ratio when the Hertzian pressure increases compared to an average power loss. This first torque curve of the maximum input torque can depend on the originally limiting design parameters, for example Hertz's pressure between the belt, for example the end faces of rocker links of a link chain, and the cone pulley set in frictional contact with this, the maximum possible system pressure of the hydraulic system and / or the maximum power loss of the friction contacts of the belt with respect to the contact surfaces of the conical disks of the conical disk sets or the like can be set, for example at the maximum input torque according to the design of the variator. The Hertzian pressure can be determined, for example, taking into account the load occurring on the contact surfaces between, for example, the end faces of rocker links of a link chain and the contact surfaces of the conical disks, depending on the number of elements such as rocker elements and / or the like forming contact with the conical disks. The system pressure can be determined, for example, as a function of a shaft strength of the shafts receiving the conical disk sets, a limit pressure for the seals used in the hydraulic system and / or the like. It has also been shown that, depending on the current running time in the first transmission range, the torque curve can be extended over a torque curve designed for long-term load, since experience has shown that the running time of the belt drive in the first transmission range is short and therefore no damage to the belt drive variator and / or sling - is to be expected. The maximum input torque can therefore be set to an average power loss, while with increasing power loss of the variator beyond the first transmission range up to a second transmission range, the torque curves are set to the lower end of the tolerance band of the power loss curve over the transmission, since these transmissions have a longer useful life exhibit.

According to an advantageous embodiment of the proposed method, a second torque profile of the maximum input torque that is higher than the first torque profile of the maximum input torque is set in a second ratio range of the variator with a medium ratio, for example with a ratio of the variator between 1.8 and 1. The lower translation corresponds to the upper translation of the first translation range. The upper ratio of the second ratio range is provided for a ratio in which the maximum possible system pressure of the hydraulic system increases compared to the lower limit of the tolerance band of the power loss curve. This torque curve is above the originally designed maximum input torque according to the design of the variator and, with the unchanged design of the belt drive, enables boost operation of the hybrid drive train at torques that are above the maximum torque of the internal combustion engine, the electric machine or their combination. The electric machine can be designed with high outputs of, for example, 20 kW to 200 kW, preferably 50 kW to 120 kW, in order to make a correspondingly high contribution to the boost operation. Here can as an alternative to a boost operation of the internal combustion engine by means of the electric machine, the electric machine forms the main drive and the internal combustion engine forms a boost function. The torque curve is set in the second transmission range in a preferred manner as a function of the maximum possible or permissible system pressure of the hydraulic system.

A third gear range follows the upper gear ratio of the second gear range up to overdrive. In this transmission range, a torque curve that initially increases, remains constant or decreases compared to the second torque curve of the maximum input torque can be set, with the torque curve preferably following the curve of the power loss at the lower limit of its tolerance band. Due to the decreasing power loss with increasing gear ratio, the torque curve can decrease after a torque maximum towards overdrive. The power loss can be determined, for example, depending on the thermal load on the contact surfaces between the belt, such as the end faces of the rocker links of a link chain and the conical pulley sets, a cooling capacity of the belt and / or the like.

The torque curves of the maximum input torque that can be set as a function of the translation or an overall limit torque curve of the maximum input torque over the spread of the belt drive can be set within a tolerance band around the power loss, with the corresponding adjustable maximum input torque in a medium tolerance band depending on the running time for the corresponding translations can be set up to a lower limit of the tolerance band. Furthermore, the torque curves or a total torque curve of the maximum adjustable input torque can be corrected depending on the time proportions in the respective gear ratios or gear ratios, so that certain running times for these ratios outside of damage to the input torques that are excessive compared to the design of the belt drive and, if necessary, the originally enabled input torque in accordance with Design of the variator is reduced when a predetermined duration is exceeded. The running time can be adapted to existing influencing variables such as the operating temperature, the operating pressure and / or the like.

The torque curves or a total torque curve of the maximum input torque can be set as a function of the link strength of the links of a looping means designed as a link chain.

The invention is explained in more detail using the embodiment shown in the single figure. This shows a diagram with the maximum adjustable input torque of a belt drive via the translation of a variator of a belt drive.

The diagram 100 shows the behavior of a belt transmission via the translation i its variator. The variator is made up of an internal combustion engine and / or an electric machine with the maximum input torque that can be set on the variator M. driven drive shaft formed with a first conical disk set with a fixed disk and a hydraulically opposite this axially displaceable loose disk. Arranged parallel to the drive shaft is an output shaft connected to an output, for example a differential, with a second conical disk set with a fixed disk and a loose disk that can be axially displaced hydraulically with respect to this. Between the conical running surfaces of the conical pulley sets is a looping means in the form of a link chain with rocker elements that connect and roll on each other, the end faces of which are each preloaded between an idler gear and a fixed gear of a conical pulley set by means of a contact pressure of a hydraulic system and depending on a different applied to the conical pulley sets Control pressure can be shifted radially on the cone pulley sets. A specified gear ratio is thereby dependent on the control pressure i between the maximum gear ratio to slow speed, the underdrive UD , for example i = 2.7 via a translation i (a) , a translation i (b) , a ratio i = 1 and a maximum speed ratio, the overdrive OD with a translation of, for example, i = 0.4 and dependent on the translation i the maximum adjustable input torque M. a specified input torque is specified on the drive shaft up to the maximum setting torque.

That from the translation i The maximum input torque that can be set is dependent on the entire spread of the variator as the total torque curve 101 shown. The overall moment curve 101 is about the translation into the individual moments 102 , 103 , 104 the translation areas I. , II , III divided.

In the translation area I. , for example from the Underdrive UD with maximum translation to slow speed up to one translation i (a) , for example 1.9>i> 1.6, preferably 1.7>i> 1.8, the torque curve becomes 102 in the Essentially set to variables that depend on the Hertz pressure, the maximum system pressure and the power loss and is essentially the input torque M (V) for which the variator was originally designed. The input torque M (V) and thus the torque curve 102 in the first translation area I. is essentially limited, since the link chain rolls with only a few rocker pieces on a narrow radius on the drive-side conical pulley set. In the translation area I. are therefore those in the curve 105 Hertzian pressure shown for the set torque curve 102 , which is in the system pressure curve 108 maximum possible system pressure shown and that in the power loss curve 109 Limiting power loss shown. Here the input torque M (V) compared to the dashed areas 106 , 107 the Hertzian pressure and the resulting input torque for setting the torque curve 102 up to an average power loss of the tolerance band 110 the power loss curve can be increased, because due to the short current running time with these translations there is no damaging effect and that in the area 107 reduced input torque to the input torque M (V) with the torque curve shown 102 can be adjusted.

The translation area I. is involved in the translation i (a) limited because of this translation i (a) the curve 105 the Hertzian pressure increases compared to the power loss curve.

In which to address the translation area I. subsequent translation area II that for example up to the translation i (b) increases, the torque curve becomes 103 of the maximum adjustable input torque M. enables. In the translation area II is the system pressure curve 108 relevant for the maximum possible system pressure of the hydraulic system with the shaft strength of the drive and output shaft, the limit pressure for the seals used in the hydraulic system and other components and / or the like, so that the maximum adjustable input torque according to the torque curve 103 of the translation area II to the system pressure curve 108 and after a transition phase from the average power loss to the lower limit of the tolerance band 110 the power loss curve 109 is adjusted.

In the translation area II the belt drive can exceed its original design with the input torque M (V) lying input torque of the torque curve 103 operate. For example, as shown in the exemplary embodiment shown, the setting torque which can be transmitted via the variator can be increased, for example, by approximately 20% to 50%. This enables a boost function of the drive train, the internal combustion engine or the electric machine being able to serve as the main drive and the electric machine or the internal combustion engine being able to serve as the boost element and the electric machine being able to be designed to be correspondingly powerful. The upper limit of the translation range II in translation i (b) results in the exemplary embodiment shown from the opposite of the lower limit of the tolerance band 110 the power loss curve 109 increasing maximum possible system pressure of the system pressure curve 108 .

In which to address the translation area II subsequent translation area III with a translation between translation i (b) and the overdrive OD is the power loss curve 109 relevant for the power loss of the rocker contacts compared to the surfaces of the conical pulley pairs with their cooling and the thermal loads. The moment curve 104 therefore follows the lower limit of the tolerance band 110 the power loss curve 109 . This moment curve 104 increases compared to the torque curve 103 at first slightly and falls as the overdrive approaches OD since the radius of the belt on the cone pulley set of the output shaft decreases in overdrive. A boost function with one above the input torque M (V) According to the original design of the variator, the maximum adjustable input torque can nevertheless be used up to gear ratios of, for example, 0.7>i> 0.6.

The torque curves 104 and partially 103 are at the lower limit of the tolerance band 110 set. Partly in the translation area II and in the translation area I. , that is, in the case of larger ratios to slow, for example with ratios i> 1.6, the damage due to short operating times with these ratios is low, so that in the area 107 torque curve shown on the torque curve 102 can be customized. Furthermore, this can be done at the beginning of the translation area II adjustable maximum input torque for this reason also within the tolerance band 110 run away.

List of reference symbols

100

diagram

101

Total torque curve

102

Torque curve

103

Torque curve

104

Torque curve

105

Curve

106

Area

107

Area

108

System pressure curve

109

Power loss curve

110

Tolerance band

I.

Translation area

II

Translation area

III

Translation area

i

translation

i (a)

translation

i (b)

translation

OD

Overdrive

M.

Input torque

M (V)

maximum adjustable input torque

UD

Underdrive

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• WO 2015/110108 A1 [0002]

Claims (10)

Method for controlling a hybrid drive train with an internal combustion engine and an electric machine as well as a continuously adjustable belt drive connected downstream with a variator controlled by a hydraulic system and a belt clamped between cone pulley sets of the variator depending on the ratio on different radii, characterized in that a maximum input torque applied to the variator (M) is set higher in at least one gear ratio range (II, III) which differs from the underdrive (UD) than an input torque (M (V)) limited by a design of the variator in the underdrive (UD) of the variator. Procedure according to Claim 1 , characterized in that different torque curves (102, 103, 104) within a tolerance band (110) arranged around a power loss curve (109) of the variator are set via the transmission ratio (i) of the variator. Procedure according to Claim 1 or 2 , characterized in that a first torque curve (102) of the maximum input torque (M) with the input torque (M (V)) limited by the design of the variator in a first ratio range (I) of the variator from underdrive (UD) to a ratio (i (a)) is set in the case of a curve (105) of the Hertz pressure which deviates from a power loss curve (109) of the variator. Procedure according to Claim 3 , characterized in that the first torque curve (102) is set depending on the Hertzian pressure between the belt and the conical pulley set in frictional contact with it, a maximum adjustable system pressure of the hydraulic system and / or a power loss of friction between the belt and the conical pulley sets . Procedure according to Claim 4 , characterized in that the first torque curve (102) is set as a function of a current running time interval of the belt in the first transmission range (I). Method according to one of the Claims 2 to 5 , characterized in that in a second gear ratio range (II) of the variator with a medium gear ratio between the gear ratio (i (a)) in the curve (105) of the Hertzian pressure deviating from the power loss curve (109) of the variator and a gear ratio (i (b)) In the case of a system pressure curve (108) of the maximum possible system pressure of the hydraulic system that deviates from a lower limit of a tolerance band (110) of the power loss curve (109), a second torque curve (103) of the maximum input torque (103), which is increased compared to the first torque curve (102) M) is set. Procedure according to Claim 5 , characterized in that the second torque curve (103) within the second transmission range (II) is set increasingly with the transmission depending on a maximum possible system pressure of the hydraulic system. Method according to one of the Claims 2 to 7th , characterized in that in a third transmission range (III) between a transmission (i (b)) with a system pressure curve (108) of the maximum possible system pressure of the hydraulic system and a lower limit of a tolerance band (110) of the power loss curve (109) deviating the overdrive (OD) of the variator of a lower limit of the tolerance band (110) of the power loss curve (109) following maximum input torque (M) is set. Method according to one of the Claims 2 to 8th , characterized in that the power loss is determined as the friction between the belt and the conical pulley sets. Method according to one of the Claims 2 to 9 , characterized in that the torque curves (102, 103, 104) are set as a function of a link strength of links of a looping means designed as a link chain.

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