Procedure for operating a hybrid vehicle

Abstract

A method for operating a hybrid powertrain of a hybrid vehicle, wherein the powertrain comprises an internal combustion engine, a first electric machine, a transmission with an input shaft, a separating element, and a first axle of the hybrid vehicle, wherein the internal combustion engine is arranged together with the first electric machine on the input shaft of the transmission for driving the first axle of the hybrid vehicle, and the internal combustion engine can be connected to the first electric machine via the separating element, wherein, with the separating element open and the internal combustion engine stationary, a speed difference arises at the separating element between the internal combustion engine and the rotating first electric machine, wherein below and up to a maximum permissible speed difference at the separating element, this is opened in order to drive, brake, or coast the hybrid vehicle purely electrically by the first electric machine.and above the maximum permissible speed difference, sailing operation is achieved by a clutch element of the gearbox that is in an open position.

Description

The invention relates to a method for operating a hybrid powertrain of a hybrid vehicle. In such a hybrid vehicle, the powertrain includes an internal combustion engine, a first electric motor, a transmission with input shaft, a separating element, and a first axle of the hybrid vehicle. In this configuration, the internal combustion engine and the first electric motor are arranged on the input shaft of the transmission to drive the first axle of the hybrid vehicle. Furthermore, the internal combustion engine can be connected to the first electric motor via the separating element. When this separating element is open, the internal combustion engine can be switched off. The first axle of the hybrid vehicle can then be driven purely electrically by the first electric machine operating as a motor, or braked by the first electric machine operating as a generator (hereinafter referred to as "recuperation"), or roll without power (hereinafter referred to as "coasting"). However, at high speeds, especially in high-performance hybrid vehicles, significant speed differences can occur between the switched-off (i.e., stationary) internal combustion engine and the rotating first electric motor. If, however, a maximum permissible differential speed is exceeded at the open separating element, thermodynamic or structural problems can arise at the separating element. US Patent 6,932,738 B2 describes a hybrid vehicle in which an electric motor can be decoupled from a purely electrically driven axle. This decoupling of the electric motor is envisaged. The object of the present invention is to provide a method for operating a hybrid powertrain of a hybrid vehicle, which avoids thermal problems or strength problems at the open separating element at high speeds of the hybrid vehicle. The problem is solved by a method with the features of claim 1. The essential feature of the inventive method is that, below a maximum permissible speed difference at the separating element, this element is opened to allow the hybrid vehicle to be driven purely electrically by the first electric motor, to recuperate energy, or to coast. Above the maximum permissible speed difference at the separating element, a clutch element in the transmission is opened, thereby disconnecting the separating element. Due to the disconnection of the separating element, the hybrid vehicle can still coast even above the maximum permissible speed difference at the separating element. Consequently, no thermodynamic or strength problems are observed at the separating element, particularly at high speeds, especially in high-performance hybrid vehicles. The method according to the invention is independent of whether the hybrid vehicle has a single, first driven axle or at least one additional electrically driven axle. Even in vehicles without an additional electrically driven axle, the method according to the invention enables coasting operation at high vehicle speeds that would otherwise cause the differential rotational speed at the separating element to be exceeded to an impermissible degree. Preferably, the hybrid vehicle operated according to the invention is designed such that the drivetrain comprises a second axle of the hybrid vehicle and at least one second electric motor for driving the second axle. It is provided that, above the maximum permissible differential speed at the separating element, the hybrid vehicle is driven or braked by means of the second electric motor. Thus, the hybrid vehicle can continue to drive purely electrically even above the maximum permissible differential speed at the separating element, by driving the second axle of the hybrid vehicle purely electrically through the second electric motor operating as a motor, or recuperate energy by being braked by the second electric motor operating as a generator. This further development therefore enables electric driving operation even outside the maximum differential speed of the separating element.However, in addition to the first axle, a second electrically driven axle is required. This design also allows for the reduction of heat input during cold starts, thus minimizing clutch wear. The key feature of the method according to the invention is the ability to use a coupling element of the transmission connected to the hybrid module to perform the function of the separating element within the hybrid module, thereby circumventing the problem of the maximum differential speed. In particular, until the differential speed is reached, the drivetrain is separated for coasting and electric driving via the separating element within the hybrid module. When the differential speed is exceeded, coasting is achieved by the coupling element of the transmission connected to the hybrid module, with the separating element within the hybrid module preferably remaining closed. If a second electric machine is available within the drivetrain, electric driving via this machine can also be implemented in this operating state. The internal combustion engine is preferably started when the first electric motor of the hybrid module is stationary, thus providing high torque. Depending on the starting dynamics, it can also be towed by clutching, in particular using the clutch element, with the connected transmission and / or dynamically coupled.

Claims

A method for operating a hybrid powertrain of a hybrid vehicle, wherein the powertrain comprises an internal combustion engine, a first electric machine, a transmission with an input shaft, a separating element, and a first axle of the hybrid vehicle, wherein the internal combustion engine is arranged together with the first electric machine on the input shaft of the transmission for driving the first axle of the hybrid vehicle, and the internal combustion engine can be connected to the first electric machine via the separating element, wherein, with the separating element open and the internal combustion engine stationary, a speed difference arises at the separating element between the internal combustion engine and the rotating first electric machine, wherein below and up to reaching a maximum permissible speed difference at the separating element, this is opened in order to drive, brake, or coast the hybrid vehicle purely electrically by the first electric machine.and above the maximum permissible speed difference, sailing operation is achieved by a clutch element of the gearbox that is in an open position. Method according to claim 1, wherein the separating element remains closed when the coupling element is in the open position. Method according to claim 1 or 2, wherein the drive train comprises a second axle of the hybrid vehicle and at least one second electric machine for driving the second axle, wherein the hybrid vehicle is driven or braked above the maximum permissible differential speed at the separating element by means of the second electric machine. Method according to one of claims 1 to 3, wherein the internal combustion engine is started with the first electric machine stationary and is towed uphill by coupling with the gearbox and / or dynamically coupled.