The invention concerns a transmission/engine control for a motor vehicle with an automatic transmission in accord with such a control more closely defined in the generic concept of the present patent.
As taken from the state of the technology in the known transmission control for an automatic transmission of a motor vehicle that possesses an electrical circuitry, the placement of gear ratio position is initiated by the options of a driver. The driver accomplishes this by means of activating a gear selection lever, wherein the position of the lever is detected by a position recognition apparatus which sends a corresponding signal to an electronic transmission control.
Should a disturbance occur in a signal transmission along the signal pathway between the gear selection lever and the control of the automatic transmission, then an emergency operating mode is activated in order to allow the automatic transmission to run a hydraulic emergency program. A disturbance can come about through a dropout of a data bus of a Controller Area Network (hereinafter, xe2x80x9cCANxe2x80x9d) or in the failure of an electronic control device, such as the electronic transmission control.
In the case of a disturbance, as a result of the then activated emergency operating mode, no further alteration of the driving program in the automatic transmission is possible, except for stopping the motor. Normally, one gear stage becomes hydraulically fixed in an emergency operating mode. It is impossible for the driver to change this situation by manipulating the position of the gear selection lever since, firstly, the electro-hydraulic actuator for the clutch control can no longer be regulated electrically and, secondly, the electrical position recognition impulses can no longer be transmitted.
The latter, relating to the position recognition apparatus, is especially problematic in the case of an automatic transmission with an exclusively electrical connection between the gear selection lever and the transmission.
For example, DE-OS 196 43 812 describes a parking-block system for an automatic transmission in which the gear selection lever is completely uncoupled and the control demands of the lever are exclusively taken over by the electronic transmission control.
DE-PS 44 22 257 describes a gear selection apparatus for an automatic transmission wherein the stages xe2x80x9cDxe2x80x9d, xe2x80x9cNxe2x80x9d, and xe2x80x9cRxe2x80x9d are exclusively shifted in by an electric motor which is controlled by an electronic transmission regulatory apparatus. In this arrangement, only in the gear selection stage xe2x80x9cPxe2x80x9d would the mechanical-hydraulic coaction between the gear selection lever and the transmission be initiated.
If, by the occurrence of a disturbance of the signal transmission, a gear position for forward travel is shifted, and the driver, by means of the gear selection lever, gives the command for change to a reverse gear, this shifting order cannot be transmitted to the transmission control and carried out and the vehicle, upon starting from rest, disadvantageously travels forward contrary to the expectation of the driver.
In order to alert the driver that the automatic transmission is in the emergency mode, as advised by the state of the technology, the instrument board of the motor vehicle is provided with a warning element or a light signal to indicate such disturbance. Further, another known procedure is to notify the driver of an activation of the emergency mode by the extinguishing of a normally illuminated display of the gear selection position display on the instrument board or elsewhere, which is in electrical communication with the electronic transmission control.
However, this arrangement is disadvantageous because these warning displays only indicate a general emergency condition so that the driver can come to a false conclusion about carrying out a change in the direction of driving.
This can lead to a situation wherein, after a driver""s movement of a gear selection lever to change the travel direction of the vehicle from a xe2x80x9cFORWARDxe2x80x9d gear selection to xe2x80x9cREVERSExe2x80x9d, the vehicle itself moves in a xe2x80x9cfalsexe2x80x9d direction upon starting.
Upon a strong activation of the gas pedal, the motor vehicle can then run into an obstruction in the vicinity since, in such an occurrence, the reaction time in which the driver has available to evaluate the situation can be too short to avoid an accident by subsequent activation of the vehicle brake. Thus, the present invention has the purpose of making available a transmission/engine control for a motor vehicle with an automatic transmission and an electrical position recognition of the placement of gear selection lever with which, in the case of a disturbance of the signal transmission between the gear selection lever and transmission and in an activated emergency mode, the danger of accident by undesired starting from rest in a xe2x80x9cfalsexe2x80x9d direction is avoided, or at least a start of motion with only a low acceleration is possible.
In accord with the invention, this purpose is achieved with a transmission/engine control as discussed below.
When the invented transmission/engine control is constructed, assurance is advantageously given that in the case of a disturbance of a signal transmission from the electrical position recognition apparatus of the gear selection lever to the control means of the automatic transmission, by means of which a disturbance in a direction of travel change can no longer be carried out, and only a slow startup of the motor vehicle is possible.
This is of particular advantage, if the driver of the motor vehicle is of the opinion that he has effected a change in a direction of travel by means of activation of the gear selection lever whereby the fact is that, because of the disturbance, no change of the existing gear stage occurred. With the achievement in accord with the invention, namely, the motor vehicle does not travel with its entire available motor capacity, but only with a lesser motor capacity, so the driver has sufficient time and is able to avoid damage to his motor vehicle.
Alternative to this, the transmission/engine control can be so designed that with this achievement of the purpose of the invention, in a simple manner assurance can be given that in the case of a disturbance of the signal transmission from the electrical position recognition apparatus of the gear selection lever to the regulatory means of the automatic transmission, by which no change in the direction of travel is possible, a driver can start up from still stand with the motor vehicle, having no acceleration, or with only a reduced acceleration, that is, the vehicle speed, in what is for him a xe2x80x9cfalsexe2x80x9d direction.
By means of the activation of the vehicle brakes, in an advantageous manner, an accident can be avoided. To accomplish this, the vehicle brakes can be activated by a processing unit, independent of the transmission, in such a manner that a startup of the motor vehicle is in general prevented, or is possible only at a very slow speed.
With the invented achieving of the purpose of the invention which, in itself alone, or in combination with one of the achievements, provision can be made to achieve the advantage that the driver of a motor vehicle can be advised, through the blocked gear selection lever, that a change in the direction of the travel by means of a change of the gear selection in the automatic transmission is not possible. This would indicate that forward travel, subsequent to reverse travel, is not possible. This invented advantage provides the driver with a clear, and unmistakable announcement, that a change of the travel direction is not possible.
An optical or acoustic advisory display presents a constructive, simple and economical advantage of the invention which can be installed on the instrument panel.
In a development of the transmission/engine control, it can be provided that the warning apparatus is at least activated for a specific time of application.
To accomplish this, advantageously the driver is first signaled that a disturbance is in force and a travel directional change of the motor vehicle is not possible. After expiration of the time of application, the motor related or brake related operational intervention can, in part, be rescinded by the warning so that a larger vehicle mobility is made available and a limited continuation of travel to a repair station is assured. This travel would take place in a hydraulic emergency mode of the automatic transmission without markedly increasing the safety risks to the driver.
Further advantages and improvements of the invention arise with the aid of the drawing, showing a sketch schematically based on the described embodiment.