Patent Application
20090099746
The invention relates to a method for controlling an electric parking brake of a utility vehicle having an electronic control unit and a manual control unit, which communicates with the electronic control unit and by which driver's requests, which are dependant on the type of activation of the manual control unit, are transmitted to the electronic control unit.
Such devices and methods are becoming increasingly important in relation to the operation of utility vehicles. For the further development of the systems, emphasis is placed on various aspects, in particular the operating comfort and safety.
DE 103 53 056 A1 discloses a manual control unit in which great value is placed on the aforesaid aspects. With respect to safety, it is proposed that it be possible to release the electric parking brake only if two activation elements, that is to say not only one activation element, are activated. Furthermore, the individual switches, which are activated by the operator control elements are configured in a redundant way in the manual control unit. Furthermore, mention is also made of the possibility of initiating a test function by use of the manual control unit, specifically releasing the brakes of a trailer in order to determine whether the parking brake of the towing vehicle alone is able to stop the entire train. The driver of a vehicle is advised to use this test function, in particular when parking the vehicle on an incline.
Although manual control units have been increasingly improved with respect to operating comfort, the operator control of the manual control unit nevertheless constitutes an additional task for the driver, which he has to carry out both reliably and, in certain driving situations, with a high frequency.
The invention is based on the object of improving the operating comfort of an electric parking brake.
The invention builds on the prior art in that the parking brake is closed on the basis of an action which is carried out by the driver of the utility vehicle and which is not connected to the activation of the manual control unit. Under certain circumstances, it is therefore possible for the driver to be relieved of his obligation to activate the manual control unit while, nevertheless, the parking brake is still applied. In particular, this facilitates handling of the utility vehicle if the action which is carried out is connected to the execution of another action.
With respect to safety, the method according to the invention provides for further conditions that have to be met for the closing of the parking brake, specifically a switched on ignition or, when the ignition is switched off, operation of the electronic control unit using the run on function, no fault being signaled by the on-board diagnostics, and a sufficiently low speed of the utility vehicle.
In this context, it is useful that the presence of a sufficiently low speed of the utility vehicle is determined by comparing the wheel speed, the vehicle speed output of a controller and the rotational speed of the transmission with predefined threshold values. The rotational speed can be determined directly by use of a sensor and the vehicle speed is generally available as an output value of a controller and is input, for example, into the CAN bus, and the rotational speed of the transmission is supplied by the electronic transmission controller and is preferably also input onto the CAN bus.
In a preferred example of the present invention, the action by the operator is the setting of the gear shift lever to the parking position. Since the driver places the gear shift lever to the parking position in any case when parking the vehicle, he is completely relieved of the need to actively close the parking brake. The parking brake closes automatically if the parking position is selected and the further known conditions are met.
Likewise, it is contemplated that the action be a specific control operation of the brake pedal. This is also useful since the application of the parking brake during operation of the vehicle frequently occurs after the vehicle has been braked by activating the brake pedal. The driver's foot is therefore already on the brake pedal so that he can close the parking brake effortlessly by way of a specific control operation of the brake pedal.
For example, it may be provided that the specific control operation of the brake pedal includes the driver keeping his foot on the brake pedal for a predefined minimum time interval when the utility vehicle is already stationary.
Likewise, it is contemplated that the specific control operation of the brake pedal includes depressing the brake pedal further after the driver's foot has been kept on the brake pedal when the utility vehicle is already stationary. The further depressing of the brake pedal can be sensed by way of a rising pressure in the service brake circuits. Likewise, it is possible to take into account just one travel sensor signal which is connected to the depressing of the brake pedal.
The present invention proves particularly advantageous in the context in which an inter-vehicle distance sensor senses measured values which are characteristic for a stop and go situation as an additional condition for the closing of the parking brake. Particularly, in the stop and go mode, frequently closing of the parking brake may be desired. If the presence of a such a stop and go situation is still considered to be plausible due to measured values of an inter-vehicle distance sensor, this can be used as a further criterion for the special control operation of the brake pedal to lead to the closing of the parking brake.
The invention will now be explained by way of example by means of a particularly preferred embodiment and with reference to the appended drawings.
In the following description of the preferred embodiments of the invention, identical reference symbols denote identical or comparable components.
Furthermore, a power unit 28 is provided, to which voltage can be fed from a double, that is to say redundant, voltage supply. The power unit 28 supplies, in particular, the microcontroller 18 with a stable voltage of preferably 5 V. A shutdown relay 32 is also provided. The shutdown relay 32 is able to place the system, in particular the solenoid valves 36 which transmit the switching functions of the parking brake pneumatics 34, in a secured state, initiated by the watchdog timer 26.
An EAC (electronic air conditioning system) pneumatic interface 38 and devices in the periphery of the electronic control unit 10 are also illustrated. For example, the EAC pneumatic interface 28 is, apart from its connection to the parking brake pneumatics 34, also connected to the trailer control module 40. The trailer control module 40 is also connected to the parking brake pneumatics 38, in particular in order to implement a test function, which will be described below. There is a further connection of the parking brake pneumatics 34 to the spring-loaded cylinders 42 of the parking brake, one of which is illustrated by way of example.
Further peripheral components are an electronic transmission controller (ETC) 44, an electronic engine controller (EEC) 46 and an electronic brake controller (EBC) 48. The electronic brake controller 48 is connected to a modulator 50 by which the pressure in the spring-loaded cylinders 42 can be changed. Furthermore, a central electronic control unit 52 is provided, which can also be implemented within the scope of a vehicle control computer or central on-board computer. The central electronic controller 52 receives, for example, signals ES09 which characterize the state of the doors and the occupancy of the seats. Relevant output signals in the context of the present invention are, for example, a parking signal AS03, a warning or fault signal AS04 and a stop signal AS05, which is output, for example, when the handbrake is pulled on during the stop and go mode.
The electronic transmission controller 44 receives, for example, signals ES10 which characterize the state of the transmission and state of the clutch, the selected gear speed and the rotational speed of the cardan shaft. The electronic brake controller 48 receives, for example, signals ES11 relating to the brake pedal situation and the service brake pressure. The aforesaid control units 44, 46, 48, 52 are connected via a CAN bus 54 to a CAN interface 56 of the electronic control unit 10. Via this CAN interface 56, a plurality of input signals can be transmitted to the microcontroller 18 via its CAN interface 58. Output signals can also be output.
The following input signals, inter alia, are possible:
Possible output signals are, in particular:
In addition to the CAN interface 58, the microcontroller 18 also has direct digital and/or analog outputs 60, in particular for actuating solenoids which provide access to the pneumatic controller.
The electronic control unit 10 also has pressure sensors 62, 64, 66, 68. The pressure sensors 62, 64 sense the pressure in the service brake circuits. The pressure sensor 66 is assigned to the trailer brake system. The pressure sensor 68 is used to measure the pressure in the spring-loaded cylinders.
Further components are provided which relate to the operation of the manual control unit 12 and which are explained with reference to the following description of the method of operation of the manual control unit 12 and its interplay with the electronic control unit 10.
The manual control unit 10 has two operator control elements 14, 16. The operator control element 14 is used to close the parking brake by pressing, while the operator control element 16 is used to open the parking brake by pulling. For the purpose of closing the parking brake, the operator control element 14 is coupled to a switch 70. If this switch is closed, a signal S1 is output to the analog/digital converter 20 of the microcontroller 18. For the purpose of releasing the parking brake, the operator control element 16 is coupled to the switch 72. If the switch 72 is closed, a signal R1 is output to the analog/digital converter 20 of the microcontroller 18.
In addition to its coupling to the switch 70, the activation element 14 is, however, also coupled to the switch 74. The switch 74 is used to generate a wakeup signal WUP, which is also output to the analog/digital converter 20 of the microcontroller 18. The wakeup signal WUP is, however, also fed to a Schmitt trigger circuit 76. The output signal of the Schmitt trigger circuit 76 is fed to a switching logic 22, which outputs an output signal whenever at least one input signal is present. An “ignition on” signal ZE, that is to say in the simplest case a voltage which is present whenever the ignition is switched on, is also fed to the switching logic 22. The output signal of the switching logic 22 influences a switch 24, which is integrated into the power unit 28. If either the “ignition on” signal ZE or the wakeup signal WUP is present, the switch 24 is closed so that the parking brake system, and in particular the microcontroller 18, are supplied with a voltage. The double supply voltage 30 is, for this purpose, fed within the power unit 28 via a coupling element 78, which generally ensures that the higher voltage of the redundant voltage supply 30 is used to supply the parking brake.
In a similar way to how the switch 74 for generating the wakeup signal WUP is assigned to the activation element 14 as well as being coupled to the switch 70 for closing the parking brake system, the switch 80 is assigned to the activation element 16 for releasing the parking brake as well as to the switch 72. When this switch 80 is closed, a signal TEST is generated, which is fed to the analog/digital converter 20 of the microcontroller 18 so that on this basis it is possible to check whether the towing vehicle alone is able to stop the entire vehicle train composed of a towing vehicle and trailer. The switch 80 is advantageously also used as a redundancy switch for the switch 72. In the same way, the switch 74 can be used as a redundancy switch for the switch 70.
Furthermore, resistors R1, R2, R3, R4, R5, R6, R7 and R8 are also provided in the manual control unit 12 and the electronic control unit 10 and are dimensioned in such a way that the suitable signals are fed to the microcontroller 18 and the Schmitt trigger circuit 76. For example, through the closing of the switch 72, the input of the analog/digital converter 20 of the microcontroller 18, which is connected to said switch, is connected to ground GND via the resistor R1 so that as a result a signal is generated. When the switch 72 opens, the corresponding input is connected again to the positive potential of the power unit 28 via the resistor R7.
As in the embodiment according to
In
The activation element 14 can be readily activated. Since the activation element 14 is pulled counter to the force of the tension spring 84, the switch 74 closes first so that in this way the signal WUP is output to the microcontroller (see
The activation element 16 can firstly be readily activated, specifically by virtue of the fact that it is pressed against the force of the compression spring 86. The slope 96 of the activation element 16 activates the spring-prestressed momentary contact switch 28 so that the switch 80 is closed. The trailer test function can be carried out in this way. However, if the activation element 16 is to be moved further, the slope 100 of the activation element 16 impacts against a blocking element, specifically a spring-centered sliding block 102. The activation element 16 can therefore not be moved any further. Only simultaneous activation of the activation element 14 causes an opening 104 in the activation element 14 to be arranged in such a way that the sliding block 102 is aligned with the opening 104. Consequently, the force which is exerted on the sliding block 102 by the activation element 16 causes the sliding block 102 to slide into the opening 104. After this sliding process has taken place, the activation element 16 is pressed further and, owing to the force effect of the slope 106 on the spring-prestressed momentary contact switch 108, it can activate the switch 72 to open the parking brake. Therefore, as a result of the activation of the activation element 16, the signals TEST and R1 are generated in succession, and the signal R1 can be generated here only after mechanical release of the sliding block 102 as a result of pulling out the activation element 14.
The manual control unit furthermore optionally includes an accumulator 110 and an assigned control unit 112. Furthermore, an LED 114 is optionally provided. The LED 114 is able to output light signals 116 via a duct which extends in the axial direction of the activation element 16. Such light signals can, for example, request the driver to carry out the trailer test function. It is also contemplated for warning signals or status signals to be output by way of the light signals 116.
Furthermore, it is checked whether at least one of the conditions B06 and B07 is met, specifically whether either the ignition is switched on (condition B06) or whether the ignition is switched off but the electronic control unit is in its run on mode. If this checking of the conditions B01 to B07 on the basis of the described logic combinations leads to positive results, this has the effect W01 on the electric parking brake, and the latter is then closed according to a predefined time/pressure characteristic curve; and the parking brake is closed completely when the vehicle is stationary. These relationships are explained in the functional diagrams, in which the service brake pressure pB is plotted against time t in one of the diagrams, while in the other diagram the pressure pF, which is measured in the spring-loaded cylinders of the parking brake, is plotted against the time t. It is apparent that the service brake pressure firstly rises to a predefined value p2 up to the time t1. The pressure in the spring-loaded cylinders pF then drops from a value pF1 to a value pF2 up to the time t2, wherein the value pF2 corresponds to a closed parking brake. This pressure profile, which is illustrated in a simple form, can, under certain circumstances, have varied forms. For example, it is possible that after the time t1 the pressure pF in the spring-loaded cylinders firstly drops slowly in accordance with a time/pressure characteristic curve, and the vehicle comes to a complete standstill before the parking brake closes completely, and from this time the further pressure drop in the spring-loaded cylinders can occur more quickly. It will also frequently be the case that at the time t1, the vehicle is already completely stationary so that subsequent to this the spring-loaded cylinders can be vented quickly immediately.
A method which is used to check the parking brake in a utility vehicle which is equipped with a trailer is explained with reference to
The stop and go mode, which is assisted by the electric parking brake, will be explained with reference to
The assistance provided to the service brake by the electric parking brake in the event of a circuit defect is explained with reference to
By reference to
The features of the invention which are disclosed in the description above, in the drawings and in the claims implement the invention either individually or else in any desired combination.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2005 042 305.1 | Sep 2005 | DE | national |
| 10 2005 043 607.2 | Sep 2005 | DE | national |
This application is the national phase filing of PCT Application No. PCT/EP2006/008674, filed on Sep. 6, 2006, which claims priority to German Patent Application Nos. 10 2005 043 607.2 filed Sep. 13, 2005, and 10 2005 042 305.1, filed Sep. 6, 2005 the disclosures of which are incorporated by reference herein. This application contains subject matter related to copending U.S. patent application Ser. Nos. 12/065,810, filed Mar. 5, 2008, and 12/065,868, filed Mar. 5, 2008.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2006/008674 | 9/6/2006 | WO | 00 | 8/29/2008 |
