DE4446109A1 - Selective utilisation of vehicle engine braking for upward gear change - Google Patents

Abstract

The microprocessor control unit is connected by signal lines to devices controlling the fuel system, retarder and antilock (ABS)/antislip (ASR) braking system. It responds to a braking program switch near the driver's left foot, a clutch-pedal switch and sources connected to the transmission mode selector lever, economy/hillclimb mode selector, retarder coolant thermometer, gearbox output shaft tachometer etc. The use of engine braking depends upon whether the braking program switch is engaged so as to raise the normal gear-change point, and whether the loss of speed during the change exceeds a predetermined threshold dependent upon the mode of operation (kickdown).

Description

The invention relates to a method specified in the preamble to claim 1 benen type and in an arrangement provided for the implementation of the method the type specified in the preamble to claim 8.

State of the art

When shifting up to higher gears, with smaller gear ratios, with transmissions from Motor vehicles have their engine speed reduced. With semi-automatic and fully automatic Chen switching systems, preferably in mechanical stepping gears, the control takes place the engine speed by regulating the amount of fuel injected, and when the Speed must be reduced when shifting up, can also during the switching process an exhaust brake (engine brake, dynamic pressure brake) are currently switched on lower the engine speed faster to a value that is synchronous with the speed of the next gear.

In US, A, 4787044 a solution is described in which the exhaust brake during a Upshift is turned on to get the engine speed faster to that with the lower the next gear synchronous speed. However, this solution relates to one Arrangement with automated clutch function, which controls the flow of power between the engine and Transmission interrupts, after which the fuel regulation and the activation of the exhaust brake take place during the upshift to the engine speed quickly to that with the lower the next gear synchronous speed.

One problem here is that each time the exhaust brake is turned on Lowering the engine speed in connection with upshifting a disturbing puffge noise is generated that is perceived as a nuisance, especially in buses.

Purpose of the invention

One purpose of the invention is in an automated circuit in motor vehicles with mechanical step gears on the gas exchange of the internal combustion engine acting engine brake organs for amplifying the engine braking power preferably by Use the exhaust brake for upshifts only when fast Upshifts are required. This allows the application of the reinforced Engine braking power, preferably by turning on the exhaust brake, as well as the Noise generation when shifting up to the minimum number of upshifts limit, which is called noise pollution for drivers, passengers and Environment diminished.

Another purpose of the invention is that when there is an actual need for reinforced Engine braking power in conjunction with switching operations automatically depends on this of predefined vehicle parameters is available without the driver having to do more Must take action.

Another purpose of the invention is that the wear on the engine and whose parts, especially in turbocharged supercharged engines, can be reduced.

The invention fulfills these purposes in a process-related manner by means of the features of Claim 1 specified features.

Another purpose of the invention is that the wear on the mechanism can reduce the exhaust brake by selective application of the exhaust brake Upshifts compared to a regular application upshifts to a fraction of the total number of upshifts reduced.

The invention fulfills these purposes in a process-related manner by means of the features of Claim 2 and arrangement-related by those specified in the characterizing part of claim 8 Features.

A purpose of a further developed embodiment of the invention is that a Fast upshifting with the exhaust brake on only in the main two operating cases is obtained if:

• - An upshift due to excessive retardation of the vehicle during the Switching process can be lost, which applies especially on steep inclines, or
• - A failure of the engine braking caused by the switching process for the shortest possible duration should be limited, which is especially true for steep slopes.

As a result, under normal operating conditions of a truck in the distribution Long-distance traffic, in connection with upshifts the activation of the exhaust brake and generating noise to 5-10 percent of the total number of times required switching operations are limited.

The invention fulfills these purposes in a process-related manner by means of the features of Claim 3 specified features.

A purpose of a still further developed embodiment of the invention is that in operating cases, when an upshift due to excessive retardation of the Vehicle criteria can be lost, differently strict decision criteria for the automatic activation of the exhaust brake can be applied. Depending on the measure The driver automatically switches on the exhaust brake obtained with an upshift at lower retardation levels if the Driver switched on a so-called uphill program or the accelerator pedal maximally in the so-called. Has depressed the kick-down position during normal operation without kick-down or ascent program the automatic switching on of the exhaust brake in connection with an upshift only at higher levels of retardation and when up switch into a lower gear, preferably in the lower range of the range group Gearbox, is obtained.

The invention fulfills these purposes in a process-related manner by the in the characteristics of Claim 4 and 5 and in relation to the specific retardation limits for each Operating case by the features specified in the characterizing part of claim 6 or 7.

Further features characterizing the invention emerge from the subclaims and the following description of an embodiment. The description takes Reference to the following figures.  

List of figures

Fig. 1 shows the basic structure of a switching system for mechanical stepping gears.

Fig. 2 shows in the form of a flow diagram how the control unit detects the vehicle parameters that result in a selective activation of the exhaust brake in connection with upshifting processes.

Description of an embodiment

Fig. 1 shows a switching system for monitoring and controlling a computer-controlled circuit of mechanical transmissions in motor vehicles. The vehicle is driven by an internal combustion engine 40 , preferably a diesel engine, the drive power of which is transmitted to the drive wheels 44 of the vehicle via a clutch 41 to be actuated by the driver, a mechanical stepping gear 42 and an articulated shaft 43 . The transmission 43 preferably has an integrated retarder 48 which can apply a controllable braking force to the drive train, which serves the purpose of generating a high braking power in the vehicle without using the normal service brake of the vehicle. The switching system provided in the exemplary embodiment comprises a manually operated clutch servo device for start and stop, but does not have an automatic coupling servo device, but the invention can also be used in systems with an automated clutch. The switching system effects the switching operations by regulating the engine speed and the engine torque during the switching operation and actuating the servo device 37 , which disengages the engaged gear and engages the next gear, without disengaging the clutch 41 . This places high demands on the engine control (the engine management) and on the speed information that the system needs so that the engine control can enable a gear to be geared up without torque and so that only the engine control can quickly achieve a synchronous speed for the next gear, which is the shortest possible torque interruption should be inserted in the mechanical stepping gear.

Mechanical step gears, preferably with or without conventional synchronizers directions in the transmission are in many ways a decidedly more advantageous choice than conventional hydraulic automatic transmission that shifts without torque interruption or as a mechanical transmission with complicated double clutches, the switching operations  enable without interrupting the moment. This is especially true with regard to the Economics, maintenance costs and acquisition costs. If that Stepper transmission is also equipped with conventional synchronizing devices, will also get increased operational reliability because of a manual shift or a semi-automatic switching, d. H. a servo-assisted laying out and loading of Gears as a result of a foot-operated disengagement while maintaining a high gear change can continue if the automated switching function is due to a system error should have failed.

The switching system comprises a control unit 12 with a microprocessor, which is connected via various signal lines 36 to the control units 23 for the fuel system, 22 for the retarder system and 24 for the service brake system. The signal lines transmit various signals to the control unit 12 in accordance with the signals 1-11 , 13-19 , 21 and 59 shown in arrows in FIG. 1.

The control unit 12 receives the following input signals:

• - Signal 1 from brake program switch 27 , which is angeord net for foot actuation by the driver. The brake program switch influences the retarder function via the control unit and also, when actuated, the switching points of the switching system.
• - Signal 2 from the clutch pedal switch 30 , which detects the position of the clutch pedal 28 .
• - Signal 3 from the foot brake pedal of the vehicle as information about the position of the brake pedal.
• - Signal 4 from the tachograph of the vehicle, with secondary information on the speed of the vehicle or the speed of the propeller shaft.
• - Signal 5 from the accelerator pedal of the vehicle as information about the current position of the accelerator pedal.
• - Signal 7 from the exhaust brake switch 45 , which is arranged in the dashboard 32 .
• - Signal 8 from the shift lever 25 as information about the mode selected by the driver in the switching system, either automatic mode A, neutral position N, manual mode M or reverse travel R, as well as any corrections made by the driver of the automatically selected gear in automatic mode A or new gear selections in one of the manual operating modes N, M, R.
• - Signal 9 from the drive program selector 26 , with which the driver z. B. can choose the economy program E (economy) for the most economical operation and smooth switching operations or the mountain climbing program H (hill), the switching points of which are set in such a way that the maximum tractive force is obtained and fast switching operations have priority over comfort and noise generation.
• - Signal 11 from the diagnostic switch 35 , with which a test program integrated in the program of the control device can be activated for maintenance purposes or for fault location by means of error messages displayed in the info field 33 of the dashboard 32 .
• - Signal 21 from the retarder control unit 21 , which modifies the switching points for the activation duration of the signal, in order thereby to obtain an increased engine braking power and an increased coolant throughput.
• Signal 19 from a speed sensor 46 arranged on the output side on the transmission 42 and preferably on the propeller shaft 43 .
• - Signal 18 from acknowledgment switches in the transmission 42 as information about the gear engaged.
• Signal 16 from a speed sensor 47 arranged on the input side on the transmission 42 and preferably on the crankshaft or the flywheel of the engine 40 .
• - Signal 59 from the temperature sensor 49 as information about the temperature of the cooling liquid speed after leaving the retarder 48th

The control device 12 controls various servo devices or effects displays in info fields in the dashboard 32 via the following output signals:

• - Signal 6 to info field 33 in the dashboard 32 to display the operating mode (ANMR) in the switching system, current gear, next gear, driving program (EH) and any error codes, warnings and messages to the driver.
• - Signal 17 to various solenoid valves in the gear 42 for activating servo devices 37 , so that they actuate the switching elements for shifting gears.
• - Signal 15 to exhaust brake 58 , which is arranged in the exhaust system of the engine, so that the exhaust brake, in addition to its function as an auxiliary brake, can be activated to quickly lower the engine speed to a synchronous speed, especially when shifting up to a gear with a lower gear ratio.

The control unit 12 also communicates in interactive mode, ie it sends output signals and receives input signals from various control units via the following communication lines:

• - Communication line 10 to diagnostic socket 34 , to which diagnostic equipment can be connected, which can query error codes from control unit 12 and perform a functional test of the control unit program.
• - Communication line 13 to control unit 24 for anti-lock braking system (ABS) and traction control system (ASR) of the brake system, as a result of which control unit 24, inter alia, can prevent gear changes when the ASR is activated.
• - Communication line 14 to control unit 23 of the fuel system; This control unit 23 regulates the fuel supply to the injection valves of the internal combustion engine via communication line 20 .

The system described above allows an automatic when the shift lever is in the A position Chen sequence of switching operations depending on detected engine parameters such as speed of the vehicle, engine load and speed, the derivation from one of these or a combination of vehicle speed-accelerator pedal position-engine speed, if necessary, fully depressed accelerator pedal (so-called kick-down position) and whether a Braking takes place. The switching process takes place automatically so that the optimal Fuel consumption and optimal performance can be obtained.

The retarder control unit 22 comprises a hand lever 61 , which is preferably arranged in the dashboard 32 . The lever has six setting positions with the designations 0 to V. 0 is the starting position, ie the retarder 48 is switched off. Positions I-II-III-IV-V correspond to a progressive increase in retarder braking power with the following braking torques: Position I-500 Nm, II-1000 Nm, III-1500 Nm, IV-2000 Nm and V - maximum retarder braking power of approx. 3000 Nm. With position V for maximum retarder power, it is also expedient to switch on the exhaust brake (EB) 58 of the vehicle, which additionally reinforces the braking power acting on the drive wheels of the vehicle. Positions 0-V are stable so that the lever remains in the selected position after releasing it. However, the retarder function is always deactivated as soon as the driver operates the accelerator pedal 31 of the vehicle, but the braking power of the retarder is automatically activated when the accelerator pedal is released and the lever is simultaneously in one of the positions IV. The retarder function can also be switched on, depending on the actuation of the brake pedal or a slide switch 63 on the lever 61 in order to keep the speed constant (cruise control). The braking power of the retarder is then automatically entered in such a way that the vehicle speed is maintained by progressively increasing the braking power as the vehicle speed increases. When the button 62 is in the appropriate position, this function for keeping the speed constant can automatically take effect as soon as the brake pedal 29 is actuated, and then remain effective as long as the accelerator pedal is not actuated thereafter.

The invention is advantageously suitable for automatic switching operations in mechanical stepping gears, in which the switching operations take place without disengaging the clutch 41 .

The invention is described in more detail with reference to FIG. 2, which shows in the form of a flowchart a control routine for the selective activation of the exhaust brake depending on vehicle parameters that indicate a need for fast upshifting. This control routine is stored in the microprocessor of the control unit 12 .

In the first question step 80 it is checked whether an upshift is pending. As long as none Upward pending, the program returns to the main program. The control route tine can preferably lie in a program loop that is at a frequency of 100 Hz is scanned. The check whether an upshift is pending is therefore carried out 100 times per Second.

If an upshift is pending, the control routine goes to step 81, in which it is checked whether a first condition for obtaining fast upshift operations by switching on the exhaust brake is fulfilled. If the driver has activated a driving program (Sprg = Shift program) for ascent (hill) via the driving program selector 26 or depressed the accelerator pedal to the so-called kick-down position, the first part of the condition is fulfilled . This first part indicates that there is a need for fast gear changes, on mountain roads where an interruption in the drive torque caused by the gear change may result in the vehicle losing speed and a gear change lost, or in acute traffic situations when the driver a quick response of the vehicle is required.

On these occasions there is a second sub-condition for switching on the exhaust gas brake during upshift to the application resulting from the retardation of the driving stuff, also as speed difference dV (= delta velocity = delta speed) designated exists. If this vehicle parameter speed difference dV over a predetermined value, the second subcondition is considered fulfilled.

If both partial conditions of the first condition in step 81 are met, the control routine goes to step 84 and causes the exhaust brake EB _{upshift to be switched on} during the upshift process.

The threshold value of this vehicle parameter dV is expediently strictly with a loss of speed of the vehicle, d. H. dV <0, causing the exhaust gas Brake is automatically switched on if the vehicle is in the process of an upshift is losing speed. Only if the vehicle doesn't lose speed what on a slope when the mountain climbing program is accidentally switched on or If the accelerator pedal reaches the kick-down position, the exhaust gas is not switched on brake, and this is not the case if the vehicle does not lose speed required when the speed of the vehicle is lowered below the upshift point and the need for upshifting no longer exists.

If one or both of the first and second parts of the first condition in step 81 are not are met, the control routine goes to step 82, where it is checked whether a second one Condition for obtaining fast upshifts by switching on the exhaust brake is satisfied.

If the next gear NG (= next gear) to which the control device is to shift is lower than a predetermined gear EB _gear , the first part of the condition is fulfilled. This first part indicates that an upshift to a smaller gear of the total number of gears should take place. The next selected gear is preferably a smaller gear below the upper half of the total number of gears, preferably a current gear in the low range of the range group of the transmission. In the low range of the range group of the transmission are all the smaller gears that are engaged when starting the vehicle and are therefore closely graded and therefore have a small increase in the gear ratios. These smaller gears are typically engaged only for very short durations, and the upshift can be prevented or quickly followed by a downshift when the vehicle loses speed so that the vehicle's speed is below the upshift point or below the downshift point for the the next higher gear in the range group of the gearbox.

When switching operations in the relatively narrowly graduated part of the transmission and preferably in the Range group of the gearbox are present, a second sub-condition for switching on occurs the exhaust brake in function during the upshift, and this second subcondition consists of the retardation or the loss of speed of the vehicle during the Switching operation.

If this vehicle parameter, retardation or the loss of speed of the vehicle is above a predetermined value, the second subcondition is also fulfilled. The control routine then goes to step 84 and causes the exhaust brake EB _{upshift to be switched} on during the upshift process.

The threshold value of this vehicle parameter dV expediently becomes less stringent as the threshold value for the second partial condition of the first condition in step 81 set. The second subcondition is only considered to be fulfilled if the vehicle during the Switching a retardation or a loss of speed of considerable size detected by the cardan shaft speed Crpm dV <-5 / s, takes place.

If both partial conditions of the second condition in step 82 are met, the control routine goes to step 84 and causes the exhaust brake EB _{upshift to be switched on} during the upshift process. As a result, the exhaust brake is automatically switched on during the upshifting process if the vehicle loses significant speed during the upshifting into a lower gear in the narrowly graded part of the transmission and preferably in the range group during the upshifting process.

If one or both of the first and second parts of the second condition in step 82 are not are met, the control routine goes to step 83, where it is checked whether a third Condition for obtaining fast upshifts by switching on the exhaust brake is satisfied.  

If an engine brake program is switched on, for example by the driver actuating the brake program switch 27 , an automatic switching on of the exhaust brake is obtained during the upshifting process. As long as switch 27 is actuated, the engine brake program causes the upshift points to be raised and the exhaust brake to be switched on, and only the raised upshift points remain after the switch is released, and only as long as the accelerator pedal 31 is not actuated after the release.

If the engine brake program EnB (= engine brake) is switched on and this is detected on the basis of the upshift points raised by the vehicle parameter, the control routine goes to step 84 and switches on the exhaust brake EB _upshift during the upshift process. As a result, the exhaust brake is automatically switched on during the upshift process, provided the engine brake program is switched on. Switching on the engine braking program indicates that the driver is requesting a particularly large amount of braking power, and consequently all torque interruptions caused by the upshifting operation, which are associated with a loss of engine braking power, must be as short as possible.

If the condition is not satisfied in the third step 83, the control routine proceeds to step 85, in which the starting of the exhaust brake EB _upshift during the upshift off (OFF).

Retardation or loss of speed are either considered as actual acceleration or detected as an actual loss of speed. The retardation is expedient is determined in a calculation routine that lies in the program loop that with a frequency of 100 Hz is sampled. For the determination of the acceleration uses a short time base of 0.5 s. The acceleration will then be 100 times per second updated, and the acceleration value is stored in the control unit memory where he of steps 81 and 82 when determining whether the retardation condition is met or is not queried. However, the acceleration value has a tendency to be strong Influenced by vibrations in the drive train of the vehicle, which also causes receive a restless signal with changing values during acceleration / retardation if the trend is a retardation. Optionally, the Speed at the start of the upshift in the memory of the control unit stored and compared in step 81 and 82 with the current speed  to determine if the speed loss is greater than the given one Threshold.

The control routine 80-84 / 85 is running during the shift-up process continuously, and for example, when the retardation of the vehicle in the initial phase of the Heraufschaltvor passage does not exceed the predetermined threshold values, a later exceeded, a switching on the exhaust gas brake during a and cause the same shift-up process. The exhaust brake is expediently switched on as a hysteresis function, in which the exhaust brake which has already been switched on is not switched on during the control of the activation of the exhaust brake in order to maintain the synchronous speed before the threshold values are undercut by a predetermined offset value. Optionally, a time function can lock off the exhaust brake due to the threshold values falling below during the switching process, this time function keeping the exhaust brake on for preferably 50 milliseconds and only then releasing a shutdown depending on the falling below the threshold values during the switching process. Switching off the exhaust brake because a synchronous speed should / has been obtained by switching on the exhaust brake always has priority over the hysteresis function.

The preferred threshold values for the retardation condition become more appropriate adapted to the response behavior of the switching system.

Shorter response times with the servo device for gear selection and gear selection when Switching on the exhaust brake and with the fuel injection control permit setting of the threshold values for higher retardations without being caused by the switching process conditional moment interruption lasts so long that there is a risk of an up Switching process is lost or the engine braking power fails for too long.

There is also the possibility to adjust the threshold values partly by setting higher retardation conditions in order to use the exhaust brake when shifting up would decrease even more, and in part by setting lower retardation conditions to get faster gear changes more often. With the same intent can other logical conditions will also be introduced.  

The predetermined threshold values are stored in the non-volatile memory 57 in the control device 12 .

The invention can be modified within the scope of the claims so that there are differences compared to the preferred embodiment. What is unique about the invention is however, a selective application of one to boost the engine's gas exchange Engine braking power of the engine braking element, preferably a switchable exhaust brake, in upshifts in shift systems for mechanical transmissions, these Application automatically depending on exceeding specified vehicle parameters takes place and this exceeding of the vehicle parameters indicates that short moment stops calculations and fast switching operations are requested, either because of the risk that an upshift is lost, or the need to interrupt the Reduce engine braking power when the driver needs additional braking power requests.

The term engine braking elements, which act on the gas exchange of the internal combustion engine, includes, in addition to the exhaust brake, also selectively switchable engine braking elements such as

• - "Jake-Brake", which is caused by briefly opening the exhaust valve at top dead center (TDC) At the end of the compression stroke, increase the engine braking power by reducing the compression pressure on the piston during its downward stroke from the TDC is reduced and thereby preventing a rebound, as well
• - Engine braking elements caused by briefly opening the exhaust valve at bottom dead center (UT) at the beginning of the compression stroke, filling the cylinder with increased pressure cause standing exhaust gases, resulting in an increased compression work and thus results in increased engine braking, and
• - Combinations of the above two engine brake functions, possibly still combined with an exhaust brake.

With a Jake-Brake brake, for example, an air cylinder can control the drain valves some or all of the cylinders cyclically in TDC during the neutral phase when raised Upshift points are present or the retardation of the vehicle during the shift pre is too strong, press down into the open position. In a corresponding way can the drain valves in the submarine to fill the cylinder at the beginning of the compression stroke  be opened during the neutral phase when there are raised upshift points or the retardation of the vehicle is too strong during the switching process.

Reference list

1 signal from brake program switch
2 Signal from clutch pedal switch
3 Service brake pedal signal
4 Tachograph signal
5 Signal from accelerator pedal
6 Signal on the dashboard information field
7 Signal from exhaust brake switch (EB)
8 Signal from shift lever
9 Signal from drive program selector
10 Communication with diagnostic socket
11 Diagnostic switch signal
12 µP control unit
13 Communication with ABS / ASR
14 Communication with EDC
15 Signal on exhaust brake (EB)
16 Engine speed sender signal
17 Signal to transmission solenoid valves
18 Signal from transmission acknowledgment switches
19 Signal from PTO shaft speed sender
20 Communication with EDC engine control
21 signal from retarder
22 Retarder control unit
23 EDC control unit
24 ABS / ASR control unit
25 shift lever
26 drive program selector
27 Brake program switch
28 clutch pedal
29 Brake pedal
30 clutch pedal switch
31 accelerator pedal
32 dashboard
33 Dashboard information panel
34 diagnostic socket
35 diagnostic switch
36 Communication line
37 Servo device
40 internal combustion engine
41 clutch
42 step gear
43 powertrain
44 drive wheels
45 Exhaust brake switch (EB)
46 Speed sensor, output shaft
47 Speed sensor, engine
48 retarders
49 Retarder coolant temperature sensor
57 Non-volatile memory
58 exhaust brake (EB)
59 Signal from retarder coolant temperature sender
61 Retarder hand lever
62 Automatic retarder button
63 Speed control slide switch
80 question step
81 Question step
82 Question step
83 Question step
84 control step
85 control step

Claims (8)

1. A method for automatic, computer-assisted switching systems for mechanical step transmissions in motor vehicles powered by internal combustion engines, in which, in conjunction with the upshifting, an engine braking element acting on the gas exchange of the engine can be switched on to reinforce the engine braking effect in order to quickly obtain a speed that is synchronous for the next gear , characterized in that the engine brake member is selectively turned on when shifting up depending on whether a vehicle parameter is above a predetermined value. 2. The method according to claim 1, wherein an exhaust brake for quickly obtaining a for the next gear synchronous speed can be switched on, characterized net that the exhaust brake when shifting up depending on whether a Pa parameter is above a predetermined value, is switched on selectively. 3. The method according to claim 2, characterized in that the exhaust brake is selectively switched on as a function of it,

• - Whether an engine braking program has been switched on, which results in increased upshift points compared to normal predetermined upshift points;
• - Whether the retardation or the loss of speed of the vehicle during the switching process are above a predetermined threshold value depending on the operating case.

4. The method according to claim 2 or 3, characterized in that the exhaust brake is selectively switched on when shifting up depending on whether during the switching process the retardation or the loss of speed of the vehicle are above a predetermined threshold value depending on the operating situation and at the same time

• - the driver has depressed the accelerator pedal to the kick-down position, or
• - The control element has been activated to switch on a mountain travel program.

5. The method according to claim 2 or 3, characterized in that the exhaust brake is selectively switched on when shifting up depending on whether during the switching process the retardation of the vehicle is above a predetermined second threshold value and at the same time

• - The next selected gear is a smaller gear below the upper half of the total number of gears and preferably a current low range gear of the range group of the transmission.

6. The method according to claim 4, characterized in that the predetermined first Threshold represents a vehicle retardation of less than 0 m / s². 7. The method according to claim 5, characterized in that the predetermined second Threshold a vehicle retardation based on a loss of speed the propeller shaft speed Crpm, less than -5 CRPM / s. 8. Arrangement for controlling the execution of automatic upshifts in computer-aided switching systems for mechanical stepping gears in motor vehicles with shifting and engaging the gears by servo devices in the transmission and with simultaneous motor control (motor management) in accordance with programs stored in the control unit ( 12 ) of the switching system in dependence of vehicle parameters recognized by the control device and with at least one for detecting the speed of the vehicle ( 46 ) by means of a speed sensor ( 47 ) arranged therefor, wherein an exhaust brake ( 58 ) arranged in the exhaust system of the engine ( 40 ) is selectively selected by the control device ( 12 ) is switched on during the upshifting operation in order to reduce the engine speed to the synchronous speed for the next higher gear, characterized in that the control unit ( 12 ) comprises the following:

• - Means ( 12 , 81 , 82 , 83 ) for the detection of the operating case by setting the driving program selector ( 26 ) to an uphill program (Hill), actuating the accelerator pedal ( 31 ) to the kick-down position Specifies shifting up to a gear below the lower gears of the transmission or by means of an engine braking program activated with the brake program switch ( 27 ), which results in raised upshift points;
• - means ( 12 , 81 , 82 , 46 ) for detecting whether the speed of the vehicle is decreasing during the upshifting process;
• - Means ( 12 , 57 ) for storing predetermined thresholds for speed reductions;
• - means ( 12 , 81 , 82 ) for detecting whether the speed of the vehicle during the upshift has dropped below a predetermined threshold value;
• - Means ( 12 , 81 , 82 , 83 , 84 ) for switching on the exhaust brake ( 58 ) during the upshifting process in order to reduce the engine speed to the synchronous engine speed for the next higher gear if the speed of the vehicle has dropped below the threshold value if the drive program selector ( 26 ) has the position for a hill travel program (Hill) or the accelerator pedal ( 31 ) has the kick-down position or is to be shifted up to a gear below the lower gears of the transmission, or if the actuation of Brake program switch ( 27 ) has led to raised remaining upshift points.