GB2153091A

GB2153091A - Method of carrying out fault detection in a computer- controlled gear changing system for a vehicle

Info

Publication number: GB2153091A
Application number: GB08432259A
Authority: GB
Inventors: Hans Valter Stahl
Original assignee: Saab Scania AB
Current assignee: Saab AB
Priority date: 1983-12-29
Filing date: 1984-12-20
Publication date: 1985-08-14
Also published as: SE8307212D0; SE437957B; DE3446577C2; NL8403944A; DE3446577A1; GB2153091B; BR8406774A; GB8432259D0

Abstract

A method of carrying out fault detection in a vehicle transmission (2,4) provided with a computer- controlled gear changing system in which there is a display unit (48) and a plurality of switches (23-29,36,38,40,42) and solenoid valves (15-21) for performing gear changing. The first operation step is started by manual actuation of a test program switch (14) in the vehicle which triggers a program stored in the control unit (7) for automatic functional testing of the display unit (48). and that one or more further operation steps are triggered by the switch (14) being subjected to further manual actuation, under each of said further operation steps the test program determines how functional testing of the switches (23-29,36,38,40,42) and/or solenoid valves (15-21) shall be performed so that for a given fault, predetermined information in the test program is displayed by the display unit (48). <IMAGE>

Description

SPECIFICATION Method of carrying out fault detection in a computer-controlled gear changing system for a vehicle The present invention relates to a method of carrying out fault detection in a computercontrolled gear changing system for a vehicle, a display unit and a plurality of switches and solenoid valves for regulating the gear changing system during operation of the vehicle being connected to an electronic control unit, said units, switches and solenoids being permanently mounted in the vehicle.

Known systems for carrying out fault detection in electronic gear changing systems in vehicles are often based on the utilization of special equipment connected to a control system already existing in the vehicle. In practice, this means that the vehicle driver has extremely limited possibilities of localizing the fault should one occur in the control system. A fault which is a mere trifle can thus cause the vehicle to have unnecessary down-time while waiting for service personnel to be called for carrying out fault detection. With heavy vehicles in commercial traffic, the costs for down-time are considerable, and there is thus a strong desire in this connection to minimize such down-time.

Against this background the invention has the task of creating a fault detection method so that without special equipment, every vehicle driver can carry out fault detection covering the most usual causes of faults. To this end, the present invention is distinguished in that fault indication is carried out in steps, a first operation step being started by manual actuation of a test program switch permanently mounted in the vehicle, which triggers a program stored in the control unit for automatic function test of the display unit, and in that one or more further operation steps are triggered by the switch being subjected to further manual actuation, the test program determining during each of said further operation steps how the function test of switches and/or solenoid valves included in the system shall be carried out so that for a given fault, predetermined information in the test program is displayed by the display unit.

In accordance with the invention it is thus possible, solely with the availability of a simple fault detection instruction, to test the function of a plurality of switches and solenoid valves included in the system. A test program permanently stored in the computer is utilized for the fault detection, this program being subdivided into different steps which are taken in order in response to manual actuation of a special test program switch. The fault detection method thus includes specific operation of means permanently mounted in the vehicle for enabling testing specific units and functions in the system. Faults which occur are denoted by a code and/or in some cases by a display unit associated with the system and permanently mounted in the vehicle. The code information is explained in the instruction, whereby the kind of fault and its possible localization may be found.

An advantageous embodiment of the invention is utilized when the vehicle gearbox is equipped with a computer-controlled gear changing system. In this system there is included at least one manually actuable operating means for changing the input signals to a control unit included in the system. The invention is distinguished in this respect in that in a subsequent operation step, preferably the second operation step, the switches which are actuable by the operating means are tested for function, the program determining that for a given actuation of a given operating means, predetermined information is displayed by the display unit.

By carrying out the test program and the fault indication steps included therein, the driver can ascertain in a simple way that the tested switches have their correct function, which is essential for the continued implementation of the fault detection method.

Other distinguishing features of the invention are apparent from the appended claims and following description of an advantageous embodiment of the invention. The invention is carried out with reference to the accompanying figures, of which Figure 1 schematically illustrates a drive unit to which there is connected a computercontrolled regulating system, and Figure 2 is a flow diagram of an inventive fault detection method.

The drive unit illustrated in Fig. 1 includes a vehicle engine 1, to which there is connected a conventional synchronized, mechanical gearbox 2. The drive is transmitted from the engine 1 to the gearbox 2 via a manually operated friction clutch 3. An auxiliary gearbox 4 is in turn connected to the gearbox 2, the output shaft 5 of the auxiliary gearbox being drivingly connected via a cardan shaft 6 to the driving wheels (not shown) of the vehicle. Such a transmission is primarily intended for heavy vehicles. With the object of facilitating gear changing work for the driver and also to enable correct gear selection, the transmission is arranged to coact with a computer-controlled regulating system.

The selection of a suitable gear during operation of the vehicle is thus catered for conventionally by an electronic control unit 7, in all essentials a computer. A gear selected by the control unit 7 is engaged during a gear changing sequence by the clutch 3 between the engine 1 and the gearbox 2 being manually operated by the driver. The process means that a conventional mechanical transmission with a main clutch 3 between engine and gearbox can be retained unaltered, and that the comparatively high efficiency of the transmission may also be utilized.

Gear changing in the gearbox 2 is performed with the aid of two pneumatic cylinder units 10, 11 of which one is intended to execute transverse gear changing movements, while the other is intended to execute longitudinal gear changing movements. In the same way, gear changes in the auxiliary gearbox 4 are executed with the aid of a pneumatic cylinder unit 1 2. Compressed air from the vehicle pneumatic system 13 is supplied via a plurality of solenoid valves 15-21 to the cylinder units 10, 11, 12, hereinafter designated cylinders. Said valves are biased into an open or closed position by means of output signals from the control unit 7.The piston position in the cylinders 10-12 is indicated by means of micro-switches 23-29, the number of which corresponds to the number of solenoid valves. For the solenoid valves 15-21 and switches 23-29 illustrated in Fig. 1, the following relationships to the piston positions of the cylinders 10-12 apply.

Solenoid valve 15 Cylinder 10-Left Switch 23 II " 16 II Right " 24 " " 17 " Forward " 25 II " 18 " Neutral " 26 II " 19 " Reverse " 27 " " 20 I1 High " 28 " " 21 UI Low " 29 To facilitate understanding of the table above, the first relation is explained according to the following.

Current supply to the solenoid valve 1 5 results in that compressed air is fed to the cylinder 10, the piston of which is then put in a left position, as acknowledged by the switch 23.

A plurality of input signals are taken to the control unit 7. As an example, via a line bunch 31, the switches 23-29 send signals to the control unit 7, which indicates the engaged gear. A signai representing the speed of a vehicle wheel is fed to the control unit 7 via a line 32. This speed is sensed by a revolutionary rate sensor 30 at the output shaft 5. Signals are also fed to the control unit 7 via a line bunch 33 from a plurality of switches placed at the driver's station in the vehicle, these switches being schematically depicted in Fig. 1 by a block 34 denoted by dashed lines. The engine load is regulated conventionally by an accelerator pedal 35, the position of which is sensed by a switch 36. The position of a conventional clutch pedal 37 is sensed by a switch 38.A function selector 39 actuable by the driver can be set in different positions, which are sensed by a switch 40. A first position of the function selector 39 is designated MAN and is intended for driving with manual gear selection, a second position is denoted AUTO and is intended for driving with automatic gear selection, a third position is designated N and is intended for neutral, i.e. no gear engaged, and a fourth position is designated R and is intended for reverse gear. A gear change member in the form of a small lever 41 has a stable intermediate position and on either side thereof are arranged instable side position which are designated UP and DOWN, respectively. These positions are sensed by a switch 42. Flipping the lever 41 to the UP position signifies changing up one step, while flipping the lever 41 to the DOWN position signifies a corresponding change down.

In response to the mentioned input signals and a gear changing program stored in the computer, the control unit 7 sends output signals to the solenoid valves 15-21 via a line bunch 44. Output signals are also fed to a buzzer 46 via a line 45 for accoustic indication, and via a line bunch 47 to visual indication means on a display unit 48. The indication means on the display unit 48 are twelve light-emitting diodes which, on being energized, show in order the following signs: R, N, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

The main and normal task of the control unit 7 is to execute gear selection in response to input signals, and after manual triggering by the driver to cause gear changing means to engage the selected gear. There is further included in the gear changing program a continuous test function, which immediately interrupts the normal function in case of certain faults. The driver is notified of such a fault by the buzzer 46 beginning to sound.

A separate test program is also included in the control unit 7 and is started manually by operating a test program switch 1 4 arranged on the control unit 7.

Certain primary sources of fault are monitored by the continuous test function. When a fault occurs, an alarm is triggered in the buzzer 46 simultaneously as a fault code is stored in a fault memory in the control unit 7. The code is displayed on the display unit 46 in the separate test program described below. Amongst the faults which are monitored in this way are anomalies arising in a code plug 22 which is connected to an outlet on the control unit 7. The code plug 22 has a code representing a given combination of engine and gearbox and determines certain basic output data for the gear selection program of the control unit 7. Also monitored are shortcircuiting in the solenoid valves 15-21, faults in the control unit 7 including its memories, faults in speed registrations and incredible acknowledgements from the switches 23-29.

The separate test program which is stored in a PROM included in the control unit 7 is activated by manual actuation of the switch 14 on the control unit 7. The switch 14, denoted by TPSS 14 in Fig. 2, may be actuated by such as a screwdriver or the like. With guidance from a book of instructions, a person carrying out fault detections can obtain directions on how the switch 14 shall be operated in different steps. By a first depression of the test program switch 14, the test program first step is triggered, which is illustrated by an operation step 51 in the flow diagram according to Fig. 2. Consequent hereon is an operation step 52 in which all the indication means on the display unit 48 are illuminated to test their function. The buzzer function is also tested in this step 52, which may last about three seconds.The program then follows a flow line 53 to a further operation step 54 in which a possible code, stored in the fault memory of the control unit 7, is fed out to the display unit 48. As examples of faults occurring, which can correspond to a given fault code, the following are mentioned: Speed registration unserviceable = R Control unit temporarily unserviceable = N Anomalies in code plug = RN After the operation step 54, the flow line 53 leads to a so-called interrogation step 55 which is arranged to identify whether the switch 14 is depressed. As long as this is not the case, the signal is fed back again via a flow line 56 to the input for the step 55. For depression of the switch 14, the program continues to an operation step 57 in which two short sound pulses are sent from the buzzer 46.This is a sign that the second step of the test program has started, the program then continuing to an operation step 58. In this step there is supervision that indication means are illuminated to show correct function of the switchs 23-29 which are actuated directly by operating means 35, 37, 39, 41. In this case, this is done by manual operation in the operation step 58 of the operating means according to the list below, the indicating means which should be illuminated for correct function also being given.

Function selector 39 in R position R Function selector 39 in AUTO position N Function selector 39 in MAN position 1 -Lever 41 in DOWN position 2 lever 41 in UP position 3 clutch pedal 37 depressed 4 -Accelerator pedal 35 depressed for partial throttle 5 -Accelerator pedal 35 depressed for full throttle 6 If the engine 1 is running, then the indication means 7 is also illuminated.

The operation step 58 is followed by a second interrogation step 59 arranged to identify whether the switch 14 is actuated. As long as this is not the case, the program returns to the input of the operation step 58 via a flow line 61. The operation step 58 can thus be run through without stopping until the switch 14 is actuated. If it is actuated, the program then continues along the flow line 53 to a further interrogation step 62 in which the program conventionally asks whether the latest registered speed value is equal to zero, i.e. whether the vehicle is stationary for the moment. If this is not the case, the test program is interrupted and a return to the main program takes place along a flow line 63.On the other hand, if the vehicle is stationary, the program continues along the flow line 53 to an operation step 64, in which three short sound pulses are sent from the buzzer 46 as a sign that the third step in the test program has been started.

The third step is introduced by an interrogation step 65, in which the position of the clutch pedal 37 is checked. If the pedal 37 is not depressed, the program follows a flow line 66 to an interrogation step 67, for checking whether the test switch 14 is depressed. If, however, the question in the interrogation step 65 can be answered in the affirmative, an operation step 68 follows in which the gear changing movements in the main gearbox 2 are checked, and in which the associated solenoids 15-21 and switches 23-29 are checked for correct function. To advantage, this takes place by manual operation of the function selector 39 and the lever 41 according to the following schedule.

function selector in R position, solenoid valve 15, lateral stroke left, switch 23, indication R.

function selector in AUTO position, solenoid valve 18, neutral, switch 26, indication 4, 5.

function selector in MAN position, solenoid valve 16, lateral stroke right, switch 24, indication 10.

lever in UP position, solenoid valve 17, longitudinal stroke forward, switch 25, indication 7.

lever in DOWN position, solenoid valve 19, longitudinal stroke backward, switch 27, indication 2.

To facilitate understanding of the relationships set forth in the schedule, the following explanation is provided for the first relationship. With the function selector 39 in the R position, current is supplied to the solenoid valve 1 5 for controlling compressed air to the cylinder 10 for carrying out a lateral gear changing movement to the left, which is acknowledged by the switch 23, resulting in, for correct function, the indication R on the display unit 48.

The operation step 68 can be preceded or even replaced by an operation step, in an alternative embodiment of the invention, where the above-mentioned gear changing movements are tested automatically according to the following sequence: (1) Current is supplied to the solenoid valve 18 so that the cylinder 11 assumes neutral position, the switch 26 by itself acknowledging within a given time.

(2) Current is fed to the solenoid valve 1 5 so that the cylinder 10 carries out a left lateral stroke, the switch 23 by itself acknowledging within a given time.

(3) Current is fed to the solenoid valve 1 6 so that the cylinder 10 carries out a right lateral stroke, the switch 24 by itself acknowledging within a given time.

(4) Current is fed to the solenoid valve 1 7 so that the cylinder 11 carries out a longitudinal forward stroke, the switch 25 by itself acknowledging within a given time.

(5) Current is fed to the solenoid valve 1 9 so that the cylinder 11 carries out a longitudinal backward stroke, the switch 27 by itself acknowledging within a given time.

If any fault is discovered in any step, this is indicated by a fault code on the display unit 48.

After performing the operation step 68, the program continues along the flow line 53 to the interrogation step 67 in which it is once again checked whether the test switch 14 is depressed.

As long as this is not the case, the program returns along a flow line 69 to the input of the interrogation step 65 and the operation step 68. This sequence is kept up continuously until depression of the test switch 14 takes place. When this is done, the program continues along the flow line 53 to an operation step 71 in which four short sound pulses are sent from the buzzer 46 as a sign that the fourth step in the test program has been started.

As with the third step in the test program, the fourth step is introduced by an interrogation step 72, in which the position of the clutch pedal 37 is checked. If the pedal 37 is not depressed, the program follows a flow line 73 directly to an interrogation step 74 where it is once again checked whether the test switch 14 is depressed. If the pedal 37 is depressed, the program follows the flow line 53 from the interrogation step 72 to an operation step 75. Here it is checked whether the gear changing movements in the auxiliary gearbox 4 and associated solenoid valves 20, 21 with switches 28, 29 function correctly. For this purpose, the driver manually actuates the lever 41 to the UP position and DOWN position, respectively.In the UP position, current is fed to the solenoid valve 20 which regulates the cylinder 1 2 to a HIGH position, which is acknowledged by the switch 28. For correct function, the indication N is illuminated on the display unit 48. In the DOWN position, current is fed to the solenoid valve 21 which regulates the cylinder 12 to a LOW position, which is acknowledged by the switch 29. For correct function, the indication 9 is illuminated on the display unit 48 in this case.

After the operation step 75, the program follows the flow line 53 to the interrogation step 74 in which the position of the test switch 14 is once again checked. If the switch 1 4 is not depressed, the program returns along a flow line 76 to the input of the interrogation step 72, whereafter the above-mentioned part of the program is gone through once again. This sequence is repeated until the switch 14 is depressed. When this is done, the program follows the flow line 53 to an operation step 77 in which two longer sound pulses are given from the buzzer 46 as a sign that the test program is terminated.

The description above of an inventive application should not be considered to restrict the usability of the invention, which can be modified in a plurality of embodiments within the scope of the following claims.

Claims

1. A method of carrying out fault detection in a computer-controlled gear changing system for a vehicle, a display unit and a plurality of switches and solenoid valves for regulating the gear changing system during operation of the vehicle being connected to an electronic control unit, said units, switches and solenoids being permanently mounted in the vehicle, characterized in that fault indication is carried out in steps, a first operation step being started by manual actuation of a test program switch permanently mounted in the vehicle which triggers a program stored in the control unit for automatic function test of the display unit, and in that one or more further opsration steps are triggered by the switch being subjected to further manual actuation, the test program determining during each of said further operation steps how the function test of switches and/or solenoid valves included in the system shall be carried out so that for a given fault, predetermined information in the test program is displayed by the display unit.

2. A method as claimed in Claim 1, wherein the computer-controlled gear changing system includes manually actuable operating means for resetting the input signals to the control unit, characterized in that in a subsequent operation step, preferably the second operation step, the switches which are actuable by the operating means are tested for function, the program determining that for a given actuation of a given operating means, predetermined information will be displayed by the display unit.

3. A method as claimed in Claim 1, wherein the computer-controlled gear changing system includes manually actuable operating means for resetting the input signals to the control unit, characterized in that in at least one subsequent operation step the solenoid valves and the switches coacting in the gear changing movements of the system are tested for function, the test program determining that for a given actuation of a given operating means, predetermined information will be displayed on the display unit.

4. A method as claimed in Claim 2 or 3, characterized in that in at least one subsequent operation step, an automatic function test is performed on the solenoid valves and the switches coacting in the gear changing movements, predetermined information being displayed on the display unit for a discovered fault.

5. A method as claimed in Claim 1, 2 or 3, characterized in that during several operation steps, a single operating means is operated manually, which during a first further operation step signifies functional testing of switches and during a second further operation step signifies functional testing of solenoid valves.

6. A method as claimed in any one of the preceding claims, characterized in that during the operation step following the functional test of the display unit, there is automatically displayed on the display unit a fault code possibly previously stored in the computer.

7. A method substantially as hereinbefore described with reference to and as shown in the accompanying drawings.