GB2081909A - Digital tachograph - Google Patents

Abstract

A digital tachograph for motor vehicle instrumentation includes a microcomputer 19 which increments specific locations in a solid state store 23 for the purpose of ascertaining the vehicle operating characteristics, e.g. velocity, engine speed, fuel consumption, when interrupt signals produced by corresponding variable frequency pulse generators 1-3 are present. The microcomputer stores the course of the journey in the form of data blocks comprising (a) velocity value, (b) distance travelled and (c) operating state signals, e.g. brake, indicator use, only when one of the quantities (a) and (c), as ascertained in the case of the quantitative signals by interrogating and zeroing the counts at the storage locations at each successive clock pulse 24, has changed or when the distance (b) since the last storage step exceeds a threshold level. The course of the journey can be outputted by way of the tachograph indicators 34, 51, 52, 54. The microcomputer ascertains the duration of the signals corresponding to the operating states by incrementing associated storage locations. The microcomputer stores other manually entered data only in the case of change together with the time and the daily reading. When the vehicle is stationary, plug 38 enables the contents of store 23 to be fed to a data collection device. <IMAGE>

Description

SPECIFICATION Digital tachograph The invention relates to a digital tachograph for motor vehicles, particularly commercial vehicles, for detecting and indicating vehicle operating characteristics and for detecting and storing vehicle operating characteristics, operating states and data which can be fed in manually by way of control elements.

Tachographs are generally known which record the detected data on tachograph charts and display it by pointers and roller-type counters. Tachographs of this kind include a large number of mechanical or electrical-mechanical components and subassemblies and can only be produced with a considerable expenditure of working time. Owing to the large number of mechanical components, the reliability and durability are less than those of electronic devices. Furthermore, it is disadvantageous that expensive reading devices having opto-electronic scanning heads are required for evaluating the data recorded on the tachograph charts. Damaged or scratched tachograph charts cannot be evaluated by automatic reading devices of this kind.

Arrangements for recording vehicle parameters are known (Offenlegungsschrift 26 11 471 ) which record operating parameters detected by measured value pick-ups and also data which is fed in manually, and write it into shift registers, that is to say, into electronic buffer memories. When the driver actuates a data input button, the contents of the buffer memories are fed into a storage device, such as a magnetic tape cassette or solid-state memory, which can be removed from the entire arrangement in order to be able to read the data and to feed it into a computer for further processing. A disadvantage of these arrangements is that the data can only be stored upon actuating a data input button. The data are stored without compression and without preprocessing, so that memories having a large capacity are required. The operating parameters detected are not indicated.

Furthermore, circuit arrangements realised by highly integrated switching circuits (Offenlegungsschrift 26 17401) are known which measure, indicate and store signals produced by measured value pick-ups mounted on the vehicle. A disadvantage of these circuit arrangements is that data fed in manually can not be processed and that special integrated switching circuits which can only be used forthis case of application are required.

Devices for recording operating data of a vehicle (Auslegeschrift 23 22 299) are known in which the last portion of the journey is stored in each case. The buffer memory is a shift register into which the signals detected by the measured value pick-ups are continuously fed. In the event of impact of the vehicle, the content of the shift register is transferred to a memory by an impact detector. The technical shortcoming of this device resides in the fact that the last portion of the journey is only stored in the event of accidents associated with impingement of the vehicle.

Electronic devices for storing and reading states and/or values (Offenlegungsschrift 26 32 438) are known which store the velocity value and the period of time which has elapsed since the proceeding storing operating in dependence upon the distance travelled, for example every 10 meters, and which include an indicator by which the stored course of the journey can be indicated backwardly in a stepwise manner. These devices have the disadvantage that the data is not compressed and therefore memories of large capacity are required.

Vehicle data recorders having data compression data known (Offenlegungsschrift 2434 135) which record the velocity, the journey and special events.

Data compression leading to a reduction in the memory spatial requirements is achieved by recording only when the velocity changes, an event occurs, or a predetermined maximum distance has been covered since the last storage operation. The velocity is measured, and it is ascertained whether a change in velocity has occurred, after a predetermined distance covered by the vehicle. The data are recorded on magnetic tape. A disadvantage of these vehicle data recorders is that a large number of electronic sub-assemblies and components are required to realise devices of this kind. Furthermore, it is disadvantages that the velocity is measured in each case after a predetermined distance travelled, since it is less expensive to perform the measurements at predetermined intervals of time.It is also very disadvantageous that a magnetic tape is used as a storage medium and has to be driven by mechanical means which are thus susceptible to trouble.

A digital tachograph is known (Offenlegungsschrift 2715527) in which the operating characteristics of the vehicle measured by vehicle sensor devices are recorded in solid-state memories, and a microprocessor system is used for processing the operating characteristics of the vehicle and for feeding them to the solid-state memory and to the digital display devices. The use of a microprocessor system, that is to say, a freely programmable microcomputer, renders it possible to realise a tachograph having only a few highly integrated switching circuits. However, a disadvantage of this digital tachograph is that the driver cannot input data manually. A further disadvantage is that the data stored in the solid-state memory cannot be made visible on the display devices of the digital tachograph.

An object of the invention is to provide a digital tachograph which avoids the above-mentioned disadvantages and which reduces the manufacturing costs both with respect to components and with respect to labour costs, and which reduces the spatial requirements.

In accordance with the invention, the measured value pick-ups are pulse generators whose frequency is proportional to the magnitude of the operating characteristics, the signal generators and the control elements produce, for example, two binary signals for the manual input of data, the output of each measured value pick-up is connected to an interrupt input of a microcomputer, the microcomputer increments a storage location in the solid-state memory, serving as a pulse counter for measured value pick-up pulses, each time a pulse is received at one of the interrupt inputs, an output of an electronic digital clock, producing timing pulses, is connected to a further interrupt input of the microcomputer, and the microcomputer stores the contents of each pulse counter at a respective operating characteristic storage location in the solid-state memory after each timing pulse at the interrupt input, and sets the pulse counters to zero.

A respective data block, comprising the operating characteristic vehicle velocity, the distance covered since the instant of the proceeding storage of a data block, and operating state signals for brakes and direction indictors produced by signal generators and picked up by the microcomputer by way of input gates, is written into a reserved region of the solid state memory at successive storage locations by the microcomputer after each timing pulse when the velocity value has changed by at least a predetermined amount relative to the velocity value at the instant of the preceding storage of a data block, or when the distance covered since the instant of the preceding storage of a data block has reached or exceeded a predetermined value, or when the operating stage signals for brakes and direction indicators have changed since the instant of the preceding storage of a data block.

In order to output the stored last portion of the distance travelled, the microcomputer interrogates the operating state of a switch, disposed on the digital tachograph, when the vehicle is stationary, interrogates the operating state of a button, disposed on the digital tachograph, when the switch is closed, reads the last stored data block from the reserved region of the solid state memory when the button is actuated, indicates the velocity value of the data block on the velocity indicator of the digital tachograph, indicates the distance travelled on the low value places of the kilometre indicator and the operating stage signals for brake and direction indicator on the high value places of the kilometre indicator. Upon renewed actuation of the button, the microcomputer reads the next data block from the solid state memory and displays it in the manner previously described.

The microcomputer interrogates a predetermined pole of a multi-pole plug connector, disposed on the tachograph, when the vehicle is stationary and, when a signal is applied which is produced by a data collection device and which is transmitted by way of a cable, transfers the contents of the solid state memory into the data collection device by way of a multipole plug connector and the cable.

The microcomputer interrogates the signal generators at predetermined intervals of time and, when logic 1 signals are present at the outputs of the signal generators, increments specific storage locations in the solid state memory which are associated with the signal generators and thus with the operating states. Furthermore, the microcomputer interrogates the data, input manually by the control elements, by way of input gates and, together with the time present at an output of a digital clock in the form of electrical, binary signals, and the distance covered at this instant, stores it as a data block in a reserved region of the solid state memory when the microcomputer, during interrogation of the data input manually, detects a change in this data compared with the data which existed at the instant of the preceding interrogation.

In a practical, particular embodiment of the invention, the measured value pick-ups are optoelectronic pulse generators. The operating characteristics are vehicle velocity, engine speed and fuel consumption. In a special embodiment of the invention, the operation states which are detected by the signal generators are the state of actuation of direction indicators, brakes, brake pressure switch and horn, and the operating state of the engine, the operating state of additional units mounted on the vehicle, and trailer operation of the vehicle.

An advantageous effect of the invention resides in increasing the serviceability and at the same time reducing the costs of material and labour. Furthermore, the present invention increases the reliability and durability of the tachograph, thus reducing repair costs and repair times which have to be met by the user of the tachograph.

The present invention reduces the technical expense and the time involved for preparing the tachograph data in a form readable by electronic data processing, and increases the reliability of data transmission. The tachograph in accordance with the invention picks up and stores additional data which are required for vehicle pool organisation but which the known tachographs do not record.

The invention will be further described hereinafter, by way of example only, with reference to the accompanying drawing which is a block circuit diagram of a digital tachograph in accordance with the invention.

Afreely programmable microcomputer 19, preferably a single chip computer, serves to control the tachograph. The operations performed by the microcomputer 19 are determined by the commands stored in the form of binary electrical signals in the program memory 61 of the microcomputer 19. Thus, the mode of operation of the digital tachograph is determined by the total of the stored commands, that is to say, the operating program. During running of the operating program, the data present at the input gates 56,57,58 of the microcomputer 19 are read in, decoded, processed and compressed and are written into the output gates 55, 60 for the purpose of controlling the speedometer 34, the electronic indicators 51, 52 and the kilometre indicator 54. Furthermore, the data are written into the output gate 62 for the purpose of storing in the solid state memory 23, and into the output gate 59 for outputting the stored data by way of the multi-pole plug connector 37,38 and the cable 39. The solid state memory 23 is a fixed write-read memory or a buffered CMOS write-read memory.

The measured value pick-ups 1, 2,3 are optoelectrical pulse generators whose frequency is proportional to the value of the associated operating characteristic. The outputs 13, 14, 15 of the measured value pick-ups 1,2,3 are each connected to a respective interrupt input 16, 17, 18 of the microcom puter.

Signal generators 4,5, 6,7,8,9 and control elements 10, 11 for the manual inputting of data produce static, binary signals which are fed to the input gates 56, 57 of the microcomputer 19.

A digital clock 12 has an output 24 which produces the timing pulses and which is connected to a further interrupt input 25 of the microcomputer 19. The time is present at the output 50 of the digital clock 12 in the form of electrical, binary signals. The output 50 of the digital clock 12 is connected to the input gate 58 of the microcomputer 19. A switch 32 and a button 33, by way of which the stepwise output of the last portion of the distance travelled is demanded, are also connected to the input gate 58.

When a pulse is received at one of the interrupt inputs 16,17, 18, the microcomputer 19 increments a respective storage location 20,21,22, serving as a pulse counterforthe measured value pick-up pulses, in the solid state memory 23. When a timing pulse is received at the interrupt input 25, the microcomputer 19 writes the contents of each pulse counter to a respective operating characteristic storage location 26, 27, 28 and sets the pulse counters 20, 21,22 to zero.After these operations have been concluded, the microcomputer 19 performs several comparison operations which will be further described hereinafter, and, in the event of a positive result of the comparison operations, stores in successive storage locations in a reserved region 29 of the solid state memory 23 a data block comprising the operating characteristic vehicle velocity, the distance covered since the instant of the preceding storage of a data block and operating state signals for brakes and direction indicators produced by the signal generators 4,5 and picked up by way of the inputs 30,31 of the input gate 56 of the microcomputer 19. The distance covered is ascertained by virtue of the microcomputer 19 adding up the velocity values which it has written into the operating characteristics storage location 26 at each timing pulse at the interrupt input 25.The microcomputer 19 only stores a data block when the velocity value has changed by at least predetermined amount relative to the velocity value at the instant of the preceding storage of a data block, or when the distance covered since the instant of the preceding storage of a data block has reached or exceeded a predetermined value or when the operating state signals for brakes and direction indicators have changed since the instant of the preceding storage of a data block. The data blocks are stored in the reserved region 29 of the solid state memory 23 by virtue of the fact that the current data block to be stored overwrites the earliest data block in each case. Thus, the last portion of the distance travelled is recorded.In order to output the last portion of the distance travelled in the event of accidents or traffic controls, the microcomputer 19 interrogates the state of actuation of the switch 32 after each timing pulse at the interrups input 25 and after performing the above-described operations, interrogates the state of actuation of the button 33 when the switch is closed, reads the last stored data block out of the reserved region 29 of the solid state memory 23 when the button is actuated, and indicates the velocity value on the speedometer 34, the distance travelled on the low value places 35 of the kilometre indicator 54, and the operating state signals for brake and direction indicators on the high-value places 36 of the kilometre indicator 54.

Upon renewed actuation of the button 33, the microcomputer 19 reads the next data block out of the solid state memory 23 and indicates it in the manner described above. It is only possible to output the last portion of the distance travelled when the vehicle velocity is zero. This is achieved in that the pulse counter 20, in which the pulses of the measured value pick-up 1 for the velocity are counter, is interrogated by the microcomputer 19 between the individual operations which are performed one after the other during the output. If the counter reading is greater than zero, the output of the last portion of the distance travelled is not commenced or is interrupted, and the microcomputer 19 performs the next operations.

It is likewise only possible to output the data stored in the solid state memory 23 by way of the output gate 29, the multi-pole plug connector 37,38 and the cable 39 when the vehicle is stationary. The microcomputer 19 interrogates a specific pole of the multi-pole connector 37, 38 and transfers the contents of the solid state memory 23 by way of the cable 39 into the data collection device connected to the cable when a specific signal supplied by the data collection device is applied to the interrogated pole of the plug connector 37,38. The data is transferred from the tachograph to the data collection device in acknowledgement operation, for which purpose the cable 39 has corresponding control leads.

The microcomputer 19 interrogates the signal generators 6,7,8,9 by way of the input gate 56 and, when logic 1 signals are present at the outputs 40, 41,42, 43, increments specific storage locations 44, 45,46,47 in the solid state memory 23 which are associated with the individual signal generators 6,7, 8, 9 and thus with the operating states. In the present embodiment, the operating states detected by the signal generators 6,7,8, 9 are the operating state of the engine, the operating state of additional units mounted on the vehicle, and the trailer operation of the vehicle.The running time of the engine, the operating period of the additional units and the duration of trailer operation are ascertained by incrementing the storage locations 44, 45, 46, 47 at predetermined intervals of time when a logic 1 signal is present at the corresponding pulse generator. After interrogating the signal generators 6,7, 8, 9 and performing the above-described operations, the microcomputer 19 interrogates the data, entered manually by the controlled elements 10, 11, by way of the inputs 48,49 of the input gate 57 and stores them in a reserved region 53 of the solid state memory 23 as a data block together with the time present in the form of electrical binary signals at the output 50 of the digital clock 12, and the distance covered up to this instant, when, during interrogation of the data entered manually, the microcomputer 19 ascertains a change relative to the data which existed at the instant of the preceding interrogation.

After running the above-described operations per formed as a result of the interrupt signals as the inputs 16,17,18,25, the microcomputer 19 indicates the operating characteristics until it again receives an interrupt signal. In orderto realisethe indication, the microcomputer 19 reads the current operating characteristics from the storage locations 26,27, 28 and the kilometre reading contained in the memory region 63 and decodes these data and writes them into the output gates 55, 60. In the present embodiment, the operating characteristics are the vehicle velocity, the engine speed and the fuel consumption.

Claims (5)

1. A digital tachograph for motor vehicles, having measured value pick-ups arranged on the vehicle for the purpose of detecting operating characteristics, having signal generatorsfordetecting operating states, control elements for manually inputting data, a solid state memory, electronic indicators for indicating the operating characteristics, a digital clock, and a microcomputer for preparing and decoding the operating characteristic signals and controlling the electronic displays, for processing and compressing the data which is fed in manually and which is detected by the measured value pick-ups and the signal generators, for transferring the detected, processed and compressed data into the solid state memory and for reading out the stored data into a data collection device by way of a cable and a multi-pole plug connector for the purpose of transferring it to a central computer, wherein the microcomputer increments specific storage locations for the purpose of ascertaining vehicle operating characteristics when interrupt signals produced by pulse generators are present, and wherein the microcomputer stores the course of the journey in the form of data blocks comprising a velocity value, distance travelled and operating store signals when one of the latter quantities has changed, the microcomputer being arranged to ascertain the duration of the signals corresponding to the operating stator by incrementing associated storage locations, manually entered data being stored only in the event of a said charge having occurred.

2. A digital tachograph for motor vehicles, having measured value pick-ups arranged on the vehicle for the purpose of detecting operating characteristics, having signal generators for detecting operating states, control elements for manually inputting data a solid state memory, electronic indicators for indicating the operating characteristics, a digital clock, and a microcomputer for preparing and decoding the operating characteristic signals and controlling the electronic displays, for processing and compressing the data which is fed in manually and which is detected by the measured value pick-ups and the signal generators, for transferring the detected, processed and compressed data into the solid state memory and for reading out the stored data into a data collection device by way of a cable and a multi-pole plug connector for the purpose of transferring it to a central computer, wherein (a) the measured value pick-ups are in the form of pulse generators whose frequency is proportional to the magnitude of the operating characteristics; (b) the signal generators and the control elements produce static binary signals for the manual input of data; (c) the output of each measured value pick-up is connected to an interrupt input of the microcomputer; (d) a storage location in the solid state memory, serving as a pulse counter for measured value pick-up pulses, is incremented by the microcomputer whenever a pulse is received at one of the interrupt inputs; (e) an output of the electronic digital clock producing timing pulses is connected to a further interrupt input of the microcomputer;; (f) after each timing pulse at the interrupt input, the microcomputer stores the contents of each pulse counter in a respective operating characteristic memory location in the solid state memory and sets the pulse counters to zero; (g) a respective data block, comprising the operating characteristic vehicle velocity, the distance covered since the instant of the preceding storage of a data block, operating state signals for brakes and direction indicators produced by the signal generators and picked up by inputs of the input gate of the microcomputer, is written into a reserved region of the solid state memory at successive storage locations by the microcomputer after each timing pulse when the velocity value has changed by at least a predetermined amount relative to the velocity value at the instant of the preceding storage of a data block, or when the distance covered since the instant of the preceding storage of a data block has reached or exceeded a predetermined value, or when the operating state signals for brakes and direction indicators have changed since the instance of the preceding storage of a data block; (h) the microcomputer interrogates the state of actuation of a switch when the vehicle is stationary forthe purpose of outputting the last portion of the distance travelled, interrogates the state of actuation of a button, when the switch is closed, reads out the last stored data block from the reserved region of the solid state memory when the button is actuated, indicates the velocity value of the data block on the speed indicator of the digital tachograph, indicates the distance travelled on the low value places of the kilometre indicator and indicates the operating state signals for brake and direction indicators on the high value places of the kilometre indicator and, upon renewed actuation of the button, reads out the next data block from the solid state memory and indicates it in the aforesaid manner; (i) the microcomputer interrogates a specific pole of the multi-pole plug connector when the vehicle is stationary and, when a signal produced by the data collection device and transmitted by way of the cable is applied, outputs the contents of the solid state memory by way of the cable and the multi-pole plug connector into the data collection device connected to the cable; (j) the microcomputer interrogates the signal;; generators at predetermined intervals of time and, when logic 1 signals are present at the outputs of the signal generators, increments the storage locations, associated with the individual signal generators and operating states, in the solid state memory; and (k) the microcomputer interrogates the data manually entered by means of the control elements and stores them as a data block in a reserved region of the solid state memory together with the time present in the form of electrical binary signals at the output of the digital clock and the distance covered up to this instant, when, during interrogation of the data entered manually, the microcomputer establishes a change in this data compared with the data which existed at the instant of the preceding interrogation.

3. A digital tachograph as claimed in claim 2, wherein the measured value pick-ups are optoelectronic pulse generators.

4. A digital tachograph as claimed in claim 1,2 or 3, wherein the operating characteristics are the vehicle velocity, the engine speed and the fuel consumption.

5. A digital tachograph as claimed in claim 2, wherein the operating states are the state of actuation of direction indicators, brakes, brake pressure switch and horn, and the operating state of the engine, the operating state of additional units mounted on the vehicle, and the trailer operation of the vehicle.