GB2055469A

GB2055469A - Improvements in or relating to trip recorders for vehicles

Info

Publication number: GB2055469A
Application number: GB8023025A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-07-20
Filing date: 1980-07-15
Publication date: 1981-03-04
Also published as: FR2461986A1; IT8023237A0; IT1131673B; DE2929396A1

Abstract

A trip recorder is provided for recording quantities such as speed and distance travelled of a vehicle and actions of a driver. The recorder includes a record carrier 7 accurately driven in time and a writing device 23 for recording the measured quantities on the record carrier. In order to provide more detailed recorded information in the event of an accident an electrical device 30 is included in casing 1. Device 30 comprises an analogue-digital converter which supplies digitised speed or acceleration values to a shift register having a capacity sufficient to store values occurring during an accident. A blocking device prevents further blocking of the shift register when the vehicle speed falls to zero so that the shift register retains the desired information. <IMAGE>

Description

SPECIFICATION Improvements in or relating to trip recorders for vehicles The invention relates to a trip recorder or "tachograph" for a vehicle, in particular a motor vehicle, for recording measured quantities, such as speed, distance, engine speed, actions of a driver and co-driver, and the like, with a record carrier which is driven accurately in time, and a writing device for recording the measuring quantities on the record carrier.

In known trip recorders of this type, a record carrier is usually constructed in the form of a circular recording disc which revolves slowly in such a manner that recording processes which take place within the interval of a few seconds cannot be resolved. For this reason, the events of an accident occurring within a short period of time cannot be reconstructed accurately from the recordings on such record discs.

According to the invention, there is provided a trip recorder for a vehicle for recording measured quantities, comprising a record carrier arranged to be driven accurately in time, and a writing device for recording the measuring quantities on the record carrier, there being further provided, for the purpose of accurate accident registration, an analogue-digital converter arranged to receive analogue measured speed or acceleration values, a clock pulse generator for supplying the measured values to the analogue-digital converter at a predetermined clock frequency, a shift register comprising a plurality of storage places sufficient for representing with respect to time a path length relevant during an accident, the shift register being arranged to be supplied continuously with the digital values from the analogue-digital converter at the clock frequency of the clock pulse generator, and a blocking device arranged to prevent further supply to the shift register of further digital values when the speed of the vehicle falls to zero.

It is thus possible to provide a trip recorder from which an accurate accident record can be obtained.

The invention will be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a plan view of a trip recorder for a motor vehicle; Figure 2 is a sectional view of the trip recorder on the line 2-2 of Figure 1; and Figure 3 is a block diagram of an arrangement for recording and evaluating travel accidents of motor vehicles.

Figures 1 and 2 illustrate a trip recorder or "tachograph" having a circular-cylindrical casing 1 which is closed at its front face by means of a cover 3 which is arranged in a pivotal manner by means of a hinge member 2. The cover 3 is provided with a lock 4 which permits the casing and the cover to be locked together. On the inside thereof the cover 3 is rigidly connected to a measuring device casing 5 which contains inter alia a time drive in a manner which is known and therefore not particularly illustrated, the time drive being for example in the form of a crystal controlled clock, for a circular disc-shaped record carrier 7 (recording disc) which is arranged on a circular disc-shaped rigid carrier 6 revolving accurately in time on the inside or underside of the measuring device casing 5.The record carrier 7 is retained on the carrier 6 by means of a clamping device 8 in a manner known per se. On the side located opposite the record carrier 7, the measuring device casing 5 is covered by a scale sheet 9 which, as shown in Figure 1, carries for example a speed scale 10 and a time scale 11.

Pointers 1 2 and 1 3, 14, respectively, move over the scales 10 and 11. Furthermore, the scale sheet 9 comprises a window 1 5 for a distance travelled meter 1 6 (kilometer counter). Above the scale sheet 9, the cover 3 has attached thereto a transparent cover disc 1 7, the field of view of which is limited by a front frame 18 of the cover 3.

A writing device 23 is arranged on a support 22 disposed on the bottom 21 of the trip recorder casing 1 and, in the constructional form shown, comprises three writing pens 27 known per se.

These writing pens engage the underside of the record carrier 7 and serve in a known manner for recording measuring value-dependent writing tracks on the revolving record carrier 7. These writing tracks may be associated for example with the speed of the vehicle and the actions of a driver and co-driver. The bottom 21 of the casing 1 is provided with a connection tube 24, e.g. for the introduction of a tachometer or speedometer shaft 25. Between the support 22 and the measuring device casing 5, which may be swung away together with the cover 3, a coupling 26 is provided for the drive of the tachometer or speedometer pointer 1 2 and the kilometer counter 16.

For the purpose of recording travel accidents, a special electrical device 30 is built into the casing 1 of the trip recorder. The device 30 is connected to the tachometer mechanism surrounded by the support 22, that is to say the speed measuring value transmitter, by means of a connection 28 symbolically indicated in Figure 2. The construction of the device 30 is illustrated in the block circuit diagram of Figure 3. The mentioned speed measuring value transmitter 31 operating in an analogue manner is connected to a following analogue-digital converter 32 known per se in which the analogue speed measuring values are converted to digital speed measuring values. A clock pulse generator 33 likewise known per se ensures that the analogue measuring values of the transmitter 31 are fed to the converter 32 at the predetermined clock frequency.

The digital measuring values from the converter 32 travel continuously at the clock frequency of the clock pulse generator 33 to an electronic shift register 34 known per se which comprises as many storage places as are normally required for representing, dependent upon time, a distance or path length which is relevant for travel accident. If the relevant path length is assumed to be for example 400 m, the number of storage places lies preferably between approximately 500 and 1000.

A correspondingly larger number of storage places must be provided when more than 400 m are to be taken into account as the relevant path length.

The measuring values stored for the relevant path length respectively travelled last permits the accident events to be reconstructed in a fairly accurate manner, for example by means of an external microprocessor 35 known per se. For this purpose, at least the actual shift register 34 is constructed in the form of a removable unit, so that the values stored therein may be evaluated by the micro-processor 35 outside the trip recorder casing.

In order to prevent the shift register 34 from continuing to operate after an accident has occurred so as to prevent the measuring values which are essential for the accident events from being clocked out of it and being lost thereby, an electrical constructional element 36 is provided, for example in the form of a micro-processor 36 similar to the device 35, which when the measured speed has dropped to zero delivers a signal which then in turn, under certain circumstances after an appropriate time delay in a time deiay member 37, blocks the input of the shift register 34 by a switch 38 symbolically indicated in Figure 3 and renders it inoperative.

Thereby the measuring values stored last in a time dependent manner for a certain period of time and for the relevant path length of the shift register 34 are available for the evaluation of the accident.

In a motor vehicle accident, it may happen that the wheels of the vehicle are locked at least during the last moments of the accident events. Since the measuring values for the path length and the speed are normally derived from the rotating wheels, the path length travelled through and the travelling speed are recorded as zero when the wheels are locked, although the vehicle may still continue to move (slidingly) for a certain distance at a certain speed in spite of the locked wheels.In order to obtain measuring data also in this case, it is proposed in another preferred constructional form of the invention to provide a special acceleration meter 39 which operates in an analogue manner and responds in the travelling direction, additionally to the speed measuring value transmitter 31 or in place of the same, and to have this meter 39 also controlled by the clock pulse generator 33 (see Figure 3). Otherwise this acceleration meter operates in exactly the same manner as the speed measuring value transmitter 31. In this case, however, the associated values for speed and path length may be calculated in a time dependent manner from the acceleration values stored in the shift register 34, for example by means of the micro-processor 5.This accident reconstruction is then based solely on measured acceleration values and is thus independent of locking of the wheels of the motor vehicle.

The writing device 23 illustrated in Figure 2 is a convential device operating with mechanically controlled writing pens 27. In another embodiment of the invention, this mechanical device may be substituted by an electronic writing device, for example by a comb electrode known per se, or the like.

It is thus possible to provide a trip recorder which has a record carrier the resolving power of which is insufficient for reconstructing an accident event, but which has built into it additionally an electrical device which responds for example to speed values and/or acceleration values and which permits a finer chronological resolution of the respective measuring data. In the constructional form illustrated, this electrical device is constructed in the form of a shift register 34.

However, in place of a shift register, alternatively other storing electronic constructional components may be used for the same purpose.

Claims

1. A trip recorder for a vehicle for recording measured quantities, comprising a record carrier arranged to be driven accurately in time, and a writing device for recording the measuring quantities on the record carrier, there being further provided, for the purpose of accurate accident registration, an analogue-digital converter arranged to receive analogue measured speed or acceleration values, a clock pulse generator for supplying the measured values to the analoguedigital converter at a predetermined clock frequency, a shift register comprising a plurality of storage places sufficient for representing with respect to time a path length relevant during an accident, the shift register being arranged to be supplied continuously with the digital values from the analogue-digital converter at the clock frequency of the clock pulse generator, and a blocking device arranged to prevent further supply to the shift register of further digital values when the speed of the vehicle falls to zero.

2. A trip recorder as claimed in claim 1, in which an acceleration meter is provided for supplying analogue values to the analogue-digital converter at the predetermined clock frequency.

3. A trip recorder as claimed in claim 1 or 2, in which at least the shift register is constructed in the form of a unit which is removable from the trip recorder to allow the measured values stored therein to be evaluated by a micro-processor.

4. A trip recorder substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.