JPH0220643Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an electronic odometer that measures and displays the distance traveled by automobiles, etc.

[Conventional technology]

As a conventional electronic odometer for a vehicle, there is one shown in FIG. 2, for example. 1 is a distance sensor, 2 is a microcomputer, 3 is a non-volatile memory for tripping, 4 is a non-volatile memory for adjusting, 5
9 is the in-vehicle battery, 9 is the ignition switch,
10 is a voltage regulator for system power supply;
12 is a display circuit, 13 is a reset switch 131
A reset pulse generation circuit 14 outputs a pulse to reset the trip data in the trip RAM (random access memory) 21 in the microcomputer 2 when the ignition switch 9 is turned on. This is a delay circuit that supplies power to the generator 10.

Therefore, under normal conditions when the ignition switch 9 is in the on state, the microcomputer 2 counts the distance pulses from the distance sensor 1 according to its distance calculation program and calculates the mileage data. By adding the mileage data to the previous cumulative distance data stored in the trip RAM 21 and the odometer RAM 22 in the microcomputer 2, new cumulative distance data is calculated, and the new cumulative distance data is calculated. RAM21 for tripping and for odometer
The data is sequentially updated and stored in the RAM 22. Further, the latest cumulative distance data is supplied to the display circuit 12 and displayed numerically.

On the other hand, when the ignition switch is turned off,
The microcomputer 2 receives the off signal of the ignition switch 9 as a memory request signal, and while the power of the system power supply voltage regulator 10 is maintained by the action of the delay circuit 14, the trip RAM 21 and the odometer RAM 22 are activated.
The cumulative distance data of each is stored in electrically erasable read-only memory EEPROM (Electrically
Erasable Programmable Read Only Memory)
or non-volatile random access memory
NVRAM (Non Volatile Random Access
The trip non-volatile memory 3 and the odd non-volatile memory 4, which are memories that do not require a power source to store data, such as memory, are saved.

The cumulative distance data stored in the trip nonvolatile memory 3 and the adjustment nonvolatile memory 4 are read out to the trip RAM 21 and adjustment RAM 22 in the microcomputer 2, respectively, when the ignition switch 9 is turned on again. It turns out.

[Problem that the invention attempts to solve]

However, in such conventional electronic odometers, the contents of the trip and odometer non-volatile memories 3 and 4 are stored in the ignition switch 9.
It is a method that rewrites each off-timing of
Moreover, non-volatile memory 3 for trip and adjustment,
Since the rewriting cycle life of the EEPROM used in 4 is approximately 5000 times, if the car is started 10 times a day, the non-volatile trip memories 3 and 4 can only be used for 500 days. That is, there was a problem in that the lifespan of the nonvolatile memories 3 and 4 for trips and odometers was shorter than the lifespan of the car.

This idea was developed by focusing on these conventional problems, and is designed to rewrite the non-volatile memory for trip and non-volatile memory only when the in-vehicle battery malfunctions, which occurs infrequently. The aim is to solve the above problems.

[Means for solving problems]

Therefore, the electronic odometer of this invention includes a distance sensor, a microcomputer, a nonvolatile memory, a capacitor that is constantly charged by receiving power directly from the on-board battery, a secondary battery, etc.
a secondary power source, a system power source that receives power from the on-board battery obtained via a power switch and supplies operating power to the microcomputer and non-volatile memory, and a system power source that receives power from the on-board battery and secondary power source. A backup power supply that constantly supplies operating power to the internal memory of the microcomputer, a battery failure detection circuit that detects failure of the vehicle battery and outputs a detection signal, and receives a detection signal from the battery failure detection circuit. and a changeover switch that is controlled to supply the charged charge of the secondary power source as power of the system power source, and the microcomputer counts distance pulses output from the distance sensor every time the vehicle travels a certain distance. a distance calculation program that calculates mileage data based on the mileage data and previous accumulated distance data stored in the nonvolatile memory, and calculates new cumulative distance data of the vehicle, and stores cumulative distance data calculated according to the program in the internal memory each time its contents are updated, and stores the cumulative distance data in the internal memory when receiving a detection signal from the battery failure detection circuit. The configuration is such that control is performed to transfer and store the accumulated distance data in the nonvolatile memory.

[Effect]

With this configuration, under normal conditions, the microcomputer counts the distance pulses output from the distance sensor every time the vehicle travels a certain distance according to its distance calculation program, calculates the distance traveled, and calculates the distance data. Calculate new cumulative distance data of the vehicle based on the mileage data and the previous cumulative distance data read from the non-volatile memory when the power is turned on and stored in the internal memory of the microcomputer, and calculate the distance. The latest cumulative distance data calculated according to the program is stored in the internal memory each time its contents are updated, and the latest cumulative distance data is displayed, for example. Upon receiving a detection signal from the failure detection circuit, the accumulated distance data stored in the internal memory is transferred to the nonvolatile memory and stored therein, and the accumulated distance data is temporarily saved.

〔Example〕

This invention will be explained below based on the drawings. FIG. 1 is a diagram showing an embodiment of this invention. First, to explain the configuration, this embodiment removes the delay circuit 14 from the conventional example shown in FIG. Holding type relay circuit 8, trip RAM 21 and odometer RAM
22 backup power supply voltage regulators 11 and backflow prevention diodes D ₁ and D ₂ are connected as shown in the figure. Components in FIG. 1 that are the same as those in FIG. 2 are designated by the same reference numerals and their explanations will be omitted.

In the electronic odometer configured as described above, if the on-board battery 5 fails for some reason and the predetermined voltage is not output or the battery is removed, the voltage of the large capacitor 6 slowly drops. . When the voltage drops to, for example, 80% of the original voltage, the voltage drop detection circuit 7 generates a pulse, operates the transistor 81 of the self-holding relay circuit 8, and excites the relay coil 82. 82 is closed to self-hold the relay coil 82, and the relay contact 84 is also closed to supply the charge in the large capacity capacitor 6 to the system power supply voltage regulator 10 to power the microcomputer 2. Then, the trip non-volatile memory 3 and the odometer non-volatile memory 4 are maintained in an operating state for a predetermined short time. In the meantime, the microcomputer 2 receives the pulse from the voltage drop detection circuit 7 as a memory request signal, and the trip RAM 21
The trip data and the ode data in the odometer RAM 22 are stored separately in the trip nonvolatile memory 3 and the odometer nonvolatile memory 4, so that the data can be held without a power source.

In the above embodiment, the voltage drop detection circuit 7 that detects the change in the terminal voltage of the capacitor 6 to determine the failure of the on-vehicle battery 5 was used as the battery failure detection circuit of the present invention. May consist of a connected relay coil,
In that case, the changeover switch of the present invention may be a normally open type relay contact controlled by the relay coil. In addition, in the above embodiment, a self-holding type relay circuit 8 was used as the changeover switch of the present invention, but if the output signal of the voltage drop detection circuit 7 is a level signal instead of a pulse signal, it is necessary to use a self-holding type. Instead, a normal relay circuit will suffice.

[Effect of idea]

As explained above, according to this idea,
The effect is that the number of times the nonvolatile memory is rewritten can be significantly reduced, and the reliability of the nonvolatile memory can be significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of an electronic odometer according to this invention, and FIG. 2 is a circuit diagram showing a conventional electronic odometer. 1...Distance sensor, 2...Microcomputer, 3...Non-volatile memory for trip, 4...Non-volatile memory for driver, 5...In-vehicle battery, 6...
...Capacitor, 7...Voltage drop detection circuit, 8...
Self-holding relay circuit, 9... Ignition switch, 10... Voltage regulator for system power supply, 11... Voltage regulator for backup power supply, 21... RAM for trip, 2
2...RAM for oddballs.

Claims (1)

[Scope of utility model registration request] A distance sensor 1, a microcomputer 2,
A secondary power source 6 that is constantly charged by receiving power directly from the non-volatile memories 3 and 4 and the on-board battery 5
, a system power supply 10 that receives power from the on-board battery 5 obtained via a power switch 9 and supplies operating power to the microcomputer 2 and non-volatile memories 3 and 4; and the on-board battery 5 and a secondary power supply. a backup power supply 11 that receives power from the microcomputer 6 and constantly supplies operating power to the internal memories 21 and 22 of the microcomputer 2; and a battery failure detection circuit that detects that the vehicle battery 5 has failed and outputs a detection signal. 7, and a changeover switch 8 which is switched and controlled in response to a detection signal from the battery failure detection circuit 7 and supplies the charge charged in the secondary power source 6 as power to the system power source 10. Distance pulses output from the distance sensor 1 every time the vehicle travels a certain distance are counted to calculate travel distance data, and the travel distance data and the cumulative total stored in the non-volatile memories 3 and 4 are calculated. The internal memory 2 has a distance calculation program that calculates new cumulative distance data of the vehicle based on the distance data, and stores the cumulative distance data calculated according to the program in the internal memory 2 every time its contents are updated.
1 and 22, and upon receiving the detection signal from the battery failure detection circuit 7, transfers and stores the accumulated distance data stored in the internal memories 21 and 22 to the nonvolatile memories 3 and 4. An electronic odometer that is characterized by its ability to perform speed control.