JPH0220644Y2 - - 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 an automobile or the like.

(Prior Art) As a conventional electronic odometer of this type, there is one shown in FIG. 2, for example. In the figure, 1 is a distance sensor, 2 is a microcomputer (hereinafter referred to as a microcomputer), 3 is a nonvolatile memory for tripping, 4 is a nonvolatile memory for adjusting, and 5 is a tripping memory in the microcomputer 2 when the reset switch 6 is turned on. RAM (Random Access Memory)
21, a reset pulse generation circuit that outputs a pulse to reset the trip data; 7, a display circuit that displays the trip data and odd data output from the microcomputer 2; 8, an in-vehicle battery; 9, an ignition switch; and 10, for system power supply. A voltage regulator 11 is a delay circuit that supplies power to the system power supply voltage regulator 10 for a predetermined period of time even after the ignition switch 9 is turned off.

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 the distance calculation program to sequentially calculate the distance traveled, and also calculates the distance traveled. By adding the distance data to the previous cumulative distance data stored in the trip RAM 21 and odometer RAM 22 in the microcomputer 2, new cumulative distance data is calculated, and the new cumulative distance data is used for the trip. for
The data is sequentially updated and stored in the RAM 21 and the Odo RAM 22. Further, the latest accumulated distance data (trip data and odometer data) is supplied to the display circuit 7 and displayed numerically.

On the other hand, when the ignition switch 9 is off, the microcomputer 2 receives the off signal of the ignition switch 9 as a memory request signal,
While the power of the voltage regulator 10 for the system power supply is maintained by the action of the delay circuit 11, the trip RAM 21 and the odo RAM 22 are
The trip data and odometer data of
(Electrically Erasable Programmable Read
Electrically Erasable Read Only Memory) or NVRAM (Non Volatile Memory)
The data is saved in a non-volatile trip memory 3 and a non-volatile memory 4, respectively, which are memories that do not require a power source to store data, such as a random access memory (non-volatile random access memory).

The trip data and odometer data stored in the trip nonvolatile memory 3 and the odometer nonvolatile memory 4 are stored in the trip RAM in the microcomputer 2 when the ignition switch 9 is turned on again.
21 and odo RAM 22, respectively.

(Problem to be Solved by the Invention) However, in such a conventional electronic odometer, the contents of the trip and odometer non-volatile memories 3 and 4 can be transferred to the ignition switch 9.
It is a method that rewrites every off timing of
Moreover, non-volatile memory 3 for trip and adjustment,
Since the rewrite cycle life of the EEPROM used in 4 was approximately 5000 times, for example,
If you start and stop the engine 10 times,
There was a problem in that the nonvolatile memories 3 and 4 for trip and adjustment could only be used for 500 days, and the lifespan of the nonvolatile memories 3 and 4 for trip and adjustment was shorter than the life of the car.

This invention was made by focusing on these conventional problems, and aims to solve the above problems by creating a structure that can reduce the number of times the nonvolatile memory for trip or adjustment is rewritten. There is.

(Means for solving the problem) Therefore, the electronic odometer of this invention consists of a distance sensor, a microcomputer, a non-volatile memory, and receives power from the on-vehicle battery obtained through a power switch. A secondary power source consisting of a capacitor, a secondary battery, etc. that is charged when the power switch is turned on, and power from the vehicle battery obtained through the power switch are received to supply operating power to the microcomputer and nonvolatile memory. a system power supply for supplying operating power to the internal memory of the microcomputer; a voltage detection circuit that detects that the output voltage has decreased and outputs a detection signal; and a timer that is switched and controlled in response to the detection signal from the voltage detection circuit and directly supplies power from the on-vehicle battery to the system power supply for a predetermined period of time. and a switch, the microcomputer counts distance pulses output from the distance sensor every time the vehicle travels a certain distance to calculate travel distance data, and stores the travel distance data and the nonvolatile memory. It has a distance calculation program that calculates new cumulative distance data of the vehicle based on the previous cumulative distance data, and the cumulative distance data calculated according to the program is updated every time the content is updated. The integrated distance data stored in the internal memory is controlled to be stored in the internal memory, and the cumulative distance data stored in the internal memory is transferred and stored in the nonvolatile memory when a detection signal from the voltage detection circuit is received. It is something.

(Function) According to this configuration, when the power switch is turned on and the vehicle is running normally, the microcomputer receives the distance pulse output from the distance sensor every time the vehicle travels a certain distance according to its distance calculation program. In addition to calculating mileage data by counting, new cumulative distance data of the vehicle is calculated based on the mileage data and previous cumulative distance data stored in the internal memory of the microcomputer; The latest cumulative distance data calculated according to the calculation program is stored in the internal memory each time its contents are updated. Note that this latest distance data is output from the microcomputer and is displayed, for example, by a display circuit, or is used together with other data such as fuel data as basic data for determining vehicle information such as fuel consumption rate. .

Furthermore, in this invention, when the power switch is turned off, the internal memory of the microcontroller receives the charge from the secondary power source as operating power and is backed up for a predetermined period of time after the power switch is turned off. The latest accumulated distance data calculated according to the distance calculation program of the microcomputer in the ON state continues to be stored in the internal memory for a while even when the power switch is turned off. Then, when the output power of the secondary power supply becomes less than a predetermined value and a detection signal is output from the voltage detection circuit, the timer switch receives the detection signal and supplies operating power to the microcomputer for a predetermined period of time. The accumulated distance data stored in the memory is saved to a non-volatile memory, so that the latest accumulated distance data can be saved without a power source.

(Example) This invention will be explained below based on the drawings.

FIG. 1 is a diagram showing an embodiment of this invention. First, the configuration will be explained. The same parts between the structure of this embodiment and the structure shown in the conventional example (FIG. 2) are given the same reference numerals as in the conventional example, and detailed explanation thereof will be omitted.

In the figure, the large-capacity capacitor designated by numeral 12 constitutes the secondary power supply of this invention.
This large-capacity capacitor 12 is connected to the vehicle battery 8 via the ignition switch 9 and backflow prevention diode 13 that constitute the power switch of this invention. (when the device is in operation). Further, 14 is a voltage regulator for backup power supply, which is connected to the large capacity capacitor 12, and when the ignition switch 9 is turned off, A trip circuit that receives the charge from the large-capacity capacitor 12 and configures the internal memory of the microcomputer 2 of this invention.
It supplies operating power to the RAM 21 and the odo RAM 22 for a while. Note that the backup of the trip and odd RAMs 21 and 22 based on the output voltage of the large capacity capacitor 12 is as follows.
By performing this for as long as possible, the effect of this invention, which is the reduction in the number of times the nonvolatile memory is rewritten, will be more effectively achieved.

On the other hand, 15 is a voltage detection circuit which detects the output voltage of the large capacity capacitor 12 and determines whether the output voltage is below the level required for backing up the trip and odd RAMs 21 and 22. A detection signal is output just before the This detection signal is supplied to the microcomputer 2 as a memory request signal, and to the timer switch 16 (described later) as a timer operation start signal. Reference numeral 16 denotes a timer switch. The timer switch 16 includes a timer that operates for a predetermined period of time in response to a detection signal from the voltage detection circuit 15, and is switched and controlled by an output signal from the timer to operate the vehicle battery 8 in the system. It consists of a switching element such as a relay connected to the power supply voltage regulator 10, and upon receiving the detection signal, energizes the system power supply voltage regulator 10 into an operating state for a predetermined period of time. Note that the timer time (the predetermined time) set by the timer switch 16 is such that at least the accumulated distance data stored in the trip and adjustment RAMs 21 and 22 of the microcomputer 2 is stored in the trip and adjustment non-volatile memories 3 and 4. The time is set to be longer than the time required to transfer to each. Also,
17 is a backflow prevention diode.

Next, the operation of this embodiment having such a configuration will be explained. When the ignition switch 9 is turned on and the vehicle is running, the system power supply voltage regulator 10 is activated, and the distance sensor 1 and the microcomputer ( RAM2 for trip and odometer
1 and 22) 2, non-volatile memory 3 for trip, non-volatile memory 4 for reset, reset pulse generation circuit 5, and display circuit 7. Operating power (system power supply) is applied to the microcomputer 2.
According to the distance calculation program, the distance pulses outputted from the distance sensor 1 every time the vehicle travels a certain distance are counted to calculate the distance data, and the trip distance data and the trip and odometer RAM 21 of the microcomputer 2 are , 22, respectively, to calculate new trip data and odometer data of the vehicle. As mentioned above, the latest trip data and odometer data calculated according to the distance calculation program are stored in the trip and odometer RAMs 21 and 22, respectively, each time their contents are updated, and are also supplied to the display circuit 7. displayed numerically.

Furthermore, when the ignition switch 9 is turned off, the system power supply voltage regulator 10
is inactive, but the backup power supply voltage regulator 14 is connected to the large capacity capacitor 12.
It operates for a predetermined period of time after the ignition switch 9 is turned off in response to the charged charge, and supplies operating power to the trip and reset RAMs 21 and 22 of the microcomputer 2. Therefore, even if the ignition switch 9 is turned off, the trip data and odometer data immediately before the ignition switch 9 is turned off are stored in the trip and odometer nonvolatile memory 3.
4, and will remain stored in the trip and reset RAMs 21 and 22 of the microcomputer 2 for a while after the ignition switch 9 is turned off. Then, if the ignition switch 9 is turned on again before the output voltage of the large-capacity capacitor 12 reaches the level necessary for backing up the trip and output RAMs 21 and 22, the normal operation mode as described above can be returned. become. However, if a relatively long period of time has passed after the ignition switch 9 is turned off, the output voltage of the large capacitor 12 will drop to a level that makes it impossible to back up the trip and reset RAMs 21 and 22; , the detection signal from the voltage detection circuit 15 is output to the timer switch 16 and the microcomputer 2, so that the timer switch 16 supplies operating power to the microcomputer 2 for a predetermined time via the system power supply voltage regulator 10. The microcomputer 2 starts the timer operation, and during that time, the microcomputer 2 saves the trip data and odd data stored in the trip and odd memories 21 and 22 to the trip and odd nonvolatile memories 3 and 4, respectively. As a result, the trip data and odd data immediately before the ignition switch 9 was turned off are held without power.

The trip data and odometer data stored in the trip nonvolatile memory 3 and the odometer nonvolatile memory 4, respectively, are stored in the trip data of the microcomputer 2 when the ignition switch 9 is turned on again.
The data will be read out to the RAM 21 and the odo RAM 22, respectively.

In the above embodiment, a case has been described in which trip data and odometer data are handled as cumulative distance data, but it goes without saying that it is also possible to handle only one of the data or a plurality of trip data. Further, in the above embodiment, the voltage detection circuit 15 includes the large capacity capacitor 12.
However, by detecting the output voltage of the voltage regulator 14 for backup power supply, the large capacity capacitor 12
It goes without saying that the output voltage may be detected indirectly.

(Effects of the invention) As explained above, according to this invention,
The non-volatile memory for storing cumulative distance data is rewritten only when the time between turning off the power switch and turning it on again is relatively long. Compared to rewriting the memory every time the power switch is turned off, the number of times the nonvolatile memory is rewritten can be significantly reduced, extending the life of the nonvolatile memory. This has the advantage of being able to provide an odometer.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram showing one embodiment of an electronic odometer according to this invention, and FIG. 2 is a schematic block diagram showing an example of a conventional electronic odometer. 1...Distance sensor, 2...Microcomputer, 3, 4...Nonvolatile memory, 8...Vehicle battery, 9...Ignition switch, 10...
Voltage regulator for system power supply, 12...
...Large capacity capacitor, 14... Voltage regulator for backup power supply, 15... Voltage detection circuit, 16... Timer switch, 21, 22... Microcomputer internal memory.

Claims (1)

[Scope of utility model registration request] A distance sensor 1, a microcomputer 2,
A secondary power source 12 receives power from the non-volatile memories 3 and 4 and an on-vehicle battery 8 obtained through a power switch 9 and is charged when the power switch 9 is turned on.
, a system power supply 10 that receives power from the on-vehicle battery 8 obtained via the power switch 9 and supplies operating power to the microcomputer 2 and nonvolatile memories 3 and 4; The internal memories 21 and 22 of the microcomputer 2 receive power from the on-vehicle battery 8 or power from the secondary power source 12.
a backup power supply 14 that supplies operating power to the
a voltage detection circuit 15 that detects a decrease in the output voltage of the secondary power source 12 and outputs a detection signal;
a timer switch 16 which is switched and controlled in response to a detection signal from the voltage detection circuit 15 and directly supplies power from the on-vehicle battery 8 to the system power supply 10 for a predetermined period of time;
calculates mileage data by counting the distance pulses output from the distance sensor 1 every time the vehicle travels a certain distance, and calculates the mileage data and the current data stored in the non-volatile memories 3 and 4. It has a distance calculation program that calculates new cumulative distance data of the vehicle based on the cumulative distance data of the vehicle, and stores the cumulative distance data calculated according to the program in the internal memory every time its contents are updated. 21, 22, and when receiving the detection signal from the voltage detection circuit 15, transfers the accumulated distance data stored in the internal memories 21, 22 to the nonvolatile memories 3, 4 and stores them therein. An electronic odometer characterized by control.