JP2858519B2 - Electronic odometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic odometer which is mounted on a vehicle and displays the traveling distance of the vehicle.

[0002]

2. Description of the Related Art An electronic odometer uses a vehicle speed sensor which is generated at every constant traveling distance of a vehicle also as a sensor unit which is a distance sensor, and counts and integrates the number of input pulses from the sensor unit to thereby measure the traveling distance of the vehicle. Is calculated and sequentially added to the previous travel distance, and the latest travel distance is displayed on an appropriate display unit.

[0003] By the way, the traveling distance data is written in an appropriate non-volatile memory unit for each predetermined traveling distance so as not to be lost, and is stored in the non-volatile memory unit when the vehicle starts running (when the ignition switch is turned on). The data is read and the mileage is displayed based on the data.

An EEPROM is used as a nonvolatile memory unit.
Are frequently used, and erasure / writing of the traveling distance data is repeated so that the latest data is always stored in the memory. However, since there is a limit to the rewriting of the EEPROM, various rewriting methods for the EEPROM have been proposed. I have.

[0005] For example, Japanese Patent Publication No. 1-29477 discloses an nxn memory unit for lower-order digits and a memory unit for upper-order digits with a small capacity. When writing from "0" to "1" is performed in bit units and writing in the lower digit memory portion is completed, writing is performed in one unit in the upper digit memory portion and the lower digit memory portion is entirely erased. A technique for starting writing to the lower digit memory unit is disclosed. In addition, Tokuhei 1
Japanese Patent Application Laid-Open Nos. -46005 and 1-46006 employ a plurality of sets of memory groups as the lower digit memory unit and the upper digit memory unit, and each time a lower digit memory unit is written in a predetermined manner, the upper digit memory unit is used. In addition to writing to the memory section, each of the first and second memory groups employs a single memory group. If one memory group overflows, the next write employs the next memory group. In addition, a technique is employed in which the number of rewrites of the memory unit is set to be equal to or less than the limit.

[0006]

Incidentally, the above-mentioned electronic odometer requires an inspection for checking whether or not it operates normally after manufacturing. This inspection means inputs a pulse signal to the instrument and confirms normal display update of the display unit. Updating the display on the display unit in this inspection process naturally involves updating the data in the nonvolatile memory unit. Therefore, when the inspection process is completed and normal operation is confirmed, the nonvolatile memory unit is shipped at the time of shipment (before installation into the vehicle). It is necessary to perform a reset for returning the data of the above to an initial value (0 km) and a preset for rewriting the data to a predetermined value (hereinafter, both are collectively referred to as a reset).

Therefore, in order to easily initialize the data in the nonvolatile memory section, a means for providing a dedicated initialization terminal and initializing the data in the nonvolatile memory section with a signal from the terminal may be considered. However, if a signal is input to the terminal due to external noise, a short circuit, or the like, the data in the non-volatile memory unit will be lost, and furthermore, there is a possibility that the mileage data may be tampered with illegally. Is also conceivable.

Accordingly, the present invention proposes an electronic odometer that solves the above-mentioned problem by saving previously stored traveling distance data when resetting data in a nonvolatile memory unit.

[0009]

According to the present invention, there is provided an electronic odometer comprising: a sensor unit for generating a pulse at every fixed traveling distance of a vehicle; a non-volatile memory unit in which traveling distance data is written; An arithmetic processing unit that calculates the latest travel distance based on the reading of the data and counts the number of pulses input from the sensor unit and appropriately rewrites the data to the nonvolatile memory unit, and displays the latest travel distance. In an electronic odometer including a display unit, the nonvolatile memory unit includes a normal mileage storage area and a save area at reset, and saves the data of the normal mileage storage area to the save area. And a reset mechanism for returning the normal mileage storage area to an initial value or a predetermined value.

[0010]

[Action] The vehicle travels a predetermined distance (unit traveling distance),
When a predetermined number of pulse signals from the sensor unit are counted,
The unit travel distance is written in the memory unit, and at the same time, the latest travel distance is displayed on the display unit.

In particular, when the reset mechanism is operated,
First, the traveling distance data in the normal area in the nonvolatile memory section is read out, this data is saved in the save area in the nonvolatile memory section, and then the data in the normal area is rewritten to an initial value or a predetermined value.

[0012]

Next, an embodiment of the present invention will be described.

In this embodiment, as shown in FIGS. 1 and 2, an electronic odometer comprises a sensor section 1, an arithmetic processing section 2, a non-volatile memory section 3, a display section 4, and a reset mechanism 5. The unit 1 is a distance sensor that generates a pulse at every constant traveling distance of the vehicle. The arithmetic processing unit 2 is formed by a CPU, counts pulse signals from the sensor unit 1, and stores a pulse at a predetermined traveling distance. The data in the nonvolatile memory unit 3 is subjected to processing such as saving, rewriting, and outputting, which will be described later, in accordance with the writing to the memory and the signal from the reset mechanism 5.

The non-volatile memory section 3 is formed of a rewritable non-volatile memory element such as an EEPROM, and has a lower digit memory section 31 (31a, 31b) of m words × n bits (20 words × 5 bits). , 31c to ensure data retention by simultaneous rewriting of the three sets) and a memory unit 32 (32a, 32b, 32c) for j words.times.k bits (4 words.times.5 bits).
) And h words × i bits (1 word × 5
Bit) save memory 33 (33a, 33b, 33)
c, 33d, 33e, and 33f), the normal mileage storage area is stored in the lower-order memory unit 31 and the upper-order memory unit 32, and the evacuation memory unit 33 saves during reset. Each area is configured.

The display unit 4 includes a driver 41 and a display 42
And receives the output from the arithmetic processing unit 2 and displays the accumulated traveling distance of the vehicle.

The reset mechanism 5 includes a terminal 51 and a terminal 51.
A terminal 51 is connected to the arithmetic processing unit 2, and a terminal 53 is connected to the terminal 5.
The arithmetic processing unit 2 saves the traveling distance data and performs a predetermined reset by using the ground 1.

When the vehicle travels a predetermined distance (unit traveling distance) and the pulse signal from the sensor unit 1 is counted by a predetermined number, the arithmetic processing unit 2 adds the unit traveling distance to the previous traveling distance. To obtain the latest traveling distance, and this traveling distance is simultaneously written in the non-volatile memory unit 3,
It is displayed on the display 42 of the display unit 4.

The lower digit memory unit 31 sequentially writes any one of 20 words.times.5 bits as "0" for each 1 km of the traveling distance. At least one bit is "0" in each word for parity check. Is written to. Therefore, when the traveling distance is 0 km, the fifth bit (the right end in the figure) of the address at address 00 is "0", and the words at the other addresses 01 to 19 are "0" in the first bit (the left end in the figure). Is written, at a mileage of 1 km, the word at address 01 is rewritten, the first bit of the word is rewritten from “0” to “1”, the fifth bit is rewritten from “1” to “0”, After rewriting the word at address 19, the fifth bit of the word at address 00 is rewritten from "0" to "1" again, and the fourth bit is rewritten from "1" to "0". That is, the same word is rewritten every 20 km, and when the traveling distance reaches 100 km, the traveling distance becomes 0.
In the same state as km, data is written to the upper digit memory 32.

The upper digit memory section 32 stores 1 for each word.
For 00km digit, For 1000km digit, For 10,000km digit, 10
It is divided into 0000 km digits, and each of the numerical values “0” to “9” is stored in a BCD code, and the upper digit is rewritten by each digit carry. Note that the most significant bit of each word is set for parity check so that the number of “0” s of the same word with odd parity is always an odd number.

The evacuation memory unit 33 stores 15 words for each word.
The bits are divided into three, and six sets of 33a to 33f are each 1km
It is divided for ~ 100,000 km digits and stored in BCD code. The most significant bit of each set is set for parity check, and the number of “0” s of the same word in odd parity is always an odd number.

Further, according to the present invention, a reset mechanism 5 for enabling data saving and presetting of the memory sections 31 and 32 is provided.
When the terminal 51 is short-circuited (grounded), the arithmetic processing unit 2 detects that the output terminal of the reset mechanism 5 has changed from "high" to "low", The data in the memory units 31 and 32 is read out and saved in the save memory unit 33, and the data in the lower and upper digit memory units 31 and 32 is rewritten to, for example, the integrated distance of 0 km as the initial value. That is, as shown in FIG. 3, 33a, 33b, 33c, 33d, 3
3e and 33f store the data (3
In the overall evaluation of 1a, 31b, 31c, for example, a value determined by majority vote), 1 km digit “5”, 10 km digit “4”,
The data (32a, 32b, 32
c, for example, a value determined by majority decision), 100 km digit “3” at address 0A, 1000 km digit “2” at address 0B, and 10 at address 0C.
"1" of 000km digit, 10000 of the same address 0D
“0” of the 0 km digit is respectively saved and written.

Therefore, the data in the memory unit 3 after the normal running is, for example, as shown in FIG.
At this time, even if the reset mechanism is erroneously operated, the mileage data is saved in the saving memory unit 33. Therefore, even if the lower and upper digit memory units 31 and 32 are reset to 0 km, the saving memory is used. By reading the data of the unit 33, the traveling distance data before reset can be known. Therefore, when the reset mechanism malfunctions,
It is possible to set normal traveling distance data in the upper digit memory units 31 and 32.

The present invention is not limited to the above embodiment. For example, the memory units 31, 32 and 33
It is not always necessary to use the same memory element. Then, the storage format of the evacuation memory unit 33 is
Similar to the upper digit memory units 31 and 32, the reliability of holding three sets may be increased. The code is not limited to the BCD code.

[0024]

As described above, according to the present invention, in the electronic odometer having the non-volatile memory section, a saving area for the traveling distance data is provided in the non-volatile memory section, and the traveling distance data is stored in the saving area at the time of reset. After the evacuation, the resetting is performed, so that the writing of the memory data generated in the inspection process can be easily performed, and the intentional unauthorized use can be prevented.

[Brief description of the drawings]

FIG. 1 is a simple block diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a bit configuration of a nonvolatile memory unit according to the embodiment.

FIG. 3 is an explanatory diagram of a reset operation of the nonvolatile memory unit according to the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sensor part 2 Operation processing part 3 Non-volatile memory part 31 Lower digit memory part 32 Upper digit memory part 33 Evacuation memory part 4 Display part 5 Reset mechanism

Claims (1)

(57) [Claims] 1. A sensor unit for generating a pulse at every constant traveling distance of a vehicle, a non-volatile memory unit in which traveling distance data is written, reading of data from the non-volatile memory unit, and the number of pulses input from the sensor unit An electronic odometer including a calculation processing unit that calculates the latest traveling distance based on the count and appropriately rewrites data to the nonvolatile memory unit, and a display unit that displays the latest traveling distance. The non-volatile memory unit is composed of a normal mileage storage area and a save area at the time of resetting, the data of the normal mileage storage area is saved to the save area, and the normal mileage storage area is initialized or reset. An electronic odometer provided with a reset mechanism for returning a predetermined value to a predetermined value.