JPS6227617A - Odometer for automobile - Google Patents

Abstract

PURPOSE:To make the service life long and to improve reliability, by providing three or more of non-volatile memories, in which counted values that are updated at every specified counted value are sequentially written, and comparing a plurality of the written counted values. CONSTITUTION:The speed of a vehicle detected by a distance sensor 1 is added in a counter 4 and the running distance data is obtained. The running distance data is integrated as specified in an operating circuit 5. The integrated running distance is displayed on a display 7 through a driver 6. At every time a flag in a the counter 4 is outputted, the running data up to that time are sequentially written in non-volatile memories 8-10. Then, the running distance data, which are updated from time to time, are written in the memories 8-10 sequentially and maintained. When a key to an automobile is pulled out and a power source is once cut OFF and thereafter the power source is turned ON, the running distance data stored in the memories 8-10 are read out and inputted to the circuit 5. After the continuity is judged, the maximum value is used as the latest running distance data, and the specified operation is performed. The result is displayed on the display 7.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides an electronic automobile odometer that has a counting circuit that totals the distance traveled and a nonvolatile memory that can retain this counted value even after the power is turned off. Regarding.

[Related technology and its problems]

In recent years, electronic display devices with improved information processing functions using microcomputers have been installed in automobile instruments, and in particular, conventional mechanical counter-type odometers have Instead, the development of an odometer using a microcomputer is underway. However, the mileage is accumulated sequentially, and for example, if the car key is removed and the power is cut off, the mileage data stored in the RAM in the conventional microcontroller will also be erased, and the mileage data will no longer function as an odometer. not fulfill the purpose.

Therefore, a method is being used in which mileage data is stored in a nonvolatile memory that can be retained even after the power is shut off. However, if the power is cut off while the mileage data is being written to the non-volatile memory, a ridiculous value will be stored, and when the power is turned back on, the new mileage will be added to that value. It turns out.

In order to prevent this kind of thing,
Publication No. 9 discloses a system in which the same mileage data is sequentially written into four or more nonvolatile memories, and accurate mileage data is obtained using the principle of majority voting. In other words, if you sequentially write the same data to four or more non-volatile memories, even if the power is cut off while data is being written to one of them and a ridiculous value is retained, the other memories will not be affected. Since accurate data is maintained, accurate mileage data can be obtained from them.

However, generally used non-volatile memories have a limit on the number of times they can be rewritten, and if rewriting is performed frequently, the life span will be shortened due to deterioration of the elements. If the above-mentioned conventional method is used to rewrite the travel distance data in the nonvolatile memory every 100 m, for example, it will be necessary to rewrite the data 10 times until the vehicle has traveled 100,000 km. However, current non-volatile memory can be rewritten only 1♂ to 1♂ cycles, and if it is rewritten so frequently, the lifespan of non-volatile memory will be shortened, reliability will decrease, and non-volatile memory will be damaged. There may also be cases where they are replaced.

[Object of the Invention] The present invention has been made based on the above circumstances, and provides an electronic device that can reduce the number of rewrites of nonvolatile memory, extend its life, improve reliability, and display accurate mileage. The object of the present invention is to provide an automobile odometer of the type.

[Structure of the invention]

To achieve the above object, the present invention provides an automobile odometer that has a counting circuit that totals the distance traveled and a non-volatile memory that can retain this counted value even after the power is turned off. Compare three or more non-volatile memories into which the counted values are sequentially written, and compare these written multiple counted values to determine continuity, and if there are discontinuous counted values, correct them and write them to the maximum value. and an arithmetic circuit that outputs the counted value as the distance traveled.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail based on the drawings.

In FIG. 1, the vehicle speed detected by a distance sensor 1 which outputs repetitive pulses with a frequency proportional to the traveling speed is added by a counter 4 via a waveform shaping circuit 2 and a frequency divider 3 to obtain traveling distance data. This mileage data is calculated by the calculation circuit 5.
A predetermined calculation is performed and the accumulated travel distance is displayed on a display 7 such as a liquid crystal display via the driver 6.

The counter 4 sets a flag every time the mileage data reaches, for example, 1km and outputs a pulse representing this to the calculation circuit 5.
Every time this flag is output, the arithmetic circuit 5 sequentially writes the mileage data up to that point into the nonvolatile memories 8, 9, and 10. That is, when the first flag is output, the mileage data A is stored in the first non-volatile memory 8, and when the next flag is output, the mileage data B is stored in the second non-volatile memory 9. When the flag is output, the mileage data C is stored in the third non-volatile memory 10, and when the next flag is output, the mileage data C is stored in the first non-volatile memory 8, and so on. The data is sequentially written into the non-volatile memories 8, 9.10, and each of the three non-volatile memories 8, 9.10 holds continuous mileage data every 1 km. Then, when the car key is removed and the power is turned off, the mileage data stored in the non-volatile memory 8.9.10 is read into the calculation circuit 5 and continuously displayed. After determining the accuracy of the vehicle, the maximum value thereof is subjected to a predetermined calculation and displayed on the display 7 as the latest mileage data up to that point.

The arithmetic circuit 5 that determines this continuity will be explained in more detail with reference to FIG. to be written. Then, when the power is turned on again, the memory control circuit 11
Three different pieces of mileage data are read from the nonvolatile memories 8.9.10, and two pieces of mileage data from among these are stored in the first RAM 12 and the second RAM 13, respectively. The subtraction circuit 14 uses this RAM 12.1.
A circuit that subtracts the mileage data from step 3 and determines the subtracted value →
Output to. In addition, the continuity of three different mileage data is determined, and if they are continuous, the maximum value is used, and if they are not continuous, the data is corrected based on the assumption that the power was cut off while writing the data to non-volatile memory. Then, it is output to the memory control circuit 11.

The operation of the present invention configured as described above will be explained in more detail.

The vehicle speed detected by the distance sensor l is integrated by a counter 4 to provide travel distance data. Then, a flag is output to the memory control circuit 11 every time 1km is traveled, and the memory control circuit 11 adds this 1ka+ to the total travel distance data up to that point, for example, 10km, to the first non-volatile memory as shown in the table. Write to memory 8. Then, when the next flag is output, the mileage data is 1ll.
ua is written to the second non-volatile memory 9. Furthermore, 12 is written in the third nonvolatile memory 10 in the same way according to the next flag. In this way, new mileage data is sequentially written into the non-volatile memory 8.9.10.

For example, after the mileage data of 14 km has been written to the second non-volatile memory 9, when the power is turned off and then turned on again, the memory control circuit 11 first controls the non-volatile memories 8 and 9. The data held in lO is read, two of them are taken out and subtracted by the subtraction circuit 14. In this case, since there are three types of two pieces of data, the subtraction circuit 14 is (C-B), (B-A),
Perform subtraction three times (A-C). If three pieces of mileage data are consecutive, each subtraction value will always be -2, +1
．． It becomes 3 values of +1. The determination circuit 15 determines that the subtraction value is (-2,
+1°+1), and if so, it is assumed that the data is continuous, and the maximum mileage data among them is selected as the latest, and from then on, new mileage data input from the counter 4 is This will be added up.

On the other hand, if the power is cut off while the mileage data of 20 km is being written into the second non-volatile memory 9, an unreasonable value, for example 27, will be retained. and,
When the power is turned on again, the determination circuit 15 is set to 3 by the same operation as described above.
Since there are subtraction values other than (-2°+1.+1), in this case 8 and -9, the three mileage data are discontinuous, that is, the power was cut off in the middle of writing. , and ignores the mileage data. Then, 1 is added to the larger value among the other two continuous mileage data, and the added value is written to the non-volatile memory that holds the incorrect mileage data to correct it. , the added value is the latest mileage data. In this case, even if one piece of data is incorrect, the other two pieces of data are continuous.

In this way, the continuity of the different mileage data stored in the three non-volatile memories 8, 9 and 10 is determined, and the
If 3 pieces of data are consecutive, the maximum value is taken as the latest mileage data, and the mileage data accumulated thereafter is added to this, and if 3 pieces of data are not consecutive, it is written. Assuming that the latest data was supposed to be written to the memory when the power was cut off during the middle of the day, the latest data was added by adding the mileage of 1km for which a flag is output to the larger data among other continuous data. Mileage data. In this way, conventionally, the same data was written to all memories every time a flag was output, but according to the present invention, the number of times the data is written is reduced to 1/3.
As a result, the lifespan of nonvolatile memory, which has a limited number of write operations, can be extended, resulting in an odometer with improved reliability.

Although one embodiment of the present invention has been described in detail above, it can be modified as appropriate within the scope of the gist of the present invention. For example, the number of nonvolatile memories should be three or more so that continuity can be determined, and in this case, the number of writes is the number of nonvolatile memories n
If it is 1/H, it becomes 1/H. Furthermore, the distance at which the flag is output is not limited to lkm, for example, 0.11u.
If three non-volatile memories are used, the subtraction value for the continuous condition is (-0, 2, +0.1. +0.1)
becomes.

〔Effect of the invention〕

As described in detail above, according to the present invention, in an automobile odometer having a counting circuit for accumulating mileage and a non-volatile memory capable of retaining this counted value even after power is cut off, -
Compare three or more non-volatile memories into which the counted values that are updated for each number of needle punctures are sequentially written, and determine continuity by comparing these written multiple counted values and if there are discontinuous counted values. By having an arithmetic circuit that corrects and outputs the maximum counted value as the distance traveled, it is possible to reduce the number of writes to nonvolatile memory, extend its life, improve reliability, and accurately calculate the distance traveled. It is possible to provide an electronic automobile odometer that displays .

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing an arithmetic circuit. 4-Counter 5--Arithmetic circuit 7--Display device 8.9.10--Non-volatile memory lt-m-Memory control circuit 14-Subtraction circuit 15--Judgment circuit

Claims (1)

[Claims] In an automobile odometer that has a counting circuit that totals the distance traveled and a nonvolatile memory that can retain this counted value even after the power is turned off, three or more nonvolatile memory cells that sequentially write the counted value that is updated at a fixed count. A memory and an arithmetic circuit that compares these written multiple counted values to determine continuity, corrects any discontinuous counted values, and outputs the maximum counted value as the distance traveled. An automobile odometer comprising: