IN-VEHICLE ELECTRONIC DEVICE AND LIFE PREDICTION METHOD FOR NONVOLATILE MEMORY

Provided is an in-vehicle electronic device including a nonvolatile memory and a heat generating component mounted on one substrate, the in-vehicle electronic device being capable of accurately measuring a temperature of the nonvolatile memory without being affected by a distance from the heat generating component or a use condition. An electronic device mounted on a vehicle includes a processing controller that processes information handled by the electronic device or controls the electronic device, a memory having a plurality of writing areas, a temperature sensor, and a remaining warranty period calculation unit that calculates a remaining warranty period of the memory based on an output from the temperature sensor. The remaining warranty period calculation unit switches between a first determination method for obtaining the remaining warranty period using a first temperature coefficient determined regardless of a distance between the memory and each of a plurality of the temperature sensors and a second determination method for obtaining the remaining warranty period using a second temperature coefficient determined in accordance with the distance between the memory and each of the plurality of the temperature sensors in accordance with a time from activation of the in-vehicle electronic device to obtain the remaining warranty period.

TECHNICAL FIELD

The present invention relates to a configuration of an electronic device mounted on a vehicle and control thereof, and particularly relates to a technique effective for application to life prediction of a nonvolatile memory mounted on the electronic device.

BACKGROUND ART

With the progress of autonomous driving (AD) and advanced driver-assistance systems (ADAS), high performance and high reliability of in-vehicle camera systems have become important issues.

An example of an in-vehicle camera used for AD and ADAS is a stereo camera capable of recording also information in a depth direction by simultaneously imaging an object with a plurality of (generally two) cameras from different directions. The sizes, positions, and speeds of the plurality of three-dimensional objects can be detected by stereoscopic processing of the images captured by the plurality of cameras.

A nonvolatile memory (generally, a flash memory) for storing a captured image is mounted on an in-vehicle camera system such as a stereo camera. In order to improve the performance and reliability of the in-vehicle camera system, it is essential to improve the performance and reliability of the nonvolatile memory.

Incidentally, since the nonvolatile memory is deteriorated by electrons through which an oxide film serving as an insulator penetrates in an operation principle, a number of times that data is rewritten is limited, and the life of the nonvolatile memory varies depending on the number of rewriting times.

Further, it is known that the number of rewriting times of the nonvolatile memory varies depending on a temperature during use. In general, in a case of use at a high temperature, the number of rewriting times is reduced.

Therefore, the life of the nonvolatile memory can be predicted based on the number of rewriting times and the temperature during the use of the nonvolatile memory.

In addition, the nonvolatile memory (flash memory) is roughly classified into a NOT-OR (NOR) type memory and a NOT-AND (NAND) type memory. However, when the both types of flash memories having the same capacity are compared, the NAND type memory has lower data holding characteristics than the NOR type memory, but is relatively low in cost. Therefore, if the life of the NAND flash memory can be accurately predicted, a low-cost in-vehicle camera system using the NAND type flash memory can be provided.

An example of the background art of the present technical field includes a technique as disclosed in PTL 1. PTL 1 discloses “a memory control device capable of appropriately leveling the degree of consumption in a nonvolatile memory”.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

In the in-vehicle camera system as described above, generally, a heat generating component such as a microcomputer equipped with an image recognition processing function is also mounted on a substrate where the nonvolatile memory is mounted, and the temperature at which the nonvolatile memory is exposed varies depending on a distance from the heat generating component to the memory on the substrate.

Further, the temperature of the nonvolatile memory is difficult to accurately measure because the manner of heat generation in the heat generating component varies depending on a use condition of the in-vehicle camera system. That is, the life of the nonvolatile memory is difficult to accurately predict.

In PTL 1 described above, a temperature sensor is provided in each of a plurality of memory cells, a priority of each memory cell is determined in accordance with measured temperatures, and writing processing is executed preferentially on a memory cell having a high priority as a data writing destination. The degree of consumption can be appropriately leveled in the nonvolatile memory.

However, PTL 1 does not describe any influence of the heat generating component on the same substrate as described above, and the life of the nonvolatile memory is difficult to accurately predict.

Therefore, an object of the present invention is to provide an in-vehicle electronic device including a nonvolatile memory and a heat generating component mounted on one substrate, the in-vehicle electronic device being capable of accurately measuring a temperature of the nonvolatile memory without being affected by a distance from the heat generating component to the memory and a use condition, and a life prediction method for the nonvolatile memory using the in-vehicle electronic device.

Solution to Problem

In order to solve the above problem, the present invention provides an in-vehicle electronic device mounted on a vehicle, the in-vehicle electronic device including a processing controller that processes information handled by the in-vehicle electronic device or controls the in-vehicle electronic device, a memory having a plurality of writing areas, a temperature sensor, and a remaining warranty period calculation unit that calculates a remaining warranty period of the memory based on an output from the temperature sensor. The remaining warranty period calculation unit switches between a first determination method for obtaining the remaining warranty period using a first temperature coefficient determined regardless of a distance between the memory and each of a plurality of the temperature sensors and a second determination method for obtaining the remaining warranty period using a second temperature coefficient determined based on the distance between the memory and each of the plurality of the temperature sensors in accordance with a time from activation of the in-vehicle electronic device to obtain the remaining warranty period.

The present invention also provides a life prediction method for a nonvolatile memory, the method including (a) comparing an elapsed time from activation of an in-vehicle electronic device with a predetermined threshold, (b) calculating a remaining warranty period of the memory using a first temperature coefficient determined regardless of a distance between the memory and each of a plurality of temperature sensors, and (c) calculating a remaining warranty period of the memory using a second temperature coefficient determined in accordance with the distance between the memory and each of the plurality of temperature sensors. The remaining warranty period of the memory is obtained by switching between the steps (b) and (c) in accordance with a time after the activation of the in-vehicle electronic device.

Advantageous Effects of Invention

According to the present invention, in the in-vehicle electronic device including the nonvolatile memory and the heat generating component mounted on one substrate, it is possible to implement the in-vehicle electronic device that can accurately measure a temperature of the nonvolatile memory without being affected by the distance from the heat generating component to the memory and a use condition, and the life prediction method for the nonvolatile memory using the in-vehicle electronic device.

Accordingly, the reliability of the nonvolatile memory and the in-vehicle electronic device using the nonvolatile memory can be improved.

Further, instead of the NOR flash memory, the NAND flash memory having the same capacity can be used, which can contribute to cost reduction of the in-vehicle electronic device.

Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, identical components are denoted by identical reference numerals, and the detailed description of overlapping components is omitted.

Further, an example of a mounting substrate mounted on an in-vehicle camera system will be described below, but the present invention is not limited thereto, and can also be applied to an in-vehicle electronic device for another application having a substrate on which a nonvolatile memory and a heat generating component are mounted. Therefore, illustration of a configuration as an in-vehicle camera is omitted.

First Embodiment

An in-vehicle electronic device according to a first embodiment of the present invention and a life prediction method for a nonvolatile memory using the electronic device will be described with reference toFIGS.1to3.FIG.1is a diagram illustrating a substrate of the in-vehicle electronic device according to the present embodiment.FIG.2is a diagram illustrating distances between temperature sensors and the nonvolatile memory on the substrate ofFIG.1.FIG.3is a flowchart illustrating a memory life prediction method for the in-vehicle electronic device according to the present embodiment.

As illustrated inFIG.1, the in-vehicle electronic device of the present embodiment includes a main substrate100a, and a complementary metal oxide semiconductor (CMOS) substrate (L)100band a CMOS substrate (R)100cdisposed on the left and right of the main substrate100a. The main substrate100a, the CMOS substrate (L)100b, and the CMOS substrate (R)100care connected by a connection cable108.

The main substrate100aincludes a processing controller (control microcomputer)101that processes information handled by the in-vehicle electronic device or controls the in-vehicle electronic device, memories102and103each having a plurality of writing areas, a temperature sensor104, and a recognition microcomputer107that is a heat generating component.

The recognition microcomputer107includes a remaining warranty period calculation unit107aas a part of the function. The remaining warranty period calculation unit107acalculates the remaining warranty periods of the memory102and the memory103based on an output from the temperature sensor104. The CMOS substrate (L)100bincludes a temperature sensor105, and the CMOS substrate (R)100cincludes a temperature sensor106.

Here, in the in-vehicle electronic device according to the present embodiment, the remaining warranty period calculation unit107aswitches between a first determination method for obtaining the remaining warranty periods of the memories102and103using a first temperature coefficient determined regardless of distances between the memories102,103and the plurality of temperature sensors104,105,106and a second determination method for obtaining the remaining warranty periods of the memories102and103using a second temperature coefficient determined in accordance with the distances between the memories102,103and the plurality of temperature sensors104,105,106to determine the remaining warranty periods.

Hereinafter, the first determination method and the second determination method will be described in detail.

In the first determination method, the remaining warranty periods of the memories102and103are calculated by using the following formulas (1) and (2). The calculation formula of the first determination method are applied under a situation of less than Xmin (for example, less than 1 minute) immediately after the activation of the in-vehicle electronic device.

Here, Wpostindicates a remaining warranty counter value, Wpreindicates a previous remaining warranty counter value, Wcurrindicates a counter value for current writing, and β1indicates a temperature coefficient.

Here, T1indicates, for example, a temperature [K] of the temperature sensor1(104).

In the second determination method, the calculation method is optimized by the distances from the recognition microcomputer107, which is the heat generating component, to the memories102and103. In the second determination method, the remaining warranty periods of the memories102and103are calculated by using the following formulas (3), (4), (5), and (6). The calculation formulas of the second determination method are applied under a situation where Xmin or more (for example, 1 or more minutes) elapses immediately after the activation of the in-vehicle electronic device.

Here, Wpost_1indicates a remaining warranty counter value of the memory1(102), Wpre_1indicates a previous remaining warranty counter value of the memory1(102), Wcurr_1indicates a counter value for current writing on the memory1(102), and β2indicates a temperature coefficient of the memory1(102).

Here, T1indicates, for example, a temperature [K] of the temperature sensor1(104), T123indicates a temperature difference [K] between the temperature sensor1(104) with maximum temperature and the temperature sensor2(105) or the temperature sensor3(106) with minimum temperature, D1indicates a distance [m] from the temperature sensor1(104) to the memory1(102), and D123indicates a distance [m] from the temperature sensor1(104) with maximum temperature to the temperature sensor2(105) or the temperature sensor3(106) with minimum temperature.

Here, Wpost_2indicates a remaining warranty counter value of the memory2(103), Wpre_2indicates a previous remaining warranty counter value of the memory2(103), Wcurr_2indicates a counter value for current writing on the memory2(103), and γ2indicates a temperature coefficient of the memory2(103).

Here, D2indicates a distance [m] from the temperature sensor1(104) to the memory2(103).

The memory life prediction method for the in-vehicle electronic device according to the present embodiment will be described with reference toFIG.3.

First, the recognition microcomputer (heat generating component)107measures the activation time. In step S300, a writing event (for example, IGN_ON) for the memories102and103occurs, and a determination is made in step S301whether a time of less than a predetermined threshold Xmin elapses (for example, less than 1 minute).

If the time of less than Xmin (No) elapses, in step S302, a remaining warranty counter value is calculated by using the temperature coefficient β1(first temperature coefficient). (The first determination method) In a case where a time of Xmin or more elapses (Yes), in step S303, the remaining warranty counter value is calculated by using β2, γ2(the second temperature coefficient). (The second determination method) Subsequently, a determination is made in step S304whether the remaining warranty counter value is 0 or more.

If the remaining warranty counter value is 0 or more (Yes), writing to the memories102and103is performed in step S305.

On the other hand, in a case where the value is less than 0 (No), a warning is displayed on an instrument panel in step S306and is notified to a driver.

As described above, the in-vehicle electronic device according to the present embodiment is an electronic device mounted on a vehicle including the processing controller (control microcomputer)101that processes information handled by the electronic device or controls the electronic device, the memories102and103each having a plurality of writing areas, the temperature sensors104,105, and106, and the remaining warranty period calculation unit107athat calculates the remaining warranty periods of the memories102and103based on outputs from the temperature sensors104,105, and106. The remaining warranty period calculation unit107aswitches between the first determination method for obtaining the remaining warranty periods using the first temperature coefficient β1determined regardless of the distances between the memories102,103and the plurality of temperature sensors104,105,106and the second determination method for obtaining the remaining warranty periods using the second temperature coefficient β2(γ2) determined in accordance with the distances between the memories102,103and the plurality of temperature sensors104,105,106in accordance with the time elapsed from the activation of the in-vehicle electronic device to obtain the remaining warranty periods.

The timing for switching between the first determination method and the second determination method is determined, for example, based on an elapsed time (Xmin or more; for example, 1 minute or more) from ignition-on of the vehicle. That is, the remaining warranty periods are calculated with the first determination method during the period from the ignition-on of the vehicle to the predetermined time, and the remaining warranty periods are calculated with the second determination method after the predetermined time elapses from the ignition-on of the vehicle.

Further, the in-vehicle electronic device of the present embodiment includes the heat generating component (recognition microcomputer)107whose temperature rises with the activation of the in-vehicle electronic device, and the second temperature coefficient β2(γ2) is determined in accordance with the distances between the temperature sensor104disposed closest to the heat generating component (recognition microcomputer)107and the memories102and103.

In the in-vehicle electronic device and the life prediction method for the nonvolatile memory of the present embodiment, the life prediction is performed in consideration of the temperature coefficient. That is, the temperature of the nonvolatile memory is estimated by using the plurality of temperature sensors104,105, and106and is used for life calculation. Division of the use conditions (for example, “immediately after activation” and “after elapse of a certain period of time”) makes it possible to improve the accuracy of estimation of an exposure temperature in the nonvolatile memory. Therefore, since the manner of a temperature rise is different between immediately after the activation of the in-vehicle electronic device and after the elapse of time even in summer and winter, the life of the nonvolatile memory can be accurately predicted by performing the life prediction using the temperature coefficient.

Further, it is possible to effectively utilize a NOT-AND (NAND) flash memory that is comparatively inexpensive but has a short life (low data holding characteristics) instead of a NOT-OR (NOR) flash memory that has high data holding characteristics but is comparatively expensive.

The nonvolatile memory can be effectively used by managing the temperature for each memory and each sector and calculating the remaining warranty period, and a large amount of data can be handled with a minimum necessary amount of a memory.

The nonvolatile memory can be used without corruption of data even in applications where data is frequently rewritten, such as a drive recorder.

Use of the in-vehicle electronic device of the present embodiment in, for example, an in-vehicle camera system improves the reliability of the in-vehicle camera system, and enables use of an NAND flash memory having the same capacity instead of the NOR flash memory, thus contributing to cost reduction of the in-vehicle camera system.

Note that, the above description has referred to the two cases where the memory1(102) and the memory2(103) are used. However, also in a case of three or more memories, the remaining warranty counter values can be calculated if the distances to memories are obtained.

Further, although the temperature sensor1(104) is disposed near the recognition microcomputer107, which is the heat generating component, the life of each memory can be predicted by measuring a temperature gradient in the main substrate100ain advance and acquiring measurement data without disposing the temperature sensor1near the heat generating component.

In addition, although the three temperature sensors (104,105, and106) are mounted, even in a case of one temperature sensor, the life can be predicted by acquiring data of a temperature distribution in advance after lapse of a time or in accordance with a surrounding situation.

However, the conditions after the lapse of time, the conditions of the surrounding situation, and the information processing amount inside the in-vehicle electronic device are wide-ranging, and many conditions for data acquisition are present. Thus, it is desirable to mount three or more temperature sensors inside the in-vehicle electronic device.

Further, in the present embodiment, it is assumed that one heat generating component is provided. However, even in a case where a plurality of heat generating components is provided, the present invention can be applied even to the case of the plurality of heat generating components by obtaining the temperature distribution in the main substrate100ain advance.

Further, in the present embodiment, the remaining warranty period is obtained by using the first temperature coefficient β1in the first determination method, and the remaining warranty period is obtained by using the second temperature coefficient β2(γ2) in the second determination method. However, a conversion table is created in advance by acquiring a relationship between a temporal temperature change in the heat generating component and the number of rewriting times (life) for the nonvolatile memory with, for example, experiment or simulation without using the temperature coefficients, and the method for calculating the remaining warranty period with the remaining warranty period calculation unit107acan be switched in accordance with the elapsed time after the activation of the in-vehicle electronic device.

Second Embodiment

An in-vehicle electronic device and a life prediction method for a nonvolatile memory using the in-vehicle electronic device according to a second embodiment of the present invention will be described with reference toFIG.4.FIG.4is a flowchart illustrating the memory life prediction method for the in-vehicle electronic device according to the present embodiment.

The present embodiment describes a method for reliably writing data of high importance to a sector (area) without corruption of data by utilizing the remaining warranty counter value calculated in the first embodiment.

After the writing event (for example, IGN_ON) to the memories102and103occurs, first, in step S400, the remaining warranty counter value is calculated by using the temperature coefficients β1, β2, and γ2for each sector.

Next, in step S401, a determination is made whether data has high importance. Examples of the “data of high importance” referred to herein include, in the case of an in-vehicle camera, information related to safety, such as “image during occurrence of pre-crash brake”, “other vehicle recognition information during occurrence of pre-crash brake”, and “sign recognition information during occurrence of pre-crash brake”, and, in the case of an in-vehicle radar, “distance to an object during occurrence of pre-crash brake” and “vehicle speed information about a brake target during occurrence of pre-crash brake”.

In the case of data of low importance (No), a check is conducted in step S402whether the remaining warranty counter value in a saving sector is 0 or more.

In a case where the remaining warranty counter value is 0 or more (Yes), the writing to the memories102and103is performed in step S403.

On the other hand, in a case where the remaining warranty counter value is less than 0 (No), a check is conducted in step S404whether the remaining warranty counter values in all sectors have been calculated.

In a case where not all the remaining warranty counter values in all the sectors have been calculated (No), a movement to another sector is made in step S405, the processing returns to step S402, and the remaining warranty counter values are checked again.

In a case where the remaining warranty counter values have been calculated in all the sectors (Yes), a warning is displayed on the instrument panel in step S406, and is notified to the driver.

In a case where the determination is made in step S401that the data has high importance (Yes), a check is conducted in step S407whether the remaining warranty counter value in the saving sector is equal to or greater than a predetermined threshold Y.

In a case where the value is equal to or greater than Y (Yes), the writing to the memories102and103is performed in step S408.

On the other hand, in a case where the remaining warranty counter value is less than Y (No), a check is conducted in step S409whether the remaining warranty counter values in all sectors have been calculated.

In a case where not all the remaining warranty counter values in all the sectors have been calculated (No), a movement to another sector is made in step S410, the processing returns to step S407, and the remaining warranty counter values are checked again.

In a case where the remaining warranty counter values have been calculated in all the sectors (Yes), a warning is displayed on the instrument panel in step S411, and is notified to the driver.

According to the present embodiment, since the writing is performed in consideration of the remaining warranty counter values and the importance of the data for each sector (area) of the nonvolatile memory, data of high importance can be written in a sector (area) having a high remaining warranty counter value (data holding characteristic), and the reliability of the nonvolatile memory and the in-vehicle electronic device using the memory can be improved.

As described above, although the remaining warranty counter values are calculated after the movement of sectors in step S405or step S410, the remaining warranty counter values in all the sectors may be calculated in advance, and the information (storage area) may be held in the memories102and103.

As a result, in a case where a writing event of data with high importance occurs, if the sector where data is scheduled to be stored has a remaining warranty counter value of less than Y, the sector can be immediately swapped (exchanged) with a sector having the largest remaining warranty counter value that is equal to or more than Y.

As described above, in the in-vehicle electronic device of the present embodiment, the remaining warranty period is calculated for each of the plurality of writing areas in the nonvolatile memory, the priority of the information to be written in the nonvolatile memory is determined, and the information of high importance is preferentially written.

Thus, data of high importance can be reliably stored by calculating the life prediction for each sector instead of the life prediction for each nonvolatile memory.

Note that the present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the described configurations. Further, a part of the configuration of a certain embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of a certain embodiment. Further, another configuration can be added to or deleted from a part of the configuration of each embodiment, or a part of the configuration of each embodiment can be replaced with another configuration.

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