Oil level detection device for internal combustion engines

Abstract

To prevent erroneous detection of an oil level caused by error assumed to be included in a detection value of an oil pressure sensor.SOLUTION: An oil level detection device of an internal combustion engine includes: an oil pressure sensor for detecting a discharge pressure of an oil pump pumping an oil stored in an oil pan and determining the discharge pressure according to combination of a temperature of the oil and a rotating speed of the internal combustion engine; an oil level drop detection portion for detecting shortage of an oil quantity in the oil pan by determining that a detection value of the oil pressure sensor is lowered than a first oil pressure value as a value for detecting the shortage of oil quantity; and a control portion for stopping the detection of oil level drop by the oil level drop detection portion when the rotating speed of the internal combustion engine is lower than a rotating speed for making the oil pump output a third oil pressure value obtained by adding a second oil pressure value as an estimation value of the error assumed to be included in the detection value of the oil pressure sensor to the first oil pressure value and determined according to the temperature of the oil.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an oil level detection device for an internal combustion engine. [Background technology]

[0002] Conventionally, there is known a technique for suppressing instability in engine operation caused by a drop in oil pressure by detecting the discharge pressure of an oil pump with a hydraulic sensor and switching the opening pressure of a relief valve based on the detected value (see, for example, Patent Document 1). Patent Document 1 lists air intake by the oil pump as one cause of a drop in oil pressure. The oil pump may also intake air when the amount of oil in the oil pan is insufficient and the oil level drops, so the oil level in the oil pan can be detected by detecting the discharge pressure of the oil pump with a hydraulic sensor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-242527 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the detection value of the pressure sensor may contain errors due to various causes. For example, the detection value may be affected by noise caused by the environment around the pressure sensor. The detection value may also be affected by variations in the quality of the pressure sensor itself. Furthermore, if the pressure sensor is a gauge pressure sensor that indicates the detection value based on the atmospheric pressure, the detection value may be affected by changes in atmospheric pressure caused by changes in the altitude at which the vehicle is located. All of these may cause errors in the detection value. If the detection value contains these errors, the detection value indicates a value lower than the oil level detection oil pressure value for determining whether the oil level is insufficient, even though the actual discharge pressure is higher than the oil level detection oil pressure value, and a false detection occurs that the oil level has dropped. If a false detection occurs, inconveniences such as a warning light being turned on or an error log being recorded even though the oil level has not actually dropped.

[0005] Therefore, an object of the oil level detection device for an internal combustion engine disclosed in this specification is to avoid erroneous detection of the oil level due to errors expected to be contained in the detection value of the oil pressure sensor. [Means for solving the problem]

[0006] The oil level detection device for an internal combustion engine disclosed in this specification includes a hydraulic sensor that pumps out oil stored in an oil pan provided in the internal combustion engine and detects the discharge pressure of an oil pump, the discharge pressure of which is determined by a combination of the temperature of the oil and the rotational speed of the internal combustion engine; an oil level drop detection unit that detects a shortage of oil in the oil pan by determining that the detection value of the hydraulic sensor is lower than a first hydraulic pressure value set as a value for detecting a shortage of oil in the oil pan; and a control unit that stops detection of a drop in the oil level by the oil level drop detection unit when the rotational speed of the internal combustion engine is in a state where the rotational speed of the internal combustion engine is lower than a rotational speed that causes the oil pump to output a third hydraulic pressure value obtained by adding a second hydraulic pressure value, which is an estimate of an error expected to be included in the detection value of the hydraulic pressure sensor, to the first hydraulic pressure value, and is determined according to the temperature of the oil. Effect of the Invention

[0007] The oil level detection device for an internal combustion engine disclosed in this specification can avoid erroneous detection of the oil level due to errors assumed to be contained in the detection value of the oil pressure sensor. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of an oil circulation system in which an oil level detection device according to an embodiment is incorporated. [Diagram 2] FIG. 2 is a flowchart showing an example of oil level detection control executed in the oil level detection device of the embodiment. [Diagram 3] FIG. 3(A) is a graph showing the relationship between the first oil pressure, the second oil pressure, and the third oil pressure in the oil level detection device of the embodiment, and FIG. 3(B) is a graph showing an example of a state in which an erroneous detection of the oil level occurs. [Figure 4] FIG. 4 is a graph showing an example of the relationship between the oil temperature and the discharge pressure (oil pressure) for each engine speed in an oil circulation system in which the oil level detection device of the embodiment is incorporated. [Diagram 5] FIG. 5 is a graph showing an example of a mask region for stopping detection of a drop in oil level. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. However, in the drawings, the dimensions, ratios, etc. of each part may not be illustrated to be completely consistent with the actual ones. In addition, some details may be omitted in the drawings.

[0010] (Embodiment) [Oil circulation system] First, with reference to FIG. 1, a schematic configuration of an oil circulation system 100 incorporating an oil level detection device for an internal combustion engine (hereinafter simply referred to as a "detection device") 101 according to an embodiment will be described.

[0011] The oil circulation system 100 includes an oil pan 10 for storing engine oil (hereinafter simply referred to as "oil"), a main gallery 11, an oil strainer 12, an oil filter 15, and an oil cooler 16. The oil circulation system 100 also includes an oil temperature and oil pressure sensor 20, a variable valve timing mechanism (hereinafter referred to as "hydraulic VVT") 30, and flow paths for supplying oil to each part 40 of an internal combustion engine (hereinafter referred to as "engine"). Each part 40 of the engine includes, for example, a crank journal and a cam journal. The oil circulation system 100 also includes a piston oil jet 41 for injecting oil toward a piston (not shown) of the engine to cool the piston, a variable displacement oil pump 50, and an OCV (Oil Control Valve) 51. The oil circulation system 100 also includes an ECU 70.

[0012] The main gallery 11 receives oil pumped up from the oil pan 10 by the operation of a variable displacement oil pump 50. Oil passages branch off from the main gallery 11. At the ends of the branched oil passages are the hydraulic VVT 30, various engine components 40, and piston oil jets 41, to which oil is supplied via the main gallery 11. An oil strainer 12 is installed in the oil pan 10 to prevent foreign matter in the oil from being sucked in when the oil is pumped up by the variable displacement oil pump 50. The oil that branches off from the main gallery 11 and is supplied to various components is returned to the oil pan 10. The oil repeats this circulation process by the oil circulation system 100.

[0013] The oil filter 15 is installed in an oil passage 61 that connects the oil strainer 12 and the main gallery 11, and filters the oil heading to the main gallery 11 to remove impurities. The oil cooler 16 is installed on the downstream side of the oil filter 15 in the oil passage 61 (the side closer to the main gallery 11) and cools the oil heading to the main gallery 11.

[0014] The oil temperature and oil pressure sensor 20 is installed in the main gallery 11, and detects the temperature of the oil discharged from the variable displacement oil pump 50 (hereinafter referred to as "oil temperature") and the discharge pressure (oil pressure). As will be described later, the oil temperature and oil pressure sensor 20 is used to detect a drop in the oil level in the oil pan 10. The part of the oil temperature and oil pressure sensor 20 that detects the oil pressure is a gauge pressure sensor. Note that, although the present embodiment employs the oil temperature and oil pressure sensor 20 that detects the oil temperature and discharge pressure, an oil temperature sensor and an oil pressure sensor may be separately arranged to detect the oil temperature and discharge pressure.

[0015] The hydraulic VVT 30 is a hydraulic movable valve mechanism that varies the valve timing of engine valves (intake valves and exhaust valves) of an engine (not shown) by hydraulic pressure generated by a variable displacement oil pump 50. Oil serves as working fluid for the hydraulic VVT 30.

[0016] The variable displacement oil pump 50 is mechanically connected to a crankshaft (not shown) of the engine and is rotated by the rotation of the crankshaft. The variable displacement oil pump 50 of this embodiment is driven by the crankshaft via a gear, but may be driven by a chain or a belt. The variable displacement oil pump 50 is disposed in an oil passage 61 connecting the main gallery 11 and the oil strainer 12, more specifically, between the oil strainer 12 and the oil filter 15. The variable displacement oil pump 50 of this embodiment is a known variable displacement oil pump. The variable displacement oil pump 50 is a trochoidal pump equipped with a control chamber, an inner rotor, and an outer rotor (all not shown) as an example of a mechanism for varying the discharge amount. The OCV 51 controls the hydraulic pressure in the control chamber to adjust the eccentricity of the outer rotor relative to the inner rotor, thereby continuously controlling the discharge amount of oil. Details of an oil pump equipped with such a capacity variable mechanism are disclosed in, for example, JP 2017-190681 A, and therefore a detailed description thereof will be omitted here.

[0017] An oil passage 61a branched off from an oil passage 61 connecting the variable displacement oil pump 50 and the main gallery 11 is connected to the variable displacement oil pump 50. The OCV 51 is provided in this oil passage 61a. The OCV 51 opens and closes under the control of an ECU (Electronic Control Unit) 70, which will be described later. The opening and closing of the OCV 51 changes the oil flow rate (oil pressure) introduced into the control chamber of the variable displacement oil pump 50. This changes the capacity of the variable displacement oil pump 50, and changes the amount of oil discharged. When the amount of oil discharged from the variable displacement oil pump 50 is changed, the discharge pressure also changes accordingly.

[0018] The discharge pressure of the variable displacement oil pump 50 is determined by a combination of the oil temperature and the engine speed (hereinafter referred to as "engine speed").

[0019] In this embodiment, a variable displacement oil pump 50 that changes the discharge pressure by combining it with the OCV 51 is used, but the type of oil pump is not limited to this, and other types of oil pumps that are conventionally known can also be used.

[0020] The ECU 70 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a backup RAM, and other storage devices. The ECU 70 executes calculation processing and various controls based on programs and maps stored in the CPU, the ROM, and other storage devices. The RAM is a memory that temporarily stores the results of calculations performed by the CPU and data input from various sensors, and the backup RAM is a non-volatile memory that stores data that should be saved when the internal combustion engine is stopped, etc.

[0021] In addition to the oil temperature and oil pressure sensor 20, the ECU 70 is electrically connected to a crank angle sensor 21 that detects the rotation angle of the crankshaft, an accelerator opening sensor 22, and a water temperature sensor 23. The engine speed is acquired based on the detection value of the crank angle sensor 21. The accelerator opening can be detected based on the detection value of the accelerator opening sensor 22. The ECU 70 is also electrically connected to the OCV 51, and operates the OCV 51 based on the engine speed. The water temperature sensor 23 detects the temperature of the cooling water circulating in a water jacket provided in a cylinder block or cylinder head (not shown).

[0022] The ECU 70 includes an oil level drop detection unit 70a and an erroneous detection avoidance unit 70b. The erroneous detection avoidance unit 70b corresponds to a control unit that stops the detection of the oil level by the oil level drop detection unit 70a, as will be described later in detail. The ECU 70 detects the drop in the oil level based on the detection value of the oil temperature and oil pressure sensor 20 by functioning as the oil level drop detection unit 70a. The oil level drop detection unit 70a judges whether the oil level in the oil pan 10 is lower than a preset value that judges the shortage of the oil amount based on the value of the discharge pressure detected by the oil temperature and oil pressure sensor 20. Here, the oil level is an evaluation of the amount of oil in the oil pan 10. The preset value that judges the shortage of the oil amount in the oil pan 10 is an oil level drop detection oil pressure value and corresponds to the first oil pressure P1. The ECU 70 stops the detection of the drop in the oil level by functioning as the erroneous detection avoidance unit 70b when there is a possibility of erroneous detection of the oil level. These controls will be described later in detail.

[0023] [Detection device] 1, among the components included in the oil circulation system 100 described above, the oil temperature and oil pressure sensor 20, the crank angle sensor 21, the accelerator opening sensor 22, the water temperature sensor 23, and the ECU 70 are included in a detection device 101. Hereinafter, an example of detection of the oil level by the detection device 101, that is, detection of a shortage of oil in the oil pan 10, will be described with reference to FIGS.

[0024] First, the ECU 70 determines whether or not the engine ignition is turned on in step S1. If the ECU 70 makes a negative determination (No determination) in step S1, it repeats the process of step S1 until it makes a positive determination (Yes determination) in step S1. When the ignition is turned on, the ECU 70 makes a positive determination in step S1 and proceeds to step S2.

[0025] In step S2, the oil level drop detection unit 70a starts the oil level drop detection control. As shown in FIG. 3(A) and FIG. 3(B), the ECU 70 stores a preset first oil pressure (oil level drop detection oil pressure value) P1. When the detection value of the discharge pressure by the oil temperature and oil pressure sensor 20 becomes lower than the first oil pressure P1, the oil level drop detection unit 70a determines that the oil level has dropped and detects a shortage of oil in the oil pan 10. The oil level drop detection unit 70a that detects a shortage of oil turns on a warning light (not shown) to notify the driver that the oil level in the oil pan 10 has dropped. Here, the value of the first oil pressure P1 is set as a value of oil pressure that the oil temperature and oil pressure sensor 20 may indicate when the oil level in the oil pan 10 has dropped to a level where air is sucked in, based on experiments and simulations performed in advance using an actual machine. After the oil level drop detection unit 70a starts the oil level drop detection control in step S2, the ECU 70 proceeds to step S3.

[0026] In step S3, the erroneous detection avoidance unit 70b acquires the engine speed Ne [rpm] and the oil temperature [°C]. The engine speed Ne is calculated and acquired based on the detection value of the crank angle sensor 21. The oil temperature is acquired as the detection value of the oil temperature detected by the oil temperature and oil pressure sensor 20. After acquiring the engine speed Ne and the oil temperature in step S3, the ECU 70 proceeds to step S4.

[0027] In step S4, the erroneous detection avoidance unit 70b determines whether the engine state is within the oil level reduction detection control mask region (hereinafter simply referred to as the "mask region") based on the engine speed Ne and oil temperature acquired in step S3.

[0028] Here, the mask area will be described in detail. Referring to FIG. 5, a hatched mask area is set on a graph with the horizontal axis representing the oil temperature [°C] and the vertical axis representing the engine speed Ne [rpm]. That is, the mask area is defined by the engine speed Ne and the oil temperature. In the mask area, an oil level detection execution oil temperature range is set with an oil temperature of 30°C as the lower limit and an oil temperature of 110°C as the upper limit. Such an oil temperature range is set in consideration of the change in oil viscosity depending on the oil temperature. That is, it is assumed that if the oil temperature is too low, the oil viscosity is too high, and if the oil temperature is too high, the oil viscosity is too low, so that the oil level drop detection cannot be performed appropriately. Therefore, the oil level drop detection control based on the discharge pressure of the variable displacement oil pump 50 is performed within the oil level detection execution oil temperature range.

[0029] The masked region is separated from the region where the oil level drop detection control is executed by the P3 iso-oil pressure line within the oil temperature range for oil level detection. The P3 iso-oil pressure line is drawn by plotting the engine speed at which the discharge pressure becomes the third oil pressure P3 for each oil temperature and connecting these.

[0030] Here, the second oil pressure P2 and the third oil pressure P3 will be explained with reference to Figures 3(A) and 3(B). With reference to Figure 3(A), the third oil pressure P3 is a value obtained by adding the second oil pressure P2 to the first oil pressure P1. The third oil pressure P3 is not a detection value of the oil pressure by the oil temperature / oil pressure sensor 20, but an actual discharge pressure (true value).

[0031] As described above, the first oil pressure P1 is the oil level drop detection oil pressure value. The second oil pressure P2 is an estimate of the error that is assumed to be included in the detection value of the oil pressure by the oil temperature oil pressure sensor 20. In this embodiment, the error estimate is the integrated value of the error caused by noise generated by the surrounding environment of the oil temperature oil pressure sensor 20, the error caused by the change in the output value due to the change in atmospheric pressure, and the error caused by the quality variation of the oil temperature oil pressure sensor 20. In this embodiment, the second oil pressure P2 is set to 30 [kPa]. The breakdown of 30 [kPa] is 5 [kPa] for the error caused by noise, 10 [kPa] for the error caused by the change in atmospheric pressure, and 15 [kPa] for the error caused by the quality variation. If the second oil pressure P2 is set to 30 [kPa] or more, false detection is less likely to occur. Therefore, when the first oil pressure P1 is set to 45 [kPa], the third oil pressure P3 is 75 [kPa]. The error included in the estimated value is not limited to these factors, and may include error based on other factors.

[0032] The third oil pressure P3 is the upper limit oil pressure of the mask region at each oil temperature. As shown in FIG. 3B, when the actual discharge pressure is lower than the third oil pressure P3, if the detection value indicates a value lower by the second oil pressure P2, the detection value indicates a value lower than the first oil pressure P1. In this case, since the actual discharge pressure is higher than the first oil pressure P1, there is no shortage of oil in the oil pan 10, and the oil level does not drop. However, since the detection value is lower than the first oil pressure P1, if no measures are taken, the oil level drop detection unit 70a detects a shortage of oil in the oil pan 10. That is, a false detection occurs. Therefore, in this embodiment, the third oil pressure P3 is set as the upper limit of the mask region. If the actual discharge pressure is higher than the third oil pressure P3, even if the detection value indicates a value lower by the second oil pressure P2, the detection value will not fall below the first oil pressure P1, and a false detection will not occur.

[0033] Next, the relationship between the third oil pressure P3, the engine speed Ne, and the oil temperature will be described with reference to Fig. 4 and Fig. 5. Fig. 4 shows the relationship between the oil temperature [°C] and the oil pressure [kPa] for the engine speed Ne in the range of 600 [rpm] to 2000 [rpm] as an example. The discharge pressure shown in Fig. 4 is the actual discharge pressure. According to Fig. 4, the oil temperature at which the discharge pressure becomes the third oil pressure P3 varies depending on the engine speed Ne. For example, when the engine speed Ne is 700 [rpm], the discharge pressure becomes the third oil pressure P3 when the oil temperature is about 85 [°C], and when the engine speed Ne is 900 [rpm], the discharge pressure becomes the third oil pressure P3 when the oil temperature is about 100 [°C].

[0034] In this way, the P3 isohydraulic line shown in FIG. 5 is drawn by plotting the engine speed Ne and the oil temperature at which the third hydraulic pressure P3 is output in FIG. 4. This sets the mask area. According to FIG. 5, when the oil temperature is 100[°C], the third hydraulic pressure P3 occurs when the engine speed Ne is 900[rpm]. Therefore, if the engine speed Ne is 900[rpm] or less when the oil temperature is 100[°C], the engine state is within the mask area, and the detection of the drop in the oil level by the oil level drop detection unit 70a is stopped. Similarly, when the oil temperature is 90[°C], the third hydraulic pressure P3 occurs when the engine speed Ne is 800[rpm]. Therefore, if the engine speed Ne is 800[rpm] or less when the oil temperature is 90[°C], the engine state is within the mask area, and the detection of the drop in the oil level by the oil level drop detection unit 70a is stopped.

[0035] 4, when the engine speed Ne is 2000 rpm, the discharge pressure of the variable displacement oil pump 50 is higher than the third hydraulic pressure P3 and is not included in the masked region. In other words, the masked region is set to a low engine speed region where the engine speed Ne is low and the discharge pressure may become the third hydraulic pressure P3. As a result, when the engine speed is maintained at the same speed as when the vehicle is traveling, detection of a drop in the oil level is performed.

[0036] Here, detection of a drop in the oil level when the engine is idling will be described with reference to FIG. 5. The target idle speed [rpm] is also shown in FIG. 5. The target idle speed [rpm] is set according to the water temperature. Therefore, the horizontal axis when reading the target idle speed [rpm] from FIG. 5 is the water temperature [°C]. According to FIG. 5, the higher the water temperature [°C], the lower the target idle speed [rpm] is set. Such a target idle speed [rpm] overlaps with the mask area in the range where the water temperature is approximately 50°C or higher. Therefore, when the engine is idling, if the water temperature is 50°C or higher, detection of a drop in the oil level by the oil level drop detection unit 70a is stopped.

[0037] In order to set the mask region shown in Fig. 5, data of the discharge pressure [kPa] for each engine speed Ne as shown in Fig. 4 is collected. At this time, the variable displacement oil pump 50 is set to a full discharge state by the OCV 51. If the mask region is set based on the full discharge state, the variable displacement oil pump 50 will also fall within the mask region when it is in a state other than the full discharge state, so that it is possible to set a mask region that is less likely to cause erroneous detection. In addition, for the second oil pressure P2, by estimating the error range to be large, it is possible to set a mask region that is less likely to cause erroneous detection.

[0038] It should be noted that the oil temperature, oil pressure, and engine speed Ne shown in FIG. 4 and FIG. 5 are all examples.

[0039] Returning to FIG. 2, if the ECU 70 determines in step S4 that the determination is affirmative, the ECU 70 proceeds to step S5, and if the ECU 70 determines in step S4 that the determination is negative, the ECU 70 proceeds to step S6.

[0040] In step S5, the ECU 70, specifically the erroneous detection avoidance unit 70b, stops the oil level drop detection control. If the erroneous detection avoidance unit 70b makes a positive determination in step S4, the oil pressure detection value of the oil temperature and oil pressure sensor 20 may output a value lower by the second oil pressure P2. For this reason, if no measures are taken, it is assumed that the oil level drop detection unit 70a will determine that the oil level has dropped. This determination is a erroneous detection that occurs because the oil pressure detection value of the oil temperature and oil pressure sensor 20 is presented as low due to an error in the detection value, even though the oil level in the oil pan 10 is maintained. Therefore, by stopping the detection of the oil level drop based on the detection value of the oil temperature and oil pressure sensor 20 performed by the oil level drop detection unit 70a in step S5, it is possible to avoid the erroneous detection.

[0041] On the other hand, in step S6, the ECU 70 executes the oil level drop detection control. If the oil level drop detection control is already being executed, step S6 is a process of continuing the oil level drop detection control. On the other hand, if the oil level drop detection control has been stopped via step S5, step S6 is a process of restarting the oil level drop detection control.

[0042] After the process of step S5 is completed and after the process of step S6 is completed, the ECU 70 proceeds to step S7. In step S7, the ECU 70 judges whether the engine ignition has been turned off. If the ECU 70 makes a negative judgment in step S7, it repeats the process from step S3. This allows the execution and stop of the oil level drop detection control to be appropriately switched on and off according to the ever-changing oil temperature and engine speed Ne, making it possible to detect a drop in the oil level while avoiding erroneous detection of a drop in the oil level. On the other hand, if the ECU 70 makes a positive judgment in step S7, it ends the series of processes (END).

[0043] According to this embodiment, the second oil pressure P2, which is an estimated value of the error assumed to be included in the detection value of the oil temperature and oil pressure sensor 20, is incorporated, and detection of a drop in the oil level is stopped when the engine speed is in a mask region set according to the oil temperature. This makes it possible to avoid erroneous detection of a drop in the oil level when the detection value of the oil temperature and oil pressure sensor 20 includes an error and the detection value falls below the oil level drop detection oil pressure value (first oil pressure P1).

[0044] The above-described embodiments are merely examples for implementing the present invention, and the present invention is not limited to these. Various modifications of these embodiments are within the scope of the present invention. Furthermore, it is self-evident from the above description that various other embodiments are possible within the scope of the present invention. [Explanation of symbols]

[0045] 10 Oil pan 11 Main gallery 20 Oil temperature / oil pressure sensor 21 Crank angle sensor 22 Accelerator opening sensor 23 Water temperature sensor 50 Variable Displacement Oil Pump 51 OCV 70 ECU 70a Oil level drop detection unit 70b False detection avoidance unit 100 Oil circulation system 101 Oil level detector

Claims

[Claim 1] a hydraulic pressure sensor that pumps out oil stored in an oil pan provided in an internal combustion engine and detects a discharge pressure of an oil pump, the discharge pressure of which is determined by a combination of a temperature of the oil and a rotation speed of the internal combustion engine; an oil level reduction detection unit that detects an insufficient amount of oil in the oil pan by determining that a detection value of the oil pressure sensor is lower than a first oil pressure value that is set as a value for detecting an insufficiency of the amount of oil in the oil pan; a control unit that stops detection of a drop in the oil level by the oil level drop detection unit when the rotation speed of the internal combustion engine is lower than a rotation speed at which the oil pump outputs a third oil pressure value obtained by adding a second oil pressure value, which is an estimate of an error expected to be included in the detection value of the oil pressure sensor, to the first oil pressure value and which is determined in accordance with the oil temperature, and that stops detection of a drop in the oil level by the oil level drop detection unit when the oil temperature is lower than a predetermined lower limit value and when the oil temperature is higher than a predetermined upper limit value; An oil level detection device for an internal combustion engine.

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