Load estimation method

Abstract

To provide a load estimation method capable of easily estimating a heat load of an oil pump.SOLUTION: A load estimating method counts the number of starts of an oil pump when the viscosity of oil discharged from the oil pump is equal to or higher than a threshold or when the temperature of the oil is equal to or lower than the threshold, and estimates the thermal load of the oil pump based on the counted number of starts.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a load estimation method. [Background technology]

[0002] For example, Patent Document 1 describes that the operating time of the oil pump is corrected according to the viscosity of the oil so as to maintain a constant flow rate in the oil circulation path that passes through the oil tank, oil pan, and engine. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 6-288215 Summary of the Invention [Problem to be solved by the invention]

[0004] The oil pump generates heat when the motor is energized during operation, but there is no easy way to estimate the heat load, making it difficult to properly understand the condition of the oil pump.

[0005] SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has an object to provide a load estimation method that can easily estimate the thermal load of an oil pump. [Means for solving the problem]

[0006] The load estimation method of the present invention is a method of counting the number of times the oil pump is started when the viscosity of the oil discharged by the oil pump is above a threshold value or when the temperature of the oil is below a threshold value, and estimating the thermal load of the oil pump based on the counted number of times the oil is started.

[0007] In the above load estimation method, the viscosity or the temperature may be measured before the oil pump is started.

[0008] In the above load estimation method, the viscosity or the temperature may be measured at a position downstream of the oil pump in the oil flow path.

[0009] In the load estimation method, the number of activations may be counted for each period from when an ignition switch of a vehicle equipped with the oil pump is turned on to when it is turned off.

[0010] In the load estimation method, the thermal load may be estimated based on a frequency distribution of the number of activations for each period. [Effects of the Invention]

[0011] According to the present invention, the thermal load of the oil pump can be easily estimated. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a configuration diagram showing an example of a vehicle system. [Figure 2] FIG. 2 is a diagram illustrating an example of the activation count table. [Figure 3] FIG. 3 is a flowchart showing an example of the operation of a pump ECU (Electronic Control Unit). [Figure 4] FIG. 4 is a configuration diagram showing another example of a vehicle system. [Figure 5] FIG. 5 is a flowchart showing another example of the operation of the pump ECU. DETAILED DESCRIPTION OF THE INVENTION

[0013] (Vehicle system configuration) 1 is a configuration diagram showing an example of a vehicle system S. The vehicle system S is mounted on a vehicle such as a hybrid vehicle or an electric vehicle, and includes a pump ECU 1, an electric oil pump 2, a vehicle control device 3, a vehicle drive mechanism 4, an oil circulation flow path 5, a viscosity sensor 6, and an ignition switch 7.

[0014] The vehicle drive mechanism 4 includes various devices and parts (not shown), such as an engine, a motor, a transmission, and gears, for driving the vehicle. Oil is supplied to at least a portion of the vehicle drive mechanism 4 from the oil pump 2 via a circulation flow path 5. This lubricates and cools at least a portion of the vehicle drive mechanism 4.

[0015] The circulation flow path 5 is an example of an oil flow path. The circulation flow path 5 includes a supply path 50, a discharge path 51, a suction path 52, and an oil reservoir tank 53. The supply path 50 is disposed downstream of the oil pump 2, and the oil discharged from the oil pump 2 flows through the supply path 50 and is supplied to the vehicle drive mechanism 4.

[0016] The discharge passage 51 is disposed downstream of the vehicle drive mechanism 4, and oil used for lubricating and cooling at least a part of the vehicle drive mechanism 4 is discharged from the discharge passage 51. The downstream end of the discharge passage 51 is connected to an oil reservoir tank 53. The oil reservoir tank 53 is, for example, an oil pan, and stores the oil discharged from the discharge passage 51.

[0017] Intake passage 52 is disposed upstream of oil pump 2, and oil pump 2 draws oil through intake passage 52. In this manner, oil circulates between oil pump 2 and vehicle drive mechanism 4 via circulation passage 5.

[0018] A viscosity sensor 6 that detects the viscosity of the oil is provided in the intake passage 52. The viscosity sensor 6 detects the viscosity of the oil at a position upstream of the oil pump 2 in the circulation passage 5 and outputs the detected value to the pump ECU 1.

[0019] The oil pump 2 has a drive circuit 20 and a motor 21. The oil pump 2 draws oil from a suction passage 52 by rotating the motor 21 and discharges it into a supply passage 50. The drive circuit 20 includes an inverter and the like, and drives the motor 21. The drive circuit 20 is controlled by a pump ECU 1. The oil pump 2 and the vehicle drive mechanism 4 operate when an ignition switch 7 is on, and stop operating when the ignition switch 7 is off.

[0020] The pump ECU 1 is an example of a computer and includes a processor 10 such as a CPU (Central Processing Unit) and a memory 11 such as a ROM (Read Only Memory) and a RAM (Random Access Memory). The processor 10 executes a series of processes in a predetermined sequence according to a program stored in the memory 11. The pump ECU 1 may be mounted in the same housing as the vehicle control device 3. The pump ECU 1 may also share the CPU, ROM, and RAM of the vehicle control device 3 for processing.

[0021] The processor 10 starts and stops the oil pump 2 in accordance with a request from the vehicle control device 3. The vehicle control device 3 calculates the required torque necessary for the vehicle in response to the driver's operation, and controls the output torque of the engine based on the required torque.

[0022] The processor 10 outputs a start signal to the drive circuit 20 of the oil pump 2. The processor 10 also outputs a target rotation speed of the motor 21 of the oil pump 2 together with the start signal to the drive circuit 20. The drive circuit 20 drives the motor 21 in response to the start signal so that the rotation speed of the motor 21 becomes the target rotation speed. This activates the motor 21 and causes the oil pump 2 to discharge oil.

[0023] Each time the oil pump 2 is started, the drive circuit 20 and the motor 21 generate heat due to the current flowing through them. At this time, the higher the viscosity of the oil in the circulation flow path 5, the greater the output torque of the motor 21, and therefore the greater the amount of heat generated. This generates a thermal load on the oil pump 2. If the oil pump 2 is started repeatedly within a short period of time, the drive circuit 20 and the motor 21 will generate heat again before they are sufficiently cooled, and the thermal load will accumulate.

[0024] For example, if the oil in the oil pump 2 is highly viscous, the rotation speed of the motor 21 may not reach the target rotation speed. In this case, the pump ECU 1 instructs the oil pump 2 to retry the start-up process. At this time, the pump ECU 1 outputs a start signal to the oil pump 2 again, so the start-up process is repeated many times. This causes the oil pump 2 to start continuously, resulting in a significant increase in thermal load.

[0025] Therefore, when the viscosity of the oil discharged by the oil pump 2 is equal to or greater than a threshold value, the processor 10 counts the number of times the oil pump 2 is started and estimates the thermal load of the oil pump 2 based on the counted number of times the oil pump 2 is started. For example, the processor 10 records the number of times the oil pump 2 is started in a start count table (TBL) 110 stored in the memory 11 and estimates the thermal load from the start count TBL 110. This load estimation method makes it easier to estimate the thermal load than, for example, when calculating the thermal load by providing multiple sensors that detect heat quantity inside the oil pump 2.

[0026] The processor 10 measures the viscosity before starting the oil pump 2. Therefore, compared to, for example, a case where the processor 10 measures the viscosity of oil stirred by starting the oil pump 2, the processor 10 can more reliably determine that the oil pump 2 will be started when the oil has a high viscosity.

[0027] The processor 10 measures the viscosity at a position downstream of the oil pump 2 in the oil circulation flow path 5 using the viscosity sensor 6. Therefore, compared to measuring the viscosity at a position upstream of the oil pump 2, for example, the processor 10 can more reliably determine that the oil pump 2 will be started when the oil is highly viscous, by using the viscosity at the destination where the oil is discharged and pushed by the oil pump 2, compared to measuring the viscosity at a position upstream of the oil pump 2, for example. Note that the viscosity sensor 6 is not limited to a downstream position, and may be provided at a position upstream of the oil pump 2, or at a midstream position on the supply path 50, or in the oil reservoir tank 53.

[0028] The processor 10 counts the number of activations during the period from when the ignition switch 7 is turned on to when it is turned off, i.e., for each trip. Therefore, the processor 10 can count the thermal load of the oil pump 2 when the ignition switch 7 is not turned off and the oil pump 2 is continuously operating as the number of activations. Therefore, compared to, for example, counting the number of activations per predetermined time, it is possible to estimate the thermal load with high accuracy. Note that the processor 10 is not limited to counting the number of activations per trip, and may also count the number of activations per predetermined time.

[0029] (Example of heat load estimation) 2 is a diagram showing an example of the start count table 110. The start count TBL 110 registers the start count and operation frequency for each trip. For example, the operation frequency when the start count is 1 is N1 times, the operation frequency when the start count is 2 is N2 times, and the operation frequency when the start count is i times is Ni times (N1, N2, Ni, i: positive integers).

[0030] Lt=K1×W1×N1+K2×W2×N2+···+Ki×Wi×Ni···(1)

[0031] The processor 10 calculates the thermal load Lt of the oil pump 2 based on the start count TBL110, for example, from the above formula (1). In formula (1), K1, K2,...,Ki are the temperature coefficients of the oil when the start count is 1, 2,...,i, respectively. Also, in formula (1), W1, W2,...,Wi are the weighting coefficients when the start count is 1, 2,...,i, respectively. The temperature coefficients K1, K2,...,Ki are the amount of heat increase corresponding to the start count, and the weighting coefficients are coefficients related to the heat increase corresponding to the structural design of the oil pump 2.

[0032] In this way, the processor 10 estimates the thermal load based on the frequency distribution of the number of activations per trip. Therefore, the above-described load estimation method of the pump ECU 1 allows the thermal load to be estimated with high accuracy according to the amount of heat generated by continuous activation of the oil pump 2 per trip. The thermal load estimated in this way can be used to notify the replacement time or lifespan of the oil pump 2, or to control the drive of the oil pump 2.

[0033] (Pump ECU operation) 3 is a flowchart showing an example of the operation of the pump ECU 1. This operation is repeatedly performed, for example, by the processor 10 executing a program in the memory 11. Note that this operation is an example of a load estimation method.

[0034] First, the pump ECU 1 determines whether or not the ignition switch (IG-SW) 7 is on (step St1). If the ignition switch 7 is off (No in step St1), this operation ends.

[0035] If the ignition switch 7 is on (Yes in step St1), the number of activations i in the new trip is set to 0 (step St2). Next, the pump ECU 1 determines whether or not there is a start-up request for the oil pump 2 from the vehicle control device 3 (step St3). If there is no start-up request (No in step St3), the operation of step St3 is executed again.

[0036] Also, when there is a startup request (Yes in step St3), the pump ECU 1 measures the viscosity of the oil using the viscosity sensor 6 (step St4). Next, the pump ECU 1 starts the oil pump 2 by outputting a startup instruction to the drive circuit 20 (step St5). Thus, the viscosity measurement is performed before starting the oil pump 2.

[0037] Next, the pump ECU 1 compares the above-mentioned viscosity measured by the viscosity sensor 6 with a threshold value (step St6). When viscosity ≧ threshold value holds (Yes in step St6), the pump ECU 1 adds 1 to the startup count i (step St7). Also, when viscosity < threshold value holds (No in step St6), the operation of step St7 is not executed. Thus, the pump ECU 1 counts the startup count i of the oil pump 2 when the oil has high viscosity. The startup count i is incremented at the time of output of the startup instruction. Note that the viscosity threshold value is determined according to the design, experiment, or simulation results of the oil pump 2, etc.

[0038] Next, the pump ECU 1 compares the rotation speed of the motor 21 notified from the drive circuit with a predetermined value K (step St8). When rotation speed < K holds (No in step St8), each operation after step St4 is executed again.

[0039] Also, when rotation speed ≧ K holds (Yes in step St8), the pump ECU 1 determines whether the ignition switch 7 is off (step St9). When the ignition switch 7 is on (No in step St9), each operation after step St3 is executed again.

[0040] [[ID=…]] Also, when the ignition switch 7 is off (Yes in step St9), the pump ECU 1 updates the startup count TBL110 (step St10) and calculates the heat load (step St11). Thus, the pump ECU 1 operates.

[0041] (Other embodiments) In the above embodiment, the pump ECU 1 measures the viscosity of the oil using the viscosity sensor 6, but this is not limiting. Since the viscosity of oil changes depending on the temperature, the pump ECU 1 may use a temperature sensor instead of the viscosity sensor 6.

[0042] FIG. 4 is a configuration diagram showing another example of the vehicle system S. In FIG. 4, components common to those in FIG. 1 are assigned the same reference numerals, and their description will be omitted. In this example, a temperature sensor 6a is provided in the intake passage 52 instead of the viscosity sensor 6. The temperature sensor 6a detects the temperature of the oil flowing through the intake passage 52. Like the viscosity sensor 6, the temperature sensor 6a is preferably provided downstream of the oil pump 2, but is not limited to this. For example, the temperature sensor 6a may be provided upstream of the oil pump 2, or midstream on the supply passage 50, or in the oil reservoir tank 53. The temperature sensor 6a outputs a detected value to the pump ECU 1.

[0043] Fig. 5 is a flowchart showing another example of the operation of the pump ECU 1. In Fig. 4, the same operations as those in Fig. 3 are denoted by the same reference numerals, and the description thereof will be omitted.

[0044] If there is a start request (Yes in step St3), the pump ECU 1 measures the oil temperature using the temperature sensor 6a (step St4a). After the oil pump 2 is started (step St5), the pump ECU 1 compares the temperature measured by the temperature sensor 6a with a threshold value (step St6a). If the temperature is less than or equal to the threshold value (Yes in step St6a), the pump ECU 1 adds 1 to the start count i (step St7). If the temperature is greater than the threshold value (No in step St6a), the operation of step St7 is not performed.

[0045] In this way, the pump ECU 1 counts the number of times the oil pump 2 is started when the oil temperature is equal to or lower than the threshold value. A characteristic of oil is that the lower the temperature, the higher the viscosity. Therefore, the pump ECU 1 can also determine that the oil has high viscosity by determining the temperature as described above. The temperature threshold is determined based on the design of the oil pump 2, experimental results, or simulation results. While the load estimation method of this example is executed by the pump ECU 1, it may instead be executed by hardware such as an ASIC (Application Specific Integrated Circuit). While the above examples have been given of the vehicle system S equipped with the viscosity sensor 6 or the temperature sensor 6a, the vehicle system S may be equipped with only one of the viscosity sensor 6 and the temperature sensor 6a because the viscosity of oil exhibits a characteristic that changes uniquely depending on the temperature.

[0046] The above-described embodiment is a preferred example of the present invention, but the present invention is not limited to this and can be modified in various ways without departing from the spirit of the present invention. [Explanation of symbols]

[0047] 1 Pump ECU, 2 Oil pump, 5 Circulation flow path (flow path), 6 Viscosity sensor, 6a Temperature sensor, 7 Ignition switch, 10 Processor, 11 Memory, 110 Startup count table

Claims

1. Counting the number of times the oil pump is started when the viscosity of the oil discharged by the oil pump is equal to or greater than a threshold value or when the temperature of the oil is equal to or less than a threshold value; a thermal load of the oil pump is estimated based on the counted number of times the oil pump is started; Load estimation method.

2. measuring the viscosity or the temperature before starting the oil pump; The load estimation method according to claim 1 .

3. measuring the viscosity or the temperature at a position downstream of the oil pump in the oil flow path; The load estimation method according to claim 2 .

4. counting the number of activations for each period from when an ignition switch of a vehicle equipped with the oil pump is turned on to when it is turned off; A load estimation method according to any one of claims 1 to 3.

5. estimating the thermal load based on a frequency distribution of the number of startups for each period; The load estimation method according to claim 4 .

Images