Method for determining deterioration of friction engagement device

Abstract

To provide a method of accurately determining deterioration of a frictional engagement device irrespective of dry type or wet type.SOLUTION: A method of determining deterioration of a frictional engagement device in the present disclosure includes calculating a heat generation amount per unit time generated on the frictional engagement device, calculating a heat radiation amount per unit time from the frictional engagement device, calculating a net heat amount per unit time from the heat generation amount and the heat radiation amount, and calculating an evaluation value which exhibits deterioration degree of the frictional engagement device based on a history of the level of heat amount. The calculation of the heat radiation amount per unit time includes acquiring rotation speed of friction material of the frictional engagement device, acquiring ambient temperature of the friction material, and calculating the heat radiation amount per unit time corresponding to the acquired rotation speed and the acquired ambient temperature based on data which correlates rotation speed of the friction material prepared beforehand and ambient temperature with the heat radiation amount per unit time.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a method for determining deterioration of a friction engagement device.

Background Art

[0002] A friction engagement device is used in an automobile transmission. The friction engagement device, particularly its friction material, deteriorates under the influence of heat. Therefore, in determining the deterioration of the friction engagement device, it is important to estimate the amount of heat to which the friction engagement device has been exposed. The amount of heat to which the friction engagement device has been exposed is the difference between the amount of heat generated in the friction engagement device and the amount of heat dissipated from the friction engagement device. Patent Document 1 discloses estimating the amount of lubricating oil passing around the friction material of the friction engagement device and using the estimated amount of lubricating oil as the amount of heat dissipated from the friction material.

[0003] However, although there is a difference in the amount of heat dissipated between when the friction engagement device is warm and when it is cold, in the method of regarding the amount of lubricating oil as the amount of heat dissipated, the amount of heat dissipated will be the same if the amount of lubricating oil is the same regardless of whether it is warm or cold. Further, the method of regarding the amount of lubricating oil as the amount of heat dissipated cannot be applied to a dry friction engagement device.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present disclosure has been made in view of the above problems. An object of the present disclosure is to provide a method for accurately determining the deterioration of a friction engagement device regardless of whether it is dry or wet.

Means for Solving the Problems

[0006] The present disclosure provides a method for determining deterioration of a friction engagement device for achieving the above object.

[0007] The method for determining the deterioration of the friction engagement device of the present disclosure includes calculating the amount of heat generated per unit time in the friction engagement device, calculating the amount of heat dissipated per unit time from the friction engagement device, calculating the net amount of heat per unit time from the amount of heat generated and the amount of heat dissipated, and calculating an evaluation value indicating the degree of deterioration of the friction engagement device based on the history of the level of the amount of heat. Calculating the amount of heat dissipated includes obtaining the rotational speed of the friction material of the friction engagement device, obtaining the ambient temperature of the friction material, and calculating the amount of heat dissipated per unit time corresponding to the obtained rotational speed and the obtained ambient temperature based on data associating the rotational speed and the ambient temperature of the friction material prepared in advance with the amount of heat dissipated per unit time.

Advantages of the Invention

[0008] According to the method for determining the deterioration of the friction engagement device of the present disclosure, by using data associating the rotational speed of the friction material and the ambient temperature with the amount of heat dissipated per unit time, the amount of heat dissipated per unit time can be accurately calculated regardless of whether it is dry or wet, and regardless of whether it is during warm-up or cold. By calculating the net amount of heat per unit time of the friction engagement device from the accurately calculated amount of heat dissipated and calculating an evaluation value indicating the degree of deterioration of the friction engagement device based on the history of the level of the amount of heat, the deterioration of the friction engagement device can be accurately determined.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of a method for determining deterioration of a friction engagement device of the present disclosure will be described with reference to the drawings. However, when referring to numbers such as the number, quantity, amount, range, etc. of each element in the embodiments shown below, unless otherwise specified or clearly specified to that number in principle, the idea related to the present disclosure is not limited to the mentioned number. Further, the structures and the like described in the embodiments shown below are not necessarily essential to the idea related to the present disclosure, unless otherwise specified or clearly specified to that in principle.

[0011] The method for determining deterioration of the friction engagement device according to this embodiment is a method automatically implemented by a computer. In this embodiment, it is assumed that the friction engagement device is mounted on the drive system of an automobile. When the friction engagement device is mounted on the drive system of an automobile, the deterioration determination method is implemented by an ECU that controls the drive system. More specifically, a plurality of instructions stored in the program memory of the ECU are executed by a processor, so that the ECU functions as a deterioration determination device for the friction engagement device, and the deterioration determination method is implemented by the ECU.

[0012] FIG. 1 is a flowchart showing a method for determining deterioration of a friction engagement device according to this embodiment. The deterioration determination method shown in this flowchart is applicable to both a dry friction engagement device and a wet friction engagement device. However, due to the difference in the structure between the dry friction engagement device and the wet friction engagement device, there are differences in the detailed calculations in some steps included in the deterioration determination method. The differences will be described in detail in the corresponding steps.

[0013] In step S01, it is determined whether the engagement of the friction engagement device has started. Until the engagement starts, the determination in step S01 is repeatedly performed.

[0014] In step S02, the amount of heat generated per unit time in the friction engagement device is calculated. The amount of heat calculated here is the net amount of heat obtained by subtracting the amount of heat dissipated per unit time from the amount of heat generated per unit time. The following formula is used for calculating the amount of heat.

Equation

[0015] In the above formula, the first term on the right side is the amount of heat generated per unit time, and the second term is the amount of heat dissipated per unit time. Q is the net amount of heat per unit time. ΔN is the difference between the driving-side rotational speed and the driven-side rotational speed. P is the fastening hydraulic pressure, and A is the area on which the hydraulic pressure acts. P×A is the pressing force between the rotating bodies of the friction engagement device. K is a conversion coefficient. And the heat dissipation MAP is a map of data associating the rotational speed and ambient temperature of the friction material, which is the object of life consideration, with the amount of heat dissipated per unit time.

[0016] The above formula is a general formula for calculating the amount of heat applicable to both dry friction engagement devices and wet friction engagement devices. However, in actual application to dry friction engagement devices and wet friction engagement devices, the calculation of the amount of heat is performed as follows considering the difference in structure.

[0017] <For the case of a dry friction engagement device> The difference between the engine rotational speed and the transmission input rotational speed is input to ΔN in the first term on the right side of the above formula. Among the clutch disc and the flywheel constituting the clutch, the clutch disc is fixed to the transmission input, and the flywheel is fixed to the output shaft of the engine.

[0018] In P×N, which is the first term on the right side of the above formula, the diaphragm spring load is input. The diaphragm spring (diaphragm spring) is used to pressurize the clutch disc onto the clutch wheel. The diaphragm spring load is determined by the stroke of the clutch release bearing. Here, FIG. 2 is a graph showing the relationship between the stroke of the clutch release bearing and the diaphragm spring load. When the clutch pedal is depressed from the state where the clutch is fully engaged, the clutch release bearing moves and presses the inside of the diaphragm spring, and the force with which the clutch cover attached to the diaphragm spring presses the clutch disc is released. As a result, the clutch disc and the flywheel are disengaged and the clutch is released. The operation when the clutch is engaged is the reverse of this operation.

[0019] In the heat dissipation amount MAP, which is the second term on the right side of the above formula, for the rotational speed of the friction material among the two parameters, the rotational speed of the transmission input is input. The friction material is attached to the clutch disc that rotates integrally with the transmission input. For the ambient temperature of the friction material, which is the other parameter of the heat dissipation amount MAP, the atmospheric temperature measured by the intake air temperature sensor or the outside air temperature sensor is input. That is, in the case of a dry friction engagement device, the atmospheric temperature is used as the temperature representing the ambient temperature of the friction material. FIG. 3 is a graph showing the relationship between the rotational speed of the transmission input, the atmospheric temperature, and the heat dissipation amount. The relationship shown in such a graph is mapped and stored in the ECU.

[0020] <In the case of a wet friction engagement device> In ΔN, which is the first term on the right side of the above formula, the difference between the rotational speed of the drive plate and the rotational speed of the driven plate is input. The drive plate and the driven plate are alternately stacked multiple times in the axial direction to form a multi-plate clutch.

[0021] In P, which is the first term on the right side of the above formula, the clutch pressure is input. The clutch pressure may be an indicated value or a measured value by a hydraulic pressure sensor. In A, which is the first term on the right side of the above formula, the effective area of the piston actuated by hydraulic pressure is input.

[0022] In the heat dissipation amount MAP of the second term on the right side of the above formula, among the two parameters, the rotational speed of the friction material is the rotational speed of the drive plate, which is input. The friction material is attached to each drive plate. As for the ambient temperature of the friction material, which is the other parameter of the heat dissipation amount MAP, the lubricating oil temperature (ATF temperature) measured by the oil temperature sensor is input. That is, in the case of a wet friction engagement device, the lubricating oil temperature is used as the temperature representing the ambient temperature of the friction material. FIG. 4 is a graph showing the relationship between the rotational speed of the drive plate, the lubricating oil temperature, and the heat dissipation amount. The relationship shown in such a graph is mapped and stored in the ECU.

[0023] Returning again to the flowchart of FIG. 1, the description of the deterioration determination method will be continued. In step S03, it is determined whether the engagement of the friction engagement device has ended. Until the engagement ends, the heat amount calculation in step S02 and the determination in step S03 are repeatedly performed.

[0024] When the engagement ends, the heat amount is determined in step S04. Subsequently, in step S05, it is determined which heat amount category the heat amount determined in step S02 belongs to among a plurality of preset heat amount categories. Then, the frequency of the corresponding heat amount category is incremented. Here, FIG. 5 is a graph showing an example of the frequency and the limit number for each heat amount category. The limit number is the frequency at which a malfunction may occur if the number of repetitions exceeds this value, and it is predetermined for each category. For example, in FIG. 5, H2 is the frequency in category A, and G2 is the limit number in category A. When the heat amount determined in step S04 belongs to category A, the value of H2 is incremented. The frequency for each heat amount category is stored in the memory of the ECU and updated each time it is incremented. The limit number for each heat amount category is stored as a fixed value in the memory of the ECU.

[0025] Returning to the flowchart of FIG. 1, the description of the deterioration determination method will be continued. In step S06, the damage degree is calculated by the following formula based on the frequency and the limit number of each heat quantity section. The damage degree is an evaluation value indicating the degree of deterioration of the friction engagement device. According to the following formula, it is possible to evaluate the degree of deterioration considering the history of the heat quantity level.

Equation

[0026] In step S07, it is determined whether the damage degree calculated in step S06 exceeds a predetermined threshold value α. The threshold value α is the damage degree at which it can be determined that the friction engagement device has reached the end of its life and is set according to the specification. Until the damage degree exceeds the threshold value α, steps S01 to S07 are repeatedly executed. While the engagement operation of the friction engagement device is repeatedly executed, the value of the damage degree gradually increases and eventually exceeds the threshold value α.

[0027] When the damage degree exceeds the threshold value α, in step S08, a notification that the friction engagement device has reached the end of its life is carried out. Examples of the notification method include a method of lighting a warning lamp displayed on the instrument panel, a method of outputting an error code by an in-vehicle diagnostic device, etc. Further, when the vehicle is remotely monitored, the remote monitoring center may be notified that the friction engagement device has reached the end of its life.

[0028] As described above, according to the deterioration determination method of the friction engagement device according to the present embodiment, the heat dissipation amount is calculated using the data associating the rotational speed of the friction material and the ambient temperature with the heat dissipation amount per unit time. According to this, it is possible to accurately calculate the heat dissipation amount per unit time regardless of whether the friction engagement device is dry or wet, and also regardless of whether it is during warm-up or cold.

[0029] According to the method for determining deterioration of the friction engagement device according to the present embodiment, the net heat amount per unit time of the friction engagement device is calculated from the accurately calculated heat dissipation amount. Then, the damage degree indicating the degree of deterioration of the friction engagement device is calculated based on the frequency of each heat amount section showing the history of the heat amount level. By performing the deterioration determination of the friction engagement device based on the damage degree, it is possible to accurately determine whether the friction engagement device has reached the end of its life.

Claims

【Claim 1】 calculating the amount of heat generated per unit time in the friction engagement device; calculating the amount of heat dissipated per unit time from the friction engagement device; calculating the net amount of heat per unit time from the amount of heat generated and the amount of heat dissipated; calculating an evaluation value indicating the degree of deterioration of the friction engagement device based on the history of the level of the amount of heat; and calculating the amount of heat dissipated includes acquiring the rotational speed of the friction material of the friction engagement device; acquiring the ambient temperature of the friction material; and selecting the amount of heat dissipated per unit time corresponding to the acquired rotational speed and the acquired ambient temperature from a heat dissipation MAP in which data associating the rotational speed and the ambient temperature of the friction material with the amount of heat dissipated per unit time, which is prepared in advance, is mapped A method for determining deterioration of a friction engagement device, characterized by the above.

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