DIAGNOSTIC DEVICE FOR A FUEL PUMP

Abstract

Diagnostic device (10) for a fuel pump (30) mounted in a fuel supply system (20), wherein the fuel pump (30) has a pump chamber (38), an impeller (44) received in the pump chamber (38) and a motor (41) for rotating the impeller (44), and the fuel pump (30) is configured to draw fuel from a fuel tank (41) and to discharge the fuel by rotating the impeller (44), wherein the diagnostic device (10) comprises: a pump control section (13) designed to actuate the fuel pump (30); and a pump diagnostic section (12) which is designed to diagnose the condition of the fuel pump (30) based on the following: a correlation between a pump speed (Np), which is a speed of the engine (41), and a fuel pressure (QP), which is the pressure of the fuel delivered by the fuel pump (30), and an initial correlation, which is the correlation in an initial operating period from the moment the fuel pump (30) is first supplied with energy until the moment a specified period has elapsed.

Description

BACKGROUND1. Area

[0001] The present disclosure relates to a diagnostic device for a fuel pump. 2. Description of the state of the art

[0002] The impeller of a fuel pump draws fuel from a fuel tank and is exposed to the fuel. This causes the impeller to gradually swell, reducing the clearance between the impeller and the inner wall of a pump chamber housing the impeller. In this case, the impeller and the inner wall of the pump chamber may come into contact with each other. Such contact can impede the rotation of the impeller and stop the fuel pump.

[0003] As disclosed in WO 2013 / 054412 A1, a fuel pump includes an impeller and a pump chamber, each having a shape determined based on an estimated impeller swelling amount to ensure a clearance that allows the impeller to swell without obstruction.

[0004] If the fuel pump stops due to impeller swelling, the fuel supply is blocked. Therefore, it is preferable to detect impeller swelling before the fuel pump stops.

[0005] In the fuel pump of the aforementioned document, the clearance is simply adjusted based on the estimated impeller swelling amount. In other words, the fuel pump is not designed to determine the fuel pump's condition during operation. However, to limit fuel pump stoppage due to impeller swelling, the fuel pump's condition must be determined during operation. Methods and systems for diagnosing a fuel pump mounted in a fuel supply system are also the subject of DE 103 42 268 B4 and DE 10 2017 201 278 A1. SUMMARY

[0006] Based on the prior art, the object of the invention is to further develop the diagnosis of a fuel pump in such a way that the disadvantages described above can be avoided. This object is achieved by the diagnostic device according to claim 1; advantageous further developments are the subject of the subclaims.

[0007] According to one aspect, a diagnostic device for a fuel pump mounted in a fuel supply system is provided. The fuel pump has a pump chamber, an impeller housed in the pump chamber, and a motor for rotating the impeller. The fuel pump is configured to draw fuel from a fuel tank and discharge the fuel through the rotation of the impeller. The diagnostic device includes a pump control section configured to actuate the fuel pump and a pump diagnostic section configured to diagnose a condition of the fuel pump.The pump diagnosis section is configured to diagnose a condition of the fuel pump based on: a correlation between a pump speed, which is a speed of the engine, and the fuel pressure, which is the pressure of the fuel discharged from the fuel pump; and an initial correlation, which is the correlation in an initial operating period from the moment the fuel pump is first energized until a specified period has elapsed.

[0008] Further features and aspects will become apparent from the following detailed description, drawings and claims. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram showing a diagnostic device for a fuel pump according to an embodiment and a fuel supply system. Fig. 2 is a cross-sectional view schematically showing an impeller of the fuel pump and the vicinity of the impeller in the fuel supply system of Fig. 1 shows. Fig. 3 is a flowchart showing a process performed by the diagnostic device of Fig. 1 is executed. Fig. 4 is a graph showing the relationships between the pump speed and the fuel pressure in the respective states of the fuel pump of Fig. 1 shows. Fig. Figure 5 is a graph showing the relationship between pump speed and axial clearance. Fig. 6 is a flowchart showing a diagnostic procedure performed by the diagnostic device of Fig. 1 is executed. Fig. 7 is a diagram relating to a diagnostic method performed by a diagnostic device according to a modification. Fig. 8 is a diagram relating to a diagnostic method performed by a diagnostic device according to another modification. Fig. Fig. 9 is a diagram relating to the diagnostic method performed by the diagnostic apparatus according to the modification of Fig. 8 is executed. Fig. 10 is a diagram relating to a diagnostic method performed by a diagnostic device according to another modification. Fig. Fig. 11 is a flowchart showing a diagnostic procedure performed by the diagnostic apparatus according to the modification of Fig. 10 is executed.

[0009] In the drawings and the detailed description, the same reference numerals refer to the same elements. The drawings are not necessarily to scale, and the relative size, proportions, and representation of elements in the drawings may be exaggerated for clarity, illustration, and convenience. DETAILED DESCRIPTION

[0010] This description provides a comprehensive understanding of the described methods, devices, and / or systems. Modifications and equivalents of the described methods, devices, and / or systems will readily occur to those skilled in the art. The sequences of operations are exemplary and may be changed as would be apparent to those skilled in the art, except for operations that necessarily occur in a particular order. Descriptions of functions and structures known to those skilled in the art may be omitted.

[0011] Example embodiments may take various forms and are not limited to the described examples. However, the described examples are thoroughly and completely set forth and will fully convey this disclosure to those of ordinary skill in the art.

[0012] A diagnostic device for a fuel pump according to an embodiment will now be described with reference to Fig. 1 to 6.

[0013] Fig. 1 shows a control unit 10, which is a diagnostic device for a fuel pump 30, and a fuel supply system 20. The fuel pump 30 is included in the fuel supply system 20. The fuel supply system 20 includes a fuel tank 21, the fuel pump 30, and fuel injectors 26.

[0014] The fuel is stored in the fuel tank 21 and delivered into a supply line 22 by means of the fuel pump 30. A check valve 23 is arranged in the supply line 22. A pressure regulator 24 is arranged on the downstream side of the check valve 23.

[0015] The supply line 22 is connected to a discharge pipe 25. The discharge pipe 25 has the fuel injection valves 26. A fuel pressure sensor 27 is arranged on the discharge pipe 25.

[0016] The fuel pump 30 comprises a tubular housing 31. A discharge section 39 for discharging fuel is arranged within the housing 31. The supply line 22 is connected to the discharge section 39. The housing 31 has an opening in an end section on the side opposite the discharge section 39. A cover 32 is attached to the opening. The cover 32 has an inlet port 33 through which fuel is drawn from the fuel tank 21.

[0017] The fuel pump 30 includes a motor 41. The motor 41 is housed in the housing 31. A housing 35 is attached to the inside of the housing 31 and has a bearing 43. The bearing 43 supports a shaft 42 of the motor 41. The housing 35 has an outlet passage 36 extending through the housing 35 in the axial direction of the shaft 42.

[0018] A plastic impeller 44 is attached to the shaft 42 of the motor 41. The impeller 44 is housed in a pump chamber 38 defined by the housing 35 and the cover 32. The impeller 44 is shaped like a disc and has first and second surfaces. The first surface faces the cover 32, and the second surface faces the housing 35. The impeller 44 includes a plurality of inlet-side fins 45. The inlet-side fins 45 are formed on the first surface and arranged in the circumferential direction. The impeller 44 includes a plurality of outlet-side fins 46. The outlet-side fins 46 are formed on the second surface and arranged in the circumferential direction. The impeller 44 has a communication hole (not shown) extending through the impeller 44 in the axial direction of the shaft 42.

[0019] The surface of the cover 32, which defines the pump chamber 38, has a first groove 34. The first groove 34 is C-shaped and communicates with the inlet port 33. The surface of the housing 35, which also defines the pump chamber 38, has a second groove 37. The second groove 37 is C-shaped and communicates with the outlet channel 36.

[0020] When the motor 41 is driven to rotate the impeller 44, the inlet-side fins 45 and the outlet-side fins 46 generate swirling flows in the first groove 34 and the second groove 37, respectively, in the fuel pump 30. As the fuel is swirled in the space between the impeller 44 and the cover 32, the pressure of the fuel increases, forcing some of the fuel out and into the space between the impeller 44 and the housing 35. The pressure of this fuel is increased by the swirling flow in the second groove 37. The fuel is then forced out of the second groove 37 through the outlet passage 36 and discharged from the discharge portion 39.

[0021] With reference to Fig. 2, clearances are formed between the impeller 44 and the cover 32 and between the impeller 44 and the housing 35. The drawing schematically shows the clearances in an enlarged manner. The axis C of the shaft 42 is also included in the drawing. The clearance (CL) between the impeller 44 and the housing 35 in the extending direction of the axis C is defined as a first clearance CLa. The clearance between the impeller 44 and the cover 32 in the extending direction of the axis C is defined as a second clearance CLb. The sum of the first clearance CLa and the second clearance CLb is defined as a clearance CL. The clearance CL is an axial clearance in the extending direction of the axis C.

[0022] The size of the clearance CL significantly influences the delivery performance of the fuel pump 30. Since the impeller 44 is exposed to the fuel, the impeller 44 swells and irreversibly increases its volume. This swelling of the impeller 44 reduces the clearance CL, thereby increasing the delivery pressure. However, the reduced clearance CL causes the impeller 44 to touch an inner wall of the pump chamber 38, which impedes the rotation of the impeller 44. This can ultimately lead to the fuel pump 30 stopping. In addition, foreign matter can be drawn into the pump chamber 38 and cause wear on the inner wall of the pump chamber 38 or the impeller 44. This increases the clearance CL, thereby reducing the delivery pressure.

[0023] As in Fig. As illustrated in Figure 1, the control unit 10 is mounted in a vehicle in which the fuel supply system 20 is located. Various sensors are connected to the control unit 10. The control unit 10 detects the fuel pressure QP in the discharge pipe 25 based on a detection signal from the fuel pressure sensor 27, which is one example of the sensors.

[0024] The control unit 10 includes an ECU 11 as a controller for the vehicle and an FPC 13 as a pump control section (a pump control circuit) for operating the fuel pump 30. The control unit 10, or each of the ECU 11 and the FPC 13 included in the control unit 10, may be processing circuits including: 1) one or more processors operating according to a computer program (software); 2) one or more dedicated hardware circuits such as application-specific integrated circuits (ASICs) that execute at least some of various processes; or 3) a combination thereof. The processor includes a CPU and memories such as RAM and ROM. The memories store program codes or instructions configured to cause the CPU to execute various processes.Storage, or computer-readable media, includes all types of media that can be accessed by general-purpose and special-purpose computers.

[0025] The ECU 11 includes a pump diagnosis section (a pump diagnosis circuit) 12. The pump diagnosis section 12 performs a diagnosis process to detect an indication of an abnormality in the fuel pump 30.

[0026] The FPC 13 actuates and controls the fuel pump 30 based on a requested delivery rate QVT. The requested delivery rate QVT is calculated by the ECU 11. The FPC 13 controls the motor 41 of the fuel pump 30 through feedforward control (hereinafter referred to as F / F control) and feedback control (hereinafter referred to as F / B control).

[0027] In F / F control, a target speed NpT is calculated as a target value of the pump speed Np based on the requested delivery rate QVT. The FPC 13 adjusts the motor voltage of the fuel pump 30 so that the pump speed Np reaches the target speed NpT and then actuates the fuel pump 30.

[0028] In F / B control, the actual discharge rate of the fuel pump 30 is estimated based on the fuel pressure QP. The pump speed Np is then controlled so that the actual discharge rate reaches the target discharge rate QVT.

[0029] A notification device 50 is connected to the control unit 10. An alarm lamp, for example, can be used as the notification device 50. When the pump diagnostic section 12 executes a diagnostic procedure and, as a result, detects an indication of an abnormality in the fuel pump 30, the pump diagnostic section 12 illuminates the alarm lamp, thus notifying the detection of the indication.

[0030] With reference to Fig. Figure 3 describes the flow of the diagnostic procedure executed by the pump diagnostic section 12. In this flow, the diagnostic procedure is executed after the FPC 13 executes the pump control.

[0031] After the FPC 13 executes the pump control in step S11, the pump diagnostic section 12 executes the diagnostic process in step S12. The diagnostic process will be described in detail later. After the diagnostic process, step S13 is executed.

[0032] In step S13, the pump diagnostic section 12 determines whether an indication of an abnormality has been detected by the diagnostic process. As will be described in detail later, the diagnostic process determines that an indication of an abnormality exists after determining that the impeller 44 is swollen or that an inner wall of the pump chamber 38 or the impeller 44 is worn. The diagnostic process determines that no indication of an abnormality exists if the diagnosis yields a different result. In this case (S13: NO), the current processing routine is terminated.

[0033] Conversely, if an abnormality indication is present (S13: YES), step S14 is executed. In step S14, the pump diagnostic section 12 executes a notification process. In the notification process, the pump diagnostic section 12 stores the fact that the abnormality indication was detected by the diagnostic process and then notifies the abnormality indication using the notification device 50. After the notification process, the current processing routine is terminated.

[0034] The relationship between the pump speed Np and the fuel pressure QP in connection with the diagnostic procedure is described below with reference to Fig. 4. The higher the pump speed Np, the higher the delivery pressure of the fuel pump 30 and the fuel pressure QP.

[0035] In the following, a fuel pump in a state where there is neither swelling of the impeller 44 nor wear of the inner wall of the pump chamber 38 or the impeller 44—that is, a state without problems—is defined as a reference fuel pump. A fuel pump in a state with advanced swelling of the impeller 44 compared to the reference fuel pump is defined as a fuel pump in a swollen state. A fuel pump in a state with advanced wear of the inner wall of the pump chamber 38 or the impeller 44 compared to the reference fuel pump is defined as a fuel pump in a worn state.

[0036] With reference to Fig. 4, the pump speed Np and the fuel pressure QP in the reference fuel pump have a proportional relationship in the initial operating period from the moment the engine is first energized until a specified period has elapsed. Such a relationship is defined as an initial correlation. More specifically, the specified period is a period in which the correlation between the pump speed Np and the fuel pressure QP is assumed to remain unchanged regardless of a change in the size of the clearance CL. As shown in Fig. As shown in Figure 4, the fuel pressure QP of the fuel pump in a swollen state tends to be higher than that of the reference fuel pump when the fuel pumps are operated at a predetermined pump speed Np. In other words, in the correlation between the number of engine revolutions Np and the fuel pressure QP of the fuel pump in a swollen state, the fuel pressure QP is higher than that in the initial correlation for the predetermined pump speed Np. In contrast, as shown in Fig. 4, the fuel pressure QP of the fuel pump in a worn state tends to be lower than that of the reference fuel pump when the fuel pumps are operated at the predetermined pump speed Np. In other words, in the correlation between the number of engine revolutions Np and the fuel pressure QP of the fuel pump in a worn state, the fuel pressure QP is lower than that in the initial correlation for the predetermined pump speed Np. The relationships between the pump speed Np and the fuel pressure QP in the respective states of the fuel pump 30, as shown in Fig. 4 are produced by varying the size of the clearance CL. Such variation is caused by swelling of the impeller 44 or wear of the inner wall of the pump chamber 38 or the impeller 44.

[0037] Next, with reference to Fig. 5 describes the relationship between the pump speed Np and the clearance CL in connection with the diagnostic procedure. The diagram shows the relationship between the size of the clearance CL and the pump speed Np at the time when the fuel pressure QP rises to a specified pressure QPx by actuation of the fuel pump 30. As shown in Fig. 4, the fuel pressure QP of the fuel pump in the swollen state is relatively high for the specified pump speed Np. In contrast, the fuel pressure QP of the fuel pump in a worn state is relatively low for the specified pump speed Np. In other words, the larger the clearance CL, the lower the fuel pressure QP for the specified pump speed Np. Therefore, with reference to Fig. 5, the clearance CL is larger the higher the pump speed Np is at the time when the fuel pressure QP rises to the predetermined pressure QPx.

[0038] The present embodiment sets a reference range of the clearance CL so that the reference range includes the size of the clearance CL of the reference fuel pump. As shown in Fig. 5, the minimum value in the reference range is defined as an acceptable lower limit value CLth2, and the maximum value in the reference range is defined as an acceptable upper limit value CLth3. If the clearance CL of the fuel pump 30 is smaller than the acceptable lower limit value CLth2, it is indicated that the impeller 44 has a tendency to swell compared to the impeller of the reference fuel pump. The fact that the impeller 44 has a tendency to swell refers to the impeller 44 being in a state where the impeller 44 has swollen but has not yet reached the state where the impeller 44 contacts the inner wall of the pump chamber 38. On the other hand, if the clearance CL of the fuel pump 30 is larger than the acceptable upper limit value CLth3, it is indicated that the inner wall of the pump chamber 38 or the impeller 44 has a wear tendency compared to the corresponding component of the reference fuel pump.

[0039] A swelling limit value CLth1 is set so that when the clearance Cl is smaller than the swelling limit value CLth1, the fuel pump 30 can stop. In other words, as long as the clearance CL of the fuel pump 30 is greater than the swelling limit value CLth1, the fuel pump 30 will not stop due to swelling of the impeller 44.

[0040] In addition, a wear limit value CLth4 is set so that when the clearance CL is larger than the wear limit value CLth4, it is determined that the discharge capacity of the fuel pump 30 is reduced.

[0041] Or in other words: points (A) to (E), as described below, are derived from the Fig. 5. Specifically, with reference to the diagram, a first threshold speed Npth1, a second threshold speed Npth2, a third threshold speed Npth3, and a fourth threshold speed Npth4 become higher, in that order. (A) When the pump speed Np at the time when the fuel pressure QP rises to the specified pressure QPx is in the range between the second threshold speed Npth2 corresponding to the acceptable lower limit value CLth2 and the third threshold speed Npth3 corresponding to the acceptable upper limit value CLth3, the size of the clearance CL of the fuel pump 30 is in the reference range. (B) When the pump speed Np at the time when the fuel pressure QP rises to the specified pressure QPx is smaller than the second threshold speed Npth2 corresponding to the acceptable lower limit value CLth2, the clearance CL is smaller than the reference range, and the impeller 44 tends to swell. (C) If the pump speed Np at the time when the fuel pressure QP rises to the specified pressure QPx is smaller than the first threshold speed Npth1 corresponding to the swell limit CLth1, the clearance CL is smaller than the reference range, and the fuel pump 30 may stop due to the swell of the impeller 44. (D) When the pump speed Np at the time when the fuel pressure QP rises to the specified pressure QPx is greater than the third threshold speed Npth3 corresponding to the acceptable upper limit value CLth3, the clearance CL is larger than the reference range, and the inner wall of the pump chamber 38 or the impeller 44 has a wear tendency. (E) When the pump speed Np at the time when the fuel pressure QP rises to the specified pressure QPx is higher than the fourth threshold speed Npth4 corresponding to the wear limit CLth4, the clearance CL is larger than the reference range, and the performance of the fuel pump 30 has been reduced due to the wear of the inner wall of the pump chamber 38 or the impeller 44.

[0042] In other words, the first threshold speed Npth1 is the value of the pump speed Np that ensures that the specified pressure QPx is obtained as the fuel pressure QP when the impeller 44 is swollen to the allowable limit at the time the fuel pump 30 is actuated. The first threshold speed Npth1 is referred to as the swell determination threshold. The fourth threshold speed Npth4 is the value of the pump speed Np that ensures that the specified pressure QPx is obtained as the fuel pressure QP when the inner wall of the pump chamber 38 or the impeller 44 is worn to the allowable limit at the time the fuel pump 30 is actuated. The fourth threshold speed Npth4 is referred to as a wear determination threshold. The clearance CL is maintained in the reference range when the speed is in the range between the second threshold speed Npth2 and the third threshold speed Npth3.A value in this range can be referred to an initial value as the value of the pump speed Np, which ensures that the specified pressure QPx is obtained as the fuel pressure QP in the initial operation period, that is, the specified period after the initial energization of the fuel pump 30.

[0043] To diagnose the state of the fuel pump 30 according to items (A) to (E), the pump diagnosis section 12 stores the pump speed Np at the time when the fuel pressure QP has risen to the predetermined pressure QPx by actuation of the fuel pump 30, and uses the stored pump speed Np in a diagnosis process.

[0044] With reference to Fig. 6, an example of the diagnosis process executed by the pump diagnosis section 12 will be described. The routine of the present processing is represented by the process flow in step S12 of Fig. 3 initiated.

[0045] In the routine, the pump diagnosis section 12 determines in step S101 whether the pump speed Np at the time the fuel pressure QP rises to the specified pressure QPx is in the range between the second threshold speed Npth2 and the third threshold speed Npth3. If the pump speed Np is within the above-mentioned range, that is, if the pump speed Np is at least as high as the second threshold speed Npth2 and at most as high as the third threshold speed Npth3 (S101: YES), step S102 is executed. In step S102, the pump diagnosis section 12 determines that the clearance size CL is within the reference range. The routine of the current processing is then terminated.

[0046] On the other hand, when the pump speed Np is outside the range between the second threshold speed Npth2 and the third threshold speed Npth3, that is, when the pump speed Np is smaller than the second threshold speed Npth2 or larger than the third threshold speed Npth3 (S101: NO), step S103 is executed.

[0047] In step S103, the pump diagnostic section 12 determines whether the pump speed Np is higher than the third threshold speed Npth3. If the pump speed Np is higher than the third threshold speed Npth3 (S103: YES), step S104 is executed. Conversely, if the pump speed Np is lower than the second threshold speed Npth2 (S103: NO), step S107 is executed.

[0048] In step S104, the pump diagnostic section 12 determines whether the pump speed Np is higher than the fourth threshold speed Npth4. If the pump speed Np is higher than the fourth threshold speed Npth4 (S104: YES), step S105 is executed. In step S105, the pump diagnostic section 12 determines that the clearance CL is larger than the reference range, the inner wall of the pump chamber 38 or the impeller 44 is worn, and there is an indication of an abnormality. The current processing routine is then terminated. On the other hand, if the pump speed Np is equal to or greater than the fourth threshold speed Npth4 (S104: NO), step S106 is executed. In step S106, the pump diagnostic section 12 determines that the clearance CL is larger than the reference range, and the inner wall of the pump chamber 38 or the impeller 44 has a wear tendency. The current processing routine is then terminated.

[0049] In step S107, the pump diagnosis section 12 determines whether the pump speed Np is less than the first threshold speed Npth1. If the pump speed Np is less than the first threshold speed Npth1 (S107: YES), step S108 is executed. In step S108, the pump diagnosis section 12 determines that the clearance CL is smaller than the reference range, the impeller 44 is swollen, and there is an indication of an abnormality. The current processing routine is then terminated. On the other hand, if the pump speed Np is at least equal to the first threshold speed Npth1 (S108: NO), step S109 is executed. In step S109, the pump diagnosis section 12 determines that the clearance CL is smaller than the reference range and the impeller 44 is prone to swelling. The current processing routine is then terminated.

[0050] The operation and advantages of the present embodiment will now be described.

[0051] In many cases, a fuel pump has a small axial clearance to improve discharge performance. Therefore, when the impeller of the fuel pump swells, the axial clearance becomes insufficient, which may cause the fuel pump to stop. However, the control unit 10 of the present embodiment estimates the clearance CL and detects an indication of an abnormality in the fuel pump 30 based on the estimated clearance CL. In other words, by estimating the clearance CL, the state of the fuel pump 30 during operation is determined. This allows an indication of an abnormality to be detected before the fuel pump 30 stops due to the problem.

[0052] The control unit 10 diagnoses the condition of the fuel pump 30 by referring to the relationship between the pump speed Np at the time the fuel pressure QP rises to the specified pressure QPx by actuation of the fuel pump 30 and the size of the clearance CL. This makes it possible to detect an indication of an abnormality that may be caused by swelling of the impeller 44 when the pump speed Np at the time the fuel pressure QP has risen to the specified pressure QPx is lower than the first threshold speed Npth1 as the swelling determination threshold. In other words, an indication of an abnormality is detected before the fuel pump 30 stops due to the problem.

[0053] The control unit 10 detects an indication of an abnormality that may be caused by wear of the inner wall of the pump chamber 38 or the impeller 44 when the value of the pump speed Np at the time the fuel pressure QP has risen to the specified pressure QPx is greater than the fourth threshold speed Npth4, which represents the wear determination threshold. This allows a sign of reduced performance to be detected before the fuel pressure QP, which is obtained by operating the fuel pump 30 at a specific pump speed Np, becomes excessively low, thus reducing the performance of the fuel pump 30.

[0054] In the Fig. 4 and Fig. As shown in Fig. 5, the diagnostic process executed by the pump diagnostic unit 12 of the control unit 10 sets the reference range of the clearance CL based on the clearance CL of the fuel pump in the initial operating period in view of the relationship between the pump speed Np and the size of the clearance CL. If the pump speed Np differs significantly from the values ​​corresponding to the reference range, it indicates that a problem is likely to occur even if the problem has not yet arisen. The diagnostic process of the present embodiment diagnoses that the impeller 44 has swollen to a more advanced stage because the pump speed Np differs more significantly from the values ​​corresponding to the reference range and is closer to the first threshold speed Npth1 than the swell determination threshold.This allows detection of advanced swelling of the impeller 44 before a problem occurs in the fuel pump 30.

[0055] The diagnostic method of the present embodiment diagnoses that the inner wall of the pump chamber 38 or the impeller 44 is worn to a more advanced stage because the pump speed Np differs more significantly from the values ​​corresponding to the reference range and is closer to the fourth threshold speed Npth4, which is the wear determination threshold. This makes it possible to detect advanced wear of the inner wall of the pump chamber 38 or the impeller 44 before a problem occurs in the fuel pump 30.

[0056] In the fuel pump 30, the swelling of the impeller 44 and the wear of the inner wall of the pump chamber 38 or the impeller 44 may progress simultaneously. In this case, the clearance CL may decrease due to swelling, but may increase due to wear and thus remain within the reference range. As a result, the discharge performance of the fuel pump 30 is maintained regardless of the wear and swelling. The diagnostic method of the present embodiment determines the state of the fuel pump 30 during operation by estimating the clearance CL based on the pump rotation speed Np. Therefore, according to the diagnostic method, if the performance of the fuel pump 30 is maintained even when wear and swelling occur, no indication of an abnormality is detected.

[0057] The above-described embodiment may be modified as follows. The above-described embodiment and the following modifications may be combined as long as the combined modifications remain technically consistent with each other.

[0058] In the embodiment described above, the method of detecting an indication of an abnormality in the fuel pump 30 was described using the flowchart in Fig. 6 than that in step S12 of Fig. 3. However, the diagnostic method executed in step S12 may be a method of detecting an indication of an abnormality using the size of the clearance CL with respect to the pump speed Np at the time the fuel pressure QP rises to the specified pressure QPx, referring to a map showing the Fig. 5 shows the relationship.

[0059] In the above-described embodiment, the diagnostic method of detecting an indication of an abnormality in the fuel pump 30 is adapted to detect an indication of an abnormality by estimating the size of the clearance CL based on the pump speed Np at the time when the fuel pressure QP rises to the specified pressure QPx. However, if the determination is made based on the Fig. 5, an indication of an abnormality, that is, swelling of the impeller 44 or wear of the inner wall of the pump chamber 38 or the impeller 44, is detected by determining into which of the zones divided according to the respective first to fourth threshold speeds Npth1 to Npth4 the pump speed Np falls. In other words, the diagnostic method of detecting an indication of an abnormality occurring in the fuel pump 30 may not necessarily include estimating the clearance CL based on the pump speed Np.

[0060] The procedure in the manner described above and in Fig. 3 can be executed repeatedly. In other words, the pump diagnostic section 12 can execute the diagnostic procedure repeatedly. While the diagnostic procedure is repeated, the pump controller of step S11 must operate the fuel pump 30 under the same conditions. For example, the motor voltage of the fuel pump 30 must remain unchanged.

[0061] When the pump diagnostic section 12 repeats the diagnostic procedure, the pump speed Np at the time the fuel pressure QP rises to the predetermined pressure QPx may become lower in the current diagnostic cycle than in the last diagnostic cycle. This indicates that the clearance CL has become larger than in the last diagnostic cycle, allowing the progressive swelling of the impeller 44 to be detected as an indication of an abnormality. On the other hand, if the pump speed Np at the time the fuel pressure QP rises to the predetermined pressure QPx in the current diagnostic cycle is higher than in the last diagnostic cycle, the clearance CL is smaller than in the last diagnostic cycle. This allows the progressive wear of the inner wall of the pump chamber 38 or the impeller 44 to be detected as an indication of an abnormality.

[0062] If the swelling of the impeller 44 and the wear of the inner wall of the pump chamber 38 or the impeller 44 progress simultaneously, and it is detected that the impeller 44 has a tendency to swell, the clearance CL may later return to the reference range depending on the rate at which the swelling or wear progresses. Therefore, the diagnostic accuracy is improved by repeatedly executing the diagnostic procedure as in the embodiment described above.

[0063] In the embodiment described above, the diagnosis method of detecting the occurrence of a sign of an abnormality in the fuel pump 30 was described based on the relationship between the pump speed Np and the clearance CL. However, the content of the diagnosis method may be modified. For example, when the fuel pump 30 is actuated by the FPC 13, the value of the pump speed Np in the F / F control may be defined as an initial speed. In this case, the amount by which the pump speed Np changes from the initial speed due to the F / B control is defined as a speed change ΔNp. A diagnosis method of detecting a sign of an abnormality occurring in the fuel pump 30 may be performed using the speed change ΔNp.

[0064] With reference to Fig. 7 describes the relationship between the speed change ΔNp and the clearance CL in connection with the diagnostic procedure. As in Fig. 4, the larger the clearance CL, the lower the fuel pressure QP for the given pump speed Np. Therefore, as shown in Fig. As shown in Figure 7, the clearance CL is larger, the larger the speed change ΔNp is.

[0065] With reference to Fig. 7, the value of the speed change ΔNp corresponding to the wear limit value CLth4 is the value rb. The value of the speed change ΔNp corresponding to the acceptable upper limit value CLth3 is the value ra. The value ra is smaller than the value rb. The value of the speed change ΔNp corresponding to the acceptable lower limit value CLth2 is the value -ra. The value of the speed change ΔNp corresponding to the swelling limit value CLth1 is the value -rc. The value -rc is smaller than the value -ra. In other words, points (F) to (J), as described below, are calculated from the value in Fig. The relationship shown in Figure 7 is derived.

[0066] (F) When the speed change ΔNp is at most as large as the value ra, that is, in the case of ΔNp ≤ |ra|, the size of the clearance CL of the fuel pump 30 is kept in the reference range.

[0067] (G) When the speed change ΔNp is smaller than the value -ra, that is, in the case of ΔNp < -ra, the clearance CL is smaller than the reference range, and the impeller 44 tends to swell.

[0068] (H) When the speed change ΔNp is smaller than the value -rc, that is, in the case of ΔNp < -rc, the clearance CL is smaller than the reference range, and the fuel pump 30 may stop due to the swelling of the impeller 44.

[0069] (I) When the speed change ΔNp is larger than the value ra, that is, in the case of ΔNp > ra, the clearance CL is larger than the reference range, and the inner wall of the pump chamber 38 or the impeller 44 may have a wear tendency.

[0070] (J) When the speed change ΔNp is larger than the value rb, that is, in the case of ΔNp > rb, the clearance CL is larger than the reference range, and the performance of the fuel pump 30 has decreased due to the wear of the inner wall of the pump chamber 38 or the impeller 44.

[0071] The condition of the fuel pump 30 is diagnosed based on the above-described points (F) to (J). For example, the FPC 13 may store the amount of change in the pump rotational speed Np in the period from the moment the F / B control is started until the actual discharge rate reaches the target discharge rate QVT as the rotational speed change ΔNp. A diagnosis process may be performed using the rotational speed change ΔNp. Alternatively, in the F / B control, the rotational speed change ΔNp may be sequentially monitored as the amount of change in the rotational speed Np. When the rotational speed change ΔNp becomes smaller than the value -ra, a determination is made that the fuel pump 30 may stop due to swelling of the impeller 44.These diagnostic methods also determine the condition of the fuel pump 30 during operation, as in the embodiment described above, and thus enable detection of an indication of an abnormality occurring in the fuel pump 30.

[0072] The contents of the diagnostic procedures can be modified as described below. The discharge quantity QV of the fuel pump 30 per unit time at the time when the pump speed Np is controlled to a certain speed is in a proportional relationship to the fuel pressure QP. Therefore, with reference to Fig. 8, Correlations that Fig. 4 between the pump speed Np and the discharge rate QV in the respective states of the fuel pump 30. In other words, in the correlation between the pump speed Np and the discharge rate QV of the fuel pump in a swollen state, the discharge rate QV is larger than in the initial correlation for a usual pump speed Np. In contrast, in the correlation between the pump speed Np and the discharge rate QV of the fuel pump in a worn state, the discharge rate QV is smaller than in the initial correlation for a usual pump speed Np. When the FPC 13 executes the F / F control, the pump speed Np is controlled to a constant target speed NpT. The time required for the fuel pressure QP to increase by a predetermined amount at the time the pump speed Np is controlled to the target speed NpT is defined as a pressure rise time T. As shown in Fig. 8, the flow rate QV for a typical pump speed Np becomes smaller the larger the clearance CL is. Therefore, with reference to Fig. 9, the pressure rise time T is longer, the larger the clearance CL is when the pump speed Np is constant. Based on the relationship between the pressure rise time T and the clearance CL, as shown in Fig. 9, a diagnostic procedure can be performed.

[0073] The points (K) to (O), as described below, result from the Fig. 9 shown relationship.

[0074] (K) When the pressure rise time T is in the range of a second threshold time Tth2 corresponding to the acceptable lower limit value CLth2 to a third threshold time Tth3 corresponding to the acceptable upper limit value CLth3, the size of the clearance CL of the fuel pump 30 is kept in the reference range.

[0075] (L) When the pressure rise time T is less than the second threshold time Tth2 corresponding to the acceptable lower limit value CLth2, the clearance CL is smaller than the reference range and the impeller 44 tends to swell.

[0076] (M) When the pressure rise time T is less than a first threshold time Tth1 corresponding to the swelling limit value CLth1, the clearance CL is smaller than the reference range and the fuel pump 30 may stop due to the swelling of the impeller 44.

[0077] (N) When the pressure rise time T is longer than the third threshold time Tth3 corresponding to the acceptable upper limit value CLth3, the clearance CL is larger than the reference range and the inner wall of the pump chamber 38 or the impeller 44 tends to wear.

[0078] (O) When the pressure rise time T is longer than a fourth threshold time Tth4 corresponding to the wear limit value CLth4, the clearance CL is larger than the reference range and the performance of the fuel pump 30 is reduced due to the wear of the inner wall of the pump chamber 38 or the impeller 44.

[0079] The condition of the fuel pump 30 can be diagnosed based on the items (K) to (O) described above. As in the above-described embodiment, this diagnostic method determines the condition of the fuel pump 30 during operation and detects an indication of an abnormality occurring in the fuel pump 30.

[0080] In the embodiment described above, the diagnosis method based on the relationship between the pump speed Np at the time when the fuel pressure QP rises to the predetermined pressure QPx and the size of the clearance CL as shown in Fig. 5. There is a correlation between the pump speed Np and the delivery rate QV in the respective states of the fuel pump 30, as shown in Fig. 8. Therefore, a diagnostic method can be performed based on the relationship between the pump speed Np at the time a certain discharge rate QV is obtained by the operation of the fuel pump 30 and the size of the clearance CL. This diagnostic method, as in the embodiment described above, determines the state of the fuel pump 30 during operation and detects an indication of an abnormality occurring in the fuel pump 30.

[0081] The content of the diagnostic procedure can be modified as described below. As in Fig. As shown in Figure 4, the larger the clearance CL, the lower the fuel pressure QP at a given pump speed Np. Therefore, with reference to Fig. 10, at a constant pump speed Np, the clearance CL is larger, the lower the fuel pressure QP is. Specifically, the pump speed Np is controlled to a constant target speed NpT when the FPC 13 executes the F / F control. Using the fuel pressure QP at the time the pump speed Np is controlled to the target speed NpT, a diagnosis procedure can be performed based on the relationship between the fuel pressure QP and the clearance CL, as shown in Fig. 10 shown.

[0082] Points (P) to (T), as described below, are derived from the Fig. 10 shown relationship.

[0083] (P) When the fuel pressure QP at the time the pump speed Np is controlled to the target speed NpT is in the range between a second threshold fuel pressure QPth2 corresponding to the acceptable upper limit value CLth3 and a third threshold fuel pressure QPth3 corresponding to the acceptable lower limit value CLth2, the size of the clearance CL is kept in the reference range.

[0084] (Q) When the fuel pressure QP is higher than the third threshold fuel pressure QPth3 corresponding to the acceptable lower limit value CLth2, the clearance CL is smaller than the reference range, and the impeller 44 tends to swell.

[0085] (R) When the fuel pressure QP is higher than a fourth threshold fuel pressure QPth4 corresponding to the swelling limit CLth1, the clearance CL is smaller than the reference range and the fuel pump 30 may stop due to the swelling of the impeller 44.

[0086] (S) When the fuel pressure QP is lower than the second threshold fuel pressure QPth2 corresponding to the acceptable upper limit value CLth3, the clearance CL is larger than the reference range and the inner wall of the pump chamber 38 or the impeller 44 tends to wear.

[0087] (T) When the fuel pressure QP is lower than a first threshold fuel pressure QPth1 corresponding to the wear limit CLth4, the clearance CL is larger than the reference range and the performance of the fuel pump 30 has been reduced due to the wear of the inner wall of the pump chamber 38 or the impeller 44.

[0088] The condition of the fuel pump 30 can be diagnosed based on points (P) to (T).

[0089] With reference to Fig. 11, an example of a diagnostic procedure executed by the pump diagnostic section 12 is described. The routine of the present processing is represented by the process flow in step S12 of Fig. 3 initiated.

[0090] In the routine, the pump diagnosis section 12 determines in step S301 whether the fuel pressure QP at the time the pump rotational speed Np is controlled to the target rotational speed NpT is in the range between the second threshold fuel pressure QPth2 and the third threshold fuel pressure QPth3. If the fuel pressure QP is in the above-mentioned range, that is, if the fuel pressure QP is at least as high as the second threshold fuel pressure QPth2 and at most as high as the third threshold fuel pressure QPth3 (S301: YES), step S302 is executed. In step S302, the pump diagnosis section 12 determines that the clearance size CL is within the reference range. The routine of the current processing is then terminated.

[0091] On the other hand, when the fuel pressure QP is outside the range between the second threshold fuel pressure QPth2 and the third threshold fuel pressure QPth3, that is, when the fuel pressure QP is lower than the second threshold fuel pressure QPth2 or higher than the third threshold fuel pressure QPth3 (S301: NO), step S303 is executed.

[0092] In step S303, the pump diagnosis section 12 determines whether the fuel pressure QP is lower than the second threshold fuel pressure QPth2. If the fuel pressure QP is lower than the second threshold fuel pressure QPth2 (S303: YES), step S304 is executed. Conversely, if the fuel pressure QP is higher than the third threshold fuel pressure QPth3 (S303: NO), step S307 is executed.

[0093] In step S304, the pump diagnosis section 12 determines whether the fuel pressure QP is lower than the first threshold fuel pressure QPth1. If the fuel pressure QP is lower than the first threshold fuel pressure QPth1 (S304: YES), step S305 is executed. In step S305, the pump diagnosis section 12 determines that the clearance CL is larger than the reference range, the inner wall of the pump chamber 38 or the impeller 44 is worn, and there is an indication of an abnormality. The current processing routine is then terminated. On the other hand, if the fuel pressure QP is at least equal to the first threshold fuel pressure QPth1 (S304: NO), step S306 is executed. In step S306, the pump diagnosis section 12 determines that the clearance CL is larger than the reference range, and the inner wall of the pump chamber 38 or the impeller 44 has a wear tendency. The current processing routine is then terminated.

[0094] In step S307, the pump diagnosis section 12 determines whether the fuel pressure QP is higher than the fourth threshold fuel pressure QPth4. If the fuel pressure QP is higher than the fourth threshold fuel pressure QPth4 (S307: YES), step S308 is executed. In step S308, the pump diagnosis section 12 determines that the clearance CL is smaller than the reference range, the impeller 44 is swollen, and an indication of an abnormality exists. The current processing routine is then terminated. On the other hand, if the fuel pressure QP is at most equal to the fourth threshold fuel pressure QPth4 (S307: NO), step S309 is executed. In step S309, the pump diagnosis section 12 determines that the clearance CL is smaller than the reference range, and the impeller 44 is prone to swelling. The current processing routine is then terminated.

[0095] As in the embodiment described above, this diagnostic method determines the condition of the fuel pump 30 during operation and detects an indication of an abnormality occurring in the fuel pump 30.

[0096] The embodiment is configured to execute the diagnostic process after the FPC 13 executes the pump control. The pump control may be a pump control in which the fuel pump 30 is operated based on the target delivery rate QVT calculated by the ECU 11 for fuel injection by the fuel injectors 26. Alternatively, the pump control may be a pump control in which the fuel pump 30 is operated to execute a diagnostic process regardless of the timing at which fuel is injected by the fuel injectors 26.

[0097] In the embodiment described above, the pump diagnostic section 12 incorporated in the vehicle's ECU 11 was exemplified. However, the pump diagnostic section 12 for executing a diagnostic process may also be incorporated into a computer device located outside the vehicle. In other words, a diagnostic device for a fuel pump may be constituted by the FPC 13 arranged in the vehicle's control unit 10 and the pump diagnostic section 12 mounted in the computer device located outside the vehicle. For example, the diagnostic device may be configured to transmit and receive data between the control unit 10 and the computer device via an external communication circuit network. This allows the computer device to receive data, including the pump rotational speed Np, from the control unit 10 and then perform a diagnostic process.As in the embodiment described above, this diagnostic method determines the condition of the fuel pump 30 during operation and detects an indication of an abnormality occurring in the fuel pump 30.

[0098] Various changes in form and detail may be made to the above examples without departing from the spirit and scope of the claims and their equivalents. The examples are for the purpose of description only and not of limitation. Descriptions of features in each example should be understood as applicable to similar features or aspects in other examples. Suitable results may be achieved if sequences are performed in a different order and / or if components in a described system, architecture, device, or circuit are combined differently and / or replaced or supplemented with other components or their equivalents. The scope of the disclosure is not defined by the detailed description, but by the claims and their equivalents.All variations within the scope of the claims and their equivalents are included in the disclosure.

Claims

[1] A diagnostic device (10) for a fuel pump (30) mounted in a fuel supply system (20), the fuel pump (30) having a pump chamber (38), an impeller (44) received in the pump chamber (38), and a motor (41) for rotating the impeller (44), and the fuel pump (30) being adapted to suck fuel from a fuel tank (41) and discharge the fuel by rotating the impeller (44), the diagnostic device (10) comprising: a pump control section (13) adapted to actuate the fuel pump (30); and a pump diagnostic section (12) configured to diagnose a condition of the fuel pump (30) based on: a correlation between a pump speed (Np), which is a speed of the engine (41), and a fuel pressure (QP), which is the pressure of the fuel delivered by the fuel pump (30), and an initial correlation, which is the correlation in an initial operating period from the moment the fuel pump (30) is first energized until a specified period of time has elapsed. [2] Diagnostic device (10) for a fuel pump (30) according to claim 1, wherein the value of the pump speed (Np) at the time at which a specified pressure (QPx) is obtained as the fuel pressure (QP) in the event that the impeller (44) has swollen to a permissible limit is a swelling determination threshold (Npth1), and the pump diagnosis section (12) is arranged to detect an indication of an abnormality that may be caused by the swelling of the impeller (44) as an indication of an abnormality occurring in the fuel pump (30) when the value of the pump rotation speed (Np) at the time the specified pressure (QPx) is obtained as the fuel pressure (QP) is lower than the swelling determination threshold (Npth1). [3] Diagnostic device (10) for a fuel pump (30) according to claim 1 or 2, wherein the value of the pump speed (Np) at the time at which a specified pressure (QPx) is obtained as the fuel pressure (QP) in the event that an inner wall of the pump chamber (38) or the impeller (44) has been worn to an allowable limit is a wear determination threshold (Npth4), and the pump diagnosis section (12) is arranged to detect an indication of an abnormality that may be caused by wear of the inner wall of the pump chamber (38) or the impeller (44) as an indication of an abnormality occurring in the fuel pump (30) when the value of the pump speed (Np) at the time the specified pressure (QPx) is obtained as the fuel pressure (QP) is higher than the wear determination threshold (Npth4). [4] Diagnostic device (10) for a fuel pump (30) according to one of claims 1 to 3, wherein the value of the pump speed (Np) at the time at which a specified pressure (QPx) is obtained as the fuel pressure (QP) in the event that the impeller (44) has swollen to a permissible limit is a swelling determination threshold (Npth1), and the value of the pump speed (Np) at the time when the specified pressure (QPx) is obtained as the fuel pressure (QP) in the initial operating period is an initial value, and the pump diagnosis section (12) is arranged to detect that the swelling of the impeller (44) progresses to a greater degree compared to the swelling in the initial operating period when the value of the pump rotational speed (Np) at the time point at which the specified pressure (QPx) is obtained as the fuel pressure (QP) moves closer to the swelling determination threshold (Npth1) than to the initial value. [5] Diagnostic device (10) for a fuel pump (30) according to one of claims 1 to 4, wherein the value of the pump speed (Np) at the time at which a specified pressure (QPx) is obtained as the fuel pressure (QP) in the event that an inner wall of the pump chamber (38) or the impeller (44) has been worn to an allowable limit is a wear determination threshold (Npth4), and the value of the pump speed (Np) at the time when the specified pressure (QPx) is obtained as the fuel pressure (QP) in the initial operating period is an initial value, and the pump diagnosis section (12) is arranged to detect that the wear of the inner wall of the pump chamber (38) or the impeller (44) progresses to a greater degree than the wear in the initial operating period when the value of the pump rotational speed (Np) at the time when the specified pressure (QPx) is obtained as the fuel pressure (QP) moves closer to the wear determination threshold (Npth4) than to the initial value. [6] Diagnostic device (10) for a fuel pump (30) according to one of claims 1 to 5, wherein the pump diagnostic section (12) is arranged to: Estimating a size of an axial clearance (CL), which is a clearance between the impeller (44) and an inner wall of the pump chamber (38) in the axial direction of a rotary shaft (42) of the motor (41), from the correlation between the pump speed (Np) and the fuel pressure (QP) and the initial correlation, and Detecting an indication of an abnormality in the fuel pump (30) based on the estimated amount of axial play (CL). [7] Diagnostic device (10) for a fuel pump (30) according to one of claims 1 to 6, wherein the pump diagnostic section (12) is arranged to: repeatedly performing the diagnosis by operating the fuel pump (30) under the same conditions as the conditions under which the fuel pump (30) was operated in the last diagnostic cycle, and Detecting that the swelling of the impeller (44) has progressed compared to the last diagnostic cycle based on a difference in pump speed (Np) between the current diagnostic cycle and the last diagnostic cycle. [8] Diagnostic device (10) for a fuel pump (30) according to one of claims 1 to 7, wherein the pump diagnostic section (12) is arranged to: repeatedly performing the diagnosis by operating the fuel pump (30) under the same conditions as the conditions under which the fuel pump (30) was operated in the last diagnostic cycle, and Detecting that the wear of the inner wall of the pump chamber (38) or the impeller (44) has progressed compared to the last diagnostic cycle, based on a difference in pump speed (Np) between the current diagnostic cycle and the last diagnostic cycle.

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