Control method of pressure relief valve, corresponding program carrier, controller and common rail system

Abstract

The present invention discloses a method for controlling a pressure relief valve (121) of a common rail (12) of a common rail system (1) of a vehicle, the method comprising at least the following steps: step S1: determining whether the vehicle is in a reverse towing condition; and step S2: when the vehicle is in the reverse towing condition, during a predetermined period of the reverse towing condition, controlling the pressure relief valve (121) of the common rail (12) not only with a set value of the rail pressure of the common rail (12) determined in the reverse towing condition as a control target, so that a center line around which the actual rail pressure of the common rail (12) changes deviates from the set value in a direction higher than the set value. The present invention also discloses a corresponding computer-readable program carrier, a corresponding controller (13) for a common rail system (1) of a vehicle, a corresponding common rail system (1) of a vehicle, and a corresponding vehicle. According to the present invention, the number of times the pressure relief valve (121) is opened and closed in the reverse towing condition of the vehicle can be reduced.

Description

Technical Field

[0001] The invention relates to a method for controlling a pressure relief valve of a common rail of a common rail system of a vehicle, a corresponding computer-readable program carrier, a corresponding controller for a common rail system of a vehicle, and a corresponding common rail system for a vehicle. Background Art

[0002] Currently, common rail technology is widely used in vehicle engine fuel supply. Common rail technology is a fuel supply method that completely separates the generation of injection pressure from the injection process in a closed-loop system consisting of a high-pressure fuel pump, pressure sensor, and electronic control unit (ECU).

[0003] The common rail pressure may also need to be adjusted based on the vehicle's specific operating conditions. For example, when the vehicle is in reverse towing mode, the set common rail pressure may decrease as the accelerator pedal is released. Furthermore, it may be necessary to control the upper limit of the common rail pressure or maintain it as close to the set value as possible. To this end, a pressure relief valve is installed on the common rail to release the pressure as needed.

[0004] The high-pressure oil pump is equipped with an oil quantity control unit that supplies fuel to its working chamber to control the oil intake of the high-pressure oil pump, thereby controlling the working state of the high-pressure oil pump and further controlling the oil supply to the common rail to maintain the desired state of the common rail.

[0005] The high-pressure fuel pump is always in operation while the vehicle is in motion. Ideally, the fuel quantity control unit should be fully closed during reverse towing to prevent the high-pressure fuel pump from continuing to supply high-pressure fuel to the common rail, which would cause an adverse increase in the common rail pressure. However, the fuel quantity control unit is often unable to fully close, allowing a small amount of fuel to enter the working chamber of the high-pressure fuel pump. As a result, the high-pressure fuel pump continues to supply high-pressure fuel to the common rail, increasing the common rail pressure. This pressure increase may cause the common rail pressure to significantly deviate from the set value or exceed the upper limit, necessitating the use of a pressure relief valve on the common rail to relieve pressure. To this end, the pressure relief valve needs to be operated frequently. For example, during reverse towing, the pressure relief valve may be opened and closed millions of times, and this frequent operation can seriously affect the service life of the pressure relief valve.

[0006] Although a zero flow hole can be set for the high-pressure oil pump so that the fuel leaked through the oil quantity control unit in the closed state can flow back to the fuel tank instead of entering the working chamber of the high-pressure oil pump, this configuration will increase the cost and structural complexity of the high-pressure oil pump.

[0007] This situation is particularly serious when the engine adopts a leak-free fuel injector. For this reason, there is an urgent need to improve the existing common rail system. Summary of the Invention

[0008] The object of the present invention is to provide an improved method for controlling a pressure relief valve of a common rail of a common rail system of a vehicle, a corresponding computer-readable program carrier, a corresponding controller for a common rail system of a vehicle, and a corresponding common rail system for a vehicle.

[0009] According to a first aspect of the present invention, a method for controlling a common rail pressure relief valve of a common rail system of a vehicle is provided, the method comprising at least the steps of: step S1: determining whether the vehicle is in a reverse towing condition; and step S2: when the vehicle is in the reverse towing condition, controlling the common rail pressure relief valve for a predetermined period during the reverse towing condition, not only using a set value of the common rail pressure determined in the reverse towing condition as a control target, such that a center line around which actual common rail pressure changes deviates from the set value in a direction above the set value.

[0010] According to a second aspect of the present invention, a computer-readable program carrier is provided, which stores program instructions. When the program instructions are executed by a processor, the method is implemented.

[0011] According to a third aspect of the present invention, a controller for a common rail system of a vehicle is provided, wherein the controller includes the computer-readable program carrier.

[0012] According to a fourth aspect of the present invention, a common rail system for a vehicle is provided, wherein the common rail system includes the controller.

[0013] According to the present invention, the number of times the pressure relief valve is opened and closed during a vehicle towing operation can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention will be described in more detail below with reference to the accompanying drawings, so that the principles, features and advantages of the present invention can be better understood. The accompanying drawings include:

[0015] Figure 1 A block diagram of a common rail system according to an exemplary embodiment of the present invention is schematically shown.

[0016] Figure 2 A method for controlling the rail pressure of a common rail according to an exemplary embodiment of the present invention is schematically shown.

[0017] Figure 3 A method for controlling the rail pressure of a common rail by actively controlling a pressure relief valve according to an exemplary embodiment of the present invention is schematically shown.

[0018] Figure 4 A flowchart illustrating a method for controlling a rail pressure of a common rail according to an exemplary embodiment of the present invention is shown.

[0019] Figure 5 An exemplary embodiment of the present invention is shown. Figure 4 A flowchart of one step is shown in . DETAILED DESCRIPTION

[0020] In order to make the technical problems, technical solutions and beneficial technical effects to be solved by the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and multiple exemplary embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the scope of protection of the present invention.

[0021] Figure 1 Schematically shows a block diagram of a common rail system according to an exemplary embodiment of the present invention. It should be noted that, for the sake of clarity, Figure 1 Only the parts that the present invention can relate to are shown in the figure; therefore, the common rail system may also include other components.

[0022] like Figure 1 As shown, the common rail system 1 may include a high-pressure fuel pump 11 for generating high-pressure fuel, a common rail 12 for receiving and storing the high-pressure fuel from the high-pressure fuel pump 11, and a controller 13 for controlling the operations of the high-pressure fuel pump 11 and the common rail 12. The high-pressure fuel pump 11 includes an oil quantity control unit 111 for controlling the oil intake amount of the high-pressure fuel pump 11, the common rail 12 includes a pressure relief valve 121 for releasing the rail pressure of the common rail 12 and a pressure sensor 122 for measuring the rail pressure of the common rail 12, and the controller 13 may obtain the rail pressure from the pressure sensor 122. Figure 1 Only dotted lines are used to schematically indicate that the controller 13 can control the oil quantity control unit 111 of the high-pressure oil pump 11 and the pressure relief valve 121 of the common rail 12 , and that the controller 13 can obtain the rail pressure from the pressure sensor 122 .

[0023] The controller 13 may be an electronic control unit (ECU) of the vehicle or a separate controller communicatively connected to the ECU.

[0024] When the vehicle is in reverse towing mode, the vehicle's engine does not need to inject fuel from the common rail 12 via the injectors (not shown). In this case, the set pressure of the common rail 12 can be set to a relatively low value by the controller 13, for example, based on parameters such as the engine speed. That is, the set value of the rail pressure of the common rail 12 can be reduced. This can be achieved by the controller 13 controlling the pressure relief valve 121. However, the high-pressure fuel pump 11 is still in operation. If the fuel quantity control unit 111 of the high-pressure fuel pump 11 is in the open state, fuel will still enter the working chamber of the high-pressure fuel pump 11, and the high-pressure fuel pump 11 will continue to supply high-pressure fuel to the common rail 12, which is disadvantageous. To this end, in this operating condition, the fuel quantity control unit 111 can be switched to a closed state, for example, by the controller 13.

[0025] The pressure relief valve 121 is electrically controlled and can be controlled by the controller 13. For example, the controller 13 controls the operation of the pressure relief valve 121 by controlling the current supplied to the pressure relief valve 121. The greater the current, the greater the pressure the pressure relief valve 121 can withstand, and the correspondingly higher rail pressure of the common rail 12. When the pressure of the common rail 12 exceeds the pressure set by the controller 13 via the pressure relief valve 121, the pressure relief valve 121 opens, releasing the pressure from the common rail 12.

[0026] The fuel quantity control unit 111 cannot usually be completely closed. Therefore, even if the fuel quantity control unit 111 is in the closed state, a small amount of fuel will enter the working chamber of the high-pressure fuel pump 11 through the fuel quantity control unit 111 (when the high-pressure fuel pump 11 does not have a zero-flow hole), and then a certain amount of fuel will still be supplied to the common rail 12 after being compressed by the high-pressure fuel pump 11. At this time, the common rail 12 does not inject fuel into the engine cylinder through the injector. For this reason, the rail pressure of the common rail 12 needs to be released through the pressure relief valve 121 to maintain the rail pressure of the common rail 12 as much as possible below the set value.

[0027] It is understood that in order to maintain the rail pressure of the common rail 12 at a set value, if the pressure relief valve 121 is controlled accurately or only with the set value determined by the controller 13 as a target, the pressure relief valve 121 will be frequently opened and closed, which is very disadvantageous.

[0028] To this end, according to an exemplary embodiment of the present invention, when the vehicle is in a reverse towing condition, since the injector does not inject fuel, the controller 13 may not be limited to accurately maintaining the set value in controlling the rail pressure of the common rail 12 .

[0029] Figure 2 A method for controlling the rail pressure of the common rail 12 according to an exemplary embodiment of the present invention is schematically shown.

[0030] like Figure 2As shown, the first dotted line 21 represents the set value of the rail pressure of the common rail 12 determined by the controller 13 based on the engine speed, etc., and the solid line 22 represents the actual rail pressure of the common rail 12 generated by controlling the pressure relief valve 121. When the vehicle is in a reverse towing condition, the common rail 12 no longer injects fuel through the injector. The controller 13 sets the rail pressure of the common rail 12 to a relatively low set value based on the reverse towing condition. To achieve the set value, the controller 13 may open the pressure relief valve 121 to reduce the rail pressure of the common rail 12, for example, to a first low point 211, and then close the pressure relief valve 121. If the high-pressure oil pump 11 continues to supply oil to the common rail 12, for example, because the oil quantity control unit 111 cannot be completely closed, the rail pressure of the common rail 12 will increase again. When the rail pressure of the common rail 12 reaches a high point 212, the pressure relief valve 121 is opened to release the rail pressure of the common rail 12, allowing the rail pressure of the common rail 12 to drop to a second low point 213. The rail pressure of the common rail 12 then increases again, and the above process is repeated. This process may be performed until the reverse towing condition ends.

[0031] According to an exemplary embodiment of the present invention, the first low point 211 may be equal to the second low point 213. Of course, they may also be unequal.

[0032] from Figure 2 As can be seen from the figure, the high point 212 deviates greatly from the set value relative to the first low point 211 and the second low point 213. Therefore, the pressure relief valve 121 opens to release the rail pressure of the common rail 12 only when the rail pressure of the common rail 12 rises to a higher pressure. Therefore, the frequency of opening and closing of the pressure relief valve 121 can be reduced, and the number of times the pressure relief valve 121 is opened and closed can be reduced.

[0033] Therefore, those skilled in the art will understand that, at this point, the controller 13 no longer accurately controls the rail pressure of the common rail 12 with the set value as the sole target, but can be considered to control the rail pressure of the common rail 12 with an average pressure value higher than the set value. In other words, the present invention allows the rail pressure of the common rail 12 to fluctuate with a larger amplitude above the set value.

[0034] like Figure 2 As shown, this pressure mean value can be shown as an example by a dot-dash line 23. Figure 2 It can be seen from FIG. 1 that the actual rail pressure of the common rail 12 tends to vary around the pressure mean value.

[0035] If the opening pressure of the pressure relief valve 121 is simply set to be constant and the pressure relief valve 121 is passively opened and closed according to the rail pressure of the common rail 12 , the above control expectations may not be achieved. Instead, the pressure may fluctuate slightly and frequently around the mean value represented by the dotted line 23 .

[0036] To this end, according to an exemplary embodiment of the present invention, the pressure relief valve 121 is actively controlled according to the rail pressure of the common rail 12 .

[0037] According to an exemplary embodiment of the present invention, the pressure at the high point 212 , ie, the opening pressure of the pressure relief valve 121 when releasing the rail pressure, is higher than the set value by a predetermined value, for example, 100 bar.

[0038] Figure 3 A method for controlling the rail pressure of the common rail 12 by actively controlling the pressure relief valve 121 according to an exemplary embodiment of the present invention is schematically shown.

[0039] like Figure 3 As shown by the second dotted line 24, at the first low point 211, the opening pressure of the pressure relief valve 121 is set from a lower value (corresponding to the first low point 211) to a value corresponding to the high point 212, so that the pressure relief valve 121 is closed, and the rail pressure of the common rail 12 gradually rises to the high point 212, and then the opening pressure of the pressure relief valve 121 is set to a lower value, for example, corresponding to the second low point 213, so that the pressure relief valve 121 can be opened to release the rail pressure of the common rail 12. When the rail pressure of the common rail 12 drops to the second low point 213, the opening pressure of the pressure relief valve 121 is set to a larger value, so that the pressure relief valve 121 is closed again, and the rail pressure of the common rail 12 rises again, and then these operations can be repeated.

[0040] In this way, through this control method, the opening pressure of the pressure relief valve 121 can be actively controlled, thereby reducing the frequency of opening and closing of the pressure relief valve 121.

[0041] Those skilled in the art will appreciate that this active control method is merely exemplary, and the pressure relief valve 121 may be controlled in any other suitable manner as long as the frequency of opening and closing of the pressure relief valve 121 can be reduced.

[0042] As described above, the controller 13 may control the opening pressure of the pressure relief valve 121 by controlling the magnitude of the current supplied to the pressure relief valve 121 .

[0043] Those skilled in the art will also understand that the above operation can be performed in any number of cycles, and can also be performed only during a certain period of the reverse towing operation, or during multiple intervals or consecutive periods. In fact, as long as such an operation is performed, even if it is only performed in one cycle, the frequency of opening and closing of the pressure relief valve 121 can be reduced to at least a certain extent.

[0044] From the above description, it can be seen that the method of the present invention does not require any new hardware devices to be added to the existing common rail system, and only requires adjustment of the corresponding control logic.

[0045] According to the technical concept of the present invention, by increasing the maximum pressure that the pressure relief valve 121 can maintain above the set value (i.e., the opening pressure), the opening time of the pressure relief valve 121 in each cycle is delayed, significantly reducing the number of times the pressure relief valve 121 opens and closes. As a result, the centerline (e.g., dotted line 23) around which the rail pressure of the common rail 12 fluctuates deviates from the set value in a direction above the set value. According to an exemplary embodiment of the present invention, the centerline may also be the average value of the rail pressure. Of course, those skilled in the art will also understand that the centerline may also be represented in other ways.

[0046] Therefore, the present invention provides a method for controlling the pressure relief valve 121 when the vehicle is in a reverse towing condition.

[0047] Figure 4 A flowchart of the method according to an exemplary embodiment of the present invention is shown. In step S1, it is determined whether the vehicle is in a reverse towing condition. In step S2, if the vehicle is in the reverse towing condition, the pressure relief valve 121 of the common rail 12 is controlled using, at least not exclusively, a set value of the common rail pressure determined in the reverse towing condition as a control target, so that a center line around which the actual pressure of the common rail 12 fluctuates deviates from the set value in a direction above the set value, at least during a certain period of the reverse towing condition.

[0048] The second step S2 can be performed by referring to Figure 3 The control method described is implemented.

[0049] Figure 5 FIG. 4 shows an implementation flow chart of step S2 according to an exemplary embodiment of the present invention. Figure 5 As shown, step S2 may include at least the following sub-steps: in sub-step S21, the actual rail pressure of the common rail 12 is reduced to at least the set value by opening the pressure relief valve 121; in sub-step S22, the opening pressure of the pressure relief valve 121 is set to be a predetermined value higher than the set value; and in sub-step S23, when the actual rail pressure of the common rail 12 rises to the set opening pressure of the pressure relief valve 121, the process returns to sub-step S21 and the process is repeated.

[0050] The present invention also relates to a controller implementing such control logic, a corresponding common rail system, and a corresponding computer-readable program carrier. In the common rail system according to the present invention, the injector may be a leak-free injector, and the high-pressure oil pump 11 may not be equipped with a zero-flow orifice.

[0051] Although specific embodiments of the present invention are described in detail herein, they are provided for illustrative purposes only and should not be considered to limit the scope of the present invention. Various substitutions, changes, and modifications may be conceived without departing from the spirit and scope of the present invention.

[0052] Reference Signs List

[0053] 1 Common rail system

[0054] 11 High-pressure oil pump

[0055] 12 Common Rail

[0056] 13 Controller

[0057] 111 Oil quantity control unit

[0058] 121 Pressure relief valve

[0059] 122 pressure sensor

[0060] 21 First dotted line

[0061] 22 solid line

[0062] 23 dot-dash line

[0063] 24 Second dotted line

[0064] 211 First Low Point

[0065] 212 High

[0066] 213 Second Low

[0067] Steps S1 and S2

[0068] Substeps S21, S22, and S23

Claims

1. A method for controlling a pressure relief valve (121) of a common rail (12) of a common rail system (1) of a vehicle, the method comprising at least the steps of: Step S1: Determine whether the vehicle is in a reverse towing condition; and Step S2: When the vehicle is in a reverse towing condition, during a predetermined period of time during the reverse towing condition, the pressure relief valve (121) of the common rail (12) is controlled using the set value of the rail pressure of the common rail (12) determined in the reverse towing condition as a control target, so that a center line around which the actual rail pressure of the common rail (12) changes deviates from the set value in a direction higher than the set value.

2. The method according to claim 1, wherein Includes at least one of the following features: The center line is characterized by the mean value of the actual rail pressure of the common rail (12); The pressure relief valve (121) is actively controlled according to the actual rail pressure of the common rail (12).

3. The method according to claim 2, wherein: Includes at least one of the following features: After the reverse towing condition starts, the actual rail pressure of the common rail (12) is reduced to a specific value less than or equal to the set value and then step S2 is executed; The oil quantity control unit (111) of the high-pressure oil pump (11) of the common rail system (1) remains closed during step S2.

4. The method according to claim 3, wherein: The step S2 at least includes the following sub-steps: Sub-step S21: opening the pressure relief valve (121) to reduce the actual rail pressure of the common rail (12) to a pressure value less than or equal to the set value; Sub-step S22: setting the opening pressure of the pressure relief valve (121) to a predetermined value higher than the set value; and Sub-step S23: When the actual rail pressure of the common rail (12) rises to the set opening pressure of the pressure relief valve (121), the process returns to sub-step S21 and is executed in a loop.

5. The method according to claim 4, wherein Includes at least one of the following features: In the sub-step S21, the actual rail pressure of the common rail (12) drops below the set value; The opening pressure of the pressure relief valve (121) is set to be 100 bar higher than the set value.

6. The method according to any one of claims 2 to 5, wherein: The opening pressure of the pressure relief valve (121) is actively controlled by controlling the magnitude of the current supplied to the pressure relief valve (121).

7. A computer-readable program carrier storing program instructions, which is used to implement the method according to any one of claims 1 to 6 when the program instructions are executed by a processor.

8. A controller (13) for a common rail system (1) of a vehicle, wherein: The controller (13) includes the computer-readable program carrier of claim 7.

9. A common rail system (1) for a vehicle, wherein: The common rail system (1) comprises a controller (13) according to claim 8.

10. The common rail system (1) according to claim 9, wherein: Includes at least one of the following features: The common rail system (1) further comprises a leak-free fuel injector; The common rail system (1) further comprises a high-pressure oil pump (11), wherein the high-pressure oil pump (11) is configured to be free of a zero-flow orifice.

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