Control method for electric vacuum pumps

Abstract

This invention provides a control method for an electric vacuum pump that can improve its operational responsiveness. [Solution] The electric vacuum pump control method according to the present invention is a control method for an electric vacuum pump of a vehicle equipped with an electric vacuum pump that supplies negative pressure to a brake booster, and determines whether a value related to brake operation exceeds a first threshold, and if it is determined that the value related to brake operation exceeds the first threshold, the electric vacuum pump is activated.

Description

Technical Field

[0001] The present invention relates to a control method for an electric vacuum pump.

Background Art

[0002] Conventionally, engine-equipped vehicles having a brake booster and an electric vacuum pump are known. For example, it is known that the electric vacuum pump operates when the negative pressure of the brake booster is equal to or lower than a threshold value due to insufficient negative pressure supply from the engine or the like, and supplies negative pressure to the brake booster.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] However, for example, in an electric vehicle or the like not equipped with an engine, when negative pressure is to be generated instantaneously, in a configuration where the electric vacuum pump is operated when the negative pressure of the brake booster falls below a threshold value, the operation of the electric vacuum pump may be delayed.

[0005] An object of the present invention is to provide a control method for an electric vacuum pump that can improve operation responsiveness.

Means for Solving the Problem

[0006] To achieve the above object, a control method for an electric vacuum pump according to the present invention is a control method for an electric vacuum pump of a vehicle including an electric vacuum pump that supplies negative pressure to a brake booster, the method comprising: determining whether or not a value related to a brake operation exceeds a first threshold value; and operating the electric vacuum pump when it is determined that the value related to the brake operation exceeds the first threshold value.

[0007] With this configuration, for example, the electric vacuum pump can be activated when a value related to brake operation exceeds a first threshold. Therefore, the operational responsiveness of the electric vacuum pump can be improved.

[0008] Furthermore, the electric vacuum pump control method according to the present invention further determines, for example, whether the negative pressure of the brake booster falls below a second threshold, and if it is determined that at least one of the following is true (the value related to brake operation is above a first threshold and the negative pressure of the brake booster is below a second threshold), the electric vacuum pump is activated.

[0009] With this configuration, for example, the electric vacuum pump can be activated when it is determined that at least one of the following conditions is met: the value related to brake operation exceeds a first threshold, and the negative pressure of the brake booster falls below a second threshold. Therefore, the responsiveness of the electric vacuum pump can be improved. [Effects of the Invention]

[0010] According to the present invention, a control method for an electric vacuum pump that can improve operational responsiveness can be provided. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a block diagram showing an example of the configuration of a control system according to an embodiment. [Figure 2] Figure 2 is a diagram illustrating the operation control of the EVP according to the embodiment. [Figure 3] Figure 3 is an exemplary flowchart showing the control flow of the control system according to the embodiment. [Modes for carrying out the invention]

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this embodiment, vehicle 1 will be described using an electric vehicle as an example. For example, a battery electric vehicle (BEV) will be described using an electric vehicle as an example, but it is not limited thereto.

[0013] For example, the electric vehicle may be a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), a fuel cell electric vehicle (FCV), or any other type of vehicle that uses electricity for propulsion. Vehicle 1 may also be an engine-powered vehicle that uses an engine for propulsion.

[0014] Figure 1 is a block diagram showing an example of the configuration of the control system 10 according to an embodiment. The control system 10 will be described in an example of how it is installed and applied to a vehicle 1.

[0015] As shown in Figure 1, the control system 10 includes a brake pedal 2, a brake booster 3, a master cylinder 4, a wheel cylinder 5, a negative pressure sensor 6, a brake ECU (Electronic Control Unit) 7, an EVP (Electric Vacuum Pump)-ECU 8, and an EVP (Electric Vacuum Pump) 9.

[0016] Brake pedal 2 is connected to brake booster 3. When pressed by the driver, brake pedal 2 transmits the input force to brake booster 3.

[0017] The brake booster 3 receives the pedal force transmitted from the brake pedal 2. The brake booster 3 amplifies (multiplies) the input pedal force using the negative pressure in the brake booster 3 and inputs the amplified pedal force to the master cylinder 4.

[0018] Here, the negative pressure refers to the absolute value of the differential pressure (relative pressure) between the atmospheric pressure and the internal pressure of the brake booster 3 relative to the atmospheric pressure. A small or insufficient negative pressure means that the differential pressure between the atmospheric pressure and the internal pressure of the brake booster 3 relative to the atmospheric pressure is small.

[0019] The master cylinder 4 generates brake fluid pressure (master cylinder pressure) corresponding to the pedal force input from the brake booster 3. The brake fluid pressure is distributed through the fluid pressure circuit to the wheel cylinder 5 of the brake provided on each wheel by the function of the brake actuator, and is used for the braking force of the wheels including the drive wheels from each brake.

[0020] The negative pressure sensor 6 is provided in the brake booster 3 and detects the negative pressure of the brake booster 3. The negative pressure sensor 6 is connected to the EVP-ECU 8.

[0021] The brake ECU 7 includes a master cylinder pressure sensor 71. The master cylinder pressure sensor 71 detects the brake fluid pressure output from the master cylinder 4. The brake ECU 7 is communicably connected to the EVP-ECU 8. The brake ECU 7 outputs the value of the brake fluid pressure to the EVP-ECU 8.

[0022] In addition, the brake ECU 7 calculates a vehicle speed value signal. The brake ECU 7 outputs the calculation result to the EVP-ECU 8.

[0023] The EVP-ECU 8 is connected to the EVP 9. The EVP-ECU 8 controls the EVP 9 to operate or stop. For example, the EVP-ECU 8 acquires the value of the negative pressure of the brake booster 3 from the negative pressure sensor 6. The EVP-ECU 8 acquires the value of the brake fluid pressure from the brake ECU 7. The EVP-ECU 8 performs failure detection of the system related to the EVP 9.

[0024] The EVP-ECU8 determines whether the brake fluid pressure exceeds the first threshold. If the EVP-ECU8 determines that the brake fluid pressure exceeds the first threshold, it controls the system to activate the EVP9. The first threshold is the threshold at which the EVP9 is activated when the brake fluid pressure exceeds the first threshold, such as during sudden braking.

[0025] The EVP-ECU8 determines whether the negative pressure of the brake booster 3 falls below the second threshold. If the EVP-ECU8 determines that the negative pressure of the brake booster 3 falls below the second threshold, it controls the system to activate the EVP9. The second threshold is the threshold at which the EVP9 is activated when the negative pressure of the brake booster 3 is insufficient.

[0026] For example, even if the EVP-ECU8 determines that the negative pressure of the brake booster 3 does not fall below the second threshold, if it determines that the brake fluid pressure exceeds the first threshold, it will control the system to activate the EVP9.

[0027] Furthermore, while the EVP9 is operating, the EVP-ECU8 determines, for example, whether the negative pressure of the brake booster 3 is above a stop threshold. If the EVP-ECU8 determines, for example, that the negative pressure of the brake booster 3 is above a stop threshold, it controls the EVP9 to stop after a predetermined time has elapsed. The stop threshold is greater than the second threshold. Note that the stop threshold is given as an example of a stop condition, but it is not limited to this.

[0028] The EVP9 is controlled by the EVP-ECU8. The EVP9 operates under the control of the EVP-ECU8 and supplies negative pressure to the brake booster 3. The EVP9 is connected to the brake booster 3, for example, by a negative pressure supply pipe.

[0029] Furthermore, the EVP9 is stopped when controlled by the EVP-ECU8 during operation. By stopping, the EVP9 ceases supplying negative pressure to the brake booster 3.

[0030] Each ECU in the control system 10 is connected to enable bidirectional communication using the CAN (Controller Area Network) communication protocol. Various sensors necessary for control are connected to each ECU, and detection signals from these connected sensors are input to each ECU. In addition to detection signals from the various sensors, each ECU also receives information necessary for control from other ECUs.

[0031] Here, we have described the case where the EVP-ECU8 directly obtains the negative pressure of the brake booster 3 from the negative pressure sensor 6, but this is not the only case. For example, the EVP-ECU8 may obtain the negative pressure of the brake booster 3 from another ECU that obtains the negative pressure of the brake booster 3 from the negative pressure sensor 6. Other ECUs are, for example, ECUs mounted on the vehicle 1, and specifically, brake ECU 7 and drivetrain ECU (not shown), etc.

[0032] Furthermore, while we have described a case where the EVP-ECU8 determines the operation of the EVP9 and controls the EVP9, this is not the only case. For example, the brake ECU7 or drivetrain ECU mounted on vehicle 1 may determine the operation of the EVP9 and control the EVP.

[0033] Furthermore, although the EVP-ECU8 was explained using the example of acquiring detection results from the brake ECU7 and controlling the system, it is also possible for one ECU to perform both the acquisition of detection results and control. Alternatively, other ECUs may also perform both the acquisition of detection results and control.

[0034] Here, we will explain a variation. The example given was when the EVP-ECU8 determines whether or not to activate the EVP9 based on brake fluid pressure. However, the condition is not limited to brake fluid pressure alone. The EVP-ECU8 controls the EVP9 based on values ​​related to brake operation.

[0035] Values ​​related to brake operation include, for example, the brake fluid pressure and its pressure gradient, the stroke amount and stroke speed of brake pedal 2, the reaction force and rate of change of brake pedal 2, and the negative pressure decrease rate of brake booster 3.

[0036] The stroke amount and reaction force of brake pedal 2 are obtained, for example, from sensors that detect the stroke amount and reaction force of brake pedal 2. The rate of decrease in negative pressure of brake booster 3 is obtained, for example, from negative pressure sensor 6.

[0037] Specifically, the EVP-ECU8 acquires values ​​related to brake operation. The EVP-ECU8 determines whether the values ​​related to brake operation exceed the first threshold. If the EVP-ECU8 determines that the values ​​related to brake operation exceed the first threshold, it activates the EVP9.

[0038] For example, even if the EVP-ECU8 determines that the negative pressure of the brake booster 3 does not fall below the second threshold, if it determines that the value related to brake operation exceeds the first threshold, it will control the system to activate the EVP9.

[0039] Figure 2 is a diagram illustrating the operation control of the EVP9 according to the embodiment. Figure 2 shows graphs G1, G2, G3, threshold a1, threshold a2, and threshold b1.

[0040] Graph G1 shows the change in negative pressure [kPa-G] of brake booster 3. Graph G2 shows the change in brake fluid pressure [MPa]. Graph G3 shows the change in vehicle speed [km / h].

[0041] Threshold a1 is the second threshold. The EVP-ECU8 controls the system to activate the EVP9 when the negative pressure of the brake booster 3, as shown in graph G1, falls below threshold a1.

[0042] Threshold a2 is the stop threshold. The EVP-ECU8 controls the EVP9 to stop when the negative pressure of the brake booster 3, as shown in graph G1, is greater than or equal to threshold a2.

[0043] Threshold b1 is the first threshold. The EVP-ECU8 controls the system to activate the EVP9 when the brake fluid pressure shown in graph G2 exceeds threshold b1.

[0044] As shown in graph G1, the negative pressure in the brake booster 3 decreases at time t1, for example, when the brake pedal 2 is operated. At time t2, the EVP 9 is activated. At this time, the negative pressure supplied to the brake booster 3 by the operation of the EVP 9 mitigates the negative pressure consumption caused by the driver's brake operation. The negative pressure in the brake booster 3 increases at time t2-t3, for example, because the EVP 9 is activated.

[0045] As shown in graph G2, the brake fluid pressure increases at time t1, for example, when brake pedal 2 is operated. At time t2, the brake fluid pressure exceeds threshold b1 (first threshold). Therefore, at time t2, the EVP-ECU8 controls the system to activate the EVP9 because the brake fluid pressure exceeds threshold b1 (first threshold).

[0046] In other words, at time t2, the negative pressure of brake booster 3 shown in graph G1 does not fall below threshold a1, but EVP-ECU8 activates EVP9 because the brake fluid pressure shown in graph G2 exceeds threshold b1 (first threshold).

[0047] Therefore, by using brake fluid pressure as the condition for activating the EVP9, for example, the responsiveness of the difference c1 between the negative pressure of the brake booster 3 and the threshold a1, as shown in graph G1 at time t2, can be improved.

[0048] EVP-ECU8 activates EVP9 between times t2 and t3. The negative pressure of brake booster 3 increases between times t2 and t3 due to the negative pressure supplied by EVP9.

[0049] The negative pressure of brake booster 3 becomes greater than or equal to threshold a2 at time t3.

[0050] In Figure 2, graph G2 was explained using brake fluid pressure as an example, but it is not limited to brake fluid pressure alone. For example, graph G2 could represent values ​​related to brake operation. Alternatively, a new graph relating to brake operation other than brake fluid pressure could be added, and the operation of EVP9 could be determined using values ​​relating to brake operation other than brake fluid pressure.

[0051] Figure 3 is an exemplary flowchart showing the control flow of the control system 10 according to the embodiment. As shown in Figure 3, the EVP-ECU 8 acquires the negative pressure of the brake booster 3 from the negative pressure sensor 6 (step S1).

[0052] The EVP-ECU8 obtains brake fluid pressure from the master cylinder pressure sensor 71 of the brake ECU7 (step S2).

[0053] The EVP-ECU8 determines whether at least one of the following is true: the brake fluid pressure is above a first threshold and the negative pressure of the brake booster 3 is below a second threshold (step S3).

[0054] If the EVP-ECU8 fails to satisfy both conditions (step S3; No), namely that the brake fluid pressure is above the first threshold and the negative pressure of the brake booster 3 is below the second threshold, it terminates the process and repeats the process from step S1 until the power to vehicle 1 is shut off again.

[0055] The EVP-ECU8 controls the activation of the EVP9 if at least one of the following conditions is met: the brake fluid pressure is above a first threshold and the negative pressure of the brake booster 3 is below a second threshold (step S3; Yes).

[0056] In other words, even if the EVP-ECU8 determines that the negative pressure of the brake booster 3 does not fall below the second threshold, if it determines that the brake fluid pressure exceeds the first threshold, it controls the system to activate the EVP 9.

[0057] The EVP-ECU8 acquires the negative pressure of the brake booster 3 while the EVP9 is operating. The EVP-ECU8 determines whether the negative pressure of the brake booster 3 is above the stop threshold (step S5). Note that the stop threshold is given as an example of a stop condition, but it is not limited to this.

[0058] If the EVP-ECU8 determines that the negative pressure of the brake booster 3 is below the stop threshold (step S5; No), it returns to step S4 and controls the operation of the EVP9 to continue.

[0059] If the EVP-ECU8 determines that the negative pressure of the brake booster 3 is above a stop threshold (step S5; Yes), it controls the EVP 9 to stop after a predetermined time has elapsed (step S6). The process ends there, and the process is repeated from step S1 until the power to the vehicle 1 is shut off again.

[0060] In Figure 3, brake fluid pressure was used as an example, but it is not limited to brake fluid pressure alone. For example, values ​​related to brake operation may be used to determine the operation of the EVP9.

[0061] As a variation, in step S3, the EVP-ECU8 may determine only whether the value related to brake operation (e.g., brake fluid pressure) exceeds the first threshold. Furthermore, in step S4, the EVP-ECU8 may control the system to activate the EVP9 if the value related to brake operation exceeds the first threshold.

[0062] The electric vacuum pump control method according to this embodiment is a control method for an electric vacuum pump in a vehicle equipped with an electric vacuum pump that supplies negative pressure to a brake booster, and determines whether a value related to brake operation exceeds a first threshold, and if it is determined that the value related to brake operation exceeds the first threshold, the electric vacuum pump is activated.

[0063] According to this configuration, the control method for the electric vacuum pump can improve the operational responsiveness of the electric vacuum pump by, for example, activating the electric vacuum pump when a value related to brake operation exceeds a first threshold.

[0064] For example, the values ​​related to brake operation include at least one of the following: brake fluid pressure, brake pedal stroke, brake pedal reaction force, and brake booster negative pressure decrease rate.

[0065] Furthermore, for example, by activating the electric vacuum pump when a value related to brake operation exceeds a first threshold, the responsiveness of the electric vacuum pump during sudden braking and other situations can be improved.

[0066] For example, in conventional engine-powered vehicles and electric vehicles with low negative pressure supply capacity, the EVP (Energy Valve Pump) may operate slowly. In this case, the EVP cannot instantly generate the necessary negative pressure when the negative pressure of the brake booster rapidly decreases, such as during sudden braking. For example, it is known to add a separate negative pressure tank in addition to the brake booster. However, adding a negative pressure tank increases costs due to the increase in parts. It also requires securing mounting space. Furthermore, adding a negative pressure tank is disadvantageous for continuous negative pressure consumption such as pumping.

[0067] According to this embodiment, operational responsiveness can be improved, allowing for a reduction in the size of the vacuum tank in vehicles equipped with one. Furthermore, because operational responsiveness can be improved, the vacuum tank can be eliminated entirely. This reduces costs and increases the flexibility of installation by reducing or eliminating the vacuum tank.

[0068] Furthermore, by limiting early activation to infrequent situations such as sudden braking, the frequency of EVP9 activation can be reduced, thereby reducing NVH (noise and vibration). Additionally, reducing the frequency of EVP9 activation can improve its durability.

[0069] The control method for the electric vacuum pump according to this embodiment further determines whether the negative pressure of the brake booster falls below a second threshold, and if it is determined that at least one of the following is true (the value related to brake operation is above a first threshold and the negative pressure of the brake booster is below a second threshold), the electric vacuum pump is activated.

[0070] With this configuration, even if the negative pressure of the brake booster does not fall below the second threshold, the electric vacuum pump can be activated, for example, if the brake fluid pressure exceeds the first threshold. Therefore, the operational responsiveness of the electric vacuum pump can be improved.

[0071] Furthermore, for example, the control method for the electric vacuum pump can improve the operational responsiveness of the electric vacuum pump by, for instance, activating the electric vacuum pump when a value related to brake operation exceeds a first threshold, compared to activating the electric vacuum pump when the negative pressure of the brake booster falls below a second threshold.

[0072] Although embodiments of the present invention have been described above, these embodiments are presented as examples only and are not intended to limit the scope of the invention. This novel embodiment can be implemented in various other forms. Furthermore, various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. Moreover, this embodiment is included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0073] 1 vehicle 3. Brake booster 7 Brake ECU 8 EVP-ECU 9. EVP (Electric Vacuum Pump) 10 Control Systems

Claims

1. A method for controlling an electric vacuum pump in a vehicle equipped with an electric vacuum pump that supplies negative pressure to a brake booster, Determine whether the value related to brake operation exceeds the first threshold. If it is determined that the value related to the brake operation exceeds the first threshold, the electric vacuum pump is activated. Control method for electric vacuum pumps.

2. Further determination is made as to whether the negative pressure of the brake booster falls below a second threshold. If it is determined that the value related to the brake operation exceeds the first threshold and the negative pressure of the brake booster falls below the second threshold, the electric vacuum pump is activated. A method for controlling an electric vacuum pump according to claim 1.

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