JP3637800B2 - Negative pressure control device for brake booster - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a brake booster negative pressure control device, and more particularly to a brake booster negative pressure control device that controls a negative pressure of a brake booster by changing a control state of an engine.
[0002]
[Prior art]
Conventionally, as disclosed in, for example, Japanese Patent Laid-Open No. 10-175464, a negative pressure control device that controls the negative pressure of a brake booster is known. The brake booster uses a negative pressure in the intake pipe downstream of the engine throttle valve (hereinafter referred to as intake pipe negative pressure) as a power source to assist the depression of the brake pedal and generate a large braking force. The conventional negative pressure control device is applied to a direct injection engine (hereinafter referred to as a direct injection engine) that includes a fuel injection valve in a combustion chamber and directly injects fuel into the combustion chamber. According to the direct injection engine, for example, during low-load operation, the throttle valve is fully opened and a large amount of air is supplied to the combustion chamber, so that fuel efficiency can be improved by stratified combustion. Therefore, in the direct injection type engine, even if the accelerator operation is not performed, the intake pipe negative pressure may be reduced by fully opening the throttle valve, and a sufficient negative pressure may not be supplied to the brake booster. Therefore, in the conventional negative pressure control device, when the vehicle speed is equal to or higher than the predetermined value and the negative pressure of the brake booster is lower than the predetermined value, it is determined that the generation of the negative pressure is necessary, and the throttle valve By forcibly reducing the opening, sufficient assisting power by the brake booster is secured.
[0003]
[Problems to be solved by the invention]
By the way, in a vehicle, the engine control apparatus which controls an engine, and the brake control apparatus which controls chassis parts, such as a brake, are provided separately, and the structure by which both control apparatuses were connected so that communication was used may be used. Many. In such a configuration, it is considered that the brake control device transmits a negative pressure generation request to the engine control device based on the brake operation state and the like, and the engine control device performs negative pressure control of the brake booster based on the negative pressure generation request. It is done. However, in this case, if communication abnormality occurs between the engine control device and the brake control device, the negative pressure of the brake booster cannot be properly controlled.
[0004]
The present invention has been made in view of the above points, and in a negative pressure control device for a brake booster that controls the negative pressure of a brake booster based on communication between two control devices, communication between the two control devices is performed. An object of the present invention is to provide a negative pressure control device for a brake booster that can prevent the negative pressure of the brake booster from being insufficient even when an abnormality occurs.
[0005]
[Means for Solving the Problems]
  The above object is to provide a negative pressure control device for a brake booster that controls the negative pressure in the negative pressure chamber of the brake booster that can communicate with the intake passage downstream of the throttle valve of the engine. And
  A negative pressure sensor for detecting the negative pressure in the negative pressure chamber of the brake booster;
  The negative pressure sensor is connected;A first control device for controlling the engine;
  The first control deviceVia the first communication path and the second communication pathConnected to communicate,A second control device for controlling the brake, wherein the negative pressure state of the negative pressure chamber of the brake booster is determined based on a detection value of the negative pressure sensor received from the first control device via the first communication path. Judgment and the determined negative pressure stateVehicle stateWhenOn the basis of theGenerateA predetermined signal to the first control device;Via the second channelA second control device for transmitting and,
  The first control device receives the predetermined signal from the second control device.Via the second channelNegative pressure control means for controlling the negative pressure of the negative pressure chamber in response to receiving,
  A communication abnormality detecting means for detecting a communication abnormality between the first control device and the second control device;
  The negative pressure control means includesAt least the first communication path between the first control device and the second control deviceThis is achieved by a negative pressure control device for a brake booster that increases the negative pressure in the negative pressure chamber when a communication abnormality is detected.
[0006]
  In the first aspect of the present invention, the second control device isNegative pressure andA predetermined signal is transmitted to the first control device based on the vehicle state. Here, the vehicle state means a state related to a negative pressure required for a brake booster such as a brake operation state or a vehicle speed. The negative pressure control means is configured such that the first control device receives a predetermined signal from the second control device.Via the second channelThe negative pressure in the negative pressure chamber is controlled in response to reception. However, between the first control device and the second control deviceAt least in the first channelWhen a communication abnormality occurs, the second control deviceSince the detection value of the negative pressure sensor cannot be received via the first communication path, the negative pressure state of the negative pressure chamber of the brake booster cannot be determined.. On the other hand, according to the present invention, between the first control device and the second control device.At least in the first channelWhen a communication abnormality occurs, the negative pressure control means increases the negative pressure in the negative pressure chamber, thereby preventing the negative pressure in the negative pressure chamber from becoming insufficient.
[0007]
In this case, the negative pressure in the intake pipe downstream from the engine throttle valve (intake pipe negative pressure) changes according to the engine control state such as throttle opening and engine speed, and this intake pipe negative pressure is braked. It is supplied to the negative pressure chamber of the booster.
Therefore, as described in claim 2, in the negative pressure control device for a brake booster according to claim 1, the negative pressure control means is realized by the first control device changing the control state of the engine. It is also good to do.
[0008]
Further, the intake pipe negative pressure increases as the throttle opening decreases. Therefore, as described in claim 3, in the negative pressure control device for a brake booster according to claim 2, the negative pressure control means reduces the negative pressure in the negative pressure chamber by reducing the opening of the throttle valve. It may be increased.
In this case, as described in claim 4, in the negative pressure control device for a brake booster according to claim 3, the engine is selectively operable in a stratified combustion state or a stoichiometric combustion state, When the negative pressure control means decreases the opening of the throttle valve, the engine may be operated in a stoichiometric combustion state.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is an overall configuration diagram of a system according to an embodiment of the present invention. The system of this embodiment includes an engine 10. The engine 10 is controlled by the engine ECU 12. The engine 10 includes a cylinder block 13. A cylinder 14 is formed inside the cylinder block 13.
[0010]
A piston 16 is disposed inside the cylinder 14. The piston 16 can slide in the vertical direction in FIG. A combustion chamber 18 is defined above the piston 16 inside the cylinder 14. An injection port of the fuel injection valve 20 is exposed in the combustion chamber 18. The fuel injection valve 20 is connected to the engine ECU 12. The fuel injection valve 20 injects fuel into the combustion chamber 18 in accordance with a control signal supplied from the engine ECU 12.
[0011]
An exhaust pipe 24 communicates with the combustion chamber 18 via an exhaust valve 22. Each branch pipe of an intake manifold 28 communicates with the combustion chamber 18 via an intake valve 26. The intake manifold 28 communicates with the surge tank 30 on the upstream side. An intake pipe 32 communicates with the upstream side of the surge tank 30.
A throttle valve 34 is disposed in the intake pipe 32. The throttle valve 34 is connected to a throttle motor 36. The throttle motor 36 is connected to the engine ECU 12. The throttle motor 36 changes the opening degree of the throttle valve 34 in accordance with a control signal supplied from the engine ECU 12. A throttle opening sensor 38 is disposed in the vicinity of the throttle valve 34. The throttle opening sensor 38 outputs an electric signal corresponding to the opening of the throttle valve 34 (hereinafter referred to as throttle opening SC) to the engine ECU 12. The engine ECU 12 detects the throttle opening SC based on the output signal of the throttle opening sensor 38.
[0012]
An intake pressure sensor 40 is disposed in a portion of the intake pipe 32 downstream of the throttle valve 34 (hereinafter referred to as a downstream intake passage 32a). The intake pressure sensor 40 outputs an electrical signal corresponding to the negative pressure in the downstream side intake passage 32a (hereinafter referred to as intake pipe negative pressure PM) to the engine ECU 12. The engine ECU 12 detects the intake pipe negative pressure PM based on the output signal of the intake pressure sensor 40.
[0013]
One end of a negative pressure supply passage 42 is connected to the downstream side intake passage 32a. The other end of the negative pressure supply passage 42 is connected to a negative pressure chamber of the brake booster 44 (hereinafter referred to as a booster negative pressure chamber 44a). A check valve 46 is disposed in the negative pressure supply passage 42. The check valve 46 is a one-way valve that allows only air flow from the booster negative pressure chamber 44a side to the intake pipe 32 side. Therefore, when the intake pipe negative pressure PM is larger than the negative pressure in the booster negative pressure chamber 44a (hereinafter referred to as booster negative pressure PB), the intake pipe negative pressure PM is supplied to the booster negative pressure chamber 44a, When the intake pipe negative pressure PM is smaller than the booster negative pressure PB, the booster negative pressure PB is prevented from escaping to the intake pipe 32 side. In the present specification, “negative pressure” is expressed as a pressure difference from atmospheric pressure. Therefore, “large negative pressure” means that the pressure difference from the atmospheric pressure is large, that is, the absolute pressure is low.
[0014]
A brake pedal 48 and a master cylinder 50 are connected to the brake booster 44. The brake booster 44 assists the depression of the brake pedal 48 using the booster negative pressure PB as a power source, and generates a large fluid pressure in each fluid chamber provided in the master cylinder 50. Hereinafter, the fluid pressure generated in each fluid chamber of the master cylinder 50 is referred to as the master cylinder pressure P._{M / C}Called. A booster negative pressure sensor 52 is disposed in the booster negative pressure chamber 44a. Booster negative pressure sensor 52 outputs an electric signal corresponding to booster negative pressure PB to engine ECU 12. The engine ECU 12 detects the booster negative pressure PB based on the output signal of the booster negative pressure sensor 52.
[0015]
A hydraulic actuator 58 communicates with each liquid chamber of the master cylinder 50 via pipes 54 and 56, respectively. The hydraulic actuator 58 is controlled by the brake ECU 60. A wheel cylinder 62 provided corresponding to each wheel communicates with the hydraulic actuator 58. A wheel speed sensor 64 for detecting the wheel speed is disposed in the vicinity of each wheel. The output signal from the wheel speed sensor 64 is supplied to the brake ECU 60. The brake ECU 60 detects the vehicle speed V based on the output signal of the wheel speed sensor 64. FIG. 1 shows only a wheel cylinder 62 and a wheel speed sensor 64 for one wheel.
[0016]
The pipe 54 has a hydraulic pressure inside thereof, that is, a master cylinder pressure P_{M / C}A master pressure sensor 66 for detecting the above is disposed. An output signal from the master pressure sensor 66 is supplied to the brake ECU 60. The brake ECU 60 determines the master cylinder pressure P based on the output signal of the master pressure sensor 66._{M / C}Is detected.
In the system according to the present embodiment, the brake ECU 60 performs the master cylinder pressure P_{M / C}By controlling the hydraulic actuator 58 so that is supplied to each wheel cylinder 62, normal brake control for generating a braking force corresponding to the brake operation amount is realized. Further, the brake ECU 60 controls the hydraulic actuator 58 based on various vehicle information related to the slip state of the wheel, the deceleration of the vehicle, the yaw rate, and the like, thereby preventing the lock of the wheel during braking (ABS). ), Automatic braking control such as traction control (TRC) for preventing wheel slippage due to excessive driving torque and vehicle stabilization control (VSC) for preventing unstable behavior of the vehicle is realized.
[0017]
The engine 10 is provided with a rotation speed sensor 68. The engine 10 outputs an electrical signal corresponding to the engine speed to the engine ECU 12. The engine ECU 12 detects the engine speed based on the output signal of the speed sensor 68. The system of this embodiment also includes an accelerator pedal 70. An accelerator opening sensor 72 is disposed in the vicinity of the accelerator pedal 70. The accelerator opening sensor 72 outputs an electric signal corresponding to the depression stroke amount of the accelerator pedal 70 (hereinafter referred to as accelerator opening AC) to the engine ECU 12. The engine ECU 12 detects the accelerator opening degree AC based on a signal supplied from the accelerator opening degree sensor 72.
[0018]
The engine ECU 12 and the brake ECU 60 are connected to each other via communication lines 74 and 76. The communication line 74 is a serial communication line in the direction from the engine ECU 12 to the brake ECU 60, and the communication line 76 is a serial communication line in the direction from the brake ECU 60 to the engine ECU 12.
[0019]
The engine ECU 12 is also connected with a warning light 78 provided at the driver's seat of the vehicle. The warning lamp 78 is turned on in response to a drive signal supplied from the engine ECU 12.
In the present embodiment, the engine 10 operates in either a stratified combustion mode or a stoichiometric combustion mode depending on the load state. The stoichiometric combustion mode realizes stoichiometric combustion in the combustion chamber 18 by controlling the throttle opening SC based on the accelerator opening AC and supplying air of a flow rate corresponding to the accelerator opening AC to the combustion chamber 18. It is an operation mode. On the other hand, in the stratified combustion mode, the throttle opening SC is fully opened and a large amount of air is supplied to the combustion chamber 18, and fuel corresponding to the accelerator opening AC is injected in the compression stroke, thereby stratified combustion in the combustion chamber 18. Is an operation mode for realizing
[0020]
According to the stratified combustion mode, the fuel consumption of the engine 10 is improved by performing combustion at a larger air-fuel ratio than stoichiometric combustion. Further, according to the stratified combustion mode, the throttle opening SC is fully opened, so that the pumping loss of the engine 10 is reduced, and the fuel efficiency is improved. Therefore, from the viewpoint of improving the fuel consumption of the engine 10, it is desirable to operate the engine 10 in the stratified combustion mode as much as possible. However, when the load of the engine 10 (that is, the accelerator opening degree AC) increases, the amount of fuel to be injected by the fuel injection valve 20 also increases. In this case, when the fuel injection amount exceeds a certain value, the amount of air sucked into the intake pipe 32 (hereinafter referred to as intake air amount Q) is insufficient with respect to the fuel injection amount even when the throttle opening SC is fully opened. Therefore, it becomes impossible to realize stratified combustion.
[0021]
Therefore, the engine ECU 12 determines the fuel injection amount based on the accelerator opening AC, and determines whether or not stratified combustion is possible based on the fuel injection amount. If it is determined that stratified combustion is possible, the throttle opening SC is fully opened and the fuel injection valve 20 injects fuel in an amount corresponding to the accelerator opening AC in the compression stroke. Realize the mode. On the other hand, when it is determined that stratified combustion is impossible, the engine ECU 12 controls the throttle opening SC to a value corresponding to the accelerator opening AC, and at the same time, an amount corresponding to the throttle opening SC in the intake stroke. By injecting fuel with the fuel injection valve 20, the stoichiometric combustion mode is realized.
[0022]
As described above, in the stratified combustion mode, the throttle opening SC is fully opened regardless of the accelerator opening AC. When the throttle opening SC is fully opened, the negative pressure generated in the downstream side intake passage 32a, that is, the intake pipe negative pressure PM decreases. On the other hand, as described above, the brake booster 44 assists the depression of the brake pedal 48 using the booster negative pressure PB as a power source. When assistance by the brake booster 44 is performed, the booster negative pressure PB is consumed as the braking force increases. For this reason, in the stratified combustion mode, sufficient negative pressure cannot be supplied from the downstream side intake passage 32a to the booster negative pressure chamber 44a, and the booster negative pressure PB gradually decreases as the brake operation is performed. Therefore, when the brake operation is performed when the engine 10 is operating in the stratified combustion mode, a situation may occur in which the booster negative pressure PB is insufficient and sufficient assist by the brake booster 44 cannot be performed.
[0023]
Such a situation can be avoided by reducing the throttle opening SC and generating a large intake pipe negative pressure PM. That is, if a large intake pipe negative pressure PM is generated, this negative pressure is supplied to the booster negative pressure chamber 44a, so that a large booster negative pressure PB can be secured. Hereinafter, the control for generating the large booster negative pressure PB by reducing the throttle opening SC is referred to as booster negative pressure control.
[0024]
In this embodiment, the engine ECU 12 transmits a signal including the value of the booster negative pressure PB as data (hereinafter referred to as a booster negative pressure signal) to the brake ECU 60 at predetermined time intervals T. The brake ECU 60 detects the booster negative pressure PB from the received booster negative pressure signal and, based on the booster negative pressure PB, signals to the engine ECU 12 indicating whether or not it is necessary to supply negative pressure to the booster negative pressure chamber 44a. Transmit at time T intervals.
[0025]
That is, the brake ECU 60 needs to supply negative pressure to the booster negative pressure chamber 44a when the booster negative pressure PB is smaller than the predetermined reference value P0, and the negative to be supplied to the booster negative pressure chamber 44a. Pressure (hereinafter, negative pressure generation request value P_req) Including a signal (hereinafter referred to as a negative pressure generation request signal). When the booster negative pressure PB is equal to or higher than the predetermined reference value P0, a signal indicating that the negative pressure supply to the booster negative pressure chamber 44a is unnecessary (hereinafter referred to as a negative pressure generation unnecessary signal) is transmitted. . When the engine ECU 12 receives the negative pressure generation request signal from the brake ECU 60, the engine ECU 12 receives the negative pressure generation request value P._reqThe booster negative pressure control is executed so as to generate the intake pipe negative pressure PM equal to.
[0026]
As described above, the booster negative pressure control is executed based on information transmitted and received between the engine ECU 12 and the brake ECU 60 via the communication lines 74 and 74. For this reason, when abnormality occurs in communication via the communication line 74 or 74, the booster negative pressure control cannot be properly executed. That is, in a state where communication abnormality has occurred between the ECUs, the engine ECU 12 cannot recognize that the brake ECU 60 has requested generation of negative pressure, and the necessary booster negative pressure PB may not be ensured. . In this embodiment, when such a communication abnormality occurs, the booster negative pressure PB is forcibly increased to prevent the booster negative pressure PB from being insufficient.
[0027]
Hereinafter, in the present embodiment, a method for determining a communication abnormality between the engine ECU 12 and the brake ECU 60 will be described. FIG. 2 shows an example of a format of data communicated via the communication lines 74 and 76. As shown in FIG. 2, data communication is performed using a frame 100. The frame 100 is composed of an ID area 102 and a data area 104.
[0028]
The ID area 102 stores an ID number corresponding to the transmission order of the frames 100. That is, for example, every time the frame 100 is transmitted from the engine ECU 12 to the brake ECU 60, the ID numbers accommodated in the ID area 102 are “001”, “002”, “003”, “004”,. . . When it reaches a predetermined maximum value (for example, “100”), it returns to “000” again. The same applies when transmission from the brake ECU 60 to the engine ECU 12 is performed.
[0029]
In the data area 104, data to be communicated is stored as a binary value having a predetermined number of bits. That is, in the case of the booster negative pressure signal, data representing the booster negative pressure PB is stored in the data area 104, and in the case of the negative pressure generation request signal, the negative pressure generation request value P_reqIs stored in the data area 104, and in the case of a negative pressure generation unnecessary signal, a specific value (for example, “000... 0”) indicating that negative pressure generation is unnecessary is stored in the data area 104.
[0030]
As described above, each of the engine ECU 12 and the brake ECU 60 transmits a signal to the other ECU at a predetermined time T interval. Therefore, the engine ECU 12 and the brake ECU 60 can determine that an abnormality such as disconnection has occurred in the communication lines 76 and 74, respectively, when the next signal cannot be received even after the predetermined time T has elapsed since the previous signal reception. As described above, the ID number accommodated in the ID area 102 is determined according to the transmission order of the frames 100. Therefore, the engine ECU 12 and the brake ECU 60 determine that an abnormality has occurred in the communication lines 76 and 74, respectively, when the ID number of the frame received this time is different from the value expected from the ID number of the previously received frame. it can. Thus, in the present embodiment, a communication abnormality between the engine ECU 12 and the brake ECU 60 is determined based on whether or not a signal is received from the other ECU and the ID number included in the received signal.
[0031]
Next, in the present embodiment, the contents of processing executed by the brake ECU 60 and the engine ECU 12 to ensure the required booster negative pressure PB will be described. First, processing executed by the brake ECU 60 will be described. FIG. 3 is a flowchart of a routine executed by the brake ECU 60. When the brake ECU 60 starts the routine shown in FIG. 3, the brake ECU 60 first executes the process of step 120.
[0032]
In step 120, it is determined whether or not an abnormality has occurred in the communication line 74 from the engine ECU 12. As described above, this determination is made based on whether or not a signal is received via the communication line 74 at a predetermined timing, and whether or not the ID number of the received frame 100 is a predetermined value. . As a result, if it is determined that an abnormality has occurred in the communication line 74, then in step 122, a predetermined communication abnormality signal indicating a communication abnormality is transmitted to the engine ECU 12, and then the current routine ends. Is done. On the other hand, if it is determined in step 120 that there is no abnormality in the communication line 74, the process of step 124 is executed next.
[0033]
In step 124, the booster negative pressure PB is detected based on the booster negative pressure signal received from the communication line 74.
In step 126, the negative pressure generation request value P based on the vehicle speed V, the brake operation state, the presence or absence of abnormality of the hydraulic actuator 58, and the like._reqIs determined. For example, as the vehicle speed V increases, the consumption of the booster negative pressure PB until the vehicle stops increases. Therefore, the brake ECU 60 increases the negative pressure generation request value P as the vehicle speed increases._reqSet to a large value. Master cylinder pressure P_{M / C}When the ascending gradient of the vehicle is large, it can be determined that the driver intends to increase the braking force quickly. Therefore, the brake ECU 60 determines the master cylinder pressure P_{M / C}The negative pressure generation request value P is greater than the case where the upward gradient of the pressure exceeds a predetermined value._reqSet to a large value. Further, when an abnormality has occurred in the hydraulic actuator 58, it can be determined that sufficient assistance should be provided by the vacuum booster 44 to ensure a required braking force. Therefore, the brake ECU 60 determines that the negative pressure generation request value P is greater when the hydraulic actuator 58 is abnormal than when it is normal._reqSet to a large value.
[0034]
In step 128 following step 126, the booster negative pressure PB is set to the negative pressure generation request value P._reqWhether it is less than or not is determined. As a result, PB <P_reqIf the above is established, next, at step 130, the negative pressure generation request signal is transmitted to the engine ECU 12 at a predetermined timing (that is, at a timing at which the time interval from the previous transmission operation becomes the predetermined time T). After this processing is executed, the current routine is terminated. On the other hand, in step 128, PB <P_reqIf not, the process of transmitting a negative pressure generation unnecessary signal to the engine ECU 12 is executed at the same timing as in step 130, and then the current routine is terminated.
[0035]
Next, processing executed by the engine ECU 12 in this embodiment will be described with reference to FIGS. 4 and 5. FIG. 4 is a flowchart of a routine executed by the engine ECU 60 to ensure the booster negative pressure PB when a communication abnormality occurs between the engine ECU 60 and the brake ECU 12. When the engine ECU 60 starts the routine shown in FIG. 4, it first executes the process of step 150.
[0036]
In step 150, it is determined whether or not a communication abnormality signal is received from the brake ECU 60. As a result, if a communication abnormality signal is received, the communication abnormality flag Fc is set to “1” in step 152, and then the current routine is terminated. On the other hand, when the communication abnormality signal is not received in step 150, the process of step 154 is executed next.
[0037]
In step 154, it is determined whether or not an abnormality has occurred in the communication line 76 from the brake ECU 60. As described above, this determination is made based on whether or not a signal is received via the communication line 74 at a predetermined timing, and whether or not the ID number of the received frame 100 is a predetermined value. . As a result, if it is determined that an abnormality has occurred in the communication line 76, the communication abnormality flag Fc is set to “1” in the next step 152, and then the current routine is terminated. On the other hand, if it is determined in step 154 that no abnormality has occurred in the communication line 76, it is determined that communication between the engine ECU 12 and the brake ECU 60 is normal, and the current routine is terminated.
[0038]
FIG. 5 is a flowchart of a routine executed by the engine ECU 12 to realize booster negative pressure control. When the routine shown in FIG. 5 is started, the process of step 160 is first executed.
In step 160, it is determined whether or not the communication abnormality flag Fc is set to “1”. As a result, when Fc = 1 is established, it is determined that the booster negative pressure control cannot be properly executed due to an abnormality in communication between the engine ECU 12 and the brake ECU 60, and then the process of step 162 is executed. . On the other hand, if Fc = 1 is not established in step 160, the process of step 164 is executed next.
[0039]
In step 162, it is determined whether or not the engine 10 is operating in the stoichiometric combustion mode. As a result, when a negative determination is made, that is, when the engine is operating in the stratified combustion mode, the operation mode of the engine 10 is forcibly switched to the stoichiometric combustion mode in step 166 in order to secure a large booster negative pressure PB. It is done. When the process of step 166 ends, the process of step 168 is executed. On the other hand, if it is determined in step 162 that the engine is operating in the stoichiometric combustion mode, the process of step 168 is then executed.
[0040]
In step 168, processing for turning on the warning lamp 78 is performed. The warning lamp 78 is turned on to warn the passenger that a communication abnormality has occurred. When the processing of step 168 is finished, the current routine is finished.
On the other hand, in step 164, it is determined whether or not the engine 10 is operating in the stratified combustion mode. As a result, if a negative determination is made, that is, if the engine 10 is operating in the stoichiometric combustion mode, it is determined that the booster negative pressure control cannot be executed. In this case, the current routine is terminated without any further processing thereafter. On the other hand, if the engine 10 is operating in the stratified combustion mode in step 164, the process of step 170 is then executed.
[0041]
In step 170, it is determined whether or not the signal received in the communication abnormality determination process in step 154 of the routine shown in FIG. 4 is a negative pressure generation request signal. As a result, when a negative determination is made, the current routine is terminated. On the other hand, if an affirmative determination is made in step 170, the process of step 172 is executed next. In step 172, the negative pressure generation request value P is calculated from the negative pressure generation request signal._reqIs detected.
[0042]
In step 174, the negative pressure generation request value P_reqA throttle opening SC (hereinafter referred to as a target throttle opening SCc) for generating an intake pipe negative pressure PM equal to is determined. The intake pipe negative pressure PM decreases as the intake air amount Q increases, and increases as the engine speed Ne increases. Further, the intake air amount Q is substantially proportional to the throttle opening SC. Therefore, in step 174, the engine speed Ne and the negative pressure generation request value P_reqBased on the above, the target throttle opening SCc is determined. When the processing of step 174 is completed, the routine proceeds to step 176.
[0043]
In step 176, the intake air amount Q0 corresponding to the target throttle opening SCc is calculated, and in the subsequent step 178, the fuel injection amount F corresponding to the accelerator opening AC in the stratified combustion mode (that is, the engine output requested by the driver). The fuel injection amount F) necessary for realizing the above is calculated. Note that when the throttle opening SC is reduced to the target throttle opening SCc, the amount of fuel injection required to obtain a constant engine output increases due to an increase in pumping loss. In step 178, the fuel injection amount F is determined in consideration of the increase in the fuel injection amount due to the pumping loss. When the process of step 178 is completed, the routine proceeds to step 180.
[0044]
In step 180, it is determined whether or not the stratified combustion mode can be maintained by the intake air amount Q0 and the fuel injection amount F while maintaining the current engine speed Ne. As a result, if it is determined that the stratified combustion mode can be maintained, then in step 182, processing for reducing the throttle opening SC to the target throttle opening SCc is executed. When the process of step 182 is executed, the intake pipe negative pressure PM is reduced to the negative pressure generation request value P while the stratified combustion mode is maintained._reqStart to rise towards. In step 184 following step 182, the intake pipe negative pressure PM is changed to the negative pressure generation request value P._reqIt is determined whether or not As a result, the intake pipe negative pressure PM becomes the negative pressure generation request value P._reqIf not, the process of step 184 is executed again. On the other hand, in step 184, the intake pipe negative pressure PM is changed to the negative pressure generation request value P._reqThen, in step 186, the throttle opening SC is fully opened again, and a process for reducing the fuel injection amount by the amount corresponding to the decrease in the pumping loss is executed. When the process of step 186 is terminated, the current routine is terminated.
[0045]
On the other hand, if it is determined in step 180 that the stratified combustion mode cannot be maintained, then in step 188, processing for switching the operation mode of the engine 10 to the stoichiometric combustion mode is executed. In the stoichiometric combustion mode, the throttle opening SC is controlled to a value corresponding to the accelerator opening AC, so that a larger intake pipe negative pressure PM is generated than in the stratified combustion mode. Therefore, when the process of step 188 is executed, the intake pipe negative pressure PM starts to rise. In step 190 following step 188, the intake pipe negative pressure PM is changed to the negative pressure generation request value P._reqIt is determined whether or not As a result, the intake pipe negative pressure PM becomes the negative pressure generation request value P._reqIf not, the process of step 190 is executed again. On the other hand, in step 190, the intake pipe negative pressure PM is changed to the negative pressure generation request value P._reqThen, the process of step 192 is executed. In step 192, a process for returning the operation mode of the engine 10 from the stoichiometric combustion mode to the stratified combustion mode is executed. When the process of step 192 is terminated, the current routine is terminated.
[0046]
As described above, in this embodiment, when an abnormality occurs in communication between the engine ECU 12 and the brake ECU 60, the operation mode of the engine 10 is forcibly switched to the stoichiometric combustion mode, so that a large booster negative pressure is obtained. PB is secured. Therefore, according to the system of the present embodiment, it is possible to prevent the booster negative pressure PB from becoming insufficient even when the engine ECU 12 cannot receive the negative pressure generation request signal from the brake ECU 60 due to a communication abnormality between the ECUs. it can.
[0047]
Note that the method for determining the communication abnormality between the engine ECU 12 and the brake ECU 60 is not limited to the method of the above embodiment, and any known method can be used.
In the above embodiment, the booster negative pressure PB is increased by decreasing the throttle opening SC. However, the present invention is not limited to this, and the booster negative pressure PB may be increased by increasing the engine speed. Is possible.
[0048]
Furthermore, in the above embodiment, the securing of the engine output is prioritized over the securing of the booster negative pressure PB, and the execution of the booster negative pressure control is permitted only when the engine 10 is operating in the stratified combustion mode. However, priority is given to securing the booster negative pressure PB, and even in the stoichiometric combustion mode, when a large booster negative pressure PB is required, negative pressure generation is performed by forcibly closing the throttle opening SC. Also good. In this sense, the present invention can also be applied to a normal engine whose engine output is controlled according to the throttle opening (that is, an engine that operates in a constant stoichiometric combustion mode).
[0049]
In the above-described embodiment, the engine ECU 12 sends a negative pressure generation request to the “first control device” described in the claims, and the brake ECU 60 sends the “second control device” described in the claims to the “second control device”. The signal corresponds to the “predetermined signal” described in the claims, and the “negative pressure control means” described in the claims by the engine ECU 12 executing the routine shown in FIG. The engine ECU 12 executes the processing of step 154 of the routine shown in FIG. 4 to realize the “communication abnormality detection means” described in the claims.
[0050]
【The invention's effect】
As described above, according to the first to fourth aspects of the present invention, the first control device receives a predetermined signal from the second control device due to a communication abnormality between the first control device and the second control device. Even if it is not possible to receive the signal, it is possible to prevent the negative pressure of the brake booster from being insufficient.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a system according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a format of data communicated between an engine ECU and a brake ECU in the present embodiment.
FIG. 3 is a flowchart of a routine executed by the brake ECU to transmit a negative pressure generation request signal or a negative pressure generation unnecessary signal in the present embodiment.
FIG. 4 is a flowchart of a routine that is executed by the engine ECU to determine an abnormality in a communication line from the brake ECU in the present embodiment.
FIG. 5 is a flowchart of a routine executed by the engine ECU to control the booster negative pressure in the present embodiment.
[Explanation of symbols]
10 engine
12 Engine ECU
32 Intake pipe
32a Downstream intake passage
34 Throttle valve
44 Brake booster
44a Booster negative pressure chamber
60 Brake ECU

Claims (4)

A negative pressure control device for a brake booster that controls negative pressure in a negative pressure chamber of a brake booster that can communicate with an intake passage downstream of a throttle valve of an engine,
A negative pressure sensor for detecting the negative pressure in the negative pressure chamber of the brake booster;
A first control device connected to the negative pressure sensor and controlling the engine;
A second control device that is communicably connected to the first control device via a first communication path and a second communication path and controls a brake, wherein the first control device The negative pressure state of the negative pressure chamber of the brake booster is determined based on the detection value of the negative pressure sensor received via the communication path, and the predetermined signal generated based on the determined negative pressure state and the vehicle state is A second control device for transmitting to the first control device via a second communication path ;
Negative pressure control means for controlling the negative pressure of the negative pressure chamber in response to the first control device receiving the predetermined signal from the second control device via a second communication path ;
A communication abnormality detecting means for detecting a communication abnormality between the first control device and the second control device;
The negative pressure control means increases the negative pressure in the negative pressure chamber when a communication abnormality is detected at least in the first communication path between the first control device and the second control device . A negative pressure control device for a brake booster characterized by that. The negative pressure control device for a brake booster according to claim 1,
The negative pressure control means is realized by the first control device changing the control state of the engine. The negative pressure control device for a brake booster according to claim 2,
The negative pressure control device for a brake booster, wherein the negative pressure control means increases the negative pressure in the negative pressure chamber by decreasing the opening of the throttle valve. The negative pressure control device for a brake booster according to claim 3,
The engine can be selectively operated in either a stratified combustion state or a stoichiometric combustion state,
A negative pressure control apparatus for a brake booster, wherein the engine is operated in a stoichiometric combustion state when the negative pressure control means decreases the opening of the throttle valve.

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