JP2014201262A - Brake system, brake system control method, and brake system abnormality diagnosis method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a brake system, a brake system control method, and a brake system abnormality diagnosis method capable of achieving cost reduction by suppressing the capability of a vacuum pump to a necessary minimum.SOLUTION: According to one aspect of the present invention, in a brake system 1, a relative pressure of a target booster negative pressure Ao to an atmospheric pressure Pa is set to a predetermined target pressure -A if the atmospheric pressure Pa is a high pressure equal to or higher than a predetermined pressure Pa_L, and set to a lower pressure than the predetermined pressure -A if the atmospheric pressure Pa is a low pressure lower than the predetermined pressure Pa_L. A relative pressure of a pump generated negative pressure pp to the atmospheric pressure Pa is set to a higher negative pressure than the relative pressure of the target booster negative pressure Ao to the atmospheric pressure Pa and to a lower negative pressure than the predetermined target pressure -A if the atmospheric pressure Pa is lower than a predetermined pressure Pa_X lower than the predetermined pressure Pa_L.

Description

  The present invention relates to a brake system having a vacuum pump for supplying a negative pressure to a negative pressure chamber of a brake booster, a control method for the brake system, and an abnormality diagnosis method for the brake system.

  Generally, in order to obtain a sufficient negative pressure in the negative pressure chamber of the brake booster, a vacuum pump is connected in parallel to the main negative pressure passage for supplying negative pressure from the intake system of the engine to the negative pressure chamber of the brake booster. It is arranged to supply negative pressure from the vacuum pump to the negative pressure chamber of the brake booster.

  Here, in Patent Document 1 relating to a brake system having a vacuum pump, a negative pressure tank is connected to a negative pressure booster, and when the atmospheric pressure is equal to or higher than a predetermined pressure, the relative pressure between the atmospheric pressure and the internal pressure of the negative pressure tank. A technique is disclosed in which the negative pressure pump is driven and controlled according to the pressure, and when the atmospheric pressure is less than a predetermined pressure, the negative pressure pump is driven and controlled according to the absolute pressure in the negative pressure tank.

Japanese Patent Laid-Open No. 9-177678

  However, in the technique of Patent Document 1, the absolute pressure in the tank in the negative pressure tank connected to the negative pressure booster is set higher than the capacity of the negative pressure pump even when the atmospheric pressure is low. Therefore, the capacity of the negative pressure pump is wasted. Moreover, since the technique of patent document 1 does not have the structure which supplies the negative pressure which generate | occur | produces with the intake pipe of an engine to a negative pressure booster, the operating frequency of a negative pressure pump will become high.

  Therefore, the present invention has been made to solve the above-described problems, and can provide a brake system, a brake system control method, and an abnormality in the brake system that can reduce the cost by suppressing the capacity of the vacuum pump to a necessary minimum. It is an object to provide a diagnostic method.

  One aspect of the present invention made to solve the above-described problems is a brake system, comprising: a brake booster; and a vacuum pump that supplies negative pressure to the negative pressure chamber of the brake booster. The relative pressure with respect to the atmospheric pressure of the target booster negative pressure chamber pressure, which is the target pressure of the pressure chamber, is a large value of the brake operation guarantee negative pressure, which is a pressure necessary in the negative pressure chamber of the brake booster to ensure the operation of the brake The negative pressure is set to be higher than the relative pressure with respect to the atmospheric pressure, the predetermined target pressure is set when the atmospheric pressure is equal to or higher than the first predetermined pressure, and the predetermined target is set when the atmospheric pressure is lower than the first predetermined pressure. The relative negative pressure to the atmospheric pressure of the pump maximum generated negative pressure, which is the maximum negative pressure that can be generated by the vacuum pump, is set to be lower than the first predetermined pressure. When the force is less than the second predetermined pressure, the target booster negative pressure is set to a negative pressure higher than the relative pressure with respect to the atmospheric pressure and set to a negative pressure lower than the predetermined target pressure. It is characterized by this.

  According to this aspect, the relative pressure with respect to the atmospheric pressure of the maximum generated negative pressure of the pump is less than the second predetermined pressure that is lower than the first predetermined pressure and the atmospheric pressure of the brake operation guarantee negative pressure with respect to the atmospheric pressure. The negative pressure is set higher than the relative pressure, and the negative pressure is set lower than a predetermined target pressure in the negative pressure chamber of the brake booster. Therefore, the pump capacity (suction capacity) of the vacuum pump can be suppressed to the minimum necessary. Therefore, the cost of the vacuum pump can be reduced.

  Another aspect of the present invention made to solve the above problems is a brake system control method, wherein the brake system includes a brake booster, a vacuum pump for supplying negative pressure to a negative pressure chamber of the brake booster, Negative pressure chamber pressure detecting means for detecting a booster negative pressure chamber pressure that is a pressure of the negative pressure chamber of the brake booster, and a target booster negative pressure chamber pressure that is a target pressure of the negative pressure chamber of the brake booster The relative pressure to the atmospheric pressure is set to a higher negative pressure than the relative pressure to the atmospheric pressure of the brake operation guarantee negative pressure, which is a pressure required in the negative pressure chamber of the brake booster in order to ensure the operation of the brake. Is set to a predetermined target pressure when the pressure is equal to or higher than the first predetermined pressure, and is set to a negative pressure lower than the predetermined target pressure when the atmospheric pressure is lower than the first predetermined pressure. And the relative pressure to the atmospheric pressure of the pump maximum generated negative pressure, which is the maximum negative pressure that can be generated by the vacuum pump, is less than a second predetermined pressure that is lower than the first predetermined pressure, The target booster negative pressure chamber pressure is set to a negative pressure higher than a relative pressure with respect to the atmospheric pressure, and set to a negative pressure lower than the predetermined target pressure, and the negative pressure chamber pressure detecting means In the negative pressure indoor pressure determination step for determining whether or not the booster negative pressure chamber pressure detected by the step is a negative pressure lower than the target booster negative pressure chamber pressure, the booster negative pressure chamber pressure is the target booster When the negative pressure is lower than the negative pressure chamber pressure, the vacuum pump is controlled to operate, and in the negative pressure chamber pressure determination step, the booster negative pressure chamber pressure is set to the target booster negative pressure chamber pressure. More negative If it is possible to control so as to stop the vacuum pump, characterized by.

  According to this aspect, the relative pressure with respect to the atmospheric pressure of the maximum generated negative pressure of the pump is less than the second predetermined pressure that is lower than the first predetermined pressure and the atmospheric pressure of the brake operation guarantee negative pressure with respect to the atmospheric pressure. The negative pressure is set higher than the relative pressure, and the negative pressure is set lower than a predetermined target pressure in the negative pressure chamber of the brake booster. Therefore, the pump capacity (suction capacity) of the vacuum pump can be suppressed to the minimum necessary. Therefore, the cost of the vacuum pump can be reduced.

  In addition, when the booster negative pressure chamber pressure is lower than the target booster negative pressure chamber pressure, the vacuum pump is operated, and the booster negative pressure chamber pressure is higher than the target booster negative pressure chamber pressure. Since the vacuum pump is controlled to be stopped, the operation of the unnecessary vacuum pump can be suppressed to reduce the operation frequency of the vacuum pump, and the operation of the brake can be ensured even at a high altitude where the atmospheric pressure is low.

  In the above aspect, the brake system includes a passage connected to the negative pressure chamber of the brake booster and the intake system, and an intake negative pressure detection unit that detects an intake negative pressure that is a pressure of the intake system. And determining whether the intake negative pressure detected by the intake negative pressure detecting means is lower than the booster negative pressure indoor pressure detected by the negative pressure indoor pressure detecting means. In the determination step, when the intake negative pressure is lower than the booster negative pressure chamber pressure, control is performed to shift to the negative pressure chamber pressure determination step, and in the intake negative pressure determination step When the intake negative pressure is higher than the booster negative pressure chamber pressure, the vacuum pump is stopped and the negative pressure is supplied from the intake system to the negative pressure chamber through the passage. To control , It is preferable.

  According to this aspect, when the intake negative pressure is a high negative pressure higher than the booster negative pressure chamber pressure, the vacuum pump is stopped so that the negative pressure is supplied from the intake system to the negative pressure chamber of the brake booster. Therefore, the operation of the vacuum pump can be further suppressed to further reduce the frequency of operation of the vacuum pump, and the operation of the brake can be ensured even at high altitude where the atmospheric pressure is low.

  Another aspect of the present invention made to solve the above-described problems is a brake system abnormality diagnosis method, wherein the brake system includes a brake booster, and a vacuum pump that supplies a negative pressure to the negative pressure chamber of the brake booster. Negative pressure chamber pressure detecting means for detecting a booster negative pressure chamber pressure that is a pressure of the negative pressure chamber of the brake booster, and a target booster negative pressure chamber pressure that is a target pressure of the negative pressure chamber of the brake booster. The relative pressure with respect to the atmospheric pressure is set to a higher negative pressure than the relative pressure with respect to the atmospheric pressure of the brake operation guarantee negative pressure, which is a pressure required in the negative pressure chamber of the brake booster in order to ensure the operation of the brake. When the atmospheric pressure is equal to or higher than the first predetermined pressure, the predetermined target pressure is set. When the atmospheric pressure is lower than the first predetermined pressure, the negative pressure is set lower than the predetermined target pressure. And the relative pressure to the atmospheric pressure of the pump maximum generated negative pressure, which is the maximum negative pressure that can be generated by the vacuum pump, is less than a second predetermined pressure that is lower than the first predetermined pressure. Further, the target booster negative pressure chamber pressure is set to a negative pressure higher than the relative pressure to the atmospheric pressure, and set to a negative pressure lower than the predetermined target pressure, and is detected by the negative pressure chamber pressure detecting means. In the negative pressure chamber pressure determining step for determining whether or not the booster negative pressure chamber pressure is lower than the target booster negative pressure chamber pressure, the booster negative pressure chamber pressure is the target booster negative pressure chamber. When the negative pressure is lower than the pressure, control is performed to operate the vacuum pump, and the booster negative pressure chamber pressure is higher than the target booster negative pressure chamber pressure in the negative pressure chamber pressure determination step. Negative pressure Is a control for stopping the vacuum pump, and a pump abnormality determination negative pressure defined according to an atmospheric pressure between the target booster negative pressure chamber pressure and the brake operation guarantee negative pressure. When the booster negative pressure chamber pressure after a predetermined time has elapsed since the vacuum pump operation was started is lower than the pump abnormality determination negative pressure, the function of the vacuum pump It is characterized by determining that there is an abnormality.

  According to this aspect, an abnormality in the function of the vacuum pump can be detected in accordance with a change in atmospheric pressure.

  In said aspect, it is preferable that the said predetermined time is set so long that atmospheric pressure is low pressure.

  According to this aspect, since the predetermined time is corrected according to the atmospheric pressure, even if the atmospheric pressure changes and the time for the booster negative pressure chamber pressure to reach the target booster negative pressure chamber pressure changes, the vacuum pump The accuracy of detecting an abnormality in the function can be improved, and the detection time can be made efficient.

  According to the brake system, the brake system control method, and the brake system abnormality diagnosis method of this configuration, it is possible to reduce the cost by suppressing the capacity of the vacuum pump to the minimum necessary.

It is a schematic block diagram of the brake system of a present Example. It is a block diagram which shows the control system of the brake system of a present Example. FIG. 3 is a diagram illustrating a control routine of the first embodiment. FIG. 4 is a relationship diagram of engine generated negative pressure, pump generated negative pressure, and target booster negative pressure with respect to atmospheric pressure (altitude). FIG. 4 is a diagram illustrating an example of a time chart of the first embodiment. FIG. 6 is a diagram illustrating a control routine of a second embodiment. FIG. 6 is a relationship diagram of engine-generated negative pressure, pump-generated negative pressure, target booster negative pressure, and V / P abnormality determination negative pressure with respect to atmospheric pressure (altitude). FIG. 6 is a diagram illustrating an example of a time chart of Example 2. It is a related figure of atmospheric pressure and V / P abnormality determination time.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Here, FIG. 1 is a schematic configuration diagram of the brake system of the present embodiment. FIG. 2 is a block diagram showing a control system of the brake system of this embodiment. In the following description, “negative pressure” refers to a pressure lower than atmospheric pressure. “High negative pressure” and “High negative pressure” mean that the difference from atmospheric pressure is large, and “Low negative pressure” and “Low negative pressure” mean that the difference from atmospheric pressure is small. Say.

<Configuration and operation of brake system>
As shown in FIGS. 1 and 2, the brake system 1 of the present embodiment includes a brake pedal 10, a brake booster 12, a master cylinder 14, a negative pressure sensor 16, and an electric vacuum pump 18 (“electric VP” in the figure). And a check valve CV1, a check valve CV2, a check valve CV3, an ECU 24, an intake pipe pressure detecting means 26, and the like.

  As shown in FIG. 1, the brake booster 12 is provided between the brake pedal 10 and the master cylinder 14. The brake booster 12 generates an assist force with a predetermined boost ratio with respect to the depression force of the brake pedal 10.

  The inside of the brake booster 12 is partitioned by a diaphragm (not shown), and a negative pressure chamber (not shown) partitioned on the master cylinder 14 side and a variable pressure chamber (not shown) capable of introducing the atmosphere. Is provided. The negative pressure chamber of the brake booster 12 is connected to the intake pipe 32 of the engine via the first passage L1. That is, the first passage L <b> 1 is connected to the negative pressure chamber of the brake booster 12 and the intake pipe 32. Thus, the negative pressure generated in the intake pipe 32 according to the opening of the throttle valve 34 when the engine is driven is supplied to the negative pressure chamber of the brake booster 12 through the first passage L1. The throttle valve 34 is provided in the intake pipe 32. The intake pipe 32 is an example of the “intake system” in the present invention.

  The master cylinder 14 increases the hydraulic pressure of the brake body (not shown) by the operation of the brake booster 12 and generates a braking force in the brake body. The negative pressure sensor 16 detects the pressure in the negative pressure chamber of the brake booster 12. The negative pressure sensor 16 is an example of the “negative pressure indoor pressure detecting means” in the present invention.

  As shown in FIG. 1, the electric vacuum pump 18 is provided on the second passage L2, and the suction port 18a is connected to the negative pressure chamber of the brake booster 12 via the second passage L2 and the first passage L1. Yes. Here, the second passage L2 is a passage branched from the first passage L1 from a position between the check valve CV1 and the check valve CV2 on the first passage L1. The discharge port 18b of the electric vacuum pump 18 is open to the atmosphere.

Further, as shown in FIG. 2, the electric vacuum pump 18 is connected to the EC via a motor or a relay.
Connected to U24. In this way, the operation of the electric vacuum pump 18 is controlled by the ECU 24. Specifically, the electric vacuum pump 18 starts to operate based on an operation start signal from the ECU 24 and passes through the second passage L2 and the first passage L1 from the suction port 18a to the negative pressure chamber of the brake booster 12. Supply negative pressure to Further, the electric vacuum pump 18 stops operating based on an operation stop signal from the ECU 24, and negative pressure enters the negative pressure chamber of the brake booster 12 from the suction port 18a via the second passage L2 and the first passage L1. Stop supplying.

  Here, the maximum negative pressure that can be generated by the electric vacuum pump 18 will be described. In the following description, the pump-generated negative pressure pp is the maximum negative pressure that can be generated by the electric vacuum pump 18. At this time, as shown in FIG. 4, the relative pressure of the pump-generated negative pressure pp to the atmospheric pressure Pa (the relative pressure between the absolute pressure of the pump-generated negative pressure pp and the atmospheric pressure Pa) is such that the atmospheric pressure Pa is less than the predetermined pressure Pa_H. In this case, the pressure is set so that the negative pressure (low pressure) becomes higher as the atmospheric pressure Pa becomes higher, and the lower negative pressure (high pressure) becomes lower as the atmospheric pressure Pa becomes lower. The relative pressure of the pump-generated negative pressure pp to the atmospheric pressure Pa is a relative pressure (target) of the target booster negative pressure Ao to the atmospheric pressure Pa when the atmospheric pressure is a low pressure less than a predetermined pressure Pa_X (for example, 70 kPa). The relative pressure between the absolute pressure of the booster negative pressure Ao and the atmospheric pressure Pa) is set to be higher than the predetermined target pressure -A. Here, the target booster negative pressure Ao is a target pressure in the negative pressure chamber of the brake booster 12.

  Returning to the description of FIG. 1 and FIG. 2, the check valve CV <b> 1 is provided in the first passage L <b> 1 between the branch portion of the second passage L <b> 2 and the brake booster 12. The check valve CV2 is provided in the first passage L1 at a position closer to the intake pipe 32 than the check valve CV1 and between the branch portion of the second passage L2 and the intake pipe 32. Yes. The check valve CV3 is provided in the second passage L2 at a position between the branch portion of the first passage L1 and the electric vacuum pump 18.

  Both the check valve CV1 and the check valve CV2 are configured to be opened only when the negative pressure on the intake pipe 32 side is higher than the negative pressure on the negative pressure chamber side of the brake booster 12. Only the flow of fluid from the negative pressure chamber side to the intake pipe 32 side is allowed. Specifically, the check valve CV1 and the check valve CV2 prevent gas from flowing from the intake pipe 32 side to the negative pressure chamber side of the brake booster 12 via the first passage L1. The check valve CV3 is configured to be opened only when the negative pressure on the electric vacuum pump 18 side is higher than the negative pressure on the negative pressure chamber side of the brake booster 12, and the negative pressure of the brake booster 12 is set. Only fluid flow from the chamber side to the electric vacuum pump 18 side is allowed.

  The ECU 24 is configured by a microcomputer, for example, and includes a ROM that stores a control program, a readable / writable RAM that stores calculation results, a timer, a counter, an input interface, and an output interface. As shown in FIG. 2, the ECU 24 is connected with a negative pressure sensor 16, an electric vacuum pump 18, an intake pipe pressure detecting means 26, and the like. The ECU 24 can perform a brake system control method, which will be described in detail later.

  The brake system 1 having such a configuration adjusts the negative pressure in the negative pressure chamber of the brake booster 12 by supplying the negative pressure in the intake pipe 32 to the negative pressure chamber of the brake booster 12 via the first passage L1. can do. In addition, the brake system 1 also operates the electric vacuum pump 18 to supply negative pressure into the negative pressure chamber of the brake booster 12 via the second passage L2 and the first passage L1, so that the brake booster 12 The negative pressure in the negative pressure chamber can be adjusted.

  The intake pipe pressure detection means 26 is, for example, a pressure sensor, and detects the pressure in the intake pipe 32. The intake pipe pressure detection means 26 is an example of the “intake negative pressure detection means” in the present invention.

  Instead of the electric vacuum pump 18, a mechanically driven vacuum pump may be used.

<Brake system control method>
Next, a control method of the brake system 1 having the above configuration will be described.

[Example 1]
First, Example 1 will be described. In the first embodiment, the ECU 24 periodically executes the control routine shown in FIG. 3 every predetermined time.

  3 is started, first, the ECU 24 takes in the atmospheric pressure Pa, the booster negative pressure chamber pressure bpm, and the engine generated negative pressure pm (steps S1 to S3). Here, the booster negative pressure chamber pressure bpm is the pressure in the negative pressure chamber of the brake booster 12 detected by the negative pressure sensor 16. The engine-generated negative pressure pm is the pressure in the intake pipe 32 detected by the intake pipe pressure detecting means 26. The engine-generated negative pressure pm is an example of the “intake negative pressure” in the present invention.

  Next, the ECU 24 obtains a target booster negative pressure Ao corresponding to the atmospheric pressure Pa from FIG. 4 (step S4). Here, the target booster negative pressure Ao is a target pressure in the negative pressure chamber of the brake booster 12.

  Here, FIG. 4 will be described. As shown in FIG. 4, the relative pressure of the engine-generated negative pressure pm to the atmospheric pressure Pa (the absolute pressure of the engine-generated negative pressure pm and the relative pressure of the atmospheric pressure Pa) increases as the atmospheric pressure Pa becomes higher. The pressure (low pressure) is set, and the negative pressure (high pressure) is set as the atmospheric pressure Pa becomes low.

  As shown in FIG. 4, the relative pressure of the target booster negative pressure Ao to the atmospheric pressure Pa (the absolute pressure of the target booster negative pressure Ao and the relative pressure of the atmospheric pressure Pa) is an allowable booster negative pressure −C (for example, Negative pressure higher than -40 kPa). Here, the allowable booster negative pressure −C is a relative pressure with respect to the atmospheric pressure Pa of a pressure (brake operation guarantee negative pressure) necessary in the negative pressure chamber of the brake booster 12 in order to ensure the operation of the brake of the brake system 1. is there.

  As shown in FIG. 4, the relative pressure of the target booster negative pressure Ao with respect to the atmospheric pressure Pa is a predetermined target pressure −A when the atmospheric pressure Pa is a high pressure equal to or higher than a predetermined pressure Pa_L (for example, 85 kPa). (For example, -65 kPa).

  Further, as shown in FIG. 4, the relative pressure of the target booster negative pressure Ao to the atmospheric pressure Pa is lower than the predetermined target pressure −A when the atmospheric pressure Pa is a low pressure less than the predetermined pressure Pa_L. Set to Specifically, the relative pressure of the target booster negative pressure Ao with respect to the atmospheric pressure Pa gradually decreases as the atmospheric pressure Pa becomes lower when the atmospheric pressure Pa is lower than the predetermined pressure Pa_L. Is set as follows.

  Thus, the target booster negative pressure Ao is changed according to the magnitude of the atmospheric pressure Pa. Thereby, when the atmospheric pressure Pa is a low pressure lower than the predetermined pressure Pa_L, it is possible to avoid the problem that the booster negative pressure chamber pressure bpm cannot reach the target booster negative pressure Ao even if the electric vacuum pump 18 is continuously operated. That is, since the target booster negative pressure Ao is set to the low negative pressure side when the atmospheric pressure Pa is low, by operating the electric vacuum pump 18, the pressure in the negative pressure chamber of the brake booster 12 is reliably set to the target booster negative pressure. The pressure Ao is reached. Therefore, the reliability of the operation of the electric vacuum pump 18 can be maintained. The predetermined pressure Pa_L is an example of the “first predetermined pressure” in the present invention.

  As shown in FIG. 4, the pump-generated negative pressure pp is set to a higher negative pressure than the target booster negative pressure Ao set as described above. The relative pressure of the pump-generated negative pressure pp to the atmospheric pressure Pa is set to a high negative pressure equal to or higher than a predetermined target pressure −A when the atmospheric pressure Pa is a high pressure equal to or higher than the predetermined pressure Pa_X. When the atmospheric pressure Pa is a low pressure lower than the predetermined pressure Pa_X, the negative pressure is set lower than the predetermined target pressure -A. As shown in FIG. 4, the predetermined pressure Pa_X is lower than the predetermined pressure Pa_L. The pump-generated negative pressure pp is an example of the “pump maximum generated negative pressure” in the present invention. The predetermined pressure Pa_X is an example of the “second predetermined pressure” in the present invention.

  Thus, when the atmospheric pressure Pa is a low pressure, the pump-generated negative pressure pp is set on the low negative pressure side in a region of higher negative pressure than the target booster negative pressure Ao. Thereby, compared with the comparative example in which the relative pressure of the pump-generated negative pressure pp with respect to the atmospheric pressure Pa is always set to a higher negative pressure than the predetermined target pressure -A regardless of the magnitude of the atmospheric pressure Pa, it is required. The maximum generated negative pressure of the electric vacuum pump 18 is suppressed. Therefore, the pump capacity (suction capacity) of the electric vacuum pump 18 can be suppressed to the minimum necessary, and the cost can be reduced.

  As shown in FIG. 4, as an example, the pump-generated negative pressure pp is a predetermined pressure β (for example, 10 kPa) from the target booster negative pressure Ao when the atmospheric pressure Pa is a low pressure equal to or lower than the predetermined pressure Pa_L. ) Minus the pressure (Ao-β). The pump-generated negative pressure pp is a predetermined value obtained by subtracting a predetermined pressure β ′ (for example, 15 kPa) from the target booster negative pressure Ao when the atmospheric pressure Pa is a high pressure equal to or higher than a predetermined pressure Pa_H (for example, 90 kPa). The target pressure is set to -A '(for example, -80 kPa).

  As a modification, the difference between the target booster negative pressure Ao and the pump generated negative pressure pp may be constant regardless of the magnitude of the atmospheric pressure Pa.

  Returning to the description of FIG. 3 again, the ECU 24 obtains the target booster negative pressure Ao corresponding to the atmospheric pressure Pa (step S4), and then subtracts a predetermined pressure α (for example, −5 kPa) from the engine generated negative pressure pm. It is determined whether or not the pressure (pm−α) is higher than the booster negative pressure chamber pressure bpm (step S5, intake negative pressure determination step). That is, the ECU 24 determines whether or not the engine generated negative pressure pm is lower than the booster negative pressure chamber pressure bpm.

  In step S5, when the pressure (pm-α) is higher than the booster negative pressure chamber pressure bpm, the ECU 24 determines whether or not the V / P operation flag Xvp = 0 (step S5). S6). Here, when the electric vacuum pump 18 is stopped, the V / P operation flag Xvp = 0 is set, and when the electric vacuum pump 18 is operated, the V / P operation flag Xvp = 1 is set. The

  When the V / P operation flag Xvp = 0 in step S6, the ECU 24 determines whether or not the booster negative pressure chamber pressure bpm is higher than the target booster negative pressure Ao (step S7, Negative pressure chamber pressure determination step). That is, the ECU 24 determines whether or not the booster negative pressure chamber pressure bpm is lower than the target booster negative pressure Ao.

  In step S7, when the booster negative pressure chamber pressure bpm is higher than the target booster negative pressure Ao (low negative pressure), the ECU 24 operates the electric vacuum pump 18, that is, performs pump operation control. This is executed (indicated as “V / P_ON” in the figure) (step S8), and the routine process is temporarily terminated. In step S8, the ECU 24 sets the V / P operation flag Xvp = 1.

  On the other hand, when the booster negative pressure chamber pressure bpm is a low pressure lower than the target booster negative pressure Ao (high negative pressure above) in step S7, the ECU 24 stops the electric vacuum pump 18, that is, the pump is operated. The control is stopped (indicated as “V / P_OFF” in the figure) (step S9), and the routine process is temporarily terminated. In step S9, the ECU 24 sets V / P operation flag Xvp = 0.

  If the V / P operation flag Xvp = 1 in step S6, the ECU 24 determines whether or not the booster negative pressure chamber pressure bpm is higher than the pressure (Ao−β) (step S10). ). That is, the ECU 24 determines whether or not the booster negative pressure chamber pressure bpm is lower than the pressure (Ao−β). Note that the pressure (Ao−β) is a pressure obtained by subtracting the predetermined pressure β from the target booster negative pressure Ao.

  If the booster negative pressure chamber pressure bpm is higher than the pressure (Ao−β) (low negative pressure) in step S10, the ECU 24 proceeds to control in step S8. On the other hand, if the booster negative pressure chamber pressure bpm is a low pressure (higher negative pressure) than the pressure (Ao-β) in step S10, the ECU 24 proceeds to the control in step S9.

  In step S5, when the pressure (pm-α) is a low pressure equal to or lower than the booster negative pressure chamber pressure bpm (high negative pressure above), the ECU 24 proceeds to the control of step S9. Thus, when the engine-generated negative pressure pm is a low pressure equal to or lower than the booster negative pressure chamber pressure bpm, the ECU 24 stops the electric vacuum pump 18 and passes through the first passage L1 from the intake pipe 32. Negative pressure is supplied to the negative pressure chamber of the brake booster 12.

  As described above, the ECU 24 controls the electric vacuum pump 18 to operate when the booster negative pressure chamber pressure bpm is higher than the target booster negative pressure Ao (low negative pressure). Further, the ECU 24 controls the electric vacuum pump 18 to be stopped when the booster negative pressure chamber pressure bpm is a low pressure (a high negative pressure above) equal to or lower than the target booster negative pressure Ao.

  When the V / P operation flag Xvp = 0, that is, when the pump operation control is stopped, the ECU 24 indicates that the booster negative pressure chamber pressure bpm is higher than the target booster negative pressure Ao. If so, perform pump actuation control. On the other hand, when the V / P operation flag Xvp = 1, that is, when the pump operation control is being executed, the ECU 24 causes the booster negative pressure chamber pressure bpm to be a low pressure equal to or lower than the pressure (Ao−β). If this happens, stop the pump operation control.

  Thus, the condition of the booster negative pressure chamber pressure bpm when the pump operation control is executed while the pump operation control is stopped, and the booster negative pressure chamber pressure bpm when the pump operation control is stopped while the pump operation control is executed. The conditions are different. Thereby, the brake system 1 can suppress the influence of the hunting phenomenon that may occur in the negative pressure chamber of the brake booster 12 when the pump operation control is stopped and the execution is switched when the brake pedal 10 is on.

  This completes the description of the control routine shown in FIG.

  And the brake system 1 can perform an example of control as shown, for example in FIG. 5, when ECU24 performs the control routine shown in FIG. 3 periodically for every predetermined time.

  Therefore, an example of the control shown in FIG. 5 will be described. In FIG. 5G, the engine-generated negative pressure pm, the booster negative pressure chamber pressure bpm, and the target booster negative pressure Ao are expressed as relative pressures with respect to the atmospheric pressure Pa.

  As shown in FIG. 5, at time T1, the atmospheric pressure Pa decreases to a predetermined pressure Pa_L, and the graph of the target booster negative pressure Ao reaches the inflection point. Then, after the time T1, the target booster negative pressure Ao gradually becomes a low negative pressure as the atmospheric pressure Pa decreases below the predetermined pressure Pa_L and the atmospheric pressure Pa becomes lower.

  At time T2, the booster negative pressure chamber pressure bpm becomes higher than the target booster negative pressure Ao, so the ECU 24 operates the electric vacuum pump 18. As a result, the negative pressure generated by the electric vacuum pump 18 is supplied to the negative pressure chamber of the brake booster 12, so that the booster negative pressure chamber pressure bpm becomes equal to or lower than the target booster negative pressure Ao.

  According to the first embodiment as described above, the following effects can be obtained.

  In the first embodiment, as shown in FIG. 4, the relative pressure of the target booster negative pressure Ao with respect to the atmospheric pressure Pa is set to a higher negative pressure than the brake operation guarantee negative pressure −C. The relative pressure of the target booster negative pressure Ao to the atmospheric pressure Pa is set to a predetermined target pressure −A when the atmospheric pressure Pa is a high pressure equal to or higher than the predetermined pressure Pa_L, and the atmospheric pressure Pa is lower than the predetermined pressure Pa_L. When the pressure is low, the negative pressure is set lower than the predetermined target pressure -A. The relative pressure of the pump-generated negative pressure pp to the atmospheric pressure Pa is greater than the relative pressure of the target booster negative pressure Ao to the atmospheric pressure Pa when the atmospheric pressure Pa is lower than the predetermined pressure Pa_X lower than the predetermined pressure Pa_L. Is set to a high negative pressure, and is set to a negative pressure lower than a predetermined target pressure -A.

  As described above, the relative pressure of the pump-generated negative pressure pp to the atmospheric pressure Pa is higher than the brake operation guarantee negative pressure −C when the atmospheric pressure Pa is lower than the predetermined pressure Pa_X lower than the predetermined pressure Pa_L. And a negative pressure lower than a predetermined target pressure -A. Therefore, the pump capacity (suction capacity) of the electric vacuum pump 18 can be suppressed to the minimum necessary. Therefore, the cost of the electric vacuum pump 18 can be reduced.

  The relative pressure of the target booster negative pressure Ao with respect to the atmospheric pressure Pa is set to a negative pressure lower than the predetermined target pressure −A when the atmospheric pressure Pa is a low pressure lower than the predetermined pressure Pa_L. Thus, since the target pressure of the negative pressure chamber of the brake booster 12 is set to the low negative pressure side when the atmospheric pressure Pa is low, the negative pressure chamber of the brake booster 12 is surely operated by operating the electric vacuum pump 18. Can reach the target pressure.

  Moreover, since the brake system 1 has a structure for supplying the engine-generated negative pressure pm to the negative pressure chamber of the brake booster 12, the operating frequency of the electric vacuum pump 18 can be reduced.

  In the first embodiment, the ECU 24 determines that the booster negative pressure chamber pressure bpm is lower than the target booster negative pressure Ao (high pressure) in the negative pressure chamber pressure determination step (step S7). The electric vacuum pump 18 is controlled to operate. Further, in the negative pressure chamber pressure determination step (step S7), when the booster negative pressure chamber pressure bpm is a high negative pressure (below the lower pressure) equal to or higher than the target booster negative pressure Ao, the ECU 24 18 is controlled to stop.

  Thereby, unnecessary operation of the electric vacuum pump 18 is suppressed, the operation frequency of the electric vacuum pump 18 is reduced, and the operation of the brake is ensured even at a high altitude where the atmospheric pressure Pa is low.

  Further, in the first embodiment, the ECU 24 performs the step when the engine generated negative pressure pm is lower than the booster negative pressure chamber pressure bpm (high pressure) in the intake negative pressure determination step (step S5). 6 to control to move to step S7 or step S10. In addition, in the intake negative pressure determination step (step S5), the ECU 24 sets the electric vacuum pump 18 when the engine generated negative pressure pm is a high negative pressure (below the low pressure) equal to or higher than the booster negative pressure chamber pressure bpm. Is controlled so that negative pressure is supplied from the intake pipe 32 to the negative pressure chamber of the brake booster 12 through the first passage L1.

  Thereby, unnecessary operation of the electric vacuum pump 18 is further suppressed, the operation frequency of the electric vacuum pump 18 is further reduced, and the operation of the brake is ensured even at a high altitude where the atmospheric pressure Pa is low.

[Example 2]
Next, the second embodiment will be described. The same components as those of the first embodiment are denoted by the same reference numerals, the description thereof will be omitted, and different points will be mainly described.

  In the second embodiment, the ECU 24 periodically executes the control routine shown in FIG. 6 every predetermined time. The control routine shown in FIG. 6 is different from the control routine shown in FIG. 3 described above. The ECU 24 determines the V / P abnormality after the electric vacuum pump 18 is started after the electric vacuum pump 18 is started in step S28. When time D elapses (step S29: YES), it is determined whether or not the booster negative pressure chamber pressure bpm is higher than the V / P abnormality determination negative pressure V / P_OBD (low negative pressure) (step S30). . The V / P abnormality determination negative pressure V / P_OBD is an example of the “pump abnormality determination negative pressure” in the present invention.

  Here, the V / P abnormality determination negative pressure V / P_OBD is set as shown in FIG. As shown in FIG. 7, the relative pressure of the V / P abnormality determination negative pressure V / P_OBD with respect to the atmospheric pressure Pa is a low pressure (allowable booster negative pressure −C or lower) and a target booster negative The pressure Ao is defined to be higher than the relative pressure with respect to the atmospheric pressure Pa (low negative pressure).

  And as shown in FIG. 7, V / P abnormality determination negative pressure V / P_OBD is prescribed | regulated according to the magnitude | size of atmospheric pressure Pa. FIG. More specifically, as shown in FIG. 7, the relative pressure of the V / P abnormality determination negative pressure V / P_OBD with respect to the atmospheric pressure Pa is a predetermined pressure − when the atmospheric pressure Pa is a high pressure equal to or higher than the predetermined pressure Pa_L. B (for example, −55 kPa). The relative pressure of the V / P abnormality determination negative pressure V / P_OBD with respect to the atmospheric pressure Pa is a predetermined pressure −B as the atmospheric pressure Pa becomes lower when the atmospheric pressure Pa is a low pressure lower than the predetermined pressure Pa_L. It changes so that it may become a high pressure (low negative pressure) gradually rather than, and it is prescribed | regulated so that the allowable booster negative pressure -C may be reached. Thus, the relative pressure of the V / P abnormality determination negative pressure V / P_OBD to the atmospheric pressure Pa is the atmospheric pressure Pa between the relative pressure of the target booster negative pressure Ao to the atmospheric pressure Pa and the allowable booster negative pressure −C. Since it is defined according to the size, the abnormality diagnosis of the electric vacuum pump 18 can be accurately performed without being affected by the change in the atmospheric pressure Pa.

  In step S30, if the booster negative pressure chamber pressure bpm is higher than the V / P abnormality determination negative pressure V / P_OBD (low negative pressure), the ECU 24 determines that the function of the electric vacuum pump 18 is abnormal. A determination is made (step S31), and the routine process is temporarily terminated. On the other hand, when the booster negative pressure chamber pressure bpm is a low pressure equal to or lower than the V / P abnormality determination negative pressure V / P_OBD (high negative pressure above) in step S30, the ECU 24 once ends the routine process.

  This completes the description of the control routine shown in FIG.

  And the brake system 1 can perform an example of control as shown, for example in FIG. 8, when ECU24 performs the control routine shown in FIG. 6 periodically for every predetermined time. In FIG. 8G, the engine-generated negative pressure pm, the booster negative pressure chamber pressure bpm, the target booster negative pressure Ao, and the V / P abnormality determination negative pressure V / P_OBD are expressed as relative pressures relative to the atmospheric pressure Pa. Has been.

  As shown in FIG. 8, at time T11, when a V / P abnormality determination time D (for example, 30 seconds) has elapsed after the operation of the electric vacuum pump 18 has started, the booster negative pressure chamber pressure bpm is determined to be V / P abnormality. Since the pressure is higher than the negative pressure V / P_OBD (low negative pressure), the ECU 24 determines that the function of the electric vacuum pump 18 is abnormal.

  As a modification of the second embodiment, as shown in FIG. 9, the V / P abnormality determination time D may be set longer as the atmospheric pressure Pa is lower. Here, the higher the atmospheric pressure Pa, the shorter the time that the booster negative pressure chamber pressure bpm can reach the target booster negative pressure Ao, while the lower the atmospheric pressure Pa, the higher the booster negative pressure chamber pressure bpm. The time for reaching the booster negative pressure Ao becomes longer. However, since the V / P abnormality determination time D is corrected according to the magnitude of the atmospheric pressure Pa as shown in FIG. 9, the accuracy of detecting an abnormality in the function of the electric vacuum pump 18 is improved, and the detection time is reduced. Increase efficiency.

  According to the second embodiment as described above, the following effects can be obtained.

  In the second embodiment, as shown in FIG. 7, the relative pressure of the V / P abnormality determination negative pressure V / P_OBD to the atmospheric pressure Pa is the relative pressure of the target booster negative pressure Ao to the atmospheric pressure Pa and the brake operation guarantee negative pressure − C is defined according to the atmospheric pressure Pa. Then, the ECU 24 determines that the booster negative pressure chamber pressure bpm after the elapse of the V / P abnormality determination time D from the start of the operation of the electric vacuum pump 18 is lower than the V / P abnormality determination negative pressure V / P_OBD. If it is, it is determined that the function of the electric vacuum pump 18 is abnormal. Thereby, the abnormality of the function of the electric vacuum pump 18 can be detected according to the change of the atmospheric pressure Pa.

  In the second embodiment, the V / P abnormality determination time D may be set longer as the atmospheric pressure Pa is lower. In this way, by correcting the V / P abnormality determination time D according to the atmospheric pressure Pa, even if the atmospheric pressure Pa changes and the time for the booster negative pressure chamber pressure bpm to reach the target booster negative pressure Ao changes. The accuracy of detecting an abnormality in the function of the electric vacuum pump 18 is improved, and the detection time can be made efficient.

  It should be noted that the above-described embodiment is merely an example and does not limit the present invention in any way, and various improvements and modifications can be made without departing from the scope of the invention.

DESCRIPTION OF SYMBOLS 1 Brake system 10 Brake pedal 12 Brake booster 14 Master cylinder 16 Negative pressure sensor 18 Electric vacuum pump (electric VP)
24 ECU
26 Intake pipe pressure detection means 32 Intake pipe-A Predetermined target pressure-A 'Predetermined target pressure-B Predetermined pressure-C Allowable booster negative pressure Ao Target booster negative pressure α Predetermined pressure β Predetermined pressure β' Predetermined pressure Pa Atmospheric pressure pp Pump generated negative pressure bpm Booster negative pressure chamber pressure pm Engine generated negative pressure Xvp V / P operation flag Pa_L Predetermined pressure Pa_X Predetermined pressure D V / P abnormality determination time V / P_OBD V / P abnormality determination negative pressure

Claims (5)

Brake booster,
A vacuum pump for supplying negative pressure to the negative pressure chamber of the brake booster,
The relative pressure of the target booster negative pressure chamber pressure, which is the target pressure of the negative pressure chamber of the brake booster, with respect to the atmospheric pressure is a brake operation that is a pressure necessary in the negative pressure chamber of the brake booster to ensure the operation of the brake. When the guaranteed negative pressure is set to a higher negative pressure than the relative pressure to the atmospheric pressure, is set to a predetermined target pressure when the atmospheric pressure is equal to or higher than the first predetermined pressure, and the atmospheric pressure is lower than the first predetermined pressure. Is set to a negative pressure lower than the predetermined target pressure,
The relative pressure with respect to the atmospheric pressure of the pump maximum generated negative pressure that is the maximum negative pressure that can be generated by the vacuum pump is less than the second predetermined pressure that is lower than the first predetermined pressure. The booster negative pressure is set to a higher negative pressure than the relative pressure to the atmospheric pressure of the indoor pressure, and is set to a lower negative pressure than the predetermined target pressure,
Brake system characterized by In the control method of the brake system,
The brake system includes a brake booster, a vacuum pump that supplies a negative pressure to the negative pressure chamber of the brake booster, and a negative pressure chamber pressure detection that detects a booster negative pressure chamber pressure that is a pressure of the negative pressure chamber of the brake booster Means relative to the atmospheric pressure of the target booster negative pressure chamber pressure, which is the target pressure of the negative pressure chamber of the brake booster, is required in the negative pressure chamber of the brake booster to ensure the operation of the brake Is set to a higher negative pressure than the relative pressure of the brake operation guarantee negative pressure, which is a negative pressure, to a predetermined target pressure when the atmospheric pressure is equal to or higher than the first predetermined pressure, and the atmospheric pressure is set to the first pressure. When the pressure is less than the predetermined pressure, the negative pressure is set lower than the predetermined target pressure, and the maximum negative pressure that can be generated by the vacuum pump is the atmospheric pressure of the pump maximum generated negative pressure. The counter pressure is set to a higher negative pressure than the relative pressure of the target booster negative pressure chamber pressure to the atmospheric pressure when the atmospheric pressure is lower than a second predetermined pressure lower than the first predetermined pressure, and The negative pressure is set lower than the predetermined target pressure,
In the negative pressure indoor pressure determination step of determining whether or not the booster negative pressure indoor pressure detected by the negative pressure indoor pressure detection means is lower than the target booster negative pressure indoor pressure, the booster negative pressure If the pressure chamber pressure is a negative pressure lower than the target booster negative pressure chamber pressure, control to operate the vacuum pump,
In the negative pressure chamber pressure determination step, when the booster negative pressure chamber pressure is a high negative pressure equal to or higher than the target booster negative pressure chamber pressure, the vacuum pump is controlled to stop.
Brake system control method characterized by the above. The control method of a brake system according to claim 2,
The brake system includes a passage connected to the negative pressure chamber of the brake booster and the intake system, and an intake negative pressure detecting means for detecting an intake negative pressure which is a pressure of the intake system.
Intake negative pressure determination step for determining whether or not the intake negative pressure detected by the intake negative pressure detection means is lower than the booster negative pressure chamber pressure detected by the negative pressure chamber pressure detection means In the case where the intake negative pressure is a negative pressure lower than the booster negative pressure chamber pressure, control is performed to shift to the negative pressure chamber pressure determination step,
In the intake negative pressure determination step, when the intake negative pressure is a high negative pressure equal to or higher than the booster negative pressure chamber pressure, the vacuum pump is stopped and the negative pressure is released from the intake system through the passage. Control so that negative pressure is supplied to the pressure chamber,
Brake system control method characterized by the above. In the brake system abnormality diagnosis method,
The brake system includes a brake booster, a vacuum pump that supplies a negative pressure to the negative pressure chamber of the brake booster, and a negative pressure chamber pressure detection that detects a booster negative pressure chamber pressure that is a pressure of the negative pressure chamber of the brake booster Means relative to the atmospheric pressure of the target booster negative pressure chamber pressure, which is the target pressure of the negative pressure chamber of the brake booster, is required in the negative pressure chamber of the brake booster to ensure the operation of the brake Is set to a higher negative pressure than the relative pressure of the brake operation guarantee negative pressure, which is a negative pressure, to a predetermined target pressure when the atmospheric pressure is equal to or higher than the first predetermined pressure, and the atmospheric pressure is set to the first pressure. When the pressure is less than the predetermined pressure, the negative pressure is set lower than the predetermined target pressure, and the maximum negative pressure that can be generated by the vacuum pump is the atmospheric pressure of the pump maximum generated negative pressure. The counter pressure is set to a higher negative pressure than the relative pressure of the target booster negative pressure chamber pressure to the atmospheric pressure when the atmospheric pressure is lower than a second predetermined pressure lower than the first predetermined pressure, and Whether or not the booster negative pressure chamber pressure detected by the negative pressure chamber pressure detecting means is set to a lower negative pressure than the predetermined target pressure and lower than the target booster negative pressure chamber pressure. When the booster negative pressure chamber pressure is lower than the target booster negative pressure chamber pressure in the negative pressure chamber pressure determining step, the vacuum pump is controlled to operate, and the negative pump chamber pressure is determined. In the pressure chamber pressure determining step, when the booster negative pressure chamber pressure is a high negative pressure equal to or higher than the target booster negative pressure chamber pressure, control is performed to stop the vacuum pump,
Set a pump abnormality determination negative pressure defined according to atmospheric pressure between the target booster negative pressure indoor pressure and the brake operation guarantee negative pressure,
If the booster negative pressure chamber pressure after the elapse of a predetermined time from the start of the operation of the vacuum pump is a negative pressure lower than the pump abnormality determination negative pressure, the vacuum pump function is abnormal. To determine,
Brake system abnormality diagnosis method characterized by the above. In the brake system abnormality diagnosis method of claim 4,
The predetermined time is set longer as the atmospheric pressure is lower,
Brake system abnormality diagnosis method characterized by the above.

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