JP2005297654A - Pneumatic servo unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic servo unit capable of improving the balance between the negative pressure filling property in an negative pressure chamber of a pneumatic servo unit and the engine controllability. <P>SOLUTION: In ejectors 14a, 14b, air inlets 20a, 20b are connected to the upstream side across a throttle 28 of an air intake pipe 26, air outlets 32a, 32b are connected to the downstream side, and negative pressure outlets 36a, 36b are connected to a negative pressure chamber of a pneumatic servo unit body 12. The ejectors 14a, 14b are arranged parallel to the air intake pipe 26. Presence/absence of the operation of the ejectors 14a, 14b is controlled by an ECU 18 according to the state of a vehicle via control valves 16a, 16b. Degradation of the fuel consumption of an engine 24 is minimized while excellently filling the negative pressure of the negative pressure chamber, and the pneumatic servo unit body 12 and the engine 24 are controlled with excellent balance. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic booster, and more particularly to an improvement of a pneumatic booster capable of improving the balance between the negative pressure filling ability of a negative pressure chamber of a booster main body and engine controllability.

  A braking device for an automobile is provided with a pneumatic booster to increase the braking force. A pneumatic booster uses, as a negative pressure source, a negative pressure that is generally generated in an intake pipe of an engine. In other words, by reducing the throttle of the intake pipe, the negative pressure generated on the downstream side of the throttle is introduced into the negative pressure chamber of the booster body, and the thrust is generated in the power piston by the pressure difference from the atmospheric pressure. It assists the operating force of the braking device (brake).

By the way, when the engine is cold immediately after the engine is started, generally, the control is performed to increase the throttle opening in order to increase the engine speed, so that there is a tendency that the negative pressure of the intake pipe does not easily occur. Similarly, the same applies when the throttle opening is intentionally increased in order to increase and maintain the vehicle speed during traveling. Therefore, there is a system for supplying negative pressure to the negative pressure chamber of the booster body using an ejector. In the ejector, a straight pipe diffuser having tapered portions on the inlet side and outlet side is arranged downstream of a straight pipe nozzle having a tapered portion formed on the inlet side, and a negative pressure outlet is provided therebetween. When a gas is flowed from the straight pipe nozzle side to the straight pipe diffuser side, a high-speed jet is generated, and a high negative pressure can be generated at the negative pressure outlet. Therefore, by connecting the negative pressure outlet to the negative pressure chamber, it becomes possible to perform negative pressure filling into the negative pressure chamber at a desired timing (see, for example, Patent Document 1 and Patent Document 2).
JP 2002-212385 A JP 2003-201927 A

  However, in general, the air flowing through the ejector is taken from the upstream side of the throttle of the intake pipe and flows downstream so as to bypass the throttle. Therefore, regardless of the throttle control, there is a problem that air exceeding the control value flows into the engine, the engine speed increases, and the fuel consumption decreases.

  Further, it is desirable that the negative pressure chamber of the booster body is always filled with a sufficient negative pressure in preparation for use of the braking device. However, there is a case where the assistance of the pneumatic booster is not needed, such as when driving at a low speed where a strong braking force is not required, or when the negative pressure chamber is not required to be filled quickly and the negative pressure chamber is not used quickly. is there. Therefore, in such a situation, it is desirable to perform control to improve fuel efficiency while performing negative pressure filling of the negative pressure chamber.

  Therefore, the present invention can perform sufficient and sufficient negative pressure filling of the negative pressure chamber of the booster body of the pneumatic booster and optimize engine control (in other words, improve fuel efficiency) in a well-balanced manner. An object of the present invention is to provide a pneumatic booster that can be used.

  The present invention relates to a pneumatic booster that obtains servo force by introducing a negative pressure of an intake pipe of an engine into a negative pressure chamber of a booster body, and an air inlet is connected upstream of the throttle of the intake pipe A plurality of ejectors arranged in parallel with each other in the intake pipe, wherein an air outlet is connected downstream and a negative pressure outlet is connected to the negative pressure chamber, and a switching valve for switching the operation of each ejector And a control unit that controls the switching valve according to the state of the vehicle and determines the number of operations of the ejector.

  Here, as long as a plurality of ejectors are arranged in parallel, the number of the ejectors is arbitrary, and the negative pressure generation capability of each ejector may be equal or may have different capabilities. The state of the vehicle for controlling the switching valve indicates whether or not the negative pressure chamber needs to be quickly filled with negative pressure, and includes the running state of the vehicle and the operating state of each device. .

  According to this configuration, the number of ejectors operated by the switching valve can be determined by whether or not the negative pressure chamber needs to be rapidly filled with negative pressure. There is a limit on the negative pressure filling capacity of one ejector, and there is a limit on the filling speed. However, the filling speed can be easily improved by causing a plurality of ejectors to function simultaneously as necessary. That is, when rapid filling is required, a plurality of ejectors are simultaneously operated. On the other hand, when rapid filling is not required, for example, when sufficient filling is possible only with the negative pressure generated on the intake pipe side, or when slow filling is sufficient, the use of the ejector is restricted and fuel consumption is reduced. It is possible to perform control giving priority to improvement.

  Moreover, the said structure WHEREIN: The said control part controls the operation number of a switching valve according to the negative pressure state of the said negative pressure chamber, It is characterized by the above-mentioned.

  Here, the negative pressure state of the negative pressure chamber can be recognized, for example, by a pressure sensor or the like disposed in the negative pressure chamber, and the number of ejector operations can be selected stepwise by setting a threshold value. It becomes possible.

  According to this configuration, it is possible to optimally control the amount of operation of the ejector according to the state of the negative pressure chamber.

  In the above configuration, the control unit controls the number of operation of the switching valve based on at least one of engine water temperature, vehicle speed, presence / absence of use of a braking device, and operation of an auxiliary device. .

  Generally, when the engine water temperature is low, control for increasing the throttle opening of the intake pipe is performed in order to improve the engine speed. Therefore, the negative pressure state of the intake pipe is reduced. Further, when the vehicle speed is high, the throttle opening is large, so the negative pressure state of the intake pipe decreases. Similarly, when the auxiliary machine is operating, the engine load increases, so that the control for increasing the throttle opening is performed, and the negative pressure state of the intake pipe decreases. Furthermore, the demand for negative pressure filling of the negative pressure chamber increases as the number of times the brake device is used increases.

  According to the above configuration, the ejector is actively used (simultaneous use of a plurality of selected ejectors) when the negative pressure filling efficiency of the negative pressure chamber is poor or the filling demand is increased. Negative pressure filling can be performed.

  In the above configuration, the switching threshold value of the switching valve of the controller can be changed between when the engine is cold and when the engine is warm.

  According to this configuration, it is possible to perform appropriate ejector switching control that further improves the balance between improved fuel efficiency and improved negative pressure charging efficiency.

  According to the pneumatic booster of the present invention, the number of ejectors used is appropriately selected according to the state of the vehicle, and the balance between the negative pressure filling ability in the negative pressure chamber and the engine controllability is improved. Can do.

  Hereinafter, embodiments of the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

  FIG. 1 shows a conceptual diagram of a system configuration including a pneumatic booster 10 according to the present embodiment. This pneumatic booster 10 includes a booster main body 12 and a plurality of ejectors 14 (in the present embodiment, two ejectors 14a and 14b are shown as an example, but two or more are optional). A switching valve (for example, electromagnetic valve) 16 (16a, 16b) for switching the presence or absence of the operation of each ejector 14a, 14b, and a control for controlling the switching valve 16 based on various information provided and determining the number of operations. Unit (ECU) 18.

  As is clear from FIG. 1, pipelines 22 having switching valves 16 a and 16 b are connected to the air inlets 20 a and 20 b of the plurality of ejectors 14 (14 a and 14 b). This pipe line 22 is connected to the upstream side, that is, the air cleaner 30 side, across the throttle 28 of the intake pipe 26 that supplies air to the engine 24, and the air that has passed through the air cleaner 30 flows therein. On the other hand, the air outlets 32 a and 32 b of the ejectors 14 a and 14 b are connected to the downstream side of the throttle 28 of the intake pipe 26, that is, the engine 24 side by a pipe line 34. Further, negative pressure outlets 36a and 36b are formed between the air inlets 20a and 20b and the air outlets 32a and 32b, and are connected to a negative pressure chamber (not shown) of the booster body 12 by a pipe line 38. Yes. The negative pressure outlets 36a and 36b of the pipe line 38 are provided with check valves 40a and 40b, and air flows from the negative pressure outlets 36a and 36b to the negative pressure chamber side of the booster main body 12. Only to allow. Further, check valves 42 a and 42 b are provided on the pipe 34 connecting side of the pipe 38 so as to allow only air flow from the intake pipe 26 side to the negative pressure chamber side of the booster body 12. It has become.

  As described above, the switching valves 16a and 16b switch the operation of the ejectors 14a and 14b, and various information provided to the ECU 18, for example, negative pressure from the pressure sensor 12a in which the negative pressure chamber is arranged. Based on pressure information, information from the water temperature sensor of the engine 24, information from the vehicle speed sensor, brake on / off information from the brake sensor, etc., that is, control of the switching valves 16a and 16b, that is, the air inlets 20a and 20b and the intake pipe Control whether or not to connect the upstream side of 26 is performed. Therefore, for example, when the switching valve 16a is controlled to close, the ejector 14a does not function. Conversely, when the switching valve 16a is controlled to open, the ejector 14a functions.

  In the structure of the ejector 14a, a straight pipe diffuser having tapered portions on the inlet side and the outlet side is arranged downstream of the straight pipe nozzle having a tapered portion formed on the inlet side, and a negative pressure outlet 36a is provided therebetween. When a gas is flowed from the straight pipe nozzle side to the straight pipe diffuser side, a high-speed jet is generated, and a high negative pressure can be generated at the negative pressure outlet 36a. That is, when the switching valve 16a is controlled to open, negative pressure can be introduced into the negative pressure chamber of the booster body 12 from the negative pressure outlet 36a. The structure of the ejector 14b is the same.

  In the present embodiment, the ejectors 14 a and 14 b are disposed in parallel to the intake pipe 26. Therefore, when the ejectors 14a and 14b have the same ability, if both are operated, the ability twice as much as when either the ejector 14a or the ejector 14b is operated is exhibited. That is, it becomes possible to quickly fill the negative pressure chamber with the negative pressure at about twice the speed.

Needless to say, when the ejectors 14a and 14b are not functioning and the negative pressure on the downstream side of the throttle 28 of the intake pipe 26 is sufficiently high, the negative pressure is boosted via the pipe 34 and the check valves 42a and 42b. It is introduced into the negative pressure chamber of the apparatus main body 12.
The booster body 12 includes a negative pressure chamber (constant pressure chamber) defined by a power piston and a variable pressure chamber, and inputs to an input rod (driver) connected to a brake pedal or the like of a braking device (brake) 44. The air is introduced into the variable pressure chamber in accordance with the brake operating force of the engine, and the servo pressure is applied to the brake operating force by generating thrust in the power piston by the differential pressure generated between the negative pressure chamber and the variable pressure chamber. It is.

  By the way, the timing at which negative pressure filling by the ejectors 14a and 14b is required is when the negative pressure is reduced on the intake pipe 26 side, for example, when the engine 24 is not warmed very much (in order to increase the rotation of the engine 24, the throttle When the opening of the throttle 28 is intentionally increased in order to increase or maintain the vehicle speed, that is, at high speed. In addition, there is a case where the use of the brake 44 is repeatedly performed in a short time, the negative pressure state of the negative pressure chamber is lowered, and quick negative pressure filling is preferable. Therefore, in the present embodiment, the ECU 18 that controls the switching valves 16a and 16b connected to the ejectors 14a and 14b has, for example, the booster device body 12 to recognize the vehicle state as described above. Information is provided from the pressure sensor 12a arranged in the negative pressure chamber for detecting the negative pressure state, the water temperature sensor for recognizing the water temperature of the engine 24, the vehicle speed sensor for recognizing the vehicle speed, the brake sensor for detecting the presence or absence of the brake operation, etc. And is used to control the switching valves 16a and 16b.

  The operation of the pneumatic booster 10 having the above configuration will be described with reference to the flowchart of FIG. First, an example in which the ejectors 14a and 14b are controlled based on information from the pressure sensor 12a disposed in the negative pressure chamber of the booster body 12 will be described. 1 shows a configuration in which information from various sensors is input to the ECU 18, but in the case of the control in FIG. 2, control is possible only with information from the pressure sensor 12a.

  When the engine 24 is driven, a negative pressure is generated on the engine 24 side, and the negative pressure is introduced into the negative pressure chamber of the booster main body 12 through the conduit 34. The negative pressure value V of the negative pressure chamber is detected by the pressure sensor 12a and supplied to the ECU 18. In the ECU 18, when the detected negative pressure value V is larger than a predetermined threshold A (for example, 50 kPa) (negative pressure state is high) (S100), that is, only the negative pressure generated in the engine 24 is negative. When the pressure is sufficiently and sufficiently charged and sufficient servo force can be generated in the booster main body 12 (Y in S100), the ECU 18 closes both the switching valves 16a and 16b (S102). That is, the operations of the ejectors 14a and 14b are stopped. As a result, since air does not flow into the engine 24 via the ejectors 14a and 14b, it is possible to perform good engine control in consideration of fuel consumption without affecting the control characteristics of the engine 24. Thereafter, the ECU 18 returns to step (S100) and continues to monitor the negative pressure state of the negative pressure chamber.

  On the other hand, if the measured negative pressure value V in the negative pressure chamber does not reach the threshold value A (N in S100), the negative pressure value V is further set such that threshold value A ≧ negative pressure value V> threshold value B (for example, 40 kPa) is determined (S104). That is, although sufficient negative pressure filling is not performed, it is determined whether or not a necessary and sufficient negative pressure filling state can be obtained if some negative pressure filling assistance is performed. If the negative pressure value V is A ≧ V> B (Y in S104), for example, in order to operate only the ejector 14a, the ECU 18 opens only the switching valve 16a and closes the switching valve 16b ( S106).

  As a result, air from the intake pipe 26 on the upstream side of the throttle 28 flows into the air inlet 20a of the ejector 14a via the switching valve 16a and escapes to the air outlet 32a. At this time, negative pressure is generated at the negative pressure outlet 36a and is introduced into the negative pressure chamber of the booster main body 12. The negative pressure chamber is filled with negative pressure so that the negative pressure value V> threshold value A is satisfied. In this case, since only one ejector 14 is driven, the unit speed for bringing the negative pressure into the desired filling state is not so fast, but the reduced negative pressure state is slight so that the booster body 12 is good. It is possible to quickly obtain a sufficient negative pressure state to be operated. At this time, since the air flowing from the ejector 14 to the engine 24 side is only the air outlet 32a of the ejector 14a, a reduction in fuel consumption of the engine 24 is minimized. Of course, the same effect can be obtained by opening the ejector 14b and closing the ejector 14a. Then, it returns to step (S100) and continues monitoring the negative pressure state of the negative pressure chamber.

  In step (S104), when the negative pressure state of the negative pressure chamber is not A ≧ V> B (N in S104), that is, the negative pressure state of the negative pressure chamber is greatly reduced, and the negative pressure chamber is filled with negative pressure. If it is necessary to perform the operation immediately, the ECU 18 controls both the switching valves 16a and 16b to open (S108), operates both the ejectors 14a and 14b, sets the negative pressure generation sources at two places, and sets the negative pressure. Perform quick negative pressure filling of the chamber. In this case, although the fuel consumption of the engine 24 is reduced, the negative pressure chamber can be quickly filled with negative pressure, and the brake 44 can receive the assistance of the booster main body 12 well.

  Thus, by performing the control of the flowchart of FIG. 2, the number of operations of the ejector 14 is appropriately selected according to the negative pressure state of the negative pressure chamber, and the negative pressure filling of the negative pressure chamber is performed appropriately. It is possible to control the booster main body 12 and the engine 24 in a balanced manner while reducing the fuel consumption of the engine 24 to the minimum necessary.

  FIG. 3 shows a flowchart in which the switching valves 16a and 16b are switched based on other information input to the ECU 18 and drive control of the ejectors 14a and 14b is performed. In this case, the control can be performed without using information from the pressure sensor 12a, and therefore the pressure sensor 12a may be omitted.

  First, when the engine 24 starts driving, the ECU 18 determines whether or not the water temperature T of the engine 24 exceeds a predetermined threshold C (for example, 60 ° C.) (S200). If T <C, that is, if the state of the engine 24 is cold (Y in S200), the ECU 18 increases the opening of the throttle 28 in order to warm up the engine 24 so that the booster It is determined that the negative pressure in the negative pressure chamber of the main body 12 cannot be sufficiently filled. Then, both the switching valves 16a and 16b are opened (S202), a negative pressure is generated by both the ejectors 14a and 14b, and a control for rapidly introducing the negative pressure into the negative pressure chamber of the booster body 12 is performed. Then, it returns to step (S200) and continues monitoring until the water temperature of the engine 24 exceeds the predetermined threshold value C.

  Subsequently, when the ECU 18 determines in step (S200) that the water temperature T is equal to or higher than the threshold C (warm) (N in S200), the vehicle speed V exceeds a predetermined threshold D (for example, 20 km / h). It is determined whether or not there is (S204). Here, attention is paid to the vehicle speed V. When the speed of the vehicle becomes higher, a stronger braking force is required, and when the speed is higher, the opening of the throttle 28 is correspondingly larger and the negative on the engine 24 side. This is because the pressure becomes insufficient.

  If the vehicle speed is slower than the threshold D (N in S204), the ECU 18 further determines whether or not the brake 44 has been operated (S206). When the brake 44 is not operated (N in S206), the ECU 18 can gradually fill the negative pressure in the negative pressure chamber with the negative pressure introduced from the engine 24 side without using the ejectors 14a and 14b. The switching valves 16a and 16b are both closed (S208), and the drive of the ejectors 14a and 14b is stopped. In this case, since air does not flow into the engine 24 via the ejectors 14a and 14b, it is possible to perform good engine control in consideration of fuel consumption without affecting the control characteristics of the engine 24. Thereafter, the process returns to step (S200), and monitoring of the water temperature and vehicle speed of the engine 24 is continued.

  On the other hand, when the brake 44 is operated in step (S206) (Y in S206), the negative pressure state in the negative pressure chamber is lowered, so that the negative pressure needs to be charged. In this case, since the speed of the vehicle is not so high as to require a strong braking force, it can be determined that there is only a slight decrease in the negative pressure state due to the use of the brake 44 and that quick filling is not necessary. Therefore, for example, in order to operate only the ejector 14a, the ECU 18 opens only the switching valve 16a and closes the switching valve 16b (S210).

  As a result, air from the intake pipe 26 on the upstream side of the throttle 28 flows into the air inlet 20a of the ejector 14a via the switching valve 16a and escapes to the air outlet 32a. At this time, a negative pressure is generated at the negative pressure outlet 36a and is introduced into the negative pressure chamber of the booster main body 12, and the negative pressure chamber is filled with the negative pressure. In this case, since only one ejector 14 is driven, the unit speed for bringing the negative pressure into the desired filling state is not so fast, but the reduced negative pressure state is slight so that the booster body 12 is good. It is possible to quickly obtain a sufficient negative pressure state to be operated. At this time, since the air flowing from the ejector 14 to the engine 24 side is only the air outlet 32a of the ejector 14a, a reduction in fuel consumption of the engine 24 is minimized. Of course, the same effect can be obtained by opening the ejector 14b and closing the ejector 14a. Then, it returns to step (S200), continues monitoring of water temperature and vehicle speed, and repeats the above-mentioned control.

  If the vehicle speed exceeds the threshold D in step (S204) (Y in S204), the ECU 18 detects whether or not the brake 44 has been operated (S212). Here, if the brake 44 is operated (Y in S212), the negative pressure state in the negative pressure chamber is lowered, so that it is necessary to fill with negative pressure. In this case, the ECU 18 determines that the vehicle speed requires a strong braking force and that the brake 44 may be repeatedly operated, and that a quick negative pressure filling is necessary. Therefore, both the switching valves 16a and 16b are controlled to open (S214), both the ejectors 14a and 14b are operated, and the negative pressure generating source is set to two places to quickly fill the negative pressure chamber with negative pressure. In this case, although the fuel consumption of the engine 24 is reduced, it is possible to quickly fill the negative pressure chamber quickly and to receive the assistance of the booster body 12 well, and the brake 44 repeatedly generates a strong braking force. It becomes possible to do.

  On the other hand, if the operation of the brake 44 is not performed in step (S212) (N in S212), the ECU 18 is sufficiently introduced with negative pressure from the engine 24 side because the throttle 28 is open to maintain the vehicle speed. However, since the brake 44 is not used, the negative pressure state in the negative pressure chamber is not greatly reduced. Therefore, for example, in order to operate only the ejector 14a, the ECU 18 opens only the switching valve 16a and closes the switching valve 16b (S216). As a result, air from the intake pipe 26 on the upstream side of the throttle 28 flows into the air inlet 20a of the ejector 14a via the switching valve 16a and escapes to the air outlet 32a. At this time, a negative pressure is generated at the negative pressure outlet 36a and is introduced into the negative pressure chamber of the booster body 12 to fill the negative pressure chamber with the negative pressure. In this case, since only one ejector 14 is driven, the unit speed for bringing the negative pressure into the desired filling state is not so fast, but the reduced negative pressure state is slight so that the booster body 12 is good. It is possible to quickly obtain a sufficient negative pressure state to be operated. At this time, since the air flowing from the ejector 14 to the engine 24 side is only the air outlet 32a of the ejector 14a, a reduction in fuel consumption of the engine 24 is minimized. Of course, the same effect can be obtained by opening the ejector 14b and closing the ejector 14a. Then, it returns to step (S200), continues monitoring of water temperature and vehicle speed, and repeats the above-mentioned control.

  In this way, the switching valves 16a and 16b are switched based on various information input to the ECU 18, and drive control of the ejectors 14a and 14b is performed, so that the number of operations of the ejector 14 corresponding to the state of the vehicle is appropriately selected. In addition, it is possible to control the booster device body 12 and the engine 24 in a balanced manner while reducing the fuel consumption of the engine 24 to a necessary minimum while performing good negative pressure filling of the negative pressure chamber.

  FIG. 4 shows another conceptual diagram similar to the system including the pneumatic booster 10 shown in FIG. In the configuration of FIG. 4, a three-position valve 16c is used as a switching valve for selecting the operation of the ejectors 14a and 14b, and switching control of the ejectors 14a and 14b is performed by one three-position valve 16c. The configuration other than the switching valve is the same as the configuration of FIG. 1, has the same function, and can obtain the same effect. In this case, it is possible to contribute to a reduction in the number of parts, a reduction in pipeline piping, and the like.

  The configuration shown in FIG. 5 is an example in which the switching valve 16b is omitted from the configuration shown in FIG. That is, the ejector 14b is configured to always function, and only the ejector 14a is selected to be operated. That is, the selection of the number of operations of the ejector 14 is “1” or “2”. In this case, since the ejector 14b always operates, negative pressure filling of the negative pressure chamber can be performed effectively. In this case, it is also possible to contribute to the reduction of the number of parts and the reduction of pipelines.

  In each structure mentioned above, although the several ejector 14 (14a, 14b) demonstrated as what has the same capability, you may use what has a different negative pressure generation capability. For example, if the ejector 14a is 10 liters / minute and the ejector 14b is 20 liters / minute, the capacity of 10 liters / minute, 20 liters / minute, and 30 liters / minute is exhibited depending on the selection and combination of the ejectors 14a and 14b. Therefore, the degree of freedom in selecting the negative pressure filling speed of the negative pressure chamber can be improved.

  In the above-described embodiment, the ECU 18 controls the switching valves 16a and 16b based on the water temperature and the vehicle speed, assuming that the water temperature and the vehicle speed of the engine 24 cause the opening degree of the throttle 28 to change. In addition, the load on the engine 24 changes and the opening degree of the throttle 28 also changes depending on whether auxiliary equipment is used, for example, whether an air conditioner (air conditioner) is used. Therefore, the switching valves 16a and 16b may be controlled based on whether or not auxiliary equipment such as an air conditioner is used.

  It is also preferable to control the switching valves 16a and 16b based on the operation of a so-called antilock brake system. That is, according to the antilock brake system, it is possible to detect that the slip ratio of the wheel has increased. Therefore, when the wheels are likely to be locked, the switching valves 16a and 16b can be operated to quickly fill the negative pressure chamber with the negative pressure and to ensure a sufficient braking force.

  Thus, according to the present embodiment, the unit speed of the negative pressure filling of the negative pressure chamber of the booster main body 12 can be optimally controlled as necessary, and a strong braking force is required. Can respond quickly to cases. In addition, when it can be determined that a strong braking force is not necessary (when it is determined that a safe stop can be performed with a normal braking force without using a boost running value), or with a slight charge When it can be determined that the negative pressure charging is completed, it is possible to gradually recover the load state while limiting the operation of the ejector 14 in consideration of the fuel consumption of the engine 24, and the balance between the recovery of the load state and the improvement of the fuel consumption. It is possible to perform control to maintain the optimum.

  In the flowchart of FIG. 2, the threshold value of the negative pressure value has been described as being fixed. However, the threshold value may be changed depending on the state of the engine 24, for example, cold and warm. That is, the opening operation timing of the switching valve 16 may be advanced when cold, and the opening operation timing of the switching valve may be delayed when warm. In this case, it is possible to perform control according to the vehicle state.

  Further, since the allowable amount of air flowing from the air outlet 32 of the ejector 14 also changes depending on the exhaust amount of the engine 24, even if the switching timing (threshold value) of the switching valve 16 is changed based on the exhaust amount of the engine 24. Good.

  The configuration shown in the present embodiment is an example, and an air inlet is connected to the upstream side across the throttle of the intake pipe, an air outlet is connected to the downstream side, and a negative pressure outlet is connected to the negative pressure chamber. A plurality of ejectors arranged in parallel with each other in the intake pipe, a switching valve for switching operation of each ejector, and a control unit for controlling the switching valve according to the state of the vehicle and determining the number of operations of the ejector Other configurations and control procedures are arbitrary, and the same effects as in the present embodiment can be obtained.

It is a composition conceptual diagram of a system containing a pneumatic booster concerning this embodiment. It is a flowchart explaining control of the switching valve in the system of FIG. It is a flowchart explaining the other control of the switching valve in the system of FIG. It is another structure conceptual diagram of the system containing the pneumatic booster which concerns on this embodiment. It is another structure conceptual diagram of the system containing the pneumatic booster which concerns on this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Pneumatic booster, 12 Booster main body, 12a Pressure sensor, 14, 14a, 14b Ejector, 16, 16a, 16b Switching valve, 16c 3 position valve, 18 ECU, 20a, 20b Air inlet, 22, 34, 38 pipe line, 24 engine, 26 intake pipe, 28 throttle, 30 air cleaner, 32a, 32b air outlet, 36a, 36b negative pressure outlet, 40a, 40b, 42a, 42b check valve, 44 braking device (brake).

Claims (4)

In a pneumatic booster that obtains servo power by introducing the negative pressure of the intake pipe of the engine into the negative pressure chamber of the booster body,
A plurality of air inlets are connected in parallel to the intake pipe, with an air inlet connected upstream of the throttle of the intake pipe, an air outlet connected downstream, and a negative pressure outlet connected to the negative pressure chamber. The ejector
A switching valve for switching the presence or absence of the operation of each ejector;
A control unit that controls the switching valve according to the state of the vehicle and determines the number of operations of the ejector;
A pneumatic booster comprising:   2. The pneumatic booster according to claim 1, wherein the control unit controls the number of operations of the switching valve in accordance with a negative pressure state of the negative pressure chamber.   2. The control unit according to claim 1, wherein the control unit controls the number of operation of the switching valve based on at least one of engine water temperature, vehicle speed, presence / absence of use of a braking device, and operation / non-operation of an auxiliary device. 2. A pneumatic booster according to 2.   4. The pneumatic booster according to claim 1, wherein the switching threshold value of the switching valve of the control unit can be changed between a cold time and a warm time of the engine. 5. .

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