JP6820752B2 - Engine negative pressure generator - Google Patents

Description

The present invention relates to an engine negative pressure generator that supplies negative pressure to a brake booster.

Vehicles such as automobiles are equipped with a brake booster that amplifies the depression force of the brake pedal in order to assist the depression force of the driver's brake pedal and secure the necessary braking force. As this brake booster, a negative pressure type brake booster that utilizes the intake negative pressure of the engine is widely adopted, but in recent years, the mixture of the engine has been diluted and the difference between the intake negative pressure and the atmospheric pressure has become smaller. There is a tendency, and measures are needed to make up for the lack of intake negative pressure.

For example, in Patent Document 1, a negative pressure generating ejector is provided integrally with a PCV valve in a blow-by gas-by recirculation passage that connects an intake passage upstream of the throttle valve to an intake passage downstream of the throttle valve via an internal combustion engine. A technique for accumulating the negative pressure generated in the negative pressure generating ejector in the brake booster in addition to the negative pressure generated in the intake passage downstream of the valve is disclosed.

Japanese Unexamined Patent Publication No. 2015-78633

Further, in recent years, it has become common to provide an EGR device that recirculates a part of the exhaust gas to the intake system and reburns it. When a large amount of EGR gas is introduced, the difference between the intake negative pressure and the atmospheric pressure becomes even greater. As the size becomes smaller, it becomes difficult to secure sufficient negative pressure with an auxiliary device such as the negative pressure generating ejector disclosed in Patent Document 1. For this reason, conventionally, a device for generating negative pressure such as a negative pressure pump must be separately provided, which not only increases the cost but also increases the weight of the vehicle, which may lead to deterioration of fuel efficiency.

The present invention has been made in view of the above circumstances, and provides an engine negative pressure generating device capable of securing a negative pressure for braking without providing a device for generating a negative pressure separately from the engine. I am aiming.

The engine negative pressure generator according to one aspect of the present invention is an engine negative pressure generator that includes at least one set of a pair of pistons facing each other about a crankshaft, and the pair of pistons reciprocate in opposite directions. there are, to the crank chamber formed on the back side of the pair of pistons is composed of a solenoid valve, respectively, and the first on-off valve which is opened and closed in response to the pressure in the crank chamber and the second on-off valve Further, the first on-off valve and the second on-off valve are provided with a control unit that controls opening and closing according to the pressure of the crank chamber, and the first on-off valve is connected to the intake system of the engine. while, the second on-off valve connected to the brake booster over, and supplies a negative pressure to the brake booster over by the reciprocating motion of the pair of pistons.

According to the present invention, it is possible to secure a negative pressure for a brake without providing a device that generates a negative pressure separately from the engine.

A block diagram of a negative pressure generator in a horizontally opposed two-cylinder engine according to the first embodiment of the present invention. Same as above, explanatory view showing the internal configuration of the engine as seen from the plane parallel to the crankshaft. Same as above, explanatory view showing the operation when the piston is lowered. The same as above, an explanatory diagram showing the operation when the piston is raised. Same as above, explanatory diagram showing the opening / closing timing of the check valve in the 2-cylinder engine. The same as above, an explanatory diagram showing an application example to a horizontally opposed 4-cylinder engine. Same as above, explanatory view showing the opening / closing timing of the check valve in the 4-cylinder engine. A block diagram of a negative pressure generator in a horizontally opposed two-cylinder engine according to the second embodiment of the present invention. Same as above, flowchart of electromagnetic on-off valve control routine

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 is an engine, and in the figure, cylinders 4 # 1 and # 2 which are # 1 cylinders in the order of combustion, centered on a crankshaft 3 supported by a substantially central portion of a cylinder block 2. A horizontally opposed two-cylinder engine in which cylinders 4 # 2, which are the number cylinders, are arranged horizontally so as to face each other is shown. Pistons 5 # 1 and 5 # 2 are slidably inserted into the cylinders 4 # 1 and 4 # 2, respectively, and these pistons 5 # 1 and 5 # 2 are paired in opposite directions. It is connected to the crankshaft 3 via connecting rods 6 # 1 and 6 # 2 so as to reciprocate.

Further, the intake manifold 9 is branched for each cylinder via the intake valves 8 # 1 and 8 # 2 in the combustion chambers 7 # 1 and 7 # 2 formed above the pistons 5 # 1 and 5 # 2. Are communicated with each other, and the exhaust manifold 11 branched for each cylinder is communicated with the exhaust valves 10 # 1 and 10 # 2. In the combustion chambers 7 # 1 and 7 # 2, the discharge parts of spark plugs (not shown) arranged in the cylinder heads 12 # 1 and 12 # 2 are exposed, and the intake valves 8 # 1 and 8 # 2 are exposed. Injectors (not shown) that inject fuel into combustion chambers 7 # 1 and 7 # 2 are arranged on the upstream side of the intake port where 2 is arranged.

The intake manifold 9 is assembled on the upstream side and communicated with the intake passage 13, and the throttle valve 13a is interposed in the intake passage 13. The upstream side of the throttle valve 13a of the intake passage 13 is communicated with an air cleaner (not shown), and fresh air purified by the air cleaner is introduced into the combustion chambers 7 # 1 and 7 # 2. On the other hand, the exhaust manifold 11 is merged on the downstream side and communicates with a muffler (not shown) from the exhaust passage 14.

Here, inside the cylinder block 2 in which the crankshaft 3 is arranged, a crank chamber 15 is formed on the back side of the pistons 5 # 1 and 5 # 2, and lubricating oil is stored in the lower portion of the crank chamber 15. Oil pans 16 are connected in series. As shown in FIG. 2, rib-shaped journal portions 17-1, 17-2, and 17-3 for holding a bearing that supports the crankshaft 3 are provided inside the crank chamber 15.

The journal portion 17-1 is provided at a position supporting the crankshaft 3 on the outside of the connecting rod 6 # 1 connected to the piston 5 # 1 of the # 1 cylinder. The journal portion 17-2 has a crankshaft between the connecting rod 6 # 1 connected to the piston 5 # 1 of the # 1 cylinder and the connecting rod 6 # 2 connected to the piston 5 # 2 of the # 2 cylinder. It is provided at a position that supports 3. Further, the journal portion 17-3 is provided at a position supporting the crankshaft 3 on the outside of the connecting rod 6 # 2 connected to the piston 5 # 2 of the # 2 cylinder.

Further, a first on-off valve 20 and a second on-off valve 21 that open and close according to the pressure of the crank chamber 15 are arranged at a portion of the cylinder block 2 where the crank chamber 15 is formed. As will be described later, the first on-off valve 20 serves as a discharge valve for discharging air containing blow-by gas in the crank chamber 15 to the outside, and the second on-off valve sucks air into the inside of the crank chamber 15 from the outside. It becomes an intake valve to do.

In the present embodiment, the first on-off valve 20 and the second on-off valve 21 are configured by a check valve that opens and closes by a pressure difference between the inside and the outside of the crank chamber 15 and allows only one-way flow. Has been done. Hereinafter, the first on-off valve 20 is simply referred to as a “check valve 20”, and the second on-off valve 21 is simply referred to as a “check valve 21”.

Although FIG. 1 shows an example in which the check valves 20 and 21 are composed of a reed valve made of an elastic thin plate material, the check valve is not limited to the reed valve, and is not limited to the reed valve. The check valve may be composed of a valve body such as the above and a spring for urging the valve body to abut on the valve seat.

An exhaust hose 22 is connected to the check valve 20 on the outside of the cylinder block 2, and the end of the exhaust hose 22 is connected to an intake system downstream of the throttle valve 13a, for example, an intake manifold 9. The check valve 20 is set to open when the pressure in the crank chamber 15 is higher than the pressure in the intake manifold 9, and the gas flows only in the direction from the crank chamber 15 to the intake manifold 9. It is arranged in an acceptable orientation.

On the other hand, a negative pressure hose 23 is connected to the check valve 21 on the outside of the cylinder block 2, and the end of the negative pressure hose 23 amplifies the pedaling force of the brake pedal 30 with a negative pressure to obtain a master cylinder (not shown). It is connected to the pressure chamber of the well-known brake booster 31 transmitted to (omitted). The check valve 21 is set to open when the pressure in the crank chamber 15 is lower than the pressure in the pressure chamber of the brake booster 31, and the pressure in the brake booster 31 is opposite to that in the check valve 20. It is arranged so as to allow the flow of gas only in the direction from the chamber to the crank chamber 15.

In this case, the flow of gas in the crank chamber 15 is the wall surface of the cylinder block 2 at the upper part of the crank chamber 15, three journal portions 17-1, 17-2, 17-3, and the oil pan at the lower part of the crank chamber 15. It may be limited by the lubricating oil stored in 16. Therefore, in the present embodiment, the check valve 20 is arranged so as to communicate with the space between the journal section 17-1 and the journal section 17-2, and the check valve 21 is arranged so as to communicate with the journal section 17-. It is arranged so as to communicate with the space between 2 and the journal portion 17-3.

In the above engine 1, the pair of pistons 5 # 1 and 5 # 2 simultaneously descend toward the bottom dead center and simultaneously rise toward the top dead center during engine operation. Therefore, the engine 1 not only outputs the driving force from the crankshaft 3, but also the pressure in the crank chamber 15 repeatedly rises and falls due to the reciprocating motion of the pistons 5 # 1 and 5 # 2, and the check valve 20, It also functions as a negative pressure generator that generates negative pressure via the 21.

Specifically, as shown in FIG. 3, when the pistons 5 # 1 and 5 # 2 descend toward the bottom dead center, the pressure in the crank chamber 15 rises, and the pressure in the crank chamber 15 increases in the intake manifold 9. When the pressure becomes higher than the pressure of, the check valve 20 on the discharge side is opened, and the gas (air containing blow-by gas) in the crank chamber 15 is discharged into the intake manifold 9 via the exhaust hose 22. At this time, the check valve 21 on the suction side is closed, and the pressure of the crank chamber 15 does not affect the brake booster 31.

Further, as shown in FIG. 4, when the pistons 5 # 1 and 5 # 2 rise toward the top dead center and the pressure in the crank chamber 15 decreases to become lower than the pressure in the pressure chamber of the brake booster 31. The check valve 21 on the suction side opens with the check valve 20 on the discharge side closed. As a result, air is sucked from the pressure chamber of the brake booster 31 into the crank chamber 15 via the negative pressure hose 23. By repeating such an operation, the pressure chamber of the brake booster 31 can have a negative pressure of atmospheric pressure or less.

The opening / closing timing of the check valves 20 and 21 with respect to the pressure change of the crank chamber 15 is illustrated in FIG. 5, for example. As shown in FIG. 5, the pressure P of the crank chamber 15 becomes maximum when the piston positions of the pistons 5 # 1 and 5 # 2 reach the bottom dead center at the crank angles of 180 ° CA and 540 ° CA. It becomes the minimum when the piston position reaches the top dead center at the crank angles of 0 ° CA, 360 ° CA, and 720 ° CA. The check valve 20 on the discharge side opens in a period A of a pressure P1 or higher, which is higher than the pressure in the intake manifold 9 before and after the bottom dead center where the pressure P of the crank chamber 15 becomes maximum. Further, the check valve 21 on the suction side is opened in a period B of a pressure P2 or less, which is lower than the pressure of the pressure chamber of the brake booster 31 before and after the top dead center where the pressure P of the crank chamber 15 becomes the minimum.

The above negative pressure generation function can be realized by a horizontally opposed engine including at least one pair of pistons facing each other. That is, not only a horizontally opposed two-cylinder engine but also a horizontally opposed engine having four or more cylinders can realize the above-mentioned negative pressure generation function with basically the same configuration.

Taking a 4-cylinder engine as an example, as shown in FIG. 6, the engine 51, which is a horizontally-opposed 4-cylinder engine, has cylinders 54 # 1, which are the # 1 cylinders in the order of combustion, in the banks before and after the cylinder block 52. The cylinders 54 # 2 of the # 2 cylinder are opposed to each other, and the cylinders 54 # 3 of the # 3 cylinder and the cylinders 54 # 4 of the # 4 cylinder are arranged so as to face each other. In the present embodiment, it is assumed that the # 1 cylinder and the # 2 cylinder are arranged in the front bank, and the # 3 cylinder and the # 4 cylinder are arranged in the rear bank.

The piston 55 # 1 inserted into the cylinder 54 # 1 of the # 1 cylinder and the piston 55 # 2 inserted into the cylinder 54 # 2 of the # 2 cylinder are connected so that they can reciprocate in opposite directions. It is connected to the crankshaft 53 via rods 56 # 1 and 56 # 2. Further, the piston 55 # 3 inserted into the cylinder 54 # 3 of the # 3 cylinder and the piston 55 # 4 inserted into the cylinder 54 # 4 of the # 4 cylinder can be reciprocated in opposite directions. It is connected to the crankshaft 53 via connecting rods 56 # 3 and 56 # 4.

Further, inside the crank chamber 65 at the center of the cylinder block 52, journal portions 57-1, 57-2, 57-3, 57-4, 57-5 for holding the bearing of the crankshaft 53 are provided. These journal portions 57-1, 57-2, 57-3, 57-4, 57-5 are formed in a rib shape like the journal portions 17-1, 17-2, 17-3 of the first form. ing.

The journal portion 57-1 is provided at a position supporting the crankshaft 53 on the outside of the connecting rod 56 # 1 of the # 1 cylinder. The journal portion 57-2 is provided at a position that supports the crankshaft 53 between the connecting rod 56 # 1 of the # 1 cylinder and the connecting rod 56 # 2 of the # 2 cylinder.

Further, the journal portion 57-3 is provided at a position where the crankshaft 53 is supported between the connecting rod 56 # 2 of the # 2 cylinder and the connecting rod 56 # 3 of the # 3 cylinder. The journal portion 57-4 is provided at a position that supports the crankshaft 53 between the connecting rod 56 # 3 of the # 3 cylinder and the connecting rod 56 # 4 of the # 4 cylinder. Further, the journal portion 57-5 is provided at a position supporting the crankshaft 53 on the outside of the connecting rod 56 # 4 of the # 4 cylinder.

In this case, since there is a concern that the gas flowability of the engine 51 may deteriorate between the front and rear banks, the check valve 20F and the brake booster 31 connected to the intake system are provided on the front bank side of the crank chamber 65. A check valve 21F connected to the pressure chamber of the above is provided, and a check valve 20R connected to the intake system and a check valve 21R connected to the pressure chamber of the brake booster 31 are provided on the rear bank side. .. The check valves 20F and 21F on the front bank side and the check valves 20R and 21R on the rear bank side can be composed of a reed valve or the like as in the first form of the check valves 20 and 21.

The check valve 20F on the front bank side is arranged so as to communicate with the space between the journal section 57-2 and the journal section 57-3, and the check valve 21F is the journal section 57-1 and the journal section 57-. It is arranged so as to communicate with the space between 2. Further, the check valve 20R on the rear bank side is arranged so as to communicate with the space between the journal section 57-3 and the journal section 57-4, and the check valve 21R is arranged between the journal section 57-4 and the journal section. It is arranged so as to communicate with the space between 57-5.

The check valves 21F and 21R connected to the pressure chamber of the brake booster 31 are installed at the farthest places in order to avoid the influence of the front and rear cylinders, but the check valves 20F and 20R connected to the intake system. Can be substituted with one check valve.

In such an engine 51, as shown in FIG. 7, when the piston position of the front bank of the piston 55 # 1 of the # 1 cylinder and the piston 55 # 2 of the # 2 cylinder reaches the bottom dead center, the crank chamber The pressure Pf of the portion corresponding to the front bank of 65 becomes the maximum, and the pressure Pf becomes the minimum at the position of the top dead center. Therefore, in the front bank, the check valve 20F on the discharge side is opened at Af during a period of pressure Pf1 or higher, which is higher than the pressure in the intake manifold 9 before and after the bottom dead center where the pressure Pf of the crank chamber 65 becomes maximum. Is set to. Further, the check valve 21F on the suction side is opened at a period Bf of pressure Pf2 or less, which is lower than the pressure of the pressure chamber of the brake booster 31 before and after the top dead center where the pressure Pf of the crank chamber 65 becomes the minimum. Set.

On the other hand, the piston 55 # 3 of the # 3 cylinder of the rear bank and the piston 55 # 4 of the # 4 cylinder are the pistons 55 # 1 and # of the # 1 cylinder of the front bank as shown by the broken line in FIG. The bottom dead center and top dead center are reached at positions where the phase of the crank angle is 180 degrees out of phase with the piston 55 # 2 of the second cylinder, and at each position, the part corresponding to the rear bank of the crank chamber 65. The pressure Pr becomes maximum and minimum. Therefore, in the rear bank, the check valve 20R on the discharge side is opened at a period Ar of pressure Pr1 or more, which is higher than the pressure in the intake manifold 9 before and after the bottom dead center where the pressure Pr of the crank chamber 65 becomes maximum. The check valve 21R on the suction side is opened for a period of Br2 or less, which is lower than the pressure of the pressure chamber of the brake booster 31 before and after the top dead center where the pressure Pr of the crank chamber 65 becomes the minimum. Set to speak.

That is, the piston 55 # 1 of the # 1 cylinder of the front bank and the piston 55 # 2 of the # 2 cylinder descend toward the bottom dead center, while the pistons 55 # 3 and # of the # 3 cylinder of the rear bank #. When the piston 55 # 4 of the 4th cylinder rises toward the top dead center, the check valve 20F on the discharge side of the front bank opens and the air containing blow-by gas in the crank chamber 65 is discharged to the intake manifold 9. At the same time, the check valve 21R on the suction side of the rear bank is opened to suck air from the pressure chamber of the brake booster 31 into the crank chamber 65.

Conversely, the piston 55 # 1 of the # 1 cylinder of the front bank and the piston 55 # 2 of the # 2 cylinder rise toward the top dead center, and the pistons 55 # 3 and # of the # 3 cylinder of the rear bank # When the piston 55 # 4 of the 4th cylinder descends toward the bottom dead center, the check valve 21F on the suction side of the front bank opens and air is sucked into the crank chamber 65 from the pressure chamber of the brake booster 31. At the same time, the check valve 20R on the discharge side of the rear bank is opened, and the air containing the blow-by gas in the crank chamber 65 is discharged to the intake manifold 9. By repeating such an operation, the pressure chambers of the crank chamber 65 and the brake booster 31 can be kept below the atmospheric pressure.

As described above, in the present embodiment, a check valve serving as a discharge valve and a check valve serving as a suction valve are provided in the crank chamber formed on the back surface side of the piston of the horizontally opposed engine, and the check valve on the suction side is provided. The check valve is connected to the pressure chamber of the brake booster and the check valve on the discharge side is connected to the intake system. As a result, the horizontally opposed engine can function as a negative pressure generator that generates negative pressure by the reciprocating motion of a pair of pistons facing each other about the crankshaft and supplies negative pressure to the brake booster.

Therefore, even when the suction negative pressure cannot be sufficiently obtained due to EGR or the like, the brake negative pressure can be secured without separately providing an electric pump or an engine-driven pump that generates a brake negative pressure. It can contribute to cost reduction and weight reduction. Moreover, the internal pressure of the crank chamber can be kept below atmospheric pressure to reduce the air density, and the pump loss on the back surface of the piston can be reduced to reduce fuel consumption.

Next, a second embodiment of the present invention will be described. In the second form, the check valve 20 (20F, 20R) on the discharge side and the check valve 21 (21F, 21R) on the suction side in the first form are replaced with electromagnetic on-off valves, respectively, and the electromagnetic on-off valve is replaced with the crank chamber 15. The opening / closing control is performed according to the pressure of (65).

As a representative example of the horizontally opposed two-cylinder engine, instead of the check valves 20 and 21 arranged in the crank chamber 15 of the engine 1 in the first embodiment, as shown in FIG. A first electromagnetic on-off valve 20E on the discharge side and a second electromagnetic on-off valve 21E on the suction side are arranged. The first electromagnetic on-off valve 20E and the second electromagnetic on-off valve 21E are controlled to open and close according to the pressure of the crank chamber 15 by the electronic control unit (ECU) 100 as a control unit. Other configurations are the same as those of the first form.

The ECU 100 is a control device mainly composed of a microcomputer, and is connected to other control devices such as an engine control device so as to be bidirectionally communicative via an in-vehicle network (not shown). The ECU 100 includes an intake pipe pressure sensor 70 that detects the intake pipe pressure of the intake system downstream of the throttle valve 13a, a crank chamber pressure sensor 71 that detects the pressure in the crank chamber 15 (crank chamber pressure), and a pressure chamber of the brake booster 31. A first electromagnetic on-off valve 20E and a second electromagnetic on-off valve 20E based on signals from a brake booster pressure sensor 72 that detects pressure (brake booster pressure), a crank angle sensor 73 that detects a crank angle, and other sensors (not shown). The valve 21E is controlled to open and close.

The intake pipe pressure by the intake pipe pressure sensor 70 and the crank angle by the crank angle sensor 73 may be received from the vehicle-mounted net as a part of the engine control information by the engine control device. Further, the pressure in the pressure chamber of the brake booster 31 by the brake booster pressure sensor 72 can also be acquired via the in-vehicle network when the pressure in the pressure chamber of the brake booster 31 is detected by the brake control device. is there.

Hereinafter, the opening / closing control of the electromagnetic on-off valve 20E by the ECU 100 will be described with reference to the flowchart of the electromagnetic on-off valve control routine shown in FIG.

This electromagnetic on-off valve control routine is a routine that is executed in the ECU 100 at predetermined time intervals after the engine is started. First, in the first step S1, the ECU 100 first, based on the signals from the intake pipe pressure sensor 70, the crank chamber pressure sensor 71, and the brake booster pressure sensor 72, the intake pipe pressure Pm, the crank chamber pressure P, and the brake booster pressure, respectively. Detect Pb.

Next, the process proceeds to step S2, and it is examined whether or not the crank chamber pressure P has risen above the intake pipe pressure Pm. As a result, when P ≧ Pm, in step S3, the first electromagnetic on-off valve 20E on the discharge side is opened, and the second electromagnetic on-off valve 21E on the suction side is closed to exit the routine. As a result, the gas in the crank chamber 15 is discharged to the intake manifold 9.

On the other hand, when P <Pm in step S2, the process proceeds from step S2 to step S4, and it is examined whether or not the crank chamber pressure P has dropped to the brake booster pressure Pb or less. As a result, in the case of P ≦ Pb, the process proceeds from step S4 to step S5, the first electromagnetic on-off valve 20E on the discharge side is closed, and the second electromagnetic on-off valve 21E on the suction side is opened. Exit the routine. As a result, air is sucked from the pressure chamber of the brake booster 31 into the crank chamber 15, and the pressure in the pressure chamber of the brake booster 31 decreases.

When opening and closing the first and second electromagnetic on-off valves 20E and 21E, it is desirable to provide a predetermined hysteresis between the valve opening and the valve closing in order to prevent the valve from vibrating operation.

Further, in step S4, when P> Pb, that is, when the crank chamber pressure P is lower than the intake pipe pressure Pm but higher than the brake booster pressure Pb, the process proceeds from step S4 to step S6, and the first step is performed. Both the electromagnetic on-off valve 20E and the second electromagnetic on-off valve 21E are closed to exit the routine. By repeating the above operation, the pressure chambers of the crank chamber 5 and the brake booster 31 can be kept below the atmospheric pressure.

In step S2, it may be checked whether or not the differential pressure (P−Pm) between the crank chamber pressure P and the intake pipe pressure Pm becomes a constant value ΔP1 (ΔP1> 0) or more. When P-Pm) <ΔP1, the process proceeds to step S4, and when (P-Pm) ≥ ΔP1, in step S3, the first electromagnetic on-off valve 20E on the discharge side is opened and the second electromagnetic on the suction side is opened. The on-off valve 21E may be closed.

Similarly, in step S4 as well, it is investigated whether or not the differential pressure (Pb−P) between the brake booster pressure Pb and the crank chamber pressure P becomes a certain value ΔP2 (ΔP2> 0) or more, and (Pb−P ) <When ΔP2, the process proceeds to step S6, and when (Pb−P) ≧ ΔP2, in step S5, the first electromagnetic on-off valve 20E on the discharge side is closed and the second electromagnetic on-off valve 21E on the suction side is closed. May be opened.

In the above electromagnetic on-off valve control routine, the ECU 100 controls opening and closing of the first electromagnetic on-off valve 20E and the second electromagnetic on-off valve 21E according to the pressure difference between the inside and the outside of the crank chamber 15. However, simply, the opening and closing control of the first electromagnetic on-off valve 20E and the second electromagnetic on-off valve 21E is performed by the crank chamber pressure detected by the crank chamber pressure sensor 71 or the crank angle detected by the crank angle sensor 73. It is also possible.

That is, the pressure in the crank chamber and the pressure in the intake pipe are known in advance for each engine, and the required brake booster pressure is also determined by the configuration of the brake system. Therefore, for example, the pressure value Pe1 for opening the first electromagnetic on-off valve 20E and the pressure value Pe2 for opening the second electromagnetic on-off valve 21E are set in advance, and these pressure values Pe1 and Pe2 and the crank By comparing with the pressure P in the chamber 15, the first electromagnetic on-off valve 20E on the discharge side is opened in a period corresponding to the period A described with reference to FIG. 5, and the second electromagnetic on-off valve 21E on the suction side is opened. It is also possible to open the valve in a period corresponding to the period B in FIG.

Further, since the pressure in the crank chamber 15 changes according to the crank angle, the crank angles θ1 and θ2 corresponding to the above-mentioned pressure values Pe1 and Pe2 are obtained in advance, and these crank angles θ1 and θ2 and the crank angle sensor are obtained. It is also possible to determine the valve opening period of the first electromagnetic on-off valve 20E and the second electromagnetic on-off valve 21E by comparing with the crank angle θ detected in 73.

However, in the control by the crank angle, in order to prevent the backflow from the intake side to the crank chamber, the first one on the discharge side is based on the control information related to the engine operating state such as the throttle opening, the engine speed, and the intake temperature. It is desirable to limit the operation of the electromagnetic on-off valve 20E. Further, backflow from the crank chamber to the brake booster side can be prevented by the check valve of the negative pressure introduction port when the negative pressure introduction port of the brake booster is provided with a check valve. When the check valve is not provided, the operation of the second electromagnetic on-off valve 21E on the suction side can be prevented, for example, by limiting the operation for a certain period of time after the engine is started or during coasting.

Further, in the above description, the horizontally opposed two-cylinder engine has been described as a representative, but the same applies to the horizontally opposed engine having four or more cylinders, and the check valves 20F, 21F, 20R, and 21R in FIG. It can be replaced with an electromagnetic on-off valve. It is desirable to provide a pressure sensor for detecting the pressure in the crank chamber for each bank. Further, in a horizontally opposed engine having four or more cylinders, when electromagnetic on-off valve control is performed using a crank angle, since there are a cylinder at the top dead center and a cylinder at the bottom dead center at the same crank angle, cylinder discrimination is performed. There is a need. For this cylinder discrimination, the cylinder discrimination result based on the signal from the cam angle sensor or the like in normal engine control can be used.

In the second mode as well, as in the first mode, the horizontally opposed engine can function as a negative pressure generator that supplies negative pressure to the brake booster by the reciprocating motion of a pair of pistons facing each other about the crankshaft. The second form can deal with differences between engines and mechanical variations with a high degree of freedom, and can contribute to total cost reduction.

1,51 Engine 3,53 Crankshaft 5,55 # 1 to 55 # 4 Piston 9 Intake manifold 13 Intake passage 13a Throttle valve 15,65 Crank chamber 20,21 Check valve 20F, 21F Check valve 20R, 21R Check valve Valve 20E, 21E Electromagnetic on-off valve 31 Brake booster 100 Electronic control unit

Claims (2)

An engine negative pressure generator that includes at least one set of a pair of pistons that face each other about a crankshaft, and the pair of pistons reciprocate in opposite directions.
A crank chamber formed on the back side of the pair of pistons is composed of a solenoid valve, respectively, and a first on-off valve which is opened and closed in response to the pressure in the crank chamber and the second on-off valve,
Further, a control unit for controlling the opening and closing of the first on-off valve and the second on-off valve according to the pressure in the crank chamber is provided.
The step of connecting the first switching valve to the intake system of the engine, the second on-off valve connected to the brake booster over, supplying negative pressure to the brake booster over by the reciprocating motion of the pair of pistons A negative pressure generator of an engine characterized by. The control unit sets the opening time of the first on-off valve as a predetermined period before and after the bottom dead center of the pair of pistons, and sets the opening time of the second on-off valve before and after the top dead center of the pair of pistons. The negative pressure generator for an engine according to claim 1, wherein the period is a predetermined period of the above.