JPS6363729B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a boost pressure control device for a supercharged engine.

[Conventional technology]

Conventionally, in supercharged engines such as automobiles that have a supercharger installed in the intake passage to increase engine output, problems such as impairing the durability of the engine occur if the supercharging pressure increases too much. A known method is to control the maximum boost pressure so that the boost pressure does not increase beyond a certain level. For example, in a turbocharger in which the turbocharger is driven by an exhaust turbine, a control valve that responds to intake pressure (pressure equivalent to boost pressure) is installed in a bypass passage that bypasses the exhaust turbine. There is a so-called waste gate system in which the bypass passage is opened to reduce the supercharger driving force by the exhaust turbine when the supply pressure exceeds a predetermined value (JP-A-54-44810).

[Problem to be solved by the invention]

Conventional control means of this type control intake pressure (supercharging pressure)
After the boost pressure reaches a predetermined value set in advance, the boost pressure is simply maintained constant. However, even if boost pressure is maintained constant in this way, the amount of intake gas per unit time increases as the engine speed increases, so especially in high-speed operating ranges, the amount of heat generated by the engine decreases due to the increase in the amount of intake gas. The excessive rise cannot be compensated for and the durability of the engine is impaired. In addition, in high-speed operation ranges, the amount of exhaust gas per unit time increases, and if the exhaust temperature rises excessively due to such an increase in the amount of exhaust gas, exhaust purification means such as catalysts installed in the exhaust system and exhaust turbine However, some drawbacks remained, such as thermal deterioration.

In view of these circumstances, the present invention has been developed to reduce the amount of heat generated by the engine in the high-speed operating range, which cannot be prevented by simply maintaining the boost pressure control value (maximum boost pressure) constant in an engine equipped with an exhaust turbo supercharger. Excessive rise can be prevented, thereby increasing the durability of the engine, and thermal deterioration of the exhaust purification means such as a catalyst provided in the exhaust system and the exhaust turbine can be prevented, and the structure is particularly simple. An object of the present invention is to provide a supercharging pressure control device for a supercharged engine that can satisfy the requirements.

[Means to solve the problem]

The present invention provides a compressor for an exhaust turbo supercharger in the intake passage, an exhaust turbine in the exhaust passage, and an exhaust gas bypass passage that communicates the upstream side and the downstream side of the exhaust turbine. A pressure-operated bypass control valve is provided in the exhaust turbine, and the pressure-operated chamber of the bypass control valve is connected to the intake passage downstream of the compressor via a communication passage, and an exhaust purification means is provided in the exhaust passage downstream of the exhaust turbine. A supercharged engine equipped with a relief passage for externally relieving a part of the intake pressure introduced into the pressure operating chamber of the bypass control valve via the communication passage, and a relief passage for relieving to the outside a part of the intake pressure introduced into the pressure operating chamber of the bypass control valve, and the exhaust pressure upstream of the exhaust purification means. A valve means is provided for closing the relief passage as the exhaust pressure increases.

[Effect]

According to the above configuration, the higher the exhaust pressure upstream of the exhaust purification means, the more the relief of the intake pressure to the relief passage is suppressed, and the more the intake pressure is introduced into the pressure operating chamber of the bypass control valve,
Therefore, the boost pressure control action is adjusted according to the exhaust pressure.

〔Example〕

Embodiments of the present invention will be described based on the drawings.

In FIG. 1, 1 is the engine body, 2 is an intake passage, 3 is an exhaust passage, 4 is a throttle valve provided in the intake passage 2, 5 is an air cleaner that purifies the air taken into the intake passage 2, and 6 is an exhaust purification means such as a catalyst device provided in the exhaust passage 3. Further, 7 is a blower-type compressor of the exhaust turbo supercharger, and 8 is the same exhaust turbine. The compressor 7 is installed in the intake passage 2, and the exhaust turbine 8 is installed in the exhaust passage 3, and both are interlocked and connected. As the exhaust gas flow rotates the exhaust turbine 8, the compressor 7
rotates to forcibly send air into the engine body 1. The exhaust purification means 6 is provided downstream of the exhaust turbine 8.

In addition, this supercharged engine includes a bypass passage 10 that connects the upstream side and the downstream side of the exhaust turbine 8 in the exhaust passage 3, and a bypass passage 10 that connects the upstream side and the downstream side of the exhaust turbine 8 in the exhaust passage 3. Pressure-operated bypass control valve 11 that opens and closes
and a communication passage 18 that communicates the pressure working chamber 15 of the bypass control valve 11 with the intake passage 2 downstream of the compressor 7. The bypass control valve 11 includes a valve body 1 provided in the bypass passage 10.
2, and a diaphragm device defining a pressure operating chamber 15 and an atmospheric chamber 16 by a diaphragm 14 connected to the valve body 12 via a rod 13,
The pressure operation chamber 15 is connected to the intake passage 2 downstream of the compressor 7 via a communication passage 18, and a spring 17 for adjusting supercharging pressure control conditions is compressed in the atmospheric chamber 16.

In this supercharged engine, there is provided a relief passage for relieving part of the intake pressure (supercharging pressure) introduced into the pressure working chamber 15 of the bypass control valve 11 to the outside, and an exhaust gas upstream of the exhaust purification means 6. Valve means is provided that receives atmospheric pressure and closes the relief passage as the exhaust pressure increases. In this embodiment, a branch passage (relief passage) 19 which is formed by branching off the communication passage 18 for introducing supercharging pressure in the middle is connected to the exhaust passage 3 upstream of the exhaust purification means 6. A check valve (valve means) 20 is provided. The check valve 20 has a check ball 21 in a valve chamber provided in the branch passage 19, and a spring 22 that biases the check ball 21 in the valve closing direction with a relatively small elastic force. Due to the relationship between the boost pressure guided to the passage 18 and the exhaust pressure applied to the branch passage 19, the valve opens when the boost pressure is higher than the exhaust pressure (including the elastic force of the spring 22), and the pressure difference is small. Indeed, the valve is designed to close when the opening becomes smaller and the exhaust pressure becomes higher than the boost pressure.

Furthermore, in the illustrated example, a fuel injection device is used as the fuel supply system, and the fuel injection valve 2 is placed facing into the intake passage 2.
5, a meter 26 that measures the flow rate of air flowing through the intake passage 2, and a control circuit 27 that controls the fuel injection valve 25 based on the signal from the flow meter 26, and controls the amount of fuel supplied according to the amount of intake air. However, the fuel supply device may be one using a carburetor.

According to the boost pressure control device as shown in this embodiment, the boost pressure characteristics with respect to changes in engine speed are shown by the solid line A in the graph of FIG. 2, and the operation and action of this device correspond to the above graph. This will be explained next.

In the bypass control valve 11, when the pressure applied to the pressure working chamber 15 is weaker than the elastic force of the spring 17, the bypass passage 10 is kept closed by the valve body 12, and in this state, the engine rotational speed is As the amount of exhaust gas increases, the amount of exhaust gas passing through the exhaust turbine 8 increases, increasing the driving force of the compressor 7, and the supercharging pressure (pressure in the intake passage 2 downstream of the compressor 7) increases accordingly. . However, the pressure applied to the pressure working chamber 15 at this time is not the supercharging pressure itself, but a pressure reduced by the amount relieved through the check valve 20 of the branch passage 19. In other words, normally the boost pressure is higher than the exhaust pressure (shown by the dashed line B in Figure 2), and especially when the boost pressure is in the process of increasing, the pressure difference between the boost pressure and the exhaust pressure is relatively large. Therefore, the check valve 20 opens to an opening degree corresponding to this pressure difference, and a pressure lower than the supercharging pressure is applied to the pressure operating chamber 15 by the amount of relief caused by this. When the engine speed reaches a certain value _r1 and the pressure applied to the pressure working chamber 15 becomes greater than the elastic force of the spring 17, the diaphragm 14 of the bypass control valve 11 is pushed and the valve body Open 12,
By letting a portion of the exhaust gas escape into the bypass passage 10, the driving force of the compressor 7 by the exhaust turbine 8 is suppressed, thereby preventing the supercharging pressure from becoming higher than the predetermined supercharging pressure P at this time. Ru.

The predetermined supercharging pressure P corresponding to this maximum supercharging pressure can be set arbitrarily in advance by adjusting the elastic force of the spring 17 in the bypass control valve 11, and the conventional supercharging pressure can be directly used for bypass control. Compared to the case where it is introduced into the pressure working chamber of the valve, the pressure working chamber 15
If the elastic force of the spring 17 is weakened to correspond to the reduction in boost pressure introduced by the relief,
The maximum boost pressure can be set to the same level as before.

Next, as the engine speed increases, the boost pressure is suppressed as described above, while the exhaust pressure increases as the engine speed increases, and the pressure difference between the two gradually decreases. The opening degree of the check valve 20 becomes smaller. Along with this, the amount of supercharging pressure relief in the check valve 20 decreases, and the degree to which supercharging pressure is introduced into the pressure operating chamber 15 of the bypass control valve 11 increases accordingly, resulting in a valve opening effect. This further promotes the supercharging pressure suppression effect. As a result, in the high-speed operating range after the boost pressure reaches its maximum value, the boost pressure gradually decreases as the engine speed increases.

Such a control operation can provide a supercharging effect that is suitable for the driving means. In other words, in a supercharged engine that is equipped with a supercharger to improve engine output (torque), this supercharging occurs in the operating range of around 3000 rpm, where an increase in output is expected due to the supercharging effect during acceleration. It is necessary to fully utilize the performance, but conversely, in higher-speed operating ranges, it is necessary to reduce the supercharging pressure as in the present invention from the viewpoint of durability of the engine body and exhaust system. Therefore, the operating range (rotational speed) in which the supercharging pressure is lowered may be appropriately set with this in mind. Furthermore, when the exhaust pressure becomes higher than the supercharging pressure, the relief is completely cut off at the check valve 20, and at higher engine speeds (revolutions _r2 or more in the graph), the supercharging pressure becomes constant. Such a region should be made as small as possible and set so that the supercharging pressure can be sufficiently lowered by then.

In addition, by changing the amount of supercharging pressure relief in the check valve 20 according to the exhaust pressure upstream of the exhaust purification means 6, in addition to the case where the displacement increases due to an increase in engine speed, the exhaust purification means 6 Even if the exhaust pressure increases due to clogging, etc., the exhaust gas is transferred to the exhaust turbine 8
The effect of lowering the supercharging pressure by bypassing the boost pressure is enhanced. In other words, the exhaust gas purification means 6 may become clogged due to the accumulation of carbon, etc. contained in the exhaust gas or thermal erosion, and if such clogging occurs, the exhaust pressure upstream of the exhaust gas purification means 6 will increase. However, the accompanying rise in exhaust temperature will cause heat damage to the exhaust turbine 8, and the rise in exhaust pressure will likely cause knocking, but even in such cases, bypass control valve 11
By opening the valve and bypassing the exhaust gas to the exhaust turbine 8, the heat received by the exhaust turbine 8 is reduced, and knocking is suppressed due to a decrease in supercharging pressure.

FIG. 3 shows another embodiment of the present invention, in which a branch passage (relief passage) 19' branches from a communication passage 18 between the pressure operating chamber 15 of the bypass control valve 11 and the intake passage 2. communicates with the intake passage 2 upstream from the compressor 7, and this branch passage 19'
is equipped with a branch passage opening/closing control valve (valve means) 30. This branch road opening/closing control valve 30 is connected to the branch road 1
Using a diaphragm mechanism in which an atmospheric chamber 34 and a pressure chamber 35 are defined by a diaphragm 33 connected to a valve body 31 provided in a valve body 9' via a rod 32, a spring 36 is compressed into the atmospheric chamber 34, and The exhaust pressure upstream of the exhaust purification means 6 is introduced into the pressure chamber 35. The other structure is the same as that of the basic embodiment. Also in the case of this second embodiment, the communication path 1
8 is relieved through the branch passage 19', and when the exhaust pressure upstream of the exhaust purification means 6 is low, the opening degree of the branch passage opening/closing valve 30 is large, and as the exhaust pressure increases, the opening/closing of the branch passage becomes large. control valve 30
By decreasing the opening degree, the same supercharging pressure control as in the basic embodiment is performed.

〔Effect of the invention〕

As described above, the present invention provides an engine that includes a bypass passage and a bypass control valve that bypass an exhaust turbine of an exhaust turbocharger, and an exhaust purification means in an exhaust passage downstream of the exhaust turbine. a relief passage that relieves a portion of the intake pressure introduced into the pressure operating chamber of the control valve via the communication passage to the outside; and a relief passage that receives the exhaust pressure upstream of the exhaust purification means and operates as the exhaust pressure increases. Since the provision of a closing valve means not only prevents the supercharging pressure from increasing unnecessarily after the supercharging pressure reaches a predetermined value, but also prevents the above-mentioned relief valve from increasing in the high-speed operation range where the exhaust pressure increases. By reducing the amount of heat generated by the exhaust gas, the boost pressure is lowered and engine heat generation is prevented from increasing excessively at high speeds, increasing engine durability. Deterioration can also be prevented. Furthermore, even when the exhaust pressure upstream of the exhaust purification means increases due to clogging of the exhaust purification means, the exhaust gas is bypassed to the exhaust turbine and the supercharging pressure is lowered. It is possible to prevent heat damage and suppress knocking. Moreover, the above-mentioned control operation can be performed with a simple structure and with high reliability without requiring any electrical control means.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of a supercharged engine equipped with a boost pressure control device of the present invention, and FIG. The graph shown in correspondence with the numbers, FIG. 3 is a schematic diagram showing another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Engine, 2... Intake passage, 3... Exhaust passage, 6... Exhaust purification means, 7... Compressor, 8... Exhaust turbine, 10... Bypass passage, 11... Bypass control valve, 18... ...Communication path,
19, 19'... Branch road, 20... Check valve, 30
... Branch road opening/closing control valve.

Claims (1)

[Claims] 1 A compressor for an exhaust turbo supercharger is interposed in the intake passage, an exhaust turbine is interposed in the exhaust passage, and pressure is maintained in the exhaust gas bypass passage that communicates the upstream and downstream sides of the exhaust turbine. An actuated bypass control valve is provided, a pressure operating chamber of the bypass control valve is connected to an intake passage downstream of the compressor via a communication passage, and an exhaust purification means is provided in the exhaust passage downstream of the exhaust turbine. In a supercharged engine, there is provided a relief passage for externally relieving part of the intake pressure introduced into the pressure operating chamber of the bypass control valve via the communication passage, and a relief passage that receives the exhaust pressure upstream of the exhaust purification means. A supercharging pressure control device for a supercharged engine, comprising a valve means for closing the relief passage as exhaust pressure increases.