JPS62240427A - Engine with mechanical supercharger - Google Patents

Abstract

PURPOSE:To improve intake air filling efficiency by detecting the temp. of discharged air from a mechanical supercharger and controlling the maximum supercharging pressure by means of said supercharger so that the detected temp. may not exceed a preset temp. CONSTITUTION:When the operating condition of an engine 1 is judged to be in the operating area which requires supercharging in accordance with the output of a throttle opening sensor 27 by a control unit 25, a control valve 23 is closed to make a bypass 22 in a closed condition. Thereby, intake air the pressure of which is increased by means of the rotation of the rotors 12, 13 of a supercharger 8 is supercharged into the engine 1. And, in this case, whether the temp. of a discharged air is about to exceed a preset reliable limit temp. or not is judged from the output of a discharged air temp. sensor 26 and, when judged yes, a control signal for opening the control valve 23 by a defined amount is outputted to an actuator 24. Thereby, it is prevented that the discharged air temp. exceeds the limit temp.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an engine with a mechanical supercharger, and is an improved method for controlling the discharge air pressure from the supercharger, that is, the supercharging pressure. It is.

(Prior Art) In recent years, as a supercharger installed in automobile engines, etc., mechanical supercharging V1 (1985
-77732) have been tried or put into practical use. According to this mechanical supercharger, a good supercharging effect can be obtained from the low rotation range of the engine and an improvement in acceleration response can be achieved, but on the other hand, the discharge from the supercharger There is a drawback that when the air temperature rises (excessively rises), its reliability or durability is significantly impaired. In other words, when a roots-type supercharger is used as the above-mentioned mechanical supercharger, thermal expansion of the rotor of the supercharger causes layer contact between the rotor and the housing, resulting in wear and seizure. In addition, when a vane type supercharger is used, thermal deformation of the vanes or housing causes abnormal wear on each sliding part, which prevents smooth rotation or operation. The reliability of other types of turbochargers also depends on the temperature of the supercharger or the temperature of the discharge air. Therefore, in this type of supercharger, an upper limit value of the discharge air temperature, that is, a reliability limit temperature, is set at which the supercharger can operate satisfactorily without causing the various heat damage described above.

However, when an engine is equipped with a mechanical supercharger as described above, the discharge air pressure, that is, the supercharging pressure, is usually controlled as follows.

That is, a supercharging pressure detection means (for example, a supercharging pressure sensor) for detecting the supercharging pressure from the supercharger is provided at a predetermined part of the intake passage, and the actual supercharging pressure detected by the means is set in advance. Adjustment is made so that the set pressure is not exceeded, and the actual supercharging pressure detected as described above is maintained at the above set pressure in the high rotation, high load range of the engine that requires a → - minute supercharging effect. For example, feedback control is performed so that the In this case, the above set pressure is set when the temperature of the discharge air from the supercharger is the highest, that is, when the outside temperature is high, for example in summer, and the engine is operating in a high rotation and high load region. The boost pressure corresponding to the above-mentioned reliability limit temperature is used.

(Problems to be Solved by the Invention) By the way, when controlling the boost pressure in a mechanical supercharger based on a constant set pressure set under specific conditions as described above, the following There are problems like this.

That is, the reliability limit temperature of the turbocharger is set to a predetermined temperature [0], which is not shown in FIG. Assuming that the pressure is set at a □, the boost pressure and discharge air temperature change as the engine speed increases.
While being gradually increased as shown in A) and (B),
When the boost pressure is at a predetermined engine speed of 10, the above set pressure aO
reached. In this case, even if the engine speed increases further, the supercharging pressure remains at the set pressure a,). In this case, the set pressure a□ is set in accordance with the engine speed at high engine speed and high load, when the temperature of the discharge air from the supercharger is the highest, as described above. Although it is possible to raise the discharge air temperature to the reliability limit temperature to within a predetermined range from the rotation speed n□ to the higher rotation side, the temperature does not reach the above-mentioned limit temperature It will not be reached. Therefore, the supercharging capacity of the supercharger is not utilized by the amount corresponding to the difference between the actual discharge air temperature and the above-mentioned limit temperature [0] in the shaded area (Bx) shown in the figure. Furthermore, since the set pressure aO is set in accordance with the summer when the outside temperature is high as described above,
When the outside or intake air temperature is low, such as in winter, the discharge air temperature decreases across the board, as shown by the broken characteristic curve (B') in the same figure, and as a result, the reliability limit temperature in high rotation and high load regions, etc. As the temperature difference from 0 becomes even larger, the degree and range in which the supercharging capacity cannot be fully utilized becomes further expanded. In addition, in a region lower than the above-mentioned predetermined engine speed no., although it is possible to actively increase the boost pressure until the discharge air temperature reaches the reliability limit temperature (0). , Since such consideration is not taken, a sufficient supercharging effect cannot be obtained.

As mentioned above, in the past, the supercharging pressure was controlled based only on a fixed set pressure, which prevented the full potential of this type of supercharger from being utilized, resulting in a higher output engine. This was an impediment to efforts to achieve this goal.

(Means for Solving the Problems) The present invention addresses the above-mentioned problems regarding engines equipped with mechanical superchargers such as roots-type superchargers and vane-type superchargers. By focusing on the characteristic that the reliability limit of the above-mentioned mechanical supercharger is determined by the discharge air temperature, the supercharging pressure control method is changed or improved to maximize the supercharging capacity of the supercharger. In addition to improving the supercharging effect and intake air filling efficiency as much as possible in the high engine speed range (high speed and high load range) that requires high output (high speed and high load range) regardless of changes in outside temperature, etc. The purpose is to suitably improve supercharging capacity and improve intake air filling efficiency. In order to achieve such an object, the present invention is characterized in that it is configured as follows. Specifically, in a configuration in which the intake system of the engine is equipped with a mechanical supercharger driven by a crankshaft or the like. , a discharge air temperature detection means for detecting the temperature of the discharge air from the supercharger is provided, and upon receiving an output signal from the means, supercharging by the supercharger is performed so that the discharge air temperature does not exceed a set temperature. A control means is provided to control the pressure, that is, the maximum boost pressure. This υ
1111 means that when the discharge air temperature rises with an increase in supercharging pressure, the temperature is set at a preset temperature, that is, a reliability limit temperature (a temperature at which the supercharger can operate without causing various heat damage). The supercharging pressure (maximum supercharging pressure) is controlled so that the temperature is maintained at this limit temperature without exceeding the upper limit value of the discharge air temperature that allows good operation. As a specific means or method, for example, a control valve may be provided in a bypass passage that bypasses the supercharger, and the control valve may be opened or closed in response to an output signal from the discharge air temperature detection means. When the discharge air temperature is about to exceed the reliability limit temperature, the control valve is opened and the air pressurized by the supercharger is released to the air cleaner side through the bypass passage. Control is performed to prevent the temperature from rising. In addition to this, a variable pitch diameter pulley is used as a component of the 8m drive mechanism provided between the crankshaft 17 feet and the supercharger, and this pulley is adjusted according to the output signal from the discharge air temperature detection means. The bridge diameter is configured to be variably controlled, thereby appropriately changing the rotational transmission ratio from the crankshaft to the supercharger (rotor shaft) to ensure that the discharge air temperature does not exceed the reliability limit temperature. The boost pressure may be increased as much as possible.

(Function) According to the above configuration, the control of the supercharging pressure of the mechanical supercharger is
Because this is done based on the temperature of the discharge air from the supercharger, and because the temperature is prevented from exceeding the reliability limit temperature, various problems occur due to thermal expansion and thermal deformation of the rotor, housing, etc. This means that the supercharger can operate well and have sufficient reliability and durability.

In particular, according to the present invention, control is performed without being constrained by boost pressure, so that the upper limit of boost pressure is unnecessarily blocked in high-speed, high-load regions of engines that require high output. This avoids the problem that the capacity of the supercharger is not fully utilized.

In other words, in the past, under the conditions where the discharge air temperature is highest, specifically in the summer when the outside temperature is high, and when the engine is running at high speed and under high load, the set pressure is not exceeded. Due to ail control of the boost pressure, the boost pressure reached the set pressure above even though the discharge air temperature would not have risen to the reliability limit temperature unless the above conditions were met. At this point, the boost pressure is prevented from increasing. This has led to a situation where the capacity of the supercharger is not fully utilized due to the difference between the actual discharge air temperature and the above-mentioned limit temperature, but according to the present invention, the supercharging pressure By performing control based on the discharge air temperature without being constrained by the size of the supercharger, it becomes possible to maximize the performance of the supercharger. As a result, especially in seasons such as winter when the outside temperature is low, the capacity of the supercharger is fully utilized, the intake air filling efficiency is increased, and the output of the engine is increased. Furthermore, when the above-mentioned variable bit diameter pulley is used as the control means, it becomes possible to actively increase the supercharging pressure even in the low and medium rotation range, so that It is also possible to fully utilize the supercharger's capacity to increase the engine's output if necessary.

Note that the reliability limit of the mechanical supercharger mentioned above is lower than that of an exhaust turbo supercharger, so as long as the reliability limit temperature is not exceeded as mentioned above, the supercharging pressure cannot be increased sufficiently. Even if it is increased, there is no risk of causing knocking or the like.

(Example) The present invention will be explained in detail below.

First, a first embodiment of the present invention will be described. As shown in FIG. 1, an intake passage 5 and an exhaust passage 6 are connected to a combustion chamber 2 of an engine 1 through intake and IJt air valves 3.4, respectively. In addition, the intake passage 5 is equipped with an air cleaner (not shown), an air flow meter 7, a mechanical supercharger 8, a throttle valve 9, a surge tank 10, and a fuel injection nozzle 11 from the upstream side. 6 is equipped with an exhaust purification device, a muffler, etc., although not shown.

In this embodiment, the mechanical supercharger 818 is a Roots blower type supercharger in which a pair of cocoon-shaped rotors 12 and 13 are rotatably held within the housing 14. The rotor shaft 13 of one rotor 13 (drive rotor) of the two rotors 12 and 13 is
The rotor shaft pulley 15 attached to a and the crankshaft pulley 1 fixed to the crankshaft 16
A transmission member 18 such as a belt is hooked between the crankshaft 1 and the piston 7, and the crankshaft 1
The rotation of 6 is transmitted to the rotor 13 (1
2), the supercharger 8 is driven. In that case, from the air cleaner to the intake passage 5
The air introduced into the suction boat 20 of the supercharger 8
The air is sucked into the housing 14 (pump chamber) through the discharge port 21 and is pressurized by the compression action caused by the rotation of the pair of rotors 12 and 13 in a predetermined direction. This pressurized air is discharged immediately upstream of the throttle valve 9 in the combustion chamber 5, and is further supplied to the combustion chamber 2 via the nerge tank 10, thereby increasing the intake air filling efficiency. Note that the shaft 13 of the drive rotor 13 in the supercharger 8
between the rotor shaft pulley 15 and the engine 1
An electromagnetic clutch is provided to drive or stop the supercharger 1!18 depending on the operating range of the supercharger 1!18.

Further, the intake passage 5 is provided with a bypass passage 22 that bypasses the supercharger 8, and this bypass passage 22 is provided with a control valve 23 that controls opening and closing of the passage 22. An actuator 24 that opens and closes 23 based on an electrical signal is disposed at a predetermined location.

In addition to the above configuration, this engine 1 includes the supercharger 18
A control unit 25 is provided to control the discharge air pressure from the engine, that is, the supercharging pressure.

This control unit 25 has the following main operations:
Temperature signal a from the discharge air temperature sensor 26 attached to the housing 14 of the supercharger 8 (near the discharge port 21)
is input, it is determined whether the discharge air temperature from supercharging 1!18 indicated by the signal a is about to exceed the preset temperature, that is, the reliability limit temperature, and based on this determination result. Based on this, a control signal is output to an actuator 24 that opens and closes a control valve 23 in the bypass passage 22. In that case, the unit 25 sends a control signal to the actuator 24 for closing the control valve 23 when the temperature of the discharged air is below the reliability limit temperature, so that the air flows through the bypass passage.
2 and is discharged to the downstream side of an intake passage 5 in a pressurized state within a supercharger 18. Further, when the discharge air temperature is about to exceed the reliability limit temperature, the unit 25 outputs a control signal for opening the control valve 23 only at a predetermined portion, thereby controlling the supercharger. The pressurized air compressed in the intake passage 8 is released to the upstream side of the intake passage 5 via the bypass passage 22. and,
Through such an operation, the supercharging pressure or the maximum supercharging pressure by the supercharger 8 is controlled. In this case, the reliability limit temperature is the rotor 12.1 in the supercharger 8.
The rotor 12.13 and the housing 1 due to thermal expansion etc.
This is set as the upper limit value of the discharge air temperature that can avoid a situation where the two are in sliding contact and abrasion or seizure occurs between the two.

The control unit 25 inputs a throttle opening signal C from an opening sensor 27 that detects the opening of the throttle valve 9, and determines whether the operating range of the engine 17 is adjusted to the supercharging effect by the supercharger 8. In addition to determining whether or not the supercharging effect is in the required region, this determination result indicates that the supercharger 8 is in a region where no supercharging effect is required, such as an idle region
When indicating that the operation is in a region where the operation is stopped by disengaging the electromagnetic clutch, a control signal for fully opening the control valve 23 is sent to the actuator 24. In addition, this control unit 25 inputs a supercharging pressure signal d from a pressure sensor 28 that detects the supercharging pressure from the supercharger 8 to determine an abnormal state (excessive rise) of the supercharging pressure, and When the state is determined, the control valve 23
By outputting a control signal for opening the supercharger 8, consideration has been given to preventing knocking caused by an excessive increase in supercharging pressure or a decrease in the durability of the supercharger 8. There is.

Next, the operation of the first embodiment will be explained.

During operation of the engine 1, when the throttle opening signal @C input to the control unit 25 indicates an operating region that requires a supercharging effect, the control valve 22 provided in the bypass passage 22 is in an open state. A control signal @b to maintain the position is sent from the unit 25 to the actuator 24, and the bypass passage 22 is closed. In such a state, if the rotational speed of the rotor 12.13 of the supercharging 18 increases with the increase in engine speed, the supercharging pressure gradually decreases as shown by the symbol (Dl) in Fig. 2. Along with this increase, the temperature of the air discharged from the supercharger 8 also gradually rises as indicated by the symbol (El) in the figure.

In this case, the control unit 25
Discharge air temperature sensor 2 provided on the discharge side of supercharging 1a8
Based on the temperature signal a from 6, it is determined whether or not the discharge air temperature is about to exceed a preset reliability limit temperature To. Until this happens, the bypass passage 22 is closed as described above, and the supercharger 8 continues to operate, regardless of the supercharging pressure. As the engine speed further increases from this state, the discharge air temperature reaches the reliability limit temperature T.

If it is determined that the bypass passage 22 is about to be exceeded, the unit 25 sends a control signal to the actuator 24 to open the control valve 23 by a predetermined distance, so that the bypass passage 22 is opened to an appropriate degree. It will be opened in ratio. As a result, a part of the pressurized air discharged from the supercharger 8 is released to the upstream side of the intake passage 5 via the bypass passage 22, and the discharge air temperature is prevented from exceeding the limit temperature To. At the same time, the same control will be performed even if the engine speed increases further than this. Therefore, in the region above the predetermined engine speed N1 where the discharge air temperature reaches the above-mentioned limit temperature fiTo, the second As shown by the symbol (Dl) in the figure, the discharge air temperature is maintained at the reliability limit temperature To.

In this way, the supercharging pressure or maximum supercharging pressure is controlled based on the discharge air temperature without being constrained by the large gaps in the supercharging pressure, so that it is possible to control the supercharging pressure or the maximum supercharging pressure based on the discharge air temperature. The shaded area ( The capacity of the supercharger 8 is utilized only in response to the temperature difference between DX and DX. As a result, the engine rotation speed reaches N, as shown by the symbol (E2) in the figure.

It becomes possible to sufficiently increase the supercharging pressure in a predetermined high rotation range from 1 to N2.

Furthermore, in seasons such as winter when the outside temperature or intake temperature is low, low-temperature air is pressurized, so by the time the discharge air temperature reaches the reliability limit temperature TO, the dotted line ( Therefore, under these conditions, the engine speed range is wide as shown by the broken line characteristic curve (E2') in the figure. It becomes possible to further increase the supercharging pressure (mainly in the high rotation range). In addition, the above supercharging a8
The reliability limit of the T0 is lower than that of an exhaust turbo supercharger, etc., so as long as the reliability limit temperature TO is not exceeded, knocking will not occur even if the supercharging pressure is sufficiently increased as described above. There is no risk of causing such problems.

As described above, according to the first embodiment, the temperature of the discharge air from the supercharger 8 is prevented from exceeding the reliability limit temperature To, and is maintained at this limit temperature To mainly in the high engine speed range. , control valve 23 in the bypass passage 22
Since the boost pressure is controlled by adjusting the opening of the
The capacity of this type of supercharger is fully utilized without impairing its reliability or durability, and the intake air filling efficiency is improved compared to conventional ones, especially in the high engine speed range where high output is required. It will be effectively enhanced.

Next, a second embodiment of the present invention shown in FIG. 3 will be described.

In this second embodiment, the present invention is applied to a four-cylinder engine, and as shown in the figure, an intake passage 31 of an engine 30 has four independent intake passages 33 on the downstream side of a surge tank 32.・After branching into 33, each combustion chamber 34...
It is connected to 34. A mechanical supercharger 35 such as a roots blower type or a vane type is provided upstream of the surge tank 32 in the intake passage 31, and a pump chamber in the supercharging ta 35 is connected to an intake boat 36 and a discharge port. A bypass passage 38 that communicates with the intake passage 31 via a passage 37 and bypasses the supercharging Wa 35 is provided with a control valve 39 that is opened when the supercharger 35 is not driven. Further, a control unit 40 is provided to control the boost pressure by the supercharger 35.
In this case, as in the first embodiment, the throttle opening signal e from the throttle valve 41 for determining the operating region requiring a supercharging effect and the abnormal state (overrise) of the supercharging pressure are detected. A temperature sensor 43 detects the supercharging pressure signal t from the pressure sensor 42 and the temperature of the discharge air from the supercharger 35.
A temperature signal q is inputted.

However, in this second embodiment, the crankshaft pulley 45a and the rotor shaft pulley 44a, which constitute the drive mechanism between the rotor shaft 44 and the crankshaft 45 of the supercharger 35, both have variable effective pitch diameters. A belt 46 is wound between the two pulleys 44a and 45a, which are formed into pitch diameter pulleys (only one of the pulleys may be a variable pitch diameter pulley). The control unit 40 sends pitch diameter control signals h+ and h to both pulleys 44a and 45a.
A control signal i is output to a boolean actuating unit 47 provided to send out a signal i. In that case, the control unit 40 controls the temperature of the discharge air from the supercharger 35 to reach the reliability limit temperature To based on the temperature signal g.
If it is determined that the effective pitch diameter of the rotor shaft pulley 44a is smaller than the effective pitch diameter of the crankshaft pulley 45a, a control signal i is sent to the pulley operating unit 47. By this, from the crankshaft 45 to the rotor shaft 4
4 to avoid increasing the supercharging effect by the supercharger 35. Further, when the discharge air temperature is about to exceed the reliability limit temperature To', the control unit 40 changes the effective pitch diameter of the rotor shaft pulley 44a to the crankshaft pulley 45a, contrary to the above case.
A control signal i is outputted to make the supercharger 35 relatively larger than the supercharger 35.

By performing such processing, in a region where the temperature of the discharge air from the supercharging 'a35 does not exceed the reliability limit temperature To' and is above a predetermined engine speed (relatively low rotation speed), the As shown by the symbol (F) in FIG. 4, the temperature is maintained at the above-mentioned limit temperature TO'.

Therefore, the supercharging pressure is increased from the conventional set pressure Po' starting from a relatively low rotational speed region as indicated by the symbol (G) in the figure.

In this way, in this second embodiment, the supercharging pressure can be actively increased not only in the high engine speed range but also in the low and medium engine speed ranges without impairing the reliability or durability of the supercharger. This makes it possible to maximize the capabilities of the supercharger and increase engine output over a wide range of operating ranges.

(Effects of the Invention) As described above, according to the present invention, in an engine equipped with a mechanical supercharger, the temperature of discharge air from the supercharger is detected, and this temperature is set to a preset temperature ( In order to avoid exceeding the reliability limit temperature (reliability limit temperature), the boost pressure was controlled using a predetermined means or configuration, so as in the past, the boost pressure was controlled so as not to exceed the set pressure. Since the capacity of the supercharger will be fully utilized compared to the previous case, the supercharging pressure will be increased as much as possible without impairing the reliability of the supercharger in the high engine speed range where high output is required. It is possible to increase the intake air filling efficiency. Furthermore, according to the present invention, it is possible to suitably adjust the supercharging pressure in the low and medium speed range of the engine, so while maximizing the capability of the supercharger over a wide operating range, This will lead to higher engine output.

[Brief explanation of drawings]

1 and 2 show a first embodiment of the present invention.
The figure is a schematic configuration diagram showing a supercharging pressure control system for a mechanical supercharged engine according to the present invention, and FIG. 2 is a graph showing the effects. 3 and 4 are the second actual IIMlf of the present invention.
4, FIG. 3 is a schematic configuration diagram showing a boost pressure control system for an engine with a mechanical supercharger according to the present invention, and FIG. 4 is a graph showing the effects. Also, Figure 5 shows
It is a graph showing the problems of the conventional method. 1.3o... Engine, 8.35... Mechanical supercharger, 23... Control valve, 24... Actuator, 25
．． 40...Control unit, 26°43...
Discharge air temperature detection means (discharge air temperature sensor), 44
a, 45a...variable pitch diameter pulley.

Claims (1)

[Claims] (1) An engine equipped with a mechanical supercharger in the intake system, including a discharge air temperature detection means for detecting the temperature of the discharge air from the mechanical supercharger, and an output signal from the means. An engine equipped with a mechanical supercharger, characterized in that a control means is provided for controlling the maximum boost pressure of the supercharger so that the temperature of the air discharged from the supercharger does not exceed a set temperature.