JPH0625642Y2 - Intake system structure of turbocharged engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to an intake system structure of a turbocharged engine,
Particularly, the present invention relates to an improvement of an exhaust turbocharger for low speeds and high speeds, in which the operation of the high speed exhaust turbocharger is stopped when the engine speed is low.

(Prior Art) Conventionally, as an engine with a turbocharger of this type, for example, as disclosed in Japanese Utility Model Laid-Open No. 60-178329,
Turbines of low-speed and high-speed exhaust turbochargers are installed in parallel in the exhaust passage, compressors of these two exhaust turbochargers are installed in parallel in the intake passage of the engine, and downstream of these two compressors. While merging the intake passage, an exhaust cut valve is provided in the exhaust passage upstream of the turbine of the high-speed exhaust turbocharger, and the exhaust cut valve is closed when the engine is running at low speed to allow the exhaust gas from the engine to exhaust at low speed. It supplies the turbines of the turbocharger intensively to secure a high boost pressure, while at the time of high engine speed, the exhaust cut valve is opened to supply the exhaust gas from the engine to the turbines of the two exhaust turbochargers. It is known that an appropriate supercharging pressure is obtained while ensuring the intake flow rate.

(Problems to be solved by the invention) However, in the above-mentioned conventional one, when the throttle valve provided downstream of the compressor is closed during deceleration of the engine, the pressure downstream of the compressor (upstream of the throttle valve) rises. There is a risk of the compressor surging due to obstruction of the movement of the compressor such as backflow to the compressor.

By the way, in addition to the case where a plurality of exhaust turbochargers operate simultaneously as described above, for example, JP-A-59-1
Japanese Patent No. 45327 discloses that an engine is provided with a plurality of exhaust turbochargers and these are selectively operated. It is disclosed that when the pressure becomes high, the high pressure is relieved by a relief valve to prevent the compressor from surging.

Therefore, even in the case where the low-speed exhaust turbocharger and the high-speed exhaust turbocharger are provided as described above, for example, a relief valve is provided in the discharge side passage of the compressor of the low-speed exhaust turbocharger that always operates, and the engine high rotation speed is increased. When the vehicle is decelerating, the relief valve is opened to relieve the high pressure downstream of the compressor for the low speed exhaust turbocharger and the high pressure downstream of the compressor for the high speed exhaust turbocharger via the confluence of the intake passage. It is conceivable to prevent the compressor from surging by relief.

However, in this case, since the relief valve is provided only in the compressor discharge side passage of one (for low speed) exhaust turbocharger, from the relief valve to the compressor for the other (for high speed) exhaust turbocharger. Therefore, the high-pressure relief downstream of the compressor is not promptly performed, and the surging cannot be quickly prevented.

The present invention has been made in view of such a point, and a relief valve is individually provided in the compressor discharge side passage of the low speed exhaust turbocharger and the discharge side passage of the compressor of the high speed exhaust turbocharger. The objective is to shorten the distance from the relief valve to the compressor together to relieve the high pressure downstream of each compressor with good response, and to quickly prevent the occurrence of surging in each compressor.

However, in that case, the high pressure downstream of each compressor can be relieved with good response, but when both relief valves are opened, the high pressure downstream of each compressor is relieved at once and a sudden pressure decrease occurs, causing a torque shock. Occurs.

Therefore, another object of the present invention is to prevent a sudden pressure decrease downstream of the compressor by changing the set pressure of each relief valve.

By the way, as described above, with the high-speed exhaust turbocharger that operates only at high engine speed, when decelerating from high engine speed, the engine speed is relatively high and the exhaust gas flow rate is still high. Since the operation of the high speed exhaust turbocharger is stopped, the rotation of the compressor does not immediately drop due to inertia. Therefore, the intake flow rate is low and the pressure downstream of the compressor is high, so that surging is more likely to occur than in a compressor of a low-speed exhaust turbocharger. Moreover, in such an engine,
As a technique for enhancing acceleration when the engine is accelerated from low engine speed, a small amount of exhaust gas is supplied to the turbine of the high-speed exhaust turbocharger prior to opening the exhaust cut valve to pre-rotate the turbine. It has been known. Even in that case, in the compressor of the high-speed exhaust turbocharger, the intake flow rate is small and the intake pressure is relatively high, so that surging easily occurs.

The present invention also aims at preventing the occurrence of surging by paying attention to the cause of such surging unique to the high-speed exhaust turbocharger.

(Means for Solving the Problems) In order to achieve the above object, according to the present invention, relief valves are individually provided in compressors of low-speed and high-speed exhaust turbochargers, and high-speed exhaust turbochargers are provided. That is, the set pressure of the side relief valve is set higher than the set pressure of the relief valve on the low speed exhaust turbocharger side.

Specifically, the solution provided by the present invention is to operate an exhaust turbocharger for low speed and high speed, which is installed in an engine and supercharges intake air by energy of exhaust gas, and an exhaust turbocharger for high speed. Stop means for stopping the engine, a rotation speed detecting means for detecting the rotation speed of the engine, and an output of the rotation speed detecting means to stop the operation of the high-speed exhaust turbocharger when the engine is running at a low speed. And a supercharger control means for controlling the supercharger operation stopping means so that the pressure downstream of the compressor is greater than or equal to a set value in the compressor discharge side passage of the low speed and high speed exhaust turbocharger. Relief valves that open from time to time are provided, and the set pressure of the relief valve on the high speed exhaust turbocharger side is set higher than the set pressure of the relief valve on the low speed exhaust turbocharger side. Than it is.

(Operation) With the above structure, according to the present invention, the supercharger control means controls the engine rotation speed detected by the rotation speed detection means to generate a high-speed exhaust gas by the supercharger operation stop means when the engine speed is low. The turbocharger is deactivated and exhaust gas is concentratedly supplied only to the low speed exhaust turbocharger to ensure a high boost pressure, while at the time of high engine speed both low speed and high speed Exhaust gas is supplied to the exhaust turbo supercharger, and an appropriate supercharging pressure is obtained while ensuring the intake flow rate.

Also, when decelerating from high engine speed, etc., the throttle valve closes rapidly and the pressure in the downstream of each compressor rises, but the high pressure in the downstream of each compressor is relieved by the opening of each relief valve. The backflow of intake air is prevented, and the occurrence of surging in each compressor is prevented.

In that case, since the relief valve is separately provided in the compressor of the exhaust turbocharger for low speed and high speed,
The distance from each relief valve to the compressor can be shortened together, the high pressure downstream of each compressor is responsively relieved, and the occurrence of surging in each compressor is quickly prevented.

Also, since the set pressure of the relief valve on the high-speed exhaust turbocharger side and the set pressure of the relief valve on the low-speed exhaust turbocharger side are different, two relief valves are required during high pressure relief downstream of each compressor. At the same time, it does not open, the relief speed is maintained moderately and sudden pressure decrease does not occur,
The occurrence of torque shock is prevented.

Moreover, in that case, since the set pressure of the relief valve on the high speed exhaust turbocharger side is higher than the set pressure of the relief valve on the low speed exhaust turbocharger side, the relief pressure on the high speed exhaust turbocharger side is reduced. The timing comes close to the timing at which the operation / stop of the exhaust turbocharger is switched, and the occurrence of surging in the compressor of the high-speed exhaust turbocharger, where surging easily occurs, is reliably prevented.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

1 and 2 show a two-rotor type rotary turbocharger-equipped rotary piston engine having an exhaust system structure according to an embodiment of the present invention. In these drawings, reference numeral 1 denotes a housing composed of an intermediate housing, a rotor housing and a side housing, and in the housing 1, two polygonal rotors 2 and 2 are arranged. The planetary rotary motion causes the three working chambers formed in the housing 1 to sequentially perform intake, compression, explosion, expansion, and exhaust strokes.

The housing 1 includes a primary port 3 and a secondary port 4 for supplying fresh air to the working chamber in the intake stroke.
Is provided. Further, the housing 1 is provided with an exhaust port 5 for exhausting exhaust gas from the working chamber in the exhaust stroke.

The primary port 3 corresponding to each rotor 2
An exhaust passage 10 is connected to the secondary port 4 at its branched downstream end, and the intake passage 10 is open to the atmosphere via an air cleaner 13. The intake passage 10 is branched into two first and second intake passages 11 and 12 on the way. Then, in the intake passage 10 downstream of the confluent portion of the intake passages 11 and 12,
From the upstream side, an intercooler 14 for cooling intake air and a throttle valve 15 for adjusting the intake air flow rate in order from the upstream side.
And a surge tank 16 for alleviating the pulsation of intake air. Further, injectors 17 and 18 for injecting and supplying fuel facing the primary port 3 and the secondary port 4 are provided at the branched downstream ends of the intake passages 10, respectively.

An exhaust passage 20 is connected to the exhaust ports 5 and 5. That is, one end of the exhaust passage 20 is branched into two first and second exhaust passages 21 and 22,
The exhaust passages 21 and 22 are connected to two exhaust ports 5 and 5, respectively.

The engine is provided with two exhaust turbochargers 31, 32 for low speed and high speed. That is, the turbine 31a of the low speed exhaust turbocharger 31 is provided in the first exhaust passage 21, and the turbine 32a of the high speed exhaust turbocharger 32 is provided in the second exhaust passage 22. The first intake passage 11 is provided with the compressor 31b of the low speed exhaust turbocharger 31 and the second intake passage 12 is provided with the compressor 32b of the high speed exhaust turbocharger 32. Trying to supercharge. Also, the first
And the second exhaust passages 21 and 22 are connected to the exhaust turbocharger 3 respectively.
The upstream side of 1, 32 are connected via a communication path 33.

Here, the turbine 31 of each exhaust turbocharger 31, 32
The connection structure between the a and 32a and the exhaust passages 21 and 22 will be described. As shown in FIG. 2, each turbine 31
a and 32a are arranged so that the discharge ports thereof face each other, and the first and second exhaust passages 21 and 22 connected to the turbines 31a and 32a, respectively, are connected to the downstream side (see FIG. 2). Turn to the front side). The collecting portion 23 is integrally provided with the turbine 32a on the high-speed exhaust turbocharger side, and the turbine 31a on the low-speed exhaust turbocharger side is connected to the collecting portion 23 by a flange via a casquette. Has been done. That is, when the engine speed rises from the low speed region to the high speed region, the high speed exhaust turbocharger side turbine 32a suddenly enters the operating state from the stopped state and receives a rapid heat load. In that case, since such a connection structure is used, no gasket is interposed between the high-speed exhaust turbocharger-side turbine 32a and the collecting portion 23, and the heat of the turbine 32a is smoothly transferred to the exhaust passage 22, The heat load on the turbine 32a can be reduced.

An exhaust cut valve 41 is provided in the second exhaust passage 22 between the high-speed exhaust turbocharger-side turbine 32a and the communication passage 33 to connect the high-speed exhaust turbocharger-side turbine 32a. The exhaust gas supply is adjusted. That is, the exhaust cut valve 41 functions as a supercharger operation stopping means for stopping the operation of the high speed exhaust turbocharger 32. Further, the second exhaust passage 22 downstream of the exhaust cut valve 41 and the communication passage 33 are connected by a leak passage 42. A leak valve 43 is provided in the leak passage 42 to adjust the supply of a small amount of exhaust gas to the high speed exhaust turbocharger side turbine 32a. Further, the communication passage 33 and the exhaust passage 20 downstream of the low speed and high speed exhaust turbochargers 31, 32 are connected by a bypass passage 44. The bypass passage 44
A waste gate valve 45 is provided in the valve to adjust the bypass amount of the exhaust gas to improve the boost pressure characteristic. These valves 41, 43, 45 are driven by pressure-responsive actuators 46-48, respectively.

Further, the first intake passage 1 in the second intake passage 12 is
An intake cut valve 51 is provided immediately upstream of the portion where it merges with 1. Further, the first intake passage 11 has a first relief passage 54 that bypasses the low-speed exhaust turbocharger-side compressor 31b, and the second intake passage 12 has a first relief passage 54 that bypasses the high-speed exhaust turbocharger-side compressor 32b. Two relief passages 52 are provided respectively. A first relief valve 55 is provided in the first relief passage 54, and a second relief valve 53 is provided in the second relief passage 52. The relief valves 53 and 55 are provided in the compressor 31.
By opening when the pressure downstream of b, 32b is equal to or higher than the set value, the upstream side and the downstream side of each compressor 31b, 32b are communicated with each other to relieve the high pressure of the set value or more downstream of each compressor 31b, 32b. ing. These valves 51, 53, and 55 are driven by pressure-responsive actuators 56 to 58, respectively.

Further, a catalyst device 60 is provided in the exhaust passage 20 downstream of the confluence of the first and second exhaust passages 21 and 22 to purify the exhaust gas.

Then, the actuators 46 to 48 and 56 to
58 is controlled by the control unit 80.
Further, 81 is an air flow sensor provided in the intake passage 10 for detecting the intake flow rate, 82 is a throttle sensor for detecting the opening of the throttle valve 15, and 83 is provided downstream of the throttle valve 15 in the intake passage 10. A boost pressure sensor for detecting the intake pressure downstream of the throttle valve 15, 84 is a rotation speed sensor as a rotation speed detecting means for detecting the rotation speed of the engine, 85 is a water temperature sensor for detecting the water temperature of the engine, and 86 is Intake cut valve 5
1 is a differential pressure sensor for detecting a differential pressure between upstream and downstream pressures. Each of these sensors 81 to 86 is connected to the control unit 80.

Next, the operation control of the control unit 80
A description will be given based on the flow of the figure. First, in step S ₁ , the signals from the sensors 81 to 86 are input, and in step S ₂ , it is determined whether or not the engine is in the low rotation range shown in FIG.

Then, the engine when it is in the low rotation region, that is, the determination in step S ₂ to stop the operation of the steps S _{3 ~} high-speed exhaust turbo supercharger 32 at the step S ₆ when the YES. Concentrating That is, the leaked valve 43 in step S _3, by closing the exhaust cut valve 41 respectively to stop the operation of the high-speed exhaust turbo supercharger 32 at the step S _4, the exhaust gas in the low-speed exhaust turbo supercharger 31 while securing the supply and high boost pressure in, the steps S ₅ at the intake cut valve 51
Is closed to prevent backflow of intake air from the intake passage 10 to the second intake passage 11. Further, in step S _6, but when the intake pressure downstream of the throttle valve 15 is equal to or less than the set pressure (during deceleration, etc.), since the pressure in each compressor downstream increases over a predetermined value, the first relief valve 55 and a second Open the relief valve 53. As a result, the relief valves 53, 55 are operated in an operating state in which the intake flow rate is low and the pressure downstream of the compressor is high, such as during deceleration from high engine speed.
Because the high pressure downstream of the compressor is relieved by
The backflow of intake air to the compressors 31b and 32b is prevented, and the occurrence of surging is prevented.

In that case, the relief valves 53 and 55 are connected to each compressor 31.
b and 32b are individually provided, the distances from the relief valves 53 and 55 to the compressors 31b and 32b are both shortened, and as shown by the broken line in FIG. The high pressure on the downstream side is relieved with good responsiveness, and the occurrence of surging is quickly prevented in each of the compressors 31b and 32b.

On the other hand, the engine actuates the steps S _{7 ~} high-speed exhaust turbo supercharger 32 in step S ₁₀ when the determination in Step S ₂ not in the low rotation region of NO. That is, beforehand, opens the leaked valve 43 at step S _7, performs run-up of the turbine 32a to supply a small amount of exhaust gas to the high-speed exhaust turbo supercharger 32. When the intake pressure downstream of the throttle valve exceeds a set pressure in step S _8, that is, when rotating at the high speed region, to open the exhaust cutoff valve 41 in step S ₉ closes the respective relief valves 53 and 55, the intake cut valve 51 in step S ₁₀ when the differential pressure between the pressure upstream and downstream is reduced by opening the intake cut valve 51 to actuate the high-speed exhaust turbo supercharger 32, both the low-speed and high-speed exhaust turbo supercharger 31, 32 To supercharge the intake air.
As a result, it is possible to obtain an appropriate boost pressure while ensuring the intake air flow rate. The reason why the relief valves 53 and 55 are closed before the exhaust cut valve 41 opens is that the turbines 31a and 32a idle when the relief valves 53 and 55 are open when the exhaust cut valve 41 opens. This is because the engine speed suddenly rises, the exhaust pressure fluctuates rapidly, the dilution gas of the engine changes greatly, and combustion fluctuations occur.

The set pressure of the second relief valve 53 (on the high speed exhaust turbocharger 32 side) is set higher than the set pressure of the first relief valve 55 (on the low speed exhaust turbocharger side). That is, as shown in FIG. 4, the opening area of the second relief valve 53 is set to be higher in rotation and load than the opening area of the first relief valve 55.

As a result, the set pressure of the second relief valve 53 (high speed exhaust turbocharger side) and the set pressure of the first relief valve 55 (low speed exhaust turbocharger side) differ, so that the high pressure downstream of the compressor is high. Two relief valves 5 during relief
3,55 do not open at the same time, the relief speed is maintained at an appropriate level, a sudden pressure decrease does not occur, and the occurrence of torque shock is effectively prevented.

Moreover, in that case, the set pressure of the second relief valve 53 is higher than the set pressure of the first relief valve 55, so that the occurrence of surging in the high-speed exhaust turbocharger-side compressor 32b where surging easily occurs is reliably prevented. be able to. That is, at the time of deceleration from the high engine speed, the operation of the high-speed exhaust turbocharger is stopped while the engine speed is relatively high and the exhaust gas flow rate is still high. However, the pressure on the downstream side of the compressor 32b becomes high, and surging tends to occur more easily than the low-speed exhaust turbocharger-side compressor 31b. However, as shown in FIG. Since the set pressure is high and the open region is set to high rotation and high load side, the relief timing of the high-speed exhaust turbocharger side compressor 32b is set to the operation / operation of the exhaust turbocharger 32.
Since the timing at which the stop is switched is approached, it is possible to reliably prevent the occurrence of surging. During acceleration from low engine speed, the leakage valve 43 opens to supply a small amount of exhaust gas to the high-speed exhaust turbocharger 32 to accelerate the turbine 32a. In the compressor 32b, the pressure downstream thereof becomes relatively high and surging easily occurs. In this case as well, the high-speed exhaust turbocharger-side compressor 32
Since the timing of relief of b becomes close to the timing at which the operation / stop of the exhaust turbocharger 32 is switched,
As in the above case, it is possible to reliably prevent the occurrence of surging.

Although the exhaust cut valve 41 can function as the leak valve 43, in the present embodiment, the exhaust cut valve 41 and the leak valve 43 are separately provided, and the accuracy of the function of the leak valve 43 is improved. Is raised.

Although not shown in the above flow, the operation of the waste gate valve 45 is also controlled by the control unit 80 according to the boost pressure.

In the above flow, steps _{S 2} ~ Step _{S 10}
The output of the rotation speed detection means (rotation speed sensor 84) is received by the high speed exhaust turbocharger 3 when the engine is running at low speed.
The supercharger control means 92 for controlling the supercharger operation stopping means (exhaust cut valve 41) so that the operation of No. 2 is stopped is configured.

Although the rotary piston engine has been described in the above embodiment, the present invention is not limited to this, and the present invention can be applied to other types of engines such as a reciprocating engine.

(Effect of the Invention) As described above, according to the intake system structure of the turbocharged engine of the present invention, the operation of the high speed exhaust turbocharger is stopped when the engine is running at low speed, and And a high-speed exhaust turbocharger compressor are provided with relief valves for relieving the high pressure downstream thereof, and the set pressure of the relief valve on the high-speed exhaust turbocharger side is set to the low-speed exhaust turbocharger. Since it is set higher than the set pressure of the relief valve on the side, the basic effect of being able to properly supercharge the intake air in all engine rotation regions is obtained, and at the same time from each relief valve to the compressor while preventing the occurrence of torque shock. Can be shortened together, the high pressure downstream of the compressor can be responsively relieved, and surges can be quickly generated in each compressor. It can be prevented.

[Brief description of drawings]

The drawings illustrate an embodiment of the present invention. FIG. 1 is a schematic overall configuration diagram, FIG. 2 is a side view of an engine, FIG. 3 is a flow chart diagram showing operation control of a control unit, and FIG. FIG. 5 is an explanatory view showing rise of pressure downstream of the compressor. 31 ... Low speed exhaust turbocharger, 32 ... High speed exhaust turbocharger, 41 ... Exhaust cut valve (supercharger operation stopping means), 53 ... First relief valve, 55 ... Second Relief valve, 84 ... Rotation speed sensor (rotation speed detection means), 92
...... Supercharger control means.

Claims (1)

[Scope of utility model registration request] 1. An exhaust turbocharger for a low speed and a high speed, which is installed in an engine and supercharges intake air by energy of exhaust gas, and a supercharger operation stop for stopping the operation of an exhaust turbocharger for high speed. Means, a rotation speed detection means for detecting the rotation speed of the engine, and an output of the rotation speed detection means so that the operation of the high speed exhaust turbocharger is stopped when the engine is running at a low speed. A supercharger control means for controlling the stop means is provided, and relief valves that open when the pressure downstream of the compressor is equal to or higher than a set value are provided in the compressor discharge side passages of the low speed and high speed exhaust turbochargers, respectively. In addition, the set pressure of the relief valve on the high speed exhaust turbocharger side is set higher than the set pressure of the relief valve on the low speed exhaust turbocharger side. The intake system structure of emissions.