Supercharged engine

Abstract: An engine (1) having a turbocharger (6) is super­ charged by an air compressor (31) and decelerated by another air compressor (32). These two air com­ pressors (31, 32) are connected to a crankshaft (10) of the engine (1). The first air compressor (31) has a capacity smaller than the second one (32). Clutches (22, 23) are provided between the air compressors (31, 32) and the crankshaft (10). When the engine (1) is operated at a low speed and the supercharging to the turbocharger (6) is in­ sufficient, the supercharging air compressor (32) is activated whereas when the engine (1) is oper­ ated at an intermediate or high speed and a large brake force is required, the brake air compressor (31) is activated to ensure the safe deceleration of a vehicle.

Description: The present invention generally relates to a supercharged engine and more particularly to an engine associated with a turbocharger, a large capacity air compressor for a brake and a small capacity air compressor for supercharging. In automobile engineering, one of the primary objects is to obtain an engine of light weight, compact but high output with low fuel consumption. Increasing degree of freedom in various aspects is an important aim in engine-designing. For this purpose, the engine has been supercharged. In other words, research on high net mean effective pressure has been conducted. However, the following problems are not yet solved: (i) An engine torque decrease at a low speed condition; and (ii) engine brake force and exhaust brake force do not change with output of the engine so that these brake forces decrease relatively. EP-A-0 292 010 discloses an arrangement represented in Figure 3. Specifically, a centrifugal compressor (b) is connected with a crankshaft (a) via a gear train (d) and a clutch (e), and the compressor (b) is operated during a braking operation to apply a brake force onto the crankshaft (a) or an engine (c). This arrangement can solve the above-mentioned problem (ii) though not the problem (i). The problem to be solved by the present invention is to provide a turbocharged engine which can exhibit an adequate torque even under low-speed condition and an adequate brake force relative to an output of the engine. The invention solves this problem by the features specified in the main claim. Further developments are described in the sub-claims. According to one aspect of the present invention, there is provided an engine associated with a turbocharger. The engine is supercharged by a first air compressor having a relatively small capacity for supercharging, a second air compressor having a relatively large capacity is provided for braking, and a first output shaft is selectively connected with a crankshaft of the engine and with the small capacity air compressor (supercharging air compressor). A second output shaft is also selectively connected with the crankshaft of the engine and with a large capacity air compressor (braking air compressor), and there are provided clutch means between said air compressors and the respective output shafts. The supercharging air compressor ensures an adequate supercharging so that the engine torque is maintained at a proper level even at low speed condition. The braking air compressor consumes energy of the engine to apply a brake force onto the engine. The braking air compressor ensures an adequate brake force at high speed condition. Figure 1 is a block diagram of a supercharged engine according to the present invention; Figure 2 is a flow chart of a controller of Figure 1; and Figure 3 is a block diagramm showing an arrangement of a relevant art. An embodiment of the present invention will be described with reference to the accompanying drawings. Referring to Figure 1, an intake passage 3 is connected with an intake port 2 of an engine 1. An exhaust passage 5 is connected with an exhaust port 4 of the engine 1. A turbocharger 6 has a blower 7 disposed at an upstream position of the intake passage 3. The turbocharger 6 further has a turbine 8 located at a downstream position of the exhaust passage 5. A charge cooler 9 is provided in the intake passage 3 at a position downstream of the blower 8. The charge cooler 9 cools supercharged air and raises the charging efficiency. A crankshaft 10 of the engine 1 is connected with a transmission 11. The transmission 11 drives two air compressors in different ways. The transmission 11 includes a hollow shaft (outer shaft) 12 and an inner shaft 13 extending through the outer shaft 12. The inner shaft 13 and the outer shaft 12 are connected with each other by a planetary gear mechanism 14. Specifically, a sun gear 15 is mounted close to one end of the inner shaft 13, and an inner gear 17 is provided on a flange 16 extending from the outer shaft 12. A plurality of planetary gears 18 are positioned between the sun gear 15 and the inner gear 17. A disk-shaped first clutch plate 20 is mounted onto a carrier 19 of the planetary gears 18. The first clutch plate 20 has a mutual center with the inner shaft 13. A second clutch plate 21 is mounted on the other end of the inner shaft 13. Electromagnetic clutches 22 and 23 are respectively provided at the periphery of the clutch plates 20 and 21 so that the rotations of the clutch plates are operatively stopped. The crankshaft 10 is connected with the outer shaft 12 by a so-called CVT (a couple of variable or changeable pulleys 24 and 24 and a variable belt 25). The variable pulley 24 has a V-groove, and the two obliques of the V-groove are defined by two pulley elements. One pulley element is movable relative to the other pulley element such that pulley width and diameter are changed as the movable pulley element is moved relative to the fixed pulley element. The movable pulley has an oil chamber at its rear and is moved by oil being fed into the oil chamber. The amount of movement is adjusted by the oil pressure of the fed oil. The variable belt 25 includes a plurality of pieces which make a chain-like endless belt in combination. A third electromagnetic clutch 28 is mounted on the crankshaft 10 in a manner such that it is connected with and disconnected from the clutch 27 integrally mounted on the pulley 26. A first impeller shaft 29 extends through the center of the first clutch plate 20 and is fixed thereto. The first impeller shaft 29 is coaxial with the inner shaft 13. A second impeller shaft 30 extends through the center of the second clutch plate 21 and is coaxially connected to the inner shaft 13. A first compressor 31 is connected to the first impeller shaft 29 and a second compressor 32 is connected to the second impeller shaft 30. The first compressor 31 serves as a brake means and the second compressor 32 serves as a supercharging means. The first compressor 31 has a capacity larger than the one of the second compressor 32. The first and second compressors 31 and 32 have radial casings, respectively, and impellers are rotatably disposed in the casings. The impeller shafts 29 and 30 extend out of the casings from the rear of the respective impellers. One end of a supercharging port 34 is connected to a discharge port 33 of the second compressor 32. The other end of the supercharging port 34 is connected to the intake passage between the charge cooler 9 and the turbocharger valve 35. The first and second clutches 22 and 23 are connected to a controller (CPU) 36, respectively. The controller 36 receives speed signals from a rotational speed sensor 37, accelerator signals from accelerator-opening degree sensor 39, pressure signals representing the supercharge pressure of the turbocharger 7, pressure signals representing the supercharge pressure of the second compressor 32, and on-off signals from a brake switch 40 of the vehicle. The speed sensor 37 detects the rotational speed of the crankshaft 10. The accelerator sensor 39 is connected with an accelerator pedal 38 and the degree of actuation of the accelerator pedal 38 is electrically detected by the accelerator sensor 39. The accelerator sensor 39 may be a movable slider. The accelerator pedal controls the rotational speed of the engine 1. The brake switch is turned on when a brake pedeal is depressed by the driver and turned off as the driver's foot leaves the pedal, or turned on and off by a manual switch operated by the vehicle driver. The controller 36 also includes a control map 41. The control map 41 includes data about the relation between the engine load (throttle opening degree) and the rotational speed of the engine. The controller 36 emits on and off signals to the first, second and third clutches 22, 23 and 28, respectively. The controller 36 also emits signals to adjust the opening degree of the flowrate valve 35. The control map 41 can be divided into two areas, i.e., the left half or low speed area (shaded area) is an engine torque insufficient area 42 and the right half or intermediate and high speed area (non-shaded area) is an engine torque sufficient area 43. The second compressor 32 is operated in the low speed area 42 and the turbocharger 6 is used in the intermediate and high speed area 43. The control function of the controller 36 will be explained with reference to the flowchart of Figure 2. The program starts with step 50. After step 50, engine running conditions such as engine revolution Ne, engine load Le and supercharging pressure Pe are input or read into the controller 36 at step 51. Then, it is checked if the accelerator pedal 38 is depressed at step 52. If the answer at step 52 is YES, it is checked at step 53 whether the supercharging value is in the low speed area 42 or in the other area 43 of the map 41 using the opening degree of the accelerator pedal 38 and the rotational speed of the engine input to the controller. When the engine is operated in the low speed area 42, the third clutch 28 is turned on (to "turn on" means to bring the clutch into an engagement state) at step 54. Then, the first clutch 22 is turned on at step 55 and the flowrate control valve 35 is adjusted to have a specified opening degree at step 56. The second clutch 23 is turned off between steps 55 and 56. On the other hand, if the engine 1 is operated in the intermediate or high speed area 43, the answer at step 53 becomes NO and the program proceeds to step 57. At step 57, the third clutch 28 is turned off (to "turn off" means to bring the clutch into a disengagement state), and then the first clutch 22 is turned off at the next step (step 58) before proceeding to step 56. The second clutch 23 is turned off between steps 57 and 58. When the accelerator pedal 38 is not depressed at step 52, the program advances to step 59. It is checked at step 59 whether the vehicle is decelarated or not based on an ON/OFF-signal of the brake switch 40. When the brake switch is turned on, the controller decides that the vehicle is in the deceleration, and the third clutch 28 is turned on at step 60. Successively, the second clutch 23 is turned on at step 61. At this time, the first clutch 22 is turned off. The ON/OFF-signal of the brake switch 40, the engine rotational speed, the engine load, the accelerator opening degree, the supercharging pressure downstream of the blower 8 and the supercharging pressure upstream of the flowrate control valve 35 are input into the controller 36 as the engine 1 is started. Data from the control map 41 is also input into the controller 36. Then, the controller 36 performs the control of the first, second and third clutches 22, 23 and 28 in accordance with the input data by using the control map 41. When the brake is not actuated (normal driving) with the accelerator pedal 38 being depressed and the controller 36 judging from the detected rotational speed and load that the engine running condition is in the area 42 of the map 41, the third clutch 28 and the first clutch 22 are turned off. Then, the first clutch plate 20 is fixed and the second clutch 23 is turned off. As a result, the carrier shafts 19 are fixed, and the power input from the crankshaft 10 through the pulley 24 and variable belt 25 drives the external gear 12 and the internal gear 17, and further drives the sun gear 15 via the planetary gears 18. The sun gear 15 drives the second impeller shaft 30 to rotate the impeller. In other words, the impeller is rotated at a speed increased by the transmission 11 and the pressurized air or supercharging air is continuously fed into the supercharging passage 34. At this time, the controller 36 computes a difference between the desired supercharging value and the actual supercharging value using the map 41 and various input data such as the rotational speed and the load. The controller 36 determines the opening degree of the flowrate control valve 35 in accordance with the difference of computed supercharging values. Therefore, the engine 1 suffers from the insufficient torque during low speed driving. The engine gains additional torque in accordance with the engine load and speed. On the other hand, the supercharging by the turbocharger 6 is sufficient during the intermediate and high speed operation (area 43). Thus, the supercharging by the second compressor 32 is unnecessary. In this case, the controller 36 turns the third clutch 28, the first clutch 22 and the second clutch 23 off such that the power transfer to the tranmission 11 is cut. During deceleration of the vehicle, the judgement of the controller 36 proceeds regardless of the engine load and speed and depends on the ON/OFF signal of the brake switch 40 only. When the brake switch 40 is turned on, the first clutch 22 is turned off, the second clutch 23 is turned on and the third clutch 28 is turned on. As a result, the second clutch plate 21 and the second impeller shaft 30 are fixed so that the power from the crankshaft 10 is transferred to the planetary gears 18 via the internal gear 17. The planetary gear 18 causes the first clutch plate 20 and the first impeller shaft 29 to rotate, and the impeller is rotated at an increased speed. Thus, the energy of the crankshaft 10 is consumed in accordance with the pressurized air volume and a brake force is applied to the crankshaft, thereby decelerating the vehicle. The controller 36 adjusts the oil pressure of the oil chamber of the CVT based on the control map 41 and determines the supercharging rate and brake force of the first and second compressors 31 and 32. An inlet 62 of the first compressor 31 may be provided with a throttle valve to raise the brake force by throttling. In addition, the mechanism transferring the power of the crankshaft 10 to the external gear 12 is not limited to the CVT. For example, an arrangement including a chain and sprocket or a gear train is satisfactory. Moreover, the planetary gear set may not be employed. Instead, the first and second impeller shafts 29 and 30 may be separately connected to the crankshaft by a speed increasable chain and a sprocket or gear train and such mechanism may be provided with clutches.

Claims: An engine (1) comprising a turbocharger (6) and a drive shaft (10); a first output shaft (29) to be selectively connected with the drive shaft (10) of the engine (1); a first compressor (31) connected with the first output shaft (29) for consuming energy of the engine (1) and to apply a brake force to the engine (1); first clutch means (22) provided between the first compressor (31) and the first output shaft (29) for selectively connecting the first compressor (31) with the first output shaft (29); characterized by a second output shaft (30) to be selectively connected with the drive shaft (10) of the engine (1); a second compressor (32) connected with the second output shaft (30) for feeding supercharged air into the engine (1), the second compressor (32) having a capacity smaller than the first compressor (31); and second clutch means (23) provided between the second compressor (32) and the second output shaft (30) for selectively connecting the second compressor (32) with the second output shaft (30). The engine of claim 1, characterized in that it further includes means (11) for adjusting the rotational speed of the first and second air compressors (31, 32). The engine of claim 2, characterized in that the rotational speed adjusting means (11) are respectively provided between the first and second output shafts (29, 30) and the drive shaft (10) of the engine (1). The engine of claim 2 or 3, characterized in that the rotational speed adjusting means (11) includes a speed increasing mechanism for driving the first and second air compressors (31, 32) at a speed beyond a predetermined value. The engine of any one of the foregoing claims, characterized in that the first and second clutch means (22, 23) include electromagnetic clutches, respectively. The engine of any one of claims 2 to 5, characterized in that the rotational speed adjusting means (11) includes: a sun gear (15) having a shaft (13); an internal gear (17); a plurality of planetary gears (18) provided between the sun gear (15) and the internal gear (17) for meshing with the sun gear (15) and the internal gear (17); carrier shafts (19) extending from the planetary gears (18), respectively; a first clutch plate (20) connected with the carrier shafts (19) and with the first output shaft (29), the first output shaft (29) being coaxial with the shaft (13) of the sun gear (15); a second clutch plate (21) connected with the shaft (13) of the sun gear (15) and with the second output shaft (30), the second clutch plate (21) having a center, the shaft (13) of the sun gear (15) extending toward the center of the second clutch plate (21), the second output shaft (30) extending toward the center of the second clutch plate (21); an outer shaft (12) connected with the internal gear (17) via a flange (16) and surrounding the shaft (13) of the sun gear (15); power transmission means (24,25) for connecting the drive shaft (10) of the engine (1) with the outer shaft (12) to transfer power from the drive shaft (10) to the outer shaft (12); and a controller (36) for connecting and disconnecting the first and second clutch plates (20, 21) with and from the first and second clutch means (22, 23), respectively, and in accordance with the load on the engine (1), the rotational speed of the engine (1) and the opening degree of an accelerator. The engine of any one of the foregoing claims, characterized in that a controller (36) includes a control map (41) having a first area (42) and a second area (43), the controller (36) allowing the second air compressor (32) to feed the pressurized air when data determined by the load on the engine (1), the rotational speed of the engine (1), the opening degree of an accelerator and the supercharging pressure is in the first area (42) whereas the controller (36) does not allow the second air compressor (32) to feed the pressurized air when said data is in the second area (43), and that when said data is in the first area (42), the first and second clutch means (22, 23) are operated in a manner such that a first clutch plate (20) is fixed and a second clutch plate (21) is not fixed whereas when the data is in the second area (43), the first and second clutch means (22, 23) are operated in a manner such that the first and second clutch plates (20, 21) are not fixed. The engine of any one of the foregoing claims, characterized in that the first and second air compressors (31, 32) are centrifugal air compressors, respectively. The engine of any one of the foregoing claims, characterized in that the second air compressor (32) has an outlet (33), that the engine (1) has an exhaust passage (5) and a supercharging passage (34) connected to the outlet (33) of the second air compressor (32), that the turbocharger (6) is disposed in the exhaust passage (5), that a flowrate control valve (35) is disposed in the inlet passage (3) downstream of the turbocharger blower (7), that the supercharging passage (34) is connected to the exhaust passage (5) via said flowrate control valve (35) and that a controller (36) adjusts said flowrate control valve (35) in accordance with a predetermined characteristic.

Inventors: OKADA MASAKI C O ISUZU MOTORS, OKADA, MASAKI, C/O ISUZU MOTORS LIMITED
Applicants: ISUZU MOTORS LTD, ISUZU MOTORS LIMITED
Application year: 1990
Main classification: F02B37
IPC codes: F02D29, F02B39, F02B67, F02B37, F02D41