Engine Control Device

The field of the present invention is engine controllers.

Engines, and specifically internal combustion engines, may be provided with intake and exhaust systems having various controls. These controls are generally operated by individual central processors or controllers. Having individual central processors for controlling the operation of each intake or exhaust system control, however, results in high costs and also creates complicated adjustment operations.

The present invention is directed to an engine control apparatus which controls the operation of a plurality of intake or exhaust system controls with a central processor, thereby achieving cost reduction and simplification of adjustment operations. Other and further objects and advantages will appear hereinafter.

In the drawings wherein similar reference characters denote similar elements throughout the central views:

FIG. 1 is a schematic view of the present engine control apparatus;

FIG. 2 is a section view taken along line II--II of FIG. 1;

FIG. 3 is a graph illustrating the target amount of rotation of the control valve drive shaft illustrated in FIG. 2;

FIG. 4 is a graph illustrating the target amount of rotation of a drive shaft of a changeover control valve;

FIG. 5 is a flow chart illustrating the control procedure of a main program of the central processor illustrated in FIG. 1;

FIG. 6 is a flow chart illustrating a control procedure of an interruption subprogram of the central processor;

FIG. 7 is a graph illustrating engine output characteristics;

FIG. 8 is a schematic view of a second embodiment of the present engine control apparatus;

FIG. 9 is a section view taken along line IX--IX of FIG. 8;

FIG. 10 is a section view taking along line X--X of FIG. 9;

FIG. 11 is a graph illustrating the target amount of rotation of the drive shaft of FIG. 8;

FIG. 12 is a graph of engine output characteristics;

FIG. 13 is a graph illustrating engine horsepower and torque obtained with the present invention in comparison to the prior art;

FIG. 14 is a schematic view of a third embodiment of the present engine control apparatus;

FIG. 15 is a section view taken along line XV--XV of FIG. 14;

FIG. 16 is a graph illustrating the target amount of rotation of the drive shaft of the valves of FIG. 15; and

FIG. 17 is a graph of engine output characteristics.

Turning now to the appended drawings, as shown in FIG. 1, an exhaust port 3 is opened and closed by a piston 2 slidably fitted within a cylinder 1 of a two-cycle engine, which may be mounted on a motorcycle. The exhaust port 3 is open to the inside surface of the cylinder 1. An exhaust control valve 4 is disposed generally above the exhaust port to control the opening and closing timing of the exhaust port 3. An exhaust pipe 5 is connected to the exhaust port 3. The exhaust pipe 5 includes a first section 5a having an expanded downstream end and a second section 5b in the form of a truncated cone with the larger diameter end thereof connected to the downstream end of the first exhaust pipe section 5a. In the downstream end of the first exhaust pipe section 5a and the second exhaust pipe section 5b is provided an expanded chamber 6. This chamber is connected to a muffler 8 through a main tailpipe 7. A sub tail pipe 9 has an upstream end connected to the second exhaust pipe section 5b and opens into the central part of the chamber 6. The downstream end of the sub tail pipe 9 is also connected to the muffler 8. Towards the middle of the main tailpipe 7 and the sub tail pipe 9, there are provided changeover control valves 10, 11 as second and third control elements or control operating means, the exhaust control valve being the first control operating means. (See FIG. 2).

The control valve 4 disposed in the exhaust port 3 is installed on a drive shaft 12 which is rotatably disposed alongside the cylinder 1. The drive shaft 12 is coupled to a servo motor 14 which acts as a driving source for the exhaust valve 4 through a power transmission mechanism 13, preferably comprising a pulley and a drive belt. The servo motor 14 includes a potentiometer 15 for detecting the position or the amount of operational movement of the servo motor 14, which corresponds to the amount of opening of the exhaust control valve 4.

With reference to FIG. 2, the change over control valves 10, 11 are secured on a common drive shaft 16 which is rotatably mounted through the main and sub tail pipes 7 and 9. The drive shaft 16 is coupled to a servo motor 18 to provide a driving source, through a power transmission 17, preferably comprising a pulley and drive belt. (See FIG. 1). The servo motor 18 includes a potentiometer 19 for detecting the position or amount of movement of the servo motor 18 which corresponds to the amount of opening of the changeover control valves 10, 11. The changeover control valves 10, 11 are arranged at different mounting angles in relation to the drive shaft 16, such that the amount of opening in the main and sub tail pipes 7 and 9 varies with the rotation of the drive shaft 16. Both servo motors 14 and 18 are connected to a common central processor 20. Detected values from an engine speed detector 21 and a throttle opening detector 22 are input to the central processor 20.

Referring to FIG. 3, the target opening of the control valve 4, i.e., the target amount of rotation .theta.t.sub.1 of the drive shaft 12 corresponding to the engine speed Ne and the throttle opening .theta.th are set within the central processor unit 20. Simultaneously, the target amount of rotation .theta.t.sub.2 of the drive shaft 16 corresponding to the engine speed Ne is set as shown in FIG. 4.

In particular, the amount of rotation of the drive shaft 16 is set such that at a low engine speed Ne, both the changeover control valve 11 in the sub tail pipe 9 and the changeover control valve 10 in the main tailpipe open slightly as shown in FIG. 2(a). The amount of rotation of the drive shaft 16 is set such that at a medium engine speed Ne, the changeover control valve 11 in the sub tail pipe 9 is wide open while the changeover control valve 10 in the main tailpipe is just slightly open as shown in FIG. 2(b). At a high engine speed Ne, the amount of rotation of the drive shaft 16 is set such that the changeover control valve 11 in the sub tail pipe 9 is only slightly open while the changeover control valve 10 in the main tailpipe is wide open, as shown in FIG. 2(c).

At the central processor 20, control is carried out in accordance with a main routine shown in FIG. 5 and an interruption subroutine shown in FIG. 6. First, in the main routine shown in FIG. 5, the amount of rotation .theta.v.sub.1, .theta.v.sub.2, of the drive shafts 12, 16 are read by potentiometer 15, 19 at a first step S1. Next, at a second step S2, whether .theta.v.sub.1 >.theta.t.sub.1 +.epsilon..sub.1 is judged; when .theta.v.sub.1 >.theta.t.sub.1 +.epsilon..sub.1, the drive shaft 12 is turned to drive the control valve 4 to the OPEN side by .vertline..theta.t.sub.1 -.theta.v.sub.1 .vertline. at a third step S3; and when .theta.v.sub.1 .ltoreq..theta.t.sub.1 +.epsilon..sub.1, at the second step S2, the control proceeds to a fourth step S4, at which whether .theta.v.sub.1 <.theta.t.sub.1 -.epsilon..sub.1 is judged. Furthermore, when .theta.v.sub.1 <.theta.t.sub.1 -.epsilon..sub.1 is judged at the fourth step S4, the control proceeds to a fifth step S5, at which the drive shaft 12 is turned to drive the control valve to the CLOSE side by .vertline..theta.t.sub.1 -.theta.v.sub.1 .vertline..That is, from the second step S2 to the fifth step S5, the amount of rotation of the drive shaft 12 is controlled such that the amount of rotation .theta.v.sub.1 of the drive shaft 12 will come within .+-..epsilon..sub.1 of the target amount of rotation .theta.t.sub.1.

When .theta.v.sub.1 .gtoreq..theta.t.sub.1 -.epsilon.1 at the fourth step S4, process at the third and fifth step S3 and S5 is finished, the operation proceeds to a sixth process S6, at which whether .theta.v.sub.2 <.theta.t.sub.2 +.epsilon..sub.2 is judged. If .theta.v.sub.2 <.theta.t.sub.2 +.epsilon..sub.2, the drive shaft 16 is driven to the HIGH SPEED OPERATION side by .vertline..theta.v.sub.2 -.theta.t.sub.2 .vertline. at a seventh step S7. When .theta.v.sub.2 >.theta.t.sub.2 at the sixth step S6, the operation proceeds to an eighth step S8, at which whether .theta.v.sub.2 >.theta.t.sub.2 -.epsilon..sub.2 is judged. When .theta.v.sub.2 >.theta.t.sub.2 -.epsilon..sub.2 has been decided at the eighth step S8, the operation proceeds to a ninth step S9, at which the drive shaft 16 is driven to the LOW SPEED side by .vertline..theta.v.sub.2 -.theta.t.sub.2 .vertline.. Namely, from the sixth step S6 to the ninth step S9, the amount of rotation of the drive shaft 16 is controlled so that the amount of rotation .theta.v.sub.2 of the drive shaft 16 will come within .+-..epsilon..sub.2 of the target amount or rotation .theta.t.sub.2.

When .theta.v.sub.2 .ltoreq..theta.t.sub.2 -.epsilon..sub.2 at the eighth step S8, and when the process at the seventh and ninth steps S7 and S9 is finished, the operation goes back to the first step S1.

The interruption subroutine in FIG. 6 interrupts the operation the aforementioned main routine at fixed intervals of time. At the first step N1, the target amount of rotation .theta.t.sub.2 of the rotating shaft 12 is retrieved on the basis of the engine speed Ne and the throttle opening .theta.th. At the second step N2 the target amount of rotation .theta.t.sub.2 of the rotating shaft 16 is retrieved on the basis of the engine speed Ne.

In the two-cycle engine E, controlling the opening of the control valve 4 in accordance with engine speed and throttle opening can increase the output of the engine E as shown by leftward descending oblique lines in FIG. 7. Also, controlling the opening of the changeover control valves 10, 11 in accordance with the engine speed can increase the output of the two-cycle engine E as shown by rightward descending oblique lines in FIG. 7. That is, since in a medium speed operation range of the two-cycle engine E, the opening of the changeover control valve 11 in the sub tail pipe 9 increases while the opening of the changeover control valve 10 in the main tail pipe decreases, stagnation of exhaust gas occurs in the expanded chamber 6 at the rear of the connection port of the sub tail pipe 9, thereby resulting in a temperature drop in the expanded chamber 6 and a variation in the velocity of exhaust pulsating wave to improve engine output in the medium-speed operation range.

In the low-speed operation range, both the changeover control valves 10, 11 are set slightly open which enables substantial deadening of exhaust noise.

Thus controlling the opening of the control valve 4 and both the changeover control valves 10, 11 can improve the output of the two-cycle engine E and at the same time can deaden exhaust sound within the low-speed operation range. However, the servomotor 14 for driving the control valve 4, and the servo motor 18 for driving both the changeover control valves 10, 11, are controlled by the single central processor 20, not only enabling cost reduction but facilitating adjustment operation because only the single central processor 20 requires adjustment.

FIGS. 8, 9 and 10 show a second embodiment of the present invention. As illustrated therein communicating pipe 23 is fitted and secured to the small-diameter end, or the downstream end, of the second pipe section 5b of the exhaust pipe. The other end of this communicating pipe 23 is connected to the muffler 8. In the second pipe section 5b, there is disposed a reflector 24 having a truncated cone or frustroconical shape as a control operation means for reflecting a positive pressure wave produced by the exhaust toward the exhaust port 3. The reflector 24 is disposed in the second exhaust pipe section 5b with its larger-diameter end on the first pipe section 5a side,and with a collar 25 fitted in the small-diameter end of the reflective pipe 24 slidably fitted on the outer periphery of the communicating pipe 23. The inner peripheral surface of the collar 25 is formed with an arcuate protuberance 25a which is in sliding contact with the pipe 23.

A servo motor 26 is connected to the reflector 24 as a driving source whose operation is controlled by the central processor 20, through a power transmission mechanism 27. Specifically, in the second pipe section 5b, a drive shaft 29 is rotatably supported on a bearing 28 which is mounted at the upper outer surface of its larger-diameter end. The drive shaft 29 and a driven shaft 30 mounted at the larger-diameter end of the reflector 24 are connected by a connecting rod 31. The power transmission mechanism 27 is connected to the drive shaft 29. To allow the rocking of the connecting rod 31, an elongated hole or slot 32 and a cutout 33 extend in the upper part of the larger-diameter end of the second pipe section 5b and the reflector 24 along the communicating pipe 23.

The servo motor 26 is proved with a potentiometer 34, which detects the position of the reflector pipe 24 and the amount of rotation of the drive shaft 29. The detected amount is inputted into the central processor 20.

The central processor 20, as in the first embodiment described above, controls the amount of opening of the control valve 4 as well as the position of the reflector pipe 24 in accordance with the engine speed. In the central processor 20, the target amount of rotation of the drive shaft 29 is set to drive the reflector 24 in the direction in which the volume of the expanded chamber 6 proportionally increases in accordance with the engine speed as shown in FIG. 11.

According to this second amendment, the output of the two-cycle engine E increases as shown in FIG. 12. That is, controlling the opening and closing of the control valve 4 can increase the engine output as indicated by the leftward descending oblique lines. Similarly, controlling the travel of the reflector 24 can improve the output in the low and medium speed operation ranges as indicated by the rightward descending oblique lines. Besides, as the servo motor 14 of the control valve 4 and the servo motor 268 of the reflector 24 are controlled by the common central processor 20, cost reduction and facilitation of adjustment operation can be realized as in the case of the first embodiment. In FIG. 13, lines P1 and T1 represent engine characteristics according to the present invention and correspond to horsepower and torque, respectively. Lines P2 and T2 represent engine characteristics according to the prior art and correspond to horsepower and torque, respectively.

FIGS. 14 and 15 show a third embodiment of the present invention. In the second pipe section 5b of the exhaust pipe 5 ar disposed a pair of openable and closable on-off valves 35, 36 as control operating means. These on-off valves 35, 36 are each formed nearly semi-circular so that they will be nearly circular when closed, and are fixed on drive shafts 37, 38 that are rotatably and parallelly pivoted in the second pipe section 5b. In addition, both the drive shafts 37, 38 are connected through a link mechanism 39, such that both the drive shafts 37, 38 and the on-off valves 35, 36, are mechanically interlocked to open and close. The servo motor 40 which is a driving source to drive these drive shafts 37, 38 is coupled with the drive shaft 37 through the power transmission mechanism 41. The servo motor 40 is provided with a potentiometer 42.

The aforementioned servo motor 40 is controlled by the central processor 20 which controls the opening of the control valve 4. The detected amount from the potentiometer 42 is also input into the central processor 20. In the central processor 20, the target amount of rotation of the drive shafts 37, 38 is set as shown in FIG. 16, to control the operation of both the on-off valves 35, 36 in accordance with the engine speed. When the engine is running at a low speed to a certain fixed speed of revolution, the on-off valves 35, 36 are closed, and when the above-mentioned fixed speed of revolution is exceeded, both the on-off valves 35, 36 are opened.

According to this third embodiment, the output of the two-cycle engine E increases as shown in FIG. 17. Controlling the opening and closing operation of the control valve 4 can increase output as indicated by the leftward descending oblique lines,and controlling the opening and closing operation of the on-off valves 35, 36 can increase output in the low- and medium-speed operation ranges as indicated by the rightward descending oblique lines.

In addition, as the control valve 4 and the on-off valves 35, 36 are controlled by the central processor 20 as in the case of the first and second embodiments described above, cost reduction and simplification of adjustment operation can be realized.

As another embodiment of the present invention, the control valve 4 and a carburetor 45 or an oil pump 46 may be controlled by the central processor 20 as indicated by phantom lines in FIGS. 1, 8, and 14.

While embodiments and applications of this invention have been shown and described, it would be apparent to those skilled in the art that many more modifications are possible without departing from the inventive concepts herein. The invention, therefore, is not be restricted except in the spirit of the appended claims.