Distributor-type Fuel Injection Pump For Internal Combustion Engines

Abstract

A distributor-type fuel injection pump for internal combustion engines, comprising at least one electrical actuator so moving together with the internal cam ring and so controlled from a control circuit operating with input signals derived from the rotating speed and accelerator position that the movement of said electrical actuator is imparted to the sleeve located around the rotor to determine the effective injection stroke, thereby making the injection quantity capable of being freely varied.

Description

This invention relates to distributor-type fuel injection pumps for internal combustion engines, and more particularly to the pumps of the kind comprising a rotor having therein a transverse bore, at least one reciprocating plunger in the bore, an annular cam surrounding the rotor for imparting inward movement to the plunger as the rotor is rotated, and a distributor having passages whereby the bore in the rotor is placed in communication alternately with an inlet port and with successive outlet ports in timed relationship with the rotation of the rotor.

In conventional pumps of the kind referred to above, usually it is impossible to adjust the initiation or beginning of injection, and it has been found that an adjustment of injection period or effective injection stroke will always affect injection timing. In other words, varying the beginning or ending of fuel injection for an adjusted injection period will result in a corresponding change of a present angular position on cam phase of the annular cam, which, in turn, will affect injection rating. On the other hand, the adjustment of injection period or injection timing requires a substantial actuating force, and this adjustment cannot be responsive to either engine rotational speed and load. It is further noted that it is difficult to make an adjustment according to the requirements of excess fuel supply upon engine starting, "full Q" characteristic, i.e., controlling of maximum fuel injection quantity in response to engine rotational speed in order to meet fuel requirements arising from correlation on the engine side between a limit on the exhaust smoke density and the effective generation of output torque, and speed regulation.

An object of this invention is to overcome these drawbacks of the conventional distributor-type fuel injection pumps. Another object of this invention is to provide a distributor-type fuel injection pump of the type which comprises an oil servo-motor for an injection timer, thereby making it possible to provide ready adjustment of injection timing at the same time preventing a possible transfer to the oil servo motor of the reaction caused by a driving force applied on the annular cam at the time of fuel injection, thus insuring stabilized injection timing.

According to this invention, the fuel injection pump has the following advantages:

1. An electrical actuator to rotate a sleeve disposed on the rotor and variation in the timing of the opening of the shut-off ports to obtain a properly adjusted initiation and/or termination of injection.

2. Actuating the injection timer synchronously with rotation of the above-mentioned sleeve to prevent the injection rating from being changed by an adjustment of injection period.

3. Provision of an apparatus in which the oil servo motor is kept free from the influence of the reaction of a driving force to drive the cam, thus insuring stability of the operation of the injection timer.

4. The excess supply of fuel for engine starting, "full Q" control characteristic and governor characteristic or speed regulation can all be freely changed as desired.

5. Number of parts needed is less, so that the cost of manufacture is reduced.

These and other objects and features of this invention will be better understood upon consideration of the following detailed description and the accompanying drawings in which:

FIGS. 1, 2 and 3 refer to a pump according to the invention, FIG. 1 is a longitudinal cross section in elevation, FIG. 2 is a transverse cross section taken along the line II--II of FIG. 1, FIG. 3 is a partial cross section in plan taken along the line III--III of FIG. 2;

FIG. 4, 5 and 6 refer to another pump according to the invention, and correspond to FIGS. 1, 2 and 3, FIG. 5 being a section taken along the line V--V of FIG. 4, FIG. 6 being a section taken along the line VI--VI of FIG. 5;

FIGS. 7 and 8 refer to still another pump according to the invention and correspond to FIGS. 1 and 2;

FIGS. 9 and 10 show a servo timer according to the invention in partial cross sections, in frontal view and in side view, respectively;

FIG. 11 is a block diagram of fuel control circuit according to this invention for internal-combustion-engine fuel injecting pump;

FIG. 12 is a circuit diagram fo the principal part of said block diagram;

FIG. 13 is a graph showing a maximum fuel injection characteristic curve;

FIG. 14 is an output characteristic curve for the circuit of FIG. 12;

FIG. 15 is a block diagram of injection-timer control circuit according to this invention for internal-combustion-engine fuel injection pump;

FIG. 16 is a circuit diagram of the principal part of the control circuit according to the invention;

FIG. 17 shows waveforms of pulse outputs at various junction points within the circuit network of FIG. 16;

FIG. 18 is a graph showing an output characteristic of the control circuit according to the invention.

Referring first to FIG. 1, fuel is supplied under pressure by vane pump 3 provided in housing 2 and drawing fuel through inlet connection fitting 1. The supplied fuel, whose pressure is adjusted by adjusting valve 4, proceeds from passage 5 within housing 2 to chamber 7, passage 8 and groove 9 formed in head 6 and housing 2, and enters inlet ports 10, the number of which is equal to the number of cylinders in the engine, and then from inlet ports 12 in rotor 11 to pumping section 13.

Rollers 15 bear against internal cam ring 14, thereby rotating to actuate plungers 16 for developing the injection pressure.

The fuel is then discharged from outlet port 17 through passage 18, passage 19 in head 6 and the delivery valve located in opening 20 toward the nozzle.

Signals from pickup 21 for detecting the rotation of rotor 11 and from pickup 22 for detecting the displacement of the accelerator are led into control circuit 23, whose output command is applied to electrical actuator 26, which is integral with cam 25 secured to internal cam ring 14 by bolts 24, such that, in the example shown, said actuator 26 operates in primary proportion to the rotating speed of rotor 11 to displace link rod 27. Primary external cam 30, whose periphery has so characterized a shape as to control the injection quantity for engine starting and "full Q," is rotated by said link rod 27, which has rack 28 in mesh with pinion 29. Primary sleeve 32, urged by tension spring 31 to bear on said cam 30, turns around rotor 11 as said cam is so rotated. Primary sleeve 32 has a shut-off slot 33 and shut-off port 34, said slot and port being in direct communication. Rotor 11 has a number of shut-off ports 35, the number being equal to that of cylinders in the engine. The position of each shut-off port 35 relative to shut-off slot 33 in the direction of rotation changes as the contacting position of primary sleeve 32 on the periphery of external cam 30 changes to displace said sleeve 32. Since the moment at which the communication between shut-off port 35 and shut-off slot 33 becomes interrupted corresponds to the beginning of fuel injection, the manner of fuel oversupply for engine starting as well as the "full Q" performance can be altered as desired by altering the characterized shape of the periphery of primary external cam 30.

To stabilize the system so constituted as above, detector 36 is provided, which feeds back the movement of link rod 27 to control circuit 23. Primary external cam 30 may be omitted and, instead, the movement of link rod 27 may be directly imparted to primary sleeve 32, with control members connected to control circuits 23 or electrical actuator 26 in such a way as to produce oversupply for engine starting and "full Q" characteristic as desired.

Output command from control circuit 23 is applied to electrical actuator 37, which is an integral part, just as electrical actuator 26 is, of cap 25 secured to internal cam ring 14, so that said actuator 37 operates in primary proportion to the rotation of rotor 11 to displace link rod 38. Said rod 38 has rack 39 with which pinion 40 is in mesh, whereby secondary external cam 41, whose peripheral shape is so characterized so as to effect speed governing action, is rotated. Consequently, secondary sleeve 43, which is urged by tension spring 42 to stay in contact with secondary external cam 41, turns around rotor 11. Secondary sleeve 43 has a shut-off slot 44 and a shut-off port 45, said slot and port being in direct communication, while rotor 11 has a number of shut-off ports 46, the number being equal to that of cylinder in the engine, such that the position of each shut-off port 46 relative to shut-off slot 44 in the direction of rotation changes as the contacting position of secondary sleeve 43 on the periphery of secondary external cam 41 changes to displace said sleeve 43. Since the fuel injection ends just when shut-off slot 44 begins to communicate with shut-off port 45, the speed governing performance can be altered as desired by altering the characterized shape of the periphery of secondary external cam 41.

The system so constituted as above can be stabilized by providing detector 47 to feed back thereby the movement of link rod 38 to control circuit 23. As in the case of primary external cam 30, secondary external cam 41 may be omitted.

Tangential with respect to the annular cam in housing 2 is a power piston 49 of an oil servo motor for the injection timer. A coaxial pilot valve 50 unidirectionally reciprocates within piston 49 under the control of a spring, as shown. A link 51 secured to link rod 27 transmits movement thereof to the pilot valve 50. The power piston 49 is connected to annular cam 14 by means of connector 48 in such a manner that the motion of the former is converted into rotational movement for driving the latter. Referring to FIG. 2, as pilot valve 50 moves toward the left, the fuel under pressure flows through passage hole 52 into passage hole 53 provided in piston 49, from which it flows into port 55 now open because of the leftward displacement of land 54, so that the fuel proceeds further through passage hole 56 into chamber 57, wherein the fuel exerts a push on piston 49 in the same direction as that of pilot valve 50. Overtravel, if any, of piston 49 in this displacement will communicate port 55 to low-pressure chamber 58, thereby preventing piston 49 to move any further.

Furthermore, link 60, mounted on cam ring 14 by means of pivot 59, has its one end resting on link rod 38 and in engagement with link 51, the other L-shaped end thereof being in permanent engagement with link rod 38. Thus movement transmitted to link rod 38 will in turn actuate pilot valve 50.

For control relative to engine temperature and atmospheric pressure, temperature sensor 61 and pressure sensor 62 are provided. These sensors are connected to control circuit 23 in order to rotate secondary sleeeve 43.

How the example of this invention thus far described operates will be explained. Fuel is drawn through inlet connection fitting 1 by vane pump 3, which then forces the fuel through passage 5, chamber 7, passage 8, groove 9, inlet ports 10 and 12 into pumping section 13, wherein the fuel is pumped further to the injection pressure and, at this pressure, flows through outlet port 17, passages 18 and 19 toward the nozzle.

Pickup 21 senses the rotation of rotor 11 and pickup 22 the displacement of the accelerator. The signals developed by the two pickups enter control circuit 23. With output command received from control circuit 23, electrical actuator 26 operates in response to rotating speed to actuate primary sleeve 32 to effect control action on engine starting and "full Q." Fuel injection begins at the moment the communication between shut-off slot 33 and shut-off port 35 is interrupted.

On command from control circuit 23, secondary actuator 37 displace link rod 38 in proportion to the rotation of the rotor thus rotating secondary cam 40 and subsequently secondary sleeve 43 as well. This causes shut-off slot 44 to come into registry with shut-off port 46, at which time injection comes to an end. Since the timing of the termination of fuel injection depends on the profile of secondary cam 40, it is important for the shape of the cam to be suitably chosen to provide the desired speed governing performance. The action of either of link rod 27 or link rod 38 actuates pilot valve 50, which in turn drives the oil servo motor.

As pilot valve 50 moves toward the left, in FIG. 2, piston 49 moves likewise owing to the action of land 54 relative to port 55 and, when it begins to overtravel in this movement, port 55 communicates to low-pressure chamber 58, thereby halting piston 49. The amount of displacement of piston 49 is thus translated into a displacement on cam ring 14, whereby the injection timijng is varied. Stated differently, sleeves 32 and 43 rotate by an amount corresponding to the change in injection timing. The angular position cam phase of annular cam 14, which has been preset with respect to the initiation or termination of full injection, is maintained constant independently of changes in injection period. In the embodiment illustrated, on injection timing, speed-responsive control is obtained when link rod 27 is moved by means of primary actuator 26 and load-responsive control is obtained when link rod 30 is actuated by means of secondary actuator 37.

Another example of this invention will be described in reference to FIGS. 4 through 6, inclusive, in which parts identical in appearance to those of the foregoing example shown in FIGS. 1 through 3, inclusive, are also identical in function and will not be explained again in the following.

Link rod 38a, whose one end is connected with tension spring 42a to depend therefrom, moves up and down as actuated by electrical actuator 37a. Arm 39a, connected with link rod 38a, is in contact with the arm that is integral with sleeve 43a urged in a pushing manner by leaf spring 40a and capable of rotating on and around rotor 11a. A number of shut-off ports 46a are provided in rotor 11a, the number being equal to that of cylinders in the engine, and the position of each shut-off port 46a relative to shut-off slot 44a in the direction of rotation is changed by a rotation of sleeve 43a as actuated in accordance with the command produced by control circuit 23a so that the end-of-injection timing can be freely varied. Thus, control over engine starting "Q" and "full Q" as well as speed governing performance can be freely obtained.

Electrical actuator 26a is similar to said actuator 26 in operation: it makes the timing vary in dependence on speed and load. This is accomplished by providing an exclusive timing circuit in control circuit 23a, such that pilot valve 50a is displaced by link rod 27a, with intermediate link 51a transmitting the movement of rod 27a as actuated by electrical actuator 26a to said valve 50a. Said link 51a has its pivot 63 mounted on plate 64. The fuel under pressure is led through passage hole 65, provided in head 6a, passage 66 formed on the periphery of rotor 11a, passage hole 67, passage holes 68, 69 in housing 2a and finally into passage hole 53a provided in piston 49a. As pilot valve 50a moves toward the left, in FIG. 5, in response to the command issuing forth form control circuit 23a, port 55a in piston 49a, which has been closed by land 54a, opens to communicate to said passage hole 53a, so that the fuel flows into port 55a, from which it proceeds through passage hole 56a, provided in piston 49a, into chamber 57a, wherein the fuel exerts a push on piston 49a by its pressure acting on the end face of the piston, thus moving the piston in the same direction as that of pilot valve 50a.

Should piston 49a begin to overtravel relative to pilot valve 50a, port 55a would communicate to low-pressure chamber 58a, thereby causing piston 49a to halt. Since piston 49a is connected to internal cam ring 14a through connector 48a, cam ring 14a too displaces itself by an amount equivalent to the displacement of piston 49a, thereby changing the injection timing. Electrical actuator 37a is held integral with cam ring 14a by cap 25a, so that sleeve 43a rotates by an amount corresponding to the change in the timing: thus, the duration of fuel injection is kept unaltered and constant by constant cam lift positions.

Still another example of this invention will be explained in reference to FIGS. 7 and 8.

Pilot valve 50b is provided on electrical actuator 26b, with spring 31b interposed in between the two. In association with another electrical actuator 37b, which rotates sleeve 43b on rotor 11b, tension spring 42b is provided, which, being secured to cap 25b at its one end and secured, by way of an intermediate link rod, to link 39b at its other end, acts on actuator 37b since link 39b is connected to link rod 38b. Link 39b has its middle part rotatably supported by pivot 70 secured to internal cam ring 14b. The other sleeve 32b is connected to pivot 70, and its phase relationship with rotor 11b is adjustable. A detector 47b mounted on cap 25b senses the movement of link 39b and transmits a corresponding signal to control circuit equivalent to control circuit 23 of FIG. 1.

Thus, by locating one electrical actuator 26b in the timer section, the whole construction is simplified; and by providing tension spring 42b to act on the other actuator 37b mounted on cap 25b the operating error of actuator 37b and the detecting error of detector 47b are reduced; and the timer pre-stroke adjustment is the only adjustment required except that primary sleeve 32b is used to preset the timing of the beginning of injection, and control of the amount of fuel injected is effected by adjusting the termination of injection by means of secondary sleeve 43b while control of injection timing is effected by an oil servo motor in a manner similar to that with reference to FIGS. 5 and 6.

Turning now to an explanation of a device for preventing the oil servo motor from being affected by a reaction to the annular cam being driven at the time of fuel injection, thereby ensuring stable operation of the injection timer. Referring to FIG. 9, fuel oil supplied under pressure from feed pump, not shown, flows into passage 71, from which it proceeds through chamber 74 formed between head 72 and housing 73, passage 75, groove 76, so many passages 77 as there are cylinders in the engine, and passage 79 within rotor 78, to pumping section 80. Rollers 82 roll along and in contact with the face of internal cam ring 81 in such a way as to actuate plungers 83 for developing injection pressure, and the fuel oil at this pressure is discharged from the outlet hole provided in rotor 78 toward the nozzle. In the periphery of rotor 78 are provided a number of slots 84, whose number is equal to that of cylinders in the engine, and which are so located as to communicate to passage 85 and groove 76 except when fuel injection is taking place.

Referring to FIG. 10, control section 86 receives two signals, one for rotating speed N and the other for accelerator displacement X, so that this control section is rendered dependent on speed and load. Its output command is led to electrical actuator 87 provided in housing 83. Said actuator 87 acts directly on pilot valve 89 provided in power piston 88. Land 92, provided in the middle section of pilot valve 89 to form chambers 90 and 91, closes passage 93 provided in power piston 88, so that the fuel coming out of slot 84 will flow through passage 94 provided in head 72, passage 95 in housing 73, and slot 96 and passage 97 in power piston 88, into chamber 90. Passage 93 communicates to piston chamber 98 formed between power piston 88 and housing 73. Power piston 88 is connected to cam ring 81 through coupling 99. Pilot valve 89 is provided with spring 100 to counter the force exerted by electrical actuator 87.

How the example constituted as above, operates will be explained.

Accelerator displacement X and rotating speed N are detected by pickups and, as input signals, apply to control section 86, whose output command goes to electrical actuator 87. Under this command, actuator 87 acts on pilot valve 89. As said valve 89 moves toward the left, passage 93, which has been closed by land 92, opens to admit the fuel, being supplied under pressure by the feed pump, into piston chamber 98 from slot 84. In said chamber 98, the fuel exerts a push to the end face of power piston 88 and, as a result, said piston 88 gets displaced toward the left, thereby turning cam ring 81 by means of coupling 99 to alter the injection timing. As power piston 88 moves further to the left, passage 93 will communicate to low-pressure chamber 91, thereby causing said piston 88 to stop moving any further. The communication between passage 85 and slot 84 is interrupted to prevent drive reaction acting to the timer when fuel injection is taking place.

Therefore, the servo timer is operated from an electrical actuator, so that the timer needs but a small control force, can avoid drive reaction to the timer, can be employed in heavy-duty applications, and can be constructed compact.

Referring to the block diagram of FIG. 11, a voltage comparison circuit C compares two voltage inputs: one from a rotating speed detector circuit P of a known type, in which a sinusoidally varying voltage induced by a magnetic body cyclically moving toward and away from a coil at a rate related to the running speed of the engine is changed to an output voltage, and the other is from an accelerator displacement detector circuit L, in which the change in coil inductance due to a core displacement varies the oscillating frequency of an oscillator circuit to adjust its output voltage.

The voltage arising from this comparison is led through an amplifier circuit A to an output circuit W, to which apply a signal from a starting fuel oversupply circuit B in association with such as a starter switch, in order to oversupply fuel at the time of engine starting so as to facilitate engine starting, another signal representing the engine cooling water temperature and produced by a temperature compensating circuit T, and still another signal representing the atmospheric pressure and produced by a negative-pressure compensating circuit G. The output of the circuit W is supplied to a fuel control member O on the fuel injection pump to control the running speed of the engine E. The control member O may be such as a solenoid. This manner of control has already been proposed by this applicants in their prior U.S. application Ser. Nos. 40,793 and 122,473.

In a fuel control circuit, this proposed control system is given a circuit that enables the maximum injection quantity characteristic, that is, "full-Q" characteristic to be freely selected for the requirements arising from changes in running speed.

As shown in the graph of FIG. 13, wherein Q represents injection quantity and N the running speed of the engine, a "full-Q" characteristic which is non-linear relative to running speed is required by the relationship in the engine between engine output and exhaust smoke density. According to this invention, a "full-Q" characteristic circuit F is composed of a plurality of monostable circuits differing in output gradient and triggered by square wave output from the rotating speed detector p, smoothing circuits H for respective monostable circuits, and an output synthesizing circuit S for comparing the outputs of these circuits.

More will be said in describing the full-Q characteristic circuit F in detail by referring to FIG. 2.

The circuit H mentioned above comprises three monostable circuits M1, M2 and M3 and integrating circuits I1, I2 and I3, one monostable circuit to one integrating circuit. Monostable circuit M1 includes transistors T1 and T2, capacitor C1 and variable resistor R1 and, at its point P1, receives the trigger signal from the rotating speed detector circuit P. The pulse output of the circuit M1 becomes integrated in its integrating circuit I1 composed of capacitor C2 and variable resistor R1a, and, as integrated, applies to the synthesizing circuit S through diode D1. Connected in parallel to said circuit M1 is monostable circuit M2 comprising transistors T3 and T4, capacitor C3 and variable resistor R2, with integrating circuit I2 comprising capacitor C4 and variable resistor R2a. This second monostable circuit M2 receives the trigger signal from the rotating speed detector circuit P, just as does circuit M1, and produces a pulse output, which is integrated by integrating circuit I2 and applied through diode D2 to said synthesizing circuit S. The collector of transistor T3 on the gate side of said circuit M2 is connected through capacitor C5 to the third monostable circuit M3 comprising PNP transistor T5. The emitter of this transistor T5 is connected to the positive conductor and the collector to the negative conductor. The output of said circuit M3 is integrated in the integrating circuit I3 comprising capacitor C6 and variable resistor R3a , and is applied through diode D3 to synthesizing circuit S. Thus, said synthesizing circuit S receives the three outputs thus far mentioned through the diodes D1, D2 and D3: it detects only the maximum value of each output and inverts it within the range of varying rotating speed.

In the range N<N1 of rotating speed shown in FIG. 14, for example, variable resistor R3a is set to maximize the output from circuit M3, and variable resistor R3 and capacitor C6 are sized to provide the desired gradient in the output. In the range N1<N<N2, variable resistor R2a is set to maximize the output of circuit M2, and the output gradient is determined by the time constant of variable resistor R2 and capacitor C3 of circuit M2. In the range N>N2, variable resistor R1a is set to maximize the output of circuit M1, and the output gradient is determined by the time constant of capacitor C1 and variable resistor R1. As the result, an output curve like the one represented by solid line as a function of output voltage V and injection-pump rotating speed N in FIG. 4 obtains. By inverting this output and applying it to said amplifier circuit A, a "full-Q" characteristic represented by solid line in FIG. 3 obtains in addition to the speed governing characteristic.

The control circuit according to this invention for fuel injection pumps may be put to work by using a fuel control member operating with electromagnetic force such as a solenoid, as was stated.

In the block diagram of FIG. 1, timer control circuit TC comprises monostable multivibrator network M, pulse synthesizing circuits S1 and S2 and load detector circuit L. To the input side of the timer control circuit TC are connected constant-voltage circuit V and rotating speed detector circuit P; and to the output side is connected output circuit W through amplifier circuit A. Block E in this diagram represents the engine, and block O the control section of the engine E.

As shown in FIG. 16, the monostable multivibrator network M is triggered by the output of rotating speed detector circuit P and has three monostable circuits M11, M12 and M13 so connected that the input of first monostable circuit M1 is connected to the output P11 of rotating speed detector circuit P, with second monostable circuit M12 being triggered by the output of said circuit M11 and third monostable circuit M13 being triggered by the output of monostable circuit M12. These circuits M11, M12 and M13 comprise transistors T11 and T12, transistor T13 and transistor T14, respectively. First pulse synthesizing circuit S1 has transistors T15 and T16 and functions as an AND circuit that synthesizes the pulse outputs of third monostable circuit M13 and first monostable circuit M11. Pulse synthesizing circuit S2 synthesizes the pulse outputs of AND circuit S1 and load detector circuit L on engine E, and its as-synthesized output is amplified in amplifier circuit A and, through output circuit W, is supplied to the pilot valve actuating member, such as a solenoid, on the injection timer.

The output of first monostable circuit M11 is connected, through diode D11, to the base of transistor T15 in first pulse synthesizing circuit S1. The output of third monostable circuit M13 similarly applies, through diode D12, to the base of transistor T15, whose base is connected to the positive conductor through resistor R11 and whose collector is connected to the base of transistor T16 on the one hand, through diode D13, to the base of transistor T17 in load detector circuit L on the other hand. The collector of transistor T16 is connected, on the one hand, to the negative conductor through variable resistor R12 which determines the gradient in the pulse output and, on the other hand, to the base of transistor T19 in second pulse synthesizing circuit S2. In addition, load detector circuit L has transistor T18, whose base is connected to the collector of transistor T17, a coil H and a variable resistor R13.

The operation of the control circuit constituted as above for the injection timer will be described in detail by referring to FIGS. 16 through 18.

Referring first to FIG. 16, since third monostable circuit M13 is triggered by the outputs of preceding monostable circuits M11 and M12, the pulse output emerging from transistor T14 of monostable circuit M13 is constant, as shown by waveform t14 in FIG. 17. The output t12 of first monostable circuit M11 will overlap the pulses t14 and the amount of overlap, represented by the shaded area in each pulse form of t14, will increase as the speed increases. This overlapping takes place in first pulse synthesizing circuit S1.

When pulses t12 and t14 arrive simultaneously at the input of first pulse synthesizing circuit S1, the current flowing through resistor R11, diodes D11 and D12 becomes blocked to raise the potential of junction point P12, thereby switching on transistor T15. As transistor T15 conducts, its collector voltage falls: in this manner negative pulses t15 are produced. Pulses t15 are then differentiated on the one hand, and diode D13 passes the positive pulses of the differentiated output through load detector circuit L to second pulse synthesizing circuit S2. On the other hand, pulses t15 are inverted and turned to positive pulses t16, which apply to the same second pulse synthesizing circuit S2.

Transistor T17 of load detector circuit L receives positive trigger pulses from transistor T15 and, with each positive pulse, becomes conductive to switch on transistor T18. Since the base of transistor T17 is connected to the collector of transistor T18, the positive feedback of output so introduced maintains transistor T17 in conducting state. However, the inductive reactance in coil H, connected between the positive conductor and the base of transistor T18, begins to decay at the moment of triggering, thereby raising the potential of the base of transistor T18 progressively to make transistor T18 less and less conductive. In time a point will be reached where transistor T17 becomes switched off to make transistor T18 much less conductive. This is the way the rectangular positive pulse train, indicated as t18 in FIG. 17, appears at the collector of transistor T18.

Both pulses t18 produced as above and the output t16 of transistor T16 apply to the base of transistor T19 of second pulse synthesizing circuit S2. Pulses t18 are in synchronism, but out of phase, with pulses t16, so that, during the period corresponding to the sum of widths of pulses t16 and t18, transistor T19 conducts to provide an output, which applies to transistor T20 of amplifier circuit A in the subsequent stage. The amplified output is then used, as stated before, to control the pilot valve in the injection timer. Tee width of pulse t16 varies directly with engine speed. Suppose the running speed of the engine increases: this will increase the width of pulse t16; fuel adjusting lever will displace itself by speed governing action in the direction for decreasing fuel injection quantity to displace the core in coil H; this core displacement is so directed as to increase the inductive reactance of coil H. Then, the width of pulse t18 increases to increase the output of this control circuit for the injection timer, thus increasing the angle of advance in the timer. Respective gradients are determined by the settings of variable resistors R12 and R13. How the angle .theta. of advance increases is illustrated in FIG. 18, in which the angle .theta., represented by output voltage V, is a function of the rotating speed N of injection pump. The speed governing action is shown as taking place, for example, at speed N1. Parameters H1, H2 and so on represent respective positions of the accelerator lever.

The control circuit according to the invention contemplates, for its application, injection pumps of known types such as one having an annular internal cam, one having a cam plate rotating with plungers in opposition to a fixed roller holder, and one having individual pumping elements in series that are actuated by a camshaft driven from the engine, and is to be applied to such as the solenoid actuating the pilot valve in a hydraulic servo mechanism for actuating said annular internal cam, roller holder or camshaft relative to its driving shaft (on the engine side).

While this invention has been described in detail with respect to its preferred embodiment it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of this invention and it is intended, therefore, to cover all such changes and modifications in the appended claims.

Claims

We claim:

1. A distributor type fuel injection pump system for an internal combustion engine, comprising a housing containing an engine driven rotor including transverse bores therein, a central pumping section, and oppositely acting plungers disposed within said bores, pump means for supplying fuel under pressure to said pumping section from an inlet port, a plurality of outlet ports, an annular cam surrounding said rotor for imparting an inward movement to said plungers during rotation of said rotor so that the fuel within said pumping section is pressurized and distributed in sequence to said outlet ports, an oil servo-motor type injection timer means comprising a power piston including a pilot valve for controlling the oil pressure acting on said piston, means for coupling said pilot valve to said annular cam so that displacement of said piston provides corresponding rotation of said annular cam relative to said rotor, at least one sleeve member, rotatably mounted on said rotor, which changes relative position in the direction of rotation between the rotor and said annular cam and which controls opening and closing of a shut-off port in the rotor in communication with said pumping section to thereby control the injection period of said pump means, first and second electromagnetically-operated electrical actuators, said first actuator being coupled to a link member for transmitting the actuating force produced by said actuator to the pilot valve of the oil servo-motor and said second actuator being coupled to support means rotatable with said annular cam for converting the actuating force produced by said second actuator into rotational movement of said at least one sleeve member, and electrical control means comprising a control circuit for receiving at least first and second input signals respectively indicating the operating speed of the engine and the position of the accelerator and for generating, responsive to said signals, an output signal for controlling actuation of said actuator so as to regulate the amounts of fuel injected to control injection timing, and means for connecting said control circuit to each said actuator so that the output signal of said control circuit is a function of the outputs of said actuators.

2. A distributor type fuel injection pump system as claimed in claim 1 wherein said means for connecting said control circuit and said actuators comprises means for connecting a portion of the output of said control circuit for controlling injection timing responsive to engine speed and said first actuator and the output of said control circuit for controlling the maximum fuel injection quantity characteristic to said second actuator.

3. A distributor type fuel injection pump system as claimed in claim 1 wherein said at least one sleeve member comprises a first sleeve member which is rotatable to adjust the timing of the closing of a corresponding shut-off port in said rotor and a second sleeve member which is rotatable to adjust the timing of the opening of a corresponding shut-off port in said rotor, to thereby control the injection period of said pump means, said system further comprising means for coupling said first and second sleeve members to said first and second actuators, respectively, and said actuators being secured to said support means which rotates with said annular cam.

4. A distributor type fuel injection pump system as claimed in claim 1 wherein said oil servo-motor of said injection timing means comprises an oil pressure-operated power piston located within a chamber defined by a housing for the motor, said pilot valve being located within said piston coaxially therewith and being coupled through said link member to one of said actuators, said power piston defining an oil passage therein for communication with a passage on the suction side of said pump means and said chamber and being hydraulically displaced responsive to the displacement of said pilot valve by said one actuator to adjust the injection timing, said rotor including a plurality of peripheral passages forming part of a fuel feed passage for the oil servo-motor, said rotor passages being arranged to open said fuel feed passage in synchronism with the pumping operation when fuel oil is sucked into said pumping section and to close said fuel feed passage at the time of fuel injection so as to close off said fuel feed passage to the oil servo motor.

5. A distributor type fuel injection pump system as claimed in claim 3 wherein said first actuator is arranged coaxially with said power piston of said oil servo-motor so that the actuating force produced by said first actuator is transmitted directly to said pilot valve, a link rod being connected to said second actuator and cooperating with a first spring to cause rotation of said second sleeve member responsive to the actuating force produced by said second actuator, said spring acting on said link rod through a lever pivotably mounted on a pivot affixed to, and rotatable with, said annular cam, said pump system further comprising detector means for detecting the magnitude of displacement of said link rod and for transmitting a feedback signal in accordance therewith to said electrical control circuit, said detector means and said spring being affixed to the support means for said actuators.

6. A distributor type fuel injection pump system as claimed in claim 3 wherein said means for coupling said first sleeve member to said first actuator and said second sleeve member to said second actuator each comprises a link rod connected to a corresponding said actuator and including a rack portion, a pinion for engaging a rack portion and rotatable responsive to the movement thereof, a cam mounted on said pinion, and spring means for urging the cam face of said cam into engagement with the corresponding said sleeve member, said system further comprising detector means for sensing the movement of the link rods of said coupling means and for transmitting feedback signals to said control circuit in accordance therewith, and a lever having one end thereof coupled to the link rod of one of said coupling means and having the other end thereof coupled to the link rod of the other said coupling means, pivot means for pivotably mounting said lever secured to and rotatable with, said annular cam, said lever being in engagement with a linkage member connected to the pilot valve of the oil servo-motor so that the pilot valve is actuated in response to rotation of said sleeve members through the corresponding link rods thereof.

7. A distributor-type fuel injection pump system according to claim 1 further comprising a plurality of monostable circuits differing in output gradient and level and connected in parallel to receive trigger pulses associated with the running speed of the engine, and a synthesizing circuit for combining the outputs of said monostable circuits into an input for controlling a fuel adjusting member.

8. A distributor-type fuel injection pump system according to claim 1 wherein said control circuit for injection timer, comprises: first monostable circuit receiving trigger pulses associated with the running speed of the engine; second monostable circuit receiving the output of first monostable circuit; third monostable circuit receiving the output of second monostable circuit; first pulse synthesizing circuit which detects the duration of overlap between the output pulse from first monostable circuit and the other output pulse from third monostable circuit; second pulse synthesizing circuit which produces a pulse output synchronized to the output of first pulse synthesizing circuit and varying in pulse width relative to the displacement of a fuel adjusting member and also the output of first pulse synthesizing circuit; said output of second pulse synthesizing circuit being connected to an operating member actuating said pilot valve.