EP0159835B1

EP0159835B1 - Method and system for controlling an engine

Info

Publication number: EP0159835B1
Application number: EP85302273A
Authority: EP
Inventors: Katsuyuki No. 6 Higashi-Hieijo-Cho Sasaki; Satoshi Sakaguchi; Yoshihiro Nagata
Original assignee: Komatsu Ltd
Current assignee: Komatsu Ltd
Priority date: 1984-03-30
Filing date: 1985-04-01
Publication date: 1987-06-10
Also published as: DE3560243D1; EP0159835A1

Description

This invention relates to methods and apparatus for controlling an engine. More particularly, the invention is concerned with the control of the engine of a construction vehicle having one or more hydraulically actuated work implements and respective operating levers therefor.
Construction vehicles such as power shovels etc. are operated for excavation and earth moving etc. with their engines running at full speed. Between any two excavating and earth moving operations, there may be intervals such as time waiting for dump trucks. During such intervals, it would be desirable for the engine to idle in order to avoid unnecessary noise and practice fuel economy. However, it is troublesome for operators to shift the fuel control lever to its idling position each time there is an interval between work operations.
In construction vehicles such as power shovels etc. when the rate of revolution of the engine has been set by means of a fuel control lever, the engine continues to run at the same rate of revolution even when excavating and earth moving operations are suspended thereby generating noise and increasing fuel consumption.
In an attempt to mitigate or overcome the abovementioned disadvantages, we have proposed an engine control system for a construction vehicle such as a shovel loader etc. in Japanese Utility Model Provisional Publication No. 58-156138, which system is arranged such that pressurized fluid is supplied into a running control circuit and an implement control circuit by at least two hydraulic pumps driven by the engine, and the rate of revolution of the engine is set by means of a governor control lever adapted to be operated by a fuel control lever, the governor control lever being provided with a hydraulic cylinder adapted to hold the governor control lever at its idling position (that is: low speed running position) when the hydraulic pump is under no load condition and to move the governor control lever to its full speed running position as the load on the hydraulic pump increases.
This engine control system utilizes the fluid pressure delivered by the hydraulic pump in the working circuit to urge the governor control lever in the direction of full speed rotation. We have found in practice that the system suffers from the difficulty that these changes in hydraulic pressure, which may occur for a number of reasons, may affect the rotational speed of the engine in an undesired fashion. For example, when an implement is lowered, its dead weight aids lowering, so reducing the rise in fluid pressure. This is true also in the case of turning of a turning unit of a vehicle where its own inertia has an influence. In these cases, fluid pressure urging the governor control lever in the direction of full speed rotation will drop thus causing a movement of the lever towards its idling position by the resilient force of a spring thereby reducing the rate of revolution of the engine. Since the fluid pressure urging the governor control lever in the direction of full speed rotation becomes unavailable when all the operating levers are shifted to their neutral positions, the rate of revolution of the engine will drop immediately thus causing a time lag in operation when excavation and earth moving operations are made successively, a deterioration in operating performance and repeated increase in the rate of revolutions of the engine thereby generating noise.
According to a first aspect of the present invention, there is provided a method for controlling the engine of a construction vehicle having one or more hydraulically actuated work implements and respective operating levers therefor, and a decelerator system, characterised in that said decelerator system is automatically actuated for a few seconds after all said operating levers have been returned to their respective neutral positions, said decelerator system thereby allowing the rate of revolution of the engine to be reduced from the full speed condition to an idling condition.
In a second and alternative aspect of this invention, we provide a method for controlling the engine of a construction vehicle having one or more hydraulically actuated work implements and respective operating ievers therefor and a decelerator system, characterised in that said decelerator system is automatically temporarily actuated immediately after all said operating levers have been returned to their respective neutral positions, said decelerator system thereby causing the rate of revolution of the engine to be reduced by a small extent, said engine is then allowed to run under such reduced revolution condition for a predetermined period, and said decelerator system is then automatically actuated again to reduce the rate of revolution of the engine to an idling speed condition.
According to a third and further alternative aspect of the present invention, there is provided apparatus for controlling the engine of a construction vehicle having one or more hydraulically actuated work implements and respective operating levers therefor; the apparatus comprising a mechanism adapted for mechanically transmitting a manipulated variable produced by a fuel control lever through the intermediary of a loose spring to a governor for the engine and an hydraulic actuator coupled to said mechanism between the loose spring and the governor and adapted when actuated to return the governor from its full speed to its idling position; said apparatus being characterised by means adapted to detect the condition in which all said operating levers are in their inoperative conditions, and timer means responsive to said detection means for actuating said hydraulic actuator when the said condition has been detected continuously for more than a predetermined period of time.
In a fourth and yet further aspect of the present invention, there is provided apparatus for controlling the engine of a construction vehicle having one or more hydraulically actuated work implements and respective operating levers therefor; the apparatus comprising a mechanism adapted for mechanically transmitting a manipulated variable produced by a fuel control lever through the intermediary of a loose spring to a governor for the engine, and a hydraulic actuator coupled to said mechanism between the loose spring and the governor and adapted when actuated to return the governor from its full speed to its idling position; said apparatus being characterised by means adapted to detect the condition in which each said operating of lever is at its neutral position; and timer means including a first timer responsive to said detection means and adapted immediately upon such detection temporarily to actuate said hydraulic actuator and a second timer adapted to actuate said hydraulic actuator again a predetermined time after the first timer.
In the arrangements described hereinbelow, an hydraulic pump is exclusively used for decelerator control of the governor without having to use fluid under pressure delivered from the hydraulic pumps for the work implements. By this means the governor control is immune to pressure fluctuations in the work implement hydraulic circuits during working for reasons such as those mentioned above. The fluid delivered from the governor hydraulic pump control is itself controlled by means of a solenoid control valve which extends and contracts the decelerator cylinder piston rod. The solenoid control valve is changed over in electrical response to the positions of the implement operating levers.
The arrangement may employ a single timer such that the governor control lever is held at its full speed running position for a few seconds (typically for about 4 seconds) after all operating levers have been returned to their neutral positions, then automatically moving to its idling position. In an alternative arrangement, the timer control is in two stages so that the governor control lever is moved towards its idling position immediately after all operating levers have been returned to their neutral positions, thus causing an initial small reduction in the rate of revolution of the engine, the governor control lever being again moved to its idling position thereafter to enable a further substantial reduction in the rate of revolution of the engine. The vehicle suitably has operating levers comprising both implement operating levers and running operation levers. In the described arrangement, the implement operating levers serve to actuate proportional pilot control valves which control the fluid pressure supplied by variable displacement pumps driven by the engine into implement operating hydraulic actuators. Detection of the condition in which all the implement operating levers are in their inoperative condition is made by means of a pressure switch which detects the pressure of the fluid discharged through the proportional pilot control valves.
In the arrangements described, the hydraulic actuator comprises a decelerator cylinder which is fixedly secured in the vehicle and has a pressure chamber therein and, on the head side thereof, a piston rod which is coupled through a yoke having an elongate hole formed therein to the transmission mechanism for the governor. A solenoid valve responds to the detection signal received from the timer indicating that all the control levers are in their inoperative condition and supplies fluid under pressure delivered by an hydraulic pump into the pressure chamber of the decelerator cylinder. It is this hydraulic pump which, as mentioned above, is independent from the implement operating hydraulic pumps. The arrangement is such that when the hydraulic actuator is under inoperative condition, movement of the mechanism caused by a fuel control lever is absorbed by the elongate hole of the yoke so that the hydraulic actuator has no influence upon the operation of the fuel control lever, while, on the other hand, when the hydraulic actuator is under operating condition, movement of the governor transmission mechanism is restricted by one end of the elongate hole of the yoke.
The invention is hereinafter more particularly described by way of example only with reference to the accompanying drawings, in which:- -

Fig. 1 is a schematic diagram illustrating a first embodiment of apparatus in accordance with the present invention for controlling an engine of a construction vehicle or the like;
Fig. 2 is a circuit diagram illustrating one embodiment of timer circuit useful in the arrangement of Fig. 1;
Fig. 3 and Fig. 4 illustrate schematically how the system works in operation;
Fig. 5 is a simplified graphical diagram illustrating how the rate of revolution of the engine varies with time through operation of the apparatus of Figs. 1 to 4;
Fig. 6 is a diagrammatic time chart for operation of a solenoid control valve in the embodiment of Fig. 1;
Fig. 7 is a schematic diagram illustrating a second embodiment of apparatus in accordance with the present invention for controlling the engine of a construction vehicle or the like; and
Fig. 8 is a flow chart for the operation of the system illustrated in Fig. 7.

Referring first to Figs. 1 to 6, in the apparatus illustrated in Figs. 1 to 4, there is shown an engine 1 having a governor 2 and a control lever 3 for controlling the governor. The arrangement is such that when the control lever 3 occupies a stop position I, an idling position II and a full speed position III, respectively, the engine 1 is respectively stopped, run idly and run at full speed. The control lever 3 is connected through a loose spring means 4, a link 5 and a rod 6 to a manual fuel control lever 7. A piston rod 10 of a decelerator cylinder 9 is connected through a yoke 8 having an elongate hole formed therein to the intermediate portion of the control lever 3. When the fluid under pressure is supplied into a pressure chamber 11 formed in the bottom side of the decelerator cylinder 9, the piston rod 10 is moved to the right in the drawing against the biasing force of a spring 15 to move the above- mentioned control lever 3 from the full speed position to the idling position or decelerating position.
The pressure chamber 11 defined in the bottom of the above-mentioned decelerator cylinder 9 is connected through a solenoid valve 12 with a hydraulic pump 13 used exclusively for controlling the decelerator. The solenoid valve 12 has an "off" (neutral) position 12a, "decelerating" position 12b and "drain" position 12c. The solenoid valve 12 is normally biased to "off" position 12a, and is changed over to "decelerating" position 12b or "draining" position 12c by selectively energizing a first solenoid 14a or a second solenoid 14b. Both the above-mentioned solenoids 14a and 14b are connected through a timer circuit 16 with a power supply 17. This timer circuit 16 is arranged as shown in Fig. 2, and comprises a normally open switch 18 interconnected between the first solenoid 14a and the power supply 17, a normally closed switch 19 interconnected between the second solenoid 14b and the power supply 17, an induction coil 20 for the normally open switch 18, an induction coil 21 for the normally closed switch 19, and a first timer 22 and a second timer 23 which are interconnected between the induction coil 20 of the normally open switch 18 and the input side thereof. The input side of the timer circuit 16 is connected through an auto-decelerating switch 24, the left and right running limit switches 25 and 26, and a pressure switch 27 with the power supply 17.
The above-mentioned running limit switches 25 and 26 are adapted to be rendered on and off by means of the left and right running operating levers 28 and 29, respectively. In brief, the limit switches 25 and 26 are turned off when the levers 28 and 29 are manipulated.
Reference numerals 30 and 31 denote proportional pilot control valves (PPC valves). Both the proportional pilot control valves 30, 31 are connected with the above-mentioned hydraulic pump 13 for controlling the decelerator. When implement operating levers 30a, 30b and 31a, 31 b of the PPC valves 30 and 31 are operated, the control fluid pressure supplied into actuators for implements, for example, directional control valves (not shown) installed in a hydraulic circuit for the boom cylinder, the arm cylinder, the bucket cylinder and the turning motor, etc., is controlled to thereby control or change over the directional control valves. The circuits of the proportional pilot control valves 30 and 31 are connected through a shuttle valve 32 with the pressure switch 27. When the proportional pilot control valves 30 and 31 are actuated by operating the levers 30a, 30b, 31 a and 31 b, the pressure switch 27 is rendered off.
Of the above-mentioned first and second timers 22 and 23, the first timer 22 is rendered on immediately after the input side of the timer circuit 16 has received an input, thereby holding the "ON" condition for an extremely short time, for example, about one second, and then rendered off. Whilst, the second timer 23 is adapted to be rendered on a predetermined time, for example, about four seconds after the timer circuit 16 has received an input. This second timer 23 is rendered off when the input to the timer circuit 16 is cut off by manipulating the operating lever for running or the operating lever for implement.
Since the manipulated variable produced by the fuel control lever 7 is transmitted to the governor 2 of the engine 1 through a rod-link assembly comprised of the rods 6 and 5, the cylinder 4 including the loose spring 4a, and the rod 3, the number of revolutions of the engine 1 is controlled in accordance with the amount of fuel injected in response to the position of the governor 2. The stop position I of the fuel control lever 7 corresponds to the position where no fuel is supplied by the governor 2. Further, the positions II and III of the fuel control lever 7 correspond to the engine idling position and the engine full speed running position, respectively.
The operation of the above-mentioned arrangement will be described below.
The engine 1 of the construction vehicle is normally run at its full speed so as to develop its maximum output. In brief, the fuel control lever 7 is normally set at a full speed running position as shown in Fig. 3. At that time, the movement of the control lever 3 of the governor 2 is not subject to any mechanical interference by the decelerator cylinder 9 because of the presence of the elongated hole 8a of the yoke 8.
If, with the auto-decelerator switch 24 being turned on, for example, all the operating levers are not manipulated and held at their neutral positions for a predetermined time, the timer circuit 16 will detect this condition and turn the solenoid valve 12 on thereby supplying fluid under pressure through the solenoid valve 12 into the decelerator cylinder 9, In consequence, the piston rod 10 within the decelerator cylinder 9 is extended as shown in Fig. 4 to engage one end 8a of the elongated hole of the yoke 8 with a pin 3a of the rod 3 and push the rod 3 back in the direction shown by arrow A.
As a result, the governor 2 is moved to the auto-decelerating position so that the number of revolutions of the engine 1 may be automatically reduced to a rotating speed lower than the full speed. Further, the movement of the rod 3 at that time is absorbed by the cylinder 4 having the loose spring 4a so as not to allow actuation of the rods 6 and 5 and the fuel control lever 7.
The operation of the auto-decelerator system of the present arrangement shown in Fig. 4 will be described below in more detail.
When all the operating levers are located at their neutral positions, the left and right running limit switches 25 and 26 and the pressure switch 27 will be turned on so that the timer circuit 16 will receive an input. Under this condition, the normally closed switch 19 is turned on and the first timer 22 is rendered on immediately for a short period, and as a result, the normally open switch 18 is rendered on for a short time, and then rendered off. When a predetermined time has passed after the timer circuit 16 has received an input, the second timer 23 is actuated thereby turning the normally open switch 18 on.
By the above-mentioned operation, when all the operating levers are located at neutral positions, the solenoid control valve 12 is moved momentarily to "decelerating" position 12b and then returned to "off" position 12a, and after that moved again to "decelerating" position 12b. Therefore, the decelerator cylinder 9 will move, stop and then move. The control lever will follow the operation of the decelerating cylinder 9 so that the number of revolutions of the engine 1 is reduced slightly in the initial phase, and then reduced to a large extent as shown by solid line in Fig. 5; that is, the number of revolutions of the engine is reduced in two stages. The dotted line in Fig. 5 shows changes in the number of revolutions of the engine provided with the prior auto-decelerator system of our Japanese Utility Model 58-156138.
The operation time chart of the solenoid control valve 12 under the above-mentioned condition is as shown in Fig. 6.
If at least one of the implement operating levers is manipulated during this decelerating condition, the input to the timer circuit 16 is rendered off, and as a result, the second timer 23 is turned off, and at the same time, the normally closed switch 19 is turned on. Consequently, the solenoid control valve 12 will occupy its drain position 12c to release the decelerating operation so that the engine 1 may be returned to the full speed running condition set by the fuel control lever 7.
If, with all the operating levers located at their neutral positions, one of the levers is shifted to its neutral position so as to interrupt the excavating or earth moving operation, and then the operation is resumed, the above-mentioned first stage deceleration is obtained. However, the reduction in the rate of revolutions of the engine at that time is extremely small. Therefore, the change in the noise generated by the engine is comparatively small as compared with that generated when the engine is changed over to the idle running condition so that the operator does not have the unpleasantness, and the engine does not suffer the adverse effects which may result from repeated substantial changes in the rate of revolutions of the engine.
A second embodiment of apparatus for controlling the rate of revolution of the engine according to the present invention will now be described with reference to Fig. 7.
Component parts shown in Fig. 7 and indicated by the same reference numerals as those used for the component parts in Fig. 1 fulfill the same or similar functions as those elements shown in the first embodiment. Therefore, detailed description of them is omitted herein to avoid duplication of explanation.
A first difference of the embodiment shown in Fig. 7 from that shown in Fig. 1 resides in that the fuel control lever 7 is provided with a potentiometer 7a which is adapted to detect the manipulated position of the lever 7 and input a detection signal to the timer circuit 16. In brief, the function of the potentiometer 7a is to detect whether or not the manipulated position of the fuel control lever 7 corresponds to a position which meets the number of revolutions of more than that required to actuate the auto-decelerator system, for example, more than 1,400 r.p.m. However, the detection of the number of revolutions of the engine is not limited to the use of the potentio- . meter 7a fitted to the fuel control lever 7, and instead the engine may be provided with a detector capable of reading out directly the number of revolutions of the engine and transmitting a detection signal to the timer circuit 16.
A second difference lies in that the construction of the solenoid valve 12 is simplified. Stating in brief, in this second embodiment, the solenoid valve 12 has two positions only, i.e., "decelerating" position 12b and "draining" position 12c, and "off" (neutral) position is omitted. Therefore, a solenoid is provided only on the side of the decelerating position. The solenoid valve 12 is normally urged by the force of a spring to the draining position.
In connection with the second difference, a third difference of the second embodiment from the first embodiment resides in that only one timer is provided in the timer circuit. However, if it is desired, as in the case of the first embodiment, to reduce the number of revolutions of the engine in two stages, it can be achieved by providing two timers in the timer circuit 16 and using solenoid valve 12 having the construction shown in Fig. 1.
Next, the operation of the embodiment shown in Fig. 7 will be described below.
In the case where the fuel control lever 7 is located at a position indicating a number of revolutions of more than that at the time of auto- deceleration (for example, the full speed running position), it is detected whether or not the circuit (detection circuit) including the aforementioned auto-decelerating switch 24, the running limit switches 25 and 26, and the pressure switch 27 connected in series is closed.
If the above-mentioned detection circuit is closed, the construction vehicle does not effect any operation, and so the timer provided in the timer circuit 16 is actuated. This timer serves to measure the time for which the above-mentioned detection circuit is closed. If the closed circuit condition continues for a predetermined time, for example, four seconds, the timer will transmit a signal which turns the solenoid valve 12 on.
As aforementioned, when the solenoid valve 12 is turned on, the decelerator cylinder 9 is actuated so that the number of revolutions of the engine 1 will be reduced to a level corresponding to the auto-decelerating position of the governor 2.
Further, the timer is reset when the detection circuit is closed. Therefore, if for example the implement operating levers are manipulated when the auto-decelerator system is actuated to reduce the number of revolutions of the engine, the above-mentioned detector circuit is opened so that the solenoid valve 12 may assume draining position 12c. In consequence, the spring 15 mounted within the decelerator cylinder 9 will push the piston rod 10 back to thereby allow the fluid under pressure within the cylinder 9 to flow into drain sump 33. At the same time, a loose spring 4a in the cylinder 4 which has been compressed will extend thereby allowing the rod 3 of the governor 2 to return to the full speed running position as shown in Fig. 3. The above- mentioned operation is shown schematically in the form of a flow chart in Fig. 8.
Further, in this embodiment, while the inoperative condition of the implement operating levers is detected by the pressure switch 27, each of the implement operating levers may be provided with a limit switch to detect the neutral position of each of the levers so that inoperative condition will occur when all the limit switches detect the neutral positions of respective levers at the same time.
When all the operating levers occupy their neutral positions, the rate of revolution of the engine will be at a rate reduced as compared with the full speed running condition, and therefore a reduction in fuel consumption and noise level can be achieved as compared with the prior systems. As soon as all the operating levers are put into their neutral positions, the engine moves to a first stage deceleration condition, and in a predetermined time it moves to a second stage deceleration condition. The first stage deceleration may serve to draw the attention of an operator to the fact that the engine is being decelerated, and if wished, the operator may then manipulate the levers accordingly.
Two systems operate in parallel. First there is the system of controlling the governor by means of the fuel control lever; and then there is the system of automatically controlling the governor by means of the controller. Therefore, even when a failure occurs in the electrical system, the number of revolutions of the engine can still be controlled. The arrangement is such that no mutual interference occurs between the two control systems.

Claims

1. A method for controlling the engine of a construction vehicle having one or more hydraulically actuated work implements and respective operating levers therefor, and a decelerator system, characterised in that said decelerator system is automatically actuated for a few seconds after all said operating levers have been returned to their respective neutral positions, said decelerator system thereby allowing the rate of revolution of the engine to be reduced from the full speed condition to an idling condition.

2. A method for controlling the engine of a construction vehicle having one or more hydraulically actuated work implements and respective operating levers therefor and a decelerator system, characterised in that said decelerator system is automatically temporarily actuated immediately after all said operating levers have been returned to their respective neutral positions, said decelerator system thereby causing the rate of revolution of the engine to be reduced by a small extent, said engine is then allowed to run under such reduced revolution condition for a predetermined period, and said decelerator system is then automatically actuated again to reduce the rate of revolution of the engine to an idling speed condition.

3. Apparatus for controlling the engine (1) of a construction vehicle having one or more hydraulically actuated work implements and respective operating levers therefor; the apparatus comprising a mechanism (3-6) adapted for mechanically transmitting a manipulated variable produced by a fuel control lever (7) through the intermediary of a loose spring (4) to a governor (2) for the engine (1) and an hydraulic actuator (8-11) coupled to said mechanism (3-6) between the loose spring (4) and the governor (2) and adapted when actuated to return the governor from its full speed to its idling position; said apparatus being characterised by means (24-27) adapted to detect the condition in which all said operating levers are in their inoperative conditions, and timer means (16) responsive to said detection means (24-27) for actuating said hydraulic actuator (8-11) when the said condition has been detected continuously for more than a predetermined period of time.

4. Apparatus for controlling the engine (1) of a construction vehicle having one or more hydraulically actuated work implements and respective operating levers therefor; the apparatus comprising a mechanism (3-6) adapted for mechanically transmitting a manipulated variable produced by a fuel control lever (7) through the intermediary of a loose spring (4) to a governor (2) for the engine (1), and a hydraulic actuator (8-11) coupled to said mechanism (3-6) between the loose spring (4) and the governor (2) and adapted when actuated to return the governor (2) from its full speed to its idling position; said apparatus being characterised by means (24-27) adapted to detect the condition in which each said operating levers is at its neutral position; and timer means (16) including a first timer (22) responsive to said detection means (24-27) and adapted immediately upon such detection temporarily to actuate said hydraulic actuator (8-11) and a second timer (23) adapted to actuate said hydraulic actuator (8-11) again a predetermined time after the first timer.

5. Apparatus according to Claims 3 or 4, wherein said operating levers comprise implement operating levers (30a, 30b, 31 a, 31b) and running operation levers (25, 26), said apparatus being further characterised in that said implement operating levers (30a, 30b, 31 a, 31 b) serve to actuate proportional pilot control valves (30, 31) adapted to control the fluid pressure supplied by variable displacement pumps driven by the engine into implement operating hydraulic actuators, and in that detection of the inoperative condition of the implement operating levers (30a, 30b, 31 a, 31 b) is made by means of a pressure switch (27) adapted to detect the pressure of the fluid discharged through the proportional pilot control valves (30,31).

6. Apparatus according to any of Claims 3, 4 or 5, further characterised in that said hydraulic actuator (8-11) comprises: a decelerator cylinder (9) fixedly secured in the vehicle and having a pressure chamber (11) therein and, on the head side thereof, a piston rod (10) coupled through a yoke (8) having an elongate hole formed therein to said mechanism (3-6); and a solenoid valve (12) adapted in response to a detection signal received from the timer means (16) to supply fluid under pressure delivered by an hydraulic pump (13), which is arranged to be driven by the engine (1) but which is independent from the implement operating hydraulic pump, into the pressure chamber (11) of said decelerator cylinder (9).

7. Apparatus according to Claim 6, further characterised in that said piston rod (10) is coupled to said mechanism (3-6) such that, when said hydraulic actuator (8-11) is under inoperative condition, the movement of said mechanism (3―6) caused by said fuel control lever (7) is absorbed by the elongate hole of said yoke (8) so that said hydraulic actuator (8-11) has no influence upon the operation of the fuel control lever (7), whilst, when the hydraulic actuator (8-11) is under operating condition, the movement of said mechanism (3―6) is restricted by one end of the elongate hole of said yoke (8).