JP2002188482A - Control device for engine rotation speed - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device for an engine rotation speed by which the rotation speed can be held maintained accurately in an idling engine rotation speed. SOLUTION: This control device holds the engine rotation speed in the idling speed, by restraining the lowering thereof in an engine (14) with the increase in the load of hydraulic actuators (5, 6) driven by an oil being discharged from the hydraulic pumps (40, 41) using the engine (14) as a power source, by adjusting the fuel amount supplied to the engine (14). In this case, a throttle (43) is installed on the discharge circuit (45) of the hydraulic pump (40), and further, there is provided a hydraulic actuator (52), which actuates according to the differential pressure between the regions, before and after the throttle (43) and controls a throttle lever (27a) for adjusting the fuel supply amount, when the differential pressure is lower than a prescribed value, to accelerate the engine rotation speed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an engine speed control device.

[0002]

2. Description of the Related Art As shown in FIG. 2, a general forklift 1 is provided with a mast 2 at the front of a body frame 11 so as to be tiltable in the front-rear direction. Is installed. The mast 2 is tilted and the fork 4 is moved up and down by a tilt cylinder 6 and a lift cylinder 5, respectively, and can be driven by operating a tilt lever 8 and a lift lever 7 provided at a front portion of the body frame 11. Further, the rotation speed of the engine 14 is controlled in accordance with the operation amount of the accelerator pedal 13 provided at the front of the driver's seat floor, and the pressure oil discharged from a hydraulic pump (not shown) driven by the power of the engine 14 is generated. It is supplied to the tilt cylinder 6 and the lift cylinder 5.

In the conventional forklift 1 as described above, when the operator releases the foot from the accelerator pedal 13, that is, operates the lift lever 7 or the tilt lever 8 when the engine 14 is idling, the lift cylinder 5 or the lift cylinder 5 is operated. The load of the tilt cylinder 6 is the engine 1
4, the engine rotation is lower than the idling rotation speed, and there is a problem that engine stalls easily.

Therefore, an idling-up device (so-called first idle control device) for preventing engine stall as shown in FIG. 3 is used. Hereinafter, the device will be described. The operation amount of the accelerator pedal 13 is controlled by the accelerator cable 2 via the swingable lever 22.
3 is transmitted to one end of the wire 23a. The other end of the wire 23a is attached to a lever 27a that opens and closes a throttle valve 27 provided in a manifold 26 that is a mixture passage of the engine 14. In addition, both ends of the cover 23b of the accelerator cable 23 are metal fittings 55,
At 56, it is fixed to the body frame 11 and the case of the engine 14. A hole 28 is provided in the manifold 26 between the combustion chamber 25 and the throttle valve 27.
And the diaphragm 30 are connected via a hose 29. The rod 31 is attached to the membrane 31 provided in the diaphragm 30.
2 is attached, and the distal end of the rod 32 is provided so as to protrude from the diaphragm 30.
6 is connected to a lever 33a of an idle control valve 33 provided therein. The rod 32 is urged toward the projecting side by a spring 34. A carburetor 3 for supplying an air-fuel mixture is provided upstream of the idle control valve 33 and the throttle valve 27.
5 are provided.

When the accelerator pedal 13 is not operated (hereinafter, this state is referred to as idling), the engine speed is maintained at the idling rotational speed. At this time, the flow rate of the air-fuel mixture in the manifold 26 is large to some extent and the intake pressure Pv is equal to or less than a predetermined value.
The negative pressure of v pulls the membrane 31 of the diaphragm 30 to the position shown by the dotted line in FIG.
pull. As a result, the opening of the idle control valve 33 is half-open, and the amount of air-fuel mixture according to the opening of the throttle valve 27 flows into the combustion chamber 25.

When the lift lever 7 or the tilt lever 8 is operated during idling in such a state, the load of the lift cylinder 5 or the tilt cylinder 6 is applied to the engine 14, so that the engine rotation is slightly lower than the idling rotation speed. I do. Then, since the suction speed of the air-fuel mixture into the combustion chamber 25 decreases, the intake pressure Pv rises above the value at the idling rotation speed and approaches the atmospheric pressure. For this reason, the urging force of the spring 34 is larger than the force due to the negative pressure of the intake pressure Pv, and the membrane 31 of the diaphragm 30 moves to the position shown by the solid line, and the idle control valve 33 is larger than the half open as shown by the solid line. The opening degree. As a result, the amount of air-fuel mixture flowing into the combustion chamber 25 increases, so that the engine speed increases,
Recovers to idling speed.

[0007]

However, the above-mentioned prior art has the following problems. If the load pressure on the lift cylinder 5 or the tilt cylinder 6 increases when the engine 14 is idling, a load is next applied to the engine 14 and the engine rotation speed decreases. When the engine rotation speed decreases, the inflow speed of the air-fuel mixture into the combustion chamber 25 decreases, and the intake pressure Pv increases. When the intake pressure Pv increases, the film 31 of the diaphragm 30 deforms due to the next change in compressible air pressure, and the idle control valve 3
3 is changed. Since the idle control valve 33 is controlled based on the intake pressure Pv changed through many steps in this order and on the basis of a change in compressible air pressure, the responsiveness of the control of the idle control valve 33 is improved. slow. For this reason, the engine rotation speed cannot be recovered in time and the idling rotation speed cannot be maintained. There is also a problem that the engine rotational speed is easily hunted due to the delay of the response even when the engine does not stall.

The present invention has been made in view of the above problems, and has as its object to provide an engine rotation speed control device capable of accurately maintaining an idling rotation speed.

[0009]

To achieve the above object, a first invention according to the present invention is a work machine actuator driven by oil discharged from a hydraulic pump powered by an engine. In the engine speed control device that suppresses the decrease in the engine idle speed due to the increase in the load by adjusting the amount of fuel supplied to the engine and maintains the engine speed at the idle speed, restrict the throttle circuit to the discharge circuit of the hydraulic pump. A hydraulic actuator that operates according to a differential pressure before and after the throttle and that controls a throttle lever that adjusts a fuel supply amount to increase an engine rotational speed when the differential pressure is smaller than a predetermined value. It has a configuration.

According to the first invention, the differential pressure before and after the throttle is:
Since the flow rate passing through the throttle, that is, the value corresponding to the engine speed, becomes equal to the differential pressure when the pressure difference becomes smaller than a predetermined value, that is, when the engine speed becomes lower than the idling speed. The hydraulic actuator controls the throttle lever to increase the amount of supplied fuel and maintain the idling rotational speed. Therefore, since this hydraulic actuator is operated by the throttle differential pressure that shows a decrease in the engine rotation speed with a high response with an increase in the load pressure,
The amount of fuel supplied can be increased quickly, and the engine speed can be restored to the idling speed with good responsiveness and maintained. As a result, the engine will not stall even during idling, and no hunting of engine rotation will occur.
A highly efficient forklift without work interruption can be realized.

A second invention is based on the first invention, wherein the throttle divides the discharge oil of the hydraulic pump into a steering control valve for controlling a steering cylinder and a working machine valve for controlling a working machine actuator. Priority control that is interposed in a circuit that connects between the priority control valve and the priority control valve that supplies priority to the steering control valve, and that applies differential pressure before and after the priority control valve to the left and right pressure receiving chambers of the priority valve The configuration is a circuit diaphragm.

According to the second aspect of the present invention, since the aperture for the steering priority circuit is also used and used as the aperture of the first invention for controlling the idling rotational speed, there is no need to newly provide an aperture. The configuration is simple and can be configured at low cost.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.
This will be described with reference to FIG. Note that the same components as those in FIGS. FIG. 1 is a configuration diagram of an engine speed control device according to the present invention. It has a mechanism section 61 and a hydraulic circuit 60.

First, the mechanism 61 will be described. A stopper 65 is provided in the double rod type cylinder 52 provided with oil chambers 62 and 63 as a hydraulic actuator, at a moving end of a piston 64 to the right in the drawing.
1 is interpolated. The spring 51 urges the piston 64 leftward in the drawing, that is, in a direction to pull one end of the wire 23a in the engine rotation speed increasing direction. The biasing force F of the spring 51
b is set so that the piston 64 abuts the stopper 65 when the longitudinal pressures P1 and P2 of the throttle 43 act on the oil chamber 62 and the oil chamber 63 of the cylinder 52 when the engine 14 is at or above the idling rotational speed. ing. A wire drive lever 53 is attached to one end of the wire 23a of the accelerator cable 23, and a side surface of the wire drive lever 53 is brought into contact with an axial end of a rod 66 protruding from the oil chamber 62 of the cylinder 52 at idle. It has become. As in FIG. 3, the operation amount of the accelerator pedal 13 is transmitted to one end of the wire 23a via the lever 22, and the other end of the wire 23a sets the opening of the throttle valve 27 as fuel supply means. Throttle lever 2
7a.

Next, the configuration and operation of the hydraulic circuit 60 will be described. The hydraulic circuit 60 shown in the present embodiment is mounted as a normal hydraulic circuit of the forklift 1, but is not limited to this. Engine 14
The pressure oil from the steering pump 40 driven by the control valve flows into the steering control valve 47 via the priority valve 42. The oil controlled by the steering control valve 47 expands and contracts the steering cylinder 48, and the expansion and contraction controls the steering angle of the steered wheels. On the other hand, pressurized oil from the work machine pump 41 driven by the engine 14 is supplied to the lift valve 49a and the tilt valve 49b, and the lift cylinder 5 and the tilt cylinder 6 expand and contract by operating the lift lever 7 and the tilt lever 8, respectively. A throttle 43 is interposed in a circuit 45 connecting the priority valve 42 and the steering control valve 47, and a pressure P <b> 1
P2 is guided to the left pressure receiving chamber 42a and the right pressure receiving chamber 42b of the priority valve 42 in the drawing. The circuits before and after the throttle 43 are connected to an oil chamber 62 and an oil chamber 63 of the cylinder 52, respectively.

When the accelerator pedal 13 is depressed to increase the rotation speed of the engine 14, the priority valve 42
, The flow rate flowing through the circuit 45 through the entire flow position A increases, the differential pressure ΔP (= P1−P2) across the throttle 43 becomes larger than a predetermined value, and acts on the right pressure receiving chamber 42b of the priority valve 42. The pressure P1 is greater than the combined force of the pressure P2 acting on the left pressure receiving chamber 42a and the force of the spring 42c, and pushes the spool to the left, thereby switching from the full flow position A to the branch position B. Since the control of the steering cylinder 48 by the steering control valve 47 does not require a predetermined flow rate or more, the steering pump 4
0, the surplus flow rate equal to or higher than the predetermined flow rate passes through the diversion position B and passes through the check valve 44 to the working machine pump 4.
Merge into one work machine circuit 46. When the engine 14 is at a rotational speed near the idling rotational speed, the normal priority valve 42 has moved to the full flow position A, and the total discharge flow rate of the steering pump 40 has passed through the throttle 43. Thus, the pressure difference ΔP before and after the throttle 43 changes according to the flow rate passing through the throttle 43, that is, the idling rotation speed of the engine 14.

The operation and effect of this embodiment having the above configuration will be described. During idling, the total discharge flow rate of the steering pump 40 is supplied to the steering control valve 47 via the priority valve 42 and the throttle 43. Since the steering control valve 47 is not operated, the entire discharge flow rate of the steering pump 40 drains to the tank 50 through the neutral position N of the steering control valve 47. The differential pressure ΔP before and after the throttle 43 is an idling differential pressure ΔPa according to the idling rotation speed, and the retracting force Fh for retracting the rod 66 is equal to the pressure receiving area on the left and right sides of the piston 64. , And is proportional to the idling differential pressure ΔPa. On the other hand, the urging force Fb for extending the rod 66 of the spring 51 is the contraction force F
Since h is set to be smaller than h, the piston 64 is in contact with the stopper 65.

When the operator operates the lift lever 7 or the tilt lever 8 during such idling, the rotational speed of the engine 14 decreases due to the load pressure applied to the lift cylinder 5 or the tilt cylinder 6. Then, since the rotational speed of the steering pump 40 also decreases, the discharge flow rate of the steering pump 40 also decreases, and the differential pressure ΔP before and after the throttle 43 becomes a differential pressure ΔPb smaller than the differential pressure ΔPa at the idling rotational speed. The contraction force Fh at this time is smaller than at the time of idling. For this reason, since the urging force Fb of the spring 51 becomes smaller, the rod 66 of the piston 64 moves to the left in the figure, pulls the wire 23a, and
The opening of 7 becomes large, and the rotational speed of the engine 14 is increased so as to recover to the idling rotational speed.

When the operator stops the operation of the lift lever 7 or the tilt lever 8, the load pressure on the lift cylinder 5 or the tilt cylinder 6 decreases, so that the engine rotation speed increases and the discharge flow rate of the steering pump 40 also increases. Since the pressure difference increases, the pressure difference ΔP before and after the throttle 43 also increases.
Then, since the rod 66 moves rightward to the position where the piston 64 contacts the stopper 65, the tension of the wire 23a is relaxed and the opening of the throttle valve 27 is set to the opening at a predetermined idling rotational speed.

As described above, according to the present embodiment, a decrease from the idling rotational speed of the engine 14 is detected based on the differential pressure ΔP before and after the throttle 43, and the cylinder 52 is operated based on the differential pressure ΔP to operate the throttle valve 27. The idling rotation speed is adjusted by controlling the opening. Thus, the change in the idling rotational speed of the engine is detected by the oil pressure, and the opening of the throttle valve 27 is directly controlled based on the detected oil pressure. As a result, the idle rotation speed can be controlled with good responsiveness, so that the forklift 1 having excellent work efficiency without stalling and without interruption of work can be obtained.

By appropriately setting the spring constant of the spring 51 inserted in the cylinder 52, the responsiveness of the entire control system is improved, the delay time is reduced, and the control of the engine speed is controlled. Hunting can be eliminated.
Further, the throttle 43, the cylinder 52, and the accelerator cable 2
3 is simpler. In addition, the throttle according to the present invention may be provided in a circuit that flows a flow rate proportional to the rotation speed of the hydraulic pump, and is limited to the throttle 43 applied to the priority valve 42 for the steering priority circuit shown in the embodiment. However, by using the throttle 43 applied to the normally mounted priority valve 42 as it is, the circuit can be configured simply and inexpensively without generating a new pressure loss in the circuit. it can.

In the present embodiment, an example has been described in which the rotation speed is maintained at a value equal to or higher than the idling rotation speed so as not to stall. An arbitrary rotation speed may be maintained. According to this, even when a load is applied, the engine rotation speed is maintained at a predetermined value, the amount of oil can be secured, and the speed of the work machine does not decrease, so that the forklift 1 with good workability can be obtained.

In this embodiment, the cover 23b
Is fixed to the vehicle body frame 11 with a bracket 55, and the wire drive lever 5 is connected to the tip of a rod 66 of the cylinder 52.
3 controls the pushing and pulling of the wire 23a,
The driving method is not limited to this. For example, the metal fitting 55 at one end of the accelerator cable 23 may be removed, and the driving lever 53 may be attached to one end of the cover 23b. Although the operation in this case has not been theoretically determined, it is commonly used in practical use.
When a wire 23a having an outer diameter smaller than the inner diameter of the accelerator cable 23 inserted into the cover 23b is laid with a predetermined curvature, one end of the cover 23b on the accelerator pedal 13 side is, for example, a throttle lever 27a. When the wire 23a is pushed in the direction of the arrow, the curvature is further reduced, so that the wire 23a having a constant length attempts to pull one end side. At this time, the wire 23a pulls one of the two ends having a smaller pulling force (in this case, the throttle lever 27a side) in the opposite direction against this pulling force, and the throttle lever 27a is increased. Can be pulled to the fast side. The opening degree of the throttle valve 27 may be controlled using such a phenomenon.

In this embodiment, the cylinder 5
Although one end of the wire 23a near the accelerator pedal 13 is moved at the shaft end of the second rod 66, the other end of the wire 23a near the throttle valve 27 may be moved.
Further, the throttle valve 27 may be directly moved at the shaft end of the rod 66. Further, in the present embodiment, the lever 22 is configured to connect between the accelerator pedal 13 and the throttle lever 27a of the throttle valve 27.
Although the example using the and the accelerator cable 23 has been described, the expansion and contraction of the cylinder 52 can be transmitted to the throttle valve 27 even when a mechanical link is used, and the same effect can be exerted. Further, the description has been given of the example of the two-pump circuit including the hydraulic pumps 40 and 41 as the hydraulic circuit. However, the present invention is not limited to this. It is needless to say that the same operation and effect as described above can be obtained even with a single pump circuit in which the flow is divided and supplied to the control valve (such as the lift valve 49a and the tilt valve 49b).

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an engine rotation speed control device according to the present invention.

FIG. 2 is an explanatory diagram of a forklift.

FIG. 3 is an explanatory diagram of a conventional idling-up device.

[Explanation of symbols]

1 ... forklift, 2 ... mast, 4 ... fork, 5 ...
Lift cylinder, 6 tilt cylinder, 7 lift lever, 8 tilt lever, 11 body frame, 13 accelerator pedal, 14 engine, 15 spring, 22 lever, 23 accelerator cable, 23a wire, 23
b: cover, 25: combustion chamber, 26: manifold, 27
... Throttle valve, 28 ... Hole, 29 ... Hose, 30 ...
Diaphragm, 31 membrane, 32 rod, 33 idle control valve, 33a lever, 34 spring, 35 carburetor, 40 steering pump, 41 work machine pump, 42
Priority valve, 43 ... Throttle, 44 ... Check valve, 4
5 circuit, 46 working machine circuit, 47 steering control valve, 48
... Steering cylinder, 49 ... Work equipment valve, 50 ... Tank, 51
... Spring, 52 ... Cylinder, 53 ... Wire drive lever, 5
5, 56 metal fittings, 60 hydraulic circuit, 61 mechanical part, 6
2, 63 ... oil chamber, 64 ... piston, 65 ... stopper, 6
6: rod, A: pressure receiving area, Fb: urging force, Fh: retraction force, P1: front pressure, P2: rear pressure, ΔP: differential pressure, Pv: intake pressure.

Claims (2)

[Claims] 1. A hydraulic pump powered by an engine (14).
Work equipment actuator driven by oil discharged from (40)
Engine speed control that suppresses a decrease in the idle speed of the engine (14) due to an increase in the load of (5, 6) by adjusting the amount of fuel supplied to the engine (14) and maintains the idle speed. In the device, a throttle (43) is provided in a discharge circuit (45) of a hydraulic pump (40), and operates according to a differential pressure before and after the throttle (43). When the differential pressure is smaller than a predetermined value, fuel is supplied. An engine speed control device comprising a hydraulic actuator (52) for controlling a throttle lever (27a) for adjusting a supply amount to increase an engine speed. 2. A steering control valve (47) according to claim 1, wherein said throttle (43) controls a steering cylinder (48) of oil discharged from said hydraulic pump (40). And a priority valve (4) that supplies priority to the steering control valve (47) when diverting to the work equipment valve (49) that controls the work equipment actuators (5, 6).
2) and the steering control valve (47) is interposed in the circuit (45) connecting, and the differential pressure before and after that was applied to the left and right pressure receiving chambers (42a, 42b) of the priority valve (42). An engine speed control device, which is a throttle for a steering priority circuit.