JPH07189915A - Control mechanism for two-throw variable pump - Google Patents

Abstract

PURPOSE:To improve output control accuracy and energy utilizing efficiency of a two-throw variable pump. CONSTITUTION:This control mechanism is provided with levers 3A, 3B which are formed integratedly with swash plates 32A, 32B for changing a slant rotating angle, and regulator pistons 4A, 4B for driving the levers 3A, 3B according to pressure supplied to oil chambers 6A, 6B. First control valves 11A, 11B are provided to control pressure in the oil chambers 6A, 6B according to rocking of common rocker arm 7. Piston 9A, 9B are provided to have moment responding to positions of the levers 3A, 3B and discharging pressure of pump units 1A, 1B applied to the rocker arm 7. A second control valve 12A or 12B for forcibly supplying high pressure to the oil chamber 6A or 6B according to operation is provided on at least one of pump unit 1A or 1B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to tilting angle control of a dual pump used in construction machines and the like.

[0002]

2. Description of the Related Art A construction machine such as a power shovel is provided with a plurality of hydraulic pumps driven by the same engine, and the hydraulic pressure generated by each hydraulic pump is selectively used according to the application.

In this case, in order to keep the engine load constant, it is necessary to control the pump tilt angle so that the output horsepower of the pump becomes constant. That is, when the discharge pressure of the pump rises, the tilt angle is decreased to reduce the discharge amount, and when the discharge pressure decreases, the tilt angle is increased to increase the discharge amount.

However, when such tilt angle control is performed independently for each pump in a dual pump, the output of each pump is fixed, and even when one pump requires only a small output, this The surplus energy generated at the other pump cannot be used by the other pump.

Therefore, the tilt angle is controlled based on the total output of the two pumps, for example, Japanese Examined Patent Publication No. 3-7030.
In JP-A No. 2004-242242, a control mechanism is proposed in which the tilt angle control of one pump is performed based on the discharge pressure of that pump and the pressure equivalent to the output horsepower of the other pump. As a result, the tilt angle of one pump not only increases or decreases according to the increase or decrease in the discharge pressure, but also increases or decreases in accordance with the change in the output of the other pump. Can be used with the other pump.

[0006]

In the case of this control mechanism, the pressure equivalent to the output horsepower of the pump is obtained by applying a pressure proportional to the pump discharge amount to the pump discharge pressure.

However, the output horsepower of the pump is proportional to the product of the discharge pressure and the discharge amount, and when the sum of the discharge pressure and the discharge amount proportional pressure is used as the parameter of the output horsepower, it is substantially equivalent to the actual output horsepower. Error will occur. Especially, twin pumps used in construction machines such as power shovels
In general, since the load fluctuation is large, this error becomes considerably large, and even with this control mechanism, the input energy may not be effectively utilized as the pump output.

The present invention has been made to solve the above problems, and improves the accuracy of output control of a dual variable pump.
The purpose is to make effective use of input energy.

[0009]

According to the present invention, the tilt angle of each swash plate of two pump units that rotate integrally by the same power source is controlled so that the sum of the output of each pump unit becomes constant. In a control mechanism of a dual variable pump, a lever integrally formed with a swash plate that changes a tilt angle by displacement around a predetermined axis, a regulator piston that displaces the lever, and a regulator piston that corresponds to a supply pressure. A first switching means for switching the discharge pressure of the pump unit and the tank to the oil chamber according to the swing of a common swing arm swinging about a predetermined swing shaft as a fulcrum. For each pump unit, and a piston for pressing the rocking arm in the rocking direction with a pressing force corresponding to the discharge pressure of the pump unit at the pressing position determined by the displacement position of the lever. Together provided comprises at least one pump unit and the second control valve for supplying a forced pressure to the oil chamber in response to the operation.

[0010]

[Operation] The regulator piston displaces the lever according to the discharge pressure of the pump unit. As a result, the swing moment that the piston exerts on the swing arm changes. This swing moment is the sum of the product of the pushing force of the piston and the arm length from the pushing position to the swing center. The pressing force of the piston is proportional to the discharge pressure of each pump unit, and the arm length is proportional to the displacement position of the lever, that is, the discharge amount of the pump unit. Therefore, the moment acting on the swing arm is exactly proportional to the total output of the pump unit. The first control valve supplies pressure to the oil chamber of the regulator piston in response to the swing of the swing arm, thereby keeping the total output of the pump unit constant. In addition, the second control valve forcibly drives the regulator piston of one pump unit to change the tilt angle, thereby keeping the total output of the pump unit constant while controlling the output of one pump unit. Change preferentially.

[0011]

1 to 5 show an embodiment of the present invention.

In FIG. 1, pump units 1A and 1B of a double variable pump are integrally driven by an engine 20. The pump units 1A and 1B are variable displacement swash plate pumps, and are symmetrically arranged inside a body 31 integrally formed with the control mechanism as shown in FIGS.

Next, the control mechanism will be described. Since the members provided in both the pump units 1A and 1B have the same structure, only the member on the pump unit 1A side will be described.

As shown in FIG. 2, the pump unit 1A is provided with an adjusting lever 3A formed integrally with the swash plate 32A for changing the tilt angle.

By rotating these levers 3A about the central axis shown by the chain line in FIG. 2, the tilt angle of the swash plate 32A supported by the bearing 30A is changed.

As shown in FIGS. 2 and 3, the lever 3A is coupled with a regulator piston 4A arranged so as to be perpendicular to the central axis.

As shown in FIG. 3, the regulator piston 4A has a small diameter portion 42 and a large diameter portion 43 which are respectively connected to the lever 3A via connecting rods 40 and 41. The small-diameter portion 42 and the large-diameter portion 43 are coaxially arranged and housed in the opposed oil chambers 5A and 6A as shown in FIG. The regulator piston 4A is displaced according to the balance of the force produced by the product of the pressure of the oil chamber 5A and the pressure receiving area of the small diameter portion 42 and the product of the pressure of the oil chamber 6A and the pressure receiving area of the large diameter portion 43, and the lever 3A. The tilt angle of the swash plate 32A is changed through the rotation of. The oil discharged from the pump unit 1A is constantly guided to the oil chamber 5A. Further, the pressure is introduced into the oil chamber 6A via the first control valve 11A.

The first control valve 11A is switched by the swing arm 7. The swing arm 7 is swingably supported by a swing shaft 8 orthogonal to the operation direction of the regulator piston 4A. Of the constituent members of the control mechanism of the two pump units 1A and 1B, only the swing arm 7 and the swing shaft 8 are common. For convenience of explanation, the swing arm 7 is shown in two places in FIG. 1, but these are the same. The swing arm 7 has a first control valve 11A biased by a spring.
Then, the piston 9A protruding from the lever 3A abuts in the opposite direction. Regulator piston 4A for piston 9A
10A formed continuously from the inside to the lever 3A
The oil pressure in the oil chamber 5A acts via the. Similarly, the control valve 11B provided in the pump unit 1B and the piston 9B come into contact with the swing arm 7 and swing according to the balance of the moments about the swing axis produced by them.

The piston 9A has a pump unit 1A.
The passage 10A that guides the discharge pressure of the oil reaches the sliding portion of the swash plate 32A and the bearing 30A through the lever 3A, and supplies the discharge oil of the pump unit 1A for lubricating the swash plate 32A and the bearing 30A.

The first control valve 11A has a high pressure port communicating with the oil chamber 5A and a low pressure port connected to the second control valve 12A, and the oil chamber 6 depends on the swing position of the swing arm 7.
Is connected to either of these two ports to hold the oil chamber 6A in the closed state at the equilibrium position of the swing arm 7.

The second control valve 12A switches and connects the discharge pressure of the pump unit 1A and the tank to the low pressure port of the first control valve 11A according to an input signal Pi ₁ from the outside. Also, as shown in FIG. 3, the feedback spring 1 exerts a switching pressure on the second control valve 12A in the opposite direction to the input signal Pi ₁ according to the rotational position of the lever 3A.
5A contacts.

The pump unit 1B side is also provided with a control mechanism having the same structure. Pump units 1A and 1B
As shown in FIGS. 5 and 6, the swing arm 7 which is a common member is housed in the central portion of the body 31 and is symmetrically arranged on both sides thereof.

Next, the operation will be described.

During operation of the pump units 1A and 1B, the discharge pressures Pa and Pb of the pump units 1A and 1B press the swing arm 7 via the pistons 9A and 9B. Assuming that the acting area of the pressing force exerted on the swing arm 7 by the pistons 9A and 9B is a, these pressing forces are a.Pa and a.
It is represented by Pb. Further, the distances of the points of action of these pressing forces from the swing shaft 8 are La and Lb, respectively, and the supporting forces of the springs of the first control valves 11A and 11B are fa and f.
b, and the distance from the swing shaft 8 to the point of action of these supporting forces is L ₀ , the moment acting on the swing arm 7 is a · Pa × La + a · Pb × Lb = L ₀ · fa + L ₀ · fb = L ₀ · (fa + fb) = constant (1).

In FIG. 1, for example, when the discharge pressure Pa of one pump unit 1A increases, the counterclockwise moment acting on the oscillating arm 7 increases, and the valve 11
A and 11B are switched at the same time, and the discharge pressures of the pump units 1A and 1B are supplied to the oil chambers 6A and 6B.

As a result, the regulator pistons 4A and 4A
B is displaced to the left in FIG. 1 due to the difference in pressure receiving area between the oil chamber 5A (5B) and the oil chamber 6A (6B). As a result, the levers 3A and 3B rotate in the direction of decreasing the tilt angle of the pump units 1A and 1B, and the discharge amounts of the pumps 1A and 1B decrease.

On the other hand, when the moment acting on the swing arm 7 is reduced by the displacement of the regulator pistons 4A and 4B, the first control valves 11A and 11B are switched to the neutral position again, and the hydraulic pressure to the oil chambers 6A and 6B is changed. Supply stops.

Thus, the regulator piston 4A and
4B is displaced so as to decrease La and Lb by the increase amount of Pa in the formula (1), and maintains the moment acting on the swing arm 7 constant. The same applies when the discharge pressure of the other pump 1B increases.

When the discharge pressure of the pump 1A drops,
Due to the reduction of the moment acting on the swing arm 7, the valves 11A and 11B are switched to the direction of connecting the oil chambers 6A and 6B to the tank, and the pressure drop in the oil chambers 6A and 6B causes the regulator pistons 4A and 4B to move to the position shown in FIG. It is displaced to the right of 1 to increase La and Lb. As a result, the levers 3A and 3B are moved in the direction of increasing the tilt angle of the pumps 1A and 1B.
Rotates, and the pump discharge amount increases. Then, when the expression (1) is satisfied again, the valves 11A and 11B are switched to the neutral position, the hydraulic oil in the oil chambers 6A and 6B is prevented from flowing in and out, and the regulator pistons 4A and 4B are held at the new balanced position. The same applies when the discharge pressure of the pump 1B decreases.

Since the distances La and Lb of the points of application of the pressing force by the pistons 9A and 9B are proportional to the tilt angles of the pumps 1A and 1B, that is, the discharge amounts of the pumps 1A and 1B, the above formula (1) is It has an accurate proportional relationship with the sum of the output horsepower of the pumps 1A and 1B. Regulator pistons 4A and 4
Since B is displaced so that this equation is always satisfied, the sum of the output horsepower of the pumps 1A and 1B is always constant, and the energy of the engine 20 is effectively utilized without exhaustion.

By the way, there are many combinations of Pb, La, and Lb that satisfy the expression (1) for the discharge pressure Pa of the pump 1A, and similarly, for the discharge pressure Pb of the pump 1B, the expression (1 There are many combinations of Pa, La, and Lb that satisfy).

In this control device, the regulator pistons 4A and 4B and the valves 11A and 11B are configured to have the same size, and the valves 11A and 11B are switched at the same time. Proportional to the flow rate of 11B.

The flow rates of the valves 11A and 11B are determined by the pressure difference before and after the flow, but in the force balance state, the oil chamber 5
The pressure ratio between A and 6A is equal to the pressure ratio between oil chambers 5B and 6B.

Therefore, in the tilt angle reducing operation in which the oil chambers 5A and 6A and the oil chambers 5B and 6B communicate with each other, for example, if the oil chamber 5A is higher than the oil chamber 5B, that is, the discharge pressure of the pump 1A is the pump 1B. If the pressure is higher, the oil chamber 5
The pressure difference between A and 6A is greater than the pressure difference between oil chambers 5B and 6B, and the flow rate of valve 11A is greater than the flow rate of valve 11B. That is, the decrease range of the tilt angle is larger in the pump having the higher discharge pressure.

Similarly, the oil chamber 6A, the tank, and the oil chamber 6B
Even in the tilting angle increasing operation in which the tank and the tank communicate with each other, the tilting angle increasing range is larger in the pump having the higher discharge pressure.

Although such control characteristics do not cause any particular problem in driving construction machines such as power shovels,
By operating the second control valves 12A and 12B via the signals Pi ₁ and Pi ₂ , it becomes possible to directly adjust the discharge amount of one of the pump units by an operator's operation.

That is, for example, when the signal Pi ₁ is input to the second control valve 12A and the discharge pressure of the pump unit 1A is supplied to the low pressure port of the first control valve 11A, the discharge pressure of the pump unit 1A rises. In any case, the discharge pressure of the pump unit 1 is supplied to the oil chamber 6A regardless of the decrease. Therefore, the regulator piston 4A slides to the left in FIG. 1 to reduce the tilt angle of the pump unit 1A and reduce the discharge amount. As a result, the regulator piston 4B is displaced rightward in the figure in the direction of increasing Lb in the equation (1), increasing the tilt angle of the pump unit 1B and increasing the discharge amount. The regulator piston 4
Due to the displacement of A in the direction of decreasing the tilt angle, the deflection of the feedback spring 15A increases and eventually the spring load causes the second
When the control valve 11A is switched to the neutral position, the decrease in the tilt angle of the pump unit 1A is stopped.

Similarly, the signal P is sent to the second control valve 12B.
Even when i ₂ is input, the discharge amount of the pump unit 1B decreases and the discharge amount of the pump unit 1A increases.

Therefore, the ratio of the discharge amounts of the pump units 1A and 1B can be arbitrarily changed by the operator's operation while maintaining the total horsepower constant control.

In this embodiment, the second control valve 12A
And 12B are provided in both pump units 1A and 1B, but it is not always necessary to provide both in both pump units 1A and 1B, and when either one pump unit 1A or 1B is always preferentially controlled, the second control valve also Only one needs to be provided.

[0041]

As described above, according to the present invention, the lever integrally formed with the swash plate for changing the tilt angle, the regulator piston for displacing the lever according to the supply pressure to the oil chamber,
The first control valve that switches and connects the discharge pressure of the pump unit and the tank to the oil chamber according to the swing of the common swing arm, and swings the moment according to the displacement position of the lever and the discharge pressure of the pump unit. Since each pump unit is provided with a piston acting on the arm, and at least one pump unit is provided with a second control valve for forcibly supplying a high pressure to the oil chamber in response to an operation, it acts on the swing arm. The total moment is exactly proportional to the sum of the outputs of each pump unit. Therefore, depending on this moment, the first
The control valve controls the supply pressure to the oil chamber, so that the total output can always be kept constant. Also, the second
The control valve allows the output of one pump unit to be changed while keeping the total output constant.

Therefore, according to the present invention, it is possible to improve the output control accuracy and energy utilization efficiency of the dual variable pump with a simple structure.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram of a control mechanism of a dual variable pump showing an embodiment of the present invention.

FIG. 2 is a vertical sectional view of a lever.

3 is a vertical cross-sectional view of the regulator piston corresponding to the view taken along the line AA in FIG.

FIG. 4 is a vertical cross-sectional view of a piston and a feedback spring, which corresponds to a view taken along the line BB in FIG.

FIG. 5 is a side view including a partial vertical cross section of the dual variable pump.

FIG. 6 is a plan view including a partial horizontal cross section of a main part of a dual variable pump.

[Explanation of symbols]

 1A, 1B Pump unit 3A, 3B Lever 4A, 4B Regulator piston 6A, 6B Oil chamber 7 Swing arm 8 Swing shaft 9A, 9B Piston 11A, 11B First control valve 12A, 12B Second control valve 20 Engine

Claims (1)

[Claims] 1. A control mechanism of a dual variable pump for controlling a tilt angle of each swash plate of two pump units that rotate integrally by the same power source so that a sum of outputs of the pump units becomes constant. , A lever integrally formed with a swash plate for changing a tilt angle by displacement around a predetermined axis, a regulator piston for displacing the lever, and an oil chamber for changing a driving force of the regulator piston according to a supply pressure A first control valve for switching and connecting the discharge pressure of the pump unit and the tank to the oil chamber according to the swing of a common swing arm that swings about a predetermined swing axis as a fulcrum; Each pump unit is provided with a piston that presses the swing arm in the swing direction with a pushing force that corresponds to the discharge pressure of the pump unit at the pushing position that is determined by the displacement position. A control mechanism for a dual variable pump, wherein at least one pump unit is equipped with a second control valve that forcibly supplies high pressure to the oil chamber.