JPH0374582A - Input torque control method for variable displacement liquid-operated pump - Google Patents

Abstract

PURPOSE:To prevent the fluctuation of engine speed by providing a device for controlling discharge according to the increase/decrease of engine speed and pump discharge. CONSTITUTION:Variable displacement pumps 11, 12 driven by an engine 2 are variable displacement controlled by the action of servo mechanisms 31, 32, and the servo mechanisms 31, 32 are drive-controlled through servo switching valves 41, 42. In this case, there is provided with a fixed capacity side charge pump 5 rotated coaxially with the variable displacement pumps 11, 12. The discharge circuit is branched into two ways after passing a fixed throttle 6, and one way is connected to the respective servo mechanisms 31, 32 and the other way to the pilot pressure circuit 8 of the respective switching valves 41, 42 through a differential pressure detecting valve 7 for detecting the fore and aft pressure difference of the fixed throttle 6. An automatic throttle valve 10 is also connected parallel to the fixed throttle valve 6, and the throttle opening is adjusted by signal pressure from the variable displacement pumps 11, 12.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for controlling the input torque of a variable displacement hydraulic pump that is driven by an engine and sets the input torque according to the input rotational speed. be. The input torque B is a torque that is applied to the input shaft when the variable displacement hydraulic pump is driven, and its value is proportional to the specific capacity and discharge pressure of the variable displacement hydraulic pump.

[Conventional technology]

This type of method is illustrated in FIG.
It is known from specification HL.

In this conventional example, the change in the discharge flow rate from the fixed displacement charge pump b, which is driven simultaneously with the variable displacement hydraulic pump (hereinafter simply referred to as variable pump) a+a2, is calculated from the charge pump b. It is detected by the pressure difference before and after the fixed throttle C through which the discharge flow passes, and as this pressure difference rises and falls, the pilot valve d is switched to transfer the pressure liquid from the charge pump b to the servo mechanism el+ e2.
The capacity of the variable pump a1+a2 is increased and decreased by acting on the variable pump a1+a2.

In this conventional example, in order to properly match the output torque of the drive source and the input torque T of the variable pump alr82, the input torque of the variable pumps a1 and a2 is set, adjusted, or changed by intervening in parallel with the fixed throttle C. This was done by setting, adjusting, or changing the opening degree of the variable aperture f.

Further, since unnecessary rotational speed fluctuations caused by the discharge pressure of the variable pump cannot be avoided using only the above method, variable pump a1. A summing valve g operated by signal pressure from a2 is provided auxiliary in the control circuit of the servo mechanism el+e2, and the servo mechanism el+e2 is controlled by the control pressure from this summing valve g.

In this figure, h1. h2 is the load and i is the engine.

[Problem to be solved by the invention]

In the above conventional method, variable pump a 1 +a2
In order to avoid fluctuations in the rotational speed of the engine i that drives the charge pump b, the summing valve g, which is operated by the signal pressure from the variable pump aj+a2, is connected to the servo mechanism 6.
1+62 control circuit, as described above, the variable pump a1. The servo mechanism e1+ 82 is controlled by a change in the control pressure from a2, and the control pressure from the summing valve g and the control pressure from the charge pump b acting via the pilot valve d are transferred via the shuttle valve. The higher one is the servo mechanism e1.
e2, it has been impossible to prevent variations in the rotational speed of engine i caused by the discharge pressure of the variable pump.

In addition to the above-mentioned conventional example, as shown in FIG. 3, there is a known system in which the input torque of the variable pump is controlled using a polygonal line A that approximates the maximum output torque of the engine.
When the engine rotational speed decreases, the polygonal line A deviates from the engine output torque curve B, resulting in the disadvantage that the engine output torque cannot be fully utilized.

It was also difficult to adjust the pump capacity to match the engine's output torque so that it touched two points on a hyperbola.

[Means and effects for solving the problems] The present invention has been made in view of the above-mentioned problems, and is capable of preventing fluctuations in engine rotational speed caused by the discharge pressure of a variable pump, and The control characteristics of the input torque can be easily changed, and even if the engine speed changes, the engine output torque and the input torque of the variable pump can be matched at the optimal matching point. The present invention aims to provide a variable pump input torque control method in which the input torque is constant and the pump capacity can be changed hyperbolically in accordance with the output torque of the engine.

In order to achieve the above object, a method for controlling a variable displacement hydraulic pump according to the present invention provides a control signal P which is driven by an engine and which acts on a control signal input section of a discharge amount control means.
In an input torque control method for a variable displacement hydraulic pump, in which the discharge rate is controlled by the discharge rate control means in proportion to an increase or decrease in out, a control signal input to the input section of the discharge rate control means; Pout is changed by signals for both an increase/decrease in the engine rotation speed and an increase/decrease in the discharge amount of the variable displacement hydraulic pump, and the above engine rotation speed increase/decrease signal is adjusted by a control signal for the target rotation speed of the engine. I try to do that. Thereby, the variable pump is controlled by the engine speed and the discharge pressure of the variable pump, and is also controlled by the engine control signal, that is, the target engine speed.

〔Example〕

Embodiments of the present invention will be described below with reference to FIG.

FIG. 1 shows a configuration for carrying out the method of the present invention. In the figure, reference numerals 1+ and 12 are variable pumps driven by the engine 2, which are controlled by the movement of servo mechanisms 31 and 32. It has become. 41 and 42 are servo switching valves. Reference numeral 5 denotes a fixed capacity charge pump which is driven to rotate coaxially with the variable pump 1, and its discharge circuit passes through a fixed throttle 6 and is branched into two directions, one of which is connected to the servo mechanism 31 and 32. , and the other one is connected via the differential pressure detection valve 7 to the pilot pressure circuit 8 of the switching valve 41.4□ of the servo mechanism 31, 32. Reference numeral 9 denotes an adjustment diaphragm for adjusting the aperture of the fixed diaphragm 6.

The differential pressure detection valve 7 is the pressure pt+ before and after the fixed throttle 6.
P2 is detected, and the output pressure Pout corresponding to the output difference (pt-P2) is sent to the pilot circuit 8 of the servo switching valves 4 and 42 of the servo mechanisms 31 and 32. The relationship between the pressure difference before and after the fixed throttle 6<1)I-1)2) and the output pressure POut of the differential pressure detection valve 7 is Pout-pat+α(p
l-P2). However, the pot is the differential pressure detection valve 7.
is the difference in the biasing force of the springs installed on both sides of , and α is a constant.

On the other hand, the servomechanisms 31 + 32 have already been implemented in many ways, such as the variable pump 1. ．． The capacitance ql·Q2 of 12 is controlled so that it becomes q1■β+ (Pout-po2) Q2-β2 (Pout-poz). However, PO2 is the servo switching valve 4. ．． 42 in the direction opposite to the output pressure Pout, β1. β2 is a constant.

From the above, assuming pot-P02, variable pump 1
The capacitance Ql of 1.12, Q2 becomes Q+=Q2-αβ(+)+-p2).

Reference numeral 10 denotes an automatic throttle valve, which is connected in parallel with the fixed throttle valve 6, and its throttle opening degree is adjusted by signal pressure P*I+P*2 from variable pumps 11 and 12. ing.

11 is a flow control valve device, and this flow control valve device j′It1
Reference numeral 1 consists of a convencator 12 interposed in a circuit between the charge pump 5 and the fixed throttle 6, and a flow control valve 13 that bypasses the upstream side of the convencator 12 to the downstream side of the fixed throttle 6. Note that 13a is a flow rate adjustment lever of the flow rate control valve 13, and 14 is an adjustment throttle.

In the above configuration, two variable pumps 1. ．． The total input torque T to 12 is: T=TI +T2 ccp, *Q 1+Pe2II
Q2, and as mentioned above, Ql-Q2-αβ(p1+p2), so T-αβ(P t -P 2 ) (P $1 +
P pz), and CF'1-P2) is the differential pressure in the throttle circuit. Therefore, it becomes. However, Q is the flow rate flowing into the parallel circuit of the automatic throttle valve 10 and the fixed throttle 6, α0 is the flow path area of the fixed throttle 6,
α* is the flow path area of the automatic throttle valve 10, and δ is a constant.

By the way, by configuring each element such as the pressure receiving surface and return spring of the automatic throttle valve 10 so that α O is established, the total human torque T becomes T −r (−) 2 α O , which is expressed as follows. is the individual discharge pressure P of the multiple variable pump
Stable regardless of l+P e2.

Here, the rotational speed of the charge pump 5 is N rpms, the capacity is q o CC/rev, and the discharge flow is Q o CC, #
gin, and the bypass flow rate by the flow rate control valve device 11 is Q cc/m1ft, then Q + Q = Qo, so α G α o q.

(However, C is a constant) Therefore, by changing the set load of the flow rate control valve 13 or the spring of the convencator 12 and changing the bypass flow mQ*, the input torque control characteristics of the variable pump 11.1□ can be easily changed. be able to.

On the other hand, the flow j1 of the flow control valve 13 of the flow control valve device 11
By interlocking the m adjustment lever 13a with the governor set lever of the engine's fuel adjustment device, the engine and variable pump can be matched at an optimal matching point.

A method for controlling the input torque of the variable displacement hydraulic pump having the above configuration will be described below.

The target rotation speed of the engine 2 is set by the fuel adjustment device, and in conjunction with this, the flow control valve 13 of the flow control valve device 11 is set to an opening corresponding to the target rotation speed of the engine 2, and the charge pump The fluid from 5 is transferred to this flow control valve 1.
Variable pump 1 through 3. ．． 12 servo mechanisms 31°3
2 actuator.

Further, the fluid from the charge pump 5 that bypasses the flow rate control valve 13 flows into a parallel circuit of the fixed throttle 6 and the automatic throttle valve 10 via the convencator 12. Therefore, the flow rate Q flowing into this circuit is throttled by the fixed throttle 6 and the automatic throttle valve 10, and the pressure difference between them is used to reduce the flow rate Q flowing into this circuit. ．． 42.

At this time, the variable pump 1. ．． 12 is the servo switching valve 4. ．． 42 so that the human torque is matched with the output torque of the engine 2 at an optimal matching point.

At this time, variable pump 1. ．． Even if there is a load fluctuation on the fixed throttle 6, the pressure difference across the fixed throttle 6 will not change unless the rotation of the engine 2 changes. Therefore, the fixed throttle valve 6 alone cannot quickly follow the load fluctuations acting on the variable pump 11.12, and the variable pump 11.12 ends up hunting due to the load fluctuation.

On the other hand, the automatic throttle valve 10 installed in parallel with the fixed throttle 6 is directly controlled by the discharge pressure of the variable pump 11.12. .

The differential pressure detection valve 7 responds sensitively to changes in the load acting on the differential pressure detection valve 7.
4. Through the servo switching valve. .

42.

Therefore, the output torque of the engine 2 and the input torque of the variable pump 11.12 are optimally matched by the fixed throttle valve 6, while the automatic throttle valve 10 matches the output torque of the engine 2 and the input torque of the variable pump 1.12. ．． The delay in the change in engine rotation with respect to the change in the load acting on the engine 12 is reduced, and control by the fixed throttle 6 is performed without hunting. This allows the variable pump 1. ．． Fluctuations in the engine rotational speed caused by changes in the discharge pressure of No. 12 are eliminated.

Now, if the discharge flow 41 Qo of the charge pump 5 increases, that is, the rotational speed of the engine 2 by the fuel adjustment device becomes larger than the target rotational speed, the flow rate Q flowing into the throttle circuit increases, and therefore the variable pump 11
．． The control pressure Pout acting on the control section of variable pump 11.12 also increases, and variable pump 11.12 is controlled in a direction to decrease its discharge amount. ．． 12 human torque becomes constant.

Therefore, variable pump 1. ．． 12 pressure P and flow rate Q M(P
XQ) becomes constant, and the control characteristic of the input torque of the variable pump can easily be made into a constant hyperbolic shape.

〔Effect of the invention〕

According to the present invention, it is possible to prevent variations in engine rotational speed caused by the discharge pressure of the variable pump. In addition, the control characteristics of the input torque of the variable pump can be easily changed, and furthermore, even if the engine rotation speed changes, the output torque of the engine and the input torque of the variable pump can be matched at an optimal matching point. Further, the controlled input torque is constant, and the pump capacity can be changed hyperbolically in accordance with the output torque of the engine.

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention, FIG. 2 is a hydraulic circuit diagram of a conventional example, and FIG. 3 is a control characteristic diagram of a variable displacement hydraulic pump. 1++ 12 is a variable displacement hydraulic pump, 2 is an engine, 31.32 is a servo mechanism, 4. ．． 42 is a servo switching valve, 5 is a charge pump, 6 is a fixed throttle, 7 is a differential pressure detection valve, and 10 is an automatic throttle valve.

Claims (1)

[Claims] A variable capacity liquid whose discharge amount is controlled by the discharge amount control means in proportion to an increase or decrease in a control signal Pout which is driven by the engine 2 and which acts on the control signal input section of the discharge amount control means. In the input torque control method for a pressure pump, a control signal Po input to the input section of the discharge amount control means
ut is changed by signals for both increases and decreases in the engine rotational speed and in the discharge amounts of the variable displacement hydraulic pumps 1_1 and 1_2, and the engine rotational speed increase and decrease signal is used as a control signal for the target rotational speed of the engine. A method for controlling input torque of a variable displacement hydraulic pump, characterized in that the input torque is adjusted by adjusting the input torque of a variable displacement hydraulic pump.