JP2979904B2 - Flow control device for positive displacement hydraulic pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow control device for a positive displacement hydraulic pump driven by an engine mounted on a vehicle.

[0002]

2. Description of the Related Art Conventionally, as a positive displacement type hydraulic pump, a radial piston pump as shown in FIG. 7 has been generally known (for example, see Japanese Patent Application Laid-Open No. 4-295191).

In FIG. 6, reference numeral 1 denotes a prime mover for driving a camshaft 2. Reference numeral 3 denotes a suction oil chamber, and reference numeral 4 denotes a piston. The working oil pressure inside the compression chamber 6 is raised by being pushed up by an eccentric cam 5 provided on the camshaft 2, and high-pressure oil is discharged through a check valve 7. Is done. When the piston 4 is lowered by the eccentric cam 5 and the suction hole 8 is opened to the suction oil chamber 3, the working oil is sucked into the compression chamber 6. By repeating this, high pressure oil is discharged. still,
9 is a tank and 10 is a pump suction path.

In a pump having such a structure, FIG.
As shown in the figure, it is known that there is a proportional flow rate region in which the discharge flow rate increases in proportion to the rotation speed, and a limited flow rate region in which the discharge flow rate discharges a constant flow rate without being proportional to the rotation speed. I have.

[0005] Because, in the low rotation speed range (proportional flow rate range),
After the inside of the compression chamber 6 is filled with the hydraulic oil during the opening time of the suction hole 8, the process proceeds to the compression process. However, the flow rate that can pass through the suction hole 8 is limited. During the opening time, the suction hole 8 is closed before the inside of the compression chamber 6 is filled with the hydraulic oil, and the suction hole 8 is 1
This is because the amount of high-pressure oil discharged per rotation decreases.

[0006]

However, when the above-described conventional positive displacement hydraulic pump is driven as a prime mover by using a vehicle engine whose rotation speed changes from a low rotation speed to a high rotation speed, for example, at the time of idling or the like, As described above, when the engine speed is low, the positive displacement hydraulic pump is operated in the proportional flow rate range, so that the pump volume efficiency is greatly reduced as compared with the operation in the limited flow rate range. If the operation is continued in the limited flow rate range where the pump volumetric efficiency is poor as described above, the driving loss of the engine will be caused, and the fuel consumption will be reduced.

That is, during operation in the proportional flow rate range, the interior of the compression chamber 6 is filled with hydraulic oil in the suction step, and then the process proceeds to the compression step, whereby the compression chamber 6 of the piston 4 and the suction chamber 3 are moved.
Since the compression operation starts from the position where the seal length is zero, the amount of leaked oil from the compression chamber 6 to the suction chamber 3 increases at the moment of shifting to the compression step, and the pump volume efficiency decreases.

On the other hand, in the limited flow rate range, since there is a space in the compression chamber 6 that is not filled with hydraulic oil in the suction process, the compression operation is not performed during the piston stroke that fills the space. Since a predetermined seal length is secured at the time of entry, the amount of leaked oil from the compression chamber 6 to the suction chamber 3 is almost nil, and the pump volume efficiency is increased.

To solve this problem, there is a plan to increase the size of the positive displacement hydraulic pump itself so as to operate in the limited flow rate region even in the idling rotation region. However, it is not preferable as a positive displacement hydraulic pump mounted on a vehicle, which requires light weight, space saving and low cost.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a flow control device for a positive displacement hydraulic pump for controlling a pump suction throttle amount in terms of weight, space, and cost. An object of the present invention is to achieve both a sufficient discharge flow rate and an improvement in volumetric efficiency at the time of pump operation in a proportional flow rate range while using an advantageous small pump.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, a flow control device for a positive displacement hydraulic pump according to the present invention has a volume which becomes a proportional flow rate range when a variable throttle provided in a pump suction passage is fully opened. During the operation of the hydraulic pump, a means for performing a suction throttle amount control for limiting the variable throttle to a throttle amount capable of obtaining a transient flow rate region.

That is, as shown in the claim correspondence diagram of FIG. 1, a prime mover a whose rotational speed fluctuates, a positive displacement hydraulic pump b operated by the prime mover a, and a discharge from the positive displacement hydraulic pump b A variable throttle e provided in a pump suction passage d of the positive displacement hydraulic pump b, the throttle amount being variably controlled by an external command, and a rotational speed. A transient flow rate determining means f for determining a transient flow rate range between a proportional flow rate range in which the discharge flow rate increases in proportion and a limited flow rate range in which the discharge flow rate is constant irrespective of an increase in the rotation speed, and the variable throttle e is fully opened. Suction throttle amount control means g for outputting a control command for restricting the variable throttle e to a throttle amount capable of obtaining a transient flow range when the positive displacement hydraulic pump b is operated in a proportional flow range. Features That.

Here, the transient flow rate range determining means f may be a means for determining a transient flow rate range by detecting a change in the rate of change of the rotational speed of the load c.

[0014]

When the positive displacement hydraulic pump b is operated by the prime mover a whose rotational speed fluctuates, the load c is driven by the working fluid discharged from the positive displacement hydraulic pump b.

During operation of the positive displacement hydraulic pump b,
When the variable throttle e provided in the pump suction passage d is fully opened and the operation is in the proportional flow rate region, the suction throttle amount control means g controls the variable throttle e to limit the variable throttle e to a throttle amount capable of obtaining a transient flow range. Is output.

Accordingly, the pump volume efficiency is proportional to the characteristic that the proportional flow rate range shifts to the low rotation side of the pump as the suction throttle amount of the positive displacement hydraulic pump b is reduced, and the difference in the leakage amount of the working fluid in the compression process. By taking advantage of the characteristic that the operation in the restricted flow area is higher than the operation in the flow area, the pump is operated in the proportional flow area where the discharge flow rate is less than the maximum flow rate even when the variable throttle e is fully opened. By controlling the suction throttle amount so that it becomes a transient flow region between the limit flow region and the limit flow region, the volumetric efficiency by securing a throttle amount close to the limit flow region while suppressing a decrease in the discharge flow rate due to excessive throttling is suppressed. Improvement will be achieved.

[0017]

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

First, the configuration will be described.

FIG. 2 is a diagram showing an engine accessory system of an automobile to which the flow control device of the positive displacement hydraulic pump according to the embodiment of the present invention is applied.

In FIG. 2, 1 is an engine (corresponding to a prime mover a), P is a radial piston pump (corresponding to a positive displacement hydraulic pump b), 9 is a tank, 10 is a pump suction passage, and 11
Is a hydraulic motor, 12 is an alternator (corresponding to load c),
13 is a pump discharge path, 14 is a motor return path, 15 is a proportional solenoid variable throttle (corresponding to a variable throttle e), 16 is an ignition switch, 17 is an alternator rotation speed sensor, 18 is a suction throttle amount controller (suction throttle amount control means). g).

The radial piston pump P is operated by the engine 1, rotates the hydraulic motor 11 with hydraulic oil discharged from the radial piston pump P, and drives the alternator 12 by the hydraulic motor 11.

The proportional solenoid variable aperture 15 is fully closed by application of the maximum solenoid current, and the aperture is expanded as the solenoid current is reduced, and the aperture is fully opened when the solenoid current is zero.

The suction throttle amount controller 18 is provided with a switch signal from an ignition switch 16 and an alternator rotation speed Nalt from an alternator rotation speed sensor 17.
And a battery output voltage (alternator terminal voltage) Ebat from the alternator 12, and outputs a solenoid current Isol as a control command to the proportional solenoid variable throttle 15 in accordance with a control process described later.

FIG. 3 is a diagram showing a radial piston pump section and a suction throttle amount control system.

In FIG. 3, reference numeral 1 denotes an engine for driving the camshaft 2. Reference numeral 3 denotes a suction oil chamber, and 4 denotes a piston. The operating oil pressure inside the compression chamber 6 is increased by being pushed up by an eccentric cam 5 provided on the camshaft 2, and high-pressure oil is discharged through a check valve 7. It is discharged to the path 13. When the piston 4 is lowered by the eccentric cam 5 and the suction hole 8 is opened to the suction oil chamber 3, the working oil is sucked into the compression chamber 6.
By repeating this, high pressure oil is discharged. 9 is a tank, 10 is a pump suction path, 15
Is a proportional solenoid variable throttle, 16 is an ignition switch, and 18 is a suction throttle amount controller.

Next, the operation will be described.

[Pump Discharge Flow Rate Characteristics] First, the pump discharge flow rate characteristics include a proportional flow rate range in which the discharge flow rate increases in proportion to the rotation speed, and a constant flow rate in which the discharge flow rate is not proportional to the rotation speed. It is known that there is a restricted flow rate range.

The pump discharge flow rate characteristic is shown in FIG.
As shown in (1), the proportional flow range shifts to the low-speed side of the pump as the suction throttle amount of the radial piston pump P is reduced, and the limited flow range is expanded.

[Pump Volume Efficiency] During operation in the proportional flow rate range, after the inside of the compression chamber 6 is filled with hydraulic oil in the suction step, the process proceeds to the compression step, whereby the compression chamber 6 of the piston 4 and the suction chamber 3 are connected. During the compression operation, the amount of leaked oil from the compression chamber 6 to the suction chamber 3 increases at the moment when the compression process starts, and the pump volume efficiency decreases.

On the other hand, in the limited flow rate range, since there is a space in the compression chamber 6 that is not filled with the hydraulic oil in the suction process, the compression operation is not performed during the piston stroke that fills the space. Since a predetermined seal length is secured at the time of entry, the amount of leaked oil from the compression chamber 6 to the suction chamber 3 is almost nil, and the pump volume efficiency is increased.

[Technical concept of the present invention] From the viewpoint of the pump volumetric efficiency, it is preferable to use the radial piston pump P in the restricted flow region. However, when the proportional solenoid variable restrictor 15 is fully opened and the proportional flow rate range is set to a low flow rate operation, and the proportional solenoid variable restrictor 15 is fully closed or close to a fully closed state, the operation of the proportional flow rate range is definitely restricted. The operation shifts to a flow rate region, and the pump volumetric efficiency is improved, but at the same time, the pump discharge flow rate is significantly reduced.

Therefore, in the present invention, the proportional solenoid variable throttle 15 is limited to a throttle amount at which a transient flow rate range can be obtained when the pump is operated in the proportional flow rate range.

For example, when the pump operating point is at point X in FIG. 4, if the suction throttle amount is fully opened, the pump will operate at point Y in the proportional flow region. , The pump is operated in the transient flow rate range Y ′, and the pump can be operated in a range close to the restricted flow rate range without substantially reducing the pump discharge flow rate.

When the pump operating point is at point X in FIG. 4, if the suction throttle amount is fully closed, the pump will operate in the limited flow rate range. When opened, the pump is operated in the transient flow rate range Y ', and the pump can be operated in a range close to the restricted flow range while securing the pump discharge flow rate.

In this embodiment, like the latter,
This is a control example in which the pump is operated in the transient flow rate range by the approach of opening the suction throttle amount from the full closing of the suction throttle amount, but of course, as in the former case, the suction throttle amount is closed from the full opening of the suction throttle amount. In this case, the pump may be controlled to operate in the transient flow rate range.

[Suction Throttle Amount Control Operation] FIG. 5 is a flowchart showing the flow of the suction throttle amount control operation process performed by the suction throttle amount controller 18, and each step will be described below.

In step 50, the control is started simultaneously with the start of operation of the engine 1.

In step 51, a solenoid maximum current value for fully closing the proportional solenoid variable throttle 15 is output.

In step 52, it is determined whether or not the engine 1 is off. When the engine 1 is off, the control is terminated.

In step 53, the battery output voltage Eba
It is determined whether or not t is less than the set voltage C1, that is, whether or not the amount of power generated by the alternator 12 is insufficient.

In step 54, the alternator rotation speed N
alt is read, and Nalt at this time is set to Nalt1.

In step 55, the proportional solenoid variable throttle 15 is enlarged by a predetermined amount by outputting a command to reduce the output solenoid current Isol by a predetermined current ΔIsol.

In step 56, the alternator rotation speed N
alt is read again, and Nalt at this time is set to Nalt2.

In step 57, the alternator rotation change rate ΔN is calculated from the following equation based on Nalt1 and Nalt2.

ΔN = Nalt2 / Nalt1 (when Nalt2> Nalt1) ΔN = Nalt1 / Nalt2 (when Nalt2 <Nalt1) In step 58, it is determined whether the alternator rotation change rate ΔN is less than the set change rate C3 indicating the transient flow region. It is determined (corresponding to the transient flow rate range determining means f).

In step 59, Ebat in step 53
When it is determined that ≧ C1, or at step 58, ΔN
When it is determined that .gtoreq.C3, a command to increase the output solenoid current Isol by a predetermined current .DELTA.Isol is output to reduce the proportional solenoid variable throttle 15 by a predetermined amount.

[Determination of Transient Flow Range] As described above, when the pump suction throttle solenoid current value and the throttle state are in inverse proportion, the relationship between the solenoid current value and the hydraulic motor rotation speed (hydraulic pump discharge flow rate) is as follows. As shown in FIG. 6 (a), when the solenoid current value is between 0 and A, the flow rate becomes a proportional flow rate range, the rotational speed of the hydraulic motor becomes a constant speed, and when the solenoid current value is between A and C, the flow rate becomes a transient flow rate range. The hydraulic motor rotation speed slightly decreases, and when the solenoid current value is equal to or higher than C, the flow rate is in a limited flow rate range, and the hydraulic motor rotation speed has a characteristic of decreasing at a predetermined gradient.

The relationship between the solenoid current value and the hydraulic motor rotation rate of change (alternator rotation rate of change) is, as shown in FIG. When the solenoid current value is between A and C, the fluctuation rate increases proportionally, and when the solenoid current value is equal to or higher than C, the fluctuation rate is constant at a high value.

The relationship between the solenoid current value and the pump volumetric efficiency is shown in FIG. 6C, where the volumetric efficiency is low and constant when the solenoid current value is 0 to A, and the solenoid current value is A. ＣC, the volumetric efficiency sharply increases, and when the solenoid current value is equal to or higher than C, the volume efficiency changes.

As described above, attention is paid to the fact that in the transitional flow range (A to C) between the proportional flow range (0 to A) and the restricted flow rate range (C to), the characteristic of the hydraulic motor rotation fluctuation varies. The determination of the transient flow rate region is defined as a point B between A and C, and the hydraulic motor rotation fluctuation rate C3 at the point B is used as a determination threshold value of the transient flow rate area.
The transient flow rate region is determined with high accuracy based on whether it is less than three.

[During Pump Low-Rotation Operation] For example, as in idling, the rotation speed of the engine 1 is low, and when the alternator 12 is driven with the discharge flow rate from the radial piston pump P, the amount of power generation is insufficient. In such a pump operation, in the flow chart of FIG. 5, the processing of steps 52 to 58 is repeated, and every time step 55 elapses, the proportional solenoid variable throttle 15 is gradually expanded, and the radial piston pump P Increase discharge flow rate.

Then, the throttle opening of the proportional solenoid variable throttle 15 becomes an opening for realizing the pump operation in the transient flow rate range. When the condition of step 58 is satisfied, the process proceeds from step 58 to step 59, where the radial piston pump P Based on the determination that the discharge flow rate can be reduced, the throttle opening of the proportional solenoid variable throttle 15 is reduced, and control is performed to slightly move the pump operating point to the limited flow rate range side.

As a result of this suction throttle amount control, a decrease in the discharge flow rate due to excessive throttling is suppressed, and as shown in FIG. 6A, the pump discharge flow rate is set to a level substantially equal to the pump operation level in the proportional flow rate range. As shown in FIG. 6 (c), the volumetric efficiency is greatly improved with respect to the pump volumetric efficiency in the proportional flow rate range by securing the throttle amount close to the limited flow rate range while securing Become.

Next, the effects will be described.

(1) In the flow control device of the radial piston pump P for controlling the pump suction throttle amount, when the proportional solenoid variable throttle 15 provided in the pump suction passage 10 is fully opened, the pump operates in the proportional flow rate range. In addition, since the proportional solenoid variable throttle 15 is a device for controlling the suction throttle amount to limit the throttle amount to obtain a transient flow range, the pump operation in the proportional flow range is performed while a small pump is advantageous in terms of weight, space and cost. At the same time, it is possible to achieve both the securing of the discharge flow rate and the improvement of the volumetric efficiency.

The improvement in the volumetric efficiency reduces the load on the engine 1 as a prime mover, leading to an improvement in fuel efficiency.

(2) The alternator rotational change rate ΔN is calculated, and the alternator rotational change rate ΔN is determined in the transient flow rate region by using the characteristic of the change in the transient flow rate range. The transient flow rate range can be accurately determined without being affected by a pump individual difference or the like.

(3) When the battery output voltage Ebat is not insufficient, or when the pump is in the transient flow range, the proportional solenoid variable throttle 15 is slightly reduced. The total energy efficiency can be improved as compared with the case where the control for fixing or increasing the aperture stop is performed.
That is, in the transient flow rate range, even if the throttle is slightly opened, the increase in the pump discharge flow rate is slight. Therefore, it is more desirable to positively close the throttle and improve the volumetric efficiency than to open the throttle and deteriorate the volumetric efficiency.

Although the embodiment has been described with reference to the drawings, the specific configuration is not limited to the embodiment, and even if there are changes and additions without departing from the gist of the invention, the invention is included in the invention. It is.

For example, in the embodiment,
Although the example of the positive displacement hydraulic pump driven by the engine has been described, the application field is not limited to this, and can be widely applied to general industrial machine fields and the like.

[0061]

As described above, according to the present invention, in the flow control device of the positive displacement hydraulic pump for controlling the pump suction throttle amount, the case where the variable throttle provided in the pump suction passage is fully opened. During the operation of the positive displacement hydraulic pump, which has a proportional flow rate range, the variable throttle is limited to a throttle amount in which a transient flow rate range can be obtained. While the pump is used, it is possible to obtain an effect that it is possible to achieve both the securing of the discharge flow rate and the improvement of the volumetric efficiency during the pump operation in the proportional flow rate range.

This technique is particularly useful in application to a positive displacement hydraulic pump mounted on a vehicle and driven by an engine.

[Brief description of the drawings]

FIG. 1 is a view corresponding to claims showing a flow control device of a positive displacement hydraulic pump of the present invention.

FIG. 2 is a diagram showing an engine accessory system of an automobile to which the flow control device of the positive displacement hydraulic pump of the embodiment is applied.

FIG. 3 is a diagram showing a radial piston pump section and a suction throttle amount control system of the embodiment.

FIG. 4 is a characteristic diagram of a pump discharge flow rate with respect to a pump rotation speed using a suction throttle amount as a parameter in the embodiment pump.

FIG. 5 is a flowchart showing a flow of a suction throttle amount control operation process performed by a suction throttle amount controller of the embodiment device.

FIG. 6 is a characteristic diagram of a hydraulic motor rotation speed, a hydraulic motor rotation fluctuation rate, and a pump volume efficiency with respect to a solenoid current in each of a proportional flow rate range, a transient flow rate range, and a limited flow rate range in the radial piston pump of the embodiment. is there.

FIG. 7 is a view showing a conventional radial piston pump.

FIG. 8 is a characteristic diagram of a pump discharge flow rate with respect to a pump rotation speed in a conventional radial piston pump.

[Explanation of symbols]

 a prime mover b positive displacement hydraulic pump c load d pump suction path e variable throttle f transient flow rate range determination means g suction throttle amount control means

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) F49 / 00-51/00

Claims (2)

(57) [Claims] 1. A system comprising: a prime mover having a variable rotational speed; a positive displacement hydraulic pump driven by the prime mover; and a load driven by a working fluid discharged from the positive displacement hydraulic pump. A variable throttle, which is provided in the pump suction path of a hydraulic pump and whose throttle amount is variably controlled by an external command, discharges regardless of the increase in the proportional flow rate range where the discharge flow rate increases in proportion to the rotation speed and the rotation speed A transient flow rate range determining means for determining a transient flow rate range from a constant flow rate range with a constant flow rate range; and A flow control device for a positive displacement hydraulic pump, comprising: a suction throttle amount control unit that outputs a control command for restricting the throttle amount to a range in which a range is obtained. 2. The flow rate control device for a positive displacement hydraulic pump according to claim 1, wherein the transient flow rate range determining means determines the transient flow rate range by detecting a change in a rate of change in the number of revolutions of the load. Means for controlling the flow rate of a positive displacement hydraulic pump.