GB2245659A

GB2245659A - Fluid pressure supplying apparatus

Info

Publication number: GB2245659A
Application number: GB8817011A
Authority: GB
Inventors: Hiroshi Sato
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-07-16
Filing date: 1988-07-16
Publication date: 1992-01-08
Also published as: GB8817011D0

Abstract

A fluid pressure supplying apparatus has a prime mover (10), a pump (20) rotatable by the prime mover, a flow rate control means (30) disposed in parallel to the pump (20) and a fluid pressure output circuit (40) disposed in parallel to the flow rate control means (30), Both the output of the pump (20) and the control means (30) may be adjustable. The control means (30) may take a variety of different forms. <IMAGE>

Description

TITLE OF THE INVENTION FLUID PRESSURE SUPPLYING APPARATUS BACKGROUND OF THE INVENTION This invention relates widely to an apparatus for supplying a fluid pressure such as an oil pressure, and particularly to a fluid pressure supplying apparatus in which fluid such as oil discharged from a pump is variable in quantity.

More specifically, the present invention relates to a fluid pressure supplying apparatus, in which fluid discharged is linearly variable in quantity.

In general, prime movers of motors, internal combustion engines and external combustion engines are all variable in speed of rotation, but the rotation thereof is very much unstable in the rotation area of low speed immediately before stopping.

Therefore, output of prime motors produces a stopping state of rotation of an output shaft and a variable state of rotation thereof by a slide plate system, a means utilizing the viscosity of oil, or a combination of a clutch such as an electromagnet and a reduction gear or the like. At the starting time of rotation, it is directly connected with a prime mover via the half-clutch state, and the rotation of the prime mover is gradually increased by returning the clutch and the speed of rotation is accelerated by shifting the gear.

Since output of a rotating equipment is expressed by the following relation, output = rotary torque x speed of rotation the output is reduced in proportion to the reduction of the speed of rotation. In a turbine engine, since the internal loss is increased during the low speed rotation, the output is further reduced. It is very difficult to obtain a stable rotation and a stable output in the area where the output is reduced.

Accordingly, a minimum speed of rotation able to rotate stably is established in usual practice and this is referred to as an idle rotation. The rate of the number of idle rotation to the maximum number of rotation is usually about 10 times to several tens. In recent time, a speed variable prime mover comprising a combination of an induction motor and an inverter has been used. However, this again cannot be used at the speed of idle rotation or less. Moreover, when a prime mover is designed, the most economical efficiency is found by assuming a constant speed of rotation.

Therefore, the efficiency becomes the worst at a low speed of rotation immediately before stopping.

There arises a problem when such prime mover is connected to an output device and operated. The problem arises because the output device is brought to be in its operating state from its stopping state. Therefore, the ratio of the minimum rotation to the maximum rotation is infinity. In order to cope with this, a stopping state of a prime mover is usually produced by a combination of a prime mover, a clutch, a reduction gear, etc. as already described.

When the driving is started, it is directly connected to the prime mover via the half-clutch state and the rotation of the prime mover is gradually increased.

Although various kinds of clutches used here have been proposed as described previously, all of them involve some problems such as lose of energy, mechanical wear and maintenance. Therefore, clutches of simple structure and of high efficiency have been demanded. In the conventional oil pressure supplying apparatus, it is a general practice that a fixed delivery hydraulic pump or a variable delivery hydraulic pump is driven by an electric motor of a constant speed. There can be seen only in construction vehicles (power shovels, cranes, etc.) in that an internal combustion engine of a variable engine speed is used as its power source.

SUMMARY OF THE PRESENT INVENTION The present invention has been accomplished in order to overcome the above-mentioned problems.

It is therefore an object of the present invention to provide a fluid pressure supplying apparatus, in which a fluid motor connected to the apparatus can be controlled more easily than in the conventional mechanical apparatus.

Another object of the present invention is to provide a fluid pressure supplying apparatus which is very simple in structure, light in weight and low in maintenance fee.

In order to achieve the above objects, there is essentially provided a fluid pressure supplying apparatus comprising a prime mover, a pump rotatable by the prime mover, a flow rate control means disposed in parallel to the pump, and a fluid pressure output circuit disposed in parallel to the flow rate control means.

Because of the afore-mentioned construction, the driving force of the apparatus is converted into a fluid pressure by the pump. The fluid is bypassed through the fluid control means which is disposed in parallel to the pump. By adequately varying the flow rate bypassed, a fluid motor such as a hydraulic motor disposed at a lower stage of the fluid pressure controlling apparatus according to the present invention can be stopped rotating, or varied in speed of rotation.

More specifically, rotary force from the prime mover causes a pump such as a hydraulic pump to be rotated. The rotation of the pump produces a pressure output such as a fluid. The output of the fluid is bypassed through a flow rate control means such as a flow rate control valve which is disposed in parallel to the pump. Accordingly, by an adequate control of the flow rate controlling means, the fluid output from the fluid pressure output circuit is adequately controlled. Therefore, the rotation of a fluid motor such as a hydraulic motor disposed at a rear stage of the fluid pressure supplying apparatus according to the present invention can be easily controlled by the fluid pressure supplying apparatus according to the present invention.

Other objects, the advantages and uses of the invention will be, or should become apparent after reading the following description and claims and after consideration of the accompanying drawings forming a part of this specification, in which: BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a circuit diagram according to one embodiment of a fluid pressure supplying apparatus of the present invention; Fig. 2 is a circuit diagram showing a modified embodiment of Fig. 1; Fig. 3 is a circuit diagram according to one embodiment of its fixed bypass type; Fig. 4 is an illustration showing the characteristic of Fig. 3; Fig. 5 is a circuit diagram showing a modified embodiment of Fig. 3; Fig. 6 is an illustration showing the characteristic of one embodiment of a proportional bypass type;; Fig. 7 is an illustration showing the characteristic of a modified embodiment of the proportional bypass type; Fig. 8 is an illustration showing the characteristic of one embodiment of a linear interpolation type; Fig. 9 is an illustration showing the characteristic of one embodiment of a step type; Fig. 10 is an illustration showing the characteristic of a modified embodiment thereof; Fig. 11 is an illustration showing the characteristic of another modified embodiment thereof; Fig. 12 is a circuit diagram according to one embodiment of a normally and reversely rotating type; Fig. 13 is an illustration showing the characteristics of one embodiment of a proportional output type in the case a fluid pressure supplying apparatus according to the present invention is applied to an automobile; Fig. 14 is an illustration showing the characteristic of a modified embodiment thereof; ; Fig. 15 is an illustration showing the characteristic of one embodiment of a fixed output type thereof; and Fig. 16 is a circuit diagram according to one embodiment of a control system in which an oil pressure supplying apparatus is used.

DETAILED

OF THE EMBODIMENT A fluid pressure supplying apparatus according to the present invention will be described hereunder in detail in the form of a preferred embodiment with reference to the accompanying drawings.

Fig. 1 is a circuit diagram according to one embodiment of a fluid pressure supplying apparatus of the present invention.

Fig. 2 is a circuit diagram according to a modified embodiment thereof.

There is provided a prime mover 10 such as a gasoline engine and electric motor. There is also provided a hydraulic pump 20 rotated by the prime mover 10. A flow rate control valve 30 as a -flow rate control means is disposed in parallel to the hydraulic pump 20. A fluid pressure output circuit 40 is disposed in parallel to the flow rate control valve 30.

A fluid pressure return circuit 42, an oil input circuit 21 of the hydraulic pump 20 and a bypass circuit 31 of the flow rate control valve 30 are jointed via a tank 50.

Instead of the hydraulic pump 20, an air pump may be used.

Various embodiments of a fluid pressure supplying device according to the present invention will be described hereunder in detail together with operation thereof and with reference to the accompanying drawings.

As the circuit diagram shown in Fig. 1, a prime mover 10a is direct]y connected with a variable delivery hydraulic pump 20a and a flow rate control valve (throttle valve) 30a which can be controlled from outside is connected thereto in parallel relation. As is shown in Fig. 2, a prime mover 10 is directly connected with a plurality of hydraulic pumps 20 of the same capacity or with a plurality of hydraulic pumps 20 of different discharging capacity, and the hydraulic pumps 20 are connected in parallel with a flow rate control valve 30 which can be controlled from outside through a switch valve 60.

With the above-mentioned circuit, when the flow rate control valve 30 is-totally opened, an oil quantity Q1, which is discharged when the prime mover 10 is idly driven, is totally bypassed and flowed into a tank 50, and as a result, is not output outside. In this case, the combination of the prime mover 10 and the variable discharging pump is represented by the following relation; Speed ratio of rotation of prime mover x variable discharge ratio of hydraulic pump = oil quantity ratio of Qw wherein Qw is oil quantity output from oil pressure supplying apparatus. In this relation, when the minimum discharging quantity is zero, the ratio of the minimum discharging quantity to the maximum discharging quantity becomes infinity.However, since it is difficult to make the minimum discharging quantity completely zero, it is risky to regard the ratio of the minimum discharging quantity to the maximum discharging quantity as infinity. i- If, for example, the ratio of rotation of a motor is set 20 : 1 and the ratio of discharge of a pump is set 20 : 1 in the above relation, the ratio of oil quantity becomes 400. Therefore, the minimum discharging quantity can be regarded as almost zero.

In order to actuate the outside output apparatus, the rotation of the prime mover 10 is increased and, at the same time, the flow rate control valve 30 is throttled. As a result, oil discharged from the hydraulic pump 20 output as an oil quantity Qw for performing all work. In this case, the method for operating the flow rate control valve 30 can be classified as follows: A. Fixed Bypass Type As shown in the circuit diagram of Fig. 3, a semifixed pressure compensated throttle valve 30b is connected in parallel to the hydraulic pump 20, and the discharging quantity is established as a constant quantity Q1 irrespective of the speed of rotation of the hydraulic pump 20. The value obtained by deducting the bypass quantity Q1 from the discharging quantity Qp is the output Qwt which exhibits the characteristics as shown in Fig. 4.Therefore, the output Qw from a fluid output circuit 40 is zero during the idle driving and the ratio to the output Qw during the maximum rotation is infinity. That is, the output Qw is zero during the idle driving and is increased as the rotation is increased.

In this case, since the output Qp from the hydraulic pump 20 is also fluctuate according to the fluctuation of the number of idle rotation, it is difficult to make the output from the fluid output circuit 40 completely zero.

Therefore, as shown in Fig. 5, a switch valve 60a may be inserted into the output side in order to return excessive oil to the tank 50 during the idle driving. In this method, the bypass quantity Q1 is always constant. Therefore, although it is not preferable in view of efficiency, the structure can be simplified and the cost is low, since the pressure compensated throttle valve 30b may be semifixed.

B. Proportional Bypass Type Next, there is a method for operating the flow rate control valve of the type in that the bypass flow oil Q1 is in inverse proportion to the number of rotation of the hydraulic pump 20 as shown in Fig. 6. Specifically, the bypassing quantity is linearly controlled as such that the bypass flow oil Q1 is maximum during the idle driving and the bypass flow oil Q1 is zero during the maximum rotation.

However, since the bypass flow oil Q1 is internal loss of the present apparatus, the bypassing quantity may be non-linearly controlled as shown in Fig. 7.

C. Linear Interpolation Type There is also a method for operate the flow rate control valve of the type in that the quantity of the bypass flow oil Q1 is gradually reduced while maintaining the idle driving and that portion is output as an output Qw from the fluid output circuit 40. In this method, if the hydraulic pump 20 is increased in its number of rotation from the time point when the bypass flow oil Q1 becomes zero and that portion becomes the output Qwt it is as if linearly interpolated in the way as shown by the broken line of Fig. 8 from zero. As a result, it looks like that the hydraulic pump 20 is stood up from the zero rotation.

D. Step Type There is also a method for operating the flow rate control valve of the type in that the bypass flow oil Q1' as shown in Fig. 9, is abruptly made zero during the idle driving and that potion is output as an output Qw In this method, if the number of rotation of the hydraulic pump 20 is simultaneously increased, the output Qw is vertically stood up from zero and thereafter, the output Qw is increased in proportion to the number of rotation. However, in this method, a shock is rendered to the load at the starting time, and this would run counter to the spirit of the shcckless -start of the present invention. In a combination of the variable capacity hydraulic pump 20a and the prime mover 10 of Fig. 1, however, since the ratio of capacity of the idle rotation and the maximum rotation becomes extremely large, even if the bypass flow oil Q1 is abruptly made zero as shown in Fig. 10, the shock rendered to the output apparatus becomes negligibly small. Moreover, if an accumulator 70 is inserted, the shock can be absorbed (Fig. 1).

As is shown in Fig. 2, when a plurality of hydraulic pumps 20 are driven in parallel, firstly, the discharging quantity is increased until the maximum number of rotation is attained in proportion to the number of rotation of the engine by oil quantity of only one piece of (small) hydraulic pump 21 as shown in Fig. 11, and then the rotation is abruptly reduced and at the same time, it is switched to the (large) hydraulic pump 22 to attain the maximum number of ratation. Thereafter when the ---- rotation is abruptly reduced

and at the same time, when both the hydraulic pumps 21 and 22 are actuated, the output Qw can be increased to the maximum level.It will be understood from the foregoing description that the output Qw can be desirably controlled from zero to maximum without stopping the prime mover.

In the foregoing, a hydraulic pump for rotating in one direction has been described. There can be also provided an oil pressure supplying apparatus for discharging in both directions by adding a direction switch valve.

Alternatively, as shown in Fig. 12, a prime mover for rotating both normally and reversely and a hydraulic pump for discharging in both directions can be used.

E. Application to Automobile In the event a fluid pressure supplying apparatus according to the present invention is applied to a hydraulic motor drive automobile, the efficiency becomes very high compared with the conventional clutch type, because there may be taken into consideration the efficiency of the hydraulic pump and the loss only for the rotation resistance of the output side. Moreover, there can be attained a stepless shift of high efficiency from the start to the maximum speed by a completely different structure from the concept of the conventional friction start type. Furthermore, regarding the manipulation, a high degree of control can be performed which is unobtainable in the conventional automobile.

El. Proportional Output Type The discharging quantity of the hydraulic pump shown in Fig. 1 is desirably fixed and the accelerator is stepped on.

Then, there can be obtained a smooth start as shown in Figs.

4, 6, 7 and 8, and the vehicle speed is increased in proportion to the number of rotation of the engine. The output of the engine is also increased in proportion to the vehicle speed as shown in Fig. 13. This means that an output is produced in proportion to the vehicle speed in the perfectly same manner as in the conventional automobile.

However, if the discharging quantity of the hydraulic pump is changed in the midway, such output as shown in Fig. 14 can also be obtained.

That is, the total capacity of the hydraulic motor is made smaller than the maximum capacity of the hydraulic pump and the number of rotation of the vehicle wheel is made larger than the number of rotation of the engine. Then, Op is set to intermediate or less during the low speed driving immediately after start and the output of the engine is established in large power. When it reaches the high speed area, the discharging quantity of the hydraulic pump is increased. By this, an over drive can be obtained without the aid of a mechanical transmission. The control so far described is only one example. With the recent electronic control art, this can be applied to wide range of technical field such as the best control of fuel consumption, the best distribution of power with respect to various vehicle speeds, the counter-measure of exhaust gas restriction, etc.

E2. Fixed Output Type It can be accelerated to the maximum speed while always maintaining the number of rotation of the engine in the vicinity of the maximum number of rotation from immediately after the start by detecting the vehicle speed and controlling the discharging quantity of the hydraulic pump 20 as shown in Fig. 15. By this, the maximum power drive can always be available which is indispensable for sport cars, racing cars, etc. When viewed from the other way, it exhibits the effect of powerful engine brake. As apparent -from the foregoing description, there can be obtained an automobile which is very simple in structure, low in loss and high in control ability.

Furthermore, a hydraulic motor can be embedded in the wheel and a differential mechanism is unnecessitated by connecting the hydraulic motor in parallel to the present oil pressure supplying apparatus. Furthermore, by inserting a flow rate control valve is inserted in the midway of an oil pressure circuit, even the brake mechanism can be eliminated.

Thus, there can be obtained an automobile which is very simple and low in cost. In spite of low cost, it can be said as a mechanism having a high controlling performance which can fully respond to the current electronic control

art.

w /2 u Here is another example. As a counter measure for eliminating the differential mechanism, there has been proposed a whole wheel drive (4WD) system in that an electric motor is built in a wheel. However, this can be applied only to light-weight automobiles or mini cars even smaller than the light-weight automobiles under the current art.

The reason is that output of the engine of the current ordinary cars is about 50 through 100 HP, and in order to produce a power corresponding thereto, an electric motor of 12.5 through 25 HP is required per one wheel. Therefore, only electric motors per one automobile weigh 400 Kg or more.

Moreover, since the under spring weight becomes too large, there are encountered with inconveniences. In addition, if the weight of dynamo or battery is additionally taken into consideration, it becomes impossible to obtain a dynamo of a large vehicles under the current level of art.

On the contrary, in the event of an oil pressure drive system, it is very easy to build a hydraulic motor into inside the wheel, and the weight under the spring does not affect adversely compared with the conventional apparatus.

Moreover, since the transmission, clutch, propeller shaft, differential mechanism, brake mechanism, etc. are all replaced with the oil pressure circuit, the mechanism can be simplified (cost down), the weight thereof can be reduced, the maintenance fee can be reduced, and adaptability to the electronic control system is excellent.

F. Control System Using Oil Pressure Supplying Apparatus Fig. 16 shows a power servo control system, in which an oil pressure supplying apparatus according to the present invention is connected with an oil pressure actuator, and which is controlled by a controller comprising a microcomputer, etc.

Since a fluid pressure supplying apparatus according to the present invention is constituted as such as described in the foregoing, a fluid motor such as a hydraulic motor connected to the present apparatus can be very easy controlled. In addition, the constitution thereof becomes very simple compared with the conventional friction start system.

Although the present invention has been described in connection with preferred embodiments thereof, it will be appreciated that many modifications and variations will readily occur to those skilled in the art without departing from the spirit and scope of the present invention.

Claims

WHAT IS CLAIMED IS:

1. A fluid pressure supplying apparatus comprising a prime mover, a pump rotatable by said prime mover, a flow rate control means disposed in parallel to said pump, and a fluid pressure output circuit disposed in parallel to said flow rate control means.

2. A fluid pressure supplying apparatus as claimed in claim 1, wherein said prime mover is an electric motor.

3. A fluid pressure supplying apparatus as claimed in claim 1, wherein said prime mover is a gasoline engine.

4. A fluid pressure supplying apparatus as claimed in claim 1, wherein said pump is a liquid pump.

5. A fluid pressure supplying apparatus as claimed in claim 4, wherein said pump is a hydraulic pump.

6. A fluid pressure supplying apparatus as claimed in claim 1, wherein said pump is an air pump.

7. A fluid pressure supplying apparatus as claimed in claim 1, wherein said pump is a variable delivery pump.

8. A fluid pressure supplying apparatus as claimed in claim 1, wherein only one piece of said pump is provided.

9. A fluid pressure supplying apparatus as claimed in claim 1, wherein a plurality of said pumps are disposed in parallel.

10. A fluid pressure supplying apparatus as claimed in claim 1, wherein said flow rate control means is a flow rate control means.

11. A fluid pressure supplying apparatus as claimed 1, wherein said flow rate control means is semi fixed.

12. A fluid pressure supplying apparatus as claimed in claim 1, wherein said prime mover has an output for rotating both normally and reversely, said pump is a both direction discharging type pump, and a pair of said flow rate control means are provided for rotating both normally and reversely.

13. A fluid pressure supplying apparatus as claimed in Claim 1 and substantially as hereinbefore described with reference to, and as shown in the accompanying drawings.