JPH0245038B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flow rate control device for an oil pump (for example, an oil pump for power steering).

Conventional oil pump flow rate control device For example, a flow rate control device for an oil pump described in Japanese Patent Application Laid-Open No. 56-34567 will be explained with reference to FIG. (not shown); c is a throttle, d is a fixed orifice, e is a variable orifice, f is a control plunger, g is a spring, h is a discharge port connected to the gear mechanism of the power steering; i is a pilot oil passage extending from the supply oil passage b to the oil chamber on the opposite side of the spring g of the control plunger f, and the hydraulic oil discharged from the oil pump is passed through the supply oil passage b through the throttle c and the fixed orifice d. It is guided to the downstream side of the fixed orifice d through the variable orifice e from the hole j next to the fixed orifice d, and further guided to the gear mechanism section of the power steering via the discharge port h. In addition, when the engine speed changes and the oil pump discharge amount changes, and the pressure difference between the pressure upstream of the throttle c and the pressure downstream of the throttle c increases, the control plunger f resists the spring g. The variable orifice e is lowered and the opening degree of the variable orifice e is narrowed to control the flow rate of the hydraulic oil that is guided from the downstream side of the fixed orifice d to the gear mechanism section of the power steering via the discharge port h.

The oil pump flow rate control device includes a control plunger f for controlling the variable orifice e.
is operated by the differential pressure between the upstream and downstream sides of a flow control valve (not shown) and a throttle c provided upstream of the variable orifice e.
Since the pressure on the downstream side of the throttle c fluctuates greatly due to the opening and closing of the variable orifice e, there is a drawback that the flow rate discharged to the gear mechanism of the power steering varies. Also, the same conventional one is
The hydraulic fluid passing through a fixed orifice d, which is installed in parallel with the variable orifice e, is detoured through a passage provided separately from the control plunger f and discharged to the gear mechanism of the power steering, which increases the size of the device and increases its weight and weight. The cost will also increase. In addition, in the conventional device, the spring force of the spring g acting on the control plunger f that controls the variable orifice e must be set small. In other words, since the diameter of the throttle c needs to be relatively large, the differential pressure between the upstream and downstream sides of the throttle c is extremely small, and the spring force of the spring g must be set small. Therefore, the sliding resistance of the control plunger f could not be ignored, and the control of the variable orifice e was unstable.

The present invention addresses the above-mentioned problems, and includes a first and a first oil supply line provided in series in the middle of a supply oil passage extending from the discharge side of an oil pump driven by an engine to supply hydraulic oil to hydraulically operated equipment. a variable orifice installed in parallel with the second fixed orifice on the downstream side of the first and second fixed orifices; a substantially cylindrical control plunger that controls the opening degree of the variable orifice according to the pressure difference between the pressure on the downstream side of the second fixed orifice, and the difference between the pressure on the upstream side and the pressure on the downstream side of the second fixed orifice. The control plunger is provided with a flow control valve that opens a bypass hole when the pressure exceeds a predetermined value and returns a portion of the hydraulic oil that has flowed into the upstream side of the second fixed orifice to the suction side of the oil pump. , a supply oil passage passing through the variable orifice in the axial direction and communicating the downstream side of the variable orifice with an oil passage connected to the hydraulically operated device; Flow rate control of an oil pump characterized by providing a pressure receiving surface that receives pressure downstream of the orifice, and a stepped portion formed on the outer circumferential surface of the axially intermediate portion to receive pressure upstream of the first fixed orifice. The purpose of the device is to prevent variations in the discharged flow rate. The device can be made smaller, reducing weight and cost. Another object of the present invention is to provide an improved oil pump flow rate control device that can stably control the opening degree of a variable orifice.

Next, the oil pump flow rate control device of the present invention will be explained with reference to an embodiment shown in FIGS. 2 to 5. 1 is a pump housing, 2 is a discharge side of an oil pump (not shown) driven by an engine. a supply oil passage extending from the 2' is a first fixed orifice;
3 is a connector fixed to the pump housing 1, 4 is a plug fixed to the lower end of the connector 3, and 5a and 5b are second fixed orifices provided in the plug 4 so as to be inclined with respect to the axis of the connector 3. , 6a, 6b are variable orifices provided in the connector 3 such that their positions are different from each other along the axis of the connector 3; 7 is a control plunger slidably inserted into the connector 3; 7a;
7b is a stopper for the connector 3 provided on the outer peripheral surface of the control plunger 7, and 7b is a large diameter pressure receiving portion provided on the outer peripheral surface of the control plunger 7. Note that the upper and lower ends of the control plunger 7 that receive the downstream pressure of the variable orifice and the second fixed orifice correspond to the pressure receiving surfaces of the control plunger described in the claims. Since there is a difference in area (the lower end surface is wider), the above pressure is
It acts as a force that pushes the control plunger 7 upward, and the pressure receiving surface mainly refers to the lower end surface. In addition, the large diameter pressure receiving part 7 of the control plunger 7
b corresponds to the stepped portion of the control plunger described in the claims section. 8 is the same pressure receiving part 7
A chamber 8 in the connector 3 facing b is connected to the supply oil passage 2 via a pilot oil passage 9. Further, 7c is a supply oil passage that passes through the control plunger 7 in the axial direction and communicates with the downstream side of the second fixed orifices 5a, 5b and variable orifices 6a, 6b, and 10 is a second fixed oil passage that is connected to the supply oil passage 2. Orifices 5a, 5b and variable orifices 6a, 6b upstream chamber, 11
a chamber 12 connected to the supply oil passage 7c;
The chamber 13 connected to the same chamber 11
is a spring that urges the control plunger 7 upward; 14 is a flow control valve slidably inserted into the pump housing 1; 15 is a spring that urges the flow control valve 14 upward; 17 is a thin spring; a chamber connected to the chamber 11 through the hole 16; a chamber 19 below the flow control valve 14 connected to the chamber 17 through the communication hole 18;
0a is a bypass hole having a diameter larger than the land width A of the flow control valve 14, and the bypass hole 20a extends to the suction side of the oil pump. Moreover, 20b is another bypass hole, and the bypass hole 20b is provided so as to face the bypass hole 20a.

Next, the operation of the oil pump flow rate control device will be explained. The hydraulic oil discharged from the oil pump driven by the engine is supplied through the supply oil path 2 → first fixed orifice 2' → chamber 10 → second fixed orifices 5a, 5b and variable orifices 6a, 6.
The oil is sent to the gear mechanism of the power steering via b→the supply oil path 7c in the control plunger 7→the chamber 11→the discharge port 12. However, the engine speed fluctuates and the pump discharge volume changes, causing the first
The pressure on the upstream side of the fixed orifice 2' (pressure in the chamber 8) and the pressure on the downstream side of the second fixed orifices 5a, 5b (the oil supply line 7c and the pressure in the chamber 11)
When the pressure difference between the internal pressure and the internal pressure exceeds a predetermined value, the control plunger 7 descends against the spring 13, narrows the opening of the variable orifices 6a and 6b, and finally closes them to activate the Oil is supplied only from the second fixed orifices 5a and 5b. Also the second
The pressure on the upstream side of the fixed orifices 5a and 5b (the pressure inside the chamber 10) and the second fixed orifice 5
When the pressure difference between the pressure on the downstream side of a and 5b (the pressure inside the supply oil path 7c chamber 11 pore 16 communication hole 18 chamber 19) becomes larger than a predetermined value, the flow control valve 14 moves down against the spring 15. , the chamber 10 communicates directly with the bypass hole 20a, and also communicates through the bypass hole 20b, and excess oil other than the hydraulic oil flowing toward the supply oil path 7c via the second fixed orifices 5a, 5b is removed from the chamber 10. It flows into the bypass hole 20a as shown by the arrow in FIG. 3 and returns to the suction side of the oil pump. Therefore, even if the engine speed fluctuates and the oil pump discharge amount changes, hydraulic oil with little pulsation is supplied from the discharge amount 12 to the gear mechanism of the power steering. The reason for providing the control plunger 7 and the flow control valve 14 is as follows. If the flow control valve 14 can follow high-frequency pulsations well, the control plunger 7 is unnecessary, but since high-pressure oil of about 80 kg/cm ² also acts on the flow control valve 14, it is necessary to counteract it. It is configured like this, and the responsiveness is not good. Therefore, while the pulsation of the discharge flow rate is small, the control plunger 7 is operated to absorb the pulsation, and when the pulsation of the discharge flow rate becomes large, the flow control valve 14 is operated.
Absorbs pulsation.

Moreover, at that time, the excess amount of hydraulic fluid in the chamber 10 is directly returned from the chamber 10 to the bypass hole 20a, and also returned through the bypass hole 20b, that is, with two bypass holes provided, and the second The oil is discharged from the fixed orifices 5a, 5b toward the supply oil path 7c in a stable state with little pulsation. At this time, the bypass flow rate Q _S flowing through the bypass hole 20a is such that the pressure inside the chamber 10 is P ₁ , the pressure inside the bypass hole 20a is P _S , and the pressure inside the bypass hole 20a is P S .
When the opening area of is S _O , it is expressed as Q _S ∝S _O √ ₁ − _S. Therefore, the stroke X of the flow control valve 14 depending on whether there is a bypass hole 20b is as shown in Fig. 10, and X ₁ <X ₂ . That is, when there is a bypass hole 20b, if you want to make the opening area of the bypass hole S _O , you only need to lower the flow control valve 14 by a stroke X ₁ , but when there is no bypass hole 20b,
In order to make the opening area of the bypass hole S _O , it is necessary to lower the flow control valve 14 by a stroke of X ₂ , and X ₁ <X ₂ . on the other hand,
The balance equation of the flow control valve 14 is:
k is the spring constant of the flow control valve, F _O
is the spring force of the flow control valve when the stroke is zero, A is the pressure receiving area of the flow control valve, Pφ is the pressure of chamber 11 on the discharge side,
If ΔP1 is the differential pressure between the pressure in chamber 11 (that is, the pressure in chamber 19) and the pressure in chamber 10 when bypass hole 20b is present, and ΔP2 is the differential pressure when bypass hole 20b is not present, then bypass hole 20b exists. If...AΔP ₁ = F _O +
X ₁ K When there is no bypass hole 20b...AΔP ₂ =F _O +
X ₂ K Therefore, as mentioned above, there is a relationship of X2>X1, so
According to the above formula, ΔP2>ΔP1. This means that under the condition that the oil pump rotates at a constant rate,
[When there is a bypass hole 20b → ΔP1 is relatively small,
The amount of variation in the discharge flow rate is relatively small] and [When there is no bypass hole 20b → ΔP2 is relatively large → the amount of variation in the discharge flow rate is relatively large]. This indicates that the bypass flow rate increases and the discharge flow rate decreases relatively. In FIG. 11, which shows the discharge flow rate characteristics when there is a bypass hole 20b, the discharge flow rate varies depending on the discharge pressure Pφ because the stroke X of the flow control valve 14 differs depending on each pressure, and ΔP changes. . For reference, FIG. 12 shows the discharge flow rate characteristics when the bypass hole 20b is not provided. From the above explanation, it can be said that
This means that the bypass hole 20b can reduce the change in the discharge flow rate due to the change in the load pressure,
This leads to the ability to make the steering force characteristics of the vehicle more stable. for example
Flow rate change at 2000 rpm (3Kg/cm ² →80Kg/
cm ² ) is 4.1 to 5.2 when there is bypass hole 20b
/min (ΔQ=1.1/min), bypass hole 20b
If there is no = 3.2 to 4.9/min (ΔQ = 1.7/min)
It is. Moreover, the bypass hole 20b does not only stabilize the discharge flow rate characteristics. That is, the hydraulic pressure (radial load) applied to the land portion of the flow control valve 14 is balanced, the sliding resistance of the flow control valve 14 is reduced, and the wear of the sliding portion is reduced.

FIG. 6 shows another embodiment in which one second fixed orifice 5 and one variable orifice 6 are provided, and the second fixed orifice 5 is provided in the connector 3. FIG. 7 shows another embodiment in which the number of the second fixed orifice 5 and the variable orifice 6 is one each, and the second fixed orifice 5 is provided in the plug 4. 8 and 9 show two each of the second fixed orifice 5 and variable orifice 6 (5a, 5b and 6a, 6).
b) while the second fixed orifices 5a, 5b
This is still another embodiment in which the plug 4 is provided horizontally. In the embodiment shown in FIG. 6, an oil passage from the chamber 10 to the second fixed orifice 5 is required, which increases the size of the connector 3.
In the embodiment shown in FIGS. 7 and 8, the above-mentioned oil passage is not required, and the connector 3 becomes compact. In addition, a part of the communication hole 18 is made into a small hole 16 to provide hydraulic damping to stabilize the operation of the flow control valve 14. In the embodiment shown in FIG. It can be provided in
It is advantageous in terms of processing. In addition, the reason why the variable orifices 6a and 6b are provided at different levels in the embodiments shown in FIGS. Make it easier to maintain balance. ()
The transient region where the discharge flow rate decreases is arbitrarily set.
That is, the degree of freedom in setting the spring force of the spring 13 is
Although there is not much space available, the diameter and height difference of the variable orifices 6a and 6b are selected to arbitrarily set the transition region where the discharge flow rate is reduced. etc. Further, in the embodiment shown in FIG. 8, the second fixed orifices 5a and 5b are provided horizontally, but the reason for this is that in the case of FIG.
The jet flow after passing directly acts on the control plunger 7, which tends to make the operation of the control plunger 7 unstable, but if it is provided as shown in Fig. 8, the jet flow after passing through the second fixed orifices 5a and 5b will interfere with each other. This is because the negative influence on the control plunger 7 can be eliminated. Note that the second fixed orifice 5 is the seventh
It can also be provided on the pump housing 1 side as shown by the broken line in the figure.

The oil pump flow rate control device of the present invention is configured as described above, and the control plunger 7 for controlling the opening degree of the variable orifice 6 or 6a, 6b is connected to the upstream side of the first fixed orifice 2' and the second fixed orifice. 5 or 5a, 5b, the fluctuation in the differential pressure caused by opening and closing of the variable orifice 6 or 6a, 6b can be suppressed to a small level, and the discharge flow rate to the gear mechanism of the power steering can be reduced. It is possible to approach the set value more accurately. Furthermore, in the present invention, the hydraulic oil that has passed through the second fixed orifice provided in parallel to the variable orifice is directly discharged to the gear mechanism section of the power steering via the supply oil passage 7c provided at the center of the control plunger 7. The device can be made compact, processing can be facilitated, and manufacturing costs can be reduced. In addition, in the present invention, the control plunger 7 that controls the opening degree of the variable orifice is controlled by the pilot oil pressure (pressure inside the chamber 8) and the first fixed orifice 2' and the second fixed orifice 5 or 5a, 5b of the supply oil path 2. Since the pressure difference between the lower pressure and the lower pressure is used to act against the spring 13, the sliding resistance acting on the control plunger 7 can be ignored, and the opening degree of the variable orifice 6 or 6a, 6b can be stabilized. It has an effect that can be controlled.

Although the present invention has been described above with reference to embodiments, it goes without saying that the present invention is not limited to such embodiments, and that various design modifications can be made without departing from the spirit of the present invention. .

[Brief explanation of drawings]

FIG. 1 is a vertical side view showing a conventional oil pump flow rate control device, FIG. 2 is a vertical side view showing an embodiment of the oil pump flow rate control device according to the present invention, and FIG. 4 is a cross-sectional plan view taken along the line of sight in FIG. 2, FIG. 5 is an enlarged longitudinal side view of the control plunger,
6 to 8 are longitudinal sectional side views showing other embodiments, FIG. 9 is a lateral plan view taken along the arrow line in FIG. 8, and FIG. 10 is an opening area of the bypass hole and a flow control valve FIG. 11 is an explanatory diagram showing the relationship with stroke, FIG. 11 is an explanatory diagram showing the discharge flow rate characteristic when there is a bypass hole 20b, and FIG. 12 is an explanatory diagram showing the discharge flow rate characteristic when there is no bypass hole 20b. 2... Supply oil path, 2'... First fixed orifice, 5
Or 5a, 5b...second fixed orifice, 6 or 6a, 6b...variable orifice, 7...control plunger, 7b...step part of control plunger 7, 7c...
Supply oil path of control plunger 7, 14...control valve.

Claims (1)

[Claims] 1. A first and a second oil passage provided in series in the middle of a supply oil passage extending from the discharge side of an oil pump driven by an engine and supplying hydraulic oil to hydraulically operated equipment.
a fixed orifice, a variable orifice provided in parallel with the second fixed orifice on the downstream side of the first and second fixed orifices, and a pressure on the upstream side of the first fixed orifice and the second fixed orifice. a substantially cylindrical control plunger that controls the opening degree of the variable orifice according to the pressure difference between the pressure on the downstream side of the fixed orifice, and the pressure difference between the pressure on the upstream side and the pressure on the downstream side of the second fixed orifice. a flow control valve that opens a bypass hole and returns a portion of the hydraulic oil that has flowed into the upstream side of the second fixed orifice to the suction side of the oil pump when A supply oil passage axially passes through the variable orifice and communicates the downstream side of the variable orifice with an oil passage connected to the hydraulically operated device, and the second fixed orifice and the variable orifice are formed at the ends in the axial direction. A flow rate control device for an oil pump, comprising: a pressure receiving surface that receives pressure on the downstream side of the first fixed orifice; and a stepped portion that is formed on the outer circumferential surface of the axially intermediate portion and receives pressure on the upstream side of the first fixed orifice. .