JPS646987B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steering system with high-speed stability, and its purpose is to be able to obtain appropriate steering force over the entire vehicle speed range and to reduce horsepower consumption. It is to do so.

In general, high-speed stabilization is being promoted in automobiles equipped with power steering devices, but in recent years there has been a strong demand for improved fuel efficiency in automobiles, and steering systems that consume less horsepower are also required. In line with this demand, so-called rotation speed sensitive pumps have been put into practical use in some areas, which reduce the flow rate supplied to the power steering device when the engine rotates at high speed, changing the steering characteristics. With the steering force control method, the amount of change in steering force can only be obtained at most about 0.1 kg・m, so a large change in steering force cannot be expected, and the speed range in which the steering force changes is also limited. be.

Therefore, in order to increase the change in steering force and obtain effective high-speed stability, a vehicle speed-sensitive power steering device is required, for example, which bypasses both chambers of the power cylinder depending on the vehicle speed. Since the flow rate supplied to the power steering device is constant, the internal resistance of the power steering device does not change and does not contribute to reducing horsepower consumption, and furthermore, the range of changes in steering force is limited to the high speed region. Ru.

The present invention has been made in view of the above-mentioned problems, and by incorporating a high-speed sensitive power steering device and a rotation speed sensitive pump into one steering system, it provides high-speed stability and at the same time reduces horsepower consumption. In addition, by dividing the steering force change range between the two into a first speed range and a second speed range higher than the first speed range, the steering system is able to obtain an appropriate steering force over the entire range of vehicle speeds. We aim to provide the following.

Embodiments of the present invention will be described below based on the drawings. In FIG. 1, a steering handle 10 is attached to one end of a handle shaft 11.
A steering shaft 13 of a power steering device 12 is connected to the other end of the steering shaft 1 . The power steering device 12 includes such a steering shaft 1
It consists of a servo valve 14 that is controlled by the manual steering torque transmitted to The signal is transmitted to the steering wheels 17 via the steering linkage 16 . The power steering device 1
a pump 19 driven by the engine 18 to supply pressure fluid to the servo valves 14 of 2;
is provided, and the discharge flow rate of this pump 19 is controlled according to the rotation speed of the pump by a flow rate control device, which will be described later.

By changing the speed of the engine 18, the rear wheels 21
Behind the transmission 22 that transmits the
A tachogenerator 23 for detecting vehicle speed is provided,
This tachogenerator 23 outputs a voltage proportional to the rotational speed of the rear wheel 21, that is, the vehicle speed.
This output voltage is applied to control circuit 24. The control circuit 24 has an output voltage at a predetermined level (vehicle speed).
(corresponding to V2) or above, the solenoid of the bypass valve 25, which will be described below, is controlled to be energized.

FIG. 2 shows an example of a bypass valve 25 that connects both end chambers of the power cylinder 15 depending on the vehicle speed. A fixed valve body 30 forming a communication passage 29 including an orifice 28 that communicates with the chamber 27;
9, a spring 32 that presses the valve sleeve 31 in the direction of closing the communication passage 29, and a spring 32 that presses the valve sleeve 31 in the direction of opening the communication passage 29 against the repulsive force of the spring 32. It is composed of a solenoid 33 that performs suction. And usually, as shown in the figure,
The valve sleeve 31 connects to the communication path 2 by spring force.
9 is held in a closed position, thereby sealingly separating both end chambers of the power cylinder 15. However, when the solenoid 33 is energized by the control circuit 24, the valve sleeve 31
is slid against the spring force, thereby opening the communication passage 29 and allowing the two end chambers of the power cylinder 15 to communicate with each other via the orifice 28. Therefore, when the solenoid 33 is energized, a portion of the pressure fluid distributed to the power cylinder 15 is bypassed from the high pressure chamber to the low pressure chamber, and the output of the power cylinder 15 is reduced.

Next, an example of a flow rate control device 40 that controls the discharge flow rate of the pump 19 according to the pump rotation speed will be described with reference to FIG. A valve housing hole 42 is passed through the pump housing 41, and a union 43 is screwed into one end of the valve housing hole 42, and a stopper 44 is fitted into the other end. The union 43 has a substantially cylindrical shape, and one end is inserted into the valve housing hole 42.
Its tip is loosely fitted into the valve storage hole 42, and the other end is opened with a pressure fluid discharge port 45 connected to the servo valve 14 of the power steering device 12. A supply passage 46 and a bypass passage 47 are opened in the valve housing hole 42 and are spaced apart in the axial direction, and the supply passage 46 is an annular restriction formed between the outer circumference of one end of the union 43 and the valve housing hole 42 The restriction passage 48 is constantly communicated with the valve housing hole 42 through the passage 48, and when the pump discharge flow rate supplied to the supply passage 45 increases, the flow passage resistance causes the restriction passage 48 to close the upstream and downstream sides, that is, the supply passage 46 and the valve housing. A pressure difference is created between the hole 42 and the hole 42. The valve storage hole 42 has a supply passage 46 and a bypass passage 47.
A flow rate adjustment spool valve 49 is slidably fitted to close the communication path and adjust the opening degree of the communication path. Two valve chambers 51 are formed. The second valve chamber 51 is provided with a spring 52 that presses the spool valve 49 toward the first valve chamber 50, and the spring force of this spring 52 normally positions the spool valve 49 in a position where it abuts the union 43. A supply passage 4 that is held and opens to the first valve chamber 50
6 and the bypass passage 47 are cut off.
A throttle member 53 is fitted into the union 43 in proximity to the discharge port 45, and the first valve chamber 50 and the discharge valve 45 communicate with the center of the throttle member 53 via a fluid passage described later. A first throttle passage 54 is formed. A second throttle passage 55 is formed in the throttle member 53 around the first throttle passage 54 and is made up of a plurality of small holes that communicate the first valve chamber 50 and the discharge port 45 via the fluid passage. As a result, the first valve chamber 50 and the discharge port 45 are communicated with each other via the first and second throttle passages 54 and 55 arranged in parallel, and the first throttle passage 54 is appropriately controlled to close by a control spool to be described later. Ru. A control hole 56 that opens toward the discharge port 45 side is opened in the diaphragm member 53.
The control hole 56 communicates with the second valve chamber 51 via the union 43 and communication holes 57 and 58 formed in the pump housing 41. As a result, the fluid that has passed through the first and second throttle passages 54 and 55 is guided to the second valve chamber 51, and pressure acts on both end surfaces of the spool valve 49 before and after passing through the throttle passages 54 and 55. In order to
The opening degree of the bypass passage 47 is adjusted so that the pressure drop due to the throttle passages 54 and 55 is maintained at a constant value. A control spool 59 is slidably inserted into the union 43, and the first valve chamber 5 is connected to the control spool 59.
0 and the throttle passages 54 and 55.
0 is passed through. At one end of the control spool 59 is a control shaft portion 61 that controls opening and closing of the first throttle passage 54.
is installed protrudingly. A spring 62 is inserted between the control spool 59 and the aperture member 53 in a stored state, and the stored force of the spring 62 locks the control spool 59 to a stepped portion 63 formed in the normal union 43. As a result, the control shaft portion 61 of the control spool 59 is separated from the throttle member 53 and the first throttle passage 54 is opened. The union 43 also includes the fluid passage 60.
The control spool 59 and the union step 6 are separated from each other.
A pressure introduction hole 64 that opens at the junction with 3 is bored, and this pressure introduction hole 64 communicates with the supply passage 56 .

When the pump rotor is rotationally driven by the automobile engine, pressure fluid is discharged from the pump chamber to the discharge chamber, and this pressure fluid is passed through the supply passage 46 and from the restriction passage 48 between the union 43 and the valve storage hole 42. The fluid is supplied to the first valve chamber 50 , and is sent from the valve chamber 50 to the power steering device 12 from the discharge port 45 via the fluid passage 60 , the first and second throttle passages 54 and 55 .

When the pump rotation speed is low and the pump discharge flow rate is low, the spool valve 49 closes the bypass passage 47 and the entire pump discharge flow rate is sent to the power steering device 12 via the first and second throttle passages 54 and 55. However, when the discharge flow rate increases as the pump rotational speed increases, the spool valve 49 is slid to keep the pressure difference between the two throttle passages 54 and 55 constant, and the bypass passage 47 is opened. Bypass excess flow. As a result, the power steering device 12
The pressure fluid supplied to the first and second throttle passages 5
The predetermined flow rate Q2 determined in steps 4 and 55 is maintained.

When the pump rotation speed further increases and the discharge flow rate supplied to the supply passage 46 increases, the restriction passage 48
The fluid pressure in the supply passage 46 increases due to the flow resistance at the supply passage 46 , creating a pressure difference between the supply passage 46 and the first valve chamber 50 . The pressure in the supply passage 46 is introduced between the joint surfaces of the control spool 59 and the union 43 through the pressure introduction hole 64, and the control spool 59 is displaced against the spring 62. Therefore, the first throttle passage 54 is gradually restricted and finally closed by the control shaft portion 61 of the control spool 59, so that the first valve chamber 50 and the discharge port 45 are connected only through the second throttle passage 55. The pressure fluid that comes into communication with the power steering device 12 and is sent to the power steering device 12 is
A predetermined amount determined by the second throttle passage 55
Reduced to Q1.

Here, the reduction ratio of the transmission 22 is set to 1:
1, the rotational speed of the pump 19 is virtually equal to the vehicle speed, and therefore the relationship between the flow rate supplied to the power steering device 12 and the vehicle speed is as shown in FIG. In the first speed range, which changes from medium speed (medium speed of /h) to V2 (high speed of 80 km/h, for example), the flow rate gradually decreases from Q2 to Q1, and as the flow rate decreases, the steering force changes as shown in Figure 5. As shown in , it gradually increases from T1 to T2.

When the vehicle speed reaches a second speed range exceeding V2, the solenoid 33 of the bypass valve 25 is energized by the control circuit 24 that responds to the output voltage from the tachometer generator 23, thereby attracting the valve sleeve 31 and 29 is opened. Therefore, since both end chambers of the power cylinder 15 are communicated with each other via the orifice 28, even if pressure fluid is supplied to one chamber of the power cylinder 15 due to the operation of the power steering device 12, a portion of the pressure fluid is is bypassed from the other chamber to the tank side via the orifice 28, and as a result of this bypass control, the steering force further increases from T2 to T3.

In this case, if the activation timing of the bypass valve 25 is set to V2', which is lower than the vehicle speed V2, the power steering device 12 will be The steering force can be changed by both the reduction of the supply flow rate and the cylinder bypass control, and the opening area of the orifice 28 as the bypass valve 25 is increased in an analog manner as the vehicle speed increases. If one is used, it is also possible to smoothly control the change in steering force from T2 to T3.

Note that a bypass valve that changes the opening area of the orifice in response to pressure depending on the vehicle speed can also be used, and a high-pressure side flow path (supply line) that connects the bypass valve to both end chambers of the power cylinder. It can also be inserted between the flow path (discharge line) and the low pressure side flow path (discharge line).

As described above, the present invention provides a vehicle speed-sensitive power steering device that communicates the high-pressure side and low-pressure side of the power cylinder according to the vehicle speed, and a power steering device that connects the high-pressure side and low-pressure side of the power cylinder according to the vehicle speed, and a power steering device that connects the high-pressure side and the low-pressure side of the power cylinder according to the vehicle speed. The configuration incorporates a speed-sensitive pump that reduces the flow rate into a single steering system, which provides high-speed stability and at the same time reduces the internal resistance by reducing the flow rate supplied to the power steering system. As a result, energy consumption can be minimized, contributing to improved fuel efficiency.

Moreover, the present invention provides a steering force change range by the above-mentioned rotational speed sensitive pump and vehicle speed sensitive power steering device, including a first speed range from medium speed to high speed and a second speed range higher than the first speed range. Since the configuration is such that the steering force is shared, an appropriate steering force can be obtained over the entire range of vehicle speeds.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a control mechanism diagram systematically showing a steering device with high-speed stability, and FIG. 2 is a sectional view showing a bypass valve of a vehicle speed-sensitive power steering device. , FIG. 3 is a sectional view showing a flow rate control device for a rotation speed sensitive pump, FIG. 4 is a diagram showing flow characteristics with respect to vehicle speed, and FIG. 5 is a diagram showing steering force characteristics with respect to vehicle speed. 10... Steering handle, 12... Power steering device, 14... Servo valve, 15... Power cylinder, 18... Engine, 19... Pump, 23
...Tachometer generator, 24...Control circuit, 25
...Bypass valve, 29...Communication passage, 31...
Valve sleeve, 33... Solenoid, 40...
Flow rate control device, 49... Spool valve for flow rate adjustment,
54, 55... throttle passage, 59... control spool.

Claims (1)

[Claims] 1 A servo valve operated based on manual steering torque applied to a steering handle, a power cylinder whose supply and discharge of pressure fluid is controlled by the operation of this servo valve, and a high pressure side and a low pressure side of this power cylinder. A vehicle speed-sensitive power steering device equipped with a bypass valve that communicates in accordance with the vehicle speed, and a first speed range in which the vehicle speed ranges from medium to high speed and is driven by an engine to supply pressurized fluid to the power steering device. a rotation speed sensitive pump equipped with a flow rate control device that reduces the flow rate supplied to the power steering device; a vehicle speed detection means that generates an output according to the vehicle speed; 1. A steering system having high-speed stability, comprising: a control means for operating the bypass valve when a second speed range higher than the first speed range is reached.