JPH0512083Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention improves the roll rigidity of the vehicle by interposing a hydraulic cylinder between the vehicle body and the wheels and controlling the pressure in the pressure chamber of this hydraulic cylinder. This invention relates to an improvement in a hydraulic pressure supply device that supplies hydraulic pressure to a hydraulic cylinder in a hydraulic suspension that controls characteristics such as pitch stiffness.

[Conventional technology]

2. Description of the Related Art As a conventional hydraulic pressure supply device for a vehicle, one having a configuration shown in FIG. 8, for example, is known.

In the conventional example shown in FIG. 8, the output shaft 2 of the engine 1 is
A hydraulic pump 3 is directly connected to the hydraulic pump 3, and a relief valve 4 for keeping the output pressure constant is connected to the output side of the hydraulic pump 3.

[Problem that the invention attempts to solve]

However, in the above-mentioned conventional vehicle hydraulic supply system, one hydraulic pump 3 is directly connected to the output shaft 2 of the engine 1, and therefore a predetermined rated flow rate is ensured regardless of the load on the hydraulic supply system (high or low line pressure). Therefore, even when the servo valve, actuator, etc. are not operating, the hydraulic pump 3 is rotating, resulting in a large loss of horsepower consumption and a large load on the engine, resulting in a problem of reduced fuel efficiency.

Therefore, this invention was made by focusing on the problems of the conventional example described above, and suppresses the discharge amount of the hydraulic pump while securing a predetermined line pressure according to load fluctuations on the discharge side of the hydraulic pump. It is an object of the present invention to provide a hydraulic pressure supply device for a hydraulic suspension that can solve the problems of the conventional example.

[Means for solving problems]

In order to achieve the above object, this invention includes a hydraulic cylinder interposed between each wheel and the vehicle body, and a pressure control valve interposed in the supply side piping between the hydraulic cylinder and the hydraulic supply device. In the hydraulic suspension, the hydraulic supply device includes a hydraulic pump connected to a rotary drive source to be rotationally driven, and whose discharge side is connected to the supply side piping, and a hydraulic pump and pressure of the supply side piping. an accumulator and a relief valve connected between the control valves, and a discharge amount control device that controls the discharge amount of the hydraulic pump itself to the supply side piping to decrease as the pressure of the supply side piping increases. It is characterized by having the following.

[Effect]

In this invention, the discharge amount of the hydraulic pump itself of the hydraulic supply device that supplies working hydraulic pressure to the pressure control valve that controls the hydraulic suspension via the supply side piping is controlled by the discharge amount control device. Since the pressure is controlled to decrease as the pressure increases, when the pressure control valve is in operation and the consumption flow increases and the pressure in the supply side piping decreases,
The pressure in the supply side piping is maintained at a constant value by increasing the number of revolutions of the hydraulic pump or by increasing the discharge amount per rotation of the hydraulic pump according to the pressure drop, and the pressure control valve is in an inactive state. When the consumption flow rate is low and the pressure in the supply side piping is high, the rotational speed of the hydraulic pump is lowered or the discharge amount per revolution is lowered to lower the horsepower consumption and thereby reduce the load on the rotary drive source.

〔Example〕

An embodiment of this invention will be described below based on the drawings.

FIG. 1 is a hydraulic circuit diagram showing a first embodiment of this invention.

In the figure, 1 is an engine as a rotational drive source, 2 is its output shaft, and 3 is a hydraulic pump connected to the output shaft 2. This hydraulic pump 3 is connected in series to the output shaft 2 of the engine 1, and the discharge amount per rotation is as shown by the solid straight line _L1 in FIG. a main hydraulic pump 3a having a capacity that can secure line pressure when not in operation;
An auxiliary hydraulic pump with a capacity indicated by the chain line _L2 in FIG. 2, which can secure the line pressure when the discharge amount per rotation is large, that is, when the pressure control valve 15 is activated, in cooperation with the main hydraulic pump 3a. 3b and a power steering hydraulic pump 3c. Note that the straight line _L3 in FIG. 2 indicates the total discharge flow rate characteristic of the main hydraulic pump 3a and the auxiliary hydraulic pump 3b.

The discharge side of the main hydraulic pump 3a is directly connected to the output side hydraulic piping 5, and the discharge side of the auxiliary hydraulic pump 3b is connected to an input port 6a of a two-position electromagnetic directional switching valve 6 constituting a discharge amount control device 12, which will be described later. One output port 6b of the directional switching valve 6 is connected to the output side hydraulic piping 5, the other output port 6c is connected to the tank 8 through the drain piping 7, and the discharge side of the power steering hydraulic pump 3c is connected to the output side hydraulic piping. 9 is connected.

9 Furthermore, a relief valve 4 for maintaining the line pressure at the rated pressure is connected between the output side hydraulic piping 6 and the tank 8, and an accumulator 10 is connected downstream of the relief valve 4, which connects the output side hydraulic piping 9 and the tank 8. 8, a relief valve 11 is connected.

Furthermore, the output side hydraulic piping 5 has its line pressure
A discharge amount control device 12 that detects P _L and controls the discharge amount of the hydraulic pump 3 is provided. This discharge amount control device 12 includes the electromagnetic directional switching valve 6, a pressure detector 13 that detects the line pressure P _L of the output side hydraulic piping 5, and a control circuit that controls the electromagnetic directional switching valve 6 based on the detection signal. It is equipped with 14. Here, as shown in FIG. 3, the control circuit 14 controls the line pressure P _L detected by the pressure detector 13 to a predetermined set value.
When P ₂ or more, the output of the control signal CS of the predetermined current value _IS is stopped and the electromagnetic directional control valve 6 is switched to the neutral position, and from this state the line pressure P _L is set to a predetermined value smaller than the predetermined set value P ₂ . When the set value P is less than ₁ ,
Hysteresis control is performed by outputting a control signal CS with a predetermined current value _IS to switch the electromagnetic directional control valve 6 to the offset position.

On the other hand, the tip of the output side hydraulic pipe 5 is connected via a pressure control valve 15 to a hydraulic cylinder 18 that constitutes an active suspension interposed between a vehicle body 16 and wheels 17. Here, pressure control valve 1
5 is a cylindrical valve housing 19 and an insertion hole 1 provided in this valve housing 19, as shown in FIG.
A spool 20 and a rod 21 are slidably disposed on the spool 9a, a spring 22 is interposed between the spool 20 and the rod 21, and the pressing force of the spring 22 is controlled via the rod 21 to offset the spool 19. It has a proportional solenoid 23 that controls movement between the position and the operating position on both ends thereof. Here, the valve housing 19 has an input port 19b whose one end communicates with the insertion hole 19a and whose other end is connected to the output side hydraulic piping 5 of the hydraulic supply device, and a hydraulic piping connected to the tank 8 of the hydraulic supply device. 24 and the pressure chamber 1 of the hydraulic cylinder 18 via the hydraulic piping 25.
An input/output port 19d communicating with the input/output port 8a is provided. The output port 19c is connected to drain passages 19e and 19f that communicate between the output port 19c and the upper and lower ends of the spool 20.

The spool 20 is formed with a land 20a facing the input port 19b and a land 20b facing the output port 19c. The land 20c has a smaller diameter than the lands 20a and 20b.
is formed at the lower end, and lands 20a and 20
A pressure control chamber C is formed between the input/output port 19c and the pressure control chamber 19c. The pressure control chamber C is connected to the input/output port 19d through a pilot passage 19g.

Furthermore, the proportional solenoid 23 is composed of an actuator 23a that is slidable in the axial direction and an excitation coil 23b that drives the actuator 23a. , a command value V is supplied from an attitude change suppression control device 26 that outputs a command value for controlling the attitude change of the vehicle body. Here, the relationship between the command value V and the working oil pressure P output from the input/output port 19d is as shown in FIG. 5. When the command value V is zero, a predetermined offset pressure P ₀ is output. , When the command value V increases in the positive direction from this state, the output pressure P increases with a predetermined proportional gain _K1 ,
When the line pressure P _L of the hydraulic supply device reaches the rated pressure P _S , it is saturated, and when the command value V increases in the negative direction, the output pressure P decreases in proportion to this.

In the pressure control valve 12, a pressing force from a proportional solenoid 23 is applied to the spool 20 via a spring 22.
In a state where the pressing force of C and the pressure of the pressure control chamber C are balanced, a relatively low frequency vibration input (or When a downward vibration input (by passing through the recess) is transmitted, the piston rod 18b of the hydraulic cylinder 18 tends to move upward (or downward), and the pressure in the pressure chamber 18a increases (or decreases). In this way, when the pressure in the pressure chamber 18a increases (or decreases), the pressure in the pressure control chamber C, which is communicated with the pressure chamber 18a through the hydraulic piping 25, the input/output port 19d, and the pilot passage 19g, increases accordingly. rise (or fall)
However, since the balance with the pressing force of the spring 22 is lost, the spool 20 moves upward (or downward),
Since the space between the input port 19b and the input/output port 19d changes in the closing direction (or opening direction), a part of the pressure in the pressure chamber 18a is transferred from the input/output port 19d via the output port 29c and the hydraulic piping 24. The oil is discharged into the tank 8 (or the oil pressure is supplied from the oil pressure supply device to the pressure chamber 18a via the input port 19b, the input/output port 19d, and the hydraulic piping 25). As a result, the pressure chamber 1 of the hydraulic cylinder 18
The pressure in the pressure chamber 8a is reduced (or increased), and the increase in pressure in the pressure chamber 18a due to upward vibration input (or the decrease in pressure in the pressure chamber 18a due to downward vibration input) is suppressed, and is transmitted to the vehicle body 16. Vibration input can be reduced.

Next, the operation of the first embodiment will be explained. now,
Assuming that the vehicle is in a stopped state with the engine 1 idling and no passengers are getting on or off the vehicle or loading or unloading luggage, in this state there is no change in the attitude of the vehicle body and no vibration input from the road surface to the wheels 17.
The command value V from the posture change suppression control device 26 is maintained at zero, the output pressure P of the pressure control valve 15 becomes the offset pressure P ₀ , and the pressure in the pressure chamber 18a of the hydraulic cylinder 18 is also maintained at the offset pressure P ₀ . ,
A predetermined distance is maintained between the vehicle body 16 and the wheels 17. Therefore, in this state, the hydraulic cylinder 1
Since there is almost no pressure fluctuation in the pressure chamber 18a of No. 8,
The amount of hydraulic oil consumed by the pressure control valve 15 is also small, and the line pressure of the output side hydraulic piping 5 of the hydraulic supply device is
P _L is the predetermined set pressure set by the relief valve 4
It has a rated pressure P _S of P ₂ or higher. Therefore,
Since the line pressure P _L is detected by the pressure detector 13, a control signal of a predetermined current value I _S is sent from the control circuit 14.
CS is not output, and the electromagnetic directional control valve 9 is maintained at the neutral position accordingly. Therefore, the hydraulic oil discharged from the auxiliary hydraulic pump 3b returns to the tank 8 via the electromagnetic directional control valve 6, and the auxiliary hydraulic pump 3b enters the no-load operating state, and the output side hydraulic piping 5
The line pressure P _L is maintained only by the discharge amount of the main hydraulic pump 3a. At this time, the load on the engine 1 is only the main hydraulic pump 3a and the power steering hydraulic pump 3c, and the load on the auxiliary hydraulic pump 3b is reduced.

Thereafter, when the vehicle is started and the engine speed increases above the idling speed, the rotation speeds of the hydraulic pumps 3a and 3b increase accordingly, so that the discharge flow rates of both also increase. At this time, when a so-called scuffing phenomenon occurs in which the rear part of the vehicle body sinks when the vehicle starts, the command value V for increasing the pressure in the rear wheel side hydraulic cylinder 18 is sent from the vehicle body change suppression control device 26 to the pressure control valve 15 in response to this phenomenon. This causes the pressure control valve 15 to operate, increasing the pressure in the rear wheel hydraulic cylinder 18 and suppressing changes in the attitude of the vehicle body. Therefore, the line pressure P _L tends to decrease by the pressure increase of the hydraulic cylinder 18, and if this cannot be absorbed by the discharge flow rate of the main hydraulic pump 3a and the accumulator 10, the line pressure P _L will decrease.

In this way, when the line pressure P _L decreases to below the predetermined set pressure P ₁ , the discharge amount control device 1
A control signal CS of a predetermined current value I _S is sent from the control circuit 14 of
is output to the solenoid 6d of the electromagnetic directional control valve 6, and the solenoid 6d is energized accordingly.
It is switched to the offset position shown in FIG. Therefore, the hydraulic oil discharged from the auxiliary hydraulic pump 3b is added to the hydraulic oil discharged from the main hydraulic pump 3a and supplied to the output side hydraulic piping 5, so that the line pressure P _L in the hydraulic piping 5 increases rapidly. The pressure is boosted to

Thereafter, when the line pressure P _L becomes equal to or higher than the predetermined set pressure P ₂ , as described above, the output of the control signal CS from the control circuit 14 is stopped, and in response, the electromagnetic directional control valve 6 returns to the neutral position. As a result, the auxiliary hydraulic pump 3b enters the no-load operation state, and the main hydraulic pump 3b
The line pressure P _L is maintained only by a.

After that, even when the vehicle changes its posture such as rolling, pitching, or bouncing, the pressure control valve 1
5 is in the operating state, the line pressure is increased in the same way as above.
In response to a decrease in P _L , the auxiliary hydraulic pump 3b is switched from a no-load operating state to a loaded operating state to maintain a predetermined line pressure P _L.

Note that, as in the first embodiment, the hydraulic pump 3
By sequentially connecting the power steering hydraulic pump 3c to the power steering hydraulic pump 3c, there is an advantage that the space in the engine room occupied by the power steering hydraulic pump 3c can be reduced.

Next, a second embodiment of this invention will be described with reference to FIG.

This second embodiment, as a discharge amount control device, detects the discharge side pressure of the main hydraulic pump 3a and returns a part of the discharge amount of the auxiliary hydraulic pump 3b to the tank 8 side based on this, thereby controlling the auxiliary hydraulic pressure. This is to reduce the load on the pump 3b.

That is, as shown in FIG. 6, the discharge amount control device 12 controls the check valve 31 interposed between the discharge side and the output side hydraulic piping 5 of the auxiliary hydraulic pump 3b.
and the discharge side of the auxiliary hydraulic pump 3b and the check valve 3.
When the pressure of the main pump 3a reaches a predetermined set pressure P2 _or more as shown in FIG. 7 due to the pilot pressure interposed between the piping between 1 and the tank 8, all of the discharge amount of the auxiliary hydraulic pump 3b is reduced. is returned to the tank 8 side, and from this state, when the predetermined set pressure P1, which is less than the set pressure _P2 , becomes lower than the predetermined set pressure _P1 , the unload valve is operated with hysteresis so that the entire discharge amount of the auxiliary hydraulic pump 3b is supplied to the check valve 31. 32, and has the same configuration as the first embodiment, except that the pressure on the discharge side of the main hydraulic pump 3a is supplied as the pilot pressure to the unload valve 32, Corresponding parts are given the same reference numerals, and detailed description thereof will be omitted.

Next, the operation of the second embodiment will be explained. now,
The line pressure P _L in the output side piping 5 is controlled by the pressure control valve 15.
The rated pressure above the predetermined set pressure _P2 supplied to
If it is in P _S , the main pump 3a at that time
Since the discharge side pressure of The system is in operation, and the line pressure P _L is maintained only by the discharge amount of the main hydraulic pump 3a.

Thereafter, when the line pressure P _L decreases due to the operation of the pressure control valve 15 and becomes less than the predetermined set pressure _P1 ,
Since the line pressure P _L at that time is supplied to the unload valve 32 as a pilot pressure, the unload valve 32 is closed, and the discharge amount of the auxiliary hydraulic pump 3b is all transferred to the output side hydraulic piping via the check valve 31. 5. Therefore, the discharge amount of both the main hydraulic pump 3a and the auxiliary hydraulic pump 3b is supplied to the output side hydraulic piping 5, so that the line pressure P _L increases. Then, when the line pressure P _L exceeds the predetermined set pressure P ₂ , as mentioned above,
Since the unload valve 32 is controlled to be in the open state, it is maintained only by the discharge amount of the main hydraulic pump 3a, and as a result, the same operation as in the first embodiment can be performed.

In each of the above embodiments, a case has been described in which the discharge amount control device 12 detects the load on the hydraulic pumps 3a, 3b based on fluctuations in line pressure and controls the operating state of the auxiliary hydraulic pump 3b. However, the present invention is not limited to this. Instead, the main hydraulic pump 3a is omitted, a transmission is interposed between the engine 1 and the hydraulic pump 3b, and the gear ratio of this transmission is set to the line pressure.
Similarly to each of the above embodiments, the deceleration side is selected when P _L is higher than the predetermined set pressure P ₂ , and the speed increase side is selected when P L is lower than the predetermined set pressure P ₁ in this state. You can get the following behavior.

Furthermore, in each of the above embodiments, the hydraulic pump 3
Although the case has been described in which the rotational driving force for the parts a and 3b is obtained from the engine, it goes without saying that the invention is not limited to this and that other rotational driving sources can be applied.

Further, the control valve for the hydraulic suspension is not limited to the pressure control valve 15 described above, and other flow control type servo valves or the like may be used.

[Effect of idea]

As explained above, according to this invention, the discharge amount of the hydraulic pump is controlled by the discharge amount control device according to the load on the hydraulic supply device, so that the horsepower consumption of the hydraulic pump can be minimized to the necessary minimum. The effect of reducing the load on the rotary drive source and improving fuel efficiency can be obtained.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing the first embodiment of this invention.
FIG. 2 is a graph showing the relationship between the hydraulic pump and the discharge flow rate to explain the operation of the first embodiment, FIG. 3 is a graph showing the control characteristics of the control circuit applicable to this invention, and FIG. 5 is a sectional view showing an example of a pressure control valve applicable to the invention; FIG. 5 is a graph showing control characteristics of the pressure control valve of FIG. 4; FIG. 6 is a system diagram showing a second embodiment of the invention; FIG. 7 is a graph showing the control characteristics of the unload valve applicable to the second embodiment, and FIG. 8 is a system diagram showing the embodiment. In the figure, 1 is the engine, 2 is the output shaft, 3 is the hydraulic pump unit, 3a is the main hydraulic pump, 3b is the auxiliary hydraulic pump, 3c is the power steering hydraulic pump, 4 is the relief valve, 5 is the output side hydraulic piping, 6 is an electromagnetic directional control valve, 10 is an accumulator, 12 is a discharge amount control device, 13 is a pressure detector, 14 is a control circuit, 15 is a pressure control valve, 18 is a hydraulic cylinder,
31 is a check valve, and 32 is an unload valve.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A hydraulic cylinder installed between each wheel and the vehicle body, and a pressure control valve installed in the supply side piping between the hydraulic cylinder and the hydraulic pressure supply device. In the hydraulic suspension, the hydraulic supply device is connected to a rotational drive source and rotationally driven,
and a hydraulic pump whose discharge side is connected to the supply side piping, an accumulator and a relief valve connected between the hydraulic pump and the pressure control valve of the supply side piping, and a discharge amount of the hydraulic pump itself to the supply side piping. A hydraulic supply device for a hydraulic suspension, comprising: a discharge amount control device that controls a discharge amount to decrease as the pressure in the supply side piping increases. (2) The above-mentioned hydraulic pump is composed of a plurality of hydraulic pumps connected to a common rotary drive source, and the load state and no-load state of each hydraulic pump are switched by a discharge amount control device. A hydraulic supply device for a hydraulic suspension according to scope 1. (3) The hydraulic pump is composed of a main hydraulic pump and a sub-hydraulic pump that are directly connected to a common rotational drive source, and each hydraulic pump is controlled by a discharge amount control device so that when the pressure in the supply side piping is low, The hydraulic suspension according to claim 1 of the utility model registration claim, which outputs the sum of the discharge volumes of both hydraulic pumps, and when the pressure in the supply side piping is high, the discharge volume of only the main hydraulic pump is output. Hydraulic supply device. (4) The discharge amount control device has a transmission interposed between the rotary drive source and the hydraulic pump, and the transmission adjusts the rotation speed of the rotary drive source as the pressure in the supply piping increases. A hydraulic pressure supply device for a hydraulic suspension according to claim 1, wherein the hydraulic pump is controlled to change speed so that the rotational speed ratio of the hydraulic pump is decreased.