JP3206485B2 - Deceleration energy regeneration device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deceleration energy regenerating device that converts kinetic energy when a vehicle decelerates into hydraulic energy and accumulates the pressure in an accumulator.

[0002]

2. Description of the Related Art As shown in Japanese Patent Application Laid-Open No. 6-156220, large vehicles (vehicles) such as trucks and buses collect the deceleration energy at the time of deceleration of the vehicle and start this energy. Some vehicles have a deceleration energy regeneration device used during acceleration.

[0003] In such a deceleration energy regenerating apparatus, as shown in FIG. 3, in a power transmission system from an engine 1 to a drive wheel 2, for example, a differential gear 3 (drive system member) is connected to A hydraulic pump / motor 5 composed of a hydraulic pump and a swash plate pump that can be switched to a hydraulic motor by tilting the plate 5a is connected, and hydraulic oil is stored in one of the inlet / outlet portions of the hydraulic pump / motor 5. A structure is used in which a hydraulic oil tank 6 is connected via a flow path 7a, and an accumulator 8 containing a compressive fluid, for example, nitrogen (N ₂ ) gas, is connected to the other via a flow path 7c having a switching valve 7b. Can be

[0004] The switching valve 7b is provided with a check valve state A, for example, in which the flow is from the hydraulic pump side to the accumulator 8 side.
And a check valve that can be switched to an open state B in which bidirectional flow is permitted to allow flow from the accumulator 8 side to the hydraulic motor side.

In this deceleration energy regenerating apparatus, when the brake pedal is depressed during driving of the vehicle to apply a braking force to the vehicle, the switching valve 7b remains in the check valve state A and the hydraulic pump / motor 5 is driven by the swash plate 5a. Function as a hydraulic pump (in a swash plate state indicated by a solid line) due to the tilting of The hydraulic pump 5 is operated by the kinetic energy of the vehicle transmitted from the differential gear 3, and pressurizes hydraulic oil from the hydraulic oil tank 6 into the accumulator 8.

As a result, the nitrogen gas in the accumulator 8 is compressed, and the kinetic energy of the vehicle is converted into hydraulic energy and stored in the accumulator 8. Then, a braking force is generated by the operation of the hydraulic pump 5 with this resistance.

When the vehicle starts and accelerates, the switching valve 7b is switched to the open state B by an accelerator opening signal or the like, and the hydraulic pump / motor 5 is tilted by the swash plate 5a to move the hydraulic motor (shown by a two-dot chain line). It functions as a swash plate state, and flows the hydraulic oil stored in the accumulator 8 in the direction opposite to the direction at the time of braking to generate torque in the hydraulic motor 5 to assist the driving force of the engine 1.

[0008]

By the way, the working oil of the deceleration energy regenerating device has a high viscosity when the oil temperature is low. In particular, at a low outside temperature such as in winter, the viscosity of the hydraulic oil is considerably high. The deceleration energy regenerating device uses the braking mode to warm up, that is, raises the oil temperature, but the internal pressure of the accumulator only gradually increases during braking, so once the oil temperature decreases, the oil temperature increases. It will take quite some time before it rises again.

In addition, since this also results in delaying the rise of the hydraulic pressure that causes the braking force, there is a problem that sufficient braking performance cannot be exhibited during braking with warm-up. for that reason,
There is a need for technology that can handle low oil temperatures.

The present invention has been made in view of the above circumstances, and an object thereof is to utilize a braking mode,
It is an object of the present invention to provide a deceleration energy regenerating apparatus capable of warming-up while achieving both early rise of low oil temperature and early rise of hydraulic pressure for obtaining a sufficient braking force.

[0011]

In order to achieve the above object, in the deceleration energy regenerating apparatus according to the first aspect, at the time of braking at a low oil temperature, the hydraulic oil discharged from the hydraulic pump is not accumulated in the accumulator. Then, it returns to the working tank through the relief valve.

At this time, the relief valve generates a hydraulic pressure equivalent to the valve opening pressure in the pipeline between the hydraulic pump and the relief valve on the upstream side of the accumulator. It rises from time to a predetermined pressure.

At the same time, when the hydraulic oil passes through the relief valve, the kinetic energy of the hydraulic pump becomes heat and is given to the hydraulic oil to raise the oil temperature. Oil temperature rises with time.

Thus, the deceleration energy regenerating device achieves both the early rise of the low oil temperature and the early rise of the oil pressure, and exhibits sufficient braking performance while warming up.

In the deceleration energy regenerating device according to the second aspect, cavitation that can occur at a low oil temperature is prevented at the start of braking when the hydraulic pressure is high. In other words, at the start of braking when the vehicle speed is considered to be the highest, the hydraulic pressure has already risen to the pump discharge pressure corresponding to the valve opening pressure of the relief valve and is high, so cavitation may occur with high-viscosity hydraulic oil. high.

Therefore, by reducing the pump discharge amount only when the discharge pressure rises, that is, only at the start of braking, cavitation at a low oil temperature, which may occur particularly at the start of braking, is avoided. After the start, the oil temperature rises early, so there is no fear of cavitation.)

In the deceleration energy regeneration device according to the third aspect of the present invention, the use of the relief valve dedicated to warm-up control facilitates setting of the valve opening pressure during warm-up control. In addition, since the burden (operating frequency) of the main relief valve is reduced, the reliability of the main relief valve is increased.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to an embodiment shown in FIGS. In the drawings, the same reference numerals are given to the parts described in the section of "Prior Art", the description thereof will be omitted, and different parts (main parts of the invention) will be described here.

This embodiment has a structure in which the hydraulic pressure is generated in the section upstream of the switching valve 7b by the discharge oil from the hydraulic pump 5 using the braking mode at a low oil temperature where the viscosity of the hydraulic oil is high. The difference is that a braking force is generated while adopting a warm-up operation to raise the oil temperature early.

Specifically, the following structure is employed. That is, the switching valve 7b is in the check valve state A and the open state B
And a three-position valve having a shut-off state S.

A first relief path 10 and a second relief path 11 communicating with the hydraulic oil tank 6 are respectively connected in parallel at two points of a flow path 7c connecting the hydraulic pump 5 upstream of the switching valve 7b. Communication is established.

The first relief passage 10 is provided with a main relief valve 12 having a high valve opening pressure. When a high pressure equivalent to the valve opening pressure is generated upstream of the flow path 7c, the main relief valve 1 is opened.
2 is opened so that the hydraulic oil can be returned from the relief path 10 to the working tank 6. Second relief road 1
1 is provided with a warming-up relief valve 13 having a lower valve opening pressure than the main relief valve 12. When a pressure equivalent to the valve opening pressure is generated upstream of the flow path 7c, the warming-up relief valve 13 opens. Thus, the working oil can be returned to the working tank 6 from the relief path 11. That is, the structure is such that the hydraulic oil can be returned from the two relief valves 12 and 13 provided in parallel.

An opening / closing valve for switching between an open state C and a closed state D, for example, a solenoid-driven electromagnetic two-way valve 14 is provided in a relief path portion on the upstream side of the warm-up relief valve 13.

By switching the switching valve 7b and the electromagnetic two-way valve 14, the operating oil from the hydraulic pump 5 is supplied not to the accumulator 8 but to the warm-up relief valve 13 at the time of low oil temperature in the braking mode. The oil is guided to the pipeline to generate a hydraulic pressure for warming up or generating a braking force in the section, that is, a hydraulic pressure equivalent to the valve opening pressure of the relief valve 13 for warming up.

For switching the switching valve 7b and the electromagnetic two-way valve 14, a control unit for controlling the opening / closing operation of the synchro clutch 4 and the switching operation (tilting) of the hydraulic pump / motor 5 according to a brake signal, an accelerator signal, and the like. Fifteen
(E.g. a microcomputer etc .:
Control means).

More specifically, the control unit 15 switches the hydraulic pump / motor 5 to the hydraulic pump in the braking mode, and switches the hydraulic pump / motor 5 to the hydraulic motor in the start / acceleration mode by a brake signal, an accelerator signal, or the like. In addition to the switching function, in the braking mode, for example, the oil temperature detected by an oil temperature sensor 6a (oil temperature detecting means) provided in the hydraulic oil tank 6 is set to a predetermined temperature (for example, 20 ° C.) for determining whether warming is necessary. When the oil pressure falls below the predetermined value, a function is set to switch the switching valve 7b from the "check valve state to the shutoff state" and the electromagnetic two-way valve 14 from the "closed to open" state. The hydraulic oil discharged from the hydraulic pump 5 operating with the kinetic energy is circulated in the order of the warm-up relief valve 13 and the operating tank 6.

Further, the control unit 15 has a function of varying the discharge amount per rotation of the hydraulic pump 5 according to the discharge pressure of the hydraulic pump 5 to generate a braking force corresponding to the amount of depression of the brake pedal. Have been.

That is, a hydraulic pump / motor 5 having a variable capacity, for example, a swash plate 5a whose tilt angle can be set arbitrarily within a range from a minimum pump capacity to a maximum pump capacity.
This is performed by controlling the swash plate 5a of this hydraulic pump by the tilt actuator 16 according to the above function.

Specifically, for example, when a certain constant K is set, the depressing force of the brake pedal (detected from the brake signal)
To the discharge pressure sensor 17 for detecting the discharge pressure of the hydraulic pump.
(Discharge pressure detecting means) multiplying the divided value by the discharge pressure of the hydraulic pump 5 output from the hydraulic pump 5 to obtain the tilting angle θ of the swash plate 5a corresponding to the braking force; The tilt angle θ is a tilt limit value θ0 (for example, a value obtained by Kθ / VH, where Kθ is a constant, and VH is the vehicle speed) for determining whether or not the braking force is fully generated by the hydraulic pump 5. If within the range of the rotation limit value θ0, the swash plate 5a is driven at the tilt angle θ obtained as it is.
The tilt angle θ of the swash plate 5a is set to the tilt limit value 0, and a braking device for a vehicle, for example, a function of operating a wheel brake is used for the insufficient braking force. Power is generated.

The control unit 15 is provided with a function of avoiding cavitation which is likely to occur at the time of warm-up braking and at the start of braking at which the vehicle speed is the highest.

That is, when the braking force is generated by using the accumulator 6, since the internal pressure of the accumulator 6 is gradually increased, the pump discharge pressure at the start of the braking with the highest vehicle speed is small, and the oil temperature is low, that is, high. Cavitation due to viscosity is unlikely to occur, but when a braking force is generated using the warm-up relief valve 13, the pump opening pressure of the warm-up relief valve 13 increases the pump speed from the start of braking at the highest vehicle speed. Since discharge pressure is generated, cavitation due to high viscosity due to low oil temperature is likely to occur.

Therefore, the control unit 15 includes:
When the pump discharge pressure detected by the discharge pressure sensor 17 rises, that is, when braking is started, a function of reducing the pump discharge amount of the hydraulic pump 5, for example, a function of narrowing down the tilt angle θ of the hydraulic pump is set.

More specifically, for example, instead of the constant Kθ in the above-described arithmetic expression for calculating the tilt limit value θ during the warm-up braking, the control unit 15 is provided with, for example, FIG.
An equation (Kθ1 / VH) for calculating a constant Kθ1 determined by a map such that the discharge flow rate decreases as the temperature becomes lower than the warm-up necessity determination temperature T0 as shown in FIG. Where Kθ is a constant and VH is the vehicle speed) to reduce the pump discharge amount at the start of braking.
Cavitation is prevented from occurring at the start of the braking.

With such a function, the warming-up of the deceleration energy regeneration device can be favorably performed. The control at the time of deceleration of the vehicle with warm-up is shown in the flowchart of FIG.

Next, according to this flowchart, the control mode during warm-up braking, that is, the warm-up braking mode, will be described in parallel with the braking mode during normal braking, that is, the normal braking mode.

For example, assume that the engine 1 is started and the automobile starts running. At this time, it is assumed that the driver who decelerates depresses the accelerator pedal and depresses the brake pedal.

As a result, the hydraulic pump / motor 5 is switched to the hydraulic pump, and proceeds to a brake control routine as shown in FIG. Hereinafter, reference numeral 5 is used as a hydraulic pump.

In this routine, first, the control unit 15 reads the oil temperature T output from the oil temperature sensor 6a, for example, the temperature of the working oil stored in the working tank 6, as shown in step S1.

Next, the control unit 15 determines in step S2 the oil temperature T and the temperature T0 for determining whether or not warm-up is necessary.
(For example, 20 ° C.), and if the oil temperature T is equal to or higher than the warming-up necessity determination temperature T0, it is determined that warming-up is unnecessary, and the process proceeds to step S3 to enter the normal braking mode. Oil temperature T
Is lower than the warm-up necessity determination temperature T0, it is determined that warm-up, that is, an increase in the oil temperature that eliminates the high viscosity of the working oil is necessary, and the process proceeds to step S20 to enter the warm-up braking mode.

The normal braking mode is performed by a routine from step S3 to step S10. Describing this routine, first, the switching valve 7b is controlled to the check valve state A and the electromagnetic two-way valve 14 is controlled to the closed state D (step S).
3).

As a result, the hydraulic oil discharged from the hydraulic pump 5 is pressure-fed into the accumulator 8, and the hydraulic resistance of the hydraulic pump 5 generated at this time becomes the braking force of the vehicle.
Subsequently, the stepping force of the brake pedal is detected from the brake signal (step S4), and the discharge pressure of the hydraulic pump 5 is detected from the discharge pressure sensor 17 (step S5), and the stepping force is determined by using the stepping force and the discharge pressure. Is determined (step S6).

Next, the tilt angle θ becomes the tilt limit value θ0.
(For example, a value obtained by Kθ / VH, where Kθ is a constant, V
H is within the range of the vehicle speed), and it is determined whether or not the braking force is fully generated by the hydraulic pump 5 (step S7).

At this time, the obtained tilt angle θ is equal to the tilt limit value θ.
If it is within 0, it is determined that the braking force corresponding to the depressing force of the brake pedal has been completely exhausted from the hydraulic pump 5, and the final step S10 is reached. To generate a braking force.

If the obtained tilt angle θ exceeds the tilt limit value θ0, it is determined that the braking force corresponding to the depressing force of the brake pedal has not been fully output from the hydraulic pump 5, and the swash plate 5a The tilt angle .theta. Is changed to the tilt limit value .theta.0 (step S8), the wheel brake of the vehicle is operated by the insufficient braking force (step S9), and a braking force corresponding to the depression force of the brake pedal is generated.

On the other hand, in the warm-up braking mode, step S20
This is performed in a routine from step S10 to step S10. Specifically, first, the switching valve 7b is controlled to the shut-off state S, and the electromagnetic two-way valve 14 is controlled to the open state C (step S20).

As a result, the communication between the accumulator 8 and the hydraulic pump 5 is cut off, so that the low oil temperature hydraulic oil discharged from the hydraulic pump 5 is not accumulated in the accumulator 8 but is provided upstream of the switching valve 7b. The hydraulic pump 5 is guided to the pipeline up to the warm-up relief valve 13, and is moved from the hydraulic pump 5 to the warm-up relief valve 1.
The hydraulic pressure is generated in the section up to 3.

Next, when the hydraulic pressure exceeds the opening pressure of the warm-up relief valve 13 and the hydraulic oil upstream of the switching valve 7b passes through the warm-up relief valve 13, the kinetic energy of the hydraulic pump 5 becomes heat and And is given to the hydraulic oil to raise the oil temperature.

Thereafter, the tilt angle θ corresponding to the braking force corresponding to the depressing force of the brake pedal is obtained by the processes from step S21 to step S23, which are the same as those in the normal control mode.

It is determined whether or not the tilt angle θ is within a range of a tilt limit value θ0 (for example, a value obtained by Kθ1 / VH, where Kθ1 is a constant and VH is the vehicle speed). It is determined whether or not the braking force is fully output (step S24).

At this time, the constant Kθ1 is different from the constant K in the normal control mode, and calculates a tilt angle limit value θ0 that decreases the discharge flow rate as the oil temperature becomes lower than the warming-up necessity determination temperature T0. It is determined by the value to do.

As a result, at the start of the braking operation at the highest vehicle speed, the hydraulic pressure equivalent to the valve opening pressure that causes the braking force is maintained at a small pump discharge flow rate. Then, as in the normal control mode, if the obtained tilt angle θ is within the previously changed tilt limit value θ 0, the braking force corresponding to the depression force of the brake pedal is completely output from the hydraulic pump 5. Is reached, the process proceeds to the final step S10, and the hydraulic pump 5 generates a braking force while maintaining the same tilt angle θ.

If the obtained tilt angle θ exceeds the tilt limit value θ 0, it is determined that the braking force corresponding to the depressing force of the brake pedal has not been fully output from the hydraulic pump 5 and the swash plate 5 a The tilt angle .theta. Is changed to the tilt limit value .theta.0 (step S25), the wheel brake of the vehicle is operated by the insufficient braking force (step S26), and a braking force corresponding to the depression force of the brake pedal is generated.

When an excessive oil pressure is generated in the pipeline, the operating oil returns from the main relief valve 12 to the operating tank 6. When the relief valve, that is, the warm-up relief valve 13 is used to generate a hydraulic pressure upstream of the switching valve 7b during vehicle deceleration and warm up while regenerating energy, the hydraulic pressure that brings the braking force is as follows: Unlike increasing the internal pressure of the accumulator 8, the pressure increases in the pipeline between the hydraulic pump 5 and the warm-up relief valve 13 on the upstream side of the accumulator 8, so that the pressure is reduced to a predetermined pressure from the start of braking in a short time. Can be raised up.

Further, when the hydraulic oil passes through the warm-up relief valve 13, the kinetic energy of the hydraulic pump 5 becomes heat and raises the oil temperature. Can be raised to a predetermined oil temperature.

Therefore, the deceleration energy regenerating device is
Both early rise of low oil temperature and early rise of hydraulic pressure can be improved, and sufficient braking performance can be exhibited while warming up.

In addition, since the discharge flow rate of the hydraulic pump 5 is reduced in response to the increase of the pump discharge pressure at the time of deceleration of the vehicle, cavitation due to low oil temperature, which is likely to occur at the start of braking at the highest vehicle speed, can be avoided.

That is, when the relief valve is used, when the hydraulic oil passes through the relief valve, the oil pressure in the pipe has already risen to the valve opening pressure of the relief valve at the start of braking, that is, the pump discharge pressure. With such hydraulic oil, cavitation is likely to occur. However, only when the discharge pressure is increased, that is, only when braking is started, the pump discharge amount is reduced, so that cavitation at a low oil temperature is avoided. Cavitation is less likely to occur as the oil temperature increases.

In addition, since the relief valve employs a structure in which a dedicated warm-up relief valve 13 is provided in parallel in addition to the main relief valve 12, the pressure can be easily set at the time of warm-up control. The reliability of the relief valve 12 is high because the burden on the relief valve 12 can be reduced, that is, the operation frequency of the main relief valve 12 can be reduced.

In one embodiment, the main relief valve 12
Although the structure using two relief valves, that is, the relief valve 13 dedicated to the warm-up control and the relief valve 13 dedicated to the warm-up control, has been described, the warm-up is performed using, for example, one relief valve set to a predetermined valve opening pressure. You may do so.

[0060]

As described above, according to the first aspect of the present invention, a high oil pressure and a high pressure resistance can be generated from the start of braking. And an early rise of the vehicle can be improved, and sufficient braking performance can be exhibited while warming up.

According to the invention described in claim 2, according to claim 1
In addition to the effects of the invention described in (1), it is possible to avoid cavitation occurring at a low oil temperature at the start of braking when the hydraulic pressure is high due to a decrease in the discharge capacity of the hydraulic pump.

According to the invention described in claim 3, according to claim 1
In addition to the effects of the invention described in (1), the valve opening pressure can be easily set during the warm-up control, and the burden on the main relief valve is reduced, so that high reliability can be secured.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a deceleration energy regenerating device according to an embodiment of the present invention, together with a control system.

FIG. 2 is a flowchart illustrating control during braking of the device.

FIG. 3 is a diagram for explaining an outline of a deceleration energy regeneration device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Engine 3 ... Differential gear (drive system member of a vehicle) 5 ... Hydraulic pump / motor 5a ... Swash plate 6 ... Hydraulic oil tank 7b ... Switching valve 8 ... Accumulator 12 ... Main relief valve 13 ... Warm-up relief valve 14 ... Electromagnetic two-way valve (open / close valve) 15: control unit (control unit) 16: tilt actuator 17: discharge pressure sensor (discharge pressure detecting means).

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B60K 25/00 B60T 1/10 F16D 61/00

Claims (3)

(57) [Claims] 1. A deceleration for driving a hydraulic pump interposed between a hydraulic oil tank and an accumulator by a driving system member of a vehicle when the vehicle decelerates, and accumulating a hydraulic pressure output from the hydraulic pump in the accumulator. In the energy regenerating device, a switching valve provided so as to be able to cut off the flow of hydraulic oil from the hydraulic pump side to the accumulator side, and a discharge side of the hydraulic pump upstream of the switching valve and communicating with the hydraulic oil tank. A relief valve that is provided in a relief passage that opens and that opens when a pressure equal to or higher than a predetermined pressure is generated on the upstream side; an oil temperature detection unit that detects an oil temperature of hydraulic oil; and an oil temperature that is detected by the oil temperature detection unit. Control means for closing the switching valve even when the vehicle decelerates when it detects that the oil temperature has dropped below a predetermined temperature. Over Regenerative unit. 2. The hydraulic pump according to claim 1, wherein said hydraulic pump is configured to have a variable capacity, and further includes discharge pressure detecting means for detecting a discharge pressure of said hydraulic pump, wherein said control means detects said discharge pressure from said discharge pressure detecting means when the vehicle decelerates. The deceleration energy regenerating apparatus according to claim 1, wherein the capacity of the hydraulic pump is reduced with respect to an increase in the discharge pressure to be performed. 3. A relief valve having a higher valve opening pressure and a warm-up relief valve having a lower valve opening pressure than the relief valve are provided in parallel in the relief passage. An on-off valve is provided on the upstream side, and the control means is configured to open the on-off valve when detecting that the oil temperature detected by the oil temperature detecting means has dropped below a predetermined temperature. The deceleration energy regeneration device according to claim 1, wherein: