JPH0444872Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Field of Application) The present invention relates to means for reducing the load at the time of starting a variable displacement pump equipped with a regulator cylinder that changes the tilt angle.

(Prior technology) Piston pumps used for supplying pressure oil to hydraulic equipment are divided into fixed displacement types, which have a constant discharge amount regardless of the discharge pressure, and variable displacement types, which change the discharge amount according to the discharge pressure. There is. As a variable capacity type, for example, there is a type in which the discharge pressure of the pump is guided to a regulator cylinder, and the displacement of the pump is changed by expanding and contracting the regulator cylinder to control the discharge amount. This type of variable capacity type has advantages over the fixed capacity type, such as being able to suppress increases in engine load and hydraulic oil temperature, and not requiring an overload relief valve.

(Problem that the invention aims to solve) By the way, even in variable capacity pumps where the engine is less prone to overload, the flow resistance in the hydraulic circuit downstream of the pump increases at low temperatures due to the increased viscosity of the hydraulic oil. Therefore, there was a problem in that a large load was placed on the engine at the time of starting, and battery power was consumed rapidly when starting the engine.

SUMMARY OF THE INVENTION In order to solve the above problems, it is an object of the present invention to provide a load adjustment mechanism that automatically minimizes the pump tilt angle when starting the pump at low temperatures.

(Means for Solving the Problems) The present invention provides a variable capacity pump equipped with a hydraulic regulator cylinder that changes the pump tilting angle, in which hydraulic pressure is supplied to and released from the regulator cylinder using a pilot pressure. A switching valve that selectively operates in response to It is equipped with a shape memory alloy spring that opens and closes at the same time.

(Function) The Paris pressure transmission circuit that switches the switching valve passes through a valve installed near the engine, and this valve is opened and closed by a shape memory alloy spring that deforms at a predetermined temperature. The regulator cylinder, which operates at This allows the pump to start at a small tilt angle at low temperatures,
The tilt angle increases as the shape memory alloy spring deforms as the engine warms up.

(Example) An embodiment of the present invention is shown in FIGS. 1 and 2.

In FIG. 1, 1 displaces the swash plate of the pump 3 to the minimum tilt angle using the oil pressure in the oil chamber 2 formed inside;
It is also a regulator cylinder that displaces the swash plate to the maximum tilt angle by releasing hydraulic pressure. Pressure oil led from a discharge port of a pump 3 through a hydraulic oil supply passage 4 is connected to the oil chamber 2 via a switching valve 6 equipped with a pilot. This switching valve 6 is switched by pilot pressure transmitted through a pilot pressure transmission passage 9 from an auxiliary pump 8 driven integrally with the pump 3, and selectively connects the oil chamber 2 to the pump 3 and the tank 5. do.

The pilot pressure transmission passage 9 is formed via a valve 10 attached to the outside of the engine 7 that drives the pump 3. This valve 10 is provided close to the engine 7, and a valve body 12 slides inside the cylinder 11 to connect or shut off the pilot pressure transmission passage 9. The valve body 12 has both ends connected to the cylinder 11. An annular recess 16 is formed in the middle of the recess 16, which is in sliding contact with the inner periphery of the recess 16 and transmits pilot pressure. Further, cylinders 1 are provided on both sides of the valve body 12.
A shape memory alloy spring 13 (on the left side in the figure) and a regular spring 14 (on the right side in the figure) are interposed between the end of the valve body 12 and the valve body 12 is held in a balanced position. The spring 13 is set to a certain stretched state as a memorized shape, and the valve body 12 retains the spring 1 state when the temperature is below the set temperature.
4, the concave portion 16 is held in a position where it communicates with the pilot pressure transmission passages 9 on both sides, and when the temperature exceeds the set temperature, the spring 13 returns to its memorized shape and is displaced to the right in the figure, cutting off the transmission of pilot pressure. do.

Note that another pilot pressure transmission passage 15 for controlling the tilt angle according to the discharge pressure of the pump 3 is also connected to the switching valve 6.

Next, the effect will be explained.

When the temperature is lower than the set temperature, the spring 13 is contracted from its memorized shape due to the repulsive force of the spring 14, and the valve 10 is in a state where the recess 16 communicates with the pilot pressure transmission passages 9 on both sides as shown in FIG. It's summery. When the engine 7 is started in this state, pilot pressure supplied from the auxiliary pump 8 acts on the switching valve 6, and the switching valve 6 connects the oil chamber 2 to the discharge side of the pump 3. As a result, the regulator cylinder 1 is expanded and the tilting angle of the pump 3 becomes the minimum state. Therefore, even if the flow resistance of the hydraulic circuit downstream of the pump 3 increases due to low temperature, the pump 3 rotates easily and the engine 7 starts smoothly. As the engine 7 warms up, the valve 10 disposed on the outside of the engine 7 is also warmed up, and when the set temperature is reached, the spring 13 returns to its memorized shape and forces the valve body 12 against the spring 14. Slide it to the right as shown in Figure 2. As a result, the transmission of the pilot pressure is cut off and the switching valve 6 is switched to connect the oil chamber 2 to the tank 5, so that the regulator cylinder 1 contracts and the tilting angle of the pump 3 becomes maximum. As a result, the pump 3 shifts to the normal operating state, and the regulator cylinder 1 thereafter controls the tilting angle according to the discharge pressure of the pump 3 transmitted from another pilot pressure transmission circuit 15.
Adjust the discharge amount.

Note that if the temperature at the time of starting the engine 7 is higher than the set value, the valve 10 has already shut off the pilot pressure transmission passage 9 from the time of starting, and the pump 3 is operated at the maximum tilt angle from the time of starting. In this case, since the resistance of the hydraulic circuit downstream of the pump 3 is small,
There is no risk that the starting load on the engine 7 will become excessive.

(Effects of the invention) As described above, the invention provides a pilot pressure transmission circuit to a switching valve with a pilot that applies hydraulic pressure to the regulator cylinder to change the pump tilt angle.
The pump is formed via a valve installed close to the engine that drives the pump, and because the opening/closing mechanism of this valve uses a shape memory alloy spring that deforms at a predetermined temperature, the regulator cylinder changes as the engine temperature changes. is activated, and when starting the pump at low temperatures, the pump tilting angle is kept at the minimum, but when the engine temperature rises and this spring deforms to its memorized shape, the tilting angle is maximized and normal pump operation resumes. Transition. Therefore, the startability of the engine is improved, and the consumption of battery power required for starting is also reduced.

[Brief explanation of drawings]

1 and 2 are composite views of a hydraulic circuit diagram and a sectional view of a valve showing an embodiment of the present invention. 1...Regulator cylinder, 3...Pump,
6...Switching valve with pilot, 7...Engine, 9
...Pilot pressure transmission circuit, 10...Valve, 1
3... Spring (shape memory alloy).

Claims (1)

[Scope of utility model registration request] In a variable capacity pump equipped with a hydraulic regulator cylinder that changes the pump tilting angle, a switching valve is provided to selectively supply and release hydraulic pressure to the regulator cylinder in response to pilot pressure. The pilot pressure transmission circuit to the switching valve is formed via a valve installed close to the engine that drives the pump, and is equipped with a shape memory alloy spring that opens and closes this valve at a predetermined temperature. Features a variable capacity pump starting load adjustment mechanism.